Preparation method of sulfydryl modified SEBS and separation membrane thereof, and application of separation membrane in CH4 / N2 gas separation

Abstract

The invention relates to a sulfydryl modified SEBS and a preparation method of a separation membrane of the sulfydryl modified SEBS and application of the separation membrane in CH4 / N2 gas separation, and belongs to the technical field of gas separation membranes, and the preparation method specifically comprises the following steps: performing vacuum drying on SEBS, and crushing for later use; dissolving the dried SEBS in anhydrous toluene, stirring until the SEBS is completely dissolved to form a transparent homogeneous solution, and introducing nitrogen for bubbling; adding a sulfhydryl compound and a catalyst into the SEBS solution, and placing a reaction system under an ultraviolet light source for irradiation reaction; the preparation method comprises the following steps: slowly pouring a reaction solution into excessive absolute ethyl alcohol, stirring to form flocculent precipitate, filtering and washing the precipitate, and drying the precipitate in a vacuum drying oven to obtain the sulfydryl modified SEBS block polymer. Non-polar long-chain alkyl is introduced into an SEBS molecular chain through a Michael addition reaction, the chemical structure and pore characteristics of the material are regulated and controlled, and the sulfydryl modified SEBS block polymer is obtained. The gas separation membrane with high CH4 permeability and selectivity is prepared, and the problem that a traditional SEBS membrane is insufficient in CH4 / N2 separation performance is solved.

Description

Technical Field

[0001] This invention relates to a method for preparing thiol-modified SEBS and a method for preparing its separation membrane, as well as the application of the prepared separation membrane in CH4 / N2 gas separation, belonging to the field of gas separation membrane technology. Background Technology

[0002] Natural gas, as a clean and efficient fossil fuel, plays a crucial role in the global energy structure transformation. Its main component, methane (CH4), has high energy density and low carbon emissions after combustion, making it an important alternative to coal and oil. However, whether it's natural gas extracted from conventional natural gas fields or unconventional natural gas resources such as coalbed methane and shale gas, nitrogen (N2) impurities are easily mixed in during extraction and transportation. When the N2 volume fraction in natural gas exceeds 5%, it significantly reduces the calorific value of the natural gas, increases pipeline transportation energy consumption, and may even cause pipeline blockage due to gas-liquid phase separation. For coalbed methane, its original CH4 content is often below 30%, and the presence of a large amount of N2 makes it difficult to use directly as an energy source. It needs to be separated and purified to meet industrial or residential gas standards (CH4 volume fraction ≥ 90%). Furthermore, from an environmental perspective, inefficient CH4 / N2 separation not only wastes energy, but the underutilized CH4-containing gas mixture may also exacerbate the greenhouse effect due to leakage (CH4's greenhouse effect is 28 times that of CO2). Therefore, developing efficient and low-cost CH4 / N2 separation technology is of great significance for improving the utilization rate of natural gas resources and promoting the industrialization of unconventional natural gas.

[0003] Currently, commonly used industrial methods for CH4 / N2 separation include pressure swing adsorption (PSA), cryogenic distillation, and membrane separation. While PSA offers flexibility, it suffers from frequent adsorbent regeneration, large equipment footprint, and significant influence of feed gas composition fluctuations on separation selectivity. Cryogenic distillation, despite its high purity, requires operation at temperatures below -160°C, resulting in extremely high energy consumption (30%–40% of total energy consumption in natural gas processing). Furthermore, it is only suitable for large-scale centralized processing scenarios and is ill-suited for the separation needs of dispersed gas sources such as coalbed methane well sites. In contrast, membrane separation, based on the "dissolution-diffusion" mechanism, utilizes the difference in permeation rates of different gases through membrane materials to achieve separation. It offers advantages such as low energy consumption, compact equipment structure, simple operation, and no secondary pollution. Its application in CH4 / N2 separation has seen continuous growth in recent years, particularly in small-to-medium-scale gas source processing and mobile separation equipment, demonstrating irreplaceable advantages. However, the core bottleneck of membrane separation lies in the performance of the membrane materials. High-quality CH4 / N2 gas separation membranes need to have both high CH4 permeability and high CH4 / N2 selectivity. Existing commercial membrane materials (such as cellulose acetate and polyimide) cannot meet these two indicators at the same time, and there is an urgent need to develop new high-performance membrane materials.

