A polystyrene-based anion exchange membrane, a preparation method and application thereof

Abstract

This invention provides a polystyrene-based anion exchange membrane, its preparation method, and its application, belonging to the field of polymer materials technology. The raw materials for preparing the polystyrene-based anion exchange membrane include monomers, crosslinking agents, initiators, and quaternizing agents; the monomers include styrene derivatives; the styrene derivatives have the structure shown in Formula I; the polystyrene-based anion exchange membrane has high ion exchange capacity, high conductivity, excellent mechanical properties, low water absorption and swelling rate, and a long lifespan. After long-term operation (1000 h), the loss of ion exchange capacity and conductivity is significantly reduced, while still maintaining high mechanical strength and tensile strength at break.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a polystyrene-based anion exchange membrane, its preparation method, and its application. Background Technology

[0002] Hydrogen energy, as a zero-carbon emission, high-energy-density renewable and clean energy carrier, is widely used in new energy storage, fuel cells, and industrial hydrogen refueling. Among these applications, water electrolysis is a commonly used green hydrogen production technology. Its core principle is to use electricity to drive the decomposition of water molecules into hydrogen and oxygen. In this process, the electrolyte membrane plays a crucial role in ion conduction, gas barrier, and electrode separation, directly determining the efficiency, cost, and long-term stability of the water electrolysis system.

[0003] Currently, commonly used water electrolysis hydrogen production technologies are mainly divided into three categories: alkaline water electrolysis (ALK), proton exchange membrane (PEM), and anion exchange membrane (AEM). Among these, AEM avoids the use of precious metal catalysts compared to PEM, effectively circumventing the scarcity and high cost of precious metal resources and significantly reducing the manufacturing cost of the electrolyzer. Compared to ALK, it solves the problems of electrolyte corrosion, gas cross-permeation, and high product purification costs. Furthermore, it offers higher electrolysis efficiency and better system stability. Therefore, AEM has significant advantages over ALK and PEM, broadening its application scope.

[0004] However, the performance (such as conductivity and mechanical properties) and lifespan of currently used AEM membranes are the main factors restricting their application; for example, traditional polystyrene-based anion exchange membranes have low conductivity and poor alkali resistance; while polyarylpiperidine / quinine-based anion exchange membranes have good alkali stability, but their mechanical strength properties are easily degraded during use, resulting in a short lifespan.

[0005] Therefore, developing an anion exchange membrane with high electrical conductivity, mechanical strength, and long lifespan is an urgent problem to be solved in this field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a polystyrene-based anion exchange membrane, its preparation method, and its application. The polystyrene-based anion exchange membrane solves the problem that existing anion exchange membranes cannot simultaneously achieve high conductivity, excellent mechanical properties, and long lifespan.

[0007] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a polystyrene-based anion exchange membrane, wherein the raw materials for preparing the polystyrene-based anion exchange membrane include monomers, crosslinking agents, initiators, and quaternizing agents; the monomers include styrene derivatives; and the styrene derivatives have the structure shown in Formula I.

[0008] Formula I.

[0009] Where R is selected from C4 to C8 nitrogen-containing saturated rings; n is selected from integers from 1 to 6.

[0010] In this invention, the polystyrene-based anion exchange membrane uses polystyrene as a backbone and introduces cationic groups with specific structures into the molecular chain, namely, groups formed after the R-quaternization of specific structures. This is beneficial to prolonging the lifespan of the anion exchange membrane, and the loss of ion exchange capacity and conductivity is significantly reduced after long-term operation. Furthermore, the introduction of cross-linking structures is beneficial to improving the mechanical properties and stability of the anion exchange membrane. Therefore, the polystyrene-based anion exchange membrane with specific structures described in this invention has high conductivity, excellent mechanical properties, and long lifespan, and low water absorption and swelling rate.

[0011] In this invention, the nitrogen-containing saturated rings of C4 to C8 can be, for example, nitrogen-containing saturated rings of C5, C6, or C7.

[0012] In this invention, n is selected from an integer from 1 to 6, for example, it can be 2, 3, 4, 5, etc., and more preferably an integer from 1 to 4.

[0013] Preferably, R is selected from any of the following structures.

[0014] Formula R-1; Formula R-2.

