Surface properties and catalytic activities of PdO/CeO2, PdO/TiO2 and PdO/gamma-Al2O3 catalysts

The surface species and dispersion of PdO on CeO2, TiO2 and gamma -Al2O3 ha ve been studied by means of XRD, XPS and SEM techniques. The results obtain ed show that there is a great difference between CeO2 support and other kin ds of supports in the crystal phase structure and particle size, which are responsible for CO and CH4 oxidation. The order of catalytic activity for t he CH4 oxidation is: PdO/CeO2 > PdO/TiO2 > PdO/gamma-Al2O3 and that for CO oxidation is: PdO/CeO2 > PdO/gamma-Al2O3 > PdO/TiO2. It is interesting to f ind that the PdO/CeO2 catalyst exhibits high catalytic activity for CO oxid ation even at a low temperature of 50 degrees C. Due to strong interaction between ceria and palladium, excellent results are obtained in the oxidatio n reaction of CO or CH4. The high dispersion of PdO is found to be the main factor for the high catalytic oxidation activity observed.