PROCESS FOR PRODUCING 1,1,1,4,4,4-HEXAFLUOROBUT-2-ENE

Abstract

A process for producing E-1,1,1,4,4,4-hexafluorobut-2-ene comprises contacting 1,1,2,4,4-pentachlorobuta-1,3-diene with hydrogen fluoride in the vapor phase in the presence of a fluorination catalyst. A process for producing Z-1,1,1,4,4,4-hexafluorobut-2-ene further comprises contacting E-1,1,1,4,4,4-hexafluoro-2-butene with chlorine in the presence of a catalyst to produce 2,3-dichloro-1,1,1,4,4,4-hexafluorobutane, followed by reaction with a base to produce 1,1,1,4,4,4-hexafluoro-2-butyne, and subsequently hydrogenating hexafluoro-2-butyne to produce Z-1,1,1,4,4,4-hexafluoro-2-butene.

Description

PROCESS FOR PRODUCING 1,1,1,4,4,4-HEXAFLUOROBUT-2-ENE FIELD OF INVENTION This description relates to a process for producing E and Zl,1,1,4,4,4-hexafluoro-2-butene, in particular, from a starting material comprising 1,1,2,4,4-pentachlorobuta-1,3-diene. The description further provides processes for producing 1,1,2,4,4-pentachlorobuta-1,3-diene. BACKGROUND OF THE INVENTION Many industries have worked for decades to find substitutes for ozone-depleting chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). CFCs and HCFCs have been used in a wide range of applications, including as refrigerants, cleaning agents, blowing agents for thermoplastic and thermoset foams, heat transfer media, gaseous dielectrics, aerosol propellants, fire extinguishing and suppressing agents, mechanical cycle working fluids, polymerization media, particulate removal fluids, carrier fluids, grinding abrasives, and displacement drying agents. In the search for substitutes for these versatile compounds, many industries have adopted the use of hydrofluorocarbons (HFCs). HFCs have zero ozone depletion potential and are therefore not seen as substitutes for these compounds. Ref. 325647 affected by the current regulatory phase-out arising from the Montreal Protocol. In addition to ozone depletion concerns, global warming is another environmental concern in many of these applications. Therefore, there is a need for compositions that meet low ozone depletion standards and have a low global warming potential. Certain hydrofluoroolefins are believed to meet both objectives. Thus, there is a need for manufacturing processes that provide useful intermediates for producing hydrofluoroolefins and chlorine-free hydrofluoroolefins. These materials have zero ozone depletion potential and low global warming potential. INCORPORATION AS A REFERENCE All publications, patents, and patent applications mentioned in this description are incorporated herein by reference to the same extent as if each individual publication, patent, or patent application were specifically and individually indicated as being incorporated by reference. In case of conflict, this application, including any definitions herein, shall prevail. SUMMARY OF THE INVENTION This description provides a process for the production of hydrofluoroolefin El,1,1,4,4,4 / υΊ Ί Ί 03 hexafluorobut-2-ene (E-CF3CH=CHCF3, E-HFO-1336mzz, E-1336mzz). The process comprises contacting 1,1,2,4,4-pentachlorobuta-1,3-diene (CC1CH=CC1CH=CC2, HCC-2320az) with hydrogen fluoride (HF) in the vapor phase in the presence of a fluorination catalyst to produce a product mixture comprising E-CF3CH=CHCF3. In some embodiments, the product mixture further comprises Z-1,1,1,4,4,4-hexafluoro-2-chloro-2-butene (Z-CF3CC1=CHCF3, ZHCFO-1326mxz, Z-1326mxz). C\......hαHF®*,αcM «f 2320az E-133Smzz In some formulations, the fluorination catalyst is a chromium-based catalyst. The chromium catalyst can be chromium oxyfluoride or chromium oxide, supported or unsupported. If supported, a chromium oxyfluoride or chromium oxide catalyst can be supported on activated carbon, graphite, fluorinated graphite, or fluorinated alumina. In some embodiments, the product mixture also includes Z-1326mxz. In some embodiments, E-1336mzz is produced with a selectivity greater than 90%, 95%, or 99% with respect to Z-1336mzz. In some embodiments, the product comprises at least 99.5% E-1336mzz. IVIA / a / ZUZl / Ul IIOO based on gas chromatography analysis. In some embodiments, E-1336mzz is recovered from the product mixture. In some embodiments, E-1336mzz can be used for another purpose, such as a blowing agent or a heat transfer fluid. In some embodiments, 1,1,2,4,4-pentachlorobuta-1,3-diene (HCC-2320az, 2320az) is produced according to a process comprising the dimerization of trichloroethylene (TCE). One process for producing 2320az comprises contacting TCE in the presence of a catalyst to produce a mixture of products comprising 2320az. ClxCl CaíCl,H>—C? I Cl H Cl Cl Cí TCE 2320az In some forms, TCE dimerization is carried out in the presence of pentachloroethane (CCl3CHCl2, HCC-120), which accelerates the dimerization process. In certain forms, 2320az is produced with a selectivity of at least 80%; in some forms, the selectivity is greater than 90%, 95%, 99%, or 99.5%. In certain forms, 2320az is recovered from the product mixture. In some forms, unreacted TCE is recovered and recycled. The present description provides a process for producing E-1336mzz comprising (a) contacting trichloroethylene in the presence of a catalyst and optionally pentachloroethane (CHCl2CCl3) to produce a mixture of products comprising 2320az; (b) contacting 2320az with hydrogen fluoride in the vapor phase in the presence of a catalyst to produce a mixture of products comprising E-1336mzz.In addition, a process is provided for producing Z1, 1, 1, 4,4,4-hexafluorobut-2-ene (E-CF3CH=CHCF3, 2-HFO-1336mzz, Z-1336mzz).This process comprises (a) contacting trichloroethylene in the presence of a catalyst and optionally pentachloroethane, to produce a mixture of products comprising 2320az; (b) contacting 2320az with hydrogen fluoride in the vapor phase in the presence of a catalyst to produce a mixture of products comprising E-1336mzz; (c) contacting E-1336mzz with chlorine to produce a mixture of products comprising 2,3-dichloro-1,1,4,4,4-hexafluorobutane (CF3CHCICHCICF3, HCFC-336mdd); (d) contacting 2,3-dichloro-1,1,4,4,4-hexafluorobutane with a base to produce a mixture of products comprising 1,1,1,4,4,4-hexafluoro-2-butyne (CFsCsCCFs); (e) contacting 1,1,1,4,4,4-hexafluoro-2-butyne with hydrogen, optionally in the presence of a catalyst, to produce a mixture of products comprising 2-1,1,1,4,4,4-hexafluoro-2-butene. This description also provides compositions / υΊ Ί Ί 03 produced according to the processes described herein. DETAILED DESCRIPTION OF THE INVENTION As used in this description, the terms comprise, which comprises, include, which includes, has, which has, or any other variant thereof are intended to encompass a non-exclusive inclusion. For example, a process, method, article, or apparatus comprising a list of elements is not necessarily limited to those elements alone, but may include other elements that are not expressly listed or are inherent to that process, method, article, or apparatus. When a quantity, concentration, or other value or parameter is given either as an interval, the preferred interval, or a list of upper preferred and lower preferred values, this shall be understood specifically as a description of all intervals formed from any pair of any upper interval limit or preferred value and any lower interval limit or preferred value, regardless of whether the intervals are described separately. Where a range of numerical values ​​is mentioned in this description, unless otherwise stated, the interval includes the limits of that range and all whole numbers and fractions within it. Recovering means sufficiently isolating the desired product so that it is available for its intended use, either as a starting material for a subsequent reaction step or, in the case of recovering 1,1,4,4,4-hexafluoro-2-butene or 2-1,1,1,4,4,4-hexafluoro-2-butene, useful, for example, as a refrigerant or foam blowing agent or solvent or fire extinguisher or electronic gas. The details of the recovery step will depend on the compatibility of the product mixture with the reaction conditions of the subsequent reaction step. For example, if the product is produced in a reaction medium that is different from or incompatible with a subsequent reaction step, then the recovery step may involve separating the desired product from the product mixture that includes the reaction medium. This separation can occur simultaneously with the contact step when the desired product is volatile under the reaction conditions. The volatilization of the desired product can constitute its isolation and, thus, its recovery. If the vapors include other materials that are to be separated from the desired product, the desired product can be separated, for example, by selective distillation. The steps to recover the desired product from the product mixture preferably comprise separating the desired product from the catalyst or other component(s) of the mixture / υΊ Ί Ί 03 of products used to produce the desired product or products produced in the process. This description provides, among other things, a process for producing E-1336mzz in one step. A starting material comprises 1,1,2,4,4-pentachlorobuta-1,3-diene, which can be produced from trichloroethylene, a process as set forth in this description. Production of 1,1,2,4,4-pentachlorobuta-l,3-diene (2320az) 1,1,2,4,4-Pentachlorobuta-1,3-diene (HCC-2320az or 2320az) can be produced according to this description by the dimerization of trichloroethylene (TCE). In some embodiments, a process is provided for producing a mixture of products comprising 2320az, wherein the process comprises contacting TCE with a dimerization catalyst at an elevated temperature. In some embodiments, the dimerization catalyst comprises iron. An iron dimerization catalyst may comprise metallic iron from any source (including a combination of sources) and may be or comprise iron powder, iron wire, iron mesh, or iron shavings. The iron catalyst may also comprise an iron salt, such as ferric chloride or ferrous chloride (FeCl₂ or FeCl₂, respectively). In some embodiments, the dimerization catalyst comprises copper. A copper dimerization catalyst may comprise metallic copper from any source (including a combination of sources) and may be either