A process for the preparation of hexafluorobutadiene

Abstract

This application provides a method for preparing hexafluorobutadiene, belonging to the field of hexafluorobutadiene manufacturing technology. The method includes the following steps: reacting 1,4-dibromooctafluorobutane, a catalyst solution, and zinc powder under heating conditions and collecting the generated gaseous hexafluorobutadiene; wherein the catalyst solution contains N,N-dimethylformamide, and the reaction temperature is lower than the boiling point of the catalyst solution with a difference of 5℃~40℃; this preparation method can produce hexafluorobutadiene in a one-step reaction using only an industrial-grade catalyst, and has the advantages of simple process steps, low energy consumption, simple catalyst system, low cost, and good safety.

Description

Technical Field

[0001] This application relates to the field of hexafluorobutadiene manufacturing technology, and more specifically, to a method for preparing hexafluorobutadiene. Background Technology

[0002] Currently, the preparation of hexafluorobutadiene typically involves multi-step reaction routes, specifically including three core preparation schemes: First, using trifluorobromoethylene as a raw material, zinc powder as a dehalogenating agent, and isopropanol as a solvent, a three-step reaction of "thermal polymerization - secondary distillation separation - dehalogenation" is carried out. This preparation route requires inert gas protection and the addition of zinc powder in batches. Second, using trifluorochloroethylene as a raw material, a three-step reaction of "addition → dimerization → dechlorination" is carried out. This preparation route uses "activated zinc + ester catalyst + polar base liquid system," and the reaction temperature needs to be gradually increased from -8~-5℃ to 60~90℃. Third, using trifluorochloroethylene as a raw material, a two-step reaction of "nickel-based catalyst-catalyzed dimerization → zinc powder dechlorination" is carried out. The dimerization stage relies on a dedicated nickel-based catalyst, and the dechlorination stage is driven solely by high temperature, without a synergistic catalytic system. Therefore, all three existing core schemes suffer from problems such as cumbersome preparation processes, high energy consumption, complex catalyst systems, high costs, and low safety.

[0003] Therefore, there is an urgent need to develop a novel preparation process for hexafluorobutadiene that is simple in process steps, low in energy consumption, and has a simple, low-cost, and safe catalyst system. Summary of the Invention

[0004] The purpose of this application is to provide a method for preparing hexafluorobutadiene, which can prepare hexafluorobutadiene through a one-step reaction using only an industrial-grade catalyst. This method has the advantages of simple process steps, low energy consumption, simple catalyst system, low cost and good safety.

[0005] The embodiments of this application are implemented as follows: In a first aspect, embodiments of this application provide a method for preparing hexafluorobutadiene, comprising the following steps: reacting 1,4-dibromooctafluorobutane, a catalyst solution, and zinc powder under heating conditions and collecting the generated gaseous hexafluorobutadiene; wherein the catalyst solution contains N,N-dimethylformamide (DMF), and the reaction temperature is lower than the boiling point of the catalyst solution and the difference between the two boiling points is 5°C to 40°C.

[0006] In the above technical solution, the reaction raw materials simultaneously contain 1,4-dibromooctafluorobutane, catalyst solution, and zinc powder. 1,4-dibromooctafluorobutane serves as a fluorine-containing raw material, zinc powder as a debromination agent, and N,N-dimethylformamide as a solvent component of the reaction system. Specifically, 1,4-dibromooctafluorobutane can be uniformly mixed with it, and zinc powder can be uniformly dispersed within it, without any side reactions occurring with either 1,4-dibromooctafluorobutane or zinc powder. Furthermore, N,N-dimethylformamide acts as a catalyst. Specifically, dimethylformamide can effectively alter the electron cloud distribution of the C-Br bond in 1,4-dibromooctafluorobutane and weaken its bond energy. Thus, under the action of zinc powder and in conjunction with the aforementioned reaction temperature, it catalyzes the bond breaking of 1,4-dibromooctafluorobutane, thereby enabling the one-step preparation of hexafluorobutadiene. Compared to traditional multi-step reaction preparation methods, the preparation method provided in this application can prepare hexafluorobutadiene through a one-step reaction using only an industrial-grade catalyst (i.e., N,N-dimethylformamide, which has the advantages of wide availability, large quantity, safety, low cost, simple system and no need for customization). It has the advantages of simple process steps, low energy consumption, simple catalyst system, low cost and good safety.

[0007] In some alternative implementations, the difference between the reaction temperature and the boiling point of the catalyst solution is 10°C to 30°C, and the reaction time is 0.5 h to 2 h.

[0008] In the above technical solution, limiting the reaction temperature and reaction time to the above range provides more suitable reaction conditions, thereby enabling 1,4-dibromooctafluorobutane to efficiently and completely break bonds to generate hexafluorobutadiene.

