A method for purifying electronic grade hexafluoro-butadiene based on extractive rectification technology

Abstract

The application belongs to the technical field of chemical industry and relates to purification of hexafluorobutadiene, in particular to a method for purifying electronic-grade hexafluorobutadiene based on extraction distillation technology. The method comprises the following steps: (1) extraction distillation: sending crude hexafluorobutadiene together with an extractant into an extraction distillation column; (2) adsorption: passing the hexafluorobutadiene after extraction distillation in step (1) into an adsorption column filled with an adsorbent to obtain hexafluorobutadiene; the adsorbent is selected from organic bases, copper salt doped modified graphene oxide adsorbents. The application first performs extraction distillation, then uses doped graphene oxide adsorbents to efficiently adsorb azeotropic fluorine-containing olefin compounds and alcohol impurities, the steps are simple, the product purity is high, and the requirements of the low-resistivity insulating film chemical vapor deposition industry on hexafluorobutadiene are met; meanwhile, the application is performed at low temperature and low pressure, does not cause hexafluorobutadiene to be heated and rearranged, has low requirements on equipment, and is easy to scale up.

Description

Technical Field

[0001] This application belongs to the field of chemical technology and relates to the purification of hexafluorobutadiene, specifically to a method for purifying electronic-grade hexafluorobutadiene based on extractive distillation technology. Background Technology

[0002] Hexafluoro-1,3-butadiene (hereinafter referred to as hexafluorobutadiene) is a high-performance etching gas for integrated circuits. It can rapidly form a low-density, thin-thickness fluorocarbon polymer protective film on the material surface, while achieving moderate etching intensity and excellent etching anisotropy, enabling the processing of almost vertical deep trench structures. At the same time, hexafluorobutadiene has a GWP value of only 290, an atmospheric lifetime of less than two days, a fast degradation rate, and does not contain chlorine in its molecules, thus posing less harm to the ozone layer. Therefore, hexafluorobutadiene is almost the only electronic specialty gas at present that can meet the requirements of high precision and high selectivity in etching while not exacerbating the greenhouse effect.

[0003] The synthesis of hexafluorobutadiene involves diverse raw materials, numerous processes, complex steps, and stringent conditions. Byproducts and raw material residues with similar properties are difficult to purify through simple distillation. To further meet the application requirements of specialty gases, existing technologies involve further refining hexafluorobutadiene. There are two main methods for synthesizing hexafluorobutadiene: 1. Coupling reaction of trifluorovinyl metal halides, as described in Chinese invention patent application CN110590495A; however, this method is limited by raw material prices and solvent activity, resulting in limited industrial application. 2. Dehalogenation reaction of fluoro-halobutanes with the participation of active metals such as zinc, as described in patent application CN110590495A. The method described in Chinese invention patent N112250541B uses inexpensive and readily available raw materials with high stability and high product selectivity, making it the mainstream application method in industry. However, in the process of preparing hexafluorobutadiene by this method, it is difficult to avoid introducing impurities such as butadiene fluorochloro compounds, fluorinated butadiene dimers, water, and alcohols. Although some impurities can be removed by distillation, azeotropic fluorinated olefin compounds such as butadiene fluorochloro compounds and fluorinated butadiene dimers, as well as alcohol solvents with hydrogen bonding, are difficult to remove completely. Therefore, the industrial-grade purity of hexafluorobutadiene prepared by this method often does not meet the application requirements of electronic specialty gases.

[0004] To address the problem of removing the aforementioned impurities, the following methods are generally used in the prior art:

[0005] 1. Water washing and dissolution method: As described in Chinese invention patent application number CN105399599A, this method utilizes the miscibility of water and alcohol solvents to wash away most of the alcohol solvents in the impurities. However, it will lead to an increase in the water content in hexafluorobutadiene, and the azeotropic fluorinated olefin compound impurities are difficult to remove. Subsequent steps require further low-temperature dehydration and adsorption to remove impurities. The process is complicated, increases production costs, and has poor practicality.