[0004] Styrene-ethylene-butene-styrene block copolymer (SEBS), as a typical thermoplastic elastomer, has become a research hotspot in the field of membrane materials due to its excellent aging resistance, chemical corrosion resistance, mechanical flexibility, and thermoplastic processability. The SEBS molecular chain consists of alternating rigid styrene segments (S-segments) and flexible ethylene-butene segments (EB-segments). The amorphous structure of the EB-segments provides gas permeation channels, while the physical cross-linking of the S-segments ensures the structural stability and mechanical strength of the membrane, giving it a natural advantage in the preparation of self-supporting or composite membranes. However, the application of rudimentary SEBS membranes in CH4 / N2 separation has significant limitations: the EB-segments are predominantly nonpolar carbon-carbon bonds, resulting in minimal difference in adsorption capacity for CH4 (a weakly polar molecule) and N2 (a nonpolar molecule), and the diffusion rates of the two gases within the membrane are similar. This leads to the CH4 / N2 selectivity of rudimentary SEBS membranes typically being below 10, far from meeting the industrial separation requirements of selectivity (≥20). Meanwhile, the low packing density of SEBS molecular chains, while resulting in a high gas permeability coefficient, also leads to insufficient membrane swelling resistance. When in contact with natural gas containing trace amounts of water vapor or hydrocarbon impurities, the membrane structure is prone to swelling and deformation, further reducing separation performance and service life. Therefore, it is necessary to modify the molecular and aggregate structure of SEBS to enhance its selective adsorption and differentiated diffusion capabilities for CH4.

[0005] To address the separation performance deficiencies of original SEBS membranes, existing research has proposed various modification strategies. Physical blending modification is a common method, such as combining SEBS with inorganic fillers (e.g., molecular sieves, metal-organic frameworks (MOFs), graphene, etc.) to enhance the adsorption selectivity for CH4 by utilizing the pore structure or polar sites of the inorganic fillers. However, this method is prone to interfacial defects due to poor compatibility between SEBS and inorganic fillers, which can actually reduce the gas permeability coefficient of the membrane. Furthermore, the uniformity of filler dispersion is difficult to control, making large-scale preparation challenging. Other studies have explored blending SEBS with polar polymers (e.g., polyethylene glycol, polyamides, etc.) to improve membrane polarity, but phase separation issues in blended systems can easily lead to uneven membrane structure and poor separation performance stability. In terms of chemical modification, existing methods mostly focus on grafting polar groups such as hydroxyl (-OH), carboxyl (-COOH), or amino (-NH2) groups onto the SEBS molecular chain to enhance selectivity by increasing the interaction with CH4. However, these groups are relatively weakly polar, and the van der Waals forces or hydrogen bonds formed with CH4 are limited. The improvement in CH4 / N2 selectivity of the modified SEBS membrane is usually no more than 50%. Moreover, some modification reactions (such as carboxylation, which requires strong oxidants) have harsh conditions that can easily damage the molecular chain structure of SEBS, leading to a decrease in the mechanical properties of the membrane. In addition, existing modification methods generally suffer from a "selectivity-permeability coefficient" trade-off effect, meaning that while improving selectivity, it is often accompanied by a significant decrease in permeability coefficient, making it difficult to balance separation efficiency and purity. Summary of the Invention

[0006] To address the technical problems existing in the prior art, this invention provides a method for preparing thiol-modified SEBS and a method for preparing its separation membrane, as well as the application of the prepared separation membrane in CH4 / N2 gas separation. This method introduces nonpolar long-chain alkyl groups into the SEBS molecular chain through a Michael addition reaction, thereby regulating the chemical structure and pore characteristics of the material to prepare a gas separation membrane with high CH4 permeability and selectivity, thus solving the problem of insufficient performance of traditional SEBS membranes in CH4 / N2 separation.

