A polyether-based random copolymer, its preparation method and carbon capture application

Abstract

This application belongs to the field of membrane material technology, and more specifically, relates to a polyether-based random copolymer, its preparation method, and its carbon capture application. This application uses two or three of the monomers selected from trioxymethylene, 1,3-dioxolane, and 4-methyl-1,3-dioxolane, and trifluoromethanesulfonic acid as a catalyst, to undergo cationic ring-opening polymerization for random copolymerization in an anhydrous and oxygen-free environment, generating a polyether-based random copolymer. In gas separation membrane applications, this random copolymer breaks the current trade-off between permeability and selectivity in polymer membrane materials, exceeding the generally accepted Robeson upper limit for gas separation. Using the polyether-based random copolymer of this invention as a selective layer, the resulting thin-layer composite membrane exhibits significant advantages such as high gas flux, excellent mixed gas separation performance, and industrial scale-up capability, achieving the performance of current mainstream international CO2 separation membranes.

Description

Technical Field

[0001] This application belongs to the field of membrane material technology, and more specifically, relates to a polyether-based random copolymer, its preparation method and carbon capture application. Background Technology

[0002] Carbon capture is widely considered a key technology for achieving net-zero emissions, and its industrial applications cover several important areas such as flue gas treatment, natural gas purification, and syngas separation. Among the many technological pathways for addressing global climate change, membrane separation has gradually stood out from numerous carbon capture technologies due to its comprehensive advantages, including high energy efficiency, scalability, and flexible modular deployment, attracting widespread attention from academia and industry. However, the performance development of these membrane materials has long been constrained by the inherent contradiction between permeability and selectivity—this widely recognized mass transfer bottleneck has made it difficult for gas separation performance to exceed the upper limit proposed by Robertson, limiting its further promotion in large-scale industrial applications.

[0003] To overcome this technological bottleneck, researchers have conducted systematic and in-depth explorations from multiple directions. Among these, hybrid matrix membranes incorporating inorganic fillers such as molecular sieves have shown significantly enhanced separation performance, promising a synergistic effect between the advantages of organic membranes and inorganic materials. However, these materials often face challenges in practical preparation, such as filler agglomeration and interfacial defects with the polymer matrix, especially in ultrathin selective layers, where ensuring the uniformity and integrity of the membrane structure is difficult, thus affecting separation efficiency. On the other hand, microporous polymers, represented by inherently microporous polymers and thermally rearranged polymers, provide rapid diffusion paths for gas molecules due to the abundant microporous channels formed by their rigid chain structures, thus achieving high permeability. However, these materials are prone to physical aging during actual operation, leading to the gradual collapse of the microporous structure over time. Furthermore, plasticization occurs in the presence of high concentrations of condensable gases (such as CO2), causing intensified chain segment movement and decreased selectivity. These factors collectively constrain their long-term operational stability. These challenges highlight the urgency and necessity of developing a novel polymer system that combines high CO2 affinity, rapid mass transfer capability, and good processability.

[0004] Among numerous polymer materials, polyether-based polymers offer a promising platform for membrane-based gas separation due to their unique intermolecular interactions. Specifically, the carbon-oxygen bonds in polyethers can form strong dipole-quadrupole interactions with CO2 molecules. This thermodynamic affinity endows the material with high solubility selectivity, giving it a natural advantage in separating CO2 / nonpolar gases (such as N2 and CH4). However, the separation performance of these materials is still constrained by the inherent contradiction between permeability and selectivity. According to the classic dissolution-diffusion model, the permeation process of gas molecules in non-porous membranes can be divided into three steps: first, adsorption and dissolution on the membrane surface; second, diffusion driven by the concentration gradient; and finally, desorption on the other side of the membrane. Under this mechanism, the gas permeability is jointly determined by the solubility coefficient and the diffusion coefficient, while the separation selectivity stems from the synergistic effect of dissolution selectivity and diffusion selectivity. Currently, to improve the solubility selectivity of materials, researchers often employ molecular design strategies that introduce polar groups to enhance the interaction between the membrane material and CO2. However, while this strategy enhances enthalpy interactions, it often restricts the mobility of polymer chain segments, leading to a reduction in free volume and a decrease in the gas diffusion coefficient, thus resulting in a loss of overall permeability. Conversely, methods that improve diffusion selectivity by introducing rigid chain structures or promoting close packing of chain segments, while effectively sieving gas molecules with different kinetic diameters, also hinder gas molecule diffusion and mass transfer, ultimately leading to a decrease in permeability. Therefore, the trade-off between permeability and selectivity is rooted in the intrinsic structure of polymer materials. Overcoming this bottleneck requires simultaneously optimizing the mutually restrictive diffusion and dissolution processes, and deeply deconstructing the intrinsic correlation and constraint mechanisms between polymer molecular structure and macroscopic separation performance, thereby achieving a fundamental breakthrough in materials design. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this application is to provide a polyether-based random copolymer, its preparation method and carbon capture application, aiming to solve the technical problem that the permeability and selectivity of the existing polyether-based polymer carbon capture membrane materials are difficult to balance.

