Abstract

The LaMn_{1 – x}Fe_xO₃ (х = 0–1) perovskites were prepared by the Pechini route and characterized by X-ray diffraction analysis, HR TEM, XPS, and BET. Their catalytic activity was investigated in methane and CO oxidation reactions. According to X-ray analysis data, the samples with х < 0.4 were orthorhombic and the samples with х > 0.4 were rhombohedral. In the sample with х = 0.4, both of the modifications were present due to a morphotropic phase transformation at х ≈ 0.4. All of the substituted perovskites were characterized with higher specific surface areas and lower normalized catalytic activity in methane and CO oxidations as compared with unsubstituted ones due to surface enrichment with La compounds. The samples with х = 0.6 and 0.8 demonstrated the lowest activity and stability in the catalytic oxidation of methane, which can be due to the accumulation of carbonates and carbon on the surface in the course of methane oxidation and the additional formation of locally ordered structure regions on the surface.

中文翻译：

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甲烷和一氧化碳氧化反应中的LaMn 1 – x Fe x O 3（x = 0–1）钙钛矿

摘要

LaMn _{1 – x} Fe _x O ₃（х = 0–1）钙钛矿是通过Pechini路线制备的，并通过X射线衍射分析，HR TEM，XPS和BET进行了表征。在甲烷和一氧化碳氧化反应中研究了它们的催化活性。根据X射线分析数据，х <0.4的样品为正交晶，而х > 0.4的样品为菱面体。在х = 0.4的样品中，由于在х处发生了同相相变，因此存在两种修饰≈0.4。与未取代的钙钛矿相比，由于具有La化合物的表面富集，与未取代的钙钛矿相比，在甲烷和CO氧化中具有更高的比表面积和更低的归一化催化活性。х = 0.6和0.8的样品在甲烷的催化氧化中表现出最低的活性和稳定性，这可能是由于甲烷氧化过程中碳酸盐和碳在表面的积累以及局部有序结构区域的额外形成所致。在表面上。