Modification of the supported palladium catalysts surface during hydrodechlorination of carbon tetrachloride

Abstract

Hydrodechlorination (HDC) of carbon tetrachloride (CCl 4) was studied in the presence of 0.5–5% palladium catalysts supported on carbon material Sibunit and TiO 2. Experiments were performed in a flow-type reactor in hydrogen at 150–220 °C. Non-chlorinated C 1–C 5 hydrocarbons were formed in the presence of all catalysts. Stable work (more than 4 h) was observed in the most cases. Conversion of carbon tetrachloride was 100%. It was assumed, that Cl, which was formed as intermediate during dissociative adsorption of CCl 4, oxidizes palladium on the catalytic surface generating active sites of oligomerization. The surface of the catalyst is covered by carbonaceous deposits during the HDC, resulting in deactivation of the catalyst. These deposits are probably a little different in nature for Pd/Sibunit and Pd/TiO 2 catalysts. For Pd/Sibunit carbonaceous deposits are more hydrocarbonaceous in nature. These carbonaceous deposits can be removed by heating in argon-flow to regenerate the catalyst.