Preparation method and application of an ultrathin carbon capture membrane
By hydrolyzing the PAN support and combining it with interfacial polymerization and diffusion methods, the growth of ZIF-8 and PA monomers was controlled, solving the problem of ZIF-8 nanoparticle aggregation and realizing the simple preparation of ultrathin carbon capture membranes and efficient CO2/N2 separation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA CONSTRUCTION INDUSTRIAL & ENERGY ENGINEERING GROUP CO LTD
- Filing Date
- 2023-08-31
- Publication Date
- 2026-06-02
AI Technical Summary
In existing technologies, ZIF-8 nanoparticles tend to agglomerate during the preparation of composite membranes, leading to a decrease in membrane permeability. Furthermore, the preparation process is complex and cumbersome, making it difficult to form a uniform separation layer.
By performing alkaline hydrolysis on the PAN support, combined with interfacial polymerization and diffusion methods, the growth of ZIF-8 and PA monomers was controlled, and the solvent and monomer concentrations were optimized to form a complete ultrathin carbon capture membrane.
The preparation process was simplified, the membrane permeability and CO2 adsorption were improved, the integrity and stability of the membrane layer were ensured, and the separation performance of CO2/N2 was enhanced.
Smart Images
Figure CN117205761B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of composite membrane technology, specifically a method for preparing and applying an ultrathin carbon capture membrane. Background Technology
[0002] Composite membranes, due to the relatively independent separation layer and support layer, can be designed and controlled separately, and have been widely used in various membrane separation processes. Generally, thin film materials with small pores and specific functions are selected as the separation layer, while materials with large pore size, high porosity, and high strength are selected as the support layer. This ensures that high selectivity can be achieved while maintaining high permeation flux, and also gives the membrane good mechanical properties.
[0003] In the preparation of composite membranes, a separation layer is typically constructed on a support layer using methods such as interfacial polymerization of polymer solutions or their monomers. To ensure high permeate flux, the support layer is often an ultrafiltration or microfiltration membrane with a pore size of tens or hundreds of nanometers. If the membrane is directly fabricated on a macroporous support layer, the solution easily permeates into the macropores, making it difficult to form a thin and uniform separation layer. To overcome this difficulty, the support layer generally needs to be pretreated, such as pre-filling the macropores with liquid or adding a transition layer to gradually reduce the pore size. These pretreatment processes not only complicate and cumbersome the membrane fabrication process but also lead to increased costs, decreased controllability, and reduced membrane flux. In recent years, researchers have utilized the characteristics of nanomaterials to obtain an intermediate layer with high porosity and small pore size during the composite membrane preparation process. This optimizes the surface structure of the macroporous support layer, avoids pore permeation during polymer solution coating, and thus obtains a thin and uniform polymer separation layer.
[0004] ZIF-8, as an excellent nanomaterial, is one of the preferred choices for preparing intermediate layers. However, during the preparation process, it was found that ZIF-8 materials directly added to the aqueous or oil phase are prone to agglomeration, which greatly limits its ability to improve membrane permeation performance. The agglomeration of ZIF-8 nanoparticles can also easily damage the dense polymer separation layer, affecting the membrane's separation performance. Summary of the Invention
[0005] The main objective of this invention, in view of the aforementioned prior art, is to improve the separation performance of ultrathin carbon capture membranes and simplify the preparation process. The technical problems to be solved include: utilizing interfacial polymerization synergistic relative diffusion to control the self-inhibited growth of ZIF-8 and PA to form a fully coated ultrathin film; screening organic solvents to control monomer diffusion and growth rate to avoid pore blockage during porous material growth and polymer growth region shift; and selecting appropriate methods to treat the support to enhance the interfacial bonding between the support and the membrane layer.
[0006] In this technical solution: First, the PAN support undergoes a simple and mild alkaline hydrolysis treatment. The obvious color change of the PAN support surface from white to pale yellow indicates that the hydrolysis process alters its surface properties. Then, the hydrolyzed support is placed in a reactor, and ZIF-8 monomer and PA monomer are added in stages. By selecting solvents of different viscosities, the pre- and post-coating growth is controlled to ensure membrane integrity. After washing and drying, a composite membrane is obtained. To obtain an ultrathin carbon capture membrane with higher separation performance, the preparation conditions, including solvent and monomer concentration, were optimized.
