Method for recycling iodine in tetrachlorohexafluorobutane preparation process

Abstract

The invention discloses a method for recycling iodine in a tetrachlorohexafluorobutane preparation process, which comprises the following steps: S1, preparing trifluorodichloroiodoethane by using refined iodine and trifluorochloroethylene as raw materials, and preparing tetrachlorohexafluorobutane reaction liquid by using trifluorodichloroiodoethane as a raw material; s2, adding water into the tetrachlorohexafluorobutane reaction liquid, oxidizing, filtering and refining a water phase to obtain refined iodine, and rectifying an organic phase to obtain refined tetrachlorohexafluorobutane, an organic solvent containing iodine and zinc iodide and organic iodide; s3, washing the organic solvent containing iodine and zinc iodide with an absorbent to obtain an iodide ion aqueous solution, and oxidizing, filtering and refining to obtain refined iodine; the organic iodide is subjected to catalytic chlorination to obtain iodine chloride which is used for preparing trifluorodichloroiodoethane. The whole process is rapid in reaction, environmentally friendly, high in iodine recovery rate and suitable for large-scale industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of chemical industry, and in particular to a method for recovering and reusing iodine in a tetrachlorohexafluorobutane preparation process. Background Art

[0002] Tetrachlorohexafluorobutane is an important chemical raw material that can be used to produce high-performance etching gas hexafluorobutadiene. The main industrial preparation route for tetrachlorohexafluorobutane is to obtain it by dehalogenation after the reaction of trifluorochloroethylene with a mutual halide. One of the important routes is the iodine chloride route. The process has mild reaction conditions and a high reaction yield, and is a very promising process route. However, the reaction process consumes iodine to generate zinc iodide. Due to the high cost of iodine, if a high iodine recovery rate (>95%) cannot be achieved, the economic efficiency of this route will be greatly reduced. In the current process flow, the iodine recovery process mainly recovers iodine from zinc iodide, but because a small amount of iodine and organic iodides are generated as by-products during the reaction process and enter the organic phase of tetrachlorohexafluorobutane (accounting for about 3% to 10% of the iodine content of the raw material), it is difficult for the original process to achieve economic goals. Summary of the invention

[0003] The invention provides a method for recovering and reusing iodine in a tetrachlorohexafluorobutane preparation process. The method has rapid reaction, is green and environmentally friendly, has a high iodine recovery rate, and is suitable for large-scale industrial production.

[0004] The technical solution adopted by the present invention is:

[0005] A method for recovering and reusing iodine in a tetrachlorohexafluorobutane preparation process comprises the following steps:

[0006] S1, using refined iodine and trifluorochloroethylene as raw materials to prepare dichlorotrifluoroethane, and using dichlorotrifluoroethane as raw material to prepare tetrachlorohexafluorobutane reaction solution;

[0007] S2, adding water to the tetrachlorohexafluorobutane reaction solution to separate the reaction solution, oxidizing, filtering and refining the aqueous phase to obtain refined iodine, and distilling the organic phase to obtain refined tetrachlorohexafluorobutane, an organic solvent containing iodine and zinc iodide, and an organic iodide;

[0008] S3, washing the organic solvent containing iodine and zinc iodide with absorbent water to obtain an iodine ion aqueous solution, and oxidizing, filtering and refining to obtain refined iodine;

[0009] The organic iodide is subjected to catalytic chlorination to obtain iodine chloride, which is used to prepare trifluorodichloroiodoethane.

[0010] Preferably, the preparation process of the tetrachlorohexafluorobutane reaction liquid in S1 is: a non-polar solvent, chlorine gas and chlorotrifluoroethylene are introduced into the refined iodine in sequence and stirred for reaction, the reaction temperature is -5°C to 25°C, and the reaction time is 3h to 15h; after the reaction is completed, zinc particles and a polar solvent are added to the reactant, and the reaction is stirred, the reaction temperature is -5°C to 25°C, and the reaction time is 5h to 10h.

