High-chemical-stability non-charged proton exchange membrane for acid recovery by diffusion dialysis, preparation method and application thereof

Abstract

The application belongs to the technical field of proton exchange membranes, and discloses a high-chemical-stability non-charged proton exchange membrane for acid recovery by diffusion dialysis, a preparation method and application thereof. A strong electron-attracting C-F bond, a sulfonyl unit [-SO2-] and a nitrogen-containing heterocycle capable of being protonated are introduced into a polybenzimidazole main chain, and two copolymerization modes are adopted, namely, copolymerization of a carboxylic acid monomer containing a strong electron-attracting group and a tetramine monomer containing a heterocyclic nitrogen, and copolymerization of a carboxylic acid monomer containing a heterocyclic nitrogen and a tetramine monomer containing a strong electron-attracting group; or a multi-monomer copolymerization strategy such as a two-monomer copolymerization strategy and a three-monomer copolymerization strategy can be simultaneously adopted, and then a solution is coated by a film coater to form a film. The non-charged proton exchange membrane prepared by the method has excellent acid recovery performance and chemical stability.

Description

Technical Field

[0001] This invention belongs to the field of proton exchange membrane technology, and relates to a high chemical stability non-charged proton exchange membrane for diffusion dialysis acid recovery, its preparation method and its application. Background Technology

[0002] Nitric acid, as an important industrial acid, is widely used in metal processing, chemical industry, and electronics manufacturing. Its waste liquid typically exhibits high acidity and strong oxidizing properties; failure to recover it not only wastes resources but also poses significant environmental and safety risks. Traditional acid recovery technologies generally suffer from limitations such as high energy consumption, stringent equipment corrosion resistance requirements, secondary pollution risks, and insufficient adaptability to highly oxidizing systems. In contrast, membrane separation acid recovery technology achieves a phase-change-free, low-energy-consumption, continuous, and green recovery process through selective ion transport. Among these, diffusion dialysis (DD), driven by a concentration gradient, requires no external electric field, resulting in lower energy consumption, simpler equipment, and greater suitability for strong acid systems, demonstrating superior green and economic potential in industrial nitric acid recovery.

[0003] Most existing diffusion dialysis membranes use quaternary ammonium anion exchange membranes (AEMs), whose typical quaternary ammonium functional groups (such as –N) + (CH3)3、–N + R3 and pyridinium / imidazolium, etc., can achieve selective migration of acid anions through the Donan repulsion effect, exhibiting excellent acid recovery capabilities under low to moderate acid concentration conditions. However, in high-concentration nitric acid systems, strong oxidizing species (NO2, N2O4, NO2) can cause acid anion migration. + (etc.) can easily trigger quaternary ammonium group dealkylation, Hofmann degradation and ring cleavage reactions, leading to a significant decrease in ion exchange capacity; at the same time, the strong acid absorption effect of quaternary ammonium groups in concentrated nitric acid causes significant swelling, which exacerbates chain relaxation and degradation, thus becoming a key bottleneck restricting the long-term stable operation of AEMs in concentrated nitric acid diffusion dialysis.

[0004] In contrast, polybenzimidazole (PBI), with its high bond energy structure of fused aromatic heterocyclic backbone and the electron delocalization effect of imidazole groups, exhibits superior chemical and antioxidant stability in strong acid, strong oxidizing, and free radical environments. Furthermore, after protonation, PBI forms stable hydrogen bonds and a proton conduction network, ensuring proton / acid transport capabilities while maintaining low permeation of small molecules and metal ions due to its dense chain structure. This achieves a balance between selectivity and durability in acid recovery, making it a potentially excellent membrane material for high-concentration strong acid recovery. Summary of the Invention

[0005] This invention aims to improve the proton conductivity and selectivity of ion exchange membranes, while providing a method for preparing a highly chemically stable non-charged proton exchange membrane for diffusion dialysis acid recovery, which can maintain long-term stability in high-concentration nitric acid systems: Strong electron-withdrawing, high-bond-energy groups such as CF and sulfone units [-SO2-], as well as protonable nitrogen-containing heterocycles, are introduced into the polybenzimidazole backbone. By controlling the structure and ratio of carboxylic acid monomers and amino monomers, a series of highly conductive and selective non-charged polymer materials with excellent stability are prepared.

[0006] The technical solution of this invention: A highly chemically stable, non-charged proton exchange membrane for diffusion dialysis acid recovery: 1. prepared by copolymerizing a carboxylic acid monomer containing a strong electron-withdrawing group with a tetraamine monomer containing a heterocyclic nitrogen; 2. prepared by copolymerizing a carboxylic acid monomer containing a heterocyclic nitrogen with a tetraamine monomer containing a strong electron-withdrawing group. This invention utilizes multi-monomer copolymerization, such as dimonomers and trimonomers, to prepare highly stable, highly conductive, and highly selective polybenzimidazole materials. The general polymer structure formula is as follows: Wherein, Ar1 is the first group, and the first group is selected from any one or a combination of two or more of the following structural formulas: Ar2 is the second group, which is selected from any one or a combination of two or more of the following structural formulas: n is 10 to 1000.

