 | 古南 博 （コミナミ ヒロシ）
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Last Updated :2024/04/19
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新規な光触媒材料の開発および新規な光触媒反応系の開拓について研究しています。太陽光などの自然エネルギーを用いて、光エネルギーの化学的貯蔵や有害汚染物質の無害化を目指しています。
研究者情報
学位
ホームページURL
ORCID ID
J-Global ID
研究キーワード
- ナノ結晶 光触媒 環境触媒 Nanocrystals Photocatalysts Environmental Catalysts
現在の研究分野（キーワード）
- 新規な光触媒材料の開発および新規な光触媒反応系の開拓について研究しています。太陽光などの自然エネルギーを用いて、光エネルギーの化学的貯蔵や有害汚染物質の無害化を目指しています。
研究分野
経歴
- 2020年04月 - 現在 近畿大学共同利用センターセンター長
- 2014年04月 - 現在 近畿大学理工学部教授
- 2007年04月 - 2014年03月 近畿大学理工学部准教授
- 2004年04月 - 2007年03月 近畿大学理工学部助教授
- 2000年04月 - 2004年03月 近畿大学理工学部講師
- 2000年 - 2004年 Assistant Professor, Faculty of Science and Engineering,
- 2004年 - Associate Professor, Faculty of Science and Engineering,
- 1993年04月 - 2000年03月 近畿大学理工学部助手
- 1993年 - 2000年 Reaearch Associate, Faculty of Science and Engineering,
学歴
- 1990年04月 - 1993年03月 京都大学大学院 工学研究科 石油化学専攻博士後期課程
- 1988年04月 - 1990年03月 京都大学大学院 工学研究科 石油化学専攻博士前期課程
- 1984年04月 - 1988年03月 京都大学 工学部 石油化学科
所属学協会
研究活動情報
論文
- Hongxuan Qiu; Akira Yamamoto; Eri Fudo; Atsuhiro Tanaka; Hiroshi Kominami; Hisao YoshidaACS Applied Energy Materials 6 22 11592 - 11601 2023年11月
- Hiroshi Kominami; Reo Akamata; Atsuhiro TanakaChemistry – A European Journal 29 43 2023年07月 [査読有り]
Abstract Deprotection of pyridine N‐oxides under mild conditions with an inexpensive and environmentally friendly reducing reagent is an important chemical procedure. The use of biomass waste as the reducing reagent, water as the solvent and solar light as the energy source is one of the most promising approaches with minimal impact on the environment. Therefore, a TiO2 photocatalyst and glycerol are suitable components of this type of reaction. Stoichiometric deprotection of pyridine N‐oxide (PyNO) with a minimal amount of glycerol (PyNO:glycerol= 7 : 1) was achieved, with only CO2 being produced as the final oxidation product of glycerol. The deprotection of PyNO was thermally accelerated. Under solar light, the temperature of the reaction system increased to 40–50 °C and PyNO was also quantitatively deprotected, indicating that solar energy, i. e., UV light and thermal energy, can be effectively used. The results provide a new approach in the fields of organic chemistry and medical chemistry using biomass waste and solar light. - Hongxuan Qiu; Akihiko Anzai; Tayyebeh Soltani; Akira Yamamoto; Eri Fudo; Atsuhiro Tanaka; Hiroshi Kominami; Hisao YoshidaACS Applied Energy Materials 2023年05月
- Eri Fudo; Yusuke Kiyota; Ryuto Osawa; Atsuhiro Tanaka; Hiroshi KominamiApplied Catalysis A: General 657 119156 - 119156 2023年05月 [査読有り]
We succeeded in one-pot synthesis of N-phenylbenzylamine (PBA) from benzaldehyde (BAD) and aniline (AN) over titanium(IV) oxide having a gold (Au) cocatalyst (Au-TiO2) without the use of hydrogen gas. This process consists of two steps: 1) formation of benzylideneaniline (BAN) and water by condensation of AN and BAD, a step that is a thermal reaction and results in an equilibrium being reached, and 2) photocatalytic hydrogenation of BAN to PBA through a hydrogen transfer reaction from alcohol. Reactions under various conditions revealed that TiO2 showed bifunctionality in the condensation process as an acid catalyst and an adsorbent of water. Among the cocatalysts examined in this study, Au showed the highest performance for PBA production. Photoirradiation to the system in equilibrium containing Au-TiO2 produced PBA in a yield of about 92%. We found that TiO2 having a gold (Au) cocatalyst (Au-TiO2) works as a trifunctional catalytic material, i.e., an acid catalyst and water adsorbent for the first step and a photocatalyst for the second step. Expandability of this reaction system in production of halogen-substituted PBA and selection of alcohol was investigated. - Kousuke Nakanishi; Sakae Araki; Kousuke Nomoto; Yuichi Onoue; Ryosuke Yagi; Hiroyuki Asakura; Atsuhiro Tanaka; Tsunehiro Tanaka; Hiroshi KominamiPhysical Chemistry Chemical Physics 25 33 21868 - 21874 2023年 [査読有り]
Our previous study showed that a rhodium (Rh) cocatalyst is indispensable for ring hydrogenation of benzoic acid over a titanium(IV) oxide (TiO2) photocatalyst. In this study, we explored ring hydrogenation under an Rh-free condition by using two kinds of cocatalyst that were inactive for this reaction when used solely. Cyclohexanecarboxylic acid as the ring hydrogenation product was successfully obtained when ruthenium (Ru) and palladium (Pd) were simultaneously loaded on TiO2, indicating that this bimetallic system can be used in place of an Rh cocatalyst in ring hydrogenation. The state and distribution of Ru and Pd in particles loaded on TiO2 were investigated by transmission electron microscopy, X-ray photon spectroscopy, and X-ray absorption near edge structure analysis. The functions of Ru and Pd as cocatalysts are discussed on the basis of results of characterization and activity tests. The effects of different contents of Ru and Pd in Ru–Pd/TiO2 prepared by a two-step photodeposition method on catalytic activity and the features of the reaction system were investigated in detail. - Eri Fudo; Hiroyuki Asakura; Atsuhiro Tanaka; Hiroshi KominamiSustainable Energy & Fuels 7 4 1077 - 1083 2023年 [査読有り]
Many investigations have been carried out on the production of hydrogen (H2) by water splitting using energy efficiently. We investigated photoelectrochemical water splitting (2H2O → 2H2 + O2) using the surface plasmon resonance of gold (Au) nanoparticles, in which tantalum pentoxide (Ta2O5) was selected as the supporting material for Au. Au/Ta2O5 powder was prepared by using the deposition precipitation (DP) method and subsequent calcination, and an Au/Ta2O5 electrode having a Ta2O5 layer of ca. 3 μm in thickness and Au0 nanoparticles of 6.4 nm in average size was fabricated by using a squeegee method. The prepared powder and electrode were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. The Au/Ta2O5/FTO electrode was used as the working electrode and the current–potential curve was measured under visible light irradiation, which showed photoresponse of more than 0.5 V vs. RHE. H2 and oxygen (O2) were continuously produced under visible light irradiation and with an externally applied potential of 0.8 V vs. RHE to a Pt counter electrode. The results of this study will provide a new strategy for photoelectrochemical water splitting using a plasmonic photoanode. - Hiroshi Kominami; Kazuhiro Onogi; Atsuhiro TanakaJournal of Photochemistry and Photobiology A: Chemistry 430 113963 - 113963 2022年09月 [査読有り]
- Hiroshi Kominami; Ryuichi Yato; Atsuhiro TanakaChemCatChem 2022年08月 [査読有り]
- Eri Fudo; Atsuhiro Tanaka; Hiroshi KominamiACS Applied Nano Materials 5 7 8982 - 8990 2022年07月 [査読有り]
- Eri Fudo; Atsuhiro Tanaka; Hiroshi KominamiCatalysis Today 2022年05月 [査読有り]
- Yuhei Yamamoto; Hibiki Toda; Atsuhiro Tanaka; Hiroshi KominamiChemCatChem 14 5 e202200174 2022年03月 [査読有り]
- Surya Pratap Singh; Akira Yamamoto; Eri Fudo; Atsuhiro Tanaka; Hiroshi Kominami; Hisao YoshidaACS Catalysis 11 22 13768 - 13781 2021年11月 [査読有り]
- Shota Imai; Yasumi Kojima; Eri Fudo; Atsuhiro Tanaka; Hiroshi KominamiApplied Catalysis A: General 624 118331 - 118331 2021年08月 [査読有り]
- Tayyebeh Soltani; Akira Yamamoto; Surya Pratap Singh; Akihiko Anzai; Eri Fudo; Atsuhiro Tanaka; Hiroshi Kominami; Hisao YoshidaACS Applied Energy Materials 4 7 6500 - 6510 2021年07月 [査読有り]
- Tayyebeh Soltani; Xing Zhu; Akira Yamamoto; Surya Pratap Singh; Eri Fudo; Atsuhiro Tanaka; Hiroshi Kominami; Hisao YoshidaApplied Catalysis B: Environmental 286 119899 - 119899 2021年06月 [査読有り]
- Eri Fudo; Atsuhiro Tanaka; Shoji Iguchi; Hiroshi KominamiSustainable Energy & Fuels 5 3303 - 3311 2021年 [査読有り]
Plasmonic water splitting (H2O → H2 + 1/2O2) over a metal-loaded metal oxide under irradiation of visible light is still difficult, although conversion of organic compounds over plasmonic photocatalysts has...
- Xing Zhu; Akira Yamamoto; Shota Imai; Atsuhiro Tanaka; Hiroshi Kominami; Hisao YoshidaApplied Catalysis B: Environmental 274 119085 2020年10月 [査読有り]
Previously a silver-manganese dual cocatalyst loaded on a potassium hexatitanate crystal photocatalyst was reported to be efficient for photocatalytic reduction of CO2 to CO by using water as an electron source. In the present study, variously prepared silver-manganese dual cocatalysts were investigated to figure out their states and functions of Ag and MnOx species. Although an impregnation method provided various states of these species such as AgOx particles, core-shell structures, and oxidized aggregates, they gave negative effects on the photocatalytic activity. On the other hand, a simultaneous photodeposition method fabricated Ag and MnOx species on the long and short facets of the rod-like crystal, respectively, and these species functioned as each efficient promoter for the reductive and oxidative reactions in the photocatalysis. It was firstly evidenced that the clear separation of the reaction sites with the proper promoters is essential for the high efficiency in the photocatalytic CO2 reduction. - Sakae Araki; Kousuke Nakanishi; Atsuhiro Tanaka; Hiroshi KominamiJournal of Catalysis 389 212 - 217 2020年09月 [査読有り]
- Yamamoto, Akifumi; Tanaka, Atsuhiro; Kominami, Hiroshi; Fujioka, Daiki; Sanada, Tomoe; Kojima, KazuoJOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 20 7 4131 - 4137 2020年07月 [査読有り]
Disk-shaped tungsten(VI) oxide (D-WO3) particles were synthesized according to a previously reported method consisting of pyrolysis, precipitation, and calcination, and the calcination temperature was changed (200-600 degrees C). The samples were characterized by field-emission scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, the Brunauer-Emmett-Teller single-point method, and diffuse reflectance spectroscopy. In addition, to evaluate the photocatalytic activities of the samples, the mineralization of acetic acid to carbon dioxide (CO2) was measured by loading Pt particles onto the surface of the samples by photodeposition and irradiating them in an aqueous suspension with a blue light-emitting diode. Increasing the calcination temperature was associated with several changes: the crystallites grew larger, increasing the crystallinity; the specific surface area decreased, decreasing the adsorption capacity; and the rate of the photocatalytic CO2 evolution reaction increased. Pt-loaded (0.1 wt%) D-WO3 calcined at 600 degrees C showed the highest activity with a CO2 evolution rate of 5.9 mu mol h(-1). These results indicated that improving the crystallinity of the D-WO3 samples was effective in increasing their photocatalytic activities. - Makoto Fukui; Atsuhiro Tanaka; Hiroshi KominamiIndustrial & Engineering Chemistry Research 59 25 11412 - 11418 2020年06月 [査読有り]
- Makoto Fukui; Atsuhiro Tanaka; Hiroshi KominamiChemCatChem 12 12 3298 - 3305 2020年06月 [査読有り]
- Xing Zhu; Akira Yamamoto; Shota Imai; Atsuhiro Tanaka; Hiroshi Kominami; Hisao YoshidaCHEMICAL COMMUNICATIONS 56 16 2514 - 2514 2020年02月Correction for 'A silver-manganese dual co-catalyst for selective reduction of carbon dioxide into carbon monoxide over a potassium hexatitanate photocatalyst with water' by Xing Zhu et al., Chem. Commun., 2019, 55, 13514-13517.
- Makoto Fukui; Atsuhiro Tanaka; Hiroshi KominamiApplied Catalysis A: General 591 117412 - 117412 2020年02月 [査読有り]
- Imai, Shota; Nakanishi, Kousuke; Tanaka, Atsuhiro; Kominami, HiroshiCHEMCATCHEM 2020年02月 [査読有り]
Selective hydrogenation of alkynes to alkenes (semihydrogenation) without the use of a poison and H-2 is challenging because alkenes are easily hydrogenated to alkanes. In this study, a titanium (IV) oxide photocatalyst having Pd core-Cu shell nanoparticles (Pd@Cu/TiO2) was prepared by using the two-step photodeposition method, and Pd@Cu/TiO2 samples having various Cu contents were characterized by electron transmission microscopy, X-ray photoelectron spectroscopy and UV-vis spectroscopy. Thus-prepared Pd@Cu/TiO2 samples were used for photocatalytic hydrogenation of 4-octyne in alcohol and the catalytic properties were compared with those of Pd/TiO2 and Cu/TiO2. 4-Octyne was fully hydrogenated to octane over Pd/TiO2 at a high rate and 4-octyne was semihydrogenated to cis-4-octene over Cu/TiO2 at a low rate. Rapid semihydrogenation of 4-octyne was achieved over Pd(0.2 mol%)@Cu(1.0 mol%)/TiO2, indicating that the Pd core greatly activated the Cu shell that acted as reaction sites. A slight increase in the reaction temperature greatly increased the rate with a suppressed rate of H-2 evolution as the side reaction. Changes in the reaction rates of the main and side reactions are discussed on the basis of results of kinetic studies. Reusability and expandability of Pd@Cu/TiO2 in semihydrogenation are also discussed. - Makoto Fukui; Wakiko Koshida; Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi KominamiApplied Catalysis B: Environmental 268 118446 - 118446 2019年12月 [査読有り]
Since reduction and oxidation reactions simultaneously occur over a photocatalyst, a hole scavenger (a hydrogen source in the field of organic chemistry) is required to obtain a reduced product. The use of organic waste as the hole scavenger is environmentally favorable because the organic waste is degraded during the photocatalytic reduction. In this study, methylamine was used as the hole scavenger for photocatalytic reduction (hydrogenation) of nitrobenzenes over a titanium(IV) oxide photocatalyst. Corresponding anilines were obtained almost quantitatively at room temperature and under atmospheric pressure without the use of a precious metal and hydrogen gas. Nitrobenzenes having reducible functional groups such as chloro and acetyl groups were chemoselectively hydrogenated to corresponding anilines with the groups being preserved. Various parameters affecting the efficiency and the rate of the photocatalytic reaction are discussed on the basis of results of the physicochemical analyses. - Xing Zhu; Akira Yamamoto; Shota Imai; Atsuhiro Tanaka; Hiroshi Kominami; Hisao YoshidaCHEMICAL COMMUNICATIONS 55 90 13514 - 13517 2019年11月 [査読有り]
A Ag-Mn dual co-catalyst deposited on a K2Ti6O13 photocatalyst significantly enhances the photocatalytic CO2 reduction into CO with an extremely high selectivity of 98% by using H2O as an electron donor, owing to the properties of Ag and MnOx species for promoting CO and O-2 formation, respectively. - Fudo, Eri; Tanaka, Atsuhiro; Kominami, HiroshiCHEMISTRY LETTERS 48 8 939 - 942 2019年08月 [査読有り]
Gold (Au)-modified tantalum(V) oxide (Ta2O5) prepared by using a colloid photodeposition method produced H-2 without the aid of a cocatalyst under visible light irradiation due to the sufficiently negative potential of electrons injected from Au nanoparticles into the conduction band of Ta2O5 (-0.47 V). - Kinoshita, Atsufumi; Nakanishi, Kousuke; Tanaka, Atsuhiro; Hashimoto, Keiji; Kominami, HiroshiCHEMPHOTOCHEM 3 7 559 - 567 2019年07月 [査読有り]
Photocatalytic ring hydrogenation of phenol proceeded in an aqueous suspension of palladium-loaded TiO2 at room temperature in the presence of oxalic acid as a hole scavenger, and cyclohexanone was produced in a high yield (90 %) without the use of hydrogen gas. Cyclohexanone was formed via keto-enol tautomerism of cyclohexenol. The effects of hole scavengers and solvents on the hydrogenation of phenol can be explained by the adsorption behaviour of phenol and hole scavengers in the solvents. Over a Pd-TiO2 photocatalyst, the apparent activation energy (Ea) in the ring hydrogenation of phenol and the Ea value in the hydrogenation of cyclohexanone were estimated to be 25 kJ mol(-1) and 36 kJ mol(-1), respectively, as calculated by using the Arrhenius equation. We concluded that the difference in the Ea values is attributable to the selective production of cyclohexanone and the decreased production of cyclohexanol in the ring hydrogenation of phenol over a Pd-TiO2 photocatalyst. - Fudo, Eri; Tanaka, Atsuhiro; Kominami, HiroshiCATALYSIS SCIENCE & TECHNOLOGY 9 12 3047 - 3054 2019年06月 [査読有り]
There is little information on the effect of the conduction band (CB) position on plasmonic hydrogen (H-2) formation under visible light irradiation over gold (Au) nanoparticles supported on semiconductors because there were no appropriate materials for which the CB position gradually changes. In this study, we analyzed the flatband potential of strontium ion (Sr2+)-doped cerium.IV) oxide (CeO2:Sr) and found that the CB position gradually shifted negatively from +0.031 V to -1.49 V vs. NHE with an increase in the Sr2+ mole fraction. Plasmonic photocatalysts consisting of Au nanoparticles, CeO2:Sr and a platinum (Pt) cocatalyst were prepared and characterized by using X-ray diffraction, UV-vis spectroscopy, and transmission electron spectroscopy. Photocatalytic reaction under visible light irradiation revealed that H-2 was produced over Au nanoparticles supported on CeO2:Sr having the CB potential of -0.61 V vs. NHE and that the negative limit of the CB position for electron injection from Au nanoparticles existed between -0.61 V and -1.49 V vs. NHE. We found that Au/CeO2:Sr plasmonic photocatalysts also produced H-2 without the aid of a Pt cocatalyst due to the sufficiently negative potential of electrons injected into the CB of CeO2:Sr. - Fukui, Makoto; Omori, Yuya; Kitagawa, Shin-ya; Tanaka, Atsuhiro; Hashimoto, Keiji; Kominami, HiroshiJOURNAL OF CATALYSIS 374 36 - 42 2019年06月 [査読有り]
Hydrogen (H-2)-free and poison (lead and quinoline)-free semihydrogenation of alkynes to cis-alkenes under gentle conditions is one of the challenges to be solved. In this study, a titanium(IV) oxide photocatalyst having two functions (visible light responsiveness and semihydrogenation activity) was prepared by modification with 2,3-dihydroxynaphthalene (DHN) and a copper (Cu) co-catalyst, respectively. The photocatalyst (DHN/TiO2-Cu) showed high performance for diastereoselective semihydrogenation of alkynes to cis-alkenes in water-acetonitrile solution under visible light irradiation without the use of H-2 and poisons. Alkynes having reducible functional groups were converted to the corresponding alkenes with the functional groups being preserved. The addition of water to acetonitrile changed the amount of alkynes adsorbed on the photocatalyst, which was a decisive factor determining the rate of hydrogenation. A relatively large apparent activation energy, 27 kJ mol(-1), was obtained by a kinetic study, indicating that the rate-determining step of this reaction was not an electron production process but a thermal catalytic semihydrogenation process over the Cu co-catalyst. Semihydrogenation and hydrogen evolution occurred competitively on Cu metals and the former became predominant at slightly elevated temperatures, which is discussed on the basis of the kinetic parameters of two reactions. (C) 2019 Elsevier Inc. All rights reserved. - Kinoshita, Atsufumi; Nakanishi, Kousuke; Yagi, Ryosuke; Tanaka, Atsuhiro; Hashimoto, Keiji; Kominami, HiroshiAPPLIED CATALYSIS A-GENERAL 578 83 - 88 2019年05月 [査読有り]
Since photocatalytic reactions are almost consistent with the concept of green chemistry, substance conversion using photocatalysts has recently attracted the attention of researchers in the fields of organic chemistry, physical chemistry and material chemistry. We investigated photoinduced ring hydrogenation of phenol over a metal-loaded titanium(IV) oxide (TiO2) photocatalyst without the use of H-2 gas and we report here the effects of various parameters, including the type and amount of metal co-catalyst loaded on TiO2 and the kinds of solvents and hole scavengers, on the ring hydrogenation. We found that the combination of an Rh co-catalyst, water and oxalic acid resulted in the highest yield of cyclohexanol. Detailed analyses revealed that phenol was first hydrogenated to cyclohexanone via keto-enol tautomerism of cyclohexenol followed by hydrogenation of cyclohexanone to cyclohexanol and that adsorption of phenol onto Rh-TiO2 is a factor of great importance for the ring hydrogenation. - Yuhei Yamamoto; Makoto Fukui; Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi KominamiCATALYSIS SCIENCE & TECHNOLOGY 9 4 966 - 973 2019年02月 [査読有り]
A titanium.IV) oxide photocatalyst modified with 2,3-dihydroxynaphthalene (DHN/TiO2) responds to visible light, and electrons are photogenerated to the conduction band of TiO2 under light irradiation in the presence of a suitable hole scavenger. The reducing potential of DHN/TiO2 was applied for photocatalytic conversion of a nitro group to an amino group of aromatics having other reducible groups under hydrogenfree and noble metal-free conditions at room temperature. Various nitro aromatics having vinyl, chloro, bromo, and acetyl groups were converted to amino aromatics with high yields with the reducible groups being preserved. Some parameters affecting the catalytic performance were investigated, and the reaction rate was almost determined by the amount of the substrate adsorbed on DHN/TiO2. - Kojima, Yasumi; Fukui, Makoto; Tanaka, Atsuhiro; Hashimoto, Keiji; Kominami, HiroshiCHEMCATCHEM 10 16 3605 - 3611 2018年08月 [査読有り]
Lindlar's catalyst, i.e., calcium carbonate-supported palladium (Pd) modified with lead, has been used for semihydrogenation of an alkynyl group in the presence of hydrogen gas (H-2). We examined hydrogenation of an alkynyl group in organosilane and hydrocarbon in methanolic suspensions of a Pd-loaded titanium(IV) oxide (Pd-TiO2) photocatalyst without the use of additives and H-2. In the photocatalytic reaction, Pd particles worked as co-catalysts for hydrogenation and alkyne hydrogenation had priority to alkene hydrogenation. Since the Pd co-catalyst was temporarily deactivated during the reaction owing to accumulation of the oxidized product(s) of methanol, the capacity of hydrogenation of the unsaturated C-C bond was limited. By optimizing the capacity and amount of alkynes, almost complete semihydrogenation of alkynes was achieved under a poison-free condition. Pd-TiO2 can be regenerated by very simple treatments, i.e., washing and drying at room temperature. - Kominami, Hiroshi; Shiba, Misaki; Hashimoto, Akimi; Imai, Shota; Nakanishi, Kousuke; Tanaka, Atsuhiro; Hashimoto, Keiji; Imamura, KazuyaPHYSICAL CHEMISTRY CHEMICAL PHYSICS 20 29 19321 - 19325 2018年08月 [査読有り]
A copper-loaded titanium(IV) oxide photocatalyst exhibited perfect selectivity in hydrogenation of alkynes to alkenes in an alcohol solution at 298 K under hydrogen-free and poison-free conditions. A slight elevation in the reaction temperature to 323 K greatly increased the reaction rate with the selectivity being preserved and the formation of an H-2 by-product being suppressed. The apparent activation energy of 4-octyne semihydrogenation was determined to be 54 kJ mol(-1), indicating that the rate determining step of this photocatalytic reaction was not an electron production process but a thermocatalytic hydrogenation process under light irradiation. - Imamura, Kazuya; Kato, Hiroko; Wada, Yuichiro; Makabe, Kazuhiro; Onda, Ayumu; Tanaka, Atsuhiro; Kominami, Hiroshi; Sato, Katsutoshi; Nagaoka, KatsutoshiCHEMICAL COMMUNICATIONS 54 53 7298 - 7301 2018年07月 [査読有り]
In the presence of a palladium-loaded TiO2 photocatalyst, the cleavage of benzyl phenyl ether in low-molecular-weight alcohol solvents under de-aerated conditions afforded toluene and phenol simultaneously in a 1:1 molar ratio. - Kaneyama, Yuka; Tanaka, Atsuhiro; Sanada, Tomoe; Kominami, Hiroshi; Kojima, KazuoMATERIALS RESEARCH BULLETIN 102 56 - 61 2018年06月 [査読有り]
We synthesized various cuboid-type tungsten trioxide (WO3) particles using a hydrothermal method followed by calcination at various temperatures between 200 and 500 degrees C. Visible-light photocatalysis of these particles was investigated for oxygen (O-2) evolution from water in the presence of sacrificial silver(I) sulfate. The calculated crystallite diameters increased with increasing calcination temperature, suggesting that the level of crystallinity increased with calcination temperature. The average specific surface area of the particles was almost the same for all calcination temperatures in the range 200-400 degrees C, but was decreased at 500 degrees C. The photocatalytic reaction rate of O-2 formation increased with increasing calcination temperature up to 400 degrees C, and then decreased as calcination temperature was further increased to 500 degrees C. We therefore concluded that the rate increased with calcination temperature up to 400 degrees C due to the increasing crystallinity, but then decreased due to the decreased specific surface area. - Nakanishi, Kousuke; Yagi, Ryosuke; Imamura, Kazuya; Tanaka, Atsuhiro; Hashimoto, Keiji; Kominami, HiroshiCATALYSIS SCIENCE & TECHNOLOGY 8 1 139 - 146 2018年01月 [査読有り]
There are various possibilities of co-catalyst-assisted photocatalytic reduction (CPR) over a titanium(IV) oxide (TiO2) photocatalyst, especially H-2-free and chemoselective CPR. We examined the photoinduced ring hydrogenation of aromatics having a carboxyl group over metal-loaded TiO2 under H-2-free conditions and found that the aromatics were almost quantitatively hydrogenated to the corresponding cyclohexanes having a carboxyl group when rhodium, water and oxalic acid were used as a metal co-catalyst, solvent and hole scavenger, respectively. The effects of different metal co-catalysts, solvents and hole scavengers on the ring hydrogenation were also examined. Based on the results obtained under various conditions, the light dependency and adsorption behavior of the aromatics and hole scavengers, the functions of TiO2 and the co-catalyst, and the reaction process are discussed. - Nakanishi, Kousuke; Tanaka, Atsuhiro; Hashimoto, Keiji; Kominami, HiroshiCHEMISTRY LETTERS 47 2 254 - 256 2018年 [査読有り]
Photocatalytic hydrogenation of furfural (FAL) was examined in 2-pentanol suspensions of TiO2 under metal-free and hydrogen-free conditions. High chemoselectivity was observed, i.e., only the carbonyl group of FAL was reduced to a hydroxymethyl group, resulting in almost quantitative conversion to furfuryl alcohol (FOL) with an apparent quantum efficiency of 17%. 2-Pentanol was simultaneously converted to 2-pentanone satisfying a high stoichiometry with FAL to FOL, indicating that double up-grading of FAL and alcohol was possible via a photocatalytic process. - Kousuke Nakanishi; Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi KominamiPHYSICAL CHEMISTRY CHEMICAL PHYSICS 19 30 20206 - 20212 2017年08月 [査読有り]
The use of metal co-catalysts broadens the application of photocatalytic reduction without the use of dihydrogen (H-2) gas. We examined photocatalytic hydrogenation of furan, a representative heterocyclic compound and a compound derived from biomass, in alcoholic suspensions of metal-loaded titanium(IV) oxide (TiO2) under a H-2-free condition and we found that furan was almost quantitatively hydrogenated to tetrahydrofuran with a high apparent quantum efficiency of 37% at 360 nm when palladium was used as a co-catalyst. Effects of different metal co-catalysts, different amounts of the co-catalyst, the type of TiO2, the type of alcohol, light wavelength and reusability for furan hydrogenation were investigated. Based on the results, the functions of TiO2 and the co-catalyst and the reaction process are discussed. - Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi KominamiCHEMICAL COMMUNICATIONS 53 35 4759 - 4762 2017年05月 [査読有り]
By using a facile calcination method, we succeeded in the preparation of partially spherical gold particles supported on TiO2 exhibiting photoabsorption due to surface plasmon resonance at around 620 nm. Surprisingly, the selective oxidation of benzyl alcohol to benzaldehyde occurred in an aqueous suspension of thus-prepared Au/TiO2 under irradiation of light from a Xe lamp with an R60 cut-off filter (lambda > 600 nm), and the apparent quantum efficiency reached 7.2% at 625 nm and 4.2% even at 700 nm. - Sho Kitano; Masaaki Sadakiyo; Kenichi Kato; Miho Yamauchi; Hiroyuki Asakura; Tsunehiro Tanaka; Keiji Hashimoto; Hiroshi KominamiAPPLIED CATALYSIS B-ENVIRONMENTAL 205 340 - 346 2017年05月 [査読有り]
For a rhodium ion-modified TiO2 (Rh3+/TiO2) photocatalyst responding to visible light, control of the structure of the Rh3+ modifier and effects of the structures of the Rh3+ modifier on photocatalytic activities were examined. A TiO2 support was pre-calcined to maintain crystallinity and specific surface area during post-calcination, and the structure of the Rh3+ modifier for Rh3+/TiO2 was changed by post-calcination without causing changes in the crystallinity and specific surface area of the TiO2 support. In mineralization of acetone under irradiation of visible light, the photocatalytic activities of the post-calcined Rh3+/TiO2 showed a volcano-like tendency as a function of post-calcination temperature. The results of this study showed that an atomically isolated structure of the Rh3+ modifier was preferable for high activities and that aggregation of the Rh species led to a decrease in the activities. (C) 2016 Elsevier B.V. All rights reserved. - Makoto Fukui; Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi KominamiCHEMICAL COMMUNICATIONS 53 30 4215 - 4218 2017年04月 [査読有り]
An organically modified titanium dioxide photocatalyst prepared by a simple impregnation method chemoselectively and almost quantitatively converted benzaldehydes having other reducible functional groups to the corresponding benzyl alcohols under visible light irradiation. - A. Tanaka; K. Teramura; S. Hosokawa; H. Kominami; T. TanakaCHEMICAL SCIENCE 8 4 2574 - 2580 2017年04月 [査読有り]
We found that plasmonic Au particles on titanium(IV) oxide (TiO2) act as a visible-light-driven photocatalyst for overall water splitting free from any additives. This is the first report showing that surface plasmon resonance (SPR) in a suspension system effectively induces overall water splitting. Modification with various types of metal nanoparticles as co-catalysts enhanced the evolution of H-2 and O-2. Among these, Ni-modified Au/TiO2 exhibited 5-times higher rates of H-2 and O-2 evolution than those of Ni-free Au/TiO2. We succeeded in designing a novel solar energy conversion system including three elemental technologies, charge separation with light harvest and an active site for O-2 evolution (plasmonic Au particles), charge transfer from Au to the active site for H-2 production (TiO2), and an active site for H-2 production (Ni cocatalyst), by taking advantage of a technique for fabricating size-controlled Au and Ni nanoparticles. Water splitting occurred in aqueous suspensions of Ni-modified Au/TiO2 even under irradiation of light through an R-62 filter. - Makoto Fukui; Hideki Kouda; Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi KominamiCHEMISTRYSELECT 2 7 2293 - 2299 2017年03月 [査読有り]
Chemoselective reduction of benzaldehydes having other reducible functional groups without the use of a reducing agent such as metal hydrides is important because metal hydrides simultaneously produce a large amount of undesirable waste containing metal compounds. Here we report that a titanium(IV) oxide (TiO2) photocatalyst is effective for heterogeneous Meerwein-Ponndorf-Verley (MPV)-type reduction of various benzaldehydes having reducible functional groups to corresponding benzyl alcohols at room temperature under a metal-free condition. We also investigated the effects of physical properties of TiO2 samples on chemoselective reduction of p-chlorobenzaldehyde (CBAD) to p-chlorobenzyl alcohol (CBAO) and we observed a linear correlation between the amount of CBAD adsorbed and the rate of CBAO formation, suggesting that ability of TiO2 for CBAD adsorption is one of the key factors for effective MPV-type reduction of CBAD to CBAO. - Makoto Fukui; Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi KominamiCHEMISTRY LETTERS 45 8 985 - 987 2016年08月 [査読有り]
