PREPARATION OF CHLOROPENTAFLUOROETHANE FROM DICHLOROTETRAFLUOROETHANE

Article abstract of DOI:10.1016/S0022-1139(00)85235-5

Gaseous fluorination with hydrogen fluoride at atmospheric pressure of the two isomers CClF2-CClF2 and CCl2F-CF3 was carried out continuously on a chromic oxide based catalyst.The fluorinated derivative, obtained in a yield greater than 90percent, was chloropentafluoroethane.Hexafluoroethane and an isomeric mixture of trichlorotrifluoroethane were obtained as by-products.The latter was recycled with unconverted C2Cl2F4 for further fluorination.Both conversion of C2Cl2F4 and selectivity to the formation of 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 was also observed in the reactivity of the two isomers CCl2F-CF3 and CClF2-CClF2.The formation of C2Cl3F3 as a by-product was due to the disproportionating activity of chromic oxide upon C2Cl2F4.