A method for preparing defect-free zeolite molecular sieve-based hybrid matrix membranes by low-temperature crosslinking

Abstract

This invention discloses a method for preparing defect-free zeolite molecular sieve-based mixed matrix membranes via low-temperature crosslinking, belonging to the field of gas separation membrane preparation technology. The invention first prepares a zeolite precursor using a silicon source, a template agent, and water as raw materials. Then, it modifies the template agent-containing zeolite precursor with carboxylic acid to obtain a template-free zeolite precursor. This template-free zeolite precursor is then used as an inorganic filler to prepare a mixed matrix membrane. The layered zeolite precursor has a richer number of hydroxyl groups on its surface than conventional zeolites, facilitating its bonding with polymers. These hydroxyl groups interact with the polymer during the low-temperature heating-initiated crosslinking reaction, effectively solving the compatibility problem between the filler and the polymer, resulting in a high-performance, defect-free zeolite molecular sieve-based mixed matrix membrane.

Description

Technical Field

[0001] This invention relates to the field of gas separation membrane preparation technology, and in particular to a method for preparing defect-free zeolite molecular sieve-based mixed matrix membranes by low-temperature crosslinking. Background Technology

[0002] Helium is widely used due to its unique properties (low boiling point, low density, low solubility, and high thermal conductivity). It is extensively used in fields such as nuclear magnetic resonance imaging, welding, leak detection, and semiconductor manufacturing. Currently, helium is mainly derived from natural gas, and the recovery and purification of helium from natural gas is a hot research topic. Compared with other separation technologies, membrane separation technology is considered a promising alternative to traditional helium recovery and purification technologies due to its advantages such as small equipment footprint, no phase change in the reaction process, and low energy consumption.

[0003] Organic-inorganic hybrid membranes, composed of inorganic-organic blends, hold promise as a next-generation high-performance membrane material due to their combination of the advantages of organic membranes (permeability and flexibility) and inorganic membranes (selectivity and stability). It has been reported that the role of inorganic materials in mixed matrix membranes is to achieve higher selectivity without affecting flux. However, due to the poor compatibility between inorganic materials and polymers, interfacial defects are easily generated, which not only affect the mechanical properties of the material but also create non-selective voids that affect separation performance, ultimately leading to a decrease in the selective sieving capacity of the gas separation membrane. Developing a gas separation membrane with good gas separation performance, excellent performance, and low production cost is currently a hot research topic. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing defect-free zeolite molecular sieve-based mixed matrix membranes by low-temperature crosslinking, so as to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] One of the technical solutions of the present invention is a method for preparing a defect-free zeolite molecular sieve-based mixed matrix membrane by low-temperature crosslinking, comprising the following steps:

[0007] A silicon source, a template agent, and water are mixed to obtain a mixed solution; the mixed solution is stirred and aged, followed by a hydrothermal reaction to obtain a zeolite precursor; the zeolite precursor is modified with carboxylic acid to obtain a template-free zeolite precursor; the template-free zeolite precursor is mixed with a polymer and a solvent to prepare a mixed matrix membrane; the mixed matrix membrane is subjected to low-temperature heating to initiate a crosslinking reaction to obtain the defect-free zeolite molecular sieve-based mixed matrix membrane.

[0008] Furthermore, the silicon source is silica sol (SiO2·nH2O) or tetraethyl orthosilicate (C8H2O). 12The silicon source contains one of the following: O8Si, sodium silicate (Na2O·nSiO2), or silicon powder (mainly composed of SiO2); the template agent is tetramethylammonium hydroxide (TMAOH); the molar ratio of silicon, template agent, and water in the mixture is 1:1-3:20-80, i.e., the molar ratio of silicon to template agent to water in the silicon source is 1:1-3:20-80.

[0009] Furthermore, the stirring aging time is 1-48 hours, and the stirring rate is 200-500 rpm; the hydrothermal reaction temperature is 120-200℃, and the time is 1-21 days.

[0010] Furthermore, the product obtained after stirring and aging is a sol, which continues to undergo the next hydrothermal reaction.

