Preparation method of hexafluoroisobutylene

Abstract

The invention provides a preparation method of hexafluoroisobutylene, which comprises the following steps: (1) mixing a first solvent, a first alkali liquor and a sulfonium salt compound in an inert gas atmosphere for primary reaction, then mixing with hexafluoroacetone for secondary reaction, and purifying to obtain 2, 2-bis (trifluoromethyl) ethylene oxide; (2) mixing a second solvent and 2, 2-bis (trifluoromethyl) ethylene oxide in an inert gas atmosphere, carrying out first cooling treatment, then mixing a reducing agent, carrying out a reduction reaction, and purifying to obtain hexafluoroisobutanol; and (3) mixing a third solvent and second alkali liquor, carrying out second cooling treatment, mixing hexafluoroisobutanol, carrying out third reaction, condensing and rectifying to obtain the hexafluoroisobutene. The preparation method provided by the invention is short in process route and mild in reaction condition, the solvent used in the preparation process can be recycled, the pollution in the preparation process is reduced, and the preparation method is less in three wastes, environment-friendly and suitable for large-scale production.

Description

Technical Field

[0001] The invention belongs to the technical field of organic chemical synthesis and relates to a method for preparing a fluorine-containing olefin compound, in particular to a method for preparing hexafluoroisobutylene. Background Art

[0002] Hexafluoroisobutylene [2-trifluoromethyl-3,3,3-trifluoro-1-propene, HFIB for short] is a multifunctional fluorinated olefin compound. It is widely used due to its unique physical and chemical properties such as excellent heat resistance, chemical resistance, low surface tension, and no ozone consumption. Its application range includes the manufacture of special electrical parts, semiconductor photolithography materials, electronic etching gas, refrigerant, foaming agent, and pharmaceutical intermediates. Therefore, hexafluoroisobutylene has important application value in many fields due to its excellent versatility, so it has attracted more and more attention, and its preparation process has been increasingly valued.

[0003] At present, there are four types of synthetic preparation methods for hexafluoroisobutylene:

[0004] (1) Elimination method: US4766238A discloses a method of using 2-trifluoromethyl-3,3,3-trifluorobutyric acid chloromethyl ester as a raw material, in the presence of a tertiary amine (preferably tributylamine), at a reaction temperature of 65°C and a reaction time of 3 hours to obtain 76% hexafluoroisobutylene. The reaction formula is as follows:

[0005]

[0006] For example, READear disclosed in the document "Tetrahedron 27 (1971) 3345-3355" that hexafluoroacetone as a raw material reacts with a methyl Grignard reagent at 0-5°C to generate hexafluoro-2-methyl-2-propanol, and the generated hexafluoro-2-methyl-2-propanol reacts with a dehydrating agent (such as SF4, PCl5 or ClCN) to generate hexafluoroisopropylene. The reaction formula is as follows:

[0007]

[0008] (2) Reverse cycloaddition method: US Pat. No. 4,244,891A discloses a method of generating hexafluoroisopropylene by cyclization and ring-opening to remove carbon dioxide from hexafluoroacetone and ketene precursor (such as acetic anhydride, acetone, acetic acid, isopropenyl acetate, acetylacetone or diene ketone) at 400-700°C, with a molar conversion rate of more than 90%. The reaction formula is as follows:

[0009]

[0010] For example, Kawashima disclosed in the document "Tetrahedron Lett. 38 (1997) 551-554" that hexacoordinated 1,2-oxophosphine is ring-opened at 80-100°C to generate hexafluoroisobutylene with a yield of 40%. The reaction formula is as follows:

[0011]

[0012] (3) Halogen exchange method (Swarts reaction): Haszeldine disclosed a method of using 3-chloro-3,3-difluoro-2-(trifluoromethyl)-1-propene as a raw material and reacting it with trifluoroantimony dichloride (SbF3Cl2) at 50°C for 3 hours to produce hexafluoroisobutylene with a yield of up to 93%. The reaction formula is as follows:

[0013]

[0014] For example, Frisch disclosed a method of using 1,3-dichloro-1,1,3,3-tetrafluoroacetone as a raw material, sequentially reacting with four reagents, methyl Grignard reagent, sulfur tetrafluoride, hydrogen fluoride and antimony trifluoride, to produce hexafluoroisobutylene with a total yield of 44% through a multi-step reaction, and the reaction formula is as follows:

[0015]

[0016] (4) Decarboxylation method: For example, JPS61291530A discloses that 3,3,3-trifluoro-2-(trifluoromethyl) propionic acid methyl ester is used as a raw material and reacted with paraformaldehyde at 90° C. for 3 hours in the presence of tri-n-butylamine to produce hexafluoroisobutylene with a yield of 49.1%. The reaction formula is as follows:

[0017]

[0018] For example, DE3635750A1 discloses a method of using 3,3,3-trifluoro-2-(trifluoromethyl) propionic acid methyl ester as a raw material. After chlorination, the obtained product is dropwise added with pyridine at 70°C and reacted for 2 hours to obtain hexafluoroisopropylene with a yield of 70%. The reaction formula is as follows:

[0019]

[0020] In summary, the above-mentioned synthesis methods have harsh reaction conditions, complex synthesis processes, and high requirements for the equipment required for synthesis; in addition, a large amount of liquid waste and solid waste will be generated during the production process, seriously polluting the environment. In order to solve the above problems, it is necessary to develop new synthesis methods. Summary of the invention

[0021] The object of the present invention is to provide a method for preparing hexafluoroisobutylene, wherein the preparation method has a short preparation route, mild reaction conditions, and the solvent used in the preparation process can be recycled, thereby reducing pollution in the preparation process, and less "three wastes", being environmentally friendly and suitable for large-scale production.

