A high-throughput composite membrane for efficient separation of gas mixtures, its preparation method and application

Abstract

This application belongs to the field of membrane separation technology, and more specifically, relates to a high-flux composite membrane for efficient separation of gas mixtures, its preparation method, and its application. The present invention provides a method for preparing a high-flux composite membrane for efficient separation of gas mixtures. By specifically controlling the prepolymerization degree of the PDMS casting solution or the initial molecular weight of PDMS, the retention rate of the casting solution on the surface of a selected support layer ultrafiltration membrane is made greater than 90%. Then, a selective layer is prepared on the surface of the intermediate layer to obtain a composite membrane. The method cleverly uses a quantified retention rate to reflect the degree of pore permeation, solving the problem of PDMS pore permeation in the support layer during the preparation of composite membranes in existing technologies. The Pebax composite membrane prepared by the method of this invention has advantages such as high gas flux, excellent mixed gas separation performance, and industrial scale-up capability.

Description

Technical Field

[0001] This application belongs to the field of membrane separation technology, and more specifically, relates to a high-throughput composite membrane for efficient separation of gas mixtures, its preparation method and application. Background Technology

[0002] With economic and social development, people's demands for living environment and personal health are increasing. Volatile organic compounds (VOCs) are a significant air pollutant, and their unchecked emission can negatively impact human health and the environment. The exhaust gas from polypropylene synthesis contains 15-25% propylene and 75-85% nitrogen. Since propylene is a VOC with significant recycling value, separating propylene and nitrogen is crucial for resource recovery and environmental protection. Carbon dioxide, as the most significant greenhouse gas, primarily originates from the combustion of fossil fuels. Methane, however, has a global warming potential 34 times that of carbon dioxide, and is considered the second largest contributor to global warming after carbon dioxide. Major sources of methane emissions include fossil fuels and biogas from livestock farming.

[0003] Membrane separation technology holds promise for reducing separation energy consumption and operating costs due to its advantages such as no phase change during separation, small footprint, and simple operation and maintenance. In practical applications, to improve processing capacity, gas separation membranes are often composite membrane structures, consisting of three parts: a selective layer providing separation selectivity, a highly permeable intermediate layer, and a porous support layer providing mechanical strength. According to the series resistance model, the high-flux intermediate layer is the foundation of the high-flux composite membrane. However, during the preparation of the intermediate layer, low-concentration casting solution inevitably seeps into the pores of the porous support layer. This seepage leads to an increase in the actual thickness of the intermediate layer and a decrease in flux. Increasing the concentration of the casting solution can reduce the degree of seepage to some extent, but it also leads to an increase in the thickness of the PDMS layer, resulting in a decrease in flux. Taking polydimethylsiloxane (PDMS), the most common intermediate layer material, as an example, current strategies modify the end groups of PDMS to achieve rapid crosslinking in order to prevent seepage. However, this method increases material costs and complicates the preparation process. Furthermore, the preparation of Pebax composite membranes is currently limited to small-area fabrication, presenting challenges for scale-up. The reason is that hydrophilic Pebax is difficult to load uniformly on the hydrophobic PDMS surface, and the currently used oxygen plasma hydrophilic treatment is limited by equipment and has a limited treatment area, which restricts its large-scale production. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the purpose of this application is to provide a high-throughput composite membrane for efficient separation of gas mixtures, its preparation method and application, aiming to solve the technical problems of low gas flux and / or poor selectivity of the composite membranes used for gas mixture separation in the prior art.

[0005] To achieve the above objectives, in a first aspect, this application provides a method for preparing a high-throughput composite membrane for efficient separation of gas mixtures, comprising the following steps:

[0006] (1) Dissolve the initially hydroxyl-terminated polydimethylsiloxane (PDMS), crosslinking agent and catalyst in a first solvent, mix and stir to allow the initially hydroxyl-terminated polydimethylsiloxane to undergo a prepolymerization reaction to obtain PDMS casting solution;

[0007] (2) Using the porous ultrafiltration membrane as the suction filtration membrane of the dead-end filtration system, the retention rate of the porous ultrafiltration membrane for the PDMS casting solution in step (1) was tested.

[0008] (3) If the retention rate measured in step (2) is greater than or equal to 90%, proceed to step (4); otherwise, increase the prepolymerization degree of the PDMS casting solution in step (1) or increase the molecular weight of the initially hydroxyl-terminated polydimethylsiloxane, so that the retention rate of the casting solution obtained after the prepolymerization reaction measured in step (2) is greater than or equal to 90%;

[0009] (4) Transfer the PDMS casting solution with a retention rate greater than or equal to 90% to the surface of the support layer ultrafiltration membrane, scrape it and dry it to remove excess first solvent to obtain a PDMS membrane; the support layer ultrafiltration membrane and the porous ultrafiltration membrane in step (2) are the same type of ultrafiltration membrane;

[0010] (5) Dissolve polyether block polyamide (Pebax) in a second solvent to obtain Pebax casting solution; transfer the Pebax casting solution to the surface of PDMS membrane, coat it and dry it to remove excess second solvent, and obtain a Pebax selective layer on the surface of PDMS membrane, thus obtaining the high-throughput composite membrane.

[0011] Preferably, in step (2), a porous ultrafiltration membrane is used as the filtration membrane of the dead-end filtration system, and the rejection rate is calculated by analyzing the PDMS concentration in the initial PDMS casting solution and the permeate-side PDMS casting solution before and after filtration using nuclear magnetic resonance hydrogen spectroscopy.

[0012] Preferably, the concentration of PDMS in the test solution is calculated using the area normalization method based on the peak areas of characteristic hydrogen atoms in the PDMS in the test solution and the first solvent. The test solution includes the initial PDMS casting solution and the permeation-side PDMS casting solution. The formula for calculating the concentration of PDMS in the test solution is shown in equation (1):

[0013]

[0014] In the formula: c i The concentration of PDMS in the test solution is wt%; Ai and A k n represents the characteristic hydrogen atom peak areas of PDMS and the first solvent in the test solution, respectively; i and n k m represents the number of characteristic hydrogen atoms in PDMS and the first solvent in the test solution, respectively; i and m k These represent the relative molecular weights of PDMS and the first solvent in the test solution, respectively.

