Reinforced composite diaphragm as well as preparation and application thereof

Abstract

The invention relates to the technical field of hydrogen production by electrolyzing water, and discloses an enhanced composite diaphragm as well as preparation and application thereof. The composite diaphragm comprises a polymer silk screen and an anion exchange resin coating layer arranged on the polymer silk screen; wherein the anion exchange resin has a structural formula as shown in a formula (1), and in the formula (1), R1 is biaryl; r < 2 > is at least one of-CH3,-CH2CH3,-CF3 and-CH2CF3; r3 is alkyl with 1 to 6 carbon atoms; x is halogen. The enhanced composite diaphragm has relatively high thermokali stability.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen production by electrolysis of water, and in particular to an enhanced composite diaphragm and preparation and application thereof. Background Art

[0002] Hydrogen, with its clean, low-carbon energy, high calorific value, diverse sources, and flexible storage and transportation, is expected to become the "ultimate energy source" of the 21st century and a crucial component of the future national energy system. Hydrogen can be categorized as gray hydrogen, blue hydrogen, and green hydrogen based on its production source and carbon emissions. Gray hydrogen refers to hydrogen produced through the combustion of fossil fuels. Blue hydrogen is produced by adding carbon capture, utilization, and storage (CCUS) technology to the hydrogen production process. Green hydrogen is produced using renewable energy sources such as wind power, hydropower, solar power, and nuclear power, and the production process is completely carbon-free. Water electrolysis is a relatively simple and convenient method for producing green hydrogen. The main processes for producing hydrogen through water electrolysis include alkaline electrolysis, fuel cell electrolysis (PEM electrolysis), anion exchange membrane electrolysis (AEM electrolysis), and solid oxide electrolysis (SOEC electrolysis). Alkaline electrolysis technology is the most mature. An isolation membrane is installed within the alkaline water electrolysis cell to prevent the diffusion of hydrogen and oxygen while allowing the permeation of hydroxide ions and water. With the advancement of alkaline electrolyzer water electrolysis technology, diaphragm materials have evolved through three generations: early asbestos diaphragms, the polyphenylene sulfide diaphragms currently in large-scale use, and the gradual emergence of composite diaphragm materials with excellent gas barrier properties, stability, and low energy consumption. The first-generation asbestos diaphragms suffered from poor high-temperature alkali corrosion resistance, poor gas barrier properties, and explosion risks. Asbestos is also toxic, leading to their gradual replacement by other materials. The second-generation polyphenylene sulfide diaphragms were thicker and resulted in low current density, resulting in high energy consumption and low efficiency. They also had a large pore structure, poor gas barrier properties, especially under fluctuating conditions, and inherent safety concerns. The third-generation composite diaphragms are based on polyphenylene sulfide mesh, coated with a mixture of polymer and zirconium oxide. However, the polymers used are mostly polysulfone and polyetheretherketone. These materials contain ether bonds, which, combined with the quaternary carbon atoms, generate a positive dipole moment, making these sites susceptible to nucleophilic attack by hydroxide ions, leading to hydrolytic chain scission and poor thermal and alkaline stability.

[0003] Therefore, there is an urgent need to develop a new type of diaphragm. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problems existing in the prior art and provide a reinforced composite diaphragm and its preparation and application. The reinforced composite diaphragm has high thermal and alkaline stability.

[0005] In order to achieve the above object, the present invention provides a composite membrane in a first aspect, comprising a polymer mesh and an anion exchange resin coating layer disposed on the polymer mesh;

[0006] Wherein, the anion exchange resin has the structural formula shown in formula (1):

[0007] Wherein, R1 is a biaryl group; R2 is at least one of -CH3, -CH2CH3, -CF3 and -CH2CF3; R3 is a C1-C6 alkyl group; and X is a halogen.

[0008] A second aspect of the present invention provides a method for preparing a composite diaphragm, the method comprising the following steps:

[0009] (1) mixing an anion exchange resin, a solvent, and a pore-forming agent to obtain a mixed solution;

[0010] (2) coating the mixed solution on a polymer mesh to form a film;

[0011] (3) contacting the membrane obtained in step (2) with an alkaline solution and then drying;

[0012] Wherein, the anion exchange resin has the structural formula shown in formula (1):

[0013] Wherein, R1 is a biaryl group; R2 is at least one of -CH3, -CH2CH3, -CF3 and -CH2CF3; R3 is a C1-C6 alkyl group; and X is a halogen.

[0014] A third aspect of the present invention provides an application of the composite membrane described in the first aspect or the composite membrane produced by the method described in the second aspect in hydrogen production by electrolysis of water.

[0015] Through the above technical solution, the beneficial effects of the present invention include:

[0016] The reinforced composite membrane provided by the present invention uses a polymer mesh as a substrate and a specific type of anion exchange resin as a coating. It exhibits high thermal and alkaline stability and a long service life. Preferably, the composite membrane has a suitable pore size distribution, further enabling a combination of physical electrolyte transport and ion transmission, achieving high electrolyte permeability and low gas permeability, thus ensuring intrinsic safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the nuclear magnetic resonance spectrum of the anion exchange resin prepared in Preparation Example 1 of the present invention. DETAILED DESCRIPTION

[0018] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0019] A first aspect of the present invention provides a composite membrane comprising a polymer mesh and an anion exchange resin coating layer disposed on the polymer mesh;

[0020] Wherein, the anion exchange resin has the structural formula shown in formula (1):

[0021] Wherein, R1 is a biaryl group; R2 is at least one of -CH3, -CH2CH3, -CF3 and -CH2CF3; R3 is a C1-C6 alkyl group; and X is a halogen.

