PRODUCTION OF 1 ,1 ,1 -TRIFLUORO-2,3-DICHLOROPROPANE (243BD) BY CATALYTIC CHLORI NATION OF 3,3,3-TRIFLUOROPROPENE (1243ZF)

The invention relates to a process for preparing (hydro)halocarbons, for example 1 ,1 , 1- trifluoro-2,3-dichloropropane. In particular, the invention relates to a process for preparing 1 ,1 , 1-trifluoro-2,3-dichloropropane from carbon tetrachloride and ethylene including the step of chlorinating 3,3,3-trifluoropropene and also the preparation of 2,3,3,3- tetrafluoropropene. (Hydro)halocarbons are typically used as refrigerant or propellant materials and as blowing agents. Over the last 20 years, the variety of (hydro)halocarbons used in these applications has changed as it has been discovered that some such materials (such as difluorodichloromethane, R12) deplete the earth's ozone layer, while others (such as 1 ,1 , 1 ,2-tetrafluoroethane, R134a) have an unacceptably high action as a greenhouse gas.

1 ,1 , 1-trifluoro-2,3-dichloropropane (243db) is, inter alia, an important intermediate in the production of (hydro)halocarbons such as fluoropropenes, which have been identified as potential replacements for saturated fluorocarbons and other hydrohalocarbons in many applications. In particular, 1 ,1 , 1-trifluoro-2,3-dichloropropane is useful as an intermediate in the production of 2,3,3,3-tetrafluoropropene (1234yf).

There is therefore a need for a reliable and efficient process for the production of 1 , 1 , 1 - trifluoro-2,3-dichloropropane. In a first aspect, the invention provides a process for preparing 1 ,1 , 1-trifluoro-2,3- dichloropropane (243db), which process comprises contacting 3,3,3-trifluoropropene (1243zf) with a molar excess of chlorine in the presence of a catalyst, wherein the catalyst comprises a transition metal and/or one or more compounds thereof supported on alumina. In a preferred embodiment, the transition metal may comprise copper, iron, nickel and/or zinc. In some embodiments, the compounds of the transition metal may comprise halides, oxides and/or nitrates. For example, the catalyst may comprise an iron oxide (e.g. Fe20z), an iron halide or an iron nitrate (e.g. Fe(NOs)3). In other embodiments, the transition metal may comprise a combination of nickel and zinc, or compounds thereof. In another aspect, the invention provides a process for preparing 1 , 1 , 1-trifluoro-2,3- dichloropropane (243db), which process comprises contacting 3,3,3-trifluoropropene (1243zf) with chlorine in the presence of a catalyst, wherein the catalyst comprises a transition metal and/or one or more compounds thereof, wherein the transition metal comprises copper and/or nickel. It is preferred that the transition metal or compound(s) thereof are supported on alumina.

In some embodiments of any aspect of the invention, the catalyst may comprise a copper, copper oxide or a copper halide (e.g. a copper chloride such as CuC ) supported on alumina. Where the copper, copper oxide or copper halide is supported on alumina or any other suitable support, it is preferably present in a proportion of up to 50wt%, for example about 35wt% to about 50wt% or about 30wt% to about 45wt%. In other embodiments, the copper, copper oxide or copper halide is present in a proportion of up to about 20wt%, for example about 1wt% to about 15wt% of the catalyst/support combination. It is preferred, for example, that elemental copper is provided in a quantity of about 12wt % or less, for example about 10wt% or less of the total catalyst/support combination. Where the catalyst is a supported copper halide, it is preferred that the copper halide is provided in a proportion from about 1wt% to about 15wt% of the catalyst/support combination. In other embodiments, the catalyst may comprise a combination of a transition metal oxide and one or more further metal oxides, for example a combination of CuO and ZnO and/or a combination of CuO, ZnO and alumina. Such a combination may be supported on a catalyst support such as a further metal oxide, for example alumina. In some preferred embodiments, such catalysts comprise about 35wt% to about 75wt% CuO, about 25wt% to about 35wt% ZnO and about 5wt% to about 40wt% alumina. In other embodiments, it is preferred that such catalysts comprise about 35wt% to about 50wt% CuO, about 25wt% to about 35wt% ZnO And about 15wt% to about 40wt% alumina. In a further preferred embodiment, such catalysts comprise about 50wt% to about 75wt% CuO, about 25wt% to about 35wt% ZnO, about 5wt% to about 10wt% alumina and optionally about 1wt% to about 2.5wt% Cu(OH)(C0 ₃ ).

Where the transition metal comprises nickel or compounds thereof (for example NiO) it may be supported on alumina, preferably such that the nickel or compound thereof is provided in a proportion of about 5wt% to about 30wt%, for example from about 10wt% to about 25wt%. In another aspect of the invention, there is provided a process for preparing 1 , 1 , 1-trifluoro- 2,3-dichloropropane (243db), which process comprises contacting 3,3,3-trifluoropropene (1243zf) with chlorine in the presence of a catalyst, wherein the catalyst comprises a transition metal supported on alumina, wherein the transition metal compounds comprise an iron nitrate (e.g. Fe(NOs)3).

In some embodiment of any aspect of the invention, the or an alumina catalyst support may comprise amorphous alumina and/or characteristics of crystalline aluminas such as a and/or γ alumina. In further embodiments the or an alumina support may comprise or consist essentially of just crystalline phases of alumina, such as a and/or γ alumina, or may comprise or consist essentially of just amorphous alumina. For example, the or an alumina catalyst support may comprise at least 80% amorphous alumina, such as from about 80 to about 100%, or from about 85 to about 95% or the or an alumina catalyst support may comprise less than about 20% characteristics of crystalline alumina such as a and/or γ alumina, such as from about 1 to about 20%, or from about 5 to about 15%.

In a further aspect the invention provides a process for preparing 1 ,1 , 1-trifluoro-2,3- dichloropropane (243db), which process comprises contacting 3,3,3-trifluoropropene (1243zf) with chlorine in the presence of a catalyst, wherein the catalyst comprises a transition metal and/or one or more compounds thereof supported on alumina, wherein the alumina comprises at least amorphous alumina and/or crystalline characteristics of alumina such as a and/or γ alumina. In further embodiments the or an alumina support may comprise or consist essentially of just crystalline phases of alumina, such as a and/or Y alumina, or may comprise or consist essentially of just amorphous alumina. For example, the or an alumina catalyst support as used in the process of the invention may comprise at least 80% amorphous alumina, such as from about 80 to about 100%, or from about 85 to about 95% or the or an alumina catalyst support may comprise at less than about 20% characteristics of crystalline alumina such as a and/or γ alumina, such as from about 1 to about 20%, or from about 5 to about 15%.

In some embodiments of any aspect of the invention, the 1243zf may be contacted with a molar excess of chlorine.

In some embodiments of any aspect of the invention, the 1243zf may be contacted with chlorine in the presence of HF where a molar 1243zf:HF ratio of greater than 2:1 , e.g. greater than 10: 1 is used. In preferred embodiments, the chlorination of 1243zf is performed in a substantially HF free atmosphere.

In preferred embodiments of all aspects of the invention, the chlorination of 1243zf yields 243db in a selectivity of at least 25%, e.g. at least 30%, 40%, 50%, 55%, 60%, 70%, 80% or 90% by weight.

In some embodiments of any aspect of the invention, the catalyst may comprise from about 0.2% by weight to about 75% by weight of the transition metal or compounds thereof. For example, the catalyst may comprise from about 0.5% by weight to about 5% (e.g. 1 % to 3%) by weight iron, iron oxide, iron halide or iron nitrate.

In some embodiments of any aspect of the invention, the transition metal or compound(s) thereof comprise an iron halide (e.g. FeCb) and/or iron nitrate (e.g. Fe(N03)39H20).

In some embodiments of any aspect of the invention, the or a transition metal or compound(s) thereof (e.g. copper or copper oxide) is or has been pre-treated with a halogen (e.g. chlorine, e.g. in the form of C or HCI). The process of the invention provides a surprisingly clean and efficient means for preparing 1 , 1 ,1-trifluoro-2,3-dichloropropane from 3,3, 3-trifluoropropene. For example, by using a catalyst comprising alumina and/or an oxide of a transition metal, lower temperatures can be used compared to without the use of such a catalyst. This is believed to result in less by-products and increase yield of 1 , 1 , 1-trifluoro-2,3-dichloropropane.

1 ,1 , 1-trifluoro-2,3-dichloropropane is also known as HCFC-243db or just 243db. Unless otherwise stated, 1 , 1 , 1-trifluoro-2,3-dichloropropane will be referred to hereinafter as 243db. 3, 3, 3-trifluoropropene is also known as HFO-1243zf or just 1243zf. Unless otherwise stated, 3, 3, 3-trifluoropropene will be referred to hereinafter as 1243zf.

A preferred group of catalysts are catalysts which comprise a transition metal and/or one or more compounds thereof supported on alumina. Preferred catalyst include, but are not limited to FeC , Fe(NOs)3 and copper based catalysts. The process of the invention may be conducted in the vapour and/or liquid phase, preferably in the vapour phase. The process may be carried in the liquid phase using the 243db product as the solvent. The heat of reaction in such a process may be removed by boiling off the 243db product/solvent.

Typically, the process of the invention as previously defined can be conducted at a temperature of from about -100 to about 400 °C, such as from about -80 to about 300 °C or -50 to about 250 °C, e.g. from about 0 to about 200 °C or about 50 to about 150 °C or about 80°C to about 110°C. In other preferred embodiments, the process may be conducted at a temperature between about 150°C and about 250°C, preferably about 200°C. The process may be conducted at a pressure of from about 0 to about 30 bara, such as from about 0.1 to about 20 bara or from about 0.5 to about 10 bara, e.g. from about 1 to about 5 bara. In other embodiments, the process may be conducted at a pressure between about 7 bara and about 10 bara, e.g. about 9 bara.

The process of the invention 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. Preferably, this or any other apparatus described herein is made from one or more materials that are resistant to corrosion by the species present in the reactor, e.g. Hastelloy® or Inconel®, stainless steels and glass. The process may be carried out batch- wise or continuously.

