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Production processesRelated Patent Categories: Distillation: Processes, Separatory, Adding Material To Distilland Except Water Or Steam Per Se, Organic Compound, Halogenated HydrocarbonProduction processes description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060108213, Production processes. Brief Patent Description - Full Patent Description - Patent Application Claims
FIELD OF INVENTION [0001] The present invention relates to processes for separating pentafluoroethane (CHF.sub.2-CF.sub.3, HFC-125) from a mixture comprising HFC-125 and chloropentafluoroethane (CF.sub.3-CClF.sub.2, CFC-115). The present invention further relates to the production of heptafluoropropane (CF.sub.3CHFCF.sub.3 or CF.sub.3CF.sub.2CHF.sub.2, HFC-227ea or HFC-227ca, collectively HFC-227). BACKGROUND OF THE INVENTION [0002] In the recent years, there has been an increasing concern about global warming. As a result, several chlorofluorocarbons (CFC's) that are known to have an adverse environmental impact have been removed from the marketplace. In their place, new compounds have been introduced as flooding agents, streaming agents, blowing agents, propellants, and refrigerants. However, some of these new compounds do not meet environmental safety requirements. Consequently, there is a constant need to develop fluorocarbon compounds, especially hydrofluorocarbons, which have no chlorine. Two hydrofluorocarbons that are known to have desirable properties are pentafluoroethane (HFC-125) and heptafluoropropane (HFC-227). [0003] HFC-125 is a valuable hydrofluorocarbon (HFC) that is especially useful as a refrigerant, blowing agent, propellant, or fire-extinguishing agent. HFC-125 can be prepared by a multi-step process starting with fluorination of tetrachloroethene (C.sub.2Cl.sub.4). The end products of the multi-step process include a mixture containing HFC-125, chloropentafluoroethane (CFC-115), and small amounts of other fluorinated compounds. [0004] HFC-227 is another valuable hydrofluorocarbon. One known starting material for the production of HFC-227 is hexafluoropropene (CF.sub.3CF.dbd.CF.sub.2, HFP). HFP can be hydrofluorinated with hydrogen fluoride (HF) in the presence of a suitable catalyst to form HFC-227 and other byproducts. Typically, in the final step of HFC-227 purification, these byproducts are separated out by simple distillation. [0005] CFC-115 is an undesirable compound because it contains chlorine, and, as a result, its use is highly regulated. Thus, in the production of HFC-125 for commercial use, it is necessary to separate HFC-125 from CFC-115. Unfortunately, the mixture of HFC-125 and CFC-115 forms a near-azeotrope. At high concentrations of HFC-125, the relative volatility of HFC-125 to CFC-115 is close to 1.0, making recovery of pure HFC-125 from a mixture of HFC-125 and CFC-115 by simple distillation difficult. [0006] An azeotrope is a liquid mixture that exhibits a maximum or minimum boiling point relative to the boiling points of its components. An azeotrope is homogeneous if only one liquid phase is present. An azeotrope is heterogeneous if more than one liquid phase is present. Regardless, a characteristic of azeotropes is that the bulk liquid composition is identical to the vapor composition in equilibrium therewith, and distillation of the azeotropic mixture is ineffective as a separation technique. For the purposes of this discussion, a near-azeotrope means a composition which behaves like an azeotrope (i.e., has constant-boiling characteristics or a tendency not to fractionate upon boiling or evaporation). Thus, the composition of the vapor formed during boiling or evaporation of such compositions is the same as or substantially the same as the original liquid composition. Hence, during boiling or evaporation, the liquid composition, if it changes at all, changes only to a minimal or negligible extent. This is to be contrasted with non-azeotrope compositions in which during boiling or evaporation, the liquid composition changes to a substantial degree. [0007] Accordingly, the essential features of an azeotrope or a near-azeotrope are that at a given pressure, the boiling point of the liquid composition is fixed and that the composition of the vapor above the boiling composition is essentially that of the boiling liquid composition (i.e., no fractionation of the components of the liquid composition takes place). It is recognized in the art that both the boiling point and the weight percentages of each component of the azeotropic composition may change when the azeotrope or near-azeotrope liquid composition is subjected to boiling at different pressures. Thus, an azeotrope or a near-azeotrope may be defined in terms of the unique relationship that exists among components or in terms of the compositional ranges of the components or in terms of exact weight percentages of each component of the composition characterized by a fixed boiling point at a specified pressure. It is also recognized in the art that various azeotropic compositions including their boiling points at particular pressures may be calculated (see, e.g., W. Schotte, Ind. Eng. Chem. Process Des. Dev. 1980, 19, pp 432-439). Experimental identification of azeotropic compositions involving the same components may be used to confirm the accuracy of such calculations and/or to modify the calculations for azeotropic compositions at the same or other temperatures and pressures. [0008] It is known that pure HFC-125 as a near-azeotropic mixture with CFC-115 can be recovered by a process of extractive