A cross-linked poly (biphenyl-piperidine) anion exchange membrane and its preparation method and application

Abstract

The present invention belongs to the technical field of anion exchange membranes for electrolysis of water, and specifically relates to a cross-linked poly(biphenyl-piperidine) anion exchange membrane and a preparation method and application thereof. The structural formula of the cross-linked poly(biphenyl-piperidine) anion exchange membrane is shown in formula (I); wherein x:y=1-18:99-82, x:z=1-18:99-82; the cross-linking degree of the cross-linked poly(biphenyl-piperidine) anion exchange membrane is 1%-18%. The present invention introduces a cross-linked structure inside the functionalized poly(biphenyl-piperidine) anion exchange membrane, while being able to ensure its electrolysis performance, effectively reducing the water absorption rate and swelling degree, thereby significantly improving the mechanical strength of the anion exchange membrane and extending its service life in the equipment.

Description

Technical Field

[0001] The invention belongs to the technical field of anion exchange membranes for water electrolysis, and specifically relates to a cross-linked poly (biphenyl-piperidine) anion exchange membrane and a preparation method and application thereof. Background Art

[0002] Anion exchange membrane (AEM) water electrolysis hydrogen production technology combines the advantages of low cost of traditional alkaline water electrolysis technology and high current density and high flexibility of proton exchange membrane (PEM) water electrolysis technology. It can be combined with renewable energy, which can not only effectively reduce the cost of hydrogen production, but also solve the problem of unstable renewable energy and long-distance transportation. However, as the core component of AEM water electrolysis technology, anion exchange membrane is difficult to operate stably in the equipment for a long time due to its poor alkaline stability.

[0003] Over the years, many universities and research institutes have made a lot of progress in improving the alkali stability of AEM. The oxygen-free main chain of polyaryl piperidine family has good alkali stability because it does not contain electron-withdrawing groups, which has attracted wide attention from researchers and has been extensively studied. Among them, the functionalized poly (biphenyl-piperidine) anion exchange membrane (structural formula shown in Formula II below) has good performance in hydrogen production by electrolysis of water, but due to its high water absorption rate and swelling degree after 100% functionalization, it is easy to swell when running in high-temperature alkali solution, resulting in serious membrane deformation and breakage, affecting the operation of the equipment.

[0004] Summary of the invention

[0005] In view of the defects existing in the prior art, the present invention provides a cross-linked poly (biphenyl-piperidine) anion exchange membrane and a preparation method and application thereof. By introducing a cross-linked structure inside the functionalized poly (biphenyl-piperidine) anion exchange membrane, while ensuring its water electrolysis performance, the water absorption rate and swelling degree are effectively reduced, thereby extending its service life in the equipment.

[0006] Specifically, the present invention provides the following technical solutions:

[0007] A cross-linked poly (biphenyl-piperidine) anion exchange membrane, the structural formula of which is shown in formula (I):

[0008]

[0009] Among them, x:y=1~18:99~82, x:z=1~18:99~82;

[0010] The cross-linking degree of the cross-linked poly(biphenyl-piperidine) anion exchange membrane is 1% to 18%.

[0011] The cross-linked poly (biphenyl-piperidine) anion exchange membrane provided by the present invention enhances its mechanical strength while maintaining the advantage of high electrical density of functionalized poly (biphenyl-piperidine) AEM, so that it can meet the high performance and long-term operation requirements in hydrogen production equipment. At the same time, it is found that if the cross-linking degree is above 20%, the cross-linked poly (biphenyl-piperidine) cannot form a membrane.

[0012] Preferably, x:y=5-15:95-85, x:z=5-15:95-85;

[0013] The cross-linking degree of the cross-linked poly(biphenyl-piperidine) anion exchange membrane is 5% to 15%.

[0014] The present invention also provides a method for preparing a cross-linked poly(biphenyl-piperidine) anion exchange membrane, firstly preparing a poly(biphenyl-piperidine) polymer main chain by superacid catalytic polycondensation reaction, then using iodomethane and 1,6-dibromohexane as functionalizing agent and cross-linking agent respectively, functionalizing and cross-linking the poly(biphenyl-piperidine) polymer by Menxiu gold reaction, and finally preparing anion exchange membrane with good mechanical strength and water electrolysis performance by ion exchange, specifically comprising the following steps:

[0015] (1) Preparation of poly(biphenyl-piperidine)

[0016] Preparation of poly(biphenyl-piperidine) by superacid-catalyzed polycondensation;

[0017] (2) Functionalization, cross-linking and film casting of poly(biphenyl-piperidine)

[0018] The poly(biphenyl-piperidine) is dissolved in an organic solvent, iodomethane and 1,6-dibromohexane are added, and the mixture is reacted at 60-80° C. for 48-72 hours. Subsequently, the reaction solution is cast on a glass plate, and the solvent is dried to form a film.

