A method for the nickel-catalyzed preparation of hexafluorobutadiene

Abstract

This invention relates to a method for preparing hexafluorobutadiene using nickel catalysis. The method includes the following steps: mixing an organic solvent, a ligand, a nickel-based catalyst, and a reducing agent; heating to the reaction temperature; and introducing trifluorochloroethylene for a closed reaction. After the closed reaction is completed, the generated gas is collected to obtain hexafluorobutadiene. This method prepares hexafluorobutadiene via a one-step reduction-coupling process catalyzed by nickel. The process route is simple, the raw materials are readily available, and the reaction exhibits good selectivity and few byproducts, showing promising prospects for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of hexafluorobutadiene synthesis technology, and relates to a method for preparing hexafluorobutadiene using nickel catalysis. Background Technology

[0002] At room temperature, hexafluorobutadiene (chemical formula C4F6, relative molecular mass 162.034) is a colorless gas with a slightly peculiar odor, a freezing point of -132℃, and a boiling point of 5.85℃. Initially, hexafluorobutadiene was mainly used in the synthesis of perfluorinated elastomers. However, in recent years, with the rapid development of the semiconductor industry, the demand for high-performance fluorinated electronic etching gases has continued to rise, leading to a deeper exploration of the etching properties of hexafluorobutadiene and a continuous expansion of its application scenarios. Compared with traditional etching gases such as CF4, C2F6, C3F8, and NF3, hexafluorobutadiene not only has a faster etching rate and higher selectivity but can also perform fine pattern etching with higher aspect ratios. Furthermore, its global warming potential is far lower than that of traditional etching gases, highlighting its environmental advantages and making it a new generation of highly efficient and green etchant with application potential in the high-end integrated circuit manufacturing field.

[0003] Haszeldine et al. used trifluorochloroethylene as a raw material, first reacting it with iodine chloride to obtain the intermediate trifluorodichloroiodomethane, then generating tetrachlorohexafluorobutane via a mercury-mediated coupling reaction, and finally obtaining hexafluorobutadiene through zinc powder dechlorination. This route has a low yield, the raw materials such as iodine chloride and mercury used are environmentally hazardous, and the procurement cost of iodine chloride in China is high. Currently, only a few countries have adopted this route to achieve ton-scale industrial production of hexafluorobutadiene.

[0004] Liu Wucan and others developed another route for the synthesis of hexafluorobutadiene: starting with trifluorochloroethylene, trifluorobromoethylene is obtained through a three-step continuous reaction involving hydrogenation dechlorination, bromine addition, and dehydrobromide removal; trifluorobromoethylene then reacts with zinc powder to generate the key organometallic reagent, trifluorovinyl zinc bromide; finally, this zinc reagent undergoes a Negishi coupling reaction with tribromoethylene in a monovalent copper catalytic system to obtain the target product, hexafluorobutadiene. Compared with the traditional iodine chloride method (which requires the use of highly toxic mercury reagent and expensive iodine chloride), this route fundamentally avoids the use of high-risk and high-cost materials, representing a significant breakthrough in both safety and economy, and is already in industrial application. However, this route also has significant shortcomings, such as lengthy reaction steps and the risk of self-polymerization of the generated trifluoroethylene intermediate, which requires strict control and poses a significant safety challenge to industrial production.

[0005] Fu Zhuhong et al. developed a nickel fluoride catalytic route: trifluorochloroethylene undergoes thermal polymerization at 500℃ to generate dichlorohexafluorobutene intermediate, which is then dechlorinated with zinc powder to obtain hexafluorobutadiene. Chen Jianhua's team also achieved the synthesis of this key intermediate using a heterogeneous catalytic system of titanium dioxide supported on molecular sieves. Yang Junhao et al.'s research further discovered that even without a catalyst, by introducing high-boiling-point stabilizers such as perfluorononenyl trifluoroethyl ether and perfluoropolyether, and then through high-temperature thermal activation, the controlled polymerization of trifluorochloroethylene can still be achieved to obtain the target intermediate. The synthetic route based on the thermal polymerization reaction of trifluorochloroethylene has become one of the mainstream directions for the industrial production of hexafluorobutadiene due to its more direct process steps and potential cost advantages. However, this process generates a byproduct, dichlorohexafluorocyclobutane, which is difficult to treat and for which efficient resource utilization technology has not yet been developed, directly restricting the overall economic efficiency of the process. Moreover, the overall yield of the target intermediate, dichlorohexafluorobutene, is generally low, usually less than 30%, resulting in not only a large amount of byproducts but also high production costs. The trace amounts of hexafluorocyclobutene remaining in the product have boiling points that differ from hexafluorobutadiene by only 1°C, requiring high-precision separation technology to obtain electronic-grade products of 4N and above, which places extremely high demands on the industrial scale-up of the process.