distillation. In this process, a suitable extracting agent that changes the relative volatility of a component or the azeotrope is used. Examples of extracting agents used in the purification of HFC-125 are disclosed in U.S. Pat. Nos. 5,087,329 and 5,928,479. [0009] Extractive distillation processes for the purification of HFC-125 usually include a step of separating the extracting agent from either HFC-125 or CFC-115 subsequent to the completion of the extractive distillation. This additional separation process may add to the cost of HFC-125 production even though the extracting agent may be reused. SUMMARY OF INVENTION [0010] The present invention provides processes for the production of halogenated hydrocarbons either alone or in combination with the synthesis of olefinic derivatives. In one embodiment of the present invention, at least one halogenated hydrocarbon is purified from a near-azeotropic mixture comprising at least one halogenated hydrocarbon and at least one halocarbon by extractive distillation using an olefinic extracting agent. In this particular embodiment, the olefinic extracting agent is converted into a derivative compound. [0011] In another embodiment of the present invention, HFC-125 is purified from a mixture containing CFC-115 by extractive distillation, using hexafluoropropene (HFP) or chlorotrifluoroethene (CClF=CF.sub.2, CFC-1113) as an extracting agent. One feature of this particular embodiment is that the extracting agent can be recovered and reused in the purification of HFC-125 as set forth herein. In an alternative embodiment, the recovered extracting agent can be used as a starting material for the production of fluorocarbons like HFC-227. [0012] In a specific embodiment of the present invention, the process of recovering HFC-125 comprises the steps of: (a) providing a first mixture comprising HFC-125 and CFC-115, (b) distilling the first mixture in the presence of hexafluoropropene (HFP) to separate HFC-125 from a second mixture comprising HFP and CFC-115. The distilling process may be extractive distillation, in which HFP is an extracting agent. [0013] According to another embodiment of the invention, the process may further include the steps of: (c) recovering HFC-125 as an overhead product and (d) recovering the second mixture as a bottom product. [0014] According to a further embodiment, the process may further include the step of: (e) purifying HFP from the second mixture to produce a third mixture comprising CFC-115 and the step of (f) recovering HFP. Optionally, the process may include the step of re-using the recovered HFP as an extracting agent, as described herein. [0015] Another embodiment of the present invention is directed to a process comprising the steps of: (a)-(d), as described, and the steps of: (g) adding HF to the second mixture to form a fourth mixture, (h) converting HFP in the fourth mixture by hydrofluorination in the presence of a suitable catalyst to HFC-227 to produce a fifth mixture, (i) separating the fifth mixture into HFC-227 and a sixth mixture comprising CFC-115, and (j) recovering HFC-227. [0016] A further embodiment of the present invention is directed to a process comprising the steps of: (a)-(f), as described, and the steps of: (k) adding HF to the recovered HFP, (l) converting the recovered HFP by hydrofluorination to HFC-227 in the presence of a suitable catalyst to produce a seventh mixture, (m) separating the seventh mixture into HFC-227 and byproducts, and (n) recovering HFC-227. [0017] In another embodiment, the process comprises the steps of: (a)-(f), as described, and the step of converting HFP to at least one HFP derivative or a fluoropolymer. [0018] In an alternative embodiment of the present invention, the process comprises the steps of: (o) providing a first mixture comprising HFC-125 and CFC-115, (p) distilling the first mixture in the presence of CFC-1113 to separate HFC-125 from an eighth mixture comprising CFC-1113 and CFC-115, (q) recovering HFC-125 as an overhead product, and (r) recovering the eighth mixture as a bottom product. The distilling process may be extractive distillation, in which HFP is an extracting agent. [0019] In still another embodiment, the process comprises the steps of (o)-(r) and the steps of: (s) adding HF to the eighth mixture to produce a ninth mixture, (t) converting CFC-1113 in the ninth mixture in the presence of a suitable catalyst to a fluoroethane to make a tenth mixture, and recycling the tenth mixture to a hydrofluorocarbon production process. In one embodiment, the fluoroethane is 1-chloro-1,2,2,2-tetrafluoroethane (CHClFCF.sub.3, HCFC-124). [0020] The above and other embodiments, aspects, alternatives and advantages of the present invention will become more apparent from the following detailed description of the present invention taken in conjunction with the examples. DETAILED DESCRIPTION OF THE INVENTION Continue reading about Production processes... Full patent description for Production processes Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Production processes patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Production processes or other areas of interest. ### Previous Patent Application: Process for the distillative separation of mixtures of substances Next Patent Application: Electrochemical reaction method and microchannel electrochemical reactor and its manufacturing method Industry Class: Distillation: processes, separatory ### FreshPatents.com Support Thank you for viewing the Production processes patent info. 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