[0022] In the present invention, the presence of the anion exchange resin can be obtained from the preparation method of the composite diaphragm, or can be detected by performing nuclear magnetic resonance on the coating layer.

[0023] According to the present invention, preferably, the weight average molecular weight of the anion exchange resin is 20,000-80,000, for example, it can be 20,000, 25,000, 30,000, 35,000, 40,000, 50,000, 55,000, 60,000, 65,000, 70,000, 75,000, 80,000 and a range value consisting of any two of these values, preferably 30,000-70,000.

[0024] According to the present invention, preferably, the molecular weight distribution index D of the anion exchange resin is 1.5-3.5, for example, it can be 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, and a range consisting of any two of these values, preferably 1.5-2.5. This preferred embodiment is more conducive to improving the thermal and alkaline stability of the resulting composite membrane.

[0025] The present invention has a wide range of selections for the type of R1, which can be various biaryl groups commonly used in the art. Preferably, R1 is selected from at least one of biphenyl, p-terphenyl, m-terphenyl, and p-quaterphenyl.

[0026] In the present invention, R2 is at least one of -CH3, -CH2CH3, -CF3 and -CH2CF3, preferably -CH3 and / or -CF3. Controlling R2 to have a smaller molecular weight is more conducive to improving the thermal and alkaline stability of the composite diaphragm material.

[0027] The present invention has a wide range of selections for the type of R3, which can be conventionally selected in the art. Preferably, R3 is selected from at least one of methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl.

[0028] According to the present invention, preferably, X is I and / or Br.

[0029] The bubble point pressure of existing composite membranes is generally no higher than 2 bar. While they offer a certain degree of permeability to ensure mass transfer, their gas barrier properties are relatively poor. The composite membrane of the present invention has a higher bubble point pressure, significantly improving its gas barrier properties while ensuring that mass transfer is not affected. Preferably, the bubble point pressure of the composite membrane is no less than 3.5 bar, and more preferably 5-10 bar.

[0030] The bubble point pressure of the composite diaphragm of the present invention is measured using a through-hole pore size analyzer.

[0031] According to the present invention, preferably, the average pore size of the composite membrane is 0.02-0.1 μm, preferably 0.05-0.07 μm.

[0032] According to the present invention, preferably, in the composite membrane, pores with a pore size of 0.05-0.07 μm account for 70-90% of the total pore volume, preferably 85-90%.

[0033] Controlling the pore distribution of the composite diaphragm within the above range is more conducive to improving the gas barrier properties of the composite diaphragm.

[0034] The pore distribution of the composite diaphragm of the present invention is measured using a through-hole pore size analyzer.

[0035] According to the present invention, preferably, the thickness of the composite separator is not greater than 220 μm, preferably 120 μm-220 μm.

[0036] The thickness of the composite diaphragm of the present invention is measured using a thickness gauge.

[0037] According to the present invention, preferably, the thickness of the polymer mesh is 100 μm-200 μm.

[0038] It should be noted that the thickness of the polymer mesh raw material used in the present invention is in the range of 100 μm-200 μm, and the thickness does not change after the composite diaphragm is prepared.

[0039] The present invention allows for a wide range of polymer mesh types, including polyphenylene sulfide mesh and polytetrafluoroethylene mesh. Preferably, the polymer mesh is polyphenylene sulfide mesh. This preferred embodiment, in combination with an anion exchange resin, further enhances thermal and alkaline stability and mechanical strength.

[0040] The present invention has no particular limitation on the source of the anion exchange resin, as long as the anion exchange resin of the above composition can be obtained. To further illustrate the preparation of the anion exchange resin, the present invention also provides a method for preparing the anion exchange resin.

[0041] Preferably, the preparation method of the anion exchange resin comprises the following steps:

[0042] S1. In the presence of a first solvent, polymerizing a piperidone, a biaryl compound, and a catalyst to obtain a polymer, and then first drying the polymer;

[0043] S2. In the presence of a second solvent, quaternizing the polymer obtained by the first drying in step (1) with an alkylating agent to obtain a quaternized polymer, and then performing a second drying on the quaternized polymer;

[0044] Wherein, the structural formula of the piperidone is Wherein, R2 is at least one of -CH3, -CH2CH3, -CF3 and -CH2CF3.

[0045] The present invention has a wide range of selections for the biaryl compound, which can be any biaryl compound commonly found in the art. Preferably, the biaryl compound is selected from at least one of biphenyl, p-terphenyl, m-terphenyl, and p-quaterphenyl.

[0046] According to the present invention, preferably, the conditions of the polymerization reaction in step S1 include: a temperature of -10 to 10°C, preferably -6 to 0°C, more preferably excluding 0, specifically, for example, -10°C, -9°C, -8°C, -7°C, -6°C, -5°C, -4°C, -3°C, -2°C, -1°C, 0, 1°C, 2°C, 3°C, 4°C, 5°C, 6°C, 7°C, 8°C, 9°C, 10°C, and any value in the range formed by any two of these point values; a time of 8-35h, preferably 8-24h, specifically, for example, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, 26h, 28h, 30h, 32h, 34h, 35h, and any value in the range formed by any two of these point values. Adopting this preferred embodiment is conducive to preparing a sample with a higher molecular weight.

