A CO2 / H2 separation membrane based on coupled absorption method and its preparation method

Abstract

This invention relates to a CO2 / H2 separation membrane based on a coupled absorption method and its preparation method, belonging to the field of separation membrane technology. Specifically, it includes a polysulfone ultrafiltration membrane and a polyvinylamine coating coated on the polysulfone ultrafiltration membrane. The polysulfone ultrafiltration membrane has a molecular weight cutoff of 6000 Daltons. The preparation of this membrane includes the following steps: synthesizing polyvinylamine and preparing a 5%-10% (w / w) aqueous solution of polyvinylamine; adding a CO2 absorbent to the polyvinylamine aqueous solution of different concentrations and stirring, then allowing it to stand and degas until no bubbles remain in the solution; coating the solution onto a pre-treated polysulfone ultrafiltration membrane with a molecular weight cutoff of 6000 Daltons; and drying the membrane in an oven to obtain a PVAM-CO2 absorbent blended composite membrane. This invention solves the problems of carrier loss and aggregation through the synergistic effect of the absorbent and the transport-promoting carrier, and is suitable for industrial preparation processes.

Description

Technical Field

[0001] This invention relates to a CO2 / H2 separation membrane based on coupling absorption method and its preparation method, belonging to the field of separation membrane technology. Background Technology

[0002] Hydrogen energy, as a core carrier of the zero-carbon energy system, has irreplaceable strategic value in fields such as fuel cell vehicles, distributed power generation, and industrial raw material substitution. However, current mainstream hydrogen production pathways (such as steam methane reforming, biomass gasification, and coal-to-hydrogen) all produce CO2-containing gas mixtures. Taking steam methane reforming as an example, the CO2 volume fraction in its product gas typically reaches 15%–30%. Without separation and purification, the presence of CO2 not only reduces the calorific value of H2 (for every 1% increase in CO2, the energy density of H2 decreases by approximately 0.8%), but also easily leads to electrode catalyst poisoning in fuel cell applications, shortening battery life by more than 50%. Furthermore, in chemical processes such as ammonia and methanol synthesis, CO2 in the feed gas needs to be removed to meet process purity requirements (e.g., ammonia synthesis requires a CO2 content of ≤500 ppm in H2). Simultaneously, the separated CO2 can be further used for carbon capture and storage (CCUS) or the preparation of chemical products such as dimethyl carbonate, achieving effective utilization of "carbon resources." Therefore, developing efficient and low-consumption CO2 / H2 separation technology is not only a key prerequisite for ensuring the quality of hydrogen energy and promoting the industrialization of hydrogen energy, but also an important technical support for reducing carbon emissions in the industrial sector and helping to achieve the "dual carbon" target. It has significant economic value and environmental significance.

[0003] Among existing CO2 / H2 separation technologies, membrane separation has become one of the core directions for replacing traditional separation technologies due to its advantages such as compact equipment, low energy consumption, and simple operation. As a high-performance material in the field of membrane separation, promoted transfer membranes exhibit outstanding advantages in low-concentration CO2 separation scenarios thanks to their unique "dissolution-diffusion-promoted transfer" mechanism. The core principle of promoted transfer membranes is to introduce a carrier (such as amines, metal ions, ionic liquids, etc.) that can specifically interact with CO2 into the membrane matrix. After the carrier and CO2 form a reversible complex, the "active transfer" of CO2 is achieved through the migration of the carrier within the membrane or the diffusion of the complex. This process makes the CO2 permeation rate much higher than that of H2 (a non-polar molecule that is difficult to interact with the carrier). Therefore, the CO2 / H2 selectivity of promoted transfer membranes can typically be 3 to 5 times that of traditional non-promoted transfer membranes (such as polyimide membranes). Some laboratory-prepared promoted transfer membranes have CO2 permeability coefficients exceeding 1000 Barrer and CO2 / H2 selectivity exceeding 200, approaching the performance threshold for industrial applications. Currently, facilitator membranes have been pilot-scale applied in small-scale hydrogen production (such as distributed methanol-to-hydrogen) and low-concentration CO2 removal from chemical tail gas. However, to achieve industrial-scale promotion, three major bottlenecks remain. First, the carrier stability is insufficient. Liquid carriers (such as ethanolamine) are prone to dissolving during gas permeation, causing the membrane separation performance to decline by 30% to 50% within 1000 hours. Second, the membrane structure compatibility is poor. Most carriers (especially metal ion carriers) tend to aggregate within the membrane, disrupting the continuous permeation channels and leading to an abnormally high H2 permeation rate and a significant decrease in selectivity. Third, large-scale preparation is difficult. Existing facilitator membranes are mostly prepared using laboratory-grade solution casting methods, resulting in uneven membrane thickness (often exceeding 20%) and the inability to achieve continuous production, making it difficult to meet the industrial demand for membrane module output (e.g., daily capacity ≥100m² for a single production line).

