Preparation method of hexafluoroisobutylene

Abstract

The invention relates to a preparation method of hexafluoroisobutene, which comprises the following steps: in a protective atmosphere, mixing 3, 3, 3-trifluoro-2-(trifluoromethyl) propionic acid, 2, 2-dimethyl propionic acid, tetramethylammonium tetrafluoroborate and a solvent, reacting under a current condition, and purifying to obtain the hexafluoroisobutene. The preparation method is simple in process route and mild in reaction condition, metal ions are not introduced in the preparation process, and pollution is reduced; and the method is short in reaction time, environment-friendly and suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of fluorochemical technology and relates to a method for preparing hexafluoroisobutylene. Background Technology

[0002] Hexafluoroisobutylene (HFIB), with the molecular formula C4H2F6 and a molecular weight of 168.04, is a transparent, colorless liquid with a variety of applications. Firstly, it can be used as a raw material for semiconductor photolithography materials, particularly for manufacturing photolithography materials with good transmittance in the 193nm–157nm wavelength range, which is crucial for the photolithography of next-generation high-density semiconductors. Secondly, HFIB can be used as an electron etching gas to improve the selectivity between silicon-containing substrates and mask materials during plasma etching, reducing damage to channel regions, forming vertical profiles, and reducing the curvature of high aspect ratio structures. Beyond the semiconductor field, HFIB can also be used as a non-ozone-consuming refrigerant and foaming agent. Furthermore, HFIB can be used as a pharmaceutical intermediate; for example, the reaction of HFIB with benzene can produce 3,3,3-trifluoro-2-trifluoromethylpropylbenzene, a pharmaceutical intermediate used in the manufacture of anti-inflammatory drugs. In summary, due to its unique physicochemical properties and wide range of applications, HFIB plays an important role in multiple industries.

[0003] Currently, there are several methods for synthesizing hexafluoroisobutylene: (1) Takamatsu et al. (Dehydration of 2-trifluoromethy1-3,3,3-trifluoropropanol with base [J]. J. Fluorine Chem. 1984, 24(4): 531-533.) reported a method for producing hexafluoroisobutylene with a yield of 80% by reacting 2-trifluoromethyl-3,3,3-trifluoroprop-1-ol as a raw material in 1,1-dichloroethane with KOH at 20°C for 5 minutes; (2) Braun et al. (Unsaturated derivatives of fluorinated tertiary alcohols [J]. J. Org. Chem. 1966, 31(10): 3090-3093.) and Murray et al. (Reactions of polyhalotertiary alcohols with halogenating agents [J]. Tetrahedron. 1971, 27(15): 3345-3355.(3) WO2001014294A1 discloses that octafluoroisobutane ((CF3)2CFCH2F) reacts with various defluorinating agents at 500℃ to produce hexafluoroisobutene in a yield of 57%~72%. 66238A discloses a reaction of 2-trifluoromethyl-3,3,3-trifluorobutyric acid chloromethyl ester with various organic bases at a temperature range of 60℃~70℃ to generate hexafluoroisobutylene with a yield of 70~76%; (5) US4244891A discloses a method for generating hexafluoroisopropene by cyclization and ring-opening decarbonylation of hexafluoroacetone and ketene precursors at a temperature range of 400℃~700℃, with a molar conversion rate of over 90%; (6) EP0068080B1 discloses a process for preparing hexafluoroisobutylene, which uses hexafluoroacetone as a precursor. A certain amount of DMF, S powder, etc., were mixed with a small amount of potassium fluoride and reacted at 60°C for 1 hour to generate hexafluoropropanethion dimer with a yield of about 90%. Then, paraformaldehyde and potassium fluoride were added and heated to 120°C, and the reaction was continued for 2-3 hours to generate hexafluoroisobutylene with a yield of 20%-48%. (7) FR1370349 reported a method using 1,3-dichloro-1,1,3,3-tetrafluoropropane as raw material, which was reacted sequentially with methyl Grignard reagent, sulfur tetrafluoride, hydrogen fluoride and antimony trifluoride through a multi-step reaction to achieve a yield of 44%. The overall yield of hexafluoroisobutylene was 49.1%; (8) JPS61291530A disclosed a method using methyl 3,3,3-trifluoro-2-(trifluoromethyl)propionate as a raw material, reacting it with paraformaldehyde at 90°C for 3 hours in the presence of tri-n-butylamine; (9) DE3635750A1 disclosed a method using methyl 3,3,3-trifluoro-2-(trifluoromethyl)propionate as a raw material, where the product obtained after chlorination was reacted with pyridine at 70°C for 2 hours to yield hexafluoroisopropene.

