Method for gas-phase synthesis of hexafluorobutadiene

Abstract

The invention belongs to the technical field of chemical synthesis, relates to a method for gas-phase synthesis of hexafluorobutadiene, and particularly discloses a method for gas-phase synthesis of hexafluorobutadiene from 1, 2-dichlorohexafluorocyclobutane. According to the invention, 1, 2-dichlorohexafluorocyclobutane and hydrogen are subjected to a hydrodechlorination coupling reaction under the action of a catalyst, such that hexafluorobutadiene gas is obtained. According to the method, hexafluorobutadiene can be efficiently prepared by adopting a gas phase reaction, the operation complexity and equipment requirements are greatly reduced, the generation of intermediate products is reduced, the reaction time is shortened, the production efficiency is improved, and economical efficiency and practicability with extremely competitive power are provided for industrial scale application.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical synthesis, and in particular relates to a method for synthesizing hexafluorobutadiene in gas phase. Background Art

[0002] With the rapid development of the domestic optoelectronic industry, especially the semiconductor industry, the demand for dry etching gas is also increasing.

[0003] Hexafluorobutadiene, also known as hexafluoro-1,3-butadiene, perfluorobutadiene, codenamed FC-2316 or R2316, has a molecular formula of C4F6 and a boiling point of 5.5°C. It is a colorless, odorless, toxic, flammable and compressible gas under standard conditions, and its application potential in the chip industry is being gradually developed. Compared with traditional plasma etching gases CF4, C2F6, C3F8, and NF3, C4F6 has faster etching speed, better selectivity and aspect ratio. When used for etching of rectifier circuit boards with low K dielectric constants, the accuracy of key dimensions can reach 100nm. In addition, hexafluorobutadiene also has excellent environmental performance, fast degradation rate, small greenhouse effect, atmospheric existence time of only 1.9d, and low GWP value (greenhouse effect potential). Compared with classic etching gases C3F8 and c-C4F8, the GWP emitted by C4F6 during the etching process is reduced by 80% and 82% respectively. At the same time, hexafluorobutadiene is not only the latest semiconductor laser etching agent, but can also be used as a monomer to synthesize new fluororesins, fluororubbers, etc.

[0004] In the prior art, multiple synthetic routes for hexafluorobutadiene have been disclosed, but the methods suitable for industrial production are relatively limited. Typical process routes include:

[0005] GB798407A discloses a synthetic route using 1,2-dichlorodifluoroethylene as a raw material. This method needs to be carried out under extremely high pressure (13.3MPa) and high temperature (275°C), and good stirring is required to ensure the effectiveness of the reaction. Its disadvantages are that the operation is complicated, the equipment and process control requirements are high, and it is not conducive to industrial application.

[0006] CN 202011579415.0 discloses a method for synthesizing hexafluorobutadiene by telomerization, wherein R22 is hydrothermally decomposed to prepare tetrafluoroethylene, tetrafluoroethylene is added with bromine on acidified activated carbon to generate 1,2-dibromotetrafluoroethane, and dibromotetrafluoroethane reacts with TFE at a certain temperature, zinc powder and a combined solvent of DMF and toluene to prepare hexafluoro-1,3-butadiene. This process is a liquid phase intermittent reaction, which is not conducive to industrial continuous production, and the selectivity of the telomerization reaction is difficult to control and is highly dangerous.

[0007] CN202011061917.4 discloses a method for preparing hexafluorobutadiene by preparing a polar base liquid, activated zinc and 1,2-dichloro-2-iodo-1,1,2-trifluoroethane, further preparing 1,2,3,4-tetrachlorohexafluorobutane, and finally dechlorinating 1,2,3,4-tetrachlorohexafluorobutane with zinc in a polar solvent. The main disadvantage of this method is that the reaction steps are numerous, the process is complicated, and a large amount of three wastes will be generated during the industrial production process, which has a heavy environmental burden.