[0047] Preferably, the polymerization reaction is carried out under an inert atmosphere. By adopting this preferred embodiment, the influence of moisture in the air on the polymerization reaction can be isolated.

[0048] The present invention has no particular limitation on the inert atmosphere, and can be selected from conventional gas in the art, for example, at least one of nitrogen, helium, neon, and argon. Nitrogen is preferably used in the present invention due to its low cost and availability.

[0049] According to the present invention, preferably, the molar ratio of piperidone to biaryl compound is 1:0.8-1.2. This preferred embodiment is more conducive to improving the thermal alkaline stability of the anion exchange membrane obtained by using the anion resin prepared by the present invention.

[0050] The present invention has a wide range of first solvents, which can be conventionally selected in the art, for example, dichloromethane, chloroform, tetrachloroethane, toluene, etc. In order to avoid the introduction of moisture into the polymerization system, the preparation example of the present invention preferably uses ultra-dry dichloromethane as the first solvent. All of the above substances can be obtained commercially.

[0051] The present invention has no particular limitation on the amount of the first solvent, as long as the polymerization reaction proceeds smoothly. Preferably, the mass content of piperidone and biaryl compound is 10-40% based on the total mass of the first solvent, piperidone and biaryl compound.

[0052] According to the present invention, preferably, the volume ratio of the catalyst to the first solvent is 5-18:5-10.

[0053] The present invention has a wide range of catalyst types, which can be conventionally selected in the art, for example, trifluoroacetic acid, methanesulfonic acid, trifluoromethanesulfonic acid, pentafluoropropionic acid and heptafluorobutyric acid, etc. Preferably, the catalyst is trifluoroacetic acid and trifluoromethanesulfonic acid.

[0054] More preferably, the volume ratio of trifluoroacetic acid, trifluoromethanesulfonic acid and the first solvent is 1-3:6-12:5-10.

[0055] According to a preferred embodiment of the present invention, trifluoroacetic acid and trifluoromethanesulfonic acid are introduced into the polymerization system in a dropwise manner.

[0056] According to a specific embodiment of the present invention, trifluoroacetic acid and trifluoromethanesulfonic acid are sequentially introduced into the polymerization system in a dropwise manner.

[0057] The present invention has no particular limitation on the order of adding the first solvent, piperidone, biaryl compound and catalyst in step S1, and they can be added together or separately. In the preparation example of the present invention, the piperidone and biaryl compound are preferably dissolved in the first solvent first, and then the catalyst is added.

[0058] According to a specific embodiment of the present invention, piperidone and biaryl compound are first dissolved in a first solvent, cooled to the polymerization temperature, and then the catalyst is added.

[0059] According to the present invention, preferably, the method for preparing the anion exchange resin further comprises: washing the polymerization product with alcohol and washing with alkali in sequence to obtain a polymer.

[0060] The specific methods of the alcohol washing and alkali washing of the present invention are not particularly limited and can be carried out according to conventional methods in the art.

[0061] The alcohol wash of the present invention is used to remove residual small molecule impurities. The present invention has a wide range of alcohol types to choose from, and can be selected from conventional sources in the art. The preparation examples of the present invention use anhydrous ethanol as an example.

[0062] According to a specific embodiment of the present invention, the alcohol washing process includes: washing the obtained polymerization product with alcohol to obtain a filter cake; and washing the filter cake with water until the pH value of the washing filtrate reaches 7.

[0063] The alkali washing of the present invention is used to remove the acidic catalyst. The present invention has a wide range of alkali types to choose from, which can be conventionally selected in the art. The preparation examples of the present invention use potassium carbonate as an example.

[0064] Preferably, the alkali used in the alkali washing is provided in the form of an alkali solution, and the concentration of the alkali solution is 0.5-5 mol / L.

[0065] According to a specific embodiment of the present invention, the alkali washing process comprises: washing the filter cake after alcohol washing with an alkali solution to obtain a filter cake; and washing the filter cake with water until the pH value of the washing filtrate reaches 7.

[0066] The present invention has no particular limitation on the first drying process, and the process can be carried out according to conventional methods in the art. In the preparation example of the present invention, vacuum drying is preferably used.

[0067] The present invention has no particular limitation on the conditions of the quaternization reaction, and the reaction can be carried out according to conventional methods in the art. Preferably, the conditions of the quaternization reaction in step S2 include: a temperature of 20-40° C. and a reaction time of 12-24 hours.

[0068] According to the present invention, preferably, the quaternization reaction in step S2 is carried out in the dark. This preferred embodiment can avoid the decomposition loss of the quaternization agent.

[0069] According to the present invention, preferably, in step S1, the mass ratio of the first dried polymer to the alkylating agent is 1:1-3.

[0070] The present invention allows for a wide range of types of alkylating agents, and can be any of various alkylating agents commonly used in quaternization reactions in the art. Preferably, the alkylating agent is at least one selected from methyl iodide, ethyl iodide, propyl iodide, butyl iodide, pentyl iodide, hexyl iodide, ethyl bromide, propyl bromide, butyl bromide, pentyl bromide, hexyl bromide, cyclopropane bromide, cyclobutane bromide, cyclopentane bromide, and cyclohexane bromide.