copper powder or copper wire, for example. The copper catalyst may also comprise a cuprous or cupric salt, such as cuprous chloride or cupric chloride (CuCl or CuCl₂, respectively). Preferably, the process is carried out in an anhydrous environment. For example, when using ferric chloride, the ferric chloride is preferably anhydrous. In some embodiments, the dimerization catalyst has a specific concentration relative to the moles of TCE reagent used. For example, in some embodiments where the catalyst comprises a metallic iron catalyst, the weight ratio of Fe wire catalyst (or Fe powder) to TCE is approximately 0.0001 to approximately 1. In other embodiments, the weight ratio of iron catalyst to TCE is approximately 0.01 to approximately 1. In some embodiments, the dimerization catalyst comprises ferric chloride, and the weight ratio of ferric chloride to TCE is approximately 0.00001 to approximately 1. For example, the weight ratio of ferric chloride to TCE is approximately 0.00001 to approximately 0.002, while in another example, the weight ratio is approximately 0.00005 to approximately 0.001. Yet another example shows a weight ratio of ferric chloride to TCE of approximately IVIA / a / ZUZl / Ul IIOO 0.0001 to approximately 1, while in an additional example the ratio of ferric chloride to TCE is approximately 0.00015 to approximately 1. In some embodiments, trichloroethylene is contacted with a dimerization catalyst and pentachloroethane. The pentachloroethane (HCC-120) accelerates the reaction to produce the product mixture comprising 2320az. In certain embodiments, the weight ratio of HCC-120 to TCE is approximately 0.001 to approximately 1. In other embodiments, the weight ratio of HCC-120 to TCE is approximately 0.005 to approximately 1. The dimerization of TCE is carried out at an elevated temperature, for example, in the range of approximately 210 to approximately 235 °C. The temperature can be higher than 200 °C. The temperature can be lower than 245 °C. The pressure is typically autogenous. The contact time (stay) is typically approximately 0.5 to 10 hours. In some modalities, the TCE conversion is at least 15%, or at least 30%, or at least 50%. In some modalities, the selectivity for 2320az is at least 80%, or at least 85%, or at least 90%. The byproducts in the dimerization reaction may include tetrachloroethane isomers, tetrachlorobutadiene isomers, hexachlorobutene isomers, and trichloroethylene oligomers. The product mixture comprising 2320az may further comprise 1,2,3,4-pentachloro-1,3-butadiene or 1,1,2,3,4-pentachloro-1,3-butadiene. Therefore, in one embodiment, there is a composition comprising 1,1,2,4,4-pentachlorobutadiene, 1,1,2,3,4-pentachlorobutadiene, and 1,1,2,3,4-pentachlorobutadiene. The process may further comprise recovering 2320az from the product mixture before using the recovered 2320az as a starting material in a process to produce E-1336mzz, HCFC-336mdd, 1,1,1,4,4,4-hexafluoro-2-butyne and HFO-Z-1336mzz, for example, as set forth in the present description. Processes for recovering 2320az from the product mixture may include one or any combination of purification techniques, such as distillation, that are known in the art. Recovering 2320az from the product mixture results in a product comprising at least 95%, 97%, or 99% of 2320az. In certain embodiments the process for producing 2320az may further comprise recovering trichloroethylene from the product mixture and recycling the recovered trichloroethylene to the dimerization process as set out in the present description. In certain embodiments, the process for producing 2320az may further comprise recovering hexachlorobutene isomers / υΊ Ί Ί 03 from the product mixture and recycling the recovered hexachlorobutene isomers to the dimerization process as set out in the present description. In certain embodiments the process for producing 2320az may further comprise recovering pentachloroethane from the product mixture and recycling the recovered pentachloroethane to the dimerization process as set out in the present description. If present, other products such as 1,1,2,3,4-pentachloro-1,3-butadiene and 1,1,2,3,4-pentachloro-1,3-butadiene can also be recovered. Production of 1,1,4,4,4-hexafluoro-2-butene This description provides a fluorination process comprising contacting 1,1,2,4,4-pentachlorobuta-1,3-diene (2320az) with HF in the presence of a fluorination catalyst to provide a product mixture comprising E-HFO-1336mzz. In this process, the E isomer of 1336mzz is produced as the predominant isomer of 1336mzz. The fluorination catalysts that can be used in the vapor-phase reaction of the invention can be selected from carbon; graphite; alumina; fluorinated alumina; aluminum fluoride; carbon-supported alumina; carbon-supported aluminum fluoride; carbon-supported fluorinated alumina; aluminum fluoride-supported magnesium fluoride; metals (including elemental metals, metal oxides, metal halides and / or other metal salts); metals supported on aluminum fluoride; metals supported on fluorinated alumina; metals supported on alumina; and metals supported on carbon; and mixtures of metals. Suitable metals for use in fluorination catalysts (optionally supported on alumina, aluminum fluoride, fluorinated alumina, or carbon) include chromium, iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, platinum, manganese, rhenium, scandium, yttrium, lanthanum, titanium, zirconium, and hafnium, copper, silver, gold, zinc, and / or metals having an atomic number from 58 to 71 (i.e., the lanthanide metals). Preferably, when used on a support, the total metal content of the catalyst shall be approximately 0.1 to approximately 20 percent by weight based on the total weight of the catalyst; typically, approximately 0.1 to approximately 10 percent by weight based on the total weight of the catalyst. Useful fluorination catalysts for the process include chromium-based catalysts, such as chromium oxyfluoride or chromium oxide. This catalyst may be unsupported or supported on a support such as activated carbon, graphite, fluorinated graphite, or fluorinated alumina. The chromium catalyst may be used alone or in the presence of a cocatalyst selected from a nickel, cobalt, manganese(II)₂O₅, or zinc salt. In some embodiments, a chromium catalyst is a large surface area chromium oxide, or chromium / nickel in alumina fluoride (Cr / Ni / Al₂F₃), the production of which is reported in European patent no. EP 486,333. Chromium oxyfluoride catalysts can be prepared by treating Cr₂O₃ (chromium oxide) with HF, CCl₃F, or hydrofluorocarbons. In some embodiments of this invention, a chromium oxyfluoride catalyst is prepared by treating dry Cr₂O₃ with a fluorinating agent such as CCl₃F or HF. This treatment can be achieved by placing the Cr₂O₃ in a suitable container (which may be the reactor to be used for carrying out the fluorination reaction) and then passing HF through the dry Cr₂O₃ for a suitable period of time (e.g., approximately 15 to 300 minutes) at a suitable temperature (e.g., approximately 200 °C to 450 °C). In other embodiments of the present invention, a chromium oxyfluoride catalyst is prepared by treating Cr₂O₃ with a hydrofluorocarbon at an elevated temperature. In other embodiments of this invention, a chromium oxyfluoride catalyst is prepared in situ. The Cr₂O₃ is commercially available from Engelhard Corporation (Iselin, NJ). Cr2Os can also be produced by processes known in the art. Preferably, chromium catalysts are activated prior to use, typically by a process comprising heating the chromium catalyst to a temperature of 350 to 400 °C under a nitrogen flow for a period of time, after which the catalyst is heated under a flow of HF and nitrogen or HF and air for a further period of time. In some embodiments, vapor-phase fluorination can be carried out in a reaction zone comprising any reaction vessel of suitable size for the scale of the reaction. In some embodiments, the reaction zone is a reaction vessel composed of corrosion-resistant materials. In some embodiments, these materials comprise alloys, such as nickel-based alloys such as Hastelloy®, commercially available nickel-chromium alloys from Special Metals Corp. under the registered trademark Inconel® (hereinafter Inconel®), or commercially available nickel-copper alloys from Special Metals Corp. (New Hartford, New York) under the registered trademark Monel®, or vessels having fluoropolymer linings. In other embodiments, the reaction vessel may be fabricated from other materials of construction, including stainless steels, particularly austenitic steels, and copper-clad steel. In some embodiments, the molar ratio of HF to 2320az is approximately 1 to approximately 35. In other embodiments, the molar ratio of HF to 2320az is approximately 1 to approximately 25. HF can be added in an amount of 10 to 30 mol per mole of 2320az. In some methods, the fluorination process is carried out at a high temperature, for example, in the range of 275 to 375 °C. In some methods, the temperature may be higher than 375 °C. In other methods, the temperature may be lower than 275 °C. In still other methods, the temperature is in the range of 300 to 350 °C. In some modalities the fluorination process is carried out at a pressure in the range of 0 to 200 psi (0 to 1.4 MPa). In some methods, the contact time for the fluoridation process can range from approximately 3 to approximately 120 seconds. In other methods, the contact time for the fluoridation process can range from approximately 20 to approximately 100 seconds. In still other methods, the contact time for the fluoridation process can range from 50 to approximately 80 seconds. In one embodiment, the mixture of products comprising E1336mzz further comprises HFC-338mf (1,1,1,2,2,4,4,4octafluorobutane, CF3CH2CF2CF3), HFC-356mff (1,1,1,4,4,4hexafluorobutane, CF3CH2CH2CF3) and E-HCFO-1326mxz (trans-2chloro-1,1,1,4,4,4-hexafluorobutene, CF3CC1=CHCF3). In another modality, the product mix that comprises E-1336mzz further comprises Z-1336mzz (Zl,1,1,4,4,4-hexafluoro-2-butene, cis-CF3CH=CHCF3), HFC-338mf (1,1,1,2,2,4,4,4-octafluorobutane, CF3CH2CF2CF3), HFC-356mff (1,1,1,4,4,4-hexafluorobutane, CF3CH2CH2CF3), f-HCFO-1326mxz (trans-2-chloro-l,1,1,4,4,4-hexafluorobutene, CF3CC1=CHCF3), HCFO-1335 