[0019] (3) Ion exchange

[0020] The obtained membrane is immersed in an alkali solution to obtain a cross-linked poly (biphenyl-piperidine) anion exchange membrane.

[0021] Preferably, the step (1) is specifically:

[0022] Dissolve biphenyl in an organic solvent, add 1-methyl-4-piperidone, and then drop trifluoroacetic acid and trifluoromethanesulfonic acid at 0-5°C to react until the solution becomes viscous; pour the reactant into a precipitant for precipitation, wash the precipitate with deionized water until it is neutral, and vacuum dry to obtain poly(biphenyl-piperidine).

[0023] Further preferably, in step (1), the molar ratio of biphenyl to 1-methyl-4-piperidone is: 1:1.1-1.2;

[0024] The molar ratio of biphenyl to trifluoroacetic acid is 1:1;

[0025] The molar ratio of biphenyl to trifluoromethanesulfonic acid is 1:9-12.

[0026] Further preferably, in step (1), the organic solvent is dichloromethane;

[0027] and / or, adding trifluoroacetic acid and trifluoromethanesulfonic acid dropwise for reaction for 3 to 4 hours (the reaction time includes the dropping time);

[0028] And / or, the precipitant is methanol or ethanol;

[0029] And / or, the vacuum drying is carried out at a temperature of 60 to 80° C. and for a time of 24 to 48 hours.

[0030] Preferably, in step (2), the molar ratio of the poly(biphenyl-piperidine) to methyl iodide is 1:0.85-1;

[0031] The molar ratio of the poly(biphenyl-piperidine) to 1,6-dibromohexane is 1:0.025-0.075.

[0032] Preferably, in step (2), the solvent B is dimethyl sulfoxide;

[0033] and / or, the poly(biphenyl-piperidine) is dissolved in an organic solvent to form a solution with a volume fraction of 5% to 15%;

[0034] And / or, the solvent is dried to form a film by standing at 60 to 80° C. for 12 to 24 hours.

[0035] Preferably, the step (3) is specifically:

[0036] The obtained membrane is peeled off from the glass plate, first immersed in a 0.5-1.5M sodium chloride solution for 12-48 hours, then immersed in a 0.5-1.5M sodium bicarbonate solution for 12-48 hours, and finally immersed in a 0.5-1.5M NaOH solution for 12-48 hours to obtain a cross-linked poly (biphenyl-piperidine) anion exchange membrane.

[0037] The I inside the anion exchange membrane can be exchanged by sequentially performing ion exchange with the above-mentioned sodium chloride solution, sodium bicarbonate solution, and NaOH solution. - Completely replaced by OH - form, while OH - The mechanical strength of the membrane in this form will be improved, ensuring that the anion exchange membrane will not be damaged during storage.

[0038] The above preparation method is used to optimize the mechanical strength of poly (biphenyl-piperidine) AEM with good water electrolysis performance, and it is applied to the field of water electrolysis hydrogen production, so that it has both high performance and high mechanical strength. The anion exchange membrane is prepared by superacid catalysis to prepare a polymer main chain with high alkali stability, and the Menxiu gold reaction is functionalized and cross-linked.

[0039] The present invention also provides the use of the cross-linked poly (biphenyl-piperidine) anion exchange membrane or the cross-linked poly (biphenyl-piperidine) anion exchange membrane prepared by the preparation method in AEM water electrolysis to produce hydrogen.

