CATALYTIC HYDROGENOLYSIS OF 1,1,2-TRICHLOROTRIFLUOROETHANE ON GAMMA-AL2O3-SUPPORTED PALLADIUM ZINC OXIDE CATALYST

摘要

The catalytic hydrogenolysis of 1,1,2-trichlorotrifluoroethane on a gamma-alumina-supported palladium/zinc oxide catalyst under flow conditions has been conducted. The results show that relative to a gamma-alumina-supported palladium system, enhanced conversion of the feedstock is achieved to give a mixture of chlorofluorohydrocarbons and hydrofluoroalkanes. Kinetic studies show that the addition of zinc to the palladium metal function alters the equilibrium for the hydrogenolysis reaction, giving higher selectivity to dechlorinated products. The lifetime of the Pd/ZnO/gamma-Al2O3 catalyst is also enhanced relative to a Pd/gamma-Al2O3 system operating under identical conditions. Differential scanning calorimetry, X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and kinetic analysis indicate a synergistic relationship between the palladium and zinc(II) oxide functions, where a zinc-rich phase evokes chemical stability and increased dispersion upon discrete metallic palladium crystallites. XPS analysis of the palladium and zinc functions respectively shows that catalyst deactivation occurs through the formation of palladium(IV) halide in conjunction with palladium enrichment of the surface. (C) 1997 Academic Press. [References: 49]