Method for recycling iodine from C4F6 synthesis process

Abstract

The invention relates to a method for recycling iodine from a C4F6 synthesis process, and belongs to the technical field of chemical engineering. Slowly adding strong acid and an oxidizing agent into the waste iodine solution for reaction; adding an organic extracting agent, uniformly mixing, standing, separating, and removing an upper-layer water phase to obtain a lower-layer iodine-containing organic solvent phase; an iodine-containing organic solvent phase is subjected to rectification to remove the redundant extraction agent and a small amount of water, and an organic extraction agent-water binary azeotrope is distilled out from the tower top and can be used in the next batch of extraction process; an iodine-extractant-containing mixed solution is obtained at the bottom of the tower and can be used in the next batch of synthesis process; further evaporating and separating the iodine-extractant mixed solution, condensing the extractant at the top of the evaporation tower, and returning to be used in the next batch of extraction process; separating out and crystallizing iodine at the bottom of the tower to obtain elemental iodine which can be used in the next batch of synthesis process; according to the method for recycling and reusing the iodine in the C4F6 synthesis process, the recovery rate of the iodine is high, the moisture content in the iodine-dichloromethane mixed solution is low, and the economic value is high.

Description

Technical Field

[0001] The present invention relates to the field of chemical engineering technology, and in particular to a method for recycling and reusing iodine in the synthesis process of C 4 F 6 synthesis process. Background Art

[0002] Hexafluorobutadiene (C 4 F 6 ) as the next-generation etching gas exhibits excellent etching performance in the semiconductor dry etching process, enabling it to achieve a higher etching rate selectivity ratio during the etching process. The global warming potential (GWP) of C 4 F 6 is almost 0, and it may be the only alternative that can provide the required etching conditions and reduce emissions. Using tetrachlorohexafluorobutane as an intermediate to synthesize C 4 F 6 is a commonly used preparation method in industry, and elemental iodine is used in this preparation method. Elemental iodine acts as a leaving group during the addition, telomerization, and elimination reactions, forming iodine salts that do not enter the final product. Since elemental iodine is expensive, the recycling and reuse of iodine in production are of great significance for reducing production costs.

[0003] Iodine recovery generally involves oxidizing (or reducing) to convert the iodine salts present in the iodine waste liquid into the elemental state. After separation, crude iodine can be obtained, and then refined iodine can be obtained by dehydrating with concentrated sulfuric acid. The current methods for iodine recovery mainly include ion exchange method, air blowing method, extraction method, adsorption method, etc.

[0004] Chinese Patent CN112938901 B proposes a method for recovering iodine from zinc iodide waste salt. Specifically, it includes: pretreatment of zinc iodide waste salt: heating the zinc iodide waste salt to 200 - 300 °C while introducing a carrier gas, and the moisture and organic matter in the zinc iodide waste salt will be carried out with the carrier gas to form tail gas, and the operation ends when the moisture content in the tail gas is less than 10 ppm; then, heating the pretreated zinc iodide waste salt to 300 - 600 °C while introducing a carrier gas, introducing an oxidant, and the reduced iodine and impurities are carried out with the carrier gas to form tail gas. The tail gas is cooled in two or more temperature intervals at a temperature of 390 - 150 °C to precipitate impurities, and the cooling time in each temperature interval is 2 - 15 min, and then cooled at a temperature of 110 - 5 °C to obtain iodine.

[0005] Chinese Patent CN103183320A proposes a method for recovering iodine. It combines electrochemical methods to control the degree of oxidation and reduction, recovers inorganic iodine in the waste liquid, and oxidizes and recovers organic iodine with sodium hypochlorite solution. The iodine ion content in the recovered waste liquid is about 0.3%, and then a strongly basic anion exchange resin is used to enrich and recover this part of iodine.

[0006] Chinese Patent CN103508420A proposes a method for recovering iodine from iodine-containing waste liquid in the laboratory. The method follows the following steps. First, use dilute H 2 SO 4 or dilute NaOH to adjust the pH value of the waste liquid to the range of 4-5. Then, take the supernatant of the waste liquid as the treatment solution, and the sediment of the waste liquid is the first batch of iodine mud. Add starch to the treatment solution, and at this time the solution shows a dark blue color. Pass O 3 into the solution. During the process of passing O 3 , the solution gradually changes from dark blue to blue-green. When the solution suddenly changes from blue-green to brown, stop passing O 3 . Use CCl 4 to extract I 2 in the solution. After separating the CCl 4 layer with a pink color, add NaOH to the solution. The solution undergoes a disproportionation reaction and layers. Recover the lower CCl 4 layer. Take the upper solution and add H 2 SO 4 to it. This part of the solution undergoes a reverse disproportionation reaction and precipitates I 2 . Let this part of the solution stand still, and after suction filtration, obtain the second batch of iodine mud. Concentrate the first batch of iodine mud and the second batch of iodine mud, mix them with fine sand, and sublime to obtain elemental iodine.

