Supported composite carbon molecular sieve membrane and preparation method and application thereof

Abstract

The invention relates to a supported composite carbon molecular sieve membrane as well as a preparation method and application thereof, and belongs to the technical field of carbon molecular sieve membranes. In order to solve the problem that an existing carbon molecular sieve membrane preparation method cannot accurately regulate and control the pore diameter, the invention provides a preparation method of a supported composite carbon molecular sieve membrane, which comprises the following steps: preparing a polymer solution by taking microporous polyvinylidene fluoride hexafluoropropylene as a polymer precursor and polyvinylpyrrolidone as an additive; a polymer precursor membrane is prepared by immersion coating on the surface of a tubular support body, and finally the supported composite carbon molecular sieve membrane is prepared by pyrolysis carbonization. The free volume of the polymer is influenced by regulating and controlling the concentration of microporous polyvinylidene fluoride hexafluoropropylene in the polymer, the comprehensive regulation and control of the pore diameter of the pyrolyzed carbon molecular sieve membrane is further realized by regulating and controlling the pyrolysis condition, and the obtained supported composite carbon molecular sieve membrane can meet the separation requirements of different gas mixtures; and the permeation selectivity of hydrogen can be improved when the catalyst is used for hydrogen separation and purification.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon molecular sieve membranes, and particularly relates to a supported composite carbon molecular sieve membrane, a preparation method thereof, and an application thereof. Background Art

[0002] Hydrogen energy is regarded as one of the clean energy sources with the most development potential in the 21st century. With the continuous increase in the global demand for clean energy, the technologies for hydrogen production, storage, transportation, and application have become the focus of attention in the field of clean energy. Mixing a certain proportion of hydrogen in the upstream of the existing natural gas pipeline, transporting the hydrogen-blended gas, and then purifying it downstream will greatly improve the spatio-temporal allocation scale and efficiency of hydrogen energy and promote the development of hydrogen energy. The membrane separation method has a small floor area and is easy to operate, and is especially suitable for the purification of hydrogen-blended natural gas with a low hydrogen blending ratio.

[0003] Carbon molecular sieve membranes are obtained by pyrolyzing and carbonizing organic polymer membranes. During the pyrolysis process, the polymer macromolecular chains break, rearrange, and stack to form slit-shaped micropores and supermicropores. Among them, the micropores provide adsorption sites, and the supermicropores can effectively screen gas molecules, allowing hydrogen molecules to pass through smoothly while effectively blocking other impurity gas molecules. However, when the pore size of the supermicropores is too large, impurity gas molecules such as oxygen and nitrogen are easily introduced into the membrane, resulting in difficult effective separation of hydrogen and reduced separation efficiency. When preparing carbon molecular sieve membranes, it is necessary to precisely control the pore size according to specific separation requirements and the composition of the gas mixture to ensure that the membrane has the best separation efficiency and selectivity. Therefore, how to precisely control the pore size of carbon molecular sieve membranes is an urgent problem to be solved. Summary of the Invention

[0004] To solve the problem that the existing preparation methods of carbon molecular sieve membranes cannot precisely control the pore size, the present invention provides a supported composite carbon molecular sieve membrane, a preparation method thereof, and an application thereof.

[0005] The technical solution of the present invention:

[0006] A preparation method of a supported composite carbon molecular sieve membrane includes the following steps:

[0007] Step 1, preparing a polymer solution:

[0008] Fully dissolve microporous polyvinylidene fluoride hexafluoropropylene in N-methylpyrrolidone, and then add polyvinylpyrrolidone to the obtained system to fully dissolve polyvinylpyrrolidone to obtain a polymer solution;

[0009] Step 2, preparing a polymer precursor membrane:

[0010] Seal one end of the tubular support and immerse it in the polymer solution obtained in Step 1. After immersion for 10 - 20 s, take it out. Immerse the tubular support with a polymer film coated on its surface in deionized water for phase inversion. After taking it out, dry it and let it stand overnight to obtain a supported polymer precursor membrane.

