Polybenzimidazole-based ion exchange membrane and its preparation method and application

Abstract

The present invention relates to a polybenzimidazole-based ion exchange membrane. The polybenzimidazole in the polybenzimidazole-based ion exchange membrane comprises a repeating unit structure shown in Formula I before cross-linking and curing: #imgabs0# The polybenzimidazole-based ion exchange membrane of the present invention greatly improves its mechanical strength by forming a cross-linked structure, and can maintain the stability of the membrane under phosphoric acid conditions.

Description

Technical Field

[0001] The present invention belongs to the technical field of proton exchange membranes for fuel cells, and in particular relates to a polybenzimidazole-based proton exchange membrane and a preparation method and application thereof. Background Art

[0002] With the rapid development of fuel cell technology in recent years, how to improve the performance and life of proton exchange membranes and reduce costs has become a bottleneck problem restricting the promotion and use of fuel cells. Studies have shown that using polybenzimidazole (PBI) as the proton exchange membrane of high-temperature fuel cells can achieve a battery operating temperature of 150-200°C, ensuring the battery system's high CO tolerance, high electrode reaction kinetics, and simplified hydrothermal management. This can reduce the fuel cell system's requirements for fuel hydrogen purity, reducing the difficulty of promoting fuel cells and reducing the cost of use. Therefore, polybenzimidazole-based proton exchange membrane materials have become one of the most ideal alternative membranes to Nafion and have become a new research hotspot.

[0003] Polybenzimidazole (PBI) is a class of aromatic heterocyclic polymers with repeating benzimidazole ring units in the backbone. Fully aromatic polybenzimidazole resins exhibit excellent heat resistance and mechanical properties, making them a high-performance specialty engineering plastic widely used in high-tech fields such as aerospace, semiconductors, fire-resistant and heat-resistant materials, and fuel cells. Commercial polybenzimidazole resins (poly[2,2'-(m-phenylene)-5,5'-dibenzimidazole], m-PBI) offer high heat resistance and strength, making them suitable for use in a variety of extreme high-temperature applications. However, poly[2,2'-(m-phenylene)-5,5'-dibenzimidazole] resins require high preparation temperatures (above 200°C), are difficult to melt, and are difficult to process. Consequently, proton exchange membranes based on this material struggle to maintain mechanical strength in the presence of high concentrations of phosphoric acid, resulting in decreased performance.

[0004] Therefore, it is urgent to propose a new exchange membrane to improve its mechanical strength and stability. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies of the prior art and provide a novel polybenzimidazole-based ion exchange membrane. The polybenzimidazole-based ion exchange membrane of the present invention greatly improves its mechanical strength by forming a cross-linked structure, which can maintain the stability of the membrane under phosphoric acid conditions.

[0006] In a first aspect, the present invention provides a polybenzimidazole-based ion exchange membrane, wherein the polybenzimidazole in the polybenzimidazole-based ion exchange membrane comprises a repeating unit structure shown in Formula I before cross-linking and curing:

[0007]

[0008] Wherein, R is selected from any one of Formula II or Formula III:

[0009]

[0010] X is selected from any one of formula (1) to formula (7):

[0011]

[0012] The R2 part is all or selected from any one of formula IV to formula I:

[0013]

[0014] R and R2 are the same or different along the molecular chain.

[0015] As a specific embodiment of the present invention, the polybenzimidazole has a number average molecular weight of 2000 g / mol to 800000 g / mol, for example, 2000 g / mol, 5000 g / mol, 8000 g / mol, 10000 g / mol, 50000 g / mol, 100000 g / mol, 200000 g / mol, 300000 g / mol, 400000 g / mol, 500000 g / mol, 600000 g / mol, 700000 g / mol, 800000 g / mol and any combination thereof.

[0016] As a specific embodiment of the present invention, the tensile modulus of the polybenzimidazole-based ion exchange membrane is not less than 2850 MPa, for example, in the range of 2850 MPa, 3050 MPa, 3250 MPa, 3450 MPa and any combination thereof.