[0007] In the above patent and the prior art, iodide ions are oxidized to precipitate iodine, or the obtained iodine is further reduced to ionic iodine by a reducing agent, and the ionic iodine is further oxidized to obtain elemental iodine, and crude iodine is prepared; then the crude iodine is mixed with concentrated sulfuric acid and heated to a molten liquid state by the melting method, the water and impurities in it are adsorbed and removed, and then high-purity iodine is obtained through steps such as cooling and crystallization. The reaction process is cumbersome, cannot be continuous with C 4 F 6 production, and the exclusion of organic solvents in the waste iodine solution causes environmental pollution, and the equipment investment and maintenance costs are high. Summary of the Invention

[0008] To solve the above problems, the present invention provides a method for recycling and reusing iodine in the C 4 F 6 synthesis process. The operation steps are as follows:

[0009] S1: Slowly add a strong acid and an oxidizing agent to the waste iodine solution using a metering pump to fully mix the oxidizing agent with the iodine waste liquid, and online real-time monitor the pH value of the reaction system; the molar ratio of the oxidizing agent to iodide ions is 1:(1-1.5), and at the same time control the flow rate of the oxidizing agent added to make the reaction proceed better; the addition amount of the strong acid is determined according to the acidity and alkalinity of the oxidation reaction system to ensure that the pH value of the oxidation reaction system is 1-3;

[0010] S2: Add an organic extractant, mix well and let it stand. The system shows a layering phenomenon. The upper layer is the aqueous phase and the lower layer is the organic solvent phase containing iodine. Separate the organic phase and the aqueous phase, remove the upper aqueous phase, and obtain the lower organic solvent phase containing iodine.

[0011] S3: The organic solvent phase containing iodine is distilled to remove the excess extractant and a small amount of water. The binary azeotrope of the organic extractant - water is distilled out from the top of the column and can be used in the next batch of extraction processes. The bottom of the column yields a mixture of iodine - extractant, which can be used in the next batch of synthesis processes. The extractant in the iodine - extractant mixture is a poor solvent for water and a good solvent for iodine.

[0012] S4: The iodine - extractant mixture is further separated by evaporation. After the extractant is condensed at the top of the evaporation column, it is recycled and used in the next batch of extraction processes. Iodine precipitates and crystallizes at the bottom of the column, and the obtained elemental iodine can be recycled and used in the next batch of synthesis processes.

[0013] Furthermore, the strong acid is one of sulfuric acid, nitric acid, and hydrochloric acid.

[0014] Furthermore, the oxidant is one of hydrogen peroxide, nitric acid, nitrous acid, perchloric acid, and chlorine.

[0015] Furthermore, the mixing method for the oxidant in S1 to be fully mixed with the iodine - containing waste liquid is stirring or mixing with a pipe mixer.

[0016] Furthermore, the oxidation reaction temperature in S1 is 20 - 40 °C and the time is 30 - 60 min.

[0017] Furthermore, the organic extractant is one of n - pentane, chloroform, carbon tetrachloride, ether, petroleum ether, and dichloromethane.

[0018] Furthermore, in the organic extractant, an iodine - containing ionic liquid accounting for 1 - 5% of the mass of the extractant is added. Its preparation method is as follows:

[0019] Under the conditions of 0 - 5 °C and stirring, 20 - 30 parts of an ammoniated solution with a mass percentage concentration of 20 - 30% is dropped into 100 - 120 parts of an absolute ethanol solution of 4 - iodo - 1 - butene with a mass percentage concentration of 20 - 30% at a rate of 1 - 2 drops per second, and the reaction lasts for 10 - 15 hours. After the reaction, the reaction solution is transferred to a separatory funnel, shaken with anhydrous ether and the upper layer is discarded. The lower layer solution is distilled under reduced pressure at 40 - 50 °C to remove the solvent, and an iodine - containing ionic liquid is obtained.

