Purification process and purification device for electronic grade hexafluoroethane

Abstract

The present invention belongs to the technical field of hexafluoroethane purification, and specifically relates to a purification process for electronic-grade hexafluoroethane and a purification device thereof. The purification process for electronic-grade hexafluoroethane comprises the following steps: passing the crude hexafluoroethane into a pretreatment device for pretreatment; passing the crude product treated by the pretreatment device into an adsorption tower for adsorption; passing the adsorbed crude product into a condenser to remove non-condensable gas to obtain a crude condensate, and passing the crude condensate into an alkali washing tank for alkali washing; the crude product after alkali washing enters a degassing tower and a distillation tower in turn, and obtains an electronic-grade hexafluoroethane product after degassing and distillation. The purification process for electronic-grade hexafluoroethane of the present invention achieves a purity of 99.999% for hexafluoroethane by designing a pretreatment agent and an adsorbent, realizes the conversion of pentafluoromonochloroethane and the removal of trifluoromethane, has a simple process and low energy consumption; the present invention also provides a purification device corresponding to the purification process for electronic-grade hexafluoroethane.

Description

Technical Field

[0001] The invention belongs to the technical field of hexafluoroethane purification, and in particular relates to a purification process and a purification device for electronic grade hexafluoroethane. Background Art

[0002] Electronic grade hexafluoroethane is widely used in the semiconductor manufacturing process because of its non-toxic, odorless and high stability. Hexafluoroethane has the advantages of extremely small edge lateral erosion, high etching rate and high precision, which solves the problem that conventional wet etching cannot meet the high-precision fine line etching of deep submicron integrated circuits of 0.18-0.25μm, and can well meet the requirements of such processes with small line widths. In various CVD processes based on SiH4, hexafluoroethane is used as a cleaning gas. Compared with methane, it has the characteristics of low emission, high gas utilization rate, high reaction chamber cleaning rate and high equipment output rate. Electronic grade hexafluoroethane is a necessary medium for ultra-large-scale integrated circuits and plays an important role in the development of the semiconductor industry. Crude hexafluoroethane contains impurities such as nitrogen, oxygen, carbon tetrafluoride, carbon dioxide, trifluoromethane, difluoromethane, pentafluoromonochloroethane, pentafluoroethane, and difluoromonochloromethane, which need to be removed by certain technical means to meet the requirements of electronic grade hexafluoroethane.

[0003] CN1049295A discloses a catalytic decomposition method for chlorofluoroalkanes. At 350-650°C and in the presence of a catalyst containing Al2O3-SiO2, chlorofluoroalkanes are contacted with excess water vapor or air to react and convert the chlorofluoroalkanes into HF, HCl, CO2, CO and 1,1,1-trihaloacetyl halide. The decomposition capacity of this method is limited and decreases rapidly. The decomposition products need to be further removed, which is disadvantageous to the production process.

[0004] CN1165509A discloses a method for purifying hexafluoroethane products, which uses a two-stage azeotropic distillation method to purify hexafluoroethane. The first stage distillation removes impurities that do not azeotropize with hexafluoroethane, and HCl is separated by cooling the top component below -50°C, and then undergoes a second stage distillation and deacidification through a resin bed. Finally, the purity of the hexafluoroethane product is 99.9999%. However, this method will introduce HCl, causing equipment corrosion, and the operating temperature is low, which is dangerous. In addition, this method consumes a lot of energy.

[0005] Therefore, there are still many problems in the hexafluoroethane purification technology. There is no efficient and simple removal method for chlorofluoroalkane impurities with a boiling point close to that of hexafluoroethane, such as trifluoromethane. In addition, the problem of partial resource waste caused by direct removal of the impurity pentafluoromonochloroethane has not been solved. Therefore, it is very necessary to develop an electronic grade hexafluoroethane purification process. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a purification process for electronic-grade hexafluoroethane. By designing a pretreatment agent and an adsorbent, the purity of hexafluoroethane reaches 99.999%, and the removal of pentafluoromonochloroethane is achieved. The process is simple and the energy consumption is low. The present invention also provides a purification device corresponding to the purification process for electronic-grade hexafluoroethane. The device is reasonably designed and the energy consumption is effectively reduced.

[0007] The purification process of electronic grade hexafluoroethane of the present invention comprises the following steps:

[0008] A. The crude hexafluoroethane product is passed into a pretreatment device, and pretreated in the presence of a pretreatment agent to convert the impurity pentafluoromonochloroethane into hexafluoroethane. After the pretreatment, a sample is taken for testing. If the sample is qualified, the subsequent treatment is continued. If the sample is unqualified, the sample is returned to the pretreatment device for re-pretreatment until the sample is qualified.

[0009] B. The crude product treated by the pre-processor is passed into an adsorption tower filled with an adsorbent for adsorption to remove trifluoromethane. After the adsorption is completed, a sample is taken for testing. If it is qualified, it continues to be treated. If it is unqualified, it is returned to the adsorption tower for re-adsorption until it is qualified;

[0010] C. The crude product after adsorption is passed through a condenser to remove non-condensable gas to obtain a crude condensate, and the crude condensate is passed through an alkali washing tank for alkali washing to remove acidic impurities. After the alkali washing is completed, a sample is taken for testing. If it is qualified, the subsequent treatment is continued. If it is unqualified, it is returned to the alkali washing tank for re-alkali washing until it is qualified;

[0011] D. The crude product after alkali washing enters the degassing tower and the distillation tower in turn. After degassing and distillation, the electronic grade hexafluoroethane product is obtained. After passing the test, the product is passed into the product tank. If it fails, it returns to step A and is reprocessed until it passes.

[0012] In the step A, the qualified index is: the content of monochloropentafluoroethane is less than 2ppm;

[0013] In the step B, the qualified index is: trifluoromethane content <0.5ppm;

[0014] In the step C, the qualified index is: acidity <0.1ppm.

[0015] The indicators of the crude hexafluoroethane are: pentafluoromonochloroethane <80ppm, trifluoromethane <5ppm, carbon dioxide <6ppm, carbon monoxide <4ppm, hydrogen <20ppm, oxygen <230ppm, nitrogen <500ppm, and other fluorocarbon impurities <140ppm.

[0016] The electronic grade hexafluoroethane has the following indicators: hexafluoroethane ≥ 99.999%, carbon dioxide < 0.5 ppm, carbon monoxide < 0.5 ppm, hydrogen < 0.5 ppm, oxygen < 1 ppm, nitrogen < 5 ppm, total fluorocarbon impurities < 5 ppm, acidity < 0.1 ppm, and total impurity content ≤ 10 ppm;

[0017] The preparation steps of the pretreatment agent are as follows: placing activated alumina in an alkaline solution, soaking it at 40-60°C for 1-3h, and drying it at 70-100°C for 4-8h to obtain a crude pretreatment agent; introducing hydrogen fluoride gas into the crude pretreatment agent, heat treating it at 200-300°C for 4-8h, then placing it in a metal salt solution, soaking it at 60-80°C for 2-4h, and then washing, drying, and reducing and activating it to obtain the pretreatment agent.

