Studies on a vapour-phase process for the manufacture of chlorofluoroethanes

Abstract

Fluorination of hexachloroethane or of tetrachloroethylene + chlorine by hydrogen fluoride at ca. 400°C in the presence of an aluminium fluoride catalyst gives the unsymmetrical isomers of dichlorotetrafluoroethane and of trichlorotrifluoroethane as the major products. Under similar conditions but using a catalyst of aluminium fluoride containing small amounts of iron, chromium and nickel, symmetrical trichlorotrifluoroethane is the major product. Analogous fluorinations of various intermediates over these catalyst systems have been studied and detailed information about the reaction pathways obtained. Under suitable conditions, s-trichlorotrifluoroethane or s-dichlorotetrafluoroethane can be prepared in a high state of purity.