| 摘要 |
<p>Fluoroform-tetrafluorethylene mixtures are separated by fractionally distilling the mixture in the presence of a perhalocarbon in which the halogen atoms are fluorine and/or chlorine and which has an atmospheric boiling point of from -40 DEG to + 100 DEG C., the weight ratio of perhalocarbon to fluoroform-tetrafluoroethylene mixture being at least 40 : 60. The process is particularly applicable to the separation of mixtures of compounds obtained by the pyrolysis of fluoroform. The perhalocarbons used in the separation may be saturated or unsaturated and cyclic or non-cyclic. Suitable extractants are, for example, hexafluoropropene, perfluorobutenes, perfluorocyclobutane, perfluoropropane, perfluorobutane, perfluoropentane, CF3CCl3, CF2ClCFCl2, CF3CFCl2, CF2ClCF2Cl, CF3CF2Cl, CF2ClCCl3, CFCl2CFCl2, CCl2Fl2 CCl3F and CCl4 with hexafluoropropene preferred. In the distillation a mixture of tetrafluoroethylene and extrantant is withdrawn from the bottom of the column and substantially pure fluoroform is withdrawn from the top. The tetrafluoroethylene may be separated from the extrantant by distillation and the extractant returned to the process. If the starting mixture is one obtained by the pyrolysis of fluoroform there may be present hexafluoropropene, hexafluoroethane and smaller amounts of other fluoro compounds and it is desirable that hexafluoropropene should be used as the extractant for such a mixture. The hexafluoroethane is then taken off at the head of the column with the fluoroform and the mixture so taken off can then be recycled to the pyrolysis reactor. Specification 918,971 is referred to.</p> |
