GB2547277A

GB2547277A - Process

Info

Publication number: GB2547277A
Application number: GB1602646.0A
Authority: GB
Inventors: Sharratt Andrew; Low Robert; Rees Claire; Doran Maxine
Original assignee: Mexichem Fluor SA de CV
Current assignee: Mexichem Fluor SA de CV
Priority date: 2016-02-15
Filing date: 2016-02-15
Publication date: 2017-08-16
Also published as: GB201602646D0

Abstract

An integrated process for preparing 2,3,3,3- tetrafluoropropene (R-1234yf) comprising a) providing a 3,3,3-trifluoropropene (R-1243zf) feed stream comprising greater than about 90%, such as about 95%, or about 99% by weight R-1243zf; b) contacting the R-1243zf feed stream with cobalt (III) fluoride, to produce a product stream comprising 1,2,3,3,3-pentafluoropropane (R-245eb); and c) dehydrofluorinating R-245eb produced in step (b) to produce R-1234yf. The R-1243zf feed stream in step (a) is provided by contacting a composition comprising R-1243zf and one or more undesired (hydro)halocarbons with an aluminium-containing adsorbent and/or activated carbon. This results in a reduction in unwanted by-products.

Description

Process

The invention relates to a process for preparing 2,3,3,3-tetrafluoropropene (R-1234yf). In particular, the invention relates to an integrated process for preparing 2,3,3,3-tetrafluoropropene comprising providing a 3,3,3-trifluoropropene (R-1243zf) feed stream comprising greater than about 90% by weight R-1243zf; contacting the R-1243zf provided with a fluorine source comprising cobalt (III) fluoride (C0F3), to produce 1,2,3,3,3-pentafluoropropane (R-245eb); and dehydrofluorinating R-245ebto produce R-1234yf.

The listing or discussion of a prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or is common general knowledge. 2,3,3,3-tetrafluoropropene is also known as HFO-1234yf, HFC-1234yf or simply R-1234yf. Hereinafter, unless otherwise stated, 2,3,3,3-tetrafluoropropene will be referred to as R-1234yf. The known processes for preparing R-1234yf typically suffer from disadvantages such as low yields, and/or the handling of toxic and/or expensive reagents, and/or the use of extreme conditions, and/or the production of toxic byproducts. Methods for the preparation of R-1234yf have been described in, for example, Journal Fluorine Chemistry (82), 1997, 171-174. In this paper, R-1234yf is prepared by the reaction of sulphur tetrafluoride with trifluoroacetylacetone. However, this method is only of academic interest because of the waste materials produced when using reagents such as sulphur tetrafluoride and the potential for contamination of the 1234yf product with highly odoriferous impurities. Another method for the preparation of R-1234yf is described in US-2931840. In this case, pyrolysis of C1 chlorofluorocarbons with or without tetrafluoroethylene was purported to yield R-1234yf. However, the yields described were very low and again it was necessary to handle hazardous chemicals under extreme conditions. It would also be expected that such a process would produce a variety of very toxic by-products.

Additionally, (hydro)fluoroalkenes are increasingly being considered as working fluids in applications such as refrigeration, heat pumping, foam blowing, fire extinguishers/retardants, propellants and solvency (e.g. plasma cleaning and etching). The processes used to make (hydro)fluoroalkenes can lead to the generation of toxic and/or otherwise undesirable by-products. The presence of small quantities of impurities may not be detrimental to the bulk physical properties of the (hydro)fluoroalkene product and for some applications their removal is unnecessary. However, some applications require very low levels of impurities, and many of these are difficult to remove from the (hydro)fluoroalkenes by recognized means.

It is desirable to provide a new method for the preparation of 1234yf that uses only readily available feedstocks and provides high levels of feed purity.

The present invention addresses one or more of the above deficiencies and provides an integrated process for preparing 2,3,3,3-tetrafluoropropene (R-1234yf), the process comprising: (a) providing a 3,3,3-trifluoropropene (R-1243zf) feed stream comprising greater than about 90% by weight R-1243zf; (b) contacting the feed stream comprising R-1243zf produced in step (a) with a fluorine source comprising cobalt (III) fluoride (CoF3) to produce a product stream comprising 1,2,3,3,3-pentafluoropropane (R-245eb); and (c) dehydrofluorinating R-245eb produced in step (b) to produce R-1234yf.

Each of the steps of the integrated process of the invention are described in detail below.

Step (a): providing a R-1243zf feed stream comprising greater than about 90% by weight R-1243zf

Commercially available R-1243zf often contain many impurities, including the highly toxic species 1,2,3,3,3- pentafluoropropene (R-1225ye), 1,1,3,3,3-pentafluoropropene (R-1225zc), and the chlorofluorocarbon species chlorofluoromethane (R-31), chlorofluoroethene (R-1131), trichlorofluoromethane (R-11), dichlorodifluoromethane ( R-12), chlorotrifluoromethane (R-13), and dichlorotetrafluoroethane (R-114) that are damaging to the environment.

In the process of the invention, the feed stream in step (a) comprises greater than about 90% by weight R-1243zf.

Typically, the feed stream in step (a) of the process of the invention is provided by the purification of a composition comprising R-1243zf and one or more undesired (hydro)halocarbon compounds, such as those noted above.

Preferably in the process of the invention, the R-1243zf feed stream in step (a) may be provided by contacting a composition comprising the R-1243zf and one or more undesired (hydro)halocarbon compounds with an aluminium-containing adsorbent, activated carbon, or a mixture thereof.

Either the aluminium-containing adsorbent or activated carbon may be porous or non-porous, but preferably porous. A preferred aluminium-containing adsorbent is an alumina or alumina-containing substrate. Advantageously, the substrate is porous. Further information on the various crystalline forms of alumina can be found in Acta. Cryst., 1991, B47, 617, the contents of which are hereby incorporated by reference.

Preferred aluminium-containing adsorbents (e.g. alumina) will have functionality that facilitates their combination with the compounds the adsorbent is removing. Examples of such functionality include acidity or basicity, which can be Lewis-type or Bronsted-type in nature, which will facilitate its combination with the compounds the adsorbent is removing. The acidity or basicity can be modified in a manner well known to those skilled in the art by using modifiers such as sodium sulphate. Examples of aluminium-containing adsorbents with acidic or basic functionality include Eta-alumina, which is acidic, and Alumina AL0104, which is basic.

Aluminosilicate molecular sieves (zeolites) are a further preferred group of aluminium-containing adsorbent. Typically, the zeolites have pores having openings which are sufficiently large to allow the desired and undesired compounds to enter into the interior of the zeolite whereby the undesired compounds are retained. Accordingly, zeolites having pores which have openings which have a size across their largest dimension in the range of 3 A to 12 A are preferred.

