Oriented ultrathin FER zeolite molecular sieve membrane as well as preparation method and application thereof

Abstract

The invention provides an oriented ultrathin FER zeolite molecular sieve membrane as well as a preparation method and application thereof. The preparation method comprises the following steps: firstly, synthesizing a monodisperse FER zeolite nanosheet with a high length-depth ratio through a hydrothermal method; preparing a seed crystal liquid, and coating the surface of a porous carrier with the seed crystal liquid to form an oriented seed crystal layer; and carrying out hydrothermal epitaxial growth in a secondary growth solution. Through innovative design of seed crystal synthesis and epitaxial growth, the FER zeolite membrane prepared by the method has a structure with high alpha-axis preferred orientation, submicron controllable thickness, compactness and no defect. The membrane can be used for accurately screening gas molecules with small size difference by utilizing six-membered ring pore channels uniformly arranged along an a axis. When helium and methane or carbon dioxide are separated, the membrane shows permeation flux and separation selectivity far superior to those in the prior art, provides a brand new technical approach for efficient and low-energy-consumption recovery of helium and other high-value gases in the industry, and has great industrial application value.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of synthesis of molecular sieve membranes, and particularly relates to an oriented ultrathin FER zeolite molecular sieve membrane, a preparation method and application thereof. BACKGROUND

[0002] Helium is a key rare gas resource related to national strategic security and high-tech industry development, and its efficient and low-cost extraction and purification technology is an important challenge in the current chemical separation field. Traditional separation methods such as low-temperature rectification and pressure swing adsorption generally have problems such as large equipment investment, high energy consumption and complex operation process, and are difficult to meet the growing global demand. Membrane separation technology is considered as a new generation of separation technology with great potential due to its energy saving, environmental protection and simple operation.

[0003] Currently, the commercial gas separation membrane is mainly a polymer membrane, but its performance is limited by the "Robinson upper limit", that is, permeability and selectivity are difficult to achieve. More importantly, when dealing with actual natural gas containing CO2, water and heavy hydrocarbon impurities, the polymer membrane is prone to plasticization or competitive adsorption, resulting in a significant decrease in separation performance and long-term stability. Inorganic zeolite membrane can fundamentally overcome the above-mentioned defects of polymer membrane due to its regular sub-nanometer pore structure and excellent thermal / chemical stability. Ferrierite (FER) is a zeolite with a two-dimensional pore structure, and the size of the six-membered ring pore along the a crystal axis direction is about 0.28 nm. This size is slightly larger than the kinetic diameter of helium gas (~ 0.26 nm), but is significantly smaller than the size of main impurity components such as CO2 (0.33 nm), N2 (0.36 nm) and CH4 (0.38 nm) in natural gas. In theory, if a dense and defect-free membrane layer and a highly oriented FER membrane with its crystal a axis perpendicular to the surface of the support can be successfully constructed, it is expected to form a high-selectivity helium separation path by using the regularly arranged six-membered ring pores along the a axis, so as to realize its efficient separation. At the same time, reducing the membrane layer thickness to the sub-micron level is the key to greatly improving the permeation flux. However, the FER membranes reported in the prior art generally have problems such as too thick membrane layer, low orientation degree and many structural defects, which limit the He / CH4 separation performance and make it difficult to meet the needs of industrial application (Microporous Mesoporous Mater. 1999, 32, 159-168; Microporous Mesoporous Mater. 2000, 38, 43-50; Mater. Lett. 2020, 260, 126940; Chem. Eng. China 2007, 1, 217-220). Therefore, developing a new method for preparing a FER membrane capable of realizing high a-axis orientation, ultrathin thickness and structural integrity is the key to promoting the technical breakthrough of zeolite membranes in the field of helium recovery. SUMMARY

[0004] To solve the above problems, the application provides an oriented ultrathin FER zeolite molecular sieve membrane, a preparation method and application thereof, a monodisperse FER nanosheet with high length-depth ratio is prepared by dynamic hydrothermal crystallization, and the oriented seed layer deposition and controllable in-plane epitaxial growth are performed to prepare a continuous and dense ultrathin FER zeolite membrane with high a-axis orientation, and the ultrathin FER zeolite membrane is used for helium gas system separation, and has excellent gas permeability and gas selectivity.

[0005] The application is achieved by the following technical solutions.

