METHOD FOR PRODUCING 1,4-DIBROMO-2,3-DICHLOROHEXAFLUOROBUTANE AND METHOD FOR PRODUCING HEXAFLUORO-1,3-BUTADIENE USING SAME

Abstract

Disclosed is a method for producing 1,4-dibromo-2,3-dichlorohexafluorobutane (BrCF.sub.2CFClCFClCF.sub.2Br), in which, through the photoreaction of 1,2-dibromo-1-chlorotrifluoroethane (BrCF2-CFClBr) with a CTFE (CF2CFCl) gas mixed with a diluent gas, 1,4-dibromo-2,3-dichlorohexafluorobutane is produced. According to an embodiment of the present disclosure, an intermediate for producing hexafluoro-1,3-butadiene (C.sub.4F.sub.6) can be produced with high production yield.

Claims

1. A method of preparing 1,4-dibromo-2,3-dichlorohexafluorobutane (BrCF.sub.2CFClCFClCF.sub.2Br), the method comprising: reacting a 1,2-dibromo-1-chlorotrifluoroethane (BrCF.sub.2CFClBr) solution diluted with a solvent with CTFE (CF.sub.2CFCl) mixed with a diluent gas by light (UV) initiation to produce 1,4-dibromo-2,3-dichlorohexafluorobutane.

2. The method of claim 1, wherein the solvent is methylene chloride (MC, CH.sub.2Cl.sub.2).

3. The method of claim 1, wherein the diluent gas comprises an inert gas.

4. The method of claim 1, wherein the diluent gas comprises hydrofluorocarbon (HFC) gas or perfluorocarbon (PFC) gas.

5. The method of claim 1, wherein the diluent gas comprises at least one inert gas and at least one gas selected from hydrofluorocarbon (HFC) gas and perfluorocarbon (PFC) gas.

6. The method of claim 1, wherein the 1,2-dibromo-1-chlorotrifluoroethane (BrCF.sub.2CFClBr) solution has a solvent content of 90 mol % or less.

7. The method of claim 1, wherein a total gas comprising the diluent gas and a CTFE gas has a CTFE gas content of 50 mol % or less.

8. The method of claim 1, further comprising: reacting CTFE (CF.sub.2CFCl) with bromine (Br.sub.2) to produce 1,2-dibromo-1-chlorotrifluoroethane (BrCF.sub.2CFClBr).

9. A method of preparing hexafluoro-1,3-butadiene (C.sub.4F.sub.6) using 1,4-dibromo-2,3-dichlorohexafluorobutane (BrCF.sub.2CFClCFClCF.sub.2Br) as an intermediate, the method comprising: a photoreaction step of preparing 1,4-dibromo-2,3-dichlorohexafluorobutan by reacting a 1,2-dibromo-1-chlorotrifluoroethane (BrCF.sub.2CFClBr) solution diluted with a solvent with a CTFE (CF.sub.2CFCl) gas mixed with a diluent gas by light (UV) initiation; and a dehalogenation step of removing halogens except fluorine from the prepared 1,4-dibromo-2,3-dichlorohexafluorobutane.

10. The method of claim 9, wherein the dehalogenation step is carried out in the presence of zinc (Zn) and isopropyl alcohol.

11. The method of claim 9, further comprising preparing 1,2-dibromo-1-chlorotrifluoroethane (BrCF.sub.2CFClBr) by reacting CTFE (CF.sub.2CPCl) with bromine (Br.sub.2) before the photoreaction step.

Description

DESCRIPTION OF DRAWINGS

[0034] FIG. 1 is a flow diagram of a method of preparing 1,4-dibromo-2,3-dichlorohexafluorobutane (BrCF.sub.2CFClCFClCF.sub.2Br) as an intermediate and C.sub.4F.sub.6 according to one embodiment of the present disclosure.

BEST MODE

[0035] Hereinafter the present disclosure will be described in detail. The following description includes specific embodiments, but the present disclosure is not intended to be limited or restricted by the embodiments described. In relation to describing the present disclosure, when the detailed description of the relevant known technology is determined to unnecessarily obscure the gist of the present disclosure, the detailed description may be omitted.

[0036] The present disclosure provides a method for preparing 1,4-dibromo-2,3-dichlorohexafluorobutane (BrCF.sub.2CFClCFClCF.sub.2Br) as an intermediate for the preparation of C.sub.4F.sub.6, and provides a method for preparing C.sub.4F.sub.6 using the intermediate.

