Influence of barium and cerium oxides on alumina supported Pd catalysts for hydrocarbons combustion

The effects of baria and ceria additions to alumina-supported palladium catalysts have been investigated. Two series of binary Al2O3-BaO and ternary oxides Al2O3-CeO2-BaO were prepared using a sol-gel method and then characterized, after high-temperature treatments, by XRD, BET, TG, TEM and EDXS analyses. The influence of baria and ceria on the thermal stability and morphology of the supports was examined. A baria content of 12 wt.% appears the most effective for alumina stabilization. Palladium catalysts were prepared by impregnation method using Pd(NH3)4(NO3)2 and were characterized by XRD and TEM. The catalysts showed high activity in the total oxidation of methane, in the temperature range 200-600 oC. The methane oxidation activity of both PdAlBa and PdAlCeBa series increases with the specific surface area (SSA), ceria addition does not produce significant differences of activities. The ethene combustion was studied, also, on the series PdAlCeBa, as a model structure-sensitive reaction chosen to investigate possible palladium-ceria interactions. The reactivity was compared with that of PdAlBa catalyst with the same baria content.