Preferred zeolites have a pore opening sufficiently large to allow the undesired compounds to enter into the interior of the zeolite whereby the undesired compounds are retained, whilst excluding the desired compound (R-1243zf) from entering the interior of the zeolite. Such zeolites typically have openings which have a size across their largest dimension in the range of 3 A to 12 A, preferably from 3 A to 10 A or 4 A to 12 A. Particularly preferred are those molecular sieves having pores which have openings having a size across their largest dimension in the range of 4 A to 10 A, such as 4 A to 8 A (e.g. 4 A to 5 A) and may include zeolite Y, ultra-stable Y (dealuminated-Y), zeolite beta, zeolite X, zeolite A and zeolite ZSM-5, AW-500.

By opening in this context we are referring to the mouth of the pore by which the undesired compound enters the body of the pore, where it may be retained. The openings to the pores may be elliptically shaped, essentially circular or even irregularly shaped, but will generally be elliptically shaped or essentially circular. When the pore openings are essentially circular, they should have a diameter in the range of about 3A across their smaller dimension. They can still be effective at adsorbing compounds provided that the size of the openings across their largest dimension is in the range of from about 3A to about 12A. Where the adsorbent has pores having elliptically shaped openings, which are below 3A across their smaller dimension, they can still be effective at adsorbing compounds provided that the size of the openings across their largest dimension is in the range of from about 3Ato about 12A.

By “activated carbon”, we include any carbon with a relatively high surface area such as from about 50 to about 3000 m2 or from about 100 to about 2000 m2 (e.g. from about 200 to about 1500 m2 or about 300 to about 1000 m2). The activated carbon may be derived from any carbonaceous material, such as coal (e.g. charcoal), nutshells (e.g. coconut) and wood. Any form of activated carbon may be used, such as powdered, granulated, extruded and pelleted activated carbon.

Activated carbon is preferred which has been modified (e.g. impregnated) by additives which modify the functionality of the activated carbon and facilitate its combination with the compounds it is desired to removed. Examples of suitable additives include metals or metal compounds, and bases.

Typical metals include transition, alkali or alkaline earth metals, or salts thereof. Examples of suitable metals include Na, K, Cr, Mn, Au, Fe, Cu, Zn, Sn, Ta, Ti, Sb, Al, Co, Ni, Mo, Ru, Rh, Pd and/or Pt and/or a compound (e.g. a halide, hydroxide, carbonate) of one or more of these metals. Alkali metal (e.g. Na or K) salts are currently a preferred group of additive for the activated carbon, such as halide, hydroxide or carbonate salts of alkali metals salts. Hydroxide or carbonate salts of alkali metals salts are bases. Any other suitable bases can be used, including amides (e.g. sodium amide).

The impregnated activated carbon can be prepared by any means known in the art, for example soaking the carbon in a solution of the desired salt or salts and evaporating the solvent.

Examples of suitable commercially available activated carbons include those available from Chemviron Carbon, such as Carbon 207C, Carbon ST1X, Carbon 209M and Carbon 207EA. Carbon ST1X is currently preferred. However, any activated carbon may be used, provided they are treated and used as described herein.

Advantageously, a combination of an aluminium-containing absorbent and activated carbon is used, particularly when each are separately effective at removing particular undesired compounds from a composition also containing R-1243zf. Examples of preferred combinations of aluminium-containing absorbent and activated carbon include zeolite and activated carbon and aluminium-containing absorbent and impregnated activated carbon.

The purification requires the composition (e.g. product stream) to be in the liquid or vapour phase. Liquid phase contacting is preferred.

Processing with a stationary bed of the adsorbent will typically be applied to continuous processes. The composition (e.g. product stream) is passed over or through the stationary bed comprising the aluminium-containing absorbent, activated carbon, or a mixture thereof.

The aluminium-containing absorbent, activated carbon, or a mixture thereof is normally pre-treated prior to use by heating in a dry gas stream, such as dry air or dry nitrogen. This process has the effect of activating the aluminium-containing absorbent, activated carbon, or a mixture thereof. Typical temperatures for the pre-treatment are in the range of from about 100 to about 400 °C (e.g. about 100 to about 300 °C).

The purification can be operated in a batch or continuous manner, although a continuous manner is preferred. In either case, during operation of the process, the absorption capability of the aluminium-containing absorbent, activated carbon, or a mixture thereof is gradually reduced as the pores become occupied with the one or more undesired (hydro)halocarbon compounds. Eventually, the ability of the aluminium-containing absorbent, activated carbon, or a mixture thereof to absorb the undesired compound(s) will be substantially impaired, at which stage it should be regenerated. Regeneration is typically effected by heating the used aluminium-containing absorbent, activated carbon, or a mixture thereof in a dry gas stream, such as dry air or dry nitrogen, at a temperature in the range of from about 100 to about 400 °C, such as from about 100 to about 300 °C (e.g. about 100 to about 200 °C), and a pressure in the range of from about 1 to about 30 bar (e.g. about 5 to about 15 bar).

The purification typically is conducted at a temperature in the range of from about -50 °C to about 200 °C, preferably from about 0°C to about 100°C, such as from about 10 to about 50 °C. This temperature range applies to the temperature of the interior of the purification vessel.

Typical operating pressures for the process for the preparation of R-1243zf are from about 1 to about 30 bar, such as from about 1 to about 20 bar, preferably from about 5 to about 15 bar.

In the (batch) purification, the aluminium-containing absorbent, activated carbon, or a mixture thereof typically is used in an amount of from about 0.1 to about 100 % by weight, such as from about 1 or 5 to about 50 % by weight, preferably from about 10 to about 50 % by weight, based on the weight of the composition comprising R-1243zf and one or more undesired compounds.

In a continuous purification, the typical feed rate of the composition (e.g. product stream) comprising the R-1243zf and one or more undesired compounds to the aluminium-containing absorbent, activated carbon, or a mixture thereof is such that in the liquid phase the contact time of the adsorbate with the adsorbent is from about 0.1 to 24 hours, preferably from about 1 to 8 hours. In a preferred mode of operation the adsorbate is continuously recycled through the adsorbent bed until the level of the undesired components has reduced sufficiently. Where vapour phase contacting is utilised, the contact time of the adsorbate with the adsorbent is from about 0.001 to 4 hours, preferably from about to 0.01 to 0.5 hours. In a preferred mode of operation the adsorbate is continuously recycled through the adsorbent bed until the level of the undesired components has reduced sufficiently.

Preferably, the purification removes at least about 50%, about 60%, about 70% or about 80% of the undesired compound(s) present in the composition comprising the R-1243zf. More preferably, the composition removes at least about 90%, about 95% or even about 99% of the undesired compound(s) present in the composition comprising the R-1243zf.

For example, the R-1243zf feed stream in step (a) typically comprises about 90% or more by weight R-1243zf, such as about 95% or more or about 99% or more by weight R-1243zf. Preferably, the R-1243zf feed stream comprises about 99.5% or more by weight or about 99.8% or more by weight R-1243zf.

