Structure insensitivity and effect of sulfur in the reaction of hydrodechlorination of 1,1-dichlorotetrafluoroethane (CF3-CFCl2) over Pd catalysts

The kinetics of the hydrodechlorination of 1,1-dichlorotetrafluoroethane (CFC 114a) was studied on Pd(III), Pd(100), and a Pd foil at atmospheric pressure, The three products formed were CF3-CFH2 (HFC 134a), CF3-CFClH (HCFC 124), and CF3-CH3 (HFC 143a) with selectivities independent of conversion. The single crystals and foil (model catalysts) were studied in an apparatus that permitted the direct transfer of samples between a high pressure cell (1 atm) and an ultrahigh vacuum chamber, The reaction rates were measured in the temperature range of 350 to 470 K, The reaction is not sensitive to the structure of the catalyst, as indicated by the similar turnover rates for all catalysts tested. The reaction is inverse first order in the reaction product HCl on all samples. Sulfur adsorbed on the Pd surface depressed the rates of formation of 134a more strongly than the rates of 124 and 143a. (C) 1998 Academic Press.