Catalytic hydrodechlorination of CCl4 over silica-supported PdCl2-containing molten salt catalysts: The promotional effects of CoCl2 and CuCl2

The hydrodechlorination of CCl4 with H-2 was tested over several silica-supported PdCl2-containing molten salt catalysts. The base catalyst was PdCl2-(C4H9)(4)NCl/SiO2; CoCl2, CuCl2, or both were doped into the catalyst as promoters to modify its activity, product selectivity, and catalyst longevity. The catalysts converted CCl4 into C-1-C-5 paraffins and C-2-C-4 olefins, CH2Cl2, CHCl3, CCl2CCl2, and CHClCCl2. Doping CoCl2 into the PdCl2-(C4H9)(4)NCl/SiO2 catalyst enhances its initial CCl4 conversion from 85 to 99.3%, shifts reaction products toward more hydrocarbons, and also prolongs the life of the catalyst. Addition of CuCl2 to the PdCl2-(C4H9)(4)NCl/SiO2 catalyst also improves the initial CCl4 conversion to 94.5% and has an even stronger stabilizing effect on the catalytic activity, while shifting reaction products toward C-1-chlorocarbons. When both CoCl2 and CuCl2 are added to the base catalyst, the promoted catalyst exhibits the highest CCl4 initial conversion of 99.5% and the greatest longevity among all four catalysts. The corresponding specific activities for the above catalysts were of 0.636 x 10(-3), 1.154 x 10(-3), 1.139 x 10(-3), and 1.184 x 10(-3) mol CCl4/g cat min at 130 degrees C, respectively. The promotional and product distribution effects were attributed to the presence of CoCl2, CuCl2, or both as additional Lewis acidic sites for activation of CCl4 molecules and to the interaction of these additives with the Pd-containing active centers in supported molten salt media. (C) 1996 Academic Press, Inc.