[0022] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0023] The present invention provides a method for preparing hexafluoroisobutylene, which comprises the following steps:

[0024] (1) under an inert gas atmosphere, mixing a first solvent, a first alkali solution and a sulfonium salt compound for a primary reaction, and then mixing hexafluoroacetone for a secondary reaction, to obtain 2,2-bis(trifluoromethyl)ethylene oxide after a first purification;

[0025] (2) under an inert gas atmosphere, mixing the second solvent and the 2,2-bis(trifluoromethyl)ethylene oxide obtained in step (1) for a first cooling treatment, then mixing with a reducing agent for a reduction reaction, and obtaining hexafluoroisobutanol after a second purification;

[0026] (3) mixing the third solvent and the second alkali solution for a second cooling treatment, and then mixing the hexafluoroisobutanol obtained in step (2) for three reactions, and then sequentially performing condensation treatment and rectification treatment to obtain the hexafluoroisobutene.

[0027] The method for preparing hexafluoroisobutylene of the present invention is: firstly, hexafluoroacetone is reacted with a sulfonium salt compound to generate 2,2-bis(trifluoromethyl)ethylene oxide, then hexafluoroisobutanol is obtained by reduction ring-opening reaction, and finally hexafluoroisobutylene is obtained by alkali dehydration. The method has the advantages of simple process, high yield, less "three wastes", and is suitable for industrialization. The preparation route of the present invention is as follows:

[0028]

[0029] Preferably, the inert gas atmosphere in step (1) and step (2) includes any one of a nitrogen atmosphere, a helium atmosphere or an argon atmosphere, or a combination of at least two of them. Typical but non-limiting combinations include: a combination of a nitrogen atmosphere and a helium atmosphere, a combination of a nitrogen atmosphere and an argon atmosphere, a combination of a helium atmosphere and an argon atmosphere, or a combination of a nitrogen atmosphere, a helium atmosphere and an argon atmosphere.

[0030] As a preferred technical solution of the present invention, the sulfonium salt compound in step (1) includes any one of trimethyl sulfoxide chloride, trimethyl sulfoxide bromide, trimethyl sulfoxide iodide, trimethyl sulfur chloride, trimethyl sulfur bromide or trimethyl sulfur iodide, or a combination of at least two thereof. Typical but non-limiting combinations include: a combination of trimethyl sulfoxide chloride, trimethyl sulfoxide bromide and trimethyl sulfoxide iodide, a combination of trimethyl sulfur chloride, trimethyl sulfur bromide and trimethyl sulfur iodide, a combination of trimethyl sulfoxide chloride and trimethyl sulfur chloride, a combination of trimethyl sulfoxide bromide and trimethyl sulfur bromide, or a combination of trimethyl sulfoxide iodide and trimethyl sulfur iodide.

[0031] Preferably, the first alkali solution comprises any one or a combination of at least two of lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium hydride, potassium hydride, methyl lithium, n-butyl lithium, tert-butyl lithium, lithium hexamethyldisilazide, sodium hexamethyldisilazide, 8-diazabicyclo[5.4.0]undec-7-ene, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium tert-butoxide or potassium tert-butoxide. Typical but non-limiting combinations include: a combination of lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium hydride and potassium hydride, a combination of methyl lithium, n-butyl lithium, tert-butyl lithium, lithium hexamethyldisilazide and sodium hexamethyldisilazide, a combination of sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium tert-butoxide and potassium tert-butoxide, or a combination of sodium hydroxide, sodium hydride, sodium methoxide, sodium ethoxide and sodium butoxide.

[0032] Preferably, the first solvent in step (1) comprises any one of dimethyl sulfoxide, tetrahydrofuran, acetonitrile, N,N-dimethylformamide, benzene, toluene, dichloromethane, chlorobenzene, methanol, ethanol or tert-butanol, or a combination of at least two thereof. Typical but non-limiting combinations include: a combination of dimethyl sulfoxide, tetrahydrofuran, acetonitrile and N,N-dimethylformamide, a combination of benzene, toluene, dichloromethane and chlorobenzene, or a combination of methanol, ethanol and tert-butanol.

[0033] Preferably, the mass ratio of the mass of the first solvent to the total mass of the sulfonium salt compound and the first alkali solution is 1.5 to 4:1, for example, it can be 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1 or 4:1, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] In the present invention, the first alkali solution reacts with the sulfonium salt compound in the first solvent to deprotonate the sulfonium salt compound to form a sulfur ylide, and the generated sulfur ylide undergoes a formal [1+2] cycloaddition with the carbon-oxygen double bond in hexafluoroacetone, and then electrons are transferred and dimethyl sulfide or dimethyl sulfoxide is simultaneously left to obtain 2,2-bis(trifluoromethyl)ethylene oxide.