[0004] To address these issues, researchers have proposed various modification strategies. Regarding carrier immobilization, physical embedding methods are used to load the carrier within the pores of porous support membranes (such as polyethersulfone and polyacrylonitrile), utilizing the mechanical structure of the support membrane to restrict carrier loss. However, this method is prone to carrier aggregation due to weak interfacial bonding between the carrier and the support membrane, and pore blockage can reduce the CO2 permeability coefficient by 20%–40%. Chemical grafting methods use covalent bonds to graft carriers (such as amino-functionalized monomers) onto the membrane matrix molecular chains. While this can improve carrier stability, the grafting reaction easily damages the active sites of the carrier, leading to a decrease in CO2 binding capacity and a selectivity improvement of less than 15%. Regarding membrane structure optimization, composite membrane preparation technologies (such as interfacial polymerization and layer-by-layer self-assembly) can balance flux and selectivity to some extent by constructing ultrathin transport-promoting layers (<1 μm thick) on the surface of the support membrane. However, the ultrathin layers have poor mechanical strength and are prone to rupture under high-pressure operating conditions. Furthermore, the reaction conditions for interfacial polymerization are demanding (requiring precise control of monomer concentration and reaction temperature), making large-scale replication difficult. In addition, some studies have attempted to improve the structural stability of membranes by adding nanofillers (such as MOFs and graphene oxide), but the dispersion of nanofillers is difficult to control and will increase the membrane preparation cost (for example, the membrane cost increases by about 5% for every 1% increase in MOF addition), which is not conducive to industrial applications.

[0005] While existing modification methods have improved local performance, none of them have broken through the synergistic bottleneck of "carrier stability-separation performance-large-scale preparation". They either focus on solving the carrier loss problem but sacrifice separation throughput, or focus on performance optimization but cannot achieve mass production. Summary of the Invention

[0006] To address the technical problems existing in the prior art, this invention provides a CO2 / H2 separation membrane based on the coupling absorption method and its preparation method. It solves the problems of carrier loss and aggregation through the synergistic effect of the absorbent and the carrier promoting the transfer, and is suitable for industrial preparation processes.

[0007] To achieve the above objectives, the technical solution adopted in this invention is a CO2 / H2 separation membrane based on coupling absorption method, comprising a polysulfone ultrafiltration membrane and a polyvinylamine coating containing a CO2 absorbent coated on the polysulfone ultrafiltration membrane, wherein the molecular weight cutoff of the polysulfone ultrafiltration membrane is 6000 Daltons.

[0008] A method for preparing a transport-enhanced CO2 / H2 separation membrane based on coupled absorption includes the following steps: S1. Synthesize polyvinylamine and prepare a polyvinylamine aqueous solution with a mass fraction of 5%-10%; S2. Polyvinylamine aqueous solutions of different concentrations are coated onto a pre-treated polysulfone ultrafiltration membrane with a molecular weight cutoff of 6000 Daltons, and then placed in an oven to dry, thus obtaining a PVAm-PSF composite membrane. S3. Add CO2 absorbent to aqueous solutions of polyvinylamine of different concentrations and stir. Then let it stand to degas until there are no bubbles in the solution. Then coat it onto a pre-treated polysulfone ultrafiltration membrane with a molecular weight cutoff of 6000 Daltons and dry it in an oven to obtain a PVAM-CO2 absorbent blended composite membrane.

[0009] Preferably, the CO2 absorbent is one of ethanolamine, piperazine, and polyethyleneimine.

[0010] Preferably, when performing the coating, a blade-driven, thickness-adjustable coating machine is used, and the drying conditions in the oven are: temperature 30°C and humidity 40%.

[0011] Preferably, in step S1, the synthesis of polyvinylamine is carried out according to the following steps: a. N-vinylformamide was distilled under reduced pressure to remove the polymerization inhibitor. The distilled N-vinylformamide, deionized water and azobisisobutyramidine hydrochloride initiator were then mixed evenly and transferred to a three-necked flask. The flask was then evacuated to a vacuum environment. Nitrogen gas was then introduced into the three-necked flask to remove dissolved O2 from the solution. After stirring thoroughly, the solution temperature was raised to 55 °C and the polymerization reaction was maintained at a constant temperature for 12 h. b. After the above reaction is completed, add concentrated hydrochloric acid and an appropriate amount of deionized water to the solution to prepare a homogeneous solution. Under N2 protection, heat the solution to 70°C and carry out the hydrolysis reaction for 8 hours. c. The hydrolyzed polymer solution is slowly added dropwise to 4 times the volume of ethanol. Most of the hydrochloric acid is removed by ethanol precipitation to obtain PVAm-HCl. d. PVAm-HCl was dissolved in deionized water to prepare a 5wt%-10wt% aqueous solution. Then, an excess of the treated 717 strong basic type I anion exchange resin was added and stirred for 1 hour to completely remove HCl. Finally, the solution was filtered using a G3 glass frit funnel to obtain a 5wt%-10wt% PVAm aqueous solution.

