Rigid framework-flexible microporous composite membrane as well as preparation method and application thereof
The rigid skeleton-flexible micropore composite membrane was prepared by the sol-gel method. Combining the rigid skeleton and flexible micropores, the permeability and selectivity problems of the existing polymer films under high pressure were solved, and the efficient helium separation effect was achieved.
Patent Information
- Application Number
- CN202510444261.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-10
- Publication Date
- 2025-07-04
AI Technical Summary
When the existing polymer films separate helium under high pressure, they cannot meet the high permeability and high selectivity at the same time, and the pore size adjustment range of traditional PSQ composite membranes is limited, making it difficult to achieve accurate molecular sieving.
A rigid skeleton-flexible micropore composite membrane is prepared by the sol-gel method. By coating sol on the support and sintering it, a membrane structure combining the rigid skeleton and flexible micropores is formed. The rigid skeleton provides mechanical support and size screening, and flexible micropores provide dynamic diffusion pathways.
It improves helium permeability and selectivity, overcomes the limitations of traditional static pores, and has good repeatability and stability, which is suitable for efficient separation of helium in natural gas.
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Figure CN120242776A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of membrane separation, and particularly to a rigid skeleton-flexible microporous composite membrane, a preparation method thereof, and an application thereof. Background Art
[0002] Due to its unique properties such as ultra-low boiling point, low density, chemical inertness, and high thermal conductivity, helium (He) is widely used in strategic fields such as semiconductor manufacturing, magnetic resonance imaging, and aerospace engineering. At present, commercial helium extraction mainly relies on cryogenic separation of helium-containing natural gas, including directly extracting helium from natural gas or indirectly extracting helium from liquefied natural gas (LNG) tail gas. This method has problems of high investment and high energy consumption.
[0003] Membrane separation technology has inherent advantages such as low energy consumption, small floor area, simple operation, and easy integration with other technologies, and has become a promising alternative technology. Due to its structural diversity, low cost, and excellent processing performance, polymer membranes have been widely studied and used in gas separation applications. However, extracting helium from natural gas usually requires high-pressure operation (2.5 to 10 MPa), so the membrane material needs to have strong compressive properties. Although polymer membranes have been commercially applied to a certain extent, they still cannot meet these strict requirements.
[0004] Poly(silsesquioxane) (PSQ) is a class of atomic-level organic-inorganic hybrid materials, usually composed of Si-O-Si units as the backbone and organic groups as side chains or bridging units, with characteristics such as narrow pore size distribution, stable and adjustable structure. These unique structural features make PSQ membranes very promising in gas separation applications, especially for the separation of helium / hydrogen from other large-molecule gases. At present, although some progress has been made, when using a single PSQ precursor as the starting material, it is still challenging to achieve precise molecular sieving because the pore size adjustment range is limited. Currently, the pore size can be effectively adjusted by controlling the topological structure and distribution of Si-O-Si units in the PSQ composite membrane, but this is mainly limited to rigid pore structures, posing a major challenge in achieving high permeability and high selectivity. Summary of the Invention
[0005] Aiming at the above deficiencies in the prior art, the purpose of the present invention is to provide a rigid skeleton-flexible microporous composite membrane, a preparation method thereof, and an application thereof, which can provide an innovative solution for the effective separation of helium from natural gas.
[0006] To achieve the above object of the invention, the technical solution adopted by the present invention is as follows:
[0007] On the one hand, a preparation method of a rigid skeleton-flexible microporous composite membrane is provided, which includes the following steps:
[0008] (1) Preparation of sol:
[0009] Using one or more organic-rich precursors (BTPDA, BTPA, BTESO) and one or more organic-poor precursors (BTESM, BTESE) as silicon precursors, dissolving them in a suitable solvent, adding a mixed solution of acid and water for hydrolysis reaction to obtain a sol; wherein, the total mass fraction of the sol is 0.01 - 10%, and the molar ratio of the organic-poor precursor to the organic-rich precursor is 0 - 50.
