発表論文

2014年

"Bimodal Cesium hydrogen Salts of 12-Tungstosilicic Acid, CsxH4-xSiW12O40, as Highly Active Solid Acid Catalysts for Transesterification of Glycerol Tributyrate with Methanol"
Yukari Iwase, Shogo Sano, Lina Mahardiani, Ryu Abe, Yuichi Kamiya
Journal of Catalysis, 318 (2014) 34-42. DOI: 10.10161/j.jcat.2014.07.008
Abstract
Bimodal CsxH4-x[SiW12O40] (Csx-bimodal) with mesopores interconnected with micropores were synthesized from microporous CsxH4-x[SiW12O40] (Csx-micro) with x = 1.0-2.5, which were prepared in advance by titrating an aqueous solution of H4[SiW12O40] with an aqueous solution of Cs2CO3, followed by treatment in refluxing ethanol to mainly dissolve the H4[SiW12O40] in the particles. Mesopore size distributions and their pore volumes changed depending on x in Csx-micro. Microporous Cs2.5-micro transformed into bimodal Cs2.5-bimodal with mesopores having average diameters of 3.7 nm and large mesopore volumes. Although Cs2.5-bimodal exhibited only low catalytic activity for the decomposition of isopropyl acetate, post-treatment in H2SO4 enhanced the catalytic activity due to substitution of the Cs+ ions on the surface with H+. H2SO4-treated Csx-bimodal showed high activity toward transesterification of glyceryl tributyrate with methanol due to its strong acid strength and mesoporosity.


"Combining the photocatalyst Pt/TiO2 and the Non-photocatalyst SnPd/Al2O3 for Effective Photocatalytic Purification of Groundwater Polluted with Nitrate"
Jun Hirayama, Yuichi Kamiya
ACS Catalysis, 4 (2014) 2207-2215. DOI: 10.1021/cs5003564
Abstract
We investigated photocatalytic reduction of NO3- in real groundwater in the presence of the photocatalyst Pt/TiO2 and the nonphotocatalyst SnPd/Al2O3, which were dispersed in the groundwater, under irradiation at λ > 300 nm, with glucose as a hole scavenger. In this system, photocatalytic H2 evolution (2H++ 2e- → H2) proceeded over Pt/TiO2, and nonphotocatalytic, that is, conventional catalytic, reduction of NO3- with H2 (NO3- + 5/2H2 → 1/2N2 + 2H2O + OH-) occurred over SnPd/Al2O3. NO3- (1.0 mmol dm-3) in the groundwater completely and selectively decomposed to N2 (yield 83%) after 120 h with a 300 W Xe lamp (λ > 300 nm) over the Pt/TiO2?SnPd/Al2O3 system in combination with photooxidative pretreatment of the groundwater over Pt/TiO2 to decompose organic compounds. The decomposition rate of NO3- in the groundwater was still slower than that in an aqueous NO3- solution even after the pretreatment of the groundwater. The lower photocatalytic performance was due to poisoning of Pt/TiO2 with sulfate and silicate ions and poisoning of SnPd/Al2O3 with polymerized silicate ions. On the other hand, cations, including Na+, K+, Mg2+, and Ca2+, in the groundwater did not affect the photocatalytic and catalytic performances of the system. Sulfate ions adsorbed on the Pt sites on Pt/TiO2, where H2 evolution occurs, and silicate ions deactivated the oxidation sites on TiO2 by reacting with the surface hydroxyl groups, leading to a decline in the photocatalytic performance of Pt/TiO2.

