Composite gas separation membrane containing ionic liquid and preparation method and application thereof

Abstract

The application belongs to the technical field of gas separation membrane materials, and particularly relates to a composite gas separation membrane containing an ionic liquid and a preparation method and application thereof. An amino-containing polyether compound, an epoxy group-containing polyether compound and an epoxy group-containing polysiloxane compound are subjected to an epoxy-amine ring-opening reaction to form a reaction product containing polyether segments and polysiloxane segments, and the reaction product, polyether amide and ionic liquid are jointly used to construct a selective separation layer. The epoxy-amine ring-opening reaction forms C-N connecting structures and beta-hydroxyl amine structures between different molecular chains, which is conducive to improving the compatibility between components, the distribution state and stability of the ionic liquid in the membrane layer, the uniformity of film formation and the structural stability of the membrane layer, and improving the carbon dioxide separation performance of the obtained composite membrane.

Description

Technical Field

[0001] This invention belongs to the field of gas separation membrane material technology, specifically relating to a composite gas separation membrane containing ionic liquid, its preparation method, and its application. Background Technology

[0002] The development of low-carbon technologies such as carbon capture and industrial exhaust gas purification has created an urgent need for efficient carbon dioxide separation. While polymer membrane separation technology offers significant advantages over traditional separation methods due to its low energy consumption, simplified equipment, and ease of scalability, conventional membrane materials often face the dilemma of not being able to simultaneously achieve optimal gas permeability, separation selectivity, and long-term stability. As a highly promising high-quality substrate, polyetheramides (such as Pebax copolymers) cleverly combine the carbon-affinity mass transfer properties of the flexible polyether phase with the physical support of the rigid polyamide phase. Even so, the strong forces between its internal rigid segments can easily lead to excessively dense membrane structures, thus hindering rapid gas diffusion and penetration. Furthermore, simply fine-tuning the inherent composition of the copolymer itself is insufficient to meet the stringent requirements of modern industry for both high throughput and excellent film-forming properties. Therefore, targeted functional modification of polyetheramide-based membranes has become an essential path to breaking through performance limitations and achieving efficient carbon dioxide separation.

[0003] Ionic liquids, with their low vapor pressure, good thermal stability, customizable structure, and strong affinity for carbon dioxide, have been widely used in the modification of polymer gas separation membranes. Introducing ionic liquids into polymer membranes helps improve the membrane material's ability to dissolve carbon dioxide, thereby enhancing carbon dioxide separation performance. However, direct blending of ionic liquids with polymers often leads to problems such as insufficient compatibility, uneven distribution within the membrane, localized enrichment, migration and loss, and membrane plasticization. Especially in thin-film composite membrane systems, where the selective layer thickness is typically small, the dispersion state, confinement degree, and stability of the ionic liquid directly affect membrane continuity, interfacial bonding, and long-term separation performance. Therefore, effectively introducing ionic liquids while improving their dispersion uniformity and stability within the polymer selective layer is a key issue in the construction of ionic liquid-containing gas separation membranes.

[0004] Besides ionic liquids, polyether and polysiloxane components are also commonly used to improve the mass transfer performance and film-forming properties of gas separation membranes. Polyether segments contain abundant etheroxy groups, which enhance the membrane material's affinity for carbon dioxide; polysiloxane segments possess high flexibility and segmental mobility, contributing to improved film-forming properties, flexibility, and gas transport capacity. In thin-film composite membrane structures, polysiloxane components can also improve the compatibility between the selective layer and the siloxane-based intermediate layer, facilitating the formation of a continuous, uniform, ultrathin selective layer. However, when ionic liquids, polyether components, polysiloxane components, and the polyether amide matrix coexist, the differences in polarity, interactions, and segmental mobility among the components make the microstructure control of the membrane layer more complex. If only simple physical blending is used, it can easily lead to phase separation of components, local enrichment of ionic liquids, increased membrane defects, and decreased preparation repeatability, thus affecting the gas separation performance of the composite membrane.

[0005] In recent years, ring-opening reactions between epoxides and amino groups have been increasingly used in the construction of functional polymer materials due to their relatively mild reaction conditions, high functional group conversion efficiency, and low likelihood of generating small molecule byproducts. During the reaction, the amino group undergoes nucleophilic attack on the epoxy group, opening the epoxy ring and forming CN-linked structures and β-hydroxyamine structures. For reactants containing two or more amino or epoxy groups, the above reaction can establish chemical bonds between different molecular chains, thereby forming cross-linked structures.

[0006] An epoxy-amine ring-opening reaction can be carried out using amino-containing polyether compounds, epoxy-containing polyether compounds, and epoxy-containing polysiloxane compounds to form a crosslinking reaction product containing both polyether and polysiloxane segments. The polyether segments contain abundant etheroxy groups, which is beneficial for improving the membrane material's affinity for carbon dioxide; the polysiloxane segments have high flexibility, which is beneficial for regulating the segmental mobility and film-forming properties of the membrane material; the hydroxyl groups formed by epoxy ring-opening can enhance the interaction between the reaction product and the polyether amide and ionic liquid, thereby improving the component compatibility, film stability, and interfacial adaptability of the ionic liquid-containing selective layer.

