Graphene modified Pebax gas separation membrane and preparation method thereof

Abstract

The invention relates to the technical field of separation membranes, in particular to a graphene modified Pebax gas separation membrane and a preparation method thereof. The preparation method of the graphene modified Pebax gas separation membrane comprises the following steps: performing polymerization reaction on graphene oxide and a silane coupling agent in a dispersing agent, and drying to obtain functionalized graphene oxide; the preparation method comprises the following steps: dispersing functionalized graphene oxide in a solvent to obtain a functionalized graphene oxide dispersion liquid, adding the functionalized graphene oxide dispersion liquid into a polyether amide solution, carrying out ultrasonic stirring to obtain a mixed solution, pouring the mixed solution into a mold, and carrying out drying and demolding to obtain the graphene modified Pebax gas separation membrane. The graphene modified Pebax gas separation membrane prepared by the preparation method of the graphene modified Pebax gas separation membrane disclosed by the invention has high gas separation performance and mechanical property.

Description

Technical Field

[0001] The present invention relates to the technical field of separation membranes, and in particular to a graphene-modified Pebax gas separation membrane and a preparation method thereof. Background Art

[0002] In recent years, with the accelerated pace of global industrialization and the rapid leap forward in science and technology, CO2 emissions have risen sharply, and global climate issues have become increasingly severe, becoming a focus of global attention. In order to meet this severe challenge, reducing CO2 emissions, strengthening resource conservation and environmental protection, and promoting the widespread formation of green and low-carbon production and lifestyles have become a general consensus and an imperative means of the international community. Against this grand background, carbon capture technology, as an effective CO2 emission reduction strategy, has increasingly received widespread attention and in-depth research from all walks of life.

[0003] Carbon capture technology aims to separate CO2 from industrial emission sources, energy consumption processes or the atmosphere to achieve a continuous reduction in carbon dioxide emissions. Traditional CO2 separation technologies, such as absorption, adsorption, and cryogenic separation, can achieve the separation and recovery of CO2 to a certain extent, but they are often accompanied by disadvantages such as high cost, huge energy consumption, and complex equipment. In contrast, membrane separation has shown extremely broad application prospects in the field of carbon capture due to its significant advantages such as low cost, environmental protection, low energy consumption, and small footprint.

[0004] Membrane separation is a technology that uses the selective permeability of membranes to achieve efficient gas separation. Among them, mixed matrix membranes, as a new membrane material, fully demonstrate the unique advantages of inorganic membrane materials and organic membrane materials by cleverly integrating organic matrix materials with inorganic fillers. In mixed matrix membranes, commonly used inorganic fillers include carbon nanomaterials, metal organic frameworks, metal oxides, etc. Graphene oxide (GO) is a carbon nanomaterial with excellent mechanical properties, large specific surface area and rich surface active sites. Its unique flaky structure is conducive to the construction of novel "nanopores" in the polymer matrix, thereby significantly improving the gas separation performance of the membrane.

[0005] However, the dispersion of GO in the matrix has become a crucial factor affecting the membrane performance. Due to the strong interaction between GO sheets, "agglomeration" is prone to occur, resulting in a significant decrease in membrane performance. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing a graphene-modified Pebax gas separation membrane, which is used to solve the problem in the prior art that the membrane performance is greatly reduced due to the "agglomeration" phenomenon between GO sheets.

[0007] The present invention also provides a graphene-modified Pebax gas separation membrane to solve the problem of poor performance of the separation membrane in the prior art.

[0008] In order to solve the above problems, the present invention proposes a method for preparing a graphene-modified Pebax gas separation membrane, and the technical solution adopted is: A method for preparing a graphene-modified Pebax gas separation membrane comprises the following steps: subjecting graphene oxide and a silane coupling agent to a polymerization reaction in a dispersant and then drying the resultant to obtain a functionalized graphene oxide; dispersing the functionalized graphene oxide in a solvent to obtain a functionalized graphene oxide dispersion, adding the dispersion into a polyetheramide solution and performing ultrasonic stirring to obtain a mixed solution, pouring the mixed solution into a mold, and performing drying and demolding to obtain a graphene-modified Pebax gas separation membrane.