[0004] In summary, the above-mentioned synthesis methods involve harsh reaction conditions, complex processes, and demanding equipment. Furthermore, the production process generates large amounts of liquid and solid waste, severely polluting the environment. To address these issues, new preparation methods need to be developed. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing hexafluoroisobutylene. The preparation method has a simple process route, mild reaction conditions, and does not introduce metal ions during the preparation process, thus reducing pollution. Furthermore, the reaction time is short, making it environmentally friendly and suitable for large-scale production.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] An embodiment of the present invention provides a method for preparing hexafluoroisobutylene, the method comprising the following steps:

[0008] In a protective atmosphere, 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid, 2,2-dimethylpropionic acid, tetramethylammonium tetrafluoroborate and solvent are mixed and reacted under an electric current. After purification, hexafluoroisobutylene is obtained.

[0009] The preparation method described in this invention involves mixing 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid with 2,2-dimethylpropionic acid and tetramethylammonium tetrafluoroborate, and reacting the mixture under an electric current to obtain hexafluoroisobutylene. This method has the advantages of simple process, fast reaction, high yield, low pollution, and suitability for industrial application.

[0010] In one embodiment of the present invention, the reaction temperature is 20°C to 50°C.

[0011] In one embodiment of the present invention, the current of the reaction is 10.5mA to 107mA.

[0012] In one embodiment of the present invention, the reaction time is 1 hour to 24 hours.

[0013] In one embodiment of the present invention, the molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid to 2,2-dimethylpropionic acid is 0.5:1 to 9.25:1.

[0014] In one embodiment of the present invention, the molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid to tetramethylammonium tetrafluoroborate is 0.5:1 to 9:1.

[0015] In one embodiment of the present invention, the solvent includes any one or a combination of at least two of the following: dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, acetonitrile, benzene, toluene, chlorobenzene, nitrobenzene, p-xylene, o-xylene, m-xylene, acetone, 1,2-dichloroethane, or 1,1-dichloroethane.

[0016] In one embodiment of the present invention, 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid, 2,2-dimethylpropionic acid and tetramethylammonium tetrafluoroborate are used as raw materials;

[0017] The mass ratio of the solvent to the raw material is 1:1 to 10:1.

[0018] In one embodiment of the present invention, the protective atmosphere includes nitrogen and / or an inert gas.

[0019] In one embodiment of the present invention, the preparation method includes the following steps:

[0020] In a protective atmosphere, 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid, 2,2-dimethylpropionic acid, tetramethylammonium tetrafluoroborate and solvent were mixed and reacted under an electric current condition. After purification, hexafluoroisobutylene was obtained.

[0021] The reaction temperature is 25℃~45℃, the reaction current is 70.5mA~107mA, and the reaction time is 2h~24h;

[0022] The molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid to 2,2-dimethylpropionic acid is 5:1 to 9.25:1.

[0023] The molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid to tetramethylammonium tetrafluoroborate is 0.5:1 to 9:1;

[0024] The solvent is used as a raw material, comprising 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid, 2,2-dimethylpropionic acid and tetramethylammonium tetrafluoroborate; the mass ratio of the solvent to the raw material is 3:1 to 10:1.