p-Chlorobenzaldehyde was almost quantitatively and chemoselectively reduced to p-chlorobenzyl alcohol in alcoholic suspensions of a metal-free titanium(IV) oxide photocatalyst under hydrogen-free conditions. Since alcohols act as electron donors and hydrogen sources, this reaction can be regarded as a heterogeneous Meerwein-Ponndorf-Verley-type reduction over a photocatalyst. Excellent chemoselectivity was also observed in the intermolecular competitive reduction of benzaldehyde (BA) and chlorobenzene (CB), i.e., only BA was reduced to benzyl alcohol, with CB not being reduced. - Sho Kitano; Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi KominamiAPPLIED CATALYSIS A-GENERAL 521 202 - 207 2016年07月 [査読有り]
Metal ion-modified TiO2 photocatalysts designated by combinations of various metal ions and TiO2 powders that respond to visible light and exhibit controllable photocatalytic oxidative performances were examined. The photocatalytic oxidative performances were evaluated by selective oxidation of benzyl alcohol in water in the presence of O-2 under irradiation of visible light. The TiO2 samples modified with Ru3+, Pd2+ and Rh3+ (Ru3+/TiO2, Pd2+/TiO2 and Rh3+/TiO2) exhibited high levels of photocatalytic activity. The effects of metal ions and the kind of TiO2 on photocatalytic performances of Rh3+/TiO2 and Ru3+/TiO2 were investigated in detail. (C) 2015 Elsevier B.V. All rights reserved. - Hiroshi Kominami; Megumi Higa; Taketo Nojima; Tomohiko Ito; Kousuke Nakanishi; Keiji Hashimoto; Kazuya ImamuraCHEMCATCHEM 8 12 2019 - 2022 2016年06月 [査読有り]
Internal alkynes were chemoselectively and diastereoselectively hydrogenated to the corresponding cis-alkenes in alcoholic suspensions of a copper-loaded titanium(IV) oxide photocatalyst without the use of additives and a reducing gas, and alkynes having functional groups such as a nitrile group were doubly chemoselectively converted into the corresponding alkenes. - Hiroshi Kominami; Shin-ya Kitagawa; Yuki Okubo; Makoto Fukui; Keiji Hashimoto; Kazuya ImamuraPHYSICAL CHEMISTRY CHEMICAL PHYSICS 18 24 16076 - 16079 2016年06月 [査読有り]
Organically modified titania having a metal catalyst (OMTC), 2,3-dihydroxynaphthalene-modified titania having palladium metal, successfully worked as a hydrogen-transfer (C=C hydrogenation) photocatalyst in the presence of triethanolamine as the hydrogen source under visible light irradiation and hydrogen-free conditions. - Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi KominamiCHEMISTRY-A EUROPEAN JOURNAL 22 13 4592 - 4599 2016年03月 [査読有り]
Gold particles supported on tin(IV) oxide (0.2wt% Au/SnO2) were modified with copper and silver by the multistep photodeposition method. Absorption around =550nm, attributed to surface plasmon resonance (SPR) of Au, gradually shifted to longer wavelengths on modification with Cu and finally reached =620nm at 0.8wt% Cu. On the other hand, the absorption shifted to shorter wavelength with increasing amount of Ag and reached =450nm at 0.8wt% Ag. These Cu- and Ag-modified 0.2wt% Au/SnO2 materials (Cu-Au/SnO2 and Ag-Au/SnO2) and 1.0wt% Au/SnO2 were used for mineralization of formic acid to carbon dioxide in aqueous suspension under irradiation with visible light from a xenon lamp and three kinds of light-emitting diodes with different wavelengths. The reaction rates for the mineralization of formic acid over these materials depend on the wavelength of light. Apparent quantum efficiencies of Cu-Au/SnO2, Au/SnO2, and Ag-Au/SnO2 reached 5.5% at 625nm, 5.8% at 525nm, and 5.1% at 450nm, respectively. These photocatalysts can also be used for selective oxidation of alcohols to corresponding carbonyl compounds in aqueous solution under visible-light irradiation. Broad responses to visible light in formic acid mineralization and selective alcohol oxidation were achieved when the three materials were used simultaneously. - Yuri Nishino; Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi KominamiCHEMISTRY LETTERS 44 4 518 - 520 2015年04月 [査読有り]
Two kinds of photoabsorption of Ag-deposited silver iodide (AgI) due to band-gap excitation of AgI and surface plasmon resonance of Ag particles each contributed to photocatalytic partial oxidation of alcohol, and a synergy effect on the reaction rate was observed when two kinds of light were simultaneously irradiated on Ag-AgI. - Kazuya Imamura; Kousuke Nakanishi; Keiji Hashimoto; Hiroshi KominamiTETRAHEDRON 70 36 6134 - 6139 2014年09月 [査読有り]
m-Nitrostyrene was chemoselectively reduced to m-aminostyrene in an acetonitrile suspension containing a titanium(IV) oxide (TiO2) photocatalyst and a suitable hole scavenger at room temperature under atmospheric pressure without the use of a precious metal or reducing gas. Addition of a small amount of water to acetonitrile increased the reaction rate, and the highest rate was obtained. Moreover, applicability of the photocatalytic system was investigated using various nitro compounds having other reducible groups (chloro, bromo, carboxyl, and acetyl groups), and only the nitro group of these compounds was chemoselectively reduced, resulting in the formation of corresponding amino compounds with high yields. (C) 2014 Elsevier Ltd. All rights reserved. - Hiroshi Kominami; Kousuke Nakanishi; Satoshi Yamamoto; Kazuya Imamura; Keiji HashimotoCATALYSIS COMMUNICATIONS 54 100 - 103 2014年09月 [査読有り]
Deoxygenation of sulfoxides was examined in acetonitrile suspensions of metal-free titanium(IV) oxide (TiO2) under irradiation of UV light at room temperature. Experimental results indicate that deoxygenation was induced by the TiO2 photocatalyst and that organic acids such as formic add and oxalic add are appropriate as hole scavengers in the photocatalytic reaction. Diphenyl sulfoxide was successfully deoxygenated to diphenyl sulfide with high yields, and the TiO2 photocatalyst could be repeatedly used for deoxygenation without loss of activity. The present photocatalytic method could be applied for deoxygenation of various sulfoxides to corresponding sulfides, and phenyl vinyl sulfoxide was chemoselectively reduced to phenyl vinyl sulfide without hydrogenation of a C=C double bond. (C) 2014 Elsevier B.V. All rights reserved. - Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi KominamiJOURNAL OF THE AMERICAN CHEMICAL SOCIETY 136 2 586 - 589 2014年01月 [査読有り]
Photocatalytic H-2 and O-2 formations under visible light irradiation (lambda > 400 nm) are demonstrated using Pt-Au nanopaticles for the reduction site and WO3 for the oxidation site in solid-state Pt/Au/WO3. - Atsuhiro Tanaka; Satoshi Sakaguchi; Keiji Hashimoto; Hiroshi KominamiCATALYSIS SCIENCE & TECHNOLOGY 4 7 1931 - 1938 2014年 [査読有り]
Titanium(IV) oxide (TiO2) having both smaller and larger gold (Au) particles was successfully prepared by a multi-step (MS) photodeposition method. When 0.25 wt% Au loading per photodeposition was repeated four times, smaller and larger Au particles having average diameters of 1.4 and 13 nm, respectively, were fixed on TiO2, and the Au/TiO2 sample exhibited strong photoabsorption around 550 nm due to surface plasmon resonance (SPR) of the larger Au particles. Various Au/TiO2 samples were prepared by changing the Au loading per photodeposition and the number of photodepositions. Effects of the conditions in MS photodeposition and sample calcination on Au particle distribution and photoabsorption properties were investigated. These samples were used for hydrogen (H-2) formation from 2-propanol and mineralization of acetic acid in aqueous suspensions under irradiation of visible light. In the case of H-2 formation under deaerated conditions, the reaction rate of Au/TiO2 having both larger and smaller particles was 4 times higher than that of the Au/TiO2 sample without smaller Au particles, indicating that smaller Au particles acted effectively as a co-catalyst, that is, as reduction sites for H-2 evolution. On the other hand, in the case of mineralization of acetic acid under aerated conditions, carbon dioxide formation rates were independent of the presence of smaller Au particles, indicating that the smaller Au particles had little effect on the mineralization of acetic acid. To extend the possibility of Au/TiO2 for H-2 formation under irradiation of visible light, H-2 formation from ammonia (NH3) as biomass waste was examined under deaerated conditions; NH3 was decomposed to H-2 and nitrogen with a stoichiometric ratio of 3 : 1. - Hiroshi Kominami; Satoshi Yamamoto; Kazuya Imamura; Atsuhiro Tanaka; Keiji HashimotoCHEMICAL COMMUNICATIONS 50 35 4558 - 4560 2014年 [査読有り]
(2,3-Epoxypropyl) benzene was chemoselectively reduced to allylbenzene along with formation of ketones in alcoholic suspensions of a silver-loaded titanium(IV) oxide photocatalyst at room temperature under atmospheric pressure without the use of reducing gases, and various epoxides were also reduced to the corresponding alkenes. - Kazuya Imamura; Yuki Okubo; Tomohiko Ito; Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi KominamiRSC ADVANCES 4 38 19883 - 19886 2014年 [査読有り]
- Sho Kitano; Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi KominamiPHYSICAL CHEMISTRY CHEMICAL PHYSICS 16 24 12554 - 12559 2014年 [査読有り]
Photocatalytic oxidation of benzyl alcohols in aqueous suspensions of rhodium ion-modified titanium(IV) oxide (Rh3+/TiO2) in the presence of O-2 under irradiation of visible light was examined. In the photocatalytic oxidation of benzyl alcohol, benzaldehyde was obtained in a high yield (97%) with >99% conversion of benzyl alcohol. Rh3+/TiO2 photocatalysts having various physical properties were prepared using commercially available TiO2 powders as supporting materials for Rh3+ to investigate the effect(s) of physical properties of TiO2 on photocatalytic activities of Rh3+/TiO2 for selective oxidation. Adsorption properties of benzyl alcohol, benzaldehyde and benzoic acid on TiO2 were also investigated to understand the high benzaldehyde selectivity over the Rh3+/ TiO2 photocatalyst. The reaction mechanism was discussed on the basis of the results of photocatalytic oxidation of various p-substituted benzyl alcohol derivatives. - Hiroshi Kominami; Ken Kitsui; Yuki Ishiyamaa; Keiji HashimotoaRSC ADVANCES 4 93 51576 - 51579 2014年 [査読有り]
Photocatalytic reduction of nitrite (NO2-) in an aqueous suspension of metal-free titanium(IV) oxide in the presence of ammonia (NH3) as a hole scavenger gave dinitrogen (N-2), indicating that NO2- and NH3 are simultaneously removed from water as N-2 at room temperature without the use of an extra reagent. - Kazuya Imamura; Takayuki Yoshikawa; Kousuke Nakanishi; Keiji Hashimoto; Hiroshi KominamiChemical Communications 49 93 10911 - 10913 2013年10月 [査読有り]
Benzonitrile (PhCN) was successfully reduced to benzyl amine in acidic aqueous suspensions of a palladium (Pd)-loaded titanium(iv) oxide (TiO2) photocatalyst in the presence of oxalic acid as a hole scavenger, although the reduction potential of PhCN is believed to be much higher than the potential of the conduction band (CB) of TiO2, indicating that a Pd co-catalyst strongly contributes to PhCN reduction and that the applicability of photocatalytic reduction is not limited by the CB position of semiconductor photocatalysts. © 2013 The Royal Society of Chemistry. - Tanaka, Atsuhiro; Nakanishi, Kousuke; Hamada, Ryosuke; Hashimoto, Keiji; Kominami, HiroshiACS CATALYSIS 3 8 1886 - 1891 2013年08月 [査読有り]
Titanium(IV) oxide (TiO2) having both small platinum (Pt) nanoparticles and large gold (Au) particles without alloying and nanoparticle coagulation was successfully prepared by the combination of traditional photodeposition of Pt and subsequent Au colloid photodeposition onto TiO2-Pt. The Au/TiO2 and Au/TiO2-Pt samples exhibiting strong photoabsorption due to surface plasmon resonance (SPR) of supported Au particles were used for the reduction of hexavalent chromium (Cr6+ in Cr2O72-) in aqueous suspensions under irradiation of visible light from a green light emitting diode (LED). These SPR-type photocatalysts reduced Cr6+ and evolved dioxygen (O-2) with O-2-reduced Cr6+ ratio of 3:4 until consumption of Cr6+, indicating that these SPR-type photocatalysts had the ability to oxidize water (H2O) utilizing visible light (lambda = 540 nm) and that a photocatalytic reaction (2Cr(2)O(7)(2-) + 16H(+) -> 4Cr(3+) + 3O(2) + 8H(2)O) occurred. The Au/TiO2 Pt sample exhibited a reaction rate about twice larger than that of Pt-free Au/TiO2, and the apparent quantum yield reached 1.0% at 550 nm and 0.47% even at 700 nm, indicating that functionalization of Au/TiO2 was successfully achieved by introduction of a Pt cocatalyst. This reaction can be used as a test reaction for evaluation of O-2 evolution ability of photocatalysts because this reaction does not induce irreversible changes in photocatalysts. - Atsuhiro Tanaka; Kojirou Fuku; Takuya Nishi; Keiji Hashimoto; Hiroshi KominamiJOURNAL OF PHYSICAL CHEMISTRY C 117 33 16983 - 16989 2013年08月 [査読有り]
Gold (Au) nanoparticles supported on titania (TiO2) and ceria have been applied to a visible-light-responding plasmonic photocatalyst and functionalization of Au/TiO2 photocatalysts with cocatalysts were achieved by separate loading of Au nanoparticles and cocatalyst nanoparticles without alloying and nanoparticle coagulation. Here we report effectiveness of another functionalization by formation of a core-shell structure in photocatalytic reaction induced by SPR of Au/TiO2. Newly functionalized core-shell gold-palladium particles supported on TiO2 (Au@Pd/TiO2) were successfully prepared by using a two-step photodeposition method, and Au@Pd/TiO2 with a shell thickness of 1.0 nm quantitatively converted chlorobenzene and 2-propanol to benzene and acetone under irradiation of visible light. Thickness control of the Pd shell was very important for both a satisfactory cocatalyst effect and absorption due to SPR of Au nanoparticles. The results of this study provide useful information for design of functionalization of plasmonic photocatalysts by formation of a core-shell structure. - Sho Kitano; Naoya Murakami; Teruhisa Ohno; Yasufumi Mitani; Yoshio Nosaka; Hiroyuki Asakura; Kentaro Teramura; Tsunehiro Tanaka; Hiroaki Tada; Keiji Hashimoto; Hiroshi KominamiJournal of Physical Chemistry C 117 21 11008 - 11016 2013年05月 [査読有り]
A rhodium(III) ion (Rh3+)-modified TiO2 (Rh 3+/TiO2) photocatalyst, prepared by a simple adsorption method and exhibiting high levels of photocatalytic activity in degradation of organic compounds, was investigated by using X-ray absorption fine structure (XAFS) measurements, (photo)electrochemical measurements, double-beam photoacoustic (DB-PA) spectroscopic measurements, and photoluminescence measurements. Based on the results, the features of the Rh3+ modifier and the working mechanism of the Rh3+/TiO2 photocatalyst are discussed. XAFS measurements revealed that the Rh3+ species were highly dispersed and almost atomically isolated on TiO2. The (photo)electrochemical measurements, DB-PA spectroscopic measurements, and photoluminescence showed a unique bifunction of the Rh3+ modifier as a promoter for O2 reductions and an electron injector to the conduction band of TiO2 for response to visible light. The reasons for the Rh3+/TiO2 photocatalyst exhibiting higher levels of photocatalytic activity than those of TiO2 photocatalysts modified with other metal ions are also discussed on the basis of obtained results. © 2013 American Chemical Society. - Kazuya Imamura; Takayuki Yoshikawa; Keiji Hashimoto; Hiroshi KominamiAPPLIED CATALYSIS B-ENVIRONMENTAL 134 193 - 197 2013年05月 [査読有り]
Photocatalytic conversion of nitrobenzenes in 2-propanol suspensions of bare titanium(IV) oxide (TiO2) under various conditions was examined. Aniline and acetone were simultaneously produced almost stoichiometrically from a 2-propanol suspension of TiO2 containing nitrobenzene under deaerated conditions without the use of a precious metal. Nitrobenzenes having another reducible group such as vinyl, chloro and bromo were chemoselectively reduced to corresponding aminobenzenes in 2-propanol suspensions of a TiO2 photocatalyst with an almost stoichiometric amount of acetone. Photocatalytic reduction of nitrobenzene and oxidation of 2-propanol occurred even in the presence of oxygen, and no re-oxidation of anilines occurred. (C) 2013 Elsevier B.V. All rights reserved. - Yasutomo Sasaki; Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi KominamiCHEMISTRY LETTERS 42 4 419 - 421 2013年04月 [査読有り]
Copper(II) oxide (CuO)-modified indium oxide (In2O3) prepared by physical mixing efficiently mineralized acetone under irradiation of light from a blue LED. The reaction rate increased with additional irradiation of light from a red LED, though no reactions occurred over CuO and In2O3 under irradiation of the red light, indicating that band-gap excitation of CuO contributed to photocatalytic reaction over CuO-In2O3. The effect of CuO modification was also observed in action spectra with and without irradiation of the red light. - Kazuya Imamura; Hikaru Tsukahara; Kenta Hamamichi; Naoko Seto; Keiji Hashimoto; Hiroshi KominamiAPPLIED CATALYSIS A-GENERAL 450 28 - 33 2013年01月 [査読有り]
Photocatalytic conversion of aromatic alcohols in acetonitrile (CH3CN) suspensions of metal-loaded titanium(IV) oxide under various conditions was examined. Benzaldehyde (PhCHO) and hydrogen (H-2) were simultaneously produced with a molar ratio of 1:1 from benzyl alcohol (BnOH) in CH3CN suspensions of platinum-loaded titanium(IV) oxide (Pt-TiO2) under deaerated conditions and BnOH was converted quantitatively with high apparent quantum efficiency of 38% at 366 nm. The yield of PhCHO in dehydrogenation under deaerated conditions (>99%) was much higher than that (53%) obtained by dehydrogenation of BnOH in the presence of oxygen accompanying the formation of water instead of H-2. When a small amount of water was intentionally added to the CH3CN suspension of Pt-TiO2, reaction rates of hydrogenation drastically decreased. Control experiments carried out under air and in the presence of water indicated that an oxygen-free condition was important for quantitative conversion of BnOH to PhCHO in two points, i.e., the reaction under oxygen-free conditions yields no water and active oxygen, that caused drastic decrease in the reaction rate and undesired oxidation of BnOH and PhCHO, respectively. Photocatalytic dehydrogenation of BnOH to PhCHO occurred even in a solvent-free condition in which Pt-TiO2 particles were suspended in BnOH. Photocatalytic hydrogenation under deaerated conditions was applied for conversions of various aromatic alcohols to corresponding aldehydes. (C) 2012 Elsevier B.V. All rights reserved. - Atsuhiro Tanaka; Satoshi Sakaguchi; Keiji Hashimoto; Hiroshi KominamiACS CATALYSIS 3 1 79 - 85 2013年01月 [査読有り]
Titanium(IV) oxide (TiO2) having both small platinum (Pt) nanoparticles and large gold (Au) particles without alloying and nanoparticle coagulation was successfully prepared by the combination of traditional photodeposition of Pt in the presence of a hole scavenger (PH) and subsequent Au colloid photodeposition in the presence of a hole scavenger (CPH) onto TiO2-Pt. Au particles having an average diameter of 13 nm were fixed on both TiO2 and TiO2-Pt samples without change in the original size of Au particles, and the Au/TiO2 and Au/TiO2 Pt samples exhibited strong photoabsorption around 550 nm as a result of surface plasmon resonance (SPR) of Au to which the large size of Au particles was attributed. Bare TiO2, TiO2-Pt, Au/TiO2, and Au/TiO2-Pt samples were used for photoinduced hydrogen (H-2) formation from 2-propanol in aqueous solutions under irradiation of visible light. The first two samples yielded no H-2 because of no response to visible light, but the latter two formed H-2, indicating that SPR photoabsorption of supported Au particles contributed to the H-2 evolution under irradiation of visible light. The H-2 formation rate of the Au/TiO2-Pt sample was similar to 7-times larger than that of the Pt-free Au/TiO2 sample, indicating that Pt nanoparticles loaded on TiO2 acted effectively as a cocatalyst, that is, as reduction sites for H-2 evolution. The combination of the PH and CPH methods was effective for preparation of Au/TiO2 having other metal cocatalysts (M) including Au, that is, Au/TiO2 Au, and H-2 evolution rates decreased in the order of M; Pt > Pd > Ru > Rh > Au > Ag > Cu > Jr. An inverse correlation between the rate and the hydrogen overvoltage (HOV) of M, that is, it was observed that the higher the HOV, the more difficult it is to reduce protons by photogenerated electrons. Since the amounts of Au and M loaded on TiO2 were changed independently, the effects on photoabsorption and the rate of H-2 evolution were examined. A linear correlation was observed between rate and light absorption due to SPR, suggesting that SPR photoabsorption by Au particles was one of the important factors determining the rate of the H-2 evolution. - Tanaka, Atsuhiro; Nishino, Yuri; Sakaguchi, Satoshi; Yoshikawa, Takayuki; Imamura, Kazuya; Hashimoto, Keiji; Kominami, HiroshiCHEMICAL COMMUNICATIONS 49 25 2551 - 2553 2013年 [査読有り]
A functionalized plasmonic Au/TiO2 photocatalyst with an Ag co-catalyst was successfully prepared by the combination of two types of photodeposition methods, and it quantitatively converted nitrobenzene and 2-propanol to aniline and acetone under irradiation of visible light. - Hiroshi Kominami; Takuya Nishi; Kojirou Fuku; Keiji HashimotoRSC ADVANCES 3 17 6058 - 6064 2013年 [査読有り]
Photocatalytic reductive dechlorination of chlorobenzene in aqueous 2-propanol suspensions of palladium-loaded titanium(IV) oxide (Pd-TiO2) particles was examined in a wide range of aerated and deaerated solutions with different water and NaOH contents. In water-free 2-propanol, the presence of dissolved NaOH and removal of oxygen (O-2) were critical for the dechlorination of chlorobenzene at a sufficient reaction rate and a redox balance (stoichiometry with the oxidation of 2-propanol) close to unity. In 50 vol% water-2-propanol solvent, the yield of benzene under aerated conditions was the same as that under deaerated conditions and was very close to the yield of acetone under aerated conditions, indicating that photogenerated electrons were selectively used for the reduction of chlorobenzene in the water-2-propanol solvent even in the presence of O-2. The low solubility of O-2 in the water-2-propanol solvents was attributed to the high selectivity of photocatalytic dechlorination. In 50 vol% water-2-propanol solvent, NaOH was unnecessary when the reaction was performed under deaerated conditions, suggesting that water played a role in removing chloride ions from the reaction site (surface of TiO2) and in suppressing the consumption of chloride ions by another side-reaction even in the absence of NaOH. Under ideal conditions, i.e., reaction in the absence of NaOH under aerated conditions, benzene was obtained in a 71% yield and a high material balance of benzene and chlorobenzene was recovered. - Tanaka, Atsuhiro; Hashimoto, Keiji; Ohtani, Bunsho; Kominami, HiroshiCHEMICAL COMMUNICATIONS 49 33 3419 - 3421 2013年 [査読有り]
Nearly second-order (1.87th) light-intensity dependence was observed for photocatalytic oxidation of formic acid in aqueous solutions induced by visible-light surface-plasmon resonance absorption of gold nanoparticles loaded on titanium(IV) oxide prepared by the colloid-photodeposition method using a hole scavenger, indicating that the photocatalytic reaction proceeds through a non-linear process. - Keiji Hashimoto; Yusuke Masuda; Hiroshi KominamiACS Catalysis 3 6 1349 - 1355 2013年 [査読有り]
1-Butene was isomerized to 2-butenes with a cis:trans ratio of ∼2:1 over Pd/TiO2 under irradiation of UV light at room temperature, suggesting that a Pd/TiO2 photocatalyst can function as an effective substitute for a Lewis acid catalyst and that the reaction rate can be controlled by photon flux as in the case of changing temperature in a thermocatalytic system. © 2013 American Chemical Society. - A. Tanaka; A. Ogino; M. Iwaki; K. Hashimoto; A. Ohnuma; F. Amano; B. Ohtani; H. KominamiLangmuir 28 36 13105 - 13111 2012年09月 [査読有り]
Au nanoparticles were prepared and successfully loaded on TiO2 without change in the original particle size using a method of CPH. The prepared Au nanoparticles supported on TiO2 showed strong photoabsorption at around 550 nm due to SPR of Au and exhibited a photocatalytic activity in mineralization of formic acid in aqueous suspensions under irradiation of visible light. A linear correlation between photocatalytic activity and the amount of Au loaded, that is, the number of Au nanoparticles, was observed, indicating that the activity of Au/TiO2 plasmonic photocatalysts can be controlled simply by the amount of Au loading using the CPH method and that the external surface area of Au nanoparticles is a decisive factor in mineralization of formic acid under visible light irradiation. - Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi KominamiJOURNAL OF THE AMERICAN CHEMICAL SOCIETY 134 35 14526 - 14533 2012年09月 [査読有り]
Au/CeO2 samples with various Au contents were prepared by the multistep (MS) photodeposition method. Their properties including Au particle size, particle dispersion, and photoabsorption were investigated and compared with properties of samples prepared by using the single-step (SS) photodeposition method. The MS- and SS-Au/CeO2 samples were used for selective oxidation of benzyl alcohols to corresponding benzaldehydes in aqueous suspensions under irradiation by visible light from a green LED, and the correlations between reaction rates and physical properties of the MS- and SS-Au/CeO2 samples were investigated. Difference in the two photodeposition methods was reflected in the average size and number of Au nanoparticles, for example, 92 nm and 1.3 x 10(12) (g-Au/CeO2)(-1) for MS photodeposition and 59 nm and 4.8 x 10(12) (g-Au/CeO2)(-1) for SS photodeposition in the case of 1.0 wt % Au samples. Fixation of larger Au particles resulted in strong photoabsorption of the MS-Au/CeO2 samples at around 550 nm due to the surface plasmon resonance, and the Kubelka-Munk function of the photoabsorption linearly increased with increase in Au content up to 2.0 wt %, in contrast to the photoabsorption of SS-Au/CeO2 samples, which was weak and was saturated even at around 0.5 wt %. Due to the strong photoabsorption, the MS-Au/CeO2 samples exhibited reaction rates approximately twice larger than those of SS-Au/CeO2 samples with the same Au contents, and apparent quantum efficiency of MS-Au/CeO2 reached 4.9% at 0.4 mW cm(-2). Linear correlations were observed between reaction rates (r) and surface area of Au nanoparticles (S) in both MS- and SS-Au/CeO2, samples, though the two slopes of r versus S plots were different, suggesting that oxidation of benzyl alcohol occurred on the Au surface and that S was one of the important factors controlling the reaction rate. Photocatalytic oxidation of benzyl alcohol having an amino group revealed that the Au/CeO2 photocatalyst exhibited high chemoselectivity toward the hydroxyl group of alcohol, i.e, the Au/CeO2 photocatalyst almost quantitatively converted aminobenzyl alcohol to aminobenzaldehyde with 99% yield. - Hiroshi Kominami; Haruhiko Nishimune; Yuichi Ohta; Yuma Arakawa; Takenori InabaAPPLIED CATALYSIS B-ENVIRONMENTAL 111 297 - 302 2012年01月 [査読有り]
Photocatalytic hydrogen (H-2) formation from ammonia and methyl amine in aqueous suspensions of metal-loaded titanium(IV) oxide (TiO2) particles was examined under various conditions. Ammonia was decomposed to H-2 and nitrogen (N-2) with a stoichiometric ratio (3:1, 2NH(3) -> 3H(2) + N-2) under a deaerated condition, and side reactions such as deep oxidation of ammonia to nitrite and nitrate did not occur. The rate of H-2 formation drastically changed depending on the co-catalyst loaded on TiO2 particles, kinds of TiO2 samples and pH of the suspension. The effect of the co-catalyst became greater with decrease in hydrogen over-voltage, the value of which was obtained when the co-catalyst metal was used as an electrode. Among the co-catalysts used in this study, platinum showed the greatest effect as a co-catalyst. The largest rate of H-2 evolution was obtained when the photocatalytic reaction was carried out at pH 10.7, and addition of an acid or base to the suspension decreased the reaction rate. Photocatalytic reaction of methyl amine in aqueous suspension of platinized TiO2 particles under a deaerated condition yielded H-2 but did not form N-2. The methyl group of methyl amine was mineralized and the amino group remained as ammonium ion without being decomposed to H-2 and N-2, resulting in storage of carbon as hydrogencarbonate (HCO3-) in the suspension. Photocatalytic reaction of methyl amine under the present conditions was totally expressed as CH3NH2 + 3H(2)O -> 3H(2) + NH4+ + HCO3-. (C) 2011 Elsevier B.V. All rights reserved. - Green LED responding photocatalytic oxidation of alcohols with Au/CeO2A. Tanaka; K. Hashimoto; H. KominamiSYNFACTS 8 1377 2012年
- Kazuya Imamura; Keiji Hashimoto; Hiroshi KominamiCHEMICAL COMMUNICATIONS 48 36 4356 - 4358 2012年 [査読有り]
m-Nitrovinylbenzene was chemoselectively reduced to m-aminovinylbenzene in a suspension of a TiO2 photocatalyst in the presence of a hole scavenger at room temperature under atmospheric pressure without the use of a precious metal or reducing gas, and nitrobenzenes having other reducible groups were also chemoselectively reduced to corresponding aminobenzenes. - Atsuhiro Tanaka; Satoshi Sakaguchi; Keiji Hashimoto; Hiroshi KominamiCATALYSIS SCIENCE & TECHNOLOGY 2 5 907 - 909 2012年 [査読有り]
Au/TiO2 samples exhibiting stronger photoabsorption at around 550 nm due to surface plasmon resonance were prepared by using a multi-step photodeposition method and the samples exhibited higher levels of activity for H-2 production from various compounds such as 2-propanol, ethanol and ammonia in aqueous suspensions under visible light irradiation. - Hitoshi Gekko; Keiji Hashimoto; Hiroshi KominamiPHYSICAL CHEMISTRY CHEMICAL PHYSICS 14 22 7965 - 7970 2012年 [査読有り]
Nitrite (NO2-) was photocatalytically reduced to dinitrogen (N-2) in an aqueous suspension of two kinds of titanium(IV) oxide particles loaded with palladium and silver (Pd-TiO2 and Ag-TiO2) at pH 8 under irradiation of UV light in the presence of sodium oxalate as a hole scavenger. The two metal-loaded TiO2 photocatalysts had different roles in conversion of NO2- to N-2 and worked in an effective ensemble without conflict: (1) Pd-TiO2 induced photocatalytic disproportionation of NO2- to N-2 and nitrate (NO3-) and (2) Ag-TiO2 selectively reduced the thus-formed NO3- back to NO2- (partially to N-2) with oxalate acting as a hole scavenger. When Pd-TiO2 was used alone for NO3- reduction in the presence of sodium oxalate, Pd-TiO2 induced fruitless photocatalytic decomposition of oxalate to carbon dioxide and dihydrogen. The presence of Ag-TiO2 suppressed the fruitless decomposition of oxalate by Pd-TiO2 because Ag-TiO2 continuously provided NO2- in the reaction system using oxalate as a hole scavenger and Pd-TiO2 therefore only worked as a photocatalyst for disproportionation of NO2- to N-2 and NO3- as it did when used alone. - Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi KominamiCHEMCATCHEM 3 10 1619 - 1623 2011年10月 [査読有り]
