Method for preparing CAU-10-H membrane for gas separation by modifying macroporous tubular carrier with aluminum sulfate

Abstract

The invention belongs to the technical field of membrane separation, and discloses a method for preparing a CAU-10-H membrane for gas separation by modifying a macroporous tubular carrier with aluminum sulfate, and the method specifically comprises the following steps: firstly, preparing a proper aluminum sulfate solution, then introducing the aluminum sulfate solution onto the carrier in a hot dipping manner, and finally preparing the CAU-10-H membrane for gas separation. Then calcining the carrier introduced with the solution through temperature programming, so that the surface smoothness of the modified carrier is obviously improved; and due to the introduction of aluminum sulfate on the surface of the carrier, the aluminum-based CAU-10-H film can be crystallized on the macroporous micron-sized carrier to form a film. The compact CAU-10-H membrane prepared on the macroporous carrier by a method of modifying the carrier by aluminum sulfate has better separation performance on H2 / CO2 gas.

Description

Technical Field

[0001] The present invention belongs to the technical field of membrane separation, and relates to a technology for modifying a macroporous tubular Al 2 O 3 support to successfully prepare a CAU-10-H metal-organic framework thin film for gas separation. Specifically, it is a method for preparing an aluminum sulfate-induced layer on a tubular macroporous alumina support and then inducing the formation of an aluminum-based MOF film. Background Art

[0002] Membrane separation technology uses a selective permeable membrane. Under the driving force of pressure or temperature gradient, according to the different permeation rates of each component of the mixture, the separation purpose can be achieved. It is a potential new separation technology with the advantages of low energy consumption, no secondary pollution, small floor area, high separation efficiency, etc., and has been widely used in the fields of gas separation or liquid separation.

[0003] Metal-Organic Frameworks (MOFs) materials are a class of crystalline materials formed by the self-assembly of inorganic metal ions or metal-oxygen clusters (secondary structure units) and monodentate or polydentate organic ligands rich in multifunctional groups through coordination bonds, and have the advantages of adjustable pore size and shape, large specific surface area, and easy functionalization of pores.

[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 common solvothermal method and systematically studied the reaction system. Its preparation method is simple, and its structural stability and functionality have shown potential application value in multiple fields. Currently, there is little research on CAU-10-H membranes for gas separation, and most of them are mixed matrix membranes. The preparation of mixed matrix membranes is less difficult than that of polycrystalline MOF membranes. The polycrystalline MOF membrane has a thinner film layer and the entire film layer has a separation effect, and it can have a higher permeation flux and separation factor when used for gas separation. At the same time, different from MOF membranes such as ZIF-8, the preparation of polycrystalline CAU-10-H membranes is more difficult. The carriers used in the reported polycrystalline CAU-10-H membrane materials are mostly sheet carriers or tubular carriers with smaller surface defects and relatively flat surfaces. For example, Zhao et al. in the paper titled "Induced Synthesis of an Al-Based CAU-10 Tubular Membrane for the Highly Efficient Separation of MeOH / MTBE by Pervaporation (Industrial & Engineering Chemistry Research, 2023, 62(44): 18694-18703.)" used γ-Al 2 O 3 to induce the preparation of a membrane for separating MeOH / MTBE on a carrier with a surface defect of only 200 nm, but its gas separation performance was not mentioned. The gas separation membrane has higher quality requirements for the membrane itself than the liquid separation membrane. Therefore, it is somewhat 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 macroporous tubular carriers, it is necessary to improve the homologous metal induction method.

[0005] For this reason, the present invention proposes a method for modifying the surface of a macroporous tubular alumina carrier with aluminum sulfate, realizing the preparation of a continuous, dense and flat CAU-10-H membrane on the surface of an inexpensive macroporous tubular carrier. Summary of the Invention

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

[0007] Inventive concept involved in the present invention: The present invention uses a cheap micron-sized carrier with large pores and no separation performance. Although it has many defects, its price is lower. The synthesis conditions of the CAU-10-H membrane on the tubular carrier are relatively harsh. It is difficult to form a film on the micron-sized macroporous carrier without any treatment of the carrier. Therefore, an aluminum sulfate solution is introduced onto the carrier to effectively modify the micron-sized macroporous defects on the carrier surface, and it also provides an aluminum source for the growth of the CAU-10-H membrane layer, which is beneficial to the heterogeneous nucleation of CAU-10-H crystals and the tight binding between the membrane layer and the carrier, enabling the CAU-10-H membrane to crystallize and form a film on the macroporous micron-sized carrier.