It has been surprisingly and unexpected found by the present inventors that the reaction vessels in which the 3,3,3-trifluoropropene (1243zf) is contacted with chlorine may enhance the chlorination reaction conducted within. For example, it has been found by the present inventors that conducting chlorination reactions within reaction vessels comprising glass and/or nickel provides better conversions that when the chlorination reaction is conducted within a reaction vessel that does not comprise glass and/or nickel.

In some embodiments of the invention it is preferred that the chlorination reaction where 3,3,3-trifluoropropene (1243zf) is contacted with chlorine is conducted within a reaction vessel that does not comprise steel and/or stainless steel. For example, in some embodiments of the invention, it is preferred that the chlorination reaction where 3,3,3- trifluoropropene (1243zf) is contacted with chlorine is conducted within a reaction vessel that comprises glass and/or a nickel alloy (e.g. Hastelloy® or Inconel®). By the term "nickel based alloy" we mean any alloy that comprises greater than about 20wt% or about 30% or about 40% by weight nickel. Such as from about 30% or about 40% by weight to about 80% by weight nickel or from about 45% or about 50% by weight to about 70% or about 75% by weight nickel.

Typically, the molar ratio of chlorine: 1243zf in the chlorination process is from about 10:1 to about 1.: 10, for example from about 4: 1 to about 1:4, for example from about 3: 1 to about 1 :3. In other embodiments, a molar excess of chlorine: 1243zf is used in the chlorination process for example between about 1.05:1 and about 5: 1 , e.g. from 2: 1 to about 4.5: 1 , e.g. about 4:1. In some embodiments, the process may include a preceding catalyst regeneration step. The regeneration step may comprise heating the catalyst (e.g. to from about 300°C to about 600°C) in the presence of a substantially inert gas (such as nitrogen or air) for a period of from about 1 hour to about 24 hours (e.g. from about 2 hours to about 15 hours). Following the chlorination step, the 243db produced and/or any other organic material in the product stream may be separated from any unreacted chlorine by distillation. Preferably, at least a portion of the recovered chlorine may be recycled to the chlorination reaction. In some embodiments, the other organic material, for example unreacted 1243zf and/or by-products of the chlorination reaction, may be separated from the 243db in the product stream by distillation. Such a separation may be effected in a single distillation column, e.g. for separation and recovery of both chlorine and organic material, or may be performed in two or more distillation columns in series.

1243zf is commercially available (e.g. from Apollo Scientific Ltd, UK). Alternatively, 1243zf may also be prepared via a synthetic route starting from the cheap feedstocks carbon tetrachloride (CCU) and ethylene (see the reaction scheme set out below). These two starting materials may be telomerised to produce 1 , 1 , 1 ,3-tetrachloropropane (see, for example, J. Am. Chem. Soc. Vol. 70, p2529, 1948, which is incorporated herein by reference) (also known as HCC-250fb, or simply 250fb).

250fb may then be fluorinated to produce 1243zf and/or 1 ,1 , 1-trifluoro-3-chloropropane (e.g. using HF, optionally in the presence of a chromia-containing catalyst, preferably a zinc/chromia catalyst as described herein). Dehydrohalogenation of 1 ,1 , 1-trifluoro-3- chloropropane (e.g. using NaOH or KOH) produces 1243zf.

Thus, in a further aspect of the invention there is provided a process for preparing 1 , 1 , 1- trifluoro-2,3-dichloropropane (243db), which process comprises:

(a) telomerising ethylene and carbon tetrachloride (CCU) to produce 1 , 1 ,1 ,3- tetrachloropropane (250fb);

(b) converting 250fb to 3,3,3-trifluoropropene ; and

(c) contacting 3,3,3-trifluoropropene with chlorine (C ) in the presence of a catalyst, as previously defined with respect to the process of the invention, to produce 1 ,1 , 1-trifluoro-2,3-dichloropropane (243db).

Step (a) of 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 1 ,1 , 1 ,3-tetrachloropropane.

Any suitable catalyst may be used in step (a), such as a catalyst which comprises iron, copper and/or peroxide.

Catalysts which comprise peroxide include benzoyl peroxide and di-te/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. CuC ), copper sulphate and/or copper cyanide.

Typically, 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 step (a) 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 carbon tetrachloride and ethylene present. An excess of the carbon tetrachloride over ethylene generally is used. For example, the molar ratio of CCkC^HU 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 step (a) typically is within the range of from 20 to 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 step (a) typically is within the range of from 0 to about 40 bara, preferably from about 1 to about 30 bara.

The reaction time for step (a) 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.

Step (a) 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. Step (a) may be carried out batch-wise or continuously. Preferably, the 1 ,1 , 1 ,3-tetrachloropropane formed in step (a) is purified and/or isolated before it is fluorinated in step (b). This purification may conveniently be achieved, for example by distillation and/or extraction.

The conversion of 1 , 1 , 1 ,3-tetrachloropropane (250fb) to 3,3,3-trifluoropropene (1243zf) in step (b) above typically involves fluorination and dehydrohalogenation sub-steps. For example, 250fb may be fluorinated to produce a compound of formula CF3CH2CH2CI (253fb), followed by dehydrohalogenation of the 253fb to produce 1243zf. This will be referred to hereinafter as route (b1).

Alternatively, 250fb may be dehydrochlorinated to produce 3,3,3-trichloropropene, followed by fluorination to produce 1243zf. This will be referred to hereinafter as route (b2).

Either or both routes (b1) and (b2) may be used to convert 1 , 1 , 1 ,3-tetrachloropropane to 3,3,3-trifluoropropene, depending on the choice of reagents and/or catalysts. The route taken and the number of steps involved may depend on factors such as the reaction conditions and the nature of catalyst employed (if any). Such factors are described in more detail below.

In route (b1), for example, 250fb may be fluorinated with HF in the presence of a catalyst to produce 253fb. Any suitable catalyst for HF fluorination may be used, such as compounds comprising aluminium (e.g. alumina-based catalysts) and/or chromium (e.g. chromia-based catalysts, especially zinc/chromia catalysts as described herein) and/or metal halides such as chlorides or fluorides (e.g. TiCU, SnCU or SbFs) and/or nitrogen- containing bases (e.g. amines and nitrogen-containing heterocycles such as pyridine).

253fb may then be dehydrohalogenated to 1243zf by any suitable method, for example by base-mediated (e.g. using a base comprising alkali or alkaline earth metal hydroxides or amides), thermal or metal catalysed (e.g. zinc/chromia-catalysed) dehydrohalogenation. The dehydrohalogenation may be conducted in the presence or absence of HF. Suitable reaction conditions for the dehydrohalogenation of the 253fb are described hereinafter in relation to the dehydrohalogenation step (iii) of a compound of formula CF3CHFCH2X (wherein X = CI or F).

The fluorination and dehydrohalogenation reactions in step (b or route b1) using HF may be conducted simultaneously (i.e. in a one-pot process) or sequentially, optionally with separation/isolation of the 253fb prior to dehydrohalogenation. Preferably, route (b1) is carried out in one-pot using a zinc/chromia catalyst.

In route (b2), the dehydrochlorination and fluorination reactions may be carried out under substantially the same reaction conditions, i.e. in a one-pot process. Thus, 250fb may be contacted with HF in the presence of a catalyst to produce 1243zf, typically via 1 ,1 , 1 ,3- tetrafluoropropane. Suitable catalysts include compounds comprising aluminium (e.g. alumina or aluminium fluoride) and/or chromium (e.g. chromia-based catalysts, especially zinc/chromia catalysts as described herein), and/or metal halides such as chlorides or fluorides (e.g. TaFs, TiCU, SnCU, SbCIs or SbFs) and/or nitrogen-containing bases (e.g. amines and nitrogen containing heterocycles such as pyridine). Examples of catalysts compounds comprising aluminium include AIF3, optionally mixed with one or more transition metal compounds. Although HF is described as a suitable fluorination agent for step (b), any suitable fluorination agent may be used. For example, in an alternative embodiment, 1243zf may be produced in one pot by treating 250fb with NaF, KF, or amine:HF complexes such as Olah's reagent.

Typically, step (b) is carried out at a temperature of about 20 to about 500 °C. For example, when using KF or Olah's reagent (pyrindinium poly(HF)), temperatures of about 50 to about 200 °C may be used. Alternatively, when using HF, higher temperatures may be employed, such as from about 100 to about 500 °C (e.g. about 120 to about 400 °C or about 150 to about 250 °C). The temperature used may vary depending on the nature of the catalyst employed. For example, when a nitrogen-containing base is used, the preferred temperature may range from about 100 to about 250 °C, whereas when a catalyst based on a compound of aluminium is employed, the preferred temperature may vary from about 200 to about 350 °C. When a zinc/chromia catalyst is used for step (ii), the temperature typically ranges from about 150 to about 400 °C, such as from about 150 to about 350 °C, e.g. from about 150 to about 300 °C or from about 150 to about 250 °C.

The reaction pressure for step (b) typically is within the range of from 0 to about 30 bara, preferably from about 1 to about 20 bara.

An excess of the fluorination agent is generally used in step (b), whether the 1243zf is produced via route (b1) or route (b2). For example, when using HF as the fluorination agent, 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 6: 1 to about 30: 1 may be used.

The reaction time for step (b) 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. In a continuous process, typical contact times of the catalyst with the reagents is 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.

Step (b) 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. Step (b) may be carried out batch-wise or continuously. Preferably, the 1243zf formed in step (b) is purified and/or isolated before it is chlorinated in step (c). This purification may conveniently be achieved, for example by distillation and/or extraction. Step (b) is described in more detail towards the end of this specification in a further embodiment denoted the 1243zf preparation process. The conditions for step (c) typically will be as defined above in the process of the invention.

In a preferred aspect of the invention, the 243db formed by the processes described herein is fluorinated to produce a compound of formula CF3CHFCH2X, wherein X is CI or F. Thus, the invention provides a process for preparing a compound of formula CF3CHFCH2X, wherein X is CI or F, the process comprising (i) contacting 3,3,3-trifluoropropene (1243zf) with chlorine (CI2) in the presence of a catalyst, as previously defined with respect to the process of the invention, to produce 1 , 1 , 1-trifluoro-2,3-dichloropropane (243db), and (ii) contacting the 243db with hydrogen fluoride (HF) in the presence of a fluorination catalyst to produce the compound of formula CF3CHFCH2X.