[0035] Preferably, the molar ratio of the sulfonium salt compound to the first alkali solution in step (1) is 1:1-2, for example, 1:1, 2:12, 1:1.4, 1:1.6, 1:1.8 or 1:2, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0036] Preferably, the molar ratio of the sulfonium salt compound to hexafluoroacetone in step (1) is 1:0.5-1, for example, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9 or 1:1, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0037] As a preferred technical solution of the present invention, the temperature of the primary reaction in step (1) is -20 to 60°C, for example, it can be -20°C, -10°C, 0°C, 10°C, 20°C, 30°C, 40°C, 50°C or 60°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0038] Preferably, the time of the single reaction in step (1) is 1.5 to 2.5 h, for example, 1.5 h, 1.7 h, 1.9 h, 2.1 h, 2.3 h or 2.5 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0039] Preferably, the temperature of the secondary reaction in step (1) is 0-30°C, for example, 0°C, 5°C, 10°C, 15°C, 20°C, 25°C or 30°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0040] Preferably, the time of the secondary reaction in step (1) is 6 to 10 hours, for example, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0041] Preferably, the purity of the 2,2-bis(trifluoromethyl)ethylene oxide in step (1) is ≥99.5%, for example, it can be 99.5%, 99.6%, 99.7%, 99.8% or 99.9%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0042] As a preferred technical solution of the present invention, the first purification in step (1) includes a first distillation.

[0043] Preferably, the bottom temperature of the first distillation tower is 40-60°C, for example, 40°C, 44°C, 48°C, 52°C, 56°C or 60°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0044] Preferably, the top temperature of the first distillation tower is 40-50°C, for example, 40°C, 42°C, 44°C, 46°C, 48°C or 50°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0045] Preferably, the distillation pressure of the first distillation is 0.1-0.2 MPa, for example, 0.1 MPa, 0.12 MPa, 0.14 MPa, 0.16 MPa, 0.18 MPa or 0.2 MPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0046] Preferably, the reflux ratio of the first distillation is 1 to 5, for example, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0047] In the present invention, the purpose of first mixing the first solvent, the first alkali solution and the sulfonium salt compound to react in the process of preparing 2,2-bis(trifluoromethyl)ethylene oxide, and then mixing hexafluoroacetone to carry out a secondary reaction is to fully convert the reactant into sulfur ylide by the primary reaction, and then add hexafluoroacetone to carry out a secondary reaction to form 2,2-bis(trifluoromethyl)ethylene oxide; if the reaction reagent and hexafluoroacetone are mixed and reacted at the same time, 2,2-bis(trifluoromethyl)ethylene oxide cannot be obtained.

[0048] As a preferred technical solution of the present invention, the reducing agent in step (2) includes any one of lithium borohydride, sodium borohydride, lithium aluminum hydride, borane or hydrogen / palladium on carbon, or a combination of at least two of them. Typical but non-limiting combinations include: a combination of lithium borohydride and sodium borohydride, a combination of lithium borohydride, sodium borohydride and lithium aluminum hydride, or a combination of borane and hydrogen / palladium on carbon.

[0049] Preferably, the second solvent in step (2) comprises any one of dimethyl sulfoxide, tetrahydrofuran, acetonitrile, N,N-dimethylformamide, benzene, toluene, dichloromethane, chlorobenzene, methanol, ethanol or tert-butanol, or a combination of at least two thereof. Typical but non-limiting combinations include: a combination of dimethyl sulfoxide, tetrahydrofuran, acetonitrile and N,N-dimethylformamide, a combination of benzene, toluene, dichloromethane and chlorobenzene, or a combination of methanol, ethanol and tert-butanol.

[0050] Preferably, the mass ratio of the second solvent to the second alkali solution to the total mass of hexafluoroisobutanol is 1.1 to 3:1, for example, it can be 1.1:1, 1.5:1, 1.9:1, 2.3:1, 2.7:1 or 3:1, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0051] Preferably, the molar ratio of the reducing agent to 2,2-bis(trifluoromethyl)ethylene oxide in step (2) is 1 to 3:1, for example, 1:1, 1.4:1, 1.8:1, 2.2:1, 2.6:1 or 3:1, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0052] As a preferred technical solution of the present invention, the terminal temperature of the first cooling treatment in step (2) is -20 to -10°C, for example, it can be -20°C, -18°C, -16°C, -14°C, -12°C or -10°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0053] In the present invention, in the process of preparing hexafluoroisobutanol, the purpose of first mixing the second solvent and 2,2-bis(trifluoromethyl)ethylene oxide and cooling the mixture is that the process of mixing the second solvent and 2,2-bis(trifluoromethyl)ethylene oxide is an exothermic reaction, and cooling the mixture is conducive to the forward reaction. In addition, cooling the mixture can also adjust the reaction rate, so that the reaction can be carried out under milder conditions.

[0054] Preferably, the temperature of the reduction reaction in step (2) is 20-30°C, for example, 20°C, 22°C, 24°C, 26°C, 28°C or 30°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0055] Preferably, the reduction reaction time in step (2) is 6 to 12 h, for example, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h or 12 h, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0056] Preferably, the purity of the hexafluoroisobutanol in step (2) is ≥97%, for example, it can be 97%, 97.5%, 98%, 98.5%, 99% or 99.5%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0057] As a preferred technical solution of the present invention, the second purification in step (2) includes a second distillation.