[0006] In summary, existing hexafluorobutadiene synthesis routes generally suffer from high starting material costs, lengthy reaction steps, harsh process conditions, and poor product selectivity. At the same time, the production process generates significant waste, which directly restricts the feasibility and economic viability of large-scale production. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing hexafluorobutadiene using nickel catalysis. This method significantly reduces production costs and equipment investment from the source by simplifying the synthesis route and operation process, thereby simplifying the process flow and showing good prospects for industrial application.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] This invention provides a method for preparing hexafluorobutadiene using nickel catalysis, the method comprising the following steps:

[0010] A mixture of organic solvent, ligand, nickel-based catalyst and reducing agent is heated to the reaction temperature, and trifluorochloroethylene is introduced to carry out a closed reaction; after the closed reaction is completed, the generated gas is collected to obtain hexafluorobutadiene.

[0011] This invention employs a nickel-catalyzed one-step method to prepare hexafluorobutadiene. By mixing an organic solvent, ligand, nickel-based catalyst, and reducing agent, heating the mixture, and then introducing trifluorochloroethylene for a closed reaction, the dechlorination coupling of two molecules of trifluorochloroethylene can be achieved in a single step, directly yielding the target product, hexafluorobutadiene. This method completely eliminates the inherent defects of existing technologies, such as multi-step continuous reactions, high-temperature thermal polymerization, and the use of highly toxic mercury reagents and iodine chloride. It shortens the process flow, reduces operational difficulty and safety risks, and avoids intermediate losses associated with multi-step reactions, significantly improving the economic efficiency of the reaction. Furthermore, the reaction conditions are mild, requiring no extreme high-temperature or high-pressure equipment, making the process highly adaptable. The product can be directly collected from the gas generated during the reaction, simplifying product separation and purification steps and facilitating large-scale, continuous industrial production.

[0012] In some embodiments, the organic solvent includes any one or a combination of at least two of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, toluene, 1,4-dioxane, acetonitrile, methyl tert-butyl ether, or tetrahydrofuran.

[0013] In some embodiments, the ligand comprises any one or a combination of at least two of tricyclohexylphosphine, triphenylphosphine, 1,1'-binaphthyl-2,2'-bisdiphenylphosphine, 1,2-bis(diphenylphosphine)ethane, pyridine, 2,2'-bipyridine, or 2-aminopyridine.

[0014] In some embodiments, the nickel-based catalyst comprises any one or a combination of at least two of nickel iodide, nickel bromide, nickel chloride, bis(1,5-cyclooctadiene) nickel, nickel acetylacetonate, or nickel dicerocene.

[0015] In some embodiments, the reducing agent includes any one or a combination of at least two of manganese powder, zinc powder, zinc-copper reagent, iron powder, triethylzinc, or triethylboron.

[0016] In some embodiments, the amount of the nickel-based catalyst is 20wt% to 60wt% of the trifluorochloroethylene.

[0017] In some embodiments, the amount of the ligand is 40wt% to 60wt% of the trifluorochloroethylene.

[0018] In some embodiments, the molar ratio of the reducing agent to the trifluorochloroethylene is 1.5:1 to 4:1.

[0019] In some embodiments, the amount of the organic solvent used is 7 to 20 times the mass of the trifluorochloroethylene.

[0020] In some embodiments, the temperature of the closed reaction is 40°C to 120°C, and the time is 5h to 12h.

[0021] As a preferred embodiment of the method provided by the present invention, the method includes the following steps:

[0022] Organic solvent, ligand, nickel-based catalyst and reducing agent are mixed in a reaction vessel, heated to the reaction temperature, and trifluorochloroethylene is introduced to carry out a closed reaction; after the closed reaction is completed, the generated gas is collected to obtain hexafluorobutadiene.

