A method for purifying high purity 1,3-perfluoropropane disulfonic difluoride

Abstract

The application belongs to the field of fluorinated chemical purification technology, and particularly relates to a purification method of high-purity 1,3-perfluoropropane disulfuryl fluoride. The high-purity 1,3-perfluoropropane disulfuryl fluoride product is finally collected from the top of the tower through the three-step continuous purification method of alkali washing neutralization, water washing purification and reduced pressure rectification. The process realizes the excellent technical effects of stable product purity of greater than or equal to 99%, total metal ions of less than or equal to 50 ppm and product yield of greater than or equal to 91% under mild operating conditions, and is suitable for industrial large-scale continuous production.

Description

Technical Field

[0001] This application belongs to the field of fluorine chemical purification technology, specifically relating to a purification method for high-purity 1,3-perfluoropropane disulfonyl fluoride. Background Technology

[0002] 1,3-Perfluoropropane disulfonyl fluoride (C3F8O4S2), also known as 1,1,2,2,3,3-hexafluoropropane-1,3-disulfonyl fluoride, is an important perfluorinated compound containing two sulfonyl fluoride functional groups in its structure. On one hand, as an additive in lithium-ion battery electrolytes, it effectively improves the interfacial chemistry of the battery, forming a stable and dense protective film on the positive electrode surface. This inhibits the oxidative decomposition of the electrolyte during continuous charge-discharge cycles, reduces gas production, and improves the battery's high-temperature storage performance, cycle life, and overall safety. On the other hand, utilizing the high reactivity of its sulfonyl fluoride groups, a series of structurally complex photoacid-generating agents (PAGs) can be further derived and synthesized. These high-value-added applications require extremely high product purity.

[0003] However, the industrial synthesis of 1,3-perfluoropropane disulfonyl fluoride, especially the mainstream electrochemical fluorination method, inevitably introduces various impurities, which mainly include: 1. Residual acidic substances in raw materials or solvents, especially highly corrosive hydrogen fluoride (HF), can cause serious corrosion to equipment in subsequent processes and directly affect the acid value of the final product. 2. Structural analogs and isomers produced during the reaction, such as perfluoroalkane disulfonyl fluoride with different chain lengths or isomers with different functional group positions; 3. Various perfluorinated compound byproducts generated by side reactions such as cyclization and chain scission; 4. Incompletely reacted intermediates or raw materials.

[0004] These impurities may have boiling points and polarities very close to the main product, forming a complex multi-component coexistence system. In addition, during synthesis and post-processing, the materials inevitably come into contact with metal equipment such as reactors, pipelines, pumps, and valves, which can cause metal ions to dissolve and mix into the product, becoming trace impurities.

[0005] However, existing technologies lack an efficient, economical, and scalable purification process specifically for 1,3-perfluoropropane disulfonyl fluoride. Therefore, there is an urgent need for a simple, effective purification scheme suitable for large-scale production to stably prepare high-purity 1,3-perfluoropropane disulfonyl fluoride to meet the application requirements of photoresists, lithium batteries, and other fields. Summary of the Invention

[0006] To address the problem that existing technologies lack an efficient, economical, and scalable purification process specifically for 1,3-perfluoropropane disulfonyl fluoride, this application proposes a purification method for high-purity 1,3-perfluoropropane disulfonyl fluoride.

[0007] To solve the above-mentioned technical problems, this application adopts the following technical solution: A method for purifying high-purity 1,3-perfluoropropane disulfonyl fluoride includes the following steps: Step S1. Alkali washing and neutralization The crude 1,3-perfluoropropane disulfonyl fluoride obtained by electrolysis was added to a washing vessel in proportion with potassium hydroxide solution and stirred thoroughly. The free HF, fluorosulfonic acid, perfluoroalkyl sulfonic acid and other strong acidic impurities in the crude product were removed by acid-base neutralization reaction. After the reaction was completed, stirring was stopped, and the mixture was allowed to settle and separate into layers. The lower organic phase was then separated and collected. Step S2. Water washing and purification The alkaline-washed organic phase obtained in step S1 is added to a washing vessel in a certain proportion with high-purity water and thoroughly mixed under stirring. The residual water-soluble salts and excess KOH in the organic phase are removed by extraction, while the pH value is adjusted to maintain a neutral range (the organic phase collected after alkaline washing is itself close to neutral, and water washing ensures the removal of water-soluble impurities and makes the organic phase neutral after water washing). After mixing is completed, stirring is stopped, and the mixture is allowed to settle and separate into layers. The lower organic phase is then separated and collected. Step S3. Vacuum distillation The water-washed organic phase obtained in step S2 is fed into a distillation column for vacuum distillation. By utilizing the difference in boiling points between different components, the low-boiling-point light component impurities and high-boiling-point heavy component impurities remaining in the organic phase are removed. Finally, high-purity 1,3-perfluoropropane disulfonyl fluoride product is collected from the top of the column.