[0018] The alkaline solution is prepared from one of ethanolamine, sodium hydroxide, sodium carbonate and potassium carbonate and water. The mass ratio of one of ethanolamine, sodium hydroxide, sodium carbonate and potassium carbonate to water is (0.5-1.5):100, and the mass ratio of activated alumina to the alkaline solution is (1-2):5.

[0019] The metal salt solution is a mixture of a Na2PdCl4 aqueous solution, a Na2PtCl6·6H2O aqueous solution, a Cu chloride solution or a nitrate solution, and a (NH4)2MoS4 aqueous solution. The mass ratio of one of the metal Pd and Pt ions and one of the metal Cu and Mo ions to water is (0.2-0.5):(5-8):100, and the mass ratio of the metal salt solution to the crude pretreatment agent is (1-3):100.

[0020] The preparation steps of the adsorbent are as follows: mixing one of allyl alcohol, 1,2,3,4-butanetetrol and pentapentol with water to prepare an organic solution; soaking activated carbon in the organic solution for 3-6 hours, then washing with deionized water and drying to obtain a crude adsorbent; adding the crude adsorbent into a 5wt.% hydrochloric acid aqueous solution for acidification, adding polysorbate 80, and finally washing with deionized water and drying to obtain the adsorbent.

[0021] The mass ratio of one of allyl alcohol, 1,2,3,4-butanetetrol, and pentapentol to water in the organic solution is (1-2):100, the mass ratio of activated carbon to the organic solution is (1-3):5; the mass ratio of 5wt.% hydrochloric acid aqueous solution, polysorbate 80 and the crude adsorbent is (20-40):(0.1-0.3):100.

[0022] The temperature of the pretreatment unit is 200-300°C; the temperature of the adsorption tower is -5-10°C, and the pressure is 0.2-0.4MPa.

[0023] The temperature of the condenser is -30~-45°C, and the pressure is 0.3-0.7MPa; the temperature of the alkali washing tank is 20-30°C, and the pressure is 0.1-0.3MPa.

[0024] The degassing tower has a bottom temperature of 18-25°C, a top temperature of 8-15°C, and a tower pressure of 2-3MPa; the distillation tower has a bottom temperature of 7-12°C, a top temperature of -2-5°C, and a tower pressure of 1.5-2.5MPa.

[0025] The purification device used in the purification process of electronic grade hexafluoroethane comprises a hexafluoroethane raw material tank, a pretreatment unit, an adsorption tower, a condenser, an alkali washing tank, a degassing tower, a distillation tower and a product tank, wherein the hexafluoroethane raw material tank is connected to a feed port at the bottom of the pretreatment unit; a discharge port at the top of the pretreatment unit is connected to a feed port at the adsorption tower; a discharge port at the adsorption tower is connected to an inlet of the condenser, and a discharge port at the bottom of the condenser is connected to an alkali washing tank; a discharge port at the bottom of the alkali washing tank is connected to a degassing tower, a discharge port at the degassing tower is connected to a feed port at the distillation tower, and a discharge port at the top of the distillation tower is connected to a product tank.

[0026] The top discharge port of the preprocessor is provided with a pipeline for reflux to the bottom feed port of the preprocessor tower, the top discharge port of the adsorption tower is provided with a pipeline for reflux to the bottom feed port of the adsorption tower, the bottom discharge port of the alkali washing tank is provided with a pipeline for reflux to the feed port of the alkali washing tank, and the top discharge port of the distillation tower is provided with a pipeline for reflux to the bottom feed port of the preprocessor tower.

[0027] The fillers in the degassing tower and the distillation tower are stainless steel Raschig rings or Theta rings.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The electronic grade hexafluoroethane purification process of the present invention can remove impurities in crude hexafluoroethane, so that the purity of hexafluoroethane is greater than 99.999%, meeting the requirements of electronic grade products.

[0030] (2) The electronic grade hexafluoroethane purification process of the present invention comprises a pretreatment agent modified with activated alumina, firstly soaked with ethanolamine or sodium hydroxide or sodium carbonate aqueous solution, all of which are alkaline. As the soaking time increases, some alkaline functional groups are introduced onto the surface of the activated alumina. After hydrogen fluoride gas is introduced, the hydrogen fluoride gas can be easily adsorbed on the surface of the pretreatment agent, providing fluoride ions for the conversion of pentafluoromonochloroethane into hexafluoroethane. In addition, the pretreatment agent is soaked with a metal salt solution and then reduced. The alloy structure formed provides catalytic active sites for the material conversion process, thereby improving the reaction efficiency of the pretreatment process. Since the content of pentafluoromonochloroethane in the crude hexafluoroethane is relatively low, the introduction of a large amount of hydrogen fluoride gas for reaction causes waste. The small amount of fluoride ions adsorbed on the pretreatment agent can meet the reaction requirements. The regeneration method is relatively simple and the energy consumption is low.

[0031] (3) The electronic grade hexafluoroethane purification process of the present invention is that the adsorbent is obtained by modifying activated carbon, introducing hydroxyl groups into the surface of the activated carbon, and then performing an acid treatment and a chlorination treatment process using polysorbate 80 as an emulsifier. In this process, the hydroxyl groups on the surface of the activated carbon react chemically with chloride ions to form chemical bonds, which significantly improves the adsorption performance of the activated carbon, thereby enhancing its adsorption capacity for fluorocarbon impurities. The chlorination treatment can also improve the surface properties of the activated carbon and increase its hydrophobicity, so that it performs better when treating trifluoromethane. For activated carbon, nonspecific interactions dominate the adsorption process, among which dispersion forces dominate. Compared with hexafluoroethane, the acidic groups introduced by the acid treatment will also enhance the dispersion effect between it and trifluoromethane, making the adsorbent more effective for trifluoromethane and easier to remove the impurity.

