A method for preparing cau-10-h membranes for gas separation by aluminum sulfate modification on macroporous tubular supports

Abstract

The application belongs to the technical field of membrane separation, and discloses a method for preparing CAU-10-H membranes for gas separation by modifying a macroporous tubular carrier with aluminum sulfate, in particular to the following steps: firstly, preparing a proper aluminum sulfate solution, then introducing the aluminum sulfate solution into the carrier by means of hot dipping, and then calcining the carrier with the introduced solution by programmed temperature rising, so that the smoothness of the surface of the modified carrier is significantly improved; and due to the introduction of aluminum sulfate on the surface of the carrier, the aluminum-based CAU-10-H membrane can be crystallized into a film on the macroporous micron-sized carrier. The dense CAU-10-H membrane prepared on the macroporous carrier by the method of modifying the carrier with aluminum sulfate has good separation performance for H2 / CO2 gas.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of membrane separation technology, and relates to a technology for successfully preparing a CAU-10-H metal organic framework film for gas separation by modifying a macroporous tubular Al2O3 carrier with aluminum sulfate, in particular to a method for preparing an aluminum sulfate-induced layer on a tubular macroporous alumina carrier and then inducing aluminum-based MOF film formation. BACKGROUND

[0002] Membrane separation technology uses a selective permeation membrane to separate a mixture according to the permeation rates of the components of the mixture under the driving force of a pressure or temperature gradient, and is a potential new separation technology with the advantages of low energy consumption, no secondary pollution, small occupied area, high separation efficiency and the like, and has been widely applied in the field of gas separation or liquid separation.

[0003] Metal-organic framework (MOFs) material is a kind of crystalline material with a regular pore channel and a periodic network structure, which is self-assembled by inorganic metal ions or metal oxide clusters (secondary structural units) and monodentate or polydentate organic ligands rich in multifunctional groups through coordination bonds, and has the advantages of adjustable pore channel size and shape, large specific surface area and easy functionalization of the pore channel.

[0004] The CAU-10-H series of metal organic framework materials were first discovered by Norbert Stock et al. They synthesized the CAU (Christian Albrechts University) series of aluminum-based MOF materials using a simple and universal solvothermal method and systematically studied the reaction system. The preparation method is simple, the structure is stable, and the functionality makes it have potential application value in multiple fields. At present, there are few studies on CAU-10-H membranes for gas separation, and most of them are mixed matrix membranes. Compared with the preparation of polycrystalline MOF membranes, the preparation of mixed matrix membranes is relatively low, and the polycrystalline MOF membrane layer is thinner and the entire membrane layer has a separation effect. When used for gas separation, it can have higher permeation flux and separation factor. At the same time, unlike MOF membranes such as ZIF-8, the preparation of CAU-10-H polycrystalline membranes is more difficult. At present, the carriers used to prepare the polycrystalline CAU-10-H membrane material reported are mostly flaky carriers or tubular carriers with small surface defects and relatively flat surfaces. For example, Zhao et al. in the paper titled Induced Synthesis of an Al-Based CAU-10Tubular Membrane for the Highly Efficient Separation of MeOH / MTBE by Pervaporation (Industrial & Engineering Chemistry Research, 2023, 62(44): 18694-18703.) used γ-Al2O3 to induce the preparation of a CAU-10-H membrane on a carrier with a surface defect of only 200 nm for separating MeOH / MTBE, but it did not mention its gas separation performance. Gas separation membranes have higher quality requirements for the membrane itself than liquid separation membranes, so it is difficult to directly apply these preparation methods to the preparation of CAU-10-H membranes on the surface of macroporous tubular carriers. Therefore, in order to prepare a continuous, dense, flat and defect-free CAU-10-H membrane on the surface of a macroporous tubular carrier, the homologous metal induction method needs to be improved.

[0005] To this end, the present application proposes a method for modifying the surface of a macroporous tubular alumina carrier with aluminum sulfate, which realizes the preparation of a continuous, dense and flat CAU-10-H membrane on the surface of a cheap macroporous tubular carrier. SUMMARY

[0006] The purpose of the present application is to provide a method for modifying a tubular macroporous carrier with aluminum sulfate, thereby preparing a CAU-10-H membrane for gas separation on a tubular macroporous alumina carrier.