[0017] As a specific embodiment of the present invention, the tensile strength of the polybenzimidazole-based ion exchange membrane is not less than 110 MPa, such as 110 MPa, 130 MPa, 150 MPa, 170 MPa and any combination thereof.

[0018] Unless otherwise specified, the raw materials in the present invention can be prepared in-house or purchased commercially, and the present invention is not particularly limited thereto.

[0019] The polybenzimidazole-based ion exchange membrane of the present invention greatly improves its mechanical strength by forming a cross-linked structure, and can maintain the stability of the membrane under phosphoric acid conditions.

[0020] In a second aspect, the present invention provides a method for preparing the polybenzimidazole-based ion exchange membrane, comprising the following steps:

[0021] Under protective gas conditions, a compound containing a tetraamine group and a compound containing a diacid group are dissolved in a clear solution containing polyphosphoric acid at a molar ratio of (0.8:1) to (1:1.2), heated to 160°C to 220°C for reaction for 1h to 48h, then a photocuring agent is added and mixed, and the mixture is poured onto a flat surface. The mixture is cured with light for 30s to 2h, washed, and then dried to obtain a polybenzimidazole-based ion exchange membrane.

[0022] As a specific embodiment of the present invention, the sum of the mass of the tetraamine group-containing compound and the diacid group-containing compound accounts for 1% to 20% of the clear solution, for example, 1%, 5%, 15%, 20% and any combination thereof.

[0023] As a specific embodiment of the present invention, the molar ratio of the tetraamine group-containing compound to the diacid group-containing compound is preferably (1.02:1) to (1:1.02), for example, 1:1, 1.02:1, 1:1.02 and any combination thereof.

[0024] As a specific embodiment of the present invention, the compound containing a tetraamino group is selected from any one of Formula II' or Formula III':

[0025]

[0026] Wherein, X is selected from any one of formula (1) to formula (7):

[0027]

[0028] As a specific embodiment of the present invention, the compound containing a diacid group is selected in whole or in part from any one of Formula IV' to Formula I':

[0029]

[0030] As a specific embodiment of the present invention, the compound containing a diacid group is prepared by dissolving a compound containing a hydroxy diacid group and a halogenated hydrocarbon in a solvent and refluxing for 2 hours to 24 hours, for example, 2 hours, 8 hours, 16 hours, 24 hours and any combination thereof.

[0031] As a specific embodiment of the present invention, the compound containing a hydroxy diacid group is selected from any one of Formula IV to Formula VIII:

[0032]

[0033] As a specific embodiment of the present invention, the halogenated hydrocarbon has the formula Structure, wherein Z is selected from any one of F, Cl, Br, and I.

[0034] As a specific embodiment of the present invention, the solvent is selected from one or more of tetrahydrofuran, acetone, ethanol, acetonitrile, N-methylpyrrolidone, dimethyl sulfoxide, N'N-dimethylformamide and N,N-dimethylacetamide.

[0035] As a specific embodiment of the present invention, the clear solution containing polyphosphoric acid further comprises phosphorus pentoxide, and the mass ratio of the phosphorus pentoxide to the polyphosphoric acid is 1:(6-15), preferably 1:(8-13).

[0036] As a specific embodiment of the present invention, a saturated sodium bicarbonate aqueous solution, a saturated potassium carbonate aqueous solution, a saturated sodium carbonate aqueous solution or ammonia water is used for the washing operation.

[0037] As a specific embodiment of the present invention, the purpose of drying is mainly to remove the solvent. The drying method can be conventional methods in the art and is not particularly limited by the present invention. The drying temperature can be 80°C to 100°C, for example, 80°C, 90°C, 100°C, and any combination thereof. The drying temperature can be adjusted according to the drying time.

[0038] As a specific embodiment of the present invention, the protective gas is nitrogen.