[0009] The beneficial effects of the present invention are: 1) Substantial improvement in membrane performance: The present invention combines graphene oxide (GO), a carbon nanomaterial with excellent mechanical properties, large specific surface area and abundant surface active sites, with polyetheramide (Pebax), a polymer matrix material, after being modified with a silane coupling agent, to form a new graphene-modified Pebax gas separation membrane. This fusion not only gives full play to the unique advantages of GO and Pebax, but also achieves a significant improvement in membrane performance through the synergistic effect between the two.

[0010] 2) Effectively solved the GO dispersion problem: By adding silane coupling agent to functionalize GO, functionalized graphene oxide (FGO) was obtained, which significantly improved the dispersion and compatibility of GO in the Pebax matrix. This modification method effectively avoided the "agglomeration" phenomenon between GO sheets, ensured the uniformity and stability of the membrane structure, and thus greatly improved the gas separation performance of the membrane.

[0011] 3) Significantly improved the gas separation efficiency of the membrane: The unique sheet structure of FGO constructs novel "nanopores" in the Pebax matrix. These pores not only provide more transmission channels for gas molecules, but also achieve efficient separation of target gases such as CO2 through their size and shape selectivity. This efficient gas separation mechanism makes graphene-modified Pebax gas separation membranes have extremely high application potential in the field of carbon capture.

[0012] 4) Reduced the cost of membrane separation technology: Compared with traditional CO2 separation technologies, such as absorption, adsorption, and cryogenic separation, the membrane separation method proposed in this invention has significant advantages such as low cost, environmental protection, low energy consumption, and small footprint. This not only reduces the economic threshold of carbon capture technology, but also provides the possibility for its application in a wider range of fields.

[0013] 5) Promotes the green development of carbon capture technology: Pebax and GO used in the present invention are both environmentally friendly materials, and no harmful substances are produced during the preparation process, which is in line with the principles of green chemistry. At the same time, the efficient gas separation performance of the graphene-modified Pebax gas separation membrane makes it play an important role in reducing CO2 emissions, strengthening resource conservation and environmental protection, and promoting the green development of carbon capture technology.

[0014] In order to further promote the functional modification of GO, preferably, the silane coupling agent is selected from any one of γ-aminopropyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane.

[0015] In order to ensure that GO can be fully and completely functionalized, preferably, the ratio of the mass of the graphene oxide to the volume of the silane coupling agent is (0.15-0.3): (2-3).

[0016] In order to further improve the gas separation efficiency of the membrane and improve the mechanical properties of the membrane, preferably, the mass ratio of the functionalized graphene oxide to the polyetheramide in the polyetheramide solution is (0.013-0.015): (1-3).

[0017] In order to make the polymerization reaction sufficient and complete, preferably, the polymerization reaction temperature is 75-90° C. and the time is 4-6 hours.

[0018] In order to improve the effect of functional modification of graphene oxide and reduce its agglomeration phenomenon, preferably, the number of layers of the graphene oxide is less than 3 and the length size is 2-5 μm.

[0019] In order to fully disperse the graphene oxide and the silane coupling agent and effectively achieve modification, preferably, the dispersant is anhydrous ethanol, and the volume ratio of the silane coupling agent to the dispersant is (2-3): (90-110).

[0020] In order to fully disperse the functionalized graphene oxide, preferably, the solvent is selected from anhydrous ethanol or a mixture of anhydrous ethanol and water, and the ratio of the mass of the functionalized graphene oxide to the volume of the solvent is (0.013-0.015): (60-80).

[0021] Preferably, the drying temperature is 100-150° C. and the drying time is 5-6 hours.

[0022] The present invention also proposes a graphene-modified Pebax gas separation membrane, and the technical solution adopted is: A graphene-modified Pebax gas separation membrane is prepared by the above-mentioned method for preparing the graphene-modified Pebax gas separation membrane.