and E-HCFO-1326mxz (cis-2-chloro-1,1,1,4,4,4hexafluorobutene, CF3CC1=CHCF3) . HCFO-1335 is one or more of E and / or Z-HCFO-1335mzz (CF3CH=CHCF2C1) and E and / or f-HCFO-1335mzx, (CF3CH=CC1CF2H) . In another embodiment, the mixture of products comprising E-1336mzz further comprises Z-1336mzz (Zl,1,1,4,4,4-hexafluoro-2-butene, cis-CF3CH=CHCF3), HFC-338mf (1,1,1,2,2,4,4,4-octafluorobutane, CF3CH2CF2CF3), HFC-356mff (1,1,1,4,4,4-hexafluorobutane, CF3CH2CH2CF3), f-HCFO-1326mxz (trans-2-chloro-l,1,1,4,4,4-hexafluorobutene, CF3CC1=CHCF3), HCFO-1335, E-HCFO-1326mxz (cis-2-chloro-1,1,4,4,4hexafluorobutene, CF3CC1=CHCF3) , 1327mz (Z and E isomers of 1, 1, 1,2,4,4,4-heptafluoro-l-butene), 346mdf, 143a (1,1,1trifluoroethane), 236fa (1, 1, 1,3,3,3-hexafluoropropane), 1233xf (2-chloro-3, 3,3-trifluoropropene), 1317 (chloroheptafluorobutene), 1314 (tetrachlorochlorotetrafluorobutene) and 1325 (dichloropentafluorobutene). HCFO-1335 is one or more of E and / or 2-HCFO-1335mzz (E and / or Z1-chloro-1, 1, 4,4,4-pentafluorobutene, CF3CH=CHCF2C1) and E and / or Z18 HCFO-1335mzx, (E and / or 2-2-chloro-1,1,4,4,4-pentafluorobutene, CF3CH=CC1CF2H). In one embodiment, there is a composition comprising E1,1,1,4,4,4-hexafluoro-2-butene, 1,1,1,2,2,4,4,4-octafluorobutane, 1,1,1,4,4,4-hexafluorobutane and 2-2-chloro1,1,1,4,4,4-hexafluorobutene. In one embodiment, there is a composition comprising E1,1,1,4,4,4-hexafluoro-2-butene, Zl,1,1,4,4,4-hexafluoro-2-butene, 1,1,1,2,2,4,4,4-octafluorobutane, 1,1,1,4,4,4hexafluorobutane, 2-2-chloro-l,1,1,4,4,4-hexafluorobutene, E2-chloro-l,1,1,4,4,4-hexafluorobutene, and HCFO-1335. In one embodiment, there is a composition comprising E1,1,1,4,4,4-hexafluoro-2-butene, 2-1,1,1,4,4,4-hexafluoro-2-butene, 1,1,1,2,2,4,4,4-octafluorobutane, 1,1,1,4,4,4-hexafluorobutane, 2-2-chloro-1,1,4,4,4-hexafluorobutene, E2-chloro-1,1,4,4,4-hexafluorobutene, HCFO-1335, Z and E1,1,1,2,4,4,4-heptafluoro-1-butene, 2-chloro-1,1,4,4,4-hexafluorobutane, 1,1,1-trifluoroethane, 1,1,1,3,3,3-hexafluoropropane, 2-chloro-3,3,3-trifluoropropene, chloroheptafluorobutene, tetrachlorochlorotetrafluorobutene and dichloropentafluorobutene. In some forms, E-CF3CH=CHCF3(E-1336mzz) is produced with a selectivity greater than 90%, 92%, 94%, 95%, 96%, 97%, 98% or 99%, with respect to Z-1336mzz. The process may further include recovering E-1336mzz from the product mixture to reduce the other components of the product mixture. Processes for recovering E-1336mzz may include one or any combination of purification techniques, such as distillation, that are known in the art. Upon recovery of E-1336mzz from the product mixture, a product comprising at least 98.5%, at least 99%, or at least 99.5% E-1336mzz is produced. In certain embodiments, the process for producing E-1336mzz may further comprise recovering 2320az from the product mixture and recycling the recovered 2320az to the fluorination process as set forth in the present description. In certain embodiments, the process for producing _E-1336mzz may further comprise recovering non-fully fluorinated products from the product mixture and recycling the recovered non-fully fluorinated products to the fluorination process as described herein. Non-fully fluorinated products are fluorinated butanes and butenes having fewer than six fluorine substituents. Examples of non-fully fluorinated products include HCFO-1335 (chloropentafluorobutene, C4H2F5Cl). In some embodiments, the process for producing E-1336mzz comprises: (a) contacting trichloroethylene in the presence of a dimerization catalyst to produce a mixture of products comprising 2320az; (b) contacting the 2320az produced in step (a) with hydrogen fluoride in phase IVIA / a / ZUZl / Ul 11 03 steam in the presence of a fluorination catalyst to produce a mixture of products comprising E-1336mzz. Optionally, 2320az is recovered after step (a) and before step (b). In some embodiments, the process for producing E-1336mzz as described herein comprises (a) contacting trichloroethylene in the presence of a dimerization catalyst and pentachloroethane to produce a product mixture comprising 2320az; (b) contacting the 2320az produced in step (a) with vapor-phase hydrogen fluoride in the presence of a fluorination catalyst to produce a product mixture comprising E-1336mzz. Optionally, the 2320az is recovered after step (a) and before step (b). The variations in the process elements in steps (a) and (b) were described earlier in this description. The purity of 2320az is typically at least 97% before proceeding to step (b). In some embodiments, the product mixture from step (a) comprising 2320az undergoes recovery steps prior to step (b). In some embodiments, the 2320az is recovered from the product mixture of step (a). Techniques for recovering 2320az from the product mixture include distillation and other techniques known to those skilled in the art. In some embodiments, the TCE conversion is less than 100%, and unreacted TCE is present in the product mixture of step (a). In some embodiments, the process further comprises step (a') between steps (a) and (b), which involves recovering the unreacted TCE from the product mixture of step (a) and recycling the recovered TCE back to step (a). Techniques for recovering TCE from the product mixture of step (a) include distillation and other techniques known to those skilled in the art. In some embodiments, the process further comprises (c) contacting E-1336mzz with a chlorine source to produce a mixture of products comprising 2,3-dichloro-1,1,1,4,4,4-hexafluorobutane (CF3CHCICHCICF3) (HCFC-336mdd); (d) contacting 2,3-dichloro-1,1,1,4,4,4-hexafluorobutane with a base to produce a mixture of products comprising 1,1,1,4,4,4-hexafluoro-2-butyne (CFsC^CGFs); and (e) contacting 1,1,1,4,4,4-hexafluoro-2-butyne with hydrogen to produce a mixture of products comprising Z-1,1,1,4,4,4-hexafluoro-2-butene. Process steps (c), (d) and (e) can be carried out as described in patent no. WO 2015 / 142981. Production of HCFC-336mdd The reaction of E-1336mzz with a chlorine source to produce a product mixture comprising 2,3-dichloro-1,1,1,4,4,4-hexafluorobutane (CF3CHCICHCICF3, HCFC-336mdd) is a chlorination process in which a chlorine source and E-1336mzz are reacted to produce a product mixture comprising the desired HCFC-336mdd product. The process can be carried out in the liquid phase in a liquid medium or in the vapor phase, each preferably in the presence of a chlorination catalyst or with photoinitiation. An example of a liquid medium is the reactant E-1336mzz itself. Photoinitiation is carried out in a suitable photoinitiation apparatus which includes a light source, a chlorine (CI2) source and E-1336mzz (the material to be chlorinated), as described, for example, in patent no. WO 2006 / 069108 Al. Examples of suitable chlorination catalysts include Lewis acids, such as transition metal chlorides or aluminum chloride. The catalysts for this liquid-phase chlorination process can be selected from ferric chloride, chromium chloride, aluminum chloride, cupric chloride, and combinations of two or more of these. The catalysts for this vapor-phase chlorination process can be selected from ferric chloride, chromium chloride, aluminum chloride, cupric chloride, and combinations of two or more of these supported on carbon. Preferably, the temperature and pressure conditions for the chlorination process are selected to be effective in producing HCFC-336mdd with high selectivity. When carrying out the process in the liquid phase, as supplied by E-1336mzz, the process is preferably performed in a closed, pressurizable reactor within which the pressure is sufficient to maintain the liquid state. The pressure within the reactor may be autogenous or high pressure. When the process is carried out in a liquid medium, the desired product, HCFC-336mdd, can be recovered from the reactor by purging the unreacted chlorine and separating the unreacted E-1336mzz by distillation. If present, the catalyst can be separated by filtration at a concentration high enough to precipitate from the product mixture before, during, or after distillation. Alternatively, the catalyst may remain in the distillate. A tubular reactor can be used to carry out the process in the vapor phase. The chlorination catalyst, such as Lewis acid, can be placed inside the reactor for effective contact with E-1336mzz, and the chlorine source can be simultaneously supplied to the reactor at a temperature and residence time effective for producing the desired reaction product, HCFC-336mdd, with the desired selectivity. The chlorination process temperature is maintained by applying heat to the reactor. Preferably, the process temperature is in the range of 100 °C to 200 °C. The pressure inside the tubular reactor is preferably approximately 0.1 to 1 MPa. The HCFC-336mdd can be recovered from the product mixture by distillation. The chlorine source can be selected from chlorine, N-chlorosuccinimide, t-butyl-hypochlorite, oxalyl chloride, and sulfuryl chloride. In one embodiment, the reaction of E-1336mzz with a chlorine source is carried out in the presence of a chlorination catalyst, and the chlorine source is chlorine (Cl2). In another embodiment, the reaction of E-1336mzz with a chlorine source is carried out in the absence of a chlorination catalyst, and the chlorine source is chlorine (Cl2). In one embodiment, the reaction of E-1336mzz with a chlorine source is carried out with photoinitiation in the presence of ultraviolet radiation and the chlorine source is chlorine. In one embodiment, the reaction of E-1336mzz with a chlorine source is carried out in the absence of a chlorination catalyst and the chlorine source is N-chlorosuccinimide, t-butyl hypochlorite, oxalyl chloride, or sulfuryl chloride. The process may further include recovering HCFC-336mdd from the product mixture to reduce the other components of the product mixture. Processes for recovering HCFC-336mdd from the product mixture may include one or any combination of purification techniques, such as distillation, that are known in the art. Upon recovery From the HCFC-336mdd product mixture, a product is produced comprising at least 98.5% or at least 99% or at least 99.5% of HCFC-336mdd. In some embodiments, the E-1336mzz