[0009] In some alternative embodiments, the catalyst solution further includes at least one of a polar aliphatic compound and an aromatic compound having a benzene ring, wherein the polar aliphatic compound is capable of forming a hydrogen bond with the amide bond in N,N-dimethylformamide.

[0010] In the above technical solution, the catalyst solution includes a polar aliphatic compound that can form hydrogen bonds with the amide bond in N,N-dimethylformamide and can also serve as a solvent component. The formation of hydrogen bonds can further enhance the "electron-induced effect" of N,N-dimethylformamide on the C-Br bond, further weakening the C-Br bond energy, thereby more effectively catalyzing the bond breaking of 1,4-dibromooctafluorobutane to generate hexafluorobutadiene (i.e., improving the catalytic efficiency of N,N-dimethylformamide). The catalyst solution also includes an aromatic compound with a benzene ring that can serve as a solvent component. The π electron cloud on the benzene ring can form a weak interaction with the carbocation formed after the C-Br bond breaks, thereby stabilizing the carbocation formed after the C-Br bond breaks and reducing the probability of reversible reaction. This is equivalent to promoting the bond breaking of 1,4-dibromooctafluorobutane to generate hexafluorobutadiene (i.e., improving the catalytic efficiency of N,N-dimethylformamide).

[0011] In some alternative embodiments, the polar group of the polar aliphatic compound is selected from at least one of hydroxyl and carboxyl groups.

[0012] In the above technical solution, a polar aliphatic compound with the aforementioned polar group is selected. After forming a hydrogen bond with the amide bond in N,N-dimethylformamide, it can effectively enhance the "electron-induced effect" of N,N-dimethylformamide on the C-Br bond, thereby effectively assisting N,N-dimethylformamide in catalyzing the bond breaking of 1,4-dibromooctafluorobutane to generate hexafluorobutadiene.

[0013] In some alternative embodiments, the polar aliphatic compound includes at least one of isopropanol, n-propanol, and sec-butanol.

[0014] In the above technical solution, the polar aliphatic compounds selected are of the aforementioned types. After forming hydrogen bonds with the amide bonds in N,N-dimethylformamide, they can more effectively enhance the "electron-induced effect" of N,N-dimethylformamide on the C-Br bonds, thereby more effectively assisting N,N-dimethylformamide in catalyzing the bond breaking of 1,4-dibromooctafluorobutane to generate hexafluorobutadiene. At the same time, a wide variety of polar aliphatic compounds are applicable, providing more feasible implementation schemes, thus facilitating the adjustment of the type of polar aliphatic compound according to actual needs.

[0015] In some alternative embodiments, the aromatic compound includes at least one of m-xylene, o-xylene, and toluene.

[0016] In the above technical solutions, by selecting the above-mentioned types of aromatic compounds, the π electron cloud on the benzene ring forms a weak interaction with the carbocation formed after the C-Br bond is broken, which can better stabilize the carbocation formed after the C-Br bond is broken, thereby more effectively reducing the probability of reversible reaction, and thus more effectively promoting the bond breaking of 1,4-dibromooctafluorobutane to generate hexafluorobutadiene.

[0017] In some alternative embodiments, the catalyst solution also includes a polar aliphatic compound that can form hydrogen bonds with the amide bond in N,N-dimethylformamide, and the volume ratio of the polar aliphatic compound to N,N-dimethylformamide is (1~4):1.

[0018] In the above technical solution, when the catalyst solution includes N,N-dimethylformamide and a polar aliphatic compound that can form hydrogen bonds with it, the volume ratio of the two is limited to the above range. After the polar aliphatic compound forms hydrogen bonds with the amide bond in N,N-dimethylformamide, it can more effectively enhance the "electron-induced effect" of N,N-dimethylformamide on the C-Br bond, thereby more effectively assisting N,N-dimethylformamide in catalyzing the bond breaking of 1,4-dibromooctafluorobutane to generate hexafluorobutadiene.

[0019] In some alternative embodiments, the volume ratio of the polar aliphatic compound to N,N-dimethylformamide is (1.5~2.5):1.

[0020] In the above technical solution, when the catalyst solution includes N,N-dimethylformamide and a polar aliphatic compound that can form hydrogen bonds with it, the volume ratio of the two is limited to the above range. After the polar aliphatic compound forms hydrogen bonds with the amide bond in N,N-dimethylformamide, it can more effectively enhance the "electron-induced effect" of N,N-dimethylformamide on the C-Br bond, thereby more effectively assisting N,N-dimethylformamide in catalyzing the bond breaking of 1,4-dibromooctafluorobutane to generate hexafluorobutadiene.