[0040] The beneficial effects achieved by the present invention are:

[0041] (1) The present invention provides a cross-linked poly (biphenyl-piperidine) anion exchange membrane and a preparation method and application thereof. The cross-linked poly (biphenyl-piperidine) anion exchange membrane has a cross-linking degree of 1% to 18%. Studies have shown that if the cross-linking degree is above 20%, the cross-linked poly (biphenyl-piperidine) cannot form a membrane;

[0042] (2) The present invention provides a cross-linked poly (biphenyl-piperidine) anion exchange membrane and its preparation method and application. The main chain of the poly (biphenyl-piperidine) prepared by superacid catalysis has good alkaline stability because it does not contain electron-withdrawing groups such as sulfone groups and ether oxygen bonds, which can ensure the long-term operation of the anion exchange membrane in the water electrolysis device;

[0043] (3) A cross-linked poly (biphenyl-piperidine) anion exchange membrane and its preparation method and application provided by the present invention. The cross-linked structure can effectively inhibit the water absorption and swelling degree of the anion exchange membrane, significantly improve the mechanical strength of the anion exchange membrane, so that the anion exchange membrane has high mechanical strength while having high performance, further extending its service life in hydrogen production equipment;

[0044] (4) The present invention provides a cross-linked poly (biphenyl-piperidine) anion exchange membrane and its preparation method and application, wherein ion exchange is performed in sequence by sodium chloride solution, sodium bicarbonate solution, and NaOH solution to remove I in the anion exchange membrane. - Completely replaced by OH - form, while OH - The mechanical strength of the membrane in this form will be improved, ensuring that the anion exchange membrane will not be damaged during storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 11H NMR spectra of the poly(biphenyl-piperidine) main chain and anion exchange membrane prepared in Comparative Example 1; in the figure, the abscissa is the chemical shift value ppm, the upper part is the spectrum of the poly(biphenyl-piperidine) main chain of the third step product, and the lower part is the spectrum of the poly(biphenyl-piperidine) main chain of the first step product.

[0046] Figure 2 The water absorption rate and swelling degree results of the anion exchange membranes prepared in Examples 1-3 and Comparative Example 1 at different temperatures are compared; the left figure is the water absorption rate result, and the right figure is the swelling degree result. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention is described clearly and completely below. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention. If no specific technology or conditions are specified in the embodiments, the technology or conditions described in the literature in the field or the product instructions are used.

[0048] Example 1

[0049] (1) Synthesis of polymer backbone

[0050] 10.00 g of biphenyl was dissolved in 60 mL of dichloromethane, 9.17 mL of 1-methyl-4-piperidone was added, and then 4.82 mL of trifluoroacetic acid and 51.85 mL of trifluoromethanesulfonic acid were added dropwise, and the mixture was reacted at 0°C for 4 hours. The reactants were poured into methanol for precipitation, and the precipitate was repeatedly washed with deionized water until it was neutral, and then dried under vacuum at 70°C for 36 hours to obtain the poly(biphenyl-piperidine) main chain.

[0051] (2) Polymer backbone functionalization, cross-linking and film casting

[0052] 2.00 g of poly(biphenyl-piperidine) main chain was dissolved in 20 mL of dimethyl sulfoxide, 470 μL of iodomethane and 40 μL of 1,6-dibromohexane were added, and the mixture was reacted at 60°C for 48 hours. The reactant was cast on a glass plate and allowed to stand at 60°C for 48 hours to obtain a membrane.

[0053] (3) Ion exchange

[0054] The membrane obtained above was peeled off from the glass plate, immersed in a 1.0M sodium chloride solution for 24 hours to wash away the free ions on the surface, immersed in a 1.0M sodium bicarbonate solution for 24 hours to wash away the free ions on the surface, and finally immersed in a 1M NaOH solution for 24 hours to obtain a cross-linked poly (biphenyl-piperidine) anion exchange membrane (PBP-Pip-5% membrane) with a cross-linking degree of 5%.

[0055] Example 2

[0056] (1) Synthesis of polymer backbone

[0057] 10.00 g of biphenyl was dissolved in 60 mL of dichloromethane, 9.33 mL of 1-methyl-4-piperidone was added, and then 4.82 mL of trifluoroacetic acid and 57.03 mL of trifluoromethanesulfonic acid were added dropwise, and the mixture was reacted at 0°C for 3.5 hours. The reactant was poured into ethanol for precipitation, and the precipitate was repeatedly washed with deionized water until it was neutral, and then dried in vacuum at 80°C for 24 hours to obtain the poly(biphenyl-piperidine) main chain.

[0058] (2) Polymer backbone functionalization, cross-linking and film casting

[0059] 2.00 g of poly(biphenyl-piperidine) main chain was dissolved in 20 mL of dimethyl sulfoxide, 450 μL of iodomethane and 80 μL of 1,6-dibromohexane were added, and the mixture was reacted at 70°C for 36 hours. The reactant was cast on a glass plate and allowed to stand at 70°C for 30 hours to obtain a membrane.