[0012] Preferably, the treatment process of the 717 strong basic type I anion exchange resin is as follows: Place the resin in a clean container and rinse with clean water until the water runs clear. Then soak the resin in deionized water for 12-24 hours to allow it to fully swell. After soaking, soak the resin in twice the volume of 2%-5% HCl solution for 2-4 hours, stirring occasionally. Then wash the resin with low-purity water until the solution pH is close to 4. Finally, treat it with 5%-8% NaOH solution and wash it with water until it becomes slightly alkaline.

[0013] Compared with existing technologies, this invention has the following technical advantages: This invention proposes a technical solution that couples the absorption method with a transport-enhancing membrane. Utilizing the high CO2 capture capacity of absorbents (such as alkanolamines and ionic liquids) in the absorption method, a specific structural design enables the absorbent and the transport-enhancing membrane to form a synergistic "intra-membrane absorption-promoted transport" system. The absorbent can pre-bind with CO2 within the membrane, reducing the consumption of the transport-enhancing carrier. Simultaneously, the liquid environment of the absorbent inhibits carrier aggregation, maintaining continuous permeation channels in the membrane. More importantly, this coupling system is adaptable to industrial-grade continuous coating-roll-to-roll manufacturing processes. By controlling parameters such as the mixing ratio of the absorbent and the membrane substrate, and the coating speed, large-scale production with a membrane thickness deviation of ≤5% can be achieved. This solves the problems of carrier loss and structural instability in traditional transport-enhancing membranes, and breaks through the technical barriers to their large-scale preparation, providing a new technical path for the industrial application of CO2 / H2 separation membranes.

[0014] Furthermore, by coupling the enhanced transfer membrane with chemical absorption, CO2 can both reversibly react with the carrier in the membrane and be absorbed by the absorbent, thus increasing the CO2 flux without increasing the flux of other gases. The gas separation membrane prepared by this method exhibits high CO2 permeation flux and separation selectivity, and is expected to be widely used in the field of gas separation membranes. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the synthesis reaction of polyvinylamine in this invention. Detailed Implementation

[0016] To make the technical problems, solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0017] Example 1: 1) N-vinylformamide (NVF) was first distilled under reduced pressure to remove the polymerization inhibitor. Then, 10g of the distilled NVF, 35g of deionized water, and 0.053g of azobisisobutyramidine hydrochloride (V-50) initiator were weighed and mixed in a three-necked flask. A vacuum was drawn, and nitrogen gas was introduced to remove some of the dissolved O2. After thorough stirring, the solution temperature was raised to 55°C under N2 protection, and a constant-temperature polymerization reaction was carried out for 12 hours. Then, 44mL of concentrated hydrochloric acid and 276mL of deionized water were added to the above solution to prepare a homogeneous solution. Subsequently, the solution was heated to 70°C under N2 protection, and a hydrolysis reaction was carried out for 8 hours. The hydrolyzed polymer solution was slowly added dropwise to 4 times the volume of ethanol. Most of the hydrochloric acid was removed by ethanol precipitation to obtain PVAm-HCl. Add an appropriate amount of deionized water to PVAm-HCl to prepare a 10wt% aqueous solution. Then, add an excess of pretreated 717 strong basic type I anion exchange resin and stir for 1 hour to completely remove HCl. Finally, filter the solution using a G3 glass frit funnel to obtain a 10wt% PVAm aqueous solution.

[0018] 2) PVAm aqueous solutions of different concentrations were coated onto a pre-treated polysulfone ultrafiltration membrane (PSF) with a molecular weight cutoff of 6000 using a knife-operated thickness adjustable coating machine to prepare a PVAm-PSF composite membrane. The membrane was then placed in an artificial climate chamber and dried for 12 hours at a set temperature of 30°C and a humidity of 40%.

[0019] 3) Test the gas separation performance of the composite membrane, as shown in Table 1.