[0007] However, in existing technologies, polyether amide gas separation membranes containing ionic liquids mostly rely on the direct physical blending of ionic liquids and polymer matrices. Effective solutions remain lacking for how to construct polyether-polysiloxane reaction products through epoxy-amine ring-opening reactions and utilize these products to regulate the dispersion and stability of ionic liquids in the polyether amide selective layer. Particularly in polyether amide thin-film composite membrane systems, simultaneously achieving stable introduction of ionic liquids, uniform film formation in the selective layer, improved interfacial compatibility, and enhanced carbon dioxide separation performance remain technical challenges. Therefore, developing a composite gas separation membrane based on the construction of polyether-polysiloxane reaction products through epoxy-amine ring-opening reactions, and using these reaction products in conjunction with polyether amides and ionic liquids in the selective separation layer, along with its preparation method, is of significant practical importance for improving the film formation uniformity, structural stability, and carbon dioxide separation performance of the composite membrane. Summary of the Invention

[0008] To address the problems of insufficient compatibility, uneven distribution, local enrichment, migration and loss, and decreased membrane structural stability that easily occur when ionic liquids are introduced into polyether amide gas separation membranes in existing technologies, this invention involves a ring-opening reaction of an amino-containing polyether compound with an epoxy-containing polyether compound and an epoxy-containing polysiloxane compound to form a reaction product containing polyether segments and polysiloxane segments. The reaction product is then combined with polyether amide and ionic liquid to construct a selective separation layer, thereby improving the distribution and stability of the ionic liquid in the membrane layer, enhancing the membrane uniformity and structural stability, and improving the carbon dioxide separation performance of the resulting composite membrane.

[0009] First, the present invention provides a composite gas separation membrane containing ionic liquid, the composite gas separation membrane comprising a base membrane and a selective separation layer disposed on the base membrane; the selective separation layer is formed by blending a polyether-polysiloxane reaction product formed by an epoxide-amine ring-opening reaction of an amino-containing polyether compound, an epoxy-containing polyether compound, and an epoxy-containing polysiloxane compound with a polyether amide and an ionic liquid.

[0010] Preferably, the amino-containing polyether compound is selected from one or more of terminal amino polyoxyethylene compounds, terminal amino polyoxypropylene compounds, terminal amino polyoxyethylene-polyoxypropylene copolymers, or terminal amino polytetrahydrofuran compounds; and / or, the epoxy-containing polyether compound is selected from one or more of epoxy-containing polyoxyethylene compounds, epoxy-containing polyoxypropylene compounds, epoxy-containing polyoxyethylene-polyoxypropylene copolymers, or epoxy-containing polytetrahydrofuran compounds; and / or, the epoxy-containing polysiloxane compound is selected from one or more of epoxy-containing polydimethylsiloxane or epoxy-containing polymethylphenylsiloxane; the polyether amide is a polyether block polyamide; and / or, the ionic liquid is an imidazole ionic liquid.

[0011] Preferably, the base film is a porous support or a porous support including an intermediate layer, wherein the porous support is selected from polysulfone porous support, polyethersulfone porous support or polyimide porous support; and the intermediate layer is a polydimethylsiloxane intermediate layer.

[0012] Preferably, the total molar ratio of the amino-containing polyether compound to the epoxy-containing polyether compound and the epoxy-containing polysiloxane compound is 1:0.1 to 1:100, more preferably, the ratio is 1:0.5 to 1:10; the molar ratio of the epoxy-containing polyether compound to the epoxy-containing polysiloxane compound is 0.1:1 to 100:1, more preferably, the ratio is 1:1 to 10:1; and the mass ratio of the polyether-polysiloxane copolymer, the polyether amide, and the ionic liquid is 45:45:10 to 5:5:90.

[0013] Secondly, the present invention also provides a method for preparing a composite gas separation membrane containing ionic liquid, which is used to prepare the above-mentioned composite gas separation membrane containing ionic liquid, characterized by comprising the following steps: (1) Dissolve an amino-containing polyether compound, an epoxy-containing polyether compound and an epoxy-containing polysiloxane compound in a mixed solvent, and carry out an epoxy-amine ring-opening reaction under stirring conditions to obtain a reaction solution containing a polyether-polysiloxane copolymer. (2) After adding the ionic liquid to the reaction solution obtained in step (1) and mixing it evenly, add polyether amide and mix to obtain the casting solution; (3) The casting liquid obtained in step (2) is coated on the surface of the base membrane and dried to form the selective separation layer, thereby obtaining the composite gas separation membrane containing ionic liquid.

[0014] Preferably, in step (1), the mixed solvent is a mixture of water and alcohol, and the mass ratio of water to alcohol is 1:99-99:1; the alcohol is selected from one or more of methanol, ethanol or isopropanol.

[0015] Preferably, in step (1), the total content of the amino-containing polyether compound, the epoxy-containing polyether compound, and the epoxy-containing polysiloxane compound in the mixed solvent is 10 wt% to 30 wt%; and / or, the ring-opening reaction in step (1) is carried out at 40°C to 100°C.

[0016] Preferably, in step (3), the base film is a porous support or a porous support with an intermediate layer pre-coated on its surface; and / or, the coating method is one or more of scraping, spraying, and dipping; and / or, the drying is carried out at room temperature or under heating conditions.

[0017] Finally, the present invention also provides an application of the above-mentioned composite gas separation membrane containing ionic liquid in gas separation.

[0018] Preferably, the feed gas contains carbon dioxide, and the carbon dioxide preferentially permeates through the composite gas separation membrane.

[0019] Preferably, the raw material gas contains one or more of nitrogen and methane in addition to carbon dioxide.

