WO2016132111A1

WO2016132111A1 - Process for the preparation of tetrafluoropropene

Info

Publication number: WO2016132111A1
Application number: PCT/GB2016/050374
Authority: WO
Inventors: Andrew Paul Sharratt; Maxine DORAN; Emma Jayne HODGSON; James Henry Murray; Stephen Flaherty
Original assignee: Mexichem UK Ltd; Mexichem Fluor SA de CV
Current assignee: Mexichem UK Ltd; Mexichem Fluor SA de CV
Priority date: 2015-02-19
Filing date: 2016-02-16
Publication date: 2016-08-25
Anticipated expiration: 2017-08-19
Also published as: GB2535512A; GB201502814D0

Abstract

A process for producing at least one tetrafluoropropene, the process comprising (i) converting Z-1233zd to TFMA in the presence of at least one base, wherein the process is conducted in the presence of water, and (ii) contacting the TFMA produced in step (i) with hydrogen fluoride (HF) in the presence of a Lewis acid metal halide catalyst to produce reaction product comprising at least one tetrafluoropropene.

Description

PROCESS FOR THE PREPARATION OF TETRAFLUOROPROPENE

This invention relates to a process for preparing a tetrafluoropropene. In particular, the invention relates to a process for producing a tetrafluoropropene from Z-1-Chloro-3,3,3- trifluoropropene (Z-1233zd) via trifluoromethyl acetylene (TFMA).

Products with reduced Global Warming Potential (GWP) based on hydrofluoroolefins (HFOs) are starting to replace hydrofluorocarbons (HFCs) for many applications. In particular, the demand for the hydrofluoroolefins 2,3,3,3-tetrafluoropropene (1234yf) and 1 ,3,3,3-tetrafluoropropene (1234ze) is expected to grow significantly in the future.

1-Chloro-3,3,3-trifluoropropene (R-1233zd) is a useful blowing agent. However, of the two isomers of R-1233zd, typically only E-1233zd is used. Processes for the production of R- 1233zd typically provide both isomers. Therefore, there is a significant amount of Z- 1233zd generated that is not used. Z-1233zd can be converted into trifluoromethyl acetylene (TFMA). TFMA is a useful intermediate in the production of (hydro)halocarbons, such as tetrafluoropropenes, which have been identified as potential replacements for saturated fluorocarbons and other hydrohalocarbons in many applications. In particular, TFMA may be useful as an intermediate in the production of 1234yf and/or 1234ze.

It would therefore be advantageous to provide a process that utilises Z-1233zd in a process to produce at least one tetrafluoropropene.

The present invention provides a process for the preparation of a tetrafluoropropene from Z-1233zd. The process comprising (i) converting Z-1233zd to TFMA in the presence of at least one base, wherein the process is conducted in the presence of water, and (ii) contacting the TFMA produced in step (i) with hydrogen fluoride (HF) in the presence of a Lewis acid metal halide catalyst to produce a reaction product comprising at least one tetrafluoropropene.

Typically, in step (i) of the process of the invention, Z-1233zd is converted to TFMA by adding at least one base to Z-1233zd, wherein the process is conducted in the presence of water. For example, in step (i) of the process of the invention, the at least one base may be added to an aqueous solution of Z-1233zd or an aqueous solution of the at least one base may be added to Z-1233zd or an aqueous solution of the at least one base may be added to an aqueous solution of Z-1233zd.

Alternatively, in step (i) of the process of the invention, an aqueous solution of Z-1233zd may be added to the at least one base or Z-1233zd may be added to an aqueous solution of the at least one base or an aqueous solution of Z-1233zd may be added to an aqueous solution of the at least one base.

Examples of methods in step (i) in which the at least one base or Z-1233zd may be added to the process include, but are not limited to, using a dropping funnel or a syringe. At industrial scale, the Z-1233zd can be introduced into the process in any known manner, for example under gravity, pumping or as a vapour following evaporation.

Typically, in step (i) of the process of the invention, the at least one base or Z-1233zd are added to the reaction in a controlled manner. Examples of controlled addition include, but are not limited to, the use of a dropping funnel or a syringe pump.

Step (i) of the process of the present invention may typically comprise:

a) introducing Z-1233zd to a reactor;

b) adding at least one base; and

c) removing the product TFMA.

The product TFMA can be removed from the reactor for purification before step (ii), or passed directly to step (ii) without purification. Alternatively, the TFMA may be stored for use in step (ii) in the future. If purification of the TFMA is required this can be done before or after storage.

Typically, in step (i) of the process of the invention, Z-1233zd and/or the at least one base are added to the reaction in the form of an aqueous solution.