[0011] Preferably, iodine chloride is passed between the non-polar solvent and the chlorine gas;

[0012] The mass ratio of non-polar solvent to refined iodine is 5:1, the amount of chlorine gas input is 101% of the theoretical input mass, and the amount of chlorotrifluoroethylene input is 125% of the theoretical input mass;

[0013] The amount of zinc particles input is 150% of the theoretical feed mass;

[0014] The polar solvent is 1% to 10% of the mass of the refined iodine;

[0015] The non-polar solvent in S1 is one of dichloromethane and chloroform; the polar solvent is one of ethanol, isopropanol and ethyl acetate.

[0016] Preferably, in the separation process of S2, the mass ratio of separation water to non-polar solvent is 1:1;

[0017] The aqueous phase is subjected to an oxidation process: after stirring the aqueous zinc iodide solution in the aqueous phase, a 36% hydrochloric acid solution is first added, and then a 27.5% hydrogen peroxide solution is continuously added. During the reaction process, the reaction temperature is kept below 30° C. After the addition of the hydrogen peroxide solution is completed, the reaction is continued for not less than 30 minutes, and solid crude iodine is obtained by filtration. The crude iodine is subjected to a heat treatment at 30° C. to 50° C. for 4 h to 16 h under vacuum at -0.093 MPa to obtain refined iodine;

[0018] The molar ratio of iodide ion, hydrogen chloride and hydrogen peroxide in the zinc iodide solution is 1:1.1:0.53.

[0019] Preferably, the process of organic phase distillation in S2 is: the oil phase solution obtained by separating the tetrachlorohexafluorobutane reaction liquid is respectively distilled through a light-removing tower, the distillation conditions are atmospheric pressure, the tower top temperature is 40°C to 65°C, a light component 1 is produced from the tower top, and all the components at the bottom of the light-removing tower are transferred to a heavy-removing tower for distillation, the distillation conditions are vacuum -0.05MPa to -0.07MPa, the tower top temperature is 50°C to 60°C, a light component 2 is produced from the top of the heavy-removing tower, refined tetrachlorohexafluorobutane is produced in the tower, and a heavy component organic iodide is produced from the bottom of the tower; the light component 1 and the light component 2 are organic solvents containing iodine and zinc iodide.

[0020] Preferably, the iodine- and zinc iodide-containing organic solvent absorption process in S3 is as follows: the iodine- and zinc iodide-containing organic solvent is heated to a gas phase and passed through a water washing tower, and the water washing absorption liquid is an iodide ion solution; the absorbent is one of sodium sulfite or sodium thiosulfate solutions, and the mass concentration of the sodium sulfite or sodium thiosulfate solution is 15%.

[0021] Preferably, when the mass concentration of iodine ions in the iodine ion solution in S3 reaches 4%, oxidation and filtration can be carried out to recover iodine; the process of oxidation, filtration and refining to obtain refined iodine in S3 is the same as the process of oxidation, filtration and refining of the aqueous phase to obtain refined iodine in S2.

[0022] Preferably, the preparation process of iodine chloride described in S3 is: the organic iodide is heated to 350° C. and gasified, chlorine is introduced into the organic iodide with an inert gas as a carrier gas, and then the mixture is chlorinated by a catalyst, and the fraction is collected, which is iodine chloride;

[0023] The reaction temperature is 200°C to 350°C; the molar ratio of organic iodide to chlorine is 100:5 to 100:15, and the molar ratio of carrier gas to organic iodide is not less than 1:1; the ratio of the mass of chlorine flowing through per hour to the mass of the catalyst is 1:1.

[0024] Preferably, the catalyst is a ferric chloride catalyst supported on activated alumina; the mass ratio of activated alumina to ferric chloride is 20:1 to 100:1; and the amount of the catalyst used is 1% to 10% of the mass of the organic iodide.

[0025] Preferably, the chlorinated gas is condensed to collect fractions below 70°C.

[0026] The reaction principle of a method for recovering and reusing iodine in the preparation process of tetrachlorohexafluorobutane is as follows:

[0027]

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

[0029] 1. The present invention fully recovers the iodine element in each component, and finally the iodine can be recycled, which significantly improves the iodine recovery rate and improves the overall economic efficiency of the process.

