Process for the selective hydrogenolysis of CCl2F2 (CFC-12) into CH2F2 (HFC-32)

The conversion of waste CCl2F2 (CFC-12) into high added value product CH2F2 (HFC-32) seems technically and economically feasible with a selected palladium on activated carbon catalyst. This catalyst shows a remarkable constant selectivity to HFC-32 in the range between 70% and 90% at all conversion levels with varying process conditions. Small amount of impurities, like Al, Fe or Cr, present in the activated carbon can have a significant effect on the catalyst performance. These impurities act as Friedel-Crafts catalyst thus catalyzing the unwanted chlorine-fluorine exchange. The chlorine-fluorine exchange can be sufficiently suppressed by removing the impurities from the activated carbon support prior to introduction of the palladium. The mechanism of the reaction follows mainly parallel rather than the expected serial pathways. A reaction scheme is proposed, which explains the high selectivity to HFG-32 by formation of a CF2-carbene, which preferentially desorbs as HFC-32.