[0020] Compared with the prior art, the present invention has the following beneficial effects: First, this invention utilizes the epoxy-amine ring-opening reaction between an amino-containing polyether compound and an epoxy-containing polyether compound and an epoxy-containing polysiloxane compound to form a reaction product containing polyether and polysiloxane segments. This reaction product is then combined with a polyether amide and an ionic liquid to construct a selective separation layer. The CN-linked structure formed by the epoxy-amine ring-opening reaction can stably connect different polymer segments, and the generated β-hydroxyamine structure enhances the interaction between the reaction product and the polyether amide and ionic liquid, thereby improving the compatibility of different components in the film layer and the dispersion uniformity and stability of the ionic liquid.

[0021] Secondly, this invention achieves synergistic regulation of the carbon dioxide affinity structure and the flexible mass transfer structure by synergistically introducing polyether segments, polysiloxane segments, and ionic liquids into the selective separation layer. Specifically, the ether radical groups in the polyether segments and the ionic liquid enhance the membrane material's ability to dissolve and transport carbon dioxide; the polysiloxane segments possess high flexibility, which improves the film-forming properties and segment mobility of the membrane layer, and enhances the interfacial compatibility between the selective separation layer and the polysiloxane intermediate layer.

[0022] Furthermore, the present invention employs a construction method that first performs an epoxy-amine ring-opening reaction and then blends it with polyether amide and ionic liquid to form a film. This method is beneficial for forming a continuous and uniform ultrathin selective separation layer, reducing the risk of component phase separation, local enrichment of ionic liquid, and non-selective defects under simple physical blending conditions, thereby improving the repeatability of composite gas separation membrane preparation and the stability of separation performance. Attached Figure Description

[0023] Figure 1 SEM images of the surface and cross-section of the Pebax / IL thin film composite film prepared in Comparative Example 1 and the PEO-PDMS / Pebax / IL thin film composite film prepared in Example 1, wherein, Figure 1 (a) is a SEM image of the surface of the Pebax / IL thin film composite prepared in Comparative Example 1. Figure 1 (b) is a cross-sectional SEM image of the Pebax / IL thin film composite prepared in Comparative Example 1. Figure 1Image (c) shows a SEM image of the surface of the PEO-PDMS / Pebax / IL thin film composite prepared in Example 1. Figure 1 Image (d) shows a cross-sectional SEM image of the PEO-PDMS / Pebax / IL thin film composite prepared in Example 1. Figure 2 The Fourier transform infrared spectra of the membrane materials of Example 1 and Comparative Example 1 are shown below. Figure 3 The 1H NMR spectra of PEG-NH2, PEGDGE, PDMS-DGE, the unreacted control solution of Example 1 with the same proportions, and the PEO-PDMS reaction solution obtained in step (1) of Example 1 are shown below. Figure 3 (a) shows the 1H NMR spectrum of PEG-NH2. Figure 3 (b) shows the 1H NMR spectrum of PEGDGE. Figure 3 (c) shows the 1H NMR spectrum of PDMS-DGE. Figure 3 Image (d) shows the 1H NMR spectrum of the unreacted control solution with the same proportions as in Example 1. Figure 3 (e) is the 1H NMR spectrum of the PEO-PDMS reaction solution obtained in step (1) of Example 1. Detailed Implementation

[0024] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. Unless otherwise specified, the raw materials used in the embodiments are all commercially available products, and the methods used are conventional methods in the art. The polymers of methyl ethylene oxide and ethylene oxide and bis(2-aminopropyl) ether used in the embodiments of this invention have CAS number 65605-36-9 (catalog number 013658236), an average molecular weight of 500 g / mol, and were purchased from Adamas; polyethylene glycol diglycidyl ether has CAS number 72207-80-8 (catalog number 011344488), an average molecular weight of 500 g / mol, and was purchased from Adamas; poly(dimethylsiloxane) diglycidyl ether has CAS number 130167-23-6 (catalog number 013686386), an average molecular weight of 800 g / mol, and was purchased from Adamas; 1-ethyl-3-methylimidazolium tricyanomethane has CAS number 666823-18-3 (catalog number 01647083), and was purchased from Adamas; the polyether block polyamide used is Pebax®. 1657, purchased from Arkema (China) Investment Co., Ltd.

[0025] In this embodiment of the invention, PEG-NH2 is an amino-containing polyether compound, PEGDGE is an epoxy-containing polyether compound, and PDMS-DGE is an epoxy-containing polysiloxane compound. During the reaction, the amino group in PEG-NH2 undergoes nucleophilic attack on the epoxy groups at the ends of PEGDGE and PDMS-DGE, causing the epoxy ring to open and form a CN-linked structure and a β-hydroxyamine structure. Since the above reactants contain two reactive end groups, the epoxy-amine ring-opening reaction can form links between different molecular chains, yielding a crosslinked reaction product containing polyether segments and polysiloxane segments. For ease of description, the reaction solution containing the polyether-polysiloxane crosslinked reaction product is simply referred to as the PEO-PDMS reaction solution.

