Quantum size effect of transition metal oxide catalysts

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Systematic investigation of 'quantum size effect' was carried out for the micro particles of oxides of magnesium, titanium, vanadium, manganese, iron, cobalt, copper, garium, niobium, molybdenum, lanthanides, rhodium and tungstenum dispersed on various metal oxide supports.1. Characterization of the samples carried out mainly by XAFS led the following structural results. (1) Over the silica support ; magnesium and copper are supported as a micro particle which exhibits quantum size effect, lanthanide is stabilized as a two-dimensional metal oxide, and titanium, vanadium, niobium, garium, and tungstenum are dispersed atomically, and atomically dispersed sample exhibits photoactivity. (2) Over alumina and magnesia support ; every metal cations are dispersed atomically and binary metal oxides are formed at a high loading. (3) Over titania support ; metal cations are stabilized atomically at a low loading. Metallic elements are converted to metal particle sizing in ca. 100 *. (4) zirconium and iron oxides form a solid solution.2. The catalysts above are able to be applied to the reactions below. (1) Selective photooxidation of light alkanes over silica-supported vanadium oxide. (2) Acid-catalyzed reaction over silica-supported lanthanide oxides. (3) Selective oxidation of olefins over silica-supported titanium oxide. (4) oxidation of methane over silica-supported tungstenum oxide. (5) Selective reduction of NOx over titanium supported copper. (6) Photoreduction of carbon dioxide over titania-supported rhodium. (7) Olefin metathesis over Mg-Mo binary metal oxide. (8) Epoxidation of olefins over supported magnesium oxide.