Method for reducing content of metal ions in perfluorinated sulfonic acid resin

Abstract

Aiming at the problems of high cost and tedious procedures of a method for reducing the content of metal impurities in perfluorinated sulfonic acid resin in the prior art, the invention provides a method for reducing the content of metal ions in the perfluorinated sulfonic acid resin, which comprises the following steps: soaking the perfluorinated sulfonic acid resin in an inorganic strong acid aqueous solution; washing the soaked perfluorinated sulfonic acid resin with water, soaking the washed perfluorinated sulfonic acid resin in an alcohol-water solvent, and heating the alcohol-water solvent to enable the alcohol-water solvent to flow back; soaking the heated perfluorosulfonic acid resin crude product in a chelating agent aqueous solution, heating the chelating agent aqueous solution, and then performing post-treatment to obtain the purified perfluorosulfonic acid resin.

Description

Technical Field

[0001] The invention belongs to the technical field of fluorine chemical industry, and specifically relates to a method for reducing the metal ion content in perfluorosulfonic acid resin and application thereof. Background Art

[0002] Perfluorosulfonic acid resin has a wide range of applications in proton exchange membrane fuel cells, water electrolysis to produce hydrogen, energy storage batteries, and organic synthesis as a catalyst. The prepared perfluorosulfonic acid resin is melt-extruded or solution-cast to obtain a perfluorosulfonic acid membrane. Before the membrane is prepared, the metal ion content of the perfluorosulfonic acid resin used needs to be tested. The metal ion content will directly affect the chemical properties of the membrane, and then affect the service life of the membrane. Therefore, it is very important to prepare a perfluorosulfonic acid resin with a low metal ion content.

[0003] Some methods for reducing the metal ion content in fluoropolymers are disclosed in the prior art. For example, EP1162212 uses high-purity raw materials to prepare fluoropolymers, but this method is extremely costly and only uses high-purity raw materials, and it is impossible to avoid the introduction of metal ions during the production process, so the effect of reducing the metal ion content is not good. CN104321350A proposes to use cation exchange resin to remove the iron ion content in the aqueous dispersion of fluoropolymers, but the whole set of procedures is cumbersome and not conducive to large-scale production.

[0004] Therefore, there is a need in the art for a method for quickly and efficiently reducing the content of metal impurities in perfluorosulfonic acid resin to prepare high-purity perfluorosulfonic acid resin. Summary of the invention

[0005] Aiming at the problem that the method for reducing the content of metal impurities in perfluorosulfonic acid resin in the prior art is high in cost and complicated in process, the present invention provides a method for reducing the content of metal ions in perfluorosulfonic acid resin.

[0006] The technical solution adopted by the present invention to solve the above technical problems is as follows: The present invention provides a method for reducing the metal ion content in a perfluorosulfonic acid resin, comprising the following steps: The perfluorosulfonic acid resin is immersed in an aqueous solution of an inorganic strong acid; Washing the perfluorosulfonic acid resin soaked in the inorganic strong acid aqueous solution with water, soaking the washed perfluorosulfonic acid resin in an alcohol-water solvent, and heating the alcohol-water solvent to reflux; The heated perfluorosulfonic acid resin is immersed in a chelating agent aqueous solution, the chelating agent aqueous solution is heated, and then post-treated to obtain a purified perfluorosulfonic acid resin.

[0007] Optionally, the alcohol-water solvent is a mixed solvent of an alcohol solvent and water, and the alcohol solvent includes at least one of methanol, ethanol, and isopropanol; And / or, the reflux time is 1-5 hours, and the reflux temperature is 25-60°C.

[0008] Optionally, the mass ratio of the perfluorosulfonic acid resin to the alcohol-water solvent is 1:5 to 1:10; And / or, the mass content of the alcohol solvent in the alcohol-water solvent is 5% to 25%.

[0009] Optionally, the inorganic strong acid includes one or more of nitric acid, sulfuric acid and hydrochloric acid; And / or, the perfluorosulfonic acid resin is immersed in an inorganic strong acid aqueous solution for 8 to 48 hours at a temperature of 25 to 80°C.