Gold and copper nanoparticles supported on cerium(IV) oxide (CeO(2)) powder, which were prepared using a simple multistep photodeposition method, showed strong absorptions at around lambda = 620 nm attributed to the surface plasmon resonance of Cu-Au nanoparticles and exhibited a higher level of activity than that of Au/CeO(2) in the mineralization of organic acids (formic acid and acetic acid) in aqueous suspensions under light irradiation (lambda = 640 nm) from a red light-emitting diode. The action spectrum in the mineralization of formic acid indicates that this mineralization involved a photoinduced step by the SPR of Cu-Au supported on CeO(2). The apparent quantum efficiency reached 7.5% at lambda = 625 nm and 5.2% even at lambda = 700 nm. - Sho Kitano; Keiji Hashimoto; Hiroshi KominamiCATALYSIS TODAY 164 1 404 - 409 2011年04月 [査読有り]
Rhodium(III) ion (Rh3+)-modified TiO2 (Rh3+/TiO2) samples having various physical properties and structures (anatase and rutile) were prepared using commercially available TiO2 samples. Thus-prepared Rh3+/TiO2 samples were used for degradation of acetaldehyde or mineralization of acetone with a constant vapor pressure under irradiation of visible light and correlations between the photocatalytic activities and physical properties were investigated. Rhodium(III) ion on the surface of TiO2 worked as an inorganic photosensitizer and the Rh3+/TiO2 samples showed a kind of volcano-like tendency against specific surface area of TiO2, indicating that the balance of surface area and crystallinity of TiO2 is important in an Rh3+/TiO2 photocatalyst. The latter reaction system was found to be a simple and convenient method to evaluate the activity of a photocatalyst in a short time. The role of Rh3+ as a catalyst for multi-electron reduction of oxygen is discussed on the basis of results obtained for Rh3+-modified rutile-type TiO2 samples. (C) 2010 Elsevier B. V. All rights reserved. - Hiroshi Kominami; Atsuhiro Tanaka; Keiji HashimotoAPPLIED CATALYSIS A-GENERAL 397 1-2 121 - 126 2011年04月 [査読有り]
Gold (Au) nanoparticles supported on cerium(IV) oxide (CeO2) were prepared by the photodeposition method. These samples showed strong absorption at around 550 nm due to localized surface plasmon resonance (LSPR) of Au. These Au/CeO2 samples were used for mineralization of organic acids (formic acid, oxalic acid and acetic acid) in the aqueous suspensions under irradiation of visible light (>ca. 520 nm) and three acids were stoichiometrically decomposed to carbon dioxide. Apparent activation energy for mineralization of formic acid was very small (2.4 kJ mol(-1)) compared with those by thermocatalytic reactions, and the action spectrum was in good agreement with the photoabsorption spectrum, indicating that the rate-determining step in mineralization of organic acids in the irradiated Au/CeO2 system was different from the thermal activation process and that this mineralization involved a photoinduced step by LSPR of Au supported on CeO2. When a green light-emitting diode (center wavelength = 530 nm) was used as the light source of visible light, mineralization of formic acid also occurred. Apparent quantum efficiency of formic acid mineralization increased with decrease in the intensity of the green light and reached 4.7% at 0.4 mW cm(-2). (C) 2011 Elsevier B.V. All rights reserved. - Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi KominamiCHEMISTRY LETTERS 40 4 354 - 356 2011年04月 [査読有り]
Photocatalytic activity of cerium(IV) oxide (CeO2) particles in decomposition of acetic acid in aqueous suspension was examined under irradiation of visible light. Acetic acid was decomposed to carbon dioxide (CO2) and the rate of CO2 formation was increased by loading of 0.1 wt% cocatalysts (Pt, Au, Rh, Ru, Pd, Ag, Cu, and Ir) on CeO2 by photodeposition. Cocatalysts showed almost the same levels of enhancement of CO2 evolution, i.e., Ag/CeO2 and Cu/CeO2 exhibited rates similar to that of Pt/CeO2. The action spectrum revealed that decomposition of acetic acid was induced by photoabsorption of CeO2. - Sho Kitano; Keiji Hashimoto; Hiroshi KominamiAPPLIED CATALYSIS B-ENVIRONMENTAL 101 3-4 206 - 211 2011年01月 [査読有り]
Using the adsorption method, small amounts of rhodium ion (Rh(3+)) or copper ion (Cu(2+)) were loaded on nanocrystalline titanium(IV) oxide (TiO(2)) with various physical properties prepared by the HyCOM (hydrothermal crystallization in organic media) method and subsequent calcination at various temperatures. In photocatalytic degradation of 2-propanol under visible light irradiation, Rh(3+)-modified HyCOM-TiO(2) samples exhibited higher levels of activity than did Cu(2+)-modified HyCOM-TiO(2) samples and the nitrogen-doped TiO(2) sample. The Rh(3+)-modified HyCOM-TiO(2) samples showed a volcano-like tendency with calcination temperature, suggesting that the balance of surface area and crystallinity of TiO(2) is important in an Rh(3+)/TiO(2) photocatalyst. Rutile-type TiO(2) modified with Cu(2) exhibited the highest level of activity among the Cu(2+)/HyCOM-TiO(2) samples. (c) 2010 Elsevier B.V. All rights reserved. - Kazuya Imamura; Shin-ichi Iwasaki; Tsuyoshi Maeda; Keiji Hashimoto; Bunsho Ohtani; Hiroshi KominamiPHYSICAL CHEMISTRY CHEMICAL PHYSICS 13 11 5114 - 5119 2011年 [査読有り]
Photocatalytic reduction of nitrobenzenes to corresponding aminobenzenes in aqueous suspensions of titanium(IV) oxide (TiO(2)) containing hole scavengers under various conditions was examined. In photocatalytic reduction of m-nitrobenzenesulfonic acid (m-NBS) in the presence of formic acid (FA) under deaerated conditions, m-aminobenzenesulfonic acid (m-ABS) was produced almost quantitatively in acidic suspensions and high efficiency (> 99%) in FA utilization as a hole scavenger was achieved. No re-oxidation of m-ABS occurred in acidic conditions both in the presence and absence of FA. The high yield of m-ABS was explained by strong ability of FA as a hole scavenger and possible repulsion of the reduced functional group (ammonium group, -NH(3)(+)) from the protonated, i.e., positively charged TiO(2) surface in acidic suspensions avoiding re-oxidation of m-ABS. Using TiO(2) samples of various physical properties, which had been synthesized by a solvothermal method and post-calcination at various temperatures, effects of physical properties of the TiO(2) samples on m-ABS yield were also investigated. A linear correlation between the amount of m-NBS adsorbed and the m-ABS yield was observed, suggesting that ability of TiO(2) for m-NBS adsorption is one of the key factors for effective photocatalytic reduction of m-NBS to m-ABS. This photocatalytic system can be applied for reduction of aminonitrobenzenes to corresponding diaminobenzenes (DAB) in the presence of oxalic acid as a hole scavenger. High yields of m-ABS and DAB were achieved even when the reactions were performed in the presence of oxygen. - Kojirou Fuku; Keiji Hashimoto; Hiroshi KominamiCATALYSIS SCIENCE & TECHNOLOGY 1 4 586 - 592 2011年 [査読有り]
Photocatalytic dechlorination of chlorobenzene in alcohol suspensions of metal-loaded TiO(2) in the presence of sodium ion sources under irradiation of UV light was examined. When palladium (Pd) (or rhodium), 2-propanol and NaOH were used as the metal co-catalyst, alcohol and Na(+) source, respectively, benzene and acetone were obtained almost quantitatively and stoichiometrically in a very short time. Chloride ions eliminated from chlorobenzene were immediately solidified as NaCl by NaOH dissolved in 2-propanol and separated from other products such as benzene and acetone dissolved in 2-propanol. Effects of the physical properties of TiO(2) and addition of water on photocatalytic dechlorination of chlorobenzene were examined. A more useful oxidized product, i.e., butanone, was successfully obtained in addition to benzene as the reduction product when 2-butanol was used as the alcohol solvent. To avoid formation of water in dechlorination of chlorobenzene in 2-propanol and 2-butanol, a Na(+)-containing LTA-type zeolite (molecular sieves 4 angstrom) was used as the Na(+) source, and almost quantitative recovery of benzene was achieved along with stoichiometric formation of the corresponding ketones. - Atsuhiro Tanaka; Keiji Hashimoto; Hiroshi KominamiCHEMICAL COMMUNICATIONS 47 37 10446 - 10448 2011年 [査読有り]
Gold nanoparticles supported on cerium(IV) oxide powder showing strong absorption at around 550 nm due to surface plasmon resonance oxidized aromatic alcohols to corresponding aldehydes almost quantitatively in an aqueous suspension under irradiation of green light. - Hiroshi Kominami; Hitoshi Gekko; Keiji HashimotoPHYSICAL CHEMISTRY CHEMICAL PHYSICS 12 47 15423 - 15427 2010年12月 [査読有り]
Photocatalytic reaction of a nitrite ion in aqueous suspensions of bare and metal-loaded TiO2 particles was examined without electron and hole scavengers under irradiation of UV light. In the bare TiO2 system, disproportionation of NO2- to N-2 (or N2O) and NO3- with nitrogen balance (NB) and redox balance (ROB) close to unity within experimental errors was observed, although the reaction was slow. Palladium (Pd)-loaded TiO2 particles exhibited an extraordinarily large rate of disproportionation of NO2- in their aqueous suspension, i.e. NO2- was almost completely converted to N-2 (or N2O) and NO3- even after only 3 h of photoirradiation, both the values of NB and ROB being close to unity. This result suggests that Pd loaded on TiO2 particles acted as storage sites for photogenerated electrons and effectively transferred the electrons to NO2- and, therefore, that the reduction process in the photocatalytic disproportionation of NO2- was accelerated by Pd loaded on TiO2. Effects of the amount of Pd and pH of the suspension on the reaction rate were also examined. - Masachiyo Imanishi; Keiji Hashimoto; Hiroshi KominamiAPPLIED CATALYSIS B-ENVIRONMENTAL 97 1-2 213 - 219 2010年06月 [査読有り]
Homogeneous photocatalytic mineralization (decomposition to carbon dioxide (CO(2))) of acetic acid in dilute aqueous solutions of various metal ions was examined at room temperature under irradiation of UV light in the presence of oxygen (O(2)). Iron ton exhibited a much higher level of activity among the metal ions studied for mineralization of acetic acid. The rate of CO(2) formation was proportional to first-order partial pressure of O(2) and concentrations of iron ion and acetic acid, whereas the rate was in inverse proportional to first-order proton concentration The rate equation, r = k Po(2) [[Fe(III)(H(2)O)(6)](3+)] [AcOH][H(+)](-1), in overall photocatalytic mineralization of acetic acid was derived from these results The mechanism of the photocatalytic mineralization of acetic acid in an aqueous solution of ion was proposed (C) 2010 Elsevier B V All rights reserved - Sho Kitano; Keiji Hashimoto; Hiroshi KominamiCHEMISTRY LETTERS 39 6 627 - 629 2010年06月 [査読有り]
Using adsorption method, a small amount of rhodium ion (Rh3+) was loaded on nanocrystalline titanium(IV) oxide (TiO2) with various physical properties prepared by HyCOM and subsequent calcinations at various temperatures. In photocatalytic degradation of 2-propanol under visible light irradiation, Rh3+-modified HyCOM-TiO2 samples exhibited higher levels of activity than did nitrogen-doped TiO2 sample and showed a volcano-like tendency with calcination temperature, suggesting that the balance of surface area and crystallinity of TiO2 is important in an Rh3+/TiO2 photocatalyst. - Masachiyo Imanishi; Keiji Hashimoto; Hiroshi KominamiCHEMISTRY LETTERS 39 4 352 - 353 2010年04月 [査読有り]
Irradiation of UV light to aqueous solutions of various organic compounds (acetic acid, alcohols, ketones, phenol, and benzenesulfonic acid) containing a small amount of metal ions was examined under an aerated condition at room temperature. These organic compounds were quantitatively decomposed to carbon dioxide in the presence of iron(III) ion, indicating that hydrated iron(III) complex acted as an efficient homogeneous photocatalyst. - Hiroshi Kominami; Hiroshi Sugahara; Keiji HashimotoCATALYSIS COMMUNICATIONS 11 5 426 - 429 2010年01月 [査読有り]
Photocatalytic oxidation of methanol in air over titanium(IV) oxide particles having a large surface area of 120 m(2) g(-1) using a flow-type reactor at room temperature yielded methyl formate with a high level of selectivity (91 mol%) without catalyst deactivation due to deposition of intermediate(s). The conversion of methanol increased with elevation of the reaction temperature up to 523 K maintaining high selectivity. (C) 2009 Elsevier B.V. All rights reserved. - Hiroshi Kominami; Atsuhiro Tanaka; Keiji HashimotoCHEMICAL COMMUNICATIONS 46 8 1287 - 1289 2010年 [査読有り]
Gold nanoparticles supported on cerium(IV) oxide powder showed strong absorption at around 550 nm due to localized surface plasmon resonance of Au and exhibited a higher level of activity than other Au-supporting samples in mineralization of organic acids in aqueous suspensions under irradiation of visible light (>ca. 520 nm). - Kojirou Fuku; Keiji Hashimoto; Hiroshi KominamiCHEMICAL COMMUNICATIONS 46 28 5118 - 5120 2010年 [査読有り]
Photocatalytic reaction of chlorobenzene in 2-propanol suspension of palladium- and rhodium-loaded titanium(IV) oxide nanocrystals in the presence of dissolved sodium hydroxide under deaerated conditions, in which 2-propanol, metal loaded (palladium and rhodium) and sodium hydroxide effectively acted as hole scavenger, co-catalyst and chloride solidifier, respectively, quantitatively gave benzene and chloride ions with a high stoichiometry. - Atsushi Kamiouji; Keiji Hashimoto; Hiroshi Kominami; Yukio Terada; Seishiro ItoJOURNAL OF THE JAPAN PETROLEUM INSTITUTE 52 5 288 - 294 2009年09月 [査読有り]
The applicability of the tubular reactor (TR) to the manufacturing of soap was investigated by saponification of mixtures of two types of oils and fats using the batch-type reactor (BR) and TR under similar conditions to those used in the manufacturing of soaps (starting materials and ratios). Effect(s) of replacement of animal fat (tallow) with vegetable oils (palm oil and rice bran oil) on the properties of the soaps produced were also investigated. For all combinations of oils and fats (tallow-coconut oil, palm oil-coconut oil, rice bran oil-coconut oil), the rates of saponification in the TR were much larger than the rates of saponification in the BR, resulting in shortening of reaction times to about one-fourth for complete saponification of oils and fats. The seven most important properties of the soaps produced using the TR were evaluated and compared with those of commercial soaps, indicating that the soaps produced using the TR satisfied all standards for these properties, and that these properties were identical to those of commercial soaps. Therefore, the TR can be applied to the manufacture of soaps from mixtures of two types of oils and fats in industrial grades in the presence of ethanol. - Atsushi Kamiouji; Keiji Hashimoto; Hiroshi Kominami; Seishiro ItoTOPICS IN CATALYSIS 52 6-7 795 - 800 2009年06月 [査読有り]
Saponification of various fatty acid methyl esters with an aqueous solution of sodium or potassium hydroxide (NaOH(aq) or KOH(aq)) using a long narrow tubular reactor (TR) was studied at 333 K to elucidate effects of their carbon number on the apparent diffusion constant (k). Saponification by a conventional method, batch-type system (BR), was also studied for comparison with that in the TR. All of the saponification rates obeyed the Nernst diffusion rate equation, and the values of k were determined from their Nernst plots. The values of k in the TR system were more than 500-times larger than those in the BR system. The diffusion constant (D) calculated from k increased with a decrease in carbon number of fatty acid methyl esters. In addition, the value of D was proportional to the reciprocal of viscosity of methyl ester. Moreover, saponification was promoted more by KOH than by NaOH, and the value of D with KOH(aq) was 2.0-times larger than that with NaOH(aq). The two-fold larger value was nearly equal to the radius ratio of potassium ion to hydrated sodium ion. Therefore, it is concluded that viscosity and ion radius contributed predominantly to the diffusion and that the diffusion of hydrated sodium ion to potassium ion was a rate-controlling step. - Keiji Hashimoto; Katutoshi Sumida; Sho Kitano; Kazuto Yamamoto; Nobuaki Kondo; Yoshiya Kera; Hiroshi KominamiCATALYSIS TODAY 144 1-2 37 - 41 2009年06月 [査読有り]
Titanium(IV) oxide samples modified with platinum or rhodium chloride (H(2)PtCl(6)/TiO(2) or RhCl(3)/TiO(2)) were prepared by an impregnation method and post-calcination at various temperatures and were used for photo-oxidation of nitrogen oxide under irradiation of visible light or UV light. Turnover numbers of both the catalysts were maintained at temperatures Lip to 350 degrees C under 24-h irradiation of visible light, although the specific surface area of the catalysts decreased greatly with increase in post-calcination temperature. The turnover number of H(2)PtCl(6)/TiO(2) was about two-times larger than that of RhCl(3)/TiO(2). Only a small amount of released NO(2) was observed in the RhCl(3)/TiO(2) catalyst, whereas in the H(2)PtCl(6)/TiO(2) catalyst, the amount of NO(2) released to gas phase increased with an increase in oxidation products. The small amount of released NO(2) indicates that most of the NOx adsorbed on RhCl(3)/TiO(2) as an adsorption form of nonvolatile NO(3), whereas the amount of adsorbed NO(2) on H(2)PtCl(6)/TiO(2) was about four-times larger than that on RhCl(3)/TiO(2). The results indicate that the oxidation rate of NO(2) to NO(3)-over RhCl(3)/TiO(2) was faster than that over H(2)PtCl(6)/TiO(2). These results strongly suggest that the Cl radical induced by visible light was not directly related to the photo-oxidation of NO to NO(2) and NO(3) and that the complex species of RhCl(3) and H(2)PtCl(6) contributed to the photo-oxidation. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved. - Hiroshi Kominami; Shin-ichi Iwasaki; Tsuyoshi Maeda; Kazuya Imamura; Keiji Hashimoto; Yoshiya Kera; Bunsho OhtaniCHEMISTRY LETTERS 38 5 410 - 411 2009年05月 [査読有り]
Nitrobenzene was effectively and selectively reduced to aniline in an acidic aqueous suspension of titanium(IV) oxide photocatalyst in the presence of oxalic acid as a hole scavenger and the aniline yield was improved in the presence of a small amount of dioxygen. - Atsushi Kamiouji; Keiji Hashimoto; Hiroshi Kominami; Seishiro ItoBULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 82 4 509 - 513 2009年04月 [査読有り]
Saponification of methyl dodecanoate with an aqueous sodium hydroxide solution in the absence and presence of alcohols was studied using a tubular reactor made of silicone tube to elucidate effects of alcohol addition on the saponification. The reaction rates of saponification were accelerated significantly when alcohols were dissolved in methyl dodecanoate and the rates were increased in the order: without alcohol << ethanol < propanol < butanol. The rates in all cases obeyed the Nernst diffusion rate equation, and the values of apparent diffusion constant, k(a), that were determined from the slope of Nernst plots were increased in the above order, indicating that diffusion of sodium ion in the aqueous solution into the mixture of methyl dodecanoate and alcohol was much easier than that to methyl dodecanoate without alcohol. The values of k(a) increased with increase in the amount of butanol both in the tubular reactor and in a beaker (batch system). The thickness of the diffusion layer, delta, decreased with increase in the amount of butanol in the saponification in the tubular reactor, suggesting that the increase in k(a) in the saponification in the presence of butanol in the tubular reactor can be explained by decrease in values of delta. - Hiroshi Kominami; Kimiyo Yukishita; Takashi Kimura; Moeko Matsubara; Keiji Hashimoto; Yoshiya Kera; Bunsho OhtaniTOPICS IN CATALYSIS 47 3-4 155 - 161 2008年04月 [査読有り]
Solvothermal decomposition of titanium(IV) tert-butoxide (TTB) in toluene at 573 K in the presence of silica gel (SiO(2)) with continuous stirring yielded a titanium(IV) oxide (TiO(2))-SiO(2) composite in which agglomerates of nanocrystalline TiO(2) were deposited on the surfaces of SiO(2) particles. Various TiO(2)-SiO(2) composites having different TiO(2) contents can be synthesized by changing the ratio of TTB and SiO(2), and the composites had large surface areas corresponding to porous properties of SiO(2). These TiO(2)-SiO(2) composites were used for photocatalytic removal of nitrogen oxides in air and their photocatalytic performances were compared with those of other TiO(2)-SiO(2) samples prepared by different methods. Solvothermally synthesized 74 wt.%TiO(2)-SiO(2) composite exhibited excellent photocatalytic performance (almost stoichiometric removal of NO(x) (98%) and very low NO(2) release (0.3%)) attributable to high photocatalytic activity of TiO(2) and high adsorption property of SiO(2). Lesser performance of 74 wt.%TiO(2)-SiO(2) composites prepared by other methods suggested that pore-mouth plugging of SiO(2) by TiO(2) and lower level of mixing of TiO(2) and SiO(2) decreased photocatalytic performance of the composites. - Atsushi Kamiouji; Keiji Hashimoto; Hiroshi Kominami; Seishiro ItoINDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH 47 5 1464 - 1467 2008年03月 [査読有り]
Saponification of methyl laurate with an aqueous solution of sodium hydroxide was carried out in long narrow tubes made of silicone rubber. The saponification rate obeyed the Nernst diffusion equation. The apparent diffusion constant in the tubular reactor with a tube of 1.7 mm inner diameter and 8 m length was about 300 times larger than that in a beaker at 333 K. The apparent activation energies of diffusion were determined to be 14 and 12 kJ mol(-1) for tubular reactors with tubes of 8 m length and 0.8 and 1.7 mm inner diameter, respectively. These values are in good agreement with those of some reagents, 12-21 kJ mol(-1), in a liquid phase. The results indicated that the rate-controlling step of the saponification is diffusion of sodium ions and/or hydroxide ions into methyl laurate. In addition, the apparent diffusion constant depended on the length and inner diameter, and it increased with an increase in surface area of the inner wall of the tubular reactor. It is concluded that a tubular reactor with a long tube and a large surface area of the inner wall is applicable to saponification without a promoter and stirring. - Hiroshi Kominami; Kenta Takenouchi; Keiji Hashimoto; Kazuhiro SayamaELECTROCHEMISTRY 76 2 118 - 120 2008年02月 [査読有り]
A titanium(IV) oxide (TiO2) sample having a large surface area and showing a large visible light absorption was prepared by modification of commercial TiO2 With a silane coupling reagent and subsequent nitrogen doping with ammonia at 500 degrees C. The thus-prepared visible light-responding TiO2 sample was used photoinduced removal of gaseous nitrogen oxides (NO.) under irradiation from blue light-emitting diodes or white fluorescent lamp and exhibited higher level of NO, removal than nitrogen-doped unmodified TiO2. A remarkable improvement in NO, removal was achieved by removing silica species with sodium hydroxide solution presumably due to the large surface area for effective adsorption of NO, and storage of nitric acid, and sufficient efficiency for both visible light and UV light. - Hiroshi Kominami; Katutoshi Sumida; Kazuto Yamamoto; Nobuaki Kondo; Keiji Hashimoto; Yoshiya KeraRESEARCH ON CHEMICAL INTERMEDIATES 34 5-7 587 - 601 2008年 [査読有り]
Various metal chloride-modified titanium(IV) oxide (TiO2) (MCMT) samples were prepared by loading metal chloride on commercial TiO2 nanoparticles (Ishihara ST-01) having a large specific surface area and used for photoinduced oxidative removal of nitrogen oxides (NO,) in air under irradiation of visible light and/or ultraviolet (UV) light. The NO, removal activity of MCMT samples under photoirradiation from a blue fluorescent lamp (BFL) with a UV cut filter decreased in the following order: RhCl3/ST-01 > HZPtCl(6)/ST-01 > RuCl3/ST-01 > ST-01 > IrCl4/ST-01 > HAuCl4/ST-01, indicating that RhCl3, H2PtCl6 and RuCl3 fixed on TiO2 effectively worked as photosensitizers for NOx removal. NOx was almost quantitatively fixed as nitrate on RhCl3/ST-01 photoirradiated with BFL or blue light-emitting diodes. Under irradiation of both visible light and UV light from a white fluorescent lamp, RhCl3/ST-01 exhibited a higher level of removal of NOx and a much lower level of release of nitrogen dioxide than did bare ST-01, indicating that RhCl3/ST-01 effectively utilized both visible light and UV light and that two types of reaction (photosensitization by fixed RhCl3 and photocatalysis by TiO2 occurred over RhCl3/ST-01. - Byonggu An; Sachiko Kaida; Tohru Miyake; Tohru Tani; Itsushi Kashimoto; Hiroshi KominamiJOURNAL OF THE JAPAN PETROLEUM INSTITUTE 50 5 283 - 286 2007年09月 [査読有り]
Combustion catalysts free from precious metals, such as platinum, for removal of volatile organic compounds were investigated. Common metal oxides (titanium(TV) oxide (TiO2), alumina and silica) were selected as candidates for a catalyst for combustion of toluene at low concentrations. Complete conversion of toluene was not achieved even at 500 degrees C without catalysts, although the ignition point of toluene is 480 degrees C. TiO2 exhibited the highest activity for combustion of toluene among representative metal oxides. Toluene was almost quantitatively converted to carbon dioxide (> 99% yield) over TiO2 under the condition of appropriate contact time at 500 degrees C. - Shin-Ya Murakami; Hiroshi Kominami; Yoshiya Kera; Shigeru Ikeda; Hidenori Noguchi; Kohei Uosaki; Bunsho OhtaniRESEARCH ON CHEMICAL INTERMEDIATES 33 3-5 285 - 296 2007年 [査読有り]
Electron-hole recombination in nano-sized titanium(IV) oxide (TiO2) particles with various physical properties, which have been shown to be highly active photocatalysts, was evaluated by quantitative analysis of reduced titanium species (Ti3+), which might be formed at crystalline defective sites in TiO2 particles through photo-irradiation in the presence of a hole scavenger under deaerated conditions. These highly active photocatalyst samples were synthesized by hydrothermal crystallization in organic media (HyCOM method) and post-calcination. The Ti3+ density decreased with increasing calcination temperature (T-c), and a linear correlation was observed between the Ti3+ density and rate constant for electron-hole recombination evaluated by femtosecond pump-probe diffuse reflection spectroscopy. Reaction rate (R-Ag) and the amount of silver ions (Ag+) adsorbed on TiO2 particles ([Ag+]ads) were measured for photocatalytic silver metal deposition along with oxygen formation from an aqueous Ag+ solution under deaerated conditions, and the slope of the R-Ag versus [Ag+](ads) plot was determined. Kinetic investigation of this reaction showed that the reciprocal of the slope was approximately related to the ratio of the rates for electron-hole recombination and electron trapping (k(r)/k(e) ratio). The k(r)/k(e) ratio decreased as T-c increased, and the logarithm of the k(r)/k(e) ratio was linearly related with Ti3+ density. These two parameters were used as a measure for the recombination properties of TiO2 photocatalysts with various physical properties. - Tomohiro Oonaka; Kenta Takenouchi; Keiji Hashimoto; Hiroshi Kominami; Yoshiya Kera; Yoshio MatsubaraJOURNAL OF THE JAPAN PETROLEUM INSTITUTE 50 1 16 - 22 2007年01月 [査読有り]
Catalytic features of supported and unsupported ruthenium containing polyoxomolybdate anion (Ru2Mo14) were evaluated using the methanol transformation reaction. Decomposition of methanol into hydrogen (H-2) and carbon monoxide (CO) predominantly occurred over unsupported Ru2Mo14 whereas no acid-catalyzed reaction (formation of dimethyl ether, DME) occurred indicating that Ru2Mo14 had a weak acidity or had no acidity. Ru2Mo14 was homogeneously loaded up to ca. 40 wt% on silica and titania that had been chemically modified with N-(2-aminoethyl-3-aminopropyltrimethoxysilane. Ru2Mo14 catalysts supported on these modified supports exhibited higher conversion of methanol than Ru2Mo14 catalysts either unsupported or supported on unmodified supports, indicating that Ru2Mo14 was highly dispersed on the modified supports. Even in the presence of water vapor, no steam reforming of methanol or shift reaction of CO occur-red over the supported Ru2Mo14 catalysts. Ru2Mo14 catalyst supported on modified alumina support converted methanol to DME by acid-catalyzed reaction together with the decomposition products, CO and H-2, indicating that the Ru2Mo14 catalyst supported on modified alumina possessed strong acidity. FT-IR measurement of the methanol species adsorbed on Ru2Mo14 catalyst supported on modified alumina and the contact time dependency of this reaction suggested that methanol decomposition proceeded via formation of formaldehyde and subsequent decomposition into CO and H-2. - T Oonaka; K Hashimoto; H Kominami; Y Kera; Y MatsubaraCATALYSIS TODAY 111 3-4 354 - 360 2006年02月 [査読有り]
A salt of ruthenium-containing polyoxomolybdate anion ([Ru2Mo14O50](10-) or [Ru2Mo14O52](14-); Ru2Mo14) was synthesized by mixing ruthenium chloride and sodium molybdate in a buffer solution (acetic acid-ammonium acetate) at PH 5. The polyanion, Ru2Mo14, was loaded on a silica carrier chemically modified with a silane coupling agent having a 1,2-diaminoethyl group (DAPS-SiO2) X-ray diffraction, FT-IR and surface area measurements revealed that Ru2Mo14 was highly dispersed on DAPS-SiO2 UP to 20 wt.% loading. The highly dispersed Ru2Mo14 exhibited a high level of activity for oxidative dehydrogenation of methanol to formaldehyde with a high selectivity, whereas combustion of methanol occurred on the bulky salt of Ru2Mo14 and ruthenium catalyst supported on a SiO2 carrier. (c) 2005 Elsevier B.V. All rights reserved. - T Oonaka; K Hashimoto; H Kominami; Y Matsubara; Y KeraJOURNAL OF THE JAPAN PETROLEUM INSTITUTE 49 1 43 - 44 2006年01月 [査読有り]
Catalytic features of ruthenium-molybdenum polyoxometalate having a composition of [Ru2Mo14O50](10-) or [Ru2Mo14O52](14-) (Ru2Mo14) were evaluated using liquid-phase selective oxidation of benzyl alcohol with oxygen. Ru2Mo14 catalyst supported on titania support chemically modified with silane coupling agent that has amino groups (Ru2Mo14/DAPS-TiO2) exhibited much higher catalytic activity than other Ru2Mo14 catalysts unsupported and supported on unmodified titania. Ru2Mo14/DAPS-TiO2 exhibited larger turnover frequency than representative polyoxometalates supported on DAPS-TiO2. - A. Satsuma; N. Furuta; T. Ogiso; M. Inoue; H. Kominami; K. Kagawa; T. HattoriSCIENTIFIC BASES FOR THE PREPARATION OF HETEROGENEOUS CATALYSTS, PROCEEDINGS OF THE 9TH INTERNATIONAL SYMPOSIUM 162 785 - 792 2006年TiO2 and TiO2-SiO2 prepared by various methods were tested as the support of V2O5 for NH3-SCR. The intrinsic activity, i.e., reaction rate per active site, was independent of the preparation method and SiO2 content, but the densities of active sites and deposited vanadium species were higher on the support with higher density of surface OH groups. It was concluded that the surface reactivity such as OH density is a key factor of TiO2 support controlling catalytic activity of V2O5/TiO2 catalyst for NH3-SCR.