[0020] Furthermore, the preparation method of the ammoniated solution is as follows:

[0021] By mass, mix 11 - 22 parts of 5 - pyrimidine methylamine (CAS No.: 25198 - 95 - 2), 0.04 - 0.5 parts of triethylboron - diethylenetriamine (CAS No.: 1187733 - 83 - 0), and 100 - 220 parts of trimethylamine evenly at room temperature to obtain an ammoniated liquid.

[0022] Further, for the separation of the organic phase and the aqueous phase in S2, after the standing is completed, decantation treatment can be carried out for dehydration to obtain an iodine - containing organic phase, or an iodine - containing organic phase can be obtained by separation using a mother - son tank.

[0023] Reaction mechanism

[0024] Preparation of nucleophile: In the ammoniated liquid, 5 - pyrimidine methylamine, triethylboron - diethylenetriamine, and trimethylamine have lone pairs of electrons on the nitrogen atoms in their molecules, becoming reagents with nucleophilic ability.

[0025] Nucleophilic attack transition: Under the conditions of 0 - 5 °C and stirring, the lone pair of electrons on the nitrogen atom of the nucleophile attacks the carbon atom connected to iodine in 4 - iodo - 1 - butene to form a transition state. In this process, the nucleophile starts to form a bond with the carbon atom, and the carbon - iodine bond gradually weakens.

[0026] Salt formation and ion generation: The transition state further transforms, the iodine atom leaves with a pair of electrons to form an iodide ion, and the nucleophile forms a stable covalent bond with the carbon atom, generating a quaternary ammonium salt - type iodine - containing ionic liquid.

[0027] Technical effects

[0028] A method for recycling and reusing iodine in the synthesis process of a certain C 4 F 6 Compared with the prior art, the method for recycling and reusing iodine in the synthesis process of the present invention has the following remarkable effects:

[0029] 1. High iodine recovery rate

[0030] Enhanced extraction ability: The iodine - containing ionic liquid has unique physical and chemical properties. The ionic groups in its molecular structure can have specific interactions with iodine molecules, such as electrostatic interactions, coordination interactions, etc. These interactions enhance the affinity of the composite extractant for iodine, making it easier for iodine to transfer from the reaction solution to the composite extractant. Compared with simply using an organic extractant, adding the iodine - containing ionic liquid can more effectively extract iodine from the reaction solution, thereby improving the iodine recovery rate.

[0031] Improved extraction selectivity: In the reaction solution of the C 4 F 6 synthesis process, there may be various impurities and other components. The iodine - containing ionic liquid can improve the selectivity of the composite extractant for iodine, making it preferentially extract iodine and reducing the extraction of other impurities. This can avoid the interference of impurities in the iodine recovery process and further improve the iodine recovery rate.

[0032] 2. The method for recycling and reusing iodine in the C4F6 synthesis process of the present invention has a high iodine recovery rate, a low water content in the iodine-dichloromethane mixture, and has high economic value. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a process flow diagram. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] To further illustrate the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following, in combination with the accompanying drawings and preferred embodiments, details the specific embodiments, structures, features and their effects according to the present invention as follows.

[0035] 1. Iodine content test: It is determined with reference to "General Test Methods for Salt Industry - Determination of Iodide Ion in GB / T 13025.7-1999".

[0036] 2. Water content test: It is determined by using the Karl Fischer method to measure the iodine-extraction agent.

[0037] Example 1

[0038] A method for recycling and reusing iodine in the C 4 F 6 synthesis process, and its operation steps are as follows:

[0039] S1: Slowly add strong acid and oxidant to the waste iodine solution by using a metering pump to make the oxidant fully mixed with the iodine waste liquid, and online real-time monitor the pH value of the reaction system; the molar ratio of the oxidant to iodide ion is 1:1, and at the same time control the addition flow rate of the oxidant to make the reaction proceed better; the addition amount of the strong acid is determined according to the acidity and alkalinity of the oxidation reaction system to ensure that the pH value of the oxidation reaction system is 1.

[0040] S2: Add an organic extraction agent, fully mix and then let it stand. A layering phenomenon appears in the system. The upper layer is the aqueous phase, and the lower layer is the iodine-containing organic solvent phase. Separate the organic phase and the aqueous phase, and remove the upper aqueous phase to obtain the lower iodine-containing organic solvent phase.