[0011] Step 3: Prepare a supported composite carbon molecular sieve membrane:

[0012] Place the supported polymer precursor membrane obtained in Step 2 under vacuum for pyrolytic carbonization to obtain a supported composite carbon molecular sieve membrane.

[0013] Furthermore, the molecular weight of the microporous polyvinylidene fluoride - hexafluoropropylene in Step 1 is 400,000, and the molecular weight of the polyvinylpyrrolidone is 80,000.

[0014] Furthermore, the complete dissolution of the microporous polyvinylidene fluoride - hexafluoropropylene and the polyvinylpyrrolidone in Step 1 is carried out under vacuum at 90 °C with stirring for 5 h.

[0015] Furthermore, in the polymer solution obtained in Step 1, the concentration of the microporous polyvinylidene fluoride - hexafluoropropylene is 16 - 20 wt%, and the concentration of the polyvinylpyrrolidone is 2 wt%.

[0016] Furthermore, the tubular support in Step 2 is porous ceramic, porous metal or porous glass. The porous ceramic is porous alumina, porous titania, porous zirconia or porous zinc oxide; the porous metal is porous stainless steel, porous nickel alloy, porous titanium alloy, porous nickel - cobalt - based alloy; the average pore diameter of the porous ceramic, porous metal or porous glass is 0.1 - 10 μm.

[0017] Furthermore, the drying in Step 2 is carried out at 80 °C for 8 h.

[0018] Furthermore, Step 2 also includes immersing the supported polymer precursor membrane that has been dried and left to stand overnight in the polymer solution obtained in Step 1. After immersion for 10 - 20 s, take it out, carry out phase inversion, drying and standing overnight in sequence, then immerse it in the polymer solution obtained in Step 1 again. After immersion for 10 - 20 s, take it out, and carry out phase inversion, drying and standing overnight again.

[0019] Furthermore, the pyrolytic carbonization program in Step 3 is as follows: First, heat up at a heating rate of 5 °C / min to 400 °C and keep it at this temperature for 20 min; then continue to heat up at a heating rate of 2 °C / min to 580 °C and keep it at this temperature for 120 min.

[0020] A supported composite carbon molecular sieve membrane prepared by the preparation method provided by the present invention, wherein the pores of the supported composite carbon molecular sieve membrane are micropores or supermicropores, the pore diameter of the micropores < 2 nm, the pore diameter of the supermicropores < 0.7 nm, and the porosity is 30-50%.

[0021] Application of a supported composite carbon molecular sieve membrane prepared by the present invention in hydrogen separation and purification.

[0022] Advantages of the present invention:

[0023] The preparation method of the supported composite carbon molecular sieve membrane provided by the present invention can realize the regulation of the pore size structure from micropores to supermicropores of the carbon molecular sieve membrane. The present invention uses microporous polyvinylidene fluoride hexafluoropropylene as a polymer precursor. The polymer chains of microporous polyvinylidene fluoride hexafluoropropylene are bent and twisted at the carbon atoms of the -C(CF3)- substituents, showing a helical configuration. This structure cannot effectively fill the internal space, and can generate a relatively large free volume. After pyrolysis, the hydrogen permeability can be improved, especially suitable for the enrichment of hydrogen in hydrogen-doped natural gas with a low hydrogen doping ratio.

[0024] The present invention regulates the free volume of the polymer by controlling the concentration of microporous polyvinylidene fluoride hexafluoropropylene in the polymer, and further controls the breaking of polymer chain chemical bonds and the overflow of small molecule gases by regulating pyrolysis conditions such as the final pyrolysis temperature, pyrolysis atmosphere, and heating rate, thereby realizing the comprehensive regulation of the pore size of the carbon molecular sieve membrane after pyrolysis.