[0007] The present invention provides an ultrathin carbon capture membrane, comprising, from top to bottom, an interfacially polymerized PA separation layer with CO2 affinity, a diffusion-based ZIF-8 layer, and a hydrolyzed PAN support layer. Its preparation method includes the following steps:
[0008] Step 1: Immerse the polyacrylonitrile (PAN) support in an alkaline solution and hydrolyze it in a water bath. Rinse it with plenty of deionized water for later use to obtain the treated polyacrylonitrile support (h-PAN).
[0009] Step 2: Place the treated polyacrylonitrile support in the middle of the reactor, pour a certain concentration of zinc nitrate solution and 2-methylimidazole solution into the two sides of the reactor respectively, let it stand for diffusion reaction, pour out the remaining solution, add deionized water to the two sides of the reactor respectively for washing and pouring out, to obtain ZIF-8 / h-PAN composite membrane.
[0010] Step 3: Pour a certain concentration of pyromellitic methyl chloride organic phase solution and a certain concentration of N'N-bis(3-aminopropyl)methylamine aqueous phase solution into both sides of the reactor, allow the polymerization reaction to stand, heat-treat the membrane obtained from the polymerization reaction for a period of time, remove the membrane and dry it to obtain an ultrathin PA / ZIF-8 / h-PAN composite membrane, i.e., an ultrathin carbon capture membrane.
[0011] Preferably, in step 1, the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution.
[0012] Preferably, in step 1, the hydrolysis treatment is carried out at a temperature of 50-60°C for 1-3 hours.
[0013] Preferably, in step 2, the zinc nitrate solution is obtained by dissolving zinc nitrate hexahydrate in deionized water, with a molar concentration of 0.035-0.28 mol / L; the 2-methylimidazole solution is obtained by dissolving 2-methylimidazole in an organic solvent, with a molar concentration of 0.56 mol / L, and the molar ratio of zinc nitrate hexahydrate to 2-methylimidazole is 1:16-1:2.
[0014] Preferably, in step 2, the static diffusion reaction time is 0.5-2 hours.
[0015] Preferably, the organic solvent for the 2-methylimidazole is methanol, ethanol, or octanol.
[0016] Preferably, in step 3, the pyromellitic trimethylol chloride is dissolved in an organic solvent, the organic solvent being n-hexane, cyclohexane, n-pentane, or n-heptane, with a molar concentration of 0.0025-0.005 mol / L; the N'N-bis(3-aminopropyl)methylamine is dissolved in water with a molar concentration of 0.0062-0.0309 mol / L.
[0017] Preferably, in step 3, the static polymerization reaction is carried out for 1-2 hours.
[0018] Preferably, in step 3, the membrane obtained by the polymerization reaction is placed in an oven for heat treatment for a period of time, and then placed in an artificial climate chamber at 30°C for drying for 12 hours to obtain an ultrathin carbon capture membrane.
[0019] The present invention also discloses the application of the ultrathin carbon capture membrane in the separation of CO2 / N2 mixed gas.
[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0021] 1. This invention provides a simple method for preparing an ultrathin carbon capture membrane and achieving efficient separation of CO2 / N2 mixtures. First, this invention develops an integrated reactor that eliminates the need for process transfer, ensuring co-situation of diffusion preparation and interfacial polymerization, simplifying the preparation process and avoiding membrane loss during reaction. Second, hydrolysis treatment causes the support surface to carry a charge, improving interlayer compatibility and bonding, ensuring the adhesion and stability of ZIF-8 growth. Third, solvent viscosity is precisely controlled by selecting appropriate solvents to precisely control the growth and positioning of ZIF-8 particles, preventing particle blockage of pores and reducing mass transfer resistance. Finally, the concentration of the two-phase monomers in the interfacial polymerization reaction is controlled to achieve uniform and defect-free coating of the ultrathin separation layer, enhancing the membrane's affinity for CO2.
[0022] 2. This invention uses a one-step interfacial polymerization-diffusion coupling method to grow ZIF-8 nanoparticles relatively uniformly on the support, increasing the free volume, providing additional transport channels, and significantly improving the membrane's permeability and carbon dioxide adsorption capacity; the iso-situ interfacial polymerization coating growth of ZIF-8 nanoparticles can ensure the integrity of the membrane layer.