[0015] Preferably, step (3) increases the prepolymerization degree of the PDMS casting solution in step (1) so that the retention rate of the casting solution obtained after the prepolymerization reaction measured in step (2) is greater than or equal to 90%. Specifically, this is achieved by extending the prepolymerization reaction time in step (1) to increase the prepolymerization degree so that the retention rate of the casting solution is greater than or equal to 90%, or by increasing the molecular weight of the initial PDMS so that the retention rate of the casting solution is greater than or equal to 90%.

[0016] Preferably, after obtaining the PDMS membrane in step (4), the step further includes: using an atmospheric plasma cleaner to hydrophilically modify the surface of the PDMS membrane to obtain a hydrophilically modified PDMS membrane.

[0017] According to another aspect of the present invention, a high-throughput composite membrane prepared by the preparation method described above is provided.

[0018] According to another aspect of the invention, an application of the high-throughput composite membrane described above in the separation of gas mixtures is provided.

[0019] Overall, the technical solutions conceived in this application have the following beneficial effects compared with the prior art:

[0020] (1) The present invention provides a method for preparing a high-throughput composite membrane for efficient separation of gas mixtures. By specially controlling the prepolymerization degree of PDMS casting solution or the molecular weight of the initial PDMS, the casting solution has a rejection rate of greater than or equal to 90% on the surface of the selected support layer ultrafiltration membrane. The quantitative rejection rate is cleverly used to reflect the degree of pore permeation, which solves the problem of PDMS pore permeation in the support layer, and thus prepares a high-throughput and highly selective Pebax composite membrane.

[0021] (2) The present invention provides a high-throughput composite membrane for efficient separation of gas mixtures, comprising a selective layer, an intermediate layer, and a porous support layer arranged sequentially along the gas inlet direction, wherein the porous support layer is a commercial ultrafiltration membrane; the intermediate layer is a polydimethylsiloxane membrane; the selective layer is a polyether block polyamide membrane; and the retention rate of the intermediate layer casting solution in the support layer is controlled to be greater than or equal to 90%. Experiments of the present invention have shown that when the retention rate of the PDMS casting solution in the support layer is controlled to be greater than or equal to 90% in the composite membrane, PDMS can be retained by the substrate to the surface of the support layer as much as possible, thereby avoiding pore permeation. In a preferred embodiment, atmospheric plasma treatment is simultaneously used to hydrophilically modify the PDMS surface, introducing hydrophilic groups such as hydroxyl groups to improve the affinity between the intermediate layer and the Pebax selective layer, thus preparing a high-throughput Pebax composite membrane.

[0022] (3) The method of the present invention does not limit the initial molecular weight of PDMS, nor does it limit the molecular weight cut-off of the porous support layer. It only needs to control the prepolymerization degree of PDMS in the casting solution and use the retention rate test formula proposed in the present invention to control the retention rate to be greater than or equal to 90% to prepare the composite membrane, which can effectively avoid the pore seepage phenomenon and improve the flux and selectivity of the mixed gas.

[0023] (4) The atmospheric plasma cleaning machine used in the method of the present invention treats the PDMS surface, which can improve the wettability of Pebax casting solution on the PDMS surface, thereby preparing an ultrathin Pebax selective layer. At the same time, the method of the present invention also has the advantages of a large processing area (up to 1200 cm²). 2 It has advantages such as good treatment effect and industrial scale-up, while the existing technology commonly used oxygen plasma cleaning machine is complicated to operate and has a small treatment area due to equipment limitations.

[0024] (5) The selective layer material of the composite membrane prepared by the method of the present invention is Pebax, which has high selectivity, good plasticization resistance, and thin selective layer thickness due to the good affinity between Pebax and the modified intermediate layer. It also has the advantage of high gas flux. Attached Figure Description

[0025] Figure 1 The results are 1H NMR spectra of PSF support layer (molecular weight cutoff: 63 kDa) collected by dead-end filtration, which retains PDMS solutions of different molecular weights (15 kDa-347 kDa) on the permeate side.

[0026] Figure 2 The results show the retention rates of PSF support layers (molecular weight cutoff: 63 kDa and 20 kDa) for PDMS of different molecular weights (15 kDa-347 kDa) in dead-end filtration tests.

[0027] Figure 3These are scanning electron microscope (SEM) images of the cross-section of the interlayer material of PDMS composite membranes prepared with PDMS of different molecular weights, tested using the vacuum filtration method.

[0028] Figure 4 The carbon dioxide / nitrogen pure gas separation performance of PDMS composite membranes with different prepolymerization times prepared in Example 1 is shown.

[0029] Figure 5 The carbon dioxide / nitrogen pure gas separation performance of the PDMS composite membrane prepared in Example 1 at different prepolymerization times of 0 and 30 minutes is shown.

[0030] Figure 6 These are scanning electron microscope images of the surface and cross-section of the PDMS composite film with a prepolymerization time of 30 min in Example 1.

[0031] Figure 7 It shows the change in the PDMS retention rate of the PSF support layer before and after 30 minutes of prepolymerization.

[0032] Figure 8 This refers to the changes in carbon dioxide flux and water contact angle after PDMS surface treatment by atmospheric plasma.

[0033] Figure 9 These are scanning electron microscope images, in which Figure 9 Content (a) is a scanning electron microscope image of the PSF ultrafiltration membrane surface in Example 1. Figure 9 Contents (b) and (c) are scanning electron microscope images of the surface and cross-section of the Pebax composite film obtained in Example 1, respectively.

[0034] Figure 10 The pure gas flux of the Pebax composite membrane prepared in Example 1 for different gases.

[0035] Figure 11 The changes in gas flux and propylene / nitrogen selectivity of the Pebax composite membrane prepared in Example 1 were measured by continuous 80-h mixed gas testing.

[0036] Figure 12 The separation performance of the Pebax composite membrane prepared in Example 1 for a carbon dioxide / methane mixture is shown. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0038] The embodiments of the present invention are implemented under the premise of the technical solution of the present invention, and detailed implementation methods and processes are given. However, the protection scope of the present invention is not limited to the following embodiments. The process parameters in the following embodiments that do not specify specific conditions are generally in accordance with conventional conditions.