[0026] Example 1 The composite gas separation membrane prepared in this embodiment includes the following steps: (1) The polymer of methyl ethylene oxide and ethylene oxide and bis(2-aminopropyl) ether (PEG-NH2), polyethylene glycol diglycidyl ether (PEGDGE), and poly(dimethylsiloxane) diglycidyl ether (PDMS-DGE) were dissolved in a water / ethanol mixed solvent, wherein the mass ratio of water to ethanol was 30:70, the total molar ratio of PEG-NH2 to PEGDGE and PDMS-DGE was 1:2, and the molar ratio of PEGDGE to PDMS-DGE was 4:1. Specifically, 1.235 g of PEG-NH2, 1.975 g of PEGDGE, and 0.790 g of PDMS-DGE were added to 16.000 g of water / ethanol mixed solvent (the mass ratio of water to alcohol was 30:70) to obtain a mixed solution with a total mass of 20.000 g and a solid content of 20 wt%. The above mixed solution was stirred at 80°C for 6 h to carry out a ring-opening reaction, and PEO-PDMS reaction solution was obtained.

[0027] (2) Take 0.018 g of the PEO-PDMS reaction solution obtained in step (1), which contains 0.0036 g of the PEO-PDMS crosslinking reaction product; add 0.018 g of the ionic liquid 1-ethyl-3-methylimidazolium tricyanomethane ([Emim][C(CN)3]), 0.0084 g of Pebax1657, and 9.9556 g of a water / ethanol mixed solvent (water to alcohol mass ratio of 30:70) to it, and continue stirring until the mixture is uniform to obtain a casting solution with a total mass of 10.000 g and a solid content of 0.3 wt%. Among them, the ionic liquid accounts for 60 wt% of the total mass of the selective layer solids, and the PEO-PDMS reaction component and Pebax1657 together account for 40 wt% of the total mass of the selective layer solids, and the mass ratio of the PEO-PDMS reaction component to Pebax1657 is 30:70.

[0028] (3) A polysulfone porous support membrane with a PDMS intermediate layer on its surface is used as the base membrane. The casting liquid obtained in step (2) is uniformly coated on the surface of the base membrane by a scraping method with a scraper gap of 0.15 mm. Then, it is placed in a 50 ℃ oven to dry for 6 h to form a continuous and dense selective separation layer, thus obtaining a PEO-PDMS / Pebax / IL thin film composite membrane.

[0029] Example 2 The composite gas separation membrane prepared in this embodiment includes the following steps: (1) PEG-NH2, PEGDGE, and PDMS-DGE were dissolved in a water / ethanol mixed solvent, wherein the mass ratio of water to ethanol was 30:70, the total molar ratio of PEG-NH2 to PEGDGE and PDMS-DGE was 1:2, and the molar ratio of PEGDGE to PDMS-DGE was 2:1. Specifically, 1.177 g of PEG-NH2, 1.568 g of PEGDGE, and 1.255 g of PDMS-DGE were added to 16.000 g of water / ethanol mixed solvent (the mass ratio of water to alcohol was 30:70) to obtain a mixed solution with a total mass of 20.000 g and a solid content of 20 wt%. The above mixed solution was stirred at 80 °C for 6 h to carry out a ring-opening reaction to obtain a PEO-PDMS reaction solution.

[0030] (2) Take 0.018 g of the PEO-PDMS reaction solution obtained in step (1), which contains 0.0036 g of the PEO-PDMS crosslinking reaction product; add 0.018 g of the ionic liquid [Emim][C(CN)3], 0.0084 g of Pebax1657 and 9.9556 g of the water / ethanol mixed solvent (the mass ratio of water to alcohol is 30:70), and continue stirring until the mixture is uniform to obtain a casting solution with a total mass of 10.000 g and a solid content of 0.3 wt%. Among them, the ionic liquid accounts for 60 wt% of the total mass of the selective layer solids, and the PEO-PDMS reaction component and Pebax1657 together account for 40 wt% of the total mass of the selective layer solids, and the mass ratio of the PEO-PDMS reaction component to Pebax1657 is 30:70.

[0031] (3) A polysulfone porous support membrane with a PDMS intermediate layer on its surface is used as the base membrane. The casting liquid obtained in step (2) is uniformly coated on the surface of the base membrane by a scraping method with a scraper gap of 0.15 mm. Then, it is placed in a 50 ℃ oven to dry for 6 h to form a continuous and dense selective separation layer, thus obtaining a PEO-PDMS / Pebax / IL thin film composite membrane.

[0032] Example 3 The composite gas separation membrane prepared in this embodiment includes the following steps: (1) PEG-NH2, PEGDGE, and PDMS-DGE were dissolved in a water / ethanol mixed solvent, wherein the mass ratio of water to ethanol was 30:70, the total molar ratio of PEG-NH2 to PEGDGE and PDMS-DGE was 1:1, and the molar ratio of PEGDGE to PDMS-DGE was 4:1. Specifically, 1.887 g of PEG-NH2, 1.509 g of PEGDGE, and 0.604 g of PDMS-DGE were added to 16.000 g of water / ethanol mixed solvent (the mass ratio of water to alcohol was 30:70) to obtain a mixed solution with a total mass of 20.000 g and a solid content of 20 wt%. The above mixed solution was stirred at 80 °C for 6 h to carry out a ring-opening reaction to obtain a PEO-PDMS reaction solution.

[0033] (2) Take 0.018 g of the PEO-PDMS reaction solution obtained in step (1), which contains 0.0036 g of the PEO-PDMS crosslinking reaction product; add 0.018 g of the ionic liquid [Emim][C(CN)3], 0.0084 g of Pebax1657 and 9.9556 g of the water / ethanol mixed solvent (the mass ratio of water to alcohol is 30:70), and continue stirring until the mixture is uniform to obtain a casting solution with a total mass of 10.000 g and a solid content of 0.3 wt%. Among them, the ionic liquid accounts for 60 wt% of the total mass of the selective layer solids, and the PEO-PDMS reaction component and Pebax1657 together account for 40 wt% of the total mass of the selective layer solids, and the mass ratio of the PEO-PDMS reaction component to Pebax1657 is 30:70.