[0008] CN202210845020.3 discloses a method for preparing hexafluorobutadiene: liquid chlorotrifluoroethylene raw material is introduced into a reactor from the bottom of a reactor for pyrolysis reaction, condensed and recovered by pyrolysis, and fractionated in a high-pressure water bath, and then the fraction is reacted in ethanol under the catalysis of elemental zinc. The collected gaseous product is pyrolyzed with hydrogen iodide gas, reacted with chlorine water under photocatalytic conditions, and then added to butyl carbitol, and finally impurities are removed by zinc catalysis to obtain hexafluorobutadiene. The disadvantage of this method is that there are many reaction steps, and there are many intermittent operation steps, the industrial production process is complicated, and it is difficult to achieve efficient and continuous production.

[0009] CN202410257444.7 discloses a method for preparing hexafluorobutadiene by a liquid caustic soda method, which uses 1,1,2,3,4,4-hexafluoro-1,4-dihalobutane, 1,1,2,3,4,4-hexafluoro-2,3-dihalobutane and 1,1,2,3,4,4-hexafluoro-1,3-dihalobutane as precursors, and prepares hexafluorobutadiene by dehydrohalogenation reaction under liquid caustic soda conditions. The main disadvantage of this process is that a variety of precursor substances are used, the reaction conditions are harsh, and liquid caustic soda operation may bring safety problems and equipment corrosion problems.

[0010] CN201510996095.1 discloses a method for preparing hexafluorobutadiene, comprising reacting 1,1-dichloro-1,2,2-trifluoroethane or 1,2-dichloro-1,1,2-trifluoroethane with hydrogen in a tubular reactor, performing a hydrodechlorination coupling reaction through a first catalyst, and then performing gas-phase thermal cracking of the generated hydrofluorochlorobutane under the action of a second catalyst to remove HCl, and finally obtaining high-purity hexafluorobutadiene. The disadvantage of this method is that the process is complicated, involving multi-step reactions, and the catalyst system may require strict process condition control, which increases the difficulty of production.

[0011] Therefore, how to provide a method for preparing hexafluorobutadiene with simple process, high yield, few steps and easy industrialization is a technical problem to be solved urgently by those skilled in the art. Summary of the invention

[0012] In view of this, the present invention discloses a method for gas-phase synthesis of hexafluorobutadiene, which is a method for preparing hexafluorobutadiene with simple process, high yield, few steps and easy industrialization.

[0013] In order to achieve the above object, the present invention adopts the following technical solution:

[0014] A method for gas phase synthesis of hexafluorobutadiene, the method being as follows:

[0015] 1,2-dichlorohexafluorocyclobutane and hydrogen undergo a hydrodechlorination coupling reaction under the action of a catalyst to obtain hexafluorobutadiene gas.

[0016] Furthermore, the volume ratio of H2 to 1,2-dichlorohexafluorocyclobutane is 2 to 10:1, preferably 5:1.

[0017] Furthermore, the catalyst is a bifunctional catalyst for hydrodechlorination, specifically a Ni-Co / Al2O3 catalyst with a loading of 2% to 10%, wherein the active metal composition is nickel-cobalt alloy (Ni-Co) and the carrier is alumina (Al2O3).

[0018] Furthermore, the catalyst is prepared by an impregnation-reduction method to achieve uniform loading of the nickel-cobalt alloy. First, a certain proportion of nickel nitrate and cobalt nitrate is dissolved in deionized water, and the molar ratio of nickel and cobalt is adjusted to 3:1 to prepare a metal precursor solution. Next, the alumina carrier is immersed in the solution and stirred continuously for several hours (2 to 3 hours) at a constant temperature of about 50°C to allow the metal ions to be uniformly adsorbed on the surface of the carrier. Subsequently, the impregnated carrier is dried at 100°C to 120°C until the water is completely evaporated (4 to 6 hours), and then calcined at 400°C to 500°C in an inert gas environment (such as nitrogen or argon) for 1 to 4 hours to ensure sufficient decomposition of the metal precursor. Finally, the calcined catalyst is placed in a hydrogen gas flow (space velocity of about 2000h -1 ) and reduced at 400°C to 450°C for 2 hours to form an active catalyst with an alloy structure.

[0019] Furthermore, the temperature of the hydrodehydrochlorination coupling reaction is 150°C to 250°C, the reaction pressure is normal pressure, and the space velocity is 1000-2000h -1 The reaction time is 1 to 200 s, preferably 10 to 60 s.

