Method for gas-phase continuous preparation of hexafluorobutadiene

Abstract

The invention provides a method for continuously preparing hexafluorobutadiene in a gas phase, which comprises the following steps: by taking chlorotrifluoroethylene as an initial raw material, carrying out a gas-phase catalytic telomerization reaction to obtain an intermediate 1, 2-dichlorohexafluorocyclobutane, then carrying out a gas-phase catalytic dichloro-removal reaction to obtain an intermediate hexafluorocyclobutene, and finally, carrying out a gas-phase catalytic telomerization reaction to obtain the hexafluorobutadiene. And finally, carrying out gas-phase catalytic isomerization reaction to obtain the target product hexafluorobutadiene. The method for synthesizing hexafluorobutadiene has the advantages of high one-way yield, high selectivity, short reaction time, easy realization of gas phase independent circulation continuous reaction, and high synthesis efficiency.

Description

Technical Field

[0001] This application belongs to the field of chemical synthesis, specifically relating to a method for the continuous gas-phase preparation of hexafluorobutadiene from trifluorochloroethylene through telomerization, dechlorination, and isomerization. Background Technology

[0002] Hexafluorobutadiene is used as a key material in advanced chip manufacturing processes of 3nm and below—an etching gas. Its mass production and stable supply are mainly controlled by international companies such as Japan's Kanto Denka Co., Ltd. and Daikin Industries, Ltd., with a domestic production rate of less than 5%.

[0003] Currently, among the many routes for synthesizing hexafluorobutadiene, the route using trifluorochloroethylene as a starting material, involving a two-step reaction of chain formation via telomerization and dechlorination, has attracted considerable attention due to its advantages of low raw material prices and relatively low overall product costs. Publicly available environmental impact assessment information reports that Shandong Feiyuan and Fujian Jianyang Jinshi have adopted this route for industrialization, with total hexafluorobutadiene yields of 42.8% and 44%, respectively. The reaction equations are as follows:

[0004]

[0005] To date, research on the aforementioned synthetic routes has mainly focused on the following:

[0006] (1) Study on the first step of the electropolymerization reaction

[0007] CN116768695A reports a catalyst using titanium dioxide supported on molecular sieves to catalyze the telomerization reaction of trifluorochloroethylene at 410 °C, simultaneously yielding 3,4-dichlorohexafluoro-1-butene and 1,2-dichlorohexafluorocyclobutane. The crude product contains only 28.1% 3,4-dichlorohexafluoro-1-butene.

[0008] US2668182A reports the telomerization reaction of trifluorochloroethylene in a tubular reactor under the conditions of "reaction temperature 550°C, contact time several seconds, and atmospheric pressure". The conversion rate of trifluorochloroethylene was 36.2%, and the yields of 3,4-dichlorohexafluoro-1-butene and 1,2-dichlorohexafluorocyclobutane were 14.4% and 7.4%, respectively.

[0009] US2733277A reports a telomerization reaction of trifluorochloroethylene at 550–600 °C and a flow rate of 30–40 g / h, with yields of 3,4-dichlorohexafluoro-1-butene and 1,2-dichlorohexafluorocyclobutane of 35% and 30%, respectively.

[0010] (2) Study on the second step of the dedichlorination reaction

[0011] CN116768695A reports that 3,4-dichlorohexafluoro-1-butene reacts with zinc powder in ethanol at 50°C, resulting in a hexafluorobutadiene yield of 19.3%.

[0012] CN113061074A reports that when 3,4-dichlorohexafluoro-1-butene reacts with zinc powder in ethanol at 40°C, the conversion rate of 3,4-dichlorohexafluoro-1-butene is 91%, the selectivity of hexafluorobutadiene is 92.9%, and the yield of hexafluorobutadiene is 84.4%.

[0013] The above route has the following disadvantages: (1) A large amount of byproduct 1,2-dichlorohexafluorocyclobutane is generated in the telomerization reaction, which is not converted into hexafluorobutadiene, but becomes reaction waste, resulting in a waste of resources; (2) The dechlorination reaction uses a large amount of solvent and reducing agent zinc powder, which generates a large amount of liquid waste and solid waste, causing serious environmental pollution; (3) The dechlorination reaction is an intermittent process, which is difficult to achieve continuous production and has the disadvantage of low efficiency. Summary of the Invention

[0014] This application provides a method for the directional conversion of 1,2-dichlorohexafluorocyclobutane to the target product hexafluorobutadiene, characterized by high single-pass yield, shorter reaction time, high synthesis efficiency, and easy continuous gas-phase preparation of hexafluorobutadiene. This application is primarily used for a method of high-conversion, high-selectivity continuous gas-phase preparation of hexafluorobutadiene.

[0015] The technical solution of this application is as follows:

[0016] A method for the continuous gas-phase preparation of hexafluorobutadiene includes the following steps:

[0017] (1) Gas-phase polymerization reaction: Using trifluorochloroethylene as raw material, 1,2-dichlorohexafluorocyclobutane is obtained by gas-phase polymerization and cyclization reaction in the presence of a polymerization catalyst.

[0018] The reaction conditions are: reaction pressure of 0.1–1.5 MPa, reaction temperature of 300–600 °C, and contact time of 0.5–100 s;

[0019] (2) Gas-phase dechlorination reaction: Using 1,2-dichlorohexafluorocyclobutane as raw material, a dechlorination reaction is carried out in the presence of a dechlorination catalyst and hydrogen to obtain hexafluorocyclobutene;

[0020] The reaction conditions are as follows: the molar ratio of hydrogen to 1,2-dichlorohexafluorocyclobutane is 1 to 3:1, the reaction pressure is 0.1 to 1.5 MPa, the reaction temperature is 200 to 400 °C, and the contact time is 0.5 to 100 s.

[0021] (3) Gas-phase isomerization reaction: Hexafluorocyclobutene is used as raw material, and a gas-phase isomerization reaction is carried out in the presence of an isomerization catalyst to obtain hexafluorobutadiene;

[0022] The reaction conditions are: reaction pressure of 0.1–1.5 MPa, reaction temperature of 400–700 °C, and contact time of 0.5–100 s.

[0023] Preferably, the telomerization catalyst in step (1) is a mixture of alkali metal fluoride and support A in a mass percentage ratio of (1% to 20%): (80% to 99%), and the sum of the mass percentages of the two is 100%.

[0024] Alkali metal fluorides are any one or more of sodium fluoride, potassium fluoride, rubidium fluoride, and cesium fluoride;

[0025] Carrier A is any one or more of aluminum fluoride, iron fluoride, magnesium fluoride, calcium fluoride, and chromium fluoride.

[0026] Preferably, in step (1), the reaction pressure is 0.1-0.5 MPa, the reaction temperature is 400-500°C, and the contact time is 5-50 s;

[0027] The mass ratio of alkali metal fluoride to carrier A is (5%–15%): (85%–95%).

[0028] Preferably, the products obtained from the gas-phase polymerization reaction in step (1) include trifluorochloroethylene, 1,2-dichlorohexafluorocyclobutane, 3,4-dichlorohexafluoro-1-butene, and trifluorochloroethylene polymer, wherein the degree of polymerization of the trifluorochloroethylene polymer is not less than 3; wherein the molar percentage of 1,2-dichlorohexafluorocyclobutane is more than 80%, and pure 1,2-dichlorohexafluorocyclobutane with a purity greater than 99% is obtained by purification in a distillation column.

[0029] Preferably, the dechlorination catalyst in step (2) is a mixture of elemental metal A and support B in a mass percentage ratio of (1% to 10%): (90% to 99%), and the sum of the mass percentages of the two is 100%.

[0030] Metallic element A is any one or more of zinc, iron, copper, cadmium, ruthenium, and silver;

[0031] Carrier B is any one or more of aluminum fluoride, iron fluoride, magnesium fluoride, calcium fluoride, and chromium fluoride.

[0032] Preferably, in step (2), the molar ratio of hydrogen to 1,2-dichlorohexafluorocyclobutane is 1.5 to 2.5:1, the reaction pressure is 0.1 to 0.5 MPa, the reaction temperature is 250 to 350 °C, and the contact time is 5 to 50 s;

[0033] The mass ratio of the elemental metal to carrier B is (3%–8%): (82%–97%).