[0039] The endpoints and any values ​​of the ranges disclosed in this invention 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 endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0040] The present invention provides a method for preparing a high-throughput composite membrane for efficient separation of gas mixtures, comprising the following steps:

[0041] (1) Dissolve the initial PDMS, crosslinking agent and catalyst in the first solvent, mix and stir to make the initial PDMS undergo a prepolymerization reaction to obtain PDMS casting solution;

[0042] (2) Using the support layer ultrafiltration membrane as the suction filtration membrane of the dead end filtration system, the retention rate of the support layer ultrafiltration membrane for the PDMS casting solution in step (1) was tested.

[0043] (3) If the retention rate measured in step (2) is greater than or equal to 90%, proceed to step (4); otherwise, it is necessary to increase the prepolymerization degree of the PDMS casting solution in step (1) or increase the molecular weight of the initially hydroxyl-terminated polydimethylsiloxane until the retention rate of the casting solution obtained after the prepolymerization reaction measured in step (2) is greater than or equal to 90%.

[0044] (4) Transfer the PDMS casting solution with a retention rate greater than or equal to 90% to the surface of the support layer ultrafiltration membrane described in step (2), coat it and dry it to remove excess first solvent to obtain a PDMS membrane; the support layer ultrafiltration membrane and the porous ultrafiltration membrane described in step (2) are the same type of ultrafiltration membrane;

[0045] (5) Dissolve the polyether block polyamide in a second solvent to obtain the Pebax casting solution; transfer the Pebax casting solution to the surface of the PDMS membrane, coat it and dry it to remove excess solvent, and obtain the Pebax selective layer on the surface of the PDMS membrane, thus obtaining the high-throughput composite membrane.

[0046] The high-flux interlayer is the foundation of high-flux composite membranes. However, during the preparation of the interlayer, low-concentration casting solution inevitably seeps into the pores of the porous support layer. This seepage leads to an increase in the actual thickness of the interlayer and a decrease in flux. Conversely, increasing the concentration of the casting solution increases the interlayer thickness and reduces the composite membrane flux (generally, the thinner the interlayer, the higher the flux). Existing technologies modify the end groups of PDMS to achieve rapid crosslinking. This rapid crosslinking of end-modified PDMS forms a network structure, thus preventing seepage. However, this method increases material costs and complicates the preparation process. This invention investigates the relationship between the prepolymerization degree of PDMS in the PDMS casting solution and PDMS pore permeation during the experimental process. A test model for the retention rate of the PDMS casting solution on the surface of the ultrafiltration membrane in the support layer was established. A novel approach to preparing high-flux composite membranes was proposed. Through experiments, a retention rate threshold that combines high flux and selectivity in the composite membrane was found. By controlling the prepolymerization degree of PDMS in the PDMS casting solution or increasing the molecular weight of the initially hydroxyl-terminated polydimethylsiloxane, the retention rate of the PDMS casting solution on the surface of the ultrafiltration membrane in the support layer is made greater than or equal to this threshold. This ingenious use of quantitative retention rate to reflect the degree of pore permeation solves the problem of PDMS pore permeation in the support layer, resulting in a composite membrane with excellent flux and selectivity. The preparation method of the composite membrane of this invention is applicable to PDMS with any initial molecular weight and has no absolute limitations or requirements on the pore size of the ultrafiltration membrane in the support layer. According to the preparation method of this invention, only the PDMS casting solution and the ultrafiltration membrane in the support layer need to be relatively matched.

[0047] Dead-end filtration systems are typically used in liquid systems to retain substances using filter media (such as ultrafiltration membranes). This application, based on the concept of preventing pore permeation from affecting the performance of the composite membrane by retaining the PDMS prepolymer solution through a supported layer ultrafiltration membrane, utilizes a dead-end filtration system to first test the retention rate of the selected supported layer ultrafiltration membrane for the PDMS casting solution. A retention rate threshold is set, and PDMS prepolymer solutions with a retention rate greater than or equal to this threshold are selected for subsequent composite membrane preparation. Experiments show that this approach can indeed produce defect-free, high-flux, and highly selective composite membranes.

[0048] Step (2) The rejection rate is calculated by analyzing the PDMS concentration in the initial PDMS casting solution and the permeation-side PDMS casting solution using nuclear magnetic resonance hydrogen spectroscopy.

[0049] Specifically, the rejection rate = (concentration of PDMS in the initial PDMS solution - concentration of PDMS in the osmotic PDMS solution) / concentration of PDMS in the initial PDMS solution × 100%.

[0050] In some embodiments, the concentration of PDMS is calculated using the area normalization method based on the peak areas of characteristic hydrogen atoms in the solution and the first solvent, as shown in equation (1):

[0051]

[0052] In the formula: c i The concentration of PDMS in the test solution is wt%; A i and A k n represents the characteristic hydrogen atom peak areas of PDMS and the first solvent in the test solution, respectively; i and n k m represents the number of characteristic hydrogen atoms in PDMS and the first solvent in the test solution, respectively; i and m k These represent the relative molecular weights of PDMS and the first solvent in the test solution, respectively.

[0053] In some embodiments, during the calculation process, the number of repeating units of –Si(CH3)2O– and the number of PDMS segments in all PDMS molecules are assumed to be x and y, respectively. Therefore, the relative molecular weight of the PDMS prepolymer in the solution can be expressed as 74x+18y, the relative molecular weight of –Si(CH3)2O– is 74, and the sum of the relative molecular weights of the hydroxyl and hydrogen atoms at both ends of the PDMS segments is 18.

[0054] Taking n-heptane as the first solvent as an example, the hydrogen atoms on the methyl groups at both ends of the n-heptane molecule and the hydrogen atoms on the methyl groups attached to the silicon atoms of PDMS are respectively used as characteristic hydrogen atoms. Since both the hydrogen atoms on the methyl groups at both ends of the n-heptane molecule and the hydrogen atoms on the silicon atoms of PDMS have symmetrical structures, each hydrogen atom... 1 The chemical shifts were the same in the 1H NMR test. The n-heptane molecule has a total of 6 characteristic hydrogen atoms, while each silicon atom in PDMS has 6 characteristic hydrogen atoms, for a total of 6x. The MestReNova software was used to analyze the chemical shifts. 1 By analyzing the H NMR results, the characteristic peak area of ​​the hydrogen atom corresponding to the first solvent n-heptane is defined as 6, and the peak area of ​​the hydrogen atom corresponding to PDMS can be obtained.