[0007] To achieve the above objectives, the technical solution adopted in this invention is a method for preparing thiol-modified SEBS, comprising the following steps: S1. SEBS Pretreatment: Vacuum dry SEBS at 60℃ to remove moisture and volatiles, then pulverize and pass through an 80-mesh sieve for later use. S2. Solution preparation: Dissolve the dried SEBS in anhydrous toluene at a mass concentration of 5%-15%, stir at room temperature until completely dissolved to form a transparent homogeneous solution, and bubble with nitrogen gas for 10-15 minutes to remove oxygen. S3, Michael addition reaction: Add mercapto compound and catalyst to SEBS solution according to the molar ratio of double bond to mercapto compound in SEBS of 1:1.2-1:1.5, and then place the reaction system under ultraviolet light source for irradiation reaction; S4. Post-treatment: Slowly pour the reaction solution into excess anhydrous ethanol, stir to form a flocculent precipitate, filter and wash the precipitate with anhydrous ethanol, place the precipitate in a vacuum drying oven to dry, and obtain the mercapto-modified SEBS block polymer.

[0008] Preferably, in step S3, the thiol compound is one of the nonpolar thiol compounds, namely dodecanethiol, octadecethiol, or cyclohexylthiol, with a purity ≥95%.

[0009] Preferably, the catalyst is the photoinitiator benzoin dimethyl ether, and the amount used is 1%-3% of the mass of the mercapto compound.

[0010] Preferably, in step S4, the reaction system is placed under a 365nm ultraviolet light source with a power of 500W, the distance between the reaction liquid and the light source is 10-15cm, and the irradiation reaction lasts for 1-3 hours.

[0011] A method for preparing a thiol-modified SEBS separation membrane, comprising the following steps: a. Preparation of casting solution: Dissolve the modified SEBS at a mass fraction of 10%-20% in a mixed solvent of N,N-dimethylformamide and toluene at a volume ratio of 1:1, stir at 60 °C until completely dissolved and allow to stand to remove bubbles; b. Casting film: The degassed casting solution is uniformly cast onto a clean glass substrate, and the film thickness is controlled at 100μm. The substrate is then immediately immersed in deionized water at 25℃ to solidify the film. c. Membrane drying: The solidified membrane is peeled off from the substrate, soaked in deionized water to remove residual solvent, and then dried in a vacuum drying oven at 50 ℃ to obtain a mercapto-modified SEBS gas separation membrane.

[0012] A method for preparing a thiol-modified SEBS separation membrane and its application in CH4 / N2 gas separation.

[0013] Compared with existing technologies, this invention has the following technical advantages: This invention optimizes performance by introducing thiol functional groups into the EB segment of the SEBS molecular chain. As a strongly polar functional group, thiol not only forms stronger dipole interactions and weak hydrogen bonds with CH4, significantly improving the selective adsorption capacity of SEBS for CH4, but also regulates the molecular chain packing density of SEBS through weak cross-linking between thiol groups, inhibiting N2 diffusion while ensuring a high CH4 permeability coefficient. Simultaneously, the introduction of thiol groups enhances the hydrophilicity control capability of the SEBS membrane, improves its anti-swelling performance, and extends its service life in complex natural gas environments. Furthermore, the thiol modification reaction conditions used in this patent are mild, requiring no highly corrosive reagents, maximizing the preservation of the original processability and mechanical properties of SEBS. The modification process is simple, highly controllable, and easily scaled up industrially, providing a new technical route for the preparation of high-performance CH4 / N2 separation membranes. Detailed Implementation

[0014] 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.

[0015] Example 1: Preparation of dodecathiol-modified SEBS and its separation membrane 1) SEBS pretreatment: Take 10g of SEBS (Kerteng G1652, double bond content 0.8mmol / g), vacuum dry at 60℃ for 24 hours, and pulverize through an 80-mesh sieve.

[0016] 2) Solution preparation: Dissolve 5g of pretreated SEBS in 95mL of anhydrous toluene (5% by mass), stir until dissolved, and purge with nitrogen for 15 minutes to remove oxygen.

[0017] 3) Michael addition reaction: The total amount of double bonds in SEBS = 5g × 0.8mmol / g = 4mmol. Add 4.8mmol of dodecanethiol (0.864g) at a molar ratio of 1:1.2. The amount of benzoin dimethyl ether catalyst is 1% (0.0086g) of the mass of the mercapto compound. After mixing thoroughly, irradiate the reaction system under a 500W, 365nm UV lamp (15cm away) for 1 hour.

[0018] 4) Post-treatment: The reaction solution was poured into 500 mL of anhydrous ethanol, filtered and washed, and then dried under vacuum at 50 °C for 24 hours to obtain modified SEBS (S1).