[0023] The organic solvent includes any one or a combination of at least two of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, toluene, 1,4-dioxane, acetonitrile, methyl tert-butyl ether, or tetrahydrofuran; the amount of the organic solvent used is 7 to 20 times the mass of the trifluorochloroethylene.

[0024] The ligand comprises any one or a combination of at least two of tricyclohexylphosphine, triphenylphosphine, 1,1'-binaphthyl-2,2'-bisdiphenylphosphine, 1,2-bis(diphenylphosphine)ethane, pyridine, 2,2'-bipyridine, or 2-aminopyridine; the amount of the ligand is 40wt% to 60wt% of the trifluorochloroethylene.

[0025] The nickel-based catalyst comprises any one or a combination of at least two of nickel iodide, nickel bromide, nickel chloride, bis(1,5-cyclooctadiene) nickel, nickel acetylacetonate, or nickel dicerocene; the amount of the nickel-based catalyst is 20 wt% to 60 wt% of the trifluorochloroethylene.

[0026] The reducing agent includes any one or a combination of at least two of manganese powder, zinc powder, zinc-copper reagent, iron powder, triethylzinc, or triethylboron; the molar ratio of the reducing agent to the trifluorochloroethylene is 1.5:1 to 4:1.

[0027] The temperature of the closed reaction is 40℃~120℃, and the time is 5h~12h.

[0028] 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.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] This invention employs a nickel-catalyzed one-step method to prepare hexafluorobutadiene. By mixing an organic solvent, ligand, nickel-based catalyst, and reducing agent, heating the mixture, and then introducing trifluorochloroethylene for a closed reaction, the dechlorination coupling of two molecules of trifluorochloroethylene can be achieved in a single step, directly yielding the target product, hexafluorobutadiene. This method completely eliminates the inherent defects of existing technologies, such as multi-step continuous reactions, high-temperature thermal polymerization, and the use of highly toxic mercury reagents and iodine chloride. It shortens the process flow, reduces operational difficulty and safety risks, and avoids intermediate losses associated with multi-step reactions, significantly improving the economic efficiency of the reaction. Furthermore, the reaction conditions are mild, requiring no extreme high-temperature or high-pressure equipment, making the process highly adaptable. The product can be directly collected from the gas generated during the reaction, simplifying product separation and purification steps and facilitating large-scale, continuous industrial production. 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] 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."

[0037] 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.

[0038] 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.

[0039] In this invention, "optional" means that something is optional, that is, it refers to either "with" or "without". 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.

[0040] This invention provides a method for preparing hexafluorobutadiene using nickel catalysis, the method comprising the following steps:

[0041] A mixture of organic solvent, ligand, nickel-based catalyst and reducing agent is heated to the reaction temperature, and trifluorochloroethylene is introduced to carry out a closed reaction; after the closed reaction is completed, the generated gas is collected to obtain hexafluorobutadiene.

[0042] This invention employs a nickel-catalyzed one-step method to prepare hexafluorobutadiene. By mixing an organic solvent, ligand, nickel-based catalyst, and reducing agent, heating the mixture, and then introducing trifluorochloroethylene for a closed reaction, the dechlorination coupling of two molecules of trifluorochloroethylene can be achieved in a single step, directly yielding the target product, hexafluorobutadiene. This method completely eliminates the inherent defects of existing technologies, such as multi-step continuous reactions, high-temperature thermal polymerization, and the use of highly toxic mercury reagents and iodine chloride. It shortens the process flow, reduces operational difficulty and safety risks, and avoids intermediate losses associated with multi-step reactions, significantly improving the economic efficiency of the reaction. Furthermore, the reaction conditions are mild, requiring no extreme high-temperature or high-pressure equipment, making the process highly adaptable. The product can be directly collected from the gas generated during the reaction, simplifying product separation and purification steps and facilitating large-scale, continuous industrial production.

[0043] In some embodiments, the organic solvent includes any one or a combination of at least two of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, toluene, 1,4-dioxane, acetonitrile, methyl tert-butyl ether, or tetrahydrofuran.

