Obtainment of pentafluorochloroethane from dichlorotetrafluoroethane-Note1

Gaseous fluorination with hydrogen fluoride at atmospheric pressure of the two isomers CClF2-CClF2 and CF3-CCl2F was continuously carried out on a chromic oxide based catalyst. The fluorinated derivative, obtained at a selectivity higher than 90%, was pentafluorochloroethane. Hexafluoroethane and an isomeric mixture of trichlorotrifluoroethanes were obtained as byproducts. The latter were recycled to fluorination together with unconverted C2Cl2F4. Both conversion of C2Cl2F4 and selectivity to C2ClF5 were affected by temperature, contact time and molar ratio of the reagents. The catalytic activity of chromic oxide was adversely affected by small amounts of water in the hydrogen fluoride. A difference in reactivity between the two isomers CF3-CCl2F and CClF2-CClF2 was also observed. It was also observed that the byproduction of C2Cl3F3 was due to the disproportionating activity of obromic oxide versus C2Cl2F4.