A flexible zeolite molecular sieve composite membrane and its preparation method

Abstract

This invention provides a method for preparing a flexible zeolite molecular sieve composite membrane. The synthesis process includes the following steps: (1) dispersing zeolite molecular sieve nanosheets in a solvent to obtain a zeolite molecular sieve nanosheet dispersion; (2) dispersing graphene oxide powder in a solvent to obtain a graphene oxide nanosheet dispersion solution; (3) mixing and dispersing the zeolite molecular sieve and graphene oxide nanosheet dispersion solutions in a certain proportion to obtain a composite nanosheet dispersion solution; (4) depositing and drying the composite nanosheet dispersion solution on an organic carrier to obtain a flexible zeolite molecular sieve composite membrane. This zeolite molecular sieve composite separation membrane is flexible, has strong bonding between the carrier layer and the membrane layer, and exhibits high separation selectivity. Compared with conventional inorganic carrier-supported zeolite molecular sieve membranes, the preparation process of this zeolite molecular sieve composite membrane is simple, the production cost is significantly reduced, and it is easy to scale up industrially.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation technology, specifically relating to a method for preparing and applying a flexible zeolite molecular sieve composite separation membrane. Background Technology

[0002] Zeolite molecular sieve membranes, due to their uniform molecular-level pore size and excellent thermal and chemical stability, have been widely studied for the efficient separation of various gas and liquid mixtures. Although zeolite molecular sieve membranes have shown promising industrial applications in areas such as natural gas decarbonization and organic solvent dehydration, their large-scale application still faces certain challenges. Firstly, due to the high brittleness of zeolite molecular sieve membranes, they are typically fabricated on porous alumina supports with greater strength to improve the membrane's mechanical strength. However, the high cost of alumina supports keeps the cost of zeolite molecular sieve membranes significantly higher than current organic membrane materials. Secondly, the synthesis process of zeolite molecular sieves is lengthy, generally requiring tens of hours under high-temperature hydrothermal conditions, resulting in relatively low production efficiency. Finally, compared to spiral-wound or hollow fiber organic membranes, the packing density of commonly used porous alumina tube-supported zeolite molecular sieve membranes is relatively low, leading to substantial processing costs for zeolite molecular sieve membrane modules. Although the packing density of zeolite molecular sieve membranes supported by hollow fibrous porous alumina tubes can be significantly improved, the weak mechanical strength of the support is detrimental to practical industrial applications. These problems greatly limit the practical industrial application of zeolite molecular sieve membranes.

[0003] Compared to commonly used porous alumina supports, porous organic supports are significantly cheaper and easier to fabricate into spiral wound and hollow fiber forms to greatly increase membrane packing density. Therefore, organically supported separation membranes have a substantial cost advantage in practical applications. However, the incompatibility of the mechanical properties of flexible organic supports and brittle zeolite molecular sieve membrane layers makes zeolite molecular sieve membranes synthesized on organic supports highly prone to cracking, posing a significant challenge to obtaining high-quality zeolite membranes. Improving the mechanical properties of the membrane layer and making them relatively compatible with the mechanical properties of the organic support is an important way to improve the performance of organically supported zeolite molecular sieve membranes.

[0004] Graphene is carbon atoms arranged in sp. 2This invention relates to a two-dimensional carbon material with a single-atom-layer thickness, formed by hybridization. Its derivative, graphene oxide (GO), possesses excellent flexibility and dispersibility and has been widely studied for constructing two-dimensional separation membranes. The present invention involves adding a small amount of flexible two-dimensional graphene oxide nanosheets to a solution of two-dimensional zeolite molecular sieve nanosheets to obtain a composite nanosheet solution, which is then deposited onto an organic support to directly obtain a two-dimensional zeolite molecular sieve composite membrane. The addition of a small amount of graphene oxide nanosheets significantly improves the membrane's flexibility and adhesion to the support, and also significantly reduces interlayer defects between the two-dimensional zeolite molecular sieve nanosheets, greatly enhancing the membrane's separation selectivity. Simultaneously, due to the excellent flexibility of this zeolite molecular sieve composite membrane, it is easily prepared into spiral-wound or hollow fiber forms, significantly reducing the membrane's production cost. The above-mentioned zeolite molecular sieve composite membrane has a simple preparation process, excellent separation performance, strong adaptability to different organic supports, and is easy to scale up for industrial applications. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a flexible zeolite molecular sieve composite membrane supported by an organic carrier. The key feature of this method is the use of a small amount of flexible graphene oxide nanosheets to improve the mechanical properties of the zeolite molecular sieve nanosheet layer, thereby ensuring mechanical compatibility between the zeolite molecular sieve composite membrane layer and the carrier layer, ultimately resulting in a high-performance zeolite molecular sieve composite membrane supported by an organic carrier.

