Method for preparing perfluorosulfonic acid solution and perfluorosulfonic acid ionic membrane by adopting waste ionic membrane

Abstract

The invention belongs to the technical field of ionic membrane recycling, and particularly relates to a method for preparing a perfluorosulfonic acid solution and a perfluorosulfonic acid ionic membrane by adopting a waste ionic membrane. The method comprises the following steps: mildly removing inorganic impurities in the waste ionic membrane by using a tetrabutylammonium bromide-lactic acid mixed solution, efficiently removing organic matters in the waste ionic membrane by using a betaine-glycerol mixed solution, and efficiently dissolving perfluororesin by using a 1-ethyl-3-methylimidazolium acetate-ethylene glycol system to separate the perfluororesin from a PTFE reinforced net. Finally, the perfluorosulfonic acid resin and the perfluorocarboxylic acid resin are separated by adopting an isopropanol-water system, triethyl phosphate and polypropylsilsesquioxane are additionally added when the perfluorosulfonic acid ion exchange membrane is prepared, and the smoothness of the prepared perfluorosulfonic acid ion exchange membrane is enhanced by adding the triethyl phosphate; by adding the polypropyl silsesquioxane, the tensile strength of the prepared perfluorosulfonic acid ionic membrane is enhanced; all the steps have a synergistic effect, and it is ensured that the prepared ionic membrane is excellent in performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of ion membrane recycling, and specifically relates to a method for preparing perfluorosulfonic acid solution and perfluorosulfonic acid ion membrane by using waste ion membranes. Background Art

[0002] Perfluorosulfonic acid resin (PFSR) has been widely used as a polymer material in fields such as hydrogen-oxygen fuel cells, electrolysis of water to produce hydrogen and oxygen, organic electrosynthesis, gas sensors, and composite membranes composed of carboxylic acid membranes for chlor-alkali industry due to its excellent mechanical, thermal, chemical, and electrochemical stabilities, and has attracted much attention. With the continuous advancement of the industrialization process of proton exchange membrane fuel cells (PEMFC) and the increasing proportion of ion membrane caustic soda production in the chlor-alkali industry, a large amount of waste perfluorosulfonic acid ion exchange membranes will inevitably be generated. Currently, the main methods for treating these waste ion membranes are "landfilling" and "incineration". The former consumes a large amount of farmland, and since the ion membrane is a perfluoropolymer and is difficult to degrade, it causes land waste and soil pollution; while the latter generates toxic and harmful gases such as fluorine oxides and sulfur oxides during the incineration process, polluting the atmosphere. Both methods are not environmentally friendly.

[0003] The perfluorocarbon backbone structure of ion exchange has very good thermal and chemical stabilities and can withstand the harsh corrosion environment in the chlor-alkali electrolytic cell. The main reason for the loss of ion membrane performance is not due to chemical degradation of the ion membrane in the electrolytic cell, but due to the deposition of impurities in the membrane during the electrolysis process. Therefore, obtaining perfluorosulfonic acid resin or perfluorocarboxylic acid resin from waste membranes may be more straightforward than obtaining the resin from raw material monomers through a cumbersome synthesis process.

[0004] In order to reduce production costs, make the most efficient use of ion membranes, and reduce the adverse impact on the environment, it is necessary to explore a new method for preparing perfluorosulfonic acid solution and perfluorosulfonic acid ion membrane by using waste ion membranes. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing perfluorosulfonic acid solution and perfluorosulfonic acid ion membrane by using waste ion membranes. The perfluorosulfonic acid ion membrane prepared by this method has good tensile strength and low linear swelling rate.

