Method for producing chlorofluorobutane (CFB)

Abstract

Provided is a method for producing chlorofluorobutane (CFB) by dimerizing trichloroethylene (TCE) to produce chlorinated butadiene and fluorinating the hydrogen atoms of the chlorinated butadiene. Trichloroethylene (TCE) is subjected to a dimerization reaction at a temperature of 100 DEG C or higher in the presence of a radical generator, using a dimer represented by formula (1) as a solvent. The dimer is subjected to chlorination and dehydrochlorination to produce hexachlorobutadiene (C4Cl6), and then hexachlorobutadiene is fluorinated to produce chlorofluorobutane (CFB). # imgabs0 #

Description

Technical Field

[0001] The present invention relates to a method for producing chlorofluorobutane (CFB), and more specifically, to a method for producing CFB by dimerizing trichloroethylene (TCE) to generate chlorinated butadiene and fluorinating hydrogen atoms of the chlorinated butadiene. Background Art

[0002] TCE is a compound that is produced as a by-product in various synthetic reactions, but has concerns about the impact on the environment. Therefore, it is required to effectively utilize TCE without accumulating it. It is known that TCE dimerizes in the presence of a free radical generator to generate chlorinated butylenes (Patent Document 1). This method is useful for forming a chlorinated butane skeleton or a chlorinated butadiene skeleton from TCE, but the method disclosed in Patent Document 1 is small-scale (TCE is used in an amount of only 5 g), and therefore, further improvement is required for mass production of dimers.

[0003] On the other hand, in recent years, a mass production method using an etching gas with low environmental load such as hexafluorobutadiene (perfluorobutadiene, HFB) has also been proposed (Patent Document 2). A method of producing HFB by fluorinating chlorinated butane or chlorinated butadiene is being studied.

[0004] Non-patent document 1 describes a method for producing chlorofluorobutane by allowing ClF3 and ClF to act on 1,2,3,4-tetrachloro-1,3-butadiene in sequence to undergo a fluorination reaction. Non-patent document 1 also describes that hexafluorobutadiene (perfluorobutadiene, HFB) can be produced by dechlorinating 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane (C4Cl4F6).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent No. 3951331

[0008] Patent Document 2: Japanese Patent No. 5005681

[0009] Non-patent literature

[0010] Non-patent document 1: J. Muray., J. Chem. Soc., p1884 (1959) Summary of the invention

[0011] Problem that the invention aims to solve

[0012] The first object of the present invention is to provide a method for efficiently producing a dimer of TCE. The second object of the present invention is to provide a series of integrated processes for producing chlorinated butane or chlorinated butadiene from TCE, and then fluorinating the chlorinated butane or fluorinated butadiene.

[0013] Solutions for solving problems

[0014] The present invention provides the following solutions.

[0015] [1] A method for producing a dimer of trichloroethylene (TCE) represented by the following formula (1) from trichloroethylene (TCE), comprising the steps of using the dimer represented by the formula (1) as a solvent and subjecting TCE to a dimerization reaction at a temperature of 100° C. or higher in the presence of a free radical generator,

[0016] [2]

[0018] The method according to [1], wherein the reaction is carried out at a temperature of 100 to 200°C. [3]

[0020] The method according to [1] or [2], wherein the reaction is carried out under atmospheric pressure. [4]

[0022] A method for producing hexachlorobutadiene (C4Cl6) by chlorination and dehydrochlorination of a dimer of trichloroethylene (TCE) represented by the following formula (1), comprising the steps of reacting the dimer of TCE with chlorine (Cl2) in the presence of a Lewis acid catalyst,

[0023] [5]

[0025] The method according to [4], wherein the reaction is carried out at a temperature of 30 to 200°C. [6]

[0027] The method according to [4] or [5], wherein the Lewis acid catalyst comprises FeCl3.

