Preparation method of hexafluoro-1, 3-butadiene

Abstract

The invention provides a preparation method of hexafluoro-1, 3-butadiene, which comprises the following steps: (1) preheating and mixing chlorotrifluoroethylene and 1, 1, 1, 2-tetrafluoroethane, introducing into a reactor filled with a first catalyst, carrying out dehydrochlorination reaction, and sequentially carrying out condensation and first rectification to obtain 1, 1, 2, 3, 4, 4, 4-heptafluoro-1-butene; and (2) introducing 1, 1, 2, 3, 4, 4, 4-heptafluoro-1-butene into a reactor filled with a second catalyst, carrying out a dehydrofluorination reaction, and sequentially carrying out condensation and second rectification to obtain the hexafluoro-1, 3-butadiene. According to the invention, through reasonable selection of reaction raw materials, continuous production of high-purity hexafluoro-1, 3-butadiene can be realized; the preparation method has the advantages of cheap raw materials, simple process, low energy consumption, simple product separation, good selectivity, convenient purification and the like, and can realize amplified continuous production.

Description

Technical Field

[0001] The invention belongs to the technical field of special gas preparation, and relates to a method for preparing laser etching gas, and in particular to a method for preparing hexafluoro-1,3-butadiene. Background Art

[0002] Hexafluoro-1,3-butadiene (HFBD), also known as hexafluorobutadiene and perfluorobutadiene, has a molecular formula of C4F6, a relative molecular mass of 162g / mol, a melting point of -132°C, and a boiling point of 4-6°C. It is a colorless, odorless, toxic, flammable and compressible gas under standard conditions. It is insoluble in water, has an ozone depletion potential (ODP) of 0, a global warming potential (GWP) of 290, and an average lifetime of 1.9d in the atmosphere. It is a green and environmentally friendly perfluorinated olefin.

[0003] Hexafluoro-1,3-butadiene is a widely used industrial raw material. Its downstream products can not only be used as cleaning agents for precision electronic circuit boards and pesticides, but also have high application value in the synthesis of fluorine-containing fine chemicals such as fluorine-containing pharmaceutical intermediates. In the synthesis of fluorine-containing polymers, it can be used as a polymer monomer to prepare polyhexafluorobutadiene, and can also be used with other monomers to synthesize fluorine-containing rubber and fluorine-containing elastomers. In addition, hexafluoro-1,3-butadiene can also be used as an etchant in the semiconductor industry.

[0004] Hexafluoro-1,3-butadiene can be used for dry etching with a width below 90nm or even narrower. Compared with traditional plasma etching gases CF4, C2F6, C3F8, c-C4F8 and NF3, C4F6 has a faster etching rate, high etching selectivity and high aspect ratio; and C4F6 will only etch silicon oxide film without affecting photoresist, silicon film and nitride film. Therefore, C4F6 is a green and environmentally friendly high-efficiency dry etching gas. With the strong global demand for ultra-large-scale integrated circuits and concerns about greenhouse gases, hexafluoro-1,3-butadiene has a high market potential and will gradually become an important high-end fluorine-containing electronic gas in the future.

[0005] At present, there are many methods for the preparation of hexafluoro-1,3-butadiene. According to the raw materials, they can be divided into chlorotrifluoroethylene (CTFE) route, R134a route, tetrafluoroethylene route, etc.; according to the important intermediates, they can be mainly divided into tetrachlorohexafluorobutane route, 3,4-dichlorohexafluoro-1-butene route, trifluoroethylene bromozinc reagent route, etc.

[0006] US3046304 discloses a process route for synthesizing hexafluoro-1,3-butadiene using chlorotrifluoroethylene as a raw material. Chlorotrifluoroethylene first reacts with iodine chloride in a sealed system to obtain 1,2-dichloro-1,2,2-trifluoroiodoethane, which is then coupled with an equivalent amount of mercury under ultraviolet light to obtain 1,2,3,4-tetrachlorohexafluorobutane. Finally, 1,2,3,4-tetrachlorohexafluorobutane is dechlorinated in an alcohol solvent under the action of zinc powder to obtain hexafluoro-1,3-butadiene. Although this process avoids the high temperature and high pressure conditions of the polymerization reaction, this method requires the use of chemically equivalent iodine chloride and mercury to participate in the reaction, and the other product is mercuric iodide, which is highly toxic.

[0007] CN 114539021A discloses a production process of hexafluorobutadiene, which uses chlorotrifluoroethylene to thermally polymerize 1,2-dichlorohexafluoro-3-butene, and then dechlorinates to synthesize hexafluoro-1,3-butadiene. The process requires separating 1,2-dichlorohexafluoro-3-butene from the thermal polymerization product, and then using a liquid phase dechlorination reaction in a zinc / ethanol solvent for 24 hours to generate hexafluoro-1,3-butadiene. However, the 1,2-dichlorohexafluorocyclobutane and 1,2-dichlorohexafluoro-3-butene generated by the process have an azeotropic phenomenon, making distillation separation difficult, and it is impossible to obtain hexafluoro-1,3-butadiene with high purity.

[0008] CN 104844411A discloses a method for synthesizing hexafluoro-1,3-butadiene, which uses R134a to catalyze dehydrofluorination at high temperature to generate trifluoroethylene (C2F3H), then undergoes bromine addition and dehydrobromination to obtain monobromotrifluoroethylene, and then couples to synthesize hexafluoro-1,3-butadiene. However, the reaction process is long, the amount of three wastes is large, and it is not suitable for continuous production.