[0020] Example 2: 1) First, N-vinylformamide (NVF) was distilled under reduced pressure to remove the polymerization inhibitor. Then, 10g of the distilled NVF, 35g of deionized water, and 0.053g of azobisisobutyramidine hydrochloride (V-50) initiator were weighed and mixed in a three-necked flask. A vacuum was drawn, and nitrogen gas was introduced to remove some of the dissolved O2. After thorough stirring, the solution temperature was raised to 55°C under N2 protection, and a constant-temperature polymerization reaction was carried out for 12 hours. Then, 44mL of concentrated hydrochloric acid and 276mL of deionized water were added to the above solution to prepare a homogeneous solution. Subsequently, under N2 protection, the solution temperature was raised to 70°C, and a hydrolysis reaction was carried out for 8 hours. The hydrolyzed polymer solution was slowly added dropwise to 4 times the volume of ethanol. Most of the hydrochloric acid was removed by ethanol precipitation to obtain PVAm-HCl. Add an appropriate amount of deionized water to PVAm-HCl to prepare a 7wt% aqueous solution. Then, add an excess of pretreated 717 strong basic type I anion exchange resin and stir for 1 hour to completely remove HCl. Finally, filter the solution using a G3 glass frit funnel to obtain a 7wt% PVAm aqueous solution.

[0021] 2) PVAm aqueous solutions of different concentrations were coated onto a pre-treated polysulfone ultrafiltration membrane (PSF) with a molecular weight cutoff of 6000 using a knife-operated thickness adjustable coating machine to prepare a PVAm-PSF composite membrane. The membrane was then placed in an artificial climate chamber and dried for 12 hours at a set temperature of 30°C and a humidity of 40%.

[0022] 3) The gas separation performance of the composite membrane is shown in Table 1.

[0023] Example 3: 1) N-vinylformamide (NVF) was first distilled under reduced pressure to remove the polymerization inhibitor. Then, 10g of the distilled NVF, 35g of deionized water, and 0.053g of azobisisobutyramidine hydrochloride (V-50) initiator were weighed and mixed in a three-necked flask. A vacuum was drawn, and nitrogen gas was introduced to remove some of the dissolved O2. After thorough stirring, the solution temperature was raised to 55°C under N2 protection, and a constant-temperature polymerization reaction was carried out for 12 hours. Then, 44mL of concentrated hydrochloric acid and 276mL of deionized water were added to the above solution to prepare a homogeneous solution. Subsequently, under N2 protection, the solution was heated to 70°C, and a hydrolysis reaction was carried out for 8 hours. The hydrolyzed polymer solution was slowly added dropwise to 4 times the volume of ethanol. Most of the hydrochloric acid was removed by ethanol precipitation to obtain PVAm-HCl. Add an appropriate amount of deionized water to PVAm-HCl to prepare a 5wt% aqueous solution. Then, add an excess of pretreated 717 strong basic type I anion exchange resin and stir for 1 hour to completely remove HCl. Finally, filter the solution using a G3 glass frit funnel to obtain a 5wt% PVAm aqueous solution.

[0024] 2) PVAm aqueous solutions of different concentrations were coated onto a pre-treated polysulfone ultrafiltration membrane (PSF) with a molecular weight cutoff of 6000 using a knife-operated thickness adjustable coating machine to prepare a PVAm-PSF composite membrane. The membrane was then placed in an artificial climate chamber and dried for 12 hours at a set temperature of 30°C and a humidity of 40%.

[0025] 3) Test the gas separation performance of the composite membrane, as shown in Table 1.

[0026] Example 4: 1) First, N-vinylformamide (NVF) was distilled under reduced pressure to remove the polymerization inhibitor. Then, 10g of the distilled NVF, 35g of deionized water, and 0.053g of azobisisobutyramidine hydrochloride (V-50) initiator were weighed and mixed in a three-necked flask. A vacuum was drawn, and nitrogen gas was introduced to remove some of the dissolved O2. After thorough stirring, the solution temperature was raised to 55°C under N2 protection, and a constant-temperature polymerization reaction was carried out for 12 hours. Then, 44mL of concentrated hydrochloric acid and 276mL of deionized water were added to the above solution to prepare a homogeneous solution. Subsequently, under N2 protection, the solution temperature was raised to 70°C, and a hydrolysis reaction was carried out for 8 hours. The hydrolyzed polymer solution was slowly added dropwise to 4 times the volume of ethanol. Most of the hydrochloric acid was removed by ethanol precipitation to obtain PVAm-HCl. Dissolve 7g of PVAm-HCl in an appropriate amount of deionized water to prepare a 7wt% aqueous solution. Then, add an excess of pretreated 717 strong basic type I anion exchange resin and stir for 1 hour to completely remove HCl. Finally, filter the solution using a G3 glass frit funnel to obtain a 7wt% PVAm aqueous solution.

[0027] 2) Add 1g piperazine to a 7wt% PVAm aqueous solution and stir for 24h. Let it stand to degas until there are no bubbles in the solution. Then, use a knife-type thickness adjustable coating machine to coat the membrane onto a pre-treated polysulfone ultrafiltration membrane (PSF) with a molecular weight cutoff of 6000 to prepare a composite membrane. Place it in an artificial climate chamber and dry it for 12h at a set temperature of 30℃ and a humidity of 40%.