[0011] Furthermore, after the hydrothermal reaction is completed, the process includes centrifugation, washing, and drying. The centrifugation speed is 1000-8000 rpm, and the time is 10-60 min. The drying temperature is 30-100℃, and the time is 6-48 h. The drying method is ventilation drying, vacuum drying, heating drying, or natural drying.

[0012] Furthermore, the zeolite precursor obtained by the above method is a layered RUB-15 precursor. This zeolite precursor has a surface richer number of hydroxyl groups than conventional zeolites.

[0013] Furthermore, the specific operation of modifying the zeolite precursor with carboxylic acid is as follows: the zeolite precursor is mixed with a carboxylic acid solution, stirred (during the stirring process, the zeolite precursor and carboxylic acid undergo ion exchange to remove template agent molecules between the zeolite precursor layers), centrifuged and washed, and dried to obtain the template agent-free zeolite precursor.

[0014] Furthermore, in the process of modifying the zeolite precursor with carboxylic acid, the stirring temperature is 25-80℃, the stirring speed is 100-400rpm, and the time is 1-8h; the centrifugal washing speed is 1000-12000rpm, the time for each centrifugal washing is 10-60min, and the centrifugal washing is repeated 5-10 times; the drying temperature is 60-100℃.

[0015] Further, the carboxylic acid solution is an aqueous solution of one or more of acetic acid, propionic acid, and butyric acid; the concentration of the carboxylic acid solution is 3-8M.

[0016] Furthermore, the template-free zeolite precursor is a template-free RUB-15 precursor, abbreviated as Ac-RUB-15.

[0017] Furthermore, the ratio of the template-free zeolite precursor to the polymer and solvent is 0.05-0.5 mg:1 mg:4 mL.

[0018] Further, the specific operation of preparing a mixed matrix membrane by mixing the template-free zeolite precursor with the polymer and solvent is as follows: the template-free zeolite precursor and the polymer are dispersed in half the volume of solvent to obtain a template-free zeolite precursor solution and a polymer solution, and then the template-free zeolite precursor solution and the polymer solution are mixed to obtain a mixed solution; the mixed solution is poured into a mold and dried to obtain a mixed matrix membrane, or the mixed solution is loaded onto a porous substrate by one of spin coating, spraying, or blade coating and dried to form a mixed matrix membrane on the surface of the porous substrate.

[0019] Further, the solvent is one or a mixture of chloroform, dichloromethane, methanol, ethanol, water, N,N-dimethylformamide, n-butanol, isobutanol, dimethyl sulfoxide, and N-methylpyrrolidone.

[0020] Further, the polymer is one or a mixture of polysulfone (PSF), polyethersulfone (PES), polyacrylonitrile (PAN), polyamide fiber (PA), polyethylene (PE), polyimide (PI), and polypropylene (PP).

[0021] Furthermore, the porous substrate is a porous α-Al2O3 membrane, a porous anodic aluminum oxide (AAO) membrane, a porous nylon membrane, a porous polyethersulfone membrane, a porous cellulose acetate membrane, a porous polytetrafluoroethylene membrane, or a porous polyvinylidene fluoride membrane.

[0022] Furthermore, the temperature of the low-temperature heating (i.e., the cross-linking reaction) is 100-400℃, and the time (i.e., the time of the cross-linking reaction) is 5-48h.

[0023] Furthermore, the temperature of the low-temperature heating (i.e., cross-linking reaction) is preferably 140-230°C.

[0024] Furthermore, the gaseous atmosphere of the crosslinking reaction is air, oxygen, nitrogen, or argon.

[0025] The second technical solution of the present invention: a defect-free zeolite molecular sieve-based mixed matrix membrane prepared according to the above method.

[0026] Furthermore, the thickness of the defect-free zeolite molecular sieve-based mixed matrix membrane is 1-150 μm.

[0027] The third technical solution of the present invention: the application of the above-mentioned defect-free zeolite molecular sieve-based mixed matrix membrane in the separation of helium (He).

[0028] Furthermore, the separation of He specifically refers to the separation of He from the He / CH4 gas mixture.