[0007] A method for preparing a highly chemically stable non-charged proton exchange membrane for diffusion dialysis acid recovery, comprising the following steps: Step 1: Synthesizing modified polybenzimidazole resin material in an oxygen-free environment: Under N2 protection, the catalytic solvent is first deoxygenated at 80-100℃ for 1 hour, then carboxylic acid monomer and tetraamine monomer are added sequentially for copolymerization, and the reaction is carried out at 100-140℃ for 6 hours. The polymer properties are controlled by adjusting the composition, structure and ratio of carboxylic acid monomer and tetraamine monomer. Then the temperature is raised to 140-200℃ and the reaction is continued until the solution becomes viscous, which takes 1.5-20 hours. Heating is then stopped. The polymer solution after reaction is quickly poured into boiling water, and the polymer solidifies into yellow-brown filaments. The washed polymer solution is then soaked in 10wt% NaHCO3 solution at 60℃ for 8-24 hours. After alkali washing, the polymer is washed until neutral and then dried in an 80℃ oven to obtain the modified polybenzimidazole resin material. The molar ratio of tetraamine monomer to carboxylic acid monomer is 1:1. The ratio of tetraamine monomer to catalytic solvent was 1 mmol: 10 g; The catalytic solvent is Eaton reagent or polyphosphoric acid (PPA). Among them, there are two copolymerization methods for carboxylic acid monomers and tetraamine monomers: (1) using carboxylic acid monomers containing strong electron-withdrawing groups, adding tetraamine monomers containing nitrogen heterocycles, and selectively adding or not adding 3,3-diaminobenzidine for copolymerization; (2) using carboxylic acid monomers containing nitrogen heterocycles, adding tetraamine monomers containing strong electron-withdrawing groups, and selectively adding or not adding 3,3-diaminobenzidine for copolymerization; The carboxylic acid monomer containing a strong electron-withdrawing group is selected from any one or a combination of two or more of the following structures: The nitrogen-containing heterocyclic carboxylic acid monomer is selected from any one or a combination of two or more of the following structures: The nitrogen-containing heterocyclic tetraamine monomer is selected from any one or a combination of two or more of the following structures: The tetraamine monomer containing a strong electron-withdrawing group is selected from any one or a combination of two or more of the following structures: The structure of the 3,3-diaminobenzidine is as follows: ; Step 2: Preparation of proton exchange membrane: Take the modified polybenzimidazole resin material prepared in Step 1, dissolve it in an organic solvent at room temperature, and after dissolution, refine and centrifuge to obtain a coating solution; place the coating solution on a coating machine, adjust to the blade height for coating, then heat to 60℃ and let stand for 24 h to dry the solvent, waiting for the membrane to form; after completion, immerse the membrane in 7M HNO3 at room temperature for 24 h to allow it to undergo sufficient ion exchange, and then rinse thoroughly with deionized water to obtain a highly chemically stable non-charged proton exchange membrane; The organic solvent is one of DMAc (N,N-dimethylacetamide), DMSO (dimethyl sulfoxide), and NMP (N-methylpyrrolidone); The modified polybenzimidazole resin material is present in a ratio of (0.08~0.10 g): 1 mL to an organic solvent. The drying temperature for coating and film formation is 60~80 ℃, and the time is 24 h. The preparation method is a coating method.

[0008] Application of a chemically stable non-charged proton exchange membrane in diffusion dialysis acid recovery.

[0009] The beneficial effects of this invention are as follows: By introducing strong electron-withdrawing groups and nitrogen-containing heterocyclic unit structures onto the polybenzimidazole backbone, the high bond energy and strong electronegativity of the strong electron-withdrawing groups can enhance the chemical stability of the material. Furthermore, the reversible protonation of the nitrogen-containing heterocycle under acidic conditions can further improve proton transport capability. Simultaneously, the hydrophilic / hydrophobic polarity difference between the two monomers can further optimize the microphase separation of the material, constructing a good ion transport channel. Detailed Implementation

[0010] The specific embodiments of the present invention will be further described below in conjunction with the technical solution.

[0011] Example 1: Copolymerization of 2,2-bis(4-carboxyphenyl)hexafluoropropane with 3,3-diaminobenzidine; (1) Polymer synthesis: 50 g of polyphosphoric acid (PPA) was weighed and added to a 100 mL three-necked flask. After thorough deoxygenation by mechanical stirring at 130 °C under a nitrogen atmosphere for 1 h, the temperature was raised to 150 °C, and 1.981 g of 2,2-bis(4-carboxyphenyl)hexafluoropropane was added. After dissolution, 1.093 g of 3,3-diaminobenzidine was added. Prepolymerization was carried out at this temperature for 5 h, and then the temperature was gradually raised to 200 °C for 8 h of polymerization. The solution changed from a light brown viscous state to a dark brown viscous state. Then it precipitated in boiling water to obtain a yellow-brown polymer. After thorough alkali washing and water washing, it was dried at 80 °C for 24 h to obtain the polymer.

[0012] (2) Preparation of proton exchange membrane: Take the functionalized polymer prepared in step (1), dissolve it in NMP at room temperature, and after dissolution, refine and centrifuge. Place a certain concentration of coating solution on a coating machine, adjust to a certain blade height for coating, and then heat to 50 ℃ and let stand for 12 h to dry the solvent and wait for the membrane to form. After completion, at room temperature, immerse the membrane in 7 MHNO3 + 0.36 M Fe(NO3)3 solution for 24 h to allow it to undergo sufficient ion exchange, and then immerse it in deionized water for 24 h to remove excess ions, thus obtaining a non-charged proton exchange membrane; The ratio of the fluorinated polybenzimidazole resin material to NMP is (0.08~0.10 g): 1 mL; Tests showed that the polymer film prepared in this embodiment exhibited good H at 25 °C. + Penetration rate U H + =2.74×10 -3 The acid / salt separation factor S=82.6, acid absorption rate is 20.0%, swelling degree is 4.94%, and it still maintains structural and performance stability after being soaked in 11 M HNO3 for 200 days.

