Effect of Co and Ce on silica supported manganese catalysts in the reactions of complete oxidation of n-hexane and ethyl acetate

Mono-component and bi-component catalysts, prepared by impregnation of silica with aqueous solution of Mn, Co, and Ce nitrates, were tested in the reactions of complete oxidation of n-hexane and ethyl acetate. The catalysts were characterized by powder X-ray diffraction, temperature-programmed reduction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy (FTIR). The catalytic activity is significantly increased by the combination between manganese and cobalt, which is explained as a result of the high mobility of lattice oxygen, the simultaneous presence of Mn4+–Mn3+ couple, decrease in the strength of the Co–O bond, and the predominance of Co in the second oxidation state on the catalyst surface. The decrease in catalytic activity of Mn–Ce sample is attributed to the predominance of Ce on the surface and lower mobility of the lattice oxygen.