[0055] Based on the above assumptions, the formula for calculating the concentration of PDMS in the test solution is as follows:

[0056]

[0057] In formula (2), the molecular weight 18y of the hydroxyl groups at both ends of PDMS is much smaller than the molecular weight 74x of the repeating unit –Si(CH3)2O–, therefore 18y is ignored to simplify the calculation; thus, according to 1 The concentration of PDMS was determined by the peak intensity of H NMR.

[0058] In some embodiments, the first solvent is n-heptane and / or n-hexane, and the concentration of PDMS in the PDMS casting solution is 0.2 wt%-3 wt%, more preferably 0.2 wt%-1.5 wt%.

[0059] In some embodiments, the mass ratio of polydimethylsiloxane (PDMS), crosslinking agent and catalyst in step (1) is 100:(10-50):(1-50).

[0060] In some embodiments, the mixing and stirring in step (1) is carried out at room temperature (20-30 °C) for a time of 20 min-240 min, preferably 30 min-60 min.

[0061] In some embodiments, the crosslinking agent is tetraethyl orthosilicate (TEOS); and the catalyst is dibutyltin dilaurate (DBTDL).

[0062] The ultrafiltration membrane in step (4) is the same type of ultrafiltration membrane as the porous ultrafiltration membrane in step (2); it can be made of porous ultrafiltration membrane materials commonly used in the prior art. In some embodiments, the ultrafiltration membrane is PSF, PAN or PVDF, etc.

[0063] In some embodiments, step (4) involves transferring the PDMS casting solution to the surface of the support layer ultrafiltration membrane, which can be done by dripping or other methods. Similarly, step (5) can also involve dripping the Pebax casting solution onto the PDMS membrane surface.

[0064] In some embodiments, the drying in step (4) is heating at 60-80 °C for 0.5-4 h; and / or, the thickness of the PDMS film is about 200-400 nm.

[0065] In some embodiments, the second solvent in step (5) is a mixture of ethanol and water or n-butanol; the concentration of Pebax in the Pebax casting solution in step (5) is 1 mg / mL-20 mg / mL; the drying in step (5) is heating at 60-80°C for 4-12 h; and the thickness of the Pebax selective layer in step (5) is 131 nm-1.38 μm.

[0066] In some embodiments, the Pebax brand name is Pebax. ® 1657, Pebax ® 2533, Pebax ® 3533, Pebax ® 4033, Pebax ®One of 6333 or any combination thereof.

[0067] In some embodiments, after obtaining the PDMS membrane in step (4), the step further includes: using an atmospheric plasma cleaner to hydrophilically modify the surface of the PDMS membrane to obtain a hydrophilically modified PDMS membrane. In a preferred embodiment, the atmospheric plasma treatment conditions are: processing speed 25-40 mm / s, power 800-1000 W, and working distance 1-3 cm.

[0068] The process parameters in the following examples, unless otherwise specified, are generally performed under conventional conditions.

[0069] The embodiments of this application will now be described with reference to the accompanying drawings.

[0070] First, the retention rate of porous support layer for PDMS of different molecular weights was tested using a dead-end filtration system. Five PDMS molecular weights were selected, namely 15 kDa, 58 kDa, 90 kDa, 167 kDa and 347 kDa. The porous support layer used was PSF, with a molecular weight cutoff of 63 kDa (data provided by the vendor, test results using polyethylene glycol as the standard substance).

[0071] The retention rate was calculated by analyzing the PDMS concentration in the initial solution and the osmotic side solution using 1H NMR spectroscopy. The specific analytical method was as follows:

[0072] The concentration of PDMS can be calculated by using the area normalization method based on the characteristic hydrogen atom peak areas of PDMS in the solution and the first solvent n-heptane, as shown in formula (1).

[0073]

[0074] In the formula: c i The concentration of PDMS in the test solution is wt%; A i and A k n represents the characteristic peak areas of PDMS and n-heptane in the test solution, respectively; i and n k m represents the number of hydrogen atoms in PDMS and the first solvent in the test solution, respectively; i and m k The relative molecular weights of PDMS and the first solvent in the test solution are represented respectively. In the calculation process, the number of repeating units of –Si(CH3)2O– and the number of PDMS segments in all PDMS molecules are assumed to be x and y respectively. Therefore, the relative molecular weight of PDMS prepolymer in solution can be expressed as 74x+18y, the relative molecular weight of –Si(CH3)2O– is 74, and the sum of the relative molecular weights of hydroxyl and hydrogen atoms at both ends of PDMS segments is 18.

[0075] Based on the above assumptions, the formula for calculating the concentration of PDMS in the solution is:

[0076]

[0077] In formula (2), the molecular weight (18y) of the hydroxyl groups at both ends of PDMS is much smaller than the molecular weight (74x) of the repeating unit –Si(CH3)2O–, therefore 18y can be ignored to simplify the calculation. The characteristic peak area A of n-heptane. k Assume the number is 6. The number of hydrogen atoms n k The value is 6, and the molecular weight is 100. Therefore, based on this... 1 The concentration of PDMS was determined by the peak intensity of H NMR.

[0078] Taking the PSF ultrafiltration membrane with a molecular weight cutoff of 63 kDa as an example, the test results of the proton NMR spectrum are as follows: Figure 1 As shown in Table 1 below, the detailed calculation results of the retention rate are as follows.

[0079] Table 1

[0080]

[0081] Note: For each molecular weight of PDMS, the first row represents the initial concentration of PDMS before filtration, and the second row represents the concentration of PDMS on the permeate side after filtration.

[0082] a) Number of –Si(CH3)2O– units repeating in PDMS

[0083] b) Number of PDMS segments

[0084] The test results of the retention rate are as follows Figure 2 As shown in the figure, for a PSF ultrafiltration membrane with a molecular weight cutoff of 63 kDa, when the mass fraction of PDMS is 0.1 wt% (n-heptane as solvent), the retention rates of the support layer for PDMS molecules with molecular weights of 15 kDa and 53 kDa are only 5.5% and 11.4%, respectively, indicating that low molecular weight PDMS can easily penetrate (pass through) the pores of the support layer. However, when the molecular weight increases above 63 kDa, the retention rate significantly improves. The retention rates of the support layer for PDMS molecules of 90 kDa, 167 kDa, and 347 kDa are 49.9%, 50.6%, and 65.6%, respectively. For a PSF ultrafiltration membrane with a molecular weight cutoff of 20 kDa, the retention rates of the support layer for PDMS molecules of 53 kDa, 90 kDa, 167 kDa, and 347 kDa are 57.2%, 65.9%, 76.6%, and 86.3%, respectively. It can be seen that for any type of support layer ultrafiltration membrane, the retention rate of the support layer for PDMS of different molecular weights can be obtained by adjusting the initial PDMS molecular weight.

