METHOD FOR SEPARATING HALOCARBONS

20100048961

12/540252

August 12, 2009

The invention provides a method for separating halocarbons. In particular, a method for separating 2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb) from 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) based on differences in melting points of these compounds. More particularly the invention pertains to a method for separating HCFC-244bb from HCFO-1233xf which are useful as intermediates in the production of 2,3,3,3-tetrafluoropropene (HFO-1234yf).

Merkel, Daniel C. (West Seneca, NY, US); Tung, Hsueh Sung (Getzville, NY, US); Pokrovski, Konstantin A. (Williamsville, NY, US)

1. A method for isolating a first halocarbon from a composition comprising a first halocarbon and at least one second halocarbon which is different from the first halocarbon, the method comprising cooling a composition comprising a first halocarbon and at least one second halocarbon at or below the freezing point of the first halocarbon but above the freezing point of the at least one second halocarbon.

2. The method of claim 1 wherein the first halocarbon is a fluorocarbon, hydrofluorocarbon, hydrofluoroolefin, chlorocarbon, hydrochlorocarbon, fluorochlorocarbon, hydrochlorofluorocarbon, hydrofluoroether or hydrochlorofluoroolefin, and the at least one second halocarbon is a different fluorocarbon, hydrofluorocarbon, hydrofluoroolefin, chlorocarbon, hydrochlorocarbon, fluorochlorocarbon, hydrochlorofluorocarbon, hydrofluoroether or hydrochlorofluoroolefin.

3. The method of claim 1 wherein the first halocarbon is a compound of the Formula (I) or Formula (II), and the at least one second halocarbon is a different compound of the Formula (I) or Formula (II) wherein: Formula (I) is a haloalkane having the formula CyHzX, wherein X=FaClbBrcId having one or more halogen atoms, or a combination of different halogen atoms independently selected from F, Cl, Br, I with the total number of halogen atoms equals to 2y+2−z; y is an integer of from 1 to 4; and z is an integer of from 0 to 9 such that z=2y+1; a, b, c, d are each an integer of from 1 to 10 and wherein a+b+c+d=2y+2−z; and Formula (II) is a haloalkene having the formula CyHzX, where X=FaClbBrcId one or more halogen atoms, or a combination of different halogen atoms independently selected from F, Cl, Br, I with the total number of halogen atoms equals to 2y−z; y is an integer of from 1 to 4; and z is an integer of from 0 to 7 such that z ranges from 0 to 2y−1; a, b, c, d are each an integer of from 1 to 8 and wherein a+b+c+d=2y−z.

4. The method of claim 1 wherein the first halocarbon and the different second halocarbon are each selected from 2-chloro-1,1,1,2-tetrafluoropropane; 2-chloro-3,3,3-trifluoropropene, trans 1,2-dichloroethylene, pentafluorobutane; pentafluoropropane; hexafluoropropane; heptafluoropropane; 1-chloro-1,2,2,2-tetrafluoroethane; and pentafluoroethane; 1,1-dichloro-1-fluoroethane (HCFC-141b) 1,1,2,2-tetrafluoroethane; 1,1,1,2-tetrafluoroethane; 1-chloro 1,1-difluoroethane; 1,1,1-trifluoroethane; 1,1-dichloro-2,2,2-trifluoroethane; 1,2-dichloro-1,2,2-trifluoroethane; 1,1,1,3,3-pentafluorobutane; 1,1,1,2,3,3,3-heptafluoropropane; trichlorofluoromethane, dichlorodifluoromethane; 1,1,1,3,3,3-hexafluoropropane; 1,1,1,2,3,3-hexafluoropropane; difluoromethane; chlorofluoromethane; difluoroethane; 1,1,1,3,3-pentafluoropropane (HFC-245fa); 1,1,1,2,3-pentafluoropropane; 1,1,1,2,2-pentafluoropropane, trifluoropropenes, pentafluoropropenes, chlorotrifluoropropenes, hydrofluoroethers, and tetrafluoropropenes including 1,3,3,3-tetrafluoropropene, 2,3,3,3-tetrafluoropropene, 1,2,3,3,3-pentafluoropropene, and 1-chloro-3,3,3-trifluoropropene.