[0008] Technical solution of the present invention:

[0009] A method for preparing a CAU-10-H membrane for gas separation on a macroporous tubular carrier by aluminum sulfate modification, the steps are as follows:

[0010] (1) Prepare an aluminum sulfate solution

[0011] Dissolve aluminum sulfate octadecahydrate in deionized water, stir well and then ultrasonically dissolve and disperse it thoroughly;

[0012] (2) Thermally dip-coat the aluminum sulfate solution

[0013] Select a polytetrafluoroethylene cylindrical plug that matches the size of the carrier tube port and wrap its surface with polytetrafluoroethylene tape, then press it into both ends of the carrier tube respectively to ensure the tightness of the carrier tube; preheat the sealed carrier tube under constant temperature conditions; perform thermal dip-coating: vertically and uniformly immerse the carrier tube completely from above the aluminum sulfate solution into the aluminum sulfate solution below the liquid level of the aluminum sulfate solution, ensuring that the longitudinal axis of the carrier tube is perpendicular to the liquid level of the aluminum sulfate solution. After the dipping is completed, slowly lift the carrier tube to ensure that a uniform liquid film is formed on the wall surface of the carrier tube; repeat the above operation for gradient coating; through prior preheating treatment, the residual water and adsorbates in the pores of the porous tubular carrier can be removed, making it easier for the aluminum sulfate to bind to the carrier surface. At the same time, due to the certain water absorption of the alumina carrier, when the preheated carrier is placed in the room-temperature solution, the carrier quickly absorbs water, causing the concentration of aluminum sulfate near the carrier tube to rapidly increase, so that more aluminum sulfate is loaded on the carrier, better modifying the surface defects of the tubular carrier.

[0014] (3) Calcination and curing

[0015] Place the coated carrier tube on an iron stand, ensure that the tube body is vertical, and place it in the center of the muffle furnace; set the program-controlled temperature curve: in the first stage, raise the temperature from room temperature to the target temperature of 400°C at a rate of 1°C / min, in the second stage, keep the temperature constant for 300 min for dehydration treatment; in the third stage, lower the temperature to below 100°C at a rate of 1°C / min, and then turn off the heating system and let it cool naturally;

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

[0017] The CAU-10-H membrane was prepared by the solvothermal method. Both ends of the carrier tube with a homologous metal-induced layer were sealed with PTFE stoppers and placed in the inner lining of a PTFE reaction kettle. After adding the synthesis solution, it was sealed and reacted at 120 °C for 8 h. The composition of the synthesis solution was as follows: the molar ratio of the metal source to the organic ligand was Al 3+ :C 8 H 6 O 4 =1:1, and the volume ratio of the solvent was DMF:H 2 O=1:4; based on the Al 3+ concentration, the concentration of the synthesis solution was 0.18 mol / L. After the reaction, it was naturally cooled to room temperature. After taking it out, it was soaked and washed with deionized water and anhydrous methanol reagents for three days respectively, and the solvents were replaced twice during this period. It was vacuum dried at 80 °C overnight. After being fully dried, it was placed in a desiccator for single-component gas permeation testing.

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

[0019] During the sealing process in step (2), it was necessary to ensure that the stopper was fully embedded more than 3 mm deep into the port to ensure that the stopper would not fall off during the impregnation process.

[0020] The sealing treatment in step (2) specifically included: double-end sealing with a sealing plug made of PTFE and combined with raw tape, and the sealing depth ≥ 3 mm; the preheating treatment temperature was 100 - 200 °C, and the duration was 1.5 - 2.5 h; the parameters of the hot impregnation method included: impregnation time 10 - 30 s, and the temperature of the impregnation solution was maintained at 15 - 30 °C; the number of gradient coating times was 2 - 4 times.

[0021] The obtained CAU-10-H membrane in step (4) was subjected to single-component gas permeation testing using a gas permeation testing device to evaluate the denseness 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 pressure on the feed side was controlled by a back pressure valve, and the pressure was controlled at 0.1 Mpa. After the permeate side was connected to the soap bubble tube, it was communicated 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 flowmeter, and the tests were all carried out at room temperature.