[0021] In some alternative embodiments, the catalyst solution also includes an aromatic compound having a benzene ring, and the volume ratio of the aromatic compound to N,N-dimethylformamide is (0.5~1.5):1.

[0022] In the above technical solution, when the catalyst solution includes N,N-dimethylformamide and an aromatic compound with a benzene ring, the volume ratio of the two is limited to the above range. After the π electron cloud on the benzene ring forms a weak interaction with the carbocation formed after the C-Br bond is broken, the carbocation formed after the C-Br bond is broken can be stabilized better, thereby effectively reducing the probability of reversible reaction and thus more effectively promoting the bond breaking of 1,4-dibromooctafluorobutane to generate hexafluorobutadiene.

[0023] In some alternative embodiments, the volume ratio of 1,4-dibromooctafluorobutane to the catalyst solution is 1:(15~20), or / and the volume-to-mass ratio of 1,4-dibromooctafluorobutane to zinc powder is 1 mL:(0.5~1) g.

[0024] In the above technical solution, the volume ratio of 1,4-dibromooctafluorobutane to the catalyst solution and the volume-mass ratio of 1,4-dibromooctafluorobutane to zinc powder are respectively limited within the above range, so that each component in the reaction raw materials has a more suitable amount and concentration, which enables 1,4-dibromooctafluorobutane to break bonds more efficiently and completely to generate hexafluorobutadiene.

[0025] In some alternative embodiments, the reaction is carried out in an inert atmosphere and under stirring conditions, wherein the stirring speed is 200 rpm to 300 rpm.

[0026] In the above technical solution, the reaction is carried out under an inert atmosphere and the above stirring conditions, which can improve the stability of the reaction system and thus prepare hexafluorobutadiene with high purity.

[0027] In some alternative embodiments, a pretreatment step of zinc powder is included before the reaction. The pretreatment step includes immersing the zinc powder in dilute hydrochloric acid with a mass concentration of 3% to 7% for 10 to 15 minutes, and then washing and drying the immersed zinc powder in sequence.

[0028] In the above technical solution, the zinc powder is pretreated according to the above process before the reaction, which can effectively remove oxide impurities on the surface of the zinc powder, thereby improving the reaction efficiency and reducing the generation of by-products. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 A process flow diagram of a method for preparing hexafluorobutadiene provided in this application embodiment; Figure 2 This is a chromatogram of hexafluorobutadiene provided in Example 1 of this application; Figure 3 This is a chromatogram of hexafluorobutadiene provided in Example 3 of this application. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0032] It should be noted that the terms "and / or" in this application, such as "feature 1 and / or feature 2", all refer to the three cases of "feature 1" alone, "feature 2" alone, and "feature 1" plus "feature 2".

[0033] In addition, in the description of this application, unless otherwise stated, "one or more" means two or more; the range of "numerical value a to numerical value b" includes the two endpoints "a" and "b"; and "unit of measurement" in "numerical value a to numerical value b + unit of measurement" represents the "unit of measurement" of both "numerical value a" and "numerical value b".

[0034] The following is a detailed description of a method for preparing hexafluorobutadiene according to an embodiment of this application.

[0035] In a first aspect, embodiments of this application provide a method for preparing hexafluorobutadiene, comprising the following steps: reacting 1,4-dibromooctafluorobutane, a catalyst solution, and zinc powder under heating conditions and collecting the generated gaseous hexafluorobutadiene; wherein the catalyst solution contains N,N-dimethylformamide, and the reaction temperature is lower than the boiling point of the catalyst solution and the difference between the temperature and the boiling point is 5°C to 40°C (for example, but not limited to, a temperature difference of any one of 5°C, 10°C, 20°C, 30°C, and 40°C, or a range between any two).

[0036] In this application, the reaction raw materials simultaneously contain 1,4-dibromooctafluorobutane, a catalyst solution, and zinc powder. 1,4-dibromooctafluorobutane serves as a fluorine-containing raw material, zinc powder as a debromination agent, and N,N-dimethylformamide as a solvent component of the reaction system. Specifically, 1,4-dibromooctafluorobutane can be uniformly mixed with it, and zinc powder can be uniformly dispersed within it, with neither 1,4-dibromooctafluorobutane nor zinc powder undergoing side reactions. Furthermore, N,N-dimethylformamide acts as a catalyst. Specifically, dimethylformamide can effectively alter the electron cloud distribution of the C-Br bond in 1,4-dibromooctafluorobutane and weaken its bond energy. Thus, under the action of zinc powder and in conjunction with the aforementioned reaction temperature, it catalyzes the bond breaking of 1,4-dibromooctafluorobutane, thereby enabling the one-step preparation of hexafluorobutadiene. Compared to traditional multi-step reaction preparation methods, the preparation method provided in this application can prepare hexafluorobutadiene through a one-step reaction using only an industrial-grade catalyst (i.e., N,N-dimethylformamide, which has the advantages of wide availability, large quantity, safety, low cost, simple system and no need for customization). It has the advantages of simple process steps, low energy consumption, simple catalyst system, low cost and good safety.

