LaMn_{1 – x}Fe_xO₃ (x = 0–1) Perovskites in Methane and Carbon Monoxide Oxidation Reactions¹

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.