[0006] The method for preparing perfluorosulfonic acid solution and perfluorosulfonic acid ion membrane by using waste ion membranes according to the present invention comprises the following steps: (1) Immerse the waste ion membrane for chlor-alkali industry in a mixed solution of tetrabutylammonium bromide - lactic acid, react at 95 - 97 °C for 7 h, and then wash the waste ion membrane for chlor-alkali industry with deionized water until the pH value is neutral; (2) Immerse the waste ion exchange membrane for chlor-alkali industry rinsed in step (1) in a mixture of betaine and glycerol, react at 65 - 70 °C for 55 - 57 min, and then wash the waste ion exchange membrane for chlor-alkali industry with deionized water until the pH value is neutral; (3) Immerse the waste ion exchange membrane for chlor-alkali industry rinsed in step (2) in a 1-ethyl-3-methylimidazolium acetate - ethylene glycol system at 100 °C for 20 - 25 min, then mechanically separate the resin from the PTFE reinforcing mesh, and wash the product with deionized water until the washing liquid is clear and transparent, and obtain a mixture of perfluorocarboxylic acid resin and perfluorosulfonic acid resin after drying; (4) Add a mixed solution of isopropanol and water to the mixture of perfluorocarboxylic acid resin and perfluorosulfonic acid resin, then react at 248 - 250 °C for 4.5 h, and filter to prepare a perfluorosulfonic acid resin solution; (5) Mix the perfluorosulfonic acid resin solution, triethyl phosphate, and polypropylsilsesquioxane evenly, and then pour it onto a flat mold to form a perfluorosulfonic acid ion exchange membrane by the casting method.

[0007] Among them: The preparation method of the mixture of tetrabutylammonium bromide - lactic acid in step (1) is to mix tetrabutylammonium bromide and lactic acid according to a molar ratio of 1:2.3 - 2.5, heat up to 68 - 70 °C and react for 4 - 4.2 h to prepare a mixture of tetrabutylammonium bromide - lactic acid.

[0008] The preparation method of the mixture of betaine - glycerol in step (2) is to mix betaine and glycerol according to a molar ratio of 0.35 - 0.4:1, heat up to 72 °C and react for 3.3 - 3.5 h to prepare a mixture of betaine - glycerol.

[0009] The preparation method of the 1-ethyl-3-methylimidazolium acetate - ethylene glycol system in step (3) is to mix 1-ethyl-3-methylimidazolium acetate and ethylene glycol according to a molar ratio of 1:3, heat up to 80 - 85 °C and react for 3.8 - 4 h to prepare a 1-ethyl-3-methylimidazolium acetate - ethylene glycol system.

[0010] The drying temperature in step (3) is 100 - 105 °C, and the drying time is 14 h.

[0011] The volume ratio of isopropanol to water in step (4) is 1:1.

[0012] The mass-volume ratio of the mixture of perfluorocarboxylic acid resin and perfluorosulfonic acid resin to the mixed solution of isopropanol - water in step (4) is 1:6.67, with the unit of g / mL.

[0013] The reaction pressure in step (4) is 5.7 MPa.

[0014] In step (5), the mass of triethyl phosphate accounts for 13 - 15% of the mass of the perfluorosulfonic acid resin solution, and the mass of polypropylsilsesquioxane accounts for 18 - 20% of the mass of the perfluorosulfonic acid resin solution.

[0015] In step (5), during mixing, the stirring speed is 500 r / min, the mixing temperature is room temperature, and the mixing time is 15 - 20 min.

[0016] In step (5), the prepared membrane is vacuum dried at 78 - 80 °C for 24 h, and then heat treated at 183 - 185 °C for 1.5 h to prepare the perfluorosulfonic acid ion membrane.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) In the method for preparing perfluorosulfonic acid solution and perfluorosulfonic acid ion membrane using waste ion membrane according to the present invention, first, a mixture of tetrabutylammonium bromide - lactic acid is used to gently remove inorganic impurities in the waste ion membrane, then a mixture of betaine - glycerol is used to efficiently remove organic substances and metal pollutants in the waste ion membrane, the perfluororesin is efficiently dissolved and separated from the PTFE reinforcing mesh through a 1 - ethyl - 3 - methylimidazolium acetate - ethylene glycol system, and finally an isopropanol - water system is used to separate the perfluorosulfonic acid resin from the perfluorocarboxylic acid resin. When preparing the perfluorosulfonic acid ion exchange membrane, triethyl phosphate and polypropylsilsesquioxane are additionally added. The addition of triethyl phosphate enhances the smoothness of the prepared perfluorosulfonic acid ion membrane, ensuring no cracking and bubbles, and the addition of polypropylsilsesquioxane enhances the tensile strength of the prepared perfluorosulfonic acid ion membrane; the various steps cooperate with each other to ensure the stable performance of the prepared perfluorosulfonic acid ion membrane.