[0025] The present invention uses polyvinylpyrrolidone as an additive, which plays a role in increasing the porosity and thermal stability of the polymer precursor membrane, and can introduce hydroxyl groups after pyrolysis, enhancing the affinity of the carbon molecular sieve membrane for hydrogen.

[0026] The preparation method provided by the present invention can accurately regulate the pore size of the carbon molecular sieve membrane according to the separation requirements and the composition of the gas mixture, improve the separation efficiency and selectivity of the supported composite carbon molecular sieve membrane, and when used for the separation and purification of hydrogen in hydrogen-doped natural gas, can improve the hydrogen permeation selectivity while ensuring economy. Description of the drawings

[0027] Figure 1 Microscopic photograph of the surface of the supported composite carbon molecular sieve membrane prepared in Example 1;

[0028] Figure 2 Microscopic photograph of the cross-section of the supported composite carbon molecular sieve membrane prepared in Example 1;

[0029] Figure 3 Thermogravimetric analysis comparison diagrams of the polymer precursor membrane PHF-PVP prepared in Example 2 and the polymer precursor membrane PHF prepared in Comparative Example 1 at heating rates of 2 °C / min, 5 °C / min, and 9 °C / min;

[0030] Figure 4 Infrared spectrum comparison diagrams of the polymer precursor film PHF and the supported composite carbon molecular sieve membrane PHF-CMSM580 before and after pyrolytic carbonization in Example 1. Detailed implementation manners

[0031] The technical solutions of the present invention will be further described below in conjunction with the embodiments, but are not limited thereto. Any modification or equivalent replacement of the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention shall be covered by the protection scope of the present invention. For the process equipment or devices not specifically noted in the following embodiments, conventional equipment or devices in the art are used. If not specifically specified, the raw materials and the like used in the embodiments of the present invention can be obtained commercially; if not specifically specified, the technical means used in the embodiments of the present invention are all conventional means well-known to those skilled in the art.

[0032] Example 1

[0033] This example provides a method for preparing a supported composite carbon molecular sieve membrane, which includes the following steps:

[0034] Step 1: Prepare a polymer solution:

[0035] Add microporous polyvinylidene fluoride hexafluoropropylene to N-methylpyrrolidone. After evacuating the container, place it in a water bath at 90 °C and stir magnetically for 5 h to fully dissolve the microporous polyvinylidene fluoride hexafluoropropylene. Then add polyvinylpyrrolidone to the obtained system. After evacuating the container, place it in a water bath at 90 °C and stir magnetically for 5 h to fully dissolve the polyvinylpyrrolidone, obtaining a polymer solution with a concentration of 16 wt% of microporous polyvinylidene fluoride hexafluoropropylene and a concentration of 2 wt% of polyvinylpyrrolidone;

[0036] Step 2: Prepare a polymer precursor membrane:

[0037] The porous alumina tubular support used in this example has an outer diameter of 10 mm, an inner diameter of 8 mm, and an average pore diameter of 2.0 μm.

[0038] Seal one end of the alumina tubular support with glass glue and immerse it in the polymer solution obtained in Step 1. After immersing for 15 s, take it out evenly. Immerse the tubular support with the polymer film coated on the surface in deionized water for phase inversion. Take it out and place it in an oven to dry at 80 °C for 8 h and then let it stand overnight to obtain a supported polymer precursor membrane;

[0039] Immerse the supported polymer precursor membrane that has been dried and left standing overnight in the polymer solution obtained in Step 1. After immersion for 15 s, take it out, and successively carry out phase inversion, drying, and leaving standing overnight. Then immerse it again in the polymer solution obtained in Step 1. After immersion for 15 s, take it out, and carry out phase inversion, drying, and leaving standing overnight again. Repeating the processes of immersion, phase inversion, drying, and leaving standing overnight can prevent the polymer precursor membrane from breaking during carbonization.