[0006] II. Adsorption Method: As described in US Patent No. 6544319, this method is low-cost and mild, and can effectively adsorb azeotropic fluorinated olefin compounds and alcohol impurities. However, this method is exothermic when adsorbing alcohol impurities, and hexafluorodienes are prone to rearrangement isomerization when heated, generating impurities such as hexafluoro-2-butyne that are difficult to remove. Therefore, the product yield and purity of this method need to be improved. At the same time, the temperature and pressure in the system will increase when using this method, which poses certain safety hazards.

[0007] Therefore, there is a need to develop a simple method for preparing hexafluorobutadiene that involves low-temperature and low-pressure production, high product purity, and high yield. Summary of the Invention

[0008] To address the issues of high cost, numerous steps, poor yield, and safety hazards in existing hexafluorobutadiene preparation methods, this application provides a method for purifying electronic-grade hexafluorobutadiene based on extractive distillation technology. This method effectively removes azeotropic fluorinated olefin compounds and alcohol impurities from hexafluorobutadiene, resulting in high product yield, enabling low-temperature and low-pressure production, and ensuring high safety performance. This method effectively overcomes the shortcomings of existing hexafluorobutadiene preparation methods.

[0009] This application provides a method for purifying electronic-grade hexafluorobutadiene based on extractive distillation technology, which employs the following technical solution:

[0010] A method for purifying electronic-grade hexafluorobutadiene based on extractive distillation technology includes the following steps:

[0011] (I) Extractive distillation

[0012] The crude hexafluorobutadiene, along with the extractant, is fed into an extractive distillation column. The crude hexafluorobutadiene and the extractant are introduced at a mass ratio of 1:3 to 10, and the reflux ratio is 5 to 15:1 to obtain crude purified hexafluorobutadiene.

[0013] (II) Adsorption

[0014] The crude purified hexafluorobutadiene obtained from the extractive distillation in step (I) is passed into an adsorption tower containing adsorbent, and the temperature is controlled at 20℃, the tower pressure at 0.5MPa, and the flow rate at 3L / h to obtain hexafluorobutadiene.

[0015] In step (ii) above, the adsorbent selected is an organic base and copper salt-doped modified graphene oxide adsorbent.

[0016] By adopting the above technical solution, firstly, the method of this application extracts and distills crude hexafluorobutadiene to remove most of the azeotropic fluorinated olefin compound impurities, and secondly, further adsorbs and purifies hexafluorobutadiene, which greatly reduces the probability of hexafluorobutadiene rearrangement isomerization caused by the release of heat during the adsorption process.

[0017] Graphene oxide has high porosity and specific surface area, and can play a role in adsorption and impurity removal in the industrial preparation of many organic chemicals; however, this application aims to prepare electronic grade hexafluorobutadiene, so relying solely on the adsorption capacity of graphene oxide itself is slightly insufficient and it is difficult to purify hexafluorobutadiene to the electronic grade.

[0018] When organic bases are doped with graphene oxide, the organic bases contain lone pairs of electrons or conjugated double bonds, which can form P-π conjugation or π-π conjugation with carbon-oxygen double bonds on the surface of graphene oxide, or form hydrogen bonds. This allows the organic bases to be firmly grafted onto the surface of graphene oxide, which can intercept and block azeotropic fluorinated olefin compounds and alcohol impurities, thereby separating the above impurities and purifying hexafluorobutadiene.

[0019] Copper salts are rich in copper ions. When copper ions are doped with graphene oxide, they are reduced to cuprous ions. Cuprous ions can specifically complex with azeotropic fluorinated olefin compounds, further improving the adsorption capacity and adsorption ability of the adsorbent for azeotropic fluorinated olefin compounds.