[0006] An oriented ultrathin FER zeolite molecular sieve membrane has a thickness of 200nm-400nm, a dense and continuous membrane layer and high a-axis orientation.

[0007] The preparation method of the oriented ultrathin FER zeolite molecular sieve membrane comprises the following steps.

[0008] S1: mixing a silicon source, an aluminum source, an alkali source, an organic structure directing agent and deionized water, stirring and aging at 40-100 DEG C for 4-18h to obtain a precursor sol; placing the precursor sol in a reaction kettle, performing a crystallization reaction under dynamic hydrothermal conditions, performing centrifugal washing and freeze-drying to obtain a monodisperse two-dimensional FER nanosheet with high length-depth ratio; the alkali source comprises a mixture of NaOH and KOH, and n(K + ) / n(K + +Na + )=0.3-0.8;

[0009] S2: dispersing the FER nanosheet powder synthesized in S1 in a solvent to prepare a nanosheet suspension, and coating the nanosheet suspension on the surface of a porous carrier to obtain a continuous and dense seed layer, and drying and calcining the seed layer to solidify the seed layer;

[0010] S3: mixing a silicon source, an aluminum source, an alkali source, an organic structure directing agent and deionized water, stirring and aging at 40-100 DEG C for 4-18h to obtain a secondary growth solution; placing the carrier coated with the seed layer obtained in S2 in the secondary growth solution to perform a crystallization reaction, taking out the obtained membrane material after the reaction, washing with water, drying and calcining to remove the organic structure directing agent, and obtaining a FER zeolite membrane; the molar ratio of Al2O3:SiO2:OH - :OSDA:H2O in the secondary growth solution is 1:(10-500):(5-600):(20-500):(400-16000), and the silicon source, the aluminum source, the alkali source, the organic structure directing agent and water are counted as SiO2, Al2O3, OH - , OSDA and H2O respectively.

[0011] The silicon source in step S1 includes one or more of tetramethyl orthosilicate, tetraethyl orthosilicate, water glass, silica sol and silica aerogel; the aluminum source includes one or more of aluminum hydroxide, aluminum sulfate octadecahydrate, aluminum chloride or aluminum nitrate; and the organic structure directing agent includes one or more of pyridine, pyrrolidine and ethylenediamine.

[0012] The molar ratio of Al2O3:SiO2:OH:OSDA:H2O in the precursor sol in step S1 is 1:(10-300):(5-200):(20-400):(800-4000). -

[0013] The hydrothermal reaction temperature in step S1 is 100-180°C, and the hydrothermal reaction time is 15-100h.

[0014] The lateral size of the FER nanosheet in step S1 is 0.5-5μm, the thickness is 5-10nm, and the maximum plane corresponds to the a-axis.

[0015] The solvent in step S2 is methanol, ethanol, propanol, sec-butanol or deionized water, and the concentration of the suspension is 0.01-0.5wt.%.

[0016] The material of the porous carrier is alumina, zirconia, mullite or stainless steel; the shape of the porous carrier is tubular, flat plate, hollow fiber or porous channel carrier; the average pore size of the porous carrier is 0.02-3μm, and the porosity is 30%-60%.

[0017] The base source in step S3 includes one or more of NaOH, KOH or LiOH, the silicon source includes one or more of tetramethyl orthosilicate, tetraethyl orthosilicate, water glass, silica sol and silica aerogel, the aluminum source includes one or more of aluminum hydroxide, aluminum sulfate octadecahydrate, aluminum chloride or aluminum nitrate, and the organic structure directing agent includes one or more of pyridine, pyrrolidine and ethylenediamine.

[0018] When the conventional hydrothermal secondary growth method is used in step S3, the crystallization temperature is 100-200°C, and the crystallization time is 6-72h; meanwhile, the secondary growth method can be assisted by microwave, and when the microwave-assisted secondary growth method is used, the crystallization temperature is 80-140°C, and the crystallization time is 30-140min.

[0019] ​The FER zeolite membrane in step S3 is calcined by one of a muffle furnace, ultraviolet irradiation, oxygen plasma treatment, a tube furnace in an ozone atmosphere, or a rapid heating process, at a temperature of 120-600 DEG C for 0.5-70 hours. Further, the FER zeolite membrane is calcined by a tube furnace in an ozone atmosphere at a temperature of 140-280 DEG C, which requires a lower calcination temperature and shorter time, while ensuring the integrity of the membrane layer to the greatest extent.