[0039] As a specific embodiment of the present invention, the photocuring agent is a free radical photoinitiator.

[0040] Preferably, the photocuring agent is selected from benzophenone compounds.

[0041] More preferably, the photocuring agent is at least one selected from benzophenone, 2-hydroxy-2-methyl-1-phenylpropanone, 2-isopropylthioxanthone and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0042] As a specific embodiment of the present invention, the mass of the photocuring agent accounts for 0.01% to 10% of the total mass of the compound containing tetraamine groups and the compound containing diacid groups, and preferably 0.3% to 5%.

[0043] In a third aspect, the present invention proposes another method for preparing the polybenzimidazole-based ion exchange membrane.

[0044] The preparation method of the polybenzimidazole-based ion exchange membrane comprises the following steps:

[0045] A polybenzimidazole having a repeating unit structure represented by formula I is dissolved in an organic solvent to obtain a solution having a polybenzimidazole mass fraction of 2% to 20%, a curing agent is then added and mixed, and the solution is poured onto a flat surface. The solution is cured by light and / or heat for 10 seconds to 8 hours, and then naturally dried at a temperature of 60° C. to 120° C. for 2 hours to 10 hours, and then vacuum dried at a temperature of 60° C. to 120° C. for 2 hours to 12 hours to obtain a polybenzimidazole-based ion exchange membrane.

[0046] As a specific embodiment of the present invention, when light curing is adopted, the curing agent is a free radical photoinitiator; preferably, the light curing agent is selected from benzophenone compounds; more preferably, the light curing agent is at least selected from one of benzophenone, 2-hydroxy-2-methyl-1-phenylpropanone, 2-isopropylthioxanthone and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

[0047] As a specific embodiment of the present invention, when heat curing is adopted, the heating temperature is 50°C to 200°C, and the curing agent is a free radical initiator. Preferably, the curing agent is selected from peroxide curing agents and / or azo curing agents; more preferably, the curing agent is at least selected from one of cumene hydroperoxide, azobisisobutyronitrile and dicumyl peroxide.

[0048] As a specific embodiment of the present invention, the curing agent accounts for 0.01% to 10% of the mass of the polybenzimidazole, preferably 0.3% to 5%.

[0049] In a third aspect, the present invention proposes the application of the polybenzimidazole-based ion exchange membrane and / or the preparation method of the polybenzimidazole-based ion exchange membrane in the fields of aerospace materials, semiconductor materials, fireproof and heat-resistant materials, and fuel cells.

[0050] The polybenzimidazole proton exchange membrane of the present invention has high mechanical strength, can increase the loading amount of phosphoric acid, and can maintain stable performance under high-concentration phosphoric acid loading conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The present invention will be described in further detail below with reference to the accompanying drawings.

[0052] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of Vinyl-O-PBI in Example 1 when it is not cross-linked. DETAILED DESCRIPTION

[0053] In order to make the present invention easier to understand, the present invention will be described in detail below with reference to embodiments and drawings. These embodiments are only for illustration and do not limit the application scope of the present invention.

[0054] The test methods or standards used in the following examples and comparative examples are as follows:

[0055] H NMR spectroscopy: Agilent Technologies, Inc., USA, instrument model 400-MR DD2, 1H resonance frequency of 399.87 MHz. The solvent was deuterated sulfuric acid, and the test temperature was 50°C. H-12 spectra were acquired using a 45° pulse, a 5 s recycle delay, and a 2 s sampling time.

[0056] The mechanical strength is determined by the tensile strength of the electrolyte membrane product specimens, which is tested using an Instron 5965 universal material testing machine. The specimen test length is 15 mm, and the width and thickness are obtained through testing.

