The effect of precursors salts on surface state of Pd/Al2O3 and Pd/CeO2/Al2O3 catalysts

The influence of the precursors on the promoting effect of ceria on Pd/Al2O3 catalyst, when ceria is coated over alumina was studied. The reaction of propane oxidation proceeded under different feed conditions and the surface active sites were characterized by X-ray photoelectron spectroscopy (XPS) and in situ diffuse reflectance spectroscopy (DRS). XPS and DRS results show that PdO/Pd0 interface are the active sites independent of the precursor, while the catalysts containing CeO2 showed formation of palladium species in the highest oxidation state, probably PdO2 (338 eV) after the oxidation of propane. Besides, the O/Al and O/Ce ratios evidenced the increase of oxygen storage in the presence of CeO2. In addition, the precursor acetylacetonate favors the oxygen storage in the lattice.