CD (at) HZ composite material with electrostatic gating, preparation method thereof and application of CD (at) HZ composite material in carbon capture

Abstract

The invention provides a CD (at) HZ composite material with electrostatic gating, a preparation method of the CD (at) HZ composite material and application of the CD (at) HZ composite material in carbon capture, and belongs to the technical field of composite material preparation, mixed matrix membrane material preparation and carbon capture. The preparation method comprises the following steps: compounding CD and HZ to obtain a CD-coated HZ composite material with electrostatic gating, and physically blending the CD-coated HZ composite material serving as a filling agent with a Pebax matrix to form a mixed matrix membrane; in the mixed matrix membrane, CD selectively recognizes CO2 and CH4 through electrostatic interaction force, HZ provides a rapid CO2 transfer channel, and the mixed matrix membrane has excellent selectivity on CO2 / CH4, can efficiently separate CO2 / CH4 and has good application in carbon capture.

Description

Technical Field

[0001] This invention belongs to the fields of composite material preparation, mixed matrix membrane material preparation and carbon capture technology, specifically relating to an electrostatically gated CD@HZ composite material, its preparation method and its application in carbon capture. Background Technology

[0002] Methane (CH4), with its high hydrogen-to-carbon ratio, is considered a cleaner fossil fuel and plays a "bridging" role in the transition to renewable energy. However, in addition to methane (CH4), natural gas also contains undesirable impurities such as acidic carbon dioxide (CO2), which can cause pipeline corrosion and reduce calorific value. Therefore, effectively removing carbon dioxide from natural gas is crucial for increasing its energy content and reducing the burden of pipeline transportation.

[0003] Traditional technologies such as chemical adsorption, water washing, and cryogenic distillation can effectively remove carbon dioxide, but they are often energy-intensive, contradicting global goals for reducing carbon emissions. To address this significant challenge, developing environmentally friendly and energy-efficient CO2 removal methods is crucial. Membrane separation technology has attracted considerable interest in CO2 separation due to its advantages of high energy efficiency, small footprint, and environmental friendliness. To date, polymer membranes have been widely used in various separation scenarios in industrial production and daily life, but they still fall short of fully meeting the growing demand. Although the microstructure can be optimized through molecular design, the gas separation performance of traditional polymer membrane materials remains difficult to further improve. Therefore, designing and preparing hybrid matrix membranes (MMMs) by combining inorganic packing materials and polymers has become a core strategy to overcome the performance bottlenecks of traditional polymer membranes and achieve efficient CO2 / CH4 separation. Since the gas separation performance of MMMs mainly depends on the physical and chemical properties of the packing material, selecting a suitable packing material is a key factor in improving the CO2 separation performance of MMMs.

[0004] Metal-organic frameworks (MOFs) are a class of porous compounds composed of organic ligands and inorganic clusters. They possess regular pore structures and high specific surface areas, making them readily suitable as packing materials for high-performance MMMs. Currently, most MOFs enhance their affinity for CO2 by introducing specific functional groups (-OH, -NH2, -COOH, etc.) within the pores. However, these in-pore functionalization strategies are often constrained by pore space, easily leading to functional group aggregation, pore blockage, and electrostatic repulsion within the framework, resulting in MOF structural instability. By confining functionalization to the outer surface, the spatial limitations of the internal micropores can be circumvented, and related mass transfer barriers can be eliminated. Therefore, designing packing materials capable of selectively recognizing CO2 outside the pores is crucial for significantly improving the gas separation performance of MMMs. Summary