[0020] The application also provides a use of the FER zeolite membrane in helium recovery, which exhibits excellent separation performance for helium / carbon dioxide, helium / nitrogen, and helium / methane systems.

[0021] Compared with the prior art, the application has the following beneficial effects: by using a set of innovative preparation strategies, the FER zeolite membrane with a high a-axis preferred orientation, a controllable sub-micron thickness, and a dense defect-free microstructure is prepared for the first time by using FER nanosheets with a high aspect ratio (about 180, the highest value reported in the literature) as seeds and combining controllable epitaxial growth technology, and the thickness of the membrane is only 200 nm. The thickness of the membrane is the lowest value reported in the literature, and the unique a-axis preferred orientation constructs a vertical and uniform 6-membered ring (6-MR) molecular sieve channel in the membrane, which is an unprecedented membrane structure. The unique pore structure endows the membrane with excellent molecular sieving performance: the permeation flux of He is as high as 500.8 GPU, and the selectivity of He / CO2, He / N2, and He / CH4 is 367, 426, and 586, respectively, which comprehensively exceeds the existing technical level. Therefore, the application not only solves the bottleneck of preparing high-quality oriented FER zeolite membranes, but also provides a key technical solution for the industrialized and efficient recovery of high-value gases such as helium. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a gas separation test device diagram of the patent.

[0023] Figure 2 is an (a) SEM image and (b) XRD image of the FER nanosheet prepared in Example 1.

[0024] Figure 3 is an AFM image of the FER nanosheet prepared in Example 1.

[0025] Figure 4 is a nitrogen adsorption-desorption isotherm graph of the FER nanosheet prepared in Example 1 at 77K.

[0026] Figure 5 is an (a) SEM image and (b) XRD image of the FER seed layer prepared in Example 1.

[0027] Figure 6 is a (a) planar SEM image and (b) cross-sectional SEM image of the FER zeolite membrane prepared in Example 1.

[0028] Figure 7 is an XRD pattern of the FER zeolite membrane prepared in Example 1.

[0029] Figure 8 is an SEM image of (a) FER nanosheets and (b) FER zeolite membranes prepared in Example 2.

[0030] Figure 9 is an SEM image of the FER zeolite membrane prepared in Example 3.

[0031] Figure 10 is an SEM image of the FER zeolite membrane prepared in Example 4.

[0032] Figure 11 is an SEM image of the FER zeolite membrane prepared in Example 5.

[0033] Figure 12 is an SEM image of the FER zeolite prepared in Comparative Example 1.

[0034] Figure 13 is an SEM image of the FER seed layer prepared in Comparative Example 3.

[0035] Figure 14 is an SEM image of the FER zeolite membrane prepared in Comparative Example 4.

[0036] Figure 15 is an SEM image of the FER zeolite membrane prepared in Comparative Example 5. DETAILED DESCRIPTION

[0037] The application will be further described in the following specific examples. The following examples will help further understand the application for those skilled in the art, but do not limit the application in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the application. These all belong to the protection scope of the application.

[0038] The test conditions for the gas separation test in this application are as follows: the molar ratio of the two-component mixed gas feed is 1:1, the test temperature is 100°C, the permeation side is vacuumed, the transmembrane pressure difference is 1 bar, and the device diagram is shown in Figure 1 .

[0039] Example 1

[0040] (1) FER nanosheet seed preparation: NaOH, KOH, silica sol, aluminum sulfate octadecahydrate and pyridine were added into deionized water in sequence to form a precursor sol, and the molar ratio of the sol was 1 Al203: 120 Si02: 25 NaOH: 15 KOH: 75 C5H5N: 2400 H20. After aging at 50 °C for 6 h with vigorous stirring, the obtained aged sol was transferred into a stainless steel autoclave for crystallization at 160 °C for 72 h under dynamic hydrothermal conditions. The product was obtained by centrifugation, washing and freeze-drying to obtain two-dimensional FER nanosheets.

[0041] (2) Oriented FER seed layer preparation: The freeze-dried FER nanosheets were dispersed in an ethanol solution by strong ultrasonic dispersion to prepare a uniform FER nanosheet suspension (0.01 wt.% ethanol solution). Then, the nanosheet seed liquid was coated on the surface of the porous carrier to obtain a continuous and dense oriented FER seed layer, which was dried and calcined to solidify the seed layer.