[0037] It should be noted that controlling the reaction temperature within the above range can achieve both high purity and a short reaction time.

[0038] To better understand the advantages of the preparation method provided in the embodiments of this application, supplementary explanations are provided here in conjunction with conventional preparation methods.

[0039] (1) Simple process steps and low energy consumption: Existing mainstream preparation methods usually require 2 to 3 reaction steps, and intermediates (such as hexachlorohexafluorobutane) must be prepared and separated. Therefore, multi-tower distillation equipment is required, and the reaction temperature fluctuates greatly (such as -8℃ to 90℃). Temperature control energy consumption accounts for 30% to 40% of the total energy consumption. The intermediates are also prone to moisture absorption and corrosion of equipment and introduction of impurities during storage. The preparation method provided in the embodiments of this application is characterized by a single raw material one-step double debromination reaction, which can eliminate the intermediate preparation and separation steps. The reaction temperature tends to be stable overall, which can greatly simplify the process and reduce energy consumption.

[0040] (2) The catalyst system is simple, low-cost, and safe: Existing mainstream preparation methods rely on nickel-based special catalysts, copper salt-phosphine ligand composite catalytic systems, or alkyl aluminum initiators. The catalysts are expensive and difficult to recover. The ligand ratio is strictly controlled and prone to generating by-products. Alkyl aluminum is also prone to hydrolysis to generate flammable and explosive gases, requiring inert gas protection. The preparation method provided in the embodiments of this application is characterized by: a single N,N-dimethylformamide (which is an industrial-grade reagent) serving as both a solvent component and a catalyst. No additional special catalysts or initiators are required, only conventional zinc powder is needed. Furthermore, it can reduce costs and safety risks.

[0041] (3) High electron transfer efficiency and purity: In existing technologies, electron transfer during the dehalogenation / coupling stage relies on "intermediate substances," resulting in an electron loss rate as high as 15%~20%. Byproducts (polyhalogenated alkanes, olefin dimers) account for 3%~5%, making it difficult to achieve a stable product purity of 7N. Furthermore, metal catalysts are prone to residue accumulation. The preparation method provided in this application is characterized by: zinc powder directly providing electrons to carbocations, improving electron transfer efficiency, reducing byproducts, achieving a product purity of 6N~7N, and avoiding the accumulation of metal impurities.

[0042] It should be noted that, at present, in order to improve the shortcomings of traditional preparation methods, some technicians have designed a one-step preparation process based on Grignard reagents. For example, patent document US5082981A discloses a method that uses 1,4-dibromooctafluorobutane as a fluorine-containing raw material and a mixed system of tetrahydrofuran and Grignard reagent (C2H5MgBr) as a catalyst, which can also prepare hexafluorobutadiene in one step.

[0043] Although this preparation method achieves the one-step preparation of hexafluorobutadiene, it still has some defects due to the need to use Grignard reagent. Specifically: (1) Grignard reagent is extremely unstable and reacts violently with water and air (generating flammable and explosive ethane gas). During operation, an anhydrous and oxygen-free environment must be strictly controlled (such as inert gas protection throughout the process). In addition, local overheating during the reaction can easily cause material overflow and explosion; (2) The use of Grignard reagent requires complicated operation. Grignard reagent usually needs to be prepared in advance (usually reacted in anhydrous diethyl ether / tetrahydrofuran, and the process requires temperature control). During the reaction, the dropping rate must be strictly controlled (to avoid local high concentrations that cause side reactions). In addition, post-treatment requires quenching excess Grignard reagent (usually using dilute acid, which easily produces foam); (3) Grignard reagent needs to be customized or purchased at high prices, resulting in high costs and making it difficult to apply to industrial mass production.

[0044] As an example, the difference between the reaction temperature and the boiling point of the catalyst solution is 10°C to 30°C (e.g., but not limited to any one of 10°C, 15°C, 20°C, 25°C and 30°C or any range between the two), and the reaction time is 0.5 h to 2 h (e.g., but not limited to any one of 0.5 h, 1 h, 1.5 h and 2 h or any range between the two).

[0045] In this embodiment, limiting the reaction temperature and reaction time to the above-mentioned ranges provides more suitable reaction conditions, thereby enabling 1,4-dibromooctafluorobutane to efficiently and completely break bonds to generate hexafluorobutadiene.

[0046] As an example, the catalyst solution also includes at least one of a polar aliphatic compound and an aromatic compound having a benzene ring, wherein the polar aliphatic compound is capable of forming a hydrogen bond with the amide bond in N,N-dimethylformamide.