[0030] 2. The oxidizing agent used for recovering iodine in the present invention is a process raw material (chlorine) or hydrogen peroxide, and the oxidation product can reduce waste generation.

[0031] 3. The gas absorption liquid of the present invention can be applied to the same process as the iodine recovery process in zinc iodide, thus reducing the waste of investment in raw materials and equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The process flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The following is combined with Figure 1 The present invention is described in detail with reference to the following examples. The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents, materials and equipment described are all commercially available unless otherwise specified.

[0034] Embodiment 1

[0035] Step 1: Prepare trifluorodichloroiodoethane using refined iodine as raw material: 80g of refined iodine (99.8% iodine mass fraction) was sequentially introduced into 400g of dichloromethane, 4.8g of iodine chloride, 22.57g of chlorine, and 96.08g of trifluorochloroethylene, and stirred at a temperature of -5°C to 0°C for 10h. 32.38g of zinc particles and 1.84g of ethanol were added to the reactants, stirred, and the reaction temperature was 20°C.

[0036] React at ~25℃ for 5h.

[0037] Step 2: Add 400g of water to the tetrachlorohexafluorobutane reaction solution to separate the liquids. After the aqueous phase solution is transferred to the reactor and stirred, 73.52g of 36% hydrochloric acid is first added, and then 43.26g of 27.5% hydrogen peroxide aqueous solution is continuously and slowly added. During the reaction process, the reactor temperature is kept <30°C. After the addition of hydrogen peroxide, the reaction is carried out for 30 minutes, and the material is filtered to obtain solid crude iodine. The crude iodine is heat-treated at 30°C to 35°C for 16 hours under vacuum -0.093MPa to obtain 78.57g of refined iodine (99.8% iodine mass fraction).

[0038] Step 3: The oil phase solution obtained by separating the tetrachlorohexafluorobutane reaction liquid is respectively passed through a light fractionation tower, and a light component 1 (normal pressure, tower top temperature 40°C) is obtained from the top of the tower. The bottom components of the light fractionation tower are all transferred to a heavy fractionation tower, and a light component 2 (vacuum-0.07MPa, tower top temperature 60°C) is obtained from the top of the heavy fractionation tower. 91.3g of refined tetrachlorohexafluorobutane (purity 98%, yield 89.24%) is obtained from the tower, and 15.04g of heavy component organic iodide is obtained from the bottom of the tower. After the light component 1 and the light component 2 are mixed, they are heated and gasified and passed through a spray washing tower. The spray tower absorption liquid adopts a 15% sodium sulfite solution to obtain 54.14g of iodine ion solution with an iodine content of 5.3%. The iodine ion solution is oxidized, filtered, and refined to obtain 2.88g of refined iodine (iodine mass fraction 99.8%). The reaction conditions refer to step 2.

[0039] The organic iodide is heated to 350°C and gasified. Chlorine gas (organic iodide: chlorine: nitrogen molar ratio = 100:15:100) is introduced with nitrogen as carrier gas to mix with the organic iodide and then chlorinated through an activated alumina-supported ferric chloride catalyst (the ratio of activated alumina to ferric chloride is 20:1 by mass, and the amount of catalyst is 1% of the mass of the organic iodide). The mass ratio of chlorine gas flowing per hour to the mass of the catalyst is 1:1. The chlorinated gas is condensed and collected as a fraction below 70°C, containing 0.19g of iodine chloride and 0.15g of iodine.

[0040] After the reaction was completed, a total of 81.44 g of elemental iodine was recovered, with an iodine recovery rate of 97.42%.

[0041] Embodiment 2

[0042] Step 1: Prepare trifluorodichloroiodoethane using refined iodine as raw material: 80g of refined iodine (99.8% iodine mass fraction) is sequentially introduced into 400g of chloroform, 22.57g of chlorine, and 91.78g of chlorotrifluoroethylene, and stirred at a reaction temperature of 5°C to 10°C for 15h. 30.93g of zinc particles and 1.76g of ethyl acetate are added to the reactants, stirred, and reacted at a reaction temperature of 5°C to 10°C for 10h.