[0071] The present invention has a wide range of types for the second solvent, which can be conventionally selected in the art, such as dimethyl sulfoxide, 1-methyl-2-pyrrolidone, dimethylformamide, and dimethylacetamide. The preparation examples of the present invention use dimethyl sulfoxide as an example.

[0072] The present invention has no particular limitation on the amount of the second solvent, as long as the quaternization reaction proceeds smoothly. Preferably, in step S1, the amount of the first dried polymer is 5-10 wt% of the amount of the second solvent.

[0073] The present invention does not specifically limit the order of adding the second solvent in step S2, the first dried polymer in step S1, and the alkylating agent; they may be added together or separately. In the preparation example of the present invention, the first dried polymer in step S1 is preferably dissolved in the second solvent first, followed by the addition of the alkylating agent. Stirring or ultrasonication may be used during the addition of these materials to accelerate mixing.

[0074] According to the present invention, preferably, the method for preparing the anion exchange resin further comprises: washing the quaternization reaction product with an organic solvent to obtain a quaternized polymer.

[0075] Preferably, the organic solvent is ethyl acetate and / or diethyl ether. The above substances are conventionally selected in the art and can be obtained commercially.

[0076] The specific method of washing with an organic solvent according to the present invention is not particularly limited and can be carried out according to conventional methods in the art.

[0077] According to a specific embodiment of the present invention, the organic solvent washing process comprises: adding the quaternization reaction product dropwise to an organic solvent, filtering to obtain a filter cake, and then washing the filter cake with the organic solvent until the filtrate is colorless.

[0078] The present invention has no particular limitation on the second drying step, and the drying step can be carried out according to conventional methods in the art. The preparation example of the present invention preferably adopts vacuum drying.

[0079] A second aspect of the present invention provides a method for preparing a composite diaphragm, the method comprising the following steps:

[0080] (1) mixing an anion exchange resin, a solvent, and a pore-forming agent to obtain a mixed solution;

[0081] (2) coating the mixed solution on a polymer mesh to form a film;

[0082] (3) contacting the membrane obtained in step (2) with an alkaline solution and then drying;

[0083] Wherein, the anion exchange resin has the structural formula shown in formula (1):

[0084] Wherein, R1 is a biaryl group; R2 is at least one of -CH3, -CH2CH3, -CF3 and -CH2CF3; R3 is a C1-C6 alkyl group; and X is a halogen.

[0085] According to the present invention, preferably, the weight average molecular weight of the anion exchange resin is 20,000-80,000, preferably 30,000-70,000.

[0086] According to the present invention, preferably, the molecular weight distribution index D of the anion exchange resin is 1.5-3.5, preferably 1.5-2.5.

[0087] The present invention has a wide range of selections for the type of R1, which can be various biaryl groups commonly used in the art. Preferably, R1 is selected from at least one of biphenyl, p-terphenyl, m-terphenyl, and p-quaterphenyl.

[0088] In the present invention, R2 is at least one of -CH3, -CH2CH3, -CF3 and -CH2CF3, preferably -CH3 and / or -CF3. Controlling R2 to have a smaller molecular weight is more conducive to improving the thermal and alkaline stability of the composite diaphragm material.

[0089] The present invention has a wide range of selections for the type of R3, which can be conventionally selected in the art. Preferably, R3 is selected from at least one of methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl.

[0090] According to the present invention, preferably, X is I and / or Br.

[0091] According to the present invention, preferably, in the mixed solution obtained in step (1), the mass content of the anion exchange resin is 5%-20%, preferably 10%-15%, based on the total weight of the mixed solution; the mass content of the pore-forming agent is 5%-20%, preferably 5%-10%; and the mass content of the solvent is 60%-90%, preferably 80%-90%. This preferred embodiment is advantageous for obtaining the composite diaphragm described in the first aspect.

[0092] According to the present invention, preferably, the mixing temperature in step (1) is 20°C-40°C.

[0093] It should be noted that, at the above temperature, the pore-forming agent in step (1) does not play a pore-forming role.

[0094] According to the present invention, preferably, the weight average molecular weight of the pore-forming agent is 1000-6000, preferably 2000-4000. This preferred embodiment is more conducive to obtaining the composite diaphragm with the pore distribution described in the first aspect.

[0095] The present invention has a wide range of choices for the type of pore-forming agent, and can be any pore-forming agent commonly used in the art, as long as its molecular weight meets the above range. In the present invention, polyethylene glycol is preferably used as the pore-forming agent.

[0096] According to the present invention, preferably, the thickness of the polymer mesh is 100 μm-200 μm.

[0097] According to the present invention, preferably, the mesh size of the polymer mesh is 60-200 mesh.

[0098] The present invention adopts the polymer mesh with the above characteristics to improve the mechanical strength of the diaphragm and has a suitable coverage range of the anion exchange resin.

[0099] The present invention has a wide range of choices for the type of polymer mesh, as long as the characteristic parameters meet the above conditions. Preferably, the polymer mesh is a polyphenylene sulfide mesh.

[0100] The present invention has a wide range of solvents to choose from, and can be various solvents commonly used in the art. The present invention uses dimethyl sulfoxide as an example. Other types of solvents commonly used in the art are also within the scope of protection of the present invention.