Step (i) of the process of the invention may be conducted in the vapour and/or liquid phase. Preferably, step (i) in the process is conducted in the liquid phase.

By the term "in the presence of water" we mean that the reaction is conducted using water as a solvent. Typically, in step (i), water is present as the only solvent, such that Z-1233zd and/or the at least one base are added to the process in the form of an aqueous solution. However, it is to be appreciated that other solvents may be present so long as they do not interfere with the process of the invention.

Step (i) of the process of the invention may be conducted in the absence of alcohol, for example in the absence of methanol.

It has been surprisingly found by the present inventors, that when step (i) of the process of the invention is conducted in the absence of methanol, the formation of the by-product 1-methoxy-3,3,3-trifluoropropene, can be avoided.

As used herein, the term "water" encompasses water that may also comprise suspended and/or dissolved compounds or compositions. To avoid possible problems of contamination it may be considered desirable to use purified water, for example distilled water or deionised water.

Typically, in step (i) of the process of the invention, a phase transfer catalyst is not present. It has been found by the present inventors, that when the process of the invention is conducted in the absence of phase transfer catalyst, the formation of polymers of Z-1233zd and/or TFMA can be avoided, resulting in an increase in the conversion of Z-1233zd to TFMA.

Step (i) of the process of the invention may typically be conducted at a temperature of from about -100 to about 100 °C, such as from about -50 to about 70 °C or -10 to about 50 °C, e.g. from about 0 to about 60 °C or about 20 to about 40 °C.

Step (i) of the process of the invention may typically be conducted at a pressure of from about 0 to about 30 bara (3 MPa), such as from about 0.1 (0.001 MPa) to about 20 bara (2 MPa) or from about 0.5 (0.005 MPa) to about 10 bara (1 MPa), e.g. from about 1 (0.01 MPa) to about 5 bara (5 MPa).

Step (i) of the process of the invention may typically be conducted over a period of from about 1 to about 10 hours, such as from about 2.5 to about 7.5 hours, or about 5 hours.

Step (i) of the process of the invention may typically convert from about 80 to about 100% Z-1233zd to TFMA, for example from about 85 to about 95%, with from about 90 to about 100% selectivity for TFMA, such as from about 90 to about 95%. Step (i) of the process of the invention may typically 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 (i) of the process of the invention may be conducted using an autoclave and a cold trap, such as a Whitey bomb in a dry ice/acetone bath. Preferably, this apparatus and any other apparatus described herein is made from one or more materials that are resistant to corrosion, e.g. Hastelloy® or Inconel®.

In step (i) of the process of the invention, the TFMA product may typically be removed as it is formed. For example, the TFMA product may be continually removed via a cold trap, such as a Whitey bomb in a dry ice/acetone bath.

The process may be carried out batch-wise or continuously. Any suitable base may be used in step (i). Suitable bases include, but are not limited to alkali metal bases and alkali earth metal bases. For example, the at least one base may be selected from the group consisting of LiOH, NaOH, KOH and combinations thereof.

Typically, in step (i), the molar ratio of at least one base:Z-1233zd 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 2: 1 , preferably with excess base, or at least 1 :1.

The Z-1233zd used for this invention can be produced by any known means, for example by hydrofluorination of 1 ,1 ,1 ,3,3-pentachloropropane or 1 ,1 ,3,3-tetrachloropropene in the presence or absence of a catalyst.

Accordingly, the present invention provides a pre-step, wherein the Z-1233zd used in step (i) is prepared by hydrofluorinating 1 ,1 ,1 ,3,3-pentachloropropane or 1 ,1 ,3,3- tetrachloropropene in the presence or absence of a hydrofluorination catalyst to produce Z-1233zd. The Z-1233zd product may be fed directly into step (i) with or without further purification; or may be collected, optionally purified, and stored until required.

Suitable hydrofluorination catalysts for use in the pre-step described above include Lewis acids such as Lewis acid metal halides of Ti(IV), Ta(V), Sn(IV) and Sb(V). For example, the process of the invention may comprise a pre-step of hydrofluorinating 1 ,1 ,1 ,3,3-pentachloropropane or 1 ,1 , 3, 3-tetrachloropropene in the presence or absence of a hydrofluorination catalyst to produce Z-1233zd. The Z-1233zd produced in the pre-step may then be used in step (i). For example, the Z-1233zd produced may be converted to TFMA in a step in which the at least one base, such as KOH, is added to Z-1233zd in a controlled manner, for example by drop-wise addition, in the absence of a catalyst, such as a phase transfer catalyst, at a temperature of from about 20 to about 40 °C, wherein the TFMA product is continually removed from the process. In step (ii) of the process of the invention, TFMA is fluorinated to produce a reaction product comprising at least one tetrafluoropropene such as 1234yf and/or 1234ze.

