Dehalogenative oligomerization of dichlorodifluoromethane catalyzed by activated carbon-supported Pt-Cu catalysts: effect of Cu to Pt atomic ratio

Activated carbon-supported Pt-Cu catalysts with a Cu to Pt atomic ratio in the range of 2-18 catalyze the formation of oligomerization hydrocarbon products from an equimolar mixture of CF2Cl2 and H-2 at 523 K. The steady-state selectivity toward C2+ products is 42% for the Pt1Cu2/C and increases to more than 70% when the Cu/Pt atomic ratio reaches 18:1. All catalysts deactivate with time on stream. The results of the TEM investigation are consistent with the suggestion that deactivation is attributed to carbon deposition and not to particle sintering. All of the catalysts have approximately the same average size of Pt-containing particles, independent of Cu/Pt atomic ratio, and the average size is essentially the same for the freshly reduced and used Pt-Cu catalysts. As the Cu to Pt atomic ratio is increased, a larger fraction of Cu is unalloyed with Pt. The performance of the catalysts in the CF2Cl2 + H-2 reaction is discussed in terms of the different active sites, which catalyze different elementary reaction steps. (C) 2003 Elsevier B.V. All rights reserved.