[0041] S3: The iodine-containing organic solvent phase is distilled to remove the excess extraction agent and a small amount of water. The binary azeotrope of the organic extraction agent-water is distilled out from the top of the tower and can be used in the next batch of extraction processes; the iodine-containing extraction agent mixture is obtained at the bottom of the tower and can be used in the next batch of synthesis processes; the extraction agent in the iodine-extraction agent mixture is a poor solvent for water and a good solvent for iodine.

[0042] S4: The iodine-extraction agent mixture is further separated by evaporation. After the extraction agent at the top of the evaporator is condensed, it is recycled and used in the next batch of extraction processes; iodine precipitates and crystallizes at the bottom of the tower, and the obtained elemental iodine can be recycled and used in the next batch of synthesis processes.

[0043] The strong acid described above is sulfuric acid.

[0044] The oxidant described above is hydrogen peroxide.

[0045] The mixing method of fully mixing the oxidant of S1 with the iodine waste liquid is stirring.

[0046] The oxidation reaction temperature of S1 is 20 °C and the time is 30 min.

[0047] The organic extractant described above is n-pentane.

[0048] In the organic extractant described above, an iodine ion-containing liquid accounting for 1% of the mass percentage of the extractant is added. Its preparation method is as follows:

[0049] Under the conditions of 0 °C and stirring, 20 g of an ammoniated liquid with a mass percentage concentration of 20% is dropped into 100 g of an absolute ethanol solution of 4-iodo-1-butene with a mass percentage concentration of 20% at a rate of 1 drop per second, and the reaction is carried out for 10 hours; after the reaction is completed, the reaction solution is transferred to a separating funnel, shaken with anhydrous ether for layering, and the upper layer is discarded; the lower layer solution is distilled under reduced pressure at 40 °C to remove the solvent, and an iodine ion-containing liquid is obtained.

[0050] The preparation method of the ammoniated liquid described above is as follows:

[0051] 11 g of 5-pyrimidine methylamine CAS No.: 25198-95-2, 0.04 g of triethylboron-diethylenetriamine CAS No.: 1187733-83-0, and 100 g of trimethylamine are mixed evenly at room temperature to obtain an ammoniated liquid.

[0052] After the separation of the organic phase and the aqueous phase of S2 and the standing is completed, decantation treatment can be carried out to dehydrate and obtain an iodine-containing organic phase, or an iodine-containing organic phase can be obtained by separation using a mother and son tank.

[0053] Example 2

[0054] A method for recycling and reuse of iodine in the synthesis process of C 4 F 6 The operation steps are as follows:

[0055] S1: Slowly add a strong acid and an oxidant to the waste iodine solution using a metering pump to fully mix the oxidant with the iodine waste liquid, and online real-time monitor the pH value of the reaction system; the molar ratio of the oxidant to the iodide ion is 1:1.1, and at the same time control the flow rate of the oxidant added to make the reaction proceed better; the addition amount of the strong acid is determined according to the acidity and alkalinity of the oxidation reaction system to ensure that the pH value of the oxidation reaction system is 2;

[0056] S2: Add an organic extractant, mix well and let it stand. A layering phenomenon appears in the system. The upper layer is the aqueous phase and the lower layer is the organic solvent phase containing iodine. Separate the organic phase and the aqueous phase, remove the upper aqueous phase, and obtain the lower organic solvent phase containing iodine.

[0057] S3: The organic solvent phase containing iodine is stripped of the excess extractant and a small amount of water by distillation. The binary azeotrope of the organic extractant - water is distilled out from the top of the column and can be used in the next batch of extraction processes; a mixed solution of iodine - extractant is obtained at the bottom of the column and can be used in the next batch of synthesis processes; the extractant in the iodine - extractant mixed solution is a poor solvent for water and a good solvent for iodine.

[0058] S4: The iodine - extractant mixed solution is further separated by evaporation. After the extractant is condensed at the top of the evaporation column, it is recycled and used in the next batch of extraction processes; iodine precipitates and crystallizes at the bottom of the column, and the obtained elemental iodine can be recycled and used in the next batch of synthesis processes.

[0059] The strong acid described is nitric acid.

[0060] The oxidizing agent described is nitric acid.

[0061] The mixing method of the oxidizing agent in S1 and the iodine waste liquid is stirring.

[0062] The oxidation reaction temperature in S1 is 25 °C and the time is 40 min.

[0063] The organic extractant described is chloroform.