[0006] To achieve the above objectives, the following technical solution is adopted:

[0007] A method for preparing a flexible zeolite molecular sieve composite membrane includes the following steps:

[0008] (1) The zeolite molecular sieve nanosheets with the template agent removed are dispersed in an appropriate amount of solvent to obtain a zeolite molecular sieve nanosheet dispersion of appropriate concentration.

[0009] (2) Disperse graphene oxide powder in an appropriate amount of solvent to obtain a graphene oxide nanosheet dispersion of appropriate concentration.

[0010] (3) Mix and disperse the zeolite molecular sieve nanosheet dispersion in step (1) and the graphene oxide nanosheet dispersion in step (2) to obtain a zeolite molecular sieve / graphene oxide composite nanosheet dispersion.

[0011] (4) Deposit an appropriate amount of zeolite molecular sieve / graphene oxide composite nanosheet dispersion from step (3) onto an organic carrier, and obtain a flexible zeolite molecular sieve / graphene oxide nanosheet composite membrane after drying.

[0012] In step (1), the concentration of the zeolite molecular sieve nanosheet dispersion solution is 0.01-500 mg / mL.

[0013] In step (1), the solvent is one or a combination of water, methanol, ethanol, isopropanol, acetonitrile, diethyl ether, acetone, ethyl acetate, chloroform, dichloromethane, cyclohexane, N,N-dimethylformamide, N-methylpyrrolidone, tetrahydrofuran, benzene, toluene, and xylene.

[0014] In step (1), the zeolite molecular sieve nanosheets are one of MFI, MWW, or CHA types.

[0015] In step (2), the concentration of the graphene oxide nanosheet dispersion is 0.01-500 mg / mL.

[0016] In step (2), the solvent is one or a combination of several of the following: water, methanol, ethanol, isopropanol, acetonitrile, diethyl ether, acetone, ethyl acetate, chloroform, dichloromethane, cyclohexane, N,N-dimethylformamide, N-methylpyrrolidone, tetrahydrofuran, benzene, toluene, and xylene.

[0017] In step (3), the mass ratio of zeolite molecular sieve to graphene oxide nanosheets in the formulation is 100-1. The concentration of the resulting zeolite molecular sieve / graphene oxide composite nanosheet dispersion is 0.01-500 mg / mL.

[0018] In step (4), the organic carrier is one of nylon, polyethersulfone, polyimide, polycarbonate, polytetrafluoroethylene, polyvinylidene fluoride, and cellulose.

[0019] In step (4), the organic carrier may be in the form of a flat plate, a rolled plate, or a hollow fiber.

[0020] In step (4), the membrane deposition method can be one of drop coating, spin coating, or vacuum filtration.

[0021] In step (4), the separation selectivity of the flexible zeolite molecular sieve / graphene oxide nanosheet composite membrane does not change significantly after bending 0 to 60°.

[0022] This invention provides a method for preparing a flexible zeolite molecular sieve / graphene oxide nanosheet composite membrane. The zeolite molecular sieve / graphene oxide nanosheet composite membrane prepared by this method has strong adhesion to the organic carrier, the membrane layer is flexible and bendable, the production cost is low, the membrane performance has good repeatability, and it is easy to scale up industrially. Attached Figure Description

[0023] Figure 1 The image shows a surface SEM image of the flexible MWW / GO composite separation membrane prepared in Example 1 after bending.

[0024] Figure 2The image shows a surface SEM image of the flexible MWW / GO composite separation membrane prepared in Example 2.

[0025] Figure 3 SEM images of the surface of the MWW nanosheet film prepared in the comparative example after bending. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the invention is not limited thereto. For process parameters not specifically noted, conventional techniques can be referred to.