[0023] 3. This invention achieves the stepwise growth of porous materials and polymers through an integrated reactor, promoting the full-range coating of porous materials by polymer materials, and effectively screening solvents to prevent the growth of porous materials from clogging the pores of the support.
[0024] 4. By optimizing the preparation conditions of each layer of the composite membrane, the present invention produces an ultrathin composite membrane at 25°C with a CO2 permeability of 329 GPU and a CO2 / N2 selectivity of 84.
[0025] 5. The preparation method of this invention is simple and controllable, and the prepared ultrathin PA / ZIF-8 / h-PAN composite membrane has a higher CO2 permeability compared with commercial membrane materials. This invention can be used in flue gas carbon capture processes and has broad application prospects. Attached Figure Description
[0026] Figure 1 The diagram shows the structure of the reactor in this embodiment of the invention, where 1 is a clamping cavity; 2 is a support; 3 is a monomer solution injection port; 4 is a solution outlet; and 5 is a bracket.
[0027] Figure 2 The images show the XRD patterns of the PAN support before and after hydrolysis in Example 1 of this invention.
[0028] Figure 3 These are scanning electron microscope images of the PAN support before and after hydrolysis in Embodiment 1 of the present invention.
[0029] Figure 4 This is a scanning electron microscope image of the surface of the ultrathin PA / ZIF-8 / h-PAN composite film in Example 1 of the present invention. Detailed Implementation
[0030] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific illustrations.
[0031] Example 1
[0032] A method for preparing an ultrathin carbon capture membrane includes the following steps:
[0033] Step 1: Prepare a 2 mol / L sodium hydroxide solution, immerse the polyacrylonitrile support in it, and place it in a water bath for hydrolysis modification at 50℃ for 3 hours. After hydrolysis modification, wash the support surface with deionized water to remove any residual alkali until the support surface is neutral. Compared to unhydrolyzed PAN, the surface of the hydrolyzed PAN (h-PAN) support exhibits a more porous morphology. The surface of the hydrolyzed PAN support carries a negative charge, while the ZIF-8 particles carry a positive charge. The subsequent growth of the ZIF-8 layer and the h-PAN support will generate electrostatic interactions, which can strengthen the interfacial bonding between the film layers.
[0034] Step 2: Place the h-PAN support obtained in Step 1 in the middle of the reactor, such as... Figure 1As shown, the reactor is an integrated reactor with a central cavity 1 for housing the h-PAN support 2. The cavity 1 is in contact with and flows through the cavities on both sides. Each cavity has a monomer solution injection port 3 at the top and a solution outlet 4 at the bottom. The reactor is mounted and fixed using a bracket 5. Two monomer solutions are prepared: 0.008 g (0.28 mmol) of zinc nitrate hexahydrate is dissolved in 100 mL of deionized water, and 0.046 g (0.56 mmol) of 2-methylimidazole is dissolved in octanol, determining the concentration ratio to be 1:2. The two solutions are dispersed in an ultrasonic cleaner and then poured into the cavities on both sides of the h-PAN support, allowing for a static diffusion reaction for 2 hours at room temperature. After the reaction, the resulting ZIF-8 / h-PAN composite membrane is repeatedly washed several times in the cavities with deionized water and then stored in the reactor for later use.
[0035] Step 3: Prepare a two-phase monomer solution. The ZIF-8 / h-PAN composite membrane obtained in Step 2 is reacted on its surface to synthesize polyimide. Here, the ZIF-8 / h-PAN composite membrane does not need to be removed from the container. First, dissolve 0.09 g (0.006 mmol) of N'N-bis(3-aminopropyl)methylamine in 100 mL of deionized water, and then dissolve 0.8 g (0.03 mmol) of trimesoyl chloride in 100 mL of n-hexane. Disperse the two solutions in an ultrasonic cleaner, and then pour them into the cavities on both sides of the support. Add 0.4% sodium carbonate to the aqueous solution to remove hydrogen chloride generated during the reaction and increase the molecular weight of the polymer membrane. Add 0.05% sodium dodecyl sulfate to improve the adsorption of N'N-bis(3-aminopropyl)methylamine in the pores. After allowing the polymerization reaction to stand for 2 hours, rinse the membrane surface with an organic solvent to remove residual acyl chloride and other residues. The membrane was heat-treated in an oven for a period of time, and then dried in an artificial climate chamber at 30°C for 12 hours to obtain an ultrathin PA / ZIF-8 / h-PAN composite membrane, i.e., an ultrathin carbon capture membrane.