[0032] (4) The purification device used in the purification process of electronic grade hexafluoroethane of the present invention has a reasonable design, uses adsorption to remove impurities that are difficult to separate, uses condensation to remove oxygen and nitrogen, uses alkali washing to remove carbon dioxide, and then uses a distillation system to remove light components and heavy components. It is simple to operate, low in cost, environmentally friendly, and has low energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic diagram of the structure of a purification device used in the purification process of electronic grade hexafluoroethane of the present invention;

[0034] In the figure: 1. Hexafluoroethane raw material tank; 2. Pretreatment unit; 3. Adsorption tower; 4. Condenser; 5. Alkaline washing tank; 6. Degassing tower; 7. Distillation tower; 8. Product tank. DETAILED DESCRIPTION

[0035] The present invention is further described below in conjunction with specific examples and comparative examples, but the present invention is not limited to these specific embodiments. All raw materials used in the examples are commercially available unless otherwise specified. The impurity content of the crude hexafluoroethane used in the examples and comparative examples meets the indicators of the crude hexafluoroethane: pentafluoromonochloroethane <80ppm, trifluoromethane <5ppm, carbon dioxide <6ppm, carbon monoxide <4ppm, hydrogen <20ppm, oxygen <230ppm, nitrogen <500ppm, and other fluorocarbon impurities <140ppm.

[0036] like Figure 1 As shown, the purification device used in the purification process of electronic grade hexafluoroethane includes a hexafluoroethane raw material tank 1, a pretreatment device 2, an adsorption tower 3, a condenser 4, an alkali washing tank 5, a degassing tower 6, a distillation tower 7, and a product tank 8, wherein the hexafluoroethane raw material tank 1 is connected to the bottom feed port of the pretreatment device 2; the top discharge port of the pretreatment device 2 is connected to the feed port of the adsorption tower 3; the discharge port of the adsorption tower 3 is connected to the inlet of the condenser 4, and the bottom discharge port of the condenser 4 is connected to the alkali washing tank 5; the bottom discharge port of the alkali washing tank 5 is connected to the degassing tower 6, the discharge port of the degassing tower 6 is connected to the feed port of the distillation tower 7, and the top discharge port of the distillation tower 7 is connected to the product tank 8.

[0037] The top discharge port of the preprocessor 2 is provided with a pipeline for reflux to the bottom feed port of the preprocessor 2, the top discharge port of the adsorption tower 3 is provided with a pipeline for reflux to the bottom feed port of the adsorption tower 3, the bottom discharge port of the alkali washing tank 5 is provided with a pipeline for reflux to the feed port of the alkali washing tank 5, and the top discharge port of the distillation tower 7 is provided with a pipeline for reflux to the bottom feed port of the preprocessor 2.

[0038] The fillers in the degassing tower 6 and the distillation tower 7 are stainless steel Raschig rings or Theta rings.

[0039] The following examples and comparative examples were all completed using the above purification device.

[0040] The preparation steps of the pretreatment agent are as follows: mixing one of ethanolamine, sodium hydroxide, sodium carbonate and potassium carbonate with a mass ratio of (0.5-1.5):100 with water to prepare an alkaline solution; placing activated alumina in the alkaline solution, wherein the mass ratio of activated alumina to the alkaline solution is (1-2):5, soaking at 40-60°C for 1-3h, and drying at 70-100°C for 4-8h to obtain a crude pretreatment agent; introducing hydrogen fluoride gas into the crude pretreatment agent, heat treating at 200-300°C for 4-8h, wherein the mass ratio of hydrogen fluoride gas to the crude pretreatment agent is (15-25):1, and then placing it in a metal salt solution at 60-80°C. ℃ soak for 2-4h; after washing with deionized water, drying at 60℃ for 4h, treating in 10% H2 / N2 mixed gas at 400-800℃ for 4h to obtain a pretreatment agent; wherein the metal salt solution is a mixture of one of Na2PdCl4 aqueous solution and Na2PtCl6·6H2O aqueous solution and one of Cu chloride solution or nitrate solution and (NH4)2MoS4 aqueous solution, the mass ratio of one of metal Pd and Pt ions and one of metal Cu and Mo ions to water is (0.2-0.5):(5-8):100, and the mass ratio of the metal salt solution to the crude pretreatment agent is (1-3):100.

[0041] The preparation steps of the adsorbent are as follows: mixing one of allyl alcohol, 1,2,3,4-butanetetrol and pentapentol with water to prepare an organic solution; soaking activated carbon in the organic solution for 3-6 hours, then washing with deionized water and drying to obtain a crude adsorbent; adding the crude adsorbent to a 5wt.% hydrochloric acid aqueous solution for acidification, and adding polysorbate 80 as an emulsifier for chlorination treatment; finally, washing with deionized water and drying at 60°C for 4-6 hours to obtain the adsorbent; wherein the mass ratio of one of allyl alcohol, 1,2,3,4-butanetetrol and pentapentol to water in the organic solution is (1-2):100, the mass ratio of activated carbon to the organic solution is (1-3):5; the mass ratio of the 5wt.% hydrochloric acid aqueous solution, polysorbate 80 and the crude adsorbent is (20-40):(0.1-0.3):100.

[0042] The purification process of electronic grade hexafluoroethane comprises the following steps:

[0043] A. The crude hexafluoroethane product is passed into the pretreatment device 2, and pretreated in the presence of a pretreatment agent at a pretreatment temperature of 200-300°C to convert the impurity pentafluoromonochloroethane into hexafluoroethane. After the pretreatment, a sample is taken for testing. If it is qualified, the subsequent treatment is continued. If it is unqualified, it is returned to the pretreatment device 2 for re-pretreatment until it is qualified. The qualified index is: the content of pentafluoromonochloroethane is <2ppm;

[0044] B. The crude product treated by the pretreatment device 2 is passed into the adsorption tower 3 filled with adsorbent for adsorption, the adsorption temperature is -5-10 ° C, the adsorption pressure is 0.2-0.4 MPa, and trifluoromethane is removed. After the adsorption is completed, sampling is carried out for testing. If it is qualified, it continues to be processed. If it is unqualified, it returns to the adsorption tower 3 for re-adsorption until it is qualified. The qualified index is: trifluoromethane content <0.5ppm;

[0045] C. The crude product after adsorption is passed into the condenser 4, the condensation temperature is controlled to be -30~-45℃, the pressure is 0.3-0.7MPa, and the non-condensable gases such as oxygen and nitrogen are removed by condensation to obtain the crude product condensate, and the crude product condensate is passed into the alkali washing tank 5 for alkali washing, the alkali washing temperature is 20-30℃, the pressure is 0.1-0.3MPa, and the acidic impurities are removed. After the alkali washing is completed, a sample is taken for testing, and if it is qualified, the subsequent treatment is continued. If it is unqualified, it is returned to the alkali washing tank 5 for re-alkali washing until it is qualified. The qualified index is: acidity <0.1ppm;

[0046] D. The crude product after alkali washing enters degassing tower 6 and distillation tower 7 in turn. Degassing tower 6 removes impurities such as carbon tetrafluoride and methane, and distillation tower 7 removes impurities such as 1,1,1-trifluoroethane, pentafluoroethane, tetrafluoromonochloroethane, difluoromonochloromethane, etc. Finally, hexafluoroethane product can be obtained. After passing the test, the product is passed into product tank 8. If it is unqualified, it returns to step A for reprocessing. The bottom temperature of degassing tower 6 is 18-25°C, the top temperature is 8-15°C, and the tower pressure is 2-3MPa; the bottom temperature of distillation tower 7 is 7-12°C, the top temperature is -2-5°C, and the tower pressure is 1.5-2.5MPa; the fillers in degassing tower 6 and distillation tower 7 are stainless steel Raschig rings or Theta rings.