[0027] Example 1

[0028] A method for preparing a flexible MWW / GO composite separation membrane and its application in H2 / CO2 separation, the steps of which are as follows:

[0029] 0.06 g of MWW zeolite molecular sieve nanosheets were dissolved in 20 mL of water and stirred for 12 h to completely disperse the nanosheets in the aqueous solution. 0.002 g of graphene oxide was weighed and mixed with 20 mL of water, and the solution was sonicated for 30 min to disperse it uniformly. The above MWW zeolite molecular sieve nanosheet solution and graphene oxide solution were mixed at a volume ratio of 1:1 and sonicated for 1 h to obtain an MWW / GO nanosheet dispersion. 1 mL of the MWW / GO nanosheet dispersion was dropped onto a nylon carrier. After it was evenly dispersed on the carrier surface, it was vacuum filtered for 30 min to obtain a flexible MWW / GO composite separation membrane. This membrane showed no obvious defects after being bent back and forth from 0-60°. Figure 1 As shown in the figure, when the pressure difference across the membrane is 0.1 MPa and the temperature is 90℃, the measured hydrogen permeability is 8.25 × 10⁻⁶. -8 mol·Pa -1 ·s -1 ·m -2 The separation selectivity for H2 / CO2 was 28.6.

[0030] Example 2

[0031] A method for preparing a flexible MWW / GO composite separation membrane and its application in H2 / C3H8 separation, the steps are as follows:

[0032] 0.06 g of MWW zeolite molecular sieve nanosheets were dissolved in 20 mL of water and stirred for 12 h to ensure complete dispersion. 0.002 g of graphene oxide was weighed and mixed with 20 mL of water, and the mixture was sonicated for 30 min to achieve uniform dispersion. The MWW zeolite molecular sieve nanosheet solution and the graphene oxide solution were mixed at a volume ratio of 1:1 and sonicated for 1 h to obtain an MWW / GO nanosheet dispersion. 1.5 mL of the MWW / GO nanosheet dispersion was drop-coated onto a nylon support. After uniform dispersion on the support surface, vacuum filtration was performed for 30 min to obtain a flexible MWW / GO composite separation membrane. When the pressure difference across the membrane was 0.1 MPa and the temperature was 90 °C, the hydrogen permeability was measured to be 7.0 × 10⁻⁶. -8 mol·Pa -1 ·s -1 ·m -2 The selectivity for gas separation of H2 / C3H8 is 37.9.

[0033] Example 3

[0034] A method for preparing a flexible MWW / GO composite separation membrane and its application in H2 / i-C4H 10 Separation, the steps are as follows:

[0035] 0.06 g of MWW zeolite molecular sieve nanosheets were dissolved in 20 mL of water and stirred for 12 h to completely disperse the nanosheets in the aqueous solution. 0.002 g of graphene oxide was weighed and mixed with 20 mL of water, and the solution was sonicated for 30 min to disperse it evenly. The above MWW zeolite molecular sieve nanosheet solution and graphene oxide solution were mixed at a 1:1 ratio and sonicated for 1 h to obtain an MWW / GO nanosheet dispersion. 1 mL of the MWW / GO nanosheet dispersion was dropped onto a nylon support. After it was evenly dispersed on the support surface, it was vacuum filtered for 30 min to obtain a flexible MWW / GO composite separation membrane. When the pressure difference across the membrane was 0.1 MPa and the temperature was 90 °C, the hydrogen permeability was measured to be 7.5 × 10⁻⁶. -8 mol·Pa -1 ·s -1 ·m -2 H2 / i-C4H 10 The separation selectivity was 128.2.

[0036] Example 4

[0037] A method for preparing a flexible MWW / GO composite separation membrane and its application in H2 / CO2 separation, the steps of which are as follows:

[0038] 0.06 g of MWW zeolite molecular sieve nanosheets were dissolved in 20 mL of water and stirred for 12 h to completely disperse the nanosheets in the aqueous solution. 0.004 g of graphene oxide was weighed and mixed with 20 mL of water, and the solution was sonicated for 30 min to disperse it uniformly. The above MWW zeolite molecular sieve nanosheet solution and graphene oxide solution were mixed at a volume ratio of 1:1 and sonicated for 1 h to obtain an MWW / GO nanosheet dispersion. 1 mL of the MWW / GO nanosheet dispersion was dropped onto a nylon carrier. After it was evenly dispersed on the carrier surface, it was vacuum filtered for 30 min to obtain a flexible MWW / GO composite separation membrane. When the pressure difference across the membrane was 0.1 MPa and the temperature was 150 °C, the hydrogen permeability was measured to be 1.50 × 10⁻⁶. -7 mol·Pa -1 ·s -1 ·m -2 The separation selectivity of H2 / CO2 was 40.8.

