Preparation method and preparation device of electronic-grade hexafluorobutadiene

Abstract

The invention belongs to the technical field of chemical engineering, particularly relates to a preparation method and a preparation device of electronic-grade hexafluorobutadiene, and aims to provide a brand-new hexafluorobutadiene synthesis route which can fundamentally solve the bottleneck problem in the existing hexafluorobutadiene production or preparation method. According to the preparation method, chlorotrifluoroethylene is taken as a main raw material, and the electronic grade 4N hexafluorobutadiene meeting the application of the semiconductor industry is prepared through two steps of catalytic polymerization and finished product rectification. The process raw materials and the device are high in utilization rate, impurities such as heptafluorobutene and hexafluorocyclobutene which are difficult to purify do not exist, the quality of the produced finished product can be effectively guaranteed under the condition that the cost is low, and then the technology is more competitive.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology, specifically relating to a method and apparatus for preparing electronic-grade hexafluorobutadiene. Background Technology

[0002] 1,1,2,3,4,4-Hexafluoro-1,3-butadiene, also known as perfluoro-1,3-butadiene, hexafluorobutadiene, or perfluorobutadiene, is abbreviated as HFBD. Its molecular formula is C4F6, its chemical formula is CF2=CF-CF=CF2, its relative molecular mass is 162.03, and its CAS number is 685-63-2. At room temperature and pressure, it is a colorless, odorless, toxic, flammable, compressible, liquefiable gas, insoluble in water. Its main application is in the dry etching of very large-scale integrated circuits, where it exhibits high selectivity and high aspect ratio.

[0003] Currently, there are three main methods for preparing hexafluorobutadiene with practical value: the iodine chloride method, the bromine method, and the trifluorochloroethylene thermal polymerization method.

[0004] One of the core raw materials for the iodine chloride process is iodine chloride, and its reaction equation is shown below:

[0005] 1) CF2=CFCl+ICl→CF2Cl-CFICl (core step);

[0006] 2) 2CF2Cl-CFICl+Zn→CF2Cl-CFCl-CFCl-CF2Cl+ZnI2;

[0007] 3) CF2Cl-CFCl-CFCl-CF2Cl+2Zn→CF2=CF-CF=CF2+2ZnCl2;

[0008] The iodine chloride process was first successfully developed in Russia. It relies on relatively inexpensive iodine resources to synthesize high-purity hexafluorobutadiene. Currently, a small number of companies in China also use this process for production.

[0009] The bromine process was first industrialized by Sinochem Lantian. Its process eliminated the use of expensive raw material ICl, replacing it with inexpensive Br2. The synthesis route is as follows:

[0010] 1) CF2=CF2 (can be replaced by CF2=CFCl or CF2=CFH)+Br2→CF2Br-CF2Br;

[0011] 2) CF2Br-CF2Br→CF3-CFBr2;

[0012] 3) 4CF3-CFBr2+5Zn→2CF2=CF-CF=CF2+4ZnBr2+ZnF2;

[0013] The thermal polymerization of trifluorochloroethylene is a method that our electronic specialty gases research team has been paying close attention to in the past two years. Several industrialization projects are currently underway in China. This method avoids the two methods mentioned above that require the grafting of other halogens, and instead uses high temperature or catalysis to directly carry out thermal polymerization. The reaction equation is as follows:

[0014] 1) 4CF2=CFCl→C4F6Cl2( (dichlorohexafluorobutene) + C4F6Cl2 Dichlorohexafluorocyclobutane);

[0015] 2)

[0016] From a comprehensive cost perspective, the three industrialized process routes each have their own advantages and disadvantages:

[0017] 1) The iodine chloride process is currently the technology with the highest purity of finished products. However, its development in China is hampered by high iodine source costs and the need to use highly toxic chlorine gas to recover iodine during the process. Furthermore, the high production cost is due to the impact of iodine recovery rate.

