Cross-linked anion exchange membrane and preparation method thereof

Abstract

The preparation method comprises the following steps: carrying out acid-catalyzed polymerization on p-terphenyl and a ketone monomer under the action of a first organic solvent and trifluoromethanesulfonic acid, and precipitating, filtering, washing and drying a reaction product to obtain a first polymer; carrying out quaternization reaction on the first polymer and quaternary ammonium salt under the action of a second organic solvent, cooling to room temperature, and adding 1, 6-hexamethylenediamine to obtain a second polymer solution; and coating a substrate with the second polymer solution, and carrying out drying membrane formation, heat treatment and hydroxyl anion exchange to obtain the cross-linked hydroxyl ion exchange membrane. The preparation method disclosed by the invention is simple and suitable for large-scale production, and the prepared anion exchange membrane has high ionic conductivity, excellent dimensional stability and mechanical property and relatively good machinability and application potential, and has a good application prospect in a water electrolysis hydrogen production technology.

Description

Technical Field

[0001] The present invention relates to the field of ion exchange membranes, and particularly to a crosslinked anion exchange membrane and a preparation method thereof. Background Art

[0002] With the in-depth promotion of the global energy structure transformation, hydrogen energy, as a clean, efficient and renewable energy form, has become increasingly prominent in strategic significance. Among various hydrogen production technologies, anion exchange membrane water electrolysis (AEMWE) technology has become a focus in the industry due to its outstanding advantages of achieving efficient and low-cost hydrogen production under relatively mild conditions. Anion exchange membrane (AEM), as a key component of AEMWE, needs to have the function of transporting OH- ions and blocking gases.

[0003] Currently, the research on anion exchange membrane (AEM) materials mainly focuses on quaternized polyarylether sulfone, polyphenylene ether oxide, polystyrene, etc. However, these traditional AEM materials generally have problems such as poor stability and low ionic conductivity during long-term operation in an alkaline environment, which greatly limits their practical application and development. In recent years, polyaryl anion exchange membranes have become an important research direction in anion exchange membrane materials due to their excellent chemical stability and good mechanical properties. Traditional linear polyaryl AEM materials have certain advantages in ionic conduction performance, but there are obvious problems of excessive swelling and decreased mechanical strength, thus seriously affecting the microstructure stability and long-term operation performance of the membrane. Therefore, developing crosslinked anion exchange membrane materials with high chemical stability, excellent ionic conductivity and good mechanical properties has become an important research trend and technical requirement in the current membrane material field. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a crosslinked anion exchange membrane and a preparation method thereof. By constructing a crosslinked network and a branched structure, closer intermolecular interactions are formed between molecular chains, thereby effectively reducing the swelling degree of the membrane material during actual application and improving its mechanical strength to solve the performance deficiencies of existing anion exchange membranes in terms of ionic conductivity, chemical stability and dimensional stability.

[0005] The object of the present invention is achieved through the following technical solutions:

[0006] First, the present invention provides a crosslinked anion exchange membrane, and the chemical structural formula of the anion exchange membrane is:

[0007]

[0008] Wherein, x and y are natural numbers.

[0009] Second, the present invention provides a preparation method of a crosslinked anion exchange membrane, which includes the following steps:

[0010] S1. Dissolve p - terphenyl and 7 - bromo - 1,1,1 - trifluoro - 2 - heptanone in a first organic solvent in a certain ratio. After complete dissolution, add a certain amount of trifluoromethanesulfonic acid for acid - catalyzed polymerization reaction. After the reaction ends, pour the reaction product into a precipitant for precipitation, filter, wash, and dry to obtain a first polymer;

[0011] S2. Carry out a quaternization reaction on the first polymer and (N’,N’ - dimethylamino) - 6 - (N,N,N - trimethylammonium) hexane iodide under the action of a second organic solvent, then cool to room temperature, and add a certain amount of 1,6 - hexanediamine to obtain a second polymer solution;

[0012] S3. Coat the second polymer solution on a substrate, carry out drying to form a film and heat treatment, and then carry out hydroxide anion exchange to obtain a cross - linked hydroxide ion exchange membrane.

[0013] Furthermore, the molar ratio of p - terphenyl to 7 - bromo - 1,1,1 - trifluoro - 2 - heptanone is 1:(1.0 - 1.2);

[0014] The mass ratio of p - terphenyl to the first organic solvent is 1:(15 - 20);

[0015] The mass ratio of p - terphenyl to trifluoromethanesulfonic acid is 1:(4 - 7).

[0016] Furthermore, in step S1, the reaction temperature of the acid - catalyzed polymerization reaction is 0 - 50 °C, and the reaction time is 1 - 36 h.

[0017] Furthermore, the precipitant in step S1 is one of water, ethanol, methanol, acetone, and ethyl acetate.

[0018] Furthermore, in step S2:

[0019] The mass ratio of the first polymer to (N’,N’ - dimethylamino) - 6 - (N,N,N - trimethylammonium) hexane iodide is (4 - 6):(1 - 2);

[0020] The mass ratio of the first polymer to the second solvent is 1:(15 - 25);

[0021] The mass ratio of the first polymer to 1,6 - hexanediamine is 1:(0.02 - 0.05).