[0034] (3) A polysulfone porous support membrane with a PDMS intermediate layer on its surface is used as the base membrane. The casting liquid obtained in step (2) is uniformly coated on the surface of the base membrane by a scraping method with a scraper gap of 0.15 mm. Then, it is placed in a 50 ℃ oven to dry for 6 h to form a continuous and dense selective separation layer, thus obtaining a PEO-PDMS / Pebax / IL thin film composite membrane.

[0035] Comparative Example 1 The membrane sample prepared in Comparative Example 1 included the following steps: (1) Dissolve Pebax1657 in a water / ethanol mixed solvent, wherein the mass ratio of water to ethanol is 30:70, and stir until completely dissolved to obtain a Pebax1657 mother liquor with a solid content of 3 wt%.

[0036] (2) Preparation of the selective layer casting solution. Take 0.400 g of the Pebax1657 mother liquor obtained in step (1), which contains 0.012 g of Pebax1657; add 0.018 g of the ionic liquid [Emim][C(CN)3] and 9.582 g of the water / ethanol mixed solvent (water to alcohol mass ratio of 30:70), and continue stirring until uniformly mixed to obtain a casting solution with a total mass of 10.000 g and a solid content of 0.3 wt%. Among them, the ionic liquid accounts for 60 wt% of the total mass of the selective layer solids, and Pebax1657 accounts for 40 wt% of the total mass of the selective layer solids.

[0037] (3) A polysulfone porous support membrane with a PDMS intermediate layer on its surface is used as the base membrane. The casting liquid obtained in step (2) is uniformly coated on the surface of the base membrane by a scraping method with a scraper gap of 0.15 mm. Then, it is placed in a 50 ℃ oven to dry for 6 h to form a continuous and dense selective separation layer, and Pebax1657 / IL thin film composite membrane is obtained.

[0038] Comparative Example 2 The steps for preparing the thin film composite membrane in this comparative example are as follows: (1) PEGDGE and PDMS-DGE were dissolved in a water / ethanol mixed solvent, wherein the mass ratio of water to ethanol was 30:70 and the molar ratio of PEGDGE to PDMS-DGE was 4:1. Specifically, 2.857 g of PEGDGE and 1.143 g of PDMS-DGE were added to 16.000 g of water / ethanol mixed solvent (the mass ratio of water to alcohol was 30:70) to obtain a PEGDGE / PDMS-DGE mixture with a total mass of 20.000 g and a solid content of 20 wt%. The mixture was then stirred at 80 °C for 6 h.

[0039] (2) Take 0.018 g of the PEGDGE / PDMS-DGE mixture obtained in step (1), which contains a total of 0.0036 g of PEGDGE and PDMS-DGE; add 0.018 g of ionic liquid [Emim][C(CN)3], 0.0084 g of Pebax1657, and 9.9556 g of water / ethanol mixed solvent (the mass ratio of water to alcohol is 30:70) to it, and continue stirring until the mixture is uniform, to obtain a casting solution with a total mass of 10.000 g and a solid content of 0.3 wt%. Among them, the ionic liquid accounts for 60 wt% of the total mass of the selected layer solids, and the total mass of PEGDGE and PDMS-DGE and Pebax1657 accounts for 40 wt% of the total mass of the selected layer solids, and the mass ratio of the PEGDGE and PDMS-DGE mixture to Pebax1657 is 30:70.

[0040] (3) A polysulfone porous support membrane with a PDMS intermediate layer on its surface is used as the base membrane. The casting liquid obtained in step (2) is uniformly coated on the surface of the base membrane by a scraping method with a scraper gap of 0.15 mm. Then, it is placed in a 50 ℃ oven to dry for 6 h to form a continuous and dense selective separation layer, thus obtaining the thin film composite membrane of Comparative Example 2.

[0041] Comparative Example 3 The steps for preparing the thin film composite membrane in this comparative example are as follows: (1) PEG-NH2 and PEGDGE were dissolved in a water / ethanol mixed solvent, wherein the mass ratio of water to ethanol was 30:70 and the molar ratio of PEG-NH2 to PEGDGE was 1:2. Specifically, 1.333 g of PEG-NH2 and 2.667 g of PEGDGE were added to 16.000 g of water / ethanol mixed solvent (the mass ratio of water to alcohol was 30:70) to obtain a mixed solution with a total mass of 20.000 g and a solid content of 20 wt%. The above mixed solution was stirred at 80 °C for 6 h to carry out a ring-opening reaction to obtain a reaction solution containing the polyether crosslinking reaction product, referred to as the polyether reaction solution.

[0042] (2) Take 0.018 g of the polyether reaction solution obtained in step (1), which contains 0.0036 g of polyether reaction component; add 0.018 g of ionic liquid [Emim][C(CN)3], 0.0084 g of Pebax1657 and 9.9556 g of water / ethanol mixed solvent (water to alcohol mass ratio of 30:70) to it, and continue stirring until the mixture is uniform to obtain a casting solution with a total mass of 10.000 g and a solid content of 0.3 wt%. Among them, the ionic liquid accounts for 60 wt% of the total mass of the selective layer solids, and the polyether reaction component and Pebax1657 together account for 40 wt% of the total mass of the selective layer solids, and the mass ratio of polyether reaction component to Pebax1657 is 30:70.