can be recovered and recycled back into the process or used for another purpose. Chlorination of E-1336mzz preferably provides a selectivity for HCFC-336mdd of at least 85%, with greater preference at least 90%, and with maximum preference at least 95%, whether the reaction is carried out in liquid phase or vapor phase. The product mixture comprising 336mdd may further comprise one or more of HCFC-336mfa (2,2-dichloro-1,1,1,4,4,4-hexafluorobutane, CF3CCI2CH2CF3) and HCFC-326mda (2,3,3-trichloro-1,1,4,4,4-trifluoropropane, CF3CHC1CC12CF3), which may be recovered from the product mixture. Alternatively, HCFC-336mfa and / or HCFC-326mda may be retained in the product mixture and carried to a further step to produce hexafluoro-2-butyne. In certain embodiments, the process to produce 336mdd may further comprise recovering unconverted E-1336mzz from the chlorination product mixture and recycling the recovered E-1336mzz to the chlorination process as set forth in the present description. In some forms, unconverted E-1336mzz is recovered from the product mix. In some forms, the / υΊ IIOO E-1336mzz can be used for other purposes, such as a blowing agent or heat transfer fluid. Production of 1,1,1,4,4,4-hexafluoro-2-butyne This description further provides a process comprising contacting HCFC-336mdd with a base to produce a product mixture comprising 1,1,1,4,4,4-hexafluoro-2-butyne (CFsC^CCFs) in a dehydrochlorination reaction. The base is preferably a basic aqueous medium. Preferably, this reaction step is carried out in the presence of a catalyst. Preferably, the basic aqueous medium comprises a solution of an alkali metal hydroxide or alkali metal halide salt or another base in water. Preferably, the catalyst is a phase-transfer catalyst. As used herein, a phase-transfer catalyst is a substance that facilitates the transfer of ionic compounds between an organic phase and an aqueous phase. In this step, the organic phase comprises the reactant HCFC-336mdd, and the aqueous phase comprises the basic aqueous medium.The phase transfer catalyst facilitates the reaction of these different and incompatible components. Although the various phase-transfer catalysts may function in different ways, their mechanism of action is not determining their usefulness in the present invention, provided that the phase-transfer catalyst facilitates the dehydrochlorination reaction. A preferred phase-transfer catalyst is a quaternary alkylammonium salt. In some embodiments, at least one alkyl group of the quaternary alkylammonium salt contains at least eight carbon atoms. An example of a quaternary alkylammonium salt in which three alkyl groups contain at least eight carbon atoms is trioctylmethylammonium chloride. Aliquat® 336 is a commercially available phase-transfer catalyst containing trioctylmethylammonium chloride. An example of a quaternary alkylammonium salt in which four alkyl groups contain at least eight carbon atoms is tetraoctylammonium chloride. The anions of such salts can be halides such as chloride or bromide, hydrogen sulfate, or any other commonly used anion.Specific quaternary alkylammonium salts include tetraoctylammonium chloride, tetraoctylammonium hydrogen sulfate, tetraoctylammonium bromide, methyltrioctylammonium chloride, methyltrioctylammonium bromide, tetradecylammonium chloride, tetradecylammonium bromide, and tetradodecylammonium chloride. According to these formulations, the phase-transfer catalyst and reaction conditions are effective in achieving the conversion of HCFC-336mdd, preferably at at least 50% per hour. In other embodiments, the alkyl groups of the quaternary alkylammonium salt contain 4 to 10 carbon atoms, and a nonionic surfactant is present in the aqueous basic medium. According to such embodiments, the phase-transfer catalyst and reaction conditions are effective in achieving the conversion of HCFC-336mdd, preferably at at least 20% per hour. The anions of the quaternary alkylammonium salt, where the alkyl group contains 4 to 10 carbon atoms, can be halides, such as chloride or bromide, hydrogen sulfate, or any other commonly used anion. The quaternary alkylammonium salts mentioned above can be used in this embodiment provided their alkyl groups contain 4 to 10 carbon atoms. Specific additional salts include tetrabutylammonium chloride, tetrabutylammonium bromide, and tetrabutylammonium hydrogen sulfate. Preferred nonionic surfactants include ethoxylated nonylphenol or a C12-C15 ethoxylated linear aliphatic alcohol. Nonionic surfactants including Bio-soft® N25-9 and Makon® 10 useful in the present invention can be obtained from Stepan Company, Northfield, IL. In some embodiments, the quaternary alkylammonium salt is added in an amount of 0.5 mol% to 2 mol% of HCFC-336mdd. In other embodiments, the quaternary alkylammonium salt is added in an amount of 1 mol% to 2 mol% of HCFC-336mdd. Still in other embodiments, the quaternary alkylammonium salt is added in IVIA / a / ZUZl / Ul IIOO an amount of 1 mol% to 1.5 mol% of HCFC-336mdd. In some embodiments, the quaternary alkylammonium salt is added in an amount of 1 mol% to 1.5 mol% of HCFC-336mdd, and the weight of the added nonionic surfactant is 1 to 2 times the weight of the quaternary alkylammonium salt. These amounts apply to each of the above-mentioned embodiments of the quaternary alkylammonium salt used. In some embodiments, the reaction is preferably carried out at a temperature of approximately 60 to 90 °C, with the highest preference at 70 °C. A basic aqueous medium is a liquid (whether a solution, dispersion, emulsion, or suspension, etc.) that is primarily an aqueous liquid with a pH greater than 7. In some embodiments, the basic aqueous solution has a pH greater than 8. In some embodiments, the basic aqueous solution has a pH greater than 10. In some embodiments, the basic aqueous solution has a pH of 10–13. In some embodiments, the basic aqueous solution contains small amounts of organic liquids that may be miscible or immiscible in water. In some embodiments, the liquid in the basic aqueous solution is at least 90% water. In some embodiments, the water is tap water; in others, the water is deionized or distilled. The base is selected from hydroxide, oxide, carbonate, or phosphate salts of alkali metals, alkaline earth metals, and mixtures thereof. In some embodiments, the base is selected from lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium oxide, calcium oxide, sodium carbonate, trisodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, tripotassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, and mixtures thereof. These basic aqueous medium and base configurations apply to all the phase transition catalysts, quantities, and reaction conditions mentioned above. The selectivity for the formation of 1,1,1,4,4,4-hexafluoro-2-butyne is preferably at least 85%. In some embodiments, the dehydrochlorination reaction of 336mdd to 1,1,1,4,4,4-hexafluoro-2-butyne is carried out in the presence of an alkali metal halide salt. The alkali metal can be sodium or potassium. The halide can be chloride or bromide. A preferred alkali metal halide salt is sodium chloride. Without intending to link to any particular theory, it is believed that the alkali metal halide salt stabilizes the phase-transfer catalyst. Although the dehydrochlorination reaction itself produces alkali metal chloride, and in particular sodium chloride, if sodium hydroxide is used as a base, the addition of more sodium chloride provides the additional effect of increasing the yield of / υΊ IIOO 1,1,1,4,4,4-hexafluoro-2-butyne. In some embodiments, the alkali metal halide is added at approximately 25 to approximately 100 equivalents per mole of phase-transfer catalyst. In other embodiments, the alkali metal halide is added at approximately 30 to approximately 75 equivalents per mole of phase-transfer catalyst. In still other embodiments, the alkali metal halide is added at approximately 40 to approximately 60 equivalents per mole of phase-transfer catalyst. These amounts apply to each of the quaternary alkylammonium salts mentioned above. The product 1,1,1,4,4,4-hexafluoro-2-butyne (boiling point -25 °C) can be recovered from the product mixture by distillation, where the butyne is evaporated from the aqueous medium and then condensed. In addition, the product mixture may also contain 1,1,1,4,4,4-hexafluoro-2-chloro-2-butene (HCFC-1326, Z isomer, E isomer, or a mixture thereof), which can be separated from the product mixture and recycled to the process step comprising contacting HCFC-336mdd with a base to produce a product mixture comprising CFsC^CGFs in a dehydrochlorination reaction. Production of Zl,1,1,4,4,4-hexafluoro-2-butene This description also provides a process for IVIA / a / ZUZl / Ul 1103 hydrogenation comprising contacting 1,1,1,4,4,4 hexafluoro-2-butyne with hydrogen to produce a mixture of products comprising 1,1,4,4,4-hexafluoro-2-butene (Z1336mzz). This process is preferably carried out in the presence of an alkyne to alkene catalyst. In some embodiments, the hydrogenation of 1,1,1,4,4,4hexafluoro-2-butyne is carried out as a batch process in liquid phase. In some embodiments, the hydrogenation of 1,1,1,4,4,4hexafluoro-2-butyne is carried out as a continuous vapor-phase process. In some embodiments, an alkyne-to-alkene catalyst is a palladium catalyst, such as palladium dispersed in aluminum oxide or titanium silicate, doped with silver and / or a lanthanide. The palladium loading on the aluminum oxide or titanium silicate is relatively low. In some embodiments, the palladium loading is approximately 100 ppm to approximately 5000 ppm. In other embodiments, the palladium loading is approximately 200 ppm to approximately 5000 ppm. In some embodiments, the palladium catalyst is doped with at least one of silver, cerium, or lanthanum. In some embodiments, the molar ratio of cerium or lanthanum to palladium is approximately 2:1 to approximately 3:1. In some embodiments, the molar ratio of silver to palladium is approximately 0.5:1. Another embodiment of an alkyne-to-alkene catalyst is the Lindlar catalyst, which is a heterogeneous palladium catalyst on a calcium carbonate support that has been deactivated or conditioned with a lead compound. The lead compound can