[0020] In summary, this application first performs extractive distillation, then uses organic base and copper salt doped with graphene oxide as adsorbents. This achieves efficient adsorption of azeotropic fluorinated olefin compounds and alcohol impurities from two different directions: physical interception and chemical complexation. It can purify hexafluorobutadiene to the 5N grade with high yield, simple steps, and high product purity, meeting the requirements of the chemical vapor deposition industry for hexafluorobutadiene in low resistivity insulating films. At the same time, this application can be carried out at low temperature and low pressure, which will not cause hexafluorobutadiene to undergo thermal rearrangement isomerization, has low equipment requirements, is easy to scale up production, has low safety risks, and has good market applicability.

[0021] Preferably, the preparation method of the organic base, copper salt doped modified graphene oxide adsorbent is as follows: the mass ratio of organic base: copper salt: graphene oxide is controlled at 3:2:5, and the three are dissolved in 1-3L of ethanol, heated at 150℃ for 24h, cooled to room temperature, and then vacuum dried at 120℃ to obtain the organic base, copper salt doped modified graphene oxide adsorbent.

[0022] By adopting the above technical solution, the organic base and copper salt doped modified graphene oxide prepared under the above conditions has a highly efficient adsorption effect on azeotropic fluorinated olefin compounds and alcohol impurities, which increases the purification depth of hexafluorobutadiene by the method of this application.

[0023] Preferably, the copper salt includes one or more of copper nitrate, copper sulfate, and tetrahydroxycopper sulfate.

[0024] By adopting the above technical solutions, the copper salts can all be ionized to produce copper ions, thereby reducing the copper ions to cuprous ions and complexing them with azeotropic fluorinated olefin compounds. At the same time, the copper salts are inexpensive and have low cost, making them suitable for industrial-scale production.

[0025] Preferably, the organic base includes one or more of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 7-methylindole, 1,5,7-triazidobicyclo[4.4.0]dec-5-ene (TBD), and 1,4-diazabicyclo[2.2.2]octane (DABCO).

[0026] By adopting the above technical solution, the organic bases all contain N atoms and unsaturated double bonds, which can easily form P-π conjugation, π-π conjugation or hydrogen bonds with carbon and oxygen double bonds on the surface of graphene oxide, thereby grafting the organic bases onto the surface of graphene oxide and increasing the adsorption capacity of graphene oxide.

[0027] Preferably, in step (i), crude hexafluorobutadiene is fed into the lower middle part of the side wall of the extractive distillation column, and the extractant enters from the top of the extractive distillation column; the hexafluorobutadiene after extractive distillation is collected from the top of the extractive distillation column; the heavy component containing the extractant is collected from the bottom of the column and sent to the extractant recovery column; the extractant is collected at the bottom of the extractant recovery column and then re-enters the extractive distillation column for reuse.

[0028] By adopting the above technical solutions, the recycling of extractant improves the utilization rate of extractant, reduces the generation of waste, and lowers production costs.

[0029] Preferably, the extractant includes one or more of furfural, methyl ethyl ketone, and cyclopentanone.

[0030] By adopting the above technical solutions, the above extractants all have good solubility for azeotropic fluorinated olefin compounds, and can extract and separate most of the azeotropic fluorinated olefin compounds, thereby reducing the amount of relatively expensive adsorbents used and lowering production costs.

[0031] Preferably, the pressure of the extractive distillation column in step (i) is 0.05 MPa to 0.1 MPa, the temperature of the column is 15 to 30°C, and the temperature of the top of the column is 0 to 10°C.

[0032] By adopting the above technical solution, the above extraction process is carried out at low temperature and low pressure, under mild conditions, with low equipment requirements, and can efficiently extract and separate azeotropic fluorinated olefin compounds. Compared with the existing technology, the product has higher purity and stronger practicality.