[0058] Preferably, the bottom temperature of the second distillation is 110-150°C, for example, it can be 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C or 150°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0059] Preferably, the top temperature of the second distillation tower is 100-130°C, for example, it can be 100°C, 105°C, 110°C, 115°C, 120°C, 125°C or 130°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0060] Preferably, the distillation pressure of the second distillation is 0.1-0.2 MPa, for example, 0.1 MPa, 0.12 MPa, 0.14 MPa, 0.16 MPa, 0.18 MPa or 0.2 MPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0061] Preferably, the reflux ratio of the second distillation is 5 to 10, for example, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5 or 10, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0062] As a preferred technical solution of the present invention, the second alkali solution in step (3) comprises any one of lithium hydroxide, sodium hydroxide, potassium hydroxide, 8-diazabicyclo[5.4.0]undec-7-ene, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium tert-butoxide, potassium tert-butoxide, diethylamine, dipropylamine, dibutylamine, triethylamine, tributylamine, piperidine or pyridine, or a combination of at least two thereof. Typical but non-limiting combinations include: a combination of lithium hydroxide, sodium hydroxide and potassium hydroxide, a combination of 8-diazabicyclo[5.4.0]undec-7-ene, piperidine and pyridine, a combination of sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium tert-butoxide and potassium tert-butoxide, or a combination of diethylamine, dipropylamine, dibutylamine, triethylamine and tributylamine.

[0063] In the present invention, the second alkaline solution has the function of simultaneously removing the hydroxyl group and the hydrogen on the β-carbon of the hydroxyl group in the hexafluoroisobutanol molecule.

[0064] Preferably, the third solvent includes any one of dimethyl sulfoxide, tetrahydrofuran, acetonitrile, N,N-dimethylformamide, benzene, toluene, dichloromethane, 1,1-dichloroethane, 1,2-dichloroethane, chlorobenzene, methanol, ethanol or tert-butanol, or a combination of at least two thereof. Typical but non-limiting combinations include: a combination of dimethyl sulfoxide, tetrahydrofuran, acetonitrile and N,N-dimethylformamide, a combination of benzene, toluene and chlorobenzene, a combination of dichloromethane, 1,1-dichloroethane and 1,2-dichloroethane, or a combination of methanol, ethanol and tert-butanol.

[0065] Preferably, the mass ratio of the third solvent to the total mass of the second alkali solution and hexafluoroisobutanol is 1.3 to 4.5:1, for example, it can be 1.3:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1 or 4.5:1, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0066] Preferably, in step (3), the molar ratio of the second alkali solution to hexafluoroisobutanol is 1 to 10:1, for example, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0067] In the present invention, the principle of preparing hexafluoroisobutylene using the second alkali solution and hexafluoroisobutanol as raw materials is that the second alkali solution acts as a dehydrating agent to simultaneously remove the hydroxyl group and the hydrogen on the β-carbon of the hydroxyl group in the hexafluoroisobutanol molecule, that is, to remove one molecule of water to generate hexafluoroisobutylene.

[0068] As a preferred technical solution of the present invention, the terminal temperature of the second cooling treatment in step (3) is -20 to -10°C, for example, it can be -20°C, -18°C, -16°C, -14°C, -12°C or -10°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0069] In the present invention, the third solvent and the second alkali solution are first mixed and cooled during the preparation of the hexafluoroisobutylene in order to avoid boiling during the feeding of hexafluoroisobutanol, thereby preventing positive pressure in the system and loss of hexafluoroisobutylene.

[0070] Preferably, the temperature of the three reactions in step (3) is 35-50°C, for example, 35°C, 38°C, 41°C, 44°C, 47°C or 50°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0071] As a preferred technical solution of the present invention, the temperature of the condensation treatment in step (3) is -70 to -90°C, for example, it can be -70°C, -74°C, -78°C, -82°C, -86°C or -90°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0072] As a preferred technical solution of the present invention, the bottom temperature of the distillation treatment in step (3) is 20-40°C, for example, it can be 20°C, 24°C, 28°C, 32°C, 36°C or 40°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0073] Preferably, the top temperature of the distillation treatment in step (3) is 10-30°C, for example, 10°C, 14°C, 18°C, 22°C, 26°C or 30°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0074] Preferably, the distillation pressure of the distillation treatment in step (3) is 0.1-0.2 MPa, for example, it can be 0.1 MPa, 0.12 MPa, 0.14 MPa, 0.16 MPa, 0.18 MPa or 0.2 MPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0075] Preferably, the reflux ratio of the distillation treatment in step (3) is 5 to 15, for example, it can be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0076] As a preferred technical solution of the present invention, the method for preparing hexafluoroisobutylene provided by the present invention comprises the following steps:

[0077] (1) under an inert gas atmosphere, a first solvent, a first alkali solution and a sulfonium salt compound are mixed for a primary reaction at -20 to 60° C. for 1.5 to 2.5 hours, and then hexafluoroacetone is mixed for a secondary reaction at 0 to 30° C. for 6 to 10 hours, and 2,2-bis(trifluoromethyl)ethylene oxide having a purity of ≥99.5% is obtained after a first purification;

[0078] Wherein, the molar ratio of the sulfonium salt compound to the first alkali solution is 1:1-2; the molar ratio of the sulfonium salt compound to hexafluoroacetone is 1:0.5-1;

[0079] (2) under an inert gas atmosphere, mixing the second solvent and the 2,2-bis(trifluoromethyl)ethylene oxide obtained in step (1) for a first cooling treatment to -20 to -10°C, and then mixing with a reducing agent for a reduction reaction at 20 to 30°C for 6 to 12 hours, and obtaining hexafluoroisobutanol with a purity of ≥97% after a second purification;

[0080] Wherein, the molar ratio of the reducing agent to 2,2-bis(trifluoromethyl)ethylene oxide is 1 to 3:1;

[0081] (3) mixing the third solvent and the second alkali solution for a second cooling treatment to -20 to -10°C, and then mixing the hexafluoroisobutanol obtained in step (2) for three reactions at 35 to 50°C, and then condensing and rectifying at -70 to -90°C to obtain the hexafluoroisobutene;

[0082] Wherein, the molar ratio of the second alkali solution to hexafluoroisobutanol is 1 to 10:1;

[0083] The tower bottom temperature of the distillation treatment is 20-40°C, the tower top temperature is 10-30°C, the distillation pressure is 0.1-0.2MPa, and the reflux ratio is 5-15.