[0007] The application relates to the following application concept: the application uses a cheap micrometer-sized carrier with large holes and no separation performance, which is low in price and has many defects. The synthesis conditions of the CAU-10-H film on the tubular carrier are harsh, and it is difficult to form the film on the micrometer-sized large-hole carrier without any treatment on the carrier, so the aluminum sulfate solution is introduced to the carrier to effectively modify the micrometer-sized large-hole defects on the surface of the carrier, and the growth of the CAU-10-H film layer is provided with an aluminum source, which is beneficial to the heterogeneous nucleation of the CAU-10-H crystal and the close combination of the film layer and the carrier, so that the CAU-10-H film can be crystallized and formed on the micrometer-sized large-hole carrier.

[0008] The technical scheme of the application is as follows:

[0009] A method for preparing a CAU-10-H film for gas separation on a large-hole tubular carrier by means of aluminum sulfate modification, and the steps are as follows:

[0010] (1) configuring an aluminum sulfate solution

[0011] Aluminum sulfate octadecahydrate is dissolved in deionized water, and after being fully stirred, ultrasonic is used to make it dissolve and disperse uniformly;

[0012] (2) hot dip coating of the aluminum sulfate solution

[0013] A polytetrafluoroethylene cylindrical plug matched with the size of the carrier tube port is selected, the surface of the plug is wound with a polytetrafluoroethylene raw material belt, and then the plug is pressed into the two ends of the carrier tube to ensure the airtightness of the carrier tube; the sealed carrier tube is preheated under constant temperature conditions; hot dip coating is carried out: the carrier tube is vertically and uniformly fully immersed in the aluminum sulfate solution from above the aluminum sulfate solution, the longitudinal axis of the carrier tube is kept perpendicular to the liquid surface of the aluminum sulfate solution, and after the immersion is completed, the carrier tube is slowly taken out to ensure that a uniform liquid film is formed on the surface of the wall of the carrier tube; the above operation is repeated to perform gradient coating; through the preheating treatment, residual water and adsorbents in the pores of the tubular carrier can be removed, so that the combination of the aluminum sulfate and the surface of the carrier becomes easy. At the same time, since the alumina carrier has a certain water absorption, the preheated carrier is placed in the solution at room temperature, the carrier quickly absorbs water, the concentration of the aluminum sulfate near the carrier tube slowly increases, so that more aluminum sulfate is loaded on the carrier, and the surface defects of the tubular carrier are better modified.

[0014] (3) calcination and solidification

[0015] The coated carrier tube is placed on an iron stand to ensure that the tube body is vertical and is placed in the center of a muffle furnace; a program-controlled temperature curve is set: in the first stage, the temperature is raised from room temperature to 400 DEG C at a rate of 1 DEG C / min, in the second stage, the temperature is kept constant for 300 min for dehydration treatment, in the third stage, the temperature is lowered to below 100 DEG C at a rate of 1 DEG C / min, and then the heating system is turned off for natural cooling.

[0016] (4) Preparation of CAU-10-H membrane

[0017] CAU-10-H membranes were prepared using a solvothermal method. The carrier tube with the introduced homologous metal induction layer was sealed at both ends with PTFE stoppers and placed in a PTFE-lined reactor. The synthesis solution was added, and the reactor was sealed again and reacted at 120°C for 8 hours. The composition of the synthesis solution was: metal source to organic ligand molar ratio Al... 3+ The ratio of DMF to H2O is 1:4, with a solvent volume ratio of C8H6O4 = 1:1; using Al 3+ The concentration meter showed that the concentration of the synthesis solution was 0.18 mol / L. After the reaction was completed, the solution was naturally cooled to room temperature. After being removed, it was soaked and cleaned with deionized water and anhydrous methanol for three days, with the solvent being changed twice during each period. It was then vacuum dried overnight at 80°C. After being fully dried, it was placed in a desiccator for single-component gas permeation testing.