[0018] (2) The method for preparing perfluorosulfonic acid solution and perfluorosulfonic acid ion membrane using waste ion membrane according to the present invention has a simple process, easy - to - control parameters, and is easy to realize industrial production. The perfluorosulfonate ion membrane prepared by this method has good tensile strength and low linear swelling rate. Specific Embodiments

[0019] The present invention will be further described below in conjunction with embodiments.

[0020] Example 1 The method for preparing perfluorosulfonic acid solution and perfluorosulfonic acid ion membrane using waste ion membrane described in this Example 1 consists of the following steps: (1) Immerse the waste ion membrane used in the chlor - alkali industry in a mixture of tetrabutylammonium bromide - lactic acid, react at 96 °C for 7 h, and then wash the waste ion membrane used in the chlor - alkali industry with deionized water until the pH value is neutral; (2) Immerse the waste ion exchange membrane for chlor-alkali industry rinsed in step (1) in the mixture of betaine and glycerol, react at 67 °C for 56 min, and then wash the waste ion exchange membrane for chlor-alkali industry with deionized water until the pH value is neutral. (3) Immerse the waste ion exchange membrane for chlor-alkali industry rinsed in step (2) in the 1-ethyl-3-methylimidazolium acetate-ethylene glycol system at 100 °C for 23 min, then separate the resin from the PTFE reinforcing mesh by mechanical method, and wash the product with deionized water until the cleaning solution is clear and transparent, and obtain the mixture of perfluorocarboxylic acid resin and perfluorosulfonic acid resin after drying. (4) Add the mixed solution of isopropanol and water to the mixture of perfluorocarboxylic acid resin and perfluorosulfonic acid resin, then react at 249 °C for 4.5 h, and filter to prepare the perfluorosulfonic acid resin solution. (5) Mix the perfluorosulfonic acid resin solution, triethyl phosphate and polypropylsilsesquioxane evenly, and then pour it onto a flat mold to make a perfluorosulfonic acid ion exchange membrane by the casting method.

[0021] Among them: The preparation method of the mixture of tetrabutylammonium bromide-lactic acid in step (1) is to mix tetrabutylammonium bromide and lactic acid according to the molar ratio of 1:2.4, heat up to 69 °C and react for 4.1 h to prepare the mixture of tetrabutylammonium bromide-lactic acid.

[0022] The preparation method of the mixture of betaine-glycerol in step (2) is to mix betaine and glycerol according to the molar ratio of 0.37:1, heat up to 72 °C and react for 3.4 h to prepare the mixture of betaine-glycerol.

[0023] The preparation method of the 1-ethyl-3-methylimidazolium acetate-ethylene glycol system in step (3) is to mix 1-ethyl-3-methylimidazolium acetate and ethylene glycol according to the molar ratio of 1:3, heat up to 83 °C and react for 3.9 h to prepare the 1-ethyl-3-methylimidazolium acetate-ethylene glycol system.

[0024] In step (3), the drying temperature is 103 °C and the drying time is 14 h.

[0025] In step (4), the volume ratio of isopropanol to water is 1:1.

[0026] In step (4), the mass-volume ratio of the mixture of perfluorocarboxylic acid resin and perfluorosulfonic acid resin to the mixed solution of isopropanol and water is 1:6.67, with the unit of g / mL.

[0027] In step (4), the reaction pressure is 5.7 MPa.

[0028] In step (5), the mass of triethyl phosphate accounts for 14% of the mass of the perfluorosulfonic acid resin solution, and the mass of polypropylsilsesquioxane accounts for 19% of the mass of the perfluorosulfonic acid resin solution.

[0029] In step (5), the stirring speed during mixing is 500 r / min, the mixing temperature is room temperature, and the mixing time is 17 min.

[0030] In step (5), the prepared membrane is vacuum dried at 79 °C for 24 h, and then heat treated at 184 °C for 1.5 h to prepare a perfluorosulfonic acid ion exchange membrane.