Any suitable fluorination catalyst may be used in step (ii), including but not limited to catalysts comprising activated carbon, alumina and/or an oxide of a transition metal (as described hereinbefore in relation to the chlorination step (i)) and supported (e.g. on carbon) or unsupported Lewis acid metal halides, including TaXs, SbXs, SnX ₄ , TiX ₄ , FeCb, NbX ₅ , VX ₅ , AIX3 (wherein X = F or CI).

Catalysts comprising chromia are a preferred group of catalysts for use in step (ii). For example, chromia (Cr203) that has been modified by the addition of Zn, Mn, Zr, Ni, Al and/or Mg and/or a compound of one or more of these metals may be used. Suitable chromia-based catalysts include those described in EP-A-0502605, EP-A-0773061 , EP- A-957074, WO 98/10862 and WO 2006/106353. A preferred chromia-based catalyst is a zinc/chromia catalyst.

By the term "zinc/chromia catalyst" we mean any catalyst comprising chromium or a compound of chromium and zinc or a compound of zinc. Such catalysts are known in the art, see for example EP-A-0502605, EP-A-0773061 , EP-A-0957074 and WO 98/10862, which are incorporated by reference herein. However, the present inventors have surprisingly found that zinc/chromia catalysts may be used promote the dehydrohalogenation of 243db to produce 1233xf, and/or the fluorination of 1233xf to produce the compound of formula CF3CFXCH3, and/or the dehydrohalogenation of the compound of formula CF3CFXCH3 to produce 1234yf. 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.

In other embodiments, the catalyst conveniently comprises 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 used in the invention may include an additional metal or compound thereof. Typically, the additional metal is a divalent or trivalent 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 used in 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 zinc/chromia 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 fluorination/dehydrohalogenation 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.

The percentage of crystalline material in the catalysts of the invention can be determined by any suitable method known in the art. Suitable methods include X-ray diffraction (XRD) techniques. When X-ray diffraction is used the amount of crystalline material such as the amount of crystalline chromium oxide can be determined with reference to a known amount of graphite present in the catalyst (e.g. the graphite used in producing catalyst pellets) or more preferably by comparison of the intensity of the XRD patterns of the sample materials with reference materials prepared from suitable internationally recognised standards, for example NIST (National Institute of Standards and Technology) reference materials.

The zinc/chromia catalysts of the invention typically have a surface area of at least 50 m ² /g and preferably from 70 to 250 m ² /g and most preferably from 100 to 200 m ² /g before it is subjected to pre-treatment with a fluoride containing species such as hydrogen fluoride or a fluorinated hydrocarbon. During this pre-treatment, which is described in more detail hereinafter, at least some of the oxygen atoms in the catalyst are replaced by fluorine atoms. The zinc/chromia catalysts of the invention typically have an advantageous balance of levels of activity and selectivity. Preferably, they also have a degree of chemical robustness that means that they have a relatively long working lifetime. The catalysts of the invention preferably also have a mechanical strength that enables relatively easy handling, for example they may be charged to reactors or discharged from reactors using known techniques. The zinc/chromia catalysts of the invention may be provided in any suitable form known in the art. For example, they may be provided in the form of pellets or granules of appropriate size for use in a fixed bed or a fluidised bed. The catalysts may be supported or unsupported. If the catalyst is supported, suitable supports include AIF3, fluorinated alumina or activated carbon.

The zinc/chromia catalysts of the invention include promoted forms of such catalysts, including those containing enhanced Lewis and/or Bronsted acidity and/or basicity. The amorphous catalysts which may be used in the present invention can be obtained by any method known in the art for producing amorphous chromia-based catalysts. Suitable methods include co-precipitation from solutions of zinc and chromium nitrates on the addition of ammonium hydroxide. Alternatively, surface impregnation of the zinc or a compound thereof onto an amorphous chromia catalyst can be used.

Further methods for preparing the amorphous zinc/chromia catalysts include, for example, reduction of a chromium (VI) compound, for example a chromate, dichromate, in particular ammonium dichromate, to chromium (III), by zinc metal, followed by co-precipitation and washing; or mixing as solids, a chromium (VI) compound and a compound of zinc, for example zinc acetate or zinc oxalate, and heating the mixture to high temperature in order to effect reduction of the chromium (VI) compound to chromium (III) oxide and oxidise the compound of zinc to zinc oxide.

The zinc may be introduced into and/or onto the amorphous chromia catalyst in the form of a compound, for example a halide, oxyhalide, oxide or hydroxide depending at least to some extent upon the catalyst preparation technique employed. In the case where amorphous catalyst preparation is by impregnation of a chromia, halogenated chromia or chromium oxyhalide, the compound is preferably a water-soluble salt, for example a halide, nitrate or carbonate, and is employed as an aqueous solution or slurry. Alternatively, the hydroxides of zinc and chromium may be co-precipitated (for example by the use of a base such as sodium hydroxide or ammonium hydroxide) and then converted to the oxides to prepare the amorphous catalyst. Mixing and milling of an insoluble zinc compound with the basic chromia catalyst provides a further method of preparing the amorphous catalyst precursor. A method for making amorphous catalyst based on chromium oxyhalide comprises adding a compound of zinc to hydrated chromium halide. The amount of zinc or a compound of zinc introduced to the amorphous catalyst precursor depends upon the preparation method employed. It is believed that the working catalyst has a surface containing cations of zinc located in a chromium-containing lattice, for example chromium oxide, oxyhalide, or halide lattice. Thus the amount of zinc or a compound of zinc required is generally lower for catalysts made by impregnation than for catalysts made by other methods such as co-precipitation, which also contain the zinc or a compound of zinc in non-surface locations.

Any of the aforementioned methods, or other methods, may be employed for the preparation of the amorphous catalysts which may be used in the process of the present invention.

The zinc/chromia catalysts described herein are typically stabilised by heat treatment before use such that they are stable under the environmental conditions that they are exposed to in use. This stabilisation is often a two-stage process. In the first stage, the catalyst is stabilised by heat treatment in nitrogen or a nitrogen/air environment. In the art, this stage is often called "calcination". Fluorination catalysts are then typically stabilised to hydrogen fluoride by heat treatment in hydrogen fluoride. This stage is often termed "pre-fluorination".

By careful control of the conditions under which these two heat treatment stages are conducted, crystallinity can be induced into the catalyst to a controlled degree.

For example, an amorphous catalyst may be heat treated at a temperature of from about 300 to about 600 °C, preferably from about 400 to 600 °C, more preferably from 500 to 590 °C, for example 520, 540, 560 or 580 °C for a period of from about 1 to about 12 hours, preferably for from about 2 to about 8 hours, for example about 4 hours in a suitable atmosphere. Suitable atmospheres under which this heat treatment can be conducted include an atmosphere of nitrogen or an atmosphere having an oxygen level of from about 0.1 to about 10 %v/v in nitrogen. Other oxidizing environments could alternatively be used. For example, environments containing suitable oxidizing agents include, but are not limited to, those containing a source of nitrate, CrC or O2 (for example air). This heat treatment stage can be conducted in addition to or instead of the calcining stage that is typically used in the prior art to produce amorphous catalysts. Conditions for the pre-fluorination stage can be selected so that they do not substantially introduce crystallinity into the catalyst. This may be achieved by heat treatment of the catalyst precursor at a temperature of from about 200 to about 500 °C, preferably from about 250 to about 400 °C at atmospheric or super atmospheric pressure for a period of from about 1 to about 16 hours in the presence of hydrogen fluoride, optionally in the presence of another gas such as nitrogen.

Conditions for the pre-fluorination stage can be selected so that they induce a change in the crystallinity of the catalyst or so that they do not induce such a change. The present inventors have found that heat treatment of the catalyst precursor at a temperature of from about 250 to about 500 °C, preferably from about 300 to about 400 °C at atmospheric or super atmospheric pressure for a period of from about 1 to about 16 hours in the presence of hydrogen fluoride, optionally in the presence of another gas such as air, can produce a catalyst in which the crystallinity is as defined above, for example from 0.1 to 8.0 % by weight of the catalyst (typically from 0.1 to less than 8.0 % 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 the at least one additional metal.

The skilled person will appreciate that by varying the conditions described above, such as by varying the temperature and/or time and/or atmosphere under which the heat treatment is conducted, the degree of crystallinity of the catalyst may be varied. Typically, for example, catalysts with higher degrees of crystallinity (e.g. from 8 to 50 % by weight of the catalyst) may be prepared by increasing the temperature and/or increasing the calcination time and/or increasing the oxidising nature of the atmosphere under which the catalyst pre-treatment is conducted.

The variation of catalyst crystallinity as a function of calcination temperature, time and atmosphere is illustrated by the following table showing a series of experiments in which 8 g samples of a 6 % zinc/chromia catalyst were subjected to calcination across a range of conditions and the level of crystallinity induced determined by X-Ray diffraction. Calcination Time (t, Calcination Atmosphere % Cryst

hrs) Temperature (T, nitrogen:air (D, v/v) Cr ₂ 0 ₃

°C) Content

4 400.0 15 1

4 400.0 15 1

2 450.0 20 9

6 350.0 20 0

2 450.0 10 18

2 350.0 10 0

6 450.0 20 20

6 350.0 10 0

6 450.0 10 30

4 400.0 15 1

2 350.0 20 0

The pre-fluorination treatment typically has the effect of lowering the surface area of the catalyst. After the pre-fluorination treatment the catalysts of the invention typically have a surface area of 20 to 200 m ² /g, such as 50 to 150 m ² /g, for example less than about 100m ² /g.

In use, the zinc/chromia catalyst may be regenerated or reactivated periodically by heating in air at a temperature of from about 300 °C to about 500 °C. Air may be used as a mixture with an inert gas such as nitrogen or with hydrogen fluoride, which emerges hot from the catalyst treatment process and may be used directly in fluorination processes employing the reactivated catalyst. Alternatively, the catalyst can be regenerated continuously whilst in use by introducing an oxidising gas into the reactor e.g. oxygen or chlorine.