[0057] The sources of materials for the following examples are as follows:

[0058] Raw material name purity factory 3,3'-Diaminobenzidine ≥98％ Sigma-Aldrich Polyphosphoric acid 86％ Beijing Bailingwei Technology Co., Ltd. Phosphorus pentoxide 98％ Beijing Bailingwei Technology Co., Ltd. 2,5-Dihydroxyterephthalic acid 98％ Beijing Bailingwei Technology Co., Ltd. 4,4-Dicarboxydiphenyl ether 98％ Beijing Bailingwei Technology Co., Ltd. 4-Hydroxypyridine-2,6-dicarboxylic acid 95％ Beijing Bailingwei Technology Co., Ltd. Allyl bromide 98％ Beijing Inokai Technology Co., Ltd. potassium carbonate AR China National Pharmaceutical Group Corporation Sodium bicarbonate AR China National Pharmaceutical Group Corporation

[0059] [Example 1]

[0060] Weigh 2,5-dihydroxyterephthalic acid (20 mmol), allyl bromide (40 mol), potassium carbonate (2 mmol) and tetrabutylammonium bromide (2 mmol) in 10 ml of tetrahydrofuran, stir at room temperature for 1 day and night, filter, and remove the solvent by rotary evaporation to obtain

[0061] Weigh phosphorus pentoxide (6 g) and dissolve it in polyphosphoric acid (60 g) to form a clear solution. Add VDA (10 mmol) and 3,3-diaminobenzidine (10 mmol) under nitrogen and heat to 160 ° C under stirring for 5 hours. Add benzophenone (0.05 g) to the reaction solution, stir evenly, pour the reaction solution onto a flat glass, scrape it flat with a spatula, place it under a UV lamp to cure for 10 minutes, rinse with plenty of water, and place it in a vacuum oven at 80 ° C to dry to obtain a cross-linked polybenzimidazole (Vinyl-O-PBI cross-linked) proton exchange membrane. The structure of Vinyl-O-PBI when not cross-linked is as follows, and its nuclear magnetic resonance hydrogen spectrum is as follows Figure 1 shown.

[0062]

[0063] The tensile modulus of the cross-linked polybenzimidazole proton exchange membrane can reach 3250 MPa, and the tensile breaking strength can reach 130 MPa.

[0064] [Example 2]

[0065] Weigh 0.5g of polybenzimidazole (Vinyl-pyr-PBI) and 0.05g of lithium chloride and dissolve them in 5g of N,N-dimethylacetamide to form a homogeneous solution. Weigh 0.0003g of 2-hydroxy-2-methyl-1-phenylpropanone and mix thoroughly with the above solution. Cast the solution onto a flat glass plate and apply it with a spatula to form a uniform film. Curing and crosslinking the film under UV light for 30 minutes, transfer the film to an 80°C forced air oven and let it stand for 2 hours. Transfer the film to an 80°C vacuum oven to remove any residual solvent.

[0066] Vinyl-pyr-PBI:

[0067] The tensile modulus of the cross-linked proton exchange membrane can reach 2850 MPa, and the tensile breaking strength can reach 110 MPa.

[0068] Synthesis of Vinyl-pyr-PBI: To polyphosphoric acid, add 4-hydroxypyridine-2,6-dicarboxylic acid and 3,3-diaminobenzidine under nitrogen and heat to 200°C with stirring for 5 hours. The intermediate product is washed with sodium bicarbonate until neutral and filtered. After drying, it is dissolved in N,N-dimethylacetamide with allyl bromide and potassium carbonate. The reaction is stirred at 80°C overnight. The solvent is removed by rotary evaporation, and the precipitate is washed in water to obtain Vinyl-pyr-PBI.

[0069] [Example 3]

[0070] Weigh 0.5g of polybenzimidazole (co-OH-PBI) and 0.05g of lithium chloride and dissolve them in 5g of N,N-dimethylacetamide to form a homogeneous solution. Weigh 0.0003g of 2-hydroxy-2-methyl-1-phenylpropanone and mix them evenly. Pour the solution onto a glass plate and apply it with a spatula to form a uniform film. Curing and crosslinking the film under UV light for 30 minutes, transfer the film to an 80°C forced air oven and let it stand for 2 hours. Transfer the film to an 80°C vacuum oven to remove any residual solvent.