[0037] A flow diagram of a method of the preparation of 1,4-dibromo-2,3-dichlorohexafluorobutane as an intermediate and C.sub.4F.sub.6 according to an embodiment of the present disclosure is illustrated in FIG. 1.

[0038] Referring to FIG. 1, a method of preparing 1,4-dibromo-2,3-dichlorohexafluorobutane (BrCF.sub.2CFClCFClCF.sub.2Br) as an intermediate according to an embodiment of the present disclosure includes: a process (step S1) of reacting CTFE (CF.sub.2CFCl) with bromine (Br.sub.2) to prepare 1,2-dibromo-1-chlorotrifluoroethane (Br(CF.sub.2CFCl)Br) (step S1); and a process (step S2) of preparing 1,4-dibromo-2,3-dichlorohexafluorobutane as an intermediate by an UV-initiated reaction of a solution of 1,2-dibromo-1-chlorotrifluoroethane with CTFE in the presence of a diluent gas.

[0039] In addition, the method of preparing C.sub.4F.sub.6 according to one embodiment of the present disclosure may include a dehalogenation process (step S3) to detach halogens, except fluorine, from the 1,4-dibromo-2,3-dichlorohexafluorobutane intermediate. Here, the dehalogenation reaction can be carried out by using a metal such as zinc (Zn) in the presence of a solvent such as isopropyl alcohol.

[0040] Hereinafter, the method will be described step by step in detail.

<Preparation of 1,2-dibromo-1-chlorotrifluoroethane (Step S1)>

[0041] Step S1 is the step of reacting CTFE (CF.sub.2CFCl) with bromine (Br.sub.2) to prepare 1,2-dibromo-1-chlorotrifluoroethane (Br(CF.sub.2CFCl)Br), and the step may proceed according to Reaction Formula (9).

CF.sub.2CFCl+Br.sub.2.fwdarw.Br(CF.sub.2CFCl)Br(9)

[0042] The process of Reaction Formula (9) may be carried out by introducing CTFE in a gaseous state and bromine (Br.sub.2) in a liquid state into a Teflon tube immersed in an external temperature-controlled bath at the same time. CTFE gas comes into contact with liquid bromine while passing through the Teflon tube, thereby producing 1,2-dibromo-1-chlorotrifluoroethane. Excess CTFE that has passed through the tube can be recovered at the end of the tube and reused.

<Preparation of 1,4-dibromo-2,3-dichlorohexafluorobutane (Step S2)>

[0043] Step S2 is the step of reacting CTFE with a 1,2-dibromo-1-chlorotrifluoroethane solution which is prepared by mixing the 1,2-dibromo-1-chlorotrifluoroethane prepared in step S1 with a solvent, to prepare 1,4-dibromo-2,3-dichlorohexafluorobutane. Step S2 which may proceed according to Reaction Formula (10).

Br(CF.sub.2CFCl)Br+CF.sub.2CFCl.fwdarw.BrCF.sub.2CFClCFClCF.sub.2Br(10)

[0044] Step S2 can then proceed by light (UV) initiation in the presence of a dilute gas.

[0045] In addition, the solvent used to prepare the 1,2-dibromo-1-chlorotrifluoroethane solution is not limited to any particular solvent, but can be any solvent capable of stabilizing light (UV) initiated radicals. Preferably, the solvent may be methylene chloride (MC, CH.sub.2Cl.sub.2).

[0046] The diluent gas used in step S2 may be an inert gas such as nitrogen, helium, argon, etc. Alternatively, the diluent gas may be a hydrofluorocarbon (HFC) gas such as R-23 (CHF.sub.3), R32 (CH.sub.2F.sub.2), R-41 (CH.sub.3F), R-134a (CF.sub.3CH.sub.2F), R-125 (CF.sub.3CHF.sub.2), or a perfluorocarbon (PFC) gas such as CF.sub.4, C.sub.2F.sub.6, or C.sub.3F.sub.8.

[0047] Alternatively, a mixture of one inert gas and either one of HFC and PFC gas may be used. Preferably, a mixture of at least one inert gas and at least one gas selected from HFC and PFC gases may be used.

[0048] The process of Reaction Formula (10) can be carried out by filling a photoreactor equipped with a radical initiation lamp with a solution of 1,2-dibromo-1-chlorotrifluoroethane as a reaction raw material, performing a purging process composed of vacuuming and inert gas feeding several times, and then supplying diluent gas and CTFE gas in a certain ratio to the photoreactor. The diluent gas and the CTFE gas can be circulated through the photoreactor by using a compressor.