[0022] Furthermore, the chemical structure of (N’,N’ - dimethylamino) - 6 - (N,N,N - trimethylammonium) hexane iodide in step S2 is:

[0023]

[0024] In the step S2, the reaction temperature of the quaternization reaction is 20-80°C, and the reaction time is 1-72 h.

[0025] Furthermore, in the step S3, the drying temperature for drying into a film is 40-100°C, and the drying time is 4-48 hours; the heat treatment temperature is 20-140°C, and the heat treatment time is 1-24 hours.

[0026] Furthermore, the specific process of hydroxide anion exchange in the step S3 is as follows: The film after heat treatment is soaked in 1M sodium hydroxide solution at room temperature for 48 hours for ion exchange, so that the anions are converted into hydroxide ions, and a crosslinked anion exchange membrane with hydroxide ions as anions is obtained.

[0027] Furthermore, the first organic solvent is selected from at least one of dichloromethane, dichloroethane, tetrahydrofuran, chloroform, tetrachloroethane, and toluene; the second organic solvent is at least one of dimethyl sulfoxide, tetrahydrofuran, and N-methylpyrrolidone.

[0028] The beneficial effects of the present invention are as follows:

[0029] The crosslinked anion exchange membrane provided by the present invention has a crosslinked structure that can better inhibit the dimensional stability of the membrane material, reduce the swelling rate (≤15%, 80°C), and can also promote polymer self-assembly to form a microphase separation structure, thereby obtaining a relatively high ionic conductivity (≥141 mS / cm, 80°C). When the anion exchange membrane is assembled into an electrolytic cell, it has a high current density performance of ≥2.5 A / cm 2 at 80°C and 1.8V.

[0030] By adopting steps such as acid-catalyzed polymerization, Menshutkin reaction, flat film casting, and ion exchange, the present application optimizes the structure of the anion exchange membrane by introducing branched and crosslinked structures, which can form closer intermolecular interactions between molecular chains, thereby effectively reducing the swelling degree of the membrane material during actual application, improving its mechanical strength, and increasing the ionic conductivity, chemical stability, and dimensional stability of the anion exchange membrane. Its preparation method is simple and suitable for large-scale production, and can meet the actual application requirements of the electrolytic water hydrogen production technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram showing the relationship between the ionic conductivity and temperature of the crosslinked anion exchange membrane prepared in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] In order to further understand the present invention, the preferred embodiments of the present invention will be described below in conjunction with examples. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0033] Unless otherwise specified, all reagents and instruments used in the present invention are conventional products that can be obtained through commercial purchase.

[0034] Example 1

[0035] The preparation method of the crosslinked anion exchange membrane in this example includes the following steps:

[0036] S1: Dissolve 2.3 g of p-terphenyl and 2.6 g of 7-bromo-1,1,1-trifluoro-2-heptanone in 30.0 mL of dichloromethane. After complete dissolution, add 8.0 mL of trifluoromethanesulfonic acid and stir at 20 °C for 24 h. Pour the resulting mixture into ethanol to precipitate a pale yellow block polymer. After filtering and washing with ethanol three times, dry it overnight at 60 °C to obtain a poly(triphenylalkyl) polymer;

[0037] S2: Mix 4.6 g of the poly(triphenylalkyl) obtained in step S1 and 92.0 mL of N-methylpyrrolidone and stir evenly. Then add 1.7 g of (N’,N’-dimethylamino)-6-(N,N,N-trimethylammonium) hexane iodide and stir and react at 60 °C for 12 h. Subsequently, cool to room temperature and add 0.1 g of 1,6-hexanediamine to obtain a functionalized polymer solution.

[0038] S3: Filter the functionalized polymer solution obtained in step S2. Then, use the flat casting method to coat the casting solution on a glass plate and dry it at 60 °C for 12 hours to form a film. Subsequently, heat-treat it at 100 °C for 2 hours; Immerse the film in 1 M sodium hydroxide solution at room temperature for 48 hours to convert the anions into hydroxide ions, obtaining a crosslinked hydroxide ion exchange membrane, as Figure 1 shown.

[0039] The test results show that: the ion conductivity of the crosslinked hydroxide ion exchange membrane in this example at 80 °C is 142 mS / cm (as Figure 1 shown), and the swelling rate is 14.8%. Immerse the crosslinked hydroxide ion exchange membrane in this example in 1 M NaOH solution at 80 °C for 1000 hours, and the ion conductivity only decreases by 5.6%.

[0040] Install the crosslinked hydroxide ion exchange membrane in this example into an alkaline membrane electrolytic cell, and the current density at 80 °C and 1.8 V reaches 2.8 A / cm 2 .

