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 Mn(4+)-Mn(3+) 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.