"Catalytic oxidation of ammonium ion in water with ozone over metal oxide catalysts"
Sho-ichi Ichikawa, Lina Mahardiani, Yuichi Kamiya
Catal. Today., 232 (2014) 192-197. DOI:10.1016/j.cattod.2013.09.039
Abstract
Oxidative decomposition of NH4+ (10 mmol L-1) with O3 in water was studied at 333 K over a variety of metal oxide catalysts without pH control of the solution. Although MgO and NiO had the highest catalytic activities, large amounts of undesired NO3- formed due to low selectivity to gaseous products as well as high activity. Co3O4, which was slightly less active than MgO and NiO, was the best catalyst in terms of activity, selectivity to gaseous products, and dissolution degree among the metal oxide catalysts studied. Over Co3O4, NH4+ was selectively oxidized to N2 with 88% selectivity in water, and the dissolution degree of Co3O4 was less than 1%. Fe2O3, SnO2, Mn3O4, CuO, MgO, and Al2O3 were less selective to gaseous products or much less active for the reaction. The selectivities to gaseous products were strongly related to the standard enthalpy changes of formation per mol of oxygen atom (ΔH01) of the metal oxides. The metal oxide catalysts with low ΔH01, like Co3O4, showed high selectivity to gaseous products probably due to the low surface density of the active oxygen formed from O3 on the catalysts. Chloride ions (Cl-) present in the reaction solution significantly accelerated the reaction rate for NH4+ decomposition with O3 in the presence of Co3O4. This was due to the involvement of Cl- in the catalytic cycle. For instance, ClO-, which may form by the reaction of Cl- with O3 over Co3O4, could further oxidize NH4+.

"Combinational effect of Pt/SrTiO3:Rh photocatalyst and SnPd/Al2O3 non-photocatalyst for photocatalytic reduction of nitrate to nitrogen in water under visible light irradiation"
Jun Hirayama, Ryu Abe, Yuichi Kamiya
Appl. Catal. B., 144 (2014) 721-729. DOI: 10.1016/j.apcatb.2013.08.005
Abstract
Photocatalytic reduction of nitrate in water in the co-presence of Pt/SrTiO3:Rh and SnPd/Al2O3 under visible light irradiation (λ > 420 nm) was investigated. This reaction system efficiently and selectively promoted the photocatalytic reduction of nitrate to nitrogen, whereas Pt/SrTiO3 :Rh or SnPd/Al2O3 alone showed little activity under the reaction conditions. The selectivity to N2 was 94% under the optimum reaction conditions, where the amounts of Pt/SrTiO3 :Rh and SnPd/Al2O3 loaded in the reaction system were 500 mg and 150 mg, respectively. This reaction system showed a superior nitrate decomposition rate and superior selectivity to nitrogen compared with SrTiO3:Rh directly modified with SnPd bimetal. From analysis of the reaction mechanism, hydrogen formed by photoreduction of water over Pt/SrTiO3:Rh acted as the reductant for a non-photocatalytic nitrate conversion reaction over SnPd/Al2O3. Moreover, the products, including formaldehyde and formic acid, formed by photo-oxidation of methanol over Pt/SrTiO3:Rh acted as reductants for nitrate over SnPd/Al2O3.

学会発表

2014年度

第115回触媒討論会(3月23日〜24日、東京)
(ポスター発表)神谷 “水中NH4+の酸化分解反応への酸化コバルト触媒の反復使用による活性向上効果”
化学系学協会北海道支部2015年冬季研究発表会(1月27日〜28日、札幌)
(口頭発表)山本 “水中硝酸イオン光還元分解に対するSn-Pd/SrTiO3:Rhの性能支配因子”
(口頭発表)野島 “地下水浄化のための担持ニッケル触媒による水中硝酸イオン還元分解”
第45回中部化学関係学協会支部連合秋季大会(11月29日〜30日、春日井)
(口頭発表)安田 “担持金属酸化物触媒による酸素共存下での水中亜硝酸イオンの選択還元分解”
第44回石油・石油化学討論会(10月16日〜17日、旭川)
(招待講演)神谷 “Selective conversion of butenes over silica-supported 12-tungstosilicic acid catalyst”
(口頭発表)Lina “Increase in catalytic activity of cobalt oxide by repeated use for oxidative decomposition of ammonia with ozone in water”
第114回触媒討論会(9月25日〜27日、東広島)
(口頭発表)福西 “金属酸化物触媒による水中アニリンのオゾン酸化分解”
(口頭発表)保田 “12-モリブドリン酸触媒上でのメタクロレイン選択酸化反応における水蒸気の添加効果”
石油学会第57回年会(5月27日〜28日、東京)
(口頭発表)神谷 “TiO2およびAl2O3に加持したH4SiW12O40の酸性質”
Seminar of Chemistry and Chemical Education Y(6月21日、Solo、インドネシア)
(招待講演)神谷 “Water Purification by Catalytic and Photocatalytic Reactions : Nitrate-Polluted Groundwater as an Example”