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

[0023]

[0024] Advantages of the present invention:

[0025] (1) The present invention has successfully prepared a dense CAU-10-H membrane on a macroporous alumina support tube. The flat supports with smaller defects, usually less than 200 nm, are used for the reported CAU-10-H polycrystalline membranes in the existing literature. However, the present invention is applicable to tubular supports with larger defects and low cost. The method of preparing the induction layer with aluminum sulfate can make the induction layer thinner and have stronger binding force, improving the continuity of the prepared membrane and shortening the time required for the crystallization step.

[0026] (2) By modifying the surface of the macroporous support with aluminum sulfate, it not only fills the defects on the rough surface of the macroporous support but also plays an inducing role, strengthening the binding force between the support surface and the membrane layer while reducing film formation inside the support, retaining the well-developed gas transmission channels inside the macroporous support. The obtained CAU-10-H membrane has relatively high gas permeability while maintaining good H 2 / CO 2 ideal selectivity. Description of the drawings

[0027] Figure 1 is a scanning electron microscope (SEM) image of the surface of the homologous metal induction layer prepared in Example 1;

[0028] Figure 2 is a scanning electron microscope (SEM) image of the surface of the homologous metal induction layer prepared in Example 3;

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

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

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

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

[0033] Figure 7It is a test chart of the gas separation performance of the prepared CAU-10-H membrane. (a) Ideal selectivity, (b) Permeability. Detailed implementation manners

[0034] The following further describes the detailed implementation manners of the present invention in combination with the attached 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 diameter is greater than 1 μm, and the porosity is about 30-40%. The carrier pretreatment is divided into the following steps: First step, the outer surface of the carrier tube is polished successively with 800-mesh, 1500-mesh, and 3000-mesh sandpapers, and it is cut into short tubes of 5 cm; Second step, ultrasonic cleaning with deionized water, ultrasonic cleaning with 1 mol / L HCl solution, ultrasonic cleaning with deionized water until neutral, ultrasonic cleaning with 1 mol / L NaOH solution, and ultrasonic cleaning with deionized water until neutral. Each cleaning lasts for 30 min. The cleaned carrier tube is placed in an 80°C oven and dried overnight; Third step, calcination at 550°C for 360 min, with the heating and cooling rates both being 1°C / min. After calcination, it is stored at room temperature in a desiccator and waiting for subsequent use.

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

[0039] (2.1) Preparation of aluminum sulfate solution

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

[0041] (2.2) Thermal impregnation coating of aluminum sulfate solution

[0042] First, select a polytetrafluoroethylene cylindrical plug that matches the size of the carrier tube port and wrap its surface with polytetrafluoroethylene tape. Press the plug into both ends of the carrier tube respectively to ensure the tightness of the carrier tube. During the sealing process, it is necessary to ensure that the plug is completely embedded more than 3 mm deep into the port to ensure that the plug will not fall off during the impregnation process. Transfer the sealed carrier tube to an electric drying oven at a constant temperature of 100°C for preheating, and maintain a constant temperature state for a continuous 2-hour uniform preheating treatment. After preheating, use high-temperature-resistant tweezers to vertically transfer the carrier tube above an open container filled with an aluminum sulfate solution with a mass fraction of 0.5%. Slowly immerse the preheated carrier tube completely under the liquid surface at a uniform speed, ensuring that the longitudinal axis of the carrier tube is perpendicular to the liquid surface. After impregnation, slowly lift the carrier tube to ensure that a uniform liquid film is formed on the tube wall surface. Repeat the above operation for a total of two coatings.

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

[0044] Place the coated carrier tube on an iron stand, ensure the tube is vertical, and place it in the center of the muffle furnace. Set the programmed temperature control curve: in the first stage, raise the temperature from room temperature to the target temperature of 400 °C at a rate of 1 °C / min; in the second stage, keep the temperature constant for 300 min for dehydration treatment; in the third stage, lower the temperature to below 100 °C at a rate of 1 °C / min, and then turn off the heating system and let it cool naturally.