[0034] Preferably, the products obtained by the gas-phase dechlorination reaction in step (2) include 1,2-dichlorohexafluorocyclobutane, hexafluorocyclobutene, hexafluorobutadiene, hydrogen and hydrogen chloride; wherein hexafluorocyclobutene accounts for more than 80% of the molar percentage of the organic products, and pure hexafluorocyclobutene with a purity greater than 99% is obtained by purification in a distillation column.

[0035] Preferably, the isomerization catalyst in step (3) is a mixture of elemental metal B and support C in a mass percentage ratio of (0.1% to 10%): (90% to 99.9%), and the sum of the mass percentages of the two is 100%.

[0036] Metallic element B can be any one or more of Pt, Pd, Ni, and Co;

[0037] The carrier C is any one or more of aluminum fluoride, iron fluoride, magnesium fluoride, calcium fluoride, and chromium fluoride.

[0038] Preferably, in step (3), the reaction pressure is 0.1-0.5 MPa, the reaction temperature is 500-600°C, and the contact time is 5-50 s;

[0039] The mass ratio of elemental metal B to carrier C is (0.5%–5%): (95%–99.5%).

[0040] Preferably, the products of the gas-phase isomerization reaction include hexafluorobutadiene, hexafluorocyclobutene, and hexafluoro-2-butyne; wherein the molar percentage of hexafluorobutadiene is more than 80%, and pure hexafluorobutadiene with a purity greater than 99.99% is obtained by purification in a distillation column.

[0041] Compared with the prior art, the beneficial effects of this application are as follows:

[0042] (1) In this application, the intermediate 1,2-dichlorohexafluorocyclobutane is not waste and can be converted into hexafluorobutadiene through dechlorination and isomerization reactions;

[0043] (2) Compared with the prior art, the preparation method of hexafluorobutadiene in this application not only has a higher single-pass yield and higher selectivity, but also a shorter reaction time and can easily realize gas-phase independent circulation continuous reaction, which has the characteristics of high synthesis efficiency.

[0044] (3) This application uses a gas phase method to prepare hexafluorobutadiene. Through the gas phase independent circulation process, the incompletely reacted materials are independently circulated, which can make the initial raw materials almost completely converted into the target product. Finally, the target product is extracted from the process system, so as not to generate liquid waste and waste gas, and to achieve green production. Attached Figure Description

[0045] Figure 1 This is a diagram of the reaction equation for the present invention.

[0046] Figure 2 A process flow diagram is shown for preparing hexafluorobutadiene from trifluorochloroethylene as the starting material via gas-phase cyclopolymerization, gas-phase dechlorination, and gas-phase isomerization.

[0047] Figure reference numerals: 1-First reactor; 2-First distillation column; 3-Second distillation column; 4-Second reactor; 5-Third distillation column; 6-Fourth distillation column; 7-Fifth distillation column; 8-Sixth distillation column; 9-Third reactor; 10-Seventh distillation column; 11-First pipeline; 12-Second pipeline; 13-Third pipeline; 14-Fourth pipeline; 15-Fifth pipeline; 16-Sixth pipeline; 17-Seventh pipeline; 18-Eighth pipeline; 19-Ninth pipeline; 20-Tenth pipeline; 21-Eleventh pipeline; 22-Twelfth pipeline; 23-Thirteenth pipeline; 24-Fourteenth pipeline; 25-Fifteenth pipeline; 26-Sixteenth pipeline; 27-Seventeenth pipeline; 28-Eighteenth pipeline; 29-Nineteenth pipeline; 30-Twentieth pipeline; 31-Twenty-first pipeline; 32-Twenty-second pipeline. Detailed Implementation

[0048] The following examples further illustrate this application. It should be understood that the examples are only used to further illustrate and explain this application and are not intended to limit this application.

[0049] Unless otherwise defined, technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art. While similar or identical methods and materials may be applied in experimental or practical applications, materials and methods are described herein. In case of conflict, the definitions included herein shall prevail. Furthermore, materials, methods, and examples are for illustrative purposes only and are not intended to be limiting. The following description, in conjunction with specific experimental examples, further illustrates this application but is not intended to limit its scope.

[0050] This application provides a method for the continuous gas-phase preparation of hexafluorobutadiene, comprising three steps: gas-phase telomerization, gas-phase dedichlorination, and gas-phase isomerization. Details are as follows:

[0051] (1) First step reaction: gas phase zeolite reaction

[0052] Using trifluorochloroethylene as a raw material, 1,2-dichlorohexafluorocyclobutane is obtained by gas-phase polymerization and cyclization reaction in the presence of a polymerization catalyst.

[0053] The telomerization catalyst is composed of an alkali metal fluoride and support A in a mass percentage ratio of (1%–20%):(80%–99%), with the sum of the mass percentages of the two being 100%.

[0054] The alkali metal fluorides are any one or more of sodium fluoride, potassium fluoride, rubidium fluoride, and cesium fluoride.

[0055] Carrier A is any one or more of aluminum fluoride, iron fluoride, magnesium fluoride, calcium fluoride, and chromium fluoride.

[0056] The telomerization catalyst was prepared by the following method: according to the mass percentage composition of alkali metal fluoride and support A, alkali metal fluoride was impregnated on support A, filtered, dried and calcined to obtain the telomerization catalyst.

[0057] Traditional telomerization of trifluorochloroethylene generally does not use a catalyst, resulting in telomerization products of 1,2-dichlorohexafluorocyclobutane and 3,4-dichlorohexafluoro-1-butene, with little difference in their content. This leads to poor selectivity for either 1,2-dichlorohexafluorocyclobutane or 3,4-dichlorohexafluoro-1-butene, resulting in the generation of a large amount of waste 1,2-dichlorohexafluorocyclobutane using existing technologies.

[0058] Furthermore, in the existing literature on the synthesis of 1,2-dichlorohexafluorocyclobutane, most of the reactions were carried out in a batch-type closed-bed reactor (numbers 1 to 9 in Table A), while some were carried out in a continuous fixed-bed reactor (numbers 10 to 12 in Table A). The experimental results are shown in Table A below:

[0059] Table A

[0060]

[0061]

[0062]

[0063] As shown in Table A, the existing technologies for synthesizing 1,2-dichlorohexafluorocyclobutane generally suffer from a serious deficiency of low yield.

[0064] This application employs a specific catalyst to achieve the directional conversion of trifluorochloroethylene to 1,2-dichlorohexafluorocyclobutane through telomerization. This not only results in a high conversion rate of trifluorochloroethylene but also high selectivity for 1,2-dichlorohexafluorocyclobutane, enabling a continuous gas-phase synthesis process for 1,2-dichlorohexafluorocyclobutane and significantly improving synthesis efficiency.

[0065] In some embodiments of this application, the mass ratio of alkali metal fluoride to carrier A is (5% to 15%): (85% to 95%).

[0066] In some embodiments of this application, the mass ratio of alkali metal fluoride to support A can be 5%:95%, 6%:94%, 7%:93%, 8%:92%, 9%:91%, 10%:90%, 11%:89%, 12%:88%, 13%:87%, 14%:86%, 15%:85%, or any range thereof. If the content of alkali metal fluoride is less than 5%, the concentration of the active component is too low to facilitate rapid and efficient catalytic reaction; if the content of alkali metal fluoride is higher than 30%, the active component may severely clog the pores of the support, thereby hindering the efficient catalytic reaction.

[0067] In some embodiments of this application, the drying conditions in the preparation of the telomerization catalyst are as follows: drying temperature is 120℃~200℃, and drying time is 6~15 hours. The drying temperature can be any range of 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃ or above, and the drying time can be any range of 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours or above.

[0068] In some embodiments of this application, the calcination conditions in the preparation of the telomerization catalyst are as follows: calcination temperature is 250℃~500℃, and calcination time is 6~15 hours. The calcination temperature can be any range from 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, 370℃, 380℃, 390℃, 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, or the range thereof. The calcination time can be any range from 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, or the range thereof.

[0069] The gas-phase polymerization reaction conditions are as follows: in the presence of a polymerization catalyst, using trifluorochloroethylene as raw material, the reaction pressure is 0.1-0.5 MPa, the reaction temperature is 300-600℃, and the contact time is 0.5-100 s.

[0070] In some embodiments of this application, the gas-phase polymerization reaction conditions are as follows: in the presence of a polymerization catalyst, using trifluorochloroethylene as raw material, the reaction pressure is 0.1–0.5 MPa, the reaction temperature is 400–500 °C, and the contact time is 5–50 s.