[0085] In this embodiment, a direct filtration film was formed on the surface of the porous support layer (PSF with a molecular weight cutoff of 63 kDa) using a vacuum filtration method. The relationship between the molecular weight of PDMS and the pore size of the support layer was verified by scanning electron microscopy and gas flux testing. The reason for using the vacuum filtration method is that the casting solution used in vacuum filtration has a lower concentration, which can minimize the influence of concentration-induced polymer clusters on the experimental results.

[0086] The experimental steps for vacuum filtration are as follows:

[0087] (1) Fix the PSF ultrafiltration membrane in a vacuum filtration flask as a vacuum filtration membrane, and use water-ethanol-water-ethanol repeated vacuum filtration to remove the filling agent and other substances in the ultrafiltration membrane.

[0088] (2) Take 10 mL of n-heptane solution of PDMS with different molecular weights (PDMS mass fraction of 0.1 wt%) and add it to the vacuum filtration flask. The solution passes through the ultrafiltration membrane under vacuum filtration.

[0089] (3) After the solution in step (2) is completely dried, the membrane is transferred to a 60 °C oven to dry in order to remove excess solvent, thus obtaining the separation membrane.

[0090] Figure 3 The images show surface and cross-sectional SEM images of the PDMS intermediate layer obtained by vacuum filtration. Combined with the SEM images, it can be observed that the membrane surface gradually changes from rough to smooth as the molecular weight of PDMS increases. Furthermore, when the molecular weight of PDMS exceeds the molecular weight cutoff of the support layer, a polymer layer clearly appears on the PSF surface through the cross-sectional SEM images, with its thickness increasing from 683 nm to 2.07 μm. This indicates that higher molecular weight PDMS is indeed more retained on the surface of the support layer, rather than penetrating (through) the pores of the support layer, which is consistent with the retention rate test results.

[0091] Example 1

[0092] Preparation of high-throughput PDMS intermediate layer:

[0093] 1. Weigh 0.05 g of PDMS (molecular weight 90 kDa), add it to 8.95 g of n-heptane, dissolve and stir thoroughly to obtain solution A, and prepare four sets of solution A.

[0094] 2. Add 0.025 g of TEOS and 0.025 g of DBTDL to each of the four groups of solutions A to obtain solution B, and stir at a constant temperature of 25°C.

[0095] 3. The four solutions were prepolymerized for 5, 10, 20, and 30 min, respectively. After reaching the prepolymerization time, 2.5 mL of solution B prepared in step 2 above (with a PDMS mass fraction of 0.5 wt%) was taken and dropped onto the surface of four commercial PSF ultrafiltration membranes (molecular weight cutoff: 63 kDa). The resulting PDMS composite membranes were quickly coated using a 100 μm thick doctor blade and then transferred to an 80 ℃ oven for heating for 2 h.

[0096] 4. The remaining solutions were subjected to dead-end filtration, and the retention rate of the PSF ultrafiltration membrane for PDMS casting solutions with different prepolymerization times was tested.

[0097] Figure 4 and Figure 5 This example demonstrates the carbon dioxide / nitrogen pure gas separation performance of PDMS composite membranes with different prepolymerization times prepared in this instance. Figure 5 In the bar chart, the red-filled area represents the rejection rate, the green fill represents the carbon dioxide gas flux, and the purple fill represents the carbon dioxide / nitrogen selectivity. For PDMS with a molecular weight of 90 kDa, as the prepolymerization time increased from 10 minutes to 20 minutes, the carbon dioxide / nitrogen selectivity significantly improved from 1.4 to 10.6. The separation performance reached its optimal level at a prepolymerization time of 30 minutes, with a carbon dioxide flux of 9471 GPU and a carbon dioxide / nitrogen selectivity of 10.6. For comparison, the figure also shows the carbon dioxide / nitrogen pure gas separation performance of PDMS with an initial molecular weight of 15 kDa under the same prepolymerization conditions. It can be seen that within a 30-minute prepolymerization time, the flux and selectivity did not change significantly, remaining close to those of the porous support layer. This may be because the rejection rate of PDMS for PSF with a molecular weight cutoff of 15 kDa is less than 90% within a 30-minute prepolymerization time.

[0098] Figure 6 Contents (a) and (b) are scanning electron microscope images of the surface and cross-section of the PDMS composite film after a prepolymerization time of 30 min, respectively. Figure 1 As can be seen from content (b), the thickness of the PDMS intermediate layer is approximately 300 nanometers.

[0099] Figure 7 The retention rate of PDMS by PSF was tested at 0 min and 30 min for 0.5 wt% PDMS prepolymerization according to the above method. The retention rate increased from 52.7% before prepolymerization to 93.2%. (Although the prepolymer solution contains crosslinking agent and catalyst in addition to PDMS and n-heptane, when calculating the retention rate based on the characteristic hydrogen atom peak area using the area normalization method, since the characteristic hydrogen atom peak positions of different substances are different, PDMS and n-heptane are still treated as a whole 1, and the parameters of the two are calculated according to formulas (1) and (2).)

[0100] Table 2 shows the flux and selectivity of the PDMS composite membrane prepared in Example 1 under different conditions for carbon dioxide / nitrogen mixture.

[0101] Table 2

[0102]

[0103] As shown in Table 2, for PDMS with an initial concentration of 0.5%, the rejection rate of PDMS on the ultrafiltration membrane of the support layer increases and the flux of the mixed gas decreases as the prepolymerization time increases. However, unexpectedly, the selectivity of CO2 / N2 increases from 0.9 corresponding to 5 minutes of prepolymerization to 10.9 corresponding to 30 minutes of prepolymerization (corresponding to a rejection rate of 93.2%), while the CO2 flux can still be maintained at 9471 GPU.

