钙钛石型复合氧化物催化剂LaMn~yCo~1-yO~3的催化性能研究Ⅰ.在氨氧化反应中氧的形态和催化性能的关系

用XRD,XPS和TPD等手段研究了钙钛石(ABO~3)型复合氧化催化剂LaMn~yCo~1-yO~3中氧的形态;研究了催化剂在氨氧化反应中的活性,发现这类氧化物中存在三种形态氧种(α,β,β').它们所对应的脱附温度分别为293K≤T~α≤773K.773K≤T~β≤1073K,Tβ'≥1073K.研究了它们与催化剂组成、结构及催化性能之间的关系,并用缺陷化学反应和B位离子之间的相互作用模型进行了解释.α氧的吸附强度和吸附量与催化活性成正比关系.B位离子之间的协同作用有利于氨氧化反应的进行.

A study of catalytic properties of perovskite-type oxides LaMn~yCo~1-y O~3.Ⅰ.the relationship between the type of oxygen species and the catalytic property in ammonia oxidation

The type of O species in perovskite-type oxides LaMnyCo1-yO3(y = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9, 1.0) was studied by XRD, XPS and TPD. The catalytic activity in NH3 oxidation was also studied. There were 3 desorption peaks in TPD curve corresponding to 3 types of O species (a, b, b'). The desorption temps. were 293 K ?Ta ?773 K, 773 K ?Tb ?1073 K and Tb' ?1073 K, resp. The relation among the composition, structure and the catalytic property of the catlyst was correlated and could be explained with a model based on solid defect reaction and the interaction between Co and Mn ions. The adsorption strength and quantity of a O are proportional to the catalytic activity. The synergetic effect between B-site ions seems to the benefit of the NH3 oxidation reaction.