# Patent

## Title
Process for making 1,3,3,3-tetrafluoropropene

## Abstract

The present invention describes a process for making CF3CH═CHF (HFO-1234ze). The process involves the addition of carbon tetrachloride (CCl4) to 1,2-dichloroethylene to form CCl3CHClCHCl2. The compound CCl3CHClCHCl2 thus can then either be treated with HF to produce CF3CHClCHClF as the main product, or it can be converted to CCl2═CHCHCl2 (1230za) by dechlorination. CCl2═CHCHCl2 can be treated with HF such that the main product obtained is CF3CHClCHClF. CF3CH═CHCl may be produced as a by-product, but upon treatment with HF, it affords the compound CF3CHClCHClF. The desired compound, CF3CH═CHF (HFO-1234ze), is obtained as a trans/cis mixture by dehydrochlorination of CF3CH2CHClF or by dechlorination of CF3CHClCHClF.

## Background
CROSS-REFERENCE TO RELATED APPLICATION
This application claims domestic priority under 35 U.S.C. 119(e) to commonly owned U.S. Provisional Application Ser. No. 61/598,531, filed 14 Feb. 2012, the disclosure of which is hereby incorporated herein by reference.


FIELD OF THE INVENTION
The present invention describes a process for making a tetrafluorinated propene compound. More specifically, the invention describes a process for making the compound 1,3,3,3-tetrafluoropropene (CF3CH═CHF, HFO-1234ze or 1234ze).
BACKGROUND OF THE INVENTION
The tetrafluoropropene compound HFO-1234ze, is a useful compound with low global warming potential. HFO-1234ze is useful in numerous applications including as a foam blowing agent, refrigerant, and as monomer for homopolymers and copolymers.
Several methods are known for the preparation of HFO-1234ze. For example, U.S. Pat. No. 6,548,719 describes the production of many fluoro-olefins including CF3CH═CHF from CF3CH2CF2H (245fa) by dehydrohalogenation in the presence of a phase transfer catalyst. U.S. Pat. Nos. 5,986,151 and 6,124,510 describe the gas phase catalytic dehydrofluorination of CF3CH2CF2H to afford CF3CH═CHF. These documents are hereby incorporated herein by reference.
Gas phase dehydrochlorination of CF3CH2CHFCl (244fa) is reported to give CF3CH═CHF as described in U.S. Pat. No. 7,829,748. Vapor phase fluorination of CF3CH═CHCl (1233zd) with HF and SbF5 catalyst affords HFO-1234ze along with 245fa and CHClF—CF2—CF3. See, for example, U.S. Pat. No. 7,829,748. This document is hereby incorporated herein by reference.
The main disadvantages of the above described methods are that in each case the starting materials, for example CF3CH2CF2H, typically need to be made by multiple reaction steps, and/or with relatively expensive raw materials, and thus there is a need to provide an improved process for the production of HFO-1234ze, at least from a cost effectiveness viewpoint.
Accordingly, the present invention has been developed, namely a process which utilizes relatively inexpensive and commercially available starting materials for making HFO-1234ze as detailed below.
SUMMARY OF THE INVENTION
The present invention is directed to a process for making CF3CH═CHF (HFO-1234ze). The process involves the addition of carbon tetrachloride to 1,2-dichloro-ethylene to form CCl3CHClCHCl2. The compound CCl3CHClCHCl2 can then either be treated with HF to produce CF3CHClCHClF as the main product, or it can be converted to CCl2═CHCHCl2 (HCC-1230za) by dechlorination. CCl2═CHCHCl2 can be treated with HF such that the main product obtained is CF3CHClCHClF.
CF3CH═CHCl may be produced as a by-product, but upon treatment with HF, it affords CF3CHClCHClF. The desired compound, CF3CH═CHF (HFO-1234ze), is obtained as a trans/cis mixture by dehydrochlorination of CF3CH2CHClF or by dechlorination of CF3CHClCHClF, respectively. These reactions are shown in the following schemes:

Scheme 1

CCl4+CHCl═CHCl→CCl3CHClCHCl2→CCl2═CHCHCl2  (1)

CCl2═CHCHCl2+4HF→CF3—CH2CHClF+4HCl  (2)

CF3CH2CHClF→CF3CH═CHF+HCl  (3)