[0023] The beneficial effects of the present invention are: the graphene-modified Pebax gas separation membrane of the present invention has a uniform and stable structure, and at the same time, has high gas separation performance and mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The diagrams are the reaction mechanism diagrams of the silane coupling agents (KH550, KH560, KH570) of the present invention and GO, and the action mechanism diagrams of FGO and Pebax molecular chains; Figure 2 SEM images of FGO-KH-550, FGO-KH-560 and FGO-KH-570 obtained in the method for preparing the graphene-modified Pebax gas separation membrane of Examples 1-3 of the present invention and the GO raw material used, wherein: (a) GO raw material, (b) FGO-KH-550, (c) FGO-KH-560, (d) FGO-KH-570; Figure 3 FT-IR images of FGO-KH-550, FGO-KH-560 and FGO-KH-570 obtained in the method for preparing the graphene-modified Pebax gas separation membrane of Examples 1-3 of the present invention and the GO raw material used; Figure 4 FT-IR images of the Pebax / FGO-KH-550 composite membrane, the Pebax / FGO-KH-560 composite membrane and the Pebax / FGO-KH-570 composite membrane obtained by the preparation method of the graphene-modified Pebax gas separation membrane of Examples 1-3 of the present invention, the Pebax / FGO composite membrane prepared in Comparative Example 1, and the pure Pebax membrane; Figure 5 SEM images of the Pebax / FGO- KH-550 composite membrane, Pebax / FGO- KH-560 composite membrane and Pebax / FGO- KH-570 composite membrane obtained by the preparation method of the graphene-modified Pebax gas separation membrane of Examples 1-3 of the present invention, the Pebax / FGO composite membrane prepared in Comparative Example 1 and the pure Pebax membrane, wherein: (a) pure Pebax membrane, (b) Pebax / FGO composite membrane, (c) Pebax / FGO- KH-550 composite membrane, (d) Pebax / FGO- KH-560 composite membrane, (e) Pebax / FGO-KH-570 composite membrane; Figure 6XRD patterns of the Pebax / FGO-KH-550 composite membrane, the Pebax / FGO-KH-560 composite membrane and the Pebax / FGO-KH-570 composite membrane obtained by the preparation method of the graphene-modified Pebax gas separation membrane of Examples 1-3 of the present invention, the Pebax / FGO composite membrane prepared in Comparative Example 1, and the pure Pebax membrane; Figure 7 Gas separation performance graphs of the Pebax / FGO-KH-550 composite membrane, Pebax / FGO-KH-560 composite membrane and Pebax / FGO-KH-570 composite membrane obtained by the preparation method of the graphene-modified Pebax gas separation membrane of Examples 1-3 of the present invention, the Pebax / FGO composite membrane prepared in Comparative Example 1, and a pure Pebax membrane. DETAILED DESCRIPTION

[0025] In the prior art, the performance of the membrane is greatly reduced due to the "agglomeration" phenomenon between GO sheets. The present invention provides a method for preparing a graphene-modified Pebax gas separation membrane, comprising the following steps: performing a polymerization reaction on graphene oxide and a silane coupling agent in a dispersant and then drying the mixture to obtain a functionalized graphene oxide; dispersing the functionalized graphene oxide in a solvent to obtain a functionalized graphene oxide dispersion, adding the dispersion to a polyetheramide solution and performing ultrasonic stirring to obtain a mixed solution, pouring the mixed solution into a mold, drying the mixture, and demolding the mixture to obtain a graphene-modified Pebax gas separation membrane.

[0026] The technical concept of the present invention is: GO is used as an inorganic filler, and is a carbon nanomaterial with excellent mechanical properties, a large specific surface area and abundant surface active sites, and is used as a filler; graphene oxide and a silane coupling agent are polymerized in a dispersant to achieve functional modification of graphene oxide by the silane coupling agent, and obtain functionalized graphene oxide; the functionalized graphene oxide is dispersed in a solvent to obtain a functionalized graphene oxide powder dispersion, and the functionalized graphene oxide is prevented from agglomerating, and is added to a polyetheramide solution for ultrasonic stirring to obtain a mixed solution, at which time, the functionalized graphene oxide is also used as a filler, and the addition of the functionalized graphene oxide to the polyetheramide solution will increase the mobility of the Pebax molecular chain segment, reduce the crystallinity of the polymer membrane, and significantly improve the gas separation performance of the polymer membrane. Among them, polyetheramide, as a polymer matrix material, is a thermoplastic elastomer containing alternating crystalline polyamide and amorphous polyether blocks, which can be compounded with functionalized graphene oxide to prepare a graphene-modified Pebax gas separation membrane. The graphene-modified Pebax gas separation membrane of the present application has high gas separation performance and mechanical properties.

