Method for recycling iodine in preparation of tetrachlorohexafluorobutane
By reacting refined iodine with trifluorochloroethylene to produce trifluorodichloroiodoethane, and combining aqueous phase oxidation, organic phase distillation, and catalytic chlorination, the problem of low iodine recovery rate in the preparation of tetrachlorohexafluorobutane was solved, achieving efficient iodine recovery and improved process economy.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- PERIC SPECIAL GASES CO LTD
- Filing Date
- 2024-12-02
- Publication Date
- 2026-05-19
AI Technical Summary
In the existing technology, the iodine recovery rate in the preparation of tetrachlorohexafluorobutane is low, resulting in insufficient economic efficiency. Furthermore, the iodine in zinc iodide is difficult to recover efficiently, which affects the economic efficiency of the process.
The process involves reacting refined iodine with trifluorochloroethylene to produce trifluorodichloroiodoethane, followed by aqueous phase oxidation, filtration, and purification to obtain refined iodine. This is then combined with organic phase distillation and iodide catalytic chlorination to achieve efficient iodine recovery.
It significantly improved the iodine recovery rate, enhanced the overall economics of the process, reduced waste generation, and lowered investment in raw materials and equipment.
Smart Images
Figure CN119569528B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of chemical technology, specifically to a method for iodine recovery and reuse in the preparation process of tetrachlorohexafluorobutane. Background Technology
[0002] Tetrachlorohexafluorobutane (THB) is an important chemical raw material used to produce the high-performance etching gas hexafluorobutadiene. The main industrial route for preparing THB involves the dehalogenation of trifluorochloroethylene after reacting with interhalogenated compounds. One important route is the iodine chloride route. This process has mild reaction conditions and high yields, making it a very promising route. However, this reaction consumes iodine to generate zinc iodide. Due to the high cost of iodine, the economic viability of this route is significantly reduced if a high iodine recovery rate (>95%) cannot be achieved. Current processes primarily recover iodine from zinc iodide, but a small amount of byproducts, including iodine and organic iodides, enter the organic phase of THB (approximately 3%–10% of the raw material iodine content). Therefore, the original process struggles to achieve its economic goals. Summary of the Invention
[0003] This invention provides a method for iodine recovery and reuse in the preparation process of tetrachlorohexafluorobutane. This method is fast, environmentally friendly, and has a high iodine recovery rate, making it suitable for large-scale industrial production.
[0004] The technical solution adopted in this invention is:
[0005] A method for iodine recovery and reuse in the preparation process of tetrachlorohexafluorobutane includes the following steps:
[0006] S1. Trifluorodichloroiodoethane was prepared from refined iodine and trifluorochloroethylene as raw materials, and tetrachlorohexafluorobutane was prepared from trifluorodichloroiodoethane as raw material.
[0007] S2, the reaction solution of tetrachlorohexafluorobutane is diluted with water, the aqueous phase is oxidized, filtered and purified to obtain purified iodine, and the organic phase is distilled to obtain purified tetrachlorohexafluorobutane, organic solvent containing iodine and zinc iodide and organic iodides.
[0008] S3. The iodine-containing organic solvent and zinc iodide are washed with an absorbent to obtain an aqueous solution of iodide ions, which is then oxidized, filtered, and purified to obtain refined iodine.
[0009] The organic iodide is catalytically chlorinated to obtain iodine chloride, which is used to prepare trifluorodichloroiodoethane.
[0010] Preferably, the preparation process of the tetrachlorohexafluorobutane reaction solution in S1 is as follows: a nonpolar solvent, chlorine and trifluorochloroethylene are sequentially introduced into refined iodine and stirred to react at a reaction temperature of -5℃ to 25℃ for 3h to 15h; after the reaction is completed, zinc granules and a polar solvent are added to the reactants and stirred to react at a reaction temperature of -5℃ to 25℃ for 5h to 10h.