[0018] The ultrasonic treatment conditions in step (1) include: ultrasonic frequency 20-40kHz, treatment time 20-40min, and treatment temperature maintained at 20-40℃; the mass fraction of aluminum sulfate in the impregnation solution is controlled within the range of 0.5%-2%.

[0019] During the sealing process in step (2), it is necessary to ensure that the plug is fully embedded in the port to a depth of more than 3mm to ensure that the plug will not fall off during the immersion process.

[0020] The sealing process in step (2) specifically includes: using a polytetrafluoroethylene sealing plug in conjunction with raw material tape for double-end sealing, with a sealing depth ≥3mm; the preheating temperature is 100-200℃, and the duration is 1.5-2.5h; the hot impregnation parameters include: impregnation time 10-30s, impregnation liquid temperature maintained at 15-30℃; and gradient coating times 2-4 times.

[0021] The CAU-10-H membrane obtained in step (4) was subjected to a single-component gas permeation test using a gas permeation testing device to evaluate the compactness and gas separation performance of the prepared CAU-10-H membrane. The specific operation was as follows: The membrane was sealed in a tubular membrane module using an O-ring. One end of the membrane was sealed, and the other end was connected to a soap bubble tube. The feed side pressure was controlled at 0.1 MPa using a back pressure valve. The permeate side was connected to the soap bubble tube and then allowed to circulate with the atmosphere. The time taken for a certain volume of gas to pass through the membrane was obtained using a stopwatch and a soap bubble flow meter. All tests were conducted at room temperature.

[0022] The gas permeation rate is represented by P, and the unit is mol / (m²). 2• s • Pa), which is defined as the number of moles of gas per unit membrane area per unit time per unit transmembrane pressure, and the ideal gas selectivity is denoted by a, which is defined as the ratio of the permeation rates of two different gases:

[0023]

[0024] Advantages of the present application:

[0025] (1) The present application successfully prepared a dense CAU-10-H membrane on a macroporous alumina support tube. The CAU-10-H polycrystalline membrane reported in the literature uses a flat support with fewer defects, usually less than 200 nm, while the present application is suitable for a larger defect tube support, which is low in price. The method of preparing an induced layer by aluminum sulfate can make the induced layer thinner and the binding force stronger, improve the continuity of the prepared membrane and shorten the time required for the crystallization step.

[0026] (2) The surface of the macroporous support is modified by aluminum sulfate, which not only fills the defects of the rough surface of the macroporous support, but also plays an inducing role, strengthens the binding force of the support surface to the membrane layer, and at the same time reduces the membrane formation inside the support, retains the developed gas transmission channels inside the macroporous support, and the obtained CAU-10-H membrane has a high gas permeation rate, while maintaining good H2 / CO2 ideal selectivity. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Scanning electron microscope (SEM) image of the surface of the homologous metal induced layer prepared in Example 1;

[0028] Figure 2 Scanning electron microscope (SEM) image of the surface of the homologous metal induced layer prepared in Example 3;

[0029] Figure 3 Scanning electron microscope (SEM) image of the empty support tube;

[0030] Figure 4 Scanning electron microscope (SEM) image of the CAU-10-H membrane synthesized in Example 1, (a) surface, (b) cross section;

[0031] Figure 5 Scanning electron microscope (SEM) image of the CAU-10-H membrane synthesized in Example 3, (a) surface, (b) cross section;

[0032] Figure 6 X-ray diffraction (XRD) pattern of the CAU-10-H membrane synthesized in Example 1 and Example 3;

[0033] Figure 7Figure is the gas separation performance test diagram of the prepared CAU-10-H membrane, (a) ideal selectivity, (b) permeation rate. DETAILED DESCRIPTION

[0034] The specific embodiments of the present application are further described below in conjunction with the accompanying drawings and technical solutions.

