Mechanistic investigation of the hydrodechlorination of 1,1,1,2-tetrafluorodichloroethane on metal fluoride-supported Pt and Pd

The hydrodechlorination of CF3CCl2F over Pd and Pt supported on β-AlF3 and MgF2 with D2 gas has been investigated employing temperature programmed isotope exchange (TPIE) under static conditions. The isotope exchange observed between the H-loaded metal catalyst and the D2 gas phase demonstrates the significantly higher hydrogen uptake capability of Pd-based catalysts. Both Pd and Pt on β-AlF3, show significantly higher hydrogen/deuterium uptake and isotope exchange activity as compared with the MgF2 support, probably due to the presence of hexagonal channels in β-AlF3 and its higher Lewis acidity. The combination of these properties make Pd/β-AlF3 a superior catalyst for selective hydrodechlorination of CF3CCl2F. Based on the results of the hydrodechlorination of CF3CCl2F with D2, a competitive rather than a consecutive mechanism is proposed. The data from H/D-TPIE are best interpreted by the formation of surface carbene species as intermediates.