Following purification, the level of undesired compound(s) in the composition comprising the R-1243zf typically will be from not detectable (by currently available techniques, such as capillary gas chromatography) to about 10ppm, such as from about 0.01 ppm to about 5ppm, preferably from not detectable to about 1ppm.

The purification of a composition comprising R-1243zf and one or more undesired (hydro)halocarbon compounds to provide the feed stream in step (a) may be conducted continuously with step (b) described below. For example, a feed stream comprising greater than about 90% by weight R-1243zf may be directly transferred, (for example, in the liquid phase) into the reactor for step (b).

Step (b): Fluorination ofR-1243zfto R-245eb

The feed stream provided in step (a) is contacted with C0F3.

The use of C0F3 as a reagent in processes for preparing R-1234yf has been found to be desirable as C0F3 is a powerful fluorinating agent that is relatively inexpensive to use and has been found to be highly selective for the desired R-245eb product when contacted with R-1243zf.

In certain embodiments of the invention, the fluorine source comprising C0F3 used in step (b) may additionally comprise cobalt (II) fluoride (C0F2). For example, within the fluorine source comprising C0F3, the ratio of C0F3 to C0F2 may be from about 9:1 to 2:8.

Alternatively, the fluorine source comprising C0F3 used in step (b) may consist of or consist essentially of C0F3.

By the term “consist essentially of, we include the meaning that the compositions/fluorine source contain substantially no other components. For example, a fluorine source consisting essentially of cobalt (III) fluoride would contain substantially no other cobalt compounds. We include the term “consist of within the meaning of “consist essentially of.

By “substantially no” and “substantially free of, we include the meaning that the compositions/fluorine source contain 0.5% by weight or less of the stated component, preferably 0.1% or less, based on the total weight of the composition/fluorine source.

Typically, in the process of the invention, step (b) is carried out with a stoichiometric excess of CoF3. For example, the molar ratio of CoF3:R-1234zf is from about 2:1 to about 20:1, such as from about 4:1 to about 10:1

Contacting 3,3,3-trifluoropropene (R-1243zf) with a fluorine source comprising CoF3 in step (b) produces 1,2,3,3,3-pentafluoropropane (R-245eb) and CoF2. The CoF2 produced in step (b) may optionally be regenerated. For example, CoF2 may be transferred to a further reactor and contacted with fluorine gas to regenerate CoF3, which can optionally be recycled back into step (b) of the process of the invention.

In the process of the invention, step (b) may be carried out in the liquid or the vapour phase. Typically, in the process of the invention, step (b) is carried out in the vapour phase at atmospheric, sub- or super-atmospheric pressure, preferably from about 0 (0.1 MPa) to about 30 bara (3 MPa) and more preferably from about 0 (0.1 MPa) to about 10 bara (1 MPa).

In the process of the invention, step (b) is typically carried out at a temperature of from about 100 to about 400 °C, such as from about 150 to 300 °C or from about 200 to 250 X.

Step (b) can be carried out in any suitable apparatus, such as a static mixer, or a stirred tank reactor. Preferably the apparatus used is one where the reactants can be quickly brought into contact in a controlled manner and the heat of reaction rapidly dissipated such as a moving bed reactor, for example a fluidised bed reactor. Preferably, this or any other apparatus described herein is made from one or more materials that are resistant to corrosion, e.g. Hastelloy® or Inconel® or fluoropolymers such as PTFE and FEP.

Step (b) of the present invention may be carried out either batch-wise or continuously, preferably continuously. For example, in a reactor designed to allow good mixing of the reactants and efficient dissipation of the heat of reaction.

In the process of the invention, the product stream comprising 1,2,3,3,3-pentafluoropropane (R-245eb) produced in step (b) may optionally be purified before being used in step (c) or may optionally be used in step (c) without any further separation or purification.

Any suitable purification methods may be used. Suitable purification methods include, but are not limited to, distillation, phase separation, adsorption e.g. using molecular sieves and/or activated carbon, and scrubbing.

The product stream comprising R-245eb may comprise unreacted R-1243zf. Unreacted R-1243zf may be removed from the product stream comprising R-245eb and optionally recycled back into step (b).

In the process of the invention, step (b) preferably comprises continuously contacting a fluorine source comprising CoF3 with R-1243zf in the vapour phase.

Typically in this preferred step (b) the molar ratio of CoF3:R-1234zf is from about 2:1 to about 20:1, such as from about 4:1 to about 10:1.

Typically in this preferred step (b) the temperature is of from about 150 to 300 °C or from about 200 to about 250 °C.

Typically in this preferred step (b) the pressure is from about 0 (0.1 MPa) to about 30 bara (3 MPa), more preferably from about 0 (0.1 MPa) to about 10 bara (1 MPa).

For example, step (b) may comprise contacting a fluorine source comprising CoF3 with R-1243zf in the vapour phase, wherein the molar ratio of CoF3:R-1234zf is from about 2:1 to about 20:1, the temperature is from about 200 to about 250 °C and the pressure is from about 0 (0.1 MPa) to about 10 bara (1 MPa).

Step (c): Dehydrofluorination of R-245eb to R-1234yf

Step (c) of the process of the invention may be carried out using any suitable reaction conditions effective to dehydrofluorinate R-245eb to produce R-1234yf.

Typically, step (c) in the process of the invention is typically conducted in a dehydrofluorination reactor that is separate from the reactor used to conduct step (b), where the product stream comprising 1,2,3,3,3-pentafluoropropane (R-245eb) produced in step (b) is fed into the dehydrofluorination reactor.

Steps (b) and (c) in the process of the invention, are typically conducted continuously. For example, the product stream comprising 1,2,3,3,3-pentafluoropropane (R-245eb) produced in step (b) may be directly transferred (for example, in the vapour phase) into a reactor for step (c). For example, the product stream comprising 1,2,3,3,3-pentafluoropropane (R-245eb) produced in step (b) may be transferred into the dehydrofluorination reactor for step (c) without any further purification.

In the process of the present invention, typically the R-245eb used in step (c) is obtained using the process of step (b) without any further purification. However, the skilled person would appreciate that the product stream comprising 1,2,3,3,3-pentafluoropropane (R-245eb) produced in step (b) can optionally be purified before passing to the reactor for step (c). For example, the product stream from step (b) may be passed through a distillation column or other purification means, as described above, before commencing step (c).

Step (c) may be conducted in the vapour or the liquid phase. It is preferred that step (c) in the process of the invention is carried out in liquid phase.

Step (c) may be induced thermally, may be base-mediated and/or may be catalysed by any suitable catalyst. Suitable catalysts include metal and carbon based catalysts such as those comprising activated carbon, alkali metals, main group (e.g. alumina-based or indium catalysts) and transition metals, such as chromia-based catalysts, nickel-based catalysts (e.g. nickel mesh) or supported zirconium catalyst (e.g. zirconium supported on alumina).