[0043] Step 2: Add 400g of water to the tetrachlorohexafluorobutane reaction solution to separate the liquids. After the aqueous phase solution is transferred to the reactor and stirred, 70.23g of 36% hydrochloric acid is first added, and then 41.32g of 27.5% hydrogen peroxide aqueous solution is continuously and slowly added. During the reaction process, the reactor temperature is kept <30°C. After the addition of hydrogen peroxide, the reaction is carried out for 30 minutes, and the material is filtered to obtain solid crude iodine. The crude iodine is heat-treated at 30°C to 35°C for 4 hours under vacuum -0.093MPa to obtain 77.2g of refined iodine (99.8% iodine mass fraction).

[0044] Step 3: The oil phase solution obtained by separating the tetrachlorohexafluorobutane reaction liquid is respectively passed through a light fractionation tower, and a light component 1 (normal pressure, tower top temperature 65°C) is obtained from the top of the tower. The bottom components of the light fractionation tower are all transferred to a heavy fractionation tower, and a light component 2 (vacuum-0.05MPa, tower top temperature 50°C) is obtained from the top of the heavy fractionation tower. 93.4g of refined tetrachlorohexafluorobutane (purity 99%, yield 96.55%) is obtained from the tower, and 16.28g of heavy component organic iodide is obtained from the bottom of the tower. After the light component 1 and the light component 2 are mixed, they are heated and gasified and passed through a spray washing tower. The spray tower absorption liquid adopts a 15% sodium thiosulfate solution to obtain 48.75g of an iodine ion solution with an iodine content of 4.3%. The iodine ion solution is oxidized, filtered, and refined to obtain 2.10g of refined iodine (iodine mass fraction 99.8%). The reaction conditions refer to step 2.

[0045] The organic iodide is heated to 350°C and gasified. Chlorine gas (organic iodide: chlorine: nitrogen molar ratio = 100:15:100) is introduced with nitrogen as carrier gas to mix with the organic iodide and then chlorinated by ferric chloride catalyst supported by activated alumina (the ratio of activated alumina to ferric chloride is 100:1 by mass, and the amount of catalyst is 10% of the mass of the organic iodide). The mass ratio of chlorine gas flowing per hour to the mass ratio of catalyst is 1:1. The chlorinated gas is condensed and collected as the fraction below 70°C, containing 0.12g of iodine chloride and 0.1g of iodine.

[0046] After the reaction was completed, a total of 79.24 g of elemental iodine was recovered, with an iodine recovery rate of 99.25%.

[0047] Embodiment 3

[0048] Step 1: Prepare trifluorodichloroiodoethane using refined iodine as raw material: 95g of refined iodine (99.5% iodine mass fraction) is sequentially introduced into 475g of dichloromethane, 6.5g of iodine chloride, 26.81g of chlorine gas, and 114.81g of chlorotrifluoroethylene, and stirred at a reaction temperature of 20°C to 25°C for 3h. 38.69g of zinc particles and 2.2g of isopropanol are added to the reactants, stirred, and reacted at a reaction temperature of -5°C to 0°C for 10h.

[0049] Step 2: Add 475g of water to the tetrachlorohexafluorobutane reaction solution to separate the liquids. After the aqueous phase solution is transferred to the reactor and stirred, 87.86g of 36% hydrochloric acid is first added, and then 51.69g of 27.5% hydrogen peroxide aqueous solution is continuously and slowly added. During the reaction process, the reactor temperature is kept <30°C. After the addition of hydrogen peroxide, the reaction is carried out for 30 minutes, and the material is filtered to obtain solid crude iodine. The crude iodine is heat-treated at 30°C to 35°C for 8 hours under vacuum -0.093MPa to obtain 78.57g of refined iodine (99.5% iodine mass fraction).