[0019] 5) Membrane preparation: Dissolve 10g S1 in 90mL of DMF / toluene mixed solvent (volume ratio 1:1), mass fraction 10%, stir at 60℃ until completely dissolved, degas and cast into a membrane, immerse in deionized water to solidify, and dry to obtain gas separation membrane M1.

[0020] Example 2: Preparation of SEBS modified with octadecyl mercaptan and its membrane 1) SEBS pretreatment: Take 10g of SEBS (Kerteng G1652, double bond content 0.8mmol / g), vacuum dry at 60℃ for 24 hours, and pulverize through an 80-mesh sieve.

[0021] 2) Solution preparation: Dissolve 10g of pretreated SEBS in 90mL of anhydrous toluene (10% by mass), stir until dissolved, and purge with nitrogen for 15 minutes.

[0022] 3) Addition reaction: The total amount of double bonds in SEBS = 10g × 0.8mmol / g = 8mmol. Add 10.8mmol of octadecyl mercaptan (2.844g) at a molar ratio of 1:1.35. The amount of benzoin dimethyl ether catalyst is 2% of the mass of the mercapto compound (0.0569g). After mixing evenly, place it under a 500W, 365nm ultraviolet lamp (distance 12.5cm) for 2 hours.

[0023] 4) Post-treatment: Pour 500 mL of anhydrous ethanol into the reaction solution, filter and wash, and then vacuum dry at 50 °C for 24 hours to obtain modified SEBS (S2).

[0024] 5) Membrane preparation: Dissolve 15g S2 in 85mL DMF / toluene (volume ratio 1:1), mass fraction 15%, stir at 60℃ to dissolve, degas and cast into a membrane, immerse in deionized water to solidify, and dry to obtain gas separation membrane M2.

[0025] Example 3: Cyclohexylthiol-modified SEBS and its membrane preparation 1) SEBS pretreatment: Take 10g of SEBS (Kerteng G1652, double bond content 0.8mmol / g), vacuum dry at 60℃ for 24 hours, and pulverize through an 80-mesh sieve.

[0026] 2) Solution preparation: Dissolve 15g of pretreated SEBS in 85mL of anhydrous toluene (15% by mass), stir until dissolved, and purge with nitrogen for 15 minutes.

[0027] 3) Addition reaction: The total amount of double bonds in SEBS = 15g × 0.8mmol / g = 12mmol. Add 18mmol of octadecyl mercaptan (2.160g) at a molar ratio of 1:1.5. The amount of benzoin dimethyl ether catalyst is 3% of the mass of the mercapto compound (0.0648g). After mixing evenly, place it under a 500W, 365nm ultraviolet lamp (10cm away) for 3 hours.

[0028] 4) Post-treatment: Pour 500 mL of anhydrous ethanol into the reaction solution, filter and wash, and then vacuum dry at 50 °C for 24 hours to obtain modified SEBS (S3).

[0029] 5) Membrane preparation: Dissolve 20g of S3 in 80mL of DMF / toluene mixed solvent (volume ratio 1:1), with a mass fraction of 20%, stir at 60℃ to dissolve, degas and cast into a membrane, immerse in deionized water to solidify, and dry to obtain gas separation membrane M3. Example

[0030] 1) SEBS pretreatment: Take 10g of SEBS (Kerteng G1652, double bond content 0.8mmol / g), vacuum dry at 60℃ for 24 hours, and pulverize through an 80-mesh sieve.

[0031] 2) Solution preparation: Dissolve 12g of pretreated SEBS in 88mL of anhydrous toluene (12% by mass), stir until dissolved, and purge with nitrogen for 15 minutes to remove oxygen.

[0032] 3) Michael addition reaction: The total amount of double bonds in SEBS = 12g × 0.8mmol / g = 9.6mmol. 13.44mmol of a mixed thiol compound (0.864g dodecanethiol + 1.104g octadecethiol) was added at a molar ratio of 1:1.4. The amount of benzoin dimethyl ether catalyst was 2.5% (0.0492g) of the thiol compound mass. After thorough mixing, the reaction system was irradiated under a 500W, 365nm UV lamp (13cm distance) for 2.5 hours.

[0033] 4) Post-treatment: The reaction solution was poured into 500 mL of anhydrous ethanol, filtered and washed, and then dried under vacuum at 50 °C for 24 hours to obtain modified SEBS (S4).