Step (c) may be carried out in the presence of a catalyst, such as a metal oxide catalyst. Advantageously, the catalyst may comprise chromia. The chromia may be supported or unsupported. The chromia catalyst may also contain promoters such as zinc.

If step (c) is conducted in the presence of a catalyst, zinc/chromia catalysts are preferred for step (c). By the term “zinc/chromia catalyst” we mean any catalyst comprising chromium or a compound of chromium and zinc or a compound of zinc.

Typically, the chromium or compound of chromium present in the zinc/chromia catalysts of the invention is an oxide, oxyfluoride or fluoride of chromium such as chromium oxide.

The total amount of the zinc or a compound of zinc present in the zinc/chromia catalysts of the invention is typically from about 0.01% to about 25%, preferably 0.1% to about 25%, conveniently 0.01% to 6% zinc, and in some embodiments preferably 0.5% by weight to about 25 % by weight of the catalyst, preferably from about 1 to 10 % by weight of the catalyst, more preferably from about 2 to 8 % by weight of the catalyst, for example about 4 to 6 % by weight of the catalyst.

The catalyst may alternatively comprise 0.01% to 1%, more preferably 0.05% to 0.5% zinc.

The preferred amount depends upon a number of factors such as the nature of the chromium or a compound of chromium and/or zinc or a compound of zinc and/or the way in which the catalyst is made. These factors are described in more detail hereinafter.

It is to be understood that the amount of zinc or a compound of zinc quoted herein refers to the amount of elemental zinc, whether present as elemental zinc or as a compound of zinc.

The zinc/chromia catalysts that may be used in step (c) of the invention may include an additional metal or compound thereof. Typically, the additional metal is a divalent ortrivalent metal, preferably selected from nickel, magnesium, aluminium and mixtures thereof. Typically, the additional metal is present in an amount of from 0.01 % by weight to about 25 % by weight of the catalyst, preferably from about 0.01 to 10 % by weight of the catalyst. Other embodiments may comprise at least about 0.5 % by weight or at least about 1 % weight of additional metal.

The zinc/chromia catalysts that may be used in step (c) of the present invention may be amorphous. By this we mean that the catalyst does not demonstrate substantial crystalline characteristics when analysed by, for example, X-ray diffraction.

Alternatively, the catalysts may be partially crystalline. By this we mean that from 0.1 to 50 % by weight of the catalyst is in the form of one or more crystalline compounds of chromium and/or one or more crystalline compounds of zinc. If a partially crystalline catalyst is used, it preferably contains from 0.2 to 25 % by weight, more preferably from 0.3 to 10 % by weight, still more preferably from 0.4 to 5 % by weight of the catalyst in the form of one or more crystalline compounds of chromium and/or one or more crystalline compounds of zinc.

During use in a reaction the degree of crystallinity may change. Thus it is possible that a catalyst of the invention that has a degree of crystallinity as defined above before use in a fluorination/dehydrohalogenation reaction and will have a degree of crystallinity outside these ranges during or after use in a fluorination/dehydrohalogenation reaction.

Step (c) is preferably base-mediated. This base-mediated dehydrohalogenation process of step (c) comprises contacting a product stream comprising 1,2,3,3,3-pentafluoropropane (R-245eb) produced in step (b) with base such as a metal hydroxide, metal oxide or metal amide (preferably a basic metal hydroxide or amide, e.g. an alkali or alkaline earth metal hydroxide, oxide or amide).

Unless otherwise stated, as used herein, the term “alkali metal hydroxide”, means a compound or mixture of compounds selected from lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide and caesium hydroxide. Similarly, by the term “alkali metal amide”, we refer to a compound or mixture of compounds selected from lithium amide, sodium amide, potassium amide, rubidium amide and caesium amide.

Unless otherwise stated, as used herein, the term “alkaline earth metal hydroxide”, means a compound or mixture of compounds selected from beryllium hydroxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide and barium hydroxide. By the term “alkaline earth metal oxide”, we refer to a compound or mixture of compounds selected from beryllium oxide, magnesium oxide, calcium oxide, strontium oxide and barium oxide.

Similarly, by the term “alkaline earth metal amide”, we refer to a compound or mixture of compounds selected from beryllium amide, magnesium amide, calcium amide, strontium amide and barium amide.

Typically, the base-mediated dehydrohalogenation process of step (c) is conducted at a temperature of from about -50 to about 300 °C. Preferably, the process is conducted at a temperature of from about 20 to about 250 °C, for example from about 50 to about 200 °C. The base-mediated dehydrohalogenation may be conducted at a pressure of from about 0 to about 30 bara.

The reaction time for the base-mediated dehydrohalogenation process of step (c) may vary over a wide range. However, the reaction time will typically be in the region of from about 0.01 to about 100 hours, such as from about 0.1 to about 50 hours, e.g. from about 1 to about 20 hours.

The skilled person will appreciate that the preferred conditions (e.g. temperature, pressure and reaction time) for conducting the base-mediated dehydrohalogenation may vary depending on a number of factors such as the base being employed and/or presence of a catalyst.

The base-mediated dehydrohalogenation process of step (c) may be carried out in the presence or absence of a solvent. If no solvent is used, the 245eb may be passed into or over molten base or hot base, for example in a tubular reactor. If a solvent is used, in some embodiments a preferred solvent is water, although many other solvents may be used. In some embodiments solvents such as alcohols (e.g. propan-1-ol), diols (e.g. ethylene glycol) and polyols such as polyethylene glycol (e.g. PEG200 or PEG300) may be preferred. These solvents can be used alone or in combination. In further embodiments, solvents from the class known as polar aprotic solvents may be preferred. Examples of such polar aprotic solvents include diglyme, sulfolane, dimethylformamide (DMF), dioxane, acetonitrile, hexamethylphosphoramide (HMPA), dimethyl sulphoxide (DMSO) and N-methyl pyrrolidone (NMP). The boiling point of the solvent is preferably such that it does not generate excessive pressure under reaction conditions.

In a preferred process of the invention, step (c) is conducted in the presence of a polar aprotic solvent comprising NMP or NMP alone. A preferred base is an alkali metal hydroxide selected from the group consisting of lithium hydroxide, sodium hydroxide and potassium hydroxide, more preferably sodium hydroxide and potassium hydroxide and most preferably potassium hydroxide. A preferred base is an alkaline earth metal hydroxide selected from the group consisting of magnesium hydroxide and calcium hydroxide, more preferably calcium hydroxide.

Another preferred base is an alkaline earth metal oxide, selected from the group consisting of magnesium oxide and calcium oxide, more preferably calcium oxide. A base that is particularly suitable for use in step (c) of the process of the invention is Ca(OH)2 or CaO, or a mixture thereof.

The base is typically present in an amount of from about 1 to about 50 weight % based on the total weight of the components present in step (c). Preferably, the base is present in an amount of from about 5 to about 30 weight %.