[0044] The organic solvent used in this invention can efficiently dissolve trifluorochloroethylene, placing the reactants and the catalytic center in the same homogeneous system, achieving sufficient molecular-level contact, and significantly improving the reaction rate and conversion efficiency. Moreover, the organic solvent can fully dissolve the metal chloride byproducts generated during the reaction, preventing the byproducts from covering the reducing agent surface and causing the reducing agent to become deactivated. In addition, the organic solvent can maintain a stable liquid phase environment during the reaction, avoiding system instability caused by excessive solvent volatilization, reducing the occurrence of side reactions such as trifluorochloroethylene polymerization, and improving the selectivity of the target product.

[0045] In some embodiments, the ligand comprises any one or a combination of at least two of tricyclohexylphosphine, triphenylphosphine, 1,1'-binaphthyl-2,2'-bisdiphenylphosphine, 1,2-bis(diphenylphosphine)ethane, pyridine, 2,2'-bipyridine, or 2-aminopyridine.

[0046] The ligands used in this invention can form strong coordination bonds with nickel in nickel-based catalysts, effectively inhibiting nickel agglomeration to form inactive nickel black, improving catalytic stability and cycle life. At the same time, the ligands are electron-donating ligands, which can significantly increase the electron cloud density of nickel centers and enhance catalytic activity. Moreover, the ligands can regulate the coordination environment of nickel centers through their own steric hindrance, effectively inhibiting side reactions such as trifluorochloroethylene polymerization and hydrodehalogenation, and improving the selectivity of trifluorochloroethylene to hexafluorobutadiene.

[0047] In some embodiments, the nickel-based catalyst comprises any one or a combination of at least two of nickel iodide, nickel bromide, nickel chloride, bis(1,5-cyclooctadiene) nickel, nickel acetylacetonate, or nickel dicerocene.

[0048] The nickel-based catalyst used in this invention includes zero-valent nickel and divalent nickel. Divalent nickel can be reduced in situ by a reducing agent to zero-valent nickel with high catalytic activity, eliminating the need to prepare an active catalytic center in advance and simplifying the process. At the same time, the nickel-based catalyst can form stable catalytically active complexes with ligands, achieving selective activation of the C-Cl bond and directional construction of the C-C bond in trifluorochloroethylene, enabling high-efficiency conversion at low loading.

[0049] In some embodiments, the reducing agent includes any one or a combination of at least two of manganese powder, zinc powder, zinc-copper reagent, iron powder, triethylzinc, or triethylboron.

[0050] The reducing agent used in this invention can reduce divalent nickel to catalytically active zero-valent nickel, while continuously providing electrons during the reaction process to continuously reduce and regenerate the divalent nickel generated in the oxidative addition step into zero-valent nickel active centers, thus preventing the catalyst from becoming deactivated due to an increase in valence state. The reducing agent can also react rapidly with chloride ions removed during the reaction to generate stable metal chlorides, achieving in-situ capture of chloride ions, preventing chloride ions from oxidizing the catalytic system, and pushing the reaction equilibrium towards the formation of hexafluorobutadiene, further improving the conversion rate.

[0051] Too little nickel-based catalyst can lead to insufficient catalytic active sites, incomplete conversion of trifluorochloroethylene, and slow reaction rate; too much nickel-based catalyst can lead to increased production costs, more by-products, and increased difficulty in product separation.

[0052] In some embodiments, the amount of the nickel-based catalyst is 20wt% to 60wt% of the trifluorochloroethylene, for example, it can be 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt% or 60wt%, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0053] Appropriate ligand dosage can ensure sufficient coordination between the ligand and the nickel center, exert the ligand's stabilizing and regulating effect on the catalytic active center, and also inhibit the aggregation and deactivation of zero-valent nickel through excessive ligand, thus ensuring the stability of the catalytic system throughout the reaction process.

[0054] In some embodiments, the amount of the ligand is 40wt% to 60wt% of the trifluorochloroethylene, for example, 40wt%, 45wt%, 50wt%, 55wt% or 60wt%, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0055] A suitable amount of reducing agent can reduce divalent nickel to zero-valent nickel while continuously providing sufficient electrons, avoiding mid-process deactivation of nickel-based catalysts, ensuring stable operation of the catalytic system throughout the entire reaction cycle, and also preventing chloride ions from poisoning the reaction system.

[0056] In some embodiments, the molar ratio of the reducing agent to the trifluorochloroethylene is 1.5:1 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. Other unlisted values ​​within the range are also applicable.