[0047] Example 1

[0048] The preparation steps of the pretreatment agent are as follows: adding sodium hydroxide to water to prepare an alkaline solution, wherein the mass ratio of sodium hydroxide to water is 0.5:100; placing activated alumina in the alkaline solution, wherein the mass ratio of activated alumina to the alkaline solution is 1.5:5, soaking at 50°C for 2h, and drying at 70°C for 8h to obtain a crude pretreatment agent; introducing hydrogen fluoride gas into the crude pretreatment agent, heat treating at 200°C for 6h, wherein the mass ratio of hydrogen fluoride gas to the crude pretreatment agent is 25:1, and then Place it in a metal salt solution of Pd and Cu (the mass ratio of Pd ions to Cu ions to water is 0.2:8:100, the Pd metal salt solution is a Na2PdCl4 aqueous solution, and the Cu salt solution is a CuCl2 aqueous solution), soak it at 60°C for 2 hours, and the mass ratio of the metal salt solution to the crude pretreatment agent after treatment with hydrogen fluoride is 3:100; after washing with deionized water, dry it at 60°C for 4 hours, and treat it at 500°C in a 10% H2 / N2 mixed gas for 4 hours to obtain a pretreatment agent.

[0049] The preparation steps of the adsorbent are as follows: allyl alcohol and water are mixed to prepare an organic solution, wherein the mass ratio of allyl alcohol to water is 2:100; activated carbon is immersed in the organic solution for 4 hours, then washed with deionized water and dried to obtain a crude adsorbent, wherein the mass ratio of activated carbon to the organic solution is 1:5; the crude adsorbent is added to a 5wt.% hydrochloric acid aqueous solution for acidification, and polysorbate 80 is added as an emulsifier for chlorination treatment, wherein the mass ratio of the 5wt.% hydrochloric acid aqueous solution, polysorbate 80 and the adsorbent is 20:0.2:100; finally, washed with deionized water, and dried at 60°C for 4 hours to obtain the adsorbent.

[0050] The purification process of electronic grade hexafluoroethane comprises the following steps:

[0051] A. The crude hexafluoroethane product is passed into the pretreatment device 2, and pretreated in the presence of a pretreatment agent at a pretreatment temperature of 200° C. The impurity pentafluoromonochloroethane is converted into hexafluoroethane. After the pretreatment, a sample is taken for testing. The content of pentafluoromonochloroethane is 0.16ppm<2ppm, which meets the index requirements, and the subsequent treatment is continued;

[0052] B. The crude product treated by the pre-processor 2 is passed into the adsorption tower 3 filled with adsorbent for adsorption at a temperature of -5°C and a pressure of 0.4MPa to remove trifluoromethane. After the adsorption is completed, a sample is taken for detection. The trifluoromethane content is 0.02ppm<0.5ppm, which meets the index requirements, and the subsequent treatment is continued;

[0053] C. The crude product after adsorption is passed into the condenser 4, the condensation temperature is controlled to be -30°C, the pressure is 0.7MPa, and the non-condensable gases such as oxygen and nitrogen are removed by condensation to obtain the crude product condensate, and the crude product condensate is passed into the alkali washing tank 5 for alkali washing, the alkali washing temperature is 20°C, the pressure is 0.2MPa, and the acidic impurities are removed. After the alkali washing is completed, the sample is taken for detection, and the acidity is 0.13ppm>0.1ppm, and the alkali washing is repeated. After the second alkali washing, the acidity is 0.008ppm<0.1ppm, and the subsequent treatment is continued;

[0054] D. The crude product after alkali washing enters degassing tower 6 and distillation tower 7 in turn. Degassing tower 6 removes impurities such as carbon tetrafluoride and methane, and distillation tower 7 removes impurities such as 1,1,1-trifluoroethane, pentafluoroethane, tetrafluoromonochloroethane, difluoromonochloromethane, etc. Finally, hexafluoroethane product with purity > 99.999% is obtained and placed in product tank 8. The bottom temperature of degassing tower 6 is 18°C, the top temperature is 8°C, and the tower pressure is 2MPa; the bottom temperature of distillation tower 7 is 7°C, the top temperature is -2°C, and the tower pressure is 1.5MPa; the fillers in degassing tower 6 and distillation tower 7 are stainless steel hexafluoroethane rings.

[0055] Example 2

[0056] The preparation steps of the pretreatment agent are as follows: adding ethanolamine to water to prepare an alkaline solution, wherein the mass ratio of ethanolamine to water is 1.5:100; placing activated alumina in the alkaline solution, wherein the mass ratio of activated alumina to the alkaline solution is 1:5, soaking at 40°C for 3h, and drying at 80°C for 5h to obtain a crude pretreatment agent; introducing hydrogen fluoride gas into the crude pretreatment agent, heat treating at 300°C for 4h, wherein the mass ratio of hydrogen fluoride gas to the crude pretreatment agent is 15:1, and then placing the crude pretreatment agent in a The pretreatment agent was prepared by soaking in a metal salt solution of Pd and Mo (the mass ratio of Pd ions to Mo ions to water was 0.2:6:100, the Pd metal salt solution was a Na2PdCl4 aqueous solution, and the Mo salt solution was a (NH4)2MoS4 aqueous solution) at 60°C for 3 hours. The mass ratio of the crude pretreatment agent after treatment with metal salt solution and hydrogen fluoride was 1:100. After washing with deionized water, the pretreatment agent was dried at 60°C for 4 hours and treated at 500°C in a 10% H2 / N2 mixed gas for 4 hours to obtain the pretreatment agent.

[0057] The preparation steps of the adsorbent are as follows: 1,2,3,4-butanetetrol and water are mixed to prepare an organic solution, wherein the mass ratio of 1,2,3,4-butanetetrol to water is 2:100; activated carbon is immersed in the organic solution for 4 hours, then washed with deionized water and dried to obtain a crude adsorbent, wherein the mass ratio of activated carbon to the organic solution is 2:5; the crude adsorbent is added into a 5wt.% hydrochloric acid aqueous solution for acidification, and polysorbate 80 is added as an emulsifier for chlorination treatment, wherein the mass ratio of the 5wt.% hydrochloric acid aqueous solution, polysorbate 80 and the adsorbent is 20:0.1:100; finally, washed with deionized water, and dried at 60°C for 4 hours to obtain the adsorbent.

