Abstract: The manganese oxide catalysts supported on mesoporous Al₂O₃ modified by LaCeZr or YCeZr were prepared by successive impregnation. The structure of the catalysts was characterized by X-ray diffraction, N₂ adsorption-desorption, X-ray absorption fine structure, X-ray photoelectron spectroscopy, and temperature-programmed reduction by H₂. The state of manganese species and their reducibility were investigated and correlated with the CO and C₃H₈ oxidation performance of the catalysts. The results demonstrate that the manganese species mainly exist as Mn₃O₄ crystallites, which interact with the support Al₂O₃. The different interaction strength determines the reducibility and catalytic properties of the catalysts. The promoters LaCeZr or YCeZr effectively inhibit the interaction between Mn and Al oxides, increasing the mobility of Mn–O bond and the catalytic activity of the corresponding catalysts. Compared with YCeZr, the promoter LaCeZr improves the reducibility of MnO_x to a larger extent, enhancing the activity more obviously. The catalysts modified by LaCeZr calcined at 650 ^oC exhibits high oxidation performance and sulfur resistance. In the presence of 0.035% SO₂ in the feed, the CO oxidation activity of the catalyst can be well maintained, and the C₃H₈ oxidation activity decreases only a little.

Key words: manganese oxide, alumina, modification, carbon monoxide, oxidation, propane, oxidation, fine structure