[0010] Optionally, the mass ratio of the perfluorosulfonic acid resin to the inorganic strong acid aqueous solution is 1:1 to 1:10; And / or, the mass content of the inorganic strong acid in the inorganic strong acid aqueous solution is 8% to 30%.

[0011] Optionally, the chelating agent is selected from aminocarboxylic acid chelating agents; And / or, the perfluorosulfonic acid resin is immersed in the amino acid chelating agent aqueous solution for 12 to 48 hours at a temperature of 25 to 90°C.

[0012] Optionally, the aminocarboxylic acid chelating agent includes at least one of ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid.

[0013] Optionally, the mass content of the chelating agent in the chelating agent aqueous solution is 1% to 10%; And / or, the mass ratio of the perfluorosulfonic acid resin to the chelating agent aqueous solution is 1:5 to 1:10.

[0014] Optionally, the post-treatment includes filtering, washing and drying the perfluorosulfonic acid resin soaked in the chelating agent aqueous solution.

[0015] Optionally, in the step of “washing the perfluorosulfonic acid resin soaked in the inorganic strong acid aqueous solution”, the resin is washed with water until the conductivity of the washing water is ≤5 μS / cm.

[0016] In the present invention, by immersing the perfluorosulfonic acid resin in an inorganic strong acid aqueous solution, most of the metal ions on the surface or inside of the perfluorosulfonic acid resin and pollutants such as oxides and hydroxides produced by the metal ions are removed, and then the perfluorosulfonic acid resin is swollen by an alcohol-water solvent, so that the metal ions remaining in the perfluorosulfonic acid resin are transferred to an organic aqueous solution, and then the remaining metal ions are removed by the chelation of a chelating agent. Compared with the prior art, the purification method of the present invention has the characteristics of simple operation, high metal ion removal rate, and organic solvent recyclable. The purification method of the present invention can effectively reduce the metal ion content in the perfluorosulfonic acid resin, especially the iron ion content can be reduced to less than 50ppb, and the purification method is energy-saving and environmentally friendly, and is suitable for large-scale production. DETAILED DESCRIPTION In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0017] The embodiment of the present invention provides a method and application for reducing the metal ion content in a perfluorosulfonic acid resin, comprising the following steps: S1 acid leaching: immersing the perfluorosulfonic acid resin in an aqueous solution of an inorganic strong acid; specifically, the perfluorosulfonic acid resin is prepared by a common polymerization method, and is washed with alkali and acid to obtain the perfluorosulfonic acid resin product to be purified in this embodiment.

[0018] S2 swelling: washing the perfluorosulfonic acid resin soaked in the inorganic strong acid aqueous solution with water, soaking the washed perfluorosulfonic acid resin in an alcohol-water solvent, and heating the alcohol-water solvent to reflux; S3 Chelation: soaking the heated perfluorosulfonic acid resin in a chelating agent aqueous solution, heating the chelating agent aqueous solution, and then post-treating to obtain the purified perfluorosulfonic acid resin.

[0019] In the present embodiment, by immersing perfluorosulfonic acid resin in an inorganic strong acid aqueous solution, pollutants such as oxides and hydroxides produced by most of the metal ions on the surface or inside of the perfluorosulfonic acid resin and the metal ions are removed, and then the perfluorosulfonic acid resin is swollen by an alcohol-water solvent so that the metal ions remaining in the perfluorosulfonic acid resin are transferred to an organic aqueous solution, and then the remaining metal ions are removed by the chelation of a chelating agent. Compared with the prior art, the purification method of the present invention has the characteristics of simple operation, high metal ion removal rate and organic solvent recyclability. The purification method of the present invention can effectively reduce the metal ion content in the perfluorosulfonic acid resin, especially the iron ion content can be reduced to less than 50ppb, and the purification method is energy-saving and environmentally friendly, and is suitable for large-scale production. In some embodiments, the alcohol-water solvent is a mixed solvent of an alcohol solvent and water, and the alcohol solvent includes at least one of methanol, ethanol, and isopropanol; The reflux time is 1-5 hours, the reflux temperature is 25-60° C. The perfluorosulfonic acid resin is fully swollen by reflux, so that the residual metal ions are transferred to the alcohol-water solvent.

