Khouloud Sadouki, Imen Ben Said, Shemseddine. Fessi, Jorge Quesada, Eva Diaz, Zouhaier. Ksibi, Abdelhamid Gorbel , Tunisia
CexZr1-xO2/SiO2 (CeZr-O2/SiO2) mixed oxides were synthesized using sol-gel process and supercritical drying methods. Pd/CexZr1-xO2/SiO2 catalysts have been evaluated in methane combustion in an attempt to investigate the effects of the preparation method and the different addition step of palladium precursor on the oxidation activity of supported Pd catalysts for this greenhouse gas. The metal was deposited by impregnation of palladium acetate (Pd(OAc)2) on dried or calcined CeZr-O2/SiO2 support or in situ by sol- gel process during the preparation of the support. The properties of the as-synthesized catalysts, such as textural structure, surface chemical state, surface acidity and the oxygen storage capacity (OSC) were determined using N2-physical adsorption/desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption of NH3 (TPD-NH3) and O2 (TPD-O2) in order to correlate their activity with their physiochemical properties.
Among all the catalysts tested the sample prepared by impregnation (on dried or calcined CeZr-O2/SiO2 support) presented the higher activity for methane combustion. These results could be due to the good dispersion and stability of PdO species on CeZr-O2/SiO2 surface, the large surface area, the weak acidity and the higher OSC compared to the catalyst prepared by sol-gel process.