- T Oonaka; K Hashimoto; H Kominami; Y Matsubara; Y KeraJOURNAL OF THE JAPAN PETROLEUM INSTITUTE 48 3 178 - 179 2005年05月 [査読有り]
Needle-like crystals of ruthenium-molybdenum polyoxometalate having a composition of Na-4(NH4)[RuMo7O25]center dot 8H(2)O (RuMo7) were synthesized with high reproducibility With cetylpyridinium cation, RuMo7 was modified and its catalytic features were evaluated using oxidation of cyclohexanol to cyclohexanone with t-butyl hydroperoxide or hydrogen peroxide (H2O2). The results indicated that RuMo7 exhibits high rate for the former reaction and that RuMo7 has high potential for H2O2 decomposition. - H Kominami; T Nakaseko; Y Shimada; A Furusho; H Inoue; S Murakami; Y Kera; B OhtaniCHEMICAL COMMUNICATIONS 23 2933 - 2935 2005年 [査読有り]
Nitrate was photocatalytically reduced to nitrogen molecules with a high selectivity in a basic aqueous suspension of palladium and copper-loaded titanium(IV) oxide powders in the presence of oxalate anion as a hole scavenger. - Y Kera; T Oonaka; K Yamanaka; S Hirayama; H KominamiAPPLIED CATALYSIS A-GENERAL 276 1-2 187 - 195 2004年11月 [査読有り]
The molecular units of polyoxomolybdates containing transition metal ions [XMo6O24n-; XMo6, X = Fe, Co, Ni] were quite homogeneous and thus could be densely dispersed on alumina chemically modified with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane by an equilibrium adsorption method [XMo6/DAPS-Al2O3]. The catalytic features of XMo6/DAPS-Al2O3 thus prepared for methanol-oxidation were extensively examined. On XMo6/DAPS-Al2O3, the methanol-conversion increased up to 100% with an increase in the reaction temperature (200 --> 300 degreesC) while maintaining the formaldehyde-selectivity at a high level such as 80-90% or more; e.g., the high selectivity of 91% was found in the 83%-conversion on the most efficient catalyst, FeMo6/DAPS-Al2O3, at 300 degreesC. Such catalytic features were found to be induced from the disk-like XMo6-molecular units that were projected perpendicular and densely over the DAPS-Al2O3 surfaces in the saturated states. The mechanistic aspects were also easy to explain based on the XMo6-dispersed model. Finally, we proposed that the premodification method of the carrier surfaces with silane agents should be widely applied as a very useful technique for the preparation of fixed-polyoxometalate catalysts. (C) 2004 Elsevier B.V. All rights reserved. - Synthesis of thermally stable χ-alumina by thermal decomposition of aluminum isopropoxide in tolueneOkorn Mekasuwandumrong; Okorn Mekasuwandumrong; Hiroshi Kominami; Piyasan Praserthdam; Masashi InoueJournal of the American Ceramic Society 87 8 1543 - 1549 2004年 [査読有り]
Thermal decomposition of aluminum isopropoxide in toluene at 315°C resulted in χ-alumina that had high thermal stability, whereas the reaction at lower temperatures resulted in formation of an amorphous product. The χ-alumina thus obtained directly transformed to α-alumina at ∼1150°C, bypassing the other transition alumina phases, whereas the amorphous product transformed to α-alumina and then to θ-alumina before final transformation to α-alumina. When the χ-alumina, solvothermally synthesized at 315°C, was recovered by the removal of the solvent at the reaction temperature, thermal stability of the product was improved further. This procedure is convenient because it avoids bothersome work-up processes that yield large-surface-area and large-pore-volume alumin. - H Kominami; Y Ishii; M Kohno; S Konishi; Y Kera; B OhtaniCATALYSIS LETTERS 91 1-2 41 - 47 2003年11月 [査読有り]
Nanocrystalline brookite-type titanium(IV) oxide (TiO2) powder was synthesized by solvothermal treatment of oxobis(2,4-pentanedionato- O, O') titanium in a 1,2-ethanediol-water system in the presence of sodium acetate followed by hydrothermal treatment at 373 K in order to remove organic moieties contaminating the powder. The powder was calcined at various temperatures to change its physical properties and then used for three types of photocatalytic reaction: mineralization of acetic acid ( AcOH) in an aerated aqueous suspension of bare TiO2 powder, evolution of molecular hydrogen from 2-propanol in an aqueous suspension of in situ platinized powder and formation of molecular oxygen (O-2) from silver sulfate in a deaerated aqueous suspension of bare TiO2 powder. Dependence of the photocatalytic activities on calcination temperature (T-c) and correlations with the physical properties of brookite- type TiO2 samples were examined. In the case of mineralization of AcOH, the uncalcined brookite TiO2 sample having the largest surface area showed the highest rate of carbon dioxide evolution (R-CO2), which was equal to that of representative commercial TiO2 (Degussa P-25), and R-CO2 decreased monotonously with T-c, i.e., with decrease in surface area. On the other hand, in the case of O-2 formation, the photocatalytic activity was enhanced by calcination at a higher temperature, despite the simultaneous decrease in surface area. Overall, the effects of calcination on the photocatalytic activities for the three reaction systems strongly suggested that photocatalytic activity of brookite- type TiO2 depends on two significant factors, adsorbability and recombination probability, corresponding to the specific surface area and crystallinity, respectively, and that the balance of these two factors determines T-c dependence. - H Kominami; J Kato; S Murakami; Y Ishii; M Kohno; K Yabutani; T Yamamoto; Y Kera; M Inoue; T Inui; B OhtaniCATALYSIS TODAY 84 3-4 181 - 189 2003年09月 [査読有り]
Thermal treatment of titanium(IV) butoxide dissolved in 2-butanol at 573 K under autogenous pressure (alcohothermal treatment) yielded microcrystalline anatase-type titanium(W) oxide (TiO2). Thermal treatment of oxobis(2,4-pentanedionato-O,O')titanium (TiO(acac)(2)) in ethylene glycol (EG) in the presence of sodium acetate and a small amount of water at 573 K yielded microcrystalline brookite-type TIO2. Tungsten(VI) oxide (WO3) powders of monoclinic crystal structure with high crystallinity were synthesized by hydrothermal treatment (HTT), at 523 or 573 K, of aqueous tungstic acid (H2WO4) solutions prepared from sodium tungstate by ion-exchange (IE) with a proton-type resin. Anatase and brookite TiO2 products were calcined at various temperatures and then used for photocatalytic mineralization of acetic acid in aqueous solutions under aerated conditions and dehydrogenation of 2-propanol under deaerated conditions. Almost all the anatase-type TiO2 samples showed the activities more than twice higher than those of representative active photocatalysts, Degussa P-25 and Ishihara ST-01 in both reactions. A brookite sample with improved crystallinity and sufficient surface area obtained by calcination at 973 K exhibited the hydrogen evolution rate almost equal to P-25. HTT WO3 powders with various physical properties were used as photocatalyst for evolution of oxygen (O-2) from an aqueous silver sulfate solution. WO3 powder of high crystallinity, e.g., IE-HTT-WO3 synthesized at 573 K, gave much higher O-2 yield than commercially available WO3 samples. (C) 2003 Elsevier B.V. All rights reserved. - H Kominami; H Kumamoto; Y Kera; B OhtaniJOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY 160 1-2 99 - 104 2003年08月 [査読有り]
Titanium(IV) oxide (TiO2) nano-particles with various physical properties, which had been prepared by hydrothermal crystallization in organic media (HyCOM) and post-calcination, were used for photocatalytic decomposition of malachite green (MG) in an aqueous suspension under aerated conditions. The amount of MG adsorbed on TiO2 ([MG](ad)) increased as the surface area of HyCOM TiO2 increased. The apparent initial rate constant of pseudo zero-order kinetics, k(0), for decolorization of MG in an early stage (similar to 15 min) coincided well with [MG]ad, indicating that adsorptivity is a decisive factor for the initial bleaching of MG. However, in a 1 h irradiation experiment, a HyCOM sample with a smaller [MG](ad) but improved crystallinity exhibited higher decolorization activity than did HyCOM TiO2 with the largest [MG](ad), suggesting that this reaction process includes deactivation of the photocatalyst due to deposition of intermediate(s) that had been formed by degradation of MG. Longer irradiation was required for mineralization of MG. Total organic carbon (TOC) in the suspension of HyCOM TiO2 with improved crystallinity continuously decreased whereas TOC in Degussa P-25 TiO2 did not decrease any more after 5 h of irradiation, although one-third of the initial TOC still remained in the suspension. (C) 2003 Elsevier Science B.V. All rights reserved. - B Pal; S Ikeda; H Kominami; Y Kera; B OhtaniJOURNAL OF CATALYSIS 217 1 152 - 159 2003年07月 [査読有り]
Photocatalytic (> 300 nm) conversion of L-(S)-lysine (L-Lys), in its neutralized aqueous solution, into L-pipecolinic acid (L-PCA) under deaerated conditions at 298 K was investigated in detail using suspended TiO2 powders (Degussa P-25, Ishihara ST-01, and HyCOM TiO2) loaded with platinum (Pt), rhodium (Rh), or palladium (Pd). A common feature of the results of experiments using a wide variety of metalloaded TiO2 photocatalysts is that the rate of PCA formation (r(PCA)) was greatly reduced when higher optical purity of PCA (OPPCA), i.e., enantio excess of the L-isomer of PCA, was obtained; higher rPCA was achieved by the use of Pt-loaded TiO2 powders, while these powders gave relatively low OPPCA. Selectivity of PCA yield (S-PCA), i.e., amount of PCA production based on L-Lys consumption, also tended to increase with decrease in OPPCA, giving a master curve in the plots of OPPCA versus S-PCA. Among the TiO2 powders used in this study, HyCOM TiO2 showed relatively high OPPCA and S-PCA but not optimum S-PCA and OPPCA simultaneously. In order to interpret such relations, the mechanism of stereoselective synthesis of the L-isomer of PCA (L-PCA) was investigated using isotope-labeled alpha-N-15-L-lysine with quantitative analysis of incorporation of N-15 in PCA and ammonia (NH3), a by-product. It was observed for several photocatalysts that the N-15 proportion (P-15) in PCA was almost equal to OPPCA, suggesting that oxidative cleavage by photogenerated positive holes of the epsilon-amino moiety of L-Lys gave optically pure L-PCA through retention of chirality at the alpha-carbon in the presumed intermediate, a cyclic Schiff base (alpha-CSB), which undergoes reduction by photoexcited electrons into PCA. From P-15 in NH3 and PCA, the selectivity of oxidation between alpha and epsilon-amino groups in L-Lys by photoexcited positive holes (h(+)) and the efficiency of reduction of alpha-CSB (produced via epsilon-amino group oxidation to give optically pure PCA) and epsilon-CSB (produced via alpha-amino group oxidation to give racemic PCA) by photoexcited electrons (e(-)) were calculated. The former was found to be independent of the kind of photocatalyst, especially the loaded metal, while the latter was influenced markedly only by the loaded metal. It was clarified that OPPCA and S-PCA obtained for various TiO2 powders used in the present study were strongly governed by the reduction stage, i.e., the efficiency of reduction of two types of CSB. When S-PCA was relatively low, photocatalysts, favoring the reduction of alpha-CSB rather than epsilon-CSB, gave higher OPPCA but lower S-PCA, since some epsilon-CSB remained unreduced to give racemic PCA. In contrast, at higher S-PCA, both CSBs were reduced nonselectively and OPPCA was found to be determined mainly by the selectivity in the oxidation stage. The relatively low yield of molecular hydrogen (H-2) when higher S-PCA was achieved is consistent with the mechanism in which H-2 liberation occurs instead of the reduction of CSBs by e(-). Thus, the general tendency of plots between OPPCA and S-PCA could be explained by the above-described redox-combined mechanism of photocatalysis. (C) 2003 Elsevier Science (USA). All rights reserved - S Ikeda; N Sugiyama; S Murakami; H Kominami; Y Kera; H Noguchi; K Uosaki; T Torimoto; B OhtaniPHYSICAL CHEMISTRY CHEMICAL PHYSICS 5 4 778 - 783 2003年 [査読有り]
The molar amounts of defective sites (M-d) in several titanium(IV) oxide (TiO2) powders were determined using photoinduced reactions of electron accumulation in deaerated aqueous solutions containing sacrificial hole scavengers and subsequent reduction of methylviologen to its cation radical. Measurements of pH dependence of typical anatase and rutile TiO2 powders showed that these defective sites were of electronic energy just below the conduction band edge of TiO2 in ranges of 0-0.35 V for anatase and 0-0.25 V for rutile, A linear relation of M-d with the rate constant of electron-hole recombination determined by femtosecond pump-probe diffuse reflection spectroscopy revealed that M-d could be a quantitative parameter of recombination between a photoexcited electron and a positive hole. The fact that there was no linear relation between M-d and the specific surface area suggests that the surface area was not directly reflected on M-d. A reciprocal correlation between photocatalytic activity for water oxidation in aqueous silver sulfate solution and M-d revealed that the rate of recombination is one of the predominant physical properties governing the activities of TiO2 powders in this reaction system. - Hiroshi Kominami; Shin-Ya Murakami; Jun-Ichi Kato; Yoshiya Kera; Bunsho OhtaniJournal of Physical Chemistry B 106 40 10501 - 10507 2002年10月 [査読有り]
Nanocrystalline anatase titanium(IV) oxide (TiO2) particles were synthesized by hydrothermal crystallization in organic media (HyCOM) followed by calcination at various temperatures up to 1273 K, and they were characterized by analysis of surface adsorption of the substrates, as well as by X-ray diffraction (XRD) and Brunauer-Emmet-Teller (BET) surface area measurements. These HyCOM TiO2 samples were used for three kinds of photocatalytic reactions: mineralization of acetic acid (AcOH) in aerated aqueous suspensions, dehydrogenation of 2-propanol (2-PrOH) by in situ platinized powders, and silver-metal deposition from silver ions (Ag+) in deaerated aqueous suspensions of bare TiO2 samples. Dependence of the photocatalytic activities on calcination temperature (Tc) and on the amount of adsorbed substrates in each reaction and correlations with the physical properties of HyCOM TiO2 were examined. In the case of mineralization of AcOH, the activitiy of each sample was almost proportional to the amount of surface-adsorbed AcOH in the dark, and the uncalcined (as-prepared) HyCOM TiO2 showed the highest activity, which was monotonically reduced with Tc, that is, with decrease in the amount of surface-adsorbed AcOH. On the other hand, in the case of silver-metal deposition, the photocatalytic activity was enhanced by calcination at higher temperature, despite the simultaneous decrease in the amount of surface-adsorbed Ag+ in the dark. Overall, the effects of calcination on the photocatalytic activities for several reaction systems strongly suggested that photocatalytic activity depends on two significant factors, adsorbability and recombination probability, corresponding to the specific surface area and crystallinity, respectively, and that the balance of these two factors determines the Tc dependence. - H Kominami; S Murakami; J Kato; Y Kera; B OhtaniJOURNAL OF PHYSICAL CHEMISTRY B 106 40 10501 - 10507 2002年10月 [査読有り]
Nanocrystalline anatase titanium(IV) oxide (TiO2) particles were synthesized by hydrothermal crystallization in organic media (HyCOM) followed by calcination at various temperatures up to 1273 K, and they were characterized by analysis of surface adsorption of the substrates, as well as by X-ray diffraction (XRD) and Brunauer-Emmet-Teller (BET) surface area measurements. These HyCOM TiO2 samples were used for three kinds of photocatalytic reactions: mineralization of acetic acid (AcOH) in aerated aqueous suspensions, dehydrogenation of 2-propanol (2-PrOH) by in situ platinized powders, and silver-metal deposition from silver ions (Ag+) in deaerated aqueous suspensions of bare TiO2 samples. Dependence of the photocatalytic activities on calcination temperature (T-c) and on the amount of adsorbed substrates in each reaction and correlations with the physical properties of HyCOM TiO2 were examined. In the case of mineralization, of AcOH, the activitiy of each sample was almost proportional to the amount of surface-adsorbed AcOH in the dark, and the uncalcined (as-prepared) HyCOM TiO2 showed the highest activity, which was monotonically reduced with T-c, that is, with decrease in the amount of surface-adsorbed AcOH. On the other hand, in the case of silver-metal deposition, the photocatalytic activity was enhanced by calcination at higher temperature, despite the simultaneous decrease in the amount of surface-adsorbed Ag+ in the dark. Overall, the effects of calcination on the photocatalytic activities for several reaction systems strongly suggested that photocatalytic activity depends on two significant factors, adsorbability and recombination probability, corresponding to the specific surface area and crystallinity, respectively, and that the balance of these two factors determines the T-c dependence. - H Kominami; H Inoue; S Konishi; Y KeraJOURNAL OF THE AMERICAN CERAMIC SOCIETY 85 9 2148 - 2150 2002年09月 [査読有り]
Perovskite-type lanthanum, iron oxide (LaFeO3) powders were synthesized by glycothermal reaction at 300degreesC of a precursor that had been previously prepared by solvothermal decomposition of a mixture of lanthanum(III) isopropoxide and iron(III) butoxide (or methoxide) in toluene. Direct glycothermal reaction of the mixture yielded no double oxide, indicating that preparation of the precursor was important for crystallization of LaFeO3 by the glycothermal method. - Yoshiya Kera; Atsushi Inagaki; Yuuji Mochizuki; Hiroshi Kominami; Shunro Yamaguchi; Junko IchiharaJournal of Molecular Catalysis A: Chemical 184 1-2 413 - 429 2002年06月Selective oxidation of 1-octen-3-ol to 1,2-epoxy-3-octanol and 1-octen-3-on with H2O2 catalyzed by {C5H5N(CH2)15 CH3}7 H2Ho(III)W10O36(cetyl-HoW10) in a CHCl3-H2O2 aqueous biphasic system, adapted as a test catalytic reaction, was kinetically investigated. The rate equations for the epoxide and enon formation were successfully described by equations: Repoxy = k1.epoxy[substrate][H2O2]1.6, and Renon = k1.enon[substrate][H2O2]-0.6. A working mechanism in which H2O2 molecule acts additionally to the substrate molecule which has been activated by interaction with a peroxo-species formed on the cetyl-LnW10 catalyst was proposed the H2O2 molecule promotes the epoxide formation, but suppresses the enon formation. 2-Hexen-1-ol was easily oxidized in the catalyst system, although 2-octene without a terminal OH-group was not. Moreover, the activity decreased drastically as the olefinic-group was far away from the terminal position. These results indicate that the terminal OH-group plays an important role in the activation of the substrates. The working state and the activity of catalyst were greatly influenced by the polarity of the solvent used. Especially, in the organic solvent-free system, the activity was very much promoted. Thus, cetyl-LnW10 is a suitable catalyst, from the environmental viewpoint. With the oxidations of both 1-octen-3-ol and 2-hexen-1-ol catalyzed by a series of Ln(III)W10 Ln: La-Er, the activities varied regularly according to the tendency of contraction of the Ln(III) ion. Those findings were interpreted reasonably by the mode of interaction and the working mechanism postulated, and clearly support the proposal that the 4fn-electrons of the Ln(III) ion participate in the catalysis. © 2002 Elsevier Science B.V. All rights reserved.
- Y Kera; A Inagaki; Y Mochizuki; H Kominami; S Yamaguchi; J IchiharaJOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL 184 1-2 413 - 429 2002年06月 [査読有り]
Selective oxidation of 1-octen-3-ol to 1,2-epoxy-3-octanol and 1-octen-3-on with H2O2 catalyzed by {C5H5N(CH2)(15)CH3}(7) H2Ho(III)W10O36(cetyl-HoW10) in a CHCl3-H2O2 aqueous biphasic system, adapted as a test catalytic reaction, was kinetically investigated. The rate equations for the epoxide and enon formation were successfully described by equations: R-epoxy = k(1.epoxy) [substrate] [H2O2](1.6), and R-enon = k(1.enon) [substrate] [H2O2](-0.6). A working mechanism in which H2O2 molecule acts additionally to the substrate molecule which has been activated by interaction with a peroxo-species formed on the cetyl-LnW10 catalyst was proposed the H2O2 molecule promotes the epoxide formation, but suppresses the enon formation. 2-Hexen-1-ol was easily oxidized in the catalyst system, although 2-octene without a terminal OH-group was not. Moreover, the activity decreased drastically as the olefinic-group was far away from the terminal position. These results indicate that the terminal OH-group plays an important role in the activation of the substrates. The working state and the activity of catalyst were greatly influenced by the polarity of the solvent used. Especially, in the organic solvent-free system, the activity was very much promoted. Thus, cetyl-LnW10 is a suitable catalyst, from the environmental viewpoint. With the oxidations of both 1-octen-3-ol and 2-hexen-1-ol catalyzed by a series of Ln(III)W10; Ln: La-Er, the activities varied regularly according to the tendency of contraction of the Ln(III) ion. Those findings were interpreted reasonably by the mode of interaction and the working mechanism postulated, and clearly support the proposal that the 4f(n)-electrons of the Ln(III) ion participate in the catalysis. (C) 2002 Elsevier Science B.V. All rights reserved. - H Kominami; M Itonaga; A Shinonaga; S Kagawa; S Konishi; Y KeraSCIENTIFIC BASES FOR THE PREPARATION OF HETEROGENEOUS CATALYSTS 143 1089 - 1096 2002年A titania (TiO2) sample with a large surface area (300 m(2)g(-1)) was chemically modified with 3-aminopropyltrimethoxysilane (APS) under a reflux of toluene. The thermal stability of the modified TiO2 (APS-TiO2) and the adsorptivity of metavanadate anion WOO on APS-TiO2 from an aqueous solution were investigated. Modification with APS suppressed crystal growth and transformation of anatase crystallite to rutile upon calcination, and the anatase phase was preserved even after calcination at 1000degreesC, while transformation to rutile in the unmodified TiO2 samples was observed at around 800degreesC. Since there was little crystal growth in APS-TiO2, it possessed a large surface area of 205 m(2)g(-1) after calcination at 700degreesC. The amount of VO3- adsorbed on APS-TiO2 was ca. 1.5-times larger than that on unmodified TiO2 due to a strong affinity caused by acid-base interaction between VO3- and the amino group of APS-TiO2. A supported V2O5 catalyst that was prepared by decomposition of a VO3--adsorbing APS-TiO2 sample had a large surface area despite the large V2O5 loading and exhibited higher activity than that of a catalyst prepared from an unmodified TiO2 sample.
- Hiroshi Kominami; Hiroaki Inoue; Shunsuke Konishi; Yoshiya KeraJournal of American Ceramic Society 85 9 2148 - 2150 2002年Perovskite-type lanthanum iron oxide (LaFeO3) was synthesized by glycothermal reaction of a lanthanum-iron precursor. The low-temperature synthesis of the oxide was done by a two-step solvothermal decomposition of starting materials in an inert organic solvent. The direct glycothermal reaction of the mixture yielded no double oxide, indicating that preparation of the precursor was important for crystallization of the oxide by the glycothermal method.
- H Kominami; S Murakami; M Kohno; Y Kera; K Okada; B OhtaniPHYSICAL CHEMISTRY CHEMICAL PHYSICS 3 18 4102 - 4106 2001年09月 [査読有り]
Nano-sized anatase titanium(IV) oxide (TiO2) particles, synthesized by hydrothermal crystallization in organic media (HyCOM), were calcined, platinized, and then used as a photocatalyst for stoichiometric decomposition of liquid water to H-2 and O-2. The Pt-loaded HyCOM TiO2 photocatalysts showed superior ability to decompose water into H-2 and O-2 in a molar ratio of 2:1 when they were suspended in water, and their photocatalytic activity depended strongly on the post-calcination temperature (T-c) as well as on the direction of photoirradiation. When the suspension was photoirradiated from the side of a cell, the activity increased with increasing T-c, and HyCOM TiO2 of high crystallinity prepared by calcination at 1273 K exhibited a rate of H-2 and O-2 libration three-times higher than that of Degussa P-25, one of the most active TiO(2)s. In a top-irradiation system, the activity was much higher than that of the side-irradiation system and increased with increasing T up to 973 K but then decreased, suggesting that the dispersion of TiO2 powders in water, in addition to the crystallinity, is an important factor for stoichiometric water decomposition in this irradiation system. - T Hirakawa; H Kominami; B Ohtani; Y NosakaJOURNAL OF PHYSICAL CHEMISTRY B 105 29 6993 - 6999 2001年07月 [査読有り]
The effect of calcination on photocatalytic activities was studied for highly crystalline TiO2 powder, which was synthesized by the method of hydrothermal crystallization in organic media (HyCOM). The productions Of O(2)(.-)and H2O2 under ambient condition were monitored by means of luminol chemiluminescence probing. The amount of produced O-2(.-) was decreased with the calcination at lower temperatures in parallel to the decrease of inner Ti3+ signal observed at 77 K by ESR spectroscopy. The formation route for H2O2 under aerated condition is mainly two-step O-2 reduction in the presence of oxidizable organic molecules such as luminol. Oxidization activity was significantly high when HyCOM-TiO2 was calcined at higher temperatures, 973-1173 K, as monitored by the amount of oxidized luminol. The observation in ESR measurements and other evidences indicated that the luminol is oxidized via hydroxyl radicals rather than the direct oxidation by photoinduced surface trapped holes. - H Kominami; M Kohno; Y Matsunaga; Y KeraJOURNAL OF THE AMERICAN CERAMIC SOCIETY 84 5 1178 - 1180 2001年05月 [査読有り]
Silica-modified titanium oxide (S-TIO2) powders that have an anatase structure were synthesized via the thermal decomposition of mixtures of titanium(IV) isopropoxide (TIP) and tetramethyl orthosilicate (TMOS) in toluene at 300 degreesC. These S-TIO2 materials had high rutile-transformation temperatures and maintained large surface areas at elevated temperatures (550 degrees -1000 degreesC). For example, the product that was prepared from a 9:1 TIP:TMOS mixture transformed to rutile at similar to 1100 degreesC and possessed a surface area of 160 m(2)/g, even after calcination at 800 degreesC for 1 h. - M Kohno; T Furushima; H Kominami; K Kagawa; Y KeraJOURNAL OF THE CERAMIC SOCIETY OF JAPAN 109 4 332 - 337 2001年04月 [査読有り]
Phosphorous-modified titanium oxide (P-TiO2's) nano-crystals in anatase form were synthesized by thermal decomposition of mixtures of titanium(IV) isopropoxide and ethyl phosphate in toluene in autoclave at 300 degreesC. These P-TiO2's had high rutile-transformation temperatures and maintained large specific surface areas even at elevated temperatures (550-800 degreesC). For example, the product prepared from a mixture of Ti/P molar ratio of 19 transformed into rutile at around 1000 degreesC, and it possessed a specific surface area of 54 m(2). g(-1), even after calcination at 800 degreesC for 1 h. - 河野 将明; 古島 利美; 古南 博; 香川 公司; 計良 善也日本化学会誌 3 179 - 182 2001年03月 [査読有り]
Alumina-modified titania sample (Al-TiO2) in anatase form was synthesized by thermal decomposition of mixtures of alkoxides of titanium and aluminum in toluene at 300 degreesC. The Al-TiO2 prepared from titanium(IV) isopropoxide (TIP) and aluminum ethoxide (Ti/Al mole ratio 9) transformed into rutile at around 1000 degreesC, and it possessed a surface area of 48 m(2) g(-1), even after calcination at 800 degreesC for 1 h. Another Al-TiO2 prepared from TIP and aluminum isopropoxide showed lesser thermal stability (39 m(2) g(-1) at 800 degreesC), suggesting that reactivity of aluminum alkoxides determines the thermal stability of produced Al-TiO2. - K Hashimoto; K Wasada; M Osaki; E Shono; K Adachi; N Toukai; H Kominami; Y KeraAPPLIED CATALYSIS B-ENVIRONMENTAL 30 3-4 429 - 436 2001年03月 [査読有り]
The photooxidation of NO with oxygen over Hycom TiO(2) and zeolite (A and Y form zeolite: TiO(2)-AZ and TiO(2)-YZ) composite catalysts was studied to remove NO, in the atmosphere. The photocatalytic oxidation activity of the titania in the composite catalyst in a proportion of AZ:TiO2 = 3:7 is about three times lager than that in the ban titania. The adsorption behaviors of NO and NO(2) for the bare titania sample obey Langmuir adsorption equations of NO and NO2, respectively. In the titania-zeolite composite catalysts, the adsorption data indicate the increase in the amount of NO adsorption on the TiO(2) phase and the decrease in the amount of NO(2) adsorption, compared with the bare titania. The acceleration of NO photooxidation rate, resulting from the increase in the amount of NO adsorbed and the decrease in the amount of NO(2) adsorbed, thus occurs on the TiO(2) phase. IR spectra, when irradiating the catalysts with UV, showed the immediate formation of nitrate and NO(2) species on the catalyst. The results lead to the conclusion that the zeolites promote the photocatalytic oxidation of NO over the titania. (C) 2001 Elsevier Science B.V. All rights reserved. - H Kominami; H Kumamoto; Y Kera; B OhtaniAPPLIED CATALYSIS B-ENVIRONMENTAL 30 3-4 329 - 335 2001年03月 [査読有り]
Titanium(IV) oxide (TiO(2)) powders synthesized by HyCOM (hydrothermal crystallization in organic media) method, which had been proved to exhibit ultra-high photocatalytic activity in several reaction systems, were used as starting material for fabrication of transparent TiO(2) thin films. HyCOM-TiO(2) powders were dispersed in aqueous sol of nitric acid to yield a TiO(2) sol stable for more than 90 days. Transparent TiO(2) thin films were successfully produced by dip-coating from the TiO(2) sol and used for photocatalytic decomposition of malachite green (MG) in an aqueous sol under aerated conditions. These films exhibited much higher rate of MO decomposition compared with those prepared from a commercially available TiO(2) sol developed for photocatalytic use (Ishihara STS-01), indicating that the excellent photocatalytic activity of original HyCOM-TiO(2) particles was preserved after immobilization on glass substrates by the present method. (C) 2001 Elsevier Science B.V. All rights reserved. - Y Kera; M Kamada; Y Hanada; H KominamiCOMPOSITE INTERFACES 8 2 109 - 119 2001年Several metal oxides were modified with gamma -anilinopropyltrimethoxysilane (AnPS). Variations in the physicochemical properties with the modification were investigated in detail. The adsorptivity of 12-tungstophosphate anion (PW12) was shown to be greatly improved in the carriers such as SiO2, TiO2, and Al2O3, which are porous and have a high surface area, but it was not increased in SnO2 and MgO, which have a small surface area and a high isoelectric point. With TiO2-carrier, quantitative studies on the adsorptivity were carried out further, and the interaction modes of PW12 on the AnPS-modified surfaces were discussed based on FT-IR and XPS analyses. The isotherm attained quite steeply to a monomolecular layer of PW12. The FT-IR bands ascribed to the anilino group deformed considerably and the N1s-peak in XPS shifted along with the PW12-adsorption. From the findings it was strongly suggested that PW12 was effectively fixed through an acid-base interaction on the AnPS-TiO2. Catalytic activity of PW12 fixed on AnPS-TiO2 for 2-propanol dehydration as a test reaction were examined; in the pretreatment at 300 degreesC the activity was limited to a low level but after the treatment at 450 degreesC it increased in proportion to the PW12-loading on the AnPS-TiO2 surfaces. Thus, it was inferred that PW12 was quite regularly dispersed over the modified surface. In conclusion, it is suggested that the modification technique is applicable to the preparation of a metal oxide-supported heteropolyacid catalyst.
- H Kominami; M Miyakawa; S Murakami; T Yasuda; M Kohno; S Onoue; Y Kera; B OhtaniPHYSICAL CHEMISTRY CHEMICAL PHYSICS 3 13 2697 - 2703 2001年 [査読有り]
Tantalum(v) oxide (Ta(2)O(5)) powders were synthesized by a solvothermal reaction of tantalum pentabutoxide (TPB) in toluene at 473-573 K in the presence of water. Ta(2)O(5) powder with a large surface area (> 200 g(-1)) was obtained at 473 and 523 K, and its X-ray diffraction patterns showed no clear peaks of crystallites, while crystalline beta -phase Ta(2)O(5) was obtained in the solvothermal process at 573 K. Post-calcination of the amorphous Ta(2)O(5) at 973 K also induced crystallization into the beta -phase. These amorphous and crystalline Ta(2)O(5) particles were platinized and then used for photocatalytic production of hydrogen from 2-propanol in aqueous solution under deaerated conditions by irradiation at a wavelength > 300 nm. As-synthesized amorphous and crystalline beta -phase samples exhibited negligible rates of hydrogen evolution, whereas crystalline beta -phase samples formed by post-calcination showed higher activity. Calcination of amorphous Ta(2)O(5) prepared by hydrolysis of TPB under atmospheric pressure also increased the rate, which is, however, ca. one third of that of Ta(2)O(5) obtained via the solvothermal route. Mineralization of acetic acid under aerated conditions was conducted as a test reaction for photocatalytic decomposition of organic compounds. Also, in this reaction system, bare (not platinized) solvothermal Ta(2)O(5) exhibited a higher rate of CO(2) formation than other Ta(2)O(5) samples. Photoirradiation at > 200 nm onto an aqueous 2-propanol suspension of platinized Ta(2)O(5) under deaerated conditions yielded hydrogen and acetone in an early stage, but CO(2) was liberated by prolonged irradiation, suggesting that decomposition of acetone to CO(2) proceeds even under deaerated conditions. - Abe, I; T Fukuhara; S Iwasaki; K Yasuda; K Nakagawa; Y Iwata; H Kominami; Y KeraCARBON 39 10 1485 - 1490 2001年 [査読有り]
In order to improve adsorption capacity per unit volume of carbonaceous adsorbent, a method that decreases macropore volume was investigated. Sapwood of Japanese cedar (C. japonica) was compressed under three different pressures, 1, 2 and 3x10(3) kgf/cm(2), and the compressed wood carbonized at 600 degreesC. The total volume (V-HG) of all pores in the range of 30 nm to 13 mum in diameter was decreased by two-thirds and apparent density increased threefold. However, at all three pressures, there was little change in total volume (V-N2) Of all pores of less than 30 nm in diameter or in specific surface area. Next, the compressed wood charcoal was crushed into pellets, inserted in a rotary kiln and activated with steam at 850 degreesC for various periods of time. Activation yield decreased linearly with increasing activation time, and showed a good linear relationship with iodine adsorption capacity. These relations were not affected by compression treatment. This result indicates that the formation of micropores by steam reaction is not affected by macropore volume. Activated carbon of double density can thus be produced by compression treatment. (C) 2001 Elsevier Science Ltd. All rights reserved. - H Kominami; K Oki; M Kohno; S Onoue; Y Kera; B OhtaniJOURNAL OF MATERIALS CHEMISTRY 11 2 604 - 609 2001年 [査読有り]
Niobium(v) oxide (Nb(2)O(5)) powders were synthesized by the solvothermal reaction of niobium(v) pentabutoxide (NPB) in toluene at 573 K in the absence or presence of water. Nb(2)O(5) powder with a large surface area (> 200 m(2) g(-1)) was obtained in the absence or presence of only a small amount of water. Its X-ray diffraction (XRD) pattern showed no clear peaks, and the Raman spectrum suggested formation of an Nb-O-Nb network, i.e., an amorphous Nb(2)O(5) structure without long-range order. A further increase in the amount of water used in the synthetic procedure induced crystallization of Nb(2)O(5) into the TT-phase. The surface area of the solvothermal products decreased with increases in the amount of water used, indicating growth of particles via water-induced extension of the Nb-O-Nb network. These Nb(2)O(5) particles were platinized and then used for photocatalytic dehydrogenation of methanol in an aqueous solution under deaerated conditions. The amorphous Nb(2)O(5) produced by the solvothermal process exhibited a rate of hydrogen evolution higher than that of the crystalline Nb(2)O(5) samples or other amorphous Nb(2)O(5) samples supplied as niobic acid (Nb(2)O(5). nH(2)O) and those prepared by hydrolysis of NPB under atmospheric conditions. Photocatalytic mineralization of acetic acid in aqueous solution was also conducted with bare Nb(2)O(5) under aerated conditions. The amorphous Nb(2)O(5) samples, especially catalysts prepared by the solvothermal method, exhibited a rate of carbon dioxide formation much higher than that of the crystalline Nb(2)O(5) samples also used in this photocatalytic reaction system. - H Kominami; A Furusho; S Murakami; H Inoue; Y Kera; B OhtaniCATALYSIS LETTERS 76 1-2 31 - 34 2001年 [査読有り]
Photocatalytic reduction of nitrate ion (NO,) in an aqueous suspension of metal-loaded titanium(IV) oxide (TiO2) was examined in the presence of oxalic acid (OA) as a hole scavenger. Conversion of NO3- into ammonia (NH3) competed with hydrogen liberation, and the NH3 production selectivity increased with the order of loaded metal, (Pt, Pd, Co) < (Ni, Au) < (Ag, Cu), which was attributable to the efficiency of reduction of protons by photogenerated electrons at the loaded metal, i.e., hydrogen overvoltage of the loaded metal. TiO2 powder loaded with Cu showed higher NH3 yield and selectivity as well as higher efficiency of OA consumption. TiO2 with in situ deposited Cu gave results comparable to those of a Cu pre-loaded photocatalyst. - H Kominami; K Yabutani; T Yamamoto; Y Kara; B OhtaniJOURNAL OF MATERIALS CHEMISTRY 11 12 3222 - 3227 2001年 [査読有り]
Tungsten(VI) oxide (WO(3)) powders of monoclinic crystal structure with high crystallinity have been synthesized by hydrothermal treatment (HTT), at 523 or 573 K, of aqueous tungstic acid (H(2)WO(4)) solutions prepared from sodium tungstate by ion-exchange (IE) with a proton-type resin. HTT and/or calcination of home-made and commercial H(2)WO(4) solids of tungstite structure also produced WO(3). These WO(3) powders with various physical properties were used as photocatalysts for evolution of oxygen (O(2)) from an aqueous silver sulfate solution, and the correlation between their physical properties and photocatalytic activity was examined. WO(3) powders of high crystallinity, e.g., IE-HTT-WO(3) synthesized at 573 K, gave the highest O(2) yield, suggesting that the crystallinity of WO(3) is a key factor in its high activity for this reaction system. Calcination at < 1073 K improved the crystallinity of some WO(3) powders, resulting in increases in their activities; however, calcination at a higher temperature reduced the activity, presumably due to formation of oxygen vacancies acting as recombination centers. - K Hashimoto; K Wasada; N Toukai; H Kominami; Y KeraJOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY 136 1-2 103 - 109 2000年08月 [査読有り]
The titania prepared by high-temperature hydrolysis of titanium alkoxides in a hydrocarbon solvent is highly active for the photocatalytic oxidation of NO to NO(2) and NO(3), The photocatalytic oxidation activity decreases with an increase in post-calcination temperature of the titania. The surface area and crystal size of the titania make some contributions to the photocatalytic oxidation activity. IR spectra show that ultraviolet (UV) irradiation of the titania promotes the formation of nitrate species. The data of ESR and IR lead to the conclusions that NO, when irradiating the titania with UV rays, reacts with O(2)(-) to form NO(2) and NO(3)(-), but the radicals generated as a result of secondary products of O(-) make no contribution to the photocatalytic oxidation. Tn addition, the concentration of free electron and O(2)(-) decreases significantly with an increase in post-calcination temperature of the titania. (C) 2000 Elsevier Science S.A. All rights reserved. - H Kominami; M Kohno; Y KeraJOURNAL OF MATERIALS CHEMISTRY 10 5 1151 - 1156 2000年05月 [査読有り]
Thermal treatment of oxobis(2,4-pentanedionato-O,O')titanium (TiO(acac)(2)) in ethylene glycol (EG) in the presence of sodium laurate and a small amount of water at 300 degrees C was examined. X-Ray diffraction, transmission electron microscopy and Raman spectroscopy revealed that microcrystalline brookite-type titanium(IV) oxide (TiO2) having an average size of 14 x 67 nm was formed and that this brookite sample was not contaminated with other TiO2 phases such as anatase and rutile. Sodium salts, water and TiO(acac)(2) as the titanium source were indispensable for the formation of brookite crystals and the use of EG as the reaction medium was essential to avoid contamination by other phases. This brookite TiO2 began to directly transform to the rutile phase on calcination at around 700 degrees C and completely converted at 900 degrees C. - S Kambe; K Murakoshi; T Kitamura; Y Wada; S Yanagida; H Kominami; Y KeraSOLAR ENERGY MATERIALS AND SOLAR CELLS 61 4 427 - 441 2000年04月 [査読有り]
Single-phase anatase nanocrystalline HyCOM-TiO2, (Hydrothermal Crystallization in Organic Media) to label this method was synthesized by high-temperature hydrolysis of titanium tetrabutoxide in toluene. The resulting HyCOM-TiO2, nanocrystalites were found to be covered by n-butoxide, yielding mesoporous, transparent anatase films with a narrow pore size distribution and good electron transport characteristic when sintered at 350-550 degrees C on optically transparent conducting glass. Dye-sensitized solar cells made of the Ru-dye-adsorbed mesoporous HyCOM films as photoanodes achieved better photo-energy conversion efficiency as compared to those prepared using commercially available Degussa P25 films. (C) 2000 Elsevier Science B.V. All rights reserved. - Hiroshi Kominami; Jun Ichi Kato; Shin Ya Murakami; Masaaki Kohno; Yoshiya Kera; Sei Ichi Nishimoto; Masashi Inoue; Tomoyuki Inui; Bunsho OhtaniStudies in Surface Science and Catalysis 130 B 1937 - 1942 2000年01月Thermal treatment of titanium(IV) alkoxide in organic solvent was examined. Titanium tert-butoxide was decomposed in inert organic solvents at 573 K to give microcrystalline anatase titanium(IV) oxide (TiO2) powders with crystallite size of ca. 9 nm and a surface area of >100 m2g-1. Primary and secondary alkoxides of titanium(IV), however, were not decomposed under the similar conditions, indicating that the thermal stability of C-O bonds in the alkoxides was a decisive factor for their decomposition. Reaction of titanium n-butoxide in alcohols yielded microcrystalline TiO2, suggesting that water generated from alcohols hydrolyzed the alkoxide. The as-prepared TiO2powders exhibited much higher rate of carbon dioxide formation than any other active photocatalysts such as Degussa P-25 and Ishihara ST-01 in the photocatalytic mineralization of acetic acid in aerated aqueous solutions. The higher activity of the present TiO2photocatalysts is attributed to their high crystallinity and large surface area. © 2000 Elsevier Science B.V. All rights reserved.