[0010] (2) Preparation of composite membrane:
[0011] Coating the sol obtained in step (1) on a ceramic membrane support body that has been appropriately treated, and sintering it at a certain temperature. This process is repeated multiple times to finally obtain a rigid skeleton-flexible microporous composite membrane.
[0012] Furthermore, in step (1), stirring and reacting at 0 - 100 °C to obtain the required sol.
[0013] Furthermore, in step (2), sintering is carried out in an air or N2 atmosphere at a temperature of 100 - 300 °C.
[0014] Furthermore, in step (2), the support body is coated with a transition layer having nanoscale pores such as γ-Al2O3 and SiO2-ZrO2. The preparation method includes the following steps:
[0015] Support body pretreatment: Select a support body with an average pore diameter of 100 - 2000 nm (tubular / plate / hollow fiber, etc.), and calcine it in a muffle furnace at a high temperature for more than 30 min to remove surface grease and impurities;
[0016] Coating the particle layer: Uniformly disperse α-Al2O3 particles with an average particle diameter of 100 - 200 nm in sols such as SiO2-ZrO2, TiO2, or ZrO2 to prepare a dispersion with a concentration of 2 - 20 wt%. Use processes such as air spraying, wiping, or dipping to uniformly coat the dispersion on the surface of the support body, and then calcine it in an air atmosphere at 500 - 1200 °C for more than 10 min. Repeat multiple times to reduce defects and form an α-Al2O3 transition layer;
[0017] Coating the boehmite layer: Use the above-mentioned processes such as air spraying, wiping, or dipping to uniformly coat a 1 - 10 wt% γ-Al2O3 sol on the α-Al2O3 layer prepared above, and then calcine it in an air atmosphere at 300 - 600 °C for more than 2 h to form a γ-Al2O3 transition layer;
[0018] Coating the SiO2-ZrO2 layer: Using the above air spraying, wiping, dipping and other processes, a SiO2-ZrO2 sol with a concentration of 0.1-10 wt% is uniformly coated on the above-prepared γ-Al2O3 transition layer, and then calcined in an air atmosphere at 300-600 °C for more than 10 min to form a SiO2-ZrO2 transition layer.
[0019] On the other hand, there is provided the use of the rigid framework-flexible microporous composite membrane prepared by any of the above methods for helium extraction from natural gas.
[0020] The beneficial effects of the present invention are as follows:
[0021] The present invention prepares a rigid framework-flexible microporous composite membrane by the sol-gel method. In this membrane, the rigid framework units provide mechanical support, while the flexible units disperse stress, enhancing the plasticity and high-pressure resistance of the membrane. In addition, during the separation process, the rigid framework provides size and configuration screening capabilities, while the flexible micropores provide additional configuration screening and dynamic diffusion pathways. This rigid-flexible combination design overcomes the limitations of traditional static pores, while improving the permeability and selectivity. Description of the Drawings
[0022] Figure 1 Relationship between the dimensionless permeability of N2 of the supports involved in Examples 1-6 and the Kelvin diameters of (a) the γ-Al2O3 layer and (c) the SiO2-ZrO2 layer; (b) pore size distributions of the γ-Al2O3 layer and (d) the SiO2-ZrO2 layer;
[0023] Figure 2 Graph comparing the performance of membranes with different ratios prepared in Examples 1-5;
[0024] Figure 3 Graph for verifying the repeatability of the membrane prepared in Example 5;
[0025] Figure 4 Nanoscale indentation graph of the membrane prepared in Example 5;
[0026] Figure 5 Stability graph of the membrane prepared in Example 5. Detailed Embodiments
[0027] The following describes the detailed embodiments of the present invention to facilitate those skilled in the art of the present technology to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the detailed embodiments. For those of ordinary skill in the art of the present technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions created using the concept of the present invention are within the scope of protection.