[0050] Step 3: The oil phase solution obtained by separating the tetrachlorohexafluorobutane reaction liquid is respectively passed through a light fractionation tower, and a light component 1 (normal pressure, tower top temperature 40°C) is obtained from the tower top. The components at the bottom of the light fractionation tower are all transferred to a heavy fractionation tower, and a light component 2 (vacuum-0.07MPa, tower top temperature 60°C) is obtained from the tower top. 111.2g of refined tetrachlorohexafluorobutane (purity 98.5%, yield 91.42%) is obtained from the tower, and 21.57g of heavy component organic iodide is obtained from the tower bottom. After the light component 1 and the light component 2 are mixed, they are heated and gasified and passed through a spray washing tower. The spray tower absorption liquid adopts a 15% sodium sulfite solution to obtain 55.11g of an iodine ion solution with an iodine content of 4.2%. The iodine ion solution is oxidized, filtered, and refined to obtain 2.33g of refined iodine (iodine mass fraction 99.5%). The reaction conditions refer to step 2.

[0051] The organic iodide is heated to 350°C and gasified. Chlorine (organic iodide: chlorine: nitrogen molar ratio = 100:15:100) is introduced with nitrogen as carrier gas to mix with the organic iodide and then chlorinated by ferric chloride catalyst supported by activated alumina (the ratio of activated alumina to ferric chloride is 50:1 by mass, and the amount of catalyst is 4% by mass of the organic iodide). The mass ratio of chlorine flowing per hour to the mass of the catalyst is 1:1. The chlorinated gas is condensed and collected in the fraction below 70°C, containing 0.22g of iodine chloride and 0.17g of iodine.

[0052] After the reaction was completed, a total of 95.91 g of elemental iodine was recovered, with an iodine recovery rate of 96.29%.

[0053] The technical solutions provided by the embodiments of the present invention are described in detail above. Specific examples are used herein to illustrate the principles and implementation methods of the embodiments of the present invention. The description of the above embodiments is only applicable to help understand the principles of the embodiments of the present invention. At the same time, those skilled in the art may make changes in the specific implementation methods and application scopes according to the embodiments of the present invention. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A method for recovering and reusing iodine in the process of preparing tetrachlorohexafluorobutane, characterized in that: The following steps are involved: S1, using refined iodine and trifluorochloroethylene as raw materials to prepare dichlorotrifluoroethane, and using dichlorotrifluoroethane as raw material to prepare tetrachlorohexafluorobutane reaction solution; S2, adding water to the tetrachlorohexafluorobutane reaction solution to separate the reaction solution, oxidizing, filtering and refining the aqueous phase to obtain refined iodine, and distilling the organic phase to obtain refined tetrachlorohexafluorobutane, an organic solvent containing iodine and zinc iodide, and an organic iodide; S3, washing the organic solvent containing iodine and zinc iodide with absorbent water to obtain an iodine ion aqueous solution, and oxidizing, filtering and refining to obtain refined iodine; The organic iodide is subjected to catalytic chlorination to obtain iodine chloride, which is used to prepare trifluorodichloroiodoethane.

2. The method for recovering and reusing iodine in the preparation process of tetrachlorohexafluorobutane according to claim 1, characterized in that: The preparation process of the tetrachlorohexafluorobutane reaction liquid in S1 is as follows: a non-polar solvent, chlorine gas and chlorotrifluoroethylene are introduced into the refined iodine in sequence and stirred for reaction, the reaction temperature is -5°C to 25°C, and the reaction time is 3h to 15h; after the reaction is completed, zinc particles and a polar solvent are added to the reactant, and the reaction is stirred, the reaction temperature is -5°C to 25°C, and the reaction time is 5h to 10h.

3. The method for recovering and reusing iodine in the process of preparing tetrachlorohexafluorobutane according to claim 2, characterized in that: Iodine chloride is passed between the non-polar solvent and chlorine gas; The mass ratio of non-polar solvent to refined iodine is 5:1, the amount of chlorine gas input is 101% of the theoretical input mass, and the amount of chlorotrifluoroethylene input is 125% of the theoretical input mass; The amount of zinc particles input is 150% of the theoretical feed mass; The polar solvent is 1% to 10% of the mass of the refined iodine; The non-polar solvent in S1 is one of dichloromethane and chloroform; the polar solvent is one of ethanol, isopropanol and ethyl acetate.