[0036] In this embodiment, the XRD patterns and surface scanning electron microscope images of the PAN support before and after hydrolysis are as follows: Figure 2 , 3 As shown, the surface scanning electron microscope image of the ultrathin PA / ZIF-8 / h-PAN composite film is as follows. Figure 4 As shown.
[0037] Example 2
[0038] A method for preparing an ultrathin carbon capture membrane includes the following steps:
[0039] Step 1: Prepare a sodium hydroxide solution with a molar concentration of 2 mol / L, immerse the polyacrylonitrile support in it, and place it in a water bath for hydrolysis treatment to modify it. The hydrolysis temperature is 60℃ and the hydrolysis time is 1 h.
[0040] Step 2: Place the h-PAN support obtained in Step 1 in the middle of the reactor, which is the same as in Example 1. Prepare the two-phase monomer solution: Dissolve 0.008 g (0.28 mmol) zinc nitrate hexahydrate in 100 mL of deionized water, and dissolve 0.046 g (0.56 mmol) 2-methylimidazole in octanol, determining the concentration ratio of the two solutions to be 1:2. Disperse the two solutions in an ultrasonic cleaner, and then pour them into the cavities on both sides of the h-PAN support respectively. Allow the diffusion reaction to proceed for 2 hours at room temperature. After the reaction is complete, repeatedly wash the resulting ZIF-8 / h-PAN composite membrane in the cavities on both sides with deionized water several times, and leave it in the reactor for later use.
[0041] Step 3: Prepare a two-phase monomer solution. The ZIF-8 / h-PAN composite membrane obtained in Step 2 is reacted on its surface to synthesize polyimide. Here, the ZIF-8 / h-PAN composite membrane does not need to be removed from the container. First, dissolve 0.09 g (0.006 mmol) of N'N-bis(3-aminopropyl)methylamine in 100 mL of deionized water, and then dissolve 0.8 g (0.03 mmol) of trimesoyl chloride in 100 mL of n-hexane. Disperse the two solutions in an ultrasonic cleaner, and then pour them into the cavities on both sides of the support. Add 0.4% sodium carbonate to the aqueous solution to remove hydrogen chloride generated during the reaction and increase the molecular weight of the polymer membrane. Add 0.05% sodium dodecyl sulfate to improve the adsorption of N'N-bis(3-aminopropyl)methylamine in the pores. After allowing the polymerization reaction to stand for 2 hours, rinse the membrane surface with an organic solvent to remove residual acyl chloride and other residues. The membrane was heat-treated in an oven for a period of time, and then dried in an artificial climate chamber at 30°C for 12 hours to obtain an ultrathin PA / ZIF-8 / h-PAN composite membrane, i.e., an ultrathin carbon capture membrane.
[0042] Example 3
[0043] A method for preparing an ultrathin carbon capture membrane includes the following steps:
[0044] Step 1: Prepare a sodium hydroxide solution with a molar concentration of 2 mol / L, immerse the polyacrylonitrile support in it, and place it in a water bath for hydrolysis treatment to modify it. The hydrolysis temperature is 50℃ and the hydrolysis time is 3h.
[0045] Step 2: Place the h-PAN support obtained in Step 1 in the middle of the reactor, which is the same as in Example 1. Prepare the two-phase monomer solution: Dissolve 0.001 g (0.035 mmol) zinc nitrate hexahydrate in 100 mL of deionized water, and dissolve 0.046 g (0.56 mmol) 2-methylimidazole in octanol, determining the concentration ratio of the two solutions to be 1:16. Disperse the two solutions in an ultrasonic cleaner, and then pour them into the cavities on both sides of the h-PAN support respectively. Allow the diffusion reaction to proceed statically for 0.5 h at room temperature. After the reaction is complete, repeatedly wash the resulting ZIF-8 / h-PAN composite membrane several times with deionized water in the cavities on both sides, and leave it in the reactor for later use.