[0040] Step 3. Prepare a supported composite carbon molecular sieve membrane:

[0041] Place the supported polymer precursor membrane obtained in Step 2 in a quartz boat, and then put it into the quartz glass tube of a high-temperature tube furnace. After sealing both ends of the quartz glass tube, evacuate it, and then carry out pyrolytic carbonization. The pyrolytic carbonization procedure is as follows: First, heat it at a heating rate of 5 °C / min to 400 °C and keep it at this temperature for 20 min; then continue to heat it at a heating rate of 2 °C / min to 580 °C and keep it at this temperature for 120 min to obtain a supported composite ultra-microporous carbon molecular sieve membrane.

[0042] Example 2

[0043] This example provides a method for preparing a supported composite carbon molecular sieve membrane, which includes the following steps:

[0044] Step 1. Prepare a polymer solution:

[0045] Add microporous polyvinylidene fluoride hexafluoropropylene to N-methylpyrrolidone. After evacuating the container, place it in a water bath at 90 °C and stir magnetically for 5 h to fully dissolve the microporous polyvinylidene fluoride hexafluoropropylene. Then add polyvinylpyrrolidone to the obtained system. After evacuating the container, place it in a water bath at 90 °C and stir magnetically for 5 h to fully dissolve the polyvinylpyrrolidone, obtaining a polymer solution with a concentration of 18 wt% of microporous polyvinylidene fluoride hexafluoropropylene and a concentration of 2 wt% of polyvinylpyrrolidone;

[0046] Step 2. Prepare a polymer precursor membrane:

[0047] The porous alumina tubular support used in this example has an outer diameter of 10 mm, an inner diameter of 8 mm, and an average pore diameter of 2.0 μm.

[0048] Seal one end of the alumina tubular support with glass glue and immerse it in the polymer solution obtained in Step 1. After immersion for 15 s, take it out at a uniform speed. Immerse the tubular support with the polymer film coated on its surface in deionized water for phase inversion. Take it out and put it into an oven to dry at 80 °C for 8 h and then leave it standing overnight to obtain a supported polymer precursor membrane;

[0049] Immerse the supported polymer precursor membrane that has been dried and left standing overnight in the polymer solution obtained in Step 1. After immersion for 15 s, take it out, perform phase inversion, drying, and leave it standing overnight in sequence. Then immerse it again in the polymer solution obtained in Step 1. After immersion for 15 s, take it out, and perform phase inversion, drying, and leave it standing overnight again. Repeating the processes of immersion, phase inversion, drying, and leaving it standing overnight can prevent the polymer precursor membrane from breaking during carbonization.

[0050] Step 3. Prepare a supported composite carbon molecular sieve membrane:

[0051] Place the supported polymer precursor membrane obtained in Step 2 in a quartz boat, and then put it into the quartz glass tube of a high-temperature tube furnace. After sealing both ends of the quartz glass tube and evacuating, perform pyrolytic carbonization. The pyrolytic carbonization program is as follows: First, heat up to 400 °C at a heating rate of 5 °C / min and keep it at this temperature for 20 min; then continue to heat up to 580 °C at a heating rate of 2 °C / min and keep it at this temperature for 120 min to obtain a supported composite ultra-microporous carbon molecular sieve membrane.

[0052] Example 3

[0053] This example provides a method for preparing a supported composite carbon molecular sieve membrane, which includes the following steps:

[0054] Step 1. Prepare a polymer solution:

[0055] Add microporous polyvinylidene fluoride hexafluoropropylene to N-methylpyrrolidone. After evacuating the container, place it in a water bath at 90 °C and stir magnetically for 5 h to fully dissolve the microporous polyvinylidene fluoride hexafluoropropylene. Then add polyvinylpyrrolidone to the obtained system. After evacuating the container, place it in a water bath at 90 °C and stir magnetically for 5 h to fully dissolve the polyvinylpyrrolidone, obtaining a polymer solution with a concentration of 20 wt% of microporous polyvinylidene fluoride hexafluoropropylene and a concentration of 2 wt% of polyvinylpyrrolidone.