[0071] co-OH-PBI:

[0072]

[0073] The tensile modulus of the cross-linked proton exchange membrane can reach 2980 MPa, and the tensile breaking strength can reach 125 MPa.

[0074] Synthesis of co-OH-PBI: To polyphosphoric acid, 2,5-dihydroxyterephthalic acid, 4,4-dicarboxydiphenyl ether, and 3,3-diaminobenzidine are added under nitrogen and heated to 200°C with stirring for 3 hours. The intermediate product is washed with sodium bicarbonate until neutral, filtered, dried, dissolved with allyl bromide and potassium carbonate in N,N-dimethylacetamide, stirred at 80°C for 5 hours, and the solvent is removed by rotary evaporation. The precipitate is washed in water to obtain co-OH-PBI.

[0075] [Comparative Example 1]

[0076] Weigh 0.5g of polybenzimidazole (1-PBI) and 0.05g of lithium chloride and dissolve them in 5g of N,N-dimethylacetamide to form a homogeneous solution. Cast the solution onto a glass plate and apply it with a doctor blade to form a uniform film. Place the film in an 80°C forced air oven for 2 hours. Transfer the film to an 80°C vacuum oven to remove any residual solvent.

[0077] 1-PBI:

[0078] The tensile modulus of the proton exchange membrane can reach 1600 MPa and the tensile breaking strength is 60 MPa.

[0079] [Comparative Example 2]

[0080] Weigh 0.5g of polybenzimidazole (co-PBI) and 0.05g of lithium chloride and dissolve them in 10g of N,N-dimethylacetamide to form a homogeneous solution. Cast the solution onto a glass plate and apply it with a doctor blade to form a uniform film. Place the film in an 80°C forced air oven for 2 hours. Transfer the film to an 80°C vacuum oven to remove any residual solvent.

[0081] co-PBI: m / n=3 / 7

[0082]

[0083] The tensile modulus of the proton exchange membrane can reach 2200 MPa, and the tensile breaking strength is 82 MPa.

[0084] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation of the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A polybenzimidazole-based ion exchange membrane, characterized in that: The polybenzimidazole in the polybenzimidazole-based ion exchange membrane comprises a repeating unit structure shown in Formula I before cross-linking and curing: Wherein, R is selected from any one of Formula II or Formula III: X is selected from any one of formula (1) to formula (7): R2 is partially or entirely selected from any one of formula IV to formula I: The number average molecular weight of the polybenzimidazole is 2000 g / mol to 800000 g / mol.

2. The method for preparing the polybenzimidazole-based ion exchange membrane according to claim 1, wherein: The steps include: Under protective gas conditions, a compound containing a tetraamine group and a compound containing a diacid group are dissolved in a clear solution containing polyphosphoric acid at a molar ratio of (0.8:1) to (1:1.2), heated to 160° C. to 220° C. for reaction for 1 hour to 48 hours, then a photocuring agent is added and mixed, and then poured onto a flat surface, cured with light for 30 seconds to 2 hours, washed, and then dried to obtain a polybenzimidazole-based ion exchange membrane; Wherein, the compound containing a tetraamino group is selected from any one of Formula II' or Formula III': Wherein, X is selected from any one of formula (1) to formula (7): The compound containing a diacid group is selected in whole or in part from any one of formula IV' to formula I':

3. The method for preparing a polybenzimidazole-based ion exchange membrane according to claim 2, wherein: The compound containing a diacid group is prepared by dissolving a compound containing a hydroxy diacid group and a halogenated hydrocarbon in a solvent and refluxing for 2 hours to 24 hours; Wherein, the compound containing a hydroxy diacid group is selected from any one of Formula IV to Formula VIII: The halogenated hydrocarbon has the formula Structure, wherein Z is selected from any one of F, Cl, Br, and I.