[0041] Example 2

[0042] The preparation method of the crosslinked anion exchange membrane in this example includes the following steps:

[0043] S1: Dissolve 4.6 g of p-terphenyl and 5.2 g of 7-bromo-1,1,1-trifluoro-2-heptanone in 60.0 mL of dichloromethane, mix and stir evenly, then add 15.0 mL of trifluoromethanesulfonic acid, stir at room temperature for 24 h, pour the obtained mixture into ethanol to precipitate a pale yellow block polymer, filter and wash it 3 times with methanol, and dry it overnight at 60 °C to obtain a poly(triphenylalkyl) polymer;

[0044] S2: Stir 4.6 g of the poly(triphenylalkyl) obtained in step S1 evenly in 92.0 mL of N-methylpyrrolidone, then add 1.6 g of (N’,N’-dimethylamino)-6-(N,N,N-trimethylammonium) hexane iodide, stir and react at 60 °C for 24 h, then cool to room temperature, and add 0.2 g of 1,6-hexanediamine to obtain a functionalized polymer solution.

[0045] S3: Filter the functionalized polymer solution obtained in step S2, then use the doctor blade method to coat the casting solution on a glass plate, dry it at 80 °C for 6 h to form a film, and then heat-treat it at 110 °C for 1 h; soak the film in 1 M sodium hydroxide solution at room temperature for 48 h to convert the anions into hydroxide ions, and obtain a crosslinked hydroxide ion exchange membrane.

[0046] The test results show that: the ion conductivity of the crosslinked hydroxide ion exchange membrane in this example at 80 °C is 129 mS / cm, and the swelling rate is 15.0%. Immerse the crosslinked hydroxide ion exchange membrane in this example in 1 M NaOH solution at 80 °C for 1000 h, and the ion conductivity only decreases by 5.3%. Assemble the crosslinked hydroxide ion exchange membrane in this example into an alkaline membrane electrolyzer, and the current density at 80 °C and 1.8 V reaches 2.6 A / cm 2 。

[0047] According to the disclosure of the above specification, those skilled in the art to which the present invention pertains can also make appropriate changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims

1. A crosslinked anionic exchange membrane, characterized in that: The chemical structural formula of the anion exchange membrane is as follows: Wherein, x and y are natural numbers.

2. A method for preparing a crosslinked anionic exchange membrane as described in claim 1, characterized in that: It includes the following steps: S1. Dissolve p-terphenyl and 7-bromo-1,1,1-trifluoro-2-heptanone in a first organic solvent in a certain ratio, then add a certain amount of trifluoromethanesulfonic acid for acid-catalyzed polymerization reaction. Pour the reaction product into a precipitant for precipitation, filter, wash, and dry to obtain a first polymer; S2. Perform a quaternization reaction on the first polymer and (N’,N’-dimethylamino)-6-(N,N,N-trimethylammonium) hexane iodide in a certain ratio under the action of a second organic solvent, then cool to room temperature, and add an appropriate amount of 1,6-hexanediamine to obtain a second polymer solution; S3. Coat the second polymer solution on a substrate, perform drying to form a film and heat treatment, and then perform hydroxide anion exchange to obtain a crosslinked hydroxide ion exchange membrane.

3. The preparation method according to claim 2, characterized in that: In the step S1: The molar ratio of p-terphenyl to 7-bromo-1,1,1-trifluoro-2-heptanone is 1:(1.0 - 1.2); The mass ratio of p-terphenyl to the first organic solvent is 1:(15 - 20); The mass ratio of p-terphenyl to trifluoromethanesulfonic acid is 1:(4 - 7).

4. The preparation method according to claim 2, characterized in that: In the step S1, the reaction temperature of the acid-catalyzed polymerization reaction is 0 - 50 °C, and the reaction time is 1 - 36 h.

5. The preparation method according to claim 2, characterized in that: The precipitant in the step S1 is one of water, ethanol, methanol, acetone, and ethyl acetate.

6. The preparation method according to claim 2, wherein: In the step S2: The mass ratio of the first polymer to (N’,N’-dimethylamino)-6-(N,N,N-trimethylammonium) hexane iodide is (4 - 6):(1 - 2); The mass ratio of the first polymer to the second solvent is 1:(15 - 25); The mass ratio of the first polymer to 1,6-hexanediamine is 1:(0.02 - 0.05).

7. The preparation method according to claim 2, characterized in that: In the step S2, the reaction temperature of the quaternization reaction is 20 - 80 °C, and the reaction time is 1 - 72 h.

8. The preparation method according to claim 2, characterized in that: In the step S3, the drying temperature for drying to form a film is 40 - 100 °C, and the drying time is 4 - 48 hours; the temperature of the heat treatment is 20 - 140 °C, and the heat treatment time is 1 - 24 hours.

9. The preparation method according to claim 2, characterized in that: The specific process of the hydroxide anion exchange in the step S3 is as follows: Immerse the heat-treated membrane in a 1M sodium hydroxide solution at room temperature for 48 hours for ion exchange to convert the anions into hydroxide ions, and obtain a crosslinked anion exchange membrane with hydroxide ions as the anions.

10. The preparation method according to claim 2, characterized in that: The first organic solvent is selected from at least one of dichloromethane, dichloroethane, tetrahydrofuran, chloroform, tetrachloroethane, and toluene; the second organic solvent is at least one of dimethyl sulfoxide, tetrahydrofuran, and N-methylpyrrolidone.

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