Role of tetrachloromethane as a gas-phase additive in the oxidative dehydrogenation of propane over cerium oxide

In the absence of tetrachloromethane (TCM) carbon dioxide is the principal product formed in the oxidation of propane on ceria. The introduction of sm all partial pressures of TCM increases the conversion of propane with selec tivities to propene up to 80%. Except under special circumstances no eviden ce of chlorinated species from TCM is found in the bulk structure while the surface region is shown to contain chlorine, although its form is not know n. The enhancement of conversion and selectivity to propene is shown to be dependent upon the presence of chlorine, in whatever form, in the surface r egion of the catalyst. (C) 2000 Academic Press.