[0057] Using an appropriate amount of organic solvent is beneficial for constructing a stable homogeneous reaction system, ensuring the smooth progress of the reaction, fully dissolving trifluorochloroethylene in a closed reaction, constructing a stable homogeneous reaction environment, achieving full contact between the reactants and the catalytically active centers, and also enabling heat transfer during the reaction process through sufficient organic solvent, avoiding the problems of increased side reactions and system instability caused by local overheating, and reducing the occurrence of polypolymerization side reactions of trifluorochloroethylene.

[0058] In some embodiments, the amount of organic solvent used is 7 to 20 times the mass of the trifluorochloroethylene, for example, it can be 7, 8, 9, 10, 12, 15, 16, 18 or 20 times, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0059] The method provided by this invention does not require a high reaction temperature, which can reduce energy consumption and avoid the problems of increased polymerization side reactions and raw material decomposition.

[0060] In some embodiments, the temperature of the closed reaction is 40°C to 120°C, and the time is 5h to 12h.

[0061] The temperature of the closed reaction is 40℃~120℃, for example, it can be 40℃, 50℃, 60℃, 70℃, 80℃, 90℃, 100℃, 110℃ or 120℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0062] The closed reaction time is 5h to 12h, for example, it can be 5h, 6h, 7h, 8h, 9h, 10h, 11h or 12h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0063] As a preferred embodiment of the method provided by the present invention, the method includes the following steps:

[0064] Organic solvent, ligand, nickel-based catalyst and reducing agent are mixed in a reaction vessel, heated to the reaction temperature, and trifluorochloroethylene is introduced to carry out a closed reaction; after the closed reaction is completed, the generated gas is collected to obtain hexafluorobutadiene.

[0065] The organic solvent includes any one or a combination of at least two of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, toluene, 1,4-dioxane, acetonitrile, methyl tert-butyl ether, or tetrahydrofuran; the amount of the organic solvent used is 7 to 20 times the mass of the trifluorochloroethylene.

[0066] The ligand comprises any one or a combination of at least two of tricyclohexylphosphine, triphenylphosphine, 1,1'-binaphthyl-2,2'-bisdiphenylphosphine, 1,2-bis(diphenylphosphine)ethane, pyridine, 2,2'-bipyridine, or 2-aminopyridine; the amount of the ligand is 40wt% to 60wt% of the trifluorochloroethylene.

[0067] The nickel-based catalyst comprises any one or a combination of at least two of nickel iodide, nickel bromide, nickel chloride, bis(1,5-cyclooctadiene) nickel, nickel acetylacetonate, or nickel dicerocene; the amount of the nickel-based catalyst is 20 wt% to 60 wt% of the trifluorochloroethylene.

[0068] The reducing agent includes any one or a combination of at least two of manganese powder, zinc powder, zinc-copper reagent, iron powder, triethylzinc, or triethylboron; the molar ratio of the reducing agent to the trifluorochloroethylene is 1.5:1 to 4:1.

[0069] The temperature of the closed reaction is 40℃~120℃, and the time is 5h~12h.

[0070] Example 1

[0071] This embodiment provides a method for preparing hexafluorobutadiene using nickel catalysis, comprising the following steps:

[0072] Organic solvent, ligand, nickel-based catalyst and reducing agent were mixed in a 5L high-pressure reactor, heated to the reaction temperature, and 340g of trifluorochloroethylene was introduced for a closed reaction; after the closed reaction was completed, the generated gas was collected to obtain hexafluorobutadiene.

[0073] The organic solvent is N,N-dimethylformamide; the amount of the organic solvent used is 15 times the mass of the trifluorochloroethylene;

[0074] The ligand is 2,2'-bipyridine; the amount of the ligand is 50 wt% of the trifluorochloroethylene.

[0075] The nickel-based catalyst is nickel iodide; the amount of the nickel-based catalyst used is 40 wt% of the trifluorochloroethylene.

[0076] The reducing agent is a zinc-copper reagent (CAS: 53801-63-1); the molar ratio of the reducing agent to the trifluorochloroethylene is 3:1;

[0077] The closed reaction was carried out at a temperature of 60°C for 6 hours.