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

[0046] Prepare the CAU-10-H membrane by the solvothermal method. Seal both ends of the carrier tube with the introduced homologous metal-induced layer using PTFE stoppers, place it in the inner lining of a PTFE reaction kettle, add the synthesis solution and seal it, and react at 120 °C for 8 h; the composition of the synthesis solution is: the molar ratio of the metal source to the organic ligand Al 3+ :C 8 H 6 O 4 = 1:1, the solvent volume ratio DMF:H 2 O = 1:4; the concentration of the synthesis solution is 0.18 mol / L (calculated based on the Al 3+ concentration). After the reaction, let it cool naturally to room temperature. Take it out and soak and wash it with deionized water and anhydrous methanol reagents for three days respectively, changing the solvent twice during this period. Dry it overnight at 80 °C under vacuum. After drying thoroughly, put it in a desiccator for single-component gas permeation testing.

[0047] Example 2

[0048] (1) Carrier pretreatment

[0049] The outer diameter of the tube is 12 mm, the inner diameter of the tube is 8 mm, the average pore diameter is greater than 1 μm, and the porosity is about 30-40%. The carrier pretreatment is divided into the following steps: First step, polish the outer surface of the carrier tube successively with 800-mesh, 1500-mesh, and 3000-mesh sandpapers, and cut it into short tubes of 5 cm; Second step, ultrasonically clean with deionized water, ultrasonically clean with 1 mol / L HCl solution, ultrasonically clean with deionized water until neutral, ultrasonically clean with 1 mol / L NaOH solution, and ultrasonically clean with deionized water until neutral. Each cleaning lasts for 30 min. Place the cleaned carrier tube in an oven at 80 °C and dry it overnight; Third step, calcine at 550 °C for 360 min, with the heating and cooling rates both being 1 °C / min. After calcination, store it at room temperature in a desiccator and wait for subsequent use.

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

[0051] (2.1) Preparation of aluminum sulfate solution

[0052] Weigh 10 g of aluminum sulfate octadecahydrate, add it to 49.73 g of deionized water, stir well for 10 min, then transfer it to an ultrasonic cleaner and ultrasonicate for 30 min to dissolve it and disperse it evenly, obtaining an aluminum sulfate aqueous solution with a mass fraction of 2%.

[0053] (2.2) Hot impregnation coating of aluminum sulfate solution

[0054] First, select a polytetrafluoroethylene cylindrical plug that matches the size of the carrier tube port and wrap its surface with polytetrafluoroethylene tape. Press the plugs into both ends of the carrier tube respectively to ensure the tightness of the carrier tube. During the sealing process, it is necessary to ensure that the plugs are completely embedded more than 3 mm deep into the port to ensure that the plugs will not fall off during the impregnation process. Transfer the sealed carrier tube to an electric drying oven at a constant temperature of 180 °C for preheating, and maintain a constant temperature state for a uniform preheating treatment for 2 hours. After preheating, use high-temperature-resistant tweezers to vertically transfer the carrier tube above an open container containing an aluminum sulfate solution with a mass fraction of 0.5%. Slowly immerse the preheated carrier tube completely below the liquid surface at a uniform speed, ensuring that the longitudinal axis of the carrier tube is perpendicular to the liquid surface. After impregnation, slowly lift the carrier tube out to ensure that a uniform liquid film is formed on the tube wall surface. Repeat the above operation for a total of two coatings.

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

[0056] Place the coated carrier tube on an iron stand, ensure that the tube body is vertical, and place it in the center of the muffle furnace. Set the program temperature control curve: in the first stage, raise the temperature from room temperature to the target temperature of 400 °C at a rate of 1 °C / min, in the second stage, keep the temperature constant for 300 min for dehydration treatment; in the third stage, lower the temperature to below 100 °C at a rate of 1 °C / min, and then turn off the heating system and let it cool naturally.