[0006] To achieve the above objectives, in a first aspect, this application provides a polyether-based random copolymer, said random copolymer comprising: Repeating units derived from the first monomer and repeating units derived from the second monomer; The first monomer is 1,3-dioxolane; The second monomer is selected from one or both of trioxymethylene and 4-methyl-1,3-dioxolane; The repeating units derived from the first monomer and the repeating units derived from the second monomer are randomly distributed in the polymer chain; In the random copolymer, the molar ratio of repeating units derived from the first monomer to repeating units derived from the second monomer is (1-9):(1-9). The random copolymer has a number-average molecular weight greater than 60 kDa; The random copolymer has a molecular weight distribution (PDI) of 1.1-2.

[0007] Preferably, the number average molecular weight of the random copolymer is 60 kDa-350 kDa, and more preferably 60 kDa-310 kDa.

[0008] Preferably, when the second monomer is trioxymethylene, the molar ratio of the repeating units of the first monomer to the repeating units of the second monomer is (1-6):1; more preferably (2-4):1. When the second monomer is 4-methyl-1,3-dioxolane, the molar ratio of the repeating unit of the first monomer to the repeating unit of the second monomer is (8-10):1. When the second monomer simultaneously comprises trioxymethylene and 4-methyl-1,3-dioxolane, the molar ratio of the repeating unit of 1,3-dioxolane, the repeating unit of trioxymethylene, and the repeating unit of 4-methyl-1,3-dioxolane is (5-10):(1-5):5, and more preferably (6-9):(1-4):5.

[0009] According to another aspect, a method for preparing the aforementioned random copolymer is provided, comprising the following steps: (1) After the first monomer, the second monomer and the catalyst are mixed evenly, a cationic ring-opening polymerization reaction is carried out under anhydrous and oxygen-free conditions to obtain the reaction product; (2) After the reaction is completed, the reaction product of step (1) is dissolved in a good solvent and an amine terminator is added. The product is precipitated in a poor solvent and purified repeatedly to obtain the random copolymer.

[0010] Preferably, when the second monomer is trioxymethylene, the molar ratio of the first monomer 1,3-dioxolane to the second monomer trioxymethylene is (1-6):1; more preferably (2-4):1. When the second monomer is 4-methyl-1,3-dioxolane, the molar ratio of the first monomer 1,3-dioxolane to the second monomer 4-methyl-1,3-dioxolane is (8-10):1. When the second monomer contains both trioxymethylene and 4-methyl-1,3-dioxolane, the molar ratio of 1,3-dioxolane, trioxymethylene, and 4-methyl-1,3-dioxolane is (5-10):(1-5):5, and more preferably (6-9):(1-4):5.

[0011] Preferably, the molar amount of the catalyst is 0.01-0.02% of the total molar amount of the first monomer and the second monomer.

[0012] Preferably, the amine terminator in step (2) is one or more of triethylamine, ethylenediamine, n-butylamine and ethanolamine; the volume ratio of the amine terminator to the catalyst is 1000:(0.5-2).

[0013] Preferably, the good solvent is one or more of dichloromethane, N,N-dimethylformamide and N-methylpyrrolidone, and the bad solvent is one or more of methanol, ethanol and water, wherein the volume of the bad solvent is 5-10 times that of the good solvent.

[0014] According to another aspect of the invention, the use of the aforementioned polyether-based random copolymer in the preparation of membrane materials for separating and / or concentrating gases is provided.

[0015] According to another aspect of the invention, a separation membrane for separating and / or concentrating gases is provided, comprising the aforementioned polyether-based random copolymer.

[0016] Preferably, the separation membrane comprises a porous support layer, an intermediate layer, and a selective layer, wherein the selective layer is made of the aforementioned polyether-based random copolymer.

[0017] Overall, the technical solutions conceived in this application have the following beneficial effects compared with the prior art: (1) This invention uses trifluoromethanesulfonic acid as a catalyst and two or three of 1,3-dioxolane (DXL), trioxymethylene (TX), and 4-methyl-1,3-dioxolane (MDXL) as monomers to undergo cationic ring-opening polymerization to generate a novel random polyether copolymer PDTM. The polyether-based copolymer prepared by this invention has high CO2 capture performance when used as a gas separation membrane material. Its CO2 separation performance is superior to other polyether-based materials and exceeds the Robeson upper limit.

[0018] (2) The polyether-based copolymer of the present invention has mild synthesis conditions and is easy to produce on an industrial scale. The copolymer has good mechanical strength and solution processability when used as a gas separation membrane material.

[0019] (3) The synthesis method of the present invention can effectively inhibit polymer crystallization, and the synthesized polyether-based copolymer membrane material has good CO2 separation performance.

[0020] (4) The thin-layer composite membrane prepared by using the polyether-based random copolymer of the present invention as the selective layer has significant advantages such as high gas flux, excellent mixed gas separation performance and industrial scale-up, and reaches the current international mainstream CO2 separation membrane performance (CO2 permeation flux greater than 1000 GPU, CO2 / N2 selectivity greater than 20). Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the synthesis route of the random polyether copolymer PDTM of the present invention.

[0022] Figure 2 The content describes the solubility and film-forming properties of the copolymer PDTM in Example 1, wherein (a) shows the solubility of the copolymer in different solutions (EA: ethyl acetate; THF: tetrahydrofuran; DMF, NN-dimethylformamide; DCM: dichloromethane; TCM: trichloromethane), and (b) shows the film made from the copolymer in Example 1.