[0071] In some embodiments of this application, the reaction pressure can be any range of 0.1 MPa, 0.15 MPa, 0.2 MPa, 0.25 MPa, 0.3 MPa, 0.35 MPa, 0.4 MPa, 0.45 MPa, 0.5 MPa, or above; the reaction temperature can be any range of 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, or above; and the contact time can be any range of 5 s, 10 s, 15 s, 20 s, 25 s, 30 s, 35 s, 40 s, 45 s, 50 s, or above.

[0072] In this application, the material stream of the gas-phase polymerization reaction consists of trifluorochloroethylene, 1,2-dichlorohexafluorocyclobutane, 3,4-dichlorohexafluoro-1-butene, and trifluorochloroethylene polymer (degree of polymerization greater than or equal to 3), wherein the molar percentage of 1,2-dichlorohexafluorocyclobutane is more than 80%, and pure 1,2-dichlorohexafluorocyclobutane is obtained by purification in a distillation column.

[0073] In this application, contact time refers to the time it takes for the reactants to pass through the catalyst bed, i.e., the time for a single pass reaction in a fixed bed.

[0074] In this application, 1,2-dichlorohexafluorocyclobutane is a mixture of two isomers, trans-1,2-dichlorohexafluorocyclobutane and cis-1,2-dichlorohexafluorocyclobutane, wherein cis-1,2-dichlorohexafluorocyclobutane is a more stable configuration than trans-1,2-dichlorohexafluorocyclobutane, and the content of cis-1,2-dichlorohexafluorocyclobutane in 1,2-dichlorohexafluorocyclobutane is greater than or equal to 50%.

[0075] (2) Second step reaction: gas-phase dechlorination reaction

[0076] Using 1,2-dichlorohexafluorocyclobutane as a raw material, a dechlorination reaction occurs in the presence of a dechlorination catalyst and an appropriate amount of hydrogen.

[0077] The dechlorination catalyst is composed of metal A and support B in a mass percentage ratio of (1%–10%):(90%–99%), with the sum of the mass percentages of the two being 100%.

[0078] Metallic element A can be any one or more of zinc, iron, copper, cadmium, ruthenium, and silver.

[0079] Carrier B is any one or more of aluminum fluoride, iron fluoride, magnesium fluoride, calcium fluoride, and chromium fluoride.

[0080] The dechlorination catalyst was prepared by the following method: according to the mass percentage composition of elemental metal A and support B, a soluble salt of metal A was impregnated on support B, filtered, and then dried, calcined and activated to obtain the dechlorination catalyst.

[0081] The traditional dechlorination reaction of 1,2-dichlorohexafluorocyclobutane generally does not use a catalyst, but rather employs zinc powder, a reducing agent, in an organic solvent to dechlorinate 1,2-dichlorohexafluorocyclobutane. Existing publicly available literature is shown in Table B:

[0082] Table B

[0083]

[0084]

[0085] As shown in Table B, the existing dechlorination reaction of 1,2-dichlorohexafluorocyclobutane uses a large amount of reducing agent zinc powder and flammable solvent ethanol or methanol, which not only increases the hazard level of the reaction equipment, but also easily generates a large amount of waste liquid and solid waste, causing serious environmental pollution.

[0086] This application employs a dechlorination catalyst to induce a dechlorination reaction in 1,2-dichlorohexafluorocyclobutane under a hydrogen atmosphere. The principle is that the elemental metal A (A = zinc, iron, copper, cadmium, ruthenium, or silver) in the catalyst first removes the dichloride atoms from 1,2-dichlorohexafluorocyclobutane, yielding hexafluorocyclobutene and the metal chloride ACl. n (The oxidation state of element A in the metal chloride is n+); then hydrogen gas reacts with the metal chloride in the catalyst to form ACl. n Activation yields elemental metal A and hydrogen chloride. The dechlorination process of this invention has the advantages of high conversion rate, high selectivity, and being green and efficient, and can be easily implemented for large-scale continuous gas-phase production.

[0087] In some embodiments of this application, the mass ratio of elemental metal A to carrier B is (3% to 8%): (92% to 97%).

[0088] In some embodiments of this application, the mass ratio of elemental metal A to support B can be 3%:97%, 4%:96%, 5%:95%, 6%:94%, 7%:93%, 8%:92%, or any range thereof. If the content of elemental metal is less than 3%, the concentration of the active component is too low to facilitate rapid and efficient catalysis; if the content of elemental metal is higher than 8%, the active component may severely clog the pores of the support, thus hindering the efficient catalytic reaction.

[0089] In some embodiments of this application, the drying conditions in the preparation of the dechlorination catalyst are as follows: drying temperature is 120℃~200℃, and drying time is 6~15 hours. The drying temperature can be any range of 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃ or above, and the drying time can be any range of 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours or above.

[0090] In some embodiments of this application, the calcination conditions in the preparation of the dechlorination catalyst are as follows: calcination temperature is 300℃~500℃, and calcination time is 6~15 hours. The calcination temperature can be any range from 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, 370℃, 380℃, 390℃, 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, or the range thereof. The calcination time can be any range from 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, or the range thereof.

[0091] In some embodiments of this application, the activation conditions for preparing the dechlorination catalyst are as follows: activation is carried out in a mixed gas of nitrogen and hydrogen, with a molar ratio of nitrogen to hydrogen of (1-10):1; the activation temperature is 250℃-450℃; and the activation time is 8-20 hours. The activation temperature can be any range from 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, 370℃, 380℃, 390℃, 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, or any such range. The activation time can be any range from 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, or any such range.

[0092] The gas-phase dechlorination reaction conditions are as follows: in the presence of a dechlorination catalyst, using 1,2-dichlorohexafluorocyclobutane and hydrogen as raw materials, with a molar ratio of hydrogen to 1,2-dichlorohexafluorocyclobutane of 1–3:1, a reaction pressure of 0.1–0.5 MPa, a reaction temperature of 200–400 °C, and a contact time of 0.5–100 s.

[0093] In some embodiments of this application, the gas-phase dechlorination reaction conditions are as follows: in the presence of a dechlorination catalyst, using 1,2-dichlorohexafluorocyclobutane as raw material, the molar ratio of hydrogen to 1,2-dichlorohexafluorocyclobutane is 1.5 to 2.5:1, the reaction pressure is 0.1 to 0.5 MPa, the reaction temperature is 250 to 350 °C, and the contact time is 5 to 50 s.

[0094] In some embodiments of this application, the reaction pressure can be any range of 0.1 MPa, 0.15 MPa, 0.2 MPa, 0.25 MPa, 0.3 MPa, 0.35 MPa, 0.4 MPa, 0.45 MPa, 0.5 MPa, or above; the reaction temperature can be any range of 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, or above; and the contact time can be any range of 5 s, 10 s, 15 s, 20 s, 25 s, 30 s, 35 s, 40 s, 45 s, 50 s, or above.

[0095] In this application, the feed stream of the gas-phase dechlorination reaction consists of 1,2-dichlorohexafluorocyclobutane, hexafluorocyclobutene, hexafluorobutadiene, hydrogen and hydrogen chloride, wherein hexafluorocyclobutene accounts for more than 80% of the molar percentage of the organic product, and pure hexafluorocyclobutene is obtained by purification in a distillation column.

[0096] (3) Third step reaction: gas-phase isomerization reaction

[0097] Hexafluorobutadiene was obtained by gas-phase isomerization reaction of hexafluorocyclobutene as a raw material in the presence of an isomerization catalyst.

[0098] The isomerization catalyst is composed of elemental metal B and support C in a mass percentage ratio of (0.1%–10%):(90%–99.9%), with the sum of their mass percentages being 100%.

[0099] The metallic element B can be any one or more of Pt, Pd, Ni, and Co.

[0100] The carrier C is any one or more of aluminum fluoride, iron fluoride, magnesium fluoride, calcium fluoride, and chromium fluoride.

[0101] The isomerization catalyst was prepared by the following method: according to the mass percentage composition of elemental metal B and support C, a metal soluble salt was impregnated on support C, filtered, dried, calcined and activated to obtain the isomerization catalyst.

[0102] The results of existing literature on the isomerization of hexafluorocyclobutene to prepare hexafluorobutadiene are shown in Table C.