[0015] Among them, Y1-Y 11 Each is independently selected from CH2 or -NR N And at least one of Y1-Y6 is selected from -NR N Y7-Y 11 At least one of them is selected from -NR N R N Selected from C1-C4 straight-chain or branched alkyl groups, and R N It is either not connected to adjacent ring structures or is linked to them by chemical bonds to form a ring. Dashed lines indicate connection sites.

[0016] In this invention, the C1 to C4 straight-chain or branched alkyl groups can be, for example, C2 or C3 straight-chain or branched alkyl groups, including but not limited to methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, etc.; the same expressions in the following text have the same meaning.

[0017] In this invention, the chemical bonds can be connected by single bonds or by -(CH2)n1-, where n1 is an integer selected from 1 to 2.

[0018] In this invention, when Y1-Y 11 When either of them is a connection site, the corresponding Y is selected from CH.

[0019] Preferably, R is selected from any of the following structures.

[0020] , , .

[0021] Among them, R N1 R N2 Each is independently selected from C1 to C4 straight-chain or branched alkyl groups.

[0022] Preferably, the styrene derivative is selected from any one of the following structures; .

[0023] Among them, R N11 R N12 R N13 Each is independently selected from straight-chain or branched alkyl groups of C1 to C4; n is selected from integers from 1 to 6.

[0024] In some specific embodiments of the present invention, R N11 R N12 R N13 Each is independently selected from methyl groups.

[0025] Preferably, the monomer further includes styrene.

[0026] Preferably, the molar ratio of the styrene derivative to styrene is 100:(0~40), wherein the specific values ​​of 0~40 can be, for example, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, etc.

[0027] Preferably, the crosslinking agent comprises an aromatic vinyl crosslinking agent; the aromatic vinyl crosslinking agent has the structure shown in Formula II.

[0028] Formula II.

[0029] Among them, ring Ar is selected from C6~C20 aromatic rings; m is selected from integers from 2 to 5.

[0030] In this invention, the C6 to C20 aromatic rings can be, for example, C6, C8, C10, C12, C14, C16, C18 aromatic rings, including but not limited to benzene rings, biphenyl rings, naphthalene rings, etc.

[0031] In this invention, m is selected from integers from 2 to 5, such as 3, 4, etc.

[0032] Preferably, the crosslinking agent is selected from at least one of the following compounds.

[0033] .

[0034] Preferably, the molar ratio of the styrene derivative to the crosslinking agent is 100:(1~10), wherein the specific values ​​of 1~10 can be, for example, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, etc.

[0035] Preferably, the mass of the initiator is 2 to 6% of the total mass of the monomer and crosslinking agent, for example, it can be 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, etc.

[0036] In this invention, the type of initiator is not limited too much. Commonly used initiators in the art that can initiate polymerization reactions can be used. For example, the initiator can be selected from organic peroxides, such as benzoyl peroxide; it can also be selected from azo initiators, such as azobisisobutyronitrile.

[0037] Preferably, the quaternizing agent comprises a haloalkyl compound with the structural formula RX; wherein R is selected from C1-C4 straight-chain or branched alkyl groups, and X is selected from halogens.

[0038] In this invention, X is selected from F, Cl, Br, and I.

[0039] In this invention, the haloalkyl compound includes CH3I.

[0040] In this invention, the equivalent of the styrene derivative is 1 eq, and the equivalent of the quaternizing agent is 1.5~2 eq.

[0041] In a second aspect, the present invention provides a method for preparing a polystyrene-based anion exchange membrane according to the first aspect, the method comprising: (1) Mix the monomer, initiator and crosslinking agent, react to obtain a polymer viscous liquid; (2) The polymer viscous liquid is coated into a film and cured to obtain an amine film; (3) The amine membrane is mixed with a quaternizing agent to quaternize it, thereby obtaining the polystyrene anion exchange membrane.

[0042] Preferably, the reaction temperature in step (1) is 60~80 ℃, for example, 62 ℃, 65 ℃, 68 ℃, 70 ℃, 72 ℃, 75 ℃, 78 ℃, etc.; the time is 6~36 h, for example, 8 h, 10 h, 12 h, 15 h, 18 h, 20 h, 22 h, 25 h, 28 h, 30 h, 32 h, 35 h, etc.

[0043] Preferably, the viscosity of the polymer viscous liquid in step (1) is 1000~2000 cps, for example, it can be 1100 cps, 1200 cps, 1300 cps, 1400 cps, 1500 cps, 1600 cps, 1700 cps, 1800 cps, 1900 cps, etc.