[0058] The purification process of electronic grade hexafluoroethane comprises the following steps:

[0059] A. The crude hexafluoroethane product is passed into the pretreatment device 2, and pretreated in the presence of a pretreatment agent at a pretreatment temperature of 250° C. The impurity pentafluoromonochloroethane is converted into hexafluoroethane. After the pretreatment, a sample is taken for testing. The content of pentafluoromonochloroethane is 0.22ppm<2ppm, which meets the index requirements, and the subsequent treatment is continued;

[0060] B. The crude product treated by the pretreatment device 2 is passed into the adsorption tower 3 filled with adsorbent for adsorption at a temperature of -5°C and a pressure of 0.4MPa to remove trifluoromethane. After the adsorption is completed, a sample is taken for detection. The trifluoromethane content is 0.03ppm<0.5ppm, which meets the index requirements, and the subsequent treatment is continued;

[0061] C. The crude product after adsorption is passed into the condenser 4, the condensation temperature is controlled to be -40°C, the pressure is controlled to be 0.45MPa, and the non-condensable gases such as oxygen and nitrogen are removed by condensation to obtain the crude product condensate, and the crude product condensate is passed into the alkali washing tank 5 for alkali washing, the alkali washing temperature is 25°C, the pressure is 0.2MPa, and the acidic impurities are removed. After the alkali washing is completed, the sample is taken for testing, and the acidity is 0.005ppm<0.1ppm, which meets the index requirements, and the subsequent treatment is continued;

[0062] D. The crude product after alkali washing enters degassing tower 6 and distillation tower 7 in turn. Degassing tower 6 removes impurities such as carbon tetrafluoride and methane, and distillation tower 7 removes impurities such as 1,1,1-trifluoroethane, pentafluoroethane, tetrafluoromonochloroethane, difluoromonochloromethane, etc. Finally, hexafluoroethane product with purity > 99.999% is obtained and placed in product tank 8. The bottom temperature of degassing tower 6 is 20°C, the top temperature is 11°C, and the tower pressure is 2.3MPa; the bottom temperature of distillation tower 7 is 10°C, the top temperature is 3°C, and the tower pressure is 1.9MPa; the fillers in degassing tower 6 and distillation tower 7 are stainless steel Raschig rings.

[0063] Example 3

[0064] The preparation steps of the pretreatment agent are as follows: adding potassium carbonate to water to prepare an alkaline solution, wherein the mass ratio of potassium carbonate to water is 1:100; placing activated alumina in the alkaline solution, wherein the mass ratio of activated alumina to the alkaline solution is 2:5, soaking at 60°C for 1 hour, and drying at 100°C for 4 hours to obtain a crude pretreatment agent; introducing hydrogen fluoride gas into the crude pretreatment agent, heat treating at 250°C for 8 hours, wherein the mass ratio of hydrogen fluoride gas to the crude pretreatment agent is 20:1, and then placing the crude pretreatment agent in a The pretreatment agent was immersed in a metal salt solution of Pt and Cu (the mass ratio of Pt ion, Cu ion and water was 0.4:5:100, the Pt metal salt solution was a Na2PtCl6·6H2O aqueous solution, and the Cu salt solution was a CuCl2 aqueous solution) at 80°C for 4 hours, and the mass ratio of the metal salt solution to the crude pretreatment agent after treatment with hydrogen fluoride was 2:100; after washing with deionized water, it was dried at 60°C for 4 hours, and treated at 800°C in a 10% H2 / N2 mixed gas for 4 hours to obtain the pretreatment agent.

[0065] The preparation steps of the adsorbent are as follows: mixing pentapentol and water to prepare an organic solution, wherein the mass ratio of pentapentol to water is 1:100; soaking activated carbon in the organic solution for 6 hours, then washing with deionized water and drying to obtain a crude adsorbent, wherein the mass ratio of activated carbon to the organic solution is 3:5; adding the crude adsorbent to a 5wt.% hydrochloric acid aqueous solution for acidification, and adding polysorbate 80 as an emulsifier for chlorination treatment, wherein the mass ratio of the 5wt.% hydrochloric acid aqueous solution, polysorbate 80 and the adsorbent is 40:0.3:100; finally, washing with deionized water, and drying at 60°C for 5 hours to obtain the adsorbent.

[0066] The purification process of electronic grade hexafluoroethane comprises the following steps:

[0067] A. The crude hexafluoroethane product is passed into the pretreatment device 2, and pretreated in the presence of a pretreatment agent at a pretreatment temperature of 300° C. The impurity pentafluoromonochloroethane is converted into hexafluoroethane. After the pretreatment, a sample is taken for testing. The content of pentafluoromonochloroethane is 0.13ppm<2ppm, which meets the index requirements, and the subsequent treatment is continued;

[0068] B. The crude product treated by the pretreatment device 2 is passed into the adsorption tower 3 filled with adsorbent for adsorption at an adsorption temperature of 10° C. and an adsorption pressure of 0.2 MPa to remove trifluoromethane. After the adsorption is completed, a sample is taken for detection. The trifluoromethane content is 0.03ppm<0.5ppm, which meets the index requirements, and the subsequent treatment is continued;

[0069] C. The crude product after adsorption is passed into the condenser 4, the condensation temperature is controlled to be -45°C, the pressure is controlled to be 0.3MPa, and the non-condensable gases such as oxygen and nitrogen are removed by condensation to obtain the crude product condensate, and the crude product condensate is passed into the alkali washing tank 5 for alkali washing, the alkali washing temperature is 30°C, the pressure is 0.3MPa, and the acidic impurities are removed. After the alkali washing is completed, the sample is taken for testing, and the acidity is 0.004ppm<0.1ppm, which meets the index requirements, and the subsequent treatment is continued;

[0070] D. The crude product after alkali washing enters degassing tower 6 and distillation tower 7 in turn. Degassing tower 6 removes impurities such as carbon tetrafluoride and methane, and distillation tower 7 removes impurities such as 1,1,1-trifluoroethane, pentafluoroethane, tetrafluoromonochloroethane, and difluoromonochloromethane. Finally, hexafluoroethane product with a purity of >99.999% is obtained and placed in product tank 8. The bottom temperature of degassing tower 6 is 25°C, the top temperature is 15°C, and the tower pressure is 3MPa; the bottom temperature of distillation tower 7 is 12°C, the top temperature is 5°C, and the tower pressure is 2.5MPa; the fillers in degassing tower 6 and distillation tower 7 are stainless steel hexafluoroethane rings.