[0103] Table C

[0104]

[0105] As shown in Table C, the traditional isomerization reaction of hexafluorocyclobutene generally does not use a catalyst, and its reaction efficiency is very low, resulting in a very low yield of the target product, hexafluorobutadiene; while using a catalyst has the disadvantage of excessively high reaction temperature.

[0106] This application employs a specific catalyst to achieve the directional conversion of hexafluorocyclobutene to hexafluorobutadiene through isomerization. This not only results in a high conversion rate of hexafluorocyclobutene but also high selectivity for hexafluorobutadiene, enabling a continuous gas-phase synthesis process for hexafluorobutadiene and significantly improving synthesis efficiency.

[0107] In some embodiments of this application, the mass ratio of elemental metal B to carrier C is (0.5% to 5%): (95% to 99.5%).

[0108] In some embodiments of this application, the mass ratio of elemental metal B to support C can be 0.5%:99.5%, 1%:99%, 1.5%:98.5%, 2%:98%, 2.5%:97.5%, 3%:97%, 3.5%:96.5%, 4%:96%, 4.5%:95.5%, 5%:95%, or any range thereof. If the content of elemental metal B is less than 0.5%, the concentration of the active component is too low to facilitate rapid and efficient catalytic reaction; if the content of elemental metal B is higher than 5%, the active component may severely clog the pores of the support, thereby hindering the efficient catalytic reaction.

[0109] In some embodiments of this application, the drying conditions in the preparation of the isomerization catalyst are as follows: drying temperature is 120℃~200℃, and drying time is 6~15 hours. The drying temperature can be any range of 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃ or above, and the drying time can be any range of 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours or above.

[0110] In some embodiments of this application, the calcination conditions in the preparation of the isomerization catalyst are as follows: calcination temperature is 250℃~500℃, and calcination time is 6~15 hours. The calcination temperature can be any range from 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, 370℃, 380℃, 390℃, 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, or the range thereof. The calcination time can be any range from 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, or the range thereof.

[0111] In some embodiments of this application, the activation conditions for preparing the isomerization catalyst are as follows: activation is carried out in a mixed gas of nitrogen and hydrogen, the molar ratio of nitrogen to hydrogen is (1-10):1, the activation temperature is 250℃-450℃, and the activation time is 8-20 hours. The activation temperature can be any range from 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, 370℃, 380℃, 390℃, 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, or any such range. The activation time can be any range from 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, or any such range.

[0112] In the presence of an isomerization catalyst, hexafluorocyclobutene was used as a raw material, with a reaction pressure of 0.1–0.5 MPa, a reaction temperature of 400–700 °C, and a contact time of 0.5–100 s.

[0113] In some embodiments of this application, the gas-phase isomerization reaction conditions are as follows: in the presence of an isomerization catalyst, using hexafluorocyclobutene as a raw material, the reaction pressure is 0.1–0.5 MPa, the reaction temperature is 500–600 °C, and the contact time is 5–50 s.

[0114] In some embodiments of this application, the reaction pressure can be any range of 0.1 MPa, 0.15 MPa, 0.2 MPa, 0.25 MPa, 0.3 MPa, 0.35 MPa, 0.4 MPa, 0.45 MPa, 0.5 MPa, or above; the reaction temperature can be any range of 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, or above; and the contact time can be any range of 5 s, 10 s, 15 s, 20 s, 25 s, 30 s, 35 s, 40 s, 45 s, 50 s, or above.

[0115] In this application, the material stream of the gas-phase isomerization reaction consists of hexafluorobutadiene, hexafluorocyclobutene, and hexafluoro-2-butyne, wherein the molar percentage of hexafluorobutadiene is more than 80%, and pure hexafluorobutadiene is obtained by purification in a distillation column.

[0116] This application provides a method for the high-conversion, high-selectivity, gas-phase continuous cyclic production of hexafluorobutadiene.

[0117] To achieve the objectives of this application, this application describes a method for obtaining hexafluorobutadiene from trifluorochloroethylene as a starting material via gas-phase polymerization, gas-phase dechlorination, and gas-phase isomerization. The intermediates are, sequentially, 1,2-dichlorohexafluorocyclobutane and hexafluorocyclobutene. The reaction equations are as follows: Figure 1 As shown.

[0118] This application provides a method for the continuous gas-phase preparation of hexafluorobutadiene as follows: in the presence of an isomerization catalyst, hexafluorocyclobutene undergoes a gas-phase isomerization reaction in a tubular reactor to obtain hexafluorobutadiene.

[0119] The raw material hexafluorocyclobutene can be obtained by the dechlorination reaction of 1,2-dichlorohexafluorocyclobutane in the presence of a dechlorination catalyst and an appropriate amount of hydrogen.

[0120] The raw material 1,2-dichlorohexafluorocyclobutane can be obtained by directional cyclopolymerization of trifluorochloroethylene in the presence of a cyclopolymerization catalyst.

[0121] The described gas-phase polymerization, dechlorination, and isomerization reactions enable a continuous gas-phase cycle process. Due to the significant difference in boiling points between the raw materials and reaction products, phase separators and distillation towers are typically used to effectively separate the raw materials, intermediates, and products. Unreacted raw materials and incompletely reacted intermediates are recycled back to the reactor to continue the reaction, while the product hexafluorobutadiene and the byproduct HCl are collected separately from the system. The boiling point of hexafluorobutadiene is 7–8℃ (760 mmHg); the boiling point of hexafluorocyclobutene is 5–6℃ (760 mmHg); the boiling point of hexafluorodibutyne is -25℃ (760 mmHg); the boiling point of 1,2-dichlorohexafluorocyclobutane is 59.9℃ (760 mmHg); the boiling point of 3,4-dichlorohexafluoro-1-butene is 65–66℃ (760 mmHg); the boiling point of trifluorochloroethylene is -28.4℃ (760 mmHg); the boiling point of H2 is -252.77℃ (760 mmHg); the boiling point of HCl is -85.1℃ (760 mmHg); and so on.

[0122] This application employs a fixed-bed reactor. When the catalyst is placed in the isothermal zone of the fixed-bed reactor, a catalyst bed is obtained. When gaseous or liquid feedstock flows through the fixed bed at a relatively low velocity, the upward resistance of the flowing feedstock does not cause a change in the motion state of the initiator or catalyst, and the bed height remains constant; the bed pressure drop increases with the logarithm of the flow velocity.

[0123] The type of reactor used for the reaction in this application is not critical; tubular reactors, fluidized bed reactors, etc., can be used. Additionally, adiabatic or isothermal reactors can also be used.