[0023] Figure 3 The 1H NMR spectrum of the polymer prepared for Comparative Example 1.

[0024] Figure 4 The 1H NMR spectra of the polymer representative samples (1-3) prepared in Example 1.

[0025] Figure 5 The 1H NMR spectrum of the polymer sample prepared in Example 2.

[0026] Figure 6 The 1H NMR spectrum of the representative polymer sample (3-3) prepared in Example 3. Figure 7 The X-ray diffraction (XRD) patterns of the polymers in Comparative Example 1, Example 1, and Example 3 are shown.

[0027] Figure 8 The thermal analysis curves of the polymers in Comparative Example 1 and Examples 1-3 are shown, where (a) is the differential scanning calorimetry (DSC) curve and (b) is the thermogravimetric analysis (TGA) curve.

[0028] Figure 9 The gas separation performance of each copolymer at 5 bar and 25 °C is given, where (a) is the gas permeability coefficient of the separation membrane and (b) is the membrane separation selectivity.

[0029] Figure 10 This is a comparison chart showing the gas separation performance of the polymers prepared in the examples and comparative examples with other polymer membrane materials.

[0030] Figure 11Scanning electron microscope image of the thin-layer composite film prepared in Example 4.

[0031] Figure 12 The performance (CO2 / N2 selectivity) of the thin-layer composite membrane prepared in Example 4 is compared with that of other membrane materials.

[0032] Figure 13 The performance (CO2 / CH4 selectivity) of the thin-layer composite membrane prepared in Example 4 is compared with that of other membrane materials.

[0033] Figure 14 The changes in gas flux and carbon dioxide / nitrogen selectivity of the thin-layer composite membrane prepared in Example 4 were measured by continuous 100-h mixed gas testing. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0035] This application provides a polyether-based random copolymer comprising: Repeating units derived from the first monomer and repeating units derived from the second monomer; The first monomer is 1,3-dioxolane; The second monomer is selected from one or both of trioxymethylene and 4-methyl-1,3-dioxolane; The repeating units derived from the first monomer and the repeating units derived from the second monomer are randomly distributed in the polymer chain; In the random copolymer, the molar ratio of repeating units derived from the first monomer to repeating units derived from the second monomer is (1-9):(1-9). The number-average molecular weight of the random copolymer is greater than 60 kDa (determined by gel permeation chromatography, GPC). The random copolymer has a molecular weight distribution (PDI) of 1.1-2.

[0036] In some embodiments, the random copolymer contains repeating units as shown in Formula (I):

[0037] Formula (1) Where x, y, and z represent the number of repeating units, and optionally either y or z can be 0 or neither can be 0; ran represents the random distribution of each unit.

[0038] Preferably, the number average molecular weight of the random copolymer is 60 kDa-350 kDa, more preferably 60 kDa-310 kDa, and even more preferably 90 kDa-310 kDa.

[0039] Preferably, when the second monomer is trioxymethylene, the molar ratio of the repeating units of the first monomer to the repeating units of the second monomer is (1-6):1; more preferably (2-4):1. When the second monomer is 4-methyl-1,3-dioxolane, the molar ratio of the repeating unit of the first monomer to the repeating unit of the second monomer is (8-10):1. When the second monomer simultaneously comprises trioxymethylene and 4-methyl-1,3-dioxolane, the molar ratio of the repeating unit of 1,3-dioxolane, the repeating unit of trioxymethylene, and the repeating unit of 4-methyl-1,3-dioxolane is (5-10):(1-5):5, more preferably (6-9):(1-4):5.

[0040] The present invention also provides a method for preparing the random copolymer, comprising the following steps: (1) After the first monomer, the second monomer and the catalyst are mixed evenly, a cationic ring-opening polymerization reaction is carried out under anhydrous and oxygen-free conditions to obtain the reaction product; (2) After the reaction is completed, the reaction product of step (1) is dissolved in a good solvent and an amine terminator is added. The product is precipitated in a poor solvent and purified repeatedly to obtain the random copolymer.

[0041] In some embodiments, in step (1), both the first monomer and the second monomer are dehydrated using molecular sieves, and oxygen and water vapor are strictly isolated during the reaction process, with continuous stirring during the reaction.

[0042] In some embodiments, when the second monomer is trioxymethylene, the molar ratio of the first monomer 1,3-dioxolane to the second monomer trioxymethylene is (1-6):1; more preferably (2-4):1. When the second monomer is 4-methyl-1,3-dioxolane, the molar ratio of the first monomer 1,3-dioxolane to the second monomer 4-methyl-1,3-dioxolane is (8-10):1. When the second monomer contains both trioxymethylene and 4-methyl-1,3-dioxolane, the molar ratio of 1,3-dioxolane, trioxymethylene, and 4-methyl-1,3-dioxolane is (5-10):(1-5):5, more preferably (6-9):(1-4):5.

[0043] The catalyst can be any catalyst capable of catalyzing this type of cyclic acetal ring-opening polymerization reaction, including but not limited to one or more of trifluoromethanesulfonic acid, Lewis acid, and rare earth trifluorides. In a preferred embodiment, the molar amount of the catalyst is 0.01-0.02% of the total molar amount of the first monomer and the second monomer.