[0013] Example 2: Copolymerization of 2,2-bis(3,4-diaminophenyl)hexafluoropropane with pyrazine-2,5-dicarboxylic acid; (1) Polymer synthesis: 5 g of P2O5 was placed in a 100 ml beaker, 35 ml of methanesulfonic acid was added, and the mixture was dissolved at 80 °C for 30 min. Then, 6 mmol of 2,2-bis(3,4-diaminophenyl)hexafluoropropane was added, and the mixture was dissolved at 80 °C for 30 min. An equimolar amount of pyrazine-2,5-dicarboxylic acid was added, and the mixture was dissolved for 30 min. The temperature was then raised to 100 °C for prepolymerization for 60 min, and then to 160 °C for polymerization for 90 min. The solution changed from a light brown viscous state to a dark brown viscous state. The polymer was then precipitated in boiling water to obtain a yellow-brown polymer. After thorough alkali washing and water washing, the polymer was dried at 80 °C for 24 h to obtain the polymer.

[0014] (2) Preparation of proton exchange membrane: Take the functionalized polymer prepared in step (1), dissolve it in NMP at room temperature, and after dissolution, refine and centrifuge. Place a certain concentration of coating solution on a coating machine, adjust to a certain blade height for coating, and then heat to 50 ℃ and let stand for 12 h to dry the solvent and wait for the membrane to form. After completion, at room temperature, immerse the membrane in 7 MHNO3 + 0.36 M Fe(NO3)3 solution for 24 h to allow it to undergo sufficient ion exchange, and then immerse it in deionized water for 24 h to remove excess ions, thus obtaining a non-charged proton exchange membrane; The ratio of the fluorinated pyrazine-based polybenzimidazole resin material to NMP is (0.08~0.10 g): 1 mL; Tests showed that the polymer film prepared in this embodiment exhibited good H at 25 °C. + Penetration rate U H + =7.74×10 -3 The acid / salt separation factor S = 182.6, the acid absorption rate is 33.0%, the swelling degree is 8.04%, and the structure and performance remain stable after soaking in 11 M HNO3 for 180 days.

[0015] Example 3: Copolymerization of 4,4'-bis(3,4-diaminophenyl) sulfone with 2,6-dicarboxycarbazole; (1) Polymer synthesis: 5 g of P2O5 was placed in a 100 ml beaker, 35 ml of methanesulfonic acid was added, and the mixture was dissolved at 80 °C for 30 min. Then, 8 mmol of 4,4'-bis(3,4-diaminophenyl) sulfone was added, and the mixture was dissolved at 80 °C for 30 min. Then, an equimolar amount of 2,6-dicarboxycarbazole was added, and the mixture was dissolved for 30 min. The temperature was then raised to 100 °C for prepolymerization for 60 min, and then polymerized at 160 °C for 2 h 30 min. The solution changed from a light brown viscous state to a dark brown viscous state. After that, it precipitated in boiling water to obtain a yellow-brown polymer. After thorough alkali washing and water washing, the polymer was dried at 80 °C for 24 h to obtain the polymer.

[0016] (2) Preparation of proton exchange membrane: Take the functionalized polymer prepared in step (1), dissolve it in NMP at room temperature, and after dissolution, refine and centrifuge. Place a certain concentration of coating solution on a coating machine, adjust to a certain blade height for coating, and then heat to 50 ℃ and let stand for 12 h to dry the solvent and wait for the membrane to form. After completion, at room temperature, immerse the membrane in 7 MHNO3 + 0.36 M Fe(NO3)3 solution for 24 h to allow it to undergo sufficient ion exchange, and then immerse it in deionized water for 24 h to remove excess ions, thus obtaining a non-charged proton exchange membrane; The ratio of the sulfonated carbazole-based polybenzimidazole resin material to NMP is (0.08~0.10 g): 1 mL; Tests showed that the polymer film prepared in this embodiment exhibited good H at 25 °C. + Penetration rate U H + =8.06×10 -3 The acid / salt separation factor S = 102.7, the acid absorption rate is 29.0%, the swelling degree is 7.84%, and the structure and properties remain stable after soaking in 11 M HNO3 for 120 days.

[0017] Example 4: Copolymerization of 2,2-bis(3,4-diaminophenyl)hexafluoropropane with 1,10-phenanthroline-2,9-dicarboxylic acid; (1) Polymer synthesis: 50 g of polyphosphoric acid (PPA) was weighed and added to a 100 mL three-necked flask. After thorough deoxygenation under a nitrogen atmosphere at 130 °C for 1 h, the temperature was raised to 150 °C, and 1.891 g of 2,2-bis(3,4-diaminophenyl)hexafluoropropane was added. After dissolution, 1.345 g of 1,10-phenanthroline-2,9-dicarboxylic acid was added. After prepolymerization at this temperature for 5 h, the temperature was gradually raised to 220 °C for polymerization for 18 h. The solution changed from a light brown viscous state to a dark brown viscous state. Then, it precipitated in boiling water to obtain a yellow-brown polymer. After thorough alkali washing and water washing, it was dried at 80 °C for 24 h to obtain the polymer.

[0018] (2) Preparation of proton exchange membrane: Take the functionalized polymer prepared in step (1), dissolve it in NMP at room temperature, and after dissolution, refine and centrifuge. Place a certain concentration of coating solution on a coating machine, adjust to a certain blade height for coating, and then heat to 50 ℃ and let stand for 12 h to dry the solvent and wait for the membrane to form. After completion, at room temperature, immerse the membrane in 7 MHNO3 + 0.36 M Fe(NO3)3 solution for 24 h to allow it to undergo sufficient ion exchange, and then immerse it in deionized water for 24 h to remove excess ions, thus obtaining a non-charged proton exchange membrane; The ratio of the fluorinated phenanthrene-pyrrolidone-based polybenzimidazole resin material to NMP is (0.08~0.10 g): 1 mL; Tests showed that the polymer film prepared in this embodiment exhibited good H at 25 °C. + Penetration rate U H + =8.65×10 -3 The acid / salt separation factor S=98.6, acid absorption rate is 35.0%, swelling degree is 9.46%, and it still maintains structural and performance stability after being soaked in 11 M HNO3 for 180 days.