[0018] 2) Compared with the iodine chloride method, the biggest advantage of the bromine method is its high process conversion rate and the fact that it does not involve expensive iodine resources in the production process, which greatly reduces the cost of the main process product. However, the problem with this process is that it uses a large amount of solvent and Zn powder. After the synthesis is completed, there is no effective resource utilization plan for the waste solvent, waste zinc powder and zinc salt. They are generally treated as hazardous waste, and the amount generated is generally more than 10 times that of hexafluorobutadiene products. As a result, although the cost of this technology is significantly lower than that of the iodine chloride method, it is still relatively high, making the market price of the finished hexafluorobutadiene much higher than that of other mainstream fluorocarbon etching gases.

[0019] In addition, the hexafluorobutadiene produced by this method contains heptafluorobutene, an impurity that is more difficult to separate (its boiling point is only 1°C higher than that of hexafluorobutadiene), compared to that produced by the iodine chloride method. This means that the crude product obtained by this process requires more stringent purification techniques to obtain electronic-grade hexafluorobutadiene products of 4N grade or higher. Furthermore, the yield during the purification process is also lower, which affects the cost of the finished product.

[0020] 3) Compared to the iodine chloride and bromine methods mentioned above, the trifluorochloroethylene thermal polymerization process can directly achieve the dimerization of the raw material olefin without introducing other halogens, thus directly generating a four-carbon olefin. Hexafluorobutadiene is then obtained through zinc powder dechlorination, effectively reducing production costs. However, it is worth noting that this process contains a difficult-to-handle impurity, C4F6Cl2 (structural formula: Dichlorohexafluorocyclobutane), although it can be distilled to react with the main product C4F6Cl2 (structural formula: The process can separate 3,4-dichlorohexafluoro-1-butene, but its subsequent resource utilization is a technical bottleneck. Although there are many reports that it can be further converted into hexafluorobutadiene, no industrial projects have been implemented yet.

[0021] In addition, C4F6Cl2, the core intermediate product of the trifluorochloroethylene thermal polymerization process, The overall yield is generally no more than 27%, which results in numerous byproducts and relatively high costs. Current data shows that its synthesis cost is lower than that of the iodine chloride method and the bromine method, but the difference is not significant. Furthermore, the trifluorochloroethylene thermal polymerization process produces a small amount of hexafluorocyclobutene as a byproduct, whose boiling point differs from hexafluorobutadiene by only 1°C. This also requires stringent purification techniques to produce 4N grade or higher electronic-grade hexafluorobutadiene products from the crude synthetic product.

[0022] In summary, the various technologies currently reported and industrialized each possess their own advantages and characteristics, but also have technical problems or bottlenecks that cannot be effectively solved at present. Therefore, there is an urgent need to develop a new industrialization technology for electronic-grade hexafluorobutadiene products, enabling further cost reduction. This would significantly lower application costs while meeting the needs of the semiconductor industry, thereby providing impetus for the further development of my country's semiconductor industry. Summary of the Invention

[0023] In view of this, the present invention relates to a method and apparatus for preparing electronic-grade hexafluorobutadiene, which aims to provide a novel synthetic route for hexafluorobutadiene that can fundamentally solve the bottleneck problems existing in current hexafluorobutadiene production or preparation methods.

[0024] To achieve the above objectives, the present invention adopts the following technical solution:

[0025] The first technical objective of this invention is to provide a method for preparing electronic-grade hexafluorobutadiene, the preparation steps of which are as follows:

[0026] 1) Prepare slurry A by mixing zinc powder, catalyst, and solvent according to process requirements;

[0027] Furthermore, the solvent refers to one or more of methanol, ethanol, n / isopropanol, n / iso / tert-butanol, DMSO, THF, and DMF; the mass ratio of zinc powder to solvent is 1:1-100, preferably 1:15-25; the mass ratio of catalyst to solvent is 1:1-100, preferably 1:5-8.

