Influence of CuO on Ce-Zr-O2 Dispersion on Catalytic Properties in CO Oxidation

Ce-Zr-O-2 solid solution was prepared by citric acid method and 10% M/Ce0.8Zr0.2O2(M = Co, Mn, Cu) and 1% Pt/Ce0.8Zr0.2O2 were prepared by incipient-wetness impregnation method. It was found that Cu was the best active composition in CO oxidation over M/Ce0.8Zr0.2O2 which CO was completely converted into CO2 at ca. 120 degrees C and was more active than 1% Pt/Ce0.8Zr0.2O2. It was found that the optimum ratio of Ce to Zr was 4, Cu/Ce0.8Zr0.2O2 showed the best activity in CO oxidation. Deposition method(DP), incipient-wetness precipitation method(IW), hydro-thermal method(HT) and citric acid method(CA) were used to prepare 20% Cu/Ce0.8Zr0.2O2 catalysts. Cu/Ce0.8Zr0.2O2 prepared by deposition method showed better activity in CO oxidation, which CO was completely converted into CO2 at ca. 100 degrees C. The data from H-2-TPR showed that the redox of Cu/Ce0.8Zr0.2O2 was not a determining factor to control the CO oxidation. TEM results showed that the CuO was well dispersed on Ce0.8Zr0.2O2. Based on adsorption data of CO and O-2, the high activity of Cu-based catalyst should be ascribed to the week competitive adsorption between CO and O-2 over Ce0.8Zr0.2O2. The oxygen vacancy on Ce0.8Zr0.2O2 was a crucial factor to affect the CuO dispersion and to reduce the competitive adsorption between CO and O-2.