Method for producing hexafluoro-1,3-butadiene

Abstract

Provided is a method for producing hexafluoro-1,3-butadiene, and the method can produce hexafluoro-1,3-butadiene at an industrially sufficient level of yield. In a reaction liquid containing a halogenated butane represented by chemical formula, CF.sub.2X.sup.1—CFX.sup.2—CFX.sup.3—CF.sub.2X.sup.4 (X.sup.1, X.sup.2, X.sup.3, and X.sup.4 are each independently a halogen atom other than a fluorine atom), zinc, and an organic solvent, a reaction is conducted to eliminate the halogen atoms other than a fluorine atom, X.sup.1, X.sup.2, X.sup.3, and X.sup.4, from the halogenated butane, yielding hexafluoro-1,3-butadiene. During the reaction, the concentration of a zinc halide generated by the reaction, in the reaction liquid is not more than the solubility of the zinc halide in the organic solvent.

Claims

1. A method for producing hexafluoro-1,3-butadiene, the method comprising: conducting a reaction, in a reaction liquid containing a halogenated butane represented by chemical formula CF.sub.2X.sup.1-CFX.sup.2-CFX.sup.3-CF.sub.2X.sup.4 (X.sup.1, X.sup.2, X.sup.3, and X.sup.4 are each independently a chlorine atom, a bromine atom or an iodine atom), zinc, and an organic solvent selected from the group consisting of an alcohol, a cyclic ether, acetone, acetonitrile, an aromatic hydrocarbon, an amide solvent, an organic acid, and a mixed solvent thereof, to eliminate X.sup.1, X.sup.2, X.sup.3, and X.sup.4, which are selected from the group consisting of the chlorine atom, the bromine atom and the iodine atom, from the halogenated butane, yielding hexafluoro-1,3-butadiene, wherein during the reaction, a concentration of a zinc halide generated by the reaction in the reaction liquid is not more than a solubility of the zinc halide in the organic solvent, and as the reaction proceeds, an organic solvent is added to the reaction liquid to reduce the concentration of the zinc halide in the reaction liquid.

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

3. The method for producing hexafluoro-1,3-butadiene according to claim 2, wherein the alcohol is at least one of methanol, ethanol, 1-propanol, and 2-propanol.

4. The method for producing hexafluoro-1,3-butadiene according to claim 2, wherein each of X.sup.1, X.sup.2, X.sup.3, and X.sup.4 is a chlorine atom.

5. The method for producing hexafluoro-1,3-butadiene according to claim 3, wherein each of X.sup.1, X.sup.2, X.sup.3, and X.sup.4 is a chlorine atom.

6. The method for producing hexafluoro-1,3-butadiene according to claim 1, wherein each of X.sup.1, X.sup.2, X.sup.3, and X.sup.4 is a chlorine atom.

7. A method for producing hexafluoro-1,3-butadiene, the method comprising: conducting a reaction, in a reaction liquid containing a halogenated butane represented by chemical formula CF.sub.2X.sup.1-CFX.sup.2-CFX.sup.3-CF.sub.2X.sup.4 (X.sup.1, X.sup.2, X.sup.3, and X.sup.4 are each independently a chlorine atom, a bromine atom or an iodine atom), zinc, and an organic solvent selected from the group consisting of an alcohol, a cyclic ether, acetone, acetonitrile, an aromatic hydrocarbon, an amide solvent, an organic acid, and a mixed solvent thereof, to eliminate X.sup.1, X.sup.2, X.sup.3, and X.sup.4, which are selected from the group consisting of the chlorine atom, the bromine atom and the iodine atom, from the halogenated butane, yielding hexafluoro-1,3-butadiene, wherein during the reaction, a concentration of a zinc halide generated by the reaction in the reaction liquid is not more than a solubility of the zinc halide in the organic solvent, and in the reaction, steps include: extracting a portion of the reaction liquid to provide an extraction liquid as the extracted reaction liquid, removing some or all of the dissolved zinc halide from the extraction liquid, and returning the extraction liquid from which the zinc halide has been removed to the original reaction liquid to reduce the concentration of the zinc halide in the reaction liquid.

8. The method for producing hexafluoro-1,3-butadiene according to claim 7, wherein the organic solvent is an alcohol.

9. The method for producing hexafluoro-1,3-butadiene according to claim 7, wherein each of X.sup.1, X.sup.2, X.sup.3, and X.sup.4 is a chlorine atom.

Description

EXAMPLES

(1) The present invention will next be described in further detail with reference to examples and comparative examples.

Example 1

(2) In an SUS 316 autoclave having an internal volume of 500 mL, 119 g of 2-propanol as an organic solvent and 82.4 g of granular metal zinc were placed. The autoclave had a jacket with a cooling structure and a stirrer at the upper part, and the heating system was a jacket heating system.