[0028] [7] A method for producing 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane from trichloroethylene (TCE), comprising:

[0029] Step (A) is to produce a dimer of trichloroethylene (TCE) represented by the following formula (1), wherein step (A) comprises using the dimer represented by the formula (1) as a solvent and subjecting TCE to a dimerization reaction at a temperature of 100° C. or higher in the presence of a free radical generator,

[0030]

[0031] Step (B) of producing hexachlorobutadiene (C4Cl6) by chlorination and dehydrochlorination of the dimer of TCE represented by the above formula (1), wherein step (B) comprises reacting the dimer of TCE with chlorine gas (Cl2) in the presence of FeCl3 as a reaction catalyst;

[0032] Step (C), fluorinating hexachlorobutadiene (C4Cl6) using a fluorinating agent to produce a fluorinated product containing 1,1,2,3,4,4-hexachloro-1,2,3,4-tetrafluorobutane; and

[0033] In step (D), the fluorinated product obtained in step (C) is reacted with chlorine monofluoride (ClF) to produce 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane. [8]

[0035] The method according to [7], wherein the fluorination product obtained in the above step (C) further comprises 1,1,1,2,3,4,4-heptachloro-1,2,3-trifluorobutane (C4Cl7F3) and 1,1,2,3,4-pentachloro-1,2,3,4,4-pentafluorobutane (C4Cl5F5).

[0036] Effects of the Invention

[0037] According to the present invention, a dimer of TCE can be efficiently produced. In addition, according to the present invention, chlorinated butane or chlorinated butadiene can be efficiently produced from relatively easily available TCE. Furthermore, by fluorinating the obtained chlorinated butane or chlorinated butadiene, fluorinated butane or fluorinated butadiene can be produced, and therefore, etching gases with low environmental load such as HFB can be cheaply produced in large quantities through a series of integrated processes. DETAILED DESCRIPTION

[0038] (effect)

[0039] Regarding the dimerization reaction of trichloroethylene (TCE), it is known that setting the reaction temperature to 100°C or higher is effective for efficiently carrying out the free radical reaction (Patent Document 1). On the other hand, the boiling point of TCE is 87°C, so in order to set the reaction temperature to 100°C or higher, it is necessary to carry out the pressurized reaction in a sealed pressure vessel. The present inventors focused on the following formula (1):

[0040]

[0041] The boiling point of the dimer of TCE shown is 205° C. (calculated value), and by using this dimer as the reaction solvent, the reaction was successfully carried out at a temperature of 100° C. or higher without using a pressure vessel. Since the dimer as the product is the reaction solvent, the product can be easily purified by removing TCE as the raw material.

[0042] A method of allowing fluorine gas (F2) not disclosed in non-patent document 1 to act in the fluorination of TCE dimers was attempted, and it was found that chlorine gas (Cl2) was first allowed to act on TCE dimers in the presence of a catalyst to generate hexachlorobutadiene (HCB), and then F2 was allowed to act on the HCB, thereby efficiently producing 1,1,2,3,4,4-hexachloro-1,2,3,4-tetrafluorobutane (C4Cl6F4). The obtained C4Cl6F4 was converted into 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane (C4Cl4F6) by the action of ClF, and the C4Cl4F6 was dechlorinated, thereby producing hexafluorobutadiene (perfluorobutadiene, HFB).

[0043] (Dimerization reaction of trichloroethylene (TCE))

[0044] In the present invention, the dimerization reaction can be carried out by heating to a temperature of 100°C or more under atmospheric pressure, so a pressure-resistant container is not required. The reaction temperature is preferably 100 to 200°C, more preferably 120 to 150°C. The product contains unreacted TCE and its dimer, but TCE can be easily removed by distillation. The reaction product from which TCE has been removed is substantially composed of TCE dimers and can be used directly in the next step.

[0045] (Chlorination and dehydrochlorination reaction of TCE dimer)

[0046] The present invention is characterized in that a process of producing hexachlorobutadiene (C4Cl6) from a dimer of TCE by chlorination and dehydrochlorination is carried out, in which the dimer of TCE is reacted with chlorine (Cl2) in the presence of a Lewis acid catalyst. By using hexachlorobutadiene (C4Cl6) as an intermediate, the position to be fluorinated in the next process can be limited, and the selectivity of the target product can also be improved. The temperature of the chlorination and dehydrochlorination reaction of the TCE dimer is preferably 30 to 200°C, more preferably 50 to 200°C, and further preferably 120 to 150°C. Examples of Lewis acid catalysts include AlCl3, SnCl4, TiCl4, FeCl3, ZnCl2, AlF3, MgF2, CaF2, CrF3, ZrF4, etc., and FeCl3 is most preferred.