- M Inoue; T Nishikawa; H Kominami; T InuiJOURNAL OF MATERIALS SCIENCE 35 6 1541 - 1547 2000年 [査読有り]
The reaction of rare earth acetate hydrate in ethylene glycol at 300 degrees C yielded two novel crystalline products, one from La-Gd and the other from Tb-Lu and Y. IR and NMR spectra of these products suggested the presence of both acetate groups and ethylene glycol moieties, and it was concluded that these products are ethylene glycol complexes of rare earth acetate (hydroxide) oxide. On the other hand, the reaction of rare earth acetate hydrate in other glycols such as 1,3-propanediol and 1,4-butanediol yielded rare earth diacetate hydroxide, two morphs of rare earth acetate oxide and rare earth acetate dihydroxide, depending on the ionic size of rare earth element, but the glycol complexes were not formed. In all cases, acetate groups of rare earth acetate were not completely eliminated from the coordination sites of the rare earth element by the reaction in glycols but the reaction in ethylene glycol could liberate the acetate groups more easily than other glycols because of high coordination ability of ethylene glycol. (C) 2000 Kluwer Academic Publishers. - H Kominami; M Kohno; Y Takada; M Inoue; T Inui; Y KeraINDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH 38 10 3925 - 3931 1999年10月 [査読有り]
Nanosized titanium(IV) oxide in the anatase form was synthesized by hydrolysis of titanium(IV) alkoxide in toluene with water that was dissolved from the gas phase at high temperatures (150-300 degrees C). With elevation of the reaction temperature and an increase of the reaction time, the crystallite size of the anatase was,gradually increased from several to ca. 20 nm in the present reaction medium. Corresponding to the crystal growth, surface areas of the products were decreased while the rutile-transformation temperature became higher and the thermal stability was improved. For example, the product obtained by the reaction at 300 degrees C for 24 h possessed a surface area of 54 m(2) g(-1) even after calcination at 900 degrees C and began to transform to the rutile phase at around 1000 degrees C. - H Kominami; S Onoue; S Nonaka; Y KeraJOURNAL OF THE CERAMIC SOCIETY OF JAPAN 107 7 682 - 685 1999年07月 [査読有り]
Thermal treatment of lanthanum acethylacetonate dihydrate (EAA) in toluene in the presence of a small amount of water at 300 degrees C was examined and the product was characterized by ISC-NMR, FT-IR, thermal analysis and scanning electron microscope (SEM). Only acetoxy group (CH3COO-) was confirmed by the NMR measurement and hydroxyl group (-OH) was also observed in addition to the acetoxy group in the FTIR spectrum, indicating the LAA was hydrolyzed and the acetylacetonate group was decomposed under the present condition. From the results of thermal analysis and elemental analysis, the product was determined to be lanthanum diacetate hydroxide (La(CH3COO)(2)(OH)). SEM observation revealed that the product consisted of thin plate while LAA was bulky mass, suggesting that the product was formed via a dissolution-recrystallization mechanism. - H Kominami; J Kato; S Murakami; Y Kera; M Inoue; T Inui; B OhtaniJOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL 144 1 165 - 171 1999年07月 [査読有り]
Thermal treatment of titanium(IV) alkoxides dissolved in alcohols at temperature of 523-573 K under autogenous pressure yielded microcrystalline anatase titanium(IV) oxide (TiO2) with diameter of 11-31 nm and surface area of 42-138 m(2) g(-1). Similar treatment in hydrocarbons such as toluene gave no solid products, indicating that both hydrolysis of alkoxides with water liberated homogeneously from solvent alcohols and crystallization of anatase phase occurred simultaneously. These TiO2's were thermally stable, e.g., BET surface area of TiO2 synthesized at 573 K, 63 m(2) g(-1), was reduced only 30% (45 m(2) g(-1)) even by calcination at 973 K. Their photocatalytic activity was examined in mineralization of acetic acid in aqueous solutions under aerated conditions and dehydrogenation of 2-propanol under deaerated conditions; almost all the samples showed the activity more than twice higher than those of representative active photocatalysts, Degussa P-25 and Ishihara ST-01. The superior activity of the present TiO2 photocatalysts was attributable to compatibility of high crystallinity and large surface area owing to the newly developed synthetic procedure. (C) 1999 Elsevier Science B.V. All rights reserved. - H Kominami; S Onoue; K Matsuo; Y KeraJOURNAL OF THE AMERICAN CERAMIC SOCIETY 82 7 1937 - 1940 1999年07月 [査読有り]
Microcrystalline magnetite (Fe3O4) particles having diameters of 7-34 nm were synthesized by thermal treatment of iron(III) acetylacetonate in organic solvents at high temperatures (423-573 K) and under autogenous pressures of the solvents. When the treatment was conducted in l-propanol containing a small amount of water (1-3 vol%), nanosized hematite (alpha-Fe2O3) crystallized, which then was reduced to magnetite after a prolonged reaction time, indicating that a small amount of water in l-propanol drastically changed the reaction mechanism for the formation of iron oxides. - 古南 博; 尾上 誠一; 野中 聡美; 計良 善也ニホン セラミックス キョウカイ ガクジュツ ロンブンシ 107 1247 682 - 685 1999年 [査読有り]
- 安部 郁夫; 岩崎 訓; 岩田 良美; 古南 博; 計良 善也炭素 185 277 - 284 THE CARBON SOCIETY OF JAPAN 1998年12月Charcoals were prepared from Japanese cypress (C. obtusa) and Japanese oak (Q. mongolica) by threecarbonization methods, (a) in a nitrogen stream, (b) in an air stream, (c) in a container with cover. The relationshipbetween the carbonization methods and the adsorption properties of the charcoals was investigated and the followingresults were obtained.
Regardless of the carbonization method or the kind of wood used, the surface of charcoals prepared at lowtemperature was acidic and that of charcoals prepared at high temperature basic. The surface of charcoals preparedby method (c) showed the highest acidity.
When benzene, iodine and phenol were adsorbed for short periods onto charcoals prepared by methods (a) and (c), the charcoal prepared at 600°C had the largest mean pore size, and also showed the fastest adsorption rate and thehighest adsorption capacity. Of the charcoals prepared by method (b), the charcoal prepared at 900°C had the highestadsorption capacity. The charcoal prepared at 1000°C showed a decrease in adsorption capacity because of thermalshrinkage of the pores.
For all methods, adsorption capacity for water vapor was lowest in the charcoal prepared at 600°C. However, the amount of water vapor desorbed when humidity decreased was highest in the charcoal prepared at 600°C It was found that the 600°C charcoal is the best for use in humidity-control. - B Ohtani; H KominamiDENKI KAGAKU 66 11 1099 - 1110 1998年11月 [査読有り]
- H Kominami; K Matsuo; Y KeraJOURNAL OF THE AMERICAN CERAMIC SOCIETY 81 11 3035 - 3037 1998年11月 [査読有り]
Vanadyl(2+) hydrogen phosphate hemihydrate (VOHPO4. 0.5H(2)O, VHP) that had high crystallinity and showed a strong (001) peak in its X-ray diffractometry (XRD) pattern was synthesized via thermal treatment of a mixture of vanadyl(2+) acetylacetonate and triethyl phosphate at 200 degrees C in organic solvents that contained a small amount of water. Scanning electron microscopy observations revealed that the product consisted of thin plates (2-4 mu m wide and <0.5 mu m thick). When the reaction was conducted at 250 degrees C, a VHP sample was formed that exhibited stronger XRD peaks and had a plate width of >20 mu m. The present VHP sample was topotactically transformed to divanadyl(2+) pyrophosphate, which showed a strong (020) XRD peak, via thermal treatment in a nitrogen atmosphere at 500 degrees C. - B Ohtani; RM Bowman; DP Colombo; H Kominami; H Noguchi; K UosakiCHEMISTRY LETTERS 7 579 - 580 1998年07月 [査読有り]
Pump-probe diffuse reflectance measurements were carried out on particulate titanium(IV) oxide photocatalysts in the form of aqueous suspension and dry powder. A linear relation between second-order rate constants of electron-hole recombination for the suspension and powder systems was seen by analyses of decay profile of charge carriers. Presence of air gave negligible effect on the recombination kinetics, but loading of platinum (Pt) significantly reduced the rate constant. - M Inoue; T Nishikawa; H Otsu; H Kominami; T InuiJOURNAL OF THE AMERICAN CERAMIC SOCIETY 81 5 1173 - 1183 1998年05月 [査読有り]
Single-phase rare-earth gallium garnets were obtained by the reaction of stoichiometric mixtures of gallium acetyl-acetonate and rare-earth (Nd-Lu) acetates in 1,4-butanediol at 300 degrees C (glycothermal reaction). Particles of gadolinium gallium garnet (GGG) and other gallium garnets with rare-earth elements larger than Gd were spherical with diameters of 0.5-2 mu m, while particles of garnets with smaller rare-earth ions (Tb-Lu and Y) were much smaller (100-300 nm) with particle size distributed in a quite narrow range, TEM observation revealed that each particle was essentially a single crystal grown from one nucleus, but that defects frequently occurred during the crystal growth. Cerium and praseodymium gallium garnets were also formed when the reaction was carried out in the presence of GGG seed crystals. Hydrothermal reactions of the same starting materials under identical conditions yielded mixtures of gamma-Ga2O3 and the garnet phase. - H Kominami; S Murakami; Y Kera; B OhtaniCATALYSIS LETTERS 56 2-3 125 - 129 1998年 [査読有り]
Microcrystalline anatase titanium(IV) oxide (TiO2) particles were synthesized by hydrothermal crystallization in organic media (HyCOM) followed by calcination, and used in a photocatalytic reaction system of silver metal deposition. Upon elevating the post-calcination temperature, the photocatalytic activity was enhanced in spite of the simultaneous decrease in amount of surface-adsorbed Ag+. Comparison with the effect of calcination temperature on the other reaction systems revealed that the annealing effect became more significant with increasing number of electrons (or holes) required to complete the photocatalytic reaction process. - M Inoue; H Kominami; T InuiRESEARCH ON CHEMICAL INTERMEDIATES 24 5 571 - 579 1998年 [査読有り]
The reaction of zirconium n-propoxide in glycol at 300 degrees C yielded microcrystalline tetragonal zirconia (ZrO2). The crystallite size of the product depended on the carbon number of the glycol and increased in the following order (carbon number of glycol): 2 < 6 < 4, which suggested that the heterolytic cleavage of O-C bond of gylcoxide formed by transesterification is the prime factor for the formation of the product. In toluene, zirconium isopropoxide also gave tetragonal zirconia at 300 degrees C, and zirconium tert-butoxide decomposed at 200 degrees C yielding amorphous zirconia, while zirconium n-propoxide was stable at 300 degrees C. These results suggest that the reaction in toluene depends on the structure of the alkyl group of the alkoxides. Thus-obtained tetragonal zirconias maintained large surface areas (90-160 m(2)/g) even after calcination at 500 degrees C. - K Hashimoto; K Fukuhara; Y Fujiwara; H Kominami; H Mishima; Y KeraAPPLIED CATALYSIS A-GENERAL 165 1-2 451 - 459 1997年12月 [査読有り]
Titania highly dispersed on mordenite, TiO2/MZ, was prepared by hydrolysis of titanium tetraethoxide. The selective reduction of NOx over the catalyst was studied. The titania dispersion significantly enhances the reduction activity at temperature of 200 to 300 degrees C. Little change of the activity occurs at temperature of 400-600 degrees C. FTIR spectra indicate that the titania dispersion increases the amounts of the adsorption species of NO and (NO)(2). The adsorbed species of NO disappeared rapidly upon exposure to NH3 + O-2 at 300 degrees C, but (NO)(2) disappeared slowly. The main path of NO --> (NO)(ad) --> N-2 hence is proposed as the reduction mechanism of NO over the catalyst. The shifts in the binding energies of Ti2p and Ols for the TiO2/MZ and ESR data indicate that the supported titania interacts with the mordenite. XRD spectra support that the titania is highly dispersed in the mordenite. From the XPS peak intensities, the amount of titania in the outer surface regions is estimated to be only 1.3 mol% of total titania in the TiO2/MZ at the most. These findings support the incorporation of the most of titania into the mordenite cavities. Hence, the incorporation and high dispersion of titania accelerate the reduction. (C) 1997 Elsevier Science B.V. - HASHIMOTO K; MATZUO K; KOMINAMI H; KERA Y英国化学会児;ファラティー会報 93 20 3729 - 3732 1997年10月 [査読有り]
Mordenite catalysts incorporating CeO2 in their cavities have been prepared by the hydrolysis of Ce3+ ions in the cavities with moist ammonia gas, following calcination at 550 degrees C. The CeO2 mordenite zeolite (CeO2/MZ) is active for oxidation of p-xylene at 130 degrees C with oxygen, but CeO2 and mordenite are inactive even at 160 degrees C. X-Ray photoelectron spectroscopy (XPS) analyses indicate that the concentration of Ce in the mordenite surface regions is nearly equal to that in the bulk. The amount of saturated nitrogen adsorbed and the effective pore distribution decrease in CeO2/MZ has been compared with that for H+/MZ. The decreasing amount of adsorbed saturated nitrogen is nearly equal to the CeO2 volume in CeO2/MZ. Thus, the nitrogen adsorption isotherm for the CeO2/MZ indicates a decrease in the effective pore size due to the incorporation of CeO2 into the cavities. In addition, 1,3,5-trimethylbenzene is not oxidized at 160 degrees C over CeO2/MZ; the molecular size is larger than the diameter of the cavities. It has been concluded that CeO2 is incorporated into the mordenite cavities, and that this incorporation accelerates oxidation. - R Siozaki; A Inagaki; H Kominami; S Yamaguchi; J Ichihara; Y KeraJOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL 124 1 29 - 37 1997年09月 [査読有り]
Catalytic properties of holmiumdecatungstate modified with cetylpyridinium cations [Cetyl-Ho(III)W10] for H2O2-oxidations of alcohols and olefins were investigated under various organic solvents-aqueous H2O2 biphasic conditions, Generally, secondary alcohols and benzyl alcohols and internal olefins such as cyclooctene were efficiently catalyzed by Cetyl-Ho(III)W10, while primary alcohols and terminal olefins were almost not. The activity for 2-octanol grew much by using a smaller amount of nonpoler solvents such as CHCl3. Especially, in an organic solvent-free condition as a limited case, Cetyl-Ho(III)W10 was elucidated to be workable as a highly active but quite mild catalyst in comparison with the other heteropolyoxometalates well known. A schematical model on the working states was successfully presented. The present H2O2-Cetyl-Ho(III)W10 catalyst system will be insisted, finally, to be responsible for industrial oxidation processes such as being performed in a non-organic solvent system as environmental concerns. - R Shiozaki; A Inagaki; A Ozaki; H Kominami; S Yamaguchi; J Ichihara; Y KeraJOURNAL OF ALLOYS AND COMPOUNDS 261 1-2 132 - 139 1997年09月 [査読有り]
The catalytic activities of a series of lanthanide decatungstates [Ln(III)W10O369-; Ln(III)W10, Ln: La-Yb] modified with cetylpyridinium cations for H2O2-oxidation of both cyclooctene to epoxycyclooctane and benzyl alcohol to benzaldehyde were investigated in a CHCl3-aqueous H2O2 biphasic system. The activity for the former reaction decreased almost linearly along with the contraction of the Ln(III) ion in Ln(III)W10, and on the contrary, that for the latter tended to increase. The activity for the alcohol correlated, additionally, with the physicochemical parameters of Ln(III)10. A chemical effect of the 4f ''-electrons in the lanthanide(III) ion on such catalytic behavior will be discussed from a mechanistic viewpoint. (C) 1997 Elsevier Science S.A. - M Inoue; H Kominami; Y Kondo; T InuiCHEMISTRY OF MATERIALS 9 7 1614 - 1619 1997年07月 [査読有り]
The reaction of gibbsite (a modification of Al(OH)(3)) in glycol at elevated temperatures yielded the glycol derivative of boehmite together with a small amount of well-crystallized boehmite and a residue of unreacted gibbsite. The addition of water to the medium increased the reactivity of gibbsite and yielded a novel phase having a large basal spacing. Pure product of this phase was obtained by the reaction of microcrystalline gibbsite (<0.2 mu m) in 75 vol % ethylene glycol-water or in 95% 1,4-butanediol-water at 250 degrees C for 2 h. XRD analysis showed that the products had the boehmite layer structure and that the difference between the basal spacings of the present products and those of the corresponding glycol derivatives of boehmite obtained in pure glycols was about the same as the thickness of a boehmite layer. IR spectra of the present products exhibited a band due to hydrogen bonding between the boehmite layers. These results suggest that the products are the glycol derivatives of boehmite having the second stage structure. 2-Methoxyethyl and 2-(dimethylamino) ethyl derivatives of boehmite having the second stage structure were also formed by the similar reactions in 2-methoxyethanol and N,N-dimethylethanolamine, respectively. - Hiroshi Kominami; Satoko Kurimoto; Masahiro Kubota; Ryuji Shiozaki; Yoshiya KeraJournal of the Ceramic Society of Japan 105 707 - 709 1997年01月 [査読有り]
Peroxomolybdate (VI) anion with tartrate as a ligand ([Mo2O2(O2)4(C4H2O6)]4-, PMA) was intercalated into layers of Mg-Al type layered double hydroxide (LDH) by anion exchange reaction with terephthalate anion previously intercalated in the layers. The intercalation compounds were characterized by FT-IR, UV, X-ray diffraction and thermal analysis equipped with a mass spectroscope. Both in aqueous solution and in the LDH layers suspended in water, the peroxo groups (-O-O-) in PMA were released at 80°C to yield oxomolybdate (s) having a tartrate ligand, and the oxomolybdate (s) reverted to PMA by addition of hydrogen peroxide. - H Kominami; J Kato; Y Takada; Y Doushi; B Ohtani; S Nishimoto; M Inoue; T Inui; Y KeraCATALYSIS LETTERS 46 3-4 235 - 240 1997年 [査読有り]
Thermal decomposition of titanium(IV) tetra-tert-butoxide (TTB) in inert organic solvents at 573 K yielded microcrystalline anatase (titanium(IV) oxide, TiO2) powders with a crystallite size of ca. 9 mm and a surface area of > 100 m(2) g(-1). Primary and secondary alkoxides of titanium(IV), however, were not decomposed under similar conditions, indicating that the thermal stability of CO bonds in the alkoxides was a decisive factor for their decomposition. The TiO2 prepared from TTB by this manner was thermally stable upon calcination in air and retained high surface area of ca. 100 m(2) g(-1) even after calcination at 823 K. The as-prepared TiO2 powders, without calcination, exhibited much higher rate of carbon dioxide formation than any other active photocatalysts such as Degusssa P-25 and Ishihara ST-01 in the photocatalytic mineralization of acetic acid in aerated aqueous solutions. The higher activity of the present TiO2 photocatalysts is attributed to both high crystallinity and large surface of the present product. The calcination of the as-prepared TiO2 in air reduced the photocatalytic activity, but it was still higher than the other commercially available TiO2's. - M Kamada; H Kominami; Y KeraJOURNAL OF COLLOID AND INTERFACE SCIENCE 182 1 297 - 300 1996年09月 [査読有り]
Silica gel was chemically modified with (3-anilinopropyl) trimethoxysilane (AnPS) under a reflux of toluene (abbreviated as AnPS-SiO2). The adsorptivity of phosphododecatungstate anion (PW12) on AnPS-SiO2 from an aqueous solution was investigated quantitatively, The amounts adsorbed rose quite steeply to a coverage (theta) of 0.90 with increasing PW12 concentrations in solution, while they rose gradually to 0.33 on the unmodified SiO2 as a reference, It was verified, from the changes in bands due to the anilino group in FT-IR spectra and XP-spectra, that such a strong affinity was caused by acid-base interaction of PW12 with the amino group of AnPS-SiO2. (C) 1996 Academic Press, Inc. - KOMINAMI H; MATSUO K; KERA YJournal of American Ceramic Society 79 9 2506 - 2508 1996年09月 [査読有り]
Aluminum orthophosphate (AlPO4) samples were synthesized by high-temperature (200-300 degrees C) hydrolysis of a mixture of aluminum triisopropoxide and triethyl phosphate with a small amount of water dissolved in an organic solvent from the gas phase. At 250 degrees C, cristobalite-type AlPO4, which is the metastable phase at that temperature, was first crystallized from the amorphous phase and then transformed to stable quartz-type AlPO4 (berlinite) with a prolonged reaction time. When the amount of water charged into the system was increased, berlinite was formed immediately. The formation of the metastable phase could be attributed to the low solubility of AlPO4 in the organic solvent containing a small amount of water. - SHIOZAKI R; NISHIO E; MORIMOTO M; KOMINAMI H; MAEKAWA M; KERA YApplied Spectroscopy 50 4 541 - 544 1996年04月 [査読有り]
- M Kamada; H Kominami; Y KeraNIPPON KAGAKU KAISHI 3 300 - 302 1996年03月 [査読有り]
The oxidative dehydrogenation of isobutyric acid has been investigated using the heteropolymolybdophosphoric acid (HPNo) catalyst supported on the SiO2 modified with (3-anilinopropyl)trimethoxy-silane (AnPS) as silane coupling agent. HPMo fixed on the modified SiO2 indicated extremely higher conversion oi isobutyric acid and selectivity to methacrylic acid at 250-300 degrees C than the unmodified catalyst. - M Inoue; H Kominami; T InuiJOURNAL OF THE AMERICAN CERAMIC SOCIETY 79 3 793 - 795 1996年03月 [査読有り]
Thermal decomposition of a mixture of aluminum isopropoxide and tetraethoxysilane (Al/Si = 3) in toluene at 300 degrees C was examined. The reaction completely proceeded and yielded an amorphous product. The DTA profile of the product showed a sharp peak at approximate to 1000 degrees C which was associated with crystallization of mullite and a small amount of the spinel phase. The mullite prepared by calcination of the product at 1300 degrees C was composed of microcrystals having an average diameter of 30 nm and had a large surface area of 41 m(2)/g. - H Kominami; Y Takada; H Yamagiwa; Y Kera; M Inoue; T InuiJOURNAL OF MATERIALS SCIENCE LETTERS 15 3 197 - 200 1996年02月 [査読有り]
- R Shiozaki; A Inagaki; A Nishino; E Nishio; M Maekawa; H Kominami; Y KeraJOURNAL OF ALLOYS AND COMPOUNDS 234 2 193 - 198 1996年02月 [査読有り]
A series of sodium lanthanide decatungstates, Na(7)H(2)Ln(III)(W5O18)(2) . nH(2)O (Ln = La-Yb) was synthesized and characterized by spectroscopic analyses. The W-183-NMR chemical shifts for the W adjacent to Ln(III) correlated well. with the contact parameter in the lanthanide induced shifts, (Sz), which had been theorized by Golding. The FT-Raman stretching frequencies for the Ln-O-W bonding also correlated with the theoretical magnetic moments induced from the 4f(n) electrons in the lanthanide ions in addition to the ionic radii of Ln(III). A direct contribution of the 4f(n) electrons to the bonding interaction among Ln(III) and the oxotungstates is suggested. - M Inoue; H Otsu; H Kominami; T InuiINDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH 35 1 295 - 306 1996年01月 [査読有り]
Mixtures of aluminum isopropoxide and tetraethoxysilane in 1,4-butanediol were autoclaved at 300 degrees C for 2 h. The products were then calcined in air to yield silica-modified aluminas. These silica-modified aluminas had high alpha-alumina-transformation temperatures and maintained significantly large surface areas at elevated temperatures (1000-1300 degrees C). For example, the. product prepared from a mixture of Al/Si ratio 8 transformed into alpha-alumina at around 1500 degrees C, and it possessed a surface area of 55 m(2)/g, even after calcination at 1300 degrees C for 30 min. - Y Hanada; M Kamada; K Umemoto; H Kominami; Y KeraCATALYSIS LETTERS 37 3-4 229 - 233 1996年 [査読有り]
Phosphotetradecavanadate (PV14) was dispersed on a silica gel chemically modified with a silane coupling agent (AnPS-SiO2) by an equilibrium adsorption method. The PV14 contents approximately correlated with the V(TV) spin contents by ESR. PV14 dispersed on AnPS-SiO2 resulted in a quite high selectivity for formaldehyde such as 97% in methanol oxidation. - R Shiozaki; H Kominami; Y KeraSYNTHETIC COMMUNICATIONS 26 9 1663 - 1668 1996年 [査読有り]
Catalytic activity of Ce(IV) contained Weakley-type heteropolyoxometalate for the H2O2 oxidation of primary and secondary alcohols was evaluated for the first time. It was found that this catalyst exhibited a mild and thus guile selective activity, especially for benzylalcohols. - H Kominami; JI Kato; M Kohno; Y Kera; B OhtaniCHEMISTRY LETTERS 12 1051 - 1052 1996年 [査読有り]
Anatase titanium(IV) oxide synthesized by high-temperature hydrolysis of titanium(IV) tetrabutoxide in toluene was used for photocatalytic mineralization of acetic acid in aerated aqueous solutions, and showed the rate of carbon dioxide production much higher than representative active photocatalysts (Degussa P-25 and Ishihara ST-01). The catalyst of the larger crystallite size showed the higher activity, suggesting the importance of reduction of crystal defects. - INOUE M; OTSU H; KOMINAMI H; INUI TJournal of Materials Science Letters 14 18 1303 - 1305 1995年09月 [査読有り]
- H KOMINAMI; T MATSUURA; K IWAI; B OHTANI; S NISHIMOTO; Y KERACHEMISTRY LETTERS 8 693 - 694 1995年08月 [査読有り]