[0033] In summary, this application has the following beneficial effects:

[0034] 1. The method of this application extracts and distills crude hexafluorobutadiene, removing most of the azeotropic fluorinated olefin compound impurities. In the second step, organic base and copper salt are doped with graphene oxide as adsorbents, achieving efficient adsorption of azeotropic fluorinated olefin compounds and alcohol impurities from two different directions: physical interception and chemical complexation. The process is simple, the product has high purity, and it meets the requirements of the chemical vapor deposition industry for hexafluorobutadiene in low resistivity insulating films. At the same time, this application can be carried out at low temperature and low pressure, which will not cause hexafluorobutadiene to undergo thermal rearrangement and isomerization. It has low equipment requirements, is easy to scale up production, has low safety risks, and has good market applicability.

[0035] 2. The copper salts provided in this application can all ionize to produce copper ions, thereby reducing the copper ions to cuprous ions, which then complex with azeotropic fluorinated olefin compounds. At the same time, the copper salts provided in this application are inexpensive and have low cost, making them suitable for industrial-scale production.

[0036] 3. The organic bases provided in this application all contain N atoms and unsaturated double bonds, which can easily form P-π conjugation, π-π conjugation or hydrogen bonds with carbon and oxygen double bonds on the surface of graphene oxide, thereby grafting the organic bases onto the surface of graphene oxide and increasing the adsorption capacity of graphene oxide.

[0037] 4. This application recycles and reuses the extractant, which improves the utilization rate of the extractant, reduces the generation of waste, and lowers production costs;

[0038] 5. The extractants provided in this application all have good solubility for azeotropic fluorinated olefin compounds, and can extract and separate most of the azeotropic fluorinated olefin compounds, thereby reducing the amount of relatively expensive adsorbents used and lowering production costs. Attached Figure Description

[0039] Figure 1 This is a process flow diagram of the method provided in this application.

[0040] Explanation of reference numerals in the attached diagram: 1. Extractive distillation column; 2. Adsorption column; 3. Extractant recovery column. Detailed Implementation

[0041] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0042] In this embodiment, preparation example, and comparative example, all materials used are commercially available. The graphene oxide used has a particle size of 200 mesh.

[0043] Preparation Example

[0044] Preparation of Organic Base and Copper Salt Doped Modified Graphene Oxide Adsorbent

[0045] Weigh 300g of organic base, 200g of copper salt and 500g of graphene oxide and dissolve them in 2L of ethanol. After stirring evenly, heat at 150℃ for 24h, cool to room temperature and then vacuum dry at 120℃ to obtain organic base and copper salt doped modified graphene oxide adsorbent.

[0046] Among them, the organic base is 7-methylindole, and the copper salt is copper nitrate.

[0047] Example

[0048] Examples 1-5

[0049] As shown in Table 1, the main difference between Examples 1 to 5 lies in the different process parameters. Example 1 is used as an example below, in which the organic base and copper salt-doped modified graphene oxide adsorbent was prepared in the preparation example, and furfural was used as the extractant.

[0050] Example 1 provides a method for purifying electronic-grade hexafluorobutadiene based on extractive distillation technology as follows:

[0051] (I) Extractive distillation

[0052] Crude hexafluorobutadiene is fed into extractive distillation column 1 from the lower middle part of the side wall. The extractant is fed into extractive distillation column 1 from the top of the column. The crude hexafluorobutadiene and extractant are introduced at a mass ratio of 1:3 to 10. The reflux ratio is set to 1:3, the pressure is 0.1 MPa, the temperature is 30°C, and the temperature at which the hexafluorobutadiene is collected from the top of the column is 0°C, thus obtaining crude purified hexafluorobutadiene.

[0053] The extractant and other heavy components are collected from the bottom of the column and enter the extractant recovery column 3. The extractant is collected from the bottom of the column and sent back to the top of the extractive distillation column 1 for recycling.

[0054] (II) Adsorption

[0055] The crude purified hexafluorobutadiene obtained from the extractive distillation in step (I) is passed into adsorption tower 2, which contains an organic base and copper salt-doped modified graphene oxide adsorbent. The temperature is controlled at 15°C, the tower pressure at 0.3 MPa, and the flow rate at 2 L / h to obtain hexafluorobutadiene.