In step (ii) of the process of the invention, TFMA is contacted with hydrogen fluoride (HF) in the presence of a fluorination catalyst.

In step (ii) of the process of the invention, Lewis acid metal halides are used. Examples of suitable supported (e.g. on carbon) or unsupported Lewis acid metal halides include, but are not limited to TaX₅, SbX₅, SnX₄, TiX₄, FeCI₃, NbX₅, VX₅, AIX₃ (wherein X = F or CI). Typically in step (ii), the catalyst metal is selected from the group consisting of Sb, Ta and Sn. For example, Sb(V) halides, such as SbFe or mixed chlorofluorides of Sb(V), such as SbCl3F₂ or any species represented by the formula SbCl_xF₅-x.

Step (ii) of 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.

Step (ii) of the process of the invention may be carried out batch-wise or continuously and in the gas or liquid phase. Preferably, step (ii) of the process of the invention is carried out in the liquid phase.

Step (ii) of the process of the invention may be conducted at a temperature of from about 25 to about 380 °C (e.g. from about 50 to about 350 °C) and may be carried out at a pressure of from about 5 to about 28 bara (e.g. about 10 to about 25 bara). Typically, in step (ii) of the process of the invention, the TFMA is contacted with the Lewis acid metal halide catalyst in the presence of HF for less than 600 minutes, preferably less than 400 minutes. Such as from about 150 to about 350 minutes, e.g. from about 200 to about 300 minutes. By choosing the right combination of reaction conditions, for example temperature and reaction time, the products of the reaction will comprise at least one tetrafluoropropene such as 1234yf and 1234ze in different ratios relative to each other.

In the process of the invention, steps (i) and (ii) may both be carried out in the liquid phase or both in the vapour phase. Alternatively, step (i) may be carried out in the liquid phase and step (ii) vapour phase, or vice versa. It is preferred that both step (i) and (ii) are conducted in the liquid phase.

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 reactions, respectively, as explained below. For example, step (i) is typically conducted in the absence of a catalyst, whereas a fluorination catalyst as previously described is used for step (ii).

Step (i) is conducted in the absence of HF, whereas a relatively high ratio of HF:TFMA can be used in step (ii). For example, a typical molar ratio of HF:TFMA 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 step (i). Thus, step (i) may be conducted at a temperature of from about -100 to about 100 °C, such as from about -50 to about 70 °C or -10 to about 50 °C, e.g. from about 0 to about 60 °C or about 20 to about 40 °C, whereas step (ii) may be conducted at a temperature of from about 25 to about 380 °C (e.g. from about 50 to about 350 °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).

It may, in some circumstances, be advantageous to purify the TFMA produced in step (i) before further reaction. Suitable methods for its purification include, but are not limited to, distillation, phase separation and contacting with adsorbents such as zeolites/aluminosilicates/molecular sieves, carbon, alumina, silica and the like. In the process of the invention step (i) is conducted as defined previously, the resulting TFMA may be transferred directly into step (ii) or purified before being transferred into step (ii), with any unreacted Z-1233zd optionally being recycled back into step (i). For example, Z-1233zd may be provided to a reactor in the liquid phase and at least one base, such as NaOH added, wherein the temperature is from about -100 to about 100 °C, the pressure is from about 0 to about 30 bara (3 MPa). The TFMA produced may be removed from the reactor and transferred in the liquid phase to a further reactor to be used in step (ii). Optionally, the TFMA may be passed through a suitable purification set up before being transferred to the reactor to be used in step (ii) with any unreacted Z-1233zd optionally being recycled back into step (i). The TFMA produced in step (i) may be provided to the reactor to be used in step (ii) in the liquid phase and contacted with HF in the presence of a Lewis acid metal halide catalyst to produce a reaction product comprising at least one tetrafluoropropene.

Typically, Step (i) and step (ii) of the process of the invention may be used together in an integrated process. In such a process, the TFMA formed in step (i) may be continually removed from the process of step (i), for example via a cold trap, such as a Whitey bomb in a dry ice/acetone bath and optionally purified and/or isolated prior to fluorination in step (ii). The TFMA removed from the process of step (i), may be transferred to a different reaction vessel or zone for conducting the hydrofluorination step (ii). The TMFA may be transferred directly to a different reaction vessel, i.e. may be transferred without being recovered from the reaction system or the TFMA may be recovered from the reaction and stored before being transferred to a different reaction vessel.

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

A Brief Description of the Figures

Figure 1 provides a graphic illustration of how the reaction of TFMA with HF proceeds with respect to time.