[0028] Furthermore, the catalyst is a transition metal organometallic complex catalyst, wherein the transition metal is selected from metal elements of Groups IIIB to IIB of the periodic table, with preference given to transition metals of Groups VIII to IIB, including iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd), platinum (Pt), copper (Cu), silver (Ag), gold (Au), zinc (Zn), and cadmium (Cd). The ligand can be monodentate, multidentate, or macrocyclic ligands, with preference given to amine, ketone, phosphine, crown ether, and olefin ligands. Examples include ferrocene catalysts, π-allyl nickel, bis(tri-tert-butylphosphine)palladium, palladium acetate, and oxamide copper complexes.

[0029] 2) The raw material trichlorofluoroethylene gas and the pre-mixed slurry A are continuously pumped into a two-stage series reactor in a countercurrent manner to carry out a countercurrent reaction, and the reaction temperature and feed flow rate are controlled during the process.

[0030] Furthermore, the reaction temperature in the two-stage reactor is controlled at 0-150℃, preferably 30-100℃; the pressure (gauge pressure) during the reaction is controlled at 0-2 MPa, preferably 0.05-0.5 MPa; the reaction residence time is controlled at 0.1-100 h, preferably 1-4 h; the reactor is a stirred tank, reaction tower, tubular reactor or microchannel reactor, preferably a stirred tank; the mass ratio of trichlorofluoroethylene to slurry A is 1:1-100, preferably 1:2-8.

[0031] 3) Cool the gaseous product obtained from the primary reactor and reflux it to recover the evaporated solvent. Collect the gaseous product by low-temperature condensation to obtain crude hexafluorobutadiene, unreacted raw material trifluorochloroethylene, and a small amount of by-products.

[0032] 4) The crude hexafluorobutadiene obtained from the condensed gaseous product in step 3) is purified by a three-stage distillation: the top of the first-stage distillation column yields unreacted raw material and a small amount of by-products, while the bottom of the column contains crude hexafluorobutadiene, which is then fed into the second-stage distillation column by pressure difference to further remove light components; the bottom material of the second-stage distillation column is then fed into the third-stage distillation column to remove heavy components, thereby obtaining electronic-grade hexafluorobutadiene product with a purity of 4N or higher.

[0033] Furthermore, the distillation pressure of the first-stage distillation column is controlled at 0-5 MPa, preferably 0.1-2 MPa; the top temperature of the first-stage distillation column is controlled at -150-100℃, preferably -100-50℃; and the bottom temperature of the first-stage distillation column is controlled at -100-150℃, preferably -50-100℃.

[0034] Furthermore, the distillation pressure of the secondary distillation column is controlled at 0-5 MPa, preferably 0.1-2 MPa; the top temperature of the secondary distillation column is controlled at -100-100℃, preferably -50-100℃; and the bottom temperature of the secondary distillation column is controlled at -50-150℃, preferably 0-150℃.

[0035] Furthermore, the distillation pressure of the three-stage distillation column is controlled at 0-5 MPa, preferably 0.1-2 MPa; the top temperature of the three-stage distillation column is controlled at -50-150℃, preferably 0-150℃; and the bottom temperature of the three-stage distillation column is controlled at 50-350℃, preferably 100-300℃.

[0036] 5) The slurry flowing out of the secondary reactor is the solvent and the raw material trifluorochloroethylene, catalyst, unreacted Zn powder and byproduct ZnCl2 dissolved in it; it is pumped into the degassing unit to heat and recover the unreacted raw material trifluorochloroethylene dissolved in it.

[0037] Furthermore, the temperature in the degassing device is controlled at 10-200℃, preferably 50-80℃; the degassing device is a stirred tank or a packed tower, preferably a packed tower.

[0038] It should be noted that the present invention uses a continuous process for synthesis, with a high single-pass conversion rate of trifluorochloroethylene, up to 80% or more; the product hexafluorobutadiene has high selectivity, up to 80% or more; the incompletely converted trifluorochloroethylene and zinc powder can be recycled during the process, further reducing the process cost; and the solvent can be recovered and reused during the reaction, which basically avoids the generation of hazardous waste, making the overall cost advantage more obvious.