[0056] Step 2. Prepare a polymer precursor membrane:

[0057] The porous alumina tubular support used in this example has an outer diameter of 10 mm, an inner diameter of 8 mm, and an average pore diameter of 2.0 μm.

[0058] Seal one end of the alumina tubular support with glass glue and immerse it in the polymer solution obtained in Step 1. After immersion for 15 s, take it out at a uniform speed. Immerse the tubular support with the polymer film coated on its surface in deionized water for phase inversion. Take it out and place it in an oven to dry at 80 °C for 8 h and then leave it standing overnight to obtain a supported polymer precursor membrane.

[0059] The supported polymer precursor membrane that has been dried and left standing overnight is immersed in the polymer solution obtained in Step 1. After immersion for 15 s, it is taken out, followed by phase inversion, drying, and leaving standing overnight. Then it is immersed again in the polymer solution obtained in Step 1. After immersion for 15 s, it is taken out, and phase inversion, drying, and leaving standing overnight are carried out again. Repeating the processes of immersion, phase inversion, drying, and leaving standing overnight can prevent the polymer precursor membrane from breaking during carbonization.

[0060] Step 3: Preparation of the supported composite carbon molecular sieve membrane:

[0061] The supported polymer precursor membrane obtained in Step 2 is placed in a quartz boat and then put into the quartz glass tube of a high-temperature tube furnace. After the two ends of the quartz glass tube are sealed and evacuated, pyrolytic carbonization is carried out. The pyrolytic carbonization program is as follows: First, it is heated to 400 °C at a heating rate of 5 °C / min and kept at this temperature for 20 min; then it is continuously heated to 580 °C at a heating rate of 2 °C / min and kept at this temperature for 120 min to obtain the supported composite ultra-microporous carbon molecular sieve membrane.

[0062] Comparative Example 1

[0063] This comparative example provides a method for preparing a supported composite carbon molecular sieve membrane without adding polyvinylpyrrolidone, including the following steps:

[0064] Step 1: Preparation of the polymer solution:

[0065] Microporous polyvinylidene fluoride hexafluoropropylene is added to N-methylpyrrolidone. After the container is evacuated, it is placed in a water bath at 90 °C and magnetically stirred for 5 h to fully dissolve the microporous polyvinylidene fluoride hexafluoropropylene, obtaining a polymer solution with a concentration of 18 wt% of microporous polyvinylidene fluoride hexafluoropropylene.

[0066] Step 2: Preparation of the polymer precursor membrane:

[0067] The porous alumina tubular support used in this comparative example has an outer diameter of 10 mm, an inner diameter of 8 mm, and an average pore diameter of 2.0 μm.

[0068] One end of the alumina tubular support is sealed with glass glue and then immersed in the polymer solution obtained in Step 1. After immersion for 15 s, it is taken out at a uniform speed. The tubular support with a polymer film coated on its surface is immersed in deionized water for phase inversion, taken out and placed in an oven to be dried at 80 °C for 8 h and then left standing overnight to obtain the supported polymer precursor membrane;

[0069] The supported polymer precursor membrane that has been dried and left standing overnight is immersed in the polymer solution obtained in Step 1. After immersion for 15 s, it is taken out, followed by phase inversion, drying, and leaving standing overnight, and then immersed again in the polymer solution obtained in Step 1. After immersion for 15 s, it is taken out, and phase inversion, drying, and leaving standing overnight are carried out again. Repeating the processes of immersion, phase inversion, drying, and leaving standing overnight can prevent the supported polymer precursor membrane from breaking during carbonization.