[0029] The present invention discloses the following technical effects:

[0030] (1) In this invention, a zeolite precursor is first prepared using silicon source, template agent and water as raw materials. Then, the zeolite precursor containing template agent is modified with carboxylic acid to obtain a zeolite precursor without template agent. The zeolite precursor without template agent is then used as an inorganic filler to prepare a mixed matrix membrane. The zeolite precursor prepared using silicon source, template agent and water as raw materials has abundant hydroxyl groups on its surface, which facilitates the clever combination of filler and polymer. These hydroxyl groups interact with the polymer during the crosslinking reaction initiated by low temperature heating, and undergo hydroxyl condensation reaction to form Si-OC bonds and achieve crosslinking. Crosslinking can effectively improve the interfacial interaction between filler and polymer and effectively solve the compatibility problem between filler and polymer.

[0031] (2) This invention uses low-temperature crosslinking technology to prepare zeolite molecular sieve-based mixed matrix membranes, solving the problem of poor compatibility between inorganic materials and polymers. The prepared zeolite molecular sieve-based mixed matrix membranes are free of interfacial defects, have high strength, strong environmental adaptability, and strong separation performance. In practical applications, they can greatly save costs and are suitable for large-scale industrial production. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 The image shows the XRD patterns of the mixed matrix membrane before and after the crosslinking reaction in Example 1 (compared with Ac-RUB-15 powder);

[0034] Figure 2 The infrared spectra of the mixed matrix membrane before and after the crosslinking reaction in Example 1 are shown (compared with Ac-RUB-15 powder, PI, and 3D SOD powder prepared in Comparative Example 2).

[0035] Figure 3 The images show the surface (left) and cross-section (right) of the defect-free zeolite molecular sieve-based mixed matrix membrane Ac-RUB-15&PI prepared in step (4) of Example 1.

[0036] Figure 4 The images show TEM images of the mixed matrix membrane before and after the crosslinking reaction in Example 1, where (a) is before crosslinking and (b) is after crosslinking.

[0037] Figure 5 The image shows the XRD patterns of the mixed matrix membrane before and after the low-temperature heating reaction in Comparative Example 1. Detailed Implementation

[0038] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0039] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0040] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0041] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0042] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0043] In the following examples, room temperature refers specifically to 20-25°C.

[0044] All raw materials used in the following examples and comparative examples are commercially available products, with PI specifically being PI with the brand name matrix 5218.

[0045] Example 1

[0046] A method for preparing defect-free zeolite molecular sieve-based hybrid matrix membranes via low-temperature crosslinking, comprising the following steps:

[0047] (1) Preparation of layered RUB-15 zeolite precursor: 5.75 g (0.063 mol) tetramethylammonium hydroxide, 12 g (0.045 mol) tetraethyl orthosilicate and 17.25 g (0.957 mol) water were mixed at room temperature to obtain a mixed solution. The mixed solution was stirred and aged at 300 rpm for 12 h to obtain a sol. The sol was transferred to a 100 mL Teflon-lined autoclave and then placed in an oven at 140 °C for hydrothermal reaction for 3 days. After the reaction was completed, the autoclave was allowed to cool naturally to room temperature. Finally, the mixture was centrifuged and washed at 8000 rpm for 30 min. After washing, the pH value of the washing solution dropped to 7. The mixture was then dried at 70 °C to obtain the layered RUB-15 zeolite precursor.

[0048] (2) Carboxylic acid modification of zeolite precursor: 200 mg of layered RUB-15 zeolite precursor was mixed with 50 mL of 3 M acetic acid solution and stirred at 200 rpm and 25 °C for 1 h. The product was centrifuged and washed 5 times at 12000 rpm for 10 min each time. The filter cake was dried at 70 °C to obtain template-free zeolite precursor Ac-RUB-15 powder.

[0049] (3) Preparation of mixed matrix membrane: 80 mg Ac-RUB-15 powder and 720 mg PI were dispersed in 4 mL of N,N-dimethylformamide and stirred evenly to obtain Ac-RUB-15 solution and PI solution. The Ac-RUB-15 solution and PI solution were mixed to obtain a mixed solution. 4 mL of the mixed solution was poured into a glass culture dish with a diameter of 6 cm and placed in a vacuum drying oven at 80 °C for 12 h to obtain the mixed matrix membrane Ac-RUB-15 / PI.