[0101] The present invention does not particularly limit the order in which the anion exchange resin, solvent, and pore-forming agent are added during the mixing process described in step (1). They may be added together or separately. To ensure uniform mixing, the present embodiment preferably employs a method of adding the anion exchange resin and pore-forming agent to the solvent. Stirring or ultrasound may be used to accelerate mixing during the mixing process described in step (1).

[0102] According to a specific embodiment of the present invention, anion exchange resin and pore-forming agent are added to a solvent and stirred until completely dissolved, and then ultrasonic defoaming is performed to obtain a mixed solution.

[0103] The present invention has no particular limitation on the film forming process in step (2), and the film forming process can be carried out according to conventional methods in the art.

[0104] According to a preferred embodiment of the present invention, the film forming process in step (2) comprises the following steps:

[0105] a. At room temperature, place the polymer mesh in the mold and fix it around the edges to keep the mesh flat and attached to the bottom of the mold;

[0106] b. Pour the mixed solution of step (1) into the mold, and repeatedly stir the solution with a scraper to make the mixed solution contact with the polymer mesh without leaving any bubbles or pores;

[0107] c. Place the mold after treatment in step b in an oven, adjust the mold level, fix the mold to keep it horizontal, adjust the oven temperature to the set temperature of 85-125°C, and evaporate the solvent to form a film.

[0108] Step (3) of the present invention primarily involves pore formation. After pore formation, the pore-forming agent remains in the alkaline solution; it also serves to exchange negative ions from the anion exchange resin. Preferably, the contact conditions in step (3) include a temperature of 80°C to 120°C and a duration of 12 to 36 hours. This preferred embodiment further facilitates pore formation, thereby obtaining the composite membrane with the pore distribution described in the first aspect.

[0109] According to the present invention, preferably, the concentration of the alkaline solution is 1M-5M.

[0110] The present invention has a wide range of choices for the type of alkaline solution, which can be various alkaline solutions commonly used in the art. Preferably, the alkaline solution is an aqueous potassium hydroxide solution.

[0111] The present invention has no particular limitation on the specific drying method, and various drying methods commonly used in the art can be used. The embodiment of the present invention uses air drying as an example.

[0112] Preferably, the method further comprises: washing the material after contact in step (3) before drying.

[0113] The present invention has no particular limitation on the specific conditions of the washing, and the washing can be carried out according to conventional methods in the art, and the washing can be carried out until the washing liquid becomes neutral.

[0114] A third aspect of the present invention provides an application of the composite membrane described in the first aspect or the composite membrane produced by the method described in the second aspect in hydrogen production by electrolysis of water.

[0115] The present invention will be described in detail below through examples.

[0116] In the following examples,

[0117] Test method for thermal alkali stability: The composite diaphragms prepared in the examples and comparative examples were cut into 5 cm × 5 cm sizes, immersed in 1 M KOH solution at 80°C for 24 hours, placed in a fixture to measure their conductivity, and the thermal alkali stability of the membrane was evaluated by the change in conductivity (conductivity retention rate) between the membrane and subsequent different time periods (1000 hours, 2000 hours, and 4000 hours).

[0118] The preparation example of the present invention is used to illustrate the preparation of anion exchange resin

[0119] Preparation Example 1

[0120] (1) Polymerization reaction

[0121] Piperidineacetophenone and biphenyl were dissolved in ultra-dry dichloromethane at a molar ratio of 1:1, with the combined concentration of piperidineacetophenone and biphenyl reaching 20 wt%. The mixture was cooled to -5°C under nitrogen atmosphere, and trifluoroacetic acid and trifluoromethanesulfonic acid (in a volume ratio of 1:12:10 to ultra-dry dichloromethane) were added dropwise. The mixture was then allowed to react at -5°C for 24 h.

[0122] (2) Precipitation and washing

[0123] After the polymerization reaction is completed, the obtained polymerization product is poured into an anhydrous ethanol solution with a volume ratio of anhydrous ethanol to polymerization product of 5:1, filtered to obtain a filter cake, and washed with deionized water until the pH value of the washing filtrate is 7.

[0124] (3) Neutralization washing

[0125] The filter cake after washing in step (2) was dispersed in 1M potassium carbonate solution, placed at 60°C for 24 hours, and filtered to obtain a filter cake. The filter cake was washed with deionized water until the pH value of the washing filtrate was 7 to obtain a polymer.

[0126] (4) Vacuum drying

[0127] The obtained polymer was dried at 60 °C under vacuum for 24 h.

[0128] (5) Quaternization reaction

[0129] The dried polymer was dispersed in dimethyl sulfoxide solvent at room temperature, with the mass fraction of the dried polymer in the dimethyl sulfoxide solvent being 5 wt %. Iodomethane twice the mass of the polymer was added while stirring, and the mixture was reacted at room temperature in the dark for 24 h.

[0130] (6) Precipitation and washing

[0131] After the quaternization reaction is completed, the quaternization reaction product is added dropwise to ethyl acetate in a volume ratio of ethyl acetate to quaternization reaction product of 6:1, filtered to obtain a filter cake, and washed with ethyl acetate six times.

[0132] (7) Vacuum drying

[0133] The quaternized polymer was dried at 60° C. under vacuum for 24 h to obtain an anion exchange resin having a weight average molecular weight of 48,000 and a molecular weight distribution index D of 1.9.