[0070] Step 3. Preparation of the supported composite carbon molecular sieve membrane:

[0071] The supported polymer precursor membrane obtained in Step 2 is placed in a quartz boat, and then put into the quartz glass tube of a high-temperature tube furnace. After the two ends of the quartz glass tube are sealed and evacuated, pyrolytic carbonization is carried out. The pyrolytic carbonization program is as follows: First, it is heated to 400 °C at a heating rate of 5 °C / min and kept at this temperature for 20 min; then it is continuously heated to 580 °C at a heating rate of 2 °C / min and kept at this temperature for 120 min to obtain the supported composite carbon molecular sieve membrane.

[0072] The performance of the supported composite carbon molecular sieve membrane prepared in the examples of the present invention is investigated:

[0073] I. Figure 1 and Figure 2 are respectively the micrographs of the surface and cross-section of the supported composite carbon molecular sieve membrane prepared in Example 1; as Figure 1 and Figure 2 shown, after carbonization, the pore distribution of the supported composite carbon molecular sieve membrane prepared in Example 1 is uniform and there is almost no breakage, indicating that the blend of microporous polyvinylidene fluoride hexafluoropropylene and polyvinylpyrrolidone has good compatibility.

[0074] II. Under a N2 atmosphere, thermogravimetric analysis is respectively carried out on the polymer precursor membranes prepared in Example 2 and Comparative Example 1, with heating rates of 2 °C / min, 5 °C / min, and 9 °C / min, and a final pyrolysis temperature of 800 °C. The results are as Figure 3 shown. When the heating rate is 5 °C / min, the weight loss of the polymer precursor membrane in Example 2 is reduced by 15% compared with that of the polymer precursor membrane in Comparative Example 1. The characterization results show that the addition of polyvinylpyrrolidone increases the thermal stability of the polymer precursor membrane.

[0075] III. Infrared spectrum analysis is carried out on the polymer precursor membrane and the supported composite carbon molecular sieve membrane before and after pyrolytic carbonization in Example 1. The results are as Figure 4 shown. After pyrolysis, a new characteristic peak at 3450 cm -1(-OH). It indicates that the lactam ring breaks to produce -OH. The introduction of polar groups improves gas selectivity and increases the permeation selectivity of hydrogen. In addition, after the polymer precursor membrane is pyrolyzed at 580 °C, the characteristic peaks significantly decrease or disappear, indicating that the structure is damaged. Among them, the characteristic peak of the C-F bond disappears, indicating that the -CF3 side group is decomposed. This will generate a large number of cavities, resulting in the gradual formation of a loose carbon structure in the microporous polyvinylidene fluoride hexafluoropropylene-derived carbon molecular sieve membrane. At this time, the fractional free volume (FFV) increases, which is also the main reason why the permeability of the carbon molecular sieve membrane is higher than that of the polymer precursor membrane.

[0076] IV. The gas permeation performance of the supported composite carbon molecular sieve membranes prepared in Examples 1-3 was tested. The test gases included H2, CH4, and CO2, and the single-gas method was used for determination.

[0077] The gas permeability was calculated by the following formula:

[0078] P = Q / (A·Δp) (1)

[0079] In the formula: Q is the permeation flux, mol / s; A is the membrane area, m 2 ; ΔP is the pressure difference across the membrane, Pa; P is the permeability coefficient, mol·s -1 ·m -2 ·Pa -1 .

[0080] The index of membrane selectivity is represented by the separation factor α:

[0081]

[0082] In the formula: α is the gas selectivity; P H2 is the hydrogen permeability coefficient; P CH4 is the methane permeability coefficient.

[0083] The gas permeability measured at 30 °C is shown in Table 1.

[0084] Table 1

[0085]

[0086] As can be seen from the results in Table 1, the supported composite ultra-microporous carbon molecular sieve membranes with different pore sizes prepared by the preparation method provided by the present invention have higher hydrogen permeation selectivity and better separation effect. Among them, the micropore aperture of the supported composite ultra-microporous carbon molecular sieve membrane prepared in Example 2 is <2 nm, the ultra-micropore aperture is <0.7 nm, and the porosity is 30-50%. Its separation and purification effect on hydrogen is the best.