[0078] Example 2

[0079] This embodiment provides a method for preparing hexafluorobutadiene using nickel catalysis, comprising the following steps:

[0080] Organic solvent, ligand, nickel-based catalyst and reducing agent were mixed in a 5L high-pressure reactor, heated to the reaction temperature, and 340g of trifluorochloroethylene was introduced for a closed reaction; after the closed reaction was completed, the generated gas was collected to obtain hexafluorobutadiene.

[0081] The organic solvent is N,N-dimethylformamide; the amount of the organic solvent used is 7 times the mass of the trifluorochloroethylene;

[0082] The ligand is 2,2'-bipyridine; the amount of the ligand is 40 wt% of the trifluorochloroethylene.

[0083] The nickel-based catalyst is nickel iodide; the amount of the nickel-based catalyst used is 20 wt% of the trifluorochloroethylene.

[0084] The reducing agent is a zinc-copper reagent (CAS: 53801-63-1); the molar ratio of the reducing agent to the trifluorochloroethylene is 1.5:1;

[0085] The closed reaction was carried out at a temperature of 40°C for 12 hours.

[0086] Example 3

[0087] This embodiment provides a method for preparing hexafluorobutadiene using nickel catalysis, comprising the following steps:

[0088] Organic solvent, ligand, nickel-based catalyst and reducing agent were mixed in a 5L high-pressure reactor, heated to the reaction temperature, and 340g of trifluorochloroethylene was introduced for a closed reaction; after the closed reaction was completed, the generated gas was collected to obtain hexafluorobutadiene.

[0089] The organic solvent is N,N-dimethylformamide; the amount of the organic solvent used is 20 times the mass of the trifluorochloroethylene;

[0090] The ligand is 2,2'-bipyridine; the amount of the ligand used is 60 wt% of the trifluorochloroethylene.

[0091] The nickel-based catalyst is nickel iodide; the amount of the nickel-based catalyst used is 60 wt% of the trifluorochloroethylene.

[0092] The reducing agent is a zinc-copper reagent (CAS: 53801-63-1); the molar ratio of the reducing agent to the trifluorochloroethylene is 4:1;

[0093] The closed reaction was carried out at a temperature of 120°C for 5 hours.

[0094] Example 4

[0095] This embodiment provides a method for preparing hexafluorobutadiene using nickel catalysis. Except for the organic solvent being tetrahydrofuran, the method is the same as in Example 1.

[0096] Example 5

[0097] This embodiment provides a method for preparing hexafluorobutadiene using nickel catalysis. Except for the nickel-based catalyst being nickel chloride, the rest is the same as in Example 1.

[0098] Example 6

[0099] This embodiment provides a method for preparing hexafluorobutadiene using nickel catalysis, which is the same as in Example 1 except that the ligand is triphenylphosphine.

[0100] Example 7

[0101] This embodiment provides a method for preparing hexafluorobutadiene using nickel catalysis. Except for the reducing agent being zinc powder, the method is the same as in Example 1.

[0102] Example 8

[0103] This embodiment provides a method for preparing hexafluorobutadiene using nickel catalysis. Except that the amount of ligand used is 30 wt% of the trifluorochloroethylene, the rest is the same as in Example 1.

[0104] Example 9

[0105] This embodiment provides a method for preparing hexafluorobutadiene using nickel catalysis. Except that the amount of ligand used is 70 wt% of the trifluorochloroethylene, the rest is the same as in Example 1.

[0106] Example 10

[0107] This embodiment provides a method for preparing hexafluorobutadiene using nickel catalysis. Except that the amount of nickel-based catalyst used is 10 wt% of the trifluorochloroethylene, the rest is the same as in Example 1.

[0108] Example 11

[0109] This embodiment provides a method for preparing hexafluorobutadiene using nickel catalysis. Except that the amount of nickel-based catalyst used is 70 wt% of the trifluorochloroethylene, the rest is the same as in Example 1.

[0110] Example 12

[0111] This embodiment provides a method for preparing hexafluorobutadiene using nickel catalysis. Except for the molar ratio of the reducing agent to the trifluorochloroethylene being 1:1, all other aspects are the same as in Example 1.

[0112] Example 13

[0113] This embodiment provides a method for preparing hexafluorobutadiene using nickel catalysis. Except for the molar ratio of the reducing agent to the trifluorochloroethylene being 5:1, all other aspects are the same as in Example 1.