[0060] (3) Ion exchange

[0061] The membrane obtained above was peeled off from the glass plate, immersed in a 1.0M sodium chloride solution for 24 hours to wash away the free ions on the surface, immersed in a 1.0M sodium bicarbonate solution for 24 hours to wash away the free ions on the surface, and finally immersed in a 1M NaOH solution for 24 hours to obtain a cross-linked poly (biphenyl-piperidine) anion exchange membrane (PBP-Pip-10% membrane) with a cross-linking degree of 10%.

[0062] Example 3

[0063] (1) Synthesis of polymer backbone

[0064] 10.00 g of biphenyl was dissolved in 60 mL of dichloromethane, 9.57 mL of 1-methyl-4-piperidone was added, and then 4.82 mL of trifluoroacetic acid and 62.22 mL of trifluoromethanesulfonic acid were added dropwise, and the mixture was reacted at 0°C for 3 hours. The reactant was poured into ethanol for precipitation, and the precipitate was repeatedly washed with deionized water until it was neutral, and then dried at 80°C in vacuum for 24 hours to obtain the poly(biphenyl-piperidine) main chain.

[0065] (2) Polymer backbone functionalization, cross-linking and film casting

[0066] 2.00 g of poly(biphenyl-piperidine) main chain was dissolved in 20 mL of dimethyl sulfoxide, 425 μL of iodomethane and 120 μL of 1,6-dibromohexane were added, and the mixture was reacted at 80°C for 24 hours. The reactant was cast on a glass plate and allowed to stand at 80°C for 24 hours to obtain a membrane.

[0067] (3) Ion exchange

[0068] The membrane obtained above was peeled off from the glass plate, immersed in a 1.0M sodium chloride solution for 24 hours to wash away the free ions on the surface, immersed in a 1.0M sodium bicarbonate solution for 24 hours to wash away the free ions on the surface, and finally immersed in a 1M NaOH solution for 24 hours to obtain a cross-linked poly (biphenyl-piperidine) anion exchange membrane (PBP-Pip-15% membrane) with a cross-linking degree of 15%.

[0069] Comparative Example 1

[0070] (1) Synthesis of polymer backbone

[0071] 10.00 g of biphenyl was dissolved in 60 mL of dichloromethane, 8.77 mL of 1-methyl-4-piperidone was added, and then 4.82 mL of trifluoroacetic acid and 46.66 mL of trifluoromethanesulfonic acid were added dropwise, and the reaction was carried out at 5°C for 4 hours. The reactants were poured into ethanol for precipitation, and the precipitate was repeatedly washed with deionized water until neutral, and dried at 60°C in vacuum for 48 hours to obtain a poly(biphenyl-piperidine) main chain, the 1H NMR spectrum of which is shown in Figure 1 .

[0072] (2) Polymer backbone functionalization, cross-linking and film casting

[0073] 2.00 g of poly(biphenyl-piperidine) main chain was dissolved in 20 mL of dimethyl sulfoxide, 1 mL of iodomethane was added, and the mixture was reacted at 60° C. for 48 hours. The reactant was cast on a glass plate and allowed to stand at 60° C. for 48 hours to obtain a membrane.

[0074] (3) Ion exchange

[0075] The membrane obtained above was peeled off from the glass plate, immersed in a 1.0M sodium chloride solution for 24 hours to wash away the free ions on the surface, immersed in a 1.0M sodium bicarbonate solution for 24 hours to wash away the free ions on the surface, and finally immersed in a 1M NaOH solution for 24 hours to obtain a main chain poly (biphenyl-piperidine) anion exchange membrane (PBP-Pip membrane), the 1HNMR spectrum of which can be found in Figure 1 .

[0076] Depend on Figure 1 It can be seen that after functionalization, a new proton peak appeared at 3.3 ppm on the poly(biphenyl-piperidine) main chain, which is the methyl proton peak on the quaternary ammonium group. This indicates that the tertiary amine group on the poly(biphenyl-piperidine) main chain has been successfully grafted by iodomethane and the functionalization reaction is successful.