[0044] In this invention, the viscosity of the polymer viscous liquid refers to its viscosity at 60 °C.

[0045] In this invention, the temperature and time of the reaction in step (1) are such that the viscosity of the polymer viscous liquid is in the range of 1000~2000cps. Too high a viscosity is not conducive to processing; too low a viscosity is not conducive to achieving the required film thickness.

[0046] Preferably, the curing temperature in step (2) is 80~100 ℃, for example, 82 ℃, 85 ℃, 88 ℃, 90 ℃, 92 ℃, 95 ℃, 98 ℃, etc.; the time is 10~30 h, for example, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h, 24 h, 26 h, 28 h, etc.

[0047] Thirdly, the present invention provides an application of the polystyrene-based anion exchange membrane according to the first aspect in water electrolysis.

[0048] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0049] Compared with the prior art, the beneficial effects of the present invention are as follows: The polystyrene-based anion exchange membrane provided by this invention introduces cationic groups and cross-linking structures with specific structures into the polystyrene molecular structure, which makes the polystyrene-based anion exchange membrane have high ion exchange capacity, high conductivity, excellent mechanical properties, low water absorption and swelling rate, and long life. After long-term operation (1000h), the loss of ion exchange capacity and conductivity is significantly reduced, and it can still maintain high mechanical strength and tensile strength at break. In appearance, it maintains good membrane flexibility. Detailed Implementation

[0050] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0051] All materials used in this invention can be purchased commercially or prepared using conventional methods.

[0052] Example 1 This embodiment provides a polystyrene-based anion exchange membrane, the preparation method of which includes the following steps: (1) Styrene derivative B1 ( Styrene and crosslinking agent C1 are mixed in a molar ratio of 100:20:2, and then 4% benzoyl peroxide is added. The mixture is reacted at 80 °C until the viscosity of the system is 1500 cps to obtain a polymer viscous liquid. (2) The polymer viscous liquid is coated into a film and cured at 90°C for 10 h to obtain an amine film with a thickness of 85 μm; (3) The amine membrane was placed in a methanol solution of CH3I (CH3I mass fraction was 20%, the equivalent of styrene derivative B1 was 1 eq, and the equivalent of CH3I was 1.5 eq) and quaternized at room temperature for 20 h to obtain the polystyrene-based anion exchange membrane.

[0053] Examples 2-8 and Comparative Examples 1-2 each provide a polystyrene-based anion exchange membrane. The difference between them and Example 1 lies in the preparation raw materials, reaction temperature, and curing time, as shown in Table 1. In the table, B represents a styrene derivative, C represents a crosslinking agent, and "-" indicates that no crosslinking agent is added.

[0054] Table 1 Performance testing The polystyrene-based anion exchange membranes provided in the examples and comparative examples were subjected to the following performance tests.

[0055] (1) Ion exchange capacity (IEC): The method described in the reference is: Wang L, Rojas-Carbonell S, Hu K, Setzler BP, Motz AR, Ueckermann ME and Yan Y (2022)Standard Operating Protocol for Ion-Exchange Capacity of Anion ExchangeMembranes. Front. Energy Res. 10:887893. doi: 10.3389 / fenrg.2022.887893.

[0056] (2) Conductivity at room temperature: GB / T 20042.3-2022.

[0057] (3) Water absorption and swelling rate: GB / T 20042.3-2022.

[0058] (4) Tensile strength: GB / T 20042.3-2022.

[0059] (5) Elongation at break: GB / T 20042.3-2022.

[0060] (6) Stability: The polystyrene-based anion exchange membrane was placed in a 10×10 cm AEM electrolysis fixture, and the temperature was 60℃ and the current density was 1A / cm. 2 The membrane was run for 1000 hours under 1 M KOH conditions. After the test, the ion exchange capacity, conductivity, tensile strength and elongation at break of the polystyrene-based anion exchange membrane were tested according to the aforementioned method. The stability of the polystyrene-based anion exchange membrane was characterized by the changes in ion exchange capacity, conductivity, tensile strength and elongation at break before and after the electrochemical test.

[0061] The test results of the polystyrene-based anion exchange membranes provided in the examples and comparative examples for ion exchange capacity, conductivity, water absorption swelling rate, tensile strength and elongation at break are shown in Table 2; the test results of the corresponding indicators after running for 1000 h are shown in Table 3.