Step (ii) 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. Step (ii) may be carried out batch-wise or continuously and in the gas or liquid phase.

Step (ii) may be carried out simultaneously with step (i). In other words, the process may comprise contacting 3,3,3-trifluoropropene (1243zf) with chlorine (C ) and HF in the presence of a catalyst, as previously defined with respect to the process of the invention, to produce a compound of formula CF3CHFCH2X, wherein X is CI or F. Thus, in this process, the catalyst, as previously defined with respect to the process of the invention acts as both a chlorination and fluorination catalyst.

When steps (i) and (ii) are carried out simultaneously, the process conditions used (e.g. temperature, pressure and molar ratio of 1243zf:chlorine) typically are the same as set out above in relation to the first aspect of the invention for the chlorination of 1243zf to 243db (i.e. step (i)). The preferred temperature for this simultaneous process may be somewhat higher than for step (i) alone, such as from 0 to about 350 °C, e.g. from about 50 to about 300 °C.

Typically, when steps (i) and (ii) are carried out simultaneously, HF will be used in a molar excess compared to the amount of 1243zf and/or chlorine. For example, the molar ratio of HF: 1243zf may be in the range of from about 1 :1 to about 200: 1 , such as from about 2:1 to about 150: 1 , e.g. from about 5: 1 to about 100: 1.

In another aspect of the invention, the hydrofluorination step (ii) may be carried out subsequent to the chlorination step (i). The 243db formed in step (i) may be purified and/or isolated prior to fluorination in step (ii), e.g. by removal and/or recycling from the reaction vessel of some or all of the chlorine and/or 1243zf in step (i). For example, the 243db may be separated (e.g. by distillation, condensation and phase separation, and/or scrubbing with water or aqueous base) from the chlorine and 1243zf in step (i) and transferred to a different reaction vessel or zone for conducting the fluorination step (ii).

By conducting step (i) and (ii) consecutively and in separate reaction zones or vessels, the reagents, temperature, pressure and type of catalyst can be chosen to facilitate the chlorination and fluorination reactions, respectively, as explained below.

For example, a catalyst as previously defined with respect to the process of the invention may be preferred in step (i) and a chromia-based (e.g. zinc/chromia) catalyst may be preferred for step (ii).

Step (i) is typically conducted in the absence of HF, whereas a relatively high ratio of HF:243db can be used in step (ii). For example, a typical molar ratio of HF:1243zf in step (i) is from about 0.01 : 1 to about 10: 1 (e.g. about 0.1 to about 5: 1), whereas molar ratio of HF:243db in step (ii) is generally from about 1 : 1 to about 100: 1 (e.g. about 3: 1 to about 50: 1). Still further, higher temperature and/or pressure conditions may be used in the fluorination step (ii) compared to the chlorination step (i). Thus, step (i) may be conducted at a temperature of from about -100 to about 400 °C (e.g. from about -50 to about 250 °C), whereas step (ii) may be conducted at a temperature of from about 100 to about 380 °C (e.g. from about 200 to about 370 °C). Step (i) may be carried out at a pressure of from about 0.1 to about 20 bara (e.g. about 0.5 to about 10 bara), whereas step (ii) may be carried out at a pressure of from about 5 to about 28 bara (e.g. about 10 to about 25 bara). Steps (i) and (ii) may both be carried out in the liquid phase or in the vapour phase. Alternatively, steps (i) and (ii) may be carried out in the liquid phase and vapour phase, respectively.

In another aspect of the invention, the compound of formula CF3CHFCH2X (wherein X is CI or F) may be dehydrohalogenated to produce 2,3,3,3-tetrafluoropropene. 2,3,3,3- tetrafluoropropene is also known as HFO-1234yf or 1234yf. Unless otherwise stated, 2,3,3,3-tetrafluoropropene will be referred to hereinafter as 1234yf.

Thus the invention provides a process for preparing 1234yf, the process comprising (i) contacting 3,3,3-trifluoropropene (1243zf) with chlorine (C ) in the presence of a catalyst, as previously defined with respect to the process of the invention, to produce 1 , 1 , 1- trifluoro-2,3-dichloropropane (243db), (ii) contacting the 243db with hydrogen fluoride (HF) in the presence of a fluorination catalyst to produce a compound of formula CF3CHFCH2X, wherein X is CI or F, and (iii) dehydrohalogenating the compound of formula CF3CHFCH2X to produce 1234yf.

Unless otherwise stated, as used herein, by the term "dehydrohalogenation" (or dehydrohalogenating), we refer to the removal of hydrogen chloride (HCI) or hydrogen fluoride (HF) from the compound of formula CF3CHFCH2X. Thus the term "dehydrohalogenation" includes "dehydrofluorination" and "dehydrochlorination" of the compound of formula CF3CHFCH2X.

Step (iii) of the process defined above may be carried out by any suitable reaction conditions effective to dehydrohalogenate (i.e. dehydrochlorinate or dehydrofluorinate) the compound of formula CF3CHFCH2X to produce 1234yf. Preferably, the dehydrohalgenation is carried out in the vapour and/or liquid phase and may be carried out at a temperature of from about -70 to about 1000 °C (e.g. about 0 to about 400 °C). The process may be carried out at atmospheric sub- or super atmospheric pressure, preferably from about 0 to about 30 bara. The dehydrohalogenation 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, main group (e.g. alumina-based catalysts) and transition metals, such as chromia-based catalysts (e.g. zinc/chromia) or nickel-based catalysts (e.g. nickel mesh).

Step (iii) can be carried out in any suitable apparatus, such as a static mixer, a stirred tank reactor or a stirred vapour-liquid disengagement vessel. The process may be carried out batch-wise or continuously and in the liquid or gas phase. One preferred method of effecting the dehydrohalogenation of the compound of formula CF3CHFCH2X to produce 1234yf is by contacting CF3CHFCH2X with a catalyst based on chromia such as those described in EP-A-0502605, EP-A-0773061 , EP-A-957074, WO 98/10862 and WO 2006/106353 (e.g. a zinc/chromia catalyst). Thus, when both steps (ii) and (iii) are carried out in the presence of a catalyst based on chromia (e.g. a zinc/chromia catalyst), they may be carried out in a "one-pot" manner. Alternatively, when both steps (ii) and (iii) are carried out in the presence of a catalyst comprising chromia, the fluorination and dehydrohalogenation reactions may be carried out in two discrete steps, for example using two or more discrete reaction zones or vessels. When both steps (ii) and (iii) are carried out in the presence of a catalyst based on chromia, the reaction conditions for each step (ii) and (iii) may be the same (e.g. in a one-pot process) or different. Preferably, the reaction conditions when both steps (ii) and (iii) are carried out in the presence of a catalyst based on chromia can be selected to be different (e.g. when using two or more discrete reaction zones or vessels) so as to optimise the fluorination and dehydrohalogenation reactions, respectively. This is explained in more detail below.

Fluorination step (ii) preferably is conducted at a temperature of from about 0 to about 390 °C, such as from about 100 to about 380 °C or from about 200 to about 370 °C (e.g. from about 240 to about 260 °C). When conducted in the presence of a catalyst based on chromia (e.g. a zinc/chromia catalyst), step (b) preferably is conducted at a temperature of from about 200 to about 360 °C, such as from about 240 to about 340 °C.

It is currently considered to be advantageous to use a higher pressure in step (ii) (to promote fluorination) than in step (iii) (to promote dehydrohalogenation). Thus, step (ii) preferably is carried out from about 5 to about 28 bara, such as from about 10 to about 25 bara (e.g. 15 to 20 bara), whereas step (iii) preferably is carried out from about 0.01 to about 25 bara or about 0.1 to about 20 bara, such as from about 1 to about 10 bara (e.g. 1 to 5 bara).

Fluorination step (ii) is carried out by contacting 243db with HF. Step (iii) of the invention may be carried out in the presence of HF. For example residual HF from step (ii) may be present, and/or HF from a separate feed. Alternatively, step (iii) may be carried out in the absence of HF, for example following separation of the compound of formula CF3CHFCH2X from HF prior to step (iii), and with no additional co-feed of HF. In certain embodiments it may be desirable to use some HF in order to prevent and/or retard excessive decomposition of the organic feed and/or coking of the catalyst in step (iii).

When both steps (ii) and (iii) are carried out in the presence of a catalyst based on chromia (e.g. a zinc/chromia catalyst) and HF, the molar ratio of HF:organics can be selected to be different in each step so as to promote fluorination in step (ii) and dehydrohalogenation in step (iii). For example, the molar ratio of HF:organics (e.g. 243db) in step (ii) preferably is from about 1 : 1 to about 100: 1 , such as from about 2: 1 to about 50: 1 , for example from about 5: 1 to about 40: 1 (e.g. from about 10: 1 to about 30: 1). For step (iii), the molar ratio of HF:organics (e.g. the compound of formula CF3CHFCH2X) preferably is from about 0.01 :1 to about 50: 1 , such as from about 0.1 :1 to about 40: 1 , for example from about 0.5: 1 to about 30: 1 or about 2:1 to about 15: 1 (e.g. from about 5: 1 to about 10: 1).

Another way of decreasing the concentration of HF in step (iii) relative to step (ii) (thereby facilitating the fluorination/dehydrohalogenation reactions in these steps) is by adding a diluent gas (e.g. nitrogen) to step (iii).

Another preferred method of effecting the dehydrohalogenation of the compound of formula CFsCHFCH2X to produce 1234yf is by contacting CFsCHFCH2Xwith a base (base- mediated dehydrohalogenation). This base-mediated dehydrohalogenation process of step (iii) comprises contacting the hydro(halo)fluoroalkane with base such as a metal hydroxide or amide (preferably a basic metal hydroxide or amide, e.g. an alkali or alkaline earth metal hydroxide or amide). Unless otherwise stated, as used herein, by the term "alkali metal hydroxide", we refer to 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, by the term "alkaline earth metal hydroxide", we refer to a compound or mixture of compounds selected from beryllium hydroxide, magnesium hydroxide, calcium hydroxide, strontium hydroxide and barium hydroxide. 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 (iii) is conducted at a temperature of from -50 to 300 °C. Preferably, the process is conducted at a temperature of from 20 to 250 °C, for example from 50 to 200 °C. The base-mediated dehydrohalogenation may be conducted at a pressure of from 0 to 30 bara.