[0104] The separation performance of carbon dioxide and nitrogen pure gas by the PDMS interlayer material prepared in Example 1 (with a molecular weight of 90 kDa and PDMS prepolymerized at a concentration of 0.5 wt% for 30 minutes) and the composite membrane interlayer material prepared by the prior art is compared and listed in Table 3.

[0105] Table 3

[0106]

[0107] Compared with existing composite membranes, the composite membrane intermediate material prepared in this embodiment of the invention has a selectivity of over 10 and a carbon dioxide flux of up to 9471 GPU, which is much higher than the composite membranes numbered 1 to 5, which are also OH-PDMS. Although the intermediate material AC-PDMS prepared in reference [9] also has high carbon dioxide selectivity and flux, its practical application is greatly limited because its end group is acryloyloxy, which requires free radical polymerization under anaerobic conditions.

[0108] References:

[0109] [1] X. Xu, J. Dong, X. Xiao, X. Zhao, Q. Zhang. Constructing thin and cross-linked polyimide membranes by interfacial reaction for efficientCO2separation. ACS Sustainable Chemistry&Engineering. 2021, 9(16): 5546-5556.

[0110] [2] X. Jiang, K. Goh, R. Wang. Air plasma assisted spray coating ofPebax-1657 thin-film composite membranes for post-combustion CO2capture.Journal of Membrane Science. 2022, 658: 120741.

[0111] [3] P. Li, Z. Wang, W. Li, Y. Liu, J. Wang, S. Wang. High-performancemultilayer composite membranes with mussel-inspired polydopamine as aversatile molecular bridge for CO2separation. ACS Applied Materials&Interfaces. 2015, 7(28): 15481- 15493.

[0112] [4] C. Z. Liang, T. S. Chung. Ultrahigh flux composite hollow fibermembrane via highly crosslinked PDMS for recovery of hydrocarbons: propaneand propene. Macromolecular Rapid Communications. 2018, 39(5): 1700535.

[0113] [5] P. Li, H. Z. Chen, T. Chung. The effects of substratecharacteristics and pre-wetting agents on PAN–PDMS composite hollow fibermembranes for CO2 / N2and O2 / N2separation. Journal of Membrane Science. 2013,434: 18-25.

[0114] [6] Fu Q, Halim A, Kim J, Scofield JMP, Gurr PA, SEKentish, et al. Highly permeable membrane materials for CO2 capture. Journalof Materials Chemistry A. 2013, 1(44):13769.

[0115] [7] Halim A, Fu Q, Yong Q, Gurr PA, Kentish SE, Qiao GG.Soft polymeric nanoparticle additives for next generation gas separation membranes. Journal of Materials Chemistry A. 2014, 2(14): 4999-5009.

[0116] [8] Scofield JMP, Gurr PA, Kim J, Fu Q, Kentish SE, Qiao GG. Development of novel fluorinated additives for high performanceCO2separation thin-film composite membranes. Journal of Membrane Science.2016, 499: 191-200.

[0117] [9] Y. Pan, G. Chen, J. Liu, J. Li, X. Chen, H. Zhu, et al. PDMSthin-film composite membranes fabricated by ultraviolet crosslinkingacryloyloxy-terminated monomers. Journal of Membrane Science. Rev. 2022, 658:1

[0118] Polymerous cylindrical snowflakes in mPDMS:

[0119] The principle of atmospheric plasma treatment is to break the Si-C bonds on the PDMS surface and introduce hydroxyl groups onto the silicon atoms, thereby forming a silicon dioxide-like structure, SiO. x SiO x While the structure improves the hydrophilicity of the PDMS surface, it also hinders gas transport, resulting in a reduction in gas flux. Figure 8 This shows the changing trends of carbon dioxide and surface water contact angles under different atmospheric plasma treatment times. Increasing the treatment time from 0 seconds to 2.8 seconds reduced the carbon dioxide flux from 9471 GPU to 3941 GPU and the water contact angle from 107° to 56°. Considering all factors, an atmospheric plasma treatment time of 2.0 seconds was selected as the condition for preparing the hydrophilic modified PDMS intermediate layer, with a carbon dioxide permeability of 4976 GPU and a water contact angle of 72.1°.

[0120] Preparation and separation performance of Pebax / PDMS / PSF composite membrane

[0121] Preparation of Pebax / PDMS / PSF composite membrane:

[0122] 1. Preparation of PDMS composite membrane:

[0123] 1.1 Weigh 0.05 g of PDMS and add it to 8.95 g of n-heptane. Dissolve and stir thoroughly to obtain solution A.

[0124] 1.2 Add 0.025 g of TEOS and 0.025 g of DBTDL to solution A, and stir at 25 °C for 30 min to obtain solution B.

[0125] 1.3 Take 2.5 mL of solution B (PDMS mass fraction of 0.5 wt%) prepared in step 1.2 above, drop it onto the surface of a commercial ultrafiltration membrane, and quickly coat it with a 100 μm thick doctor blade.

[0126] 1.4 Transfer the PDMS composite membrane obtained in step 1.3 to an 80 ℃ oven and heat for 2 h for later use.

[0127] 2. Preparation of hydrophilic modified mPDMS composite membrane

[0128] 2.1 Place the PDMS membrane obtained in step 1 into an atmospheric plasma cleaner, set the parameters as follows: processing power 800 W, processing height 1.2 cm, and nozzle moving speed 35 mm / s.

[0129] 2.2 Set the nozzle moving path and process the PDMS membrane surface in a zigzag pattern to obtain the mPDMS membrane.

[0130] 3. Preparation of Pebax composite membrane

[0131] 3.1 Dissolve 0.5 g of Pebax ® 1657 particles were dissolved in a mixed solution of 30 mL of deionized water and 70 mL of ethanol, and stirred at 70 °C for 5 h to obtain a homogeneous solution C (Pebax mass-volume concentration of 5 mg / mL).

[0132] 3.2 Dilute solution C with a mixture of ethanol / water (v / v=7 / 3) to a Pebax mass-volume concentration of 3 mg / mL. Take 2.5 mL of casting solution and drop it onto the surface of the mPDMS membrane. Use a 100 μm thick doctor blade to quickly coat the membrane.

[0133] 3.3 After transferring the Pebax membrane obtained in step 3.2 to an 80 °C oven and heating for 4 h to evaporate excess solvent, a Pebax selective layer is formed on the surface of the mPDMS membrane, thus preparing a composite membrane.