[0028] Example 1
[0029] (1) Weigh 86.068 g of ethanol, add 2.95 g of BTPDA and 0.349 g of BTESE, mix them evenly under magnetic stirring, and then dropwise add a mixed solution of 22.032 g of HNO3 and 18.601 g of H2O to the above solution as a catalyst to promote the hydrolysis and polymerization processes. Stir for 12 h at room temperature to obtain the required sol. Among them, the mass fraction of the sol is 1 wt.%, the molar ratio of BTESE to BTPDA monomers is 0.2, and the molar ratio of the organosilicon precursor, water, and nitric acid is 1:180:2.5;
[0030] (2) Coating the sol obtained in step (1) on the optimized support (SiO2-ZrO2 layer) by dip coating method, sintering in N2 atmosphere at 250 °C, and repeating this process 2 times to finally obtain a rigid skeleton-flexible microporous composite membrane.
[0031] Example 2
[0032] (1) Weigh 87.965 g of ethanol, add 2.295 g of BTPDA and 1.046 g of BTESE, mix them evenly under magnetic stirring, and then dropwise add a mixed solution of 17.136 g of HNO3 and 21.558 g of H2O to the above solution as a catalyst to promote the hydrolysis and polymerization processes. Stir for 12 h at room temperature to obtain the required sol. Among them, the mass fraction of the sol is 1 wt.%, the molar ratio of BTESE to BTPDA monomers is 0.8, and the molar ratio of the organosilicon precursor, water, and nitric acid is 1:180:2.5;
[0033] (2) Coating the sol obtained in step (1) on the optimized support (SiO2-ZrO2 layer) by dip coating method, sintering in N2 atmosphere at 250 °C, and repeating this process 2 times to finally obtain a rigid skeleton-flexible microporous composite membrane.
[0034] Example 3
[0035] (1) Weigh 89.862 g of ethanol, add 1.639 g of BTPDA and 1.743 g of BTESE, mix them evenly under magnetic stirring, and then dropwise add a mixed solution of 12.240 g of HNO3 and 24.516 g of H2O to the above solution as a catalyst to promote the hydrolysis and polymerization processes. Stir for 12 h at room temperature to obtain the required sol. Among them, the mass fraction of the sol is 1 wt.%, the molar ratio of BTESE to BTPDA monomers is 2, and the molar ratio of the organosilicon precursor, water, and nitric acid is 1:180:2.5;
[0036] (2) The sol obtained in step (1) was coated on the optimized support (SiO2-ZrO2 layer) by dip coating method and sintered in N2 atmosphere at 250 °C. This process was repeated twice to finally obtain a rigid framework-flexible microporous composite membrane.
[0037] Example 4
[0038] (1) Weigh 91.759 g of ethanol, add 0.983 g of BTPDA and 2.440 g of BTESE, mix them evenly under magnetic stirring, and then gradually add a mixed solution of 7.344 g of HNO3 and 27.473 g of H2O to the above solution as a catalyst to promote the hydrolysis and polymerization process. Stir at room temperature for 12 h to obtain the required sol. Among them, the mass fraction of the sol is 1 wt.%, the molar ratio of BTESE to BTPDA monomer is 4, and the molar ratio of organosilicon precursor, water, and nitric acid is 1:180:2.5;
[0039] (2) The sol obtained in step (1) was coated on the optimized support (SiO2-ZrO2 layer) by dip coating method and sintered in N2 atmosphere at 250 °C. This process was repeated twice to finally obtain a rigid framework-flexible microporous composite membrane.
[0040] Example 5
[0041] (1) Weigh 93.656 g of ethanol, add 0.328 g of BTPDA and 3.138 g of BTESE, mix them evenly under magnetic stirring, and then gradually add a mixed solution of 2.448 g of HNO3 and 30.430 g of H2O to the above solution as a catalyst to promote the hydrolysis and polymerization process. Stir at room temperature for 12 h to obtain the required sol. Among them, the mass fraction of the sol is 1 wt.%, the molar ratio of BTESE to BTPDA monomer is 16, and the molar ratio of organosilicon precursor, water, and nitric acid is 1:180:2.5;
[0042] (2) The sol obtained in step (1) was coated on the optimized support (SiO2-ZrO2 layer) by dip coating method and sintered in N2 atmosphere at 250 °C. This process was repeated twice to finally obtain a rigid framework-flexible microporous composite membrane.