[0043] (3) A polysulfone porous support membrane with a PDMS intermediate layer on its surface is used as the base membrane. The casting liquid obtained in step (2) is uniformly coated on the surface of the base membrane by a scraping method with a scraper gap of 0.15 mm. Then, it is placed in a 50 ℃ oven to dry for 6 h to form a continuous and dense selective separation layer, thus obtaining the thin film composite membrane of Comparative Example 3.

[0044] Test Example 1 Membrane morphology characterization The membrane samples prepared in Example 1 and Comparative Example 1 were subjected to scanning electron microscopy to observe the surface and cross-sectional morphology of the membranes.

[0045] like Figure 1As shown, the left side displays the Pebax1657 / IL thin film composite membrane prepared in Comparative Example 1, and the right side displays the PEO-PDMS / Pebax / IL thin film composite membrane prepared in Example 1. The surface morphology shows that no obvious cracks were observed on the surfaces of either membrane, indicating that the ionic liquid selective layer can continuously cover the PDMS intermediate layer surface. Although the surface of the membrane in Example 1 exhibits some fine texture, it remains continuous and intact overall, without obvious phase separation or localized damage, indicating that the reactive component of PEO-PDMS has good film-forming compatibility with the Pebax1657 / IL system.

[0046] The cross-sectional morphology shows that the upper layer thickness of the membrane in Comparative Example 1 is approximately 180 nm, while that in Example 1 is approximately 150 nm, both forming a continuous nanoscale selective layer. Compared to Comparative Example 1, Example 1, even after introducing the polyether-polysiloxane crosslinking reaction products formed by PEG-NH2, PEGDGE, and PDMS-DGE, still achieves a continuous, dense, and relatively thin selective separation layer. This indicates that the reactive components do not damage the composite membrane structure and help regulate the film formation state of the ionic liquid-containing selective layer. These results demonstrate that the PEO-PDMS / Pebax / IL composite membrane prepared in this invention possesses good structural integrity, providing a stable membrane morphology basis for subsequent CO2 / N2 separation performance.

[0047] Test Example 2 Infrared spectroscopy characterization The membrane materials obtained in Example 1 and Comparative Example 1 were subjected to Fourier transform infrared spectroscopy to analyze the composition of the main functional groups in the membrane materials.

[0048] As shown in Figure 2, the membrane materials of both Example 1 and Comparative Example 1 are at 2168 cm⁻¹. - The presence of a characteristic absorption peak for the C≡N stretching vibration in the tricyanomethane anion near ¹ indicates that the ionic liquid [Emim][C(CN)3] has been successfully introduced into both selective separation layers. Both membranes show an absorption peak at 1730 cm⁻¹. - ¹ The absorption peak near this point can be attributed to carbonyl-related vibrations, 1638 cm⁻¹ - ¹ and 1540 cm - ¹ The absorption peaks near the film correspond to the characteristic absorption of the amide I and amide II bands of the polyamide, respectively, indicating that the polyamide structure in the Pebax1657 matrix is ​​still retained after film formation.

[0049] Example 1 and Comparative Example 1 were measured at 1245 cm. - ¹ and 1100 cm -¹ Absorption peaks appeared near all points. Although the selective separation layer of Comparative Example 1 did not contain polysiloxane components, the infrared test signal under the nanoscale ultrathin selective layer condition included the contribution of the underlying intermediate layer because its base film surface was coated with a PDMS intermediate layer. Compared with Comparative Example 1, Example 1 showed a higher absorption peak at 1245 cm⁻¹. - ¹ (corresponding to Si-CH3 related vibrations) and 1100 cm - The absorption peak near ¹ (corresponding to the stretching vibration of the polyether chain segment COC) shows a more significant relative enhancement, which strongly proves that the polyether and polysiloxane components composed of PEG-NH2, PEGDGE and PDMS-DGE have been successfully introduced into the selective separation layer.

[0050] At 3293 cm - ¹ Near this point, both membranes exhibited distinct absorption peaks. In Comparative Example 1, this absorption peak primarily originated from the extremely strong NH stretching vibrations of the Pebax1657 polyamide hard segment and the contribution of a small amount of adsorbed water. However, in Example 1, with the introduction of the polyether-polysiloxane component, the absolute mass percentage of the Pebax1657 matrix decreased. Although the epoxy-amine ring-opening reaction generated a β-hydroxyamine structure (containing OH and secondary amine NH), its absorption intensity was much weaker than the original dense polyamide hydrogen bond network. This resulted in a reasonable decrease in the relative intensity of the absorption peak at this location in Example 1, which is consistent with the objective law that the matrix is ​​effectively diluted by the polyether-polysiloxane crosslinking network without an NH backbone.

[0051] More importantly, the asymmetric ring deformation vibration of free epoxy groups is typically at 910 cm⁻¹. - ¹ A characteristic absorption peak is observed near this location. If Example 1 were merely a simple physical blend of the raw materials, the system would inevitably retain a large amount of PEGDGE and PDMS-DGE containing terminal epoxy groups, thus exhibiting a distinct epoxy group characteristic peak at this position. However, no distinct epoxy group characteristic peak was observed at this position in the infrared spectrum of Example 1. This indicates that a large amount of epoxy groups in the raw materials have been consumed.

