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

Hydrodechlorination (HDC) of carbon tetrachloride (CCl4) was studied in the presence of 0.5-5% palladium catalysts supported on carbon material Sibunit and TiO2. Experiments were performed in a flow-type reactorin hydrogen at 150-220 degreesC. 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 CCl4, 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/TiO2 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. (C) 2002 Elsevier Science B.V. All rights reserved.