Scheme 2

CCl4+CHCl═CHCl→CCl3CHClCHCl2  (4)

CCl3CHClCHCl2+4HF→CF3CHClCHClF+4HCl  (5)

CF3CHClCHClF+Zn→CF3CH═CHF+ZnCl2  (6)



DETAILED DESCRIPTION OF THE INVENTION
As described above, the process involves the addition of carbon tetrachloride (CCl4) to 1,2-dichloroethylene (trans, cis or a mixture) to form CCl3CHClCHCl2. The compound CCl3CHClCHCl2 can be either be fluorinated with HF such that the main product obtained is CF3CHClCHClF, or it can be converted to CCl2═CHCHCl2 (1230za) by dechlorination. CCl2═CHCHCl2 can be fluorinated with HF such that the main product obtained is CF3CHClCHClF. CF3CH═CHCl may be produced as a by-product, but upon treatment with HF, it affords CF3CHClCHClF. The desired compound, CF3CH═CHF (HFO-1234ze), is obtained as a trans/cis mixture by dehydrochlorination of CF3CH2CHClF or by dechlorination of CF3CHClCHClF.
Addition of CCl4 to CHCl═CHCl (trans, cis or mixture) can be conducted with a catalyst comprising, for example, a copper or ruthenium complex catalyst at about 80° C. to afford mainly CCl3CHClCHCl2, as described in J. Molecular Catalysis, 77, (1992) 51-60. Chlorotris(triphenylphosphine)rhodium can also be used as a catalyst instead of RuCl2(PPh3)3. Additionally, commercially available immobilized catalyst such as polymer bound RuCl(PPh3)3 also effects this addition.
The compound CCl3CHClCHCl2 is converted to CCl2═CHCHCl2 (1230za) via dechlorination with Zn. The reaction conditions can be optimized to afford CCl2═CHCHCl2 in good yield. It should be noted that CCl2═CHCHCl2 can also be obtained by pyrolysis of tetrachlorocyclopropane (see J. Chem. Soc. Section C (Organic), 1969, 165-172) or from polyhaloacrolein reacted with HCl and aluminum halides as described in Bulletin de la Societe Chimique de France 1963, 10, 2147-53.
The compound 1230za (CCl2═CHCHCl2) is fluorinated with HF (see U.S. Pat. No. 5,811,603 and PCT Publication No. WO 2010/059493A1) to afford CF3CH2CHClF (244fa) or CF3CH═CHCl (1233zd); the latter is readily converted to CF3CH2CHClF (see U.S. Patent Pub. No. 2011-0201853). Fluorination reactions are typically carried out with hydrogen fluoride, preferably anhydrous HF (AHF) and a fluorination catalyst. These catalysts are well known, and one can fine tune the reaction conditions to afford mainly the desired product CF3CH2CHClF. These documents are hereby incorporated herein by reference.
In the last step, dehydrochlorination of CF3CH2CHClF affords CF3CH═HF (HFO-1234ze). Alternately, any CCl3CHClCHCl2 formed can be fluorinated with HF to afford CF3CHClCHClF which can then be dechlorinated with zinc to afford HFO-1234ze.
Example 1
Addition of CCl4 to CHCl═CHCl
Into a clean, dry 1 L autoclave was added CHCl═CHCl (trans and/or cis) (24.0 g, 0.250 mol), carbon tetrachloride (400 mL) and RuCCl2(PPh3)3 (2.3 g, 2.5 mmol) under nitrogen purge. The sealed autoclave was then heated to and maintained at 80° C. for about 8 hours. The reaction mixture was filtered through silica gel pad and analyzed by GC which indicated greater than 80% conversion. The product CCl3CHClCHCl2 was isolated by distillation, and the yield ranged from 40% to 50% over three runs.
Example 1a
This reaction was conducted in the same manner as Example 1, except for the fact that chlorotris(triphenylphosphine)rhodium, RhCl(PPh3)3, was used instead of RuCl2(PPh3)3. The yield ranged from 35-55%.
Note that the reaction can also be conducted using an immobilized catalyst, for example, polymer bound RuCl(PPh3)3 which is commercially available.
Example 2
Conversion of CCl3CHClCHCl2 to CCl2═CHCHCl2 
To a heated (50° C. to 60° C.) mixture of zinc dust (25 mmol) and methanol (50 mL) was added CCl3CHClCHCl2 (50 mmol) drop-wise. The product, CCl2═CHCHCl2, formed was collected in a cold trap to afford 60% to 70% yield; the remaining product was CCl3CH═CHCl. The latter can be converted to CF3CH2CHClF with HF.