[0052] In summary, the relative weakening of the original NH peak intensity (matrix dilution effect) and the "polyether / polysiloxane backbone peak (1100 cm⁻¹)" are mentioned. - ¹and 1245 cm - The enhancement of "¹)" and the characteristic peak of the epoxy group of the raw material (910 cm⁻¹) -The disappearance of ¹) corroborates each other, forming a complete chain of evidence for structural evolution, which fully proves that Example 1 is not a simple physical blending of the raw material components, but rather that an epoxy-amine ring-opening chemical reaction has occurred, and a cross-linked polyether-polysiloxane reaction product has been successfully constructed in the membrane.

[0053] Test Example 3 To further verify the epoxy-amine ring-opening reaction between PEG-NH2, PEGDGE, and PDMS-DGE, 1H NMR spectra were performed on PEG-NH2 monomer, PEGDGE monomer, PDMS-DGE monomer, the unreacted control solution of Example 1 with the same proportions, and the PEO-PDMS reaction solution obtained in step (1) of Example 1. The unreacted control solution used the same raw material types, feed ratios, solvent composition, and reaction component content as in step (1) of Example 1. The three raw materials were directly sampled after mixing, without undergoing a reaction treatment at 80 °C for 6 h. Figure 3 As shown, both PEGDGE and PDMS-DGE exhibit characteristic signals of protons in the epoxy ring of the glycidyl ether end group within the ranges of δ = 3.10–3.04 ppm and δ = 2.70–2.52 ppm. The δ = 3.10–3.04 ppm range primarily corresponds to methylene protons in the epoxy ring, while the δ = 2.70–2.52 ppm range primarily corresponds to non-equivalent protons in the methylene group of the epoxy ring. The strong signal within the δ = 3.41–3.68 ppm range mainly originates from the polyether backbone and methylene protons adjacent to oxygen atoms in the end groups of PEG-NH2 and PEGDGE. PDMS-DGE exhibits a characteristic signal of Si-CH3 near δ = 0.02–0.04 ppm. The NMR results of the three monomers clearly define the characteristic peak positions of the epoxy end group, polyether segment, and polysiloxane segment, providing a basis for comparing structural changes before and after the reaction.

[0054] In Example 1, the unreacted control solution with the same ratio still clearly retained the epoxy ring proton signal near δ=3.05 ppm and δ=2.69 ppm; when the Si-CH3 signal at δ=0.02~0.04 ppm, which does not participate in the epoxy-amine ring-opening reaction, was used as a reference and normalized to 1.00, the relative integrals of the above two epoxy proton regions were approximately 0.20 and 0.27, respectively. In the PEO-PDMS reaction solution obtained in step (1) of Example 1, the epoxy ring proton signals near δ=3.05 ppm and δ=2.69 ppm were significantly weakened and close to the baseline, while the Si-CH3 characteristic signal and the polyether segment signal in the range of δ=3.41~3.68 ppm were still retained. Since both samples used the same raw material composition and feed ratio, the selective attenuation of the proton signal of the epoxy ring after the reaction indicates that the epoxy groups in PEGDGE and PDMS-DGE were significantly consumed during the reaction in step (1) of Example 1, confirming that the amino group in PEG-NH2 underwent an epoxy-amine ring-opening reaction with the epoxy groups in PEGDGE and PDMS-DGE. This result is consistent with the infrared spectrum at 910 cm⁻¹. -1 No obvious epoxy group characteristic absorption was observed nearby, 3293 cm -1 The absorption profile of NH / OH in the vicinity changes, as does the 1100 cm⁻¹. -1 and 1245 cm -1 The changes in the absorption of nearby polyether and polysiloxane corroborate each other, indicating that the PEO-PDMS reaction solution obtained in step (1) of Example 1 is not a simple physical mixture of the three raw materials, but contains the polyether-polysiloxane crosslinking reaction product formed by the ring-opening reaction of epoxy-amine.

[0055] Test Example 4 Mixed gas separation performance test The membrane composite membranes prepared in Examples 1-3 and Comparative Examples 1-3 were tested for CO2 / N2 mixed gas separation performance, and the results are shown in Table 1. During the test, the membrane samples were sealed in a membrane cell. A CO2 / N2 mixed gas was introduced into the feed gas side, and He was used as the purge gas on the permeate side at atmospheric pressure. The gas composition on the permeate and feed sides was analyzed by gas chromatography. The permeation rate (in GPU) of each gas component was calculated based on the effective membrane area, gas flow rate, and gas composition. The separation factor of the two gases was the ratio of the corresponding gas permeation rates.

[0056] Permeation rate ( R The definition of ) is shown in equation (1-1): (1-1) In the above formula, R i Components i The permeation rate of the separation membrane is expressed in GPUs (1 GPU = 10^10).-6 cm 3 (STP) cm - 2 s -1 cmHg -1 = 3.35×10 -10 mol m -2 s -1 Pa -1 ); Q i Components i The volumetric flow rate through the gas separation membrane at standard temperature and pressure, expressed in cm. 3 (STP) / s; P i It is a component i The partial pressure difference across the gas separation membrane, expressed in cmHg; A Effective membrane area, in cm² 2 .

[0057] Meanwhile, the selectivity of the separation membrane is usually measured by the separation factor ( The separation factor reflects the rate at which different components pass through the separation membrane. i and j The ratio of permeability coefficients ( ) or permeation rate ratio ( The ideal separation factor is defined as shown in equation (1-2): (1-2).

