Thermal stability, structural properties and catalytic activity of Pd catalysts supported on Al2O3-CeO2-BaO mixed oxides prepared by sol-gel method.

Al2O3-CeO2-BaO oxides with constant Al/Ba mass ratio and increasing cerium content were prepared, using the sol-gel procedure, and calcined at 1000 °C for 5h. The influence of barium oxide on the thermal stability and on the morphological and structural properties of the corresponding supports, in terms of increasing surface area of alumina and ceria dispersion, was studied. The corresponding Pd (1wt%) catalysts were prepared by a stepwise impregnation method with a solution of palladium acetyalcetonate in benzene. Palladium was introduced in two sequential steps by impregnation 0.5wt% of Pd each time. The structural and textural properties of the materials were studied by XRD (X-ray diffraction) analysis, BET surface area and pore size distribution measurements. The effect of ceria on structural properties and methane combustion activity of the Pd-based catalysts was investigated. The light-off temperatures of low-ceria loaded catalysts are both shifted 60-90 °C, respectively, below the corresponding temperature observed on high-ceria loaded samples.