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

Of course, 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 nature of the compound of formula CF3CHFCH2X, the base being employed, and/or the presence of a catalyst etc.

The base-mediated dehydrohalogenation process of step (iii) may be carried out in the presence or absence of a solvent. If no solvent is used, the compound of formula CF3CHFCH2X 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. 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.

Another preferred base is an alkaline earth metal hydroxide selected from the group consisting of magnesium hydroxide and calcium hydroxide, more preferably calcium hydroxide.

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

The molar ratio of base to compound of formula CF3CHFCH2X 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 preferably employ water as the solvent. Thus, the dehydrohalogenation reaction may preferably 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 by- products, 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 (iii) is preferably 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 can 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 compound of formula CF3CHFCH2X present is from 0.001 to 20 mol %, such as from 0.01 to 10 mol %, e.g. from 0.05 to 5 mol %.

Crown ethers are cyclic molecules in which ether groups are connected by dimethylene linkages. Crown ethers form a molecular structure that is believed to be capable of receiving or holding the alkali metal ion of the hydroxide and to thereby facilitate the reaction. Particularly useful crown ethers include 18-crown-6 (especially in combination with potassium hydroxide), 15-crown-5 (especially in combination with sodium hydroxide) and 12-crown-4 (especially in combination with lithium hydroxide).

Derivatives of the above crown ethers are also useful, such as dibenzyl-18-crown-6, dicyclohexanyl-18-crown-6, dibenzyl-24-crown-8 and dibenzyl-12-crown-4. Other compounds analogous to the crown ethers and useful for the same purpose are compounds which differ by the replacement of one or more of the oxygen atoms by other kinds of donor atoms, particularly N or S. Fluorinated derivatives of all the above may also be used. Cryptands are another class of compounds useful in the base-mediated dehydrohalogenation as phase transfer catalysts. These are three dimensional polymacrocyclic chelating agents that are formed by joining bridgehead structures with chains that contain properly spaced donor atoms. The donor atoms of the bridges may all be O, N, or S, or the compounds may be mixed donor macrocycles in which the bridge strands contain combinations of such donor atoms. Suitable cryptands include bicyclic molecules that result from joining nitrogen bridgeheads with chains of (-OCH2CH2-) groups, for example as in [2.2.2]cryptand (4,7,13, 16,21 ,24-hexaoxa-1 ,10- diazabicyclo[8.8.8]hexacosane, available under the brand names Kryptand 222 and Kryptofix 222). Onium salts that may be used as catalysts in the base-mediated process of the step (iii) include quaternary phosphonium salts and quaternary ammonium salts, which may be represented by the formulae R ¹ R ² R ³ R ⁴ P ⁺ Z ^" and R ¹ R ² R ³ R ⁴ N ⁺ Z ^" , respectively. In these formulae, each of R ¹ , R ² , R ³ and R ⁴ typically represent, independently, a CMO alkyl group, an aryl group (e.g. phenyl, naphthyl or pyridinyl) or an arylalkyl group (e.g. benzyl or CMO alkyl-substituted phenyl), and Z ^" is a halide or other suitable counterion (e.g. hydrogen sulphate).

Specific examples of such phosphonium salts and quaternary ammonium salts include tetramethylammonium chloride, tetramethylammonium bromide, benzyltriethylammonium chloride, methyltrioctylammonium chloride (available commercially under the brands Aliquat 336 and Adogen 464), tetra-n-butylammonium chloride, tetra-n-butylammonium bromide, tetra-n-butylammonium hydrogen sulphate, tetra-n-butylphosphonium chloride, tetraphenylphosphonium bromide, tetraphenylphosphonium chloride, triphenylmethylphosphonium bromide and triphenylmethylphosphonium chloride. Benzyltriethylammonium chloride is preferred for use under strongly basic conditions.

Other useful onium salts include those exhibiting high temperature stabilities (e.g. up to about 200 °C), for example 4-dialkylaminopyridinium salts, tetraphenylarsonium chloride, bis[tris(dimethylamino)phosphine]iminium chloride and tetrakis[tris(dimethylamino)phosphinimino]phosphonium chloride. The latter two compounds are also reported to be stable in the presence of hot, concentrated sodium hydroxide and, therefore, can be particularly useful.

Polyalkylene glycol compounds useful as phase transfer catalysts may be represented by the formula R ⁶ 0(R ⁵ 0) _m R ⁷ wherein R ⁵ is a CMO alkylene group, each of R ⁶ and R ⁷ are, independently H, a CMO alkyl group, an aryl group (e.g. phenyl, naphthyl or pyridinyl) or an arylalkyl group (e.g. benzyl or CMO alkyl-substituted phenyl), and m is an integer of at least 2. Preferable both R ⁶ and R ⁷ are the same, for example they may both by H.

Such polyalkylene glycols include diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, diisopropylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol and tetramethylene glycol, monoalkyl glycol ethers such as monomethyl, monoethyl, monopropyl and monobutyl ethers of such glycols, dialkyl ethers such as tetraethylene glycol dimethyl ether and pentaethylene glycol dimethyl ether, phenyl ethers, benzyl ethers of such glycols, and polyalkylene glycols such as polyethylene glycol (average molecular weight about 300) and polyethylene glycol (average molecular weight about 400) and the dialkyl (e.g. dimethyl, dipropyl, dibutyl) ethers of such polyalkylene glycols.

Combinations of phase transfer catalysts from within one of the groups described above may also be useful as well as combinations or mixtures from more than one group. Crown ethers and quaternary ammonium salts are the currently preferred groups of catalysts, for example 18-crown-6 and its fluorinated derivatives and benzyltriethylammonium chloride.

In a further aspect of the invention, 1234yf may be prepared starting from the above- described chlorination of 1243zf to 243db, but then from a different route from 243db than defined above in steps (ii) and (iii). This alternative route involves the dehydrochlorination of 243db to produce 3,3,3-trifluoro-2-chloro-prop-1-ene (CF ₃ CCI=CH ₂ , 1233x . 1233xf may then be fluorinated to produce a compound of formula CF3CFXCH3 (wherein X = CI, or F), which may then be dehydrohalogenated to produce 1234yf.

Thus there is provided a process for preparing 1234yf comprising (w) contacting 1243zf with C in the presence of a catalyst, as previously defined with respect to the process of the invention, to produce 243db, (x) converting 243db to 3,3,3-trifluoro-2-chloro-prop-1- ene (CF3CC CH2), (y) contacting CF3CC CH2 with a fluorinating agent to produce a compound of formula CF3CFXCH3, wherein X = CI or F, and (z) dehydrohalogenating the compound of formula CF3CFXCH3 to produce 1234yf.

Step (w) corresponds to the process described hereinbefore for the chlorination of 1243zf to 243db, e.g. step (i). The above process comprising steps (w), (x), (y) and (z) may be carried out batch-wise or continuously. Each step (w), (x), (y) and (z) may independently be carried out batch-wise or continuously. 3,3,3-trifluoro-2-chloro-prop-1-ene (CF ₃ CCI=CH ₂ ) is also known as HFO-1233xf or 1233xf. Unless otherwise stated, this compound will be referred to as 1233xf. The compound of formula CF ₃ CFXCH ₂ may be CF3CFCICH3, which is also known as HCFC-244bb or 244bb, or CF3CF2CH3, which is also known as HFC-245cb or 245cb. Unless otherwise stated, these compounds will be referred to as 244bb and 245cb, respectively.

Step (x) of the invention comprises converting 243db to 1233xf. Thus, step (x) involves the dehydrochlorination of 243db to produce 1233xf. Step (x) preferably is carried out in a first reactor in the presence of a first catalyst. This reaction may be carried out in the liquid phase or the gas phase, preferably the gas phase.

The catalyst used in step (x) may be any suitable catalyst that is effective to dehydrochlorinate 243db. Preferred catalysts are those comprising activated carbon, alumina and/or an oxide of a transition metal. Such catalysts are described in more detail above in relation to the conversion of 1243zf to 243db. A further group of preferred catalysts for step (x) are supported (e.g. on carbon) or unsupported Lewis acid metal halides, including TaX ₅ , SbX ₅ , SnX ₄ , TiX ₄ , FeCI ₃ , NbX ₅ , VX ₅ , AIX ₃ (wherein X = F or CI).

A preferred group of catalysts for step (x) are catalysts which comprise activated carbon, alumina and/or chromia. Catalysts based on chromia currently are particularly preferred. A preferred chromia-based catalyst is a zinc/chromia catalyst. Catalysts comprising activated carbon currently are also particularly preferred. The use of the same catalyst(s) for steps (w) and (x) allows these steps to be carried out simultaneously in "one-pot".

The catalyst in step (x) may be used in an amount of from about 0.01 to about 50 % by weight, such as from about 0.1 to about 30%, for example from about 0.5 to about 20%, based on the weight of 243db.

It is preferable for step (x) to be carried out in the presence of hydrogen fluoride (HF). For example, when alumina or an oxide of a transition metal is used as a catalyst in step (e.g. a chromia-based catalyst such as zinc/chromia), HF may be used to prevent and/or retard excessive decomposition of the catalyst. Step (x) may also be carried out in the presence of C , for example when steps (w) and (x) are carried out in simultaneously in a one-pot conversion of 1243zf to 1233xf.

Step (x) may be carried out at a temperature of from about -70 to about 450 °C and at atmospheric, sub- or super-atmospheric pressure, preferably from about 0 to about 30 bara.

Preferably, step (x) is conducted at a temperature of from about 0 to about 390 °C, such as from about 100 to about 380 °C or from about 200 to about 370 °C (e.g. from about 240 to about 260 °C).

Step (x) preferably is carried out at a pressure of from about 0.01 to about 25 bara or about 0.1 to about 20 bara, such as from about 1 to about 10 bara (e.g. 1 to 5 bara). Step (y) of the invention comprises contacting CF3CC CH2 with a fluorinating agent to produce a compound of formula CF3CFXCH3, wherein X = CI or F. Thus, step (y) involves the fluorination of 1233xf to produce 244bb and/or 245cb. Step (y) preferably is carried out in a second reactor in the presence of a second catalyst. This reaction may be carried out in the liquid phase or the gas phase, preferably the liquid phase.