[0124] Reference Figure 2Fresh trifluorochloroethylene, via the first pipeline 11, is combined with trifluorochloroethylene recycled via the third pipeline 13 and then via the second pipeline 12 into the first reactor 1, which is packed with a polymerization catalyst, for reaction. The product flows through the fourth pipeline 14 into the first distillation column 2 for separation. The top component is trifluorochloroethylene, and the bottom component is 1,2-dichlorohexafluorocyclobutane and 3,4-dichlorohexafluoro-1-butene. The top component is recycled back to the first reactor 1 via the third pipeline 13 and the second pipeline 12 for further reaction. The bottom component flows through the fifth pipeline 15 into the second distillation column 3 for further separation. The top component is 1,2-dichlorohexafluorocyclobutane with a purity greater than 99%, and the bottom component is 3,4-dichlorohexafluoro-1-butene. 3,4-Dichlorohexafluoro-1-butene, the bottom component of the column, can be collected through the seventh pipeline 17 and prepared into hexafluorobutadiene through a traditional dechlorination reaction (such as with a zinc powder suspension in ethanol). The top component is then fed through the sixth pipeline 16, along with fresh hydrogen introduced through the eighth pipeline 18, hydrogen recycled through the twelfth pipeline 22, and 1,2-dichlorohexafluorocyclobutane recycled through the pipeline, into the second reactor 4 via the tenth pipeline 20 for dechlorination. The product flows through the eleventh pipeline 21 into the third distillation column 5 for separation. The top component of the third distillation column 5 is hydrogen, which is recycled into the second reactor 4 via the twelfth pipeline 22. The bottom component consists of hydrogen chloride, hexafluorocyclobutene, and hexafluorobutadiene. The bottom components of the distillation column, consisting of hexafluorocyclobutene, hexafluorobutadiene, and 1,2-dichlorohexafluorocyclobutane, are fed into the fourth distillation column 6 via pipeline 13 (23) for further separation. The top component of the fourth distillation column 6 is hydrogen chloride, which is collected and sold as hydrogen chloride or formulated into hydrochloric acid. The bottom components of the fifth distillation column 7 are hexafluorocyclobutene, hexafluorobutadiene, and 1,2-dichlorohexafluorocyclobutane. The bottom components of the fifth distillation column 7 are fed into the fifth distillation column 7 via pipeline 15 (25) for further separation. The bottom component of the fifth distillation column 7 is 1,2-dichlorohexafluorocyclobutane. The bottom components of the fifth distillation column 7 are fed into the second reactor 4 via pipelines 19 and 10 (20) for further reaction. The top components of the second reactor 4 are hexafluorocyclobutene and hexafluorobutadiene. The top components of the second reactor 8 are fed into the sixth distillation column 8 via pipelines 16 and 17 (27) for further separation. The top component of column 8 is hexafluorocyclobutene with a purity greater than 99%, and the bottom component is hexafluorobutadiene. The top component enters the third reactor 9, which is equipped with an isomerization catalyst, via the eighteenth pipeline 28 for isomerization reaction. The product flows through the twentieth pipeline 30 into the seventh distillation column for further separation. The top component of the seventh distillation column is hexafluoro-2-butyne, which is collected via the twenty-first pipeline 31 and sold as a by-product. The bottom component is hexafluorocyclobutene and hexafluorobutadiene. The bottom component enters the sixth distillation column 8 via the twenty-second pipeline 32 and the seventeenth pipeline 27 for further separation. The bottom component of the eighth distillation column is hexafluorobutadiene. After subsequent drying and distillation, high-purity hexafluorobutadiene with a purity greater than 99.99% is obtained.

[0125] Analytical instrument: Agilent 8860 gas chromatograph, column model J&W GS-GasPro (id 0.32mm; length 60m).

[0126] Gas chromatography analysis method: High-purity helium and hydrogen are used as carrier gases. Detector temperature 240℃, vaporization chamber temperature 150℃, column initiation temperature 40℃, hold for 10 minutes, then increase the temperature to 240℃ at a rate of 20℃ / min, hold for 10 minutes.

[0127] The following examples further elaborate on this application, but do not limit the scope of this application.

[0128] Preparation of supports A, B, and C: A precipitation method was used. 10% ammonia solution was added dropwise to an aqueous solution of a metal-soluble salt until the pH reached 9.0. The solution was then filtered and washed until the pH of the filtrate reached 7.0, yielding a solid. This solid was dried at 80–200°C for 10–20 h under a nitrogen atmosphere, and then calcined at 250–500°C for 10–20 h under a nitrogen atmosphere. The calcined solid was then pressed into catalyst particles with a particle size of 3–5 mm, packed into a fixed bed, and activated under an HF or NF3 atmosphere for 10–20 h to prepare a metal fluoride, which served as support A, B, or C. The metal-soluble salt was any one of chloride, nitrate, or acetate. The final product was any one or more of aluminum fluoride, iron fluoride, magnesium fluoride, calcium fluoride, and chromium fluoride.

[0129] Example 1

[0130] Preparation of telogen polymerization catalyst: Cesium fluoride and aluminum fluoride were impregnated on a support with a mass ratio of 10:90. The catalyst precursor was obtained by filtration and then dried at 150°C for 10 hours in a nitrogen atmosphere and calcined at 400°C for 10 hours to prepare the telogen polymerization catalyst.

[0131] Example 2

[0132] The only difference between Example 2 and Example 1 is that the mass ratio of cesium fluoride to aluminum fluoride is 5:95, while the other conditions are the same.

[0133] Example 3

[0134] The only difference between Example 3 and Example 1 is that the mass ratio of cesium fluoride to aluminum fluoride is 15:85, while the other conditions are the same.

[0135] Example 4

[0136] The only difference between Example 4 and Example 1 is that the mass ratio of cesium fluoride to aluminum fluoride is 1:99, while the other conditions are the same.

[0137] Example 5

[0138] The only difference between Example 5 and Example 1 is that the mass ratio of cesium fluoride to aluminum fluoride is 20:80, while the other conditions are the same.

[0139] Example 6

[0140] The only difference between Example 6 and Example 1 is that the mass ratio of cesium fluoride to iron fluoride is 10:90, while the other conditions are the same.

[0141] Example 7

[0142] The only difference between Example 7 and Example 1 is that the mass ratio of cesium fluoride to magnesium fluoride is 10:90, while the other conditions are the same.

[0143] Example 8

[0144] The only difference between Example 8 and Example 1 is that the mass ratio of cesium fluoride to calcium fluoride is 10:90, while the other conditions are the same.

[0145] Example 9

[0146] The only difference between Example 9 and Example 1 is that the mass ratio of cesium fluoride to chromium fluoride is 10:90, while the other conditions are the same.

[0147] Example 10

[0148] The only difference between Example 10 and Example 1 is that the mass ratio of sodium fluoride to aluminum fluoride is 10:90, while the other conditions are the same.

[0149] Example 11

[0150] The only difference between Example 11 and Example 1 is that the mass ratio of potassium fluoride to aluminum fluoride is 10:90, while the other conditions are the same.

[0151] Example 12

[0152] The only difference between Example 12 and Example 1 is that the mass ratio of rubidium fluoride to aluminum fluoride is 10:90, while the other conditions are the same.

[0153] Table 1 Preparation of telomerization catalysts

[0154]

[0155]

[0156] Example 13

[0157] Preparation of dechlorination catalyst: The soluble salt of Zn was impregnated onto chromium fluoride with a mass percentage composition of Zn to chromium fluoride of 5:95. The catalyst precursor was obtained by filtration. The precursor was dried at 150°C for 10 hours, calcined at 400°C for 10 hours, and then activated at 300°C with a mixed gas of nitrogen and hydrogen in a molar ratio of 2:1 for 10 hours to obtain the dechlorination catalyst.

[0158] Example 14

[0159] The only difference between Example 14 and Example 13 is that the mass ratio of Zn to chromium fluoride is 3:97, while the other conditions are the same.

[0160] Example 15

[0161] The only difference between Example 15 and Example 13 is that the mass ratio of Zn to chromium fluoride is 8:92, while the other conditions are the same.

[0162] Example 16

[0163] The only difference between Example 16 and Example 13 is that the mass ratio of Zn to chromium fluoride is 1:99, while the other conditions are the same.

[0164] Example 17

[0165] The only difference between Example 17 and Example 13 is that the mass ratio of Zn to chromium fluoride is 10:90, while the other conditions are the same.

[0166] Example 18

[0167] The only difference between Example 18 and Example 13 is that the mass ratio of Zn to aluminum fluoride is 5:95, while the other conditions are the same.

[0168] Example 19

[0169] The only difference between Example 19 and Example 13 is that the mass ratio of Zn to iron fluoride is 5:95, while the other conditions are the same.

[0170] Example 20

[0171] The only difference between Example 20 and Example 13 is that the mass ratio of Zn to magnesium fluoride is 5:95, while the other conditions are the same.

[0172] Example 21

[0173] The only difference between Example 21 and Example 13 is that the mass ratio of Zn to calcium fluoride is 2:98, while the other conditions are the same.

[0174] Example 22

[0175] The only difference between Example 22 and Example 13 is that the mass ratio of Fe to chromium fluoride is 2:98, while the other conditions are the same.

[0176] Example 23

[0177] The only difference between Example 23 and Example 13 is that the mass ratio of Cu to chromium fluoride is 2:98, while the other conditions are the same.

[0178] Example 24

[0179] The only difference between Example 24 and Example 13 is that the mass ratio of Cd to chromium fluoride is 2:98, while the other conditions are the same.

[0180] Example 25

[0181] The only difference between Example 25 and Example 13 is that the mass ratio of Ru to chromium fluoride is 2:98, while the other conditions are the same.

[0182] Example 26

[0183] The only difference between Example 26 and Example 13 is that the mass ratio of Ag to chromium fluoride is 2:98, while the other conditions are the same.

