Characterization and reactivity of Pd/MgO and Pd/gamma-Al2O3 catalysts in the selective hydrogenolysis of CCl2F2

Al2O3 and MgO supported Pd catalysts with 6 wt % loading are prepared by the wet impregnation method. The catalysts are made into two parts; one of them is dried at 110 °C, and the other one is calcined at 500 °C. Conversion of CCl2F2 in hydrogen is carried out under identical reaction conditions on both dried and calcined catalysts after the catalysts are prereduced in H2 at 400 °C for 3h. The fresh and the used catalysts are characterized by BET-surface area, X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed desorption (TPD) of NH3, and X-ray photoelectron spectroscopy (XPS). XPS data shows that surface Pd species are more in MgO supported catalyst than in Al2O3 supported one. In used catalysts, surface F- concentration is more on MgO than on Al2O3 supported Pd catalyst. The MgO supported Pd catalyst (dried) showed higher reactivity and CH2F2 selectivity compared to other catalysts. MgO support is found to be superior to Al2O3 support for Pd for the reaction.