Conversion of 1,1,2-trichlorotri¯uoroethane to 1,1,1-trichlorotri¯uoroethane and 1,1-dichlorotetra¯uoroethane over aluminium-based catalysts H. Bozorgzadeh a , E. Kemnitz a , M. Nickkho-Amiry b , T. Skapin c , J.M. Win®eld b,* a Institute of Inorganic Chemistry, Humboldt University, Hessische Strasse 1-2, D-10115 Berlin, Germany b Department of Chemistry, University of Glasgow, Glasgow G12 8QQ, UK c Joz Âef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia Received 31 July 2000; accepted 28 August 2000 Abstract Conversion of CCl 2 FCClF 2 to CCl 2 FCF 3 is achieved in the temperature range, 593±713 K, under ¯ow conditions by using the catalysts, b-AlF 3 or g-alumina, pre¯uorinated with CCl 2 F 2 or SF 4 . Aluminium-based catalysts favour the formation of asymmetric isomers in the chloro¯uoroethane series, hence CCl 3 CF 3 is also a signi®cant product. More highly chlorinated materials, containing 4 Cl atoms, and CClF 2 CF 3 are minor products. Product composition data provided evidence for the possible pathway CCl 2 FClF 2 ! CCl 3 CF 3 ! CCl 2 FCF 3 . The isomerisation step is believed to be intramolecular and is facile. The apparent ¯uorination step is best described as a dismutation. # 2001 Elsevier Science B.V. All rights reserved. Keywords: Isomerization; Dismutation; CFC; Aluminium; Fluoride 1. Introduction Chloro¯uorocarbons (CFCs) which were discovered in 1930 by Thomas Midgley, had a variety of industrial appli- cations. The compounds are highly stable and remarkably unreactive. Hence, once released into the atmosphere, delib- erately or inadvertently, they are very long-lived. They are sources of stratospheric chlorine and as such, perturb the O 3 / O 2 equilibrium. Therefore, CFCs have been classi®ed as controlled substances in the Montreal Protocol and its amendments. Accordingly, their production and usage have been terminated in the developed countries and will ®nish by 2010 in developing countries. This situation resulted in two major research and devel- opment activities. The ®rst involves the design and imple- mentation of routes to the large-scale synthesis of CFC- alternatives, notably 1,1,1,2-tetra¯uoroethane, CF 3 CH 2 F (HFC-134a), since it can be used as a `drop-in' replacement for the widely used refrigerant, CCl 2 F 2 . Work in this area has been carried out largely by chemical companies in the developed world [1], although our research groups have been heavily involved in researching fundamental aspects of this topic ([2±4] and references therein). The second activity involves devising methods for the destruction of CFCs in situations where recycling is not an option. Equally impor- tant is the requirement for stocks of CFCs, presently held in developed and developing countries, to be converted to useful, environmentally-friendly chemical feedstock. Hence, there exists an urgent need either to destroy CFCs or to convert them into useful compounds. Incineration of CFCs is energy intensive and, if not properly performed, can result in the release of toxic pro- ducts. Dehalogenation by chemical means is a more elegant alternative; several routes, with or without photochemical intervention, have been described [5±9] but, although they are excellent laboratory methods and could be feasible for CFC removal from gas streams after condensation, scale-up is likely to present economic and technical dif®culties. An alternative approach is the catalytic oxygenation over acidic oxide catalysts of C 1 and C 2 CFCs to give CO 2 and hydrogen halides. A variety of catalysts, for example, zeolites, TiO 2 , ZrO 2 or V 2 O 5 , modi®ed in some cases by sulfuric or phosphoric acid, has been reported [10±18]. Relatively high temperatures (ca. 800 K) are required, particularly for C 2 CFCs, and catalyst deactivation due to metal ¯uoride Journal of Fluorine Chemistry 107 (2001) 45±52 * Corresponding author. Tel.: 44-141-330-5134; fax: 44-141-330-4888. E-mail address: j.winfield@chem.gla.ac.uk (J.M. Winfield). 0022-1139/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved. PII:S0022-1139(00)00350-X