[0047] (Fluorination reaction of hexachlorobutadiene (C4Cl6))

[0048] In the present invention, hexachlorobutadiene (C4Cl6) is fluorinated with a fluorinating agent to produce a fluorinated product containing 1,1,2,3,4,4-hexachloro-1,2,3,4-tetrafluorobutane. In this reaction, in addition to 1,1,2,3,4,4-hexachloro-1,2,3,4-tetrafluorobutane, 1,1,1,2,3,4,4-heptachloro-1,2,3-trifluorobutane (C4Cl7F3) and 1,1,2,3,4-pentachloro-1,2,3,4,4-pentafluorobutane (C4Cl5F5) are also generated and included in the fluorinated product, but any compound can be converted into the target 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane (C4Cl4F6) in the next step, so there is no need to separate by purification.

[0049] The fluorinating agent is not particularly limited, and examples thereof include fluorine gas (F2), chlorine trifluoride (ClF3), chlorine monofluoride (ClF), etc. From the viewpoint of selectivity for 1,1,2,3,4,4-hexachloro-1,2,3,4-tetrafluorobutane, fluorine gas (F2) is preferred.

[0050] (Contains the reaction of the fluorination product of 1,1,2,3,4,4-hexachloro-1,2,3,4-tetrafluorobutane with chlorine monofluoride (ClF))

[0051] The reaction can be carried out by contacting ClF with 1,1,2,3,4,4-hexachloro-1,2,3,4-tetrafluorobutane. The reaction temperature is preferably 50 to 200°C, more preferably 80 to 150°C. In this reaction, 1,1,1,2,3,4,4-heptachloro-1,2,3-trifluorobutane (C4Cl7F3) and 1,1,2,3,4-pentachloro-1,2,3,4,4-pentafluorobutane (C4Cl5F5) produced as by-products in the previous step are also converted into the target 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane (C4Cl4F6). The advantage of adopting this process is that 1,1,1,2,3,4,4-heptachloro-1,2,3-trifluorobutane (C4Cl7F3) and 1,1,2,3,4-pentachloro-1,2,3,4,4-pentafluorobutane (C4Cl5F5) can be converted into tetrachlorohexafluorobutane, so no purification process is required. That is, as reaction conditions for improving the selectivity of the target product, it can be listed that ClF is introduced at a low flow rate to make 1,1,2,3,4,4-hexachloro-1,2,3,4-tetrafluorobutane and ClF react evenly and gently. Specifically, the following conditions are preferred.

[0052] <Reaction Conditions>

[0053] (a) ClF flow rate: For example, when reacting on a laboratory scale with 20 to 1000 g of the raw material solution, the flow rate is preferably 0.6 to 30 L / hr, more preferably 0.6 to 12 L / hr.

[0054] (b) It is preferred that an aeration plate such as a sintered metal filter be used as the nozzle for blowing ClF to reduce the bubbles to micron. It is more preferred to use a sintered metal filter having a pore size of 5 to 500 μm.

[0055] The reactor (c) may be made of stainless steel, alloys such as monel, Inconel, Hastelloy, glass, nickel, polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), etc. In order to ensure a sufficient residence time, a vertical reactor is preferably used.

[0056] (Dechlorination of 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane)

[0057] Hexafluorobutadiene (HFB) can be produced by dechlorinating 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane. This reaction is well known in the art, but in the present invention, HFB can be produced in large quantities from TCE at low cost by reflecting new insights in a series of intermediate steps.

[0058] As reaction conditions, the following conditions can be exemplified.

[0059] Type of metal as a reaction catalyst: magnesium, zinc, cadmium, aluminum, copper, sodium, lithium, etc. can be used, and magnesium and zinc are preferred.

[0060] · Form of the metal as a reaction catalyst: preferably in a granular or powdery form.

[0061] Reaction solvent: An organic solvent or a mixed solvent of an organic solvent and water can be used. Alternatively, water can be used alone. The organic solvent is preferably an alcohol, and methanol, ethanol, isopropanol, octanol, etc. can be used.

[0062] Reaction temperature: preferably 20 to 150°C, more preferably 30 to 90°C.

[0063] Example

[0064] The present invention will be specifically described based on the following examples, but the scope of the present invention is not limited to the following examples. The following examples are carried out according to the following reaction scheme.

[0065]

[0066] (Example 1: Dimerization reaction of TCE (2C2Cl3H→C4Cl6H2))

[0067] In a 300 ml glass flask connected to a dropping funnel and a condenser, 75 g of the dimer of TCE (C4Cl6H2) represented by the above formula (1) as a reaction solvent, 25 g of TCE as a raw material, 0.5 g of di-tert-butyl peroxide as a free radical generator, the reactor was heated to 140°C, TCE was refluxed, and the reaction was carried out for 20 hours (hr). The reaction solution was analyzed, and the result showed that the dimer of TCE (C4Cl6H2) was obtained from TCE with a yield of 53%. TCE can be separated from the reaction solution using an evaporator, etc., and the dimer of TCE (C4Cl6H2) can be recovered as a product.