[0011] Preferably, iodine chloride is introduced between the nonpolar solvent and chlorine gas;
[0012] Non-polar solvent: Refined iodine mass ratio 5:1, chlorine input is 101% of the theoretical feed mass, and trichlorofluoroethylene input is 125% of the theoretical feed mass;
[0013] The amount of zinc granules added is 150% of the theoretical feed mass;
[0014] The polar solvent is 1% to 10% of the mass of purified iodine;
[0015] The nonpolar solvent in S1 is one of dichloromethane and trichloromethane; the polar solvent is one of ethanol, isopropanol and ethyl acetate.
[0016] Preferably, in the separation process described in S2, the mass ratio of water used for separation to non-polar solvent is 1:1.
[0017] Aqueous phase oxidation process: After stirring the aqueous zinc iodide solution, add a 36% hydrochloric acid solution, followed by a 27.5% hydrogen peroxide solution. Cool the reaction process and keep the reaction temperature below 30°C. After the hydrogen peroxide solution is added, react for at least 30 minutes. Filter to obtain solid crude iodine. The crude iodine is then heat-treated under vacuum at -0.093 MPa and 30°C to 50°C for 4 to 16 hours to obtain refined iodine.
[0018] The molar ratio of iodide ions, hydrogen chloride, and hydrogen peroxide in the zinc iodide solution is 1:1.1:0.53.
[0019] Preferably, the organic phase distillation process in S2 is as follows: the oil phase solution obtained by separating the tetrachlorohexafluorobutane reaction liquid is distilled in a light phase removal column under atmospheric pressure and a column top temperature of 40℃~65℃. Light component one is produced at the top of the column, and all the components at the bottom of the light phase removal column are transferred to a heavy phase removal column for distillation under vacuum of -0.05MPa~-0.07MPa and a column top temperature of 50℃~60℃. Light component two is produced at the top of the heavy phase removal column, purified tetrachlorohexafluorobutane is produced in the middle of the column, and heavy component organic iodide is produced at the bottom of the column. Light component one and light component two are organic solvents containing iodine and zinc iodide.
[0020] Preferably, the absorption process of the iodine-containing and zinc iodide-containing organic solvent in S3 is as follows: the iodine-containing and zinc iodide-containing organic solvent is heated to the gas phase and passed through a water washing tower, and the water washing absorbent is an iodide ion solution; the absorbent is one of sodium sulfite or sodium thiosulfate solution, and the mass concentration of sodium sulfite or sodium thiosulfate solution is 15%.
[0021] Preferably, when the iodide ion mass concentration in the iodide ion solution in S3 reaches 4%, iodine can be recovered by oxidation and filtration; the process of obtaining refined iodine by oxidation, filtration and purification in S3 is the same as the process of obtaining refined iodine by oxidation, filtration and purification of the aqueous phase in S2.
[0022] Preferably, the preparation process of iodine chloride described in S3 is as follows: the organic iodide is heated and vaporized at 350°C, chlorine gas is introduced as a carrier gas and mixed with the organic iodide, and then chlorination is carried out through a catalyst. The distillate is collected, which is iodine chloride.
[0023] The reaction temperature is 200℃~350℃; the molar ratio of organic iodide to chlorine is 100:5~100:15, and the molar ratio of carrier gas to organic iodide is not less than 1:1; the mass ratio of chlorine flowing through per hour to catalyst is 1:1.
[0024] Preferably, the catalyst is an activated alumina-supported ferric chloride catalyst; the mass ratio of activated alumina to ferric chloride is 20:1 to 100:1; and the amount of catalyst used is 1% to 10% of the mass of the organic iodide.
[0025] Preferably, the chlorinated gas is condensed and the fraction below 70°C is collected.
[0026] The reaction principle of a method for iodine recovery and reuse in the preparation of tetrachlorohexafluorobutane is as follows:
[0027]
[0028] Compared with the prior art, the present invention has the following advantages:
[0029] 1. This invention fully recovers iodine from each component, and ultimately all iodine is recovered and reused, significantly improving the iodine recovery rate and the overall economic efficiency of the process.