Claims

1. A method for preparing a supported composite carbon molecular sieve membrane, characterized in that: The steps include: Step 1: Prepare polymer solution: After fully dissolving microporous polyvinylidene fluoride hexafluoropropylene in N-methylpyrrolidone, adding polyvinyl pyrrolidone to the obtained system to fully dissolve the polyvinyl pyrrolidone to obtain a polymer solution; Step 2: Preparation of polymer precursor film: After sealing one end of the tubular support, immerse it in the polymer solution obtained in step 1, take it out after immersion for 10 to 20 seconds, immerse the tubular support coated with the polymer film on the surface in deionized water for phase inversion, take it out, dry it, and let it stand overnight to obtain a supported polymer precursor film; Step 3: Preparation of supported composite carbon molecular sieve membrane: The supported polymer precursor membrane obtained in step 2 is placed under vacuum conditions for pyrolysis and carbonization to obtain a supported composite carbon molecular sieve membrane.

2. The method for preparing a supported composite carbon molecular sieve membrane according to claim 1, characterized in that: In step 1, the molecular weight of the microporous polyvinylidene fluoride hexafluoropropylene is 40W, and the molecular weight of the polyvinyl pyrrolidone is 8W.

3. A method for preparing a supported composite carbon molecular sieve membrane according to claim 1 or 2, characterized in that: Step 1: The microporous polyvinylidene fluoride hexafluoropropylene and the polyvinyl pyrrolidone are fully dissolved under vacuum conditions and stirred at 90° C. for 5 hours.

4. The method for preparing a supported composite carbon molecular sieve membrane according to claim 3, characterized in that: In the polymer solution obtained in step 1, the concentration of microporous polyvinylidene fluoride hexafluoropropylene is 16-20wt%, and the concentration of polyvinyl pyrrolidone is 2wt%.

5. The method for preparing a supported composite carbon molecular sieve membrane according to claim 4, characterized in that: In step 2, the tubular support is a porous ceramic, a porous metal or a porous glass. The porous ceramic is a porous aluminum oxide, a porous titanium oxide, a porous zirconium oxide or a porous zinc oxide. The porous metal is a porous stainless steel, a porous nickel alloy, a porous titanium alloy or a porous nickel-cobalt-based alloy. The average pore size of the porous ceramic, porous metal or porous glass is 0.1 to 10 μm.

6. The method for preparing a supported composite carbon molecular sieve membrane according to claim 5, characterized in that: The drying step in step 2 is performed at 80° C. for 8 hours.

7. A method for preparing a supported composite carbon molecular sieve membrane according to claim 6, characterized in that: Step 2 also includes immersing the supported polymer precursor membrane after drying and standing overnight into the polymer solution obtained in step 1, taking it out after immersion for 10 to 20 seconds, performing phase inversion, drying and standing overnight in sequence, and then immersing it in the polymer solution obtained in step 1 again, taking it out after immersion for 10 to 20 seconds, performing phase inversion, drying and standing overnight again.

8. The method for preparing a supported composite carbon molecular sieve membrane according to claim 7, characterized in that: The pyrolysis carbonization procedure in step 3 is as follows: first, the temperature is increased to 400°C at a heating rate of 5°C / min, and the temperature is maintained at this temperature for 20 minutes; then, the temperature is continued to be increased to 580°C at a heating rate of 2°C / min, and the temperature is maintained at this temperature for 120 minutes.

9. A supported composite carbon molecular sieve membrane prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The pores of the supported composite carbon molecular sieve membrane are micropores or ultramicropores, the pore size of the micropores is less than 2nm, the pore size of the ultramicropores is less than 0.7nm, and the porosity is 30-50%.

10. Use of the supported composite carbon molecular sieve membrane as claimed in claim 9 in hydrogen separation and purification.

Images