[0009] CN 111187145A discloses a method for preparing hexafluorobutadiene, wherein 1,2-dibromotetrafluoroethane is reacted in an organic solvent containing AlX3 and zinc to generate a metal organic reagent, the metal organic reagent continues to react with 1,2-dibromotetrafluoroethane at 60-110°C for 1.5-5h, then C2F3Br is added at 0-45°C, the temperature is adjusted to -5-65°C, and the reaction is carried out under a Pd catalyst for 12-28h to synthesize hexafluorobutadiene. The process is a liquid phase intermittent reaction with many steps, a long cycle, frequent temperature switching, complex operation, and the use of a precious metal palladium catalyst, which is not conducive to industrial production.

[0010] CN 116693365A discloses a method and a system for preparing hexafluorobutadiene, which specifically discloses that hexafluorobutadiene is prepared by coupling reaction of chlorotrifluoroethylene and trifluoroethylene under the condition of a catalyst. However, the palladium catalyst used in this method is relatively expensive, and the olefin polymerization reaction between two olefins will generate olefin polymerization byproducts, which is not conducive to industrial production.

[0011] In summary, it is an urgent problem for technicians in this field to develop a method for preparing hexafluoro-1,3-butadiene with cheap raw materials, convenient sources, simple operation, mild conditions, low energy consumption, low cost, simple product separation, good selectivity, and scalable continuous production. Summary of the invention

[0012] The object of the present invention is to provide a method for preparing hexafluoro-1,3-butadiene, wherein the raw materials are cheap and readily available, the process is simple, the energy consumption is low, the product separation is simple, the selectivity is good, the purification is convenient, and the scaled-up continuous production can be realized.

[0013] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0014] The present invention provides a method for preparing hexafluoro-1,3-butadiene, which comprises the following steps:

[0015] (1) preheating and mixing chlorotrifluoroethylene and 1,1,1,2-tetrafluoroethane, and then introducing them into a reactor filled with a first catalyst to carry out a dehydrochlorination reaction, and then sequentially condensing and performing a first distillation to obtain 1,1,2,3,4,4,4-heptafluoro-1-butene;

[0016] (2) The 1,1,2,3,4,4,4-heptafluoro-1-butene obtained in step (1) is introduced into a reactor filled with a second catalyst to carry out a dehydrofluorination reaction, and then condensed and distilled for the second time to obtain the hexafluoro-1,3-butadiene.

[0017] In the present invention, two raw materials, chlorotrifluoroethylene and 1,1,1,2-tetrafluoroethane, are subjected to an intermolecular dehydrochlorination reaction under the catalysis of a first catalyst to obtain an intermediate product, 1,1,2,3,4,4,4-heptafluoro-1-butene (the reaction process is shown in formula (I)), and then subjected to an intramolecular dehydrofluorination reaction under the catalysis of a second catalyst to obtain hexafluoro-1,3-butadiene (the reaction process is shown in formula (II)):

[0018]

[0019] The invention can realize continuous production of high-purity hexafluoro-1,3-butadiene by reasonable selection of reaction raw materials; the preparation method has the advantages of low-cost raw materials, simple process, low energy consumption, simple product separation, good selectivity, easy purification, etc., and can realize scaled-up continuous production.

[0020] In addition, in the preparation method of the present invention, the dehydrochlorination reaction in step (1) and the dehydrofluorination reaction in step (2) are carried out in different fixed bed reactors, respectively.

[0021] As a preferred technical solution of the present invention, the molar ratio of trifluorochloroethylene to 1,1,1,2-tetrafluoroethane in step (1) is 1:1.2 to 1.6, for example, 1:1.2, 1:1.3, 1:1.4, 1:1.5 or 1:1.6, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0022] Preferably, the preheating temperature of step (1) is 80-120°C, for example, 80°C, 90°C, 100°C, 110°C or 120°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0023] As a preferred technical solution of the present invention, the first catalyst in step (1) comprises metal oxide and / or metal fluoride.

[0024] Preferably, the metal oxide includes any one of copper oxide, aluminum oxide or iron oxide, or a combination of at least two of them.

[0025] Preferably, the metal fluoride includes any one of aluminum fluoride, iron fluoride or potassium fluoride, or a combination of at least two of them.

[0026] As a preferred technical solution of the present invention, the temperature of the dehydrochlorination reaction in step (1) is 120-200°C, for example, it can be 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C or 200°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable; preferably, it is 150-170°C.

[0027] Preferably, the pressure of the dehydrochlorination reaction in step (1) is 0 to 1.0 MPa, excluding 0, for example, 0.1 MPa, 0.2 MPa, 0.4 MPa, 0.6 MPa, 0.8 MPa or 1.0 MPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable; preferably 0.1 to 0.3 MPa.

[0028] Preferably, the residence time of the dehydrochlorination reaction in step (1) is 0.1 to 20 s, for example, 0.1 s, 1 s, 4 s, 8 s, 12 s, 16 s or 20 s, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0029] The present invention can improve the selectivity and yield of the intermediate product (1,1,2,3,4,4,4-heptafluoro-1-butene) by controlling parameters such as the temperature, pressure and residence time of the dehydrochlorination reaction.

[0030] As a preferred technical solution of the present invention, the condensation in step (1) is performed once;

[0031] Preferably, the temperature of the primary condensation is -10 to 0°C, for example, it can be -10°C, -9°C, -8°C, -7°C, -6°C, -5°C, -4°C, -3°C, -2°C, -1°C or 0°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0032] Preferably, the first material obtained by the primary condensation is subjected to a first distillation.