[0044] In some embodiments, during the cationic ring-opening polymerization reaction, the catalyst is added dropwise to the homogeneously mixed monomer for the reaction, which is carried out at room temperature, generally 20-30 °C, for 5-15 min.

[0045] In a preferred embodiment, a dispersant for dispersing the catalyst is also added during the cationic ring-opening polymerization reaction in step (1). The dispersant is selected from one or more of dichloromethane, N,N-dimethylformamide and N-methylpyrrolidone. The volume ratio of the dispersant to the catalyst is 1000:(0.5-2) to avoid uneven reaction caused by excessively high local catalyst concentration.

[0046] In some embodiments, the amine terminator in step (2) is one or more of triethylamine, ethylenediamine, n-butylamine and ethanolamine; the volume ratio of the amine terminator to the catalyst is 1000:(0.5-2).

[0047] In some embodiments, the good solvent is one or more of dichloromethane, N,N-dimethylformamide, and N-methylpyrrolidone, and the bad solvent is one or more of methanol, ethanol, and water, wherein the volume of the bad solvent is 5-10 times that of the good solvent.

[0048] In some embodiments, the separation and purification specifically involves: dissolving the reaction mixture in a good solvent, adding an amine terminator to neutralize the catalyst, stirring thoroughly, pouring it into a poor solvent, collecting the precipitated product, continuing to dissolve it in a good solvent, precipitating out the poor solvent, repeating this process three times to obtain the product.

[0049] The polyether-based random copolymer described in this invention can be used as a membrane material for separating and / or concentrating gases. Therefore, this invention also provides a separation membrane for separating and / or concentrating gases, comprising the polyether-based random copolymer described in this invention.

[0050] More preferably, the membrane material for separating and / or concentrating the gas is a membrane material for separating and / or concentrating carbon dioxide, or a membrane material for carbon capture.

[0051] This invention provides a membrane for separating and / or concentrating gases, wherein the selective layer material contains the polyether-based random copolymer described in this invention. When using the random copolymer provided in this invention to prepare a separation membrane, it is mixed and dispersed uniformly with an organic solvent to form a casting solution. After ultrasonic defoaming, the solution is poured into a mold, dried to remove the organic solvent, and a copolymer film is obtained. This film is then directly used for gas separation, and its intrinsic properties are tested.

[0052] The polyether-based copolymer provided by this invention can also be used to prepare thin-layer composite films. The composite film includes a composite structure comprising a layer coated with the random copolymer of this invention, which serves as a selective layer in the composite structure, and further comprising a support layer and an intermediate layer. The support layer and intermediate layer can be made of materials commonly used in the art.

[0053] This application provides a novel polyether-based random copolymer, its preparation method, and its application. By using two or three of 1,3-dioxolane (DXL), trioxymethylene (TX), and 4-methyl-1,3-dioxolane (MDXL) as monomers and trifluoromethanesulfonic acid as a catalyst, a series of novel high molecular weight random copolymer polyether materials (PDTM) with different compositions are synthesized and prepared into gas separation membranes with high CO2 capture performance. By adjusting the proportion of different monomers, the free volume, crystallinity, and aggregate structure of the polymer material are effectively controlled, achieving both high CO2 affinity and good chain segment mobility, breaking the trade-off effect of permeability and selectivity. Finally, the separation membrane exhibits excellent mechanical strength, processability, separation stability, and water vapor resistance.

[0054] The method for preparing polyether random copolymers provided in this application has the advantages of short preparation time, high yield, and easy scale-up. In gas separation membrane applications, by controlling the proportions of different monomers, the polymer's gas affinity and aggregate structure can be controllably adjusted, breaking the trade-off between permeability and selectivity in current polymer membrane materials and exceeding the generally accepted Robeson upper limit for gas separation. Using polyether-based random copolymers as the selective layer, the resulting thin-layer composite membrane exhibits significant advantages such as high gas flux, excellent mixed gas separation performance, and industrial scale-up capability, achieving the performance of current mainstream international CO2 separation membranes (CO2 permeate flux greater than 1000 GPU, CO2 / N2 selectivity greater than 20).

[0055] The embodiments of the present invention are implemented under the premise of the technical solution of the present invention, and detailed implementation methods and processes are given. However, the protection scope of the present invention is not limited to the following embodiments. The process parameters in the following embodiments that do not specify specific conditions are generally in accordance with conventional conditions.

[0056] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0057] The embodiments of this application are described below with reference to the accompanying drawings.

[0058] Comparative Example 1 The reaction beaker was cleaned and dried beforehand and placed in a glove box for later use. The reaction monomer 1,3-dioxolane (DXL) was dried in a molecular sieve for 24 h. After the dried DXL was filtered through a 0.22-micron filter membrane, 0.1125 mol was placed in the reaction beaker. At the same time, 1 μl of trifluoromethanesulfonic acid and 1 ml of dichloromethane were mixed evenly and gradually added dropwise to the reaction beaker at room temperature while stirring continuously. As the polymerization reaction occurred, the solution gradually became viscous. The reaction was stopped after 5 min. All the above operations were carried out in a glove box, where the water vapor and oxygen content were both below 0.01 ppm.