[0020] Furthermore, the method also includes: obtaining a high-purity hexafluorobutadiene product through filtering, alkali washing, water washing, drying, compressing, and distillation purification.

[0021] It should be noted that the reaction mechanism of the above-mentioned gas phase synthesis of hexafluorobutadiene is as follows:

[0022] First, 1,2-dichlorohexafluorocyclobutane molecules are adsorbed onto the catalyst surface, and the metal active sites of the catalyst polarize and activate the C-Cl bonds, weakening their bond energy. At the same time, hydrogen molecules dissociate at the active sites of the Ni-Co alloy to generate highly active hydrogen atoms, which react with the chlorine atoms of the adsorbed 1,2-dichlorohexafluorocyclobutane to gradually remove hydrogen chloride (HCl) and generate intermediates. In this process, the Ni-Co bimetallic structure effectively promotes the transfer of hydrogen atoms and the breaking of C-Cl bonds, achieving efficient hydrogenation and dechlorination simultaneously. Subsequently, the intermediate further reacts with activated hydrogen to complete the final hydrogenation step to ultimately generate the target product hexafluorobutadiene.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. High-efficiency bimetallic synergistic effect: The present invention significantly increases the active site density on the catalyst surface through the bimetallic synergistic effect of nickel-cobalt alloy, thereby accelerating the hydrogenation and dechlorination process. This bimetallic system can achieve a hexafluorobutadiene yield of up to 96.3% under appropriate reaction conditions, fully demonstrating the unique catalytic activity and selectivity control ability in this reaction.

[0025] 2. Simplified gas phase preparation process: Different from the traditional multi-step synthesis method, the present invention can efficiently prepare hexafluorobutadiene by gas phase reaction. This process greatly reduces the operation complexity and equipment requirements, reduces the generation of intermediates, shortens the reaction time, and not only improves production efficiency, but also provides highly competitive economy and practicality for industrial-scale applications.

[0026] 3. Excellent reaction selectivity: The Ni-Co / Al2O3 catalyst of the present invention exhibits excellent selectivity in the hydrodechlorination reaction of 1,2-dichlorohexafluorocyclobutane. By optimizing the loading amount of the nickel-cobalt alloy, the catalyst significantly reduces the generation of by-products and greatly improves the purity and yield of the target product hexafluorobutadiene. This selectivity advantage demonstrates the applicability of the method in the production of fine chemicals and is significantly innovative.

[0027] 4. High dispersibility and long-term stability: The Ni-Co / Al2O3 catalyst is prepared by an optimized impregnation-reduction method, so that the active metal is evenly distributed on the alumina carrier, forming a highly dispersed catalytic structure. Compared with traditional single metal catalysts, this structure effectively inhibits particle agglomeration, significantly prolongs the stability and activity of the catalyst in long-term reactions, and has a long-life industrial application prospect.

[0028] 5. Long service life of the catalyst: After 300h of reaction, the Ni-Co / Al2O3 catalyst can still maintain excellent catalytic activity, and the yield of hexafluorobutadiene is maintained at about 96.3%. Figure 2 This feature significantly reduces the frequency of catalyst replacement and production costs, further improving the economy and sustainability of the process, and is highly applicable for industrial-scale use.

[0029] 6. Environmental friendliness: The Ni-Co / Al2O3 catalyst prepared by the present invention avoids the use of precious metals, is low-cost and more environmentally friendly, and significantly reduces the demand for processing waste catalysts, which is in line with the trend of green chemistry and sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0031] Figure 1 It is the GCMS detection spectrum of the hexafluorobutadiene synthesized by the present invention.

[0032] Figure 2 It is a graph showing the change in yield of hexafluorobutadiene synthesized by the present invention over time. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] The word "embodiment" used here as an "exemplary" does not necessarily mean that any embodiment described is superior to or better than other embodiments. Unless otherwise specified, the performance index tests in the embodiments of this application are performed using conventional test methods in the art. It should be understood that the terms described in this application are only used to describe specific implementation methods and are not used to limit the content disclosed in this application.