[0134] Scanning electron microscope image of the PSF ultrafiltration membrane surface, as shown below Figure 9 As shown in content (a), the surface scanning electron microscope image of the Pebax composite film is as follows: Figure 9 As shown in content (b), the cross-sectional scanning electron microscope is as follows: Figure 9 As shown in content (c), it can be seen from the figure that Pebax is uniformly loaded on the membrane surface, and the total thickness of the Pebax layer and the PDMS layer is 554 nm.

[0135] Figure 10 These are the pure gas fluxes of the Pebax composite membrane prepared in this example: carbon dioxide flux is 432 GPU, propylene flux is 273 GPU, methane flux is 24 GPU, and nitrogen flux is 9 GPU. The propylene / nitrogen selectivity is 30, the carbon dioxide / methane selectivity is 18, and the carbon dioxide / nitrogen selectivity is 48.

[0136] Figure 11 The figure shows the changes in gas flux and propylene / nitrogen selectivity of the Pebax composite membrane prepared in this example after a continuous 80-hour mixed gas test. As can be seen from the figure, changing the test pressure and feed gas composition resulted in a propylene flux of 200 GPU and a propylene / nitrogen selectivity remaining above 20 for the composite membrane.

[0137] Figure 12 This describes the carbon dioxide / methane mixture separation performance of the Pebax composite membrane prepared in this example. The carbon dioxide flux is 366 GPU, the methane flux is 30 GPU, and the carbon dioxide / methane selectivity is 12 (test conditions: carbon dioxide to methane volume ratio of 50:50, test temperature of 25 ℃, and test pressure of 2 bar).

[0138] Table 4

[0139]

[0140] The preparation conditions were the same as those for the Pebax / PDMS / PSF composite membrane in Example 1. The flux and selectivity of the mixed gas were tested under different types of mixed gas at different Pebax mass-volume concentrations, and the results are shown in Table 4.

[0141] As shown in Table 4, the composite membrane prepared according to the method of this embodiment is suitable for various mixed gas systems. For the CO2 / CH4 mixed gas system, when the concentration of Pebax is 3 mg / mL, the selectivity of CO2 / CH4 can reach above 11, and the CO2 flux is 365.8 GPU. For the C3H6 / N2 mixed gas system, when the concentration of Pebax is 3 mg / mL, the selectivity of C3H6 / N2 can reach above 21, and the C3H6 flux is 209.9 GPU.

[0142] Example 2

[0143] Preparation of Pebax composite membrane

[0144] 1. Preparation of PDMS intermediate layer

[0145] 1.1 Weigh 0.05 g of PDMS and add it to 8.95 g of n-heptane. Dissolve and stir thoroughly to obtain solution A.

[0146] 1.2 Add 0.025 g of TEOS and 0.025 g of DBTDL to solution A, and stir at 25 °C for 30 min to obtain solution B.

[0147] 1.3 Take 2.5 mL of solution B (PDMS mass fraction of 0.5 wt%) prepared in step 1.2 above, drop it onto the surface of a commercial ultrafiltration membrane, and quickly coat it with a 100 μm thick doctor blade.

[0148] 1.4 Transfer the PDMS composite membrane obtained in step 1.3 to an 80 ℃ oven and heat for 2 h for later use.

[0149] 2. Preparation of Pebax composite membrane

[0150] 2.1 Dissolve 1.5 g of Pebax1657 granules in 100 mL of n-butanol solution and stir at 125 °C for 5 h to obtain a homogeneous solution C (Pebax mass-volume concentration of 15 mg / mL).

[0151] 2.2 Take 2.5 mL of solution C and drop it onto the surface of the mPDMS membrane. Use a 100 μm thick doctor blade to quickly coat the membrane.

[0152] 2.3 After transferring the Pebax membrane obtained in step 3.2 to an 80 °C oven and heating it for 4 h to evaporate excess solvent, the Pebax composite membrane shown in this invention is obtained.

[0153] In this example, since n-butanol has a good affinity with PDMS, the atmospheric plasma hydrophilic modification step can be omitted.

[0154] The Pebax composite membrane prepared in this example has a carbon dioxide flux of 142 GPU, a nitrogen flux of 2.7 GPU, and a carbon dioxide / nitrogen selectivity of 52.6 (test conditions: pure gas, test temperature of 25 °C, and test pressure of 2 bar).

[0155] Example 3

[0156] Preparation of Pebax composite membrane

[0157] 1. Preparation of PDMS intermediate layer

[0158] 1.1 Weigh 0.05 g of PDMS (molecular weight 90 kDa) and add it to 8.95 g of n-heptane. Dissolve and stir thoroughly to obtain solution A.

[0159] 1.21 Add 0.025 g of TEOS and 0.025 g of DBTDL to solution A, and stir at 25 °C for 10 min to obtain solution B1.

[0160] 1.22 The retention rate of the prepolymer solution B1 on the PSF ultrafiltration membrane (molecular weight cutoff: 63kDa) was tested using the above-mentioned retention rate test method. The retention rate was found to be less than 90%. Therefore, the prepolymer solution was stirred at 25 °C for 20 min to obtain solution B2. The retention rate of the prepolymer solution B2 was tested again and found to be 93.8%, which is greater than 90%.

[0161] 1.3 Take 2.5 mL of solution B2 (PDMS mass fraction of 0.5 wt%) prepared in step 1.22 above, drop it onto the surface of the PSF ultrafiltration membrane, and quickly coat it with a 100 μm thick doctor blade.

[0162] 1.4 Transfer the PDMS membrane obtained in step 1.3 to an 80 ℃ oven and heat for 2 h for later use.

[0163] 2. Preparation of Pebax composite membrane

[0164] 2.1 Dissolve 1.5 g of Pebax1657 granules in 100 mL of n-butanol solution and stir at 125 °C for 5 h to obtain a homogeneous solution C (Pebax mass-volume concentration of 15 mg / mL).

[0165] 2.2 Take 2.5 mL of solution C and drop it onto the surface of the mPDMS membrane. Use a 100 μm thick doctor blade to quickly coat the membrane.

[0166] 2.3 After transferring the Pebax membrane obtained in step 3.2 to an 80 °C oven and heating it for 4 h to evaporate excess solvent, the Pebax composite membrane shown in this invention is obtained.