[0059] The product after the reaction was removed from the glove box, and 50 ml of dichloromethane and 1 ml of triethylamine were added. The mixture was stirred thoroughly for 8 hours. After the product was completely dissolved, it was poured into 250 ml of ethanol. The precipitated solid was collected and dissolved again with dichloromethane. Ethanol precipitated. This process was repeated three times to obtain the final product.

[0060] 0.1 g of polymer was mixed with 5 mL of dichloromethane and magnetically stirred for 5 h to obtain a uniformly dispersed casting solution. After sonicating for 5 min to remove bubbles, the solution was poured into a leveled polytetrafluoroethylene mold with dimensions of 50*50*4 mm and dried at room temperature and pressure for 6 h. Then, it was vacuum dried at 30 ℃ for 6 h to evaporate the residual solvent, thus obtaining the polymer film of this comparative example.

[0061] The polymer film in this embodiment was characterized using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The gas permeability coefficient and CO2 / N2 and CO2 / CH4 selectivity of the copolymer film in this embodiment were determined at 25 °C and 5 bar, and the results are shown in Table 1. The product was characterized using gel permeation chromatography (GPC), yielding a molecular weight of 219 kDa. The chemical structure was characterized using proton nuclear magnetic resonance (NMR). The polymer was thermally analyzed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The crystalline structure of the film was characterized using X-ray diffraction (XRD).

[0062] Table 1 Characterization results of the copolymer films obtained in Comparative Example 1

[0063] Example 1 The reaction beaker was cleaned and dried beforehand and placed in a glove box for later use. The reaction monomers 1,3-dioxolane (DXL) and trioxymethylene (TX) were mixed evenly at molar ratios of 6:1, 4:1, 2:1, and 1:1, respectively. 0.1125 mol of each mixture (meaning that the total number of moles of the mixture was 0.1125 mol) was dried in a molecular sieve for 24 h. The dried monomer mixture was filtered through a 0.22-micron filter membrane and placed in the reaction beaker. At the same time, 1 μl of trifluoromethanesulfonic acid and 1 ml of dichloromethane were mixed evenly and gradually added dropwise to the reaction beaker at room temperature while stirring continuously. As the polymerization reaction occurred, the solution gradually became viscous. The reaction was stopped after 5 min. All the above operations were carried out in a glove box, where the water vapor and oxygen content were both below 0.01 ppm.

[0064] The product after the reaction was removed from the glove box, and 50 ml of dichloromethane and 1 ml of triethylamine were added. The mixture was stirred thoroughly for 8 hours. After the product was completely dissolved, it was poured into 250 ml of ethanol. The precipitated solid was collected and dissolved again with dichloromethane. Ethanol precipitated. This process was repeated three times to obtain the final product.

[0065] 0.1 g of polymer was mixed with 5 mL of dichloromethane and magnetically stirred for 5 h to obtain a uniformly dispersed casting solution. After sonicating for 5 min to remove bubbles, the solution was poured into a leveled polytetrafluoroethylene mold with dimensions of 50*50*4 mm and dried at room temperature and pressure for 6 h. Then, it was vacuum dried at 30 ℃ for 6 h to evaporate the residual solvent, thus obtaining the polymer film of this embodiment.

[0066] The copolymer films in this embodiment were characterized using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The gas permeability coefficient and CO2 / N2 and CO2 / CH4 selectivity of the copolymer films in this embodiment were determined at 25 °C and 5 bar. The results are shown in Table 2. Considering both permeability and selectivity, a 2:1 ratio of polymers 1-3 was the optimal composition. The optimal product in this embodiment was characterized using gel permeation chromatography (GPC), yielding a molecular weight of 245 kDa. The product was characterized using proton nuclear magnetic resonance (NMR) spectroscopy, and the content of each component was calculated. The optimal polymer in this embodiment was thermally analyzed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The crystalline structure of the optimal copolymer film was characterized using X-ray diffraction (XRD).

[0067] Table 2 Characterization results of copolymer films obtained with different monomer ratios in Example 1

[0068] Example 2 The reaction beaker was cleaned and dried beforehand and placed in a glove box for later use. The reaction monomers 1,3-dioxolane (DXL) and 4-methyl-1,3-dioxolane (MDXL) were mixed evenly at a molar ratio of 9:1. 0.1125 mol of the mixture (total moles of the mixed monomers were 0.1125 mol) was dried in a molecular sieve for 24 h. The dried mixed monomers were filtered through a 0.22-micron filter membrane and placed in the reaction beaker. At the same time, 1 μl of trifluoromethanesulfonic acid and 1 ml of dichloromethane were mixed evenly and gradually added dropwise to the reaction beaker at room temperature while stirring continuously. As the polymerization reaction occurred, the solution gradually became viscous. The reaction was stopped after 15 min. All the above operations were carried out in a glove box, where the water vapor and oxygen content were both below 0.01 ppm.

[0069] The product after the reaction was removed from the glove box, and 50 ml of dichloromethane and 1 ml of triethylamine were added. The mixture was stirred thoroughly for 8 hours. After the product was completely dissolved, it was poured into 250 ml of ethanol. The precipitated solid was collected and dissolved again with dichloromethane. Ethanol precipitated. This process was repeated three times to obtain the final product.