5. The method of claim 1 wherein the first halocarbon and the at least one second halocarbon form an azeotrope or azeotrope-like composition.

6. The method of claim 1 wherein the first halocarbon and the at least one second halocarbon do not form an azeotrope or azeotrope-like composition.

7. The method of claim 1 wherein a temperature difference between the freezing point of the first halocarbon and the freezing point of the at least one second halocarbon is about 3° C. or more.

8. The method of claim 1 wherein the result of the cooling is the first halocarbon in solid form and the at least one second halocarbon in liquid or gaseous form.

9. The method of claim 8 further comprising the subsequent step of separating the liquid or gaseous second halocarbon from the solid first halocarbon.

10. The method of claim 9 wherein the separating is conducted by decantation, filtration, centrifuging, or outgassing under vacuum.

11. The method of claim 1 wherein the separating is conducted by decantation, filtration, centrifuging, or outgassing under vacuum.

12. The method of claim 1 wherein the cooling is conducted at a temperature of from about −150° C. to about 75° C.

13. The method of claim 1 wherein the cooling is conducted at a temperature of from about −130° C. to about 50° C.

14. The method of claim 1 wherein the cooling is conducted at a temperature of from about −120° C. to about 25° C.

15. The method of claim 1 wherein the first halocarbon is 2-chloro-1,1,1,2-tetrafluoropropane and the second halocarbon is 2-chloro-3,3,3-trifluoropropene.

16. The method of claim 1 wherein the 2-chloro-1,1,1,2-tetrafluoropropane and the 2-chloro-3,3,3-trifluoropropene form an azeotrope or azeotrope-like composition.

17. The method of claim 16 wherein the result of the cooling is solid 2-chloro-1,1,1,2-tetrafluoropropane and liquid or gaseous 2-chloro-3,3,3-trifluoropropene.

18. The method of claim 16 further comprising the subsequent step of separating 2-chloro-3,3,3-trifluoropropene from 2-chloro-1,1,1,2-tetrafluoropropane.

19. The method of claim 16 further comprising the subsequent step of separating liquid or gaseous 2-chloro-3,3,3-trifluoropropene from solid 2-chloro-1,1,1,2-tetrafluoropropane.

20. The method of claim 19 wherein the separating is conducted by decantation, filtration, centrifugation, degassation under vacuum.

21. The method of claim 16 wherein the cooling is conducted at a temperature of from about −85° C. to about −75° C.

22. The method of claim 16 wherein the cooling is conducted at a temperature of from about −81° C. to about −78° C.

23. A method for the production of 2,3,3,3-tetrafluoropropene which comprises (i) continuously reacting 2-chloro-3,3,3-trifluoropropene with hydrogen fluoride, in a liquid phase reaction, in the presence of a liquid phase fluorination catalyst to produce a composition comprising unreacted HF, unreacted 2-chloro-3,3,3-trifluoropropene, and 2-chloro-1,1,1,2-tetrafluoropropane; and then (ii) isolating an azeotrope or azeotrope-like composition of 2-chloro-1,1,1,2-tetrafluoropropane and 2-chloro-3,3,3-trifluoropropene; and then (iii) isolating 2-chloro-1,1,1,2-tetrafluoropropane from the azeotrope or azeotrope-like composition by cooling the azeotrope or azeotrope-like composition at or below the freezing point of 2-chloro-1,1,1,2-tetrafluoropropane but above the freezing point of 2-chloro-3,3,3-trifluoropropene; and then (iv) dehydrochlorinating the isolated 2-chloro-1,1,1,2-tetrafluoropropane under conditions effective to produce 2,3,3,3-tetrafluoropropene; and (v) optionally, recycling the isolated 2-chloro-3,3,3-trifluoropropene back to the reaction of step (i).

24. The method of claim 23 wherein step (v) is performed.

25. The method of claim 23 wherein step (v) is not performed.

570/160

07; 07

edspap.20100048961