[0027] in, Figure 1The following are the reaction mechanism diagrams of silane coupling agents γ-aminopropyl triethoxysilane (KH-550), γ-glycidyloxypropyl trimethoxysilane (KH-560) and γ-methacryloxypropyl trimethoxysilane (KH-570) with GO, as well as the action mechanism diagram of FGO with Pebax molecular chain. Silane coupling agent can be recorded as Y-Si-X3, where Y is an organic functional group (such as -NH2, -C=C, epoxy group, etc.); X is a hydrolyzed group (alkoxy group). Specifically, Si-O-CH3 of the silane coupling agent is hydrolyzed to form Si-OH, which undergoes polymerization reaction with the oxygen-containing functional groups on the surface of GO, thereby being grafted onto the surface of GO to obtain FGO. When FGO is added to Pebax solution to prepare gas separation membranes, the Pebax molecular segments are in a highly mobile state and can interact with the Si-O-Si network on the FGO surface to form a "semi-interpenetrating network structure", which can improve the interface compatibility between the filler and the matrix, thereby improving the mechanical properties of the mixed matrix membrane.

[0028] Specifically, the preparation method of the graphene-modified Pebax gas separation membrane comprises the following steps: First, a certain amount of GO is added to a certain amount of dispersant, the mixture is sealed with plastic wrap, and ultrasonic treatment is performed for 1 h; then a certain amount of silane coupling agent is added, and the mixture is stirred for 5-6 h by a magnetic stirrer in a constant temperature oil bath at 90-110°C, and stirring is stopped after the polymer is fully reacted. The mixture is cooled to room temperature and filtered, and the unadsorbed silane coupling agent is washed with anhydrous ethanol for 3 times, and then dried in an oven at 100-150°C for 5-6 h to remove the dispersant, thereby obtaining FGO; wherein the silane coupling agent is selected from any one of KH-550, KH-560 and KH-570; the ratio of the mass of graphene oxide to the volume of the silane coupling agent is (0.15-0.3):(2-3); the dispersant is anhydrous ethanol, and the volume ratio of the silane coupling agent to the dispersant is (2-3):(90-110); the polymerization reaction temperature is 75-90°C, and the time is 4-6 h; Secondly, a certain amount of FGO is added to a certain amount of solvent, sealed with plastic wrap, and magnetically stirred for 1 hour, ultrasonicated for 15 minutes, and repeated three times to obtain a uniform dispersion; wherein the solvent is selected from anhydrous ethanol or a mixture of anhydrous ethanol and water, and the ratio of the mass of functionalized graphene oxide to the volume of the solvent is (0.013-0.015): (60-80); Then, the dispersion was added to a certain amount of Pebax solution, sealed with plastic wrap, and magnetically stirred at room temperature for 12 hours to obtain a Pebax / FGO mixed solution; wherein the mass ratio of the functionalized graphene oxide to the polyetheramide in the polyetheramide solution was (0.013-0.015): (1-3); Finally, the obtained Pebax / FGO mixed solution was poured into a mold, left to stand at room temperature to evaporate the solvent for 48 h, then transferred to an oven for drying at 50 °C for 30 min, and demolded to obtain a graphene-modified Pebax gas separation membrane.

[0029] The implementation process of the present invention is described in detail below in conjunction with specific embodiments. However, it will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. It should also be noted that, for ease of description, only the parts related to the invention are shown in the embodiments. It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail with reference to the embodiments below. It should be noted that the endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this article.

[0030] In the following examples, the raw materials used are: graphene oxide: number of layers <3, length size 2~5 μm; Pebax: model MH 1657, purity >99.0%; silane coupling agent (KH-550, KH-560, KH-570): purity >99.0%, purchased from Shandong Youso Chemical Technology Co., Ltd. The remaining raw materials are all common commercial products that can be directly purchased or can be prepared according to conventional techniques in the field.