[0184] Table 2 Preparation of dechlorination catalysts

[0185]

[0186]

[0187] Example 27

[0188] Preparation of isomerization catalyst: Pt and magnesium fluoride were impregnated with soluble salts of Pt at a mass percentage ratio of 2:98. The catalyst precursor was obtained by filtration. The precursor was dried at 150°C for 10 hours, calcined at 400°C for 10 hours, and then activated at 350°C with a mixture of nitrogen and hydrogen in a molar ratio of 2:1 for 10 hours to obtain the isomerization catalyst.

[0189] Example 28

[0190] The only difference between Example 28 and Example 27 is that the mass ratio of Pt to magnesium fluoride is 0.5:99.5, while the other conditions are the same.

[0191] Example 29

[0192] The only difference between Example 29 and Example 27 is that the mass ratio of Pt to magnesium fluoride is 5:95, while the other conditions are the same.

[0193] Example 30

[0194] The only difference between Example 30 and Example 27 is that the mass ratio of Pt to magnesium fluoride is 0.1:99.9, while the other conditions are the same.

[0195] Example 31

[0196] The only difference between Example 31 and Example 27 is that the mass ratio of Pt to magnesium fluoride is 10:90, while the other conditions are the same.

[0197] Example 32

[0198] The only difference between Example 32 and Example 27 is that the mass ratio of Pt to aluminum fluoride is 2:98, while the other conditions are the same.

[0199] Example 33

[0200] The only difference between Example 33 and Example 27 is that the mass ratio of Pt to iron fluoride is 2:98, while the other conditions are the same.

[0201] Example 34

[0202] The only difference between Example 34 and Example 27 is that the mass ratio of Pt to calcium fluoride is 2:98, while the other conditions are the same.

[0203] Example 35

[0204] The only difference between Example 35 and Example 27 is that the mass ratio of Pt to chromium fluoride is 2:98, while the other conditions are the same.

[0205] Example 36

[0206] The only difference between Example 36 and Example 27 is that the mass ratio of Pd to magnesium fluoride is 2:98, while the other conditions are the same.

[0207] Example 37

[0208] The only difference between Example 37 and Example 27 is that the mass ratio of Ni to magnesium fluoride is 2:98, while the other conditions are the same.

[0209] Example 38

[0210] The only difference between Example 38 and Example 27 is that the mass ratio of Co to magnesium fluoride is 2:98, while the other conditions are the same.

[0211] Table 3 Preparation of isomerization catalysts

[0212]

[0213]

[0214] Experimental Example

[0215] Experimental Example 1

[0216] Ten milliliters of the catalyst prepared in Example 1 were packed into a tubular reactor made of Incon alloy with an inner diameter of 1 / 2 inch and a length of 30 cm. The reactor was heated to 300 °C, and trifluorochloroethylene was introduced to carry out a telomerization reaction with a contact time of 10 seconds and a reaction pressure of 0.1 MPa. After 10 h of reaction, the crude product was collected, and its composition was analyzed by gas chromatography. The results are shown in Table 4.

[0217] Experiment 2 was conducted using the same procedure as Experiment 1, except that the reaction temperature was changed to 400℃. The results are shown in Table 4.

[0218] Experiment 3 was performed using the same procedure as Experiment 1, except that the reaction temperature was changed to 450℃. The results are shown in Table 4.

[0219] Experiment 4 was conducted using the same procedure as Experiment 1, except that the reaction temperature was changed to 500℃. The results are shown in Table 4.

[0220] Experiment 5 was performed using the same procedure as Experiment 1, except that the reaction temperature was changed to 600℃. The results are shown in Table 4.

[0221] Experiment 6 was performed using the same procedure as Experiment 3, except that the contact time was changed to 0.5 seconds. The results are shown in Table 4.

[0222] Experiment 7 was performed using the same procedure as Experiment 3, except that the contact time was changed to 5 seconds. The results are shown in Table 4.

[0223] Experiment 8 was performed using the same procedure as Experiment 3, except that the contact time was changed to 50 seconds. The results are shown in Table 4.

[0224] Experiment 9 was performed using the same procedure as Experiment 3, except that the contact time was changed to 100 seconds. The results are shown in Table 4.

[0225] Experiment 10 was performed under the same procedure as Experiment 3, except that the reaction pressure was changed to 0.5 MPa. The results are shown in Table 4.

[0226] Experiment 11 was performed under the same procedure as Experiment 3, except that the reaction pressure was changed to 1 MPa. The results are shown in Table 4.

[0227] Experiment 12 was performed under the same procedure as Experiment 3, except that the reaction pressure was changed to 1.5 MPa. The results are shown in Table 4.

[0228] The catalyst used in Experiment 13 was derived from Example 2, and the rest was the same as in Experiment 3. The results are shown in Table 4.

[0229] The catalyst used in Experiment 14 was derived from Example 3, and the rest was the same as in Experiment 3. The results are shown in Table 4.

[0230] The catalyst used in Experiment 155 was derived from Example 4, and the rest was the same as in Experiment 3. The results are shown in Table 4.

[0231] The catalyst used in Experiment 16 was derived from Example 5, and the rest was the same as in Experiment 3. The results are shown in Table 4.

[0232] The catalyst used in Experiment 17 was derived from Example 6, and the rest was the same as in Experiment 3. The results are shown in Table 4.

[0233] The catalyst used in Experiment 18 was derived from Example 7, and the rest was the same as in Experiment 3. The results are shown in Table 4.

[0234] The catalyst used in Experiment 19 was derived from Example 8, and the rest was the same as in Experiment 3. The results are shown in Table 4.

[0235] The catalyst used in Experiment 20 was derived from Example 9, and the rest was the same as in Experiment 3. The results are shown in Table 4.

[0236] The catalyst used in Experiment 21 was derived from Example 10, and the rest was the same as in Experiment 3. The results are shown in Table 4.

[0237] The catalyst used in Experiment 22 was derived from Example 11, and the rest was the same as in Experiment 3. The results are shown in Table 4.

[0238] The catalyst used in Experiment 23 was derived from Example 12, and the rest was the same as in Experiment 3. The results are shown in Table 4.

[0239] Comparative Example 1

[0240] Comparative Example 1 did not use a catalyst, and the rest was the same as in Experimental Example 3. The results are shown in Table 4.

[0241] Table 4

[0242]

[0243]

[0244] Note: (1) There is no catalyst in Comparative Example 1. The contact time here is strictly speaking the residence time of the reactants in the reactor. Compared with Example 3, the reaction temperature, reaction pressure and trifluorochloroethylene flow rate are the same, except that no catalyst is used.

[0245] As shown in Table 4, and in Examples 1-23, the catalyst prepared in this application, used for the telomerization of trifluorochloroethylene to prepare 1,2-dichlorohexafluorocyclobutane, exhibits high conversion rates (up to 100%) and high selectivity (up to 99.4%) for 1,2-dichlorohexafluorocyclobutane. It is suitable for the continuous gas-phase synthesis of 1,2-dichlorohexafluorocyclobutane, significantly improving synthesis efficiency. During the gas-phase telomerization reaction, reaction temperature, reaction pressure, and contact time have a certain impact on reaction efficiency. Specifically, within the reaction temperature range of 400-500℃, the conversion rate of trifluorochloroethylene and the selectivity for 1,2-dichlorohexafluorocyclobutane are both high; when the contact time is 5-50 seconds, both the conversion rate of trifluorochloroethylene and the selectivity for 1,2-dichlorohexafluorocyclobutane are high, resulting in high reaction efficiency.

[0246] Experimental Example 24

[0247] Ten mL of the catalyst prepared in Example 13 was packed into a tubular reactor made of Incon alloy with an inner diameter of 1 / 2 inch and a length of 30 cm. The reactor was heated to 200 °C, and 1,2-dichlorohexafluorocyclobutane and hydrogen were introduced to carry out a dedichlorination reaction, wherein the molar ratio of hydrogen to 1,2-dichlorohexafluorocyclobutane was 2:1, the contact time was 20 seconds, the reaction pressure was 0.1 MPa, and the reaction was carried out for 10 h. After the reaction product was washed with water, alkali, and dried, the crude organic product was collected, and the composition of the crude organic product was analyzed by gas chromatography. The results are shown in Table 5.

[0248] Experiment 25 was performed using the same procedure as Experiment 24, except that the reaction temperature was changed to 250℃. The results are shown in Table 5.

[0249] Experiment 26 was performed under the same procedure as Experiment 24, except that the reaction temperature was changed to 300℃. The results are shown in Table 5.