[0025] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The reagents used in the preparation method provided by the present invention are all conventional reagents, which are inexpensive and readily available on the market, and have obvious cost advantages;

[0028] (2) The preparation method provided by the present invention has a simple process route, mild reaction conditions, and no harsh conditions such as high temperature and high pressure;

[0029] (3) The preparation method provided by the present invention is easy to operate, the solvent used in the preparation process can be recycled, no metal ions are introduced, the pollution in the preparation process is reduced, and there is less "three wastes", which is environmentally friendly and suitable for large-scale production;

[0030] (4) The raw materials and products generated by the reaction in the preparation method provided by the present invention are easy to separate, and the purification process is simple. Detailed Implementation

[0031] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0032] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0033] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0034] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0035] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0036] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0037] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0038] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0039] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0040] In this invention, "optional" means that something is optional, that is, it refers to any one of the two parallel solutions of "having" or "not having". If there are multiple "optional" options in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, then each "optional" option is independent.

[0041] An embodiment of the present invention provides a method for preparing hexafluoroisobutylene, the method comprising the following steps:

[0042] In a protective atmosphere, 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid, 2,2-dimethylpropionic acid, tetramethylammonium tetrafluoroborate and solvent are mixed and reacted under an electric current. After purification, hexafluoroisobutylene is obtained.

[0043] The preparation method described in this invention involves mixing 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid with 2,2-dimethylpropionic acid and tetramethylammonium tetrafluoroborate, and reacting the mixture under an electric current to obtain hexafluoroisobutylene. This method has the advantages of simple process, fast reaction, high yield, low pollution, and suitability for industrial application.

[0044] Specifically, compared with existing technologies, this invention effectively solves the problems commonly found in traditional hexafluoroisobutylene preparation methods, such as harsh reaction conditions, numerous byproducts, low product yield and purity, high raw material costs, or complex steps. It offers the advantages of mild reaction conditions, readily available and cost-controllable raw material combinations, and strong directional product formation. Under the synergistic effect of a protective atmosphere and current flow, tetramethylammonium tetrafluoroborate, as an electrolyte, ionizes to generate stable ions, providing good conductivity to the reaction system to ensure efficient electron transfer and providing a basic environment for reaction initiation and continuation. 2,2-Dimethylpropionic acid acts as a proton acceptor or electron mediator, reducing the activation energy of the decarboxylation reaction of the carboxyl group of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid, thus reducing the reaction's dependence on extreme conditions. It also inhibits excessive decomposition and intermolecular polymerization of the main raw material during the reaction. Finally, under the synergistic effect of the above components, the main raw material is efficiently converted into hexafluoroisobutylene through a directional decarboxylation reaction, achieving simultaneous optimization of reaction mildness, product quality, and yield.

[0045] The specific preparation route is as follows:

[0046]

[0047] In one embodiment of the present invention, the reaction temperature is 20°C to 50°C, for example, it can be 20°C, 30°C, 40°C or 50°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 25°C to 45°C.

[0048] In one embodiment of the present invention, the reaction current is 10.5mA to 107mA, for example, it can be 10.5mA, 20.5mA, 30.5mA, 40.5mA, 50.5mA, 60.5mA, 70.5mA, 80.5mA, 90.5mA or 107mA, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 10.5mA to 70.5mA.

[0049] In one embodiment of the present invention, the reaction time is 1h to 24h, for example, it can be 1h, 2h, 5h, 10h, 15h, 20h or 24h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 2h to 24h.

[0050] In one embodiment of the present invention, the molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid to 2,2-dimethylpropionic acid is 0.5:1 to 9.25:1, for example, it can be 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 9.25:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 5:1 to 9.25:1.

[0051] In one embodiment of the present invention, the molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid to tetramethylammonium tetrafluoroborate is 0.5:1 to 9:1, for example, it can be 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1 or 9:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0052] In one embodiment of the present invention, the solvent includes any one or a combination of at least two of the following: dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, acetonitrile, benzene, toluene, chlorobenzene, nitrobenzene, p-xylene, o-xylene, m-xylene, acetone, 1,2-dichloroethane, or 1,1-dichloroethane.

[0053] In one embodiment of the present invention, 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid, 2,2-dimethylpropionic acid and tetramethylammonium tetrafluoroborate are used as raw materials;

[0054] The mass ratio of the solvent to the raw material is 1:1 to 10:1, for example, it can be 1:1, 2:1, 4:1, 5:1, 6:1, 8:1 or 10:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable, preferably 3:1 to 10:1.