[0035] Example 1

[0036] (1) Carrier pretreatment

[0037] The outer diameter of the tube is 12 mm, the inner diameter of the tube is 8 mm, the average pore size is greater than 1 μm, and the porosity is about 30-40%. The carrier pretreatment is divided into the following steps: first, polish the outer surface of the carrier tube with 800 mesh, 1500 mesh, and 3000 mesh sandpaper in turn, cut it into a short tube of 5 cm; second, ultrasonic cleaning with deionized water, ultrasonic cleaning with 1 mol / L HCl solution, ultrasonic cleaning with deionized water to neutral, ultrasonic cleaning with 1 mol / L NaOH solution, and ultrasonic cleaning with deionized water to neutral, each time for 30 min, and the cleaned carrier tube is placed in an oven at 80℃ for drying overnight; third, calcination at 550℃ for 360 min, the heating and cooling rates are both 1℃ / min, and the calcined tube is stored in a desiccator at room temperature for subsequent use.

[0038] (2) Preparation of homologous metal-induced layer

[0039] (2.1) Preparation of aluminum sulfate solution

[0040] Take 2.5 g of aluminum sulfate octadecahydrate, add 49.93 g of deionized water, stir thoroughly for 10 min, then transfer to an ultrasonic cleaner and ultrasonic for 30 min to dissolve and disperse uniformly to obtain a 0.5% aluminum sulfate aqueous solution.

[0041] (2.2) Hot dip coating of aluminum sulfate solution

[0042] First, select a polytetrafluoroethylene cylindrical plug that matches the size of the carrier tube port and wrap the surface with a polytetrafluoroethylene raw material belt, press the plug into the carrier tube at both ends to ensure the airtightness of the carrier tube, and ensure that the plug is embedded in the port for more than 3 mm in depth during the sealing process to ensure that the plug will not fall off during the dipping process. Transfer the sealed carrier tube to an electric heating drying oven at 100℃ for preheating, maintain the constant temperature state for uniform preheating for 2 hours. After preheating, use a high-temperature resistant tweezers to vertically transfer the carrier tube to the top of the open container containing the 0.5% aluminum sulfate solution, uniformly immerse the preheated carrier tube completely below the solution surface, ensure that the longitudinal axis of the carrier tube is perpendicular to the liquid surface, and slowly lift the carrier tube after the dipping is completed to ensure that a uniform liquid film is formed on the surface of the tube wall. Repeat the above operation for a total of two times.

[0043] (2.3) Calcination to prepare homologous metal-induced layer

[0044] Put the finished coated support tube on the iron stand, make sure the tube is vertical, and place it in the center of the muffle furnace. Set the program temperature curve: the first stage is to rise from room temperature to 400°C target temperature at a rate of 1°C / min, the second stage is to dehydrate for 300 min at constant temperature; the third stage is to decrease to below 100°C at a rate of 1°C / min, and then turn off the heating system and cool naturally.

[0045] (3) Preparation of CAU-10-H membrane

[0046] The CAU-10-H membrane was prepared by solvothermal method. The ends of the support tube with the homologous metal-induced layer were sealed with polytetrafluoroethylene plugs, placed in the polytetrafluoroethylene reactor liner, and sealed after adding the synthesis solution. The reaction was carried out at 120°C for 8h. The composition of the synthesis solution was: molar ratio of metal source to organic ligand Al 3+ : C8H6O4 = 1:1, volume ratio of solvent DMF:H2O = 1:4; the concentration of the synthesis solution was 0.18 mol / L (calculated by Al 3+ After the reaction was completed, it was naturally cooled to room temperature. After taking out, it was soaked and cleaned with deionized water and anhydrous methanol reagent for three days, during which the solvents were replaced twice. It was vacuum dried at 80°C overnight, and then placed in a desiccator for single-component gas permeation test after sufficient drying.

[0047] Example 2

[0048] (1) Support pretreatment

[0049] The outer diameter of the tube is 12mm, the inner diameter is 8mm, the average pore size is greater than 1μm, and the porosity is about 30-40%. The support pretreatment is divided into the following steps: first, polish the outer surface of the support tube with 800 mesh, 1500 mesh, and 3000 mesh sandpaper in turn, and cut it into 5cm short tubes; second, ultrasonic cleaning with deionized water, 1mol / L HCl solution, deionized water to neutral, 1mol / L NaOH solution, and deionized water to neutral, each for 30min. The cleaned support tube was placed in an 80°C oven for drying overnight; third, calcination at 550°C for 360min, with a heating rate of 1°C / min, and then stored in a desiccator at room temperature after calcination, waiting for subsequent use.