Example 3
Reaction of CCl3CHClCHCl2 with HF
The fluorination reaction was conducted in a Monel® tube reactor (2.54 cm diameter, 80 cm long). The reactor was charged with 150 g fluorination catalyst SbCl5 (or SbF5, or SbClxFy, where x+y=5) on activated carbon (Togo Colon PCB, 4×10 mesh) and heated to 85° C. as described in U.S. Pat. No. 7,829,748. Then, a mixture of vaporized CCl3CHClCHCl2 and anhydrous HF (about 1:10) was passed through the heated catalyst with a contact time of between 2 sec. to 10 sec. Contact time=bulk volume of catalyst/volumetric flow rate of reactants in ml/sec.
The flow rate of each reactant was controlled with a mass flow meter/controller in such a way that the contact time was in the range of 2 sec. to 10 sec. The effluent mainly consisted of CF3CHClCHClF. For example, with a contact time of 2 sec., at 60° C. to 70° C., the yield of CF3CHClCHClF ranged from 30% to 40% as determined by GC area; the remainder being by-products, CF3CHClCHF2 and CF3CHFCHF2; CF3CHClCHClF was separated by distilling (bp=71° C.).
Example 4
Reaction of HF with CCl2═CHCHCl2 
Fluorination of CCl2═CHCHCl2 was conducted as in Example 3. The main product obtained was CF3CH2CHClF along with CF3CH═CHCl (20% to 30%); the latter product formed can be converted to the former with more HF.
Example 5
Conversion of CF3CHClCHClF to CF3CH═CFH
Dechlorination of CF3CHClCHClF was accomplished as described in Example 2. Thus, 65% yield of HFO-1234ze (CF3CH═CHF) was obtained when 0.2 mol of CF3CHClCHClF was dechlorinated with Zn (0.11 mol) dust in methanol (50 mL) at 50° C. to 60° C.
Example 6
Dehydrochlorination of CF3CH2CHClF
Liquid Phase
Into a 0.5 L Teflon lined autoclave was charged 300 g of 20% aq. KOH solution, 1 g Aliquat 336 or 18-crown ether and 20 g CF3CH2CHClF. The contents in the autoclave were heated to and maintained at 50° C. to 55° C. for 6 hours. The progress of the reaction was monitored by GC. After 12 hours, the product HFO-1234ze (65% yield) was collected in a steel cylinder cooled at −78° C.
Vapor Phase
In a Monel tube reactor, 20 cc of acid treated (HCl or HNO3) activated carbon catalyst was loaded and heated to 350° C. to 370° C. Then vapor stream of CF3CH2CHClF at a rate about 6 g/h was passed through the heated catalyst bed in the reactor for from 1 hour to 8 hours. The conversion of 244fa ranged from 40% to 60% with a selectivity of HFO-1234ze greater than 95%. Further purification was accomplished by distillation.
Continuous Operation
Each of the reactions described above can be operated in either a batch mode or in a continuous mode. In a continuous operation mode the various reaction starting materials are continuously fed into the reactor at desired ratio. Catalyst and/or any other desired reaction additives can be added into reactor periodically or continuously, but the continuous mode is preferred. The reactions are preferably carried out at a residence time of from about 0.01 hours to about 24 hours, preferably from about 1 hour to about 12 hours. The reaction conditions are judicially selected for high reaction efficiency.
As used herein, the singular forms “a”, “an” and “the” include plural unless the context clearly dictates otherwise. Moreover, when an amount, concentration, or other value or parameter is given as either a range, preferred range, or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. Where a range of numerical values is recited herein, unless otherwise stated, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the invention be limited to the specific values recited when defining a range.
It should be understood that the foregoing description is only illustrative of the present invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances that fall within the scope of the appended claims.

