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

A good catalyst for the selective hydrogenolysis of waste CCl2F2 (CFC-12) into the high added value product CH2F2 (HFC-32) has been developed. This catalyst is based on palladium on activated carbon and shows a high selectivity (70-90%) at all conversion levels. It is important to purify the activated carbon support prior to impregnation of the palladium salt. A nitrogen heat pretreatment enhances the stability and activity. During reaction an increase in selectivity to CH2F2 has been found. This increase, without loss in activity, can be explained by further lowering the amount of accessible impurities by the produced HF and HCl. These impurities, like iron and aluminium are responsible for chlorine/fluorine exchange and total hydrogenolysis activities. The activity, selectivity to CH2F2, and the stability of the catalyst is a strong function of the hydrogen to CFC ratio. It was found that during reaction the palladium is converted into palladium carbide. (C) 1998 Elsevier Science B.V. All rights reserved.