[0056] Table 1

[0057]

[0058] In Example 2, during step (ii) of the adsorption process, the temperature, pressure, and flow rate in adsorption tower 2 are the same as in Example 1; in Example 3, during step (ii) of the adsorption process, the temperature of adsorption tower 2 is 20°C, the pressure is 0.5 MPa, and the flow rate is 3 L / h; in Examples 4 and 5, during step (ii) of the adsorption process, the temperature of adsorption tower 2 is 25°C, the pressure is 0.6 MPa, and the flow rate is 4 L / h.

[0059] Example 6

[0060] The difference between this embodiment and Example 3 is that the type of extractant is different; in this embodiment, methyl ethyl ketone is used as the extractant.

[0061] Example 7

[0062] The difference between this embodiment and Example 3 is that the type of extractant is different; in this embodiment, cyclopentanone is used as the extractant.

[0063] Examples 8-11

[0064] As shown in Table 2, the difference between Examples 8 to 11 and Example 3 is that the types of organic bases or copper salts used in preparing organic base and copper salt-doped modified graphene oxide are different; among them, DBU is 1,8-diazabicyclo[5.4.0]undec-7-ene, TBD is 1,5,7-triazidobicyclo[4.4.0]dec-5-ene, and DABCO is 1,4-diazabicyclo[2.2.2]octane.

[0065] Table 2

[0066]

[0067] Comparative Example

[0068] Comparative Example 1

[0069] Compared with Example 3, the difference in this comparative example is that the preparation method lacks step (i) extraction and distillation.

[0070] Comparative Example 2

[0071] Compared with Example 3, the difference in this comparative example is that step (ii) adsorption is missing in the preparation method.

[0072] Comparative Example 3

[0073] Compared with Example 3, the difference in this comparative example is that the adsorbent used is unmodified graphene oxide.

[0074] Comparative Example 4

[0075] Compared with Example 3, the difference in this comparative example is that only organic bases are doped and no copper salts are doped when preparing the doped modified graphene oxide.

[0076] Comparative Example 5

[0077] Compared with Example 3, the difference in this comparative example is that only copper salts were doped and no organic bases were doped when preparing the doped modified graphene oxide.

[0078] Detection methods / test methods

[0079] The products prepared in each example and comparative example were tested by gas chromatography, and the test results are shown in Table 3.

[0080] Performance testing

[0081] Table 3

[0082]

[0083]

[0084] Combining Examples 1-5 and Table 3, it can be seen that the purity of hexafluorobutadiene in Examples 1-5 is above 4N7, especially the purity of Example 3, which reaches the 5N level, and the content of fluorinated organic compounds and methanol is low. This may be due to the superior process parameters and conditions in Example 3. The data of Examples 1-5 are all quite impressive because the preparation methods of Examples 1-5 are divided into two steps: First, hexafluorobutadiene is subjected to extractive distillation, and the crude product is fed from the lower middle part of the extractive distillation column 1, while the extractant is fed from the top of the column. This allows the extractant and the crude hexafluorobutadiene to collide, increasing the contact area between them and thus making the extraction of hexafluorobutadiene by the extractant more thorough. Second, the hexafluorobutadiene after the above extractive distillation is subjected to adsorption treatment, and the adsorbent is an organic base and copper salt-doped modified graphene oxide adsorbent. In this adsorbent, graphene oxide itself has good... The adsorption capacity of the organic base is enhanced by the fact that the lone pair electrons in the organic base can undergo p-π conjugation with the unsaturated bonds such as carbon-oxygen double bonds on the surface of graphene oxide, and the unsaturated bonds such as carbon-carbon double bonds and carbon-nitrogen double bonds in the organic base can also undergo π-π conjugation with the unsaturated bonds on the surface of graphene oxide, or form hydrogen bonds. The above interactions firmly "graft" the organic base onto the surface of graphene oxide. When methanol and fluorine-containing organic compounds come into contact with graphene oxide, the graphene oxide itself can adsorb some impurities, and the grafted organic base can also play a blocking role, intercepting and separating some impurity molecules. In addition, copper salts contain copper ions. When divalent copper ions are doped with graphene oxide, the graphene oxide reduces the copper ions to cuprous ions. Due to their chemical properties, cuprous ions can specifically complex with fluorine-containing organic compounds to form relatively stable complex particles, which increases the specific adsorption effect of the adsorbent on fluorine-containing organic compounds.