[0064] In the organic extractant, an ionic liquid containing iodine accounting for 2% of the mass percentage of the extractant is added. Its preparation method is as follows:

[0065] Under the conditions of 0 °C and stirring, 23 g of ammoniated liquid with a mass percentage concentration of 25% is dropped into 105 g of an absolute ethanol solution of 4 - iodo - 1 - butene with a mass percentage concentration of 25% at a rate of 1 drop per second, and the reaction lasts for 12 hours; after the reaction, the reaction solution is transferred to a separatory funnel, and anhydrous ether is added and shaken to form layers, then the upper layer is discarded; the lower layer solution is distilled under reduced pressure at 45 °C to remove the solvent, and an ionic liquid containing iodine is obtained.

[0066] The preparation method of the ammoniated liquid described is as follows:

[0067] Mix 16 g of 5 - pyrimidine methylamine (CAS No.: 25198 - 95 - 2), 0.2 g of triethylboron - diethylenetriamine (CAS No.: 1187733 - 83 - 0), and 150 g of trimethylamine evenly at room temperature to obtain the ammoniated liquid.

[0068] For the separation of the organic phase and the aqueous phase in S2, after standing, decantation can be carried out to dehydrate and obtain the organic phase containing iodine, or the organic phase containing iodine can be obtained by separation using a mother - son tank.

[0069] Example 3

[0070] A method for recycling and reusing iodine in the synthesis process of C 4 F 6 The operation steps are as follows:

[0071] S1: Slowly add strong acid and oxidant to the waste iodine solution using a metering pump to fully mix the oxidant with the iodine waste solution, and monitor the pH value of the reaction system in real time online; the molar ratio of the oxidant to iodide ion is 1:1.4, and at the same time control the flow rate of the oxidant added to make the reaction proceed better; the addition amount of the strong acid is determined according to the acidity of the oxidation reaction system to ensure that the pH value of the oxidation reaction system is 2;

[0072] S2: Add an organic extractant, fully mix and then let it stand. The system shows a layering phenomenon. The upper layer is the aqueous phase, and the lower layer is the organic solvent phase containing iodine. Separate the organic phase and the aqueous phase, and remove the upper aqueous phase to obtain the lower organic solvent phase containing iodine;

[0073] S3: The organic solvent phase containing iodine is stripped of the excess extractant and a small amount of water by distillation. The binary azeotrope of the organic extractant - water is distilled out from the top of the column and can be used in the next batch of extraction processes; the bottom of the column obtains a mixture of iodine - extractant, which can be used in the next batch of synthesis processes; the extractant in the iodine - extractant mixture is a poor solvent for water and a good solvent for iodine;

[0074] S4: The mixture of iodine - extractant is further separated by evaporation. After the extractant is condensed at the top of the evaporation column, it is returned and reused in the next batch of extraction processes; iodine precipitates and crystallizes at the bottom of the column, and the obtained elemental iodine can be reused in the next batch of synthesis processes.

[0075] The strong acid described is nitric acid.

[0076] The oxidant described is nitrous acid.

[0077] The mixing method for fully mixing the oxidant in S1 with the iodine waste solution is stirring.

[0078] The oxidation reaction temperature in S1 is 35°C and the time is 50 min.

[0079] The organic extractant described is carbon tetrachloride.

[0080] In the organic extractant described, an iodine - ion - containing solution accounting for 4% of the mass of the extractant is added. Its preparation method is:

[0081] Under the conditions of 5 °C and stirring, 28 g of ammoniated liquid with a mass percentage concentration of 28% was dropped into 115 g of an anhydrous ethanol solution of 4-iodo-1-butene with a mass percentage concentration of 25% at a rate of 2 drops per second, and the reaction was carried out for 14 hours; after the reaction was completed, the reaction solution was transferred to a separatory funnel, shaken with anhydrous ether for layering, and the upper layer was discarded; the lower layer solution was distilled under reduced pressure at 45 °C to remove the solvent, and an iodine ion-containing solution was obtained.

[0082] The preparation method of the ammoniated liquid is as follows:

[0083] 20 g of 5-pyrimidine methylamine (CAS No.: 25198-95-2), 0.4 g of triethylboron-diethylenetriamine (CAS No.: 1187733-83-0), and 200 g of trimethylamine were mixed evenly at room temperature to obtain the ammoniated liquid.

