Turnover rate and kinetic mechanism for the reaction of hydrodechlorination of 1,1-dichlorotetrafluoroethane (CF3-CFCl2) over a polycrystalline Pd foil

The kinetics (turnover rate, activation energy, reaction order) of catalytic hydrodechlorination of 1,1-dichlorotetrafluoroethane or CFC 114a (CF3-CFCl2) were determined on a similar to 0.5 cm(2) palladium polycrystalline foil as a catalyst. The reaction rates were measured in the temperature range of 80-200 degrees C at a total pressure of 770 Torr. Using a reaction cell that was connected to an ultrahigh vacuum surface characterization chamber the composition of the metal surface was monitored before and after reaction. The products formed in a parallel reaction network and the turnover rates at 150 degrees C, 50 Torr CFC 114a, 100 Torr H-2, and 0.1 Torr HCl were 2.1 s(-1) for CF3-CFH2, 3.0 x 10(-1) s(-1) for CF3-CFClH, and 6.4 x 10(-2) s(-1) for CF3-CH3. For the two most abundant products, the reaction order is 1 in CF3-CFCl2, 0.5 in H-2 and -1 in the reaction product HCl. These results suggest that the rate determining step for the reaction is the associative chemisorption of CF3-CFCl2 on the palladium surface. The palladium surface was free of adsorbates after the reaction with the exception of sulfur impurity that may accumulate during reaction.