[0055] In one embodiment of the present invention, the protective atmosphere includes nitrogen and / or an inert gas.

[0056] This invention does not specifically limit the purification method; any purification method conventional in the art can be used to purify the product.

[0057] In one embodiment of the present invention, the preparation method includes the following steps:

[0058] In a protective atmosphere, 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid (CAS: 564-10-3), 2,2-dimethylpropionic acid (CAS: 75-98-9), tetramethylammonium tetrafluoroborate (CAS: 661-36-9) and solvent were mixed and reacted under an electric current. After purification, hexafluoroisobutylene was obtained.

[0059] The reaction temperature is 25℃~45℃, the reaction current is 70.5mA~107mA, and the reaction time is 2h~24h;

[0060] The molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid to 2,2-dimethylpropionic acid is 5:1 to 9.25:1.

[0061] The molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid to tetramethylammonium tetrafluoroborate is 0.5:1 to 9:1;

[0062] The solvent is used as a raw material, comprising 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid, 2,2-dimethylpropionic acid and tetramethylammonium tetrafluoroborate; the mass ratio of the solvent to the raw material is 3:1 to 10:1.

[0063] Example 1

[0064] This embodiment provides a method for preparing hexafluoroisobutylene, including the following steps:

[0065] In a nitrogen atmosphere, 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid (58 g, 0.3 mol), 2,2-dimethylpropionic acid (6 g, 0.06 mol), tetramethylammonium tetrafluoroborate (6.4 g, 0.04 mol), and acetone (300 mL) were mixed in a 500 mL dry three-necked flask and reacted under an electric current. After purification, hexafluoroisobutylene (53.766 g, purity 92.7 wt%) was obtained.

[0066] The reaction temperature was 25℃, the reaction current was 70.5mA, and the reaction time was 2h.

[0067] The molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid to 2,2-dimethylpropionic acid is 5:1.

[0068] The molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid to tetramethylammonium tetrafluoroborate is 7.5:1;

[0069] The solvent is used as a raw material, comprising 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid, 2,2-dimethylpropionic acid and tetramethylammonium tetrafluoroborate; the mass ratio of the solvent to the raw material is 3.36:1.

[0070] Example 2

[0071] This embodiment provides a method for preparing hexafluoroisobutylene. Except for adjusting the molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid to 2,2-dimethylpropionic acid to 5.25:1, all other parameters are the same as in Example 1.

[0072] Example 3

[0073] This embodiment provides a method for preparing hexafluoroisobutylene. Except for adjusting the molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid to 2,2-dimethylpropionic acid to 7.25:1, all other parameters are the same as in Example 1.

[0074] Example 4

[0075] This embodiment provides a method for preparing hexafluoroisobutylene. Except for adjusting the molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid to 2,2-dimethylpropionic acid to 9.25:1, all other parameters are the same as in Example 1.

[0076] Example 5

[0077] This embodiment provides a method for preparing hexafluoroisobutylene. Except for the reaction temperature of 35°C, all other parameters are the same as in Example 1.

[0078] Example 6

[0079] This embodiment provides a method for preparing hexafluoroisobutylene. Except for the reaction temperature of 40°C, all other parameters are the same as in Example 1.

[0080] Example 7

[0081] This embodiment provides a method for preparing hexafluoroisobutylene. Except for the reaction temperature of 45°C, all other parameters are the same as in Example 1.

[0082] Example 8

[0083] This embodiment provides a method for preparing hexafluoroisobutylene, which is the same as in Example 1 except that the reaction current is 60.5mA.

[0084] Example 9

[0085] This embodiment provides a method for preparing hexafluoroisobutylene, which is the same as in Example 1 except that the reaction current is 50.5mA.

[0086] Example 10

[0087] This embodiment provides a method for preparing hexafluoroisobutylene, which is the same as in Example 1 except that the reaction current is 40.5mA.

[0088] Example 11

[0089] This embodiment provides a method for preparing hexafluoroisobutylene, which is the same as in Example 1 except that the reaction current is 30.5mA.