The molar ratio of base to R-245eb is typically from 1:20 to 50:1, preferably from 1:5 to 20:1, for example from 1:2 to 10:1.

As mentioned above, the base-mediated dehydrohalogenation may employ water as the solvent. Thus, the dehydrohalogenation reaction may use an aqueous solution of at least one base, such as an alkali (or alkaline earth) metal hydroxide, without the need for a co-solvent or diluent. However, a co-solvent or diluent can be used for example to modify the system viscosity, to act as a preferred phase for reaction byproducts, or to increase thermal mass. Useful co-solvents or diluents include those that are not reactive with or negatively impact the equilibrium or kinetics of the process and include alcohols such as methanol and ethanol; diols such as ethylene glycol; ethers such as diethyl ether, dibutyl ether; esters such as methyl acetate, ethyl acetate and the like; linear, branched and cyclic alkanes such as cyclohexane, methylcyclohexane; fluorinated diluents such as hexafluoroisopropanol, perfluorotetrahydrofuran and perfluorodecalin.

The base-mediated dehydrohalogenation of step (c) may be conducted in the presence of a catalyst. If step (c) is conducted in the presence of a catalyst, the catalyst is preferably a phase transfer catalyst which facilitates the transfer of ionic compounds into an organic phase from, for example, a water phase. If water is used as a solvent, an aqueous or inorganic phase is present as a consequence of the alkali metal hydroxide and an organic phase is present as a result of the fluorocarbon. The phase transfer catalyst facilitates the reaction of these dissimilar components. While various phase transfer catalysts may function in different ways, their mechanism of action is not determinative of their utility in the present invention provided that they facilitate the dehydrohalogenation reaction. The phase transfer catalyst may be ionic or neutral and is typically selected from the group consisting of crown ethers, onium salts, cryptands and polyalkylene glycols and derivatives thereof (e.g. fluorinated derivatives thereof).

An effective amount of the phase transfer catalyst should be used in order to effect the desired reaction, influence selectivity to the desired products or enhance the yield; such an amount can be determined by limited experimentation once the reactants, process conditions and phase transfer catalyst are selected. Typically, the amount of catalyst used relative to the amount of R-245eb present is from 0.001 to 20 mol %, such as from 0.01 to 10 mol %, e.g. from 0.05 to 5 mol %.

In the process of the invention, step (c) is preferably conducted in the liquid phase in the presence of CaO, Ca(OH)2 as the base and a polar aprotic solvent comprising NMP or NMP alone.

Typically in this preferred step (c), the molar ratio of base to R-245eb is from about 1:20 to about 50:1, preferably from about 1:5 to about 20:1, such as from about 1:2 to about 10:1.

Typically in this preferred step (c), the temperature is from about 20 to about 250 °C, such as from about 50 to 200 °C.

Typically in this preferred step (c), the pressure is from about 0 (0.1 MPa) to about 30 bara (3 MPa).

For example, step (c) may comprise dehydrofluorinating R-245eb in the presence of CaO, Ca(OH)2, or mixtures thereof, in the presence of a polar aprotic solvent comprising NMP or NMP alone; wherein the molar ratio of base to R-245eb is from about 1:5 to about 20:1, such as from about 1:2 to about 10:1, the temperature is from about 50 to about 200 °C, and at a pressure of from about 0 (0.1 MPa) to about 30 bara (3 MPa).

In the process of the invention, the product stream produced in step (c) comprises R-1234yf. The R-1234yf produced in step (c) may optionally be purified before being stored or used.

In the process of the invention, the product stream produced in step (c) comprising R-1234yf, may comprise unreacted R-245eb. Unreacted R-245eb may be removed from the product stream comprising R-1234yf and optionally recycled back into step (c).

An example of a preferred process of the invention is as follows: A liquid phase feed stream comprising about 90% or more R-1243zf is fed into a reactor, the feed stream is then continuously contacted with a fluorine source comprising C0F3 in the vapour phase to produce a product stream comprising R245eb; the R-245eb product stream is then dehydrofluoinated in the liquid phase in the presence of CaO, Ca(OH)2 or mixtures thereof and a polar aprotic solvent comprising NMP or NMP alone. Typically, this process the temperature of step (b) is from about 200 to about 250°C and/or the pressure is from about 0 (0.1 MPa) to about 10 bara (1 MPa) and/or the molar ratio of CoF3:R-1243zf is from about 2:1 to about 20:1; and the temperature of step (c) is from about 50 to about 200°C, and/or the pressure is from about 0 (0.1 MPa) to about 30 bara (3 MPa) and/or the molar ratio of base:R-245eb is from about 1:5 to about 20:1, such as from about 1:2 to about 10:1.

Sources of R-1243zf R-1234zf used in the process of the invention can be obtained from any suitable source. For example, R-1243zf used in step (a) of the invention may be prepared from the fluorination of 1,1,1,3-tetrachloropropane (R-250fb) with HF.

The fluorination of R-250fb to R-1243zf may be carried out batch-wise or (semi-) continuously. The reaction can be carried out in the liquid or vapour phases. Typically, the process is carried out in the vapour phase.

The process for the preparation of R-1243zf may be carried out at atmospheric, sub-or super atmospheric pressure, typically at from 0 to about 30 bara, preferably from about 1 to about 20 bara, such as about 15 bara.

Typically, the process for the preparation of R-1243zf is carried out a temperature of from about 100 °C to about 500 °C (e.g. from about 150 °C to about 500 °C or about 100 to about 450 °C). Preferably, the process is conducted at a temperature of from about 150 °C to about 450 °C, such as from about 150 °C to about 400 °C, e.g. from about 175 °C to about 300 °C. Lower temperatures may also be used in the conversion of 250fb to 1243zf, such as from about 150 °C to about 350 °C, e.g. from about 150 °C to about 300 °C or from about 150 °C to about 250 °C.

The process for the preparation of R-1243zf typically employs a molar ratio of HF:organics of from about 1:1 to about 100:1, such as from about 3:1 to about 50:1, e.g. from about 4:1 to about 30:1 or about 5:1 or 6:1 to about 20:1 or 30:1.

Advantageously, the process for the preparation of R-1243zf is carried out in the presence of a catalyst, such as metal and carbon based catalysts such as those comprising activated carbon, alkali metals, main group (e.g. alumina-based or indium catalysts) and transition metals, such as chromia-based catalysts, nickel-based catalysts (e.g. nickel mesh), supported zirconium catalyst (e.g. zirconium supported on alumina), or pentavalent antimony compounds such as chloride, fluoride and mixed chlorofluorides(e.g. SbCI5 SbF5, SbCUF, SbCI3F2, SbCI2F3, SbCIF4), trivalent antimony compounds such as antimony trichloride and trifluoride and chlorofluorides or mixtures of tri- and pentavalent antimony compounds, tantalumn pentachloride and perntafluoride and niobium pentafluoride and pentafluoride catalysts.

Preferably, R-1243zf is prepared using a catalyst comprising chromia for example zinc/chromia catalyst.