[0020] In some embodiments, the mass ratio of the perfluorosulfonic acid resin to the alcohol-water solvent is 1:5 to 1:10; The mass content of the alcohol solvent in the alcohol-water solvent is 5% to 25%. By selecting the alcohol-water solvent of the above mass, the perfluorosulfonic acid resin can be fully swollen during the swelling process.

[0021] In some embodiments, the strong inorganic acid includes one or more of nitric acid, sulfuric acid, and hydrochloric acid; The perfluorosulfonic acid resin is immersed in an inorganic strong acid aqueous solution for 8 to 48 hours at a temperature of 25 to 80° C. By controlling the temperature and time of the acid immersion, most of the metal ions on the surface or inside of the perfluorosulfonic acid resin and pollutants such as oxides and hydroxides generated by the metal ions are removed.

[0022] In some embodiments, the mass ratio of the perfluorosulfonic acid resin to the inorganic strong acid aqueous solution is 1:1 to 1:10; The mass content of the inorganic strong acid in the inorganic strong acid aqueous solution is 8% to 30%. By controlling the mass and concentration of the inorganic strong acid aqueous solution, most of the metal ions on the surface or inside of the perfluorosulfonic acid resin and pollutants such as oxides and hydroxides generated by the metal ions can be removed.

[0023] In some embodiments, the chelating agent is selected from aminocarboxylic acid chelating agents; The perfluorosulfonic acid resin is immersed in the amino acid chelating agent aqueous solution for 12 to 48 hours at a temperature of 25 to 90° C. By selecting an amino acid chelating agent, the metal ion content of the perfluorosulfonic acid resin is effectively reduced. Specifically, during the chelation process in step S3, the chelating agent aqueous solution is refluxed by heating to facilitate full chelation with metal ions.

[0024] In some embodiments, the aminocarboxylic acid chelating agent includes at least one of ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid.

[0025] In some embodiments, the mass content of the chelating agent in the chelating agent aqueous solution is 1% to 10%, and the amount of the chelating agent used is low, thereby reducing the purification cost.

[0026] The mass ratio of the perfluorosulfonic acid resin to the chelating agent aqueous solution is 1:5-1:10.

[0027] In some embodiments, the post-treatment comprises filtering, washing and drying the perfluorosulfonic acid resin soaked in the chelating agent aqueous solution.

[0028] In some embodiments, in the step of "washing the perfluorosulfonic acid resin soaked in the inorganic strong acid aqueous solution", the resin is washed with water until the conductivity of the washing water is ≤5 μS / cm.

[0029] In a preferred embodiment, the number of water washing in step S2 is 5 to 10 times, and the water washing is considered qualified when the conductivity of the washing water is ≤2μS / cm.

[0030] The present invention is further described below by way of examples.

[0031] The perfluorosulfonic acid resins used in the following examples and comparative examples were all immersed in a 10% sulfuric acid aqueous solution at 60° C. for 24 h and then washed with water until the conductivity was ≤5 μS / cm.

[0032] Example 1 500 g of perfluorosulfonic acid resin and 2500 g of ethanol aqueous solution (concentration of 10%) were added to a glass reactor, stirred and refluxed at 30° C. for 4 hours, cooled and filtered to obtain a crude perfluorosulfonic acid resin.

[0033] Take 125 g of ethylenediaminetetraacetic acid and add it to water to prepare an ethylenediaminetetraacetic acid aqueous solution with a mass concentration of 2500 g and a mass concentration of 5%.

[0034] The aqueous solution of ethylenediaminetetraacetic acid was added to the crude perfluorosulfonic acid resin, stirred and refluxed at 30°C for 12 hours, cooled, filtered, washed with water, and dried to obtain a perfluorosulfonic acid resin product. The residual amount of metallic iron ions in the product was measured by ICP to be 49 ppb.

[0035] Example 2 500 g of perfluorosulfonic acid resin and 3000 g of ethanol aqueous solution (concentration of 15%) were added to a glass reactor, stirred and refluxed at 45° C. for 6 hours, cooled and filtered to obtain a crude perfluorosulfonic acid resin.