[0031] 1. Specific embodiment of the method for preparing the graphene-modified Pebax gas separation membrane of the present invention Example 1 The method for preparing the graphene-modified Pebax gas separation membrane provided in this embodiment comprises the following steps: First, 0.2 g of GO was added to 100 mL of anhydrous ethanol, sealed with plastic wrap, and ultrasonicated for 1 h. Then, 2.5 mL of KH-550 was added, and stirred with a magnetic stirrer for 5 h in a constant temperature oil bath at 80 °C. After the polymer was fully reacted, stirring was stopped, and the mixture was cooled to room temperature and filtered. The unadsorbed KH-550 was washed with anhydrous ethanol for 3 times, and then dried in an oven at 100 °C for 5 h to remove the anhydrous ethanol, thereby obtaining FGO-KH-550. Secondly, 0.014 g of FGO-KH-550 was added to a mixture of 65 mL of anhydrous ethanol and 15 mL of water, sealed with plastic wrap, magnetically stirred for 1 h, and ultrasonicated for 15 min, and repeated three times to obtain a uniform dispersion. Then, the dispersion was added to the Pebax solution, sealed with plastic wrap, and magnetically stirred at room temperature for 12 h to obtain a Pebax / FGO- KH-550 mixed solution, wherein the mass of Pebax in the Pebax solution was 2 g; Finally, the obtained Pebax / FGO-KH-550 mixed solution was poured into a mold, left to stand at room temperature to evaporate the solvent for 48 hours, then transferred to an oven for drying at 50 °C for 30 minutes, and demolded to obtain a graphene-modified Pebax gas separation membrane, recorded as Pebax / FGO-KH-550 composite membrane.

[0032] Example 2 The method for preparing the graphene-modified Pebax gas separation membrane provided in this embodiment comprises the following steps: First, 0.2 g of GO was added to 100 mL of anhydrous ethanol, sealed with plastic wrap, and ultrasonicated for 1 h. Then, 2.5 mL of KH-560 was added, and stirred with a magnetic stirrer for 5 h in a constant temperature oil bath at 80 °C. After the polymer was fully reacted, stirring was stopped, and the mixture was cooled to room temperature and filtered. The unadsorbed KH-560 was removed by washing with anhydrous ethanol for 3 times, and then dried in an oven at 100 °C for 5 h to remove the anhydrous ethanol, thereby obtaining FGO-KH-560. Secondly, 0.014 g of FGO-KH-560 was added to a mixture of 65 mL of anhydrous ethanol and 15 mL of water, sealed with plastic wrap, magnetically stirred for 1 h, and ultrasonicated for 15 min, and repeated three times to obtain a uniform dispersion. Then, the dispersion was added to the Pebax solution, sealed with plastic wrap, and magnetically stirred at room temperature for 12 h to obtain a Pebax / FGO- KH-560 mixed solution, wherein the mass of Pebax in the Pebax solution was 2 g; Finally, the obtained Pebax / FGO-KH-560 mixed solution was poured into a mold, left to stand at room temperature to evaporate the solvent for 48 hours, then transferred to an oven for drying at 50 °C for 30 minutes, and demolded to obtain a graphene-modified Pebax gas separation membrane, recorded as Pebax / FGO-KH-560 composite membrane.

[0033] Example 3 The method for preparing the graphene-modified Pebax gas separation membrane provided in this embodiment comprises the following steps: First, 0.2 g of GO was added to 100 mL of anhydrous ethanol, sealed with plastic wrap, and ultrasonicated for 1 h. Then, 2.5 mL of KH-570 was added, and stirred with a magnetic stirrer for 5 h in a constant temperature oil bath at 80 °C. After the polymer was fully reacted, stirring was stopped, and the mixture was cooled to room temperature and filtered. The unadsorbed KH-570 was washed with anhydrous ethanol for 3 times, and then dried in an oven at 100 °C for 5 h to remove the anhydrous ethanol, thereby obtaining FGO-KH-570. Secondly, 0.014 g of FGO-KH-570 was added to a mixture of 65 mL of anhydrous ethanol and 15 mL of water, sealed with plastic wrap, magnetically stirred for 1 h, and ultrasonicated for 15 min, and repeated three times to obtain a uniform dispersion. Then, the dispersion was added to the Pebax solution, sealed with plastic wrap, and magnetically stirred at room temperature for 12 h to obtain a Pebax / FGO-KH-570 mixed solution, wherein the mass of Pebax in the Pebax solution was 2 g; Finally, the obtained Pebax / FGO-KH-570 mixed solution was poured into a mold, left to stand at room temperature to evaporate the solvent for 48 hours, then transferred to an oven for drying at 50°C for 30 minutes, and demolded to obtain a graphene-modified Pebax gas separation membrane, recorded as Pebax / FGO-KH-570 composite membrane.