[0049] The 1,4-dibromo-2,3-dichlorohexafluorobutane as an intermediate produced in the photoreactor and the 1,2-dibromo-1-chlorotrifluoroethane solution as a reaction raw material can be transferred to a separation column. The separation column may include a first separation column and a second separation column.

[0050] A mixed solution of the 1,4-dibromo-2,3-dichlorohexafluorobutane intermediate produced in the photoreactor and the 1,2-dibromo-1-chlorotrifluoroethane reaction raw material solution produced in the photoreactor may be transferred from the photoreactor to the first separation column. The reaction raw material solution separated at the top of the first separation column can be circulated back to the photoreactor for further photoreaction.

[0051] At the bottom of the first separation column, a mixture of the intermediate, which is a photoreaction product, byproducts (high BP materials), and the reaction raw materials may be collected. When the concentration of the intermediate in the mixture exceeds a certain level, the mixture may be transferred to the second separation column for purification of the intermediate. In the second separation column, the 1,2-dibromo-1-chlorotrifluoroethane solution, which is a low boiler and a reaction raw material, is first separated and re-fed to the photoreactor, and the intermediate, 1,4-dibromo-2,3-dichlorohexafluorobutane, is then recovered by distillation. Other BP materials can be separately collected in the lower part of the second separation column after the distillation and recovery of the intermediate and are then disposed of.

[0052] The solvent used in the reaction and the inert gas in the diluent gas serve to inhibit the generation higher BP materials than 1,4-dibromo-2,3-dichlorohexafluorobutane. Here, the high BP materials may be Br(CF.sub.2CFCl).sub.nBr (n is an integer greater than or equal to 3). More specifically, selectivity for products during the reaction may vary depending on the concentration of the CTFE gas dissolved in the reaction raw material, i.e., 1,2-dibromo-1-chlorotrifluoroethane. The higher the CTFE gas concentration, the more likely that high boiling materials can be generated, and the lower the CTFE gas concentration, the more likely that the generation of high boiling materials will be suppressed and 1,4-dibromo-2,3-dichlorohexafluorobutane will be easily generated. The proportion of 1,2-dibromo-1-chlorotrifluoroethane in the 1,2-dibromo-1-chlorotrifluoroethane solution may range from 10 to 100 mol %, the proportion being chosen taking into account reactivity and selectivity.

[0053] The ratio of the CTFE gas to the diluent gas may be adjusted such that the CTFE gas content is in a range of 1 to 50 mol %, preferably a range of 1 to 25 mol %, based on the mole numbers of the entire gas including the diluent gas and the CTFE gas.

[0054] In addition, the HFC or PFC gases in the diluent gas can inhibit the formation of 1,4-dibromo-1,3-dichlorohexafluorobutane (BrCF.sub.2CFClCF.sub.2CFClBr), which is an isomer of 1,4-dibromo-2,3-dichlorohexafluorobutane (BrCF.sub.2CFClCFClCF.sub.2Br). That is, the yield of the intermediate, i.e., 1,4-dibromo-2,3-dichlorohexafluorobutane, can be improved by performing the reaction in the presence of a dilute gas.

[0055] When a diluent gas containing HFC or PFC gases, which are insensitive to light (UV), are used in the reaction, the generation of radicals (Br+CF.sub.2CFClBr) that contribute to the formation of isomers can be suppressed, and radicals (BrCF.sub.2CFCl+Br) that favor the formation of the intermediate, 1,4-dibromo-2,3-dichlorohexafluorobutane, can be stably generated. Therefore, the use of a diluent gas containing HFC or PFC gases during the photoreaction can suppress the formation of isomers and improve the yield of the intermediate, 1,4-dibromo-2,3-dichlorohexafluorobutane.

<Preparation of hexafluoro-1,3-butadiene (C.sub.4F.sub.6) (Step S3)>

[0056] Step S3 is a step of producing C.sub.4F.sub.6 by removing halogen atoms (Br and Cl) other than fluorine atoms from the 1,4-dibromo-2,3-dichlorohexafluorobutane intermediate prepared in step S2. To this end, zinc (Zn) as a metal and isopropyl alcohol as a solvent may be used. Step S3 can proceed by Reaction Formula (11).

BrCF.sub.2CFClCFClCF.sub.2Br+2Zn/i-PrOH.fwdarw.C.sub.4F.sub.6+2ZnClBr(11)

[0057] As described above, according to one embodiment of the present disclosure, CTFE, which is relatively easy to transport and obtain, is used as a starting material to prepare 1,4-dibromo-2,3-dichlorohexafluorobutane, which is an intermediate, and C.sub.4F.sub.6 is prepared from the intermediate. Therefore, it is possible to produce the intermediate and C.sub.4F.sub.6 at relatively low cost.