[0134] Its structural formula is shown below:

[0135] The nuclear magnetic resonance spectrum of the anion exchange resin prepared in Preparation Example 1 is shown as follows: Figure 1 As shown. Figure 1 It can be seen that the nuclear magnetic resonance hydrogen spectrum is Figure 1 As shown, the peak at 7.18ppm-7.75ppm is the signal peak of hydrogen on the skeleton benzene ring; the signal peak at 3.83ppm is attributed to the connection N + The signal peak of hydrogen on the benzene ring; the peak at 3.38ppm is the signal peak of water; the signal peak at 3.15ppm is attributed to the connection of N + The peak at 2.54 ppm is the signal of the hydrogen on the piperidine ring; the peak at 2.50 ppm is the signal peak of the solvent DMSO. According to the attribution of the peaks, it can be seen that the target product was successfully prepared.

[0136] Preparation Example 2

[0137] (1) Polymerization reaction

[0138] Piperidineacetophenone and biphenyl were dissolved in ultra-dry dichloromethane at a molar ratio of 1:0.8, with the combined mass concentration of piperidineacetophenone and biphenyl reaching 10 wt%. The mixture was cooled to -5°C under nitrogen atmosphere, and trifluoroacetic acid and trifluoromethanesulfonic acid (the volume ratio of trifluoroacetic acid, trifluoromethanesulfonic acid, and ultra-dry dichloromethane in the solution was 1:6:5) were added dropwise. The mixture was then reacted at -5°C for 8 h.

[0139] (2) Precipitation and washing

[0140] After the polymerization reaction is completed, the obtained polymerization product is poured into an anhydrous ethanol solution with a volume ratio of anhydrous ethanol to polymer solution of 1:1, filtered to obtain a filter cake, and washed with deionized water until the pH value of the washing filtrate is 7.

[0141] (3) Neutralization washing

[0142] The filter cake after washing in step (2) was dispersed in 1M potassium carbonate solution, placed at 60°C for 6 hours, and filtered to obtain a filter cake. The filter cake was washed with deionized water until the pH value of the washing filtrate was 7 to obtain a polymer.

[0143] (4) Vacuum drying

[0144] The obtained polymer was dried at 60 °C under vacuum for 6 h.

[0145] (5) Quaternization reaction

[0146] The dried polymer was dispersed in dimethyl sulfoxide solvent at room temperature, with the mass fraction of the dried polymer in the dimethyl sulfoxide solvent being 5 wt %. Iodomethane (1.5 times the mass of the polymer) was added while stirring, and the mixture was reacted at room temperature in the dark for 12 h.

[0147] (6) Precipitation and washing

[0148] After the quaternization reaction is completed, the quaternization reaction product is added dropwise to ethyl acetate, with the volume ratio of ethyl acetate to polymer solution being 3:1, and filtered to obtain a filter cake, which is washed with ethyl acetate three times.

[0149] (7) Vacuum drying

[0150] The quaternized polymer was dried at 60° C. under vacuum for 6 h to obtain an anion exchange resin having a weight average molecular weight of 45,000 and a molecular weight distribution index D of 1.6.

[0151] Preparation Example 3

[0152] (1) Polymerization reaction

[0153] Piperidineacetophenone and biphenyl were dissolved in ultra-dry dichloromethane at a molar ratio of 1:1.2, with the combined mass concentration of piperidineacetophenone and biphenyl reaching 40 wt%. The mixture was cooled to -2°C under nitrogen atmosphere, and trifluoroacetic acid and trifluoromethanesulfonic acid (the volume ratio of trifluoroacetic acid, trifluoromethanesulfonic acid, and ultra-dry dichloromethane in the solution being 3:12:10) were added dropwise. The mixture was then allowed to react at this temperature for 24 hours.

[0154] (2) Precipitation and washing

[0155] After the polymerization reaction is completed, the obtained polymerization product is poured into an anhydrous ethanol solution with a volume ratio of anhydrous ethanol to polymer solution of 5:1, filtered to obtain a filter cake, and washed with deionized water until the pH value of the washing filtrate is 7.

[0156] (3) Neutralization washing

[0157] The filter cake after washing in step (2) was dispersed in 1M potassium carbonate solution, placed at 80°C for 24 hours, and filtered to obtain a filter cake. The filter cake was washed with deionized water until the pH value of the washing filtrate was 7 to obtain a polymer.

[0158] (4) Vacuum drying

[0159] The obtained polymer was dried at 60 °C under vacuum for 24 h.

[0160] (5) Quaternization reaction

[0161] The dried polymer was dispersed in dimethyl sulfoxide solvent at room temperature, with the mass fraction of the dried polymer in the dimethyl sulfoxide solvent being 10 wt %. Iodomethane 3 times the mass of the polymer was added while stirring, and the mixture was reacted for 24 h at room temperature in the dark.

[0162] (6) Precipitation and washing

[0163] After the quaternization reaction is completed, the quaternization reaction product is added dropwise to ethyl acetate, with the volume ratio of ethyl acetate to polymer solution being 6:1, and filtered to obtain a filter cake, which is washed with ethyl acetate six times.

[0164] (7) Vacuum drying

[0165] The quaternized polymer was dried at 60° C. under vacuum for 24 h to obtain an anion exchange resin.