[0034] 2. Comparison Comparative Example 1 The method for preparing the graphene-modified Pebax gas separation membrane provided in this comparative example is different from that in Example 1 in that no silane coupling agent is used, and comprises the following steps: First, 0.014 g of GO was added to a mixture of 65 mL of anhydrous ethanol and 15 mL of water, sealed with plastic wrap, magnetically stirred for 1 h, and ultrasonicated for 15 min, and repeated three times to obtain a uniform dispersion. Then, the dispersion was added to the Pebax solution, sealed with plastic wrap, and magnetically stirred at room temperature for 12 h to obtain a Pebax / FGO mixed solution, wherein the mass of Pebax in the Pebax solution was 2 g; Finally, the obtained Pebax / FGO mixed solution was poured into a mold, left to stand at room temperature to evaporate the solvent for 48 h, then transferred to an oven and dried at 50 °C for 30 min, and demolded to obtain a graphene / Pebax separation membrane, recorded as Pebax / FGO composite membrane.

[0035] 3. Experimental Examples Experimental Example 1 The surface morphology of FGO-KH-550, FGO-KH-560 and FGO-KH-570 obtained in the preparation process of the above Examples 1-3 and the GO raw materials used were detected. Specifically, the microscopic morphology of FGO-KH-550, FGO-KH-560 and FGO-KH-570 and the GO raw materials used were observed using a JEM 2100 transmission electron microscope at an acceleration voltage of 120 kV. The detection results are as follows: Figure 2 shown.

[0036] It can be seen that GO maintains a sheet structure before and after modification. Due to the rich oxygen-containing groups, its surface has more wrinkles. After modification with KH-550, KH-560 and KH-570, the reduction effect of the silane coupling agent on GO makes its wrinkles less, the surface is smoother, and the edges of the nanosheets are not damaged, indicating that the polymerization reaction is relatively mild.

[0037] Experimental Example 2 The molecular structure, functional group structure and molecular arrangement of FGO-KH-550, FGO-KH-560 and FGO-KH-570 obtained in the preparation process of the above Examples 1-3 and the GO raw materials used were detected. Specifically, Nicolet 6700 Fourier transform infrared spectrometer was used for detection with a scanning range of 400-4000 cm -1 , the number of scans is 64, and the test results are as follows Figure 3 shown.

[0038] It can be seen that in Figure 3 The characteristic peak of GO raw material is: 1040 cm -1 The CO absorption peak at 1730 cm -1 The C=O stretching vibration peak at 3370 cm -1 The stretching vibration absorption peak of -OH at 1130 cm -1 and 2930 cm -1 The Si-OC / Si-O-Si and -CH2 stretching vibration peaks appear on the left and right, indicating that the alkyl coupling agents used have been grafted onto the GO surface. Due to the different structures of the three coupling agents, the characteristic peaks of different FGOs are also different. Specifically, compared with the GO raw material, FGO-KH-550 has a peak at 1628 cm -1 The C=O absorption peak of amide appears at 1562 cm -1 The NH absorption peak appears at 1087 cm, indicating that -NH2 in KH-550 reacts with -COOH in GO to produce amide groups. -1The CO characteristic absorption peak at 2978 cm-1 was enhanced, indicating that the Si-OH produced by the hydrolysis of KH-560 reacted with the -OH in GO to form Si-OC, thereby enhancing the CO absorption peak intensity. -1 and 1130 cm -1 The characteristic peak at , indicates that the silanol produced by the hydrolysis of KH-570 reacted with the hydroxyl groups on GO. This shows that the silane coupling agent used in this application can successfully modify GO to obtain FGO.

[0039] The molecular structure, functional group structure and molecular arrangement of the Pebax / FGO-KH-550 composite membrane, Pebax / FGO-KH-560 composite membrane and Pebax / FGO-KH-570 composite membrane prepared in Examples 1-3, the Pebax / FGO composite membrane prepared in Comparative Example 1 and the pure Pebax membrane were tested. Specifically, a Nicolet 6700 Fourier transform infrared spectrometer was used for the test with a scanning range of 400-4000 cm -1 , the number of scans is 64, and the test results are as follows Figure 4 shown.

[0040] It can be seen that in Figure 4 The characteristic peaks of pure Pebax membrane are: 1505 cm -1 The carbonyl stretching vibration peak of HNC=O at 1740 cm -1 The carbonyl peak of OC=O at 3005 cm -1 The CH bending vibration peak at 3135 cm -1 Compared with pure Pebax membrane, there is no obvious GO characteristic peak and FGO characteristic peak in the FT-IR curve of each composite membrane. This is because the amount of nanofillers (GO, FGO) added is small, but it also shows that the addition of GO and FGO will not destroy the internal structure of Pebax. The dispersion of modified FGO in the Pebax matrix is ​​significantly improved, and the agglomeration phenomenon is reduced, which proves the successful preparation of the mixed matrix membrane.