[0068] (Comparative Example 1: Dimerization reaction of TCE (2C2Cl3H→C4Cl6H2))

[0069] 30 g of TCE was placed in a 50 ml fluororesin sealed container, and 0.2 g of di-tert-butyl peroxide as a free radical generator was added without using a solvent, and the reactor was heated to 150° C. and reacted for 5 hours (hr). The reaction solution was analyzed, and the result showed that the dimer of TCE (C4Cl6H2) was obtained at a yield of 50%.

[0070] Comparing Example 1 with Comparative Example 1, according to the present invention, the dimer of TCE can be obtained with a good yield (53%) without using a sealed pressure vessel. The dimer of TCE can be easily purified by distilling off the unreacted raw materials. It can be seen that in the present invention, since a pressure vessel is not required, it is suitable as a step of a continuous integrated process.

[0071] (Example 2: Chlorination, dechlorination and hydrochlorination reaction (C4Cl6H2→C4Cl6)

[0072] In a 500 ml glass flask connected to a condenser, 390 g of TCE dimer (C4Cl6H2) was added, 0.4 g of FeCl3 as a reaction catalyst was added, the reactor was heated to 90°C, chlorine gas (Cl2) was blown in at 6 liters / hour (L / hr), and the reaction was stopped after 8 hours. Then, the reactor heating temperature was changed to 150°C and heating was continued for 4 hours. Nitrogen was blown in from the gas inlet to discharge the chlorine gas dissolved in the reaction solution, and then the reactor was opened to take out the reaction solution. The reaction solution was analyzed by GC, and hexachlorobutadiene (C4Cl6) was obtained with a yield of 93%.

[0073] (Example 3: Fluorine addition reaction using fluorine gas (F2))

[0074] 450 g of hexachlorobutadiene (C4Cl6) was added to a SUS reactor equipped with a gas inlet, a gas outlet, and a thermometer, and fluorine gas (F2) was blown in at a flow rate of 24 L / hr for 17 hours with respect to the total volume of nitrogen and fluorine gas under ice cooling. Then, nitrogen was blown in at the same flow rate for 1 hour to obtain 544 g of a reaction liquid. In the analysis of the reaction liquid using NMR, 1,1,2,3,4,4-hexachloro-1,2,3,4-tetrafluorobutane generated by fluorine addition to the unsaturated bonds of hexachlorobutadiene was contained at a composition ratio of 54% by mass. In addition, the intermediates C4Cl7F3 (1,1,1,2,3,4,4-heptachloro-1,2,3-trifluorobutane) and C4Cl5F5 (1,1,2,3,4-pentachloro-1,2,3,4,4-pentafluorobutane), which can become the raw materials of the target product 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane in the subsequent step (Example 4), are contained in a composition ratio of 12% by mass and 7% by mass, respectively.

[0075] (Example 4: Fluorination reaction using chlorine monofluoride (ClF))

[0076] 200 g of the reaction solution of the fluorine addition reaction of 1,1,2,3,4,4-hexachloro-1,2,3,4-tetrafluorobutane obtained in Example 3 was added to a SUS reactor equipped with a gas inlet, a gas outlet, and a thermometer. An ice-cold trap and a -20°C condenser were set on the gas outlet side of the reactor. The reactor was heated to 120°C and chlorine monofluoride was blown in at a flow rate of 2.4 L / hr for 16 hours. Then, nitrogen was blown in at the same flow rate for 1 hour to obtain 161 g of the reaction solution. The reaction solution was analyzed, and the result showed that 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane was contained in a composition ratio of 56% by mass.

[0077] (Example 5: Fluorine addition reaction using chlorine trifluoride (ClF3))

[0078] 345 g of hexachlorobutadiene (C4Cl6) was added to a SUS reactor equipped with a gas inlet, a gas outlet, and a thermometer, and chlorine trifluoride gas was blown in at a flow rate of 4.8 L / hr for 21 hours with respect to the total concentration of nitrogen and chlorine trifluoride. Then, nitrogen was blown in at a flow rate of 12 L / hr for 1 hour to obtain 460 g of a reaction solution. In the analysis of the reaction solution using NMR, 1,1,2,3,4,4-hexachloro-1,2,3,4-tetrafluorobutane generated by fluorine addition to the unsaturated bonds of hexachlorobutadiene was contained at a composition ratio of 31% by mass. In addition, the intermediates C4Cl7F3 (1,1,1,2,3,4,4-heptachloro-1,2,3-trifluorobutane) and C4Cl5F5 (1,1,2,3,4-pentachloro-1,2,3,4,4-pentafluorobutane), which can become the raw materials of the target product 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane in the subsequent step (Example 4), are contained in a composition ratio of 17% by mass and 3% by mass, respectively.