[0043] Example 6
[0044] (1) Weigh 57.312 g of ethanol, add 0.656 g of BTPDA and 6.275 g of BTESE, mix them evenly under magnetic stirring, and then dropwise add a mixed solution of 4.896 g of HNO3 and 60.861 g of H2O to the above solution as a catalyst to promote the hydrolysis and polymerization process. Stir for 12 h at room temperature to obtain the required sol. Among them, the mass fraction of the sol is 2 wt.%, the molar ratio of BTESE to BTPDA monomer is 16, and the molar ratio of the organosilicon precursor, water, and nitric acid is 1:180:2.5;
[0045] (2) Coating the sol obtained in step (1) on the optimized support (SiO2-ZrO2 layer) by dip coating method, sintering in N2 atmosphere at 250 °C, and repeating this process 2 times to finally obtain a rigid skeleton-flexible microporous composite membrane.
[0046] In order to establish a thin and continuous separation layer with ultra-micropores, it is necessary to refine the large pore size and minimize the surface roughness of the ceramic substrate. The preparation methods of the supports involved in Examples 1-6 are as follows:
[0047] Support pretreatment: Select a support (tubular type) with an average pore size of 300 nm, calcine it in a muffle furnace at high temperature for 1 h, and then boil it in water for a period of time to remove the grease and impurities on the surface.
[0048] Coating the particle layer: Uniformly disperse α-Al2O3 particles (average particle size of 200 nm) in SiO2-ZrO2 sol to prepare a 10 wt% sol, and uniformly coat the sol on the outer surface of the support by air spraying process, and then bake it in air atmosphere at 550 °C for 15 min. Repeat multiple times to reduce defects and form an α-Al2O3 layer.
[0049] Coating the boehmite layer: Dilute commercial γ-Al2O3 to 5 wt%, coat it on the α-Al2O3 layer prepared above by dip coating method, and then calcine it at 600 °C for 2 h to form a γ-Al2O3 layer.
[0050] Coating the SiO2-ZrO2 layer: Coat 1 wt% SiO2-ZrO2 sol on the γ-Al2O3 layer prepared above by dip coating method, and then calcine it at 550 °C for 15 min to form a SiO2-ZrO2 layer.
[0051] Figure 1 The pore size distribution of the optimized transition layer is shown, where the pore size of the γ-Al2O3 layer is 4-5 nm, and the pore size of the SiO2-ZrO2 layer is 1-2 nm.
[0052] Test Example
[0053] The gas separation performance of the rigid framework-flexible microporous composite membranes prepared in Examples 1-6 was tested as follows:
[0054] (1) Single gas permeability test
[0055] The single gas permeability of the composite membranes prepared in Examples 1-5 was evaluated using a gas separation device. Before the test, the membranes were treated in a continuous He flow of 50 cm 3 / min at 150 °C for at least 6 hours to remove any possible water molecules adsorbed on the inner and outer surfaces of the membranes. When the temperature of the membranes and the pressure difference across the membranes reached a stable state, the test was started. As Figure 2 can be seen, the increase in the BTESE ratio increased the He permeability and decreased the CH4 permeability. This trend indicates that the incorporation of rigid units restricted the migration of flexible chains, forming a uniform pore structure favorable for the diffusion of small molecules.
[0056] (2) Repeatability test
[0057] To address the key technical challenge of batch repeatability in industrial applications, the gas separation performance of the composite membranes prepared using the method of Example 5 was systematically evaluated in this test example. As Figure 3 shown, all batches exhibited excellent gas permeability consistency while maintaining stable separation selectivity, which is a key prerequisite for scaling up industrial production.