[0042] (3) Oriented FER zeolite membrane preparation: A secondary growth solution was prepared using a formulation with a molar ratio of 1 Al203: 100 Si02: 30 KOH: 70 C5H5N: 9800 H20, and the preparation process of the secondary growth solution was the same as that of the precursor sol for the FER zeolite nanosheet seed. The seed layer coated carrier was placed in the secondary growth solution, sealed and placed in an oven at 170 °C for 10 h. After the reaction was completed, the membrane was taken out, washed with deionized water until it was neutral, dried overnight and placed in a tubular furnace in an ozone atmosphere for calcination at 250 °C for 40 h to remove the template. The temperature rising and falling rates were both 1 °C / min. The FER zeolite membrane prepared in this process is denoted as Ml.

[0043] The scanning electron microscopy characterization of the FER nanosheets is shown in Figure 2 a, and the obtained product exhibits a monodisperse nanosheet morphology with a lateral size of 0.7-1.8 μm. At the same time, the related XRD diffraction peaks Figure 2 b) confirm the phase purity thereof, and the diffraction peaks thereof are completely consistent with the simulated FER phase standard spectrum, indicating that the product is a pure-phase FER zeolite. The AFM measurement results Figure 3 a, b) confirm that the thickness of the synthesized FER nanosheets is about 9.5 nm (equivalent to 5 FER cell units), and thus the length-depth ratio thereof is as high as ~180, which is the highest value of FER zeolite reported in the literature so far. In addition, the N2 adsorption-desorption isotherm Figure 4 ) presents a typical type I curve, proving the inherent microporous structure of the material; the calculated BET specific surface area is 325.6 m 2 g -1 , which is comparable to the FER zeolite material reported in the literature. The scanning electron microscopy characterization of the prepared seed layer is shown in Figure 5As shown in figure a, the seed crystals are uniformly and densely packed on the support surface, with a seed layer thickness of approximately 120 nm. The corresponding XRD pattern ( Figure 5 b) also confirms that the seed layer has a significant a-axis preferred orientation. From Figure 6 As can be seen from a, after secondary growth, the surface of the obtained FER zeolite film is smooth, the film is dense and continuous and without defects, and the cross-sectional scanning electron microscopy characterization is as follows. Figure 6 As shown in b, the film thickness is approximately 200 nm. XRD results ( Figure 7 The results indicate that the prepared membrane material has a pure-phase FER structure, high crystallinity, and a high degree of α-axis orientation. Gas separation performance tests were conducted on membrane M1 in He / CO2, He / N2, and He / CH4 systems. The results showed that its He permeation flux reached 500.8 GPU, while the selectivity for He / CO2, He / N2, and He / CH4 reached 367, 426, and 586, respectively. Its overall performance comprehensively surpasses the existing technology level.

[0044] Example 2

[0045] The difference from Example 1 is that in Example 2, the molar ratio of the FER nanosheet seed sol preparation in step (1) is: 1Al2O3:120SiO2:25NaOH:15KOH:75C5H5N:4000H2O. The remaining steps are the same as in Example 1. The film prepared by this process is denoted as M2. SEM characterization shows that... Figure 8 a) The FER nanosheets prepared in this process are monodisperse with complete morphology, making them suitable for subsequent film fabrication. The subsequently prepared films are continuous and dense, with almost no twinning on the surface, and also exhibit a high degree of α-axis orientation. Figure 8 b). The gas separation performance of membrane M2 in He / CO2, He / N2 and He / CH4 systems was also tested. The results showed that its He permeation flux was 489.8 GPU, and the selectivity for He / CO2, He / N2 and He / CH4 reached 356, 414 and 581, respectively.

[0046] Example 3

[0047] The difference from Example 1 is that in Example 3, step (3) of preparing the oriented FER zeolite film uses a secondary growth solution with a molar ratio of 1Al2O3:100SiO2:30KOH:70C5H5N:16000H2O, and the crystallization conditions are 180℃ for 14h. The remaining steps are the same as in Example 1, and the film prepared by this process is denoted as M3. Figure 9As shown, the prepared membrane layer is continuous and dense with high a-axis orientation. The gas separation performance test of He / CO2, He / N2 and He / CH4 system was conducted on the membrane M3, and the results show that the He permeation flux is 700.5 GPU, and the selectivity of He / CO2, He / N2 and He / CH4 is 152, 268 and 356 respectively.