The reaction time for the process for the preparation of R-1243zf generally is from about 1 second to about 100 hours, preferably from about 10 seconds to about 50 hours, such as from about 1 minute to about 10 or 20 hours. In a continuous process, typical contact times of the catalyst with the reagents are from about 1 to about 1000 seconds, such from about 1 to about 500 seconds or about 1 to about 300 seconds or about 1 to about 50, 100 or 200 seconds.

In an embodiment, the reaction products from the process for the preparation of R-1243zf would pass downstream into a separation train to recover and recycle any unreacted HF, R-250fb and any partially-fluorinated intermediates (such as R-251fb, R-252fb and R-253fb). Separations are preferably carried out by distillation and/or phase separation.

Advantageously, the separation train includes HCI removal apparatus, allowing for the production of anhydrous or aqueous HCI. Preferably, the HCI removal occurs prior to the removal or recovery of HF, which precedes the separation of R-1243zf from the remaining organic components.

In an alternative embodiment, R-250fb is fluorinated in the liquid phase to produce R-253fb using a liquid phase catalyst (such as SbCI5, SbCI3, mixtures of SbCI5 and SbCI3, SnCLt or TiCU).

The dehydrochlorination of R-253fb to R-1243zf may be carried out batch-wise or (semi-) continuously. The reaction can be carried out in the liquid or vapour phases. Typically, the process is carried out in the vapour phase.

The process for the preparation of R-1243zf from 253fb may be carried out at atmospheric, sub- or super- atmospheric pressure, typically at from 0 to about 30 bara, preferably from about 1 to about 20 bara, such as about 15 bara.

Typically, the process for the preparation of R-1243zf from 253fb is carried out a temperature of from about 100 °C to about 500 °C (e.g. from about 150 °C to about 500 °C or about 100 to about 450 °C). Preferably, the process is conducted at a temperature of from about 150 °C to about 450 °C, such as from about 150 °C to about 400 °C, e.g. from about 175 °C to about 300 °C. Lower temperatures may also be used in the conversion of 253fb to 1243zf, such as from about 150 °C to about 350 °C, e.g. from about 150 °C to about 300 °C or from about 150 °C to about 250 °C.

The process for the preparation of R-1243zf typically employs a molar ratio of HF:organics of from about 1:1 to about 100:1, such as from about 3:1 to about 50:1, e.g. from about 4:1 to about 30:1 or about 5:1 or 6:1 to about 20:1 or 30:1. Alternatively the process can be conducted without any co-fed HF.

Advantageously, the process for the preparation of R-1243zf is carried out in the presence of a catalyst, such as metal and carbon based catalysts such as those comprising activated carbon, alkali metals, main group (e.g. alumina-based or indium catalysts) and transition metals, such as chromia-based catalysts, nickel-based catalysts (e.g. nickel mesh), supported zirconium catalyst (e.g. zirconium supported on alumina).

Preferably, R-1243zf is prepared using a catalyst comprising chromia for example a zinc/chromia catalyst.

The reactor off-gases containing R-1243zf, can also contain under-reacted organics (such as R-250, R-251, R-252) unreacted 253, HF and HCI. Preferably, a separation train returns any under-reacted organics to the reactor and allows HCI to be produced as above. Any azeotropes formed between under reacted organic compounds and HF can be separated or recovered by any method known in the art, e.g. adsorption into sulphuric acid, azeotropic distillation, or scrubbing with water or a basic solution for example sodium or potassium hydroxide; then drying with sulphuric acid, molecular sieve, silica gel, calcium chloride or other drying method.

Advantageously, the R-1243zf produced can be purified as described above to provide a feed stream suitable for use in step (a).

Sources of R-250fb R-250fb, which may be used to produce R-1243zf can be obtained from any suitable source. For example, R-250fb may be prepared from carbon tetrachloride and ethylene. R-250fb may be prepared by the telomerising of ethylene and carbon tetrachloride (CCU).

The above process typically comprises contacting ethylene with CCU in the liquid and/or vapour phase in presence of a catalyst under conditions suitable to produce 250fb.

Any suitable catalyst may be used, such as a catalyst which comprises iron, copper and/or peroxide. Preferably, the catalyst comprises iron (e.g. iron powder)

Catalysts which comprise peroxide include benzoyl peroxide and di-f-butyl peroxide. Catalysts which comprise iron include iron powder and ferric/ferrous halides (e.g. chlorides). Catalysts which comprise copper include salts of copper such as copper halides (e.g. CuCI2), copper sulphate and/or copper cyanide.

Optionally, the catalysts which comprise copper and iron are used with a co-catalyst or ligand. Suitable co-catalysts include triethylorthoformate (HC(OEt)3), nitrogen/phosphorus-containing ligands, and/or ammonium/phosphonium salts. Preferred nitrogen-containing ligands include amines (e.g. primary and secondary amines), nitriles and amides. Preferred phosphorus containing ligands include phosphates, phosphites (e.g. triethylphosphite) and phosphines. Preferred ammonium and phosphonium salts include ammonium and phosphonium halides (e.g. chlorides).

The catalyst for the preparation of R-250fb typically is used in an amount from about 0.01 to about 50 mol % (e.g. about 0.1 to about 10 %), based on the molar sum of CCI4 and ethylene present. An excess of the carbon tetrachloride over ethylene generally is used. For example, the molar ratio of CCI4:C2H4 typically is from about 1:1 to about 50:1, such as from about 1.1:1 to about 20:1, for example from about 1.2:1 to about 10:1 or about 1.5:1 to about 5:1.

The reaction temperature for the preparation of R-250fb typically is within the range of from about 20 to about 300 °C, preferably from about 30 to about 250 °C, such as from about 40 to about 200 °C, e.g. from about 50 to about 150 °C.

The reaction pressure for the preparation of R-250fb typically is within the range of from 0 to about 40 bara, preferably from about 1 to about 30 bara.

The reaction time for the preparation of R-250fb from carbon tetrachloride and ethylene generally is from about 1 second to about 100 hours, preferably from about 10 seconds to about 50 hours, such as from about 1 minute to about 10 hours.

The preparation of R-250fb from carbon tetrachloride and ethylene can be carried out in any suitable apparatus, such as a static mixer, a tubular reactor, a stirred tank reactor or a stirred vapour-liquid disengagement vessel. The preparation of R-250fb may be carried out batch-wise or continuously. Preferably, the 1,1,1,3-tetrachloropropane formed in the process is purified and/or isolated before the subsequent step. The purification may be achieved by separation of the R-250fb from any other products or reagents by one or more distillation, condensation or phase separation steps and/or by scrubbing with water or aqueous base.

In an embodiment, the conversion of carbon tetrachloride and ethylene to R-1234yf is carried out as an integrated process involving all four reaction stages described above, optionally with any of the features or combination of features described herein.