[0166] The weight average molecular weight of the obtained anion exchange resin was 43,000, and the molecular weight distribution index D was 2.3.

[0167] Comparative Preparation Example 1

[0168] The method of Preparation Example 1 was followed, except that an equimolar amount of N-methyl-4-piperidone was used instead of piperidine acetophenone.

[0169] The weight average molecular weight of the obtained anion exchange resin was 41,000, and the molecular weight distribution index D=2.

[0170] Comparative Preparation Example 2

[0171] The method of Preparation Example 1 was followed, except that an equal molar amount of 1-phenylethyl-4-piperidone was used instead of piperidine acetophenone.

[0172] The weight average molecular weight of the obtained anion exchange resin was 42,000, and the molecular weight distribution index D=2.

[0173] The examples of the present invention are used to illustrate the preparation of composite membranes.

[0174] Example 1

[0175] (1) The anion exchange resin prepared in Preparation Example 1 and polyethylene glycol (weight-average molecular weight: 2000) were added to a container containing 80% by weight of dimethyl sulfoxide at room temperature in a ratio of 15% and 5% by weight of the mixed solution, respectively. The mixture was stirred until completely dissolved, and then ultrasonically defoamed to obtain a mixed solution.

[0176] (2) At room temperature, polyphenylene sulfide mesh (thickness 100 μm, mesh size 200) is spread in the mold and fixed around to keep the mesh flat and attached to the bottom of the mold.

[0177] (3) Pour the mixed solution of step (1) into the mold of step (2), and repeatedly stir the solution with a scraper to ensure that the solution is in full contact with the screen without leaving any bubbles or pores.

[0178] (4) Place the mold treated in step (3) in an oven, adjust the mold level, fix the mold to keep it in a horizontal state, adjust the oven temperature to a set temperature of 110°C, and volatilize the solvent to form a film.

[0179] (5) The prepared membrane was immersed in a 1 M potassium hydroxide solution at 80°C for 36 h, then rinsed in deionized water until neutral and air-dried to obtain a reinforced composite membrane. Its characteristic parameters are shown in Table 1. Its thermal alkaline stability results are shown in Table 2.

[0180] Example 2

[0181] (1) The anion exchange resin prepared in Preparation Example 2 and polyethylene glycol (weight-average molecular weight of 4000) were added to a container containing 80% by weight of dimethyl sulfoxide at room temperature in a ratio of 10% and 10% by weight of the mixed solution, and the mixture was stirred until completely dissolved. The mixture was then ultrasonically defoamed to obtain a mixed solution.

[0182] (2) At room temperature, polyphenylene sulfide mesh (thickness 200 μm, mesh size 60) is spread in the mold and fixed around to keep the mesh flat and attached to the bottom of the mold.

[0183] (3) Pour the mixed solution of step (1) into the mold of step (2), and repeatedly stir the solution with a scraper to ensure that the solution is in full contact with the screen without leaving any bubbles or pores.

[0184] (4) placing the mold treated in step (3) in an oven, adjusting the mold level, fixing the mold so that it remains horizontal, adjusting the oven temperature to a set temperature of 120° C., and volatilizing the solvent to form a film.

[0185] (5) The prepared membrane was immersed in a 3M potassium hydroxide solution at 80°C for 24 h, then rinsed in deionized water until neutral and air-dried to obtain a reinforced composite membrane. Its characteristic parameters are shown in Table 1. Its thermal alkaline stability results are shown in Table 2.

[0186] Example 3

[0187] (1) The anion exchange resin prepared in Preparation Example 3 and polyethylene glycol (weight-average molecular weight: 2000) were added to a container containing 85% by weight of dimethyl sulfoxide at room temperature in a ratio of 10% and 5% by weight of the mixed solution, respectively. The mixture was stirred until completely dissolved, and then ultrasonically defoamed to obtain a mixed solution.

[0188] (2) At room temperature, polyphenylene sulfide mesh (thickness 160 μm, mesh size 120) is spread in the mold and fixed around to keep the mesh flat and attached to the bottom of the mold.

[0189] (3) Pour the mixed solution of step (1) into the mold of step (2), and repeatedly stir the solution with a scraper to ensure that the solution is in full contact with the screen without leaving any bubbles or pores.

[0190] (4) placing the mold treated in step (3) in an oven, adjusting the mold level, fixing the mold so that it remains horizontal, adjusting the oven temperature to a set temperature of 90° C., and volatilizing the solvent to form a film.

[0191] (5) The prepared membrane was immersed in a 5 M potassium hydroxide solution at 120°C for 12 h, then rinsed in deionized water until neutral and air-dried to obtain a reinforced composite membrane. Its characteristic parameters are shown in Table 1. Its thermal alkaline stability results are shown in Table 2.

[0192] Example 4

[0193] The method of Example 2 was followed, except that a polytetrafluoroethylene mesh was used instead of a polyphenylene sulfide mesh.

[0194] The characteristic parameters of the obtained composite membrane are shown in Table 1. The results of its thermal alkali stability are shown in Table 2.

[0195] Example 5

[0196] The method of Example 1 was followed, except that the weight average molecular weight of the polyethylene glycol used was 6000.

[0197] The characteristic parameters of the obtained composite membrane are shown in Table 1. The results of its thermal alkali stability are shown in Table 2.