[0090] Example 12

[0091] This embodiment provides a method for preparing hexafluoroisobutylene, which is the same as in Example 1 except that the reaction current is 20.5mA.

[0092] Example 13

[0093] This embodiment provides a method for preparing hexafluoroisobutylene, which is the same as in Example 1 except that the reaction current is 10.5mA.

[0094] Example 14

[0095] This embodiment provides a method for preparing hexafluoroisobutylene, which is the same as in Example 1 except that the reaction time is 5 hours.

[0096] Example 15

[0097] This embodiment provides a method for preparing hexafluoroisobutylene, which is the same as in Example 1 except that the reaction time is 10 hours.

[0098] Example 16

[0099] This embodiment provides a method for preparing hexafluoroisobutylene, which is the same as in Example 1 except that the reaction time is 15 hours.

[0100] Example 17

[0101] This embodiment provides a method for preparing hexafluoroisobutylene, which is the same as in Example 1 except that the reaction time is 20 hours.

[0102] Example 18

[0103] This embodiment provides a method for preparing hexafluoroisobutylene, which is the same as in Example 1 except that the reaction time is 24 hours.

[0104] Example 19

[0105] This embodiment provides a method for preparing hexafluoroisobutylene. Except for adjusting the molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid to tetramethylammonium tetrafluoroborate to 9:1, all other parameters are the same as in Example 1.

[0106] Example 20

[0107] This embodiment provides a method for preparing hexafluoroisobutylene. Except for adjusting the molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid to tetramethylammonium tetrafluoroborate to 8:1, all other parameters are the same as in Example 1.

[0108] Example 21

[0109] This embodiment provides a method for preparing hexafluoroisobutylene. Except for adjusting the molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid to tetramethylammonium tetrafluoroborate to 7:1, all other parameters are the same as in Example 1.

[0110] Example 22

[0111] This embodiment provides a method for preparing hexafluoroisobutylene. Except for adjusting the molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid to tetramethylammonium tetrafluoroborate to 6:1, all other parameters are the same as in Example 1.

[0112] Example 23

[0113] This embodiment provides a method for preparing hexafluoroisobutylene. Except for adjusting the molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid to tetramethylammonium tetrafluoroborate to 4:1, all other parameters are the same as in Example 1.

[0114] Example 24

[0115] This embodiment provides a method for preparing hexafluoroisobutylene. Except for adjusting the molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid to tetramethylammonium tetrafluoroborate to 2:1, all other parameters are the same as in Example 1.

[0116] Example 25

[0117] This embodiment provides a method for preparing hexafluoroisobutylene. Except for adjusting the molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid to tetramethylammonium tetrafluoroborate to 1:1, all other parameters are the same as in Example 1.

[0118] Example 26

[0119] This embodiment provides a method for preparing hexafluoroisobutylene. Except for adjusting the molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid to tetramethylammonium tetrafluoroborate to 0.5:1, all other parameters are the same as in Example 1.

[0120] Example 27

[0121] This embodiment provides a method for preparing hexafluoroisobutylene, except that the solvent (acetone) is replaced by acetonitrile, and everything else is the same as in Example 1.

[0122] Example 28

[0123] This embodiment provides a method for preparing hexafluoroisobutylene, except that the solvent (acetone) is replaced with toluene by mass, and everything else is the same as in Example 1.

[0124] Example 29

[0125] This embodiment provides a method for preparing hexafluoroisobutylene, except that the solvent (acetone) is replaced by p-xylene, and everything else is the same as in Example 1.

[0126] Example 30

[0127] This embodiment provides a method for preparing hexafluoroisobutylene, except that the solvent (acetone) is replaced by N,N-dimethylformamide by mass, and everything else is the same as in Example 1.

[0128] Example 31

[0129] This embodiment provides a method for preparing hexafluoroisobutylene, except that the solvent (acetone) is replaced by N,N-dimethylacetamide by mass, and everything else is the same as in Example 1.

[0130] Example 32

[0131] This embodiment provides a method for preparing hexafluoroisobutylene, except that the solvent (acetone) is replaced by nitrobenzene, and everything else is the same as in Example 1.