[0071] Example 4

[0072] The preparation steps of the pretreatment agent are as follows: adding sodium carbonate to water to prepare an alkaline solution, wherein the mass ratio of sodium carbonate to water is 1:100; placing activated alumina in the alkaline solution, wherein the mass ratio of activated alumina to the alkaline solution is 1:5, soaking at 60°C for 1 hour, and drying at 80°C for 6 hours to obtain a crude pretreatment agent; introducing hydrogen fluoride gas into the crude pretreatment agent, heat treating at 200°C for 6 hours, wherein the mass ratio of hydrogen fluoride gas to the crude pretreatment agent is 25:1, and then placing the crude pretreatment agent on a Pt and The pretreatment agent was prepared by soaking the pretreatment agent in a metal salt solution of Mo (the mass ratio of Pt ion, Mo ion and water was 0.5:6:100, the Pt metal salt solution was a Na2PtCl6·6H2O aqueous solution, and the Mo salt solution was a (NH4)2MoS4 aqueous solution) at 70°C for 3 hours. The mass ratio of the crude pretreatment agent after treatment with metal salt solution and hydrogen fluoride was 3:100. After washing with deionized water, the pretreatment agent was dried at 60°C for 4 hours and treated at 400°C in a 10% H2 / N2 mixed gas for 4 hours to obtain the pretreatment agent.

[0073] The preparation steps of the adsorbent are as follows: allyl alcohol and water are mixed to prepare an organic solution, wherein the mass ratio of allyl alcohol to water is 1.5:100; activated carbon is immersed in the organic solution for 3 hours, then washed with deionized water and dried to obtain a crude adsorbent, wherein the mass ratio of activated carbon to the organic solution is 1:5; the crude adsorbent is added to a 5wt.% hydrochloric acid aqueous solution for acidification, and polysorbate 80 is added as an emulsifier for chlorination treatment, wherein the mass ratio of the 5wt.% hydrochloric acid aqueous solution, polysorbate 80 and the adsorbent is 30:0.1:100; finally, washed with deionized water, and dried at 60°C for 4 hours to obtain the adsorbent.

[0074] The purification process of electronic grade hexafluoroethane comprises the following steps:

[0075] A. The crude hexafluoroethane product is passed into the pretreatment device 2, and pretreated in the presence of a pretreatment agent at a pretreatment temperature of 200° C. The impurity pentafluoromonochloroethane is converted into hexafluoroethane. After the pretreatment, a sample is taken for testing. The content of pentafluoromonochloroethane is 0.10ppm<2ppm, which meets the index requirements, and the subsequent treatment is continued;

[0076] B. The crude product treated by the pretreatment device 2 is passed into the adsorption tower 3 filled with adsorbent for adsorption at an adsorption temperature of 5° C. and an adsorption pressure of 0.3 MPa to remove trifluoromethane. After the adsorption is completed, a sample is taken for detection. The trifluoromethane content is 0.02ppm<0.5ppm, which meets the index requirements, and the subsequent treatment is continued;

[0077] C. The crude product after adsorption is passed into the condenser 4, the condensation temperature is controlled to be -45°C, the pressure is controlled to be 0.3MPa, and the non-condensable gases such as oxygen and nitrogen are removed by condensation to obtain the crude product condensate, and the crude product condensate is passed into the alkali washing tank 5 for alkali washing, the alkali washing temperature is 25°C, the pressure is 0.2MPa, and the acidic impurities are removed. After the alkali washing is completed, the sample is taken for testing, and the acidity is 0.006ppm<0.1ppm, which meets the index requirements, and the subsequent treatment is continued;

[0078] D. The crude product after alkali washing enters degassing tower 6 and distillation tower 7 in turn. Degassing tower 6 removes impurities such as carbon tetrafluoride and methane, and distillation tower 7 removes impurities such as 1,1,1-trifluoroethane, pentafluoroethane, tetrafluoromonochloroethane, difluoromonochloromethane, etc. Finally, hexafluoroethane product with purity > 99.999% is obtained and placed in product tank 8. The bottom temperature of degassing tower 6 is 18°C, the top temperature is 8°C, and the tower pressure is 2MPa; the bottom temperature of distillation tower 7 is 7°C, the top temperature is -2°C, and the tower pressure is 1.5MPa; the fillers in degassing tower 6 and distillation tower 7 are stainless steel Raschig rings.

[0079] Example 5

[0080] The preparation steps of the pretreatment agent are as follows: adding sodium hydroxide to water to prepare an alkaline solution, wherein the mass ratio of sodium hydroxide to water is 1:100; placing activated alumina in the alkaline solution, wherein the mass ratio of activated alumina to the alkaline solution is 1:5, soaking at 60°C for 2h, and drying at 70°C for 6h to obtain a crude pretreatment agent; introducing hydrogen fluoride gas into the crude pretreatment agent, heat treating at 300°C for 4h, wherein the mass ratio of hydrogen fluoride gas to the crude pretreatment agent is 25:1, and then placing it in a P The pretreatment agent was prepared by mixing the pretreatment agent with a metal salt solution of Pt and Cu (the mass ratio of Pt ion, Cu ion and water was 0.2:8:100, the Pt metal salt solution was a Na2PtCl6·6H2O aqueous solution, and the Cu salt solution was a Cu(NO3)2 aqueous solution), and the pretreatment agent was immersed at 70°C for 3 hours. The mass ratio of the metal salt solution to the crude pretreatment agent after treatment with hydrogen fluoride was 3:100. The pretreatment agent was washed with deionized water and dried at 60°C for 4 hours, and treated at 400°C in a 10% H2 / N2 mixed gas for 4 hours to obtain the pretreatment agent.

[0081] The preparation steps of the adsorbent are as follows: allyl alcohol and water are mixed to prepare an organic solution, wherein the mass ratio of allyl alcohol to water is 2:100; activated carbon is immersed in the organic solution for 3 hours, then washed with deionized water and dried to obtain a crude adsorbent, wherein the mass ratio of activated carbon to the organic solution is 1:5; the crude adsorbent is added to a 5wt.% hydrochloric acid aqueous solution for acidification, and polysorbate 80 is added as an emulsifier for chlorination treatment, wherein the mass ratio of the 5wt.% hydrochloric acid aqueous solution, polysorbate 80 and the adsorbent is 30:0.1:100; finally, washed with deionized water, and dried at 60°C for 6 hours to obtain the adsorbent.