[0050] (2) Preparation of homologous metal-induced layer

[0051] (2.1) Preparation of aluminum sulfate solution

[0052] Take 10 g of aluminum sulfate octadecahydrate, add 49.73 g of deionized water, stir thoroughly for 10 min, then transfer to an ultrasonic cleaner and ultrasonic for 30 min to dissolve and disperse evenly, obtaining a 2% aluminum sulfate aqueous solution.

[0053] (2.2) Hot dipping of aluminum sulfate solution

[0054] First, select a polytetrafluoroethylene cylindrical plug that matches the size of the carrier tube port and wrap the surface with a polytetrafluoroethylene raw material belt. Press the plug into the carrier tube at both ends to ensure the airtightness of the carrier tube. During the sealing process, ensure that the plug is fully embedded in the port for more than 3 mm in depth to ensure that the plug does not fall off during the dipping process. After sealing, transfer the carrier tube to an electric heating drying oven at 180°C for preheating. Maintain the constant temperature for uniform preheating treatment for 2 hours. After preheating, use a high-temperature resistant tweezers to vertically transfer the carrier tube to the top of the open container containing the 0.5% aluminum sulfate solution. Uniformly immerse the preheated carrier tube completely below the solution surface, ensuring that the longitudinal axis of the carrier tube is perpendicular to the liquid surface. Slowly pull out the carrier tube after dipping to ensure that a uniform liquid film forms on the surface of the tube wall. Repeat the above operation for a total of two times.

[0055] (2.3) Calcination to prepare homologous metal-induced layer

[0056] Place the coated carrier tube on an iron stand, ensuring that the tube is vertical and placed in the center of the muffle furnace. Set the program temperature curve: the first stage increases from room temperature to 400°C at a rate of 1°C / min, the second stage maintains a constant temperature for 300 min for dehydration treatment; the third stage decreases to below 100°C at a rate of 1°C / min, then the heating system is turned off and the system is naturally cooled.

[0057] (3) Preparation of CAU-10-H membrane

[0058] CAU-10-H membrane was prepared by solvothermal method. The carrier tube with homologous metal-induced layer was sealed at both ends with polytetrafluoroethylene plugs and placed in the inner liner of a polytetrafluoroethylene reactor. After adding the synthesis solution, seal it and react at 120°C for 8h. The composition of the synthesis solution is: molar ratio of metal source to organic ligand Al 3+ : C8H6O4 = 1:1, volume ratio of solvent DMF:H2O = 1:4; the concentration of the synthesis solution is 0.18 mol / L (calculated by Al 3+ concentration). After the reaction is completed, it is naturally cooled to room temperature. After taking out, it is soaked and cleaned with deionized water and anhydrous methanol reagent for three days, during which the solvents are replaced twice. Vacuum drying at 80°C overnight, then put it in a desiccator for single-component gas permeation test.

[0059] Example 3

[0060] (1) Carrier pretreatment

[0061] The tube outer diameter is 12 mm, the tube inner diameter is 8 mm, the average pore size is greater than 1 pm, and the porosity is about 30-40%. The carrier pretreatment is divided into the following steps: first, polish the outer surface of the carrier tube with 800 mesh, 1500 mesh, and 3000 mesh sandpaper in turn, cut it into a short tube of 5 cm; second, ultrasonic cleaning with deionized water, ultrasonic cleaning with 1 mol / L HCl solution, ultrasonic cleaning with deionized water to neutral, ultrasonic cleaning with 1 mol / L NaOH solution, and ultrasonic cleaning with deionized water to neutral, each time for 30 min, and the cleaned carrier tube is placed in an 80°C oven to dry overnight; third, calcination at 550°C for 360 min, the heating and cooling rates are both 1°C / min, after calcination, store it in a desiccator at room temperature for subsequent use.

[0062] (2) Preparation of homologous metal-induced layer

[0063] (2.1) Preparation of aluminum sulfate solution

[0064] Weigh 5g of aluminum sulfate octadecahydrate, add 49.86g of deionized water, stir thoroughly for 10min, then transfer to an ultrasonic cleaner and ultrasonic for 30min to dissolve and disperse uniformly to obtain a 1% aluminum sulfate aqueous solution.