be lead acetate, lead oxide, or any other suitable lead compound. In some embodiments, the catalyst is produced by reducing a palladium salt in the presence of a calcium carbonate suspension, followed by the addition of the lead compound. In some embodiments, the palladium salt is palladium chloride. In other embodiments, the Lindlar catalyst is deactivated or conditioned with quinoline. The amount of palladium on the support is typically about 5 wt%, but it can be any catalytically effective amount. In other embodiments, the amount of palladium on the support in the Lindlar catalyst is greater than 5 wt%. Still in other embodiments, the amount of palladium on the support can range from about 5 wt% to about 1 wt%. In some embodiments, the amount of catalyst used is approximately 0.5 wt% to approximately 4 wt% of the amount of 1,1,1,4,4,4-hexafluoro-2-butyne. In other embodiments, the amount of catalyst used is approximately 1 wt% to approximately 3 wt% of the amount of butyne. Still in other embodiments, the amount of catalyst used is approximately 1 wt% to approximately 2 wt% of the amount of butyne. / υΊ IIOO In some embodiments, this reaction step is a batch reaction and is carried out in the presence of a solvent. In one such embodiment, the solvent is an alcohol. Typical alcoholic solvents include ethanol, ipropanol, and n-propanol. In other embodiments, the solvent is a fluorocarbon or hydrofluorocarbon. Typical fluorocarbons or hydrofluorocarbons include 1,1,1,2,2,3,4,5,5,5-decafluoropentane and 1,1,2,2,3,3,4-heptafluorocyclopentane. In some embodiments, the reaction of 1,1,1,4,4,4-hexafluoro-2-butyne with hydrogen is preferably carried out by adding hydrogen in portions, with increases in vessel pressure of no more than approximately 100 psi (0.69 MPa) with each addition. In other embodiments, the addition of hydrogen is controlled so that the vessel pressure increases by no more than approximately 50 psi (0.35 MPa) with each addition. In some embodiments, after sufficient hydrogen has been consumed in the hydrogenation reaction to convert at least 50% of the butyne to Z-1336mzz, hydrogen may be added in larger increments during the remainder of the reaction. In other embodiments, after sufficient hydrogen has been consumed in the hydrogenation reaction to convert at least 60% of the butyne to the desired butene, hydrogen may be added in larger increments during the remainder of the reaction.Even in other embodiments, after sufficient hydrogen has been consumed in the hydrogenation reaction to convert at least 70% of the butyne to the desired butene, hydrogen can be added in larger increments during the remainder of the reaction. In some embodiments, the largest increments of hydrogen addition can be 300 psi (2.07 MPa). In other embodiments, the largest increments of hydrogen addition can be 400 psi (2.76 MPa). In some embodiments, the molar ratio is approximately 1 mole of hydrogen to approximately 1 mole of 1,1,1,4,4,4-hexafluoro-2-butyne. In other embodiments, the molar ratio is approximately 0.9 mol to approximately 1.3 mol of hydrogen to butyne. Still in other embodiments, the amount of hydrogen added is approximately 0.95 mol of hydrogen to approximately 1.1 mol of butyne. Still in other embodiments, the amount of hydrogen added is approximately 0.95 mol of hydrogen to approximately 1.03 mol of butyne. In some methods, hydrogenation is carried out at room temperature (15 °C to 25 °C). In other methods, hydrogenation is carried out above room temperature. Still in other methods, hydrogenation is carried out below room temperature. And still in other methods, hydrogenation is carried out at a temperature below approximately 0 °C. In one form of a continuous process, a mixture of 1,1,1,4,4,4-hexafluoro-2-butyne and hydrogen are passed through a reaction zone containing the catalyst. A reaction vessel, e.g., a metal tube, filled with the catalyst, can be used to form the reaction zone. In some embodiments, the molar ratio of hydrogen to butyne is approximately 1:1. In other embodiments of a continuous process, the molar ratio of hydrogen to butyne is less than 1:1. Still in other embodiments, the molar ratio of hydrogen to butyne is approximately 0.67:1.0. In some forms of a continuous process, the reaction zone is maintained at room temperature. In other forms of a continuous process, the reaction zone is maintained at a temperature of 30 °C. In still other forms of a continuous process, the reaction zone is maintained at a temperature of approximately 40 °C. In some embodiments of a continuous process, the flow rate of 1,1,1,4,4,4-hexafluoro-2-butyne and hydrogen is maintained to provide a residence time in the reaction zone of approximately 30 seconds. In other embodiments of a continuous process, the flow rate of butyne and hydrogen is maintained to provide a residence time in the reaction zone of approximately 15 seconds. Still in other embodiments of a continuous process, the flow rate of butyne and hydrogen is maintained to provide a residence time in the reaction zone of approximately 7 seconds. The residence time in the reaction zone is understood to decrease as the flow rate of 1,1,1,4,4,4-hexafluoro-2-butyne and hydrogen in the reaction zone increases. As the flow rate increases, the amount of butyne hydrogenated per unit time also increases. Since hydrogenation is exothermic, depending on the length and diameter of the reaction zone and its heat dissipation capacity, at higher flow rates it may be desirable to provide an external cooling source to the reaction zone to maintain the desired temperature. The contact stage conditions, including the choice of catalyst, are preferably selected to produce 2-1336mzz at a selectivity of at least 85%, with greater preference at least 90%, and with maximum preference at least 95%. In some embodiments, after the completion of a continuous or batch hydrogenation process, 2-1336mzz can be recovered by any conventional process, including, for example, fractional distillation. The unconverted hexafluoro-2-butyne can be recovered and recycled back to the hydrogenation process. In other embodiments, after the completion of a continuous or batch hydrogenation process, Z-1336mzz is of sufficient purity to not require further purification steps. / υΊ IIOO EXAMPLES Materials Trichloroethylene, ferric chloride, chromium chloride, alumina chloride, cupric chloride, chlorine, pentachloroethane (HCC-120), trioctylmethylammonium chloride (Aliquat® 336), NaOH, Lindlar's catalyst, K2HPO4, and KH2PO4 are available from Sigma Aldrich, St. Louis, MO. Hydrogen fluoride and E1,1,1,4,4,4-hexafluoro-2-butene are available from Synquest Labs, Inc., Alachua, EL. The GC analysis for Examples 1-4 was performed using an Agilent® 5975GC, RESTEK Rtx-1 column. Example 1: Preparation of 1,1,2,4,4-pentachlorobuta-1,3-diene (HCC-2320az) Trichloroethylene (100 g, 0.76 mol) was added to a stirrer tube containing 30 mg of anhydrous FeCla. The reaction mixture was heated to 230 °C for 2 h. The reactor contents were cooled to room temperature and analyzed by GC to determine conversion and selectivity. The results are provided in Table 1. Example 2: Preparation of 1,1,2,4,4-pentachlorobuta-1,3-diene (HCC-2320az) Trichloroethylene (100 g, 0.76 mol) was added to a stirrer tube containing 1 g of iron wire. The reaction mixture was heated to 230 °C for 2 h. The reactor contents were cooled to room temperature and analyzed by GC to determine conversion and selectivity. The results are provided in Table 1. Example 3: Preparation of 1,1,2,4,4-pentachlorobuta-l,3-diene (HCC-2320az) Trichloroethylene (100 g, 0.76 mol) was added to a stirrer tube containing 20 mg of anhydrous FeCla and 1 g of HCC-120. The reaction mixture was heated to 230 °C for 2 h. The reactor contents were cooled to room temperature and analyzed by GC to determine conversion and selectivity. The results are provided in Table 1. Example 4: Preparation of 1,1,2,4,4-pentachlorobuta-1,3-diene (HCC-2320az) Trichloroethylene (100 g, 0.76 mol) was added to a stirrer tube containing 1 g of iron wire and 1 g of HCC-120. The reaction mixture was heated to 230 °C for 2 h. The reactor contents were cooled to room temperature and analyzed by GC to determine conversion and selectivity. The results are provided in Table 1. Table 1. Dimerization of trichloroethylene at 230 °C Example Catalyst Time (hours) Conversion / Selectivity (%) 1 FeCh (30 mg) 16 26.9 / 81.6 2 Fe Wire (1 g) 8 28.0 / 86.7 3 FeCh (20 mg) / HCC-120 (1 g) 2 35.4 / 84.3 4 Fe Wire (1 g) / HCC-120 (1 g) 2 32.3 / 87.4 As can be seen in Table 1, the presence of HCC-120 increases the conversion rate of trichloroethylene to 2320az when using a FeCl3 or Fe wire catalyst. Example 5: Preparation of 1,1,4,4,4-hexafluoro-2-butene An Inconel® tube (0.5 in. (1.27 cm) outside diameter, 15 in. (38.1 cm) length, 0.34 in. (0.86 cm) wall thickness) was filled with 12 cc (16.35 g) of chromium oxide catalyst. The reactor was heated in a Lindberg furnace to 275 °C, and 2320az (prepared according to the examples mentioned above) was supplied at 0.09 mL / hr and gaseous HF at 5.3 sccm (standard cubic centimeters per minute) through a vaporizer controlled at 200 °C. During the course of the test, the temperature was raised to 325 °C. All sample experiments were conducted at 1–2 psig (714 kPa). The reactor effluent was analyzed online using an Agilent® 6890 GC / 5973 MS and a Restek® PC2618 5% Krytox® CBK-D / 60 / 80 packed column, 6 meters long x 2 mm internal diameter x 1 / 8" external diameter, purged with helium at 30 sccm. Test conditions are provided in Table 2. Samples were taken at hourly intervals.Sample analyses are provided in Table 3. IVIA / a / ZUZl / Ul IIOO Table 2. Example 5 Test conditions for vapor-phase fluorination Sample No. Temp. oven temperature, °C Pressure, psi 2320az flow rate, ml / h n2, sccm HF, sccm Contact time, s 1 275 1.8 0.09 2.51 5.40 53.8 2 275 1.6 0.09 2.52 5.40 53.1 3 275 1.6 0.09 2.51 5.40 53.2 4 300 1.6 0.09 2.53 5.40 50.7 5 300 1.5 0.09 2.53 5.40 50.4 6 300 1.5 0.09 2.53 5.40 50.4 7 325 1.5 0.09 2.56 5.40 48.1 8 325 1.6 0.09 2.52 5.40 48.7 9 325 1.6 0.09 2.56 5.40 48.4 Table 3, Products of vapor-phase fluorination of 2320az (expressed as molar %) Sample No. E-1336mzz 338mf 356mff