[0084] It is worth noting that, in the present invention, water is added to the reaction solution of the secondary reaction in step (1) to quench the reaction; and ethanol is slowly added dropwise to the reaction solution of the reduction reaction in step (2) and stirred continuously for 1 hour to quench the reaction.

[0085] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0086] Compared with the prior art, the present invention has the following beneficial effects:

[0087] (1) The method for preparing hexafluoroisobutylene provided by the present invention has a short preparation route, mild reaction conditions, and no harsh conditions such as high temperature and high pressure;

[0088] (2) In the method for preparing hexafluoroisobutylene provided by the present invention, the raw materials and the products of the reaction are easy to separate, and the purification process is simple;

[0089] (3) The preparation method provided by the present invention is easy to operate, and the solvent used in the preparation process can be recycled, which reduces the pollution in the preparation process, and has less "three wastes", is environmentally friendly, and is suitable for large-scale production;

[0090] (4) The reagents used in the preparation method provided by the present invention are all conventional reagents, which are low in price and easily available in the market, and have obvious cost advantages. DETAILED DESCRIPTION

[0091] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0092] Example 1

[0093] This embodiment provides a method for preparing hexafluoroisobutylene, which comprises the following steps:

[0094] (1) In a nitrogen atmosphere, 200 mL of tetrahydrofuran, 8.51 g of sodium hydride (0.35 mol) and 65 g of trimethylsulfoxide iodide (0.29 mol) were mixed in a 500 mL dry three-necked flask, and the mixture was reacted at 60° C. for 2 h, and then 49.03 g of hexafluoroacetone (0.29 mol) was mixed and reacted at 0° C. for 6 h. After the first purification, 49.2 g of 2,2-bis(trifluoromethyl)ethylene oxide with a purity of 99.71% was obtained;

[0095] Wherein, the first purification is a first distillation, the tower bottom temperature of the first distillation is 50° C., the tower top temperature is 42° C., the distillation pressure is 0.15 MPa, and the reflux ratio is 5;

[0096] (2) In a 250 mL dry three-necked flask under a nitrogen atmosphere, 100 mL of tetrahydrofuran and 45 g of 2,2-bis(trifluoromethyl)ethylene oxide (0.25 mol) obtained in step (1) were mixed and subjected to a first cooling treatment to -10°C, and then mixed with 20.75 g of borane (0.75 mol) and subjected to a reduction reaction at 25°C for 12 h, and after a second purification, 40.2 g of hexafluoroisobutanol with a purity of 97.82% was obtained;

[0097] Wherein, the second purification is a second distillation, the tower bottom temperature of the second distillation is 140°C, the tower top temperature is 120°C, the distillation pressure is 0.15MPa, and the reflux ratio is 5;

[0098] (3) In a 250 mL dry three-necked flask, 100 mL of 1,1-dichloroethane and 43.14 g of potassium hydroxide (0.77 mol) were mixed and subjected to a second cooling treatment to -10°C, and then 35 g of the hexafluoroisobutanol (0.19 mol) obtained in step (2) was mixed and reacted three times at 35°C, and then condensed at -80°C and distilled to obtain 30.7 g of the hexafluoroisobutene;

[0099] The bottom temperature of the distillation treatment is 30°C, the top temperature is 15°C, the distillation pressure is 0.15MPa, and the reflux ratio is 10.

[0100] Example 2

[0101] This embodiment provides a method for preparing hexafluoroisobutylene, which comprises the following steps:

[0102] (1) In a nitrogen atmosphere, 200 mL of ultra-dry dimethyl sulfoxide, 7.64 g of sodium hydride (0.32 mol) and 50 g of trimethylsulfur iodide (0.24 mol) were mixed in a 500 mL dry three-necked flask and reacted at 0° C. for 2 h, and then 38.9 g of hexafluoroacetone (0.23 mol) was mixed and reacted at 25° C. for 8 h. After the first purification, 38.9 g of 2,2-bis(trifluoromethyl)ethylene oxide with a purity of 99.62% was obtained;

[0103] The first purification is a first distillation, the tower bottom temperature of the first distillation is 50° C., the tower top temperature is 45° C., the distillation pressure is 0.15 MPa, and the reflux ratio is 2;

[0104] (2) In a 250 mL dry three-necked flask under a nitrogen atmosphere, 100 mL of ultra-dry tetrahydrofuran and 35 g of 2,2-bis(trifluoromethyl)ethylene oxide (0.19 mol) obtained in step (1) were mixed and subjected to a first cooling treatment to -15°C, and then a reduction reaction was carried out at 20°C for 12 h with a mixed reducing agent, and after a second purification, 28.6 g of hexafluoroisobutanol with a purity of 98.76% was obtained;

[0105] Wherein, the second purification is a second distillation, the tower bottom temperature of the second distillation is 140°C, the tower top temperature is 120°C, the distillation pressure is 0.15MPa, and the reflux ratio is 5;

[0106] (3) In a 250 mL dry three-necked flask, 100 mL of 1,1-dichloroethane and 38.52 g of potassium hydroxide (0.7 mol) were mixed and subjected to a second cooling treatment to -15°C, and then 25.5 g of hexafluoroisobutanol (0.14 mol) obtained in step (2) was mixed and reacted three times at 40°C, and then condensed at -70°C and distilled to obtain 21.9 g of hexafluoroisobutene with a purity of 99.96%;

[0107] The bottom temperature of the distillation treatment is 30°C, the top temperature is 15°C, the distillation pressure is 0.15MPa, and the reflux ratio is 10.