[0031] After testing, the tensile strength of the perfluorosulfonic acid ion exchange membrane prepared in Example 1 is 35.3 MPa, and the linear swelling rate at 25 °C is 2.1%.

[0032] Example 2 The method for preparing a perfluorosulfonic acid solution and a perfluorosulfonic acid ion membrane using a waste ion membrane described in this Example 2 consists of the following steps: (1) Immerse the waste ion membrane for chlor-alkali industry in a mixed solution of tetrabutylammonium bromide - lactic acid, react at 95 °C for 7 h, and then wash the waste ion membrane for chlor-alkali industry with deionized water until the pH value is neutral; (2) Immerse the waste ion membrane for chlor-alkali industry rinsed in step (1) in a mixed solution of betaine - glycerol, react at 65 °C for 57 min, and then wash the waste ion membrane for chlor-alkali industry with deionized water until the pH value is neutral; (3) Immerse the waste ion membrane for chlor-alkali industry rinsed in step (2) in a 1-ethyl-3-methylimidazolium acetate - ethylene glycol system at 100 °C for 20 min, and then mechanically separate the resin from the PTFE reinforcing mesh. Rinse the product with deionized water until the cleaning solution is clear and transparent, and obtain a mixture of perfluorocarboxylic acid resin and perfluorosulfonic acid resin after drying; (4) Add a mixed solution of isopropanol - water to the mixture of perfluorocarboxylic acid resin and perfluorosulfonic acid resin, and then react at 248 °C for 4.5 h, and filter to prepare a perfluorosulfonic acid resin solution; (5) Mix the perfluorosulfonic acid resin solution, triethyl phosphate, and polypropylsilsesquioxane evenly, and then pour it onto a flat mold to form a perfluorosulfonic acid ion membrane by the casting method.

[0033] Among them: The preparation method of the mixed solution of tetrabutylammonium bromide - lactic acid described in step (1) is to mix tetrabutylammonium bromide and lactic acid according to a molar ratio of 1:2.5, and heat up to 70 °C and react for 4.2 h to prepare the mixed solution of tetrabutylammonium bromide - lactic acid.

[0034] The preparation method of the betaine-glycerol mixture described in step (2) is to mix betaine and glycerol in a molar ratio of 0.35:1, heat up to 72 °C and react for 3.5 h to obtain the betaine-glycerol mixture.

[0035] The preparation method of the 1-ethyl-3-methylimidazolium acetate-ethylene glycol system described in step (3) is to mix 1-ethyl-3-methylimidazolium acetate and ethylene glycol in a molar ratio of 1:3, heat up to 80 °C and react for 4 h to obtain the 1-ethyl-3-methylimidazolium acetate-ethylene glycol system.

[0036] In step (3), the drying temperature is 100 °C and the drying time is 14 h.

[0037] In step (4), the volume ratio of isopropanol to water is 1:1.

[0038] In step (4), the mass-volume ratio of the mixture of perfluorocarboxylic acid resin and perfluorosulfonic acid resin to the isopropanol-water mixed solution is 1:6.67, with the unit of g / mL.

[0039] In step (4), the reaction pressure is 5.7 MPa.

[0040] In step (5), the mass of triethyl phosphate accounts for 13% of the mass of the perfluorosulfonic acid resin solution, and the mass of polypropylsilsesquioxane accounts for 20% of the mass of the perfluorosulfonic acid resin solution.

[0041] In step (5), the stirring speed during mixing is 500 r / min, the mixing temperature is room temperature, and the mixing time is 15 min.

[0042] In step (5), the prepared membrane is vacuum dried at 78 °C for 24 h, and then heat treated at 183 °C for 1.5 h to obtain the perfluorosulfonic acid ion exchange membrane.

[0043] After testing, the tensile strength of the perfluorosulfonic acid ion exchange membrane prepared in Example 2 is 34.8 MPa, and the linear swelling rate at 25 °C is 2.3%.