[0039] The second technical objective of this invention is to provide an apparatus for preparing electronic-grade hexafluorobutadiene, comprising: a raw material mixing device, a two-stage series reactor, and a three-stage series distillation column; wherein,

[0040] The two-stage series reactor includes a primary reactor and a secondary reactor, and the three-stage series distillation column includes a primary distillation column, a secondary distillation column and a tertiary distillation column;

[0041] The raw material mixing device is connected in sequence to a two-stage series reactor and a three-stage series distillation column, and the end of the two-stage reactor is connected to a degassing device.

[0042] Compared with existing technologies, this invention uses trifluorochloroethylene as the main raw material and prepares electronic-grade 4N hexafluorobutadiene that meets the requirements of the semiconductor industry through two steps: catalytic polymerization and product distillation. Compared with commonly reported processes, this invention has the following characteristics:

[0043] 1) This invention uses only trifluorochloroethylene as raw material and does not introduce other halogen raw materials, resulting in lower raw material costs for the product;

[0044] 2) This invention achieves a one-step conversion of trifluorochloroethylene to hexafluorobutadiene by introducing a transition metal organometallic complex catalyst. The selectivity of hexafluorobutadiene in this invention is much higher than that of the thermal polymerization method of trifluorochloroethylene, reaching up to 80%, while no dichlorohexafluorocyclobutane or hexafluorocyclobutene byproducts are produced. The raw material utilization rate is higher and the cost is also significantly reduced.

[0045] 3) This invention adopts a continuous flow production process, which has high equipment utilization, high raw material recovery rate, low initial investment in industrial-scale equipment, and lower product cost;

[0046] 4) The crude product distillation section of the present invention has a relatively larger boiling point difference and no impurities that are difficult to purify, such as heptafluorobutene and hexafluorocyclobutene. This makes it easier to purify the crude product into hexafluorobutadiene of grade 4N or higher. While ensuring low cost, the quality of the finished product can also be effectively guaranteed, thus making the technology of the present invention more competitive. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0048] Figure 1 This is a schematic diagram of the apparatus for preparing electronic-grade hexafluorobutadiene disclosed in this invention.

[0049] Figure 1 middle,

[0050] 1-1: Solvent; 1-2: Zinc powder; 1-3: Catalyst; 1-4: Trichlorofluoroethylene;

[0051] 2: Raw material mixing device;

[0052] 3-1: Primary reactor; 3-2: Secondary reactor; 3-3: Degassing unit; 3-4: Unreacted raw materials

[0053] 4-1: Primary distillation column; 4-2: Secondary distillation column; 4-3: Tertiary distillation column; 4-4: Recovered raw materials; 4-5: Finished electronic-grade hexafluorobutadiene. Detailed Implementation

[0054] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0055] The term "embodiment" used herein, as an example, is not necessarily to be construed as superior to or better than other embodiments. Performance testing in the embodiments of this application, unless otherwise specified, employs conventional testing methods in the art. It should be understood that the terminology used in this application is merely for describing particular implementations and is not intended to limit the scope of this disclosure.

[0056] Unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; other experimental methods and technical means not specifically mentioned herein refer to experimental methods and technical means commonly used by one of ordinary skill in the art.

[0057] In the description of this invention, it should be understood that the terms "middle", "upper", "lower", "rise", "fall", "vertical", "surface", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0058] To better illustrate the content of this application, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this application can be implemented even without certain specific details. In the embodiments, some methods, means, instruments, and devices well-known to those skilled in the art are not described in detail in order to highlight the main points of this application.

[0059] Without conflict, the technical features disclosed in the embodiments of this application can be combined arbitrarily, and the resulting technical solution belongs to the content disclosed in the embodiments of this application.

[0060] This invention discloses a method and apparatus for preparing electronic-grade hexafluorobutadiene.

[0061] To better understand the present invention, the following embodiments are provided for further detailed description of the present invention, but they should not be construed as limiting the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above-described invention are also considered to fall within the protection scope of the present invention.