## Claims

1. A process for making CF3CH═CHF comprising the steps of:
(a) converting 1,2-dichloroethylene to the compound CCl3CHClCHCl2 by an addition reaction with CCl4;
(b) converting CCl3CHClCHCl2 to the compound CCl2═CHCHCl2 by a dechlorination reaction;
(c) fluorinating the product of step (b) to form the compound CF3CH2CHClF; and
(d) dehydrochlorinating the product of step (c) to form the compound CF3CH═CHF.

2. The process of claim 1, wherein the reaction of step (a) is conducted with a catalyst.

3. The process of claim 2, wherein the catalyst comprises a copper catalyst.

4. The process of claim 2, wherein the catalyst comprises a ruthenium catalyst.

5. The process of claim 1, wherein the dechlorination reaction of step (b) is conducted using zinc.

6. The process of claim 1, wherein the fluorination reaction of step (c) is conducted with hydrogen fluoride and a fluorination catalyst.

7. The process of claim 6, wherein the hydrogen fluoride is anhydrous.

8. The process of claim 6, wherein the fluorination catalyst has the formula SbClxFy, where x+y=5.

9. The process of claim 6, wherein the fluorination catalyst comprises SbCl5.

10. The process of claim 6, wherein the fluorination catalyst comprises SbF5.

11. The process of claim 6, wherein the fluorination catalyst is supported on activated carbon.

12. The process of claim 1, wherein the dehydrochlorination reaction of step (d) is conducted in either the liquid phase or the gas phase, with a dehydrochlorination catalyst.

13. The process of claim 12, wherein the dehydrochlorination reaction is conducted in the liquid phase.

14. The process of claim 13, wherein the catalyst comprises an alkali metal hydroxide with a phase transfer catalyst.

15. The process of claim 14, wherein the alkali metal hydroxide comprises sodium hydroxide.

16. The process of claim 14, wherein the alkali metal hydroxide comprises potassium hydroxide.

17. The process of claim 12, wherein the dehydrochlorination reaction is conducted in the gas phase.

18. The process of claim 17, wherein the catalyst comprises acid treated activated carbon.

19. The process of claim 18, wherein the acid treatment is selected from HCl and HNO3.

20. The process of claim 17, wherein the dehydrochlorination reaction is conducted at a temperature range of from about 300° C. to 500° C.

21. The process of claim 17, wherein the dehydrochlorination reaction is conducted at a temperature range of from about 350° C. to 370° C.

22. A process for making CF3CH═CHF comprising the steps of:
(a) reacting carbon tetrachloride with 1,2-dichloroethylene to form the compound CCl3CHClCHCl2;
(b) fluorinating the compound CCl3CHClCHCl2 with HF to produce the compound CF3CHClCHClF; and
(c) dechlorinating CF3CHClCHClF to produce the compound CF3CH═CHF.

23. The process of claim 22, wherein the dechlorination reaction is conducted with zinc.

24. The process of claim 22, wherein a portion of the compound CCl3CHClCHCl2 is converted to the compound CCl2=CHCHCl2 (HCC-1230za) by a dechlorination reaction.

25. The process of claim 22, wherein a portion of the compound CCl3CHClCHCl2 is fluorinated with HF and a fluorination catalyst to afford the compound CF3CHClCHClF.

26. The process of claim 25, wherein the fluorination catalyst has the formula SbClxFy, where x+y=5.

27. The process of claim 26, wherein the fluorination catalyst comprises SbCl5.

28. The process of claim 26, wherein the fluorination catalyst comprises SbF5.

29. The process of claim 26, wherein the fluorination catalyst is supported on activated carbon.

30. The process of claim 24, further comprising the step wherein the compound CCl2═CHCHCl2 is fluorinated with HF and a fluorination catalyst to produce the compound CF3CHClCHClF.

31. The process of claim 30, further comprising the step wherein the dechlorination of CF3CHClCHClF affords the compound CF3CH═HF (HFO-1234ze).

32. The process of claim 22, wherein the dechlorination reaction also produces the compound CF3CH═CHCl as a by-product.

33. The process of claim 32, further comprising the step wherein the by-product compound CF3CH═CHCl is fluorinated with hydrogen fluoride and a fluorination catalyst to produce the compound CF3CHClCHClF.

34. The process of claim 1, wherein the reactions are conducted in a continuous manner.

35. The process of claim 22, wherein the reactions are conducted in a continuous manner.