[0198] Comparative Example 1

[0199] The method of Example 1 was followed, except that the anion exchange resin prepared in Preparation Example 1 was not used, but the anion exchange resin prepared in Comparative Preparation Example 1 was used.

[0200] The characteristic parameters of the obtained composite membrane are shown in Table 1. The results of its thermal alkali stability are shown in Table 2.

[0201] Comparative Example 2

[0202] The method of Example 1 was followed, except that the anion exchange resin prepared in Preparation Example 1 was not used, but the anion exchange resin prepared in Comparative Preparation Example 2 was used.

[0203] The characteristic parameters of the obtained composite membrane are shown in Table 1. The results of its thermal alkali stability are shown in Table 2.

[0204] Table 1

[0205]

[0206] The results in Table 1 indicate that the composite membrane provided by the present invention has a significantly higher bubble point pressure and a suitable pore distribution, which helps improve the gas barrier properties of the composite membrane while ensuring mass transfer. Furthermore, the composite membrane provided by the present invention is thinner, which further helps reduce membrane resistance and increase current density.

[0207] Table 2

[0208]

[0209] Note: The commercially available composite diaphragm is a commercial product of Carbon Energy Technology (Beijing) Co., Ltd. with the brand name TNCM-500.

[0210] The results in Table 2 show that the composite membrane provided by the present invention has significantly higher thermal alkali stability and longer lifespan. Its application in hydrogen production by water electrolysis is more conducive to the long-term stable operation of the system.

[0211] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A composite diaphragm, characterized in that: The composite diaphragm includes a polymer mesh and an anion exchange resin coating layer disposed on the polymer mesh; Wherein, the anion exchange resin has the structural formula shown in formula (1): Wherein, R1 is a biaryl group; R2 is at least one of -CH3, -CH2CH3, -CF3 and -CH2CF3; R3 is a C1-C6 alkyl group; and X is a halogen.

2. The composite diaphragm according to claim 1, wherein The weight average molecular weight of the anion exchange resin is 20,000-80,000, preferably 30,000-70,000; Preferably, the molecular weight distribution index D of the anion exchange resin is 1.5-3.5, preferably 1.5-2.5; Preferably, the R1 is selected from at least one of biphenyl, p-terphenyl, m-terphenyl and p-quaterphenyl; Preferably, X is I and / or Br.

3. The composite diaphragm according to claim 1 or 2, wherein: The bubble point pressure of the composite membrane is not less than 3.5 bar, preferably 5-10 bar; Preferably, the average pore size of the composite membrane is 0.02-0.1 μm, preferably 0.05-0.07 μm; Preferably, in the composite membrane, pores with a pore size of 0.05-0.07 μm account for 70-90% of the total pore volume, preferably 85-90%.

4. The composite diaphragm according to any one of claims 1 to 3, wherein: The thickness of the composite diaphragm is not greater than 220 μm, preferably 120 μm-220 μm; Preferably, the thickness of the polymer mesh is 100 μm-200 μm; Preferably, the polymer mesh is polyphenylene sulfide mesh.

5. A method for preparing a composite diaphragm, comprising the following steps: (1) mixing an anion exchange resin, a solvent, and a pore-forming agent to obtain a mixed solution; (2) coating the mixed solution on a polymer mesh to form a film; (3) contacting the membrane obtained in step (2) with an alkaline solution and then drying; Wherein, the anion exchange resin has the structural formula shown in formula (1): Wherein, R1 is a biaryl group; R2 is at least one of -CH3, -CH2CH3, -CF3 and -CH2CF3; R3 is a C1-C6 alkyl group; and X is a halogen.

6. The method according to claim 5, wherein: The weight average molecular weight of the anion exchange resin is 20,000-80,000, preferably 30,000-70,000; Preferably, the molecular weight distribution index D of the anion exchange resin is 1.5-3.5, preferably 1.5-2.5; Preferably, the R1 is selected from at least one of biphenyl, p-terphenyl, m-terphenyl and p-quaterphenyl; Preferably, X is I and / or Br.

7. The method according to claim 5, wherein: In the mixed solution obtained in step (1), based on the total weight of the mixed solution, the mass content of the anion exchange resin is 5%-20%, preferably 10%-15%; the mass content of the pore-forming agent is 5%-20%, preferably 5%-10%; and the mass content of the solvent is 60%-90%, preferably 80%-90%. Preferably, the mixing temperature in step (1) is 20°C-40°C.

8. The method according to any one of claims 5 to 7, wherein: The weight average molecular weight of the pore-forming agent is 1000-6000, preferably 2000-4000; Preferably, the pore-forming agent is polyethylene glycol; Preferably, the thickness of the polymer mesh is 100 μm-200 μm; Preferably, the mesh size of the polymer mesh is 60-200 mesh; Preferably, the polymer mesh is polyphenylene sulfide mesh.

9. The method according to any one of claims 5 to 8, wherein: The contacting conditions in step (3) include: temperature of 80°C-120°C; time of 12h-36h; Preferably, the concentration of the alkaline solution is 1M-5M; Preferably, the alkaline solution is an aqueous potassium hydroxide solution.

10. Use of the composite membrane according to any one of claims 1 to 4 or the composite membrane produced by the method according to any one of claims 5 to 9 in hydrogen production by water electrolysis.

Images