Quantum size effect of transition metal oxide catalysts

系统地研究了分散在各种金属氧化物载体上的镁、钛、钒、锰、铁、钴、铜、镓、铌、钼、镧系元素、铑和钨的氧化物微粒的“量子尺寸效应”.主要通过XAFS进行的样品表征导致以下结构结果。(1)在二氧化硅载体上;镁和铜被负载为表现出量子尺寸效应的微粒，镧系元素被稳定为二维金属氧化物，钛、钒、铌、镓和钨原子级分散，原子级分散的样品表现出光活性。(2)在氧化铝和氧化镁载体上，每种金属阳离子以原子形式分散，并在高负载下形成二元金属氧化物。(3)在二氧化钛载体上，金属阳离子在低负载下原子稳定。金属元素被转化为金属颗粒尺寸在ca。100 *。(4)锆和铁的氧化物形成固溶体。上述催化剂能够应用于以下反应。(1)二氧化硅负载钒氧化物上低碳烷烃的选择性光氧化。(2)二氧化硅负载镧系氧化物上的酸催化反应。(3)烯烃在二氧化硅负载的氧化钛上的选择性氧化。(4)甲烷在二氧化硅负载的氧化钨上的氧化。(5)在钛载铜上选择性还原NOx。(6)二氧化碳在二氧化钛负载铑上的光还原。(7)Mg-Mo二元金属氧化物上的烯烃复分解反应。(8)负载型氧化镁催化烯烃环氧化反应。

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.