Z-1336mzz Z-1326mxz 1335 E-1326mxz Other* 1 63.90% 6.16% 20.64% 0.51% 7.76% 0.19% 0.27% 0.58% 2 64.88% 6.52% 19.50% 0.50% 7.73% 0.18% 0.27% 0.42% 3 64.71% 6.48% 18.85% 0.49% 8.61% 0.20% 0.30% 0.36% 4 67.28% 5.67% 13.39% 0.55% 11.80% 0.11% 0.45% 0.75% 5 66.30% 5.80% 13.22% 0.54% 12.83% 0.11% 0.50% 0.70% 6 65.35% 5.11% 11.35% 0.56% 16.12% 0.16% 0.63% 0.72% 7 71.99% 3.82% 2.53% 0.70% 19.22% 0.10% 0.82% 0.82% 8 71.57% 3.82% 2.10% 0.70% 19.99% 0.10% 0.85% 0.69% 9 71.67% 3.97% 1.81% 0.70% 20.36% 0.10% 0.86% 0.54% * Others contain 1327mz (Z and E isomers of 1,1,1,2,4,4,4-heptafluoro-l-butene), 346mdf (1,1,1,4,4,4-hexafluorobutane), 143a (1,1,1-trifluoroethane), 236fa (1,1,1,3,3,3hexafluoropropane), 1233xf (2-chloro-3,3,3-trifluoropropene), 1317 (chloroheptafluorobutene), 1314 (tetrachlorochlorotetrafluorobutene) and 1325 (dichloropentafluorobutene). Example 6: Preparation of 2,3-dichloro-l,1,1,4,4,4-hexafluorobutane (HCFC-336mdd) in liquid phase In this example, E-1336mzz is thermally chlorinated catalytically in the liquid phase to produce HCFC-336mdd. Lewis acids are used as catalysts. The liquid-phase reaction was carried out in a Hastelloy® C reactor. The liquid medium was reactant E-1336mzz. When used, the catalyst was present in the liquid phase. The reactor contents were transferred to a graduated cylinder and analyzed by GC to determine conversion and selectivity. HCFC-336mdd was recovered from the reaction by purging unreacted chlorine, separating unreacted E-1336mzz by distillation, and separating the catalyst by filtration. The reaction conditions and results are shown in Table 4. Table 4. Liquid-phase thermal cloning of E-1336mzz Examples Catalyst T(°C) Time (h) Conversion / selectivity (%) 6-1 FeCh 150 0.5 60 / 100 6-2 FeCh 130 2 12 / >99 6-3 FeCh 100 1 0 / 0 6-4 CrCl3 150 1 60 / 87.3 6-5 AlCh 150 2 69 / 97.6 6-6 CuCl2 150 2 60 / 98 6-7 None 120 2 0 / 0 6-8 None 180 2 63 / 40 / υΊ IIOO For each of Examples 6-1 to 6-6, E-1336mzz (20 g, 0.122 mol) and chlorine (8.65 g, 0.122 mol) were heated to the indicated temperature in the presence of FeCls, CrCls, AlCl3, or CuCl2 catalyst (0.4 g, 0.0025 mol) in the Hastelloy® C reactor for the indicated time. The indicated temperatures and times are provided in Table 4. For Examples 6-7 and 6-8, E-1336mzz (20 g, 0.122 mol) and chlorine (8.65 g, 0.122 mol) were heated to the temperatures indicated in Table 2 in a 210 mL Hastelloy® C reactor for 2 hours. No catalyst was present. Comparing the results for Examples 6-1 to 6-8 indicates a preference for the reaction carried out in the presence of a catalyst, as well as at a temperature of at least 130 °C or at least 150 °C. Example 7: Preparation of 2,3-dichloro-l,1,1,4,4,4hexafluorobutane (HCFC-336mdd) in vapor phase The procedure for the vapor-phase reaction was as follows: an Inconel® tube (0.5 in. (1.27 cm) outside diameter, 15 in. (38.1 cm) length, 0.34 in. (0.86 cm) wall thickness) was filled with 2 cc (1.10 g) of ferric chloride on acid-washed Takeda® carbon. The reactor was heated in a Lindberg furnace to 125 °C, and CF3CH=CHCF3 (E-1336mzz) was supplied at 2,424.83 mL / hour and chlorine gas at 6.2–13.0 sccm (standard cubic centimeters per minute) through a vaporizer controlled at 80 °C. During the course of the test, the temperature was raised to 175 °C. All subsequent experiments were conducted at 4951 psig (0.34–0.35 MPa). The reactor effluent was analyzed online using an Agilent® 6890 GC / 5973 MS and a 6 m x 2 mm I.D. x 1 / 8 in. O.D. Restek® PC2618 5% Krytox® CBKD / 60 / 80 packed column, purged with helium at 30 sccm. HCFC336mdd was recovered by distillation. The data are shown in Table 5. Samples are taken at hourly intervals. Table 5 Chlorination of E-1336mzz in vapor phase Cell. % 73.9 62.1 59.4 56.9 80.9 81.0 82.3 94.5 X- 93.7 99.1 99.3 99.4 Conv. % 2.8 2.9 2.9 2.8 5.3 5.2 5.1 11.6 10.3 9H- 11.4 11.4 12.4 14.9 17.6 ω w X- 14 14 14 X- X- 14 x— 2 x- OO X— 2 sccm 12.96 12.96 12.96 12.96 12.97 12.97 oomba co oo3 ml 4.8.8 co 6.24 6.24 6.24 4.83 4.83 OO oo 4.83 4.83 4.83 4.83 2.42 2.42 2.42 Pressure (MPa) 0.337 0.337 0.344 0.357 0.355 Oven °C 125 125 125 125 150 150 150 175 175 175 175 175 175 1795 1.centes 175 Pores% 1.73% 1.62% 1.52% 4.10% 4.01 % 4.01 % 10.44% % 33 6 10.27% 10.33% 10.26% 11.67% 14.02% 16.303 % 0.1 0.35 0.36 0.36 0.37 0.38 0.39 0.38 0.37 0.37 0.37 0.39 0.40 133a % 4.13 4.02 4.07 4.08 4.13 490 401 4.08 4.02 4.75 4.43 4.89 1336 % 92.91 92.70 92.74 0676 90.46 90.47 99'06 O 84.53 85.82 236fa % 00Ό 0.12 0.12 00Ό 00Ό 0.12 0.12 00'0 00Ό 00Ό 0.12 0.12 0.13 0.11 0.13 Unknown % 0.69 1.06 1.11 1.15 0.97 0.94 0.86 IT LO / υΊ IIOO 84.6 86.5 89.5 77.0 69.2 67.8 co 6.3 co 4.1 3.3 3.2 28 27 28 28 28 28 6.25 6.24 6.25 6.25 6.24 6.25 2.42 2.42 2.42 2.42 2.42 2.42 0.344 0.323 0.377 0.344 0.344 0.344 150 150 150 125 125 CM 5.91 % 5.27 % 4.56 % 3.10% 2.20 % 2.19% co 0.36 0.40 0.34 0.36 0.37 3.91 4.02 3.76 4.04 4.06 4.05 oó oo 89.64 88.51 91.61 92.29 92.38 00Ό 00Ό 00Ό 0.12 0.11 0.12 1.08 0.80 0.77 0.90 0.98 0.99 IVIA / a / ¿U¿1 / υΊ 1100 In Table 5, 236fa (HFC-236fa, 1,1,1,3,3,3hexafluoropropane) and 123 (HCFC-123, 2,2-dichloro-1,1,1trifluoroethane) are impurities in the reactor feed. Reaction conditions that produce a contact time of 27 to 29 seconds at a reactor temperature of 175 °C produce the best selectivities in the production of HCFC-336mdd. Example 8: Preparation of 1,1,1,4,4,4-hexafluorobutane (HCFC336mdd) In this example, the reaction is photoinitiated. A 50-gallon (190 L) stirred reaction vessel was equipped with a column, top condenser, immersion tube, and quartz light cavity with a cooling jacket. The light cavity is equipped with a 450-watt mercury arc lamp. This reactor was charged with 158 kg of E-1336mzz, and the liquid was cooled to 0 °C. The stirrer was started at 100 rpm, the upper condenser was cooled to approximately -20 °C, and the light was turned on. 69 kg of chlorine were slowly added to this system through the immersion tube over 51 hours, using the feed rate to control the temperature and pressure. The temperature and pressure of the reaction liquid were not allowed to rise above 10 °C and 1 psig (0.07 MPa), respectively. After the chlorine addition was completed, the light was turned off and the solution was allowed to warm to room temperature. The system was vented to room temperature through a caustic scrubber and the crude reaction mixture was emptied into a storage vessel. HCFC-336mdd recovery was carried out by combining three batches of the resulting crude reaction mixture (663 kg / 422 L). This combined mixture was then slowly added through an immersion tube to a 200-gallon (750 L) stirred vessel equipped with a bottom discharge valve and charged with 80 gallons (300 L) of a 10% aqueous K₂HPO₄ / KH₂PO₄ solution. After the addition was complete, this mixture was vigorously stirred for three hours, after which stirring was stopped. The lower organic phase was then decanted from the reactor, and conductivity measurements were used to determine the phase change. The resulting neutralized organic oil was a white liquid and had a pH of 5-6.The oil was passed through a bed of molecular sieves for drying and stored for final purification. The isolated chemical yield from 7 batches was 98%. The resulting GC assay (% FID) was 93.5% for the combination of the two 336mdd diastereomers, with the remainder being approximately 6% heavy unknowns, presumably oligomers of the product / starting materials. Therefore, the reaction selectivity was 93.5%. Final purification was performed by distillation. Example 9. Preparation of 1,1,1,4,4,4-hexafluoro-2-butyne The HCFC-336mdd was produced by the vapor-phase process described in Example 7 according to the specific information in Table 4 to provide an HCFC-336mdd selectivity of 99.4%. HCFC-336mdd (23.5 g, 0.1 mol) and water (5.6 mL) at room temperature were mixed with Aliquat® 336 (0.53 g, 0.001325 mol), which is trioctylmethylammonium chloride, and aqueous NaOH solution (22 mL, 0.22 mol) was added. After the addition, the reaction temperature was raised to 70 °C, and gas chromatography was used to monitor the reaction. The reaction was completed after 2 hours, and 14 g of 1,1,1,4,4,4-hexafluoro-2-butyne (conversion: 100%; yield: 86%) were obtained in a dry ice trap. The butyne was purified by distillation. Example 10: Preparation of Zl,1,1,4,4,4-hexafluoro-2-butene The 1,1,1,4,4,4-hexafluoro-2-butyne produced according to Example 9 was reacted with hydrogen to produce the desired Z isomer of 1,1,1,4,4,4-hexafluoro-2-butene by the following procedure: A 1.3 L stirred pump was charged with 5 g of Lindlar's catalyst (5% Pd on CaCO3 poisoned with lead). 480 g (2.96 mol) of hexafluoro-2-butyne was charged into the stirrer. The reactor was cooled (-78 °C) and evacuated. After warming the pump to room temperature, H2 was added slowly, in increments that did not IVIA / a / ZUZl / Ul 11 03 exceeded Δρ= 50 psi (0.35 MPa). A total of 3 mol of H2 was added to the reactor. Gas chromatography analysis of the crude product indicated that the mixture consisted of CFsC^CCFs (0.236%), trans isomer E-CF3CH=CHCF3 (0.444%), saturated CF3CH2CH2CF3 (1.9%), CF2=CHC1, impurity from the starting butyne (0.628%), cis isomer 2-CF3CH=CHCF3 (96.748%). Distillation of the crude product yielded 287 g (59% yield) of 100% pure cis-CF3CH=CHCF3 (boiling point 33.3 °C). MS: 164 [MI], 145 [M-19], 95 [CF3CH=CH], 69 [CF3]. 1H NMR: 6.12 ppm (multiplet), 19F NMR: -60.9 ppm (triplet J = 0.86 Hz). The selectivity of this reaction for the formation of the Z isomer was 96.98%. The Z isomer was recovered by distillation. Other modalities 1. In some embodiments, the present description provides a fluorination process for producing E1,1,1,4,4,4-hexafluorobut-2-ene, comprising: contacting 1,1,2,4,4-pentachlorobut-1,3-diene with hydrogen fluoride in a vapor-phase reaction zone in the presence of a fluorination catalyst to produce a mixture of products comprising E1,1,1,4,4,4-hexafluorobut-2-ene. 2. In some embodiments the fluorination catalyst is selected from carbon; graphite; alumina; fluorinated alumina; aluminum fluoride; carbon-supported alumina; carbon-supported aluminum fluoride; carbon-supported fluorinated alumina; magnesium fluoride supported on aluminum fluoride; metals (including elemental metals, metal oxides, metal halides and / or other metal salts); metals supported on aluminum fluoride; metals supported on fluorinated alumina; metals supported on alumina; and metals supported on carbon; mixtures of metals. 