[0070] 0.1 g of polymer was mixed with 5 mL of dichloromethane and magnetically stirred for 5 h to obtain a uniformly dispersed casting solution. After sonicating for 5 min to remove bubbles, the solution was poured into a leveled polytetrafluoroethylene mold with dimensions of 50*50*4 mm and dried at room temperature and pressure for 6 h. Then, it was vacuum dried at 30 ℃ for 6 h to evaporate the residual solvent, thus obtaining the polymer film of this embodiment.

[0071] The copolymer film in this example was characterized using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The gas permeability coefficient and CO2 / N2 and CO2 / CH4 selectivity of the copolymer film in this example were determined at 25 °C and 5 bar. The results are shown in Table 3. The product in this example was characterized using gel permeation chromatography (GPC), and its molecular weight was found to be 68 kDa. The product was characterized using proton nuclear magnetic resonance (NMR) spectroscopy, and the content of each component was calculated.

[0072] Table 3 Characterization results of the copolymer films obtained in Example 2

[0073] Example 3 The reaction beaker was cleaned and dried beforehand and placed in a glove box for later use. The reaction monomers 1,3-dioxolane (DXL), 4-methyl-1,3-dioxolane (MDXL), and trioxymethylene (TX) were mixed evenly in molar ratios of 9:1:5, 8:2:5, 7:3:5, and 6:4:5, respectively. 0.1125 mol of each monomer was dried in a molecular sieve for 24 h. The dried monomer mixture was filtered through a 0.22-micron filter membrane and placed in the reaction beaker. At the same time, 1 μl of trifluoromethanesulfonic acid and 1 ml of dichloromethane were mixed evenly and gradually added dropwise to the reaction beaker at room temperature with continuous stirring. As the polymerization reaction occurred, the solution gradually became viscous. The reaction was stopped after 15 min. All the above operations were carried out in a glove box, where the water vapor and oxygen content were both below 0.01 ppm.

[0074] The product after the reaction was removed from the glove box, and 50 ml of dichloromethane and 1 ml of triethylamine were added. The mixture was stirred thoroughly for 8 hours. After the product was completely dissolved, it was poured into 250 ml of ethanol. The precipitated solid was collected and dissolved again with dichloromethane. Ethanol precipitated. This process was repeated three times to obtain the final product. Figure 1 This is a flowchart illustrating the synthesis route of the random copolymer in this embodiment.

[0075] 0.1 g of polymer was mixed with 5 mL of dichloromethane and magnetically stirred for 5 h to obtain a uniformly dispersed casting solution. After sonicating for 5 min to remove bubbles, the solution was poured into a leveled polytetrafluoroethylene mold with an inner diameter of 50*50*4 mm and dried at room temperature and pressure for 6 h. Then, it was vacuum dried at 30 ℃ for 6 h to evaporate the residual solvent, thus obtaining the polymer film of this embodiment.

[0076] At 25 °C and 2 bar, the gas permeability coefficient and CO2 / N2 and CO2 / CH4 selectivity of the copolymer film in this example were determined. The results are shown in Table 4. Considering both permeability and selectivity, the 2-3 polymer with a ratio of 7:3:5 is the optimal composition. The optimal product in this example was characterized by gel permeation chromatography (GPC), and its molecular weight was found to be 142 kDa. The product was characterized by proton nuclear magnetic resonance (NMR) spectroscopy, and the content of each component was calculated. The optimal polymer in this example was thermally analyzed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The crystalline structure of the optimal copolymer film was characterized by X-ray diffraction (XRD).

[0077] Table 4 Characterization results of copolymer films obtained with different monomer ratios in Example 3

[0078] Example 4 The preparation process of the thin-layer composite membrane is as follows: A polysulfone (PSF) base membrane (molecular weight cutoff of approximately 90,000 Da) was selected as the porous support layer. First, the PSF base membrane was immersed in water for two days to remove residual material from the pores. Subsequently, a classic polydimethylsiloxane (PDMS) layer was coated onto the PSF surface using a blade coating method. The coating was cured at 80 °C for 2 h, followed by atmospheric plasma treatment (900 W, 2 s) to enhance its surface energy, resulting in a PDMS / PSF membrane.

[0079] 2 g of each copolymer 1-3 from Example 1 and copolymer 2-3 from Example 2 were dissolved in a propanol / water mixed solvent (77:23, w / w) to prepare a 1.5 wt% solution at 70 °C. The solutions were then spin-coated onto the PDMS / PSF substrate at room temperature (8000 rpm, 60 s) and subsequently dried and cured in a 60 °C oven. The resulting thin-film composite films were designated as PDTM1 / PDMS / PSF film and PDTM2 / PDMS / PSF film, respectively. The coating structure and morphology were characterized using scanning electron microscopy. Figure 10 As shown in sections (a), (b), and (c), section (a) is the PSF porous support layer, section (b) is the composite layer after coating the PSF porous support layer with an intermediate PDMS layer, and section (c) is the thin-film composite membrane obtained after further coating with PDTM1 as a selective layer. The separation performance of pure gases CO2, CH4, and N2 was investigated at 25 °C and 5 bar. Furthermore, by simulating flue gas components, a CO2 / N2 (1:9, v / v) mixture was prepared, and the separation performance of the composite membrane in the actual separation process was studied under conditions of 25 °C and 1.5 bar. Water vapor (RH greater than 90%) was introduced during the test to study its stability.

