Process for manufacture of high purity 1,1-dichlorotetrafluoroethane

A process for producing CH2FCF.sub.3 by hydrodehalogenating CCl.sub.2 FCF.sub.3 characterized by:

• (i) contacting a mixture of perhalogenated hydrocarbons which is essentially free of 1,2-dichlorotetrafluoroethane and comprises 20 to 80 mole percent 1,1,1-trichlorotrifluoroethane and 5 to 80 mole percent of at least one compound selected from the group consisting of tetrachloroethylene, pentachlorofluoroethane, tetrachloro-1,2-difluoroethane and tetrachloro-1,1-difluoroethane with hydrogen fluoride and optionally chlorine, provided that when the mixture comprises tetrachloroethylene, chlorine is supplied in a chlorine to tetrachloroethylene mole ratio of at least 1:2, in the vapor phase over a fluorination catalyst at an elevated temperature no higher than 375.degree. C., to provide a product mixture comprising 1,1,2-trichlorotrifluoroethane and dichlorotetrafluoroethane wherein the ratio of 1,2-dichlorotetrafluoroethane to 1,1-dichlorotetrafluoroethane is less than about 1:50;
• (ii) recovering said dichlorotetrafluoroethane from the product mixture;
• (iii) isomerizing 1,1,2-trichlorotrifluoroethane from the product mixture to 1,1,1-trichlorotrifluoroethane in the presence of an isomerization catalyst;
• (iv) recycling the 1,1,1-trichlorotrifluoroethane produced by the isomerization of step (iii) to step (i);
• and
• (v) hydrodehalogenating the dichlorotetrafluoroethane from step (ii).

A process for producing a product comprising 1,1-dichlorotetrafluoroethane substantially free of 1,2-dichlorotetrafluoroethane, comprising the steps of:

• (i) contacting a mixture of perhalogenated hydrocarbons which is essentially free of 1,2-dichlorotetrafluoroethane and comprises from 20 to 80 mole percent 1,1,1-trichlorotrifluoroethane and from 5 to 80 mole percent tetrachloroethylene, with hydrogen fluoride and chlorine, provided that chlorine is supplied in a chlorine tetrachloroethylene mole ratio of at least 1:2, in the vapor phase over a fluorination catalyst at an elevated temperature no higher than 375.degree. C., to provide a product mixture comprising 1,1,2-trichlorotrifluoroethane and dichlorotetrafluoroethane wherein the ratio of 1,2-dichlorotetrafluoroethane to 1,1-dichlorotetrafluoroethane is less than about 1:50;
• (ii) recovering said dichlorotetrafluoroethane from the product mixture;
• (iii) isomerizing 1,1,2-trichlorotrifluoroethane from the product mixture to 1,1,1-trichlorotrifluoroethane in the presence of an isomerization catalyst;
• and
• (iv) recycling the 1,1,1-trichlorotrifluoroethane produced by the isomerization of step (iii) to step (i).