[0019] Example 5: Copolymerization of 2,3,5,6-tetraaminopyridine with 4,4'-sulfonyl dibenzoic acid; (1) Polymer synthesis: 50 g of polyphosphoric acid (PPA) was weighed and added to a 100 mL three-necked flask. The mixture was mechanically stirred thoroughly under a nitrogen atmosphere at 130 °C. 0.947 g of 2,3,5,6-tetraaminopyridine and 1.447 g of 4,4'-sulfonyldibenzoic acid were added and prepolymerized at this temperature for 5 h. Then the temperature was gradually increased to 210 °C and polymerized for 20 h. The solution changed from a light brown viscous state to a dark brown viscous state. It was then precipitated in boiling water to obtain a yellow-brown polymer. After thorough alkali washing and water washing, the polymer was dried at 80 °C for 24 h to obtain the polymer.

[0020] (2) Preparation of proton exchange membrane: Take the functionalized polymer prepared in step (1), dissolve it in NMP at room temperature, and after dissolution, refine and centrifuge. Place a certain concentration of coating solution on a coating machine, adjust to a certain blade height for coating, and then heat to 50 ℃ and let stand for 12 h to dry the solvent and wait for the membrane to form. After completion, at room temperature, immerse the membrane in 7 MHNO3 + 0.36 M Fe(NO3)3 solution for 24 h to allow it to undergo sufficient ion exchange, and then immerse it in deionized water for 24 h to remove excess ions, thus obtaining a non-charged proton exchange membrane; The ratio of the sulfonylpyridinyl polybenzimidazole resin material to NMP is (0.08~0.10 g): 1 mL; Tests showed that the polymer film prepared in this embodiment exhibited good H at 25 °C. + Penetration rate U H + =7.54×10 -3 The acid / salt separation factor S = 119.0, the acid absorption rate is 35.8%, the swelling degree is 10.46%, and the structure and performance remain stable after soaking in 11 M HNO3 for 160 days.

[0021] Example 6: Copolymerization of 90% 2,2-bis(4-carboxyphenyl)hexafluoropropane, 10% 2,6-pyridinedicarboxylic acid, and 3,3-diaminobenzidine; (1) Polymer synthesis: 50 g of polyphosphoric acid (PPA) was weighed and added to a 100 mL three-necked flask. After thorough deoxygenation under a nitrogen atmosphere at 130 °C for 1 h, the temperature was raised to 150 °C, and 1.783 g of 2,2-bis(4-carboxyphenyl)hexafluoropropane was added, followed by 0.085 g of 2,6-pyridinedicarboxylic acid. After dissolution, 1.093 g of 3,3-diaminobenzidine was added. Prepolymerization was carried out at this temperature for 5 h, followed by gradual heating to 200 °C for 9 h of polymerization. The solution changed from a light brown viscous state to a dark brown viscous state. The solution then precipitated in boiling water to obtain a yellow-brown polymer. After thorough alkali washing and water washing, the polymer was dried at 80 °C for 24 h to obtain the final product.

[0022] (2) Preparation of proton exchange membrane: Take the functionalized polymer prepared in step (1), dissolve it in NMP at room temperature, and after dissolution, refine and centrifuge. Place a certain concentration of coating solution on a coating machine, adjust to a certain scraper height for coating, and then heat to 50 ℃ and let stand for 12 h to dry the solvent and wait for the membrane to form. After completion, at room temperature, immerse the membrane in 7 MHNO3 + 0.36 M Fe(NO3)3 solution for 24 h to allow it to undergo sufficient ion exchange, and then immerse it in deionized water for 24 h to remove excess ions, thus obtaining a non-charged proton exchange membrane; The ratio of the 10% pyridyl fluorinated polybenzimidazole resin material to NMP is (0.08~0.10 g): 1 mL; Tests showed that the polymer film prepared in this embodiment exhibited good H at 25 °C. + Penetration rate U H + =3.26×10 -3 The acid / salt separation factor S = 105.2, the acid absorption rate is 22.33%, the swelling degree is 5.45%, and the structure and performance remain stable after soaking in 11 M HNO3 for 180 days.

[0023] Example 7: Copolymerization of 70% 2,2-bis(4-carboxyphenyl)hexafluoropropane, 30% 2,6-pyridinedicarboxylic acid, and 3,3-diaminobenzidine; (1) Polymer synthesis: 50 g of polyphosphoric acid (PPA) was weighed and added to a 100 mL three-necked flask. After thorough deoxygenation under a nitrogen atmosphere at 130 °C for 1 h, the temperature was raised to 150 °C, and 1.387 g of 2,2-bis(4-carboxyphenyl)hexafluoropropane was added, followed by 0.255 g of 2,6-pyridinedicarboxylic acid. After dissolution, 1.093 g of 3,3-diaminobenzidine was added. Prepolymerization was carried out at this temperature for 5 h, followed by gradual heating to 200 °C for 12 h of polymerization. The solution changed from a light brown viscous state to a dark brown viscous state. The polymer was then precipitated in boiling water, yielding a yellow-brown polymer. After thorough alkali washing and water washing, the polymer was dried at 80 °C for 24 h to obtain the final product.

[0024] (2) Preparation of proton exchange membrane: Take the functionalized polymer prepared in step (1), dissolve it in NMP at room temperature, and after dissolution, refine and centrifuge. Place a certain concentration of coating solution on a coating machine, adjust to a certain scraper height for coating, and then heat to 50 ℃ and let stand for 12 h to dry the solvent and wait for the membrane to form. After completion, at room temperature, immerse the membrane in 7 MHNO3 + 0.36 M Fe(NO3)3 solution for 24 h to allow it to undergo sufficient ion exchange, and then immerse it in deionized water for 24 h to remove excess ions, thus obtaining a non-charged proton exchange membrane; The ratio of the 30% pyridyl fluorinated polybenzimidazole resin material to NMP is (0.08~0.10 g): 1 mL; Tests showed that the polymer film prepared in this embodiment exhibited good H at 25 °C. + Penetration rate U H + =3.86×10 -3 The acid / salt separation factor S = 125.2, the acid absorption rate is 26.21%, the swelling degree is 6.85%, and the structure and performance remain stable after soaking in 11 M HNO3 for 180 days.

