Process for producing hexafluoro-1,3-butadiene

1. A process for producing hexafluoro-1,3-butadiene comprising:

(1) a step comprising allowing a compound having four carbon atoms each which bonds to an atom selected from the group consisting of a bromine atom, an iodine atom and a chlorine atom, to react with a fluorine gas in the presence of a diluting gas in a gas phase, thereby preparing a mixture containing a product (A), and

(2) a step comprising eliminating halogens excluding a fluorine atom with a metal from the product (A) prepared in the step (1) in the presence of a solvent, thereby preparing a mixture containing hexafluoro-1,3-butadiene.

2. The process for producing hexafluoro-1,3-butadiene according to claim 1 wherein the step (1) comprises allowing a compound having four carbon atoms to react with a fluorine gas in the absence of a catalyst, thereby preparing a mixture containing the product (A).

3. The process for producing hexafluoro-1,3-butadiene according to claim 1 which process further comprises a step (3) of halogenating 1,3-butadiene, thereby preparing the compound having four carbon atoms wherein the step (1) comprises allowing the compound having four carbon atoms prepared in the step (3) to react with a fluorine gas, thereby preparing a mixture containing the product (A).

4. The process for producing hexafluoro-1,3-butadiene according to claim 1 wherein the diluting gas is at least one gas selected from the group consisting of nitrogen, helium, argon, neon and hydrogen fluoride.

5. The process for producing hexafluoro-1,3-butadiene according to claim 1 wherein the step (1) comprises allowing 1,2,3,4-tetrachlorobutane to react with a fluorine gas in the presence of a diluting gas in a gas phase, thereby preparing a mixture containing 1,2,3,4-tetrachlorohexafluorobutane, and the step (2) comprises dechlorinating the 1,2,3,4-tetrachlorohexafluorobutane prepared in the step (1) with a metal in the presence of a solvent, thereby preparing a mixture containing hexafluoro-1,3-butadiene.

6. The process for producing hexafluoro-1,3-butadiene according to claim 5 wherein the step (1) comprises allowing 1,2,3,4-tetrachlorobutane to react with a fluorine gas in a reactor (A) having at least two feed openings by feeding a mixed gas (A) of 1,2,3,4-tetrachlorobutane and the diluting gas from at least one feed opening and feeding a mixed gas (B) of a fluorine gas and the diluting gas from at least one of the other openings, thereby preparing a mixture containing 1,2,3,4-tetrachlorohexafluorobutane, and the concentration of 1,2,3,4-tetrachlorobutane is from 0.5 to 4% by mole based on the total amount of the mixed gases (A) and (B).

7. The process for producing hexafluoro-1,3-butadiene according to claim 5 wherein the step (1) comprises allowing 1,2,3,4-tetrachlorobutane to react with a fluorine gas in a reactor (A) having at least two feed openings by feeding a mixed gas (A) of 1,2,3,4-tetrachlorobutane and the diluting gas from at least one feed opening and feeding a mixed gas (B) of a fluorine gas and the diluting gas from at least one of the other openings, thereby preparing a mixture containing 1,2,3,4-tetrachlorohexafluorobutane, and the concentration of a fluorine gas is from 0.5 to 10% by mole based on the total amount of the mixed gases (A) and (B).

8. The process for producing hexafluoro-1,3-butadiene according to claim 5 wherein the step (1) comprises allowing 1,2,3,4-tetrachlorobutane to react with a fluorine gas at a pressure of from 0.05 to 1 MPa, thereby preparing a mixture containing 1,2,3,4-tetrachlorohexafluorobutane.

9. The process for producing hexafluoro-1,3-butadiene according to claim 5 wherein the step (1) comprises allowing 1,2,3,4-tetrachlorobutane to react with a fluorine gas at a temperature of from 50 to 500° C., thereby preparing a mixture containing 1,2,3,4-tetrachlorohexafluorobutane.

10. The process for producing hexafluoro-1,3-butadiene according to claim 1 or 5 wherein the solvent is an organic solvent and/or water.

11. The process for producing hexafluoro-1,3-butadiene according to claim 10 wherein the organic solvent is an alcohol.

12. The process for producing hexafluoro-1,3-butadiene according to claim 11 wherein the alcohol is at least one selected from the group consisting of methanol, ethanol, isopropyl alcohol and octanol.

13. The process for producing hexafluoro-1,3-butadiene according to claim 1 or 5 wherein the metal is at least one selected from the group consisting of Mg, Zn, Al, Cu, Na and Li.

14. The process for producing hexafluoro-1,3-butadiene according to claim 5 wherein the step (2) comprises dechlorinating the 1,2,3,4-tetrachlorohexafluorobutane prepared in the step (1), with a metal at a temperature of from 20 to 150° C., thereby preparing a mixture containing hexafluoro-1,3-butadiene.

15. The process for producing hexafluoro-1,3-butadiene according to claim 5 which further comprises:

a step (4) of liquid-liquid separating the mixture containing 1,2,3,4-tetrachlorohexafluorobutane prepared in the step (1) and allowing a resulting 1,2,3,4-tetrachlorohexafluorobutane-rich phase to contact with an alkali, thereby preparing crude 1,2,3,4-tetrachlorohexafluorobutane, and

a step (5) of dehydrating the crude 1,2,3,4-tetrachlorohexafluorobutane prepared in the step (4), thereby preparing crude 1,2,3,4-tetrachlorohexafluorobutane, wherein the step (2) comprises dechlorinating the crude 1,2,3,4-tetrachlorohexafluorobutane prepared in the step (5), with a metal, thereby preparing a mixture containing hexafluoro-1,3-butadiene.

16. The process for producing hexafluoro-1,3-butadiene according to claim 15 which further comprises a step (6) of feeding the crude 1,2,3,4-tetrachlorohexafluorobutane prepared in the step (5), to a distillation column, separating an intermediate in the step (1) and feeding at least a part of the intermediate to the reactor (A).

17. The process for producing hexafluoro-1,3-butadiene according to claim 5 which further comprises:

a step (7) of allowing the mixture containing the hexafluoro-1,3-butadiene prepared in step (2) to contact with an alkali, thereby preparing crude hexafluoro-1,3-butadiene, and

a step (8) of dehydrating the crude hexafluoro-1,3-butadiene prepared in the step (7), thereby preparing crude hexafluoro-1,3-butadiene.

18. The process for producing hexafluoro-1,3-butadiene according to claim 17 which further comprises a step (9) of purifying the crude hexafluoro-1,3-butadiene prepared in the step (8) by means of at least two distillation columns.

19. The process for producing hexafluoro-1,3-butadiene according to claim 18 wherein the step (2) comprises dechlorinating the 1,2,3,4-tetrachlorohexafluorobutane prepared in the step (1) with a metal in a reactor (B), thereby preparing a mixture containing hexafluoro-1,3-butadiene, and at least a part of a high boiling component taken out from a column bottom of the distillation column is fed to the reactor (B).