[0030] 2. The oxidizing agent used in the recovery of iodine in this invention is the process raw material (chlorine) or hydrogen peroxide, and the oxidation product can reduce waste generation.
[0031] 3. The gas absorption liquid of this invention can be processed using the same process as iodine recovery from zinc iodide, reducing the waste of raw material and equipment investment. Attached Figure Description
[0032] Figure 1 This is a process flow diagram of an embodiment of the present invention. Detailed Implementation
[0033] The following is in conjunction with the appendix Figure 1 The present invention will be described in detail with reference to specific embodiments. Unless otherwise specified, the experimental methods described in the following embodiments are conventional methods; the reagents, materials, and equipment described are commercially available unless otherwise specified.
[0034] Example 1
[0035] Step 1: Preparation of trifluorodichloroiodoethane using refined iodine as raw material: 80g of refined iodine (iodine mass fraction 99.8%) was sequentially introduced into 400g of dichloromethane, 4.8g of iodine chloride, 22.57g of chlorine gas, and 96.08g of trifluorochloroethylene, with stirring. The reaction temperature was -5℃ to 0℃ for 10 hours. Then, 32.38g of zinc granules and 1.84g of ethanol were added to the reactants, and the mixture was stirred. The reaction temperature was 20℃.
[0036] React at ~25℃ for 5 hours.
[0037] Step 2: Add 400g of water to the tetrachlorohexafluorobutane reaction solution and separate the aqueous phase. Transfer the aqueous solution to the reaction vessel and start stirring. First, add 73.52g of 36% hydrochloric acid, followed by 43.26g of 27.5% hydrogen peroxide aqueous solution. Cool the reaction vessel during the reaction process to maintain the temperature <30℃. After the hydrogen peroxide is added, react for 30 minutes. Filter the material to obtain solid crude iodine. Heat treat the crude iodine under vacuum at -0.093MPa at 30℃~35℃ for 16 hours to obtain 78.57g of refined iodine (iodine mass fraction 99.8%).
[0038] Step 3: The oil phase solutions obtained from the tetrachlorohexafluorobutane reaction liquid are separately passed through a light component removal distillation column. Light component one is discharged from the top of the column (atmospheric pressure, top temperature 40℃). The bottom components are all transferred to a heavy component removal distillation column. Light component two is discharged from the top of the heavy component removal column (vacuum -0.07MPa, top temperature 60℃). 91.3g of purified tetrachlorohexafluorobutane (98% purity, 89.24% yield) is discharged from the column, and 15.04g of heavy component organic iodide is discharged from the bottom. Light components one and two are mixed and heated to vaporize, then passed through a spray washing column. The absorbent in the spray washing column is a 15% sodium sulfite solution, yielding 54.14g of an iodide ion solution with an iodine content of 5.3%. The iodide ion solution is oxidized, filtered, and purified to obtain 2.88g of purified iodine (iodine mass fraction 99.8%). The reaction conditions are the same as in Step 2.
[0039] The organic iodide is vaporized by heating to 350℃. Chlorine gas (organic iodide:chlorine:nitrogen molar ratio = 100:15:100) is introduced as a carrier gas and mixed with the organic iodide. The mixture is then passed through an activated alumina-supported ferric chloride catalyst (activated alumina to ferric chloride mass ratio = 20:1, catalyst amount = 1% of the organic iodide mass) for chlorination. The chlorine gas flow rate per hour is 1:1 with the catalyst mass ratio. The chlorinated gas is condensed and the fraction below 70℃ is collected, yielding 0.19g of iodine chloride containing 0.15g of iodine.
[0040] The reaction was completed and a total of 81.44g of iodine was recovered, with an iodine recovery rate of 97.42%.