Microcrystalline titanium(IV) oxide (TiO2) powders having high surface area and high crystallinity were synthesized by high-temperature hydrolysis of titanium(IV) alkoxide in organic media. They were platinized and then used for photocatalytic dehydrogenation of 2-propanol in aqueous solution. The TiO2 catalysts exhibited much higher production rates of hydrogen and acetone than representative active TiO2 catalysts (P-25). - B OHTANI; K IWAI; H KOMINAMI; T MATSUURA; Y KERA; S NISHIMOTOCHEMICAL PHYSICS LETTERS 242 3 315 - 319 1995年08月 [査読有り]
Titanium(IV) oxide (TiO2) powder was prepared by the high-temperature hydrolysis of titanium(IV) tetrabutoxide in toluene as anatase crystallites of average diameter approximate to 15 nm. They were platinized by impregnation from aqueous chloroplatinic acid solution followed by hydrogen reduction. The catalyst was suspended in an aqueous L-lysine (Lys) solution and photoirradiated under argon at ambient temperature to obtain L-pipecolinic acid (PCA). Among several platinized commercial TiO2 powders, the present TiO2 showed the highest photocatalytic activity for both Lys consumption and PCA production. This result is attributed to both the higher activity owing to the larger surface area with lesser defects and the higher dispersion of platinum deposits acting as an efficient reduction site for a Schiff base intermediate into PCA. - M INOUE; H OTSU; H KOMINAMI; T INUIJOURNAL OF ALLOYS AND COMPOUNDS 226 1-2 146 - 151 1995年08月 [査読有り]
The reaction of a stoichiometric mixture of aluminium isopropoxide and yttrium acetate in 1,4-butanediol at 300 degrees C yielded crystalline yttrium aluminium garnet having an approximate particle size of 30 nm. No other phases were detected. Similarly, all the lanthanide elements from Nd to Lu gave essentially single-phase aluminium garnets. Samarium and europium aluminium garnets were also formed by this method, but the products contained corresponding lanthanide acetate oxide. The use of ethylene glycol instead of 1,4-butanediol afforded amorphous products. - M INOUE; H KOMINAMI; T INUIAPPLIED CATALYSIS A-GENERAL 121 1 L1 - L5 1995年01月 [査読有り]
Zirconium alkoxide which was thermally pre-treated in an inert organic solvent was hydrolyzed at 250-300-degrees-C with a limited amount of water dissolved in the solvent from the gas phase. This procedure afforded microcrystalline (5.8 nm) monoclinic zirconia which showed a high thermal stability and retained large surface areas of 162 and 76 m2/g even after calcination at 500 and 900-degrees-C, respectively. Thermal pre-treatment in the absence of water above 250-degrees-C was essential to avoid the formation of the tetragonal form. - M INOUE; H OTSU; H KOMONAMI; T NAKAMURA; T INUIJOURNAL OF MATERIALS SCIENCE LETTERS 13 11 787 - 789 1994年06月 [査読有り]
- 古南博; 沢井一喜; 人見充則; 安部郁夫; 計良善也日本化学会誌 6 582 - 584 1994年06月 [査読有り]
The reactivity of nitrogen monoxide (NO) with several kinds of commercial charcoals for the fuel use was examined at 300-500-degrees-C by using a pulse reaction technique (Table 1). Among the charcoals studied mitsumata (Edgeworthia) charcoal that contained the highest level of potassium exhibited the highest activity for reduction of NO into N2. The NO-C reaction was remarkably enhanced by Cu-Cr metal loaded on charcoals. Conversion of NO significantly increased in the presence of propene because, in addition to the NO-C reaction, the NO-propene reaction was promoted by potassium present in the charcoal (Table 2). - INOUE M; KOMINAMI H; INUI TJournal of Materials Science 29 9 2459 - 2466 1994年05月 [査読有り]
Aluminas were prepared by calcination of the products obtained by glycothermal treatment of aluminium alkoxides, and their pore structures investigated by means of the nitrogen adsorption technique and mercury porosimetry. The product had a honeycomb-like texture which developed well with increasing crystallite size of the product. The crystallite size of the product was in turn controlled by the glycol used, and increased in the following order (carbon number of glycol): 2 < 3 < 6 much less than 4. The honeycomb-like texture was preserved even after calcination. Because of the well-developed honeycomb-like texture, the alumina derived from the product obtained by the treatment of aluminium isopropoxide in 1,4-butanediol had quite large pore diameters (70 and 700 nm) and a large pore volume (2.4 cm3 g-1) with a sufficient surface area (184 M2 g-1). - H KOMINAMI; M INOUE; T INUICATALYSIS TODAY 16 3-4 309 - 317 1993年05月 [査読有り]
Thermal reaction of niobium alkoxide in organic media at 300-degrees-C yielded amorphous niobia, which maintained a surface area above 130 m2/g after calcination at 500-degrees-C. Niobium double oxides (LiNbO3, Zr6Nb2O17, CaNb2O6, CrNbO4, FeNbO4, ZnNb2O6 and R3NbO7 (R; rare earth)) were directly obtained by the reaction of niobium alkoxide with the corresponding metal alkoxide, acetate or acetylacetonate in 1,4-butanediol at 300-degrees-C. In some cases, amorphous product was obtained; however, double oxides (SrNb2O6, Co4Nb2O9, etc.) crystallized from the products at low temperatures. - M INOUE; H KOMINAMI; T INUIAPPLIED CATALYSIS A-GENERAL 97 2 L25 - L30 1993年04月 [査読有り]
Thermal treatment of zirconium n-propoxide in glycol at 300-degrees-C yielded microcrystalline tetragonal zirconia (ZrO2). The crystallite size of the product depended on the carbon number of the glycol and increased in the following order (carbon number of glycol): 2 < 6 < 4. Zirconium isopropoxide also decomposed in toluene giving tetragonal zirconia while zirconium n-propoxide did not, which suggests that the reaction in toluene depends on the structure of the alkyl group of the alkoxides. Tetragonal zirconias obtained in this manner maintained large surface areas (90-160 m2/g) even after calcination at 500-degrees-C. - H KOMINAMI; M INOUE; T INUINIPPON KAGAKU KAISHI 5,605 5 605 - 611 1993年 [査読有り]
Glycothermal treatments of hydrous acetates of lanthanide(Ln) elements in 1,4-butanediol at 300-degrees-C were examined. Each product was composed of one or a few phases, which varied systematically according to the atomic number of lanthanide elements and four phases having different structure were observed in total (Fig. 1 and Table 1). IR spectra (Fig. 2) and elemental and thermal analyses (Tables 2 and 5) confirmed that these phases were diacetate hydroxide (Ln(CH3COO)2(OH) ; phase A), novel acetate dihydroxide (Ln(CH3COO)(OH)2; phase C), and two modifications of acetate oxide (Ln(CH3COO)O ; phases B and D), one of which (phase D) has not been reported thus far. One of the modifications of acetate oxide (phase B) was also formed by thermal decomposition of the corresponding acetates while two acetate hydroxide salts and the other modification of acetate oxide (phase D) were not. Glycothermal reaction completely altered the morphology of particles ; the products were composed of thin plates (Fig. 5), while the original acetates were large (> 100 mum) crystals, which suggests that the product is formed via a dissolution-crystallization mechanism, lanthanide acetates being dissolved into a mixture of 1,4-butanediol and water originated from the crystallization water of the acetates. The modifications of acetate oxide thermally decomposed into lanthanide oxides uia carbonate oxide salts, while thermal decomposition of the two salts of acetate hydroxide led to dehydration into acetate oxide (phase B) which further decomposed into carbonate oxide and the oxide. - M INOUE; T NAKAMURA; H OTSU; H KOMINAMI; T INUINIPPON KAGAKU KAISHI 5,612 5 612 - 616 1993年 [査読有り]
Glycothermal reaction of acetate hydrates of lanthanide elements with triethyl phosphate in 1,4-butanediol at 315-degrees-C afforded corresponding lanthanide orthophosphates (LnPO4). The monoclinic modification of the phosphates was obtained from the acetates of La-Eu and the tetragonal one from Tb-Lu. Gadolinium acetate yielded a mixture of the tetragonal and monoclinic modifications ; the former form of GdPO4 had been synthesized only by calcination of the monoclinic form at about 1700-degrees-C. With the decrease in the reaction temperature, the proportion of the tetragonal modification decreased. The monoclinic modification of TbPO4 was also formed at the reaction temperature 225-degrees-C together with the tetragonal form. The products were comprised of micro crystals (15-40 nm). - M INOUE; H KOMINAMI; T INUIJOURNAL OF THE AMERICAN CERAMIC SOCIETY 75 9 2597 - 2598 1992年09月 [査読有り]
Thermal decomposition of aluminum sec-alkoxide in inert organic solvents at 300-degrees-C yielded a product composed of agglomerates of 4- to 20-nm particles having the chi-alumina structure. The chi-alumina was stable and maintained a surface area above 100 m2/g until its transformation at 1150-degrees-C to alpha-alumina. - M INOUE; H OTSU; H KOMINAMI; T INUIJOURNAL OF MATERIALS SCIENCE LETTERS 11 5 269 - 271 1992年03月 [査読有り]
- M INOUE; H KOMINAMI; T INUIJOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS 12 3331 - 3336 1991年12月 [査読有り]
The reaction of Al(OR)3 (R = Pr(i) or Bu(s)) with glycols was examined. The XRD patterns and IR spectra of the products suggest that they have the layer structure of boehmite with the glycol moiety incorporated between its layers through covalent bonding. The crystallite size of the product increased in the following order (carbon number of glycol): 2 < 3 < 6 < 4. When butane-1,4-diol was used the crystallite size of the product was the largest. This order suggests that heterolytic cleavage of C-O bonds is the prime factor controlling the growth of the boehmite structure. - M INOUE; H OTSU; H KOMINAMI; T INUINIPPON KAGAKU KAISHI 10,1358 10 1358 - 1360 1991年10月 [査読有り]
The crystallization of yttrium aluminum garnet (YAG) was investigated for the gelatinous product obtained by the reaction of yttrium acetate with aluminum isopropoxide in ethylene glycol at 280-degrees-C under spontaneous vapor pressure of the glycol (glycothermal method). Crystallization of YAG started at 880-degrees-C and completed at 1000-degrees-C. During these temperatures, a small amount of YA1O3 (hexagonal), was also detected. The crystallization temperature was as low as the reported temperatures for the products prepared by the alkoxide processes (Refs. 5 and 6). Therefore, glycothermal method provides a new route to prepare a gel for the preparation of mixed oxides. - M INOUE; H OTSU; H KOMINAMI; T INUINIPPON KAGAKU KAISHI 7 1036 - 1038 1991年07月 [査読有り]
Reaction of zinc acetate with aluminum isopropoxide (or gallium acetylacetonate) in 1,4-butanediol at 300-degrees-C under the spontaneous vapor pressure of the glycol (glycothermal reaction) yielded single-phase zinc aluminate, ZnAl2O4, (or zinc gallate, ZnGa2O4), having a spinel structure. The product had a high surface area, 290 m2/g, and the TEM observation showed the product was comprised of agglomerates of fine particles (diameter, ca. 5 nm). Thus-obtained zinc aluminate maintained its large surface area at relatively high temperatures (up to 700-degrees-C), and therefore, it has potential use for catalyst materials. - M INOUE; H OTSU; H KOMINAMI; T INUIJOURNAL OF THE AMERICAN CERAMIC SOCIETY 74 6 1452 - 1454 1991年06月 [査読有り]
The reaction of a stoichiometric mixture of aluminum isopropoxide and yttrium acetate in 1,4-butanediol at 300-degrees-C yielded crystalline yttrium aluminum garnet having an approximate particle size of 30 nm. No other phases were detected. The use of ethylene glycol in place of 1,4-butanediol afforded an amorphous product. - Masashi Inoue; Yasuhiko Kondo; Hiroshi Kominami; Hirokazu Tanino; Tomoyuki InuiNippon Kagaku Kaishi 1991 10 1339 - 1345 1991年 [査読有り]
Reaction of fine-particle gibbsite in glycol under the spontaneous vapor pressure of the glycol (glycothermal treatment) yields a glycol derivative of boehmite (Ref. 5). In this paper, the mechanisms of this reaction were explored. With an increase in the particle size of gibbsite, the yield of the boehmite derivative decreased and the yield of well-crystallized boehmite and the amount of unreacted gibbsite increased (Table 2). Autocatalytic nature was observed during the course of the reaction (Figs. 2 and 3). Addition of a small amount of water facilitated the formation of the glycol derivative of boehmite. A honeycomb like texture composed of plate-like crystals of the boehmite derivative was developed on the exterior of the particle when coarse gibbsite was used, whereas the glycothermal treatment of fine-particle gibbsite yielded bulky aggregates composed of honeycomb-like texture, combining the original particles (Figs. 4~6). These results suggest that aluminum hydroxide was dissolved into a mixture of glycol and water formed by partial dehydration of gibbsite followed by ligand exchange between the water molecule in the coordination site of aluminum and the glycol molecule and then crystallization of the glycol derivative of boehmite. Formation of boehmite was interpreted by the intra-particle hydrothermal reaction originally proposed by de Boer et al. for the formation of boehmite during the thermal dehydration of gibbsite. A chimney-like structure composed of honeycomb-like texture of the glycol derivative of boehmite was found in the product from coarse gibbsite (Fig. 7). This structure may have been formed when closed pore filled with water, where the intraparticle hydro-thermal reaction took place, reached to the surface of the particle and a large amount of water together with aluminum species was released from the pore into the bulk solvent. © 1991, The Chemical Society of Japan. All rights reserved. - Masashi Inoue; Hiroshi Kominami; Hiroyuki Otsu; Tomoyuki InuiNippon Kagaku Kaishi 1991 10 1254 - 1260 1991年 [査読有り]
Glycothermal treatment of lanthanum acetate sesquihydrate in 1, 4-butanediol at 300 °C was examined and found to afford lanthanum diacetate hydroxide (La(CH3COO)2(OH)), which was confirmed by 13C-NMR spectrum (Fig. 5), IR spectrum(Fig. 4), elemental analysis (Table 2), and thermal analysis. The product decomposed into lanthanum oxide according to the following sequence : La(CH3COO)2(OH) La(CH3COO)OLa2(CO3)O2 La2O3 diacetate hydroxide acetate oxide carbonate oxide oxide This thermal decomposition behavior was similar to that of lanthanum acetate which decomposed as follows : sesquihydrate monohydrateamorphous anhydrous acetate crystalline anhydrous acetateacetate oxidecarbonate oxideoxide Glycothermal reaction completely altered the morphology of the particles the product was composed of thin plates, while the starting crystals were bulky mass (Fig. 7). These observations indicate that the product is formed via a dissolution-crystallization mechanism, lanthanum acetate being dissolved into a mixture of 1,4-butanediol and water originated from the crystallization water of the sesquihydrate. Thermal decomposition into the acetate oxide preserved the morphology and both samples showed strong orientation in XRD pattern, suggesting that topotactic decompostion took place. © 1991, The Chemical Society of Japan. All rights reserved. - Masashi Inoue; Hiroshi Kominami; Hiroyuki Otsu; Tomoyuki InuiNippon Kagaku Kaishi 1991 10 1364 - 1366 1991年 [査読有り]
Reaction of oxobis(2,4-pentanedionato-O, O′) titanium (TiO(acac)2) or titanium isopro-poxide (TIP) in various organic media was examined and found to afford microcrystalline anatase. The product having the smallest crystallite size and the largest surface area was obtained by the reaction of TiO(acac)2 in toluene at 250 °C. The product preserved relatively high surface area even after calcination at 550 °C in an air flow. © 1991, The Chemical Society of Japan. All rights reserved. - Masashi Inoue; Hiroshi Kominami; Tomoyuki InuiJournal of the Chemical Society, Dalton Transactions 12 3331 - 3336 1991年 [査読有り]
The reaction of Al(OR)3 (R = Pri or Bus) with glycols was examined. The XRD patterns and IR spectra of the products suggest that they have the layer structure of boehmite with the glycol moiety incorporated between its layers through covalent bonding. The crystallite size of the product increased in the following order (carbon number of glycol): 2 < 3 < 6 < 4. When butane-1,4-diol was used the crystallite size of the product was the largest. This order suggests that heterolytic cleavage of C-O bonds is the ′ factor controlling the growth of the boehmite structure. - M INOUE; H KOMINAMI; T INUIJOURNAL OF THE AMERICAN CERAMIC SOCIETY 73 4 1100 - 1102 1990年04月 [査読有り]
書籍
- 光触媒作用：科学と技術古南 博; 計良 善也; 村上伸也; 大谷文章 (担当:共著範囲:)講談社 2002年10月第3章（Design, Preparation and Characterization of Highly Active Metal Oxide Photocatalysts）担当。酸化チタンを中心とする酸化物系の光触媒の調製法について概説した上で、高活性光触媒の設計、調製法およびその評価した結果について解説した。（英文）
- 有機シランで修飾されたチタニア担体を用いる酸化窒素の選択的触媒還元用のバナジウム系触媒の調製Studies in Surface Science and Catalysis 2002年
- Preparation of vanadium-based catalysts for selective catalytic reduction of nitrogen oxide using titnia supports chemically modified with organosilaneStudies in Surface Science and Catalysis 2002年
講演・口頭発表等
- 表面プラズモン共鳴誘起型光触媒の機能化 [通常講演]古南 博; 田中 淳皓; 橋本 圭司第32回光がかかわる触媒化学シンポジウム 2013年06月 東京工業大学 大岡山キャンパス 第32回光がかかわる触媒化学シンポジウム
近年、可視光を豊富に含む太陽光でも効率的に駆動する光触媒の開発が精力的に行われている。新たな可視光応答型光触媒として、金（Au）ナノ粒子の表面プラズモン共鳴（SPR）に誘起された触媒系が多く報告されている。Auナノ粒子は特定の波長の光を照射すると、大きさや形状により光吸収の強度や波長が変わる。通常、金属中の電子は光と相互作用しないが、金属表面やナノ微粒子中の電子はある条件で光と相互作用する。我々は、Au修飾酸化セリウムがSPRによる強い吸収を示し、この触媒系が可視光照射条件において、水中有機化合物の無機化反応や芳香族アルコールのアルデヒドへの選択酸化反応に活性を示すことを見い出した。本研究ではコロイド電着法により調製したAuと光析出法により調製した金属助触媒を共存させた酸化チタン系光触媒材料を調製し、これを用いた各種光触媒反応について検討した。 - 強い表面プラズモン共鳴を示す金ナノ粒子による多光子光触媒反応 [通常講演]古南 博; 田中 淳皓; 橋本 圭司第111回触媒討論会 2013年03月 関西大学 千里山キャンパス 第111回触媒討論会
近年、金ナノ粒子の表面プラズモン共鳴に誘起された可視光光触媒反応が数例報告されている。我々はコロイド電着法で金ナノ粒子を酸化チタン(IV)に担持した触媒を用いた各種有機酸の分解反応における光強度依存性を検討した。反応速度は光強度の1.2～1.8次に比例し、本系が多光子反応系であることが示唆された。ここでは、反応次数の影響と反応機構について報告する。 - 助触媒修飾金－酸化チタン(IV)による含塩素芳香族化合物の可視光誘起脱塩素反応 [通常講演]古南 博; 田中 淳皓; 橋本 圭司第93回日本化学会春季年会 2013年03月 立命館大学 びわこ・くさつキャンパス 第93回日本化学会春季年会
有機性廃棄物処理に関する様々な問題が生じている。特に含塩素芳香族化合物は人体に有害なものが多い。本研究は含塩素芳香族化合物を光触媒的に脱塩素化し、脱塩素芳香族化合物の回収・再利用することを目的とする。金ナノ粒子と金属助触媒を担持した酸化チタン(IV)を用いたクロロベンゼンの脱塩素反応を可視光照射下で行ったところ、化学量論量通りに反応が進行し、定量的にベンゼンが生成することを見いだした。 - 可視光応答型金属イオン修飾酸化チタン光触媒の特性評価 [通常講演]古南 博; 北野 翔; 橋本圭司東京大学 2012年12月 東京都目黒区 東京大学
- 表面プラズモン共鳴を利用した可視光応答型光触媒の調製とその評価 [通常講演]古南 博; 田中 淳皓; 橋本 圭司第31回固体・表面光化学討論会 2012年11月 大阪大学 第31回固体・表面光化学討論会
表面プラズモン共鳴誘 起型光触媒の新たな調製法と可視光光触媒反応について検討したので、その結果を報告する。 - Gold-Titanium(IV) Oxide Plasmonic Photocatalysts Prepared by Newly Developed Colloid-Photodeposition Method: Correlation Between Physical Properties and Photocatalytic Activities [通常講演]古南 博; 田中 淳皓; 橋本 圭司Gold2012 2012年09月 東京 Gold2012
In this study, we examined preparation of Au/TiO2 having a sharp size distribution of Au nanoparticles without agglomeration by using various methods. Here we report preparation of Au/TiO2 with various amounts of Au loading and correlation between the amount of Au, TiO2 properties and photocatalytic activity in mineralization of organic acids under irradiation of visible light. - 表面プラズモン共鳴誘起型光触媒による可視光水素生成反応の高速化 [通常講演]古南 博; 田中 淳皓; 橋本 圭司第110回触媒討論会 2012年09月 九州大学 第110回触媒討論会
近年、可視光応答性光触媒材料により、水素を生成する研究が精力的に行われている。我々は表面プラズモン共鳴誘起型光触媒による可視光水素生成に成功した。本研究では、この光触媒の高活性化について検討したので、その結果を報告する。 - Gold nanoparticle-modified cerium(IV) oxide inducing plasmonic selective oxidation of aromatic alcohols under irradiation of visible light [通常講演]古南 博; 田中 淳皓; 橋本 圭司Gold2012 2012年09月 東京 Gold2012
Gold nanoparticles supported on cerium(IV) oxide powder showing strong absorption at around 550 nm due to surface plasmon resonance oxidized aromatic alcohols to corresponding aldehydes almost quantitatively in an aqueous suspension under irradiation of green light. - Au/CeO2: A new-type photocatalyst for selective oxidation of aromatic alcohols to aldehydes working under visible light irradiation [通常講演]古南 博; 田中 淳皓; 橋本 圭司IPS-19 2012年08月 Pasadena, USA IPS-19
we found that a new material, i.e., Au/CeO2, exhibited a much higher level of activity than did other supported Au materials such as Au/TiO2 and Au/silica in photoinduced mineralization of organic acids in an aqueous suspension under irradiation of visible light matching the absorption due to SPR of Au. In this study, we report a new photocatalysis of Au/CeO2, i.e., almost stoichiometric oxidation of benzyl alcohols to benzaldehydes under irradiation of green light from an LED. A linear correlation was observed between the external surface area of Au nanoparticles loaded on CeO2 and the rate of photocatalytic benzaldehyde formation, indicating that the external surface area of Au loaded on CeO2 rather than the amount of Au loaded is an important factor controlling the photocatalytic activity of Au/CeO2 under visible light irradiation. - Selective photocatalytic oxidation of aromatic alcohols in aqueous suspension of Rh3+ modified TiO2 under visible light irradiation [通常講演]古南 博; 北野 翔; 田中淳皓; 橋本圭司2012年07月 Germany, Munich
- 水溶媒中における可視光応答型パラジウムイオン修飾酸化チタン光触媒によるベンジルアルコールの選択酸化 [通常講演]古南 博; 北野 翔; 田中淳皓; 橋本圭司慶應義塾大学 2012年03月 神奈川県横浜市 慶應義塾大学
Selective photocatalytic oxidation of alcohol to aldehyde was performed in aqueous suspension of titanium(IV) oxide (TiO2) modified with palladium ion (Pd2+) under visible light irradiation. In selective oxidation of benzyl alcohol to benzaldehyde as a model reaction, the high yield (96%) was obtained by the use of rutile-type TiO2. - 金ナノ粒子修飾酸化セリウム(IV)光触媒による 芳香族アルコールのアルデヒドへの選択酸化反応: 多段階光析出法の効果 [通常講演]古南 博; 田中淳皓; 橋本圭司触媒討論会 2012年03月 東京工業大学 大岡山キャンパス 触媒討論会
- 多段階光析出法による 金ナノ粒子修飾酸化チタン(IV)の調製と可視光照射下における光誘起水素生成 [通常講演]古南 博; 田中淳皓; 橋本圭司日本化学会 2012年03月 慶應義塾大学 日吉キャンパス、矢上キャンパス 日本化学会
- 可視光応答型酸化インジウム光触媒によるVOC分解とその反応解析 [通常講演]古南 博; 佐々木康友; 橋本圭司日本化学会 2012年03月 慶應義塾大学 日吉キャンパス、矢上キャンパス 日本化学会
近年、太陽光や室内の照明光に多く含まれる可視光に応答する光触媒の研究が行われている。当研究室では各種助触媒を修飾した酸化インジウム（In2O3）が可視光照射下、VOCの分解反応において高い光触媒活性を示すことを見出している1)。また、酸化銅(II)を担持した触媒は赤色光に応答し、青赤2色光の照射により、その分解活性が高くなることを報告している2)。そこで本研究では、本触媒系の助触媒効果および照射光の波長依存性、基質適合性について検討した。 - バイオマスを利用した光触媒水素生成反応に対する白金担持酸化チタンの物性の影響 [通常講演]古南 博; 橋本 圭司; 巻野 友唯光触媒シンポジウム光触媒反応の最近の展開 2012年 東京大学駒場リサーチキャンパス 光触媒シンポジウム光触媒反応の最近の展開
白金担持酸化チタン(IV)光触媒は、廃バイオマスのひとつであるグリセリンやグリシンから水素を生成できる。この反応系は、水の完全分解による水素生成に比べ熱力学的に有利で、しかも廃棄物を処理しながら水素を生成できる。しかしながら、この反応系の高活性化を試みた研究は少ない。我々はこの反応系において、酸化チタンの比表面積が水素生成活性に比例すること、また助触媒として安価なニッケルを担持した酸化チタンを用いても水素生成が可能であることを報告してきた。本研究では、さらなる物性－活性相関の調査を進め、触媒学会参照酸化チタン各種へのグリセリン及びグリシンの飽和吸着量が水素生成に与える影響を検討した。 - 酸化銅－酸化インジウム可視光応答型光触媒によるVOC分解反応 [通常講演]古南 博; 佐々木康友; 橋本圭司第18回光触媒シンポジウム 2011年12月 東京大学駒場リサーチキャンパス 第18回光触媒シンポジウム
近年、ホルムアルデヒドなどの揮発性有機化合物（VOC）による室内環境の汚染が問題となっている。光触媒の代表例である酸化チタン（TiO2）は高い活性を示し、化学的に安定である。しかし、TiO2の光触媒活性の発現には紫外光の照射が必要であり、可視光には応答しないため、室内の光源や空気清浄機の光源としてLED照明が普及すると紫外光応答型の光触媒は全く使用できなくなる。したがって、可視光のみが存在する条件において効率的に作用する可視光応答型光触媒の開発は重要であり、現在まで精力的に研究されている。一例として、可視光によりバンドギャップ励起が起こる酸化タングステン(VI)と助触媒を組み合わせた触媒系1-3)が報告されている。本研究室では、新規な可視光応答型光触媒として酸化銅(II)（CuO）を酸化インジウム（In2O3）に担持した酸化銅担持酸化インジウム（CuO-In2O3）が高い光触媒活性を示すことを報告した4)。本研究では、可視光照射下におけるVOC分解性能 - 可視光を利用した酸化銅-酸化インジウム複合光触媒による有機物分解反応 [通常講演]古南 博; 佐々木康友; 橋本圭司日本エネルギー学会関西支部 2011年12月 京都教育文化センター 日本エネルギー学会関西支部
光触媒の代表例である酸化チタン（TiO2）は有機化合物の分解に対して高い活性を示し、化学的に安定であるが、光触媒活性の発現には紫外光の照射が必要であり、可視光には応答しない。そのため、室内光源として紫外光を含まないLED照明が普及すると、TiO2の光触媒作用は全く利用できなくなる。したがって、可視光のみが存在する条件において効率的に作用する可視光応答型光触媒の開発は重要であり、現在まで精力的に研究されている。その一例として、可視光によりバンドギャップ励起が起こる酸化タングステン（VI）と助触媒を組み合わせた触媒系などが報告されている。本研究では、新規な可視光応答型光触媒として酸化銅（II）（CuO）を酸化インジウム（In2O3）に担持した酸化銅担持酸化インジウム（CuO-In2O3）が可視光照射下において、高い光触媒活性を示すことを見出し、本触媒の揮発性有機化合物の分解性能を評価した。 - 可視光応答型酸化タングステン(VI)光触媒の高活性化 [通常講演]古南 博; 阪口聡; 橋本圭司光触媒シンポジウム光触媒反応の最近の展開 2011年12月 東京大学駒場リサーチキャンパス 光触媒シンポジウム光触媒反応の最近の展開
揮発性有機化合物の無機化活性があるCu-WO3 と安価な吸着材のシリカを複合することでCu-WO3の使用量の削減および光触媒活性の向上に成功した。 - 酸化インジウム光触媒に対する酸化銅の担持効果 [通常講演]古南 博; 佐々木康友; 橋本圭司日本化学会 2011年11月 早稲田大学 日本化学会
代表的な光触媒である酸化チタンは紫外光照射下で高い活性を示す。しかし、屋内には紫外光がほとんど存在しないので、わずかな光触媒活性を示すだけである。そのため、太陽光や照明光に多く含まれる可視光に応答する光触媒の研究が多く行われている。近年、助触媒を担持した酸化タングステンが可視光照射下において高い光触媒活性を示すことが報告された。我々は、これまで報告例の少ない酸化インジウムに注目し、助触媒として酸化銅を組み合わせた酸化銅複合酸化インジウム光触媒が可視・紫外光照射下における揮発性有機化合物分解反応において、高い光触媒活性を示すことを報告した。本研究では、可視光照射下における揮発性有機化合物分解能の向上および長波長光である赤色光照射の影響を検討した。その結果、酸化インジウムが吸収する青色光に加えて、酸化銅のみが吸収する赤色光を照射することで、酸化銅複合酸化インジウム光触媒の光触媒活性が向上するこ - 可視光応答型酸化銅担持酸化インジウム光触媒における赤色光照射効果の解析 [通常講演]古南 博; 佐々木康友; 橋本圭司近畿化学協会触媒･表面部会 2011年11月 関西大学 近畿化学協会触媒･表面部会
酸化インジウムに酸化銅を複合することで、長波長の可視光である赤色光までも有効に利用できる新規可視光応答性光触媒の調製に成功した。 - 古南 博; 増田悠佑; 橋本圭司近畿化学協会触媒･表面部会 2011年11月 関西大学 近畿化学協会触媒･表面部会
酸化チタンへのパラジウム担持により1‐ブテンの異性化が室温で進行し、パラジウムの熱触媒作用を酸化チタンの励起電子と正孔が加速させる反応機構を明らかにした。 - 細管を反応場とする二液相分離型クネーフェナーゲル縮合反応 [通常講演]古南 博; 三桝忠祐; 橋本圭司日本化学会 2011年11月 早稲田大学 日本化学会
クネーフェナーゲル縮合反応は、有機合成において重要なC－C結合を形成させる反応である。近年、高効率化及び触媒のリサイクルの観点から、不均一系触媒やイオン性液体のような溶媒が使用されている。 本研究は、更なる高効率化および、簡便な触媒回収手段の構築のため、流通型チューブラーリアクター（TR）及び均一系触媒を用い、油相（基質）と触媒水相の2相分離系で反応を行った。この系は、反応後触媒が自発的分離するので、触媒と生成物の分離が容易であった。さらにTRを用いることで、従来のバッチ型リアクターに比べ高い生産性を示すと共に連続生産を可能になった。 - 流通型反応器を用いる触媒水溶液‐基質二液相反応 [通常講演]古南 博; 橋本圭司; 三桝忠祐近畿化学協会 2011年11月 関西大学 近畿化学協会
細管を反応場とする二液相分離型クネーフェナーゲル縮合反応を検討した。 - Selective photocatalytic oxidation of benzyl alcohol to benzaldehyde in aqueous suspension of metal ion-modified TiO2 under visible light irradiation [通常講演]古南 博; 北野翔; 田中淳皓; 橋本圭司2011年11月 兵庫県姫路市Aldehyde compounds play an important role in the synthesis of drugs, fragrances and flavor, and they are generally synthesized through selective oxidation of alcohols. Titanium(IV) oxide (TiO2) is known as an excellent photocatalyst. Recently, selective oxidation of benzyl alcohols to benzaldehydes in aqueous suspension of TiO2 under UV light irradiation was reported.1 We have previously reported metal ion-modified TiO2 (Mn+/ TiO2) photocatalysts responding to visible light.2 In this study, we carried out selective oxidation of benzyl alcohol to benzaldehyde as a model reaction in aqueous suspension of Mn+/ TiO2 under visible light irradiation.
