Method for producing 1, 1-dichloro-2,2,3,3,3-pentafluoropropane

1. A method for producing 1,1-dichloro-2,3,3,3-tetrafluoropropene comprising contacting a mixture of dichloropentafluoropropane comprising 1,1-dichloro-2,2,3,3,3-pentafluoropropane with an aqueous alkali solution in the presence of a phase transfer catalyst, wherein said mixture of dichloropentafluoropropane is obtained by subjecting a starting material comprising one isomer or a mixture of at least two isomers of dichloropentafluoropropane and having a 1,1-dichloro-2,2,3,3,3-pentafluoropropane content of less than 60 mol %, to an isomerization reaction in the presence of a Lewis acid catalyst or a metal oxide catalyst so as to increase the 1,1-dichloro-2,2,3,3,3-pentafluoropropane content in the product to be higher than the content in the starting material.

2. The method of claim 1 , wherein said starting material comprises 1,3-dichloro-1,2,2,3,3-pentafluoropropane, and said 1,3-dichloro-1,2,2,3,3-pentafluoropropane is subjected to an isomerization reaction to form 1,1-dichloro-2,2,3,3,3-pentafluoropropane.

3. The method of claim 2 , wherein said starting material further comprises 2,2-dichloro-1,1,1,3,3-pentafluoropropane.

4. The method of claim 1 , wherein said isomerization reaction is carried out in a liquid phase in the presence of a Lewis acid catalyst at a temperature of from 0 to 150° C.

5. The method of claim 1 , wherein said isomerization reaction is carried out in a gas phase in the presence of a metal oxide catalyst at a temperature of from 50 to 500° C.

6. A method for producing 2,3,3,3-tetrafluoropropene, which comprises reacting the 1,1-dichloro-2,3,3,3-tetrafluoropropene obtained by the method as defined in claim 1 with hydrogen in the presence of a catalyst.

7. The method of claim 6 , wherein said 1,1-dichloro-2,3,3,3-tetrafluoropropene is reacted with hydrogen in the presence of a catalyst and an inert gas.

8. The method of claim 1 , wherein said aqueous alkali solution comprises at least one alkali selected from the group consisting of sodium hydroxide and potassium hydroxide.

9. The method of claim 1 , wherein said aqueous alkali solution has an alkali concentration of from 0.5 to 40 mass %.

10. The method of claim 1 , wherein an amount of said aqueous alkali solution is 0.5 to 1.5 mol equivalents to an amount of 1,1-dichloro-2,2,3,3,3-pentafluoropropane.

11. The method of claim 1 , wherein said phase transfer catalyst is at least one catalyst selected from the group consisting of a quaternary ammonium salt, a quaternary phosphonium salt substituted by a hydrocarbon group and a crown ether.

12. The method of claim 1 , wherein said phase transfer catalyst is in an amount of 0.0001 to 5 mass % to a mass of said 1,1-dichloro-2,2,3,3,3-pentafluoropropane.

13. The method of claim 1 , wherein dehydrofluorination is conducted.

14. The method of claim 1 , wherein dehydrofluorination is conducted at a temperature of from 0 to 80° C.

15. The method of claim 1 , wherein dehydrofluorination is conducted at a temperature of from 0 to 50° C.

16. The method of claim 1 , wherein said 1,1-dichloro-2,2,3,3,3-pentafluoropropane is selectively dehydrofluorinated.

17. The method of claim 1 , wherein a content of said 1,1-dichloro-2,2,3,3,3-pentafluoropropane is increased by at least 10 mol % relative to said starting material.

18. The method of claim 1 , wherein a content of said 1,1-dichloro-2,2,3,3,3-pentafluoropropane is increased by at least 30 mol % relative to said starting material.

19. The method of claim 3 , wherein a content of said 2,2-dichloro-1,1,1,3,3-pentafluoropropane in said starting material is decreased during said isomerization reaction.

20. The method of claim 1 , wherein a content of said 1,1-dichloro-2,2,3,3,3-pentafluoropropane in said product is from 78-80 mol %.

21. The method of claim 11 , wherein said mixture of dichloropentafluoropropane comprises 1,1-dichloro-2,2,3,3,3-pentafluoropropane, 1,3-dichloro-1,2,2,3,3-pentafluoropropane and 2,2-dichloro-1,1,3,3,3-pentafluoropropane and said 1,3-dichloro-1,2,2,3,3-pentafluoropropane and 2,2-dichloro-1,1,3,3,3-pentafluoropropane are not reacted by contacting with said aqueous alkali solution.

22. The method of claim 1 , wherein said mixture of dichloropentafluoropropane comprises 1,1-dichloro-2,2,3,3,3-pentafluoropropane and 2,2-dichloro-1,1,3,3,3-pentafluoropropane.