[0036] Take 300 g of diethylenetriaminepentaacetic acid and add it to water to prepare an aqueous solution of ethylenediaminetetraacetic acid with a mass concentration of 3000 g and a mass concentration of 1%.

[0037] The aqueous solution of diethylenetriaminepentaacetic acid was added to the crude perfluorosulfonic acid resin, stirred and refluxed at 45°C for 24 hours, cooled, filtered, washed with water, and dried to obtain a perfluorosulfonic acid resin product. The residual amount of metallic iron ions in the product was measured by ICP to be 38 ppb.

[0038] Example 3 1000 g of perfluorosulfonic acid resin and 8000 g of methanol aqueous solution (concentration of 20%) were added to a glass reactor, stirred and refluxed at 30° C. for 4 hours, cooled and filtered to obtain a crude perfluorosulfonic acid resin.

[0039] Take 1000 g of ethylenediaminetetraacetic acid and add it to water to prepare an ethylenediaminetetraacetic acid aqueous solution with a mass concentration of 10,000 g and a mass concentration of 10%.

[0040] The aqueous solution of ethylenediaminetetraacetic acid was added to the crude perfluorosulfonic acid resin, stirred and refluxed at 60°C for 48 hours, cooled, filtered, washed with water, and dried to obtain a perfluorosulfonic acid resin product. The residual amount of metallic iron ions in the product was measured by ICP to be 22 ppb.

[0041] Example 4 This embodiment is substantially the same as embodiment 1, except that 5000 g of 10% ethanol aqueous solution is used. The residual amount of metallic iron ions in the product measured by ICP is 40 ppb.

[0042] Example 5 This embodiment is substantially the same as embodiment 1, except that 2000 g of 10% ethanol aqueous solution is used. The residual amount of metallic iron ions in the product measured by ICP is 180 ppb.

[0043] Example 6 This embodiment is substantially the same as embodiment 1, except that 6000 g of 10% ethanol aqueous solution is used. The residual amount of metallic iron ions in the product measured by ICP is 42 ppb.

[0044] Example 7 This embodiment is substantially the same as embodiment 1, except that the mass concentration of the ethanol aqueous solution is 25%. The residual amount of metallic iron ions in the product measured by ICP is 38 ppb.

[0045] Example 8 This embodiment is substantially the same as embodiment 1, except that the mass concentration of the ethanol aqueous solution is 5%. The residual amount of metallic iron ions in the product measured by ICP is 64 ppb.

[0046] Example 9 This embodiment is substantially the same as embodiment 1, except that the mass concentration of the ethanol aqueous solution is 30%. The residual amount of metallic iron ions in the product measured by ICP is 110 ppb.

[0047] Example 10 This embodiment is substantially the same as embodiment 1, except that the mass concentration of the ethanol aqueous solution is 2%. The residual amount of metallic iron ions in the product measured by ICP is 260 ppb.

[0048] Comparative Example 1 The same perfluorosulfonic acid resin particles as those in Example 1 were prepared, but were not treated with the ethanol aqueous solution and the ethylenediaminetetraacetic acid aqueous solution. The residual amount of metallic iron ions in the product was measured to be 245 ppm.

[0049] Comparative Example 2 This embodiment is substantially the same as embodiment 1, except that the swelling treatment with ethanol aqueous solution is not performed. The residual amount of metallic iron ions in the product measured by ICP is 150 ppm.

[0050] Comparative Example 3 This embodiment is substantially the same as embodiment 1, except that the chelation treatment with ethylenediaminetetraacetic acid aqueous solution is not performed. The residual amount of metallic iron ions in the product measured by ICP is 180 ppm.

[0051] The metal ion content test method in the above embodiments and comparative examples is as follows: 100 g of perfluorosulfonic acid resin particles are placed in 100 mL of ion extraction solution (20% by mass ultra-high purity nitric acid), immersed at 60° C. for 24 hours, and after cooling, the metal ion content is measured by ICP-MS.

[0052] According to the test data of Examples 1 to 3 and Comparative Examples 1-3, in this embodiment, the perfluorosulfonic acid resin is swollen by an alcohol aqueous solution, and the residual metal ions in the perfluorosulfonic acid resin are transferred to an organic aqueous solution, and then the remaining metal ions are removed by the chelating action of an aminocarboxylic acid chelating agent, which can effectively reduce the metal ion content in the perfluorosulfonic acid resin, especially the iron ion content to below 50 ppb.