[0028] 3) Test the gas separation performance of the composite membrane, as shown in Table 1.

[0029] Example 5: 1) First, N-vinylformamide (NVF) was distilled under reduced pressure to remove the polymerization inhibitor. Then, 10g of the distilled NVF, 35g of deionized water, and 0.053g of azobisisobutyramidine hydrochloride (V-50) initiator were weighed, mixed, and placed in a three-necked flask. A vacuum was drawn, and nitrogen gas was introduced to remove some of the dissolved O2. After thorough stirring, the solution temperature was raised to 55°C under N2 protection, and a constant-temperature polymerization reaction was carried out for 12 hours. Then, 44mL of concentrated hydrochloric acid and 276mL of deionized water were added to the above solution to prepare a homogeneous solution. Subsequently, under N2 protection, the solution temperature was raised to 70°C, and a hydrolysis reaction was carried out for 8 hours. The hydrolyzed polymer solution was slowly added dropwise to 4 times the volume of ethanol, and most of the hydrochloric acid was removed by ethanol precipitation to obtain PVAm-HCl. Dissolve 5g of PVAm-HCl in an appropriate amount of deionized water to prepare a 5wt% aqueous solution. Then, add an excess of pretreated 717 strong basic type I anion exchange resin and stir for 1 hour to completely remove HCl. Finally, filter the solution using a G3 glass frit funnel to obtain a 5wt% PVAm aqueous solution.

[0030] 2) Add 10g piperazine to a 5wt% PVAm aqueous solution and stir for 24h. Let it stand to degas until there are no bubbles in the solution. Then, use a knife-type thickness adjustable coating machine to coat the membrane onto a pre-treated polysulfone ultrafiltration membrane (PSF) with a molecular weight cutoff of 6000 to prepare a composite membrane. Place it in an artificial climate chamber and dry it for 12h at a set temperature of 30℃ and a humidity of 40%.

[0031] 3) Test the gas separation performance of the composite membrane, as shown in Table 1.

[0032] Example 6: 1) N-vinylformamide (NVF) was first distilled under reduced pressure to remove the polymerization inhibitor. Then, 10g of the distilled NVF, 35g of deionized water, and 0.053g of azobisisobutyramidine hydrochloride (V-50) initiator were weighed and mixed in a three-necked flask. A vacuum was drawn, and nitrogen gas was introduced to remove some of the dissolved O2. After thorough stirring, the solution temperature was raised to 55°C under N2 protection, and a constant-temperature polymerization reaction was carried out for 12 hours. Then, 44mL of concentrated hydrochloric acid and 276mL of deionized water were added to the above solution to prepare a homogeneous solution. Subsequently, the solution was heated to 70°C under N2 protection, and a hydrolysis reaction was carried out for 8 hours. The hydrolyzed polymer solution was slowly added dropwise to 4 times the volume of ethanol. Most of the hydrochloric acid was removed by ethanol precipitation to obtain PVAm-HCl. Dissolve 5g of PVAm-HCl in an appropriate amount of deionized water to prepare a 5wt% aqueous solution. Then, add an excess of pretreated 717 strong basic type I anion exchange resin and stir for 1 hour to completely remove HCl. Finally, filter the solution using a G3 glass frit funnel to obtain a 5wt% PVAm aqueous solution.

[0033] 2) Add 20g of ethanolamine to a 5wt% PVAm aqueous solution and stir for 24h. Let it stand to remove bubbles until there are no more bubbles in the solution. Then, use a knife-type thickness adjustable coating machine to coat the membrane onto a pre-treated polysulfone ultrafiltration membrane (PSF) with a molecular weight cutoff of 6000 to prepare a composite membrane. Place it in an artificial climate chamber and dry it for 12h at a set temperature of 30℃ and a humidity of 40%.

[0034] 3) Test the gas separation performance of the composite membrane, as shown in Table 1.