[0025] Example 8: Copolymerization of 50% 2,2-bis(4-carboxyphenyl)hexafluoropropane, 50% 2,6-pyridinedicarboxylic acid, and 3,3-diaminobenzidine; (1) Polymer synthesis: 50 g of polyphosphoric acid (PPA) was weighed and added to a 100 mL three-necked flask. After thorough deoxygenation under a nitrogen atmosphere at 130 °C for 1 h, the temperature was raised to 150 °C, and 0.991 g of 2,2-bis(4-carboxyphenyl)hexafluoropropane was added, followed by 0.425 g of 2,6-pyridinedicarboxylic acid. After dissolution, 1.093 g of 3,3-diaminobenzidine was added. Prepolymerization was carried out at this temperature for 5 h, followed by gradual heating to 200 °C for 12 h of polymerization. The solution changed from a light brown viscous state to a dark brown viscous state. The polymer was then precipitated in boiling water, yielding a yellow-brown polymer. After thorough alkali washing and water washing, the polymer was dried at 80 °C for 24 h to obtain the final product.

[0026] (2) Preparation of proton exchange membrane: Take the functionalized polymer prepared in step (1), dissolve it in NMP at room temperature, and after dissolution, refine and centrifuge. Place a certain concentration of coating solution on a coating machine, adjust to a certain blade height for coating, and then heat to 50 ℃ and let stand for 12 h to dry the solvent and wait for the membrane to form. After completion, at room temperature, immerse the membrane in 7 MHNO3 + 0.36 M Fe(NO3)3 solution for 24 h to allow it to undergo sufficient ion exchange, and then immerse it in deionized water for 24 h to remove excess ions, thus obtaining a non-charged proton exchange membrane; The ratio of the 50% pyridyl fluorinated polybenzimidazole resin material to NMP is (0.08~0.10 g): 1 mL; Tests showed that the polymer film prepared in this embodiment exhibited good H at 25 °C. + Penetration rate U H + =4.73×10 -4 The structure and properties remain stable after being soaked in 11 M HNO3 for 160 days, with an acid / salt separation factor S=144.9, an acid absorption rate of 28.36%, and a swelling degree of 8.55%.

[0027] Example 9: Copolymerization of 90% 2,2-bis(4-carboxyphenyl)hexafluoropropane, 10% 2,2-bispyridine-5,5-dicarboxylic acid and 3,3-diaminobenzidine; (1) Polymer synthesis: 50 g of polyphosphoric acid (PPA) was weighed and added to a 100 mL three-necked flask. After thorough deoxygenation under a nitrogen atmosphere at 130 °C for 1 h, the temperature was raised to 150 °C, and 1.783 g of 2,2-bis(4-carboxyphenyl)hexafluoropropane was added, followed by 0.127 g of 2,2-bispyridine-5,5-dicarboxylic acid. After dissolution, 1.093 g of 3,3-diaminobenzidine was added. Prepolymerization was carried out at this temperature for 5 h, followed by gradual heating to 200 °C for 12 h of polymerization. The solution changed from a light brown viscous state to a dark brown viscous state. The solution then precipitated in boiling water to obtain a yellow-brown polymer. After thorough alkali washing and water washing, the polymer was dried at 80 °C for 24 h to obtain the final product.

[0028] (2) Preparation of proton exchange membrane: Take the functionalized polymer prepared in step (1), dissolve it in NMP at room temperature, and after dissolution, refine and centrifuge. Place a certain concentration of coating solution on a coating machine, adjust to a certain blade height for coating, and then heat to 50 ℃ and let stand for 12 h to dry the solvent and wait for the membrane to form. After completion, at room temperature, immerse the membrane in 7 MHNO3 + 0.36 M Fe(NO3)3 solution for 24 h to allow it to undergo sufficient ion exchange, and then immerse it in deionized water for 24 h to remove excess ions, thus obtaining a non-charged proton exchange membrane; The ratio of the 10% bipyridyl fluorinated polybenzimidazole resin material to NMP is (0.08~0.10 g): 1 mL; Tests showed that the polymer film prepared in this embodiment exhibited good H at 25 °C. + Penetration rate U H + =3.45×10 -3 The acid / salt separation factor S = 128.4, the acid absorption rate is 24.56%, the swelling degree is 5.05%, and the structure and properties remain stable after soaking in 11 M HNO3 for 160 days.

[0029] Example 10: Copolymerization of 70% 2,2-bis(4-carboxyphenyl)hexafluoropropane, 30% 2,2-bispyridine-5,5-dicarboxylic acid and 3,3-diaminobenzidine; (1) Polymer synthesis: 50 g of polyphosphoric acid (PPA) was weighed and added to a 100 mL three-necked flask. After thorough deoxygenation under a nitrogen atmosphere at 130 °C for 1 h, the temperature was raised to 150 °C, and 1.387 g of 2,2-bis(4-carboxyphenyl)hexafluoropropane was added, followed by 0.381 g of 2,2-bispyridine-5,5-dicarboxylic acid. After dissolution, 1.093 g of 3,3-diaminobenzidine was added. Prepolymerization was carried out at this temperature for 5 h, followed by gradual heating to 200 °C for 12 h of polymerization. The solution changed from a light brown viscous state to a dark brown viscous state. The solution then precipitated in boiling water to obtain a yellow-brown polymer. After thorough alkali washing and water washing, the polymer was dried at 80 °C for 24 h to obtain the final product.