[0035] Unless otherwise specified, the technical and scientific terms used in this document have the same meanings as commonly understood by ordinary technicians in the technical field to which this application belongs; other experimental methods and technical means not specifically specified in this application refer to experimental methods and technical means commonly used by ordinary technicians in this field.

[0036] In order to better illustrate the content of the present application, numerous specific details are provided in the specific examples below. It should be understood by those skilled in the art that the present application can also be implemented without certain specific details. In the embodiments, some methods, means, instruments, equipment, etc. well known to those skilled in the art are not described in detail in order to highlight the main purpose of the present application.

[0037] Under the premise of no conflict, the technical features disclosed in the embodiments of the present application can be combined arbitrarily, and the resulting technical solutions belong to the contents disclosed in the embodiments of the present application.

[0038] The invention discloses a method for synthesizing hexafluorobutadiene in gas phase.

[0039] In order to better understand the present invention, the present invention is further specifically described below through the following examples, but it should not be understood as a limitation of the present invention. Some non-essential improvements and adjustments made by technicians in this field based on the above invention content are also considered to fall within the protection scope of the present invention.

[0040] Example 1

[0041] 1,2-dichlorohexafluorocyclobutane and H2 are used as the reaction raw materials, and the product hexafluorobutadiene is prepared by hydrogenation dechlorination coupling reaction. The specific preparation steps are as follows:

[0042] Before the reaction, nickel nitrate and cobalt nitrate were dissolved in deionized water at a molar ratio of nickel to cobalt of 3:1 to prepare a metal precursor solution; an alumina carrier was immersed in the metal precursor solution, the solution volume was controlled to ensure that the metal loading was 2%, and the solution was stirred at a constant temperature of 50°C for 2 hours and then allowed to stand; subsequently, the solution was dried at 100°C for 6 hours, and then calcined at 400°C for 2 hours under the protection of an inert gas (nitrogen or argon); finally, the calcined catalyst was placed in a tubular reactor and heated to 400°C under a hydrogen flow rate of 2000 h / min. - 1) under the conditions of reduction at 450°C for 2 hours to obtain a Ni-Co / Al2O3 catalyst with an alloy structure.

[0043] The flow rate of H2 is controlled by a mass flow meter (400 mL / min), 1,2-dichlorohexafluorocyclobutane is placed in a bubbler, the aforementioned H2 is introduced into the bubbler to entrain 1,2-dichlorohexafluorocyclobutane, the temperature of the bubbler is adjusted, the flow rate of H2 and the flow rate ratio of 1,2-dichlorohexafluorocyclobutane (volume ratio) is adjusted to 5, the reaction temperature is stabilized at 250°C, the reaction pressure is normal pressure, and the reaction time is 10s. After the reaction is completed, the hydrogen is stopped, and the tail gas generated by the reaction is quenched, alkali washed, washed with water, dried, compressed, and distilled to obtain hexafluorobutadiene with a purity of ≥99.9%, the selectivity of hexafluorobutadiene is 80.3%, and the conversion rate of 1,2-dichlorohexafluorocyclobutane is 78.8%.

[0044] Example 2

[0045] 1,2-dichlorohexafluorocyclobutane and H2 are used as the reaction raw materials, and the product hexafluorobutadiene is prepared by hydrogenation dechlorination coupling reaction. The specific preparation steps are as follows:

[0046] Before the reaction, the solution volume was controlled to ensure the preparation of a Ni-Co / Al2O3 catalyst with a metal loading of 5%. The other preparation procedures were the same as those in Example 1.

[0047] The flow rate of H2 is controlled by a mass flow meter (400 mL / min), 1,2-dichlorohexafluorocyclobutane is placed in a bubbler, the aforementioned H2 is introduced into the bubbler to entrain 1,2-dichlorohexafluorocyclobutane, the temperature of the bubbler is adjusted, the flow rate of H2 and the flow rate ratio of 1,2-dichlorohexafluorocyclobutane (volume ratio) is adjusted to 5, the reaction temperature is stabilized at 250°C, the reaction pressure is normal pressure, and the reaction time is 60s. After the reaction is completed, the hydrogen is stopped, and the tail gas generated by the reaction is quenched, alkali washed, washed with water, dried, compressed, and distilled to obtain hexafluorobutadiene with a purity of ≥99.9%, the selectivity of hexafluorobutadiene is 86.3%, and the conversion rate of 1,2-dichlorohexafluorocyclobutane is 80.8%.