Any suitable fluorinating agent may be used in step (y), including any suitable source of nucleophilic fluoride, optionally in a polar aprotic or protic solvent. Examples of suitable fluorinating agents include HF, NaF, KF and amine:HF complexes such as Olah's reagent. HF is a preferred fluorinating agent, as is KF in a polar aprotic or protic solvent.

The catalyst used in step (y) may be any suitable catalyst that is effective to fluorinate 1233xf. Preferred catalysts are those comprising activated carbon, alumina and/or an oxide of a transition metal and/or supported or unsupported Lewis acid metal halides as described above in relation to the chlorination of 1243zf to 243db and step (x).

Preferred catalysts for step (y) are those which comprise chromia (particularly for vapour phase reactions) and Lewis acid metal halide catalysts (particularly for liquid phase reactions). A preferred chromia-based catalyst for use in step (y) is a zinc/chromia catalyst. The same catalyst may be used for step (x) and (y), e.g. a chromia-based catalyst. Typically, step (y) is conducted at a temperature of from about -100 to about 400 °C and a pressure of 0 to about 50 bara.

If step (y) is carried out in the liquid phase, it preferably is conducted at a temperature of from about -50 to about 250 °C, such as from about 0 to about 200 °C or from about 10 to about 150 °C (e.g. from about 50 to about 100 °C), and conducted at a pressure of from about 1 to about 50 bara or about 5 to about 40 bara, such as from about 10 to about 30 bara (e.g. 15 to 25 bara). If step (y) is carried out in the gas phase, it preferably is conducted at a temperature of from about 0 to about 390 °C, such as from about 100 to about 350 °C or from about 200 to about 300 °C, and conducted at a pressure of from about 0.1 to about 30 bara or about 0.5 to about 25 bara, such as from about 1 to about 20 bara (e.g. 5 to 15 bara). Steps (x) and (y) preferably are carried out in separate first and second reactors, respectively. Any suitable apparatus may be used as a reactor for steps (x) and (y), such as a static mixer, a stirred tank reactor or a stirred vapour-liquid disengagement vessel.

It is believed that there are advantages associated with the use of separate reactors for these two steps, including modifying the conditions in each reactor to facilitate the reactions in steps (x) and (y) respectively.

For example, step (x) can be carried out in the gas phase and step (y) in the liquid phase. A higher temperature can be used in step (x) compared to step (y). A higher pressure can be used in step (y) compared to step (x).

Step (x) can be carried out in the absence of HF whereas HF can be used as the fluorination agent in step (y). Alternatively, if HF is used in step (x), for example to stabilise the catalyst, it may be used in lower concentrations compared to step (y). For example, the molar ratio of HF:organics (e.g. 243db) in step (x) preferably is from about 0.01 : 1 to about 50: 1 , such as from about 0.1 : 1 to about 40: 1 , for example from about 0.5: 1 to about 30: 1 or about 2: 1 to about 15: 1 (e.g. from about 10: 1 to about 20:1 or from about 5: 1 to about 10: 1). The molar ratio of HF:organics (e.g. 1233xf) in step (y) preferably is from about 1 : 1 to about 100: 1 , such as from about 2: 1 to about 50: 1 , for example from about 5:1 to about 40: 1 (e.g. from about 10: 1 to about 30: 1). When separate reactors are used, 1233xf produced in step (x) may be transferred from the first reactor directly to the second reactor for fluorination in step (y). Preferably, however, 1233xf is subjected to a purification step before being passed to the second reactor. The purification may be achieved by separation of the 1233xf 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 step (z), the compound of formula CF3CFXCH3 (wherein X = CI or F) is converted to 1234yf by dehydrochlorination of 244bb (i.e. wherein X = CI) and/or dehydrofluorination of 245cb (i.e. wherein X = F).

Step (z) of the process of the invention may be carried out in any suitable reactions conditions effective to dehydrohalogenate the compound of formula CF3CFXCH3 to produce 1234yf. The dehydrohalogenation may be carried out in the vapour and/or liquid phase and typically is carried out at a temperature of from about -70 to about 1000 °C (e.g. about 0 to about 400 °C). Step (c) may be carried out at atmospheric sub- or super atmospheric pressure, preferably from about 0 to about 30 bara.

The dehydrohalogenation 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, main group (e.g. alumina-based catalysts) and transition metals, such as chromia-based catalysts (e.g. zinc/chromia) or nickel-based catalysts (e.g. nickel mesh). One preferred method of effecting the dehydrohalogenation of the compound of formula CF3CFXCH3 to produce 1234yf is by contacting CF3CFXCH3 with a metal catalyst, such as a chromia-based (e.g. zinc/chromia) catalyst.

When the catalyst used in step (y) is the same as in step (z) (e.g. when using a chromia- based catalyst such as a zinc/chromia catalyst), steps (y) and (z) may be carried out in a "one-pot" manner, i.e. simultaneously. Alternatively, when both steps (y) and (z) are carried out in the presence of the same catalyst, the fluorination and dehydrohalogenation reactions may be carried out in two discrete steps, for example using two or more discrete reaction zones or reactors. When both steps (y) and (z) are carried out in the presence of the same catalyst, the reaction conditions for each step (y) and (z) may be the same (e.g. in a one-pot process) or different. Preferably, the reaction conditions when steps (y) and (z) are carried out in the presence of the same catalyst can be selected to be different so as to optimise the fluorination and dehydrohalogenation reactions, respectively. This is explained in more detail below.

The preferred conditions for fluorination step (y) are set out above. Dehydrohalogenation step (z) may be carried out in the vapour or liquid phase, preferably the vapour phase. When conducted in the vapour phase, typically in the presence of a metal catalyst, such as a chromia-based (e.g. zinc/chromia) catalyst, step (z) preferably is conducted at a temperature of from about 200 to about 360 °C, such as from about 240 to about 340 °C.

It is currently considered to be advantageous to use a higher pressure in step (y) (to promote fluorination) than in step (z) (to promote dehydrohalogenation). Thus, step (z) preferably is carried out from about 0.01 to about 25 bara or about 0.1 to about 20 bara, such as from about 1 to about 10 bara (e.g. 1 to 5 bara).

Fluorination step (y) preferably is carried out by contacting 1233xf with HF. Step (z) of the invention may be carried out in the presence of HF. For example residual HF from step (y) may be present, and/or HF from a separate feed. Alternatively, step (z) may be carried out in the absence of HF, for example following separation of the compound of formula CF3CFXCH3 from HF prior to step (y), and with no additional co-feed of HF. In certain embodiments it may be desirable to use some HF in order to prevent and/or retard excessive decomposition of the organic feed and/or coking of the catalyst in step (z).

When both steps (y) and (z) are carried out in the presence of HF, the molar ratio of HF:organics can be selected to be different in each step so as to promote fluorination in step (y) and dehydrohalogenation in step (z). For example, the molar ratio of HF:organics (e.g. the compound of formula CF3CFXCH3) in step (z) preferably is from about 0.01 : 1 to about 50: 1 , such as from about 0.1 : 1 to about 40: 1 , for example from about 0.5: 1 to about 30: 1 or about 2: 1 to about 15: 1 (e.g. from about 10: 1 to about 20:1 or from about 5: 1 to about 10:1). Another way of decreasing the concentration of HF in step (z) relative to step (y) (thereby facilitating the fluorination/dehydrohalogenation reactions in these steps) is by adding a diluent gas (e.g. nitrogen) to step (z). Another preferred method of effecting the dehydrohalogenation of the compound of formula CF3CFXCH3 to produce 1234yf is by contacting CF3CFXCH3 with a base (base- mediated dehydrohalogenation). The conditions which may be used for base-mediated dehydrohalogenation step (z) broadly are the same as described above in relation to the dehydrohalogenation of the compound of formula CF3CHFCH2X in step (iii).

In a further embodiment, the subject invention provides a process for preparing 3,3,3- trifluoropropene (1243zf), the process comprising contacting a compound of formula CX3CH2CH2X or CX ₃ CH=CH ₂ , with hydrogen fluoride (HF) in the presence of a zinc/chromia catalyst, wherein each X independently is F, CI, Br or I, provided that in the compound of formula CX3CH=CH2, at least one X is not F. Unless otherwise stated, this will be referred to hereinafter as the 1243zf preparation process (of the invention).

In a preferred embodiment, this process relates to the reaction of a compound of formula CX3CH2CH2X to produce 1243zf.

The compound of formula CX3CH2CH2X represents any halopropane wherein X = F, CI, Br or I. In a preferred aspect, X = F or CI. Examples of compounds of formula CX3CH2CH2X include 1 , 1 , 1 ,3-tetrachloropropane (CCI ₃ CH ₂ CH ₂ CI, 250fb), 1 , 1 ,3-trichloro- 1-fluoropropane (CCI ₂ FCH ₂ CH ₂ CI), 1 ,3-dichloro-1 ,1-difluoropropane (CCIF ₂ CH ₂ CH ₂ CI), 3- chloro-1 , 1 , 1-trifluoropropane (CF ₃ CH ₂ CH ₂ CI, 253fb) and 1 , 1 , 1 ,3-tetrafluoropropane

In one aspect, the compound of formula CX3CH2CH2X is selected from 250fb, 253fb and 254fb. In a preferred embodiment, the compound of formula CX3CH2CH2X is 253fb. In a further preferred embodiment, the compound of formula CX3CH2CH2X is 254fb. In a particularly preferred embodiment, the compound of formula CX3CH2CH2X is 250fb.

The compound of formula CX3CH=CH2 represents any halopropene wherein X = F, CI, Br or I, provided that at least one X is not F. Preferably, X is F or CI (provided that at least one X is not F). Examples of compounds of formula CX3CH=CH2 include 3,3,3- trichloropropene (CCI ₃ CH=CH ₂ ), 3,3-dichloro-3-fluoropropene (CCI ₂ FCH=CH ₂ ) and 3- chloro-3,3-difluoropropene (CCIF2CI- CH2). In a preferred aspect, the compound of formula CX3CI- CH2 represents 3,3,3-trichloropropene.