[0077] Figure 2 The results of water absorption and swelling degree of the anion exchange membranes prepared in Examples 1-3 and Comparative Example 1 at different temperatures are compared. Figure 2It can be seen that compared with the control group (PBP-Pip) data, the membrane with a cross-linked structure (PBP-Pip-5, 10, 15%) has lower water absorption and swelling degree. At the same time, these two important parameters remain almost unchanged during the temperature increase. This shows that the cross-linked structure can effectively inhibit the water absorption and swelling degree of the membrane, weaken its sensitivity to temperature in deformation, and effectively improve the mechanical strength of the membrane.

[0078] Although the present invention has been described in detail above by general description, specific implementation methods and experiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A cross-linked poly (biphenyl-piperidine) anion exchange membrane, characterized in that: The structural formula is shown in formula (I): Among them, x:y=1~18:99~82, x:z=1~18:99~82; The cross-linking degree of the cross-linked poly(biphenyl-piperidine) anion exchange membrane is 1% to 18%.

2. The cross-linked poly (biphenyl-piperidine) anion exchange membrane according to claim 1, characterized in that: x: y=5~15: 95~85, x: z=5~15: 95~85; The cross-linking degree of the cross-linked poly(biphenyl-piperidine) anion exchange membrane is 5% to 15%.

3. A method for preparing a cross-linked poly (biphenyl-piperidine) anion exchange membrane, characterized in that: The following steps are involved: (1) Preparation of poly(biphenyl-piperidine) Preparation of poly(biphenyl-piperidine) by superacid-catalyzed polycondensation; (2) Functionalization, cross-linking and film casting of poly(biphenyl-piperidine) The poly(biphenyl-piperidine) is dissolved in an organic solvent, iodomethane and 1,6-dibromohexane are added, and the mixture is reacted at 60-80° C. for 48-72 hours. Subsequently, the reaction solution is cast on a glass plate, and the solvent is dried to form a film. (3) Ion exchange The obtained membrane is immersed in an alkali solution to obtain a cross-linked poly (biphenyl-piperidine) anion exchange membrane.

4. The preparation method according to claim 3, characterized in that: The step (1) is specifically: Dissolve biphenyl in an organic solvent, add 1-methyl-4-piperidone, and then drop trifluoroacetic acid and trifluoromethanesulfonic acid at 0-5°C to react until the solution becomes viscous; pour the reactant into a precipitant for precipitation, wash the precipitate with deionized water until it is neutral, and vacuum dry to obtain poly(biphenyl-piperidine).

5. The preparation method according to claim 4, characterized in that: In step (1), the molar ratio of biphenyl to 1-methyl-4-piperidone is 1:1.1-1.2; The molar ratio of biphenyl to trifluoroacetic acid is 1:1; The molar ratio of biphenyl to trifluoromethanesulfonic acid is 1:9-12.

6. The preparation method according to claim 4 or 5, characterized in that: In step (1), the organic solvent is dichloromethane; and / or, adding trifluoroacetic acid and trifluoromethanesulfonic acid dropwise and reacting for 3 to 4 hours; And / or, the precipitant is methanol or ethanol; And / or, the vacuum drying is carried out at a temperature of 60 to 80° C. and for a time of 24 to 48 hours.

7. The preparation method according to claim 3, characterized in that: In step (2), the molar ratio of the poly(biphenyl-piperidine) to methyl iodide is 1:0.85-1; The molar ratio of the poly(biphenyl-piperidine) to 1,6-dibromohexane is 1:0.025-0.

075.

8. The preparation method according to claim 3 or 7, characterized in that: In step (2), the solvent B is dimethyl sulfoxide; and / or, the poly(biphenyl-piperidine) is dissolved in an organic solvent to form a solution with a volume fraction of 5% to 15%; And / or, the solvent is dried to form a film by standing at 60 to 80° C. for 12 to 24 hours.

9. The preparation method according to claim 3, characterized in that: The step (3) is specifically: The obtained membrane is peeled off from the glass plate, first immersed in a 0.5-1.5M sodium chloride solution for 12-48 hours, then immersed in a 0.5-1.5M sodium bicarbonate solution for 12-48 hours, and finally immersed in a 0.5-1.5M NaOH solution for 12-48 hours to obtain a cross-linked poly (biphenyl-piperidine) anion exchange membrane.

10. Use of the cross-linked poly(biphenyl-piperidine) anion exchange membrane according to claim 1 or 2, or the cross-linked poly(biphenyl-piperidine) anion exchange membrane prepared by the preparation method of any one of claims 3 to 9 in AEM water electrolysis for hydrogen production.

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