[0047] In this embodiment, the catalyst solution includes a polar aliphatic compound that can form hydrogen bonds with the amide bond in N,N-dimethylformamide and can also serve as a solvent component. The formation of hydrogen bonds can further enhance the "electron-induced effect" of N,N-dimethylformamide on the C-Br bond, further weakening the C-Br bond energy, thereby more effectively catalyzing the bond breaking of 1,4-dibromooctafluorobutane to form hexafluorobutadiene (i.e., improving the catalytic efficiency of N,N-dimethylformamide). The catalyst solution also includes an aromatic compound with a benzene ring that can serve as a solvent component. The π electron cloud on the benzene ring can form a weak interaction with the carbocation formed after the C-Br bond breaks, thereby stabilizing the carbocation formed after the C-Br bond breaks and reducing the probability of reversible reaction. This is also equivalent to promoting the bond breaking of 1,4-dibromooctafluorobutane to form hexafluorobutadiene (i.e., improving the catalytic efficiency of N,N-dimethylformamide).

[0048] Polar aliphatic compounds can be used as solvent components, specifically meaning that 1,4-dibromooctafluorobutane and N,N-dimethylformamide can be mixed uniformly with them, zinc powder can be uniformly dispersed in them, and 1,4-dibromooctafluorobutane, N,N-dimethylformamide and zinc powder will not undergo side reactions with them.

[0049] Aromatic compounds with benzene rings can be used as solvent components. Specifically, this means that 1,4-dibromooctafluorobutane and N,N-dimethylformamide can be mixed uniformly with it, zinc powder can be uniformly dispersed in it, and 1,4-dibromooctafluorobutane, N,N-dimethylformamide and zinc powder will not undergo side reactions with it.

[0050] As an example, the polar group of a polar aliphatic compound is selected from at least one of hydroxyl and carboxyl groups.

[0051] In this embodiment, a polar aliphatic compound having the above-mentioned polar groups is selected. After forming hydrogen bonds with the amide bonds in N,N-dimethylformamide, it can more effectively enhance the "electron-induced effect" of N,N-dimethylformamide on the C-Br bond, thereby more effectively assisting N,N-dimethylformamide in catalyzing the bond breaking of 1,4-dibromooctafluorobutane to generate hexafluorobutadiene.

[0052] As an example, polar aliphatic compounds include at least one of isopropanol, n-propanol, and sec-butanol.

[0053] In this embodiment, the polar aliphatic compound selected is of the aforementioned type. After forming hydrogen bonds with the amide bond in N,N-dimethylformamide, it can more effectively enhance the "electron-induced effect" of N,N-dimethylformamide on the C-Br bond, thereby more effectively assisting N,N-dimethylformamide in catalyzing the bond breaking of 1,4-dibromooctafluorobutane to generate hexafluorobutadiene. At the same time, a wide variety of polar aliphatic compounds are applicable, providing more feasible implementation schemes, thus facilitating the adjustment of the type of polar aliphatic compound according to actual needs.

[0054] As an example, aromatic compounds include at least one of m-xylene, o-xylene, and toluene.

[0055] In this embodiment, the above-mentioned aromatic compounds are selected. After the π electron cloud on the benzene ring forms a weak interaction with the carbocation formed after the C-Br bond is broken, the carbocation formed after the C-Br bond is broken can be stabilized better, thereby more effectively reducing the probability of reversible reaction and thus more effectively promoting the bond breaking of 1,4-dibromooctafluorobutane to generate hexafluorobutadiene.

[0056] As an example, the catalyst solution also includes a polar aliphatic compound that can form hydrogen bonds with the amide bond in N,N-dimethylformamide, and the volume ratio of the polar aliphatic compound to N,N-dimethylformamide is (1~4):1, for example, but not limited to any one of the volume ratios of 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1 and 4:1 or any range between the two.

[0057] In this embodiment, when the catalyst solution includes N,N-dimethylformamide and a polar aliphatic compound that can form hydrogen bonds with it, the volume ratio of the two is limited to the above-mentioned range. After the polar aliphatic compound forms hydrogen bonds with the amide bonds in N,N-dimethylformamide, it can more effectively enhance the "electron-induced effect" of N,N-dimethylformamide on the C-Br bond, thereby more effectively assisting N,N-dimethylformamide in catalyzing the bond breaking of 1,4-dibromooctafluorobutane to generate hexafluorobutadiene.

[0058] As an example, the volume ratio of the polar aliphatic compound to N,N-dimethylformamide is (1.5 to 2.5):1, for example, but not limited to any one of the volume ratios of 1.5:1, 1.75:1, 2:1, 2.25:1 and 2.5:1, or any range between the two.