[0030] (2) Preparation of proton exchange membrane: Take the functionalized polymer prepared in step (1), dissolve it in NMP at room temperature, and after dissolution, refine and centrifuge. Place a certain concentration of coating solution on a coating machine, adjust to a certain blade height for coating, and then heat to 50 ℃ and let stand for 12 h to dry the solvent and wait for the membrane to form. After completion, at room temperature, immerse the membrane in 7 MHNO3 + 0.36 M Fe(NO3)3 solution for 24 h to allow it to undergo sufficient ion exchange, and then immerse it in deionized water for 24 h to remove excess ions, thus obtaining a non-charged proton exchange membrane; The ratio of the 30% bipyridyl fluorinated polybenzimidazole resin material to NMP is (0.08~0.10 g): 1 mL; Tests showed that the polymer film prepared in this embodiment exhibited good H at 25 °C. + Penetration rate U H + =5.15×10 -3 The acid / salt separation factor S = 148.8, the acid absorption rate is 28.21%, the swelling degree is 8.05%, and the structure and performance remain stable after soaking in 11 M HNO3 for 140 days.

[0031] Example 11: Copolymerization of 50% 2,2-bis(4-carboxyphenyl)hexafluoropropane, 50% 2,2-bispyridine-5,5-dicarboxylic acid and 3,3-diaminobenzidine; (1) Polymer synthesis: 50 g of polyphosphoric acid (PPA) was weighed and added to a 100 mL three-necked flask. The mixture was mechanically stirred at 130 °C under a nitrogen atmosphere to remove oxygen for 1 h. The temperature was then raised to 150 °C, and 0.991 g of 2,2-bis(4-carboxyphenyl)hexafluoropropane was added, followed by 0.634 g of 2,2-bispyridine-5,5-dicarboxylic acid. After dissolution, 1.093 g of 3,3-diaminobenzidine was added. Prepolymerization was carried out at this temperature for 5 h, followed by gradual heating to 200 °C for 15 h of polymerization. The solution changed from a light brown viscous state to a dark brown viscous state. The polymer was then precipitated in boiling water, yielding a yellow-brown polymer. After thorough alkali washing and water washing, the polymer was dried at 80 °C for 24 h to obtain the final product.

[0032] (2) Preparation of proton exchange membrane: Take the functionalized polymer prepared in step (1), dissolve it in NMP at room temperature, and after dissolution, refine and centrifuge. Place a certain concentration of coating solution on a coating machine, adjust to a certain blade height for coating, and then heat to 50 ℃ and let stand for 12 h to dry the solvent and wait for the membrane to form. After completion, at room temperature, immerse the membrane in 7 MHNO3 + 0.36 M Fe(NO3)3 solution for 24 h to allow it to undergo sufficient ion exchange, and then immerse it in deionized water for 24 h to remove excess ions, thus obtaining a non-charged proton exchange membrane; The ratio of the 50% bipyridyl fluorinated polybenzimidazole resin material to NMP is (0.08~0.10 g): 1 mL; Tests showed that the polymer film prepared in this embodiment exhibited good H at 25 °C. + Penetration rate U H + =6.37×10 -3 The acid / salt separation factor S = 174.50, the acid absorption rate is 32.21%, the swelling degree is 10.45%, and the structure and performance remain stable after soaking in 11 M HNO3 for 200 days.

[0033] Example 12: Copolymerization of 90% 2,2-bis(4-carboxyphenyl)hexafluoropropane, 10% 4,6-pyrimidinedicarboxylic acid, and 3,3-diaminobenzidine; (1) Polymer synthesis: 50 g of polyphosphoric acid (PPA) was weighed and added to a 100 mL three-necked flask. The mixture was mechanically stirred at 130 °C under a nitrogen atmosphere to remove oxygen for 1 h. The temperature was then raised to 150 °C, and 1.783 g of 2,2-bis(4-carboxyphenyl)hexafluoropropane was added, followed by 0.174 g of 4,6-pyrimidine dicarboxylic acid. After dissolution, 1.093 g of 3,3-diaminobenzidine was added. Prepolymerization was carried out at this temperature for 5 h, followed by gradual heating to 200 °C for 20 h of polymerization. The solution changed from a light brown viscous state to a dark brown viscous state. The polymer was then precipitated in boiling water to obtain a yellow-brown polymer. After thorough alkali washing and water washing, the polymer was dried at 80 °C for 24 h to obtain the final product.

[0034] (2) Preparation of proton exchange membrane: Take the functionalized polymer prepared in step (1), dissolve it in NMP at room temperature, and after dissolution, refine and centrifuge. Place a certain concentration of coating solution on a coating machine, adjust to a certain blade height for coating, and then heat to 50 ℃ and let stand for 12 h to dry the solvent and wait for the membrane to form. After completion, at room temperature, immerse the membrane in 7 MHNO3 + 0.36 M Fe(NO3)3 solution for 24 h to allow it to undergo sufficient ion exchange, and then immerse it in deionized water for 24 h to remove excess ions, thus obtaining a non-charged proton exchange membrane; The ratio of the 10% pyrimidinyl fluorinated polybenzimidazole resin material to NMP is (0.08~0.10 g): 1 mL; Tests showed that the polymer film prepared in this embodiment exhibited good H at 25 °C. + Penetration rate U H + =3.47×10 -3 The acid / salt separation factor S = 133.50, the acid absorption rate is 25.46%, the swelling degree is 5.95%, and the structure and properties remain stable after soaking in 11 M HNO3 for 160 days.

