CATALYTIC HYDRODECHLORINATION OF 1,2-DICHLOROETHANE AND TRICHLOROETHYLENE OVER Rh/Si0 2 CATALYSTS

Reactions of hydrogen with 1,2-dichloroethane and trichloroethylene have been investigated over Rh/Si0 2 catalysts at 365-553K and 0.1 MPa. The major products of the reactions are HCl and C 2 H 6. The selectivity for C 2 H 6 increases with increasing temperature. C 2 HC 5 Cl is a minor product for the dichloroethane reaction; partially dechlorinated products, i.e. C 2 H 5 Cl, C 2 H 4 CI 2, C 2 H 3 Cl, and C 2 H 2 CI 2, constitute the minor products for the trichloroethylene reaction. The selectivity for the partially dechlorinated C 2 hydrocarbons decreases with increasing temperature. Cl dissociated from chlorinated hydrocarbons poisons the catalyst. Regeneration of catalyst by hydrogen treatment restores the catalyst to more than 70% of the initial activity for the trichloroethylene reaction. Probing the hydrogenation activity of the used Rh/Si0 2 and RhCl 3 /Si0 2 with ethylene hydrogenation shows that the presence of CI on Rh/Si0 2 decreases hydrogenation but increases ethylene hydrogenolysis activities.