[0048] Example 3

[0049] 1,2-dichlorohexafluorocyclobutane and H2 are used as the reaction raw materials, and the product hexafluorobutadiene is prepared by hydrogenation dechlorination coupling reaction. The specific preparation steps are as follows:

[0050] Before the reaction, the solution volume was controlled to ensure the preparation of a Ni-Co / Al2O3 catalyst with a metal loading of 7%. The other preparation procedures were the same as those in Example 1.

[0051] The flow rate of H2 is controlled by a mass flow meter (400 mL / min), 1,2-dichlorohexafluorocyclobutane is placed in a bubbler, the aforementioned H2 is introduced into the bubbler to entrain 1,2-dichlorohexafluorocyclobutane, the temperature of the bubbler is adjusted, the flow rate of H2 and the flow rate ratio of 1,2-dichlorohexafluorocyclobutane (volume ratio) is adjusted to 5, the reaction temperature is stabilized at 250°C, the reaction pressure is normal pressure, and the reaction time is 10s. After the reaction is completed, the hydrogen is stopped, and the tail gas generated by the reaction is quenched, alkali washed, washed with water, dried, compressed, and distilled to obtain hexafluorobutadiene with a purity of ≥99.9%, the selectivity of hexafluorobutadiene is 96.3%, and the conversion rate of 1,2-dichlorohexafluorocyclobutane is 90.2%.

[0052] Example 4

[0053] 1,2-dichlorohexafluorocyclobutane and H2 are used as the reaction raw materials, and the product hexafluorobutadiene is prepared by hydrogenation dechlorination coupling reaction. The specific preparation steps are as follows:

[0054] Before the reaction, the solution volume was controlled to ensure the preparation of a Ni-Co / Al2O3 catalyst with a metal loading of 10%. The other preparation procedures were the same as those in Example 1.

[0055] The flow rate of H2 is controlled by a mass flow meter (400 mL / min), 1,2-dichlorohexafluorocyclobutane is placed in a bubbler, the aforementioned H2 is passed into the bubbler to entrain 1,2-dichlorohexafluorocyclobutane, the temperature of the bubbler is adjusted, the flow rate of H2 and the flow rate ratio of 1,2-dichlorohexafluorocyclobutane (volume ratio) is adjusted to 5, the reaction temperature is stabilized at 250°C, the reaction pressure is normal pressure, and the reaction time is 100s. After the reaction is completed, the hydrogen is stopped, and the tail gas generated by the reaction is quenched, alkali washed, washed with water, dried, compressed, and distilled to obtain hexafluorobutadiene with a purity of ≥99.9%, the selectivity of hexafluorobutadiene is 88.3%, and the conversion rate of 1,2-dichlorohexafluorocyclobutane is 81.2%.

[0056] Example 5

[0057] The ratio of H2 flow rate to 1,2-dichlorohexafluorocyclobutane flow rate (volume ratio) was adjusted to 8, the reaction temperature was stabilized at 200°C, and the rest was the same as Example 1. The selectivity of hexafluorobutadiene was 79.3%, and the conversion rate of 1,2-dichlorohexafluorocyclobutane was 71.8%.

[0058] Example 6

[0059] The ratio of H2 flow rate to 1,2-dichlorohexafluorocyclobutane flow rate (volume ratio) was adjusted to 5, the reaction temperature was stabilized at 150°C, and the rest was the same as Example 1. The selectivity of hexafluorobutadiene was 86.7%, and the conversion rate of 1,2-dichlorohexafluorocyclobutane was 80.9%.

[0060] Example 7

[0061] The ratio of H2 flow rate to 1,2-dichlorohexafluorocyclobutane flow rate (volume ratio) was adjusted to 3, the reaction temperature was stabilized at 150°C, and the rest was the same as Example 1. The selectivity of hexafluorobutadiene was 84.7%, and the conversion rate of 1,2-dichlorohexafluorocyclobutane was 78.9%.