[0082] The purification process of electronic grade hexafluoroethane comprises the following steps:

[0083] A. The crude hexafluoroethane product is passed into the pretreatment device 2, and pretreated in the presence of a pretreatment agent at a pretreatment temperature of 200° C. The impurity pentafluoromonochloroethane is converted into hexafluoroethane. After the pretreatment, a sample is taken for testing. The content of pentafluoromonochloroethane is 0.14ppm<2ppm, which meets the index requirements, and the subsequent treatment is continued;

[0084] B. The crude product treated by the pretreatment device 2 is passed into the adsorption tower 3 filled with adsorbent for adsorption at a temperature of -5°C and a pressure of 0.2MPa to remove trifluoromethane. After the adsorption is completed, a sample is taken for detection. The trifluoromethane content is 0.02ppm<0.5ppm, which meets the index requirements, and the subsequent treatment is continued;

[0085] C. The crude product after adsorption is passed into the condenser 4, the condensation temperature is controlled to be -40°C, the pressure is controlled to be 0.45MPa, and the non-condensable gases such as oxygen and nitrogen are removed by condensation to obtain the crude product condensate, and the crude product condensate is passed into the alkali washing tank 5 for alkali washing, the alkali washing temperature is 25°C, the pressure is 0.1MPa, and the acidic impurities are removed. After the alkali washing is completed, the sample is taken for testing, and the acidity is 0.005ppm<0.1ppm, which meets the index requirements, and the subsequent treatment is continued;

[0086] D. The crude product after alkali washing enters degassing tower 6 and distillation tower 7 in turn. Degassing tower 6 removes impurities such as carbon tetrafluoride and methane, and distillation tower 7 removes impurities such as 1,1,1-trifluoroethane, pentafluoroethane, tetrafluoromonochloroethane, difluoromonochloromethane, etc. Finally, hexafluoroethane product with purity > 99.999% is obtained and placed in product tank 8. The bottom temperature of degassing tower 6 is 18°C, the top temperature is 8°C, and the tower pressure is 2MPa; the bottom temperature of distillation tower 7 is 7°C, the top temperature is -2°C, and the tower pressure is 1.5MPa; the fillers in degassing tower 6 and distillation tower 7 are stainless steel hexafluoroethane rings.

[0087] Comparative Example 1

[0088] This comparative example is the same as Example 1, except that the preparation process of the pretreatment agent is different. The pretreatment agent is not treated with an alkaline solution, and subsequent steps such as hydrogen fluoride treatment are directly performed. The remaining steps are the same as Example 1.

[0089] Comparative Example 2

[0090] This comparative example is the same as Example 1, except that the preparation process of the pretreatment agent is different. After the activated alumina is soaked in alkali solution to obtain a crude pretreatment agent, it does not need to be treated with hydrogen fluoride, and the metal salt solution soaking step is directly performed. The remaining steps are the same as Example 1.

[0091] Comparative Example 3

[0092] This comparative example is the same as Example 1, except that the preparation process of the pretreatment agent is different. After the crude pretreatment agent is heat-treated with hydrogen fluoride, it does not need to be immersed in a metal salt solution, and the reduction activation step is directly performed. The remaining steps are the same as Example 1.

[0093] Comparative Example 4

[0094] This comparative example is the same as Example 1, except that this comparative example directly uses activated alumina without any treatment as a pretreatment agent, and the remaining steps are the same as Example 1.

[0095] Comparative Example 5

[0096] This comparative example is the same as Example 1, except that, during the preparation of the pretreatment agent, only Na2PdCl4 aqueous solution is used as the metal salt solution for the metal salt solution immersion treatment, and the remaining steps are the same as Example 1.

[0097] Comparative Example 6

[0098] This comparative example is the same as Example 1, except that the adsorbent preparation process is different, the activated carbon does not need to be soaked in an organic solution, and is directly subjected to acidification treatment, and the remaining steps are the same as Example 1.

[0099] Comparative Example 7

[0100] This comparative example is the same as Example 1, except that the adsorbent preparation process is different. In the preparation process, there is no chlorination process of polysorbate 80 as an emulsifier, and the remaining steps are the same as Example 1.

[0101] Comparative Example 8

[0102] This comparative example is the same as Example 1, except that the adsorbent preparation process is different, there is no hydrochloric acid acidification process in the preparation process, and the remaining steps are the same as Example 1.

[0103] Comparative Example 9

[0104] This comparative example is the same as Example 1, except that the adsorbent preparation process is different. During the preparation process, 5 wt.% nitric acid of the same mass is used instead of 5 wt.% hydrochloric acid for acidification treatment, and the remaining steps are the same as Example 1.

[0105] Comparative Example 10

[0106] This comparative example is the same as Example 1, except that this comparative example directly uses activated carbon without any treatment as the adsorbent, and the remaining steps are the same as Example 1.

[0107] The electronic grade hexafluoroethane products obtained in Examples 1-5 and Comparative Examples 1-10 were subjected to gas chromatography to detect the content of each substance. The results are shown in Table 1, wherein the data for pentafluorochloroethane and trifluoromethane are the detection results of the gases after being treated in the pretreatment unit and the adsorption tower for the same time. The acidity detection results of all Examples and Comparative Examples were <0.1ppm.

[0108] Table 1 Content of each substance in the products obtained in Examples 1-5 and Comparative Examples 1-10 (unit: ppm)

[0109]

[0110] As can be seen from Table 1, the total impurity content in Examples 1-5 is <10ppm, and all indicators meet the index requirements of electronic grade hexafluoroethane. Compared with Example 1, Example 1 is not treated with an alkaline solution, and the content of pentafluoromonochloroethane is significantly increased. This is because as the immersion time in the alkaline solution increases, some alkaline functional groups are introduced to the surface of the activated alumina. After the introduction of hydrogen fluoride gas, the hydrogen fluoride gas can be easily adsorbed on the surface of the pretreatment agent. Without alkaline solution treatment, the amount of adsorbed hydrogen fluoride gas is less. Compared with Example 1, Example 2 is not treated with hydrogen fluoride, and fluoride ions cannot be provided for the conversion of pentafluoromonochloroethane into hexafluoroethane, so the content of pentafluoromonochloroethane is relatively high. Compared with Example 1, Example 3 is not treated with a metal salt solution, and there is no alloy structure. In Example 1, the alloy structure formed by the pretreatment agent can provide catalytic active sites for the conversion of pentafluoromonochloroethane into hexafluoroethane, thereby improving the reaction efficiency of the pretreatment process. Compared with Example 1, in Comparative Example 4, the pretreatment agent is activated alumina, which has basically no effect on the process. Compared with Example 1, in Comparative Example 5, the pretreatment agent is treated with only one metal salt solution, which has a certain pretreatment effect compared with other comparative examples, but is poorer than the examples, because in the substance conversion process, the catalytic effect of the single metal site is far lower than that of the metal alloy site.