[0008] Preferably, the concentration of KOH solution in step S1 is 1 mol / L. This concentration ensures complete neutralization of the strong acid impurities while avoiding excessive hydrolysis of the -SO2F group in the 1,3-perfluoropropane disulfonyl fluoride molecule due to excessive alkali concentration, thus reducing product loss.

[0009] Preferably, in step S1, the mass ratio of crude 1,3-perfluoropropane disulfonyl fluoride to KOH solution is 25:1. This ensures that all acidic impurities in the crude product are completely neutralized, while minimizing the amount of alkali used and the amount of wastewater generated in subsequent washing processes, thus reducing treatment costs.

[0010] Preferably, the settling time of the mixture in step S1 is 120 minutes. This settling time ensures complete separation of the organic phase and the aqueous phase, reduces the risk of the organic phase carrying water-soluble impurities such as fluoride salts and excessive alkali from the aqueous phase, and alleviates the burden on subsequent washing processes.

[0011] Preferably, in step S2, the mass ratio of crude 1,3-perfluoropropane disulfonyl fluoride to high-purity water is 10:1. This ratio, while ensuring sufficient removal of water-soluble impurities, reduces the trace dissolution loss of 1,3-perfluoropropane disulfonyl fluoride in the aqueous phase, thereby increasing the overall product yield.

[0012] Preferably, the settling time of the mixture in step S2 is 60 minutes. This settling time allows for rapid separation of the two phases, avoids entrainment of the aqueous phase due to excessively short settling time, and also takes into account production efficiency, making it suitable for continuous industrial production.

[0013] Preferably, the operating temperature of the vacuum distillation is 70~90℃, and the system vacuum degree is -0.04~-0.07MPa. 1,3-Perfluoropropane disulfonyl fluoride has a normal boiling point of approximately 165℃, and is prone to thermal decomposition and hydrolysis side reactions at high temperatures. This application lowers the boiling point of the product by reducing the vacuum level, thus controlling the distillation operating temperature below 90℃, effectively avoiding the thermal decomposition of the product. The aforementioned temperature and vacuum degree achieve efficient separation of light and heavy components from the target product while also considering production energy consumption and equipment investment costs, making it suitable for large-scale continuous industrial production.

[0014] The beneficial effects of this application are as follows: This application employs a three-step process—alkali washing to neutralize acidic impurities, water washing to remove water-soluble salts, and distillation to separate organic impurities—to systematically remove various impurities from the crude product. The final product achieves a stable purity of over 99% and a total metal ion content of ≤50ppm, meeting the application requirements in fields such as lithium battery electrolyte additives and high-end photoresist photoacid generators.

[0015] This application features a simple process that requires no complex specialized equipment or expensive reagents, operates under mild conditions, and consumes little energy. All process parameters have been industrially validated, and the overall product yield is ≥91%. By controlling the material ratios, operating times, and process parameters at each step, this application enables continuous and stable operation of the purification process, resulting in high batch-to-batch consistency of product quality. Attached Figure Description

[0016] Figure 1 This is a process flow diagram for this application. Detailed Implementation

[0017] To further illustrate the technical means and effects adopted by this application in order to achieve the intended purpose of the invention, the following detailed description of the specific implementation methods, structures, features and effects of this application is provided in conjunction with the accompanying drawings and preferred embodiments.

[0018] Example 1

[0019] This embodiment provides a method for purifying high-purity 1,3-perfluoropropane disulfonyl fluoride. A simple process involving alkali washing, water washing, and vacuum distillation is used to purify the crude 1,3-perfluoropropane disulfonyl fluoride. See also... Figure 1 The specific steps are as follows: Step S1. Alkali washing The crude 1,3-perfluoropropane disulfonyl fluoride was mixed thoroughly with KOH solution to remove acidic impurities such as HF. After sedimentation, the organic phase was collected. The concentration of KOH solution was 1 M; the mass ratio of crude 1,3-perfluoropropane disulfonyl fluoride to KOH solution was 25:1; and the sedimentation time of the mixture was 120 min.

[0020] Step S2. Wash with water The crude 1,3-perfluoropropane disulfonyl fluoride, after alkali washing, was mixed thoroughly with high-purity water to remove water-soluble impurities and maintain the pH of the crude product at neutral. After sedimentation, the organic phase was collected. The mass ratio of crude 1,3-perfluoropropane disulfonyl fluoride to high-purity water was 10:1; the sedimentation time of the mixture was 60 min.