[0250] Experiment 27 was performed under the same procedure as Experiment 24, except that the reaction temperature was changed to 350℃. The results are shown in Table 5.

[0251] Experiment 28 was performed under the same procedure as Experiment 24, except that the reaction temperature was changed to 400℃. The results are shown in Table 5.

[0252] Experiment 29 was performed using the same procedure as Experiment 26, except that the molar ratio of hydrogen to 1,2-dichlorohexafluorocyclobutane was changed to 1:1. The results are shown in Table 5.

[0253] Experiment 30 was performed using the same procedure as Experiment 26, except that the molar ratio of hydrogen to 1,2-dichlorohexafluorocyclobutane was changed to 1.5:1. The results are shown in Table 5.

[0254] Experiment 31 was performed under the same procedure as Experiment 26, except that the molar ratio of hydrogen to 1,2-dichlorohexafluorocyclobutane was changed to 2.5:1. The results are shown in Table 5.

[0255] Experiment 32 was performed using the same procedure as Experiment 26, except that the molar ratio of hydrogen to 1,2-dichlorohexafluorocyclobutane was changed to 3:1. The results are shown in Table 5.

[0256] Experiment 33 was performed under the same procedure as Experiment 26, except that the contact time was changed to 0.5 seconds. The results are shown in Table 5.

[0257] Experiment 34 was performed under the same procedure as Experiment 26, except that the contact time was changed to 5 seconds. The results are shown in Table 5.

[0258] Experiment 35 was performed under the same procedure as Experiment 26, except that the contact time was changed to 50 seconds. The results are shown in Table 5.

[0259] Experiment 36 was performed under the same procedure as Experiment 26, except that the contact time was changed to 100 seconds. The results are shown in Table 5.

[0260] Experiment 37 was performed under the same procedure as Experiment 26, except that the reaction pressure was changed to 0.5 MPa. The results are shown in Table 5.

[0261] Experiment 38 was performed under the same procedure as Experiment 26, except that the reaction pressure was changed to 1 MPa. The results are shown in Table 5.

[0262] Experiment 39 was performed under the same procedure as Experiment 26, except that the reaction pressure was changed to 1.5 MPa. The results are shown in Table 5.

[0263] Experimental Example 40: The catalyst used in Experimental Example 40 was derived from Example 14, and the rest was the same as in Experimental Example 26. The results are shown in Table 5.

[0264] The catalyst used in Experiment 41 was derived from Example 15, and the rest was the same as in Experiment 26. The results are shown in Table 5.

[0265] The catalyst used in Experiment 42 was derived from Example 16, and the rest was the same as in Experiment 26. The results are shown in Table 5.

[0266] The catalyst used in Experiment 43 was derived from Example 17, and the rest was the same as in Experiment 26. The results are shown in Table 5.

[0267] The catalyst used in Experiment 44 was derived from Example 18, and the rest was the same as in Experiment 26. The results are shown in Table 5.

[0268] The catalyst used in Experiment 45 was derived from Example 19, and the rest was the same as in Experiment 26. The results are shown in Table 5.

[0269] The catalyst used in Experiment 46 was derived from Example 20, and the rest was the same as in Experiment 26. The results are shown in Table 5.

[0270] The catalyst used in Experiment 47 was derived from Example 21, and the rest was the same as in Experiment 26. The results are shown in Table 5.

[0271] The catalyst used in Experiment 48 was derived from Example 22, and the rest was the same as in Experiment 26. The results are shown in Table 5.

[0272] The catalyst used in Experiment 49 was derived from Example 23, and the rest was the same as in Experiment 26. The results are shown in Table 5.

[0273] The catalyst used in Experiment 50 was derived from Example 24, and the rest was the same as in Experiment 26. The results are shown in Table 5.

[0274] The catalyst used in Experiment 51 was derived from Example 25, and the rest was the same as in Experiment 26. The results are shown in Table 5.

[0275] The catalyst used in Experiment 52 was derived from that in Example 26, and the rest was the same as in Experiment 26. The results are shown in Table 5.

[0276] Comparative Example 2 did not use a catalyst, and the rest was the same as in Experimental Example 26. The results are shown in Table 5.

[0277] Table 5

[0278]

[0279]

[0280] Note: (1) There is no catalyst in Comparative Example 2. The contact time here is strictly speaking the residence time of the reactants in the reactor. Compared with Example 26, the reaction temperature, reaction pressure, hydrogen flow rate and 1,2-dichlorohexafluorocyclobutane flow rate are the same, except that no catalyst is used.

[0281] As shown in Table 44, and as demonstrated in Examples 24-52, the catalyst prepared in this application, used for the gas-phase dechlorination reaction of 1,2-dichlorohexafluorocyclobutane with hydrogen to prepare hexafluorocyclobutene, exhibits high conversion rates (up to 100%) and high hexafluorocyclobutene selectivity (over 99%). It is suitable for continuous gas-phase synthesis of hexafluorocyclobutene, significantly improving synthesis efficiency. During the gas-phase dechlorination reaction, reaction temperature, reaction pressure, and contact time have a certain impact on reaction efficiency. Specifically, within the reaction temperature range of 250-350℃, the conversion rate of 1,2-dichlorohexafluorocyclobutane and the selectivity of hexafluorocyclobutene are high; when the contact time is 5-50 seconds, the conversion rate of 1,2-dichlorohexafluorocyclobutane and the selectivity of hexafluorocyclobutene are both high, resulting in high reaction efficiency.

[0282] Experimental Example 53

[0283] Ten mL of the catalyst prepared in Example 27 was packed into a tubular reactor made of Incon alloy with an inner diameter of 1 / 2 inch and a length of 30 cm. The reactor was heated to 400 °C, and hexafluorocyclobutene was introduced to carry out a telomerization reaction. The contact time was 30 seconds, the reaction pressure was 0.1 MPa, and after 10 h of reaction, the crude product was collected. The composition of the crude product was analyzed by gas chromatography, and the results are shown in Table 6.

[0284] Experimental Example 54

[0285] The same procedure was followed as in Experiment 53, except that the reaction temperature was changed to 500℃. The results are shown in Table 6.

[0286] Experimental Example 55

[0287] The same procedure was followed as in Experiment 53, except that the reaction temperature was changed to 550℃. The results are shown in Table 6.

[0288] Experimental Example 56

[0289] The same procedure was followed as in Experiment 53, except that the reaction temperature was changed to 600℃. The results are shown in Table 6.

[0290] Experimental Example 57

[0291] The same procedure was followed as in Experiment 53, except that the reaction temperature was changed to 700℃. The results are shown in Table 6.

[0292] Experimental Example 58

[0293] The same procedure was performed as in Experiment 55, except that the contact time was changed to 0.5 seconds. The results are shown in Table 6.

[0294] Experimental Example 59

[0295] The same procedure was performed as in Experiment 55, except that the contact time was changed to 5 seconds. The results are shown in Table 6.

[0296] Experimental Example 60

[0297] The same procedure was performed as in Experiment 55, except that the contact time was changed to 50 seconds. The results are shown in Table 66.

[0298] Experimental Example 61

[0299] The same procedure was performed as in Experiment 55, except that the contact time was changed to 100 seconds. The results are shown in Table 6.

[0300] Experimental Example 62

[0301] The same procedure was performed as in Experiment 55, except that the reaction pressure was changed to 0.5 MPa. The results are shown in Table 6.

[0302] Experimental Example 63

[0303] The same procedure was performed as in Experiment 55, except that the reaction pressure was changed to 1 MPa. The results are shown in Table 6.

[0304] Experimental Example 64

[0305] The same procedure was followed as in Experiment 55, except that the reaction pressure was changed to 1.5 MPa. The results are shown in Table 6.

[0306] Experimental Example 65

[0307] The catalyst used in Experiment 65 was derived from Example 28, and the rest was the same as in Experiment 55. The results are shown in Table 6.

[0308] Experimental Example 66

[0309] The catalyst used in Experiment 66 was derived from Example 29, and the rest was the same as in Experiment 55. The results are shown in Table 6.

[0310] Experimental Example 67

[0311] The catalyst used in Experiment 67 was derived from Example 30, and the rest was the same as in Experiment 55. The results are shown in Table 6.

[0312] Experimental Example 68

[0313] The catalyst used in Experiment 68 was derived from Example 31, and the rest was the same as in Experiment 55. The results are shown in Table 6.