3. The process of modality 1 or 2 in which HE is added in an amount of 10 to 30 mol per mole of 1,1,2,4,4pentachlorobuta-1,3-diene. 4. The process of modality 1 or 2 or 3 where the process is carried out at a temperature of 300 to 350 °C. 5. The process of mode 1 or 2 or 3 or 4 where the process is carried out at a pressure in the range of 0 to 200 psi (0 to 1.4 MPa). 6. The process of the Io2o3o4o5 modality, wherein the fluorination catalyst comprises a metal. 7. The process of modality 6 where the metal is supported on aluminum fluoride, fluorinated alumina, or carbon. 8. The process of the Io2o3o4o5 modality, where the fluorination catalyst is a chromium-based catalyst. 9. The process of modality 8, wherein the fluorination catalyst comprises chromium oxyfluoride or chromium oxide. 10. The process of modality 9 where the fluorination catalyst is supported. 11. The process of modality 9, wherein the fluorination catalyst is supported on a support selected from activated carbon, graphite, fluorinated graphite, and fluorinated alumina. 12. The process of modality 9 where the fluorination catalyst is not supported. 13. The process of modality 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12, wherein HE is added in an amount of 10 to 30 mol per mole of 1,1,2,4,4-pentachlorobuta-1,3-diene. 14. The process of modality 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 13 where the process is carried out at a temperature of 300 to 350 °C. 15. The process of modality 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, or 13 or 14 further comprising producing 1,1,2,4,4-pentachlorobuta-1,3-diene by contacting trichloroethylene with a dimerization catalyst comprising iron to produce a mixture of products comprising 1,1,2,4,4-pentachlorobuta-1,3-diene. 16. The process of modality 15 in which trichloroethylene is brought into contact with a dimerization catalyst comprising iron and pentachloroethane. 17. In some embodiments, the present description provides a process for producing E-1,1,1,4,4,4-hexafluoro-2-butene comprising: (a) producing 1,1,2,4,4-pentachlorobuta-1,3-diene by contacting trichloroethylene with a dimerization catalyst to produce a mixture of products comprising 1,1,2,4,4-pentachlorobuta-1,3-diene; and (b) contacting 1,1,2,4,4-pentachlorobuta-1,3-diene with HF in the presence of a chromium oxyfluoride catalyst to produce a product comprising 1,1,4,4,4-hexafluorobut-2-ene, wherein the process is a vapor-phase process. 18. In some embodiments, the present description provides a process for producing 1,1,4,4,4-hexafluoro-2-butene comprising: (c) producing 1,1,2,4,4-pentachlorobuta-1,3-diene by contacting trichloroethylene with a dimerization catalyst and pentachloroethane to produce a mixture of products comprising 1,1,2,4,4-pentachlorobuta-1,3-diene; and (d) contacting 1,1,2,4,4-pentachlorobuta-1,3-diene with HF in the presence of a chromium oxyfluoride catalyst to produce a product comprising 1,1,4,4,4-hexafluorobut-2-ene, wherein the process is a vapor-phase process. 19. The process of modality 17 or 18 further comprising step (a') between steps (a) and (b) comprising recovering unreacted trichloroethylene from the product mixture of step (a). 20. The process of modality 17 or 18 further comprising step (a') between steps (a) and (b) comprising / ui 11 oo recovering unreacted trichloroethylene from the product mixture of step (a) and step (a) recycling the recovered trichloroethylene to step (a). 21. The process of modality 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 15, 16, 17, 18, 19 or 20 further comprising recovering E-1,1,1,4,4,4-hexafluorobut-2-ene from the product mixture and / or purifying the product mixture comprising E-1,1,1,4,4,4-hexafluorobut-2-ene to reduce the other components of the product mixture. 22. In some embodiments, the present description provides a process for producing 1,1,2,4,4-pentachlorobuta-1,3-diene comprising contacting trichloroethylene with pentachloroethane and a dimerization catalyst comprising iron to produce a mixture of products comprising 1,1,2,4,4-pentachlorobuta-1,3-diene. 23. In some embodiments, the present description provides a process for producing 2-1,1,1,4,4,4-hexafluorobut-2-ene, comprising: (a) producing 1,1,2,4,4-pentachlorobuta-1,3-diene by contacting trichloroethylene with a dimerization catalyst to produce a mixture of products comprising 1,1,2,4,4-pentachlorobuta-1,3-diene; (b) contacting 1,1,2,4,4-pentachlorobuta-1,3-diene with HE in the presence of a fluorination catalyst to produce a mixture of products comprising 1,1,4,4,4-hexafluoro-2-butene, wherein the process is a vapor-phase process; (c) contacting 1,1,4,4,4-hexafluoro-2-butene with a chlorine source to produce a mixture of products comprising 2,3-dichloro-1,1,4,4,4-hexafluorobutane; (d) contacting 2,3-dichloro-1,1,4,4,4-hexafluorobutane with a base to produce a mixture of products comprising 1,1,1,4,4,4-hexafluoro-2-butyne; and (e) contacting 1,1,1,4,4,4-hexafluoro-2-butyne with H2 to produce a mixture of products comprising Z1,1,1,4,4,4-hexafluorobut-2-ene. 24. The process of modality 23 which further comprises recovering 1,1,2,4,4-pentachlorobuta-l,3-diene from the product mixture of step (a). 25. The process of modality 23 or 24 which also includes recovering trichloroethylene from the product mixture of stage (a). 26. The process of modality 23, 24 or 25 which further comprises recovering 1,1,4,4,4-hexafluoro-2-butene from the product mixture of step (b). 27. The process of modality 23, 24, 25 or 26 which further comprises recovering 2,3-dichloro-l,1,1,4,4,4hexafluorobutane from the product mixture of step (c). 28. The process of modality 23, 24, 25, 26 or 27 which also includes recovering 1,1,1,4,4,4-hexafluoro-2-butyne from IVIA / a / ZUZl / Ul IIOO the mixture of products from stage (d). 29. The process of modality 23, 24, 25, 26, 27 or 28 which further comprises recovering Zl, 1, 1,4,4,4-hexafluoro-2-butene from the product mixture of step (e). 30. In some embodiments, the present description provides a mixture of products comprising E-1336mzz, Z-1336mzz (cis-CF3CH=CHCF3), HFC-338mf (1,1,1,2,2,4,4,4-octafluorobutane, CF3CH2CF2CF3), and one or more of HFC-356mff (1,1,1,4,4,4-hexafluorobutane or CF3CH2CH2CF3), Z-HCFO-1326mxz (trans-2-chloro-l,1,1,4,4,4-hexafluorobutene, CF3CC1=CHCF3), HCFO-1335, E-HCFO-1326mxz (cis-2-chloro-l,1,1,4,4,4-hexafluorobutene, CF3CC1=CHCF3). HCFO-1335 may include one or more of HCFO-1335mzz (CF3CH=CHCF2C1), HCFO-1335mzx, (CF3CH=CC1CF2H), E-HCFO-1335mzz, Z-HFO1335mzz, E-HCFO-1335mzx, and Z-HCF0-1335mzx. 31. In some embodiments, the present description provides a mixture of products comprising E-1336mzz, Z-1336mzz (cis-CF3CH=CHCF3), HFC-338mf (1,1,1,2,2,4,4,4-octafluorobutane, CF3CH2CF2CF3), and two or more of HFC-356mff (1,1,1,4,4,4-hexafluorobutane, or CF3CH2CH2CF3), Z-HCFO-1326mxz (trans-2-chloro-1,1,4,4,4-hexafluorobutene, CF3CC1=CHCF3), HCFO-1335, E-HCFO-1326mxz (cis-2-chloro-1,1,4,4,4-hexafluorobutene, CF3CC1=CHCF3), wherein HCFO-1335 includes one or more of HCFO-1335mzz (CF3CH=CHCF2C1) , HCFO-1335mzx, (CF3CH=CC1CF2H) , E-HCFO-1335mzz, Z-HFO1335mzz, E-HCFO-1335mzx, and Z-HCFO-1335mzx. 32. In some embodiments, the present description provides a mixture of products comprising E-1336mzz, Z-1336mzz (cis-CF3CH=CHCF3), HFC-338mf (1,1,1,2,2,4,4,4-octafluorobutane, CF3CH2CF2CF3), and three or more of HFC-356mff (1,1,1,4,4,4-hexafluorobutane, or CF3CH2CH2CF3), Z-HCFO-1326mxz (trans-2-chloro-1,1,4,4,4-hexafluorobutene, CF3CC1=CHCF3), HCFO-1335, E-HCFO-1326mxz (cis-2-chloro-1,1,4,4,4-hexafluorobutene, CF3CC1=CHCF3), wherein HCFO-1335 includes one or more of HCFO-1335mzz (CF3CH=CHCF2C1) , HCFO-1335mzx, (CF3CH=CC1CF2H) , E-HCFO-1335mzz, Z-HFO1335mzz, E-HCFO-1335mzx, and Z-HCFO-1335mzx. 33. In some embodiments, the present description provides a mixture of products comprising E-1336mzz, Z-1336mzz (cis-CF3CH=CHCF3), HFC-338mf (1,1,1,2,2,4,4,4-octafluorobutane, CF3CH2CF2CF3), and HFC-356mff (1,1,1,4,4,4-hexafluorobutane, or CF3CH2CH2CF3), Z-HCFO-1326mxz (trans-2-chloro-1,1,1,4,4,4-hexafluorobutene, CF3CC1=CHCF3), HCFO-1335, E-HCFO-1326mxz (cis-2-chloro-1,1,4,4,4-hexafluorobutene, CF3CC1=CHCF3), wherein HCFO-1335 includes one or more of HCFO1335mzz (CF3CH=CHCF2C1) , HCFO-1335mzx, (CF3CH=CC1CF2H) , E-HCFO1335mzz, E-HFO1335mzz, E-HCFO-1335mzx, and Z-HCFO-1335mzx. 34. In one embodiment, there is a composition comprising E, 1,1,4,4,4-hexafluoro-2-butene, 1,1,1,2,2,4,4,4-octafluorobutane, 1,1,1,4,4,4-hexafluorobutane and E-2-chloro 1,1,1,4,4,4-hexafluorobutene. 35. Modality 34 which further comprises Fl,1,1,4,4,4hexafluoro-2-butene, E-2-chloro-l,1,1,4,4,4-hexafluorobutene, and HCFO-1335. 36. Modality 35 further comprising a composition comprising Z and El,1,1,2,4,4,4-heptafluoro-l-butene, 2chloro-1,1,1,4,4,4-hexafluorobutane, 1,1,1-trifluoroethane, 1,1,1,3,3,3-hexafluoropropane, 2-chloro-3,3,3-trifluoropropene, chloroheptafluorobutene, tetrachlorotetrafluorobutene and dichloropentafluorobutene. It should be understood that, although the invention has been described in conjunction with its detailed description, the foregoing description is intended to illustrate, and not limit, the scope of the invention, which is defined by the scope of the appended claims. Other aspects, advantages, and modifications are within the scope of the following claims. Those skilled in the art(s) to which the present invention relates should appreciate that any of the features described herein in relation to any particular aspect and / or embodiment of the present invention may be combined with one or more of any of the other features of any other aspects and / or embodiments of the present invention described herein, with appropriate modifications to ensure compatibility of the combinations. Such combinations are deemed to be part of the present invention as described herein. It is hereby stated that, as of this date, the best method known to the applicant for putting the aforementioned invention into practice is the one that is clear from the present description of the invention.