[0084] After the separation of the organic phase and the aqueous phase in S2 and the standing is completed, decantation treatment can be carried out to dehydrate and obtain an iodine-containing organic phase, or an iodine-containing organic phase can be obtained by separation using a mother and son tank.

[0085] Example 4

[0086] A method for recycling and reusing iodine in the synthesis process of C 4 F 6 The operation steps are as follows:

[0087] S1: Slowly add a strong acid and an oxidant to the waste iodine solution using a metering pump to fully mix the oxidant with the iodine waste liquid, and online real-time monitor the pH value of the reaction system; the molar ratio of the oxidant to the iodide ion is 1:1.5, and at the same time control the flow rate of the oxidant added to make the reaction proceed better; the addition amount of the strong acid is determined according to the acidity and alkalinity of the oxidation reaction system to ensure that the pH value of the oxidation reaction system is 3;

[0088] S2: Add an organic extractant, mix well and then let it stand. The system shows a layering phenomenon, with the upper layer being the aqueous phase and the lower layer being the iodine-containing organic solvent phase. Separate the organic phase and the aqueous phase, and remove the upper aqueous phase to obtain the lower iodine-containing organic solvent phase;

[0089] S3: The iodine-containing organic solvent phase is distilled to remove the excess extractant and a small amount of water through rectification. The binary azeotrope of the organic extractant - water is distilled out from the top of the column and can be used in the next batch of extraction processes; the iodine - extractant mixture is obtained at the bottom of the column and can be used in the next batch of synthesis processes; the extractant in the iodine - extractant mixture is a poor solvent for water and a good solvent for iodine;

[0090] S4: The iodine - extractant mixture is further separated by evaporation. After the extractant at the top of the evaporation tower is condensed, it is recycled and used in the next batch of extraction processes; iodine precipitates and crystallizes at the bottom of the tower, and the obtained elemental iodine can be recycled and used in the next batch of synthesis processes.

[0091] The strong acid described above is hydrochloric acid.

[0092] The oxidant described above is chlorine gas.

[0093] The mixing method for fully mixing the oxidant of S1 with the iodine waste liquid is stirring.

[0094] The oxidation reaction temperature of S1 is 40 °C and the time is 60 min.

[0095] The organic extractant described above is dichloromethane.

[0096] In the organic extractant described above, an iodine ion-containing solution accounting for 5% of the mass percentage of the extractant is added, and its preparation method is as follows:

[0097] Under the conditions of 5 °C and stirring, 30 g of ammoniated liquid with a mass concentration of 30% is dropped into 120 g of an absolute ethanol solution of 4-iodo-1-butene with a mass concentration of 30% at a rate of 2 drops per second, and the reaction is carried out for 15 hours; after the reaction is completed, the reaction solution is transferred to a separating funnel, shaken with anhydrous ether for layering, and the upper layer is discarded; the lower layer solution is distilled under reduced pressure at 50 °C to remove the solvent to obtain the iodine ion-containing solution.

[0098] The preparation method of the ammoniated liquid described above is as follows:

[0099] 22 g of 5-pyrimidine methylamine CAS No.: 25198-95-2, 0.5 g of triethylboron-diethylenetriamine CAS No.: 1187733-83-0, and 220 g of trimethylamine are mixed evenly at room temperature to obtain the ammoniated liquid.

[0100] After the separation of the organic phase and the aqueous phase of S2 and the standing is completed, decantation treatment can be carried out to dehydrate and obtain the iodine-containing organic phase, or the iodine-containing organic phase can be obtained by separation using a mother and son tank.

[0101] Comparative Example 1

[0102] The iodine ion-containing solution is not added, and the others are the same as in Example 1.

[0103] Comparative Example 2

[0104] The ammoniated liquid is not added, and the others are the same as in Example 1.

[0105] Comparative Example 3

[0106] Triethylboron-diethylenetriamine is not added, and the others are the same as in Example 1.

[0107] Iodine recovery rate / % Moisture content in iodine-dichloromethane mixture / ppm Example 1 97.6 7.5 Example 2 98.3 7.0 Example 3 99.1 6.1 Example 4 99.6 5.7 Comparative Example 1 80.5 20.3 Comparative Example 2 90.1 11.8 Comparative Example 3 92.2 10.7

[0108] Through the data analysis of the above examples and comparative examples, the method for recycling and reuse of iodine in the C4F6 synthesis process of the present invention has a high iodine recovery rate and a low water content in the iodine-dichloromethane mixture, and has high economic value.