[0058] In addition, according to one embodiment of the present disclosure, when reacting 1,2-dibromo-1-chlorotrifluoroethane, which is a reaction raw material, with CTFE, a solvent is used to dilute the 1,2-dibromo-1-chlorotrifluoroethane, and a diluent gas including an inert gas is used to suppress the generation of high BP materials during the intermediate generation process, thereby improving the intermediate production yield.

[0059] In addition, according to one embodiment of the present disclosure, when reacting 1,2-dibromo-1-chlorotrifluoroethane, which is a reaction raw material, with CTFE, a diluent gas including HFC or PFC gas is used, thereby suppressing the generation of isomers during the intermediate generation process, and improving the intermediate production yield.

[0060] The effectiveness of the present disclosure depending on the type of diluent gas and the ratio of the diluent gas and the CTFE gas in step S2 according to Reaction Formula (10) will be described below through specific experimental examples.

1. Preparation of 1,4-dibromo-2,3-dichlorohexafluorobutane Intermediate

[0061] A 34-L photoreactor equipped with a radical lamp was filled with 26 L of a diluted solution in which 1,2-dibromo-1-chlorotrifluoroethane as a reaction raw material and methylene chloride (MC, CH.sub.2Cl.sub.2) as a solvent are mixed in varying proportions, a vacuum was created to remove the air in the reactor before supplying a diluent gas and CTFE gas to the reactor. These gases were circulated through the photoreactor under constant pressure, with the lamp operating to initiate a photoreaction, and gas chromatography (GC) analysis was performed on products sampled from the bottom of the photoreactor at hourly intervals. During the reaction, the CTFE gas was continuously injected through a regulator to maintain a constant pressure.

[0062] First, the effect of the solvent content in the 1,2-dibromo-1-chlorotrifluoroethane solution was investigated by varying the ratio of 1,2-dibromo-1-chlorotrifluoroethane to solvent under 100 mol % CTFE (Comparative Examples 1 to 4). Methylene chloride (CH.sub.2Cl.sub.2) was used as the solvent, but similar results were obtained with other solvents such as chloroform (CHCl.sub.3) and Carbon tetrachloride (CCl.sub.4).

[0063] To investigate the effect of the ratio of the diluent gas to the CTFE gas, nitrogen (N.sub.2) was used as the diluent gas under the solution condition of Comparative Example 3, and the content of the CTFE gas in the total gas (sum of the nitrogen gas and the CTFE gas) was varied from 2 to 50 mol % (Examples 1 to 4).

[0064] In addition, to investigate the effect of the number of lamps for light (UV) initiation in the reaction, the number of operating lamps was increased to three (Example 5) and seven (Example 6) before proceeding with the reaction.

[0065] In addition, to investigate the effect of the diluent gas containing HFC or PFC gas, the reaction was carried out while varying the ratio of nitrogen gas to HFC or PPC gas while maintaining the CTFE gas content at 25 mol %. R-23 (CHF.sub.3) was used as the HFC or PFC gas, but similar results could be achieved with other HPC gases such as R-32 (CH.sub.2F.sub.2), R-41 (CH.sub.3F), R-134a (CF.sub.3CH.sub.2F), R-125 (CF.sub.3CHF.sub.2), and PFC gases such as CF.sub.4, C.sub.2F.sub.6, and C.sub.3F.sub.8.

2. Gas Chromatography Analysis Results

[0066] The results of gas chromatography analysis according to the comparative examples and examples are shown in Table 1 below. Table 1 lists the content of each of the sampled products in units of % by volume: intermediate [1,4-dibromo-2,3-dichlorohexafluorobutane (BrCF.sub.2CFClCFClCF.sub.2Br)], isomer [1,4-dibromo-1,3-dichlorohexafluorobutane (BrCF.sub.2CFClCF.sub.2CFClBr)], high boiler A [1,6-dibromo-2,3,5-trichlorononafluorohexane (Br(CF.sub.2CFCl).sub.3Br)], and high boiler B [1,8-dibromo-2,3,5,7-tetrachlorodecafluoroheptane (Br(CF.sub.2CFCl).sub.4Br)].