[0108] Example 3

[0109] This embodiment provides a method for preparing hexafluoroisobutylene, which comprises the following steps:

[0110] (1) In a nitrogen atmosphere, 200 mL of N,N-dimethylformamide, sodium ethoxide and trimethylsulfur chloride were mixed in a 500 mL dry three-necked flask and reacted at 20° C. for 2.5 h, and then hexafluoroacetone was mixed and reacted at 20° C. for 10 h. After the first purification, 2,2-bis(trifluoromethyl)ethylene oxide was obtained;

[0111] Wherein, the molar ratio of trimethyl sulfide chloride to sodium ethoxide is 1:2; the molar ratio of trimethyl sulfide chloride to hexafluoroacetone is 1:0.5;

[0112] The first purification is a first distillation, the tower bottom temperature of the first distillation is 50° C., the tower top temperature is 42° C., the distillation pressure is 0.15 MPa, and the reflux ratio is 5;

[0113] (2) In a 250 mL dry three-necked flask under a nitrogen atmosphere, 100 mL of acetonitrile and the 2,2-bis(trifluoromethyl)ethylene oxide obtained in step (1) were mixed and subjected to a first cooling treatment to -20°C, and then mixed with lithium borohydride for a reduction reaction at 20 to 30°C for 6 to 12 hours, and hexafluoroisobutanol was obtained after a second purification;

[0114] Wherein, the molar ratio of lithium borohydride to 2,2-bis(trifluoromethyl)ethylene oxide is 3:1;

[0115] The second purification is a second distillation, the tower bottom temperature of the second distillation is 140° C., the tower top temperature is 120° C., the distillation pressure is 0.15 MPa, and the reflux ratio is 5;

[0116] (3) mixing chlorobenzene and sodium methoxide for a second cooling treatment to -20°C, and then mixing the hexafluoroisobutanol obtained in step (2) for three reactions at 50°C, and then condensing at -90°C and then distilling to obtain the hexafluoroisobutene;

[0117] Wherein, the molar ratio of sodium methoxide to hexafluoroisobutanol is 10:1;

[0118] The bottom temperature of the distillation treatment is 30°C, the top temperature is 15°C, the distillation pressure is 0.15MPa, and the reflux ratio is 10.

[0119] Example 4

[0120] This embodiment provides a method for preparing hexafluoroisobutylene, which differs from the preparation method in Embodiment 1 only in that:

[0121] In this embodiment, the reaction temperature of the secondary reaction in step (1) is adjusted to 60°C.

[0122] Example 5

[0123] This embodiment provides a method for preparing hexafluoroisobutylene, which differs from the preparation method in Embodiment 1 only in that:

[0124] In this embodiment, the reaction temperature of the secondary reaction in step (1) is adjusted to -10°C.

[0125] Example 6

[0126] This embodiment provides a method for preparing hexafluoroisobutylene, which differs from the preparation method in Embodiment 1 only in that:

[0127] In this embodiment, the reaction temperature of the primary reaction in step (1) is adjusted to -30°C.

[0128] Example 7

[0129] This embodiment provides a method for preparing hexafluoroisobutylene, which differs from the preparation method in Embodiment 1 only in that:

[0130] In this embodiment, the end point temperature of the first cooling treatment in step (2) is adjusted to 0°C.

[0131] Example 8

[0132] This embodiment provides a method for preparing hexafluoroisobutylene, which differs from the preparation method in Embodiment 1 only in that:

[0133] In this embodiment, the reaction temperature of the reduction reaction in step (2) is adjusted to 0°C.

[0134] Example 9

[0135] This embodiment provides a method for preparing hexafluoroisobutylene, which differs from the preparation method in Embodiment 1 only in that:

[0136] In this embodiment, the end point temperature of the second cooling treatment in step (3) is adjusted to 0°C.

[0137] Example 10

[0138] This embodiment provides a method for preparing hexafluoroisobutylene, which differs from the preparation method in Embodiment 1 only in that:

[0139] In this embodiment, the reaction temperature of the three reactions in step (3) is adjusted to 30°C.

[0140] Comparative Example 1

[0141] This comparative example provides a method for preparing hexafluoroisobutylene, which differs from Example 1 only in that:

[0142] In this comparative example, step (1) was adjusted as follows: under a nitrogen atmosphere, 200 mL of tetrahydrofuran, 8.51 g of sodium hydride (0.35 mol), 65 g of trimethylsulfoxide iodide (0.29 mol) and 34.33 g of hexafluoroacetone (0.21 mol) were mixed in a 500 mL dry three-necked flask and reacted at 60° C. for 6 h.

[0143] Comparative Example 2

[0144] This comparative example provides a method for preparing hexafluoroisobutylene, which differs from Example 1 only in that:

[0145] In this comparative example, step (2) was adjusted as follows: under a nitrogen atmosphere, 100 mL of tetrahydrofuran, 45 g of 2,2-bis(trifluoromethyl)ethylene oxide (0.25 mol) and 20.75 g of borane (0.75 mol) were mixed in a 250 mL dry three-necked flask and subjected to a reduction reaction at 25° C. for 12 h.