[0050] (4) Preparation of defect-free zeolite molecular sieve-based mixed matrix membrane by low-temperature crosslinking reaction: The Ac-RUB-15 / PI mixed matrix membrane was crosslinked in an oven at 180℃ (air atmosphere) for 24h to obtain the defect-free zeolite molecular sieve-based mixed matrix membrane Ac-RUB-15&PI (denoted as M1).

[0051] Figure 1 The XRD patterns of the mixed matrix membranes before and after the crosslinking reaction are shown (compared with Ac-RUB-15 powder, PI, and 3D SOD powder prepared in Comparative Example 2). The comparison shows that the positions of the diffraction peaks changed after the crosslinking reaction. Figure 2 The infrared spectra of the mixed matrix film before and after the crosslinking reaction are shown (compared with Ac-RUB-15 powder, PI, and 3D SOD powder prepared in Comparative Example 2). The comparison shows that the hydroxyl absorption peaks of Ac-RUB-15 and PI have disappeared, proving that hydroxyl condensation has occurred between Ac-RUB-15 and the polymer.

[0052] The surface and cross-sectional SEM images of the defect-free zeolite molecular sieve-based hybrid matrix membrane Ac-RUB-15&PI obtained in step (4) are shown below. Figure 3 As shown, by Figure 3 It can be seen that the membrane surface is smooth and the thickness is about 70 μm.

[0053] Figure 4 These are TEM images of the mixed matrix membrane before and after the crosslinking reaction, where (a) is before crosslinking and (b) is after crosslinking. Figure 4 It can be seen that the interfacial defects of the membrane disappear after cross-linking.

[0054] Example 2

[0055] Same as Example 1, except that the temperature of the crosslinking reaction in step (4) is 160°C and the time is 24h. The final defect-free zeolite molecular sieve-based mixed matrix membrane is denoted as M2.

[0056] Example 3

[0057] Same as Example 1, except that the temperature of the crosslinking reaction in step (4) is 140°C and the time is 24h. The final defect-free zeolite molecular sieve-based mixed matrix membrane is denoted as M3.

[0058] Example 4

[0059] Same as Example 1, except that the temperature of the crosslinking reaction in step (4) is 200°C and the time is 24h. The final defect-free zeolite molecular sieve-based mixed matrix membrane is denoted as M4.

[0060] Example 5

[0061] Same as Example 1, except that the crosslinking reaction in step (4) was carried out at a temperature of 230°C for 24 hours. The final defect-free zeolite molecular sieve-based mixed matrix membrane is designated as M5.

[0062] Comparative Example 1

[0063] (1) Preparation of layered RUB-15 zeolite precursor: 5.75 g (0.063 mol) tetramethylammonium hydroxide, 12 g (0.045 mol) tetraethyl orthosilicate and 17.25 g (0.957 mol) water were mixed at room temperature to obtain a mixed solution. The mixed solution was stirred and aged at 300 rpm for 12 h to obtain a sol. The sol was transferred to a 100 mL Teflon-lined autoclave and then placed in an oven at 140 °C for hydrothermal reaction for 3 days. After the reaction was completed, the autoclave was allowed to cool naturally to room temperature. Finally, the mixture was centrifuged and washed at 8000 rpm for 30 min. After washing, the pH value of the washing solution dropped to 7. The mixture was then dried at 70 °C to obtain the layered RUB-15 zeolite precursor.

[0064] (2) Preparation of mixed matrix membrane: 80 mg of layered RUB-15 zeolite precursor powder and 720 mg of PI were dispersed in 4 mL of N,N-dimethylformamide and stirred evenly to obtain layered RUB-15 solution and PI solution. The layered RUB-15 solution and PI solution were mixed to obtain a mixed solution. 4 mL of the mixed solution was poured into a glass culture dish with a diameter of 6 cm and dried in a vacuum drying oven at 80 °C for 12 h to obtain the mixed matrix membrane RUB-15 / PI.

[0065] (3) Low-temperature heating reaction: The RUB-15 / PI mixed matrix membrane was reacted in an oven at 180℃ (air atmosphere) for 24h to obtain the zeolite molecular sieve-based mixed matrix membrane RUB-15&PI (denoted as M6).