- 銅修飾銀ナノ粒子の表面プラズモン共鳴およびその光触媒機能 [通常講演]古南 博; 平郡陽子; 田中淳皓; 橋本圭司近畿化学協会 2011年11月 大阪 近畿化学協会
銀（Ag）を担持した酸化チタンの光触媒活性を青色LEDの可視光照射下で水中シュウ酸ナトリウムの分解で評価した。Ag担持酸化チタンは可視光応答性を示し、水中有機酸の分解に有効であることがわかった。少量の銅（Cu）をAg担持酸化チタンに導入することによりAgの表面プラズモン共鳴が増強され、光触媒活性が向上した。またそれとともに触媒劣化の防止効果も得られた。この触媒状態の観察も本研究では行った。 - 流通型光触媒反応器を用いるアルコールの酸化的脱水素 [通常講演]古南 博; 宮本歩実; 橋本圭司触媒表面化学研究発表会 2011年10月 関西大学 触媒表面化学研究発表会
酸化チタンに代表される光触媒は紫外光を照射することで、強い酸化力を示し、有害物質の分解や除去などの完全酸化分解に主に使用されている。 当研究室では触媒を固定化させ、基質を流通させる流通型光触媒反応器を用いて、メタノールから有用なギ酸メチルを高選択的に、かつ一段階で生成する特異な反応を報告している。 本研究では同様に流通型光触媒反応器を用い、基質をエタノールに変更し、既存の報告例と同様に一段階で酢酸エチルが生成するのかを確認した。 本反応を検討したところ、酢酸エチルは生成せず、アセトアルデヒドが高選択的に生成することを見出した。このアセトアルデヒドをより高選択的に生成する触媒と反応条件の検討を行った。 - バイオマスを利用した光触媒水素生成反応に対する白金担持酸化チタンの物性の影響 [通常講演]古南 博; 橋本 圭司; 巻野 友唯触媒表面化学研究発表会 2011年10月 関西大学 触媒表面化学研究発表会
白金担持酸化チタン(IV)光触媒は、廃バイオマスのひとつであるグリセリンやグリシンから水素を生成できる。この反応系は、水の完全分解による水素生成に比べ熱力学的に有利で、しかも廃棄物を処理しながら水素を生成できる。しかしながら、この反応系の高活性化を試みた研究は少ない。本研究では、さらなる物性－活性相関の調査を進め、触媒学会参照酸化チタン各種へのグリセリン及びグリシンの飽和吸着量が水素生成に与える影響を検討した。 - 古南 博; 阪口聡; 橋本圭司触媒表面化学研究発表会 2011年10月 関西大学 触媒表面化学研究発表会
ソルボサーマル法によって調製した酸化タングステンと吸着剤を複合させることで劇的な光触媒活性の向上に成功した。 - 可視光応答性ロジウムイオン修飾酸化チタン光触媒の電荷移動特性 [通常講演]古南 博; 北野翔; 橋本圭司; 多田弘明; 村上直也; 横野照尚; 朝倉博行; 寺村謙太郎; 田中庸裕; 野坂芳雄2011年10月 名古屋大学酸化チタンは優れた光触媒であり、揮発性有機化合物の酸化に用いられているが、その駆動は紫外光照射下に限られる。光触媒の使用を考えると屋内環境でも多量に存在する、可視光を利用できる可視光応答型光触媒の開発が期待されている。近年、われわれは新たな可視光応答型光触媒としてロジウムイオンを修飾した酸化チタンが可視光応答性を示し、VOCの分解に優れた活性を示すことを報告した。また、修飾したRh3+が可視光応答に起因する酸化機能を有する他に、酸素の還元機能を有している可能性が示唆された。しかし、その駆動メカニズムは未だに不明な部分が多い。今回は、可視光照射下におけるRh/TiO2の駆動メカニズムと電子移動を解析するため、各種測定・キャラクタリゼーションを行った。
- 可視光応答型酸化銅担持酸化インジウム光触媒に対する赤色光照射の効果 [通常講演]古南 博; 佐々木康友; 橋本圭司触媒学会 2011年09月 北見工業大学 触媒学会
可視光に応答する酸化銅（CuO）担持酸化インジウム（In2O3）光触媒のさらなる活性向上を検討した． さらに，In2O3が吸収する青色光に加えて，赤色光を照射することにより，その光触媒活性が向上した． - 古南 博; 増田悠佑; 橋本圭司触媒学会 2011年09月 北見工業大学 触媒学会
酸化チタンへのパラジウム担持により1‐ブテンの異性化が室温で進行し、パラジウムの熱触媒作用を酸化チタンの励起電子と正孔が加速させることを明らかにした。 - 古南 博; 阪口聡; 橋本圭司触媒討論会 2011年09月 北見工業大学 触媒討論会
Cu-WO3 に対し、各種吸着剤を組み合せ、そのWO3 削減効果と活性向上に成功した。 - 可視光応答型金属イオン修飾酸化チタン光触媒によるベンジルアルコールの選択酸化 [通常講演]古南 博; 北野翔; 田中淳皓; 橋本圭司触媒学会 2011年09月 北見工業大学 触媒学会
ロジウムイオン（Rh3+）を修飾した様々な酸化チタン（Rh3+/TiO2）を用い，水溶媒，酸素雰囲気，可視光照射下において，ベンジルアルコールからベンズアルデヒドへの選択酸化反応を行った．どのTiO2を用いても比較的高い収率が得られた．収率はTiO2の物性に依存し，反応速度はRh3+の担持量に依存した．Rh3+/F-6を用いた時，収率は97.0%に達した． - 酸化物担持銀ナノ粒子の表面プラズモン共鳴特性と光触媒機能 [通常講演]古南 博; 平郡陽子; 田中淳皓; 橋本圭司触媒学会 2011年09月 北海道北見市 触媒学会
酸化物に担持した金（Au）や銀（Ag）などのナノ粒子は、表面プラズモン共鳴（SPR）に基づき発色する。当研究室では、AuのSPRを利用したAu担持酸化セリウムが可視光照射下で水中有機酸の分解において高い光触媒活性を示すことを報告している。ここでAu担持酸化チタンの光触媒作用の報告例は数例あるが，A担持酸化チタンのものはほとんどないため本研究ではAgのSPRを利用した可視光応答型光触媒の検討を行った。光析出法を用いて酸化チタンにAgを担持し、可視光照射下で光触媒活性評価を行い、また銅（Cu）を光析出法で修飾した試料についても同様に光触媒反応を行った。Ag担持酸化チタンは可視光照射下で水中の有機酸を分解し、少量のCuを修飾することでAg担持酸化チタンの変性を抑制し、光触媒活性を向上させる効果が得られた。 - Photocatalytic Chemoselective Reduction of Nitrobenzenes to Anilines [通常講演]古南 博; 今村和也; 橋本圭司EuropaCat X 2011年08月 The University of Glasgow EuropaCat X
- ANALYSIS OF PHOTOCATALYTIC PROPERTIES OF RHODIUM ION-MODIFIED TITANIUM(IV) OXIDE [通常講演]古南 博; 北野翔; 橋本圭司; 多田弘明; 横野照尚; 村上直也2011年08月 グラスゴー大学Titanium(IV) oxide (TiO2) is known as highly active photocatalyst under irradiation of UV light. However, there was only a small amount of UV light at indoor environment. It is expeted to create photocatalysts responding to visible light. Recently, we eported a new TiO2-based photocatalyst responding to visible light, rhodium ion (Rh3+)-modified TiO2, and the photocatalytic activity of that photocatalyst was dependent on the physical properties of TiO2. In addition, the results that Rh3+ modified on TiO2 is a candidate as an inorganic photosensitizer and a cocatalyst for multi-electron reduction of O2 were observed. In this study, the function of Rh3+ was investigated in detail by electrochemical and photoacoustic spectroscopic (PAS) measurement.
- Photocatalytic Redox Reaction of Nitro Aromatics and Secondly Alcohols to Amino Aromatics and Ketones in Suspension of Titanium(IV) Oxide [通常講演]古南 博; 今村和也; 岩崎伸一; 前田剛志; 橋本圭司CIMTEC 2010 2011年06月 Montecatini Terme, Tuscany, Italy CIMTEC 2010
- 酸化チタン(IV)光触媒を用いた芳香族ニトロ化合物の化学選択的還元反応 [通常講演]古南 博; 今村和也; 橋本圭司光がかかわる触媒化学シンポジウム 2011年06月 東京工業大学（大岡山キャンパス） 光がかかわる触媒化学シンポジウム
- 酸化チタン(IV)光触媒によるニトロベンゼン類からアニリン類への化学選択的還元反応における基質拡張性 [通常講演]古南 博; 今村和也; 橋本圭司第44回錯体化学若手の会・近畿地区勉強会 2011年06月 第44回錯体化学若手の会・近畿地区勉強会
- Electron transfer properties of rhodium ion-modified titanium(IV) oxide photocatalyst [通常講演]古南 博; 北野翔; 橋本圭司触媒学会 2011年06月 大阪府立大学 触媒学会
Titanium(IV) oxide (TiO2) photocatalyst has been used for removal of harmful compounds in air and water. However, TiO2 was driven under only UV light irradiation. It is demanded to prepare photocatalysts responding to visible light for indoor application. Recently, we reported that rhodium ion modified TiO2 responded to visible light and showed high photocatalytic activity for decomposition of VOC under visible light irradiation. But, it is not enough to analyze the mechanism of the phohocatalyst. In this work, we investigated the charge transfer in Rh3+-TiO2 and the status of rhodium ion on TiO2 by various measurements. - 修飾酸化インジウムによる 可視・紫外光光触媒反応 [通常講演]古南 博; 佐々木康友; 橋本圭司日本化学会 2011年03月 神奈川大学 横浜キャンパス 日本化学会
代表的な光触媒である酸化チタン（TiO2）は紫外光照射下で高い活性を示す。しかし、屋内には紫外光がほとんど存在しないので、わずかな光触媒活性を示すだけである。そのため、太陽光や照明光に多く含まれる可視光に応答する光触媒の研究が多く行われている。近年、助触媒を担持した酸化タングステンが可視光照射下において高い光触媒活性を示すことが報告された。本研究ではこれまで報告例のない酸化インジウム（In2O3）に注目し、可視・紫外光照射下における光触媒特性を詳細に評価した。その結果、各種助触媒を修飾することにより、VOCの分解反応においてIn2O3はWO3を超える光触媒活性を示すことが明らかになった。 - 酸化チタン(IV)光触媒を用いた化学選択的還元反応による芳香族アミンの合成 [通常講演]古南 博; 今村和也; 橋本圭司第107回触媒討論会 2011年03月 首都大学東京（南大沢キャンパス） 第107回触媒討論会
- 金属担持酸化チタンを用いたバイオマスからの光触媒的水素生成反応における物性依存性 [通常講演]古南 博; 橋本 圭司; 巻野 友唯日本化学会 2011年03月 神奈川大学横浜キャンパス 日本化学会
白金担持酸化チタン光触媒は、バイオマスのひとつであるグリセリンから水素を生成できる。しかしながら、この反応系においてその高活性化を試みた研究は少ない。我々はこの反応系において、酸化チタンの比表面積が水素生成活性に比例することを報告してきた。本研究では、さらなる物性－活性相関の調査を進め、水素生成に与える各種酸化チタンへのグリセリンの吸着量の影響を検討した。 - 古南 博; 濱田裕弥; 福康二郎; 橋本圭司日本化学会 2011年03月 神奈川大学横浜キャンパス 日本化学会
懸濁擬固定床反応器を用いて、ブラックライトの紫外光照射下、パラジウムまたはロジウム担持酸化チタンによるクロロベンゼンの脱塩素化を行った結果、ロジウム担時酸化チタンがパラジウム担時酸化チタンに匹敵する活性を有すること、酸化チタン上の金属ロジウムが酸化物を形成しているため、定常活性に達するまでパラジウムよりも時間がかかることを見出した。 - 金属担持酸化チタンによるブテンの光触媒的異性化反応 [通常講演]古南 博; 増田悠佑; 橋本圭司日本化学会 2011年03月 神奈川大学横浜キャンパス 日本化学会
酸化チタンへの金属担持により1‐ブテンの異性化が進行し、熱力学的平衡値以上の高選択率でシス‐2‐ブテンが生成することを見い出した。 - 可視光応答性助触媒－酸化タングステン光触媒の高活性化 [通常講演]古南 博; 阪口聡; 橋本圭司日本化学会 2011年03月 神奈川大学横浜キャンパス 日本化学会
酸化タングステン(VI)に安全・安価であるシリカを複合させることにより、酸化タングステン(VI)使用量の削減と高活性化に成功した。 - 細管を反応場とする二液相分離系のエステル交換反応 [通常講演]古南 博; 三桝忠祐; 橋本圭司日本化学会 2011年03月 神奈川大学横浜キャンパス 日本化学会
近年、バイオディーゼル燃料の製造は、塩基触媒の存在下、油脂とアルコールのエステル交換反応によって行われている。しかし、反応後に生成物と触媒の分離が必要であり、多くの廃液が発生するという課題がある。本研究では、チューブリアクターで酸触媒の存在下、メタノールとラウリン酸エチルのエステル交換反応を行ったところ、ラウリン酸メチルと触媒を自動的に分離して効率的に得ることを見出したので報告する。 - 可視光応答型光触媒によるベンジルアルコールの選択酸化 [通常講演]古南 博; 北野翔; 田中淳皓; 橋本圭司触媒学会 2011年03月 首都大学東京 触媒学会
アナタース型酸化チタン（A-TiO2）およびルチル型酸化チタン（R-TiO2）に様々な金属イオンを修飾し，可視光応答性を付与した．酸素雰囲気，可視光照射下においてベンジルアルコールからベンズアルデヒドの選択酸化反応を行ったところ，ルテニウムイオン修飾A-TiO2，パラジウムイオン修飾R-TiO2，ロジウムイオン修飾TiO2が高い選択酸化能を示した。特にルテニウムイオン修飾A-TiO2は反応速度が大きく、97%の収率を達成した。 - 酸化物担持銀ナノ粒子の調製とその表面プラズモン共鳴特性 [通常講演]古南 博; 平郡陽子; 田中淳皓; 橋本圭司電気化学会 2011年03月 神奈川県横浜市 電気化学会
金や銀（Ag）などの貴金属ナノ粒子は、表面プラズモン共鳴（SPR）による吸収が起こり、特定の色を発色し、また金属酸化物にこれらの貴金属ナノ粒子を担持すると、SPRに基づく色が発色する。SPRは、金属ナノ粒子のサイズや形状、粒子間距離によって変化することがわかっている。酸化チタン担持Agナノ粒子では、懸濁液での調製・乾燥後に粒子が凝集することによる色変化が見られるが、この変化を詳細に検討された報告は少ない。そこで本研究では、調製時の条件の違いがAgナノ粒子のSPRに与える影響について検討した。光析出法によって代表的な市販品酸化チタン（P 25）にAgを担持すると、Agナノ粒子の表面プラズモン共鳴に由来する光吸収が発現した。クエン酸を用いて調製した試料を乾燥させても、吸収にほぼ変化はなかったが、クエン酸ナトリウムを用いて調製した試料ではAgの400 nm付近の吸収ピークが500 nm以上まで長波長シフトすることがわかった。 - 酸化チタン(IV)光触媒によるニトロベンゼン類からアニリン類への [通常講演]古南 博; 今村和也; 橋本圭司触媒学会西日本地区第１回触媒科学研究発表会 2011年01月 大阪大学（吹田キャンパス） 触媒学会西日本地区第１回触媒科学研究発表会
- Photocatalytic properties of rhodium ion-modified titanium oxide [通常講演]古南 博; 北野翔; 橋本圭司触媒学会 2011年01月 大阪大学 触媒学会
Titanium(IV) oxide (TiO2) photocatalyst has been used for removal of harmful compounds in air and water. However, TiO2 was driven under only UV light irradiation. Thus, synthesis of photocatalyst responding to visible light is attractive. Previously, we have reported that Rhodium chloride fixed TiO2 showed excellent photocatalytic activity for oxidative removal of nitrogen oxide under visible light irradiation. In this work, we modified TiO2 with rhodium ion for responding to visible light, and used for decomposition of VOC. On the other hand, photocatalytic reaction involves various processes such as photoabsorption on TiO2. Photocatalytic activity is the result of a combination of these processes. Thus, controlling the physical properties was equal to controlling the photocatalytic activities. We tried to prepare highly active photocatalyst responding to visible light in this study. - ロジウムイオン－酸化チタン可視光応答型光触媒によるVOC分解 [通常講演]古南 博; 北野翔; 橋本圭司光触媒研究会 2010年12月 神奈川県川崎市 光触媒研究会
近年、室内におけるホルムアルデヒドなどの揮発性有機化合物（VOC）の有害性が問題となっている。光触媒を代表する酸化チタン（TiO2）は、有機化合物の分解に対して優れた光触媒活性を有し、環境浄化など様々な分野で応用されている。しかし、TiO2は紫外光照射下でしか駆動せず、紫外光がほとんど存在しない室内空間においての使用は大きく制限されるため、可視光を利用できる光触媒の研究が盛んに行われている。本研究室では新規な可視光応答型光触媒としてロジウムイオン修飾TiO2を開発した。この触媒を用いて可視光照射下において様々な気相有機物の分解反応を行うとともに、様々な測定法により触媒特性を解析した。 - 可視光応答性ロジウムイオン修飾酸化チタン光触媒における担体物性の影響と電子移動の解析 [通常講演]古南 博; 北野翔; 橋本圭司2010年11月 兵庫県神戸市近年、シックハウス症候群の原因となるホルムアルデヒドなどの揮発性有機化合物（VOC）の人体に対する有害性が問題視されている。光触媒を代表する酸化チタン（TiO2）は、高い光触媒活性を有し、空気浄化など様々な分野で応用されている。しかし、TiO2光触媒が駆動するためにはそのバンドギャップ以上のエネルギーを持つ紫外光の照射が必要であり、紫外光がほとんど存在しない室内空間においての使用は大きく制限される。そのため可視光照射下において効果的に駆動する可視光応答性光触媒の研究が盛んに行われている。本研究室では新規な可視光応答型光触媒としてロジウムイオン修飾TiO2を開発した1), 2) 。可視光照射下において様々な気相VOCの分解反応を行い触媒活性に対するTiO2担体物性の影響を調べるとともに、様々な測定法により可視光照射下における触媒中での電子移動を解析した。
- 酸化チタン(IV)光触媒を利用するニトロ基の化学選択的還元反応 [通常講演]古南 博; 今村和也; 橋本圭司第3回触媒表面化学研究発表会 2010年10月 関西大学（千里山キャンパス） 第3回触媒表面化学研究発表会
- 金属担持酸化チタンを用いたグリセリンからの光触媒的水素生成 [通常講演]古南 博; 橋本 圭司; 巻野 友唯近畿化学協会 2010年10月 関西大学 近畿化学協会
白金担持酸化チタン光触媒は、バイオマスのひとつであるグリセリンから水素を生成できることを報告している。しかしながら、この反応系に用いる触媒において、高価かつ有用である白金以外の担持金属を検討した研究例は少ない。本研究では、担持金属に安価なニッケルを用いて、ニッケル担持酸化チタンを調製し、この触媒における光触媒活性を検討した。その結果、ニッケル担持酸化チタンを用いるグリセリンからの効率的水素生成に成功した。 - 古南 博; 濱田裕弥; 福康二郎; 橋本圭司近畿化学協会 2010年10月 関西大学 近畿化学協会
光触媒粒子を懸濁状態で反応器内に留められる懸濁擬固定床反応器を用いてクロロベンゼンの連続的脱塩素化を試みた結果、使用する酸化チタン担体にST-01を用いた時はP 25を用いた時よりも約2倍の活性を示した。また、ブラックライト4本で紫外光を照射した場合、ベンゼンへの転化率90％以上の定常活性を維持できることを見出した。 - 古南 博; 平郡陽子; 橋本圭司近畿化学協会 2010年10月 大阪 近畿化学協会
酸化チタンの主な結晶系のうち、ブルカイト型酸化チタンは単一相での合成が難しく、研究例が少ない。本研究では、既定の方法でチタン錯体から単一なブルカイト型酸化チタンを合成した。この酸化チタンにロジウムイオンを担持した後、青色LEDの可視光照射下、気相中のアセトン分解反応によって光触媒活性評価を行った。ロジウムイオンを担持することでブルカイト型酸化チタンは可視光活性を示し、ロジウムイオンの担持量が影響していることが分かった。 - 酸化チタン(IV)光触媒によるニトロ化合物の化学選択的還元 [通常講演]古南 博; 今村和也; 岩崎伸一; 前田剛志; 橋本圭司2010年光化学討論会 2010年09月 千葉大学（西千葉キャンパス） 2010年光化学討論会
- 芳香族ニトロ化合物の光触媒還元反応による芳香族アミンのグリーン合成 [通常講演]古南 博; 今村和也; 岩崎伸一; 前田剛志; 橋本圭司第104回触媒討論会 2010年09月 第104回触媒討論会
正孔捕捉剤共存下，酸化チタン（TiO2）光触媒による芳香族ニトロ化合物の還元反応を検討した．ニトロベンゼン（NB）， m-ニトロベンゼンスルホン酸（NBS），p-ニトロアニリン（NAN）は水中で，各種重要な芳香族アミンへと選択的に還元された．また，NBおよびNANは少量の酸素共存下で収率が改善された． - 流通型反応器を用いたエタノールの光触媒的選択酸化 [通常講演]古南 博; 宮本歩実; 橋本圭司触媒学会 2010年09月 山梨大学 触媒学会
酸化チタン光触媒は紫外光照射下で有害な有機化合物を完全に酸化する。一方、当研究室では流通型光触媒反応器を設計し、これを用いてメタノールの酸化反応を行うと、ギ酸メチルが高選択的に生成することを報告している。本研究では、この流通型反応器を用いてエタノールの光触媒選択酸化を検討したところ、選択的にアセトアルデヒドが生成すること、およびそれが金属イオンの担持で加速されることを見出した。 - ニッケル担持酸化チタンを用いたバイオマスからの光触媒的水素生成 [通常講演]古南 博; 橋本 圭司; 巻野 友唯触媒学会 2010年09月 山梨大学 触媒学会
白金担持酸化チタン光触媒は、バイオマスのひとつであるグリセリンから水素を生成できることを報告している。しかしながら、この反応系に用いる触媒において、高価かつ有用である白金以外の担持金属を検討した研究例は少ない。本研究では、担持金属に安価なニッケルを用いて、ニッケル担持酸化チタンを調製し、この触媒における光触媒活性を検討した。その結果、ニッケル担持酸化チタンを用いるグリセリンからの効率的水素生成に成功した。 - 古南 博; 濱田裕弥; 福康二郎; 橋本圭司触媒学会 2010年09月 山梨大学 触媒学会
光触媒粒子を懸濁状態で反応器内に留められる懸濁擬固定床反応器を用いてクロロベンゼンの脱塩素化を試みた結果、乾燥させた光触媒粒子を直接反応器に充填するよりも、溶媒に分散させたものを充填した方が分散性に優れ、高い反応効率が得られる事を見出した。また、定常状態に達した後は高い反応効率を維持できることを見出した。 - ロジウムイオン－酸化チタン可視光応答型光触媒における電子移動の解析 [通常講演]古南 博; 北野翔; 橋本圭司触媒学会 2010年09月 山梨大学 触媒学会
酸化チタン（TiO2）に光析出法を用いて白金を担持し，吸着法を用いて1.0 wt%のロジウムイオンを修飾した．気相濃度一定型アセトン分解反応を用いて活性評価を行ったところ，0.002 wt%の白金を担持した触媒が最も高活性を示し，それ以上の担持量では活性は減少した．これは，白金担持により電荷分離が向上すると同時に，白金の遮蔽効果で光吸収が少なくなったためと考えられる． - 古南 博; 平郡陽子; 橋本圭司触媒学会 2010年09月 山梨県甲府市 触媒学会
酸化チタンの主な結晶系のうち、ブルカイト型酸化チタンは単一相での合成が難しく、研究例が少ない。本研究では、既定の方法でチタン錯体から単一なブルカイト型酸化チタンを合成した。この酸化チタンにロジウムイオンを担持した後、青色LEDの可視光照射下、気相中のアセトン分解反応を行った。ロジウムイオン担持ブルカイト型酸化チタンは可視光応答性を示し、市販品で高活性なP 25やST-01にロジウムイオンを担持したものよりも高い光触媒活性を示すことがわかった。 - Selection of Hole Scavenger for Green Photocatalytic Reduction of Nitro Aromatics [通常講演]古南 博; 今村和也; 岩崎伸一; 前田剛志; 橋本圭司TOCAT6 2010年07月 札幌コンベンションセンター TOCAT6
- Metal ion-loaded titanium oxide photocatalysts responding to visible light: Correlation between physical properties and photocatalytic activity [通常講演]古南 博; 北野翔; 橋本圭司2010年07月 北海道札幌市Titanium(IV) oxide (TiO2) powder modified with metal ions degraded volatile organic compounds (VOC) under irradiation of visible light. Photocatalytic activity was dependent of physical properties of the TiO2 powders. Rhodium(III) ion-modified TiO2 samples exhibited a remarkable higher photocatalytic activity in mineralization of VOC than cupper(II) ion-modified TiO2 samples. Cupper(II) ion-modified rutile-type TiO2 samples showed higher activity than cupper(II) ion-modified anatase-type TiO2 samples. The absorption of Rh3+/TiO2 samples was proportional to the amount of Rh3+; however, Rh3+/HyCOM-TiO2 samples exhibited the mountain-type tendency in the photocatalytic activity toward the photoabsorption, indicating that excess loading of Rh3+ caused the decrease in photocatalytic activity.
- Photocatalytic Redox Reaction of Nitro Aromatics and Secondly Alcohols to Amino Aromatics and Ketones in Suspension of Titanium(IV) Oxide [通常講演]古南 博; 今村和也; 岩崎伸一; 前田剛志; 橋本圭司CIMTEC 2010 2010年06月 Montecatini Terme, Tuscany, Italy CIMTEC 2010
- Correlation between physical properties and photocatalytic activities of metal ion-titanium oxide responding to visible light [通常講演]古南 博; 北野翔; 橋本圭司2010年06月 イタリアIt is known that titanium(IV) oxide (TiO2) works as a semiconductor photocatalyst that is able to decompose harmful organic compounds. Since TiO2 only absorbs UV light, TiO2 does not exhibit photocatalytic activity under irradiation of visible light. Therefore, development of a photocatalyst responding to visible light is very important for effective utilization of solar energy. We have reported that TiO2 modified with RhCl3 showed excellent photocatalytic activity for oxidative removal of NOx under irradiation of visible light. In this study, TiO2 samples having various physical properties were prepared using solvothermal method and modified with Cu2+ or Rh3+. Then, correlation between physical properties and photocatalytic activities in degradation of VOC under irradiation of visible light was investigated.