[0146] Comparative Example 3

[0147] This comparative example provides a method for preparing hexafluoroisobutylene, which differs from Example 1 only in that:

[0148] In this comparative example, step (3) was adjusted as follows: 100 mL of 1,1-dichloroethane, 43.14 g of potassium hydroxide (0.77 mol) and 35 g of hexafluoroisobutanol (0.19 mol) were mixed in a 250 mL dry three-necked flask and reacted three times at 35°C.

[0149] The yields and purities of 2,2-bis(trifluoromethyl)ethylene oxide, hexafluoroisobutanol and hexafluoroisobutene in the preparation methods provided in the above examples and comparative examples were calculated and tested, and the results are shown in Table 1.

[0150] Table 1

[0151]

[0152] According to Table 1, we can know the following points:

[0153] (1) Comprehensive analysis of Examples 1-3 shows that the hexafluoroisobutylene prepared by the present invention has a high purity, and the solvent used in the preparation process can be recycled, which reduces pollution in the preparation process, and has less "three wastes", is environmentally friendly, and is suitable for large-scale production;

[0154] (2) Comprehensive analysis of Example 1 and Examples 4-6 shows that the reaction temperature of the primary reaction and the secondary reaction in the preparation process of 2,2-bis(trifluoromethyl)ethylene oxide will affect the yield or purity of the 2,2-bis(trifluoromethyl)ethylene oxide, thereby affecting the preparation of the hexafluoroisobutylene;

[0155] When the temperature of the primary reaction is too low, the reaction conversion will not be completed, and the amount of sulfur ylide generated in situ will be small, thereby reducing the yield of 2,2-bis(trifluoromethyl)ethylene oxide; when the reaction temperature of the secondary reaction is too high, the reaction selectivity will be reduced or the target product will be cracked. If the reaction temperature is too low, the degree of the formal [1+2] cycloaddition reaction between the generated sulfur ylide and the carbon-oxygen double bond in hexafluoroacetone will be reduced, thereby reducing the yield of 2,2-bis(trifluoromethyl)ethylene oxide;

[0156] (3) Comprehensive analysis of Example 1 and Examples 7-8 shows that the selection of process parameters during the preparation of hexafluoroisobutanol will affect the yield or purity of the hexafluoroisobutanol, and further affect the preparation of the hexafluoroisobutylene;

[0157] When the end temperature of the first cooling treatment is too high, when the reducing agent is added, the reaction system will quickly produce a large amount of hydrogen and easily cause the reaction liquid to boil, which may easily cause safety accidents; when the reaction temperature of the reduction reaction is too low, the reaction process will be slow and the degree of reaction completion will be reduced;

[0158] (4) Comprehensive analysis of Example 1 and Examples 9-10 shows that the selection of process parameters in step (3) will affect the yield or purity of the hexafluoroisobutylene;

[0159] When the end temperature of the second cooling treatment is too high, it will cause boiling during the feeding process of hexafluoroisobutanol, resulting in positive pressure in the system and loss of hexafluoroisobutylene; when the reaction temperature of the third reaction is too low, the ability of the second base to remove water from the hexafluoroisobutanol molecules will be reduced, resulting in a decrease in the yield of hexafluoroisobutylene;

[0160] (5) Comprehensive analysis of Example 1 and Comparative Examples 1-3 shows that the solvent mixing order and reaction conditions in the preparation process will affect the progress of the hexafluoroisobutylene reaction;

[0161] In the process of preparing 2,2-bis(trifluoromethyl)oxirane in step (1), if the sulfonium salt compound, the first alkali solution, hexafluoroacetone and the first solvent are mixed at one time for reaction, the reaction process of in-situ formation of sulfur ylide will be interfered, resulting in reduced formation of sulfur ylide and reduced reaction selectivity, and increased reaction by-products;

[0162] In the process of preparing hexafluoroisobutanol in step (2), if 2,2-bis(trifluoromethyl)ethylene oxide, the reducing agent and the second solvent are mixed at one time for reaction, a large amount of hydrogen will be rapidly generated in the reaction system and the reaction solution will easily boil over;

[0163] In step (3), if the second alkali solution, hexafluoroisobutanol and the third solvent are mixed at once for reaction, it will cause boiling during the feeding process of hexafluoroisobutanol, resulting in positive pressure in the system and loss of hexafluoroisobutylene.

[0164] In summary, the preparation method of hexafluoroisobutylene provided by the present invention has a short preparation route, mild reaction conditions, and the solvent used in the preparation process can be recycled, thereby reducing pollution in the preparation process, and less "three wastes", which is environmentally friendly and suitable for large-scale production.

[0165] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing hexafluoroisobutylene, characterized in that: The preparation method comprises the following steps: (1) under an inert gas atmosphere, mixing a first solvent, a first alkali solution and a sulfonium salt compound for a primary reaction, and then mixing hexafluoroacetone for a secondary reaction, to obtain 2,2-bis(trifluoromethyl)ethylene oxide after a first purification; (2) under an inert gas atmosphere, mixing the second solvent and the 2,2-bis(trifluoromethyl)ethylene oxide obtained in step (1) for a first cooling treatment, then mixing with a reducing agent for a reduction reaction, and obtaining hexafluoroisobutanol after a second purification; (3) mixing the third solvent and the second alkali solution for a second cooling treatment, and then mixing the hexafluoroisobutanol obtained in step (2) for three reactions, and then sequentially performing condensation treatment and rectification treatment to obtain the hexafluoroisobutene.