[0033] Preferably, the first condensation further includes a second condensation for recovering chlorotrifluoroethylene and 1,1,1,2-tetrafluoroethane.

[0034] Preferably, the temperature of the secondary condensation is -50 to -40°C, for example, -50°C, -48°C, -46°C, -44°C, -42°C or -40°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0035] As a preferred technical solution of the present invention, the bottom temperature of the first distillation in step (1) is 15-150°C, for example, it can be 15°C, 30°C, 45°C, 60°C, 75°C, 90°C, 105°C, 120°C, 135°C or 150°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0036] Preferably, the pressure of the first distillation in step (1) is 0-0.1 MPa, for example, 0 MPa, 0.01 MPa, 0.02 MPa, 0.04 MPa, 0.06 MPa, 0.08 MPa or 0.1 MPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0037] Preferably, the distillation temperature of the first distillation in step (1) is 15-23°C, for example, it can be 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C or 23°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0038] Preferably, the purity of 1,1,2,3,4,4,4-heptafluoro-1-butene in step (1) is greater than 99%, for example, it may be 99.2%, 99.4%, 99.6% or 99.8%, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0039] In the present invention, after the dehydrochlorination reaction in step (1), the obtained tail gas includes unreacted chlorotrifluoroethylene and 1,1,1,2-tetrafluoroethane, the intermediate product 1,1,2,3,4,4,4-heptafluoro-1-butene and a small amount of by-products such as 1,2-dichlorocyclobutane and 3,4-dichloro-1-butene; by performing the first distillation on the condensed tail gas, high-purity 1,1,2,3,4,4,4-heptafluoro-1-butene can be obtained, and other by-products can be recovered, among which 1,2-dichlorocyclobutane and 3,4-dichloro-1-butene can be sold as products, thereby reducing the production cost;

[0040] Furthermore, the present invention can separate the intermediate product 1,1,2,3,4,4,4-heptafluoro-1-butene and the by-products by controlling the distillation temperature range of the first distillation; the separated by-products 1,2-dichlorocyclobutane and 3,4-dichloro-1-butene can be treated as by-products.

[0041] As a preferred technical solution of the present invention, the second catalyst in step (2) comprises metal oxide and / or metal fluoride.

[0042] Preferably, the metal oxide comprises chromium oxide and / or aluminum oxide.

[0043] Preferably, the metal fluoride comprises magnesium fluoride and / or aluminum fluoride.

[0044] Preferably, the second catalyst in step (2) comprises chromium oxide, aluminum oxide, magnesium fluoride and aluminum fluoride.

[0045] As a preferred technical solution of the present invention, the temperature of the dehydrofluorination reaction in step (2) is 320-350°C, for example, 320°C, 325°C, 330°C, 335°C, 340°C, 345°C or 350°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0046] In the present invention, the temperature of the dehydrofluorination reaction in step (2) is 320-350° C. If the reaction temperature is too high, the impurity content will increase and the selectivity will deteriorate. If the reaction temperature is too low, the reaction speed will be too slow. If other conditions remain unchanged, the conversion rate will decrease.

[0047] Preferably, the residence time of the dehydrofluorination reaction in step (2) is 0.1 to 20 s, for example, 0.1 s, 0.5 s, 1 s, 2 s, 4 s, 8 s, 12 s, 16 s or 20 s, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0048] Preferably, the pressure of the dehydrofluorination reaction in step (2) is 0 to 1.0 MPa, and is not 0, for example, it can be 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa or 1.0 MPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable; preferably 0.1 to 0.3 MPa.

[0049] Preferably, the condensation in step (2) includes three condensations and four condensations performed sequentially.

[0050] Preferably, the temperature of the three condensations is 8-14°C, for example, 8°C, 9°C, 10°C, 11°C, 12°C, 13°C or 14°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0051] Preferably, the temperature of the four condensations is -10 to -5°C, for example, -10°C, -9°C, -8°C, -7°C, -6°C or -5°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0052] Preferably, the outlet of the three condensations is divided into two branches, one for performing four condensations and the other for recovering 1,1,2,3,4,4,4-heptafluoro-1-butene.

[0053] As a preferred technical solution of the present invention, the bottom temperature of the second distillation in step (2) is 20-130°C, for example, it can be 20°C, 40°C, 60°C, 80°C, 110°C or 130°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0054] Preferably, the tower top temperature of the second distillation in step (2) is 0-5°C, for example, 0°C, 1°C, 2°C, 3°C, 4°C or 5°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0055] Preferably, the pressure of the second distillation in step (2) is 0-0.1 MPa, for example, 0 MPa, 0.02 MPa, 0.04 MPa, 0.08 MPa or 0.1 MPa, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0056] Preferably, the discharge rate of the second distillation in step (2) is 30 to 50 g / h, for example, 30 g / h, 32 g / h, 35 g / h, 38 g / h, 40 g / h, 42 g / h, 45 g / h, 48 g / h or 50 g / h, but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0057] Preferably, the distillation temperature of the second distillation in step (2) is 15-23°C, for example, it can be 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, 21°C, 22°C or 23°C, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0058] Preferably, the purity of the hexafluoro-1,3-butadiene is ≥99.99%, for example, it may be 99.991%, 99.992%, 99.993%, 99.995%, 99.996%, 99.998% or 99.999%, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0059] As a preferred technical solution of the present invention, the method for preparing hexafluoro-1,3-butadiene provided by the present invention comprises the following steps:

[0060] (1) preheating and mixing chlorotrifluoroethylene and 1,1,1,2-tetrafluoroethane at a molar ratio of 1:1.2 to 1.6 at 80 to 120° C., introducing the mixture into a reactor filled with a first catalyst, performing a dehydrochlorination reaction at 120 to 200° C. and 0 to 1.0 MPa for 0.1 to 20 seconds, and then sequentially performing condensation and a first distillation to obtain 1,1,2,3,4,4,4-heptafluoro-1-butene;

[0061] The condensation includes a first condensation performed in sequence; the temperature of the first condensation is -10 to 0°C; the first material obtained by the first condensation is subjected to a first distillation; after the first condensation, a second condensation at a temperature of -50 to -40°C is further performed to recover chlorotrifluoroethylene and 1,1,1,2-tetrafluoroethane;

[0062] The first distillation has a bottom temperature of 15 to 150°C, a pressure of 0 to 0.1 MPa, and a distillation temperature of 15 to 23°C;

[0063] (2) introducing the 1,1,2,3,4,4,4-heptafluoro-1-butene obtained in step (1) into a reactor filled with a second catalyst to carry out a dehydrofluorination reaction, and then sequentially carrying out condensation and a second distillation to obtain hexafluoro-1,3-butadiene with a purity of ≥99.99%;

[0064] Wherein, the temperature of the dehydrofluorination reaction is 320-350°C, the pressure is 0-1.0MPa, and the residence time is 0.1-20s;

[0065] The condensation includes three condensations and four condensations at 8 to 14° C. in sequence, and the outlet of the three condensations is divided into two branches, one branch performs four condensations at a temperature of -10 to -5° C., and the other branch recovers 1,1,2,3,4,4,4-heptafluoro-1-butene;

[0066] The bottom temperature of the second distillation is 20-130°C, the top temperature is 0-5°C, the pressure is 0-0.1 MPa, the discharge rate is 30-50 g / h, and the distillation temperature is 15-23°C.

[0067] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0068] Compared with the prior art, the present invention has the following beneficial effects:

[0069] (1) The preparation method provided by the present invention uses chlorotrifluoroethylene and 1,1,1,2-tetrafluoroethane as catalysts to undergo a dehydrochlorination reaction to obtain an intermediate product 1,1,2,3,4,4,4-heptafluoro-1-butene, and then undergoes a first distillation separation, a dehydrofluorination reaction and a second distillation purification to obtain hexafluoro-1,3-butadiene with a purity of ≥99.99%, and the two-step yield is ≥50%;

[0070] (2) The preparation method provided by the present invention uses cheap raw materials, simple process, mild conditions, low energy consumption, and the raw materials can be recycled, which can achieve scale-up and continuous production;

[0071] (3) The product separation of the preparation method provided by the present invention is simple, has good selectivity, is easy to purify, and is easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 A schematic diagram of the structure of a system for preparing hexafluoro-1,3-butadiene provided in Examples 1-3 of the present invention;

[0073] Among them, 1 is a mixing preheating device, 2 is a first fixed bed reactor, 3 is a first condensation collection device, 4 is a second condensation collection device, 5 is a first distillation tower, 6 is a 1,1,2,3,4,4,4-heptafluoro-1-butene condensation storage tank, 7 is a second fixed bed reactor, 8 is a third condensation collection device, 9 is a fourth condensation collection device, 10 is a second distillation tower, 11 is a fifth condensation collection device, and 12 is a by-product collection device. DETAILED DESCRIPTION

[0074] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0075] The present invention provides a preparation device system of hexafluoro-1,3-butadiene, such as Figure 1 As shown, the device system includes a dehydrochlorination reaction unit, a first distillation unit, a dehydrofluorination reaction unit and a second distillation unit which are sequentially connected;

[0076] The dehydrochlorination reaction unit comprises a mixing preheating device 1, a first fixed bed reactor 2, a first condensation collection device 3 and a second condensation collection device 4 which are sequentially connected;

[0077] The outlet of the first condensation collection device 3 is divided into two branches, one of which is connected to the second condensation collection device 4, and the other is connected to the first distillation unit;

[0078] The outlet of the second condensation collection device 4 is connected to the mixing preheating device 1;

[0079] The first distillation unit comprises a first distillation tower 5; the outlet of the first distillation tower 5 is divided into two branches, one branch is connected to the 1,1,2,3,4,4,4-heptafluoro-1-butene condensation storage tank 6, and the other branch is connected to the by-product collection device 12;

[0080] The 1,1,2,3,4,4,4-heptafluoro-1-butene condensation storage tank 6 is connected to the dehydrofluorination reaction unit;

[0081] The dehydrofluorination reaction unit comprises a second fixed bed reactor 7, a third condensation collection device 8 and a fourth condensation collection device 9 which are sequentially connected; the second material outlet of the third condensation collection device 8 is connected to the 1,1,2,3,4,4,4-heptafluoro-1-butene condensation storage tank 6; the fourth condensation collection device 9 is connected to the second distillation unit;

[0082] The second distillation unit includes a second distillation tower 10 and a fifth condensation collection device 11 which are sequentially connected.