[0041] Experimental Example 3 The Pebax / FGO-KH-550 composite membrane, Pebax / FGO-KH-560 composite membrane and Pebax / FGO-KH-570 composite membrane prepared in Examples 1-3, the Pebax / FGO composite membrane prepared in Comparative Example 1 and the pure Pebax membrane were subjected to scanning electron microscopy. Specifically, a JSM-IT800 from Japan Electronics was used. The test results are as follows: Figure 5 shown.

[0042] It can be seen that in Figure 5 In the experiment, the pure Pebax film showed a smooth morphology. With the addition of different nanofillers, the cross-sectional morphology of the film became rough, and the flaky outline of GO could be observed. For different mixed matrix membranes, the flaky structures of GO and FGO were prone to π-π stacking, which led to their agglomeration in the Pebax matrix, resulting in the reduction of membrane performance. However, after GO was modified by silane coupling agent, its interfacial compatibility with Pebax was enhanced, so that the nanofillers were evenly dispersed in the Pebax matrix. Therefore, the SEM images of Pebax / FGO-KH-550, Pebax / FGO-KH-560, and Pebax / FGO-KH-570 composite membranes all showed a relatively flat morphology, among which the flaky outline of FGO-KH-550 could be vaguely observed in Pebax / FGO-KH-550, and there was no agglomeration phenomenon, indicating that FGO-KH-550 had the best compatibility with Pebax.

[0043] Experimental Example 4 The Pebax / FGO-KH-550 composite membrane, Pebax / FGO-KH-560 composite membrane and Pebax / FGO-KH-570 composite membrane prepared in the above Examples 1-3, the Pebax / FGO composite membrane prepared in Comparative Example 1 and the pure Pebax membrane were subjected to XRD detection. Specifically, an X-ray diffractometer (SmartLab, Japan) was used. The detection results are as follows: Figure 6 shown.

[0044] It can be seen that in Figure 6 From the XRD spectrum of the pure Pebax membrane in the experiment, it can be seen that due to the coexistence of PA (crystalline phase) and PEO (amorphous phase), the characteristic peak of Pebax appears at 15°-25°. With the addition of GO / FGO, the half-peak width of the characteristic peak becomes larger, indicating that GO / FGO can reduce the crystallinity of the Pebax molecular chain, thereby increasing the free volume in Pebax and improving the gas separation performance of the membrane.

[0045] Experimental Example 5 The gas separation performance of the Pebax / FGO-KH-550 composite membrane, Pebax / FGO-KH-560 composite membrane and Pebax / FGO-KH-570 composite membrane prepared in the above Examples 1-3, the Pebax / FGO composite membrane prepared in Comparative Example 1, and the pure Pebax membrane were tested. Specifically, the gas permeability of the composite membrane was tested using an Agilent 8860 gas spectrometer. The test method was to conduct a pure gas (CO2 and N2) performance permeation experiment on the prepared composite membrane using a conventional constant pressure variable volume method at room temperature of 25°C. The test pressure was 1.5 bar, and the outlet purge gas components were analyzed using a gas chromatograph equipped with a thermal conductivity detector (HP4890, Porapak N). The fluxes of CO2 and N2 were calculated by the purge gas flow rate and the purge gas components. The results are shown as follows: Figure 7 shown.

[0046] It can be seen that in Figure 7 In the experiment, the CO2 permeability coefficient of pure Pebax membrane was 65.2 Barrer, and the CO2 / N2 selectivity was 32.7. The addition of GO / FGO can form a new gas transmission path in the Pebax group, which improves the permeability and selectivity of the membrane. Among them, Pebax / FGO-KH-550 has the best CO2 / N2 separation performance, with a CO2 permeability coefficient of 92.5 Barrer, which is 41.9% higher than that of pure Pebax membrane; the CO2 / N2 separation coefficient is 49.9, which is 52.6% higher than that of pure Pebax membrane. This is because the surface of FGO-KH-550 contains amino groups. In addition to the gas channels provided by the nanosheets, the amino groups also provide affinity sites for the transfer of CO2. It can also be seen that the Pebax / FGO-KH-550 composite membrane, Pebax / FGO-KH-560 composite membrane and Pebax / FGO-KH-570 composite membrane of the present application have good gas separation performance compared with the Pebax / FGO composite membrane and the pure Pebax membrane, and have great potential application potential in the field of flue gas separation.