In view of the above, the present invention results in a more economically efficient means for producing 1234yf and, in particular, a process in which unused starting materials and/or intermediate reaction products are recycled into the process and/or commercially value by-products are recovered so that they may be sold or used in another economically valuable way

Preferences and options for a given aspect or parameter of the invention should, unless the context indicates otherwise, be regarded as having been disclosed in combination with any and all preferences and options for all other aspects, features and parameters of the invention.

The invention will now be illustrated, but not limited by, the following examples. The invention is defined by the claims following the Examples.

Examples 1 to 4 - purification of R-1243zf (Step (a))

Example 1 A range of adsorbents were screened for their efficacy in removing the undesirable compounds R-1225zc and trifluoromethylacetylene (TFMA) from R-1243zf. A sample of R-1243zf doped with 400 ppm wt/wt TFMA and 765 ppm wt/wt R-1225zc was prepared. 50 g of this R-1243zf was then treated with 5 g of adsorbent in a sealed pressure tube at ambient temperature. Samples were taken for analysis by capillary GC after 20 minutes and in some cases after 16 hours of contacting of the R-1243zf with the adsorbent. The following adsorbents were screened:

Eta-Alumina ex-BASF - an acidic form of activated alumina Chemviron Activated Carbon 207EA

10 % Potassium hydroxide on Chemviron Activated Carbon 207EA

10 % Potassium carbonate on Chemviron Activated Carbon 207EA

10 % Potassium Iodide on Chemviron Activated Carbon 207EA 10 % Potassium Hydroxide and 10 % Potassium Iodide on Chemviron Activated

Carbon 207EA

Chemviron ST1x - an activated carbon comprising 207EA impregnated with various species including base(s)

The doped samples of 207EA were prepared by aqueous impregnation. The dopant(s) (1g) was/were dissolved in 100 g water and 10 g of 207EA added. After mixing the water was removed in vacuo to leave a free running solid.

Prior to use all adsorbents were pre-activated at 250-300°C in a nitrogen purged oven for a minimum of 16 hours.

The results are presented in the Table below:

All of the adsorbents screened showed utility in removal of either or both of R-1225zc and TFMA from R-1243zf. However, the most effective adsorbents were those doped with base, either potassium hydroxide or carbonate, including the ST1x carbon.

Example 2 A sample of commercially available R-1243zf (this may be obtained from Apollo Scientific, for example) was obtained and analysed by capillary GC-MS. This R-1243zf was found to contain, amongst other, the following impurities:

R-1225zc, R-31 and R-133a are toxic compounds and it was considered desirable to remove them from the R-1243zf prior to use. Even where boiling point differences make the separation of some of these components from R-1243zf by distillation practicable, the low levels mean that such a process would be very energy intensive and inefficient. Therefore, an alternative means of removing these impurities, particularly the R-1225zc, R-31 and R-133a, from 1243zf was sought. To that end a series of experiments were performed in which the efficacy of a range of adsorbent materials for the removal of the three target compounds R-1225zc, R-31 and R-133a from R-1243zf was tested.

The range of adsorbents screened comprised:

Eta-Alumina ex-BASF - an acidic form of activated alumina Chemviron Activated Carbon 207c - derived from coconut shells Chemviron Activated Carbon 209M Chemviron Activated Carbon 207EA

Chemviron Activated Carbon 209m 13X Molecular sieve - An aluminosilicate or Zeolite AW500 - An acid stable aluminosilicate or Zeolite Alumina AL0104 - ex BASF- a basic form of alumina

The carbon based adsorbents were pre-activated at 200 °C in flowing nitrogen for 16 hours prior to use and the inorganic adsorbents activated at 300 °C in flowing nitrogen again for 16 hours. The efficacy of each of the adsorbents was then assessed by treating c.a. 100 g of R-1243zf with 2-4 g of each adsorbent in a re-circulatory system whereby the R-1243zf was continuously pumped through the adsorbent bed for 16 hours at ambient temperature. After the treatment period a small sample of the R-1243zf was taken for analysis by capillary GC-MS. The analysis of the treated R-1243zf is compared with the untreated R-1243zf (see previous table for the amounts of impurities) in the following table.

All of the adsorbents tested were effective in reducing the level of at least one contaminant. However, for the three undesirable compounds R-1225zc, R-31 and R-133a, the base impregnated activated carbon ST1x and molecular sieve AW500 were particularly effective.

Example 3 R-1243zf has previously found use as a monomer and as if it were to polymerise or react when contacted with reactive surfaces that may be present in absorbents it would give undesirable results of for example fouling or generation of additional impurities. This might limit utility of this invention. We sought therefore to investigate whether any reaction processes accompanied the adsorptive purification of R-1243zf by contacting with absorbents such as ST1x carbon and AW500.

Samples of ST1x carbon and AW500 were pre-treated at 200-300 °C under flowing nitrogen for 16 hours prior to use. 20 g samples were then taken and accurately weighed and added to a clean, dry 300ml Hastelloy autoclave either individually or together. The autoclave was sealed, purged with nitrogen and pressure tested. The autoclave was then charged with R-1243zf. The autoclave and its contents were then heated to either 80 or 120 °C for a period of 24 hours. At the end of each experiment, the R-1243zf was recovered for analysis. The adsorbent was also recovered and following drying at 105 °C was re-weighed. The results are presented in the Tables below.

At the end of each experiment the recovered R-1243zf was visually unchanged. There were no residues left behind upon evaporation of the R-1243zf following each test. The detailed analysis revealed that the adsorbents ST1x and AW500 either alone or particularly in combination were still effective under the conditions of these tests. Furthermore, there was no evidence for any undesirable side reactions including polymerisation or decomposition. Therefore these adsorbents alone and in combination were shown to be suitable for the purification of e.g. R-1243zf at commercial scale.

Example 4

An experiment was operated at commercial scale to remove trace impurities from a 180 kg batch of R-1243zf. An 85-litre adsorption bed was charged with 19.5 kg ST1x carbon and 19.5 kg AW500 molecular sieve. The Rig was sealed and evacuated to remove air. The feed vessels (total volume 270-litres) were charged with c.a. 180 kg of commercially available R-1243zf. This material contained similar impurities at similar levels to those specified in Example 2.

The crude R-1243zf was then pumped from the feed vessels up through the adsorption bed and back into the feed vessels at ambient temperature. The R-1243zf charged was recirculated in this manner through the adsorption bed for a period of 5 hours. After which period the R-1243zf was pumped to a receiver vessel where it could be recovered for storage and analysis. After analysis each 180 kg charge was split into 60 kg batches. It was found that the adsorbent charge was capable of processing at least 360 kg of R-1243zf. The analysis of three 60 kg batches of R-1243zf processed in this manner are presented in the Table below:

Example 5 - Dehvdrofluorination of R-245eb to R-1234vf

Base and solvent (as shown in the Table below) were charged to the reaction vessel. The reaction vessel was then sealed, pressure tested and evacuated. A pre-weighed amount of R-245eb was then transferred to the reactor. The reactor and its contents were then weighed before heating from room temperature to a temperature of 150°C over 45 minutes with stirring. This temperature was maintained with stirring at 1500 rpm for 6 hours. After this period the reactor and its contents were cooled to 10°C over 30 minutes and the rate of stirring reduced to 200 rpm.