[0046] Step 3: Prepare a two-phase monomer solution. The ZIF-8 / h-PAN composite membrane obtained in Step 2 is reacted on its surface to synthesize polyimide. Here, the ZIF-8 / h-PAN composite membrane does not need to be removed from the container. First, dissolve 0.09 g (0.006 mmol) of N'N-bis(3-aminopropyl)methylamine in 100 mL of deionized water, and then dissolve 0.8 g (0.03 mmol) of trimesoyl chloride in 100 mL of n-hexane. Disperse the two solutions in an ultrasonic cleaner, and then pour them into the cavities on both sides of the support. Add 0.4% sodium carbonate to the aqueous solution to remove hydrogen chloride generated during the reaction and increase the molecular weight of the polymer membrane. Add 0.05% sodium dodecyl sulfate to improve the adsorption of N'N-bis(3-aminopropyl)methylamine in the pores. After allowing the polymerization reaction to stand for 2 hours, rinse the membrane surface with an organic solvent to remove residual acyl chloride and other residues. The membrane was heat-treated in an oven for a period of time, and then dried in an artificial climate chamber at 30°C for 12 hours to obtain an ultrathin PA / ZIF-8 / h-PAN composite membrane, i.e., an ultrathin carbon capture membrane.
[0047] Example 4
[0048] A method for preparing an ultrathin carbon capture membrane includes the following steps:
[0049] Step 1: Prepare a sodium hydroxide solution with a molar concentration of 2 mol / L, immerse the polyacrylonitrile support in it, and place it in a water bath for hydrolysis treatment to modify it. The hydrolysis temperature is 50℃ and the hydrolysis time is 3h.
[0050] Step 2: Place the h-PAN support obtained in Step 1 in the middle of the reactor, which is the same as in Example 1. Prepare the two-phase monomer solution: Dissolve 0.001 g (0.035 mmol) zinc nitrate hexahydrate in 100 mL of deionized water, and dissolve 0.046 g (0.56 mmol) 2-methylimidazole in octanol, determining the concentration ratio of the two solutions to be 1:16. Disperse the two solutions in an ultrasonic cleaner, and then pour them into the cavities on both sides of the h-PAN support respectively. Allow the diffusion reaction to proceed statically for 0.5 h at room temperature. After the reaction is complete, repeatedly wash the resulting ZIF-8 / h-PAN composite membrane several times with deionized water in the cavities on both sides, and leave it in the reactor for later use.
[0051] Step 3: Prepare the two-phase monomer solution. The ZIF-8 / h-PAN composite membrane obtained in Step 2 is reacted on its surface to synthesize polyimide. Here, the ZIF-8 / h-PAN composite membrane does not need to be removed from the container. First, dissolve 0.46 g (0.0309 mmol) of N'N-bis(3-aminopropyl)methylamine in 100 mL of deionized water, and then dissolve 0.8 g (0.03 mmol) of trimesoyl chloride in 100 mL of n-hexane. Disperse the two solutions in an ultrasonic cleaner, and then pour them into the cavities on both sides of the support. Add 0.4% sodium carbonate to the aqueous solution to remove hydrogen chloride generated during the reaction and increase the molecular weight of the polymer membrane. Add 0.05% sodium dodecyl sulfate to improve the adsorption of N'N-bis(3-aminopropyl)methylamine in the pores. After allowing the polymerization reaction to stand for 1 hour, rinse the membrane surface with an organic solvent to remove residual acyl chloride and other residues. The membrane was heat-treated in an oven for a period of time, and then dried in an artificial climate chamber at 30°C for 12 hours to obtain an ultrathin PA / ZIF-8 / h-PAN composite membrane, i.e., an ultrathin carbon capture membrane.
[0052] Comparative Example 1
[0053] A method for preparing an ultrathin PA / ZIF-8 / h-PAN carbon capture composite membrane, differing from Example 1 in that 2-methylimidazole is dissolved in methanol, is described below:
[0054] Step 1: Prepare a sodium hydroxide solution with a molar concentration of 2 mol / L, immerse the polyacrylonitrile support in it, and place it in a water bath for hydrolysis treatment to modify it. The hydrolysis temperature is 50℃ and the hydrolysis time is 3h.