[0062] Example 1:

[0063] 1) Mix 600 kg of dimethylformamide, 40 kg of zinc powder, and 100 kg of bis(tri-tert-butylphosphine)palladium evenly to prepare slurry A;

[0064] 2) At 70℃ and 0.5 MPa, the raw material trichlorofluoroethylene gas and the pre-mixed slurry A were continuously pumped into two 50L stirred tanks connected in series in a countercurrent manner for a countercurrent reaction, with a residence time of 4h.

[0065] 3) Cool the gaseous product obtained from the primary reactor and reflux it to recover the evaporated solvent. Collect the gaseous product by low-temperature condensation to obtain crude hexafluorobutadiene, unreacted raw material trifluorochloroethylene, and a small amount of by-products.

[0066] 4) The crude hexafluorobutadiene obtained from the condensed gaseous products is purified by a three-stage distillation process: the top of the first-stage distillation column yields unreacted raw material and a small amount of by-products, while the bottom of the column contains crude hexafluorobutadiene, which is then fed into the second-stage distillation column under pressure differential to further remove light components; the bottom material of the second-stage distillation column is then fed into the third-stage distillation column to remove heavy components, thereby obtaining electronic-grade hexafluorobutadiene with a purity of 4N or higher; the recovered raw material can be reused in the reaction.

[0067] The distillation pressure of the first-stage distillation column is controlled at 0.1 MPa; the top temperature of the first-stage distillation column is controlled at -61.5℃; and the bottom temperature of the first-stage distillation column is controlled at -28.7℃.

[0068] The distillation pressure of the secondary distillation column is controlled at 0.1 MPa; the top temperature of the secondary distillation column is controlled at -34.2℃; and the bottom temperature of the secondary distillation column is controlled at 7.0℃.

[0069] The distillation pressure of the three-stage distillation column is controlled at 0.1 MPa; the top temperature of the three-stage distillation column is controlled at 5.5℃; and the bottom temperature of the three-stage distillation column is controlled at 101.4℃.

[0070] or

[0071] The distillation pressure of the first-stage distillation column is controlled at 2 MPa; the top temperature of the first-stage distillation column is controlled at 22.7℃; and the bottom temperature of the first-stage distillation column is controlled at 70.8℃.

[0072] The distillation pressure of the secondary distillation column is controlled at 2 MPa; the top temperature of the secondary distillation column is controlled at 59.3℃; and the bottom temperature of the secondary distillation column is controlled at 117.8℃.

[0073] The distillation pressure of the three-stage distillation column is controlled at 2 MPa; the top temperature of the three-stage distillation column is controlled at 112.0℃; and the bottom temperature of the three-stage distillation column is controlled at 290.5℃.

[0074] 5) The slurry flowing out of the secondary reactor is the solvent and the raw material trifluorochloroethylene, catalyst, unreacted Zn powder and byproduct ZnCl2 dissolved in it; it is pumped into the degassing unit to heat and recover the unreacted raw material trifluorochloroethylene dissolved in it.

[0075] 6) After feeding, the conversion rate of the raw material trifluorochloroethylene was measured to be 79.5%, the yield of the finished product hexafluorobutadiene was 78.5%, and the purity index of the finished product was 4.5N.

[0076]

[0077]

[0078] To further demonstrate the beneficial effects of the present invention and to better understand it, the technical features of the disclosed apparatus and its applications are further illustrated by the following comparative examples, but these should not be construed as limiting the present invention. Other improvements made by those skilled in the art based on the above description of the invention, without inventive effort, are also considered to fall within the protection scope of the present invention.

[0079] Comparative Example 1

[0080] Except for the zinc powder dosage of 4 kg, all other conditions were the same as in Example 1. Due to the low zinc powder dosage during the reaction, the conversion of the raw material trifluorochloroethylene was incomplete, resulting in a significant decrease in the raw material conversion rate to only 6.7%. The product yield also decreased significantly, with a product yield of 53.8%. After purification, the product purity was 4.3N.