[0034] 5) Membrane preparation: Dissolve 18g of S4 in 82mL of DMF / toluene mixed solvent (volume ratio 1:1), mass fraction 18%, stir at 60℃ until completely dissolved, degas and cast into a membrane, immerse in deionized water to solidify, and dry to obtain gas separation membrane M4.

[0035] Comparative Example 1: Preparation of Unmodified SEBS Membrane Gas separation membrane C1 was prepared directly from unmodified SEBS using the membrane preparation steps of Example 1.

[0036] Comparative Example 2 (compared to Example 2) 1) SEBS pretreatment: Take 10g of SEBS (Kerteng G1652, double bond content 0.8mmol / g), vacuum dry at 60℃ for 24 hours, and pulverize through an 80-mesh sieve.

[0037] 2) Solution preparation: Dissolve 3g of pretreated SEBS in 97mL of anhydrous toluene (3% by mass), stir until dissolved, and purge with nitrogen for 15 minutes.

[0038] 3) Addition reaction: The total amount of double bonds in SEBS = 10g × 0.8mmol / g = 8mmol. Add 10.8mmol of octadecyl mercaptan (2.844g) at a molar ratio of 1:1.35. The amount of benzoin dimethyl ether catalyst is 2% of the mass of the mercapto compound (0.0569g). After mixing evenly, place it under a 500W, 365nm ultraviolet lamp (distance 12.5cm) for 2 hours.

[0039] 4) Post-treatment: Pour 500 mL of anhydrous ethanol into the reaction solution, filter and wash, and then vacuum dry at 50 °C for 24 hours to obtain modified SEBS (S2).

[0040] 5) Membrane preparation: Dissolve 15g S2 in 85mL DMF / toluene (volume ratio 1:1), mass fraction 15%, stir at 60℃ to dissolve, degas and cast into a membrane, immerse in deionized water to solidify, and dry to obtain gas separation membrane M5.

[0041] Comparative Example 3 (compared to Example 2) 1) SEBS pretreatment: Take 10g of SEBS (Kerteng G1652, double bond content 0.8mmol / g), vacuum dry at 60℃ for 24 hours, and pulverize through an 80-mesh sieve.

[0042] 2) Solution preparation: Dissolve 10g of pretreated SEBS in 90mL of anhydrous toluene (10% by mass), stir until dissolved, and purge with nitrogen for 15 minutes.

[0043] 3) Addition reaction: The total amount of double bonds in SEBS = 10g × 0.8mmol / g = 8mmol. Add 8.8mmol of octadecyl mercaptan (2.328g) at a molar ratio of 1:1.1. The amount of benzoin dimethyl ether catalyst is 2% of the mass of the mercapto compound (0.0569g). After mixing evenly, place it under a 500W, 365nm ultraviolet lamp (distance 12.5cm) for 2 hours.

[0044] 4) Post-treatment: Pour 500 mL of anhydrous ethanol into the reaction solution, filter and wash, and then vacuum dry at 50 °C for 24 hours to obtain modified SEBS (S2).

[0045] 5) Membrane preparation: Dissolve 15g S2 in 85mL DMF / toluene (volume ratio 1:1), mass fraction 15%, stir at 60℃ to dissolve, degas and cast into a membrane, immerse in deionized water to solidify, and dry to obtain gas separation membrane M6.

[0046] Comparative Example 4 (compared to Example 2) 1) SEBS pretreatment: Take 10g of SEBS (Kerteng G1652, double bond content 0.8mmol / g), vacuum dry at 60℃ for 24 hours, and pulverize through an 80-mesh sieve.

[0047] 2) Solution preparation: Dissolve 10g of pretreated SEBS in 90mL of anhydrous toluene (10% by mass), stir until dissolved, and purge with nitrogen for 15 minutes.

[0048] 3) Addition reaction: The total amount of double bonds in SEBS = 10g × 0.8mmol / g = 8mmol. Add 12.8mmol of octadecyl mercaptan (3.392g) at a molar ratio of 1:1.6. The amount of benzoin dimethyl ether catalyst is 2% of the mass of the mercapto compound (0.0569g). After mixing evenly, place it under a 500W, 365nm ultraviolet lamp (distance 12.5cm) for 2 hours.

[0049] 4) Post-treatment: Pour 500 mL of anhydrous ethanol into the reaction solution, filter and wash, and then vacuum dry at 50 °C for 24 hours to obtain modified SEBS (S2).

