Aliovalent-substituted chromium-based catalysts for the hydrofluorination of tetrachloroethylene

New aliovalent-doped chromium oxide and fluoride catalysts have been prepared by coprecipitation techniques to obtain solid solutions. The catalysts have been characterized by, e.g., X-ray, BET, and pyridine adsorption analysis, and tested for their catalytic activity in the gas-phase reaction of C2Cl4 with HF. The latter reaction involves several consecutive steps and produces the expected C2HClxFy (x+y=5) compounds, but also some perhalogenated compounds the formation of which needs further explanation. Reaction data obtained with a (Cr,Mg)(F,OH)x catalyst were used to calculate reaction rates and activation energies of all the consecutive steps which could be successfully used to predict the reaction outcomes under varying experimental conditions.