[0083] Example 1

[0084] This embodiment provides a method for preparing hexafluoro-1,3-butadiene, wherein Figure 1 The preparation is carried out in the preparation device system shown in the figure, and the preparation method comprises the following steps:

[0085] (1) preheating and mixing chlorotrifluoroethylene and 1,1,1,2-tetrafluoroethane in a molar ratio of 1:1.4 in a mixing preheating device 1 at a temperature of 100° C., and then introducing the mixture into a first fixed bed reactor 2 filled with a first catalyst, and performing a dehydrochlorination reaction for 10 seconds at 160° C. and 0.2 MPa. After condensation, the mixture is subjected to a first distillation in a first distillation tower 5 to obtain 1,1,2,3,4,4,4-heptafluoro-1-butene with a purity of 99.5%;

[0086] Wherein, the first catalyst comprises a mixture of copper oxide and potassium fluoride;

[0087] The condensation includes a primary condensation in the first condensation collection device 3; the temperature of the primary condensation is -5°C; the first material obtained by the primary condensation is connected to the first distillation tower 5; after the primary condensation, a secondary condensation at a temperature of -45°C is also included in the second condensation collection device 4 for recovering chlorotrifluoroethylene and 1,1,1,2-tetrafluoroethane, and returning them to the mixing preheating device 1;

[0088] The bottom temperature of the first distillation tower is 100°C, the pressure is 0.05MPa, and the distillation temperature is 20°C;

[0089] (2) introducing 8 kg of 1,1,2,3,4,4,4-heptafluoro-1-butene obtained in step (1) into a second fixed bed reactor 7 filled with a second catalyst to carry out a dehydrofluorination reaction, and then condensing the 1,1,2,3,4,4,4-heptafluoro-1-butene in a second distillation tower 10 to obtain 3.78 kg of hexafluoro-1,3-butadiene with a purity of 99.995%;

[0090] Wherein, the second catalyst is a mixture of chromium oxide, aluminum oxide, iron fluoride, magnesium fluoride and aluminum fluoride;

[0091] The temperature of the dehydrofluorination reaction is 335°C, the pressure is 0.5MPa, and the residence time is 10s;

[0092] The condensation includes three condensations at 11°C in the third condensation collection device 8 and four condensations in the fourth condensation collection device 9. The outlets of the three condensations are divided into two branches, one for four condensations at a temperature of -7°C and the other for recovering 1,1,2,3,4,4,4-heptafluoro-1-butene and recycling it to the 1,1,2,3,4,4,4-heptafluoro-1-butene condensation storage tank 6;

[0093] The bottom temperature of the second distillation tower is 25°C, the top temperature is 2°C, the pressure is 0.05MPa, the discharge rate is 45g / h, and the distillation temperature is 20°C.

[0094] In this embodiment, the crude product obtained after one condensation includes a mixture of 1,1,2,3,4,4,4-heptafluoro-1-butene, 1,2-dichlorocyclobutane and 3,4-dichloro-1-butene;

[0095] The crude product obtained after three condensations includes 1.18% of crude hexafluoro-1,3-butadiene, 98.78% of 1,1,2,3,4,4,4-heptafluoro-1-butene and 0.04% of other impurities;

[0096] The crude product obtained after four condensations includes 99.48% of crude hexafluoro-1,3-butadiene, 0.5% of 1,1,2,3,4,4,4-heptafluoro-1-butene and 0.02% of other impurities.

[0097] In this embodiment, the materials at each stage were subjected to GC analysis, and the results are shown in Table 1.

[0098] Table 1

[0099]

[0100]

[0101] In this embodiment, the yield of hexafluoro-1,3-butadiene (based on CTFE feed) is 53.82%.

[0102] Example 2

[0103] This embodiment provides a method for preparing hexafluoro-1,3-butadiene, wherein Figure 1 The preparation is carried out in the preparation device system shown in the figure, and the preparation method comprises the following steps:

[0104] (1) chlorotrifluoroethylene and 1,1,1,2-tetrafluoroethane in a molar ratio of 1:1.2 are preheated and mixed in a mixing preheating device 1 at a temperature of 80° C., and then introduced into a first fixed bed reactor 2 filled with a first catalyst, and dehydrochlorination reaction is carried out for 5 seconds at 120° C. and 1.0 MPa. After condensation, 1,1,2,3,4,4,4-heptafluoro-1-butene with a purity of 99.5% is obtained after a first distillation in a first distillation tower 5;

[0105] Wherein, the first catalyst comprises a mixture of copper oxide and potassium fluoride;

[0106] The condensation includes a primary condensation in the first condensation collection device 3; the temperature of the primary condensation is -10°C; the first material obtained by the primary condensation is connected to the first distillation tower 5; after the primary condensation, a secondary condensation at a temperature of -50°C is also included in the second condensation collection device 4 for recovering chlorotrifluoroethylene and 1,1,1,2-tetrafluoroethane, and returning them to the mixing preheating device 1;

[0107] The bottom temperature of the first distillation tower is 15°C, the pressure is 0.01MPa, and the distillation temperature is 15°C;

[0108] (2) introducing the 1,1,2,3,4,4,4-heptafluoro-1-butene obtained in step (1) into a second fixed bed reactor 7 filled with a second catalyst to carry out a dehydrofluorination reaction, and then condensing the 1,1,2,3,4,4,4-heptafluoro-1-butene in a second distillation tower 10 to obtain hexafluoro-1,3-butadiene with a purity of 99.995%;

[0109] Wherein, the second catalyst is a mixture of chromium oxide, aluminum oxide, iron fluoride, magnesium fluoride and aluminum fluoride;

[0110] The temperature of the dehydrofluorination reaction is 320°C, the pressure is 1.0MPa, and the residence time is 5s;

[0111] The condensation includes three condensations at 8°C in the third condensation collection device 8 and four condensations in the fourth condensation collection device 9. The outlets of the three condensations are divided into two branches, one for four condensations at a temperature of -10°C and the other for recovering 1,1,2,3,4,4,4-heptafluoro-1-butene and recycling it to the 1,1,2,3,4,4,4-heptafluoro-1-butene condensation storage tank 6;

[0112] The bottom temperature of the second distillation tower is 20°C, the top temperature is 0°C, the pressure is 0.1 MPa, the discharge rate is 30 g / h, and the distillation temperature is 15°C.