(3) While the content in the autoclave was stirred, the temperature was increased to 70° C. To the outlet of the autoclave, a Dimroth condenser was attached. While the content in the autoclave was maintained at a temperature of 70° C. under normal pressure, 149 g of 1,2,3,4-tetrachlorohexafluorobutane was added dropwise at a drop rate of 9.31 g per hour and was reacted. After 10 hours of dropwise addition, 100 g of 2-propanol was further added to the content, and the dropwise addition of 1,2,3,4-tetrachlorohexafluorobutane was further continued.

(4) After completion of the dropwise addition for 16 hours in total, the reaction was conducted for 2 hours while the temperature of the content was maintained at 70° C. During the reaction, no precipitation of zinc chloride from the content in the autoclave was observed.

(5) After completion of the reaction for 2 hours, the reaction product was further heated to a temperature around the boiling point of 2-propanol, thus a portion of the organic solvent (2-propanol) and the product were vaporized, and the vapor of them was cooled, liquified, and collected by using a trap cooled by a mixture of dry ice and ethanol. The crude yield was then calculated from the collected product to be 99%. The collected product was analyzed by gas chromatography, and the yield of hexafluoro-1,3-butadiene was 90%.

(6) In the description, the crude yield and the yield are defined by the following formulae.
Crude yield (%)=[(mass of collected product liquified and collected])/(mass when charged HFTCB is completely converted into hexafluoro-1,3-butadiene)]×100
Yield (%)=(the above crude yield)×(content percentage of hexafluoro-1,3-butadiene in collected product determined by GC analysis)

Example 2

(7) In an SUS 316 autoclave having an internal volume of 500 mL, 119 g of 2-propanol as an organic solvent and 82.4 g of granular metal zinc were placed. The autoclave had a jacket with a cooling structure and a stirrer at the upper part, and the heating system was a jacket heating system.

(8) While the content in the autoclave was stirred, the temperature was increased to 70° C. While the content in the autoclave was maintained at a temperature of 70° C. under normal pressure, 149 g of 1,2,3,4-tetrachlorohexafluorobutane was added dropwise at a drop rate of 9.31 g per hour and was reacted. In the reaction, the following operation was performed: a portion of the content (reaction liquid) was extracted from the autoclave and was cooled to room temperature to precipitate the dissolved zinc chloride, thus 127 g of zinc chloride was removed from the content, and the residual content was returned into the autoclave. After completion of the dropwise addition of 1,2,3,4-tetrachlorohexafluorobutane for 16 hours in total, the reaction was conducted for 2 hours while the temperature of the content was maintained at 70° C. During the reaction, no precipitation of zinc chloride from the content in the autoclave was observed.

(9) After completion of the reaction for 2 hours, the reaction product was further heated to a temperature around the boiling point of 2-propanol, thus a portion of the organic solvent (2-propanol) and the product were vaporized, and the vapor of them was cooled, liquified, and collected by using a trap cooled by a mixture of dry ice and ethanol. The crude yield was then calculated from the collected product to be 99%. The collected product was analyzed by gas chromatography, and the yield of hexafluoro-1,3-butadiene was 92%. The crude yield and the yield are as defined above.

Comparative Example 1

(10) In an SUS 316 autoclave having an internal volume of 500 mL, 119 g of 2-propanol as an organic solvent and 82.4 g of granular metal zinc were placed. The autoclave had a jacket with a cooling structure and a stirrer at the upper part, and the heating system was a jacket heating system.

(11) While the content in the autoclave was stirred, the temperature was increased to 70° C. While the content in the autoclave was maintained at a temperature of 70° C. under normal pressure, 149 g of 1,2,3,4-tetrachlorohexafluorobutane was added dropwise at a drop rate of 9.31 g per hour and was reacted.

(12) After completion of the dropwise addition of 1,2,3,4-tetrachlorohexafluorobutane for 16 hours in total, the content was heated to a temperature of 90° C., and the reaction was conducted for 5 hours while the temperature was maintained at 90° C. In the reaction at 70° C., precipitation of zinc chloride from the content in the autoclave was observed.

(13) After completion of the reaction for 5 hours, the reaction product was further heated to a temperature around the boiling point of 2-propanol, thus a portion of the organic solvent (2-propanol) and the product were vaporized, and the vapor of them was cooled, liquified, and collected by using a trap cooled by a mixture of dry ice and ethanol. The crude yield was then calculated from the collected product to be 97%. The collected product was analyzed by gas chromatography, and the yield of hexafluoro-1,3-butadiene was 80%. The crude yield and the yield are as defined above.