Development of a palladium on activated carbon for a conceptual process in the selective hydrogenolysis of CCl2F2 (CFC-12) into CH2F2 (HFC-32)

The hydrogenolysis of CCl2F2 over 1 wt.% palladium, platinum, rhodium, ruthenium, iridium, and rhenium on activated carbon has been studied in a micro-flow reactor, in a temperature range of 450-540 K, H-2/CCl2F2 feed ratios between 1.5 and 20, a pressure up to 0.4 MPa, and a WHSV between 0.5 and 2 g/(g h). The main products of the reaction for all investigated catalysts were CHClF2, CH2F2, and methane. Palladium on activated carbon shows the highest selectivity to CH2F2 (70-90%) at all conversion levels. The activity, selectivity to CH2F2 and stability of the palladium catalyst is a strong function of the hydrogen to CFC ratio, methane recycle ratio and the recycle of CHClF2 is not recommended. The catalyst proves to be stable over a period of 2000 h with simulated recycle streams and an optimum temperature for the catalyst performance was found at 510 K. On the basis of the experimental data and a kinetic network a conceptual process design was made. In this design no hurdles have been encountered and this waste technology looks in economic prospective very promising. (C)2000 Elsevier Science B.V. All rights reserved.