钙钛石型复合氧化物催化剂LaMn_yCo_(1-y)O_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

A Study of Catalytic Properties of Perovskite-type Oxides——Ⅰ. The Relationship between the Type of Oxygen Species and the Catalytic Property in Ammonia Oxidation

用XRD,XPS和TPD等手段研究了钙钛石(ABO_3)型复合氧化物催化剂LaMn_yCo_(1-y)O_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的氧种(α,β,β’).它们所对应的脱附温度分别为293K≤T_α≤773K,773K≤T_β≤1073K,T_β’≥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.

The type of oxygen species in perovskite-type oxides LaMn_yCo_(1-y)O_3(y = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9, 1.0) has been studied by means of XRD, XPS and TPD. The catalytic activity in ammonia oxidation was also investigated. It was found that there were three desorption peaks in TPD curve corresponding to three types of oxygen species (α, β, β'). The desorption temperatures were 293K≤T_α≤773K, 773K≤T_β≤1073K and T_β'≥1073K respectively. The relationship among the composition, structure and the catalytic property of the catalyst was correlated and could be explainned with a model based on solid defect reaction and the interaction between Co and Mn ions. The adsorption strength and quantity of a oxygen are proportional to the catalytic activity. The result indicates that the synergetic effect between B-site ions seems to the benefit of the ammonia oxidation reaction.