2. The preparation method according to claim 1, characterized in that: The sulfonium salt compound in step (1) includes any one of trimethyl sulfoxide chloride, trimethyl sulfoxide bromide, trimethyl sulfoxide iodide, trimethyl sulfoxide chloride, trimethyl sulfoxide bromide or trimethyl sulfoxide iodide, or a combination of at least two thereof; Preferably, the first alkali solution comprises any one of lithium hydroxide, sodium hydroxide, potassium hydroxide, sodium hydride, potassium hydride, methyl lithium, n-butyl lithium, tert-butyl lithium, lithium hexamethyldisilazide, sodium hexamethyldisilazide, 8-diazabicyclo[5.4.0]undec-7-ene, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium tert-butoxide or potassium tert-butoxide, or a combination of at least two thereof; Preferably, the molar ratio of the sulfonium salt compound to the first alkali solution in step (1) is 1:1-2; Preferably, the molar ratio of the sulfonium salt compound to hexafluoroacetone in step (1) is 1:0.5-1.

3. The preparation method according to claim 1 or 2, characterized in that: The temperature of the primary reaction in step (1) is -20 to 60°C; Preferably, the time of the primary reaction in step (1) is 1.5 to 2.5 hours; Preferably, the temperature of the secondary reaction in step (1) is 0 to 30°C; Preferably, the secondary reaction time in step (1) is 6 to 10 hours; Preferably, the purity of the 2,2-bis(trifluoromethyl)ethylene oxide in step (1) is ≥99.5%.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The reducing agent in step (2) comprises any one of lithium borohydride, sodium borohydride, lithium aluminum hydride, borane or hydrogen / palladium on carbon, or a combination of at least two thereof; Preferably, the molar ratio of the reducing agent to 2,2-bis(trifluoromethyl)ethylene oxide in step (2) is 1 to 3:

1.

5. The preparation method according to any one of claims 1 to 4, characterized in that: Step (2) The terminal temperature of the first cooling treatment is -20 to -10°C; Preferably, the temperature of the reduction reaction in step (2) is 20 to 30° C. Preferably, the reduction reaction time in step (2) is 6 to 12 hours; Preferably, the purity of the hexafluoroisobutanol in step (2) is ≥97%.

6. The preparation method according to any one of claims 1 to 5, characterized in that: Step (3) the second alkali solution comprises any one of lithium hydroxide, sodium hydroxide, potassium hydroxide, 8-diazabicyclo[5.4.0]undec-7-ene, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, sodium tert-butoxide, potassium tert-butoxide, diethylamine, dipropylamine, dibutylamine, triethylamine, tributylamine, piperidine or pyridine, or a combination of at least two thereof; Preferably, in step (3), the molar ratio of the second alkali solution to hexafluoroisobutanol is 1 to 10:

1.

7. The preparation method according to any one of claims 1 to 6, characterized in that: Step (3) The terminal temperature of the second cooling treatment is -20 to -10°C; Preferably, the temperature of the three reactions in step (3) is 35-50°C.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The temperature of the condensation treatment in step (3) is -70 to -90°C.

9. The preparation method according to any one of claims 1 to 8, characterized in that: The bottom temperature of the distillation tower in step (3) is 20-40°C; Preferably, the top temperature of the distillation treatment in step (3) is 10 to 30° C. Preferably, the distillation pressure of the distillation treatment in step (3) is 0.1-0.2 MPa; Preferably, the reflux ratio of the distillation treatment in step (3) is 5 to 15.

10. The preparation method according to any one of claims 1 to 9, characterized in that: The preparation method comprises the following steps: (1) under an inert gas atmosphere, a first solvent, a first alkali solution and a sulfonium salt compound are mixed for a primary reaction at -20 to 60° C. for 1.5 to 2.5 hours, and then hexafluoroacetone is mixed for a secondary reaction at 0 to 30° C. for 6 to 10 hours, and 2,2-bis(trifluoromethyl)ethylene oxide having a purity of ≥99.5% is obtained after a first purification; Wherein, the molar ratio of the sulfonium salt compound to the first alkali solution is 1:1-2; the molar ratio of the sulfonium salt compound to hexafluoroacetone is 1:0.5-1; (2) under an inert gas atmosphere, mixing the second solvent and the 2,2-bis(trifluoromethyl)ethylene oxide obtained in step (1) for a first cooling treatment to -20 to -10°C, and then mixing with a reducing agent for a reduction reaction at 20 to 30°C for 6 to 12 hours, and obtaining hexafluoroisobutanol with a purity of ≥97% after a second purification; Wherein, the molar ratio of the reducing agent to 2,2-bis(trifluoromethyl)ethylene oxide is 1 to 3:1; (3) mixing the third solvent and the second alkali solution for a second cooling treatment to -20 to -10°C, and then mixing the hexafluoroisobutanol obtained in step (2) for three reactions at 35 to 50°C, and then condensing and rectifying at -70 to -90°C to obtain the hexafluoroisobutene; Wherein, the molar ratio of the second alkali solution to hexafluoroisobutanol is 1 to 10:1; The tower bottom temperature of the distillation treatment is 20-40°C, the tower top temperature is 10-30°C, the distillation pressure is 0.1-0.2MPa, and the reflux ratio is 5-15.

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