[0035] Example 7: 1) N-vinylformamide (NVF) was first distilled under reduced pressure to remove the polymerization inhibitor. Then, 10g of the distilled NVF, 35g of deionized water, and 0.053g of azobisisobutyramidine hydrochloride (V-50) initiator were weighed and mixed in a three-necked flask. A vacuum was drawn, and nitrogen gas was introduced to remove some of the dissolved O2. After thorough stirring, the solution temperature was raised to 55°C under N2 protection, and a constant-temperature polymerization reaction was carried out for 12 hours. Then, 44mL of concentrated hydrochloric acid and 276mL of deionized water were added to the above solution to prepare a homogeneous solution. Subsequently, the solution was heated to 70°C under N2 protection, and a hydrolysis reaction was carried out for 8 hours. The hydrolyzed polymer solution was slowly added dropwise to 4 times the volume of ethanol, and most of the hydrochloric acid was removed by ethanol precipitation to obtain PVAm-HCl. Dissolve 5g of PVAm-HCl in an appropriate amount of deionized water to prepare a 5wt% aqueous solution. Then, add an excess of pretreated 717 strong basic type I anion exchange resin and stir for 1 hour to completely remove HCl. Finally, filter the solution using a G3 glass frit funnel to obtain a 5wt% PVAm aqueous solution.

[0036] 2) Add 5g of diethanolamine to a 5wt% PVAm aqueous solution and stir for 24h. Let it stand to remove bubbles until there are no more bubbles in the solution. Then, use a knife-type thickness adjustable coating machine to coat the membrane onto a pre-treated polysulfone ultrafiltration membrane (PSF) with a molecular weight cutoff of 6000 to prepare a composite membrane. Place it in an artificial climate chamber and dry it for 12h at a set temperature of 30℃ and a humidity of 40%.

[0037] 3) Test the gas separation performance of the composite membrane, as shown in Table 1.

[0038] Comparative Example 1 (compared to Example 1) 1) First, N-vinylformamide (NVF) was distilled under reduced pressure to remove the polymerization inhibitor. Then, 10g of the distilled NVF, 35g of deionized water, and 0.053g of azobisisobutyramidine hydrochloride (V-50) initiator were weighed and mixed in a three-necked flask. A vacuum was drawn, and nitrogen gas was introduced to remove some dissolved O2. After thorough stirring, the solution temperature was raised to 55°C under N2 protection, and a constant-temperature polymerization reaction was carried out for 12 hours. Then, 44mL of concentrated hydrochloric acid and 276mL of deionized water were added to the above solution to prepare a homogeneous solution. Subsequently, the solution was heated to 70°C under N2 protection, and a hydrolysis reaction was carried out for 8 hours. The hydrolyzed polymer solution was slowly added dropwise to 4 times its volume of ethanol. Most of the hydrochloric acid was removed by ethanol precipitation to obtain PVAm-HCl. Add an appropriate amount of deionized water to PVAm-HCl to prepare a 3wt% aqueous solution. Then, add an excess of pretreated 717 strong basic type I anion exchange resin and stir for 1 hour to completely remove HCl. Finally, filter the solution using a G3 glass frit funnel to obtain a 3wt% PVAm aqueous solution.

[0039] 2) PVAm aqueous solutions of different concentrations were coated onto a pre-treated polysulfone ultrafiltration membrane (PSF) with a molecular weight cutoff of 6000 using a knife-operated thickness adjustable coating machine to prepare a PVAm-PSF composite membrane. The membrane was then placed in an artificial climate chamber and dried for 12 hours at a set temperature of 30°C and a humidity of 40%.

[0040] 3) Test the gas separation performance of the composite membrane. The PVAm concentration is too low, and the membrane layer is too thin and discontinuous.

[0041] Comparative Example 2 (compared to Example 5) 1) First, N-vinylformamide (NVF) was distilled under reduced pressure to remove the polymerization inhibitor. Then, 10g of the distilled NVF, 35g of deionized water, and 0.053g of azobisisobutyramidine hydrochloride (V-50) initiator were weighed and mixed in a three-necked flask. A vacuum was drawn, and nitrogen gas was introduced to remove some dissolved O2. After thorough stirring, the solution temperature was raised to 55°C under N2 protection, and a constant-temperature polymerization reaction was carried out for 12 hours. Then, 44mL of concentrated hydrochloric acid and 276mL of deionized water were added to the above solution to prepare a homogeneous solution. Subsequently, the solution was heated to 70°C under N2 protection, and a hydrolysis reaction was carried out for 8 hours. The hydrolyzed polymer solution was slowly added dropwise to 4 times its volume of ethanol. Most of the hydrochloric acid was removed by ethanol precipitation to obtain PVAm-HCl. Dissolve 15g of PVAm-HCl in an appropriate amount of deionized water to prepare a 15wt% aqueous solution. Then, add an excess of pretreated 717 strong basic type I anion exchange resin and stir for 1 hour to completely remove HCl. Finally, filter the solution using a G3 glass frit funnel to obtain a 15wt% PVAm aqueous solution.

[0042] 2) Add 10g piperazine to a 15wt% PVAm aqueous solution and stir for 24h. Allow the solution to stand and degas until no bubbles remain. Then, use a knife-type thickness-adjustable coating machine to coat the membrane onto a pre-treated polysulfone ultrafiltration membrane (PSF) with a molecular weight cutoff of 6000 to prepare a composite membrane. Place the membrane in an artificial climate chamber and dry it for 12h at a set temperature of 30℃ and a humidity of 40%.

