Hydrodechlorination of CCl4 over Pt/gamma-Al2O3 - Effects of reaction pressure and diluent gases on distribution of products and catalyst stability

Pt/gamma -Al2O3 catalysts were prepared by a wet impregnation method and ap plied for the hydrodechlorination of CCl4 around 400 K. The extent of catal yst deactivation was in line with the propensity of the formation of oligom ers (mainly C2Cl4). Both catalyst stability and selectivity to CHCl3 were e nhanced when the pressure was increased up to an optimum level. Above the o ptimum pressure, catalyst deactivation was accelerated with enhanced dimeri zation of abundantly adsorbed CCl4, due to the relatively hydrogen-deficien t environment on the surface. Addition of diluent gases such as CH4, N-2 im proved the catalyst stability at pressurized reaction conditions. These gas es adsorbed (albeit weakly) on platinum to reduce the selectivity to CHCl3, while improving the catalyst stability. The increased amount of hydrogen a dsorbed on the platinum catalyst at high reaction pressures appeared to be the main factor for enhancement of selectivity to CHCl3 and catalytic stabi lity. (C) 2001 Elsevier Science B.V All rights reserved.