[0085] In summary, after extraction distillation and adsorption with doped graphene oxide, the method of this application can purify crude hexafluorobutadiene to above 4N7, or even to the 5N level. The steps are simple and meet the requirements of industries such as chemical vapor deposition for low resistivity insulating films. At the same time, this application can be carried out at low temperature and low pressure, which will not cause hexafluorobutadiene to undergo thermal rearrangement and isomerization. It has low equipment requirements, is easy to scale up production, has low safety risks, and has good market applicability.

[0086] Based on Examples 6-11, Example 3, and Table 3, it can be seen that the types of extractants, copper salts, and organic bases provided in each example of this application do not have a significant impact on the purity of the final purified hexafluorobutadiene, and the data differences between the examples are not significant. Among them, the data of Example 3 is better, which may be due to: 1. The extractant used in Example 3 has a better extraction effect on hexafluorobutadiene; 2. The copper salt used in Example 3 has a greater chance of being reduced after ionizing copper ions, or graphene oxide is more conducive to converting copper ions into cuprous ions and complexing with fluorinated organic compounds, which is macroscopically reflected in the lower content of fluorinated organic compounds; 3. The organic base used in Example 3 has a more significant interception and adsorption effect on methanol and fluorinated organic compounds, or the organic base has a greater increase in the adsorption capacity of graphene oxide.

[0087] Based on Examples 1-5, Comparative Example 1, and Table 3, it can be seen that the purity of hexafluorobutadiene in Comparative Example 1 is only 3N grade, and the contents of methanol and fluorinated organic compounds are higher than those in Examples 1-5. This is because in Comparative Example 1, crude hexafluorobutadiene was directly adsorbed with an adsorbent without prior extraction distillation. Therefore, the purity of hexafluorobutadiene in Comparative Example 1 is poor. This also proves that the extraction distillation step is an important and main step in removing impurities from crude hexafluorobutadiene.

[0088] Based on Examples 1-5, Comparative Example 2, and Table 3, it can be seen that the purity of hexafluorobutadiene in Comparative Example 2 is at the 4N2 level, not reaching 4N7 or higher. This is because the purification process of Comparative Example 2 lacks the step of adsorption by doped graphene oxide. Doped graphene oxide can effectively adsorb impurities such as methanol and fluorine-containing organic matter. The lack of an adsorption step will inevitably lead to a lower purity of hexafluorobutadiene.

[0089] Combining Comparative Examples 1 and 2 with Table 3, it can be seen that for the two steps of extractive distillation and adsorption, extractive distillation removes most of the impurities, while adsorption removes the remaining small portion of impurities that are difficult to remove by extractive distillation. If only extractive distillation is performed, the purity of hexafluorobutadiene can only reach around 4N2 level at most, which cannot meet the requirements of some special fields for this special gas. If only adsorption is performed, most of the impurities are difficult to remove. At this time, the purity and economic value of the purified hexafluorobutadiene are both low. Therefore, if hexafluorobutadiene of 4N7 level or above is to be prepared, both extractive distillation and adsorption steps are indispensable.

[0090] Based on Comparative Example 3, Comparative Example 2, Example 3 and Table 3, it can be seen that compared with Example 3, Comparative Example 3 has a higher content of fluorinated organic compounds and methanol, and a lower purity of hexafluorobutadiene. This is because undoped graphene oxide was selected in the adsorption process of Comparative Example 3. Although the product purity is higher than that of the unadsorbed Comparative Example 2, it does not reach the purity of Example 3. This is because the adsorption capacity of undoped graphene oxide is limited, making it difficult to deeply separate methanol from fluorinated organic compounds.

