Hydrodechlorination over Pd–Pt/Al2O3 catalysts: A comparative study of chlorine removal from dichlorodifluoromethane, carbon tetrachloride and 1,2-dichloroethane Original Research Article

A comparative study of hydrodechlorination of dichlorodifluoromethane, carbon tetrachloride and 1,2-dichloroethane over alumina-supported Pd–Pt catalysts showed several interesting features in the catalytic behavior. Platinum, the metal which binds chlorine and chlorine-containing organic intermediate species less strongly than palladium is a better catalyst in CCl4 hydrodechlorination. However, in hydrodechlorinations of CCl2F2 and 1,2-dichloroethane platinum offers too weak binding with reaction species, and in effect, Pd/Al2O3 shows a better catalytic performance than Pt/Al2O3. Nevertheless, this positive behavior of Pd/Al2O3 can still be improved by doping it with small amounts of platinum. The formation of mixed Pd–Pt ensembles leads to an enhancement of the overall activity and selectivity for partial hydrodehalogenation. Temperature-programmed hydrogenation (TPH) of deposits accumulated on the catalysts during hydrodechlorination confirms a better resistance of platinum against carbiding. In the case of Pd/Al2O3 and Pd–Pt/Al2O3 catalysts, massive amounts of coke (and chlorine) were found after CCl4 reaction.