[0167] This invention employs a bottom-up, layer-by-layer optimization approach to improve the flux of composite membranes. By avoiding pore leakage of PDMS casting solution to prepare a high-flux intermediate layer, it primarily addresses the problem of low gas throughput in current composite membranes used for gas mixture separation. First, a high-flux commercial ultrafiltration membrane is selected as a porous support layer to provide mechanical strength to the composite membrane. The retention rate of the support layer for the PDMS casting solution is directly tested. Subsequent support layer coating and selective layer preparation are only performed when the retention rate is greater than 90%. Otherwise, the PDMS continues to be prepolymerized. This ensures that the PDMS can be retained on the support layer surface by the substrate, avoiding pore leakage and thus improving the flux of the final composite membrane when separating mixed gases. Different support layers and different initial PDMS molecular weights can be applied according to the method of this invention. By controlling the degree of prepolymerization and the retention rate, high-flux and high-selectivity gas separation can be achieved.

[0168] This invention achieves the successful preparation of an ultrathin, high-throughput PDMS interlayer. Experiments show that by controlling the retention rate of the prepolymer solution on the support layer surface, PDMS can be effectively retained on the surface by the support layer, avoiding pore seepage. In a preferred embodiment, the thickness of the obtained PDMS interlayer is approximately 300 nm, with carbon dioxide and propylene pure gas fluxes of 9471 GPUs and 20785 GPUs, respectively. After obtaining the high-throughput PDMS interlayer, to improve the affinity between the interlayer and the selective layer, atmospheric plasma treatment with large-area processing capability is used to hydrophilically modify the PDMS, providing feasibility for large-scale industrial production. Subsequently, by optimizing parameters such as the solvent and concentration of the Pebax casting solution, a high-throughput Pebax composite membrane was successfully prepared using a blade coating method.

[0169] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for preparing a high-throughput composite membrane for efficient separation of gas mixtures, characterized in that, Includes the following steps: (1) Dissolve the initially hydroxyl-terminated polydimethylsiloxane, crosslinking agent and catalyst in a first solvent, mix and stir to allow the initially hydroxyl-terminated polydimethylsiloxane to undergo a prepolymerization reaction to obtain PDMS casting solution; (2) Using the porous ultrafiltration membrane as the suction filtration membrane of the dead-end filtration system, the retention rate of the porous ultrafiltration membrane for the PDMS casting solution in step (1) was tested. (3) If the retention rate measured in step (2) is greater than or equal to 90%, proceed to step (4); otherwise, increase the prepolymerization degree of the PDMS casting solution in step (1) or increase the molecular weight of the initially hydroxyl-terminated polydimethylsiloxane so that the retention rate of the casting solution measured in step (2) is greater than or equal to 90%; (4) Transfer the PDMS casting solution with a retention rate greater than or equal to 90% to the surface of the support layer ultrafiltration membrane, scrape it and dry it to remove excess first solvent to obtain a PDMS membrane; the support layer ultrafiltration membrane and the porous ultrafiltration membrane in step (2) are the same type of ultrafiltration membrane; (5) Dissolve the polyether block polyamide in the second solvent to obtain the Pebax casting solution; transfer the Pebax casting solution to the surface of the PDMS membrane, coat it and dry it to remove excess second solvent, and obtain the Pebax selective layer on the surface of the PDMS membrane, thus obtaining the high-throughput composite membrane.

2. The preparation method according to claim 1, characterized in that, Step (2) The porous ultrafiltration membrane is used as the filtration membrane of the dead-end filtration system. The PDMS concentration in the initial PDMS casting solution and the permeate-side PDMS casting solution before and after filtration is analyzed by nuclear magnetic resonance hydrogen spectroscopy to calculate the rejection rate.

3. The preparation method according to claim 2, characterized in that, The concentration of PDMS in the test solution is calculated using the area normalization method based on the characteristic hydrogen atom peak areas in the PDMS in the test solution and the first solvent. The test solution includes the initial PDMS casting solution and the permeation-side PDMS casting solution. The formula for calculating the concentration of PDMS in the test solution is shown in equation (1). In the formula: c i The concentration of PDMS in the test solution is wt%; A i and A k These represent the characteristic hydrogen atom peak areas of PDMS and the first solvent in the test solution, respectively. n i and n k m represents the number of characteristic hydrogen atoms in PDMS and the first solvent in the test solution, respectively; i and m k These represent the relative molecular weights of PDMS and the first solvent in the test solution, respectively.

4. The preparation method according to claim 1, characterized in that, The first solvent is n-heptane and / or n-hexane, and the concentration of PDMS in the PDMS casting solution is 0.2 wt%-3 wt%; and / or, The mixing and stirring described in step (1) is carried out at 25-35℃ for 20 min-240 min.

5. The preparation method according to claim 1, characterized in that, Step (3) Increase the prepolymerization degree of the PDMS casting solution in step (1) so that the retention rate of the casting solution obtained after the prepolymerization reaction measured in step (2) is greater than or equal to 90%. Specifically, increase the prepolymerization degree by extending the time of the prepolymerization reaction in step (1) so that the retention rate of the casting solution is greater than or equal to 90%.

6. The preparation method according to claim 1, characterized in that, The crosslinking agent is tetraethyl orthosilicate; the catalyst is dibutyltin dilaurate; and / or... The porous ultrafiltration membrane in step (2) and the support layer ultrafiltration membrane in step (4) are PSF, PAN or PVDF.

7. The preparation method according to claim 1, characterized in that, The drying in step (4) is performed by heating at 60-80 °C for 0.5-4 h; and / or, In step (5), the second solvent is a mixture of ethanol and water or n-butanol; and / or, The concentration of Pebax in the Pebax casting solution described in step (5) is 1 mg / mL to 20 mg / mL; and / or, The drying process in step (5) involves heating at 60-80 ℃ for 4-12 h.

8. The preparation method according to claim 1, characterized in that, After obtaining the PDMS membrane in step (4), the method further includes the step of using an atmospheric plasma cleaner to perform hydrophilic modification on the surface of the PDMS membrane to obtain a hydrophilic modified PDMS membrane.

9. The high-throughput composite membrane prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the high-throughput composite membrane as described in claim 9 in the separation of gas mixtures.

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