[0043] 3) Test the gas separation performance of the composite membrane. If the PVAm concentration is too high, the solution viscosity is high, and the coating is uneven.

[0044] Comparative Example 3 (compared to Example 5) 1) First, N-vinylformamide (NVF) was distilled under reduced pressure to remove the polymerization inhibitor. Then, 10g of the distilled NVF, 35g of deionized water, and 0.053g of azobisisobutyramidine hydrochloride (V-50) initiator were weighed and mixed in a three-necked flask. A vacuum was drawn, and nitrogen gas was introduced to remove some dissolved O2. After thorough stirring, the solution temperature was raised to 55°C under N2 protection, and a constant-temperature polymerization reaction was carried out for 12 hours. Then, 44mL of concentrated hydrochloric acid and 276mL of deionized water were added to the above solution to prepare a homogeneous solution. Subsequently, the solution was heated to 70°C under N2 protection, and a hydrolysis reaction was carried out for 8 hours. The hydrolyzed polymer solution was slowly added dropwise to 4 times its volume of ethanol. Most of the hydrochloric acid was removed by ethanol precipitation to obtain PVAm-HCl. Dissolve 5g of PVAm-HCl in an appropriate amount of deionized water to prepare a 5wt% aqueous solution. Then, add an excess of pretreated 717 strong basic type I anion exchange resin and stir for 1 hour to completely remove HCl. Finally, filter the solution using a G3 glass frit funnel to obtain a 5wt% PVAm aqueous solution.

[0045] 2) Add 0.5g piperazine to a 5wt% PVAm aqueous solution and stir for 24h. Allow the solution to stand and degas until no bubbles remain. Then, use a knife-type thickness-adjustable coating machine to coat the membrane onto a pre-treated polysulfone ultrafiltration membrane (PSF) with a molecular weight cutoff of 6000 to prepare a composite membrane. Place the membrane in an artificial climate chamber and dry it for 12h at a set temperature of 30℃ and a humidity of 40%.

[0046] 3) The gas separation performance of the composite membrane was tested. Insufficient absorbent resulted in a weak effect on promoting gas transfer, as shown in Table 1.

[0047] Comparative Example 4 (compared to Example 6) 1) First, N-vinylformamide (NVF) was distilled under reduced pressure to remove the polymerization inhibitor. Then, 10g of the distilled NVF, 35g of deionized water, and 0.053g of azobisisobutyramidine hydrochloride (V-50) initiator were weighed and mixed in a three-necked flask. A vacuum was drawn, and nitrogen gas was introduced to remove some dissolved O2. After thorough stirring, the solution temperature was raised to 55°C under N2 protection, and a constant-temperature polymerization reaction was carried out for 12 hours. Then, 44mL of concentrated hydrochloric acid and 276mL of deionized water were added to the above solution to prepare a homogeneous solution. Subsequently, the solution was heated to 70°C under N2 protection, and a hydrolysis reaction was carried out for 8 hours. The hydrolyzed polymer solution was slowly added dropwise to 4 times its volume of ethanol. Most of the hydrochloric acid was removed by ethanol precipitation to obtain PVAm-HCl. Dissolve 5g of PVAm-HCl in an appropriate amount of deionized water to prepare a 5wt% aqueous solution. Then, add an excess of pretreated 717 strong basic type I anion exchange resin and stir for 1 hour to completely remove HCl. Finally, filter the solution using a G3 glass frit funnel to obtain a 5wt% PVAm aqueous solution.

[0048] 2) Add 25g of ethanolamine to a 5wt% PVAm aqueous solution and stir for 24h. Let it stand to remove bubbles until there are no more bubbles in the solution. Then, use a knife-type thickness adjustable coating machine to coat the membrane onto a pre-treated polysulfone ultrafiltration membrane (PSF) with a molecular weight cutoff of 6000 to prepare a composite membrane. Place it in an artificial climate chamber and dry it for 12h at a set temperature of 30℃ and a humidity of 40%.

[0049] 3) Test the gas separation performance of the composite membrane. Excessive absorbent leads to agglomeration inside the membrane, which damages the membrane's permeation channels, as shown in Table 1.