4. The method for recovering and reusing iodine in the preparation process of tetrachlorohexafluorobutane according to claim 2, characterized in that: In the separation process of S2, the mass ratio of separation water to non-polar solvent is 1:1; The aqueous phase is subjected to an oxidation process: after stirring the aqueous zinc iodide solution in the aqueous phase, a 36% hydrochloric acid solution is first added, and then a 27.5% hydrogen peroxide solution is continuously added. During the reaction process, the reaction temperature is kept below 30° C. After the addition of the hydrogen peroxide solution is completed, the reaction is continued for not less than 30 minutes, and solid crude iodine is obtained by filtration. The crude iodine is subjected to a heat treatment at 30° C. to 50° C. for 4 h to 16 h under vacuum at -0.093 MPa to obtain refined iodine; The molar ratio of iodide ion, hydrogen chloride and hydrogen peroxide in the zinc iodide solution is 1:1.1:0.

53.

5. The method for recovering and reusing iodine in the process of preparing tetrachlorohexafluorobutane according to claim 1, characterized in that: The process of organic phase distillation in S2 is as follows: the oil phase solution obtained by separating the tetrachlorohexafluorobutane reaction liquid is respectively distilled in a light-removing tower, the distillation condition is normal pressure, the tower top temperature is 40°C ~ 65°C, a light component 1 is produced from the tower top, and all the components at the bottom of the light-removing tower are transferred to a heavy-removing tower for distillation, the distillation condition is vacuum -0.05MPa ~ -0.07MPa, the tower top temperature is 50°C ~ 60°C, a light component 2 is produced from the top of the heavy-removing tower, refined tetrachlorohexafluorobutane is produced in the tower, and a heavy component organic iodide is produced from the tower bottom; the light component 1 and the light component 2 are organic solvents containing iodine and zinc iodide.

6. The method for recovering and reusing iodine in the process of preparing tetrachlorohexafluorobutane according to claim 1, characterized in that: The absorption process of the organic solvent containing iodine and zinc iodide in S3 is as follows: the organic solvent containing iodine and zinc iodide is heated to gas phase and passed through a water washing tower, and the water washing absorption liquid is an iodide ion solution; the absorbent is one of sodium sulfite or sodium thiosulfate solution, and the mass concentration of the sodium sulfite or sodium thiosulfate solution is 15%.

7. The method for recovering and reusing iodine in the process of preparing tetrachlorohexafluorobutane according to claim 6, characterized in that: When the mass concentration of iodine ions in the iodine ion solution in S3 reaches 4%, oxidation and filtration to recover iodine can be performed; The process of obtaining refined iodine by oxidation, filtration and refining in S3 is the same as the process of obtaining refined iodine by oxidation, filtration and refining of the aqueous phase in S2.

8. The method for recovering and reusing iodine in the process of preparing tetrachlorohexafluorobutane according to claim 1, characterized in that: The preparation process of iodine chloride described in S3 is as follows: the organic iodide is heated and gasified at 350° C., chlorine is introduced into the organic iodide with an inert gas as a carrier gas, and then the mixture is chlorinated by a catalyst, and the fraction is collected, which is iodine chloride; The reaction temperature is 200°C to 350°C; the molar ratio of organic iodide to chlorine is 100:5 to 100:15, and the molar ratio of carrier gas to organic iodide is not less than 1:1; the ratio of the mass of chlorine flowing through per hour to the mass of the catalyst is 1:

1.

9. The method for recovering and reusing iodine in the process of preparing tetrachlorohexafluorobutane according to claim 8, characterized in that: The catalyst is a ferric chloride catalyst supported by activated alumina; the mass ratio of activated alumina to ferric chloride is 20:1 to 100:1; The amount of the catalyst used is 1% to 10% of the amount of the organic iodide.

10. The method for recovering and reusing iodine in the process of preparing tetrachlorohexafluorobutane according to claim 8, characterized in that: The chlorinated gas is condensed and the fraction below 70°C is collected.

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