[0039] Example 5

[0040] A method for preparing a flexible MWW / GO composite separation membrane and its application in H2 / i-C4H 10 Separation, the steps are as follows:

[0041] 0.06 g of MWW zeolite molecular sieve nanosheets were dissolved in 20 mL of water and stirred for 12 h to completely disperse the nanosheets in the aqueous solution. 0.004 g of graphene oxide was weighed and mixed with 20 mL of water, and the solution was sonicated for 30 min to disperse it uniformly. The above MWW zeolite molecular sieve nanosheet solution and graphene oxide solution were mixed at a volume ratio of 1:1 and sonicated for 1 h to obtain an MWW / GO nanosheet dispersion. 1 mL of the MWW / GO nanosheet dispersion was dropped onto a nylon carrier. After it was evenly dispersed on the carrier surface, it was vacuum filtered for 30 min to obtain a flexible MWW / GO composite separation membrane. When the pressure difference across the membrane was 0.1 MPa and the temperature was 150 °C, the hydrogen permeability was measured to be 1.50 × 10⁻⁶. -7 mol·Pa -1 ·s -1 ·m -2 H2 / i-C4H 10 The separation selectivity was 172.5.

[0042] Example 6

[0043] A method for preparing a flexible MWW / GO composite separation membrane and its application in H2 / CO2 separation, the steps of which are as follows:

[0044] 0.06 g of MWW zeolite molecular sieve nanosheets were dissolved in 20 mL of water and stirred for 12 h to completely disperse the nanosheets in the aqueous solution. 0.006 g of graphene oxide was weighed and mixed with 20 mL of water, and the solution was sonicated for 30 min to disperse it uniformly. The above MWW zeolite molecular sieve nanosheet solution and graphene oxide solution were mixed at a volume ratio of 1:1 and sonicated for 1 h to obtain an MWW / GO nanosheet dispersion. 1 mL of the MWW / GO nanosheet dispersion was dropped onto a nylon support. After it was evenly dispersed on the support surface, it was vacuum filtered for 30 min to obtain a flexible MWW / GO composite separation membrane. When the pressure difference across the membrane was 0.2 MPa and the temperature was 50 °C, the hydrogen permeability was measured to be 2.57 × 10⁻⁶. -8 mol·Pa -1 ·s -1 ·m -2 The separation selectivity of H2 / CO2 was 23.1.

[0045] Example 7

[0046] A method for preparing a flexible MWW / GO composite separation membrane and its application in H2 / CO2 separation, the steps of which are as follows:

[0047] 0.06 g of MWW zeolite molecular sieve nanosheets were dissolved in 20 mL of water and stirred for 12 h to completely disperse the nanosheets in the aqueous solution. 0.006 g of graphene oxide was weighed and mixed with 20 mL of water, and the solution was sonicated for 30 min to disperse it uniformly. The above MWW zeolite molecular sieve nanosheet solution and graphene oxide solution were mixed at a volume ratio of 1:1 and sonicated for 1 h to obtain an MWW / GO nanosheet dispersion. 1.2 mL of the MWW / GO nanosheet dispersion was dropped onto a nylon carrier. After it was evenly dispersed on the carrier surface, it was vacuum filtered for 30 min to obtain a flexible MWW / GO composite separation membrane. When the pressure difference across the membrane was 0.2 MPa and the temperature was 190 °C, the hydrogen permeability was measured to be 1.12 × 10⁻⁶. -7 mol·Pa -1 ·s -1 ·m -2 The selectivity for gas separation of H2 / CO2 is 18.75.

[0048] Comparative Examples

[0049] A method for preparing an MWW nanosheet film, comprising the following steps:

[0050] 0.06 g of MWW zeolite molecular sieve nanosheets were dissolved in 20 mL of water and stirred for 12 h to uniformly disperse the zeolite nanosheets in the water. The above MWW zeolite molecular sieve nanosheet solution was ultrasonicated for 1 h to obtain a MWW zeolite molecular sieve nanosheet dispersion. 1.5 mL of the MWW zeolite molecular sieve nanosheet dispersion was dropped onto a nylon carrier. After it was uniformly dispersed on the carrier surface, it was vacuum filtered for 30 min to obtain an MWW zeolite molecular sieve nanosheet separation membrane. After bending the membrane by 30°, numerous cracks appeared on its surface, such as... Figure 2 As shown, the membrane has no separation selectivity for gases.