[0058] (3) Nanoindentation analysis
[0059] In this test example, nanoindentation technology was used to systematically evaluate the mechanical properties of the composite membranes. As Figure 4 can be seen, the BTPDA membrane had a lower elastic modulus and hardness, indicating that its microporous structure had a high degree of dynamic tunability. In contrast, the BTESE membrane had a higher elastic modulus and hardness, significantly improving the membrane's resistance to external forces. The mechanical parameters of the composite membrane prepared in Example 5 were between the two, maintaining a moderate flexibility while ensuring the structural stiffness of the membrane. This rigid-flexible coupling mechanism provides a key structural design strategy for optimizing the balance between the selectivity and permeability of membrane materials.
[0060] (4) Long-term stability
[0061] The long-term stability of the membranes is of considerable significance in industrial applications. As Figure 5 can be seen, the composite membrane prepared in Example 5 had good stability.
[0062] In summary, through the molecular-level co-design of rigid precursors and flexible precursors, the present invention constructs a composite membrane with a dual mechanism that combines size sieving and dynamic diffusion regulation functions. Its process is simple, economical, and effective. The addition of rigid precursors breaks the dense stacking in the network structure, and flexible precursors can further promote the hydrolysis and polycondensation of the network structure. The results show that the composite membrane with an appropriate ratio overcomes the limitations of traditional static pores, while improving the He permeability and He / CH4 selectivity. In addition, it also has good repeatability and stability. Therefore, the rigid framework-flexible microporous composite membrane prepared by the present invention provides an innovative solution for the effective separation of helium in natural gas.
[0063] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention.
[0064] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
Claims
1. A method for preparing a rigid skeleton-flexible microporous composite membrane, characterized in that, It includes the following steps: (1) Preparation of sol: Using one or more rich organic precursors and one or more poor organic precursors as silicon precursors, dissolving them in a suitable solvent, adding a mixed solution of acid and water for hydrolysis reaction to obtain a sol; wherein, the rich organic precursors include BTPDA, BTPA, BTESO; the poor organic precursors include BTESM, BTESE; the total mass fraction of the sol is 0.01-10%, and the molar ratio of the poor organic precursor to the rich organic precursor is 0-50; (2) Preparation of composite membrane: Coating the sol obtained in step (1) on a properly treated ceramic membrane support, sintering at a certain temperature, and repeating this process multiple times to finally obtain a rigid framework-flexible microporous composite membrane.
2. The preparation method of the rigid skeleton-flexible microporous composite membrane according to claim 1, characterized in that, In step (1), the required sol is obtained by stirring and reacting at 0-100 °C.
3. The preparation method of the rigid skeleton-flexible microporous composite membrane according to claim 1, characterized in that, In step (2), sintering is carried out in an air or N2 atmosphere at a temperature of 100-300 °C.
4. The preparation method of the rigid skeleton-flexible microporous composite membrane according to claim 1, characterized in that, In step (2), the support is coated with a transition layer having nano-scale pores, and its preparation method includes the following steps: Support pretreatment: Selecting a support with an average pore diameter of 100-2000 nm, calcining in a muffle furnace at a high temperature for more than 30 min to remove surface grease and impurities; Coating the particle layer: Uniformly dispersing α-Al2O3 particles with an average particle size of 100-200 nm in the sol to prepare a dispersion with a concentration of 2-20 wt%, uniformly coating the dispersion on the surface of the support, and then roasting in an air atmosphere at 500-1200 °C for more than 10 min, repeating multiple times to reduce defects and form an α-Al2O3 transition layer; Coating the boehmite layer: Uniformly coating a 1-10 wt% γ-Al2O3 sol on the α-Al2O3 layer prepared above, and then calcining in an air atmosphere at 300-600 °C for more than 2 h to form a γ-Al2O3 transition layer; Coating the SiO2-ZrO2 layer: Uniformly coating a 0.1-10 wt% SiO2-ZrO2 sol on the γ-Al2O3 transition layer prepared above, and then calcining in an air atmosphere at 300-600 °C for more than 10 min to form a SiO2-ZrO2 transition layer.
5. A rigid framework-flexible microporous composite membrane prepared by the method according to any one of claims 1-4.
6. An application of the rigid framework-flexible microporous composite membrane according to claim 5 in natural gas helium extraction.