Catalysis Today 62 (2000) 269–278 Hydrodechlorination of chlorofluorocarbons CF 3 –CFCl 2 and CF 3 –CCl 3 over Pd/carbon and Pd black catalysts R.M. Rioux, C.D. Thompson, N. Chen, F.H. Ribeiro ∗ Department of Chemical Engineering, Worcester Polytechnic Institute, Worcester, MA 01609-2280, USA Abstract The reaction of hydrodechlorination for the chlorofluorocarbons (CFCs) CF 3 –CFCl 2 and CF 3 –CCl 3 was studied over Pd supported on carbon and Pd black catalysts. The rates and selectivity were similar on all samples although Pd black samples had a higher selectivity for the more hydrogenated products. The difference in selectivity and rate for Pd black is attributed to the presence of an impurity on the surface. The reaction orders are about first order in CFC, half-order in H 2 , and inverse first-order in HCl. These results indicate that the irreversible adsorption of CFC is the rate-determining step and that H 2 and HCl are equilibrated with hydrogen and chlorine on the surface. Experiments with D 2 on CF 3 –CFHCl confirm that the adsorption step is irreversible. © 2000 Elsevier Science B.V. All rights reserved. Keywords: Hydrodechlorination; Chlorofluorocarbons; Pd/carbon catalyst; Pd black catalyst 1. Introduction In the 1980s, halogenated chlorofluorocarbons (CFCs) were scientifically linked to the depletion of the ozone layer [1]. The stable and inert nature of CFCs is advantageous in many applications but it also enables them to escape from the lower at- mosphere without decomposition, and contribute to stratospheric ozone depletion. Hydrofluorocarbons (HFCs) are much less harmful to the environment and have some of the useful properties of CFCs and may thus serve as a replacement for CFCs [2]. One of the routes to produce HFCs is the reaction between CFC and H 2 catalyzed by a noble metal. This reaction may also be used to transform the large amounts of CFCs that exist today into the more environmentally benign HFCs [1,3]. The transformation of CFCs into HFCs ∗ Corresponding author. E-mail address: fabio@wpi.edu (F.H. Ribeiro). requires a knowledge of catalytic hydrodechlorina- tion, the subject of this contribution. Hydrodechlorination reactions have been studied over a number of metals, such as Pd [4–9], Pt [10–12], and Rh [10,12–14], with Pd usually the most selective catalyst for this reaction. The role of the support has been studied on carbon [15,16], alumina [4] and flu- orinated alumina [5]. While some authors have sug- gested that the support play a role in the reaction [17], we have previously reported that the support (carbon) does not influence reaction kinetics beyond conden- sation of CFC reactant on microporous supports [16]. While most contributions report on supported cata- lysts, hydrodechlorination literature does include stud- ies on evaporated films [18–20], foils [7,8,21], and single crystals [8]. A limited number of studies have been reported on bulk metal powders [22,23]. In this publication, we will extend our previous reports on CF 3 –CFCl 2 and CF 3 –CCl 3 hydrodechlorination kine- tics on supported Pd catalysts [16] by reporting the results on Pd black. 0920-5861/00/$ – see front matter © 2000 Elsevier Science B.V. All rights reserved. PII:S0920-5861(00)00428-4