[0081] Comparative Examples 2-6:

[0082]

[0083]

[0084] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing electronic-grade hexafluorobutadiene, characterized in that, The preparation method steps are as follows: 1) Prepare slurry A by mixing zinc powder, catalyst, and solvent; 2) The raw material trichlorofluoroethylene gas and slurry A are continuously pumped into a two-stage reactor connected in series in a countercurrent manner to carry out a countercurrent reaction, during which the reaction temperature and feed flow rate are well controlled; 3) The gaseous product obtained from the primary reactor is cooled and refluxed to recover the volatilized solvent, and the gaseous product is collected by low-temperature condensation to obtain crude hexafluorobutadiene, unreacted raw material trifluorochloroethylene, and a small amount of by-products. 4) The crude hexafluorobutadiene obtained from the condensed gaseous product in step 3) is purified by a three-stage distillation process. The top of the first-stage distillation column yields unreacted raw material and a small amount of by-products, while the bottom of the column contains crude hexafluorobutadiene. This crude product is then fed into the second-stage distillation column under pressure differential to further remove light components. The bottom material of the second-stage distillation column is then fed into the third-stage distillation column to remove heavy components, thus obtaining electronic-grade hexafluorobutadiene with a purity of 4N or higher.

2. The method for preparing electronic-grade hexafluorobutadiene according to claim 1, characterized in that, In step 1), the solvent is one or a mixture of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, DMSO, THF, and DMF. The mass ratio of the zinc powder to the solvent is 1:1-100, and the mass ratio of the catalyst to the solvent is 1:1-100.

3. The method for preparing electronic-grade hexafluorobutadiene according to claim 1, characterized in that, In step 2), the reaction temperature in the two-stage reactor is 0-150℃, the reaction pressure (gauge pressure) is 0-2 MPa, and the reaction residence time is 0.1-100 h.

4. The method for preparing electronic-grade hexafluorobutadiene according to claim 1 or 3, characterized in that, The reactor is a stirred tank, reaction tower, tubular reactor or microchannel reactor, and the mass ratio of trichlorofluoroethylene to slurry A is 1:1-100.

5. The method for preparing electronic-grade hexafluorobutadiene according to claim 1, characterized in that, The distillation pressure of the first-stage distillation column is 0-5 MPa, the top temperature is -150-100℃, and the bottom temperature is -100-150℃.

6. The method for preparing electronic-grade hexafluorobutadiene according to claim 1, characterized in that, The distillation pressure of the two-stage distillation column is 0-5 MPa, the top temperature is -100-100℃, and the bottom temperature is -50-150℃.

7. The method for preparing electronic-grade hexafluorobutadiene according to claim 1, characterized in that, The distillation pressure of the three-stage distillation column is 0-5 MPa, the top temperature is -50-150℃, and the bottom temperature is 50-350℃.

8. The method for preparing electronic-grade hexafluorobutadiene according to any one of claims 1-7, characterized in that, Also includes: The slurry flowing out of the secondary reactor is pumped into a degassing unit and heated to recover the unreacted raw material trifluorochloroethylene dissolved therein; the slurry consists of a solvent and the raw material trifluorochloroethylene, catalyst, unreacted Zn powder, and byproduct ZnCl2 dissolved therein.

9. The method for preparing electronic-grade hexafluorobutadiene according to claim 8, characterized in that, The degassing device is a stirred tank or a packed tower, and the temperature in the degassing device is 10-200℃.

10. An apparatus for preparing electronic-grade hexafluorobutadiene, characterized in that, include: The system includes a raw material mixing unit, a two-stage series reactor, and a three-stage series distillation column; among which... The two-stage series reactor includes a primary reactor and a secondary reactor, and the three-stage series distillation column includes a primary distillation column, a secondary distillation column and a tertiary distillation column; The raw material mixing device is connected in sequence to a two-stage series reactor and a three-stage series distillation column, and the end of the two-stage reactor is connected to a degassing device.

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