[0091] Based on Comparative Example 4, Example 3 and Table 3, it can be seen that Comparative Example 4 has a lower purity and a significantly higher content of fluorinated organic compounds. This is because Comparative Example 4 uses graphene oxide that is only doped with organic bases and lacks copper salts. As a result, it cannot reduce cuprous ions and specifically complex with fluorinated organic compounds during the adsorption process. Therefore, the product has low purity and a high content of fluorinated organic compounds.

[0092] Similarly, in conjunction with Comparative Example 5, Example 3 and Table 3, Comparative Example 5 used graphene oxide doped only with copper salts and not with organic bases, which resulted in the lack of an organic base interception and blocking process for impurities during the adsorption process of Comparative Example 5, thus making the product of Comparative Example 5 have poor purity.

[0093] Based on Comparative Examples 4 and 5 and Table 3, it can be seen that Comparative Example 4 has a lower methanol content, and Comparative Example 5 has a lower fluorinated organic matter content. This may be because after the organic base is "grafted", the organic base can form intermolecular hydrogen bonds with alcohol impurities through the lone pair electrons of nitrogen, preventing the escape of trace methanol after adsorption. Fluorinated organic matter molecules are larger and difficult to remain on graphene oxide. Copper salt can be reduced to cuprous ions and specifically complex fluorinated organic matter, resulting in a better removal effect on fluorinated organic matter.

[0094] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for purifying electronic grade hexafluorobutadiene based on extractive rectification technology, characterized in that, It comprises the following steps: (I) extractive distillation The crude hexafluorobutadiene is sent into the extractive distillation column together with the extractant, the crude hexafluorobutadiene and the extractant are fed in at a mass ratio of 1:3-10, the reflux ratio is 5-15:1, and the crude purified hexafluorobutadiene is obtained; (II) adsorption The crude purified hexafluorobutadiene after the extractive distillation in step (I) is fed into the adsorption column filled with the adsorbent, the temperature is controlled at 15-25℃, the column pressure is 0.4-0.6 MPa, and the flow rate is 2-4 L / h, and the hexafluorobutadiene is obtained; In the above step (II), the adsorbent is an organic base, a copper salt doped modified graphene oxide adsorbent; The preparation method of the organic base, copper salt doped modified graphene oxide adsorbent is as follows: the mass ratio of the organic base, copper salt and graphene oxide is controlled at 3:2:5, and the three are dissolved in 1-3 L of ethanol, heated at a temperature of 150℃ for 24 h, cooled to room temperature, and then vacuum dried at 120℃ to obtain the organic base, copper salt doped modified graphene oxide adsorbent; the organic base includes one or more of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 7-methylindole, 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), and 1,4-diazabicyclo[2.2.2]octane (DABCO); The kettle pressure of the extractive distillation column in step (I) is 0.05-0.1 MPa, and the kettle temperature is 15-30℃, and the overhead temperature is 0-10℃.

2. The method for purifying electronic grade hexafluoro-butadiene based on extractive rectification technology according to claim 1, characterized in that: The copper salt includes one or more of copper nitrate, copper sulfate, and tetrakis-hydroxy-copper sulfate.

3. The method for purifying electronic grade hexafluoro-butadiene based on extractive rectification technology according to claim 1, characterized in that: In step (I), the crude hexafluorobutadiene is fed into the extractive distillation column from the middle and lower part of the side wall, the extractant is fed into the extractive distillation column from the top of the column, the hexafluorobutadiene after the extractive distillation is collected from the top of the column, the heavy components containing the extractant are collected from the bottom of the column and sent into the extractant recovery column, and the extractant is collected from the bottom of the extractant recovery column and reused in the extractive distillation column.

4. The method for purifying electronic grade hexafluoro-butadiene based on extractive rectification technology according to claim 1, characterized in that: The extractant includes one or more of furfural, methyl ethyl ketone, and cyclopentanone.

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