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

[0058] Prepare the CAU-10-H membrane by the solvothermal method. Seal both ends of the carrier tube introduced with the homologous metal-induced layer with polytetrafluoroethylene plugs, place it in the inner lining of a polytetrafluoroethylene reaction kettle, add the synthesis solution and seal it, and react at 120 °C for 8 h; the composition of the synthesis solution is: the molar ratio of metal source to organic ligand Al 3+ :C 8 H 6 O 4 = 1:1, the solvent volume ratio DMF:H 2 O = 1:4; the concentration of the synthesis solution is 0.18 mol / L (calculated based on the concentration of Al 3+ ). After the reaction, let it cool naturally to room temperature, take it out and soak and wash it with deionized water and anhydrous methanol reagents for three days respectively, change the solvent twice during this period, dry it overnight in a vacuum at 80 °C, and after sufficient drying, put it in a desiccator for single-component gas permeation testing.

[0059] Example 3

[0060] (1) Carrier pretreatment

[0061] The outer diameter of the tube is 12 mm, the inner diameter of the tube is 8 mm, the average pore diameter is greater than 1 μm, and the porosity is about 30 - 40%. The carrier pretreatment is divided into the following steps: First step, the outer surface of the carrier tube is polished successively with 800 - mesh, 1500 - mesh, and 3000 - mesh sandpapers, and it is cut into short tubes of 5 cm; Second step, ultrasonic cleaning with deionized water, ultrasonic cleaning with 1 mol / L HCl solution, ultrasonic cleaning with deionized water until neutral, ultrasonic cleaning with 1 mol / L NaOH solution, ultrasonic cleaning with deionized water until neutral, each cleaning lasts for 30 min, and the cleaned carrier tube is placed in an 80 °C oven and dried overnight; Third step, calcination at 550 °C for 360 min, with the heating and cooling rates both being 1 °C / min. After calcination, it is stored at room temperature in a desiccator and waiting for subsequent use.

[0062] (2) Preparation of homologous metal induction layer

[0063] (2.1) Preparation of aluminum sulfate solution

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

[0065] (2.2) Thermal impregnation coating of aluminum sulfate solution

[0066] First, select a polytetrafluoroethylene cylindrical plug that matches the size of the carrier tube port and wrap its surface with polytetrafluoroethylene raw tape. Press the plugs into both ends of the carrier tube respectively to ensure the airtightness of the carrier tube. During the sealing process, it is necessary to ensure that the plugs are completely embedded more than 3 mm deep inside the port to ensure that the plugs will not fall off during the impregnation process. Transfer the sealed carrier tube to an electric drying oven at a constant temperature of 180 °C for preheating, and maintain a constant temperature state for a continuous 2 - hour uniform preheating treatment. After preheating, use high - temperature - resistant tweezers to vertically transfer the carrier tube above an open container filled with an aluminum sulfate solution with a mass fraction of 0.5%. Slowly immerse the preheated carrier tube completely under the liquid surface at a uniform speed, ensuring that the longitudinal axis of the carrier tube is perpendicular to the liquid surface. After impregnation, slowly lift the carrier tube out to ensure that a uniform liquid film is formed on the tube wall surface. Repeat the above operation for a total of two coatings.

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

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

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

[0070] Prepare the CAU-10-H membrane by the solvothermal method. Seal both ends of the carrier tube with the introduced homologous metal induction layer using polytetrafluoroethylene stoppers, place it in the inner lining of a polytetrafluoroethylene reaction kettle, add the synthesis solution and seal it, and react at 120 °C for 8 h; the composition of the synthesis solution is: the molar ratio of the metal source to the organic ligand Al 3+ :C 8 H 6 O 4 =1:1, and the volume ratio of the solvents DMF:H 2 O=1:4; the concentration of the synthesis solution is 0.18 mol / L (calculated based on the Al 3+ concentration). After the reaction, let it cool naturally to room temperature. Take it out and soak and wash it with deionized water and anhydrous methanol reagents for three days respectively, changing the solvents twice during this period. Dry it overnight in a vacuum at 80 °C. After sufficient drying, put it in a desiccator for single-component gas permeation testing.

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

[0072] The testing is carried out using a self-made gas permeation testing device in the laboratory to evaluate the denseness and gas separation performance of the prepared CAU-10-H membrane. The specific operation is as follows: Seal the membrane in a tubular membrane module using an O-ring. Seal one end of the membrane and connect the other end to a soap bubble tube. Control the pressure on the feed side through a back-pressure valve and set the pressure at 0.1 Mpa. After connecting the permeate side to the soap bubble tube, it is in communication with the atmosphere. Use a stopwatch and a soap bubble flowmeter to obtain the time taken for a certain volume of gas to pass through the membrane. The testing is carried out at room temperature.