[0021] Step S3. Distillation: After alkali washing and water washing, the crude 1,3-perfluoropropane disulfonyl fluoride is fed into a distillation column for vacuum distillation to obtain high-purity 1,3-perfluoropropane disulfonyl fluoride. The operating temperature of the distillation column is controlled at 82℃ and the vacuum degree is -0.06 MPa.

[0022] Processing results: The final product purity was 99.5%; the total metal ion content was 43 ppm; and the product yield was 95%.

[0023] Example 2

[0024] This embodiment provides a purification method for high-purity 1,3-perfluoropropane disulfonyl fluoride. See [link to relevant documentation]. Figure 1 The specific steps are as follows: Step S1. Alkali washing The crude 1,3-perfluoropropane disulfonyl fluoride was mixed thoroughly with KOH solution to remove acidic impurities such as HF. After sedimentation, the organic phase was collected. The concentration of KOH solution was 1 M; the mass ratio of crude 1,3-perfluoropropane disulfonyl fluoride to KOH solution was 25:1; and the sedimentation time of the mixture was 120 min.

[0025] Step S2. Wash with water The crude 1,3-perfluoropropane disulfonyl fluoride, after alkali washing, was mixed thoroughly with high-purity water to remove water-soluble impurities and maintain the pH of the crude product at neutral. After sedimentation, the organic phase was collected. The mass ratio of crude 1,3-perfluoropropane disulfonyl fluoride to high-purity water was 10:1; the sedimentation time of the mixture was 60 min.

[0026] Step S3. Distillation: After alkali washing and water washing, the crude 1,3-perfluoropropane disulfonyl fluoride is fed into a distillation column for vacuum distillation to obtain high-purity 1,3-perfluoropropane disulfonyl fluoride. The operating temperature of the distillation column is controlled at 70℃ and the vacuum degree is -0.07 MPa.

[0027] Processing results: The final product purity was 99.3%; the total metal ion content was 45 ppm; and the product yield was 93%.

[0028] Example 3

[0029] This embodiment provides a purification method for high-purity 1,3-perfluoropropane disulfonyl fluoride. See [link to relevant documentation]. Figure 1 The specific steps are as follows: Step S1. Alkali washing The crude 1,3-perfluoropropane disulfonyl fluoride was mixed thoroughly with KOH solution to remove acidic impurities such as HF. After sedimentation, the organic phase was collected. The concentration of KOH solution was 1 M; the volume ratio of crude 1,3-perfluoropropane disulfonyl fluoride to KOH solution was 25:1; and the sedimentation time of the mixture was 120 min.

[0030] Step S2. Wash with water The crude 1,3-perfluoropropane disulfonyl fluoride, after alkali washing, was mixed thoroughly with high-purity water to remove water-soluble impurities and maintain the pH of the crude product at neutral. After sedimentation, the organic phase was collected. The mass ratio of crude 1,3-perfluoropropane disulfonyl fluoride to high-purity water was 10:1; the sedimentation time of the mixture was 60 min.

[0031] Step S3. Distillation: After alkali washing and water washing, the crude 1,3-perfluoropropane disulfonyl fluoride is fed into a distillation column for vacuum distillation to obtain high-purity 1,3-perfluoropropane disulfonyl fluoride. The operating temperature of the distillation column is controlled at 90℃ and the vacuum degree is -0.04 MPa.

[0032] Processing results: The final product purity was 99.1%; the total metal ion content was 50 ppm; and the product yield was 91%.

[0033] Comparative Example 1 The difference between this comparative example and Example 1 is that the alkaline washing and water washing processes in steps S1 and S2 are omitted. After testing, the final product purity was 98.3%; the total metal ion content was 200 ppm; and the product yield was 85%.

[0034] Without a washing step, acidic impurities, water-soluble fluoride salts, and metal ions in the crude product cannot be effectively removed. A large number of impurities enter the product during the distillation process, resulting in serious failure to meet purity and metal ion standards. At the same time, acidic impurities accelerate product hydrolysis at the high temperature of distillation, further reducing product yield.

[0035] Comparative Example 2 The difference between this comparative example and Example 1 is that the concentration of the KOH solution in step S1 was changed to 2 mol / L. After testing, the final product purity was 98.7%; the total metal ion content was 120 ppm; and the product yield was 82%.

[0036] When the KOH concentration is too high, the disulfonyl fluoride group in the 1,3-perfluoropropane disulfonyl fluoride molecule is affected by the strong electron-withdrawing effect of the perfluoroalkyl group, which increases the electrophilic reactivity and causes severe hydrolysis to generate perfluoropropane disulfonate, resulting in a significant decrease in product yield. At the same time, the hydrolysis products act as surfactants, which intensifies the two-phase emulsification, causing the organic phase to carry more aqueous impurities and increasing the metal ion content.