[0080] according to Figure 2 Contents (a) and (b) show that the synthesized polymer has good solubility and film-forming properties.

[0081] Figure 3 , Figure 4 , Figure 5 and Figure 6The 1H NMR spectra of the samples correspond to those of Example 1, Representative Samples 1-3 in Example 1, Example 2, and Representative Samples 3-3 in Example 3. The NMR results demonstrate the successful synthesis of the polymer. The content of the corresponding monomers in the polymer can be inferred from the hydrogen shifts at different positions on the NMR spectrum. In Representative Samples 1-3 of Example 1, the content of DXL was 64.9 mol%, and the content of TX was 35.1 mol%. In Example 2, the content of DXL was 93.2 mol%, and the content of MDXL was 6.8 mol%. In Representative Samples 3-3 of Example 3, the content of DXL was 56 mol%, the content of TX was 32 mol%, and the content of MDXL was 12 mol%.

[0082] Figure 7 In the XRD patterns, both the mono-DXL polymer of Comparative Example 1 and the DXL and TX copolymer film of Example 1 showed sharp peaks in the crystalline region. However, compared with Comparative Example 1, the crystalline peak intensity of Example 1 after copolymerization was significantly reduced and the half-peak width was enhanced, indicating that copolymerization interfered with the regular arrangement of the original polymer chains, thereby reducing the crystallinity of the polymer. The ternary copolymer film in Example 3 showed broad peak diffraction, indicating that it has an amorphous structure. This result confirms that by using this random copolymerization method, the chain segment arrangement is effectively interfered with, and an amorphous copolymer is obtained, providing more channels for gas transport.

[0083] Combination Figure 8 The DSC results in section (a) show that Comparative Example 1 exhibits a distinct melting peak at 55.37 °C, indicating the presence of a relatively obvious crystalline structure. After random copolymerization, the melting peaks of Examples 1-3 all show a significant leftward shift, and the area of ​​the crystalline peaks is also significantly reduced. In particular, the melting peak in Example 3 is very weak, indicating a significant reduction in the crystalline structure, hence the lack of obvious diffraction peaks in the XRD. These results further demonstrate that the polymer obtained through copolymerization of three monomers can achieve effective crystallization inhibition, providing a foundation for high-permeability separation membranes. Figure 8 Content (b) The TGA results show that the copolymer has good thermal stability, and the decomposition temperature is above 300 ℃, which can meet the operating conditions at high temperature.

[0084] like Figure 9As shown in sections (a) and (b), Comparative Example 1, which did not undergo random copolymerization, was severely affected by crystallization, resulting in a significantly lower gas permeability coefficient than the samples of Examples 1-3, with a CO2 permeability coefficient of only 16.3 Barrer. Samples 3-4 of Examples exhibited the highest CO2 permeability coefficient of 245.3 Barrer. Regarding gas selectivity, the polymer of Example 1 exhibited the highest gas selectivity, with a CO2 / N2 selectivity of 85.6 and a CO2 / CH4 selectivity of 31.1. This may be because the comonomer used in Example 1 was TX, which has the highest ether oxygen content, thus exhibiting better gas affinity than Comparative Example 1. Therefore, Example 1 had the highest gas selectivity. In Example 2, the introduction of MDXL reduced the chain segment regularity and decreased the copolymer molecular weight, thereby enhancing chain segment mobility and improving gas permeability compared to Comparative Example 1. However, due to the low ether oxygen bond content in MDXL and its low gas affinity, the gas selectivity was the worst. Example 3 combined the high ether oxygen content of TX with the steric hindrance effect of MDXL, resulting in a significant improvement in both gas permeability and selectivity compared to Comparative Example 1. Therefore, the random copolymerization strategy proposed in this invention simultaneously improves the gas permeability and gas selectivity of the polymer membrane, breaking the trade-off effect.

[0085] Figure 10 Contents (a) and (b) compare the separation performance of the polymer membranes obtained in this invention with that of other polymer membrane materials. Intuitively, the polymers of Examples 1 to 3 after random copolymerization show significantly better separation performance than Comparative Example 1, especially samples 3-2 of Example 3, whose separation performance exceeds the upper limit of gas separation and ranks among the top of many polymer membrane materials, indicating that the random copolymerization strategy effectively improves gas separation performance.

[0086] Figure 11 This is a scanning electron microscope cross-sectional image of the thin-layer composite film PDTM1 / PDMS / PSF prepared in Example 4. Figure 11 As shown in contents (a), (b) and (c), the thin-film composite film consists of a polysulfone (PSF) support layer, a polydimethylsiloxane (PDMS) interlayer, and a copolymer PDTM1 corresponding to samples 1-3 in Example 1 as a selective layer. The thickness of the selective layer is approximately 100 nm, indicating that the copolymer material prepared in this paper has excellent potential for ultrathinning.

[0087] Figure 12 and 13This figure compares the separation performance of the thin-layer composite membranes (PDTM1 / PDMS / PSF membrane and PDTM2 / PDMS / PSF membrane, denoted as This work 1 and This work 2, respectively) prepared in Example 4 with that of currently available commercial membranes. Their separation performance is already competitive with that of currently available commercial membranes.