[0073] The test results of the CAU-10-H membrane prepared by homologous metal induction are as Figure 7 shown. The H 2 flux of 1.09×10 -7 mol·m -2 ·s -1 ·pa -1 is for H 2 / CO 2 、H 2 / N 2 、H 2 / CH 4The ideal selectivities reached 31.66, 4.17, and 3.80 respectively, all of which were greater than their Knudsen diffusion selectivities (4.7, 3.7, and 2.8), proving that the obtained CAU-10-H membrane has no intercrystalline defects and the feasibility of this method. Among them, H 2 / CO 2 The ideal selectivity reached 31.66, indicating that the membrane obtained by this method has a certain gas separation ability. CO 2 The lowest permeation rate is because the cis-linked AlO in the CAU-10-H framework 6 polyhedra and the defect sites in the structure and the isophthalic acid ligands linked to them have a strong adsorption effect on CO 2 resulting in a decrease in its diffusion rate.

Claims

1. A method for preparing a CAU-10-H membrane for gas separation by modifying a macroporous tubular carrier with aluminum sulfate, characterized in that: Here are the steps: (1) preparing aluminum sulfate solution; Dissolve aluminum sulfate 18hydrate in deionized water, stir thoroughly and ultrasonicate to dissolve and disperse thoroughly; (2) Hot dip coating with aluminum sulfate solution Both ends of the carrier tube are sealed; Preheating the sealed carrier tube under constant temperature conditions; Perform hot dip coating: immerse the carrier tube vertically and uniformly from above the aluminum sulfate solution to below the aluminum sulfate solution surface, ensuring that the longitudinal axis of the carrier tube is perpendicular to the aluminum sulfate solution surface. After the immersion is completed, slowly lift the carrier tube out to ensure that a uniform liquid film is formed on the wall surface of the carrier tube; Repeat the hot dip coating operation to perform gradient coating; (3) Calcination and curing The coated carrier tube is placed vertically in the center of the muffle furnace for calcination. The calcination process includes three stages: gradient heating, constant temperature dehydration and gradient cooling. (4) Preparation of CAU-10-H membrane The CAU-10-H membrane was prepared by the solvothermal method. The two ends of the carrier tube into which the homologous metal induction layer was introduced were sealed with polytetrafluoroethylene stoppers, placed in a polytetrafluoroethylene reactor liner, sealed after adding the synthesis liquid, and reacted at 120°C for 8h. The composition of the synthesis liquid was: the molar ratio of metal source to organic ligand was Al 3+ :C8H6O4=1:1, solvent volume ratio DMF:H2O=1:4; Al 3+ The concentration of the synthetic solution was 0.18 mol / L according to the concentration meter. After the reaction was completed, it was naturally cooled to room temperature. After being taken out, it was soaked and cleaned with deionized water and anhydrous methanol reagent for three days respectively. The solvent was changed twice during this period. The membrane was vacuum dried at 80°C 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 carrier with aluminum sulfate according to claim 1, characterized in that: The ultrasonic treatment conditions in step (1) include: ultrasonic frequency 20-40kHz, treatment time 20-40min, and treatment temperature maintained at 20-40°C.

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

4. The method for preparing a CAU-10-H membrane for gas separation by modifying a macroporous tubular carrier with aluminum sulfate according to claim 1, characterized in that: The sealing treatment of both ends of the carrier tube in step (2) specifically includes: in step (2), a sealing plug made of polytetrafluoroethylene is used in combination with a raw tape to perform double-end sealing, and the sealing depth is ≥3mm.

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: The preheating treatment temperature in step (2) is 100-200° C. and the duration is 1.5-2.5 hours.

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 dip coating parameters in step (2) include: dipping time 10-30s, dipping liquid temperature maintained at 15-30°C; gradient coating times 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: The calcination process in step (3) is programmed with a temperature control curve: in the first stage, the temperature is raised from room temperature to a target temperature of 400°C at a rate of 1°C / min; in the second stage, the temperature is kept constant for 300 minutes for dehydration treatment; in the third stage, the temperature is lowered to below 100°C at a rate of 1°C / min, and then the heating system is turned off for natural cooling.

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