[0111] Compared with Example 1, the adsorbent of Comparative Example 6 was not treated with an alcohol solution. The result of not being treated with an alcohol solution was that the adsorption of chloride ions on the activated carbon was physical adsorption, and the adsorption amount was small, which could not improve the adsorption performance of the activated carbon and enhance its adsorption capacity for fluorocarbon impurities. Compared with Example 1, the adsorbent of Comparative Example 7 was not treated with polysorbate 80, resulting in incomplete contact between alcohol and hydrogen chloride, and less chemical reaction between hydroxyl and chloride ions, which affected the adsorption performance of the activated carbon. Compared with Example 1, the adsorbent of Comparative Example 8 was not treated with an aqueous hydrochloric acid solution, and could not be acidified and provide chloride ions. Acidification would enhance the dispersion effect between it and trifluoromethane, making the adsorbent more strongly adsorbent to trifluoromethane. Compared with Example 1, the adsorbent of Comparative Example 9 was treated with nitric acid instead of hydrochloric acid, and could not be chlorinated. Chlorination can improve the surface properties of activated carbon, increase its hydrophobicity, and make it perform better when treating trifluoromethane. Compared with Example 1, in Comparative Example 10, the adsorbent is activated carbon, which has basically no effect on the process without any treatment.

[0112] In summary, the purification process of electronic-grade hexafluoroethane of the present invention can remove impurities in crude hexafluoroethane, so that the purity of hexafluoroethane is greater than 99.999%, meeting the requirements of electronic-grade products; and the device is reasonably designed, easy to operate, low in cost, environmentally friendly, and low in energy consumption.

Claims

1. A purification process for electronic grade hexafluoroethane, characterized in that: The following steps are involved: A. The crude hexafluoroethane product is passed into a pretreatment device, and pretreated in the presence of a pretreatment agent to convert the impurity pentafluoromonochloroethane into hexafluoroethane. After the pretreatment, a sample is taken for testing. If the sample is qualified, the subsequent treatment is continued. If the sample is unqualified, the sample is returned to the pretreatment device for re-pretreatment until the sample is qualified. B. The crude product treated by the pre-processor is passed into an adsorption tower filled with an adsorbent for adsorption to remove trifluoromethane. After the adsorption is completed, a sample is taken for testing. If it is qualified, it continues to be treated. If it is unqualified, it is returned to the adsorption tower for re-adsorption until it is qualified; C. The crude product after adsorption is passed through a condenser to remove non-condensable gas to obtain a crude condensate, and the crude condensate is passed through an alkali washing tank for alkali washing to remove acidic impurities. After the alkali washing is completed, a sample is taken for testing. If it is qualified, the subsequent treatment is continued. If it is unqualified, it is returned to the alkali washing tank for re-alkali washing until it is qualified; D. The crude product after alkali washing enters the degassing tower and the distillation tower in turn, and the electronic grade hexafluoroethane product is obtained after degassing and distillation. After the product is qualified, it is passed into the product tank. If it is unqualified, it returns to step A and is reprocessed until it is qualified; In the step A, the qualified index is: the content of monochloropentafluoroethane is less than 2ppm; In the step B, the qualified index is: trifluoromethane content <0.5ppm; In the step C, the qualified index is: acidity <0.1ppm; The electronic grade hexafluoroethane has the following indicators: hexafluoroethane ≥ 99.999%, carbon dioxide < 0.5 ppm, carbon monoxide < 0.5 ppm, hydrogen < 0.5 ppm, oxygen < 1 ppm, nitrogen < 5 ppm, total fluorocarbon impurities < 5 ppm, acidity < 0.1 ppm, and total impurity content ≤ 10 ppm; The preparation steps of the pretreatment agent are as follows: placing activated alumina in an alkaline solution, soaking it at 40-60°C for 1-3h, and drying it at 70-100°C for 4-8h to obtain a crude pretreatment agent; introducing hydrogen fluoride gas into the crude pretreatment agent, heat treating it at 200-300°C for 4-8h, then placing it in a metal salt solution, soaking it at 60-80°C for 2-4h, and then washing, drying, and reducing and activating it to obtain a pretreatment agent; The metal salt solution is a mixture of one of a Na2PdCl4 aqueous solution and a Na2PtCl6·6H2O aqueous solution and one of a Cu chloride solution or a nitrate solution and a (NH4)2MoS4 aqueous solution, wherein the mass ratio of one of the metal Pd and Pt ions and one of the metal Cu and Mo ions to water is (0.2-0.5):(5-8):100, and the mass ratio of the metal salt solution to the crude pretreatment agent is (1-3):100; The preparation steps of the adsorbent are as follows: mixing one of allyl alcohol, 1,2,3,4-butanetetrol and pentapentol with water to prepare an organic solution; soaking activated carbon in the organic solution for 3-6 hours, then washing with deionized water and drying to obtain a crude adsorbent; adding the crude adsorbent into a 5wt.% hydrochloric acid aqueous solution for acidification, adding polysorbate 80, and finally washing with deionized water and drying to obtain the adsorbent.

2. The purification process of electronic grade hexafluoroethane according to claim 1, characterized in that: The alkaline solution is prepared from one of ethanolamine, sodium hydroxide, sodium carbonate and potassium carbonate and water, and the mass ratio of one of ethanolamine, sodium hydroxide, sodium carbonate and potassium carbonate to water is (0.5-1.5):100; the mass ratio of activated alumina to the alkaline solution is (1-2):

5.

3. The purification process of electronic grade hexafluoroethane according to claim 1, characterized in that: The mass ratio of one of allyl alcohol, 1,2,3,4-butanetetrol, and pentapentol to water in the organic solution is (1-2):100, the mass ratio of activated carbon to the organic solution is (1-3):5; the mass ratio of 5wt.% hydrochloric acid aqueous solution, polysorbate 80 and the crude adsorbent is (20-40):(0.1-0.3):

100.

4. The purification process of electronic grade hexafluoroethane according to claim 1, characterized in that: The temperature of the pretreatment unit is 200-300°C; the temperature of the adsorption tower is -5-10°C, and the pressure is 0.2-0.4MPa.

5. The purification process of electronic grade hexafluoroethane according to claim 1, characterized in that: The temperature of the condenser is -30~-45°C, and the pressure is 0.3-0.7MPa; the temperature of the alkali washing tank is 20-30°C, and the pressure is 0.1-0.3MPa.

6. The purification process of electronic grade hexafluoroethane according to claim 1, characterized in that: The degassing tower has a bottom temperature of 18-25°C, a top temperature of 8-15°C, and a tower pressure of 2-3MPa; the distillation tower has a bottom temperature of 7-12°C, a top temperature of -2-5°C, and a tower pressure of 1.5-2.5MPa.

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