[0037] Comparative Example 3 The difference between this comparative example and Example 1 is that the concentration of the KOH solution in step S1 was changed to 0.5 mol / L. After testing, the final product purity was 98.5%; the total metal ion content was 160 ppm; and the product yield was 94%.

[0038] When the KOH concentration is insufficient, it cannot completely neutralize acidic impurities such as free HF, fluorosulfonic acid, and perfluoroalkyl sulfonic acid in the crude product. The residual acidic impurities continue to corrode the equipment during subsequent water washing and distillation, releasing more metal ions and causing local hydrolysis of the product, thus reducing the product purity.

[0039] Comparative Example 4 The difference between this comparative example and Example 1 is that the mass ratio of crude 1,3-perfluoropropane disulfonyl fluoride to KOH solution in step S1 was changed to 10:1. After testing, the final product purity was 98.9%; the total metal ion content was 95 ppm; and the product yield was 88%.

[0040] When the amount of alkali solution is too large, it not only increases the contact time and contact area between the product and the strong alkali, thus aggravating hydrolysis loss, but also causes the aqueous phase to be too large, blurring the interface between the two phases, increasing the amount of aqueous impurities entrained in the organic phase, and reducing the removal efficiency of metal ions.

[0041] Comparative Example 5 The difference between this comparative example and Example 1 is that the mass ratio of crude 1,3-perfluoropropane disulfonyl fluoride to KOH solution in step S1 is changed to 50:1. After testing, the final product purity was 98.4%; the total metal ion content was 180 ppm; and the product yield was 94%.

[0042] When the amount of alkali solution is insufficient, acidic impurities cannot be completely neutralized. The residual strong acidic substances such as HF corrode the inner wall and packing of the distillation column during the distillation process, releasing a large number of metal ions, resulting in the metal ion content of the product exceeding the standard.

[0043] By comparing the above embodiments with the comparative examples, the following conclusions can be drawn: The process described in this application achieves excellent technical results under mild operating conditions, with product purity stable at ≥99%, total metal ions ≤50ppm, and product yield ≥91%, making it suitable for large-scale continuous industrial production.

[0044] The above description is merely a preferred embodiment of this application and is not intended to limit this application in any way. Although this application has been disclosed above with reference to preferred embodiments, it is not intended to limit this application. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the technical solution of this application. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A method for purifying high-purity 1,3-perfluoropropane disulfonyl fluoride, characterized in that, Includes the following steps: Step S1. Alkali washing: Mix crude 1,3-perfluoropropane disulfonyl fluoride with alkaline solution to obtain mixture A. After sedimentation, collect the organic phase to obtain alkaline washed 1,3-perfluoropropane disulfonyl fluoride. Step S2. Water washing: Alkali-washed 1,3-perfluoropropane disulfonyl fluoride is mixed evenly with high-purity water to obtain mixture B. Water-soluble impurities are removed and the pH of the crude product is kept neutral. After sedimentation, the organic phase is collected to obtain water-washed 1,3-perfluoropropane disulfonyl fluoride. Step S3. Distillation: The water-washed 1,3-perfluoropropane disulfonyl fluoride is fed to a distillation column for vacuum distillation to finally obtain high-purity 1,3-perfluoropropane disulfonyl fluoride.

2. The purification method for high-purity 1,3-perfluoropropane disulfonyl fluoride according to claim 1, characterized in that, In step S1, the alkaline solution is a KOH solution with a concentration of 1 M.

3. The purification method for high-purity 1,3-perfluoropropane disulfonyl fluoride according to claim 1, characterized in that, In step S1, the mass ratio of crude 1,3-perfluoropropane disulfonyl fluoride to alkaline solution is 25:

1.

4. The purification method for high-purity 1,3-perfluoropropane disulfonyl fluoride according to claim 1, characterized in that, The settling time of the mixture in step S1 is 120 min.

5. The purification method for high-purity 1,3-perfluoropropane disulfonyl fluoride according to claim 1, characterized in that, In step S2, the mass ratio of alkali washing of 1,3-perfluoropropane disulfonyl fluoride to high-purity water is 10:

1.

6. The purification method for high-purity 1,3-perfluoropropane disulfonyl fluoride according to claim 1, characterized in that, The settling time of the mixture in step S2 is 60 min.

7. The purification method for high-purity 1,3-perfluoropropane disulfonyl fluoride according to claim 1, characterized in that, The operating temperature of the vacuum distillation is 70~90℃ and the vacuum degree is -0.04~-0.07 MPa.

Images