[0059] In this embodiment, when the catalyst solution includes N,N-dimethylformamide and a polar aliphatic compound that can form hydrogen bonds with it, the volume ratio of the two is limited to the above-mentioned range. After the polar aliphatic compound forms hydrogen bonds with the amide bonds in N,N-dimethylformamide, it can more effectively enhance the "electron-induced effect" of N,N-dimethylformamide on the C-Br bond, thereby more effectively assisting N,N-dimethylformamide in catalyzing the bond breaking of 1,4-dibromooctafluorobutane to generate hexafluorobutadiene.

[0060] As an example, the catalyst solution also includes an aromatic compound having a benzene ring, and the volume ratio of the aromatic compound to N,N-dimethylformamide is (0.5~1.5):1, for example, but not limited to any one of the volume ratios of 0.5:1, 0.75:1, 1:1, 1.25:1 and 1.5:1 or any range between the two.

[0061] In this embodiment, when the catalyst solution includes N,N-dimethylformamide and an aromatic compound with a benzene ring, the volume ratio of the two is limited to the above range. After the π electron cloud on the benzene ring forms a weak interaction with the carbocation formed after the C-Br bond is broken, the carbocation formed after the C-Br bond is broken can be stabilized better, thereby effectively reducing the probability of reversible reaction and thus more effectively promoting the bond breaking of 1,4-dibromooctafluorobutane to generate hexafluorobutadiene.

[0062] As an example, the volume ratio of 1,4-dibromooctafluorobutane to the catalyst solution is 1:(15~20), for example, but not limited to any one of the volume ratios of 1:15, 1:16, 1:17, 1:18, 1:19 and 1:20, or any range between the two.

[0063] In this embodiment, the volume ratio of 1,4-dibromooctafluorobutane to the catalyst solution is limited to the above range so that each component in the reaction raw materials has a suitable amount and concentration, which enables 1,4-dibromooctafluorobutane to break bonds more efficiently and completely to generate hexafluorobutadiene.

[0064] As an example, the volume-to-mass ratio of 1,4-dibromooctafluorobutane to zinc powder is 1 mL:(0.5~1) g, for example, but not limited to any one of the volume-to-mass ratios of 1 mL:0.5 g, 1 mL:0.6 g, 1 mL:0.7 g, 1 mL:0.8 g, 1 mL:0.9 g and 1 mL:1 g, or any range between the two.

[0065] In this embodiment, the volume-to-mass ratio of 1,4-dibromooctafluorobutane and zinc powder is limited to the above-mentioned range, so that each component in the reaction raw materials has a suitable amount and concentration, which enables 1,4-dibromooctafluorobutane to break bonds more efficiently and completely to generate hexafluorobutadiene.

[0066] It should be noted that in the step of reacting 1,4-dibromooctafluorobutane, catalyst solution, and zinc powder under heating conditions, the order of adding materials during the feeding stage is not limited. For example, the three materials can be directly mixed and then reacted; the zinc powder and catalyst solution can be mixed first, and then 1,4-dibromooctafluorobutane can be added dropwise to the mixture; or the zinc powder and a portion of the catalyst solution can be mixed, the 1,4-dibromooctafluorobutane and the remaining portion of the catalyst solution can be mixed, and then the mixture containing 1,4-dibromooctafluorobutane can be added dropwise to the mixture containing zinc powder. The specific choice can be made according to actual needs.

[0067] As an example, during the feeding stage, zinc powder is mixed with a portion of the catalyst solution, 1,4-dibromooctafluorobutane is mixed with the remaining portion of the catalyst solution, and then the mixture containing 1,4-dibromooctafluorobutane is added dropwise to the mixture containing zinc powder.

[0068] In this embodiment, the above-mentioned feeding method can make the multiple components in the reaction raw materials mix more evenly, so that 1,4-dibromooctafluorobutane can be generated into hexafluorobutadiene more efficiently and completely by breaking the bonds.

[0069] It should be noted that the dropping rate is not limited and can be adjusted according to the stirring speed. For example, the dropping rate can be 0.1 mL / min to 1 mL / min, or any one of the following values ​​or any range between two: 0.1 mL / min, 0.2 mL / min, 0.4 mL / min, 0.6 mL / min, 0.8 mL / min and 1.0 mL / min.

[0070] As an example, the reaction is carried out in an inert atmosphere under stirring conditions, wherein the stirring speed is 200 rpm to 300 rpm, for example, but not limited to any one of 200 rpm, 210 rpm, 220 rpm, 230 rpm, 240 rpm, 250 rpm, 260 rpm, 270 rpm, 280 rpm, 290 rpm and 300 rpm or a range between any two.