[0114] Performance Characterization

[0115] The selectivity of hexafluorobutadiene and the conversion rate of trifluorochloroethylene obtained by the method provided in the above embodiments were determined by gas chromatography. The true content and purity of the product were calculated by external standard method. The results are shown in Table 1.

[0116] Table 1

[0117]

[0118] The test results of Examples 1 to 7 show that all the above examples are within the protection scope of claim 1. By adjusting process parameters such as reaction temperature, ligand type, and organic solvent type, the dechlorination coupling reaction of trifluorochloroethylene to prepare hexafluorobutadiene can be successfully achieved. Among them, the hexafluorobutadiene selectivity of Examples 1, 2, 3, and 4 is consistently above 91%, and the trifluorochloroethylene conversion rate is above 50%. Even after adjusting the process parameters, the trifluorochloroethylene conversion rate of Examples 5, 6, and 7 fluctuates, but the hexafluorobutadiene selectivity can still be stably maintained above 92%.

[0119] A comparison of Examples 8 and 9 with Example 1 shows that when the amount of ligand is too small, it cannot form sufficient coordination with the nickel center, making it difficult to effectively inhibit the agglomeration of zero-valent nickel to form inactive nickel black, thus failing to stabilize the catalytically active species. Furthermore, it cannot fully regulate the electronic effects and spatial coordination environment of the nickel center, resulting in a significant decrease in catalytic activity and a tendency to trigger side reactions such as trifluorochloroethylene polymerization and hydrodehalogenation, leading to a reduction in hexafluorobutadiene selectivity. Conversely, when the amount of ligand is too large, the excess ligand occupies the active coordination sites of the nickel center, hindering the oxidative addition process between the C-Cl bond of trifluorochloroethylene and the active nickel center. This makes it difficult for the core catalytic cycle to proceed efficiently, while also increasing the system viscosity, reducing the mass transfer efficiency of reactants, causing a decrease in the conversion rate of trifluorochloroethylene, and further increasing the cost of raw materials and the difficulty of subsequent separation and purification.

[0120] A comparison of Examples 10, 11 and Example 1 shows that when the amount of catalyst is too small, the number of catalytic active centers in the system is insufficient, and the selective activation of the C-Cl bond of trifluorochloroethylene cannot be fully realized. A large amount of raw materials cannot participate in the catalytic coupling reaction, resulting in a significant reduction in the conversion rate of trifluorochloroethylene and making it difficult to achieve efficient preparation of the target product. When the amount of catalyst is too large, the excessive nickel active centers in the system will cause excessive reaction and polypolymerization side reaction of trifluorochloroethylene, resulting in a decrease in the selectivity of hexafluorobutadiene. At the same time, it will also significantly increase the cost of raw materials and increase the pressure on subsequent product purification and waste treatment.

[0121] A comparison of Examples 12, 13 and Example 1 shows that when the amount of reducing agent is too small, the divalent nickel precursor in the system cannot be fully reduced to a catalytically active zero-valent nickel species, and it is also difficult to continuously provide sufficient electrons for the valence state cycle of nickel in the catalytic cycle, which can easily lead to the interruption of the catalytic cycle. At the same time, it is impossible to completely capture the chloride ions generated in the reaction in situ. The chloride ions will poison the catalytic active center, resulting in a decrease in the conversion rate of trifluorochloroethylene and the selectivity of hexafluorobutadiene. When the amount of reducing agent is too large, the excessive solid-phase reducing agent will reduce the mass transfer efficiency of the system, and it is also easy to trigger the hydrodehalogenation side reaction of trifluorochloroethylene, resulting in a decrease in the selectivity of hexafluorobutadiene. It will also increase the cost of raw materials and the pressure of subsequent solid waste treatment.

[0122] In summary, this invention employs a nickel-catalyzed one-step method to prepare hexafluorobutadiene. By mixing an organic solvent, ligand, nickel-based catalyst, and reducing agent, heating the mixture, and then introducing trifluorochloroethylene for a closed reaction, the dechlorination coupling of two molecules of trifluorochloroethylene can be achieved in a single step, directly yielding the target product, hexafluorobutadiene. This method completely eliminates the inherent defects of existing technologies, such as multi-step continuous reactions, high-temperature thermal polymerization, and the use of highly toxic mercury reagents and iodine chloride. It shortens the process flow, reduces operational difficulty and safety risks, and avoids intermediate losses associated with multi-step reactions, significantly improving the economic efficiency of the reaction. Furthermore, the reaction conditions are mild, requiring no extreme high-temperature or high-pressure equipment, making the process highly adaptable. The product can be directly collected from the gas generated during the reaction, simplifying product separation and purification steps and facilitating large-scale, continuous industrial production.