[0065] (2.2) Hot dip coating of aluminum sulfate solution

[0066] First, select a polytetrafluoroethylene cylindrical plug that matches the size of the carrier tube port and wrap the surface with a polytetrafluoroethylene raw material belt. Press the plug into the carrier tube at both ends to ensure the airtightness of the carrier tube. During the sealing process, ensure that the plug is fully embedded in the port for more than 3mm in depth to ensure that the plug does not fall off during the dipping process. Transfer the sealed carrier tube to a constant temperature 180°C electric heating drying box for preheating, maintain constant temperature for uniform preheating for 2 hours. After preheating, use a high-temperature resistant tweezers to vertically transfer the carrier tube to the top of the open container containing the 0.5% aluminum sulfate solution, uniformly immerse the preheated carrier tube completely below the solution surface, ensure that the longitudinal axis of the carrier tube is perpendicular to the liquid surface, slowly lift the carrier tube after dipping to ensure that a uniform liquid film is formed on the wall surface. Repeat the above operation for a total of two times.

[0067] (2.3) Calcination to prepare homologous metal-induced layer

[0068] Place the coated carrier tube on the iron stand, ensure that the tube is vertical, and place it in the center of the muffle furnace. Set the program temperature curve: the first stage is to increase the temperature from room temperature to 400°C at a rate of 1°C / min, the second stage is to maintain a constant temperature for 300min for dehydration treatment; the third stage is to decrease the temperature to below 100°C at a rate of 1°C / min, then turn off the heating system and cool naturally.

[0069] (3) Preparation of CAU-10-H membrane

[0070] The CAU-10-H membrane was prepared by a solvothermal method. The carrier tube with the induced layer of homologous metal was sealed at both ends with polytetrafluoroethylene plugs, placed in a polytetrafluoroethylene reactor liner, and then sealed after adding the synthesis solution. The reaction was carried out at 120°C for 8h. The composition of the synthesis solution was: molar ratio of metal source to organic ligand Al 3+ : C8H6O4 = 1:1, volume ratio of solvent DMF:H2O = 1:4; the concentration of the synthesis solution was 0.18 mol / L (calculated by Al 3+ After the reaction was completed, it was naturally cooled to room temperature, and then removed and soaked in deionized water and anhydrous methanol reagent for three days, respectively. During this period, the solvents were replaced twice. The sample was vacuum dried at 80°C overnight, and then placed in a desiccator for single-component gas permeation test after being fully dried.

[0071] (4) Single-component gas permeation test

[0072] The gas permeation test device was used to evaluate the compactness and gas separation performance of the prepared CAU-10-H membrane. The specific operation was as follows: the membrane was sealed in the tubular membrane assembly using an O-shaped rubber ring, one end of the membrane was sealed, and the other end was connected to a soap bubble tube. The raw material side pressure was controlled by a back pressure valve, and the pressure was controlled at 0.1 MPa. The permeation side was connected to the soap bubble tube and communicated with the atmosphere. The time taken by a certain volume of gas passing through the membrane was obtained by using a stopwatch and a soap bubble flowmeter. The test was carried out at room temperature.

[0073] The test results of the CAU-10-H membrane prepared by homologous metal induction are shown in Table 1. Figure 7 The H2 flux of 1.09 x 10 -7 mol·m -2 ·s -1 ·pa -1 The ideal selectivity of H2 / CO2, H2 / N2, and H2 / CH4 reached 31.66, 4.17, and 3.80, respectively, all of which were greater than the Knudsen diffusion selectivity (4.7, 3.7, and 2.8), proving that the obtained CAU-10-H membrane had no intergranular defects and the method was feasible. The ideal selectivity of H2 / CO2 reached 31.66, indicating that the membrane obtained by this method had a certain separation ability for gases. The lowest permeation rate of CO2 was because the cis-linked AlO6 polyhedron in the CAU-10-H framework and the defect sites in the structure and the interbenzene dicarboxylic acid ligand linked thereto had a strong adsorption effect on CO2, resulting in a reduced diffusion rate.