[0055] Step 2: Place the h-PAN support obtained in Step 1 in the middle of the reactor, which is the same as in Example 1. Prepare the two-phase monomer solution: Dissolve 0.008 g (0.28 mmol) zinc nitrate hexahydrate in 100 mL of deionized water, and dissolve 0.046 g (0.56 mmol) 2-methylimidazole in methanol, determining the concentration ratio of the two solutions to be 1:2. Disperse the two solutions in an ultrasonic cleaner, and then pour them into the cavities on both sides of the h-PAN support respectively. Allow the diffusion reaction to proceed for 2 hours at room temperature. After the reaction is complete, repeatedly wash the resulting ZIF-8 / h-PAN composite membrane in the cavities on both sides with deionized water several times, and leave it in the reactor for later use.
[0056] Step 3: Prepare the two-phase monomer solution. The ZIF-8 / h-PAN composite membrane obtained in Step 2 is reacted on its surface to synthesize polyimide. Here, the ZIF-8 / h-PAN composite membrane does not need to be removed from the container. First, dissolve 0.09 g (0.006 mmol) N'N-bis(3-aminopropyl)methylamine in 100 mL of deionized water, and then dissolve 0.8 g (0.03 mmol) trimesoyl chloride in 100 mL of n-hexane. Disperse the two solutions in an ultrasonic cleaner, and then pour them into the cavities on both sides of the support. Add 0.4% sodium carbonate and 0.05% sodium dodecyl sulfate to the aqueous solution. After allowing the polymerization reaction to stand for 2 hours, rinse the membrane surface with an organic solvent to remove residual acyl chloride and other residues. Place the membrane in an oven for heat treatment for a period of time, then remove it and dry it in a 30℃ artificial climate chamber for 12 hours to obtain an ultrathin PA / ZIF-8 / h-PAN carbon capture composite membrane.
[0057] The ultrathin PA / ZIF-8 / h-PAN composite membrane prepared in Comparative Example 1 showed a CO2 permeability of 115 GPU and a CO2 / N2 selectivity of 92 for separating CO2 / N2 mixtures at 25°C. Compared with the performance of Example 1, the permeability performance was significantly reduced. This was mainly attributed to the solvent selection during the growth of ZIF-8. Methanol has a lower viscosity and greater solution fluidity than octanol. The monomer solutions on both sides tend to concentrate into the support pores, leading to particle growth that blocks the support pores and increases mass transfer resistance.
[0058] Comparative Example 2
[0059] A method for preparing an ultrathin PA / ZIF-8 / h-PAN carbon capture composite membrane, differing from Example 1 in that the PAN support is not hydrolyzed, is as follows:
[0060] Step 1: Place the PAN support in the center of the reactor, which is the same as in Example 1. Prepare the two-phase monomer solution: Dissolve 0.008 g (0.28 mmol) zinc nitrate hexahydrate in 100 mL of deionized water, and dissolve 0.046 g (0.56 mmol) 2-methylimidazole in octanol, determining the concentration ratio of the two solutions to be 1:2. Disperse the two solutions in an ultrasonic cleaner, and then pour them into the cavities on both sides of the PAN support. Allow the diffusion reaction to proceed for 2 hours at room temperature. After the reaction is complete, repeatedly wash the resulting ZIF-8 / PAN composite membrane several times with deionized water in the cavities on both sides, and leave it in the reactor for later use.
[0061] Step 2: Prepare the two-phase monomer solution. The ZIF-8 / PAN composite membrane obtained in Step 2 is reacted on its surface to synthesize polyimide. Here, the ZIF-8 / PAN composite membrane does not need to be removed from the container. First, dissolve 0.09 g (0.006 mmol) N'N-bis(3-aminopropyl)methylamine in 100 mL of deionized water, and then dissolve 0.8 g (0.03 mmol) trimesoyl chloride in 100 mL of n-hexane. Disperse the two solutions in an ultrasonic cleaner, and then pour them into the liquid tanks on both sides of the support. Add 0.4% sodium carbonate and 0.05% sodium dodecyl sulfate to the aqueous solution. After allowing the polymerization reaction to stand for 2 hours, place the membrane in an oven for heat treatment for a period of time. After removal, place the membrane in a 30℃ artificial climate chamber for drying for 12 hours to obtain an ultrathin PA / ZIF-8 / h-PAN carbon capture composite membrane.