[0123] 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 method for preparing hexafluorobutadiene using nickel catalysis, characterized in that, The method includes the following steps: A mixture of organic solvent, ligand, nickel-based catalyst and reducing agent is heated to the reaction temperature, and trifluorochloroethylene is introduced to carry out a closed reaction; after the closed reaction is completed, the generated gas is collected to obtain hexafluorobutadiene.

2. The method according to claim 1, characterized in that, The organic solvent includes any one or a combination of at least two of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, toluene, 1,4-dioxane, acetonitrile, methyl tert-butyl ether, or tetrahydrofuran.

3. The method according to claim 1 or 2, characterized in that, The ligands include any one or a combination of at least two of the following: tricyclohexylphosphine, triphenylphosphine, 1,1'-binaphthyl-2,2'-bisdiphenylphosphine, 1,2-bis(diphenylphosphine)ethane, pyridine, 2,2'-bipyridine, or 2-aminopyridine.

4. The method according to any one of claims 1 to 3, characterized in that, The nickel-based catalyst includes any one or a combination of at least two of nickel iodide, nickel bromide, nickel chloride, bis(1,5-cyclooctadiene) nickel, nickel acetylacetonate, or nickel dicerocene.

5. The method according to any one of claims 1 to 4, characterized in that, The reducing agent includes any one or a combination of at least two of manganese powder, zinc powder, zinc-copper reagent, iron powder, triethylzinc, or triethylboron.

6. The method according to any one of claims 1 to 5, characterized in that, The amount of the nickel-based catalyst used is 20wt% to 60wt% of the trifluorochloroethylene. And / or, the amount of the ligand used is 40wt% to 60wt% of the trifluorochloroethylene.

7. The method according to any one of claims 1 to 6, characterized in that, The molar ratio of the reducing agent to the trifluorochloroethylene is 1.5:1 to 4:

1.

8. The method according to any one of claims 1 to 7, characterized in that, The amount of the organic solvent used is 7 to 20 times the mass of the trifluorochloroethylene.

9. The method according to any one of claims 1 to 8, characterized in that, The temperature of the closed reaction is 40℃~120℃, and the time is 5h~12h.

10. The method according to claim 1, characterized in that, The method includes the following steps: Organic solvent, ligand, nickel-based catalyst and reducing agent are mixed in a reaction vessel, heated to the reaction temperature, and trifluorochloroethylene is introduced to carry out a closed reaction; after the closed reaction is completed, the generated gas is collected to obtain hexafluorobutadiene. The organic solvent includes any one or a combination of at least two of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, toluene, 1,4-dioxane, acetonitrile, methyl tert-butyl ether, or tetrahydrofuran; the amount of the organic solvent used is 7 to 20 times the mass of the trifluorochloroethylene. The ligand comprises any one or a combination of at least two of tricyclohexylphosphine, triphenylphosphine, 1,1'-binaphthyl-2,2'-bisdiphenylphosphine, 1,2-bis(diphenylphosphine)ethane, pyridine, 2,2'-bipyridine, or 2-aminopyridine; the amount of the ligand is 40wt% to 60wt% of the trifluorochloroethylene. The nickel-based catalyst comprises any one or a combination of at least two of nickel iodide, nickel bromide, nickel chloride, bis(1,5-cyclooctadiene) nickel, nickel acetylacetonate, or nickel dicerocene; the amount of the nickel-based catalyst is 20 wt% to 60 wt% of the trifluorochloroethylene. The reducing agent includes any one or a combination of at least two of manganese powder, zinc powder, zinc-copper reagent, iron powder, triethylzinc, or triethylboron; the molar ratio of the reducing agent to the trifluorochloroethylene is 1.5:1 to 4:

1. The temperature of the closed reaction is 40℃~120℃, and the time is 5h~12h.

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