[0050] The performance indicators of the modified gas separation membrane in the above embodiments are shown in Table 1: Table 1 Example membranes <![CDATA[P CO2 ]]> <![CDATA[P N2 ]]> <![CDATA[P H2 ]]> <![CDATA[α CO2 / H2 ]]> <![CDATA[α CO2 / N2 ]]> 1 10%PVAm 66.9 1.2 4 16.6 55.7 2 7%PVAm 68.3 0.9 6.51 10.5 75.1 3 5%PVAm 163.4 2.4 16.7 9.8 68.6 4 7%PVAm + 1%piperazine 75.2 0.96 7.1 10.6 78.3 5 5% PVAm + 10% Piperazine 27.5 0.45 0.89 30.9 61.1 6 5% PVAm + 20% ethanolamine 72.8 1.2 3.75 19.4 60.7 7 5% PVAm + 5% Diethanolamine 98.6 1.5 10.2 9.7 67.4 8 3%PVAm 185.3 3.0 22.4 8.3 62.1 9 15% PVAm + 10% Piperazine 21.7 - 0.92 23.6 - 10 5% PVAm + 0.5% piperazine 158.9 2.4 17.3 9.2 65.8 11 5% PVAm + 25% ethanolamine 58.4 - 5.1 11.5 - The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the scope of the present invention.

Claims

1. A CO2 / H2 separation membrane based on coupled absorption method, characterized in that: The invention includes a polysulfone ultrafiltration membrane and a polyvinylamine coating containing a CO2 absorbent coated on the polysulfone ultrafiltration membrane, wherein the polysulfone ultrafiltration membrane has a molecular weight cutoff of 6,000 Daltons.

2. The method for preparing a transport-enhanced CO2 / H2 separation membrane based on coupled absorption according to claim 1, characterized in that: Includes the following steps, S1. Synthesize polyvinylamine and prepare a polyvinylamine aqueous solution with a mass fraction of 5%-10%; S2. Polyvinylamine aqueous solutions of different concentrations are coated onto a pre-treated polysulfone ultrafiltration membrane with a molecular weight cutoff of 6000 Daltons, and then placed in an oven to dry, thus obtaining a PVAm-PSF composite membrane. S3. Add CO2 absorbent to aqueous solutions of polyvinylamine of different concentrations and stir. Then let it stand to degas until there are no bubbles in the solution. Then coat it onto a pre-treated polysulfone ultrafiltration membrane with a molecular weight cutoff of 6000 Daltons and dry it in an oven to obtain a PVAM-CO2 absorbent blended composite membrane.

3. The method for preparing a transport-enhanced CO2 / H2 separation membrane based on coupling absorption according to claim 2, characterized in that: The CO2 absorbent is one of ethanolamine, piperazine, and polyethyleneimine.

4. The method for preparing a CO2 / H2 separation membrane based on coupled absorption as described in claim 2, characterized in that: When applying the coating, a blade-operated, thickness-adjustable coating machine is used, and the drying conditions in the oven are: temperature 30℃ and humidity 40%.

5. The method for preparing a CO2 / H2 separation membrane based on coupled absorption according to claim 2, characterized in that: In step S1, the synthesis of polyvinylamine is carried out according to the following steps. a. N-vinylformamide was distilled under reduced pressure to remove the polymerization inhibitor. The distilled N-vinylformamide, deionized water and azobisisobutyramidine hydrochloride initiator were then mixed evenly and transferred to a three-necked flask. The flask was then evacuated to a vacuum environment. Nitrogen gas was then introduced into the three-necked flask to remove dissolved O2 from the solution. After stirring thoroughly, the solution temperature was raised to 55 °C and the polymerization reaction was maintained at a constant temperature for 12 h. b. After the above reaction is completed, add concentrated hydrochloric acid and an appropriate amount of deionized water to the solution to prepare a homogeneous solution. Under N2 protection, heat the solution to 70°C and carry out the hydrolysis reaction for 8 hours. c. The hydrolyzed polymer solution is slowly added dropwise to 4 times the volume of ethanol. Most of the hydrochloric acid is removed by ethanol precipitation to obtain PVAm-HCl. d. Dissolve PVAm-HCl in deionized water to prepare a 5wt%-10wt% aqueous solution. Then add an excess of treated 717 strong base type I anion exchange resin and stir for 1 hour to completely remove HCl. Finally, filter the solution using a G3 glass frit funnel to obtain a 5wt%-10wt% PVAm aqueous solution. The reaction process is shown in the figure below: 。 6. The method for preparing a transport-enhanced CO2 / H2 separation membrane based on coupled absorption according to claim 5, characterized in that: The treatment process for the 717 strong basic type I anion exchange resin is as follows: Place the resin in a clean container and rinse with clean water until the water runs clear. Then soak the resin in deionized water for 12-24 hours to allow it to fully swell. After soaking, soak the resin in twice the volume of 2%-5% HCl solution for 2-4 hours, stirring occasionally. Then wash the resin with low-purity water until the solution pH is close to 4. Finally, treat it with 5%-8% NaOH solution and wash it with water until it becomes slightly alkaline.

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