[0041] Example 2
[0042] Step 1: Preparation of trifluorodichloroiodoethane using refined iodine as raw material: 80g of refined iodine (iodine mass fraction 99.8%) was sequentially introduced into 400g of chloroform, 22.57g of chlorine gas, and 91.78g of trifluorochloroethylene, and stirred. The reaction was carried out at 5℃~10℃ for 15h. Then, 30.93g of zinc granules and 1.76g of ethyl acetate were added to the reactants, stirred, and the reaction was carried out at 5℃~10℃ for 10h.
[0043] Step 2: Add 400g of water to the tetrachlorohexafluorobutane reaction solution and separate the aqueous phase. Transfer the aqueous solution to the reaction vessel and start stirring. First, add 70.23g of 36% hydrochloric acid, followed by 41.32g of 27.5% hydrogen peroxide aqueous solution. Cool the reaction vessel during the reaction process to maintain the temperature <30℃. After the hydrogen peroxide is added, react for 30 minutes. Filter the material to obtain solid crude iodine. Heat treat the crude iodine under vacuum at -0.093MPa at 30℃~35℃ for 4 hours to obtain 77.2g of refined iodine (iodine mass fraction 99.8%).
[0044] Step 3: The oil phase solutions obtained from the tetrachlorohexafluorobutane reaction liquid are separately passed through a light component removal distillation column. Light component one is discharged from the top of the column (atmospheric pressure, top temperature 65℃). The bottom components are all transferred to a heavy component removal distillation column. Light component two is discharged from the top of the heavy component removal column (vacuum -0.05MPa, top temperature 50℃). 93.4g of purified tetrachlorohexafluorobutane (99% purity, 96.55% yield) is discharged from the column, and 16.28g of heavy component organic iodide is discharged from the bottom. Light components one and two are mixed and heated to vaporize, then passed through a spray washing column. The absorbent in the spray washing column is a 15% sodium thiosulfate solution, yielding 48.75g of an iodide ion solution with an iodine content of 4.3%. The iodide ion solution is oxidized, filtered, and purified to obtain 2.10g of purified iodine (iodine mass fraction 99.8%). The reaction conditions are the same as in Step 2.
[0045] The organic iodide is vaporized by heating to 350℃. Chlorine gas (organic iodide:chlorine:nitrogen molar ratio = 100:15:100) is introduced as a carrier gas and mixed with the organic iodide. The mixture is then passed through an activated alumina-supported ferric chloride catalyst (activated alumina to ferric chloride mass ratio = 100:1, catalyst amount = 10% of the organic iodide mass) for chlorination. The chlorine gas flow rate per hour is 1:1 with the catalyst mass ratio. The chlorinated gas is condensed and the fraction below 70℃ is collected, yielding 0.12g of iodine chloride containing 0.1g of iodine.
[0046] The reaction was completed and a total of 79.24g of iodine was recovered, with an iodine recovery rate of 99.25%.
[0047] Example 3
[0048] Step 1: Preparation of trifluorodichloroiodoethane using refined iodine as raw material: 95g of refined iodine (99.5% iodine by mass) was sequentially introduced into 475g of dichloromethane, 6.5g of iodine chloride, 26.81g of chlorine gas, and 114.81g of trifluorochloroethylene, with stirring. The reaction was carried out at 20℃~25℃ for 3 hours. Then, 38.69g of zinc granules and 2.2g of isopropanol were added to the reactants, and the mixture was stirred. The reaction was carried out at -5℃~0℃ for 10 hours.
[0049] Step 2: Add 475g of water to the tetrachlorohexafluorobutane reaction solution and separate the aqueous phase. Transfer the aqueous solution to the reaction vessel and start stirring. First, add 87.86g of 36% hydrochloric acid, followed by 51.69g of 27.5% hydrogen peroxide aqueous solution. Cool the reaction vessel during the reaction process to maintain the temperature <30℃. After the hydrogen peroxide is added, react for 30 minutes. Filter the material to obtain solid crude iodine. Heat treat the crude iodine under vacuum at -0.093MPa at 30℃~35℃ for 8 hours to obtain 78.57g of refined iodine (iodine mass fraction 99.5%).