[0047] Experimental Example 6 The mechanical properties of the Pebax / FGO-KH-550 composite film, the Pebax / FGO-KH-560 composite film and the Pebax / FGO-KH-570 composite film prepared in the above Examples 1-3, the Pebax / FGO composite film prepared in Comparative Example 1 and the pure Pebax film were tested. Specifically, the breaking strength and breaking elongation were tested using an INSTRON 5982 electronic universal material testing machine with a clamping distance of 2 cm and a tensile speed of 5 cm / min. The test results are shown in Table 1.

[0048] Table 1 Mechanical properties of different composite membranes and pure Pebax membrane

[0049] As can be seen from Table 1, the fracture strength of pure Pebax film is 11.9 MPa, and the elongation at break is 433.3%. For Pebax / GO composite membrane, due to the poor dispersion of GO in the Pebax matrix, the elongation at break of Pebax / GO composite membrane is reduced to 364.4%. In contrast, GO is modified with silane coupling agent to improve its compatibility with Pebax, and the mechanical properties of Pebax / FGO composite membrane are significantly improved. Among them, Pebax / FGO-KH-550 composite membrane has the best mechanical properties, with the best fracture strength (17.8 MPa), which is 40.1% higher than the fracture strength (12.7 MPa) of Pebax / GO composite membrane; the elastic modulus reaches 67.4 MPa, which is 45.9% higher than the elastic modulus (46.2 MPa) of Pebax / GO composite membrane.

[0050] This shows that the graphene-modified Pebax gas separation membrane prepared by the method for preparing the graphene-modified Pebax gas separation membrane provided in the present application has good gas separation performance and mechanical properties.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a graphene-modified Pebax gas separation membrane, characterized in that: The method comprises the following steps: subjecting graphene oxide and a silane coupling agent to a polymerization reaction in a dispersant and then drying to obtain functionalized graphene oxide; dispersing the functionalized graphene oxide in a solvent to obtain a functionalized graphene oxide dispersion, adding the dispersion into a polyetheramide solution and performing ultrasonic stirring to obtain a mixed solution, pouring the mixed solution into a mold, and performing drying and demolding to obtain a graphene-modified Pebax gas separation membrane.

2. The method for preparing a graphene-modified Pebax gas separation membrane according to claim 1, characterized in that: The silane coupling agent is selected from any one of γ-aminopropyltriethoxysilane, γ-glycidyloxypropyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane.

3. The method for preparing a graphene-modified Pebax gas separation membrane according to claim 1, characterized in that: The ratio of the mass of the graphene oxide to the volume of the silane coupling agent is (0.15-0.3): (2-3).

4. The method for preparing a graphene-modified Pebax gas separation membrane according to claim 1, characterized in that: The mass ratio of the functionalized graphene oxide to the polyetheramide in the polyetheramide solution is (0.013-0.015): (1-3).

5. The method for preparing a graphene-modified Pebax gas separation membrane according to claim 1, characterized in that: The polymerization reaction temperature is 75-90° C. and the reaction time is 4-6 hours.

6. The method for preparing a graphene-modified Pebax gas separation membrane according to claim 1, characterized in that: The number of layers of the graphene oxide is less than 3, and the length size is 2-5 μm.

7. The method for preparing a graphene-modified Pebax gas separation membrane according to claim 1, characterized in that: The dispersant is anhydrous ethanol, and the volume ratio of the silane coupling agent to the dispersant is (2-3): (90-110).

8. The method for preparing a graphene-modified Pebax gas separation membrane according to claim 1, characterized in that: The solvent is selected from anhydrous ethanol or a mixture of anhydrous ethanol and water, and the ratio of the mass of the functionalized graphene oxide to the volume of the solvent is (0.013-0.015): (60-80).

9. The method for preparing a graphene-modified Pebax gas separation membrane according to claim 1, characterized in that: The drying temperature is 90-110° C. and the drying time is 5-6 hours.

10. A graphene-modified Pebax gas separation membrane, characterized in that: The gas separation membrane is prepared by the method for preparing a graphene-modified Pebax gas separation membrane according to any one of claims 1 to 9.

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