[0066] Figure 5 The XRD patterns of the mixed matrix membrane before and after the low-temperature heating reaction are shown. The comparison shows that after the reaction, the diffraction peaks of zeolite crystals in the zeolite molecular sieve-based mixed matrix membrane disappear, indicating that the framework of the unacidified RUB-15 precursor collapses after calcination.

[0067] Comparative Example 2

[0068] (1) Preparation of layered RUB-15 zeolite precursor: 5.75 g (0.063 mol) tetramethylammonium hydroxide, 12 g (0.045 mol) tetraethyl orthosilicate and 17.25 g (0.957 mol) water were mixed at room temperature to obtain a mixed solution. The mixed solution was stirred and aged at 300 rpm for 12 h to obtain a sol. The sol was transferred to a 100 mL Teflon-lined autoclave and then placed in an oven at 140 °C for hydrothermal reaction for 3 days. After the reaction was completed, the autoclave was allowed to cool naturally to room temperature. Finally, the mixture was centrifuged and washed at 8000 rpm for 30 min. After washing, the pH value of the washing solution dropped to 7. The mixture was then dried at 70 °C to obtain the layered RUB-15 zeolite precursor.

[0069] (2) Carboxylic acid modification of zeolite precursor: 200 mg of layered RUB-15 zeolite precursor was mixed with 50 mL of 3 M acetic acid solution and stirred at 200 rpm and 25 °C for 1 h. The product was centrifuged and washed 5 times at 12000 rpm for 10 min each time. The filter cake was dried at 70 °C to obtain template-free zeolite precursor Ac-RUB-15 powder.

[0070] (3) Conversion of Ac-RUB-15 powder into 3D SOD: Take 100mg of Ac-RUB-15 powder in a crucible and calcine it at 500℃ for 3h to obtain 3D SOD powder.

[0071] (4) Preparation of the mixed matrix membrane: 80 mg of 3D SOD powder and 790 mg of PI were dispersed in 4 mL of N,N-dimethylformamide, respectively, and stirred evenly to obtain 3D-SOD solution and PI solution. The 3D-SOD solution and PI solution were mixed to obtain a mixed solution. 4 mL of the mixed solution was poured into a glass petri dish with a diameter of 6 cm and dried in a vacuum drying oven at 80 °C for 12 h to obtain the mixed matrix membrane 3DSOD / PI (denoted as M7). The membrane prepared directly using 3D SOD obtained by calcination cannot eliminate interface defects.

[0072] Comparative Example 3

[0073] (1) Preparation of layered RUB-15 zeolite precursor: 5.75 g (0.063 mol) tetramethylammonium hydroxide, 12 g (0.045 mol) tetraethyl orthosilicate and 17.25 g (0.957 mol) water were mixed at room temperature to obtain a mixed solution. The mixed solution was stirred and aged at 300 rpm for 12 h to obtain a sol. The sol was transferred to a 100 mL Teflon-lined autoclave and then placed in an oven at 140 °C for hydrothermal reaction for 3 days. After the reaction was completed, the autoclave was allowed to cool naturally to room temperature. Finally, the mixture was centrifuged and washed at 8000 rpm for 30 min. After washing, the pH value of the washing solution dropped to 7. The mixture was then dried at 70 °C to obtain the layered RUB-15 zeolite precursor.

[0074] (2) Carboxylic acid modification of zeolite precursor: 200 mg of layered RUB-15 zeolite precursor was mixed with 50 mL of 3 M acetic acid solution and stirred at 200 rpm and 25 °C for 1 h. The product was centrifuged and washed 5 times at 12000 rpm for 10 min each time. The filter cake was dried at 70 °C to obtain template-free zeolite precursor Ac-RUB-15 powder.

[0075] (3) Preparation of mixed matrix membrane: 80 mg Ac-RUB-15 powder and 790 mg PI were dispersed in 4 mL of N,N-dimethylformamide and stirred evenly to obtain Ac-RUB-15 solution and PI solution. The Ac-RUB-15 solution and PI solution were mixed to obtain a mixed solution. 4 mL of the mixed solution was poured into a glass culture dish with a diameter of 6 cm and dried in a vacuum drying oven at 80 °C for 12 h to obtain the mixed matrix membrane Ac-RUB-15 / PI (denoted as M8).