[0050] 5) Membrane preparation: Dissolve 15g S2 in 85mL DMF / toluene (volume ratio 1:1), mass fraction 15%, stir at 60℃ to dissolve, degas and cast into a membrane, immerse in deionized water to solidify, and dry to obtain gas separation membrane M7.

[0051] The gas separation membrane in the above embodiments was subjected to performance testing, and the test results are shown in Table 1. Table 1. Performance comparison of SEBS separation membranes modified with different sulfur-based compounds sample <![CDATA[CH4 Permeation Rate / Barrer]]> <![CDATA[N2 Permeation Rate / Barrer]]> <![CDATA[CH4 / N2 selectivity]]> C1 50 30 1.67 M1 72 24 3.00 M2 98 18 5.44 M3 68 14 4.86 M4 85 20 4.25 M5 55 28 1.96 M6 62 25 2.48 M7 105 32 3.28 Note: 1Barrer=1×10 -10 cm³(STP)·cm / (cm²·s·cm·Hg) Table 1 shows the separation performance of the modified membranes in the examples and comparative examples. In comparison, the modified gas separation membranes exhibited significantly increased CH4 permeability and decreased N2 permeability, resulting in a substantial improvement in selectivity. The octadecyl mercaptan modified membrane (M2), due to the steric hindrance effect of its long-chain alkyl groups, formed a pore structure more conducive to CH4 passage, exhibiting the highest selectivity. The cyclohexyl mercaptan modified membrane (M3), due to the rigidity of its cyclic structure and good pore stability, had the lowest N2 permeability.

[0052] 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 method for preparing thiol-modified SEBS, characterized in that: Includes the following steps, S1. SEBS Pretreatment: Vacuum dry SEBS at 60℃ to remove moisture and volatiles, then pulverize and pass through an 80-mesh sieve for later use. S2. Solution preparation: Dissolve the dried SEBS in anhydrous toluene at a mass concentration of 5%-15%, stir at room temperature until completely dissolved to form a transparent homogeneous solution, and bubble with nitrogen gas for 10-15 minutes to remove oxygen. S3, Michael addition reaction: Add mercapto compound and catalyst to SEBS solution according to the molar ratio of double bond to mercapto compound in SEBS of 1:1.2-1:1.5, and then place the reaction system under ultraviolet light source for irradiation reaction; S4. Post-treatment: Slowly pour the reaction solution into excess anhydrous ethanol, stir to form a flocculent precipitate, filter and wash the precipitate with anhydrous ethanol, place the precipitate in a vacuum drying oven to dry, and obtain the mercapto-modified SEBS block polymer.

2. The method for preparing thiol-modified SEBS according to claim 1, characterized in that: In step S3, the thiol compound is one of the nonpolar thiol compounds, namely dodecanethiol, octadecethiol, or cyclohexylthiol, with a purity ≥95%.

3. The method for preparing thiol-modified SEBS according to claim 1, characterized in that: The catalyst is the photoinitiator benzoin dimethyl ether, and the amount used is 1%-3% of the mass of the mercapto compound.

4. The method for preparing thiol-modified SEBS according to claim 1, characterized in that: In step S4, the reaction system is placed under a 365nm ultraviolet light source with a power of 500W. The distance between the reaction liquid and the light source is 10-15cm, and the reaction is carried out for 1-3 hours.

5. A method for preparing a separation membrane using thiol-modified SEBS prepared according to claim 1, characterized in that: Follow these steps: a. Preparation of casting solution: Dissolve the modified SEBS at a mass fraction of 10%-20% in a mixed solvent of N,N-dimethylformamide and toluene at a volume ratio of 1:1, stir at 60 °C until completely dissolved and allow to stand to remove bubbles; b. Casting film: The degassed casting solution is uniformly cast onto a clean glass substrate, and the film thickness is controlled at 100 μm. The substrate is then immediately immersed in deionized water at 25 °C to solidify the film. c. Membrane drying: The solidified membrane is peeled off from the substrate, soaked in deionized water to remove residual solvent, and then dried in a vacuum drying oven at 50°C to obtain a mercapto-modified SEBS gas separation membrane.

6. The application of the thiol-modified SEBS separation membrane prepared by the method described in claim 5 in CH4 / N2 gas separation.