[0088] Figure 14 The separation stability of the thin-layer composite membrane PDTM1 / PDMS / PSF prepared in Example 4 was tested under continuous 100 h conditions and in the presence of water vapor. The test results show that the thin-layer composite membrane prepared using the polyether-based random copolymer of this invention as the selective layer has significant advantages such as high gas flux, excellent mixed gas separation performance, and industrial scale-up capability, far exceeding the performance of current mainstream international CO2 separation membranes (CO2 permeation flux greater than 1000 GPU, CO2 / N2 selectivity greater than 20). The membrane showed no performance degradation during 100 h of continuous operation, and its separation performance remained stable after two water vapor test cycles, demonstrating the significant application potential of the copolymer membrane material prepared in this application in the field of carbon capture.

[0089] Comparative Example 2 The rest is the same as in Example 2, except that the ratio of DXL to MDXL was adjusted to 8:2. GPC results showed that its molecular weight was only 51 kDa, its mechanical strength was poor, and the product was in a viscous liquid state, which could not be used for gas performance testing and could not meet the actual separation requirements.

[0090] Comparative Example 3 Everything else was the same as in Example 1, except that the DXL monomer was replaced with MDXL. The reaction time was extended to 8 hours, and no significant changes were observed in the reaction solution. NMR analysis revealed that neither monomer reacted.

[0091] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A polyether-based random copolymer, characterized in that, The random copolymer comprises: Repeating units derived from the first monomer and repeating units derived from the second monomer; The first monomer is 1,3-dioxolane; The second monomer is selected from one or both of trioxymethylene and 4-methyl-1,3-dioxolane; The repeating units derived from the first monomer and the repeating units derived from the second monomer are randomly distributed in the polymer chain; In the random copolymer, the molar ratio of repeating units derived from the first monomer to repeating units derived from the second monomer is (1-9):(1-9). The random copolymer has a number-average molecular weight greater than 60 kDa; The random copolymer has a molecular weight distribution (PDI) of 1.1-2.

2. The random copolymer as described in claim 1, characterized in that, The number-average molecular weight of the random copolymer is 60 kDa-350 kDa; and / or, When the second monomer is trioxymethylene, the molar ratio of the repeating units of the first monomer to the repeating units of the second monomer is (1-6):1; When the second monomer is 4-methyl-1,3-dioxolane, the molar ratio of the repeating unit of the first monomer to the repeating unit of the second monomer is (8-10):

1. When the second monomer contains both trioxymethylene and 4-methyl-1,3-dioxolane, the molar ratio of the repeating unit of 1,3-dioxolane, the repeating unit of trioxymethylene, and the repeating unit of 4-methyl-1,3-dioxolane is (5-10):(1-5):

5.

3. The method for preparing the random copolymer as described in claim 1 or 2, characterized in that, Includes the following steps: (1) After the first monomer, the second monomer and the catalyst are mixed evenly, a cationic ring-opening polymerization reaction is carried out under anhydrous and oxygen-free conditions to obtain the reaction product; (2) After the reaction is completed, the reaction product of step (1) is dissolved in a good solvent and an amine terminator is added. The product is precipitated in a poor solvent and purified repeatedly to obtain the random copolymer.

4. The preparation method according to claim 3, characterized in that, When the second monomer is trioxymethylene, the molar ratio of the first monomer 1,3-dioxolane to the second monomer trioxymethylene is (1-6):1; When the second monomer is 4-methyl-1,3-dioxolane, the molar ratio of the first monomer 1,3-dioxolane to the second monomer 4-methyl-1,3-dioxolane is (8-10):

1. When the second monomer contains both trioxymethylene and 4-methyl-1,3-dioxolane, the molar ratio of 1,3-dioxolane, trioxymethylene, and 4-methyl-1,3-dioxolane is (5-10):(1-5):

5.

5. The preparation method according to claim 3, characterized in that, During the cationic ring-opening polymerization reaction, the catalyst is added dropwise to the homogeneously mixed monomer for the reaction, the reaction temperature is 20-30 °C, and the reaction time is 5-15 min; and / or, The molar amount of the catalyst is 0.01-0.02% of the total molar amount of the first monomer and the second monomer.

6. The preparation method according to claim 3, characterized in that, In step (1), a dispersant for dispersing the catalyst is also added during the cationic ring-opening polymerization reaction. The dispersant is selected from one or more of dichloromethane, N,N-dimethylformamide and N-methylpyrrolidone. The volume ratio of the dispersant to the catalyst is 1000:(0.5-2).

7. The preparation method according to claim 3, characterized in that, The amine terminator in step (2) is one or more of triethylamine, ethylenediamine, n-butylamine and ethanolamine; the volume ratio of the amine terminator to the catalyst is 1000:(0.5-2).

8. The preparation method according to claim 3, characterized in that, The good solvent is one or more of dichloromethane, N,N-dimethylformamide and N-methylpyrrolidone, and the bad solvent is one or more of methanol, ethanol and water, wherein the volume of the bad solvent is 5-10 times that of the good solvent.

9. The use of the polyether-based random copolymer as described in claim 1 or 2 in the use of or preparation of membrane materials for separating and / or concentrating gases.

10. A separation membrane for separating and / or concentrating gases, characterized in that, Includes the polyether-based random copolymer as described in claim 1 or 2.

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