[0113] In this embodiment, the materials at each stage were subjected to GC analysis, and the results are shown in Table 2.

[0114] Table 2

[0115]

[0116] In this embodiment, the yield of hexafluoro-1,3-butadiene (based on CTFE feed) is 51.70%.

[0117] Example 3

[0118] This embodiment provides a method for preparing hexafluoro-1,3-butadiene, wherein Figure 1The preparation is carried out in the preparation device system shown in the figure, and the preparation method comprises the following steps:

[0119] (1) preheating and mixing chlorotrifluoroethylene and 1,1,1,2-tetrafluoroethane in a molar ratio of 1:1.6 in a mixing preheating device 1 at a temperature of 120° C., and then introducing the mixture into a first fixed bed reactor 2 filled with a first catalyst, and performing a dehydrochlorination reaction for 20 seconds at 200° C. and 0.01 MPa. After condensation, the mixture is subjected to a first distillation in a first distillation tower 5 to obtain 1,1,2,3,4,4,4-heptafluoro-1-butene with a purity of 99.5%;

[0120] Wherein, the first catalyst comprises a mixture of copper oxide and potassium fluoride;

[0121] The condensation includes a primary condensation in the first condensation collection device 3; the temperature of the primary condensation is 0°C; the first material obtained by the primary condensation is connected to the first distillation tower 5; after the primary condensation, a secondary condensation at a temperature of -40°C is also included in the second condensation collection device 4 for recovering chlorotrifluoroethylene and 1,1,1,2-tetrafluoroethane, and returning them to the mixing preheating device 1;

[0122] The bottom temperature of the first distillation tower is 150°C, the pressure is 0.01MPa, and the distillation temperature is 23°C;

[0123] (2) introducing the 1,1,2,3,4,4,4-heptafluoro-1-butene obtained in step (1) into a second fixed bed reactor 7 filled with a second catalyst to carry out a dehydrofluorination reaction, and then condensing the 1,1,2,3,4,4,4-heptafluoro-1-butene in a second distillation tower 10 to obtain hexafluoro-1,3-butadiene with a purity of 99.995%;

[0124] Wherein, the second catalyst is a mixture of chromium oxide, aluminum oxide, iron fluoride, magnesium fluoride and aluminum fluoride;

[0125] The temperature of the dehydrofluorination reaction is 350°C, the pressure is 0.1MPa, and the residence time is 20s;

[0126] The condensation includes three condensations at 14°C in the third condensation collection device 8 and four condensations in the fourth condensation collection device 9. The outlets of the three condensations are divided into two branches, one for four condensations at a temperature of -5°C and the other for recovering 1,1,2,3,4,4,4-heptafluoro-1-butene and recycling it to the 1,1,2,3,4,4,4-heptafluoro-1-butene condensation storage tank 6;

[0127] The bottom temperature of the second distillation tower is 130°C, the top temperature is 5°C, the pressure is 0.01MPa, the discharge rate is 50g / h, and the distillation temperature is 23°C.

[0128] In this embodiment, the materials at each stage were subjected to GC analysis, and the results are shown in Table 3.

[0129] Table 3

[0130]

[0131]

[0132] In this embodiment, the yield of hexafluoro-1,3-butadiene (based on CTFE feed) is 50.00%.

[0133] Example 4

[0134] This embodiment provides a method for preparing hexafluoro-1,3-butadiene, which differs from the preparation method in Embodiment 1 only in that:

[0135] In this embodiment, the molar ratio of chlorotrifluoroethylene to 1,1,1,2-tetrafluoroethane in step (1) is adjusted to 1:1.

[0136] Example 5

[0137] This embodiment provides a method for preparing hexafluoro-1,3-butadiene, which differs from the preparation method in Embodiment 1 only in that:

[0138] In this embodiment, the molar ratio of chlorotrifluoroethylene to 1,1,1,2-tetrafluoroethane in step (1) is adjusted to 1:2.

[0139] Example 6

[0140] This embodiment provides a method for preparing hexafluoro-1,3-butadiene, which differs from the preparation method in Embodiment 1 only in that:

[0141] In this embodiment, the temperature of the dehydrochlorination reaction in step (1) is adjusted to 100°C.

[0142] Example 7

[0143] This embodiment provides a method for preparing hexafluoro-1,3-butadiene, which differs from the preparation method in Embodiment 1 only in that:

[0144] In this embodiment, the temperature of the dehydrochlorination reaction in step (1) is adjusted to 250°C.

[0145] Example 8

[0146] This embodiment provides a method for preparing hexafluoro-1,3-butadiene, which differs from the preparation method in Embodiment 1 only in that:

[0147] In this embodiment, the pressure of the dehydrochlorination reaction in step (1) is adjusted to 0 MPa.

[0148] Example 9

[0149] This embodiment provides a method for preparing hexafluoro-1,3-butadiene, which differs from the preparation method in Embodiment 1 only in that:

[0150] In this embodiment, the pressure of the dehydrochlorination reaction in step (1) is adjusted to 1.2 MPa.