4. The method for preparing a polybenzimidazole-based ion exchange membrane according to claim 3, wherein: The light curing agent is a free radical photoinitiator; The clear solution containing polyphosphoric acid further comprises phosphorus pentoxide, and the mass ratio of the phosphorus pentoxide to the polyphosphoric acid is 1:(6-15).

5. The method for preparing a polybenzimidazole-based ion exchange membrane according to claim 4, wherein: The photocuring agent is selected from one of benzophenone, 2-hydroxy-2-methyl-1-phenylpropanone, 2-isopropylthioxanthone and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide; The mass ratio of the phosphorus pentoxide to the polyphosphoric acid is 1:(8-13).

6. The method for preparing a polybenzimidazole-based ion exchange membrane according to any one of claims 2 to 5, characterized in that: The sum of the mass of the tetraamine group-containing compound and the diacid group-containing compound accounts for 1% to 20% of the clear solution, and / or The molar ratio of the tetraamine group-containing compound to the diacid group-containing compound is (1.02:1) to (1:1.02); and / or, The mass of the photocuring agent accounts for 0.01% to 10% of the total mass of the compound containing tetraamine groups and the compound containing diacid groups.

7. The method for preparing a polybenzimidazole-based ion exchange membrane according to claim 6, wherein: The mass of the photocuring agent accounts for 0.3% to 5% of the total mass of the compound containing tetraamine groups and the compound containing diacid groups.

8. The method for preparing a polybenzimidazole-based ion exchange membrane according to any one of claims 3 to 5, characterized in that: The solvent is selected from one or more of tetrahydrofuran, acetone, ethanol, acetonitrile, dimethyl sulfoxide, N-methylpyrrolidone, N'N-dimethylformamide and N,N-dimethylacetamide; and / or, washing with a saturated aqueous solution of sodium bicarbonate, a saturated aqueous solution of potassium carbonate, a saturated aqueous solution of sodium carbonate or aqueous ammonia; and / or, the drying temperature is 80° C. to 100° C.; And / or, the protective gas is nitrogen.

9. The method for preparing the polybenzimidazole-based ion exchange membrane according to claim 1, characterized in that: The steps include: A polybenzimidazole having a repeating unit structure represented by formula I is dissolved in an organic solvent to obtain a solution having a polybenzimidazole mass fraction of 2% to 20%, a curing agent is then added and mixed, and the solution is poured onto a flat surface. The solution is cured by light and / or heat for 10 seconds to 8 hours, and then naturally dried at a temperature of 60° C. to 120° C. for 2 hours to 10 hours, and then vacuum dried at a temperature of 60° C. to 120° C. for 2 hours to 12 hours to obtain a polybenzimidazole-based ion exchange membrane.

10. The method for preparing a polybenzimidazole-based ion exchange membrane according to claim 9, wherein: When light curing is adopted, the curing agent is a free radical photoinitiator; and / or, When heat curing is adopted, the heating temperature is 50°C to 200°C, and the curing agent is a free radical initiator; and / or, The curing agent accounts for 0.01% to 10% of the mass of the polybenzimidazole.

11. The method for preparing a polybenzimidazole-based ion exchange membrane according to claim 10, wherein: When light curing is adopted, the free radical photoinitiator is selected from one of benzophenone, 2-hydroxy-2-methyl-1-phenylpropanone, 2-isopropylthioxanthone and 2,4,6-trimethylbenzoyl-diphenylphosphine oxide; and / or, When heat curing is adopted, the free radical initiator is selected from one of cumene hydrooxide, azobisisobutyronitrile and dicumyl peroxide; and / or, The curing agent accounts for 0.3% to 5% of the mass of the polybenzimidazole.

12. Application of the polybenzimidazole-based ion exchange membrane according to claim 1 or the method for preparing the polybenzimidazole-based ion exchange membrane according to any one of claims 2 to 11 in the fields of aerospace materials, semiconductor materials, fireproof and heat-resistant materials, and fuel cells.

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