Applied Catalysis A: General 212 (2001) 223–238 Deactivation of palladium on activated carbon in the selectiv hydrogenolysis of CCl 2 F 2 (CFC-12) into CH 2 F 2 (HFC-32) André Wiersma, Emile J.A.X. van de Sandt, Michiel Makkee ∗ , Jacob A. Moulijn Department of Chemical Process Technology, Section of Industrial Catalysis, Faculty of Applied Sciences, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands Abstract The stability of the selected 1 wt.% palladium on activated carbon catalyst in the selective hydrogenolysis of CCl 2 F 2 into CH 2 F 2 as function of temperature (510–540 K) and hydrogen to CCl 2 F 2 feed ratio (1.5–20 mol/mol) has been studied. A satisfactorily stable catalyst performance for at least 1600 h of operation has been obtained at 510 K and H 2 to CCl 2 F 2 feed ratios of 6 and 10. Outside this window, significant deactivation of the catalyst was observed. The conversion of CCl 2 F 2 and the selectivity for CH 2 F 2 were higher at increasing ratio H 2 to CCl 2 F 2 ratio. These differences in catalyst performance became more pronounced as a function of time on stream. At higher temperatures (520, 525,and 540 K) the catalyst deactivated independent of the H 2 to CCl 2 F 2 feed ratio. Addition of methane or CHClF 2 to the feed led to additional deactivation of the catalyst, both at lower and higher temper atures. The observed phenomena of deactivation could be well explained by the formation of carbonaceous deposits on the surface. Neither sintering nor loss of palladium was found after reaction. On the contrary, the used catalysts had a h palladium dispersion than the fresh catalyst. The degree of dispersing was dependent of the H 2 to CCl 2 F 2 feed ratio and temperature. Poisoning is concluded to be not important. Based on these experiments the operating window of an industrial liquid-cooled multi-tubular CCl 2 F 2 hydrogenolysis reactor is defined. © 2001 Elsevier Science B.V. All rights reserved. Keywords: Deactivation of palladium on activated carbon; Chlorofluorocarbons; Greenhouse effect; Hydrogenolysis; CFC-11; CFC-12 1. Introduction It is generally accepted that chlorine containing hydrocarbons exhibit unfavorable properties with re- spect to their environmental impact. This also applies to chlorofluorocarbons (CFCs), which have been used extensively because of their high stability, low toxicity, ∗ Corresponding author. Tel.: +31-15-2781391; fax: +31-15-2784452. E-mailaddress: m.makkee@tnw.tudelft.nl (M. Makkee). and favorable price. However, they contribute signifi- cantly to the greenhouse effect and ozone depletion. They are responsible for about 95% of the depletion of ozone [1]. As a result of this their production and use are prohibited and they have to be considered as waste material. This waste is well defined, nearly pure com- pounds are in use. For instance, in refrigeration and its insulation nearly 85% of the CFCs are used and the major compounds are CCl 3 F (CFC-11) and CCl 2 F 2 (CFC-12), both in almost equal amounts. In fact, these two compounds constitute over 80% of the ozone 0926-860X/01/$ – see front matter © 2001 Elsevier Science B.V. All rights reserved. PII:S 0 9 2 6 - 8 6 0 X ( 0 0 ) 0 0 8 5 7 - 7