[0048] Example 4

[0049] The difference between Example 1 and Example 4 is that the secondary growth solution for the preparation of the oriented FER zeolite membrane in step (3) of Example 4 is prepared by using a formula with a molar ratio of 1 Al2O3: 500 SiO2: 30 KOH: 70 C5H5N: 980 H2O, and the remaining steps are the same as those of Example 1. The membrane prepared in this process is denoted as M4. As shown in Figure 10 , the prepared membrane layer is continuous and dense with high a-axis orientation. The gas separation performance test of He / CO2, He / N2 and He / CH4 system was conducted on the membrane M4, and the results show that the He permeation flux is 659.0 GPU, and the selectivity of He / CO2, He / N2 and He / CH4 is 289, 345 and 501 respectively.

[0050] Example 5

[0051] The difference between Example 1 and Example 5 is that the template agent used in the secondary growth solution for the preparation of the oriented FER zeolite membrane in step (3) of Example 5 is ethylenediamine, and the remaining steps are the same as those of Example 1. The membrane prepared in this process is denoted as M5. As shown in Figure 11 , the prepared membrane layer is continuous and dense with high a-axis orientation. The gas separation performance test of He / CO2, He / N2 and He / CH4 system was conducted on the membrane M5, and the results show that the He permeation flux is 345.2.0 GPU, and the selectivity of He / CO2, He / N2 and He / CH4 is 103, 189 and 251 respectively.

[0052] Comparative Example 1

[0053] The difference between Example 1 and Comparative Example 1 is that the crystallization method used in the preparation of the FER nanosheet seeds in step (1) of Comparative Example 1 is static heating. The FER nanosheet prepared in this process is an irregular aggregate mainly composed of amorphous phase, and almost no nanosheet morphology appears Figure 12 ). This morphology is not suitable for subsequent seed layer deposition and epitaxial growth.

[0054] Comparative Example 2

[0055] The difference from Example 1 is that the single NaOH alkali source is used in the preparation of FER nanosheet seeds in step (1) of Comparative Example 1, and the specific sol formula used is: 1 Al203: 120 Si02: 40 NaOH: 75 C5H5N: 2400 H20. After hydrothermal crystallization, there is no obvious product generated in the kettle, which is not suitable for subsequent operations.

[0056] Comparative Example 3

[0057] The difference from Example 1 is that the product is washed by centrifugation and then subjected to traditional hot drying instead of freeze drying after dynamic hydrothermal crystallization in step (1) of Comparative Example 2. A large number of surface nanosheet agglomerates are generated in the seed layer prepared in this process Figure 13 , which is not suitable for subsequent epitaxial growth into a film.

[0058] Comparative Example 4

[0059] The difference from Example 1 is that the formula of molar ratio 1 Al203: 100 Si02: 700 KOH: 70 C5H5N: 9800 H20 is used to prepare the secondary growth solution in step (3) of the preparation of the oriented FER zeolite film in Comparative Example 3, and the remaining steps are the same as in Example 1. The film prepared in this process is denoted as M6. As shown in Figure 14 , the size of the nanosheet seed on the support surface has almost no obvious change, and there are a large number of intercrystalline defects in the film layer. At this time, the film layer has no separation effect on the He / CO2, He / N2 and He / CH4 systems.

[0060] Comparative Example 5

[0061] The difference from Example 1 is that the formula of molar ratio 1 Al203: 100 Si02: 30 KOH: 600 C5H5N: 9800 H20 is used to prepare the secondary growth solution in step (3) of the preparation of the oriented FER zeolite film in Comparative Example 3, and the remaining steps are the same as in Example 1. The film prepared in this process is denoted as M6. As shown in Figure 15 , a large number of twinned crystals are generated on the film surface at this time, and the film layer has poor orientation and no obvious a-axis orientation. At this time, the film layer has poor separation effect on the He / CO2, He / N2 and He / CH4 systems.