[0151] Example 10

[0152] This embodiment provides a method for preparing hexafluoro-1,3-butadiene, which differs from that of embodiment 1 only in that:

[0153] In this embodiment, the residence time of the dehydrochlorination reaction in step (1) is adjusted to 30 s.

[0154] Embodiment 11

[0155] This embodiment provides a method for preparing hexafluoro-1,3-butadiene, which differs from the preparation method in Embodiment 1 only in that:

[0156] In this embodiment, the temperature of the dehydrofluorination reaction in step (2) is adjusted to 300°C.

[0157] Example 12

[0158] This embodiment provides a method for preparing hexafluoro-1,3-butadiene, which differs from the preparation method in Embodiment 1 only in that:

[0159] In this embodiment, the temperature of the dehydrofluorination reaction in step (2) is adjusted to 380°C.

[0160] Example 13

[0161] This embodiment provides a method for preparing hexafluoro-1,3-butadiene, which differs from the preparation method in Embodiment 1 only in that:

[0162] In this embodiment, the four condensation processes described in step (2) are omitted.

[0163] Comparative Example 1

[0164] This comparative example provides a method for preparing hexafluoro-1,3-butadiene, which differs from Example 1 only in that:

[0165] In this comparative example, the first catalyst described in step (1) was omitted.

[0166] Comparative Example 2

[0167] This comparative example provides a method for preparing hexafluoro-1,3-butadiene, which differs from Example 1 only in that:

[0168] In this comparative example, the second catalyst described in step (2) was omitted.

[0169] Comparative Example 3

[0170] This comparative example provides a method for preparing hexafluoro-1,3-butadiene, which differs from Example 1 only in that:

[0171] In this comparative example, the preheating and mixing described in step (1) was omitted, that is, chlorotrifluoroethylene and 1,1,1,2-tetrafluoroethane were directly introduced into the reactor for reaction.

[0172] The materials at a certain stage in the preparation process of the above-mentioned Examples 1, 4-13 and Comparative Examples 1-3 were subjected to GC analysis, and the results are shown in Table 4.

[0173] Table 4

[0174]

[0175] According to Table 4, we can know the following points:

[0176] (1) The preparation method provided by the present invention comprises the following steps: using chlorotrifluoroethylene and 1,1,1,2-tetrafluoroethane under the catalysis of a catalyst, undergoing a dehydrochlorination reaction, and then undergoing a first distillation separation to obtain 1,1,2,3,4,4,4-heptafluoro-1-butene with a purity of ≥99%;

[0177] (2) Comprehensive analysis of Example 1 and Examples 4-5 shows that when the molar ratio of trifluorochloroethylene to 1,1,1,2-tetrafluoroethane is low, the by-products increase and the conversion rate decreases; conversely, when the molar ratio is high, the R134 reaction is incomplete, the by-products increase and the conversion rate decreases;

[0178] (3) Comprehensive analysis of Example 1 and Examples 6-7 shows that when the temperature of the dehydrofluorination reaction in step (1) is too low, the catalyst activity will be reduced and the conversion rate will be reduced. If the reaction temperature is too high, the catalyst activity will change, the selectivity will be reduced, and the impurity content will increase.

[0179] (4) Comprehensive analysis of Example 1 and Examples 8-9 shows that when the pressure of the dehydrochlorination reaction in step (1) is too low, the conversion rate of R134a will decrease, and when the reaction pressure is too high, the impurity content will increase;

[0180] (5) Comprehensive analysis of Example 1 and Example 10 shows that when the residence time of the raw material in the dehydrochlorination reaction in step (1) is too long, the impurity content will increase;

[0181] (6) Comprehensive analysis of Example 1 and Examples 11-12 shows that when the temperature of the dehydrofluorination reaction in step (2) is too low, the catalyst activity will be reduced and the conversion rate will be reduced. If the reaction temperature is too high, the impurity content will increase.

[0182] (7) Comprehensive analysis of Example 1 and Example 13 shows that when the four condensation processes described in step (2) are omitted, the impurity content will increase, and the purpose of 4N purification cannot be achieved;

[0183] (8) Comprehensive analysis of Example 1 and Comparative Examples 1-2 shows that the catalyst plays an indispensable role in the reaction process. If the first catalyst described in step (1) is omitted, no target substance will be generated; if the second catalyst described in step (2) is omitted, almost no target substance will be generated;

[0184] (9) Comprehensive analysis of Example 1 and Comparative Example 3 shows that the preheating and mixing described in step (1) is conducive to the full contact of the substances and improves the conversion rate. If the preheating process is omitted, the conversion rate will be reduced.

[0185] In summary, the present invention can achieve continuous production of high-purity hexafluoro-1,3-butadiene by reasonable selection of reaction raw materials; the preparation method has the advantages of low raw materials, simple process, low energy consumption, simple product separation, good selectivity, easy purification, etc., and can achieve scaled-up continuous production.

[0186] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing hexafluoro-1,3-butadiene, characterized in that: The preparation method comprises the following steps: (1) preheating and mixing chlorotrifluoroethylene and 1,1,1,2-tetrafluoroethane, and then introducing them into a reactor filled with a first catalyst to carry out a dehydrochlorination reaction, and then sequentially condensing and performing a first distillation to obtain 1,1,2,3,4,4,4-heptafluoro-1-butene; (2) The 1,1,2,3,4,4,4-heptafluoro-1-butene obtained in step (1) is introduced into a reactor filled with a second catalyst to carry out a dehydrofluorination reaction, and then condensed and distilled for the second time to obtain the hexafluoro-1,3-butadiene.