TABLE-US-00001 TABLE 1 Number of vol. % operating Concentration Concentration High BP High BP Classification lamps of solution of diluent gas Intermediate Isomer material A material B Comparative 1 CF.sub.2BrCFCIBr 100 mol % Nitrogen 0 mol % 0.1220 0.0085 0.1351 0.1301 Example 1 CTFE 100 mol % Comparative 1 CF.sub.2BrCFClBr 80 mol % 0.1130 0.0065 0.1051 0.1031 Example 2 MC 20 mol % Comparative 1 CF.sub.2BrCFClBr 65 mol % 0.1020 0.0053 0.0551 0.0131 Example 3 MC 35 mol % Comparative 1 CF.sub.2BrCFClBr 20 mol % 0.0720 0.0022 0.0151 0.0031 Example 4 MC 80 mol % Example 1 1 CF.sub.2BrCFClBr 65 mol % Nitrogen 50 mol % 0.1331 0.0104 0.0019 0.0011 MC 35 mol % CTFE 50 mol % Example 2 1 Nitrogen 75 mol % 0.1412 0.0110 0.0006 0.0005 CTFE 25 mol % Example 3 1 Nitrogen 90 mol % 0.1450 0.0113 0.0002 0.0001 CTFE 10 mol % Example 4 1 Nitrogen 98 mol % 0.1445 0.0112 0.0001 0.0001 CTFE 2 mol % Example 5 3 Nitrogen 90 mol % 0.4229 0.0338 0.0003 0.0002 CTFE 10 mol % Example 6 7 Nitrogen 90 mol % 1.0115 0.0787 0.0005 0.0003 CTFE 10 mol % Example 7 1 Nitrogen 0 mol % 0.1425 0.0083 0.0005 0.0003 HFC/PFC 75 mol % CTFE 25 mol % Example 8 1 Nitrogen 50 mol % 0.1422 0.0087 0.0005 0.0003 HFC/PFC 25 mol % CTFE 25 mol % Example 9 1 Nitrogen 25 mol % 0.1423 0.0081 0.0005 0.0003 HFC/PFC 50 mol % CTFE 25 mol % Example 10 7 Nitrogen 50 mol % 1.0332 0.0609 0.0005 0.0003 HFC/PFC 25 mol % CTFE 25 mol %

[0067] From Table 1 above, it can be seen that dilution with a solvent reduces the amount of high boiling point (BP) materials as compared to Example 1 in which the reaction was carried out without using a solvent in the presence of only CTPE without a diluent gas (Examples 2 to 4). The comparative examples show that the solvent (MC) inhibits the formation of the high BP materials at a solvent content of 35 mol % in the 1,2-dibromo-1-chlorotrifluoroethane solution and that at a solvent content of more than 35 mol %, the formation of the high BP materials can be reduced, but the formation of the intermediate is also reduced. Therefore, a solvent content of 35 mol % was the most effective, when taking into account selectivity and reactivity,

[0068] The variation of the diluent gas concentration was examined while maintaining the solvent content at 35 mol %, and it can be seen that the formation of high BP materials is significantly reduced when the diluent gas is added compared to Example 3 in which the reaction was conducted with CTFE alone without using a diluent gas. When Comparative Example 3 is compared with Example 1, the generation of the intermediate was increased, and the formation of high BP materials was significantly reduced by supplying 50 mol % of nitrogen gas (50 mol % of CTFE) as the diluent gas. In the case of Examples 2 through 4 in which the nitrogen gas was increased to 75 mol % or more (25 mol % of CTFE or less), the generation of the intermediate was found to be further increased and the generation of high BP materials was further suppressed.

[0069] This characteristic was also maintained in the case of Examples 5 and 6 in which the number of operating ramps was increased, and it was found that by increasing the number of operating ramps, the production of the intermediate increased proportionally to the number of the ramps.

[0070] In addition, it can be seen from Examples 7 through 10 that the formation of isomers is inhibited by the inclusion of HFC or PFC gas in the diluent gas. Examples 7 through 10 in which the CTFE content was fixed to 25 mol % and the HFC or PFC content in the diluent gas was varied in a range of 25 mol % to 75mol % showed that the generation of isomers was somewhat suppressed compared to Examples 2 in which the CTFE content was set to 25 mol %. These characteristics were achieved in Example 10 in which the number of operating ramps was increased to seven.

[0071] While the foregoing has been described with reference to some embodiments and drawings, those are illustrative only, and it will be apparent to the ordinarily skilled in the art that various modifications are possible without departing from the scope of the present disclosure.

[0072] Therefore, the scope of protection of the present disclosure should be determined by the recitation of the patent claims and their equivalents.