[0109] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the above-disclosed technical content within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for recovering iodine from a C4F6 synthesis process, the operating steps of which are: S1: using a metering pump to slowly add a strong acid and an oxidant to the waste iodine solution, so that the oxidant and the waste iodine solution are fully mixed, and the pH value of the reaction system is monitored online in real time; the molar ratio of the oxidant to the iodine ion is 1:(1-1.5), and the flow rate of the oxidant is controlled to make the reaction proceed better; the amount of the strong acid added is determined according to the pH value of the oxidation reaction system to ensure that the pH value of the oxidation reaction system is 1-3; S2: adding an organic extractant, mixing thoroughly and letting it stand, the system will be separated into layers, with an upper aqueous phase and a lower organic solvent phase containing iodine. The organic phase and the aqueous phase are separated, and the upper aqueous phase is removed to obtain a lower organic solvent phase containing iodine; S3: The iodine-containing organic solvent phase is distilled to remove excess extractant and a small amount of water, and the organic extractant-water binary azeotrope is distilled from the top of the tower and can be used in the next batch of extraction process; the iodine-extractant mixed solution is obtained at the bottom of the tower, which can be used in the next batch of synthesis process; the extractant in the iodine-extractant mixed solution is a poor solvent for water and a good solvent for iodine element; S4: The iodine-extractant mixture is further evaporated and separated, and the extractant at the top of the evaporation tower is condensed and returned to be used in the next batch of extraction process; iodine is precipitated and crystallized at the bottom of the tower to obtain elemental iodine, which can be used in the next batch of synthesis process; Adding iodine ion liquid accounting for 1-5% by mass of the extractant to the organic extractant; The iodine-containing ion liquid is a quaternary ammonium salt type iodine-containing ion liquid generated by the reaction of 5-pyrimidinemethylamine, triethylboron-diethylenetriamine and trimethylamine in an ammoniated liquid with 4-iodine-1-butene.

2. A method for recovering iodine from a C4F6 synthesis process according to claim 1, characterized in that: The strong acid is one of sulfuric acid, nitric acid and hydrochloric acid.

3. A method for recovering iodine from a C4F6 synthesis process according to claim 1, characterized in that: The oxidant is one of hydrogen peroxide, nitric acid, nitrous acid, perchloric acid and chlorine.

4. A method for recovering iodine from a C4F6 synthesis process according to claim 1, characterized in that: The oxidant S1 and the iodine waste liquid are fully mixed in a mixing method of stirring or mixing with a pipeline mixer.

5. A method for recovering iodine from a C4F6 synthesis process according to claim 1, characterized in that: The oxidation reaction temperature of S1 is 20-40°C and the time is 30-60 minutes.

6. A method for recovering iodine from a C4F6 synthesis process according to claim 1, characterized in that: The organic extractant is one of n-pentane, chloroform, carbon tetrachloride, ether, petroleum ether and dichloromethane.

7. A method for recovering iodine from a C4F6 synthesis process according to claim 6, characterized in that: The organic extractant is added with iodine ion liquid accounting for 1-5% by mass of the extractant, and the preparation method thereof is as follows: Under the condition of 0-5° C. and stirring, 20-30 parts of ammoniated liquid with a mass percentage concentration of 20-30% are dripped into 100-120 parts of an anhydrous ethanol solution with a mass percentage concentration of 20-30% of 4-iodine-1-butene at a speed of 1-2 drops / second, and the reaction is carried out for 10-15 hours; after the reaction is completed, the reaction solution is transferred to a separating funnel, anhydrous ether is added to shake and separate, and the upper layer is discarded; the lower layer solution is distilled under reduced pressure at 40-50° C. to remove the solvent, so as to obtain an iodine ion-containing liquid.

8. A method for recovering iodine from a C4F6 synthesis process according to claim 7, characterized in that: The preparation method of the ammoniated liquid is: By mass, 11-22 parts of 5-pyrimidinemethylamine, 0.04-0.5 parts of triethylborane-diethylenetriamine, and 100-220 parts of trimethylamine are mixed uniformly at room temperature to obtain an ammoniated solution.

9. A method for recovering iodine from a C4F6 synthesis process according to claim 1, characterized in that: After the separation of the organic phase and the aqueous phase of S2 is allowed to stand, the separated organic phase and the aqueous phase can be decanted to obtain an organic phase containing iodine, or separated by a mother-child tank to obtain an organic phase containing iodine.

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