[0053] It can be seen from the test data of Examples 1 and 4 to 10 that the swelling degree of the perfluorosulfonic acid resin can be regulated by controlling the concentration of the alcohol-water solvent and its mass ratio to the perfluorosulfonic acid resin. When the mass ratio of the perfluorosulfonic acid resin to the alcohol-water solvent is 1:5 to 1:10 and the mass content of the alcohol solvent in the alcohol-water solvent is 5% to 25%, the perfluorosulfonic acid resin can be fully swollen to facilitate the transfer of metal ions to the alcohol-water solvent, and the metal ion content of the perfluorosulfonic acid resin finally purified is low.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for reducing the metal ion content in a perfluorosulfonic acid resin, characterized in that: The following steps are involved: The perfluorosulfonic acid resin is immersed in an aqueous solution of an inorganic strong acid; Washing the perfluorosulfonic acid resin soaked in the inorganic strong acid aqueous solution with water, soaking the washed perfluorosulfonic acid resin in an alcohol-water solvent, and heating the alcohol-water solvent to reflux; The heated perfluorosulfonic acid resin is immersed in a chelating agent aqueous solution, the chelating agent aqueous solution is heated, and then post-treated to obtain a purified perfluorosulfonic acid resin.

2. The method for reducing the metal ion content in perfluorosulfonic acid resin according to claim 1, characterized in that: The alcohol-water solvent is a mixed solvent of an alcohol solvent and water, and the alcohol solvent includes at least one of methanol, ethanol, and isopropanol; And / or, the reflux time is 1-5 hours, and the reflux temperature is 25-60°C.

3. The method for reducing the metal ion content in perfluorosulfonic acid resin according to claim 1, characterized in that: The mass ratio of the perfluorosulfonic acid resin to the alcohol-water solvent is 1:5 to 1:10; And / or, the mass content of the alcohol solvent in the alcohol-water solvent is 5% to 25%.

4. The method for reducing the metal ion content in perfluorosulfonic acid resin according to claim 1, characterized in that: The inorganic strong acid includes one or more of nitric acid, sulfuric acid and hydrochloric acid; And / or, the perfluorosulfonic acid resin is immersed in an inorganic strong acid aqueous solution for 8 to 48 hours at a temperature of 25 to 80°C.

5. The method for reducing the metal ion content in perfluorosulfonic acid resin according to claim 1, characterized in that: The mass ratio of the perfluorosulfonic acid resin to the inorganic strong acid aqueous solution is 1:1 to 1:10; And / or, the mass content of the inorganic strong acid in the inorganic strong acid aqueous solution is 8% to 30%.

6. The method for reducing the metal ion content in perfluorosulfonic acid resin according to claim 1, characterized in that: The chelating agent is selected from aminocarboxylic acid chelating agents; And / or, the perfluorosulfonic acid resin is immersed in the amino acid chelating agent aqueous solution for 12 to 48 hours at a temperature of 25 to 90°C.

7. The method for reducing the metal ion content in perfluorosulfonic acid resin according to claim 6, characterized in that: The aminocarboxylic acid chelating agent includes at least one of ethylenediaminetetraacetic acid and diethylenetriaminepentaacetic acid.

8. The method for reducing the metal ion content in perfluorosulfonic acid resin according to claim 1, characterized in that: The mass content of the chelating agent in the chelating agent aqueous solution is 1% to 10%; And / or, the mass ratio of the perfluorosulfonic acid resin to the chelating agent aqueous solution is 1:5 to 1:

10.

9. The method for reducing the metal ion content in perfluorosulfonic acid resin according to claim 1, characterized in that: The post-treatment comprises filtering, washing and drying the perfluorosulfonic acid resin soaked in the chelating agent aqueous solution.

10. The method for reducing the metal ion content in perfluorosulfonic acid resin according to claim 1, characterized in that: In the step of "washing the perfluorosulfonic acid resin soaked in the inorganic strong acid aqueous solution", the resin is washed until the conductivity of the washing water is ≤5 μS / cm.