Catalytic fluorination of 1,1,1-trifluoro-2-chloro-ethane in the presence of oxygen over chromium based catalyst doped or not by zinc supported over partially fluorinated alumina A. Loustaunau, R. Fayolle-Romelaer, S. Celerier, S. Brunet * Laboratoire de Catalyse en Chimie Organique, UMR CNRS 6503, Universite ´ de Poitiers Faculte ´ des Sciences Fondamentales et Applique ´es 40, Avenue du Recteur Pineau, 86022 Poitiers Cedex, France 1. Introduction Chromium oxide based catalysts are commonly involved in the preparation of CFCs substitutes. For example, chromium oxides modified or not by another metal such as zinc, nickel or magnesium were used for the gas phase fluorination of CF 3 CH 2 Cl to CF 3 CH 2 F by Cl/F exchange [1–8] in the presence of hydrogen fluoride as fluorinating agent. On the other hand, several studies [9–16] showed that the presence of other elements (zinc, nickel, magnesium) could improve the catalytic properties of the chromium sites involved in Cl/F exchange by increasing the total activity and also by decreasing the contribution of secondary reactions. Winfield and co-workers [10] reported that zinc added in small amount to chromium increased its activity for the transformation of CF 3 CH 2 Cl. The presence of zinc could modify HF adsorption which became weaker. The consequence was lower apparent activation energy. Previous work [16] showed that the best promoting effect was observed, for the transformation of CF 3 CH 2 Cl, for an Zn/(Zn+Cr) atomic ratio of 0.15 and with a low (Zn+Cr) content of 2 wt%. This corresponds to a better dispersion of the different elements on the surface. On the other hand, previous studies [17–21] showed that to be active, the chromium species must be reversibly oxidizible which corresponds also to the presence of Cr VI species in the initial material. The catalytic properties depend also on the composition of the catalyst and mainly on the amount of oxygen in the material. For example, an excess of oxygen in the starting chromium oxide is necessary to obtain the highest intrinsic catalytic activity for the transformation of CF 3 CH 2 Cl. Indeed the presence of oxygen in excess maintains HF labile (corresponding to chemisorbed HF on the catalyst surface which could be involved in Cl/F exchanges) and prevents the irreversible fluorination of the catalyst. A very low catalytic activity was reported over a CrF 3 catalyst [18]. Moreover, the presence of oxygen in continuous or discontinuous regime (in the very low amount 2 wt%) [2], prevent the catalyst deactivation by main- taining the catalyst surface. However, in this case, the Deacon reaction could be observed by reaction between HCl and O 2 (Eq. (3)). This paper deals with the transformation of CF 3 CH 2 Cl in the presence of a small amount of oxygen over supported chromium based catalysts. We specially studied the effect on the activity, selectivity and stability of chromium oxide catalyst and modified by small amount of zinc supported over partially fluorinated alumina. The total amount of the active species on the support was fixed at 10 wt%. The aim was to promote the main fluorination reaction and to inhibit the secondary reactions. The Deacon reaction was studied over these catalytic systems. Main reaction: CF 3 CH 2 Cl þ HF Ð CF 3 CH 2 F þ HCl Fluorination (1) Journal of Fluorine Chemistry 132 (2011) 1262–1265 A R T I C L E I N F O Article history: Received 27 April 2011 Received in revised form 29 July 2011 Accepted 8 August 2011 Available online 17 August 2011 Keywords: Fluorination Chromium oxide Zinc 1,1,1-Trifluoro-2-chloro-ethane Deacon A B S T R A C T The addition of zinc in low amount to chromium based catalyst supported over partially fluorinated alumina has a positive effect for the fluorination reaction of CF 3 CH 2 Cl in the presence of dioxygen in order to prevent the catalyst deactivation. However, under these operating conditions, the Deacon reaction by reaction with HCl produced by Cl/F exchanges could be involved. The formation of various by-products was observed corresponding to the addition of HCl or Cl 2 into halogenated double bonds. ß 2011 Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +33 549453627; fax: +33 549453897. E-mail address: sylvette.brunet@univ-poitiers.fr (S. Brunet). Contents lists available at ScienceDirect Journal of Fluorine Chemistry jo ur n al h o mep ag e: www .elsevier .c om /loc ate/f luo r 0022-1139/$ – see front matter ß 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jfluchem.2011.08.006