[0132] Example 33

[0133] This embodiment provides a method for preparing hexafluoroisobutylene, except that the solvent (acetone) is replaced by 1,2-dichloroethane, and everything else is the same as in Example 1.

[0134] Example 34

[0135] This embodiment provides a method for preparing hexafluoroisobutylene, except that the solvent (acetone) is replaced by 1,1-dichloroethane, and everything else is the same as in Example 1.

[0136] Example 35

[0137] This embodiment provides a method for preparing hexafluoroisobutylene, except that the solvent (acetone) is replaced by chlorobenzene, and everything else is the same as in Example 1.

[0138] Example 36

[0139] This embodiment provides a method for preparing hexafluoroisobutylene, which is the same as in Example 1 except that the mass ratio of solvent to raw material is 4:1.

[0140] Example 37

[0141] This embodiment provides a method for preparing hexafluoroisobutylene, which is the same as in Example 1 except that the mass ratio of solvent to raw material is 5:1.

[0142] Example 38

[0143] This embodiment provides a method for preparing hexafluoroisobutylene, which is the same as in Example 1 except that the mass ratio of solvent to raw material is 6:1.

[0144] Example 39

[0145] This embodiment provides a method for preparing hexafluoroisobutylene, which is the same as in Example 1 except that the mass ratio of solvent to raw material is 8:1.

[0146] Example 40

[0147] This embodiment provides a method for preparing hexafluoroisobutylene, which is the same as in Example 1 except that the mass ratio of solvent to raw material is 10:1.

[0148] Performance Characterization

[0149] Based on 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid, the yield of hexafluoroisobutylene in the preparation method provided in the above examples is shown in Table 1.

[0150] Table 1

[0151]

[0152] According to Table 1, the following points can be observed:

[0153] (1) Comprehensive analysis of Examples 1 and 2 to 4 shows that when the molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid to 2,2-dimethylpropionic acid is adjusted to 5.25:1 or higher, the yield of hexafluoroisobutylene does not change significantly, but it will cause waste of 2,2-dimethylpropionic acid.

[0154] (2) A comprehensive analysis of Examples 1 and 5 to 7 shows that the choice of reaction temperature does not significantly affect the yield of hexafluoroisobutylene;

[0155] (3) Comprehensive analysis of Examples 1 and 8 to 13 shows that when the reaction current is below 70.5 mA, the yield of hexafluoroisobutylene is significantly reduced.

[0156] (4) Comprehensive analysis of Examples 1 and 14 to 18 shows that the extension of the reaction time did not increase the yield of hexafluoroisobutylene, but it would waste energy and time. Therefore, it is sufficient to make the reaction time more than 2 hours.

[0157] (5) Comprehensive analysis of Examples 1 and 19 to 26 shows that when the molar ratio of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid to tetramethylammonium tetrafluoroborate is adjusted to less than 7:1, the yield of hexafluoroisobutylene is significantly reduced; when the molar ratio is higher than 7:1, the yield does not change significantly.

[0158] (6) Comprehensive analysis of Examples 1 and 27-35 shows that the choice of solvent affects the formation of hexafluoroisobutylene; when a nonpolar aprotic solvent (such as toluene, p-xylene, etc.) is used, it has a significant effect on the formation of hexafluoroisobutylene; when a polar aprotic solvent (such as N,N-dimethylformamide, N,N-dimethylacetamide, etc.) is used, it has a certain effect on the formation of hexafluoroisobutylene.

[0159] (7) Comprehensive analysis of Examples 1 and 36 to 40 shows that after adjusting the ratio of solvent to the total mass of raw materials used (solvent mass / (3,3,3-trifluoro-2-(trifluoromethyl)propionic acid + 2,2-dimethylpropionic acid + tetramethylammonium tetrafluoroborate)), the yield does not change significantly.

