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The crystal structure of perovskite-type catalysts, Ca_xLa_(1-x)MnO_(3 λ), remains unchangedwhen x varies from 0 to 1 as identified by X-ray analysis. Both non-stoichiometric amountof oxygen (denoted by λ) and Mn~(4 ) content are functions of x. ESR analysis showed thatvarying the substitution value x in A, the oxidation state of B could simultaneously be adjust-ed, this permits one to change the oxygen chemisorpting ability of these catalysts and toraise their catalytic activity. Based upon the experimental results and from the point ofview of solid defect chemistry, a theoretical analysis for the possible formation of defecttypes is made, and the assumption that the formation of the active species O_2~- or O~- isthrough the reaction of oxygen anion defect with molecular oxygen in gas phase is proposed.This idea is supported by the data obtained by XPS investigation. The reaction mechanism ofpcrovskite-type catalyst for ammonia oxidation is discussed accordingly.  相似文献   
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本文根据X-光结构分析,Ca_xLa_1-_xMnO_(3 λ)当x值自0变化至1时,样品的晶体结构并不改变,均成钙钛石型;非计量氧(λ值)以及Mn~(4 )含量均为x值的函数.ESR-分析说明,变更钙钛石晶格中A离子的取代数x值,可以同时调整B离子的价态,从而改变催化剂化学吸附氧的能力,达到提高催化剂活性的目的.根据实验结果,从固体的缺陷理论出发,对可能形成的缺陷类型作了理论上的分析,提出反应的活性种——O_2~-O~-系由氧阴离子缺陷和氧分子反应生成的假设,并得到了表面电子能谱数据的支持.在此基础上,讨论了氨在这类催化剂上的反应机理。  相似文献   
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