[0314] Experimental Example 69

[0315] The catalyst used in Experiment 69 was derived from Example 32, and the rest was the same as in Experiment 55. The results are shown in Table 6.

[0316] Experimental Example 70

[0317] The catalyst used in Experiment 70 was derived from Example 33, and the rest was the same as in Experiment 55. The results are shown in Table 6.

[0318] Experimental Example 71

[0319] The catalyst used in Experiment 71 was derived from Example 34, and the rest was the same as in Experiment 55. The results are shown in Table 6.

[0320] Experimental Example 72

[0321] The catalyst used in Experiment 72 was derived from Example 35, and the rest was the same as in Experiment 55. The results are shown in Table 6.

[0322] Experimental Example 73

[0323] The catalyst used in Experiment 73 was derived from Example 36, and the rest was the same as in Experiment 55. The results are shown in Table 6.

[0324] Experimental Example 74

[0325] The catalyst used in Experiment 74 was derived from Example 37, and the rest was the same as in Experiment 55. The results are shown in Table 6.

[0326] Experimental Example 75

[0327] The catalyst used in Experiment 75 was derived from Example 38, and the rest was the same as in Experiment 55. The results are shown in Table 6.

[0328] Comparative Example 3

[0329] Comparative Example 3 did not use a catalyst, and the rest was the same as in Experimental Example 55. The results are shown in Table 6.

[0330] Table 6

[0331]

[0332]

[0333] Note: (1) No catalyst was used in Comparative Example 3. The contact time here is strictly speaking the residence time of the reactants in the reactor. Compared with Example 55, the reaction temperature, reaction pressure and hexafluorocyclobutene flow rate are the same, except that no catalyst was used.

[0334] As shown in Table 6, and in Examples 53-75, the catalyst prepared in this application, used for the isomerization of hexafluorocyclobutene to prepare hexafluorobutadiene, exhibits high conversion rates (up to 100%) and high selectivity for 1,2-dichlorohexafluorocyclobutane (over 99%). It is suitable for the continuous gas-phase synthesis of hexafluorobutadiene, significantly improving synthesis efficiency. During the gas-phase isomerization reaction, reaction temperature, reaction pressure, and contact time have a certain impact on reaction efficiency. Specifically, within the reaction temperature range of 500-600℃, both the hexafluorocyclobutene conversion rate and hexafluorobutadiene selectivity are high; and when the contact time is 5-50 seconds, both the hexafluorocyclobutene conversion rate and hexafluorobutadiene selectivity are high, resulting in high reaction efficiency.

[0335] Although the above-mentioned experimental examples have been disclosed in this case, they are not intended to limit this case. Anyone with ordinary knowledge in the relevant technical field may make some modifications and embellishments without departing from the spirit and scope of this case. Therefore, the scope of protection of this case shall be determined by the scope of the appended patent application.

Claims

1. A method for the continuous gas-phase preparation of hexafluorobutadiene, characterized in that, Includes the following steps: (1) Gas-phase polymerization reaction: Using trifluorochloroethylene as raw material, 1,2-dichlorohexafluorocyclobutane is obtained by gas-phase polymerization and cyclization reaction in the presence of a polymerization catalyst. The reaction conditions are: reaction pressure of 0.1–1.5 MPa, reaction temperature of 300–600 °C, and contact time of 0.5–100 s; (2) Gas-phase dechlorination reaction: Using 1,2-dichlorohexafluorocyclobutane as raw material, a dechlorination reaction is carried out in the presence of a dechlorination catalyst and hydrogen to obtain hexafluorocyclobutene; The reaction conditions are as follows: the molar ratio of hydrogen to 1,2-dichlorohexafluorocyclobutane is 1 to 3:1, the reaction pressure is 0.1 to 1.5 MPa, the reaction temperature is 200 to 400 °C, and the contact time is 0.5 to 100 s. (3) Gas-phase isomerization reaction: Hexafluorocyclobutene is used as raw material, and a gas-phase isomerization reaction is carried out in the presence of an isomerization catalyst to obtain hexafluorobutadiene; The reaction conditions are: reaction pressure of 0.1–1.5 MPa, reaction temperature of 400–700 °C, and contact time of 0.5–100 s.

2. The method for continuous gas-phase preparation of hexafluorobutadiene according to claim 1, characterized in that, The telomerization catalyst mentioned in step (1) is a mixture of alkali metal fluoride and support A in a mass percentage ratio of (1% to 20%): (80% to 99%), and the sum of the mass percentages of the two is 100%. Alkali metal fluorides are any one or more of sodium fluoride, potassium fluoride, rubidium fluoride, and cesium fluoride; Carrier A is any one or more of aluminum fluoride, iron fluoride, magnesium fluoride, calcium fluoride, and chromium fluoride.

3. The method for continuous gas-phase preparation of hexafluorobutadiene according to claim 2, characterized in that, In step (1), the reaction pressure is 0.1-0.5 MPa, the reaction temperature is 400-500℃, and the contact time is 5-50 s; The mass ratio of alkali metal fluoride to carrier A is (5%–15%): (85%–95%).

4. The method for continuous gas-phase preparation of hexafluorobutadiene according to claim 1, characterized in that, The products obtained from the gas-phase polymerization reaction in step (1) include trifluorochloroethylene, 1,2-dichlorohexafluorocyclobutane, 3,4-dichlorohexafluoro-1-butene, and trifluorochloroethylene polymer, wherein the degree of polymerization of the trifluorochloroethylene polymer is not less than 3; wherein the molar percentage of 1,2-dichlorohexafluorocyclobutane is more than 80%, and pure 1,2-dichlorohexafluorocyclobutane is obtained by purification in a distillation column.

5. The method for continuous gas-phase preparation of hexafluorobutadiene according to claim 1, characterized in that, The dechlorination catalyst mentioned in step (2) is a mixture of metal element A and support B in a mass percentage ratio of (1% to 10%): (90% to 99%), and the sum of the mass percentages of the two is 100%. Metallic element A is any one or more of zinc, iron, copper, cadmium, ruthenium, and silver; Carrier B is any one or more of aluminum fluoride, iron fluoride, magnesium fluoride, calcium fluoride, and chromium fluoride.

6. The method for continuous gas-phase preparation of hexafluorobutadiene according to claim 5, characterized in that, In step (2), the molar ratio of hydrogen to 1,2-dichlorohexafluorocyclobutane is 1.5 to 2.5:1, the reaction pressure is 0.1 to 0.5 MPa, the reaction temperature is 250 to 350 °C, and the contact time is 5 to 50 s. The mass ratio of the elemental metal to carrier B is (3%–8%): (82%–97%).

7. The method for continuous gas-phase preparation of hexafluorobutadiene according to claim 1, characterized in that, The gas-phase dechlorination reaction in step (2) yields products including 1,2-dichlorohexafluorocyclobutane, hexafluorocyclobutene, hexafluorobutadiene, hydrogen, and hydrogen chloride; wherein hexafluorocyclobutene accounts for more than 80% of the molar percentage of the organic products, and pure hexafluorocyclobutene is obtained by purification in a distillation column.

8. The method for continuous gas-phase preparation of hexafluorobutadiene according to claim 1, characterized in that, The isomerization catalyst mentioned in step (3) is a mixture of elemental metal B and support C in a mass percentage ratio of (0.1% to 10%): (90% to 99.9%), and the sum of the mass percentages of the two is 100%. Metallic element B can be any one or more of Pt, Pd, Ni, and Co; The carrier C is any one or more of aluminum fluoride, iron fluoride, magnesium fluoride, calcium fluoride, and chromium fluoride.

9. The method for continuous gas-phase preparation of hexafluorobutadiene according to claim 8, characterized in that, In step (3), the reaction pressure is 0.1-0.5 MPa, the reaction temperature is 500-600℃, and the contact time is 5-50 s; The mass ratio of elemental metal B to carrier C is (0.5%–5%): (95%–99.5%).

10. The method for continuous gas-phase preparation of hexafluorobutadiene according to claim 1, characterized in that, The products of the gas-phase isomerization reaction include hexafluorobutadiene, hexafluorocyclobutene, and hexafluoro-2-butyne; wherein the molar percentage of hexafluorobutadiene is more than 80%, and pure hexafluorobutadiene is obtained by purification in a distillation column.

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