Deactivation of Pd/C catalysts in the hydrodechlorination of the chlorofluorocarbons CFC-115 and CFC-12

The deactivation of Pd/C catalyst in the hydrodechlorination of the two chlorofluorocarbons CClF2–CF3 (CFC-115) and CF2Cl2 (CFC-12) into their corresponding hydrofluorocarbons CHF2–CF3 (HFC-125) and CF2H2 (HFC-32) has been systematically investigated. Besides Pd/C catalyst, Pd black was used as a model catalyst in order to exclude the effects of carbon support. The results show that Pd/C catalyst is more efficient for the catalytic hydrodechlorination of CFC-115 than that of CFC-12. From the XRD, TEM, and H2-TPR characterizations, it can be concluded that the deactivation of Pd/C catalysts in the hydrodechlorination of CFC-115 at 673 K, a weight hourly space velocity (WHSV) of 2400 ml g−1(catal.) h−1 and a H2:CFC-115 molar ratio of 2 is mainly attributed to the sintering of the active species Pd particles while the catalyst deactivation in the hydrodechlorination of CFC-12 at 553 K, a WHSV of 1000 ml g−1(catal.) h−1 and a H2:CFC-12 molar ratio of 4 is due to the carbonaceous deposits. Additionally, the deactivation mechanisms of Pd/C catalysts in the two different hydrodechlorination reactions are discussed.