Claims

1. A method for preparing a CAU-10-H membrane for gas separation on a macroporous tubular support modified with aluminum sulfate, characterized in that, The steps are as follows: (1) Prepare aluminum sulfate solution; Dissolve aluminum sulfate octahydrate in deionized water, stir thoroughly, and then sonicate to dissolve and disperse it completely and evenly. (2) Hot dipping coating with aluminum sulfate solution The carrier tube is sealed at both ends; the sealed carrier tube is preheated under constant temperature conditions; hot dip coating is performed: the carrier tube is vertically and uniformly immersed completely below the surface of the aluminum sulfate solution from above, ensuring that the longitudinal axis of the carrier tube is perpendicular to the surface of the aluminum sulfate solution. After the dip coating is completed, the carrier tube is slowly pulled out to ensure that a uniform liquid film is formed on the surface of the carrier tube wall. Repeat the hot dip coating process to perform gradient coating; (3) Calcination and solidification The coated carrier tube is placed vertically in the center of a muffle furnace for calcination. The calcination process includes three stages: gradient heating, isothermal dehydration, and gradient cooling. (4) Preparation of CAU-10-H membrane CAU-10-H membranes were prepared using a solvothermal method. The carrier tube with the introduced homologous metal induction layer was sealed at both ends with PTFE stoppers and placed in a PTFE-lined reactor. The synthesis solution was added, and the reactor was sealed again and reacted at 120°C for 8 h. The composition of the synthesis solution was: metal source to organic ligand molar ratio Al... 3+ The ratio of DMF to H2O is 1:1 (C8H6O4 = 1:1), and the solvent volume ratio is 1:4 (DMF:H2O = 1:4). Using Al... 3+ The concentration of the synthesis solution was 0.18 mol / L. After the reaction was completed, the solution was naturally cooled to room temperature. After removal, it was soaked and washed with deionized water and anhydrous methanol for three days, with the solvent changed twice during the period. It was then vacuum dried at 80℃ overnight to obtain the CAU-10-H membrane.

2. The method for preparing a CAU-10-H membrane for gas separation by modifying a macroporous tubular support with aluminum sulfate according to claim 1, characterized in that, The ultrasonic treatment conditions in step (1) include: ultrasonic frequency 20-40 kHz, treatment time 20-40 min, and treatment temperature maintained at 20-40℃.

3. The method for preparing a CAU-10-H membrane for gas separation by modifying a macroporous tubular support with aluminum sulfate according to claim 1, characterized in that, In step (1), the mass fraction of aluminum sulfate solution is controlled within the range of 0.5%-2%.

4. The method for preparing a CAU-10-H membrane for gas separation by modifying a macroporous tubular support with aluminum sulfate according to claim 1, characterized in that, The sealing treatment at both ends of the carrier tube in step (2) specifically includes: using polytetrafluoroethylene sealing plugs in conjunction with raw material tape to seal both ends, with a sealing depth ≥3 mm.

5. The method for preparing a CAU-10-H membrane for gas separation by modifying a macroporous tubular support with aluminum sulfate according to claim 1, characterized in that, In step (2), the preheating temperature is 100-200℃ and the duration is 1.5-2.5h.

6. The method for preparing a CAU-10-H membrane for gas separation by modifying a macroporous tubular support with aluminum sulfate according to claim 1, characterized in that, The hot immersion coating parameters in step (2) include: immersion time 10-30 s, immersion liquid temperature maintained at 15-30℃; and gradient coating number of 2-4 times.

7. The method for preparing a CAU-10-H membrane for gas separation by modifying a macroporous tubular support with aluminum sulfate according to claim 1, characterized in that, In step (3), the calcination process is set with a temperature control curve: in the first stage, the temperature is raised from room temperature to the target temperature of 400℃ at a rate of 1℃ / min; in the second stage, the temperature is kept constant for 300 min for dehydration treatment; in the third stage, the temperature is lowered to below 100℃ at a rate of 1℃ / min, and then the heating system is turned off for natural cooling.

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