The invention will now be illustrated by the following non-limiting Examples. Example 1 - Production of TFMA in water (step (i))

Z-1233zd (20.2 g) in water (19.3 g) was charged to a 100 mL autoclave fitted with a condenser connected to a sample cylinder cooled by dry ice/acetone. The autoclave was stirred and heated to 38°C before adding 40% KOH solution (43.3 g) via syringe pump over 2 h. The mixture was heated for a further 3 h. Gaseous products (7.99 g) were collected in the cooled sample cylinder and analysed by GC showing 95.1 area % TFMA and 4.67 area % Z-1233zd. No organic layer was visible in the aqueous contents of the autoclave.

Comparative Example 2 - Production of TFMA in water/methanol (comparative (step (\)) Z-1233zd (20.4 g) in methanol (19.2 g) was charged to a 100 mL autoclave fitted with a condenser connected to a sample cylinder cooled by dry ice/acetone. The autoclave was stirred and heated to 38°C before adding 40% KOH solution (43.8 g) via syringe pump over 2 h. The mixture was heated for a further 3 h. Gaseous products (10.3 g) were collected in the cooled sample cylinder and analysed by GC showing 93.96 area % TFMA and 5.8 area % Z-1233zd. An organic layer (0.9 g) was isolated from the aqueous contents of the autoclave and analysed by GC showing 98.7 area % 1-methoxy-3,3,3- trifluoropropene.

Comparative Example 3 - Production of TFMA with phase transfer catalyst (comparative step ( ))

Z-1233zd (49.05 g) and Aliquat 336 (1.5 g) were charged to a 100 mL autoclave fitted with a condenser connected to a sample cylinder cooled by dry ice/acetone. The autoclave was stirred and heated to 30°C before adding 40% KOH solution (52.6 g) over 2 h. The mixture was heated for a further 2.5 h. Gaseous products (5.8 g) were collected in the cooled sample cylinder and analysed by GC showing 91.1 area % TFMA and 8.6 area % Z-1233zd. The aqueous contents of the autoclave contained sticky black polymerisation products.

Example 4 - Preparation of 1234vf and/or 1234ze from TFMA General procedure A Lewis acid metal halide catalyst would be weighed into a reactor vessel in a glovebox. The reactor would be removed from the glovebox and placed in a heating block and charged with HF. The contents would then be stirred at 200 rpm, heated to 50 °C and left for a specified time period. The contents would then be transferred to a Whitey cylinder containing water and the vapour analysed by GC to determine TFMA conversion. Example

If a reaction using TaFe was conducted as described in the general procedure, where the specified time was 200 minutes the conversion of TFMA would be approximately 62% with a yield of approximately 38% (0.38 mole fraction) R-1234ze, as shown in Figure 1.

Liquid phase methods:

Example 4.1

TaFs (5.5 g, 0.02 mol) was weighed into a 50 mL autoclave in a glovebox. The autoclave was removed from the glovebox and placed in a heating block, then charged with HF (20 g, 1 mol) and TFMA (7.9 g, 0.08 mol). The contents were then stirred at 200 rpm, heated to 50 °C and left for 20 hours. The contents were then transferred to a 500 mL sample cylinder containing 100 mL of water and the vapour analysed via GC resulting in 99.61 % conversion of TFMA in accordance with Figure 1.

Example 4.2

TaFs (5.5 g, 0.02 mol) was weighed into a 50 mL reactor vessel in a glovebox. The reactor was removed from the glovebox and placed in the heating block, then charged with HF (20.8 g, 1.04 mol) and TFMA (8.6 g, 0.09 mol). The contents were then stirred at 1000 rpm, heated to 50 °C and left for 20 hours. The contents were then transferred to a 500 mL Whitey cylinder containing 100 mL of water and the vapour analysed via GC resulting in 84.9% conversion of TFMA.

Example 4.3 Vapour phase method: 8.1 mis (10.3 g) fresh 5.2 % Zn/chromia (chromium (III) oxide) catalyst (designated TR1189) of particle size 2-3.65 mm was loaded into a reactor tube and pre-dried at 250°C, at 3 Barg for 24 hours under purge N₂=80 mls/min.