[0062] Example 8

[0063] The ratio (volume ratio) of the H2 flow rate to the 1,2-dichlorohexafluorocyclobutane flow rate was adjusted to 8, and the rest was the same as in Example 2. The selectivity of hexafluorobutadiene was 82.3%, and the conversion rate of 1,2-dichlorohexafluorocyclobutane was 60.8%.

[0064] Example 9

[0065] The ratio (volume ratio) of the H2 flow rate to the 1,2-dichlorohexafluorocyclobutane flow rate was adjusted to 8, and the rest was the same as in Example 3. The selectivity of hexafluorobutadiene was 91.6%, and the conversion rate of 1,2-dichlorohexafluorocyclobutane was 86.9%.

[0066] Example 10

[0067] The ratio (volume ratio) of the H2 flow rate to the 1,2-dichlorohexafluorocyclobutane flow rate was adjusted to 3, and the rest was the same as in Example 3. The selectivity of hexafluorobutadiene was 90.3%, and the conversion rate of 1,2-dichlorohexafluorocyclobutane was 85.2%.

[0068] Embodiment 11

[0069] The ratio (volume ratio) of the H2 flow rate to the 1,2-dichlorohexafluorocyclobutane flow rate was adjusted to 3, and the rest was the same as in Example 4. The selectivity of hexafluorobutadiene was 77.3%, and the conversion rate of 1,2-dichlorohexafluorocyclobutane was 70.2%.

[0070] Example 12

[0071] The ratio (volume ratio) of the H2 flow rate to the 1,2-dichlorohexafluorocyclobutane flow rate was adjusted to 8, and the rest was the same as in Example 4. The selectivity of hexafluorobutadiene was 79.3%, and the conversion rate of 1,2-dichlorohexafluorocyclobutane was 69.2%.

[0072] Comparative Example 1

[0073] 1,2-dichlorohexafluorocyclobutane and H2 are used as the reaction raw materials, and the product hexafluorobutadiene is prepared by hydrogenation dechlorination coupling reaction. The specific preparation steps are as follows:

[0074] Before the reaction, nickel nitrate was dissolved in deionized water to prepare a metal precursor solution; an alumina carrier was immersed in the metal precursor solution, the solution volume was controlled to ensure that the metal loading was 7%, and the solution was stirred at a constant temperature of 50°C for 2 hours and then allowed to stand; subsequently, the solution was dried at 100°C for 6 hours, and then calcined at 400°C for 2 hours under the protection of an inert gas (nitrogen or argon); finally, the calcined catalyst was placed in a tubular reactor and heated to 400°C under a hydrogen flow rate of 2000 h / min. -1) Under the conditions of 450°C for 2 hours, a Ni / Al2O3 catalyst with an alloy structure is obtained. The flow rate of H2 is controlled by a mass flow meter (400mL / min), 1,2-dichlorohexafluorocyclobutane is placed in a bubbler, and the aforementioned H2 is passed into the bubbler to entrain 1,2-dichlorohexafluorocyclobutane, the temperature of the bubbler is adjusted, and the ratio of the flow rate of H2 to the flow rate of 1,2-dichlorohexafluorocyclobutane (volume ratio) is adjusted to 5, the reaction temperature is stabilized at 250°C, the reaction pressure is normal pressure, and the reaction time is 10s. After the reaction is completed, the hydrogen is stopped, and the tail gas generated by the reaction is quenched, alkali washed, washed with water, dried, compressed, and distilled to obtain hexafluorobutadiene with a purity of ≥99.9%, the selectivity of hexafluorobutadiene is 42.9%, and the conversion rate of 1,2-dichlorohexafluorocyclobutane is 49.2%.