[0076] Comparative Example 4

[0077] (1) Preparation of cubic SOD zeolite: 14.37g sodium hydroxide and 38g deionized water were mixed for 10min at room temperature, 0.45g aluminum powder was added, and the mixture was stirred for 20min. 10g silica sol aqueous solution (30wt%) was slowly added dropwise. The mixed solution was aged at room temperature for 24h. The sol was transferred to a 100mL Teflon-lined autoclave and then placed in an oven at 140℃ for hydrothermal reaction for 3d. After the reaction was completed, the autoclave was allowed to cool naturally to room temperature. Finally, the mixture was centrifuged and washed at 8000rpm for 30min. The pH of the washing solution dropped to 7 after washing. The mixture was then dried at 70℃ to obtain cubic SOD zeolite.

[0078] (2) Preparation of the mixed matrix membrane: 80 mg of cubic SOD powder and 790 mg of PI were dispersed in 4 mL of N,N-dimethylformamide, respectively, and stirred evenly to obtain cubic SOD solution and PI solution. The cubic SOD solution and PI solution were mixed to obtain a mixed solution. 4 mL of the mixed solution was poured into a glass culture dish with a diameter of 6 cm and dried in a vacuum drying oven at 80 °C for 12 h to obtain the mixed matrix membrane SOD. cube / PI (denoted as M9).

[0079] Effect verification

[0080] The mixed matrix membranes M1-M5 finally prepared in Examples 1-5 and the mixed matrix membranes M6-M9 finally prepared in Comparative Examples 1-4 were used to test the separation performance of each of the above mixed matrix membranes for the He / CH4 system.

[0081] Test method: The mixed matrix membrane is placed in a gas separation device. A 1:1 (25 mL / min: 25 mL / min) mixture of He and CH4 gas is introduced into the feed side, and a purge gas is introduced into the purge side. The gas on the permeate side is then introduced into a gas chromatograph for detection.

[0082] Table 1

[0083]

[0084]

[0085] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing defect-free zeolite molecular sieve-based hybrid matrix membranes via low-temperature crosslinking, characterized in that, Includes the following steps: The silicon source, template agent, and water are mixed to obtain a mixed solution; The mixed solution was stirred and aged, followed by hydrothermal reaction to obtain a zeolite precursor; The zeolite precursor was modified with carboxylic acid to obtain a template-free zeolite precursor. The template-free zeolite precursor was mixed with a polymer and a solvent to prepare a hybrid matrix membrane; The mixed matrix membrane is subjected to low-temperature heating to initiate a crosslinking reaction, thereby obtaining the defect-free zeolite molecular sieve-based mixed matrix membrane.

2. The method as described in claim 1, characterized in that, The silicon source is one of silica sol, tetraethyl orthosilicate, sodium silicate, or silicon powder; the template agent is tetramethylammonium hydroxide; the molar ratio of silicon, template agent, and water in the mixed solution is 1:1-3:20-80.

3. The method as described in claim 1, characterized in that, The stirring and aging time is 1-48 hours; the hydrothermal reaction temperature is 120-200℃ and the time is 1-21 days.

4. The method as described in claim 1, characterized in that, The specific operation of modifying the zeolite precursor with carboxylic acid is as follows: the zeolite precursor is mixed with a carboxylic acid solution, stirred, centrifuged and washed, and dried to obtain the template-free zeolite precursor.

5. The method as described in claim 4, characterized in that, The carboxylic acid solution is an aqueous solution of one or more of acetic acid, propionic acid, and butyric acid; the concentration of the carboxylic acid solution is 3-8M.

6. The method as described in claim 1, characterized in that, The ratio of the template-free zeolite precursor to the polymer and solvent is 0.05-0.5 mg:1 mg:4 mL.

7. The method as described in claim 1, characterized in that, The low-temperature heating is performed at a temperature of 100-400℃ for 5-48 hours.

8. A defect-free zeolite molecular sieve-based hybrid matrix membrane prepared by the method according to any one of claims 1-7.

9. The application of the defect-free zeolite molecular sieve-based mixed matrix membrane as described in claim 8 in the separation of helium.

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