GB1369869A - Process for the manufacture of monofluorodichloromethane and diffluoromonochloromethane - Google Patents

Abstract

1369869 CHCl 2 F and CHCIF 2 FARBWERKE HOECHST AG 25 Oct 1971 [27 Oct 1970] 49385/71 Heading C2C Monofluorodichloromethane and difluoromonochloromethane are obtained by reacting hydrogen fluoride and chloroform, in gaseous form, in the presence of a solid fluorination catalyst and at 100‹ to 200‹ C., not more than 60% (e.g. 20-40%) of the HF initially present being reacted, and subsequently separating the organic products from the HCl formed and from unreacted HF. The fluorination may be effected at an absolute pressure of 1 to 15 atm. and with a molar ratio of CHCl 3 to HF of 1 : 1 to 1 : 8. The catalyst is preferably a chromium oxifluoride obtained by fluorinating an hydrated oxide of Cr(III) (e.g. Cr 2 O 3 .2H 2 O) with HF at 150-600‹ C. and is optionally mixed with a binder, e.g. graphite, before use. The reaction mixture is generally separated by fractional condensation to remove HCl and any CHF 3 formed, the remaining condensate separating into an upper phase comprising HF (which may be recycled) and a lower phase comprising CHCl 3 , CHCl 2 F and CHClF 2 . Examples 1 to 10 describe the reaction of HF and CHCl 3 to produce CHCl 2 F and CHCIF 2 with some CHF 3 as by-product. Comparative Examples 1a and 2a which convert 70% and 97À9% respectively of the HF initially present produce CHF 3 as the major organic product.