Claims

1. A process for producing El, 1,1,4,4,4hexafluorobut-2-ene, characterized in that it comprises contacting 1,1,2,4,4-pentachlorobut-1,3-diene with vapor-phase HF in the presence of a fluorination catalyst to produce a mixture of products comprising El,1,1,4,4,4hexafluorobut-2-ene.

2. The process according to claim 1, characterized in that the fluorination catalyst is selected from carbon; graphite; alumina; fluorinated alumina; aluminum fluoride; carbon-supported alumina; carbon-supported aluminum fluoride; carbon-supported fluorinated alumina; aluminum fluoride-supported magnesium fluoride; metals (including elemental metals, metal oxides, metal halides and / or other metal salts); metals supported on aluminum fluoride; metals supported on fluorinated alumina; metals supported on alumina; and metals supported on carbon; and mixtures of metals.

3. The process according to claim 1, characterized in that HF ​​is added in an amount of 10 to 30 mol per mole of 1,1,2,4,4-pentachlorobuta-1,3-diene. / ui 11 oo 4. The process according to claim 1, characterized in that it is carried out at a temperature in the range of 300 to 350 °C.

5. The process according to claim 1, characterized in that it is carried out at a pressure in the range of 0 to 200 psi (0 to 1.4 MPa).

6. The process according to claim 1, characterized in that it further comprises producing 1,1,2,4,4-pentachlorobuta-1,3-diene by contacting trichloroethylene with a dimerization catalyst comprising iron to produce a mixture of products comprising 1,1,2,4,4-pentachlorobuta-1,3-diene.

7. The process according to claim 6, characterized in that trichloroethylene is brought into contact with a dimerization catalyst comprising iron and pentachloroethane.

8. A composition characterized in that it comprises 1,1,2,4,4-pentachlorobuta-1,3-diene, El, 1,2,3,4-pentachlorobuta-1,3-diene and Zl,1,2,3,4-pentachlorobuta-1,3-diene.

9. A process for producing 1,1,2,4,4-pentachlorobuta-1,3-diene, characterized in that it comprises contacting trichloroethylene with pentachloroethane and a dimerization catalyst to produce a mixture of products comprising 1,1,2,4,4-pentachlorobuta-1,3-diene.

10. A process for producing Z1,1,1,4,4,4-hexafluorobut-2-ene, characterized in that it comprises: (a) contacting trichloroethylene with a dimerization catalyst to produce a mixture of products comprising 1,1,2,4,4-pentachlorobuta-1,3-diene; (b) contacting 1,1,2,4,4-pentachlorobuta-1,3-diene with HF in the presence of a fluorination catalyst to produce a mixture of products comprising 1,1,4,4,4-hexafluoro-2-butene, wherein the process is a vapor-phase process; (o) contacting 1,1,4,4,4-hexafluoro-2-butene with a chlorine source to produce a mixture of products comprising 2,3-dichloro-1,1,4,4,4-hexafluorobutane; (d) contacting 2,3-dichloro-1,1,4,4,4-hexafluorobutane with a base to produce a mixture of products comprising 1,1,1,4,4,4-hexafluoro-2-butyne; and (e) contacting 1,1,1,4,4,4-hexafluoro-2-butyne with H2 to produce a mixture of products comprising Z1,1,1,4,4,4-hexafluorobut-2-ene.

11. The process according to claim 10, characterized in that it further comprises recovering 1,1,2,4,4-pentachlorobuta-1,3-diene from the product mixture of step (a); or recovering trichloroethylene from the product mixture of step (a); or recovering 1,1,4,4,4-hexafluoro-2-butene from the product mixture of step (b); or recovering 2,3-dichloro-1,1,1,4,4,4-hexafluorobutane from the product mixture of step (c); or recovering 1,1,1,4,4,4-hexafluoro-2-butyne from the product mixture of step (d); or recovering 1,1,1,4,4,4-hexafluoro-2-butene from the product mixture of step (e).

12. The process according to claim 10, characterized in that it further comprises recovering 1,1,2,4,4-pentachlorobuta-1,3-diene from the product mixture of step (a); and recovering trichloroethylene from the product mixture of step (a); and recovering 1,1,4,4,4-hexafluoro-2-butene from the product mixture of step (b); and recovering 2,3-dichloro-1,1,1,4,4,4-hexafluorobutane from the product mixture of step (c); and recovering 1,1,1,4,4,4-hexafluoro-2-butyne from the product mixture of step (d); and recovering 1,1,1,4,4,4-hexafluoro-2-butene from the product mixture of step (e).

13. A composition characterized in that it comprises E1,1,1,4,4,4-hexafluoro-2-butene, Z-1,1,1,4,4,4-hexafluoro-2-butene, 1,1,1,2,2,4,4,4-octafluorobutane, and one or more additional compounds selected from 1,1,1,4,4,4-hexafluorobutane, Z1,1,4,4,4-hexafluoro-2-chloro-2-butene, E-1,1,1,4,4,4-hexafluoro-2-chloro-2-butene and HCFO-1335, wherein HCFO-1335 is at least one of E-chloro-1,1,4,4,4-pentafluorobutene, Z1-chloro-1,1,4,4,4-pentafluorobutene, E2-chloro-1,1,4,4,4-pentafluorobutene, and 2-2-chloro-1,1,4,4,4-pentafluorobutene.

14. A composition characterized in that it comprises E- 1,1,1,4,4,4-hexafluoro-2-butene, 1,1,1,2,2,4,4,4-octafluorobutane, 1,1,1,4,4,4-hexafluorobutane and 2-2-chloro-1,1,1,4,4,4-hexafluorobutene.