[0062] Table 2 Table 3 As shown in Table 2, the polystyrene-based anion exchange membrane provided by the present invention has an IEC ≥ 2.85 meq / g; electrical conductivity ≥ 132 mS / cm; water absorption swelling rate ≤ 9%; tensile strength ≥ 35 MPa; and elongation at break ≥ 45%.

[0063] As shown in Table 3, the polystyrene-based anion exchange membrane provided by this invention has the following properties after 1000 h of operation: IEC ≥ 2.20 meq / g; conductivity ≥ 102 mS / cm; tensile strength ≥ 16 MPa; elongation at break ≥ 38%; high performance retention rate; and long service life.

[0064] As can be seen from Comparative Example 1, the polystyrene-based anion exchange membrane does not introduce cationic groups with specific structures. After 1000 h of operation, the ion exchange capacity and conductivity are significantly reduced, and the lifespan is significantly shortened.

[0065] As shown in Comparative Example 2, without a crosslinking agent, the strength of the polystyrene-based anion exchange membrane decreases, and the tensile strength and elongation at break decrease significantly after 1000 h of operation, resulting in a shorter lifespan.

[0066] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A polystyrene-based anion exchange membrane, characterized in that, The raw materials for preparing the polystyrene-based anion exchange membrane include monomers, crosslinking agents, initiators, and quaternizing agents; The monomer includes styrene derivatives; The styrene derivative has the structure shown in Formula I; Equation I; Where R is selected from C4 to C8 nitrogen-containing saturated rings; n is selected from integers from 1 to 6.

2. The polystyrene-based anion exchange membrane according to claim 1, characterized in that, The R is selected from any of the following structures; Formula R-1; Formula R-2; Among them, Y1-Y 11 Each is independently selected from CH2 or -NR N And at least one of Y1-Y6 is selected from -NR N Y7-Y 11 At least one of them is selected from -NR N ; R N Selected from C1-C4 straight-chain or branched alkyl groups, and R N It is not connected to adjacent ring structures or is linked to them by chemical bonds to form a ring; Dashed lines indicate connection points.

3. The polystyrene-based anion exchange membrane according to claim 1, characterized in that, The R is selected from any of the following structures; 、 、 ； Among them, R N1 R N2 Each is independently selected from C1 to C4 straight-chain or branched alkyl groups; the dashed line indicates the linking site.

4. The polystyrene-based anion exchange membrane according to claim 1, characterized in that, The styrene derivative is selected from any one of the following structures; ； Among them, R N11 R N12 R N13 Each is independently selected from straight-chain or branched alkyl groups of C1 to C4; n is selected from integers from 1 to 6.

5. The polystyrene-based anion exchange membrane according to claim 1, characterized in that, The monomer also includes styrene; The molar ratio of the styrene derivative to styrene is 100:(0~40); The crosslinking agent includes aromatic vinyl crosslinking agents; The aromatic vinyl crosslinking agent has the structure shown in Formula II; Formula II; Among them, ring Ar is selected from C6~C20 aromatic rings; m is selected from integers from 2 to 5.

6. The polystyrene-based anion exchange membrane according to claim 1, characterized in that, The crosslinking agent is selected from at least one of the following compounds; ； The molar ratio of the styrene derivative to the crosslinking agent is 100:(1~10).

7. The polystyrene-based anion exchange membrane according to claim 1, characterized in that, The mass of the initiator is 2-6% of the total mass of the monomer and crosslinking agent; The quaternizing agent includes a haloalkyl compound with the structural formula RX; wherein R is selected from C1-C4 straight-chain or branched alkyl groups, and X is selected from halogens.

8. A method for preparing a polystyrene-based anion exchange membrane according to any one of claims 1 to 7, characterized in that, The preparation method includes: (1) Mix the monomer, initiator and crosslinking agent, react to obtain a polymer viscous liquid; (2) The polymer viscous liquid is coated into a film and cured to obtain an amine film; (3) The amine membrane is mixed with a quaternizing agent to quaternize it, thereby obtaining the polystyrene anion exchange membrane.

9. The preparation method according to claim 8, characterized in that, The reaction in step (1) is carried out at a temperature of 60-80 °C for a time of 6-36 h. The viscosity of the polymer viscous liquid in step (1) is 1000~2000 cps; The curing temperature in step (2) is 80~100 ℃ and the time is 10~30 h.

10. The application of a polystyrene-based anion exchange membrane according to any one of claims 1 to 7 in water electrolysis.

Images