[0050] Step 3: The oil phase solutions obtained from the tetrachlorohexafluorobutane reaction liquid are separately passed through a light component removal distillation column. Light component one is discharged from the top of the column (atmospheric pressure, top temperature 40℃). The bottom components are all transferred to a heavy component removal distillation column. Light component two is discharged from the top of the heavy component removal column (vacuum -0.07MPa, top temperature 60℃). 111.2g of purified tetrachlorohexafluorobutane (purity 98.5%, yield 91.42%) is discharged from the column, and 21.57g of heavy component organic iodide is discharged from the bottom. Light components one and two are mixed and heated to vaporize, then passed through a spray washing column. The absorbent in the spray washing column is a 15% sodium sulfite solution, yielding 55.11g of an iodide ion solution with an iodine content of 4.2%. The iodide ion solution is oxidized, filtered, and purified to obtain 2.33g of purified iodine (iodine mass fraction 99.5%). The reaction conditions are the same as in Step 2.
[0051] The organic iodide was vaporized by heating to 350℃. Chlorine gas (organic iodide:chlorine:nitrogen molar ratio = 100:15:100) was introduced as a carrier gas and mixed with the organic iodide. The mixture was then passed through an activated alumina-supported ferric chloride catalyst (activated alumina to ferric chloride ratio of 50:1, catalyst amount 4% of the organic iodide mass) for chlorination. The chlorine gas flow rate per hour was 1:1 with the catalyst mass. The chlorinated gas was condensed and the fraction below 70℃ was collected, yielding 0.22g of iodine chloride containing 0.17g of iodine.
[0052] The reaction was completed and a total of 95.91g of iodine was recovered, with an iodine recovery rate of 96.29%.
[0053] The technical solutions provided by the embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to helping to understand the principles of the embodiments of the present invention. At the same time, those skilled in the art will know that there will be changes in the specific implementation methods and application scope according to the embodiments of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.
Claims
1. A method for iodine recovery and reuse in the preparation process of tetrachlorohexafluorobutane, characterized in that, Includes the following steps: S1. Trifluorodichloroiodoethane was prepared from refined iodine and trifluorochloroethylene as raw materials, and tetrachlorohexafluorobutane was prepared from trifluorodichloroiodoethane as raw material. S2, the reaction solution of tetrachlorohexafluorobutane is diluted with water, the aqueous phase is oxidized, filtered and purified to obtain purified iodine, and the organic phase is distilled to obtain purified tetrachlorohexafluorobutane, organic solvent containing iodine and zinc iodide and organic iodides. S3. The iodine-containing organic solvent and zinc iodide are washed with an absorbent to obtain an aqueous solution of iodide ions, which is then oxidized, filtered, and purified to obtain refined iodine. Organic iodides are catalytically chlorinated to obtain iodine chloride, which is used to prepare trifluorodichloroiodoethane. The preparation process of iodine chloride described in S3 is as follows: the organic iodide is heated to 350°C and vaporized. Chlorine gas is introduced with inert gas as carrier gas and mixed with the organic iodide. After chlorination, the mixture is chlorinated through a catalyst. The distillate is collected, which is iodine chloride. The molar ratio of organic iodide to chlorine is 100:5~100:15, and the molar ratio of carrier gas to organic iodide is not less than 1:1; the mass ratio of chlorine flowing through per hour to catalyst is 1:
1. The catalyst is an ferric chloride catalyst mounted on activated alumina; the mass ratio of activated alumina to ferric chloride is 20:1 to 100:1; the amount of catalyst used is 1% to 10% of the mass of the organic iodide.