2. The preparation method according to claim 1, characterized in that: The molar ratio of chlorotrifluoroethylene to 1,1,1,2-tetrafluoroethane in step (1) is 1:1.2-1.6; Preferably, the temperature of the preheating mixing in step (1) is 80-120°C.

3. The preparation method according to claim 1 or 2, characterized in that: Step (1) The first catalyst comprises a metal oxide and / or a metal fluoride; Preferably, the metal oxide includes any one of copper oxide, aluminum oxide or iron oxide, or a combination of at least two thereof; Preferably, the metal fluoride includes any one of aluminum fluoride, iron fluoride or potassium fluoride, or a combination of at least two of them.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The temperature of the dehydrochlorination reaction in step (1) is 120-200° C., preferably 150-170° C.; Preferably, the pressure of the dehydrochlorination reaction in step (1) is 0 to 1.0 MPa, excluding 0, and preferably 0.1 to 0.3 MPa; Preferably, the residence time of the dehydrochlorination reaction in step (1) is 0.1 to 20 seconds.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The condensation in step (1) includes a primary condensation; Preferably, the temperature of the primary condensation is -10 to 0°C; Preferably, the first material obtained by the primary condensation is subjected to a first distillation; Preferably, the first condensation further includes a second condensation for recovering chlorotrifluoroethylene and 1,1,1,2-tetrafluoroethane; Preferably, the temperature of the secondary condensation is -50 to -40°C.

6. The preparation method according to any one of claims 1 to 5, characterized in that: Step (1) The bottom temperature of the first distillation is 15 to 150° C. Preferably, the pressure of the first distillation in step (1) is 0 to 0.1 MPa; Preferably, the distillation temperature of the first distillation in step (1) is 15 to 23°C; Preferably, the purity of the 1,1,2,3,4,4,4-heptafluoro-1-butene in step (1) is >99%.

7. The preparation method according to any one of claims 1 to 6, characterized in that: Step (2) the second catalyst comprises a metal oxide and / or a metal fluoride; Preferably, the metal oxide comprises chromium oxide and / or aluminum oxide; Preferably, the metal fluoride comprises magnesium fluoride and / or aluminum fluoride; Preferably, the second catalyst in step (2) comprises chromium oxide, aluminum oxide, magnesium fluoride and aluminum fluoride.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The temperature of the dehydrofluorination reaction in step (2) is 320-350° C. Preferably, the residence time of the dehydrofluorination reaction in step (2) is 0.1 to 20 s; Preferably, the pressure of the dehydrofluorination reaction in step (2) is 0 to 1.0 MPa, and is not 0; preferably 0.1 to 0.3 MPa; Preferably, the condensation in step (2) comprises three condensations and four condensations performed sequentially; Preferably, the temperature of the three condensations is 8 to 14°C; Preferably, the temperature of the four condensations is -10 to -5°C; Preferably, the outlet of the three condensations is divided into two branches, one for performing four condensations and the other for recovering 1,1,2,3,4,4,4-heptafluoro-1-butene.

9. The preparation method according to any one of claims 1 to 8, characterized in that: Step (2) the second distillation bottom temperature is 20-130° C.; Preferably, the tower top temperature of the second distillation in step (2) is 0 to 5°C; Preferably, the pressure of the second distillation in step (2) is 0 to 0.1 MPa; Preferably, the discharge rate of the second distillation in step (2) is 30 to 50 g / h; Preferably, the distillation temperature of the second distillation in step (2) is 15-23°C; Preferably, the purity of the hexafluoro-1,3-butadiene is ≥99.99%.

10. The preparation method according to any one of claims 1 to 9, characterized in that: The preparation method comprises the following steps: (1) preheating and mixing chlorotrifluoroethylene and 1,1,1,2-tetrafluoroethane at a molar ratio of 1:1.2 to 1.6 at 80 to 120° C., introducing the mixture into a reactor filled with a first catalyst, performing a dehydrochlorination reaction at 120 to 200° C. and 0 to 1.0 MPa for 0.1 to 20 seconds, and then sequentially performing condensation and a first distillation to obtain 1,1,2,3,4,4,4-heptafluoro-1-butene; The condensation includes a first condensation performed in sequence; the temperature of the first condensation is -10 to 0°C; the first material obtained by the first condensation is subjected to a first distillation; after the first condensation, a second condensation at a temperature of -50 to -40°C is further performed to recover chlorotrifluoroethylene and 1,1,1,2-tetrafluoroethane; The first distillation has a bottom temperature of 15 to 150°C, a pressure of 0 to 0.1 MPa, and a distillation temperature of 15 to 23°C; (2) introducing the 1,1,2,3,4,4,4-heptafluoro-1-butene obtained in step (1) into a reactor filled with a second catalyst to carry out a dehydrofluorination reaction, and then sequentially carrying out condensation and a second distillation to obtain hexafluoro-1,3-butadiene with a purity of ≥99.99%; Wherein, the temperature of the dehydrofluorination reaction is 320-350°C, the pressure is 0-1.0MPa, and the residence time is 0.1-20s; The condensation includes three condensations and four condensations performed sequentially, and the outlet of the three condensations is divided into two branches, one branch performs four condensations at a temperature of -10 to -5°C, and the other branch recovers 1,1,2,3,4,4,4-heptafluoro-1-butene; The bottom temperature of the second distillation is 20-130°C, the top temperature is 0-5°C, the pressure is 0-0.1 MPa, the discharge rate is 30-50 g / h, and the distillation temperature is 15-23°C.

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