[0075] Comparative Example 2

[0076] 1,2-dichlorohexafluorocyclobutane and H2 are used as the reaction raw materials, and the product hexafluorobutadiene is prepared by hydrogenation dechlorination coupling reaction. The specific preparation steps are as follows:

[0077] Before the reaction, cobalt nitrate was dissolved in deionized water to prepare a metal precursor solution; the alumina carrier was immersed in the metal precursor solution, the solution volume was controlled to ensure that the metal loading was 7%, and the solution was stirred at a constant temperature of 50°C for 2 hours and then allowed to stand; then, the solution was dried at 100°C for 6 hours, and then calcined at 400°C for 2 hours under the protection of an inert gas (nitrogen or argon); finally, the calcined catalyst was placed in a tubular reactor and heated to 400°C under a hydrogen flow rate of 2000 h / min. - 1) Under the conditions of 450°C for 2 hours, a Co / Al2O3 catalyst with an alloy structure is obtained. The flow rate of H2 is controlled by a mass flow meter (400mL / min), 1,2-dichlorohexafluorocyclobutane is placed in a bubbler, and the aforementioned H2 is passed into the bubbler to entrain 1,2-dichlorohexafluorocyclobutane, the temperature of the bubbler is adjusted, and the ratio of the flow rate of H2 to the flow rate of 1,2-dichlorohexafluorocyclobutane (volume ratio) is adjusted to 5, the reaction temperature is stabilized at 250°C, the reaction pressure is normal pressure, and the reaction time is 10s. After the reaction is completed, the hydrogen is stopped, and the tail gas generated by the reaction is quenched, alkali washed, washed with water, dried, compressed, and distilled to obtain hexafluorobutadiene with a purity of ≥99.9%, the selectivity of hexafluorobutadiene is 51.9%, and the conversion rate of 1,2-dichlorohexafluorocyclobutane is 44.7%.

[0078] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for gas phase synthesis of hexafluorobutadiene, characterized in that: The method is as follows: 1,2-dichlorohexafluorocyclobutane and hydrogen undergo a hydrodechlorination coupling reaction under the action of a catalyst to obtain hexafluorobutadiene gas.

2. The method for gas phase synthesis of hexafluorobutadiene according to claim 1, characterized in that: The volume ratio of H2 to 1,2-dichlorohexafluorocyclobutane is 2 to 10:

1.

3. The method for gas phase synthesis of hexafluorobutadiene according to claim 1, characterized in that: The catalyst is a Ni-Co / Al2O3 catalyst with a loading of 2-10%, wherein the active metal component is a nickel-cobalt alloy (Ni-Co) and the carrier is alumina (Al2O3).

4. The method for gas phase synthesis of hexafluorobutadiene according to claim 3, characterized in that: The catalyst is prepared by an impregnation-reduction method, and the specific preparation is as follows: Nickel nitrate and cobalt nitrate are dissolved in deionized water, and the molar ratio of nickel to cobalt is adjusted to 3:1 to prepare a metal precursor solution; an alumina carrier is immersed in the metal precursor solution and stirred, and then the impregnated carrier is dried and calcined in an inert gas environment; the calcined catalyst is reduced in a hydrogen gas flow to obtain a catalyst.

5. The method for gas phase synthesis of hexafluorobutadiene according to claim 4, characterized in that: The stirring temperature when entering the alumina carrier is about 50°C, and the stirring time is 2 to 3 hours.

6. The method for gas phase synthesis of hexafluorobutadiene according to claim 4, characterized in that: The drying temperature is 100° C. to 120° C., and the drying time is 4 to 6 hours.

7. The method for gas phase synthesis of hexafluorobutadiene according to claim 4, characterized in that: The calcination temperature is 400° C. to 500° C., and the calcination time is 1 to 4 hours.

8. The method for gas phase synthesis of hexafluorobutadiene according to claim 4, characterized in that: The space velocity of the hydrogen gas flow is 2000h -1 The reduction temperature is 400℃~450℃, and the reduction time is 2 hours.

9. The method for gas phase synthesis of hexafluorobutadiene according to claim 1, characterized in that: The temperature of the hydrodehydrochlorination coupling reaction is 150°C to 250°C, the reaction pressure is normal pressure, and the space velocity is 1000-2000h -1 , the reaction time is 1 to 200 seconds.

10. The method for gas phase synthesis of hexafluorobutadiene according to any one of claims 1 to 9, characterized in that: Also includes: The high-purity hexafluorobutadiene product is obtained through filtration, alkali washing, water washing, drying, compression and distillation.

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