[0062] The carbon capture membrane prepared in Comparative Example 2 had a CO2 permeability of 12380 GPU and a CO2 / N2 selectivity of 7 when separating the CO2 / N2 mixture at 25°C. Compared with the performance of Example 1, the performance was significantly reduced, indicating that the support without hydrolysis had no adhesion to ZIF-8 growth, it was difficult to form a uniform separation layer on the support surface, and the overall stability was poor.
[0063] Table 1 shows a comparison of the CO2 permeability and CO2 / N2 selectivity of the membranes prepared in the various embodiments and comparative examples of the present invention:
[0064] Table 1
[0065] project <![CDATA[Membrane CO2 Permeability (GPU)]]> <![CDATA[Membrane CO2 / N2 selectivity]]> Example 1 283 91 Example 2 217 99 Example 3 329 84 Example 4 246 88 Comparative Example 1 115 92 Comparative Example 2 12380 7
[0066] The above are merely embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structures made using the contents of the present invention specification and drawings, whether directly or indirectly applied to other related technical fields, are similarly within the patent protection scope of the present invention.
Claims
1. A method for preparing an ultrathin carbon capture membrane, characterized in that, Includes the following steps: Step 1: Immerse the polyacrylonitrile support in an alkaline solution and place it in a water bath for hydrolysis treatment. Rinse with deionized water for later use to obtain the treated polyacrylonitrile support. Step 2: Place the treated polyacrylonitrile support in the middle of the reactor, pour a certain concentration of zinc nitrate solution and 2-methylimidazole solution into the two sides of the reactor respectively, let it stand for diffusion reaction, pour out the remaining solution, add deionized water to the two sides of the reactor respectively for washing and pouring out, to obtain ZIF-8 / h-PAN composite membrane. Step 3: Pour a certain concentration of pyromellitic methyl chloride organic phase solution and a certain concentration of N'N-bis(3-aminopropyl)methylamine aqueous phase solution into both sides of the reactor, allow the polymerization reaction to stand, heat-treat the membrane obtained from the polymerization reaction for a period of time, remove the membrane and dry it to obtain an ultrathin PA / ZIF-8 / h-PAN composite membrane, i.e., an ultrathin carbon capture membrane.
2. The preparation method according to claim 1, characterized in that, In step 1, the alkaline solution is a sodium hydroxide solution or a potassium hydroxide solution.
3. The preparation method according to claim 1 or 2, characterized in that, In step 1, the hydrolysis treatment is carried out at a temperature of 50-60℃ for 1-3 hours.
4. The preparation method according to claim 1 or 2, characterized in that, In step 2, the zinc nitrate solution is obtained by dissolving zinc nitrate hexahydrate in deionized water, with a molar concentration of 0.035-0.28 mol / L; the 2-methylimidazole solution is obtained by dissolving 2-methylimidazole in an organic solvent, with a molar concentration of 0.56 mol / L, and the molar ratio of zinc nitrate hexahydrate to 2-methylimidazole is 1:16-1:
2.
5. The preparation method according to claim 1 or 2, characterized in that, In step 2, the static diffusion reaction is allowed to proceed for 0.5-2 hours.
6. The preparation method according to claim 4, characterized in that, The organic solvent for the 2-methylimidazole is methanol, ethanol, or octanol.
7. The preparation method according to claim 1 or 2, characterized in that, In step 3, the pyromellitic methyl chloride is dissolved in an organic solvent, such as n-hexane, cyclohexane, n-pentane, or n-heptane, with a molar concentration of 0.0025-0.005 mol / L; the N'N-bis(3-aminopropyl)methylamine is dissolved in water with a molar concentration of 0.0062-0.0309 mol / L.
8. The preparation method according to claim 1 or 2, characterized in that, In step 3, the static polymerization reaction is allowed to proceed for 1-2 hours.
9. The preparation method according to claim 1 or 2, characterized in that, In step 3, the membrane obtained from the polymerization reaction is placed in an oven for heat treatment for a period of time. After being taken out, the membrane is placed in an artificial climate chamber at 30°C for 12 hours to dry, thus obtaining an ultrathin carbon capture membrane.
10. The application of the ultrathin carbon capture membrane obtained by the preparation method according to any one of claims 1-9 in the separation of CO2 / N2 mixed gas.