The dried catalyst was then activated (Pre-fluorinated) by treatment with hydrogen fluoride: N₂ = 80 mls/min HF = 4 mls/min 250°C <g ¾ 3 Barg for 24 hours

N₂ = 40 mls/min HF = 4 mls/min 250°C (£ ¾ 3 Barg for 2 hours

N₂ = 20 mls/min HF = 4 mls/min 250°C (∑ ¾ 3 Barg for 1 hours

N₂ = 10 mls/min HF = 4 mls/min 250°C (E § 3 Barg for 1 hour

N₂ = 5 mls/min HF = 4 mls/min 300°C (∑ § 3 Barg for 3 hours

N₂ = 0 mls/min HF = 4 mls/min 300°C tc ¾ 3 Barg for 3 hours

2: N₂ = 0 mls/min HF = 4 mls/min Temp ramped from 300°C - 380°C@25°C/hr Then held for 7 hours at 380°C @ 3 Barg before cooling to 25°C/hr to 150°C.

The results obtained across a range of conditions are shown below:

15

Claims

1. A process for producing at least one tetrafluoropropene, the process comprising:

(i) converting Z- 233zd to TFMA in the presence of at least one base, wherein the process is conducted in the presence of water, and

(ii) contacting the TFMA produced in step (i) with hydrogen fluoride (HF) in the presence of a Lewis acid metal halide catalyst to produce a reaction product comprising at least one tetrafluoropropene.

2. A process according to claim 1 , wherein in step (i) the at least one base is added to Z-1233zd.

3. A process according to claim 1 or 2, wherein in step (i) the at least one base is added to an aqueous solution of Z-1233zd or an aqueous solution of the at least one base is added to Z-1233zd or an aqueous solution of the at least one base is added to an aqueous solution of Z-1233zd.

4. A process according to claim 1 wherein step (i)comprises:

a) introducing Z-1233zd to a reactor;

b) adding at least one base to (i); and

c) removing the product TFMA.

5. A process according to claim 4, wherein the Z-1233zd and/or the at least one base are added to the process in the form of an aqueous solution.

6. A process according to any one of the preceding claims, wherein the TFMA product is continually removed from step (i).

7. A process according to any one of the preceding claims, wherein step (i) is conducted in the absence of methanol.

8. A process according to any one of the preceding claims, wherein step (i) is conducted in the absence of a phase transfer catalyst.

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

10. A process according to claim 9, wherein the temperature is from about -50 to about 70 °C or from about -10 to about 50 °C.

11. A process according to claim 10, wherein the temperature is from about 0 to about 60 °C or about 20 to about 40 °C.

12. A process according to any one of the preceding claims, wherein step (i) is conducted at a pressure of from about 0 to about 30 bara.

13. A process according to claim 12, wherein the pressure is from about 0.1 to about 20 bara or from about 0.5 to about 10 bara.

14. A process according to claim 13, wherein the pressure is from about 1 to about 5 bara.

15. A process according to any one of the preceding claims, wherein the molar ratio of base:Z-1233zd in step (i) is from about 10:1 to about 1 :10.

16. A process according to claim 15, wherein the ratio of base:Z-1233zd is from about 4:1 to about 1 :4.

17. A process according to claim 16, wherein the ratio of base:Z-1233zd is from about 3:1 to about 2:1.

18. A process according to any one of the preceding claims, wherein the Z-1233zd used in step (i) is prepared by

hhydrofluorinating 1 ,1 ,1 ,3,3-pentachloropropane or 1 ,1 ,3,3- tetrachloropropene in the presence or absence of a hydrofluorination catalyst to produce Z-1233zd.

19. A process according to any one of the preceding claims, wherein in step (ii) the Lewis acid metal halide catalyst comprises Sb, Ta or Sn.

20. A process according to claim 19, wherein the catalyst in step (ii) is a Sb(V) halide.

21. A process according to any one of the preceding claims, wherein the molar ratio of HF:TFMA in step (ii) is from about 1 :1 to about 100:1.

22. A process according to claim 21 , wherein the molar ratio of HF:TFMA is from about 3:1 to about 50:1.

23. A process according to any one of the preceding claims, wherein step (ii) is conducted at a temperature of from about 25 to about 380 °C.

24. A process according to claim 23, wherein the temperature is from about 50 to about 350 °C.

25. A process according to any one of the preceding claims, wherein step (ii) is conducted at a pressure of from about 5 to about 28 bara.

26. A process according to claim 25, wherein the pressure is from about 10 to about 25 bara.

27. A process according to any one of the preceding claims, wherein step (ii) is conducted in the liquid phase.

28. A process according to any one of the preceding claims, wherein the TFMA produced in step (i) is passed directly to step (ii).

29. A process according to any one of claims 1 to 28, wherein the TFMA produced in step (i) is purified before passing to step (ii).

30. A process according to any one of the preceding claims, wherein step (i) and step (ii) are conducted in the liquid phase.

31. A process according to any one of the preceding claims, wherein the at least one tetrafluoropropene is or comprises 1234yf and/or 1234ze.