[0160] In summary, the preparation method of this invention involves mixing 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid with 2,2-dimethylpropionic acid and tetramethylammonium tetrafluoroborate, and reacting the mixture under an electric current to obtain hexafluoroisobutylene. This method has the advantages of simple process, fast reaction, high yield, low pollution, and suitability for industrialization. Specifically, compared with existing technologies, this invention effectively solves the problems commonly found in traditional hexafluoroisobutylene preparation methods, such as harsh reaction conditions, numerous byproducts, low product yield and purity, high raw material costs, or complex steps. It offers the advantages of mild reaction conditions, readily available and cost-controllable raw material combinations, and strong directional product formation. Under the synergistic effect of a protective atmosphere and current flow, tetramethylammonium tetrafluoroborate, as an electrolyte, can ionize to generate stable ions, providing good conductivity for the reaction system to ensure efficient electron transfer and providing a basic environment for the initiation and continuation of the reaction. 2,2-Dimethylpropionic acid can act as a proton acceptor or electron mediator, on the one hand reducing the activation energy of the decarboxylation reaction of the carboxyl group of 3,3,3-trifluoro-2-(trifluoromethyl)propionic acid, reducing the dependence of the reaction on extreme conditions, and on the other hand inhibiting the excessive decomposition and intermolecular polymerization of the main raw material during the reaction. Finally, under the synergistic effect of the above components, the main raw material is efficiently converted into hexafluoroisobutylene through a directional decarboxylation reaction, achieving simultaneous optimization of reaction mildness and product quality and yield.

[0161] The applicant declares that the above description is only a specific embodiment 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 conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A process for the preparation of hexafluoroisobutene, characterized in that, The preparation method comprises the following steps: The 3,3,3-trifluoro-2-(trifluoromethyl) propionic acid, the 2,2-dimethyl propionic acid and the tetramethyl ammonium tetrafluoroborate are used as raw materials.

2. The production method according to claim 1, characterized by, The temperature of the reaction is 20-50 DEG C.

3. The production method according to claim 1, characterized by, The current of the reaction is 10.5-107 mA.

4. The production method according to claim 2 or 3, characterized by, The time of the reaction is 1-24 h.

5. The preparation method according to claim 1, characterized in that, The molar ratio of the 3,3,3-trifluoro-2-(trifluoromethyl) propionic acid to the 2,2-dimethyl propionic acid is 0.5:1-9.25:

1.

6. The method of claim 1, wherein, The molar ratio of the 3,3,3-trifluoro-2-(trifluoromethyl) propionic acid to the tetramethyl ammonium tetrafluoroborate is 0.5:1-9:

1.

7. The preparation method according to claim 1, characterized in that, The solvent comprises any one or combination of at least two of dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, acetonitrile, benzene, toluene, chlorobenzene, nitrobenzene, p-xylene, o-xylene, m-xylene, acetone, 1,2-dichloroethane or 1,1-dichloroethane.

8. The production method according to claim 1 or 7, characterized by, The 3,3,3-trifluoro-2-(trifluoromethyl) propionic acid, the 2,2-dimethyl propionic acid and the tetramethyl ammonium tetrafluoroborate are used as raw materials. The mass ratio of the solvent to the raw materials is 1:1-10:

1.

9. The method of claim 1, wherein, The gas used in the protective atmosphere comprises nitrogen and / or inert gas.

10. The method of claim 1, wherein, The preparation method comprises the following steps: The 3,3,3-trifluoro-2-(trifluoromethyl) propionic acid, the 2,2-dimethyl propionic acid and the tetramethyl ammonium tetrafluoroborate are used as raw materials. The temperature of the reaction is 25-45 DEG C, the current of the reaction is 70.5-107 mA, and the time of the reaction is 2-24 h. The molar ratio of the 3,3,3-trifluoro-2-(trifluoromethyl) propionic acid to the 2,2-dimethyl propionic acid is 5:1-9.25:

1. The molar ratio of the 3,3,3-trifluoro-2-(trifluoromethyl) propionic acid to the tetramethyl ammonium tetrafluoroborate is 0.5:1-9:

1. The 3,3,3-trifluoro-2-(trifluoromethyl) propionic acid, the 2,2-dimethyl propionic acid and the tetramethyl ammonium tetrafluoroborate are used as raw materials.

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