[0051] As can be seen from the examples and comparative examples, adding a small amount of graphene oxide to the membrane-forming solution greatly improves the membrane's flexibility, making it easier to form a continuous and dense membrane layer on a flexible carrier, and maintaining good selectivity even after bending at a certain angle. Therefore, using the above technology, organic carriers can replace traditional inorganic carriers in the development of zeolite molecular sieve membranes, which can not only significantly reduce the current production cost of zeolite molecular sieve membranes, but also greatly improve the membrane's production efficiency and facilitate industrial scale-up.

[0052] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a flexible zeolite molecular sieve composite membrane, characterized by, The method comprises the following steps: (1) dispersing the zeolite molecular sieve nanosheet from which the template has been removed in a solvent to obtain a zeolite molecular sieve nanosheet dispersion; the zeolite molecular sieve nanosheet is one of MFI, MWW and CHA; (2) dispersing graphene oxide powder in a solvent to obtain a graphene oxide nanosheet dispersion; (3) mixing and uniformly dispersing the zeolite molecular sieve nanosheet dispersion in the formulation amount in step (1) and the graphene oxide nanosheet dispersion in the formulation amount in step (2) to obtain a zeolite molecular sieve / graphene oxide composite nanosheet dispersion; the mass ratio of the zeolite molecular sieve and the graphene oxide nanosheet in the formulation amount is 100-1; the concentration of the obtained zeolite molecular sieve / graphene oxide composite nanosheet dispersion is 0.01-500 mg / mL; (4) depositing an appropriate amount of the zeolite molecular sieve / graphene oxide composite nanosheet dispersion in step (3) on an organic carrier, and drying to obtain a flexible zeolite molecular sieve / graphene oxide nanosheet composite membrane.

2. The method of claim 1, wherein the flexible zeolite molecular sieve composite membrane is prepared by the steps of: (a) preparing a zeolite molecular sieve membrane on a porous support; (b) preparing a polymer membrane on the zeolite molecular sieve membrane; and (c) removing the porous support. In step (1), the concentration of the zeolite molecular sieve nanosheet dispersion solution is 0.01-500 mg / mL.

3. The method of claim 1, wherein the flexible zeolite molecular sieve composite membrane is prepared by the steps of: (a) preparing a zeolite molecular sieve membrane on a porous support; (b) preparing a polymer membrane on the zeolite molecular sieve membrane; and (c) removing the porous support. In step (1), the solvent is one or more of water, methanol, ethanol, isopropanol, acetonitrile, diethyl ether, acetone, ethyl acetate, chloroform, dichloromethane, cyclohexane, N,N-dimethylformamide, N-methylpyrrolidone, tetrahydrofuran, benzene, toluene and xylene.

4. The method of claim 1, wherein the flexible zeolite molecular sieve composite membrane is prepared by the steps of: (a) preparing a zeolite molecular sieve membrane on a porous support; (b) preparing a polymer membrane on the zeolite molecular sieve membrane; and (c) removing the porous support. In step (2), the concentration of the graphene oxide nanosheet dispersion is 0.01-500 mg / mL.

5. The method of claim 1, wherein the flexible zeolite molecular sieve composite membrane is prepared by the steps of: (a) preparing a zeolite molecular sieve membrane on a porous support; (b) preparing a polymer membrane on the zeolite molecular sieve membrane; and (c) removing the porous support. In step (2), the solvent is one or more of water, methanol, ethanol, isopropanol, acetonitrile, diethyl ether, acetone, ethyl acetate, chloroform, dichloromethane, cyclohexane, N,N-dimethylformamide, N-methylpyrrolidone, tetrahydrofuran, benzene, toluene and xylene.

6. The method of claim 1, wherein the flexible zeolite molecular sieve composite membrane is prepared by the steps of: (a) preparing a zeolite molecular sieve membrane on a porous support; (b) preparing a polymer membrane on the zeolite molecular sieve membrane; and (c) removing the porous support. In step (4), the organic carrier is one of nylon, polyether sulfone, polyimide, polycarbonate, polytetrafluoroethylene, polyvinylidene fluoride and cellulose; The organic carrier has a shape of a flat plate, a roll or a hollow fiber.

7. The method of claim 1, wherein the flexible zeolite molecular sieve composite membrane is prepared by the steps of: (a) preparing a zeolite molecular sieve membrane on a porous support; (b) preparing a polymer membrane on the zeolite molecular sieve membrane; and (c) removing the porous support. In step (4), the deposition method of the membrane is one of drop coating, spin coating and vacuum suction filtration.

8. A flexible zeolite molecular sieve / graphene oxide nanosheet composite membrane prepared by the preparation method in any one of claims 1-7.

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