[0079] Comparing Example 3 with Example 5, it can be seen that F2 gas has a high selectivity for 1,1,2,3,4,4-hexachloro-1,2,3,4-tetrafluorobutane compared to ClF3 gas. The products obtained in Example 3 and Example 5 can be converted into the target 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane (C4Cl4F6) in the subsequent process (Example 4), and the C4Cl4F6 can be converted into hexafluorobutadiene (HFB) (Example 6) by dechlorination reaction by a known method. Through the present invention, chlorinated butane or chlorinated butadiene can be efficiently manufactured from TCE that can be obtained relatively easily, and then fluorinated butane or fluorinated butadiene can be manufactured, so etching gases with low environmental load such as HFB can be cheaply manufactured in large quantities through a series of integrated processes.

[0080] (Example 6: Dechlorination reaction using metal)

[0081] A water-cooled condenser and a dropping funnel were connected to a 300ml glass reactor, and a 500ml SUS gas capture container with a valve was connected to the front end of the cooling condenser. 70g of solvent isopropanol and 41g of granular metal zinc were added to the reactor, the temperature of the reactor was raised to 70°C while stirring, and the gas capture container was cooled with a dry ice-acetone bath. Next, a distillate containing 40g of 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane obtained by distilling the reaction solution of Example 4 was added dropwise to the reaction solution using a dropping funnel for 1 hour, and then reacted for 5 hours. After the reaction was completed, the product captured in the gas capture container was analyzed by gas chromatography, and the HFB purity was 97GC%. In addition, the yield based on 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane was 94mol%.

Claims

1. A method for producing a dimer of trichloroethylene (TCE) represented by the following formula (1) from trichloroethylene (TCE), comprising the steps of subjecting TCE to a dimerization reaction at a temperature of 100° C. or higher in the presence of a free radical generator using the dimer represented by the formula (1) as a solvent, 2. The method according to claim 1, wherein: The reaction is carried out at a temperature of 100 to 200°C.

3. The method according to claim 1 or 2, wherein: The reaction was carried out at atmospheric pressure.

4. A method for producing hexachlorobutadiene (C4Cl6) by chlorination and dehydrochlorination of a dimer of trichloroethylene (TCE) represented by the following formula (1), comprising the steps of reacting the dimer of TCE with chlorine (Cl2) in the presence of a Lewis acid catalyst, 5. The method according to claim 4, wherein: The reaction is carried out at a temperature of 30 to 200°C.

6. The method according to claim 4 or 5, wherein: The Lewis acid catalyst comprises FeCl3.

7. A method for producing 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane from trichloroethylene (TCE), comprising: Step (A) is to produce a dimer of trichloroethylene (TCE) represented by the following formula (1), wherein step (A) comprises using the dimer represented by the formula (1) as a solvent and subjecting TCE to a dimerization reaction at a temperature of 100° C. or higher in the presence of a free radical generator, Step (B), producing hexachlorobutadiene (C4Cl6) by chlorination and dehydrochlorination reaction of the TCE dimer represented by the formula (1), wherein step (B) comprises reacting the TCE dimer with chlorine gas (Cl2) in the presence of FeCl3 as a reaction catalyst; Step (C), fluorinating hexachlorobutadiene (C4Cl6) using a fluorinating agent to produce a fluorinated product containing 1,1,2,3,4,4-hexachloro-1,2,3,4-tetrafluorobutane; and In step (D), the fluorinated product obtained in step (C) is reacted with chlorine monofluoride (ClF) to produce 1,2,3,4-tetrachloro-1,1,2,3,4,4-hexafluorobutane.

8. The method according to claim 7, wherein: The fluorination product obtained in the step (C) further comprises 1,1,1,2,3,4,4-heptachloro-1,2,3-trifluorobutane (C4Cl7F3) and 1,1,2,3,4-pentachloro-1,2,3,4,4-pentafluorobutane (C4Cl5F5).

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