The next day the reactor and its contents were re-weighed and then the reactor heated to 50°C ready for product recovery. The products and any unreacted starting materials were recovered by distillation into a pre-weighed and evacuated chilled (-78°C) sample bomb. The weight of the recovered products was determined before they were analysed by GC-MS. The GC-MS was calibrated using feed and product samples where available. Unknowns were quantified using average relative response factors.

The results are presented in the table below. 245eb 1234yf

NMP = N-methyl pyrrolidone.

It is envisaged that the integrated process of the present invention may be conducted using the following procedure. The skilled person would appreciate that the following procedure is one possible exemplary process, and that the process described below may be modified using such techniques known in the art.

Example 6 - Fluorination of 1243zf with Cobalt (III) Fluoride

General procedure

Cobalt (III) fluoride would be loaded and sealed inside a 0.5” x 30 cm Inconel reactor in a nitrogen purged glove box. The reactor tube would then be inserted inside a heating black, and attached to a feed system capable of supplying dry nitrogen and/or 1243zf to the reactor. First the reactor tube would be purged with nitrogen at 1 bara pressure, and then heated to e.g. 250°C. When at the desired temperature 1243zf would be introduced into the nitrogen flow to the reactor, where it would react with the Cobalt (III) fluoride to yield primarily 245eb, plus other species in varying amounts depending on the temperature, feed rates but primarily the 1243zf feed quality.

Example

If a 1243zf feed of 99.8 % purity, prepared using the methods taught in this patent, was used as the reactor feed, the co-production of impurities such as 1225ye, 227cb and 227ea would be dramatically reduced so preventing unnecessary consumption of reactants and energy in this and subsequent steps of the integrated process.

Comparative Example

If a 1243zf feed containing olefinic impurities, such as TFMA, 1225zc and the like, was to be used, these impurities would react with cobalt (II) fluoride to form: TFMA-> 1225ye->227ca 1225zc->227ea

Thus, it can be seen how the use of impure 1243zf would lead to the production of unwanted by-products and cause unnecessary consumption of reactants and energy in this and subsequent steps of the integrated process.

Claims

1. An integrated process for preparing 2,3,3,3-tetrafluoropropene (R-1234yf), the process comprising: (a) providing a 3,3,3-trifluoropropene (R-1243zf) feed stream comprising greater than about 90% by weight R-1243zf; (b) contacting the feed stream comprising R-1243zf with a fluorine source comprising cobalt (III) fluoride (CoF3) to produce a product stream comprising 1,2,3,3,3-pentafluoropropane (R-245eb); and (c) dehydrofluorinating R-245eb produced in step (b) to produce R-1234yf.

2. A process according to claim 1, wherein the R-1243zf feed stream comprises about 95% or more by weight R-1243zf, or about 99% or more by weight R-1243zf.

3. A process according to claim 2, wherein the R-1243zf feed stream comprises from about 99.5% or more by weight or about 99.8% or more by weight R-1243zf.

4. A process according to any one of claims 1 to 3, wherein the R-1243zf feed stream in step (a) is provided by contacting a composition comprising R-1243zf and one or more undesired (hydro)halocarbon compounds with an aluminium-containing adsorbent, activated carbon, or a mixture thereof.

5. A process according to claim 4, wherein R-1243zf and one or more undesired (hydro)halocarbon compounds is contacted with an aluminium-containing adsorbent, activated carbon, or a mixture thereof in the liquid phase.

6. A process according to claims 4 or 5, wherein the contacting is carried out continuously.

7. A process according to any of the preceding claims, wherein the fluorine source in step (b) also comprises cobalt (II) fluoride.

8. A process according to any of the preceding claims, wherein step (b) is conducted in the vapour phase.

9. A process according to any of the preceding claims, wherein step (b) is carried out using a stoichiometric excess of cobalt (III) fluoride.

10. A process according to claim 9, wherein the molar ratio of cobalt (III) fluoride:R-1243zf is from about 2:1 to about 20:1.

11. A process according to any one of the preceding claims, wherein C0F2 produced in step (b) is regenerated to C0F3.

12. A process according to any one of the preceding claims, wherein step (b) is conducted at a temperature of from about 100 to about 400 °C.

13. A process according to claim 12, wherein step (b) is conducted at a temperature of from about 150 to 300 °C or from about 200 to 250 °C.

14. A process according to any one of the preceding claims, wherein step (b) is carried out continuously.

15. A process according to any one of the preceding claims, wherein the product stream comprising 1,2,3,3,3-pentafluoropropane (R-245eb) produced in step (b) is purified before being fed into the reactor for step (c).

16. A process according to any one of claims 1 to 14, wherein the product stream comprising 1,2,3,3,3-pentafluoropropane (R-245eb) produced in step (b) is fed into the reactor for step (c) without purification.

17. A process according to any of the preceding claims, wherein step (c) is carried out in the liquid phase.

18. A process according to any of the preceding claims, wherein step (c) is carried out in the presence of a base.

19. A process according to claim 17, wherein the base comprises CaO or Ca(OH)2.

20. A process according to claims 17 or 18, wherein the molar ratio of base to R-245eb is from about 1:20 to about 50:1.

21. A process according to claim 20, wherein the molar ratio of base to R-245eb is from about 1:5 to about 20:1 or from about 1:2 to about 10:1.

22. A process according to any of the preceding claims, wherein step (c) is conducted in the presence of a polar aprotic solvent.

23. A process according to claim 22, wherein the polar aprotic solvent comprises NMP or is NMP.

24. A process according to any one of the preceding claims, wherein steps (b) and (c) are conducted continuously.

25. A process according to any of the preceding claims, which further comprises contacting 1,1,1,3-tetrachloropropane (R-250fb) with HF to produce R-1243zf.

26. A process according to claim 25, wherein the reaction to produce R-1243zf is carried out in the gas phase.

27. A process according to claim 25 or 26, wherein the reaction to produce R-1243zf is carried out in the presence of a catalyst.

28. A process according to any of claims 25 to 27, wherein at least part of any HCI produced as a by-product is separated and optionally purified.

29. A process according to any of claims 25 to 28, which further comprises telomerising ethylene and carbon tetrachloride (CCU) to produce R-250fb.

30. A process according to claim 29 comprising contacting ethylene with CCU in the liquid and/or vapour phase in the presence of a catalyst in an amount of from about 0.01 to about 50 mol %.

31. A process according to claim 29 or 30, wherein the catalyst comprises iron, copper and/or peroxide.

32. A process according to claim 31, wherein the catalyst comprises iron.