Selective hydrogenolysis of CCl2F2 into CH2F2 over palladium on activated carbon Kinetic mechanism and process design

A process-development study is presented aiming at the conversion of CCl2F2 into CH2F2. The CCl2F2 is an undesired compound because of its negative impact on the environment. Palladium on activated carbon is the most appropriate catalyst for this selective hydrogenolysis. During reaction, palladium is present as the carbide (PdC0.15). Except for rhenium, all other noble metals show activity but with quite varying selectivities. The kinetic scheme is elucidated and appears to be based on parallel kinetics; one route leads to either CHClF2 or CH2F2 and the other to methane. The selectivity for CHClF2 or CH2F2 depends on the amount of adsorbed chlorine on the catalytic active surface. The readsorption of the products will not occur. Provided if excess hydrogen is present, the catalyst is sufficiently stable for a commercial process. A conceptual process design is presented. It can be concluded that the process is technically and economically feasible. (C) 2000 Elsevier Science B.V. All rights reserved.