The inventors have unexpectedly found that zinc/chromia catalysts are particularly effective for the fluorination and/or dehydrohalogenation reactions required by the 1243zf preparation process. In particular, the zinc/chromia catalysts are believed to be more active than other catalysts, such as chromia-based catalysts. This enables the 1243zf preparation process to be conducted using less forcing conditions (e.g. lower temperature and/or pressure) than would otherwise be necessary.

The zinc/chromia catalyst may be used in the 1243zf preparation process in an amount of from about 0.01 to about 50 % by weight, such as from about 0.1 to about 30%, for example from about 0.5 to about 20%, based on the combined weight of organics (e.g. compound of formula CX3CH2CH2X or CX ₃ CH=CH ₂ ) and HF.

The 1243zf preparation process can be carried out in any suitable apparatus, such as a static mixer, a stirred tank reactor or a stirred vapour-liquid disengagement vessel. Preferably, the apparatus is made from one or more materials that are resistant to corrosion, e.g. Hastelloy® or Inconel®.

The 1243zf preparation process may be carried out batch-wise or (semi-)continuously. Preferably, the process of the invention is carried out continuously. Typically, the 1243zf preparation process is carried out in the vapour phase. The process 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.

Typically, the 1243zf preparation process of the invention 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 200 °C to about 350 °C. Lower temperatures may also be used in the process of the invention, for example 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 1243zf preparation process 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. The reaction time for the 1243zf preparation process 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 is 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.

The 1243zf preparation process is particularly effective for preparing 3,3,3-trifluoropropene (1243zf) by contacting 1 , 1 , 1 ,3-tetrachloropropane (250fb) with hydrogen fluoride (HF) in the presence of a zinc/chromia catalyst.

250fb may be purchased from common suppliers of halogenated hydrocarbons, such as Apollo Scientific, Stockport, UK. Alternatively, 250fb may be prepared by the telomerisation of carbon tetrachloride (CCU) and ethylene (see, for example, J. Am. Chem. Soc. Vol. 70, p2529, 1948, which is incorporated herein by reference).

The conversion of 250fb to 1243zf typically involves fluorination and dehydrohalogenation sub-steps.

For example, 250fb may be fluorinated to produce a compound of formula CX3CH2CH2CI (wherein X = CI or F), as illustrated in the scheme below. 1243zf may be produced by a final dehydrochlorination step of the compound of formula CX3CH2CH2CI wherein X = F. This is illustrated below as route (a).

CCI ₃ CH ₂ CH ₂ CI (250fb)

route route

(b) (a)

b)

CF ₃ CH=CH ₂ (1243zf)

Alternatively, 250fb may be dehydrochlorinated to produce 3,3,3-trichloropropene, followed by step-wise fluorination to produce 1243zf. This is illustrated above as route (b). Routes (a) and (b) correspond to routes (b1) and (b2), respectively, as described herein in relation to step (b) of the process of the invention.

Either or both routes (a) and (b) may be operable to convert 250fb to 1243zf. For example, CCI2FCH2CHCI in route (a) may be dehydrochlorinated to produce CCI2FCI- CH2 in route (b). It is anticipated that some of these reactions may occur spontaneously if HF and 250fb are mixed at elevated temperatures, but the reaction will not go to completion in the absence of a zinc/chromia catalyst in any reasonable timescale.

Surprisingly, the inventors have found that zinc/chromia catalysts are effective at facilitating the one-pot conversion of 250fb and HF to 1243zf. In particular, the activity of the catalyst is believed to allow less forcing conditions (e.g. lower temperatures) compared to known (vapour phase) processes for producing 1243zf, whilst maintaining excellent conversion of 250fb and selectivity to 1243zf. The invention will now be illustrated by the following non-limiting Examples, with reference to the following drawings.

Figure 1 shows a plot of temperature against conversion/selectivity for an uncatalysed reaction of 1243zf and Cb;

Figure 2 shows a plot of temperature against conversion for a reaction performed by method according to the invention;

Figure 3 shows a plot of temperature against selectivity for a reaction performed by method according to the invention;

Figure 4 shows a chart comparing conversion at 200°C for reactions performed by methods according to the invention;

Figure 5 shows a chart comparing selectivity at 200°C for reactions performed by methods according to the invention;

Figure 6 shows plots of selectivity against temperature for reactions performed by methods according to the invention.

The catalysts used in the following examples were as follows:

TR1820 (Cu (10% as copper) on Alumina) - Engelhard Sample Code: B999-01 , 10% copper on alumina tablets.

Fe(N03)3.9H20 (1 % as iron) on Alumina (TR1823) - Impregnated as described below.

CuCl2 (1 % as copper) on Alumina (TR1823) - Impregnated as described below. CuCl2 (5% as copper) on Alumina (TR1823) - Impregnated as described below. CuCl2 (10% as copper) on Alumina (TR1823) - Impregnated as described below. CuCl2 (15% as copper) on Alumina (TR1823) - Impregnated as described below. FeCb (0.5% as iron) on Alumina (TR1823) - Impregnated as described below. FeCb (1 % as iron) on Alumina (TR1823) - Impregnated as described below.

FeCb (5% as iron) on Alumina (TR1823) - Impregnated as described below.

CuO/ZnO/AbOs (TR2624) - PRICAT® CZ 29/8T

CuO/ZnO/AbOs (TR2636) - PRICAT® CZ 40/18T

CuO/ZnO/AbOs (TR2633) - PRICAT® CZ 29/3T

NiO/AI203 (TR2628) - HTC 200 Ox - NiO content 10-25% Preparation Example 1 - Impregnation of TR1823

1. A loading percentage of transition metal was selected and the mass of the transition metal compound needed to impregnate a known amount of alumina was calculated

2. This was weighed out into a conical flask and diluted with deionised water (20ml)

3. Alumina (BASF Al 3992 E 1/8" aluminium oxide) was added and the contents mixed well and left to stand for 4-5 hours

4. The contents were then left to dry in the oven (80°C) overnight.

The reaction was also performed with an empty tube and support mesh to ensure that the observed reaction was catalytically rather than thermally induced. All examples were carried out at atmospheric pressure. Example 1 - Empty Tube Reaction

This reaction was conducted in the absence of a catalyst in order to ascertain the level of background thermal chlorination. Glass lined reactor tubes were placed in the reactor. The chlorine gas flow and flow of 1243zf was then set.

The results obtained are shown in Table 1 and Figure 1. As expected, very little conversion of 1243zf->243db was observed in the absence of a catalyst. Nevertheless some conversion was observed and it did increase with temperature. Therefore, the level of any background thermal chlorination needs to be considered when evaluating catalytic result.

Table 1 : Blank Glass-lined Reactor with 2.25: 1 mix of chlorine and 1243zf

Example 2 - Alumina Catalyst

Glass lined reactor tubes were placed in the reactor. In each tube the alumina catalyst (7ml, 4.1g) (TR1823) was held in place with a small plug of Inconel mesh. The catalyst was then dried in the reactor tube overnight at 200°C under flowing nitrogen (60ml/min). The chlorine gas flow was then set and the catalyst was pre-treated with it for 10 minutes prior to commencing the 1243zf feed. A nitrogen purge (Flow = 60ml/min) was used at the exit of the reactor to ensure that the relatively heavy 243db product did not condense. The reactor off-gases were scrubbed through water prior to sampling and GC analysis.

The results obtained are shown in Tables 2 to 5 and Figures 2 and 3.

Table 2: TR1823 with 1 :2 mix of chlorine and 1243zf and a space velocity of 148h ^"1

Table 3: TR1823 with 2:1 mix of chlorine and 1243zf and a space velocity of 148h ^"1

Table 4: TR1823 with 4:1 mix of chlorine and 1243zf and a space velocity of 122.6h ^"1

Table 5: TR1823 with 2.25: 1 mix of chlorine and 1243zf and a space velocity of 58h ^"1

The results show that the conversion of 1243zf increases

• With temperature

• As the ratio of Cl2: 1243zf increases

• As the space velocity reduces Selectivity to 243db also seemed weakly dependent on space velocity but was strongly affected by temperature and reducing sharply over 225°C.

Based on these initial results it was decided to limit the reaction temperature to less than 250 ^° C, use a 2.25: 1 mix of chlorine and 1243zf at space velocities of less than 100 h ^"1 . Under these conditions it was hoped that good conversion would be achieved at high selectivity and any differences in the effectiveness of the various catalysts would be clearly apparent. Example 3 - Alumina Supported Transition Metal Catalysts

Glass lined reactor tubes were placed in the reactor. In each tube, either TR1820 (Cu (10%) on alumina) (7ml, 6.3g), FeCI ₃ (1 %) on TR1823 (7ml, 4g) or Fe(N0 ₃ )39H ₂ 0 (1 %) on TR1823 (7ml, 4g) was held in place with a small plug of Inconel mesh. The catalyst samples were then dried in the reactor tubes overnight at 200°C under flowing nitrogen (60ml/min). The chlorine gas flow was then set and the catalyst was pre-treated with it for 10 minutes prior to commencing the 1243zf feed. A nitrogen purge (Flow = 60ml/min) was used at the exit of the reactor to ensure that the relatively heavy 243db product did not condense. The reactor off-gases were scrubbed through water prior to sampling and GC analysis.

The results obtained are shown in Tables 6 to 8 and Figures 4 and 6.

Table 6: TR1820 (10% Cu on alumina) with 2.25: 1 mix of chlorine and 1243zf and a space velocity of 58h ^"1

Table 7: FeCb (1 %) on TR1823 with 2.25: 1 mix of chlorine and 1243zf and a space velocity of 58h ^"1

Table 8: Fe(N0 ₃ )3.9H ₂ 0 (1 %) on TR1823 with 2.25: 1 mix of chlorine and 1243zf and a space velocity of 58h ^"1

When comparing the alumina supported transition metal catalyst with alumina TR1823 at 200°C the results clearly show:

• Increased activity towards conversion of 1243zf->243db

• Increased selectivity towards 243db

Example 4. - Low temperature reaction on Alumina supported transition metals

A glass lined reactor tube was placed in the reactor. 7ml, 6.3g of TR1820 (10% Cu on alumina), was held in place with a small plug of glass wool. The catalyst samples were then dried in the reactor tubes overnight at 200°C under flowing nitrogen (60ml/min). The chlorine gas flow was then set and the catalyst was pre-treated with it for 10 minutes prior to commencing the 1243zf feed. A nitrogen purge (Flow = 60ml/min) was used at the exit of the reactor to ensure that the relatively heavy 243db product did not condense. The reactor off-gases were scrubbed through water prior to sampling and GC analysis.

