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 cat alytic hydrodechlorination of 1,1-dichlorotetrafluoroethane or CFC 114 a (CF3-CFCl2) were determined on a similar to 0.5 cm(2) palladium poly crystalline foil as a catalyst. The reaction rates were measured in th e temperature range of 80-200 degrees C at a total pressure of 770 Tor r. Using a reaction cell that was connected to an ultrahigh vacuum sur face characterization chamber the composition of the metal surface was monitored before and after reaction. The products formed in a paralle l reaction network and the turnover rates at 150 degrees C, 50 Torr CF C 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. Fo r 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 ch emisorption of CF3-CFCl2 on the palladium surface. The palladium surfa ce was free of adsorbates after the reaction with the exception of sul fur impurity that may accumulate during reaction.