[0071] In this embodiment, the reaction is carried out under an inert atmosphere and the above-mentioned stirring conditions, which can improve the stability of the reaction system and thus prepare hexafluorobutadiene with high purity.

[0072] It should be noted that the type of inert atmosphere is not limited, for example, it can be at least one of nitrogen and argon.

[0073] As an example, prior to the reaction, a pretreatment step of zinc powder is included, which includes immersing the zinc powder in dilute hydrochloric acid with a mass concentration of 3% to 7% (e.g., but not limited to any one of the mass concentrations of 3%, 4%, 5%, 6%, and 7% or any range between the two) for 10 to 15 minutes (e.g., but not limited to any one of the mass concentrations of 10, 11, 12, 13, 14, and 15 minutes or any range between the two), and then sequentially washing and drying the immersed zinc powder.

[0074] In this embodiment, the zinc powder is pretreated according to the above process before the reaction, which can effectively remove oxide impurities on the surface of the zinc powder, thereby improving the reaction efficiency and reducing the generation of by-products.

[0075] As an example, the cleaning process includes washing the soaked zinc powder with anhydrous ethanol 3 to 5 times; and / or the drying process includes drying the cleaned zinc powder at 50°C to 70°C for 1 to 5 hours.

[0076] It should be noted that any processes or steps not specifically described or limited in the preparation method can be carried out in accordance with conventional processes in this field.

[0077] As an example, a process flow diagram for the preparation of hexafluorobutadiene is exemplarily provided. Figure 1 .

[0078] The features and performance of this application will be further described in detail below with reference to the embodiments.

[0079] Example 1 This application provides a method for preparing hexafluorobutadiene, comprising the following steps: (1) The reactor was alternately evacuated and purged with nitrogen to make the reactor inert atmosphere and at normal pressure; at the same time, the zinc powder was soaked in dilute hydrochloric acid with a mass concentration of 5% at room temperature for 2 min, and filtered to obtain the soaked zinc powder; the soaked zinc powder was washed repeatedly with anhydrous ethanol 3 times, and then the zinc powder was dried at 60℃ for 2 h and cooled for later use.

[0080] (2) Disperse 1 g of the above zinc powder in 12 mL of catalyst solution (composed of DMF and isopropanol in a volume ratio of 1:2) to obtain the first mixed solution; at the same time, mix 1 mL of 1,4-dibromooctafluorobutane with 6 mL of catalyst solution (composed of DMF and isopropanol in a volume ratio of 1:2) to obtain the second mixed solution.

[0081] (3) Add the first mixed solution into an inert atmosphere and a normal pressure reaction vessel, and then add the second mixed solution dropwise into the reaction vessel at a rate of 0.5 mL / min at 200 rpm to mix with the second mixed solution; then maintain the stirring speed and react at 75°C for 1 h (bubbles can be observed to be generated during the reaction), and collect the generated gaseous product.

[0082] Example 2 This application provides a method for preparing hexafluorobutadiene, which differs from Example 1 only in that: the catalyst solution is only DMF, the reaction temperature is 130°C, and bubbles can be observed to be generated during the reaction, indicating that hexafluorobutadiene is generated.

[0083] Example 3 This application provides a method for preparing hexafluorobutadiene, comprising the following steps: (1) The reactor was alternately evacuated and purged with nitrogen to make the reactor inert atmosphere and at normal pressure; at the same time, the zinc powder was soaked in dilute hydrochloric acid with a mass concentration of 5% at room temperature for 2 min, and filtered to obtain the soaked zinc powder; the soaked zinc powder was washed repeatedly with anhydrous ethanol 3 times, and then the zinc powder was dried at 60℃ for 2 h and cooled for later use.

[0084] (2) Disperse 1 g of the above zinc powder in 12 mL of catalyst solution (composed of DMF and m-xylene in a volume ratio of 1:1) to obtain the first mixed solution; at the same time, mix 1 mL of 1,4-dibromooctafluorobutane with 6 mL of catalyst solution (composed of DMF and m-xylene in a volume ratio of 1:1) to obtain the second mixed solution.

[0085] (3) Add the first mixed solution into an inert atmosphere and a normal pressure reaction vessel, and then add the second mixed solution dropwise into the reaction vessel at a rate of 0.5 mL / min at 300 rpm to mix with the second mixed solution; then maintain the stirring speed and react at 130℃ for 1 h (bubbles can be observed to be generated during the reaction), and collect the generated gaseous product.

[0086] Example 4 This application provides a method for preparing hexafluorobutadiene, which differs from Example 3 only in that the catalyst solution is only DMF, and bubbles can be observed to be generated during the reaction, indicating that hexafluorobutadiene is generated.