2. The method for iodine recovery and reuse in the preparation process of tetrachlorohexafluorobutane according to claim 1, characterized in that, Preparation process of tetrachlorohexafluorobutane reaction solution in S1: Non-polar solvent, chlorine and trifluorochloroethylene are introduced into purified iodine in sequence and stirred to react. The reaction temperature is -5℃~25℃ and the reaction time is 3h~15h. After the reaction is completed, zinc granules and polar solvent are added to the reactants and stirred to react. The reaction temperature is -5℃~25℃ and the reaction time is 5h~10h.
3. The method for iodine recovery and reuse in the preparation process of tetrachlorohexafluorobutane according to claim 2, characterized in that, Iodine chloride is introduced between a nonpolar solvent and chlorine gas; Non-polar solvent: purified iodine mass ratio 5:1, chlorine input is 101% of the theoretical feed mass, and trifluorochloroethylene input is 125% of the theoretical feed mass; The zinc granules input amount is 150% of the theoretical feed mass; The polar solvent is 1% to 10% of the mass of purified iodine; The nonpolar solvent in S1 is one of dichloromethane and trichloromethane; the polar solvent is one of ethanol, isopropanol and ethyl acetate.
4. The method for iodine recovery and reuse in the preparation process of tetrachlorohexafluorobutane according to claim 2, characterized in that, The separation process described in S2 uses a non-polar solvent with a separation water mass ratio of 1:
1. Aqueous phase oxidation process: After stirring the aqueous zinc iodide solution, add a 36% hydrochloric acid solution, followed by a 27.5% hydrogen peroxide solution. Cool the reaction process and keep the reaction temperature below 30℃. After the hydrogen peroxide solution is added, react for at least 30 minutes. Filter to obtain solid crude iodine. The crude iodine is then heat-treated under vacuum at -0.093 MPa and 30℃~50℃ for 4h~16h to obtain refined iodine. The molar ratio of iodide ions, hydrogen chloride, and hydrogen peroxide in the zinc iodide solution is 1:1.1:0.
53.
5. The method for iodine recovery and reuse in the preparation process of tetrachlorohexafluorobutane according to claim 1, characterized in that, The organic phase distillation process in S2 is as follows: the oil phase solution obtained by separating the tetrachlorohexafluorobutane reaction liquid is distilled separately in a light phase removal column under atmospheric pressure and a column top temperature of 40℃~65℃. Light component I is produced at the top of the column, and all the bottom components of the light phase removal column are transferred to a heavy phase removal column for distillation under vacuum of -0.05MPa~-0.07MPa and a column top temperature of 50℃~60℃. Light component II is produced at the top of the heavy phase removal column, purified tetrachlorohexafluorobutane is produced in the middle of the column, and heavy component organic iodide is produced at the bottom of the column. Light components I and II are organic solvents containing iodine and zinc iodide.
6. The method for iodine recovery and reuse in the preparation process of tetrachlorohexafluorobutane according to claim 1, characterized in that, The absorption process of the organic solvent containing iodine and zinc iodide described in S3 is as follows: the organic solvent containing iodine and zinc iodide is heated to the gas phase and passed through a water washing tower, and the water washing absorbent is an iodide ion solution; the absorbent is either sodium sulfite or sodium thiosulfate solution, and the mass concentration of the sodium sulfite or sodium thiosulfate solution is 15%.
7. The method for iodine recovery and reuse in the preparation process of tetrachlorohexafluorobutane according to claim 6, characterized in that, When the iodide ion mass concentration in the iodide ion solution described in S3 reaches 4%, oxidation and filtration can be performed to recover iodine. The process of obtaining refined iodine through oxidation, filtration, and purification in S3 is the same as the process of obtaining refined iodine through oxidation, filtration, and purification of the aqueous phase in S2.
8. The method for iodine recovery and reuse in the preparation process of tetrachlorohexafluorobutane according to claim 1, characterized in that, The chlorinated gas is condensed and the fraction below 70°C is collected.