[0058] Table 1. Test results of CO2 / N2 mixed gas separation performance of the thin film composite membranes prepared in Examples 1-3 and Comparative Examples 1-3 As shown in Table 1, under the condition that the ionic liquid content is 60 wt%, the PEO-PDMS / Pebax / IL thin film composite membrane prepared in Example 1 exhibits superior overall separation performance, with a CO2 flux of 1970 GPU and a CO2 / N2 selectivity of 40, both higher than those of the Pebax1657 / IL thin film composite membrane prepared in Comparative Example 1. This result indicates that introducing the polyether-polysiloxane reaction product formed by the epoxy-amine ring-opening reaction of PEG-NH2, PEGDGE, and PDMS-DGE into the Pebax1657 / IL system is beneficial to improving the membrane's CO2 transport capacity and CO2 / N2 separation performance.

[0059] The CO2 flux and CO2 / N2 selectivity of Examples 2 and 3 were lower than those of Example 1, indicating that the relative ratios of PEG-NH2, PEGDGE, and PDMS-DGE have a significant impact on the separation performance of the composite membrane. Comparative Example 2 does not contain PEG-NH2, and therefore cannot form an epoxy-amine ring-opening linkage structure; Comparative Example 3 does not contain PDMS-DGE, and the resulting system does not contain polysiloxane segments. Compared to Comparative Examples 2 and 3, Example 1 exhibited higher CO2 / N2 selectivity, indicating that the polyether-polysiloxane reaction product formed by the epoxy-amine ring-opening reaction and its suitable composition are beneficial for constructing a composite selective layer with both CO2 transport and molecular sieving capabilities.

[0060] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A composite gas separation membrane containing ionic liquid, characterized in that, The composite gas separation membrane includes a base membrane and a selective separation layer disposed on the base membrane; the selective separation layer is formed by blending a polyether-polysiloxane reaction product, which is formed by the ring-opening reaction of an amino-containing polyether compound, an epoxy-containing polyether compound, and an epoxy-containing polysiloxane compound, with a polyether amide and an ionic liquid.

2. The composite gas separation membrane containing ionic liquid according to claim 1, characterized in that, The amino-containing polyether compound is selected from one or more of terminal amino polyoxyethylene compounds, terminal amino polyoxypropylene compounds, terminal amino polyoxyethylene-polyoxypropylene copolymers, or terminal amino polytetrahydrofuran compounds; and / or, the epoxy-containing polyether compound is selected from one or more of epoxy-containing polyoxyethylene compounds, epoxy-containing polyoxypropylene compounds, epoxy-containing polyoxyethylene-polyoxypropylene copolymers, or epoxy-containing polytetrahydrofuran compounds; and / or, the epoxy-containing polysiloxane compound is selected from one or more of epoxy-containing polydimethylsiloxane or epoxy-containing polymethylphenylsiloxane; the polyether amide is a polyether block polyamide; and / or, the ionic liquid is an imidazole ionic liquid.

3. The composite gas separation membrane containing ionic liquid according to claim 1, characterized in that, The base film is a porous support or a porous support containing an intermediate layer, wherein the porous support is selected from polysulfone porous support, polyethersulfone porous support or polyimide porous support; and the intermediate layer is a polydimethylsiloxane intermediate layer.

4. The composite gas separation membrane containing ionic liquid according to claim 1, characterized in that, The total molar ratio of the amino-containing polyether compound to the epoxy-containing polyether compound and the epoxy-containing polysiloxane compound is 1:0.1 to 1:100, and the molar ratio of the epoxy-containing polyether compound to the epoxy-containing polysiloxane compound is 0.1:1 to 100:1; the mass ratio of the polyether-polysiloxane reaction product, the polyether amide, and the ionic liquid is 45:45:10 to 5:5:

90.

5. A method for preparing a composite gas separation membrane containing ionic liquid, used to prepare the composite gas separation membrane containing ionic liquid as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) Dissolve an amino-containing polyether compound, an epoxy-containing polyether compound and an epoxy-containing polysiloxane compound in a mixed solvent, and carry out an epoxy-amine ring-opening reaction under stirring conditions to obtain a reaction solution containing a polyether-polysiloxane copolymer. (2) After adding the ionic liquid to the reaction solution obtained in step (1) and mixing it evenly, add polyether amide and mix to obtain the casting solution; (3) The casting liquid obtained in step (2) is coated on the surface of the base membrane and dried to form the selective separation layer, thereby obtaining the composite gas separation membrane containing ionic liquid.

6. The method for preparing the composite gas separation membrane containing ionic liquid according to claim 5, characterized in that, In step (1), the mixed solvent is a mixture of water and alcohol, and the mass ratio of water to alcohol is 1:99-99:1; the alcohol is selected from one or more of methanol, ethanol or isopropanol.

7. The method for preparing the composite gas separation membrane containing ionic liquid according to claim 5, characterized in that, In step (1), the total content of the amino-containing polyether compound, the epoxy-containing polyether compound, and the epoxy-containing polysiloxane compound in the mixed solvent is 10 wt% to 30 wt%; and / or, the epoxy-amine ring-opening reaction in step (1) is carried out at 40°C to 100°C.

8. The method for preparing the composite gas separation membrane containing ionic liquid according to claim 5, characterized in that, In step (3), the base film is a porous support or a porous support with an intermediate layer pre-coated on its surface, and the coating method is one or more of scraping, spraying, and dipping; and / or the drying is carried out at room temperature or under heating conditions.

9. Application of a composite gas separation membrane containing ionic liquid in gas separation.

10. The application according to claim 9, characterized in that, The feed gas contains carbon dioxide, and the carbon dioxide preferentially permeates through the composite gas separation membrane.

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