- バイオマスからの光触媒的水素生成における物性－活性相関 [通常講演]古南 博; 橋本 圭司; 巻野 友唯日本化学会 2010年03月 近畿大学 日本化学会
白金担持酸化チタン光触媒は、バイオマスのひとつであるグリセリンから水素を生成できる。しかしながら、この反応系においてその高活性化を試みた研究は少ない。本研究では、酸化チタンの物性を変えて、酸化チタンの物性が水素生成活性に与える影響について検討した。その結果、酸化チタンの比表面積に比例して、光触媒活性が増加することを見出し、高活性光触媒の指針を得た。 - ロジウムイオン－酸化チタン可視光応答型光触媒の特性解析と高活性化 [通常講演]古南 博; 北野翔; 橋本圭司日本化学会 2010年03月 近畿大学 日本化学会
Titanium(IV) oxide (TiO2) powder having various physical properties and modified with metal ions degraded volatile organic compounds under visible light irradiation. Especially, TiO2 powder modified with rhodium(III) ion exhibited a remarkable high photocatalytic activity. In this study, the Rh3+-TiO2 samples were characterized and the physical properties of TiO2 were optimized. The optimized Rh3+-TiO2 sample showed higher photocatalytic activities than available visible-light-responding photocatalysts under irradiation of vis and UV-vis light. - 金属イオン－酸化チタン可視光応答型光触媒の特性に対する酸化チタン物性の影響 [通常講演]古南 博; 北野翔; 橋本圭司光触媒研究会 2009年12月 神奈川県川崎市 光触媒研究会
居住空間における空気汚染が社会問題になっており、特に揮発性有機化学種の有害性が指摘されている。その有力な改善策として光触媒が注目されている。光触媒を代表する酸化チタン（TiO2）は優れた触媒能を有し、安定、無害、安価などの理由から様々な用途で用いられているが、紫外光でのみ駆動し、居住空間に豊富に存在する可視光を利用できない。近年、銅イオンを修飾したルチル型TiO2が気相有機物の分解反応に優れた可視光活性を示すことが報告された1）。我々は、塩化ロジウムを修飾したTiO2が可視光照射下において窒素酸化物の酸化的除去反応に極めて高い活性を示すことを報告している2）。本研究では、銅イオンまたはロジウムイオンをTiO2に修飾し、可視光照射下において、様々な気相有機物の分解反応を行った。金属イオン－酸化チタンの光触媒特性とTiO2物性の相関を解析した。 - Photocatalytic Reduction of Nitrobenzene In Water-Nitrobenzene Biphasic Suspending System [通常講演]古南 博; 今村和也; 岩崎伸一; 前田剛志; 橋本圭司The 12th Japan-Korea Symposim on Catalysis 2009年10月 秋田キャッスルホテル The 12th Japan-Korea Symposim on Catalysis
- 酸化チタン(IV)光触媒による芳香族ニトロ化合物と二級アルコールの酸化還元的物質変換 [通常講演]古南 博; 今村和也; 岩崎伸一; 前田剛志; 橋本圭司第2回触媒表面化学研究発表会 2009年10月 関西大学（千里山キャンパス） 第2回触媒表面化学研究発表会
- 可視光応答型金属イオン修飾酸化チタンによる揮発性有機物分解 [通常講演]古南 博; 北野翔; 橋本圭司近畿化学協会 2009年10月 関西大学 近畿化学協会
光触媒の代表である酸化チタン（TiO2）は紫外光でのみ駆動するが、豊富に存在する可視光を利用できない。そこで本研究では、銅およびロジウムの金属イオンを用いて、酸化チタンに修飾し、可視光照射下において揮発性有機物分解反応を試みた。 - ロジウムイオン－金属酸化物系材料による可視光光触媒反応 [通常講演]古南 博; 北野翔; 橋本圭司触媒学会 2009年09月 宮崎大学 触媒学会
各種n型半導体にロジウムイオン（Rh3+）を修飾した。その光触媒特性を、簡便かつ定量的に比較できる気相濃度一定型アセトン分解反応を用いて評価した。Rh3+修飾n型半導体において、Rh3+修飾酸化チタン（TiO2）が最も高活性を示した。また、ルチル型TiO2を焼成して物性を変化させて、その影響を検討したところ、光触媒活性は大きく変化し、比表面積55-75 m2g-1のときに最高活性を示した。 - PHOTOCATALYTIC REDUCTION OF NITRO AROMATICS TO AMINO AROMATICS IN AQUEOUS SUSPENSIONS OF TITANIUM(IV) OXIDE PARTICLES IN THE PRESENCE OF OXALIC ACID [通常講演]古南 博; 今村和也; 岩崎伸一; 前田剛志; 橋本圭司; 大谷文章XXIV International Conference on Photochemistry 2009年07月 Toledo, Spain XXIV International Conference on Photochemistry
We applied photocatalytic reduction of NB to aniline (AN) for synthesis of various amino aromatics, for example, p-nitroaniline (p-NAN) to p-phenylendiamine (p-PDA) and m-nitrobenzene sulfonic acid (m-NBS) to m-aminobenzen sulfonic acid (m-ABS). We also reported effects of O2 on photocatalytic reduction of those nitro aromatics. - 芳香族ニトロ化合物の光触媒還元：水相-油相分離系の利用 [通常講演]古南 博; 今村和也; 岩崎伸一; 前田剛志; 橋本圭司日本化学会第89回春季年会 2009年03月 日本大学（船橋キャンパス） 日本化学会第89回春季年会
- 可視光応答型光触媒Rh3+/TiO2による揮発性有機化合物の分解 [通常講演]古南 博; 北野翔; 西村愛子; 角田勝俊; 橋本圭司日本化学会 2009年03月 日本大学 日本化学会
Titanium(IV) oxide powders were modified with metal ions and were used for Photo- catalytic decomposition of volatile organic compounds under visible light irradiation. Photo- catalytic activity was dependent of physical properties of the titanium(IV) oxide powders. Especially, titanium(IV) oxide powders modified with rhodium(III) ion exhibited excellent photocatalytic activity. - 水を溶媒とする芳香族ニトロ化合物の光触媒還元 [通常講演]古南 博; 今村和也; 岩崎伸一; 前田剛志; 橋本圭司社団法人石油学会関西支部第17回研究発表会社団法人日本エネルギー学会関西支部第53回研究発表会合同研究発表会 2008年12月 京都大学（桂キャンパス） 社団法人石油学会関西支部第17回研究発表会社団法人日本エネルギー学会関西支部第53回研究発表会合同研究発表会
- 光触媒作用による水中ニトロ化合物の還元反応 [通常講演]古南 博; 今村和也; 岩崎伸一; 前田剛志; 橋本圭司第15回シンポジウム「光触媒反応の最近の展開」 2008年12月 KSPホール 第15回シンポジウム「光触媒反応の最近の展開」
- 酸化チタン光触媒の還元作用を利用するニトロ化合物のアミノ化合物へのグリーン変換 [通常講演]古南 博; 今村和也; 岩崎伸一; 前田剛志; 橋本圭司第１回触媒表面化学研究会 2008年10月 関西大学 第１回触媒表面化学研究会
- 芳香族ニトロ化合物の効率的還元 [通常講演]古南 博; 今村和也; 岩崎伸一; 前田剛志; 橋本圭司第18回キャラクタリゼーション講習会 2008年10月 第18回キャラクタリゼーション講習会
- 酸化チタン光触媒反応による芳香族ニトロ化合物の効率的還元 [通常講演]古南 博; 今村和也; 岩崎伸一; 前田剛志; 橋本圭司第102回触媒討論会 2008年09月 第102回触媒討論会
正孔捕捉剤共存下，酸化チタン（TiO2）光触媒による芳香族ニトロ化合物の還元反応を検討した．p-ニトロアニリンは水中で，白髪染めなどの染料として重要なp-フェニレンジアミンへ選択的に還元された．また，ニトロベンゼン（NB）と塩酸の二相混濁系において，TiO2光触媒によるNBの還元を行ったところ，活性が低下することなくアニリンが生成した． - Effects of Reaction Conditions on Photocatalytic Reduction of Nitro Aromatics [通常講演]古南 博; 今村和也; 岩崎伸一; 前田剛志; 橋本圭司ICC 14 Pre-Symposium 2008年07月 ICC 14 Pre-Symposium
- 香族ニトロ化合物の光触媒還元反応における各種反応因子の影響 [通常講演]古南 博; 今村和也; 岩崎伸一; 前田剛志; 橋本圭司日本化学会第88回春季年会 2008年03月 日本化学会第88回春季年会
Aromatic amines are important as intermediate compounds of medicines, dye compounds etc. We have already reported photocatalytic selective reduction of nitrobenzene to aniline in aqueous suspension of TiO2 in the presence of oxalic acid as hole scavernger. In this study, we will report effects of reaction conditions such as solvents and atomosphere on photocatalytic redction of various aromatic nitro compounds. - 励起電子の反応選択性制御とニトロ化合物の光触媒還元への応用 [通常講演]古南 博; 計良 善也; 前田剛志; 村上伸也; 大谷文章光機能材料研究会 第10 回シンポジウム（東京） 2003年12月 光機能材料研究会 第10 回シンポジウム（東京）
水中ニトロベンゼンの光触媒反応において、系内に共存させたスズⅣイオンは励起電子を効率よく捕捉し、Sn Ⅱに還元される。このSn Ⅱは基質ニトロベンゼンを還元しSnⅣに戻り、光触媒反応のサイクルが回ることを見いだした。
MISC
- 田中 淳皓; 古南 博 触媒 57 (1) 51 -57 2015年01月
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- 沖 幸男; 岩崎 日出男; 古南 博; 中野 人志; 浅野 昌也 2010年12月
- 岩崎 日出男; 沖 幸男; 神山 匡; 南 武志; 田村 和朗; 古南 博; 窪堀 俊文; 梶原 伸治; 原田 孝; 橋新 裕一; 井口 信和; 向井 苑生; 保本 正芳; 森本 純司; 本西 英 2010年03月
- 東大阪の優れたモノづくり技術の継承と現代ハイテクとの融合 成果報告書（平成16年度－20年度）沖 幸男; 玉井 元治; 久米 靖文; 米田 博幸; 古南 博; 橋新 裕一; 神戸 尚志; 青山 邑里; 宮澤 三雄; 山本 昌彦; 南 武志; 井口 信和; 中山 斌義; 吉原 正邦; 森本 純司; 竹原 幸生; 五百井 清; 伊藤 征司郎; 藤原 尚; 多田 弘明; 河島 信樹; 井田 民男; 藤野 隆由 2009年05月
- 古南 博 光化学 = Photochemistry 39 (1) 3 -10 2008年05月
- 東大阪の優れたモノづくり技術の継承と現代ハイテクとの融合 成果報告書（平成16年度－18年度）沖 幸男; 玉井 元治; 久米 靖文; 米田 博幸; 古南 博; 橋新 裕一; 神戸 尚志; 青山 邑里; 宮澤 三雄; 山本 昌彦; 南 武志; 井口 信和; 中山 斌義; 吉原 正邦; 森本 純司; 河島 信樹; 井田 民男; 藤野 隆由 2007年05月
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- 古南 博 マテリアルインテグレ-ション 19 (8) 30 -34 2006年08月
- H Kominami; S Murakami; J Kato; Y Kera; B Ohtani Journal of Physical Chemistry B 106 (40) 10501 -10507 2002年10月
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- H. Kominami; K. I. Yabutani; T. Yamamoto; Y. Kera; B. Ohtani Journal of Materials Chemistry 11 (12) 3222 -3227 2001年
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- Masashi Inoue; Tomohiro Nakamura; Hiroyuki Otsu; Hiroshi Kominami; Tomoyuki Inui 日本化学会誌 1993 (5) 612 -616 1993年
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- 井上 正志 日本化学会誌 10,1364 (10) p1364 -1366 1991年
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産業財産権
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- 特開2012-206946:皮膚洗浄料 2012年10月25日古南 博, 森下 裕喜 学校法人近畿大学, マイティ株式会社 201203016637684595
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- 特開2012-001736:反応実施方法 2012年01月05日古南 博, 橋本 圭司, 神應寺 厚志 学校法人近畿大学 201203076821767021
- 特開2009-066480:反応装置 2009年04月02日古南 博, 橋本 圭司, 神應寺 厚志 学校法人近畿大学 200903093033106150
共同研究・競争的資金等の研究課題
- 日本学術振興会：科学研究費助成事業研究期間 : 2022年04月 -2025年03月代表者 : 吉田 寿雄; 古南 博; 熊谷 純; 奥村 光隆; 藤田 健一
- 日本学術振興会：科学研究費助成事業 挑戦的研究(萌芽)研究期間 : 2021年07月 -2023年03月代表者 : 古南 博TiO2を光触媒、グリセリンを電子源、溶媒を水とする物質変換反応系を探索した。また、他のアルコール類との比較を通じて、光触媒反応におけるグリセリンの特性を明らかにした。 試験管中の4-ニトロベンゼンスルホン酸（4-NBS)とグリセリンを溶解させた水溶液にTiO2を懸濁させ、アルゴン雰囲気下、水銀灯の光を照射した。気相中の二酸化炭素をガスクロマトグラフにて、液相を高速液体クロマトグラフにて分析した。3時間の紫外光照射の後、4-NBS中のニトロ基が還元された4-アミノベンゼンスルホン酸（4-ABS）が高い選択性で得られた。反応が完結した3時間以降は二酸化炭素の生成が停止し、また、副反応は進行しなかった。別途、太陽光照射下における実験を行ったところ、物質収支が高く維持され4-NBSの還元反応が進行した。 水中、TiO2光触媒による4-NBSの還元反応において、電子源となるアルコールの種類の影響について評価した。3時間の紫外光照射の後、4-NBSが完全に消費され、4-ABSが生成したものはグリセリンのみであった。1価のアルコールである1-プロパノールと2-プロパノールの場合、還元反応がほとんど進行しなかった。また、2価のアルコールであるプロパン-1,2-ジオールとプロパン-1,3-ジオールを用いたとき、還元反応が進行したが、グリセリンの結果と比較すると反応速度はかなり小さかった。また、隣り合う炭素原子に水酸基が一つずつ結合した1,2-グリコール型が電子源として有効に機能することがわかった。同様にエチレングリコールを使用した場合、プロパン-1,2-ジオールのときとほぼ同量の4-ABSが得られた。 以上のことから、グリセリンは水溶媒中の光触媒的還元反応において電子源として有効に機能すること、他のアルコールと比較すると電子源としてより利用しやすいことが明らかになった。
- 日本学術振興会：科学研究費助成事業 基盤研究(B)研究期間 : 2020年04月 -2023年03月代表者 : 古南 博①Ptナノ粒子を担持した金修飾TiO2に対するCr水酸化物の修飾と可視光水分解 TiO2上に固定化したAuおよびPtナノ粒子の表面にCr水酸化物の薄層を形成する触媒を調製し，可視光下における水分解に用いることを試みた．この系においてCr水酸化物薄層は，Au上で「正孔移動」の助触媒として，Pt上で「逆反応の抑制」のための薄層として機能すること，つまり１粒子上で２つの異なる機能を発揮することを期待した．透過型電子顕微鏡を用いた観察によって，Cr水酸化物がAuおよびPtナノ粒子上に析出していることを確認した．調製した触媒を純水に懸濁させ，可視光（λ> 400 nm）を照射して水分解反応を検討したところ，H2とO2が量論的に生成することがわかった．この時の水分解活性は，Au修飾TiO2の約８倍となり，Cr水酸化物薄層の多機能化の達成とともにプラズモニック光触媒の高機能化が達成された． ②Au修飾酸化チタンの酸化処理による水の酸化反応の加速 析出沈殿法によって調製したAu修飾酸化チタンをO2またはH2ガス流通下において，様々な温度で熱処理したところ，O2下で処理した触媒がH2下で処理したものよりも高い水の酸化活性を示す傾向があることを見いだした．X線光電子分光を用いて調製した触媒を分析するとO2下で処理した触媒のAuナノ粒子表面に薄い酸化物層が存在することが確認された．酸化物層を有する触媒をH2ガスによって還元処理することで水の酸化反応速度が小さくなったことから，Auナノ粒子表面に酸化物層が存在することによって水の酸化反応が加速されていることが明らかになった．近年では助触媒の修飾等によって触媒を高機能化させる研究が数多く行われているのに対して，この研究は，処理ガスを変えるという単純かつ簡便な方法でプラズモニック光触媒の高機能化を達成した例として位置付けできると思われる．
- 日本学術振興会：科学研究費助成事業 基盤研究(B)研究期間 : 2017年04月 -2020年03月代表者 : 古南 博本研究では、申請者らの研究成果を最大限活用し、研究課題にある、ａ）高難度選択的物質変換、ｂ）自然エネルギー（光・熱）と廃棄物の利用、ｃ）可視光応答化、を研究キーワードに掲げ、高難度な研究に挑戦し、以下の成果を得た。１）メタルフリーや水素フリー条件下において各種光触媒反応が進行する。２）助触媒を導入することにより、反応速度が著しく大きくなる。３）水を含む様々な溶媒を用いることができる。４）太陽光照射下、外的なエネルギーを一切加えないパッシブな条件においても、反応が進行する。５）廃棄物を水素源として利用できる。６）30 K程度の温度上昇により反応速度が著しく大きくなる。
- 自然エネルギー（光・熱）で機能する光触媒の創製と連続的高難度物質変換文部科学省：科学研究費補助金（基盤研究(b)）研究期間 : 2017年04月 -2020年03月代表者 : 古南 博
- 日本学術振興会：科学研究費助成事業 基盤研究(B)研究期間 : 2014年04月 -2017年03月代表者 : 古南 博酸化チタン（TiO2）粉末上に金（Au）粒子とニッケル/酸化ニッケル（Ni/NiO）粒子を修飾することにより，可視光照射下，添加剤を含まない純水の分解反応（2H2O → 2H2 + O2）に成功した。この光触媒はTiO2，Au粒子およびNi/NiO粒子がそれぞれ，電子伝達物質，可視光吸収部位・酸化反応場および還元反応場を担う「機能分離型プラズモニック光触媒」であり，この触媒設計により効率的な電荷分離が促進され，究極の反応である水分解による水素および酸素生成を達成したといえる。
- 日本学術振興会：科学研究費助成事業 挑戦的萌芽研究研究期間 : 2014年04月 -2016年03月代表者 : 古南 博光触媒反応には、「安全性が高い」、「太陽光が使える」、「常温常圧で反応が進行する」、「密閉性の高い反応器が不要」など、他の方法に比べ、優れた点が多く、次世代の物質変換反応として注目される。本研究では、水素フリー、常温常圧下における3つの光触媒反応系【１．Pd担持酸化チタンによるアルケンの水素化、２．銀担持酸化チタンによるエポキシ化合物の還元的脱酸素、３．銅担持酸化チタンによるアルキンの部分水素化】を開拓した。いずれの反応系においても、助触媒担持が重要であり、また、2級アルコールが溶媒兼電子供与剤として有効に作用した。いずれの場合も、還元生成物と酸化生成物（ケトン）が高い量論で得られた。
- 日本学術振興会：科学研究費助成事業 基盤研究(C)研究期間 : 2011年 -2013年代表者 : 古南 博可視光に応答する光触媒の合成に関する研究が精力的に行われている。本研究では、金ナノ粒子の表面プラズモン共鳴（SPR）を可視光照射下でプラズモニック光触媒として応用することを検討した。プラズモニック光触媒はユニークな光吸収特性を示し、また、可視光照射下、有機酸の無機化や選択酸化、水素生成、有機化合物の還元において、優れた光触媒特性を示した。白金、銀、パラジウム助触媒で機能化されたSPR型光触媒は、それぞれ、水素生成、ニトロベンゼン還元、クロロベンゼンの脱水素において効果的に機能した。本研究で得られた結果は、さらに優れた活性と選択性を示す新規なプラズモニック光触媒の設計と開発に応用できる。
- 日本学術振興会：科学研究費助成事業 基盤研究(C)研究期間 : 2008年 -2010年代表者 : 古南 博光触媒と熱触媒の特徴を併せ持つ触媒材料を開発し、両触媒作用が調和して機能し、あるいは機能分担することにより優れた触媒機能を発現させることに成功した。TiO_2光触媒上でメタノールからギ酸メチルが高い選択率で生成し、これが光触媒的酸化反応とティシチェンコ反応(酸塩基触媒作用)の連続反応であることを明らかにした。また、ブテンの光触媒的異性化反応がPd-TiO_2上、室温で進行し、Pdの熱触媒作用(アルケンのヒドリド引き抜きとカルベニウムイオン中間体への再付加)を励起電子と正孔が加速させることを明らかにした。
- 日本学術振興会：科学研究費助成事業 特定領域研究研究期間 : 2005年 -2006年代表者 : 古南 博1.ソルボサーマル法によるTiO_2-シリカゲル複合材料の合成と評価 シリカゲル共存下、トルエン中でTTBを300℃で熱分解(TD法)させることにより、アナタース型TiO_2ナノ結晶(結晶子径9nm)とシリカゲルの複合材料が得られた。試料の比表面積はいずれもTiO_2単独試料より大きく、シリカゲルとの複合化がTiO_2系材料の大表面積化に効果があることが明らかになった。TiO_2-シリカゲル複合材料の光触媒特性を窒素酸化物(NOx)の酸化的除去反応を用いて評価した。TD法で調製した複合材料はTiO_2量が少ないにも関わらず、TiO_2単独試料よりも高いNOx除去率を示した。さらに、中間体である二酸化窒素(NO_2)の気相への放出が低く抑えられていた。光触媒活性の高いTD-TiO_2とNOおよびNO_2、水分(H_2O)に対する吸着能力が高いシリカゲルを組み合わせることがNOx酸化的除去反応において効果的であることが明らかになった。比較のため、TD-TiO_2とシリカゲルの物理混合試料を作製したが十分な除去率は得られなかった。TD-TiO_2とシリカゲルの混合状態が不十分であり、TD-TiO_2とシリカゲル間の物質移動が効率的に進まなかったためであると考えられる。したがって、NOx酸化的除去反応においては、高活性なTiO_2と吸着特性に優れたシリカゲルを直接隣接複合化させることが重要であると考えられる。 2.金属酸化物上に固定化させた遷移金属塩化物による可視光光触媒反応特性 塩化ロジウムを酸化チタン(ST-01)に担持(1wt%)し、150℃で焼成した塩化ロジウム担持試料は紫外光領域から可視光領域へ伸びる吸収帯を確認できた。可視光照射下でのNOxの酸化的除去反応を行ったところ、光照射5時間後に、積分値で除去率99%の高い活性を示した。担持試料を水で洗浄してもRh塩はほとんど溶出せず、強固に酸化チタン表面に固定化されていると考えられ、繰り返し実験でも優れた除去率を維持した。また試料を水洗いした際、触媒表面上に蓄積した最終生成物であるNO_3^-がほぼ量論的に回収された。
- 日本学術振興会：科学研究費助成事業 基盤研究(C)研究期間 : 2004年 -2005年代表者 : 古南 博本研究では、正孔捕捉剤共存下、光触媒還元反応による硝酸イオン(NO^-_3)のN_2への還元無害化を検討した。まず、シュウ酸イオン共存下0.5wt%Cu-TiO_2を用いたときの懸濁液のpHの影響を検討した。pHを上げると還元生成物はNH_3からNO^-_2へと変化した。懸濁液をアルカリ性にすることで系内のプロトンが少なくなりNO^-_3のプロトン化が起こらなくなったためであると考えられる。光、触媒、正孔捕捉剤のいずれかが欠けると反応が進まないことから、この反応は光触媒的に進行していることを確認した。触媒にCuPd-TiO_2を用いてpH12で12h光照射するとNO^-_2は生成せず、代わりにN_2が生成し、光触媒によるNO^-_3のN_2への還元無害化が可能であることを見出した。つぎに、この条件下における窒素化合物の分布の経時変化を検討した。照射時間が短い領域でNO^-_2が一時的に生成するが、時間を延ばすとNO^-_2はすぐに減少し検出されなくなった。一方、N_2の生成は誘導期を伴って増加した。CuおよびPdの担持量の影響を検討したところ、TiO_2に対してCuが0.5wt%、Pdが1.0wt%のときに最大活性となり、いずれかの成分をさらに増加させると活性は減少した。また、基質をNO^-_2に代え、触媒としてPd-TiO_2を用いてアルカリ性条件下で光触媒還元を行うと、NO^-_2は誘導期を持たずにN_2へと還元された。このことはNO^-_2からN_2への還元においてPdが助触媒として機能していることを表している。NO^-_3の還元反応の進行と共にシュウ酸イオンの酸化生成物である炭酸イオンが系内に蓄積し反応速度が低下するが、pHスウィング等により炭酸イオンを除去することにより反応は進行することを確認した。また、金属の担持方法を改善することにより反応速度を低下させずにほぼ定量的にNO^-_3をN_2への還元することができた。
- 日本学術振興会：科学研究費助成事業 基盤研究(C)研究期間 : 2003年 -2004年代表者 : 計良 善也; 古南 博チタニア(TiO_2)はアンモニア脱硝触媒の担体として用いられている。近年、さらなる性能の向上や、より制約された条件下においても十分な特性を示すことが要求されている。本研究では、TiO_2に対し、有機官能基を有するシランカップリング剤による化学修飾を行い、シラン剤修飾が担体TiO_2の熱安定性やメタバナジン酸(VO_3^-)の吸着特性に与える影響について詳細に検討し、VO_3^-を吸着したシラン剤修飾担体TiO_2から調製したバナジウム系触媒の脱硝特性についても評価を行った。 用いたTiO_2は大表面積(300m^2g^<-1>)を有しているが、耐熱性は低く550℃で焼成すると表面積は著しく減少した。TiO_2に対して、アミノプロピルトリメトキシシラン(APS)あるいはアミノ基を二つ有するシラン剤(DAPS)処理を施すことにより、その耐熱性は劇的に改善された。シラン剤に由来するケイ素によりTiO_2シンタリングが抑制されたために、耐熱性が著しく向上したと結論した。また、シラン剤中のアミノ基の効果により、VO_3^-の吸着量は未修飾TiO_2に比べ大きく向上した。吸着したVO_3^-と修飾担体上のシラン剤のモル比は1.0および1.6となり、VO_3^-はアミノ基のプロトン化で生じたアンモニウム基と塩を形成して、TiO_2担体上に分散固定化されていると考えられる。さらに、この触媒前駆体を熱分解させて得られた酸化バナジウム触媒は、修飾担体の高い熱安定性を反映して大きな表面積を維持していた。その脱硝活性は未修飾担体を用いたものに比べ優れており、大表面積化および担持量増加が脱硝活性に対して正に作用し、とくに、DAPSで最良の脱硝活性が得られ、ジアミノ基の導入が効果的であることが明らかになった。
- 日本学術振興会：科学研究費助成事業 特定領域研究研究期間 : 2003年 -2004年代表者 : 古南 博本研究では、有機溶媒の多様性を利用して、さまざまなソルボサーマル技術を新たに開発する。これらを駆使して様々なTiO_2光触媒系を調製し、その光触媒特性の評価や新規反応系を開拓するとともに、その量子効率の向上およびゼロリコンビネーション化を目指した。 1)ソルボサーマル法によるブルカイト型酸化チタン光触媒の合成と光触媒特性評価 TiO_2はアナタース、ルチル、ブルカイトの3つの結晶系で存在する。その中でアナタースとルチルはよく知られており、これらの合成および光触媒や触媒担体への応用に関する研究例は多い。一方、純粋なブルカイト型TiO_2は合成が困難であるため、その物性や光触媒特性についてはあまり研究されていない。そこで、ソルボサーマル法によるブルカイト型TiO_2の合成を種々検討した。その結果、チタン源にチタンオキシアセチルアセトナート、溶媒にエチレングリコール-水混合系、共存物質に各種ナトリウム塩を用いるとブルカイト型酸化チタンのナノ結晶が生成することを見いだした。これを複数の光触媒反応系に用いたところ、ブルカイト酸化チタンの最適な物性は反応系に依存して大きく異なること、および、最適な物性を付与された試料は、市販高活性品P-25やST-01と比べても遜色ない特性を示すことが明らかになった 2)ソルボサーマル法を用いる酸化チタン-吸着剤コンポジットの合成とその評価 気相中に拡散した物質の分解・無害化反応を効率的に進めるためにはTiO_2-吸着剤コンポジットが有効であると考えられる。しかし、高活性な光触媒を吸着剤と複合化されるのはかなり難しい。ソルボサーマル合成条件時に吸着剤を系内に共存させ、吸着剤上に直接高活性TiO_2を生成させる手法を開発し、これが期待通り優れた光触媒特性を示した。
- 日本学術振興会：科学研究費助成事業 若手研究(B)研究期間 : 2002年 -2003年代表者 : 古南 博火力発電所で発生するNOxを除去する排煙脱硝触媒や自動車排ガス浄化用触媒は高温領域で使用されるため、触媒の耐熱性がその性能を決める重要な因子になる。これら触媒に用いられている金属酸化物担体の耐熱性を向上させれば、触媒の長寿命化や高性能化につながると考えられる。これまで様々な方法が試みられているが、その一つにシランカップリング剤(RnSIX_<(4-n)>)を担体表面に修飾する方法がある。本研究では、分子内にふたつのケイ素基をもつシラン剤ビストリエトキシシリルエタン(Bis)を用いて重要な触媒担体である酸化チタンの表面を化学修飾し、その耐熱性の改善効果ならびに担体の細孔構造について検討した。 用いたTiO_2は大表面積(300m^2g^<-1>を有しているが、耐熱性は低く550℃で焼成すると表面積は著しく減少した。得られたBis-TiO_2のIRスペクトルにはSi-O結合による吸収がみられ、また、元素分析の結果からもSiの存在が確認された。また高温で焼成することにより起こる表面積の低下、結晶子径の成長、相転移のいずれもがBis修飾により大幅に抑制された。これは表面に存在するSiが粒子間のシンタリングを抑制していると考えられ、TEMにおいて粒子成長が抑制されていることが確認された。またBis修飾量の増加とともに、耐熱性も向上した。もとのTiO_2、Bis-TiO_2の窒素吸着等温線はともにIV型であり、ヒステリシスが現れていることからこれらはメソ、マクロ孔を有していると考えられる。焼成温度が上がるにともなって、細孔半径は大きくなり細孔容積は減少した。このことは粒子がシンタリングし大きな粒子になることで、小さな細孔はつぶれ新たに半径の大きな細孔を形成することを示している。シラン剤を添加することにより、細孔構造の大きな変化は抑制され、十分な細孔容積を維持していた。
- 日本学術振興会：科学研究費助成事業 特定領域研究研究期間 : 2002年 -2002年代表者 : 古南 博有機溶媒を用いる新規な水熱結晶化法(HyCOM法)によりアナタース型TiO_2の微結晶を合成し、さらに後焼成処理を施して様々な物性を有するTiO_2を調製した。これらを用いてTiO_2の再結合速度評価法の確立を目指した。まず、無酸素下、正孔捕捉剤存在下の光照射により生成するTi^<3+>の量を定量する方法を試みた。Ti^<3+>は表面欠陥サイトで形成されると考えられ、その量は焼成温度を上げる、つまり、TiO_2の結晶化度を高くするほど単調に減少した。このTi^<3+>量はポンプ-プローブ法過渡吸収測定(PP-DRS法)により算出したk_<-r>との間にほぼ比例したことから、TiO_2の再結合特性を表す指標して利用できることがわかった。無酸素下での銀析出-酸素発生反応における銀イオン吸着量([Ag^+]_
)と銀析出速度(R_ )の間に直線関係が得られる。この反応の速度論的考察によると、[Ag^+]_ -R_ プロットの傾きの逆数が近似的にe^--h^+の再結合および電子捕捉の速度定数比(k_r/k_e)に比例すると考えられ、HyCOM(973)およびP-25のk_r/k_eは、それぞれ0.79,2.2と求められた。また、ひとつのAg_2SO_4水溶液から、一組の吸着量と反応速度を求める一点法により、各種TiO_2のk_r/k_eを簡便に求められることが明らかになった。そこで、物性の異なるHyCOMTiO_2のk_r/k_eを評価すると、Tcを上げるほどk_r/k_eは減少した。k_r/k_eのTc依存性はTi^<3+>量のTc依存性とは異なるが、k_r/k_eの対数とTi^<3+>量との間に正の相関が見られることから、k_r/k_eは、Ti^<3+>量と同様に再結合特性を表す指標して利用できることがわかった。 - 日本学術振興会：科学研究費助成事業 奨励研究(A)研究期間 : 2000年 -2001年代表者 : 古南 博発電所などから排出される窒素酸化物(NOx)に対する除去技術は既に確立されている。優れた除去技術にもかかわらず、現在大気中のNOx濃度はむしろ上昇する傾向にあり、酸性雨などによる生態系への影響が懸念される。現段階で最も効果的な対応法のひとつとして、実用触媒である酸化バナジウム系触媒の性能向上、つまり、担体である酸化チタンの表面積を大きくして、バナジウムのNOx還元サイト数を多くすることが有効であると指摘されている。しかしながら、従来の調製法あるいはその改良では大幅な大表面積化は期待できず、新規な触媒(担体)の調製法の開発が必要となってくる。本研究では有機溶媒を反応メディアとして酸化チタンを初めとする各種金属酸化物のナノ結晶を合成し、その熱的安定性を評価するとともに触媒担体材料としての可能性を検討した。 チタンアルコキシドおよびケイ酸エステルをトルエン中、300℃で加熱処理すると両成分は熱分解してシリカ修飾チタニアのナノ結晶が得られた。この生成物はアナタース構造を有しておりその格子定数の評価からケイ素はアナタース構造に固溶していることが明らかになった。ケイ素がチタニア中に高分散しているためルチルへの相転移が抑制され、1000℃焼成後もアナタース相が安定であった。ナノ結晶性と高い相転移温度により、このシリカ修飾チタニアは高い熱安定性を示し、800℃焼成後も160m^2g^<-1>という大きな表面積を維持していた。同様の手法により、高い耐熱性を有する、リンおよびアルミナ修飾が合成できることを見いだした。さらに、有機溶媒中の水熱結晶化法により調製したチタニアに対して、シランカップリング剤による修飾を施すとその耐熱性が劇的に改善されることも見いだした。
- 日本学術振興会：科学研究費助成事業 基盤研究(B)研究期間 : 1998年 -2000年代表者 : 大谷 文章; 魚崎 浩平; 古南 博; 池田 茂本研究の目的は、再結合のない極限の光触媒活性をもつ半導体触媒を調製する手法、および、活性支配因子を定量的に評価する技術を確立することにある。申請者らは、光触媒反応活性が表面積と結晶化度によって決まることを明らかにしてきた。表面積は、反応基質の吸着量を、一方、半導体の結晶化度は、結晶欠陥における再結合の度合いを決定する。結晶化度と表面積は互いに密接に関係するため、同時に最適化することは難しく、高活性化の戦略は単純ではない。たとえば、表面積を増加させて基質吸着量を増すことを目的として粒子径の小さいものを作ると、結晶化度が低いために、結果として低活性になる。申請者らは「大表面積かつ高結晶性」の酸化チタンを調製する新規手法を開発し、得られた酸化チタンが予想どおり高活性であることを示してきた。本研究では、水酸化チタン(含水酸化チタン)を経由しない新しい合成法であるHyCOM(Hydrothermal Crystallization in Organic Media:有機溶媒中での加水分解同時水熱結晶化法)、TD(Thermal Decomposition:水を使わない熱分解・結晶化法)、およびTHyCA(Transfer Hydrolytic Crystallization in Alcohols:移動型加水分解・結晶化法)の3手法を用いて酸化チタンを合成した。得られた酸化チタン粉末について、結晶および表面構造を解析するとともに、種々のにおける光触媒活性の測定、およびフェムト秒ポンプープローブ拡散反射分光法による再結合速度の評価を行い、前述の作業仮説の有効性を実証した。さらに、酸化チタン以外にも、酸化タンタル、酸化タングステン、および酸化ニオブを上記の新規手法により合成し、これらが高活性を示すことを確認した。
- 日本学術振興会：科学研究費助成事業 萌芽的研究研究期間 : 1997年 -1998年代表者 : 玉井 元治; 古南 博; 計良 善也有害ガス吸着能を有する吸音性多孔質コンクリートの研究(玉井担当) 1. 材料と配合および形状の検討 骨材粒径を1mmとした10cm厚さの多孔質コンクリートの表面積は普通コンクリートの片側表面積の約500倍にもなることが明らかになっている。また,天然のゼオライトが各種のガスを吸収するが,特にフライアッシュから合成した粒状の人工ゼオライト骨材が(NOx)を吸収し無害化できることを明らかにし,その配合と形状を検討し最適条件を決定した。 2. 機械的物性の検討 各種材料と配合で作成した供試体の強度,弾性係数等の機械的な物性を検討し,吸音板としての物性を評価した。 有害ガス吸着能と無害化法の確立(計良,古南担当) 1. 有害ガス吸着能の調査と最適条件 天然ゼオライトや人工ゼオライトとセメント混合系に関し,各種配合した供試体の有毒ガス吸着能は,既に試作したパルス吸着反応装置を用いて調査し,最適条件を検討した。 2. 吸着したガスの無害化法の検討 これにはチタニアを主とした合成触媒を用いて行い。この触媒の効果は光または熱により相違するため各種条件下における効果をほぼ明らかにし,製品化の可能性を示した。
- 日本学術振興会：科学研究費助成事業 奨励研究(A)研究期間 : 1997年 -1998年代表者 : 古南 博近年、酸化チタン光触媒を用いて環境汚染物質を分解除去したり、水を水素と酸素に分解する試みが精力的に行われているが、反応を効率よく進行させるためには触媒自身の高活性化が必要不可欠となってくる。光触媒反応の速度論的考察から、高活性な触媒がもつべき物性は高表面積と高結晶性であると提案されていたが、沈殿法などの従来の手法で調製することは困難であった。 本研究では、有機溶媒中で金属酸化物を結晶化させるという、常法とは根本的に異なる新規な手法2法を開発した。具体的には、チタンアルコキシドを不活性な有機溶媒中で熱分解させる手法、および、溶媒に用いたアルコールから均一に生成する水を用いて、アルコキシドを加水分解する手法により酸化チタンなどのナノ結晶性酸化物が容易に合成できることを見いだいした。また、これらナノ結晶を各種光触媒反応に用いると、市販の高活性触媒を越えるきわめて高い活性を示すことを見いだした。これは、本手法で合成された触媒が大表面積と高結晶性の両物性を満足しているためであると考えられる。つまり、大表面積は基質の吸着量を増やし、光照射で生成する電子-正孔対の捕捉を効率よく進行させ、また、高結晶性は電子-正孔対の再結合確率を低下させる効果があるということで説明できる。さらに、後焼成により物性を変化させた触媒・を各種光触媒反応に用いて、触媒の物性と活性の相関を解析した。反応が完結するのに必要な電子(あるいは正孔)の数(反応電子数)が増えるにしたがって、触媒の結晶性(再結合確率)が重要になることを見いだした。このような知見に基づいて、水の完全分解反応に適した触媒を設計、調製して、水分解反応に用いると、期待通り、最も活性が高いと考えられているP-25(Degussa)の性能を越える高い水素および酸素生成速度を示した。
- 日本学術振興会：科学研究費助成事業 基盤研究(C)研究期間 : 1995年 -1996年代表者 : 大谷 文章; 古南 博; 西本 清一平成7年度までに、種々の市販あるいは実験室において調製した酸化チタンにその活性を検討した結果、液相系光触媒反応に大きく影響をおよぼす触媒の物性は、表面積と結晶化度であることが明らかになった。表面積が大きいほど、反応基質の吸着量が多いので活性は増大する。一方、半導体の結晶化度が高いものほど、結晶欠陥が少なく、そのため、励起電子と正孔の再結合が抑制されるので活性が向上するものと思われる。したがって、高活性な酸化チタンの条件が「表面積が大きく、かつ結晶化度が高い」であるという作業仮説は、いずれの酸化チタンも用いた反応系の場合でも適用できることを確認した。しかし、結晶化度と表面積は互いに密接に関係するうえ、おおまかにいえば逆方向に作用するため、高活性化の戦略は単純ではない。このような条件を満足する酸化チタンを調製することは、従来法、すなわち一旦水酸化チタンあるいはオキシ水酸化チタンを調製してからこれを焼成する方法ではほぼ不可能であるとの結論に達したので、新規な方法を模索したところ、まったく新しい金属酸化物調製法であるHyCOM(Hydrothermal Crystallization in Organic Media)法が、高表面積で、かつ結晶化度の高い酸化チタン粉末の調製を行うためにきわめて有効な手法であることが明らかになった。平成8年度は、さらに新しい調製法として、チタンアルコキシドの直接熱分解法(Thermal Decomposition:TD法)と、アルコールを溶媒をとして用い、加熱により発生する水を利用する移動加水分解法(Transfer Hydrolytic Crystallization in Alcohols:THyCA法)を開発し、その光触媒活性を検討した。その結果、白金を担持させた無酸素下の反応と無担持での酸素共存下の反応の両者について、過去最高の光触媒活性を得た。
- 日本学術振興会：科学研究費助成事業 奨励研究(A)研究期間 : 1994年 -1994年代表者 : 古南 博チタンのアルコキシドを種々のアルコールやトルエンなどの無極性の有機溶媒に溶解し、これをオートクレーブ中、高温高圧下、気相からの有機溶媒に溶け込む少量の水を用いて加水分解するとともに結晶化させる手法を検討した。この手法によりアナタ-ス型酸化チタンが生成することを見いだし、また、これが結晶子径約9mmの超微結晶の集合体からなっていることをX線回析、透過型電子顕微鏡(TEM)観察から明らかにした。酸化チタンの有機溶媒に対する溶解度がかなり小さく、結晶成長が抑制されるためこのような酸化チタンの微結晶が生成したと考えられる。水を溶媒に用いる水熱法では微結晶合成は困難である。本手法で得られた酸化チタンの大きな特徴として、高温で焼成しても結晶成長が小さいことが挙げられる。通常のアルコキシド法で得られる無定形水和酸化チタンを400〜500℃で焼成するとアナタ-スが結晶化し、その結晶径も大きくなるのに対し、本手法で得られた酸化チタンは500℃で焼成しても11〜15nmの結晶子径を保ち、また、これに対応して、100m^2g^<-1>以上の表面積を維持した。細孔経分布も結晶の間隙に由来すると考えられるシャープな分布のピークが10nm付近にみられた。以上のことにより本手法で得られた酸化チタンは常法では合成困難な種々の優れた物性を示すことが明らかとなり、現在、J.Mater.Sci.Lett.に投稿中である。さらに、この酸化チタンを触媒担体および光触媒材料として利用することを現在検討している。
- Synthesis of ultra-highly active photocatalysts研究期間 : 1993年
- Study on intercalation of peroxocomplex研究期間 : 1993年
- Synthesis of nanocrystals in liquid phase研究期間 : 1993年