[0087] Comparative Example 1 This application provides a comparative method for preparing hexafluorobutadiene, which differs from Example 1 only in that the catalyst solution is only isopropanol, and no bubbles were observed to be generated during the reaction, i.e., the reaction did not proceed.

[0088] Comparative Example 2 This application provides a comparative method for preparing hexafluorobutadiene, which differs from Example 2 only in that the catalyst solution is only m-xylene, and no bubbles were observed to be generated during the reaction, i.e., the reaction did not proceed.

[0089] Test case Qualitative characterization of products Test method: The products prepared in Examples 1 and 3 were used as samples, and the specific composition of the products was tested by gas chromatography. The core chromatographic conditions were as follows: the chromatographic column was a PLOT Q capillary column (30 m × 0.32 mm), the column temperature was constant at 55℃, the carrier gas was helium (60 mL / min), the injection temperature was 150℃, the detector was FID, and the detector temperature was 80℃.

[0090] See Figure 2 and Figure 3 (The unit of the horizontal axis is min). Figure 2 and Figure 3 All peaks exhibited the same shape and retention time concentrated between 5 min and 6 min, characteristic peaks unique to hexafluorobutadiene; among them, Figure 2 The characteristic peak appears between 5.2 min and 6 min. Figure 3 The characteristic peaks appeared between 5.5 min and 6.2 min. This slight difference is within the normal fluctuation range of the chromatographic detection process, indicating that hexafluorobutadiene can be prepared in one step using only industrial-grade catalysts by the preparation method provided in the embodiments of this application.

[0091] Meanwhile, since bubble generation was also observed in Examples 2 and 4, it indicates that hexafluorobutadiene can be prepared in one step using only DMF in the catalyst solution; however, no bubble generation was observed in Comparative Examples 1 and 2, indicating that it is difficult to prepare hexafluorobutadiene in one step without DMF in the catalyst solution.

[0092] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A method for preparing hexafluorobutadiene, characterized in that, Includes the following steps: 1,4-Dibromooctafluorobutane, a catalyst solution, and zinc powder are reacted under heating conditions, and the resulting gaseous hexafluorobutadiene is collected; wherein the catalyst solution contains N,N-dimethylformamide, and the reaction temperature is lower than the boiling point of the catalyst solution and the difference between the two boiling points is 5℃~40℃.

2. The method for preparing hexafluorobutadiene according to claim 1, characterized in that, The difference between the reaction temperature and the boiling point of the catalyst solution is 10℃~30℃, and the reaction time is 0.5 h~2 h.

3. The method for preparing hexafluorobutadiene according to claim 1, characterized in that, The catalyst solution also includes at least one of a polar aliphatic compound and an aromatic compound having a benzene ring, wherein the polar aliphatic compound is capable of forming a hydrogen bond with the amide bond in the N,N-dimethylformamide.

4. The method for preparing hexafluorobutadiene according to claim 3, characterized in that, The polar aliphatic compound has a polar group selected from at least one of hydroxyl and carboxyl groups; Optionally, the polar aliphatic compound includes at least one of isopropanol, n-propanol, and sec-butanol.

5. The method for preparing hexafluorobutadiene according to claim 3, characterized in that, The aromatic compound includes at least one of m-xylene, o-xylene, and toluene.

6. The method for preparing hexafluorobutadiene according to claim 1, characterized in that, The catalyst solution also includes a polar aliphatic compound, which can form hydrogen bonds with the amide bond in the N,N-dimethylformamide, and the volume ratio of the polar aliphatic compound to the N,N-dimethylformamide is (1~4):1; Optionally, the volume ratio of the polar aliphatic compound to the N,N-dimethylformamide is (1.5~2.5):

1.

7. The method for preparing hexafluorobutadiene according to claim 1, characterized in that, The catalyst solution also includes an aromatic compound having a benzene ring, and the volume ratio of the aromatic compound to the N,N-dimethylformamide is (0.5~1.5):

1.

8. The method for preparing hexafluorobutadiene according to any one of claims 1 to 7, characterized in that, The volume ratio of the 1,4-dibromooctafluorobutane to the catalyst solution is 1:(15~20), or / and the volume-to-mass ratio of the 1,4-dibromooctafluorobutane to the zinc powder is 1 mL:(0.5~1) g.

9. The method for preparing hexafluorobutadiene according to any one of claims 1 to 7, characterized in that, The reaction was carried out under an inert atmosphere and with stirring, wherein the stirring speed was 200 rpm to 300 rpm.

10. The method for preparing hexafluorobutadiene according to claim 9, characterized in that, Before the reaction, a pretreatment step for zinc powder is included, which includes immersing the zinc powder in dilute hydrochloric acid with a mass concentration of 3% to 7% for 10 to 15 minutes, and then washing and drying the immersed zinc powder in sequence.

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