[0062] Although the preferred embodiments of the present application have been described, those skilled in the art can make additional changes and modifications to these embodiments once they understand the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0063] Obviously, many modifications and variations of the present application are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims and their equivalents, the application can be practiced otherwise than as specifically described.

Claims

1. An oriented ultra-thin FER zeolite molecular sieve membrane, characterized by: The FER zeolite molecular sieve membrane has a thickness of 200-400 nm, a dense and continuous membrane layer, and a high a-axis orientation.

2. A method for preparing an oriented ultra-thin FER zeolite molecular sieve membrane according to claim 1, characterized in that: The method comprises the following steps: S1 mixes a silicon source, an aluminum source, an alkali source, an organic structure directing agent and deionized water, stirs and ages at 40-100 ℃ for 4-18 h to obtain a precursor sol; places the precursor sol in a reaction kettle, and performs a crystallization reaction under dynamic hydrothermal conditions, centrifuges and washes, and freeze-dries to obtain monodisperse, high-length-depth-ratio two-dimensional FER nanosheets; the alkali source comprises a mixture of NaOH and KOH, and n(K + ) / n(K + +Na + ) = 0.3-0.

8. S2: dispersing the FER nanosheets synthesized in S1 in a solvent to prepare a nanosheet suspension, and coating the nanosheet suspension on a surface of a porous carrier to obtain a continuous and dense seed layer, and drying and calcining the seed layer to solidify the seed layer; S3 mixing silicon source, aluminum source, alkali source, organic structure directing agent and deionized water, stirring at 40-100 ℃ for 4-18 h to prepare secondary growth solution; the carrier of the seed layer obtained in S2 is placed in the secondary growth solution for crystallization reaction, after the reaction, the membrane material is taken out, washed with water, dried and calcined to remove the organic structure directing agent, to obtain FER zeolite membrane; the molar ratio of Al2O3:SiO2:OH - :OSDA:H2O in the secondary growth solution is 1:(10-500):(5-600):(20-500):(400-16000).

3. A method for preparing an oriented ultra-thin FER zeolite molecular sieve membrane according to claim 2, characterized in that: The silicon source comprises one or more of tetramethyl orthosilicate, tetraethyl orthosilicate, water glass, silica sol and silica aerogel; the aluminum source comprises one or more of aluminum hydroxide, aluminum sulfate octadecahydrate, aluminum chloride or aluminum nitrate; and the organic structure directing agent comprises one or more of pyridine, pyrrolidine and ethylenediamine.

4. The method for preparing an oriented ultrathin FER zeolite molecular sieve membrane as described in claim 2, characterized in that: In step S1, the precursor sol contains Al2O3:SiO2:OH - The molar ratio of OSDA:H2O is 1:(10~300):(5~200):(20~400):(800~4000).

5. The method for preparing an oriented ultrathin FER zeolite molecular sieve membrane as described in claim 2, characterized in that: In S1, the hydrothermal reaction temperature is 100-180℃, and the hydrothermal reaction time is 15-100 h.

6. The method for preparing an oriented ultrathin FER zeolite molecular sieve membrane as described in claim 2, characterized in that: In S1, the FER nanosheet has a lateral size of 0.5-5 μm, a thickness of 5-10 nm, and a maximum plane corresponding to a crystal face of an a-axis.

7. The method for preparing an oriented ultrathin FER zeolite molecular sieve membrane as described in claim 2, characterized in that: In S2, the solvent is methanol, ethanol, propanol, sec-butanol or deionized water, and the concentration of the suspension is 0.01-0.5 wt.%; and / or, The porous carrier is made of alumina, zirconia, mullite or stainless steel, has a tubular, flat plate, hollow fiber or porous channel shape, and has an average pore size of 0.02-3 μm and a porosity of 30-60%.

8. The method for preparing an oriented ultrathin FER zeolite molecular sieve membrane according to claim 2, characterized in that: In S3, the alkali source comprises one or more of NaOH, KOH or LiOH.

9. The method for preparing an oriented ultrathin FER zeolite molecular sieve membrane as described in claim 2, characterized in that: In S3, when a conventional hydrothermal secondary growth method is used, the crystallization temperature is 100-200℃, and the crystallization time is 6-72 h; when a microwave-assisted secondary growth method is used, the crystallization temperature is 80-140℃, and the crystallization time is 30-140 min.

10. Use of the FER zeolite membrane of claim 1 in helium recovery.

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