The results obtained are shown in Table 9 Table 9: TR1820 (10% Cu on alumina) with 2.25: 1 mix of chlorine and 1243zf and a space velocity of 58h ^"1

Results clearly show that selectivity decreases with increasing temperature. Example 5. Effect of varying metal loading on alumina

Glass lined reactor tubes were placed in the reactor. In each tube, either TR1820 (10% Cu on alumina) (7ml, 6.3g), Cu (1-20%) on TR1823 or FeC (0.1-5%) on TR1823 (7ml, 4g) was held in place with a small plug of Inconel mesh. The catalyst samples were then dried in the reactor tubes overnight at 200°C under flowing nitrogen (60ml/min). The chlorine gas flow was then set and the catalyst was pre-treated with it for 10 minutes prior to commencing the 1243zf feed. A nitrogen purge (Flow = 60ml/min) was used at the exit of the reactor to ensure that the relatively heavy 243db product did not condense. The reactor off-gases were scrubbed through water prior to sampling and GC analysis.

The results obtained are shown in Table 10.

Table 10: Metal impregnated Alumina-TR1820 with 2.25: 1 mix of chlorine and 1243zf and a space velocity of 58h ^"1

The addition of a transition metal to the alumina improves the 243db selectivity, a higher loading further improves the selectivity, this is more pronounced at 100°C.

Example 6. Stability of Alumina and Alumina Supported Transition Metal Catalysts.

Glass lined reactor tubes were placed in the reactor. In each tube, either Alumina TR1823 (7ml,) 10% Copper on Alumina TR1823 or 1 %FeCI ₃ on Alumina TR1823 was held in place with a small plug of glass wool. The catalyst samples were then dried in the reactor tubes overnight at 200°C under flowing nitrogen (60ml/min). The chlorine gas flow was then set and the catalyst was pre-treated with it for 10 minutes prior to commencing the 1243zf feed. A nitrogen purge (Flow = 60ml/min) was used at the exit of the reactor to ensure that the relatively heavy 243db product did not condense. The reactor off-gases were scrubbed through water prior to sampling and GC analysis.

The reaction was controlled at 80°C with 2.25: 1 mix of chlorine and 1243zf and a space velocity of 58h ^"1 The results are shown in Tables 11-13. Results

Table 11 Alumina TR1823 + 1% Fe

Table 13 TR1820 (10% Cu on Alum

All three catalysts were stable during the 89 hour run time. Example 7 - Mixed Metal Oxide Catalysts

Glass lined reactor tubes were placed in the reactor. In each tube the a catalyst was held in place with a small plug of Inconel mesh. The catalysts were selected from CuO/ZnO/AI ₂ 0 ₃ (7ml, 6.0g) (TR2624), NiO/AI ₂ 0 ₃ (TR2628), CuO/ZnO/AI ₂ 0 ₃ (TR2633) and CuO/ZnO/Ai203/CuC0 ₃ (OH) (TR2636). The catalyst was then dried in the reactor tube overnight at 200°C under flowing nitrogen (60ml/min). The chlorine gas flow was then set and the catalyst was pre-treated with it for 10 minutes prior to commencing the 1243zf feed. A nitrogen purge (Flow = 60ml/min) was used at the exit of the reactor to ensure that the relatively heavy 243db product did not condense. The reactor off-gases were scrubbed through water prior to sampling and GC analysis.

The results obtained are shown in Table 14

Table 14: Mixed metal oxide catalysts with 4:1 mix of chlorine and 1243zf and a space velocity of 1 11 h ^"1

Example 8. Stability of Alumina Supported Transition Metal Catalyst.

A glass lined reactor tube was placed in the reactor. The catalyst TR1820 (10% Cu on alumina) was held in place with a small plug of glass wool. The catalyst was dried overnight at 200°C under flowing nitrogen (60ml/min). The chlorine gas flow was then set and the catalyst pre-treated for 10 minutes prior to commencing the 1243zf feed. A nitrogen purge (Flow = 60ml/min) was used at the exit of the reactor to ensure that the relatively heavy 243db product did not condense. The reactor off-gases were scrubbed through water prior to sampling and GC analysis. The reaction was controlled at 80°C with 4: 1 mix of chlorine and 1243zf and a space velocity of 11 1 h ^"1

After continuous running for 447 h, the conversion and selectivity had dropped to 90.6 and 92.2 % respectively. The catalyst was then subjected to a regeneration step as follows; the chlorine and 1243zf feeds were turned off and the reactor temperature increased to 360°C and the catalyst treated with a mixture of flowing nitrogen (80ml/min) and air (20ml/min) for 10h. After this time the reactor was cooled to 80°C and the air/nitrogen mixture ceased. The chlorine gas flow was then set and the catalyst was pre-treated with it for 10 minutes prior to re-commencing the 1243zf feed. The reaction was controlled at 80°C with 4: 1 mix of chlorine and 1243zf and a space velocity of 11 1 h ¹ for another 644 h and found to be more stable than prior to regeneration. The catalyst maintained conversion and selectivity at an average of 99.5 and 96.3% respectively.

The results before and after regeneration are shown in Figure 7.

Example 9. The effect of the composition of the reaction vessel on the chlorination of 3,3,3-trifluoropropene (1243zf).

In view of the background chlorination that occurred during the empty reactor tube experiment (Example 1), a comparative reaction was ran to investigate whether the material of the reaction vessel in which the 3,3,3-trifluoropropene (1243zf) was contacted with chlorine, had any influence on the chlorination reaction.

Inconel® and stainless steel reactor tubes were each placed in the reactor. The chlorine gas flow and flow of 1243zf was then set.

The results obtained are shown in Table 15.

Table 15: Blank Reactors with 2.25: 1 mix of chlorine and 1243zf

The results obtained indicate that conducting the chlorination reaction within vessels that comprise nickel, such as Inconel, appear to have a greater positive effect on the chlorination than conducting the reaction within vessels such as stainless steel.

A further example was performed to investigate whether the advantageous effect on the chlorination reaction seen in the empty reaction vessels was also seen when conducting the chlorination reaction in the presence of a catalyst. Reactor tubes comprising the materials defined in Table 17 below were placed in the reactor. The catalyst TR1820 (10% Cu on alumina) was held in place with a small plug of glass wool. The catalyst was dried overnight at 200°C under flowing nitrogen (60ml/min). The chlorine gas flow was then set and the catalyst pre-treated for 10 minutes prior to commencing the 1243zf feed. A nitrogen purge (Flow = 60ml/min) was used at the exit of the reactor to ensure that the relatively heavy 243db product did not condense. The reactor off-gases were scrubbed through water prior to sampling and GC analysis.

The reaction was controlled at 80°C with 4: 1 mix of chlorine and 1243zf and a space velocity of 11 1 h ¹ . The results obtained are shown in Table 16.

Table 16: TR1820 (10% Cu on Alumina) with 4: 1 mix of chlorine and 1243zf and a space velocity of 11 1 h ^"1 .

It appears from these results that while glass lined reaction vessels provide the best yield of 243db, though stainless steel and in particular Inconel® each providing acceptable alternatives. This may be of particular interest when selecting materials to build larger reaction vessels, including for commercial scale production.

Example 10

Glass lined reactor tubes were placed in the reactor. In each tube a N1O/AI2O3 catalyst (7ml, 5.4g) (TR2628) was held in place with a small plug of Inconel mesh. The catalyst was then dried in the reactor tube overnight at 200°C under flowing nitrogen (60ml/min). The chlorine gas flow was then set and the catalyst was pre-treated with it for 10 minutes prior to commencing the 1243zf feed. A nitrogen purge (Flow = 60ml/min) was used at the exit of the reactor to ensure that the relatively heavy 243db product did not condense. The reactor off-gases were scrubbed through water prior to sampling and GC analysis. The results obtained are shown in Table 17 Table 17: NiO/AI ₂ 0 ₃ (TR2628) with 4: 1 mix of chlorine and 1243zf and a space velocity of

Example 1 1

6g (4.8ml) catalyst (TR2624 Cu/Zn on Alumina - whole pellets) were charged to a 0.5inch Inconel reactor tube on a high pressure rig. The catalyst composition was: 46.6% CuO /

The catalyst was dried over with Nitrogen (80ml/min), 16hours at 250°C and 2 Barg, then pre-chlorinated with Chlorine (5mls/min) for 4 hours at 200°C and 2Barg. Chlorine (17.5ml/min) and 1243zf (3-7ml/min) were co-fed over the catalyst at 2Barg and 100°C for 300 hours (Cl2: 1243zf ratio of 2.5: 1 to 6: 1) with good activity, selectivity and stability (contact time 25 seconds). The reactor off-gases were scrubbed through water prior to sampling and GC analysis. The results obtained are shown in Table 18.

Table 18:

Example 12 - Effect of 1243zf:CI ₂ Ratio

A Glass lined reactor tube containing CuO/ZnO/AI ₂ 0 ₃ catalyst (2ml, 1.5 g) (TR2624) held in place with a small plug of Inconel mesh was placed inside the heating block of the test apparatus. The catalyst was then dried in the reactor tube overnight at 200°C under flowing nitrogen (60ml/min). The reactor was then cooled to 80°C. The chlorine gas flow was then set and the catalyst was pre-treated with it for 10 minutes prior to commencing the 1243zf feed. A nitrogen purge (Flow = 60ml/min) was used at the exit of the reactor to ensure that the relatively heavy 243db product did not condense. The reactor off-gases were scrubbed through water prior to sampling and GC analysis.

The results obtained with varying 1243zf:Cl2 ratios are shown in Table 19. In these experiments selectivity to the desired product 243db was excellent, typically greater than 99 % and more often 100 %.

Table 19:

Preferences and options for a given aspect, feature 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.