HEXAFLUOROPROPYLENE RECOVERY PROCESS Russian patent published in 2002 - IPC

FIELD: industrial organic synthesis. SUBSTANCE: hexafluoropropylene is recovered from difluorochloromethane pyrolysis gas formed in tetrafluoroethylene production process. The following stages are involved: isolation of high-boiling products, tetrafluoroethylene, and association impurities from pyrolysis gas and extractive rectification of fraction containing difluorochloromethane and hexafluoropropylene using separating agent based on lower aliphatic halohydrocarbon, after which isolated products are separated. Invention is distinguished by that separating agent, in particular difluorochloromethane, is added to fraction containing difluorochloromethane, hexafluoropropylene, difluorodichloromethane, and trifluorochloroethylene in amount providing difluorochloromethane-to-hexafluoropropylene molar ratio 95: 5. Resulting mixture is then subjected to azeotropic rectification under pressure above 1,6 MPa to separate difluorodichloromethane and trifluorochloroethylene as bottom product. Distillate consisted of difluorochloromethane and hexafluoropropylene is separated in presence of separating agent, in particular perfluorocyclobutane or 1,1,2,2-tetrafluorodichloroethane. EFFECT: increased purity of desired product. 1 dwg, 4 tbl, 4 ex