[0044] Example 3 The method for preparing perfluorosulfonic acid solution and perfluorosulfonic acid ion membrane using waste ion membrane described in this Example 3 consists of the following steps: (1) Immerse the waste ion membrane for chlor-alkali industry in the mixture of tetrabutylammonium bromide-lactic acid, react at 97 °C for 7 h, and then wash the waste ion membrane for chlor-alkali industry with deionized water until the pH value is neutral; (2) Immerse the waste ion membrane for chlor-alkali industry rinsed in step (1) in the betaine-glycerol mixture, react at 70 °C for 55 min, and then wash the waste ion membrane for chlor-alkali industry with deionized water until the pH value is neutral; (3) Immerse the waste ion-exchange membrane for chlor-alkali industry rinsed in step (2) in the 1-ethyl-3-methylimidazolium acetate-ethylene glycol system at 100 °C for 25 min, then separate the resin from the PTFE reinforcing mesh by mechanical means, and rinse the product with deionized water until the cleaning solution is clear and transparent. After drying, a mixture of perfluorocarboxylic acid resin and perfluorosulfonic acid resin is obtained; (4) Add a mixed solution of isopropanol and water to the mixture of perfluorocarboxylic acid resin and perfluorosulfonic acid resin, then react at 250 °C for 4.5 h, and filter to prepare a perfluorosulfonic acid resin solution; (5) Mix the perfluorosulfonic acid resin solution, triethyl phosphate and polypropylsilsesquioxane evenly, and then pour it onto a flat mold to form a perfluorosulfonic acid ion-exchange membrane by the casting method.

[0045] Among them: The preparation method of the mixed solution of tetrabutylammonium bromide-lactic acid in step (1) is to mix tetrabutylammonium bromide and lactic acid according to a molar ratio of 1:2.3, and heat up to 68 °C and react for 4 h to prepare a mixed solution of tetrabutylammonium bromide-lactic acid.

[0046] The preparation method of the mixed solution of betaine-glycerol in step (2) is to mix betaine and glycerol according to a molar ratio of 0.4:1, and heat up to 72 °C and react for 3.3 h to prepare a mixed solution of betaine-glycerol.

[0047] The preparation method of the 1-ethyl-3-methylimidazolium acetate-ethylene glycol system in step (3) is to mix 1-ethyl-3-methylimidazolium acetate and ethylene glycol according to a molar ratio of 1:3, and heat up to 85 °C and react for 3.8 h to prepare a 1-ethyl-3-methylimidazolium acetate-ethylene glycol system.

[0048] In step (3), the drying temperature is 105 °C and the drying time is 14 h.

[0049] In step (4), the volume ratio of isopropanol to water is 1:1.

[0050] In step (4), the mass-volume ratio of the mixture of perfluorocarboxylic acid resin and perfluorosulfonic acid resin to the mixed solution of isopropanol and water is 1:6.67, with the unit of g / mL.

[0051] In step (4), the reaction pressure is 5.7 MPa.

[0052] In step (5), the mass of triethyl phosphate accounts for 15% of the mass of the perfluorosulfonic acid resin solution, and the mass of polypropylsilsesquioxane accounts for 18% of the mass of the perfluorosulfonic acid resin solution.

[0053] In step (5), the stirring speed during mixing is 500 r / min, the mixing temperature is room temperature, and the mixing time is 20 min.

[0054] In step (5), the prepared membrane is vacuum dried at 80 °C for 24 h, and then heat treated at 185 °C for 1.5 h to obtain a perfluorosulfonic acid ion exchange membrane.

[0055] After testing, the tensile strength of the perfluorosulfonic acid ion exchange membrane prepared in Example 3 is 34.5 MPa, and the linear swelling rate at 25 °C is 2.4%.

Claims

1. A method for preparing a perfluorosulfonic acid solution and a perfluorosulfonic acid ion membrane using discarded ion membranes, characterized in that: It consists of the following steps: (1) Immerse the waste ion membrane used in the chlor-alkali industry in a mixture of tetrabutylammonium bromide and lactic acid, react at 95-97°C for 7 hours, and then wash the waste ion membrane used in the chlor-alkali industry with deionized water until the pH value is neutral; (2) immersing the waste ion-exchange membrane used in the chlor-alkali industry rinsed in step (1) in a mixed solution of betaine-glycerol, reacting at 65-70° C. for 55-57 minutes, and then washing the waste ion-exchange membrane used in the chlor-alkali industry with deionized water until the pH value is neutral; (3) soaking the waste ion membrane for chlor-alkali industry rinsed in step (2) in a 1-ethyl-3-methylimidazolium acetate-ethylene glycol system at 100° C. for 20-25 min, then separating the resin from the PTFE reinforced mesh by a mechanical method, rinsing the product with deionized water until the cleaning solution is clear and transparent, and drying to obtain a mixture of perfluorocarboxylic acid resin and perfluorosulfonic acid resin; (4) adding a mixed solution of isopropanol-water to a mixture of a perfluorocarboxylic acid resin and a perfluorosulfonic acid resin, reacting the mixture at 248-250° C. for 4.5 hours, filtering the mixture, and preparing a perfluorosulfonic acid resin solution; (5) The perfluorosulfonic acid resin solution, triethyl phosphate and polypropylsilsesquioxane are mixed and then poured onto a flat mold to form a perfluorosulfonic acid ion membrane by a tape casting method.

2. The method for preparing a perfluorosulfonic acid solution and a perfluorosulfonic acid ion membrane using discarded ion membrane according to claim 1, characterized in that: The method for preparing the tetrabutylammonium bromide-lactic acid mixed solution in step (1) is to mix tetrabutylammonium bromide and lactic acid in a molar ratio of 1:2.3-2.5, heat to 68-70° C. and react for 4-4.2 hours to prepare a tetrabutylammonium bromide-lactic acid mixed solution.

3. The method for preparing a perfluorosulfonic acid solution and a perfluorosulfonic acid ion membrane using discarded ion membrane according to claim 1, characterized in that: The preparation method of the betaine-glycerol mixed solution in step (2) is to mix betaine and glycerol in a molar ratio of 0.35-0.4:1, heat to 72° C. and react for 3.3-3.5 hours to prepare a betaine-glycerol mixed solution.

4. The method for preparing a perfluorosulfonic acid solution and a perfluorosulfonic acid ion membrane using discarded ion membrane according to claim 1, characterized in that: The preparation method of the 1-ethyl-3-methylimidazolium acetate-ethylene glycol system in step (3) is to mix 1-ethyl-3-methylimidazolium acetate and ethylene glycol in a molar ratio of 1:3, heat to 80-85° C. and react for 3.8-4 hours to prepare the 1-ethyl-3-methylimidazolium acetate-ethylene glycol system.

5. The method for preparing perfluorosulfonic acid solution and perfluorosulfonic acid ion membrane using discarded ion membrane according to claim 1, characterized in that: In step (3), the drying temperature is 100-105°C and the drying time is 14h.

6. The method for preparing a perfluorosulfonic acid solution and a perfluorosulfonic acid ion membrane using discarded ion membrane according to claim 1, characterized in that: In step (4), the volume ratio of isopropanol to water is 1:1; The mass volume ratio of the mixture of perfluorocarboxylic acid resin and perfluorosulfonic acid resin to the mixed solution of isopropanol-water in step (4) is 1:6.67, in units of g / mL; The reaction pressure in step (4) is 5.7 MPa.

7. The method for preparing a perfluorosulfonic acid solution and a perfluorosulfonic acid ion membrane using discarded ion membrane according to claim 1, characterized in that: In step (5), the mass of triethyl phosphate accounts for 13-15% of the mass of the perfluorosulfonic acid resin solution, and the mass of polypropylsilsesquioxane accounts for 18-20% of the mass of the perfluorosulfonic acid resin solution.

8. The method for preparing a perfluorosulfonic acid solution and a perfluorosulfonic acid ion membrane using discarded ion membrane according to claim 1, characterized in that: During mixing in step (5), the stirring speed is 500 r / min, the mixing temperature is room temperature, and the mixing time is 15-20 min.

9. The method for preparing a perfluorosulfonic acid solution and a perfluorosulfonic acid ion membrane using discarded ion membrane according to claim 1, characterized in that: In step (5), the prepared membrane is vacuum dried at 78-80° C. for 24 h, and then heat treated at 183-185° C. for 1.5 h to prepare a perfluorosulfonic acid ion membrane.