[0035] Example 13: Copolymerization of 70% 2,2-bis(4-carboxyphenyl)hexafluoropropane, 30% 4,6-pyrimidinedicarboxylic acid, and 3,3-diaminobenzidine; (1) Polymer synthesis: 50 g of polyphosphoric acid (PPA) was weighed and added to a 100 mL three-necked flask. The mixture was mechanically stirred at 130 °C under a nitrogen atmosphere to remove oxygen for 1 h. The temperature was then raised to 150 °C, and 1.387 g of 2,2-bis(4-carboxyphenyl)hexafluoropropane was added, followed by 0.523 g of 4,6-pyrimidine dicarboxylic acid. After dissolution, 1.093 g of 3,3-diaminobenzidine was added. Prepolymerization was carried out at this temperature for 5 h, followed by gradual heating to 200 °C for 20 h of polymerization. The solution changed from a light brown viscous state to a dark brown viscous state. The polymer was then precipitated in boiling water to obtain a yellow-brown polymer. After thorough alkali washing and water washing, the polymer was dried at 80 °C for 24 h to obtain the final product.

[0036] (2) Preparation of proton exchange membrane: Take the functionalized polymer prepared in step (1), dissolve it in NMP at room temperature, and after dissolution, refine and centrifuge. Place a certain concentration of coating solution on a coating machine, adjust to a certain blade height for coating, and then heat to 50 ℃ and let stand for 12 h to dry the solvent and wait for the membrane to form. After completion, at room temperature, immerse the membrane in 7 MHNO3 + 0.36 M Fe(NO3)3 solution for 24 h to allow it to undergo sufficient ion exchange, and then immerse it in deionized water for 24 h to remove excess ions, thus obtaining a non-charged proton exchange membrane; The ratio of the 30% pyrimidinyl fluorinated polybenzimidazole resin material to NMP is (0.08~0.10 g): 1 mL; Tests showed that the polymer film prepared in this embodiment exhibited good H at 25 °C. + Penetration rate U H + =4.47×10 -3 The acid / salt separation factor S = 163.50, the acid absorption rate is 27.46%, the swelling degree is 8.95%, and the structure and performance remain stable after soaking in 11 M HNO3 for 160 days.

[0037] Comparative Example 1: Copolymerization of 4,4'-diphenyl ether dicarboxylic acid and 3,3-diaminobenzidine; (1) Polymer synthesis: 5 g of P2O5 was placed in a 100 ml beaker, 35 ml of methanesulfonic acid was added, and the mixture was dissolved at 80 °C for 30 min. Then, 6 mmol of 3,3-diaminobenzidine was added, and the mixture was dissolved at 80 °C for 30 min. An equimolar amount of 4,4'-diphenyl ether dicarboxylic acid was added, and the mixture was dissolved for 30 min. The temperature was then raised to 100 °C for prepolymerization for 60 min, and then to 160 °C for polymerization for 90 min. The solution changed from a light brown viscous state to a dark brown viscous state. After that, it precipitated in boiling water to obtain a yellow-brown polymer. After thorough alkali washing and water washing, the polymer was dried at 80 °C for 24 h to obtain OPBI polymer.

[0038] (2) Preparation of proton exchange membrane: Take the OPBI polymer prepared in step (1), dissolve it in NMP at room temperature, and after dissolution, refine and centrifuge. Place a certain concentration of coating solution on a coating machine, adjust to a certain blade height for coating, and then heat to 50 ℃ and let stand for 12 h to dry the solvent and wait for the membrane to form. After completion, at room temperature, immerse the membrane in 7 M HNO3 + 0.36 M Fe(NO3)3 solution for 24 h to allow it to undergo sufficient ion exchange, and then immerse it in deionized water for 24 h to remove excess ions, thus obtaining a non-charged proton exchange membrane; (2) Preparation of proton exchange membrane: Take the OPBI polymer prepared in step (1), dissolve it in NMP at room temperature, and after dissolution, refine and centrifuge. Place a certain concentration of coating solution on a coating machine, adjust to a certain blade height for coating, and then heat to 50 ℃ and let stand for 12 h to dry the solvent and wait for the membrane to form. After completion, at room temperature, immerse the membrane in 7 M HNO3 + 0.36 M Fe(NO3)3 solution for 24 h to allow it to undergo sufficient ion exchange, and then immerse it in deionized water for 24 h to remove excess ions, thus obtaining a non-charged proton exchange membrane; The ratio of OPBI resin material to NMP is (0.08~0.10 g): 1 mL; Tests showed that the polymer film prepared in this embodiment exhibited good H at 25 °C. + Penetration rate U H + =2.47×10 -3 The acid / salt separation factor S = 83.50, the acid absorption rate is 32.87%, the swelling degree is 9.85%, and cracks appear after soaking in 11 M HNO3 for 34 days.

[0039] Comparative Example 2: Copolymerization of 4,4'-diphenyl ether dicarboxylic acid with 2,3,5,6-tetraaminopyridine; (1) Polymer synthesis: 50 g of polyphosphoric acid (PPA) was weighed and added to a 100 mL three-necked flask. The mixture was mechanically stirred at 130 °C under a nitrogen atmosphere to remove oxygen for 1 h. The temperature was then raised to 150 °C, and 0.873 g of 2,3,5,6-tetraaminopyridine and 1.409 g of 4,4'-diphenyl ether dicarboxylic acid were added. Prepolymerization was carried out at this temperature for 5 h, followed by gradual heating to 220 °C for 20 h of polymerization. The solution changed from a light brown viscous state to a dark brown viscous state. The polymer was then precipitated in boiling water to obtain a yellow-brown polymer. After thorough alkali washing and water washing, the polymer was dried at 80 °C for 24 h to obtain the final product.

[0040] (2) Preparation of proton exchange membrane: Take the functionalized polymer prepared in step (1), dissolve it in NMP at room temperature, and after dissolution, refine and centrifuge. Place a certain concentration of coating solution on a coating machine, adjust to a certain blade height for coating, and then heat to 50 ℃ and let stand for 12 h to dry the solvent and wait for the membrane to form. After completion, at room temperature, immerse the membrane in 7 MHNO3 + 0.36 M Fe(NO3)3 solution for 24 h to allow it to undergo sufficient ion exchange, and then immerse it in deionized water for 24 h to remove excess ions, thus obtaining a non-charged proton exchange membrane; The ratio of Py-OPBI resin material to NMP is (0.08~0.10 g): 1 mL; Tests showed that the polymer film prepared in this embodiment exhibited good H at 25 °C. + Penetration rate U H + =7.47×10 -3 The acid / salt separation factor S = 103.23, the acid absorption rate is 35.86%, the swelling degree is 14.37%, and it breaks apart after being soaked in 11 M HNO3 for 23 days.

[0041] Analysis of the membrane performance test results of each embodiment and comparative example shows that: (1) The test results of Example 1 and Comparative Example 1, and Example 5 and Comparative Example 2 show that after introducing -CF3, sulfone units and other units to replace the ether bond (-O-) of OPBI on the polybenzimidazole main chain, the dimensional stability of the material under the 7M HNO3 acid system is improved, which is manifested as a reduction in acid absorption swelling. At the same time, in a more extreme system (11M HNO3), the long-term stability of the modified polybenzimidazole is improved due to the high bond energy and strong electronegativity of -CF3, sulfone units and other units. (2) Regarding mass transfer, the test results of Examples 1 and 8 and Comparative Examples 1-2 show that after introducing a nitrogen-containing heterocyclic pyridine group into the main chain, the imidazole and pyridine nitrogen atoms act as proton relays and can be reversibly protonated (pyridine → pyridinium ion) under acidic conditions, forming a more interconnected proton conduction pathway, which is manifested as a small-scale enhancement of acid absorption swelling; and the coordination ability of pyridine preferentially binds H + Instead of Fe 3+ (Comparison with imidazole Fe) 3+ (Coordination tendency), further enhancing ion selectivity.

Claims

1. A highly chemically stable non-charged proton exchange membrane for diffusion dialysis acid recovery, characterized in that, The polymer structure of this highly chemically stable non-charged proton exchange membrane is as follows: Wherein, Ar1 is the first group, and the first group is selected from any one or a combination of two or more of the following structural formulas: Ar2 is the second group, which is selected from any one or a combination of two or more of the following structural formulas: n is 10 to 1000.

2. A method for preparing a highly chemically stable non-charged proton exchange membrane for diffusion dialysis acid recovery, characterized in that, The steps are as follows: Step 1: Synthesizing modified polybenzimidazole resin material in an oxygen-free environment: Under N2 protection, firstly, deoxygenate the catalytic solvent at 80-100℃ for 1 hour, then sequentially add carboxylic acid monomer and tetraamine monomer for copolymerization, reacting at 100-140℃ for 6 hours; the polymer properties are controlled by adjusting the composition, structure, and ratio of carboxylic acid monomer and tetraamine monomer; then, the temperature is raised to 140-200℃ until the solution becomes viscous, for 1.5-20 hours, and heating is stopped; the polymer solution after reaction is quickly poured into boiling water, and the polymer solidifies into yellow-brown filaments; the washed polymer solution is soaked in 10wt% NaHCO3 solution at 60℃ for 8-24 hours; after alkali washing, the polymer is washed until neutral, and then placed in an 80℃ oven to dry, obtaining the modified polybenzimidazole resin material; Step 2: Preparation of proton exchange membrane: Take the modified polybenzimidazole resin material prepared in Step 1, dissolve it in an organic solvent at room temperature, and after dissolution, refine and centrifuge to obtain a coating solution; place the coating solution on a coating machine, adjust to the height of the scraper and coat the membrane, then heat to 60℃ and let stand for 24 h to dry the solvent and wait for the membrane to form; after completion, immerse the membrane in 7M HNO3 at room temperature for 24 h to allow it to undergo sufficient ion exchange, and then rinse thoroughly with deionized water to obtain a chemically stable non-charged proton exchange membrane.

3. The preparation method according to claim 2, characterized in that, In step one, The molar ratio of tetraamine monomer to carboxylic acid monomer is 1:1; The ratio of tetraamine monomer to catalytic solvent is 1 mmol: 10 g; The catalytic solvent is Eaton reagent or polyphosphoric acid.

4. The preparation method according to claim 2, characterized in that, In step one, Two copolymerization methods for carboxylic acid monomers and tetraamine monomers: (1) Use carboxylic acid monomers containing strong electron-withdrawing groups, add tetraamine monomers containing nitrogen heterocycles, and selectively add or not add 3,3-diaminobenzidine for copolymerization; (2) Use carboxylic acid monomers containing nitrogen heterocycles, add tetraamine monomers containing strong electron-withdrawing groups, and selectively add or not add 3,3-diaminobenzidine for copolymerization.

5. The preparation method according to claim 4, characterized in that, In step one, The carboxylic acid monomer containing a strong electron-withdrawing group is selected from any one or a combination of two or more of the following structures: The nitrogen-containing heterocyclic carboxylic acid monomer is selected from any one or a combination of two or more of the following structures: The nitrogen-containing heterocyclic tetraamine monomer is selected from any one or a combination of two or more of the following structures: The tetraamine monomer containing a strong electron-withdrawing group is selected from any one or a combination of two or more of the following structures: The structure of the 3,3-diaminobenzidine is as follows: 。 6. The preparation method according to claim 2, characterized in that, In step two, The organic solvent is one of N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone; The ratio of the modified polybenzimidazole resin material to the organic solvent is (0.08~0.10 g): 1 mL; The drying temperature for the coating film is 60~80 ℃, and the time is 24 h. The preparation method is a coating method.

7. The application of the high chemical stability non-charged proton exchange membrane as described in claim 1 in diffusion dialysis acid recovery.

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