Products containing isomers of C.sub.2 Cl.sub.2 F.sub.4 are produced in various degrees of isomer purity. For example, C.sub.2 Cl.sub.2 F.sub.4 can be produced by the chlorofluorination of perchloroethylene, and the product typically consists of a mixture of the isomers, CClF.sub.2 CClF.sub.2 and CCl.sub.2 FCF.sub.3 (see e.g., U.S. Pat. No. 4,605,798). If the C.sub.2 Cl.sub.2 F.sub.4 isomer mixture is then used to produce CHClFCF.sub.3 (HCFC-124), CHF.sub.2 CClF.sub.2 (HCFC-124a), CHF.sub.2 CHF.sub.2 (HFC-134) and/or CH.sub.2 FCF.sub.3 (HFC-134a) by hydrodehalogenation, the products often consist of a mixture of C.sub.2 HClF.sub.4 isomers and C.sub.2 H.sub.2 F.sub.4 isomers. GB 1,578,933 illustrates that mixtures of C.sub.2 Cl.sub.2 F.sub.4 isomers in ratios of CFC-114 to CFC-114a of about 28:1 to 1:1 can be hydrogenolyzed over a palladium on carbon catalyst to mixtures of C.sub.2 H.sub.2 F.sub.4 isomers in ratios of HFC-134 to HFC-134a of from less than 0.01:1 to about 4:1, depending on reaction conditions. Over a palladium on alumina catalyst mixtures having CFC-114 to CFC-114a ratios of about 3:1 to 1:1 are essentially completely hydrogenolyzed to HFC-134a. PCT International Application No. 9218446 discloses that mixtures of C.sub.2 Cl.sub.2 F.sub.4 isomers can be converted to mixtures of C.sub.2 H.sub.2 F.sub.4 isomers with the product containing essentially the same distribution of fluorine atoms as the starting materials.
C.sub.2 HClF.sub.4 isomers and C.sub.2 H.sub.2 F.sub.4 isomers are used as refrigeration fluids for a number of applications. C.sub.2 HClF.sub.4 isomers, like C.sub.2 Cl.sub.2 F.sub.4 isomers, are also valuable raw material feeds for a number of other commercial processes. It has been found that for many of these applications, the presence of the unwanted isomer of an isomer pair can alter the physical properties of the desired product. As a result, there have been continually increasing market and process demands for high isomer purity materials. Identification of methods for enriching a composition's content of one isomer over another represents a significant aspect of preparing products for specific applications.
Purification of fluorocarbon products has been the subject of considerable research. Of particular interest are the challenges presented in separating fluorocarbon products from materials such as impurities in the starting materials used to produce the fluorocarbon products; and in separating excess reactants, and reaction co-products and by-products which are difficult to remove by standard separation methods such as distillation. Enrichment of CFC-114 in the presence of its isomer, CFC-114a, by distillation is not considered practical since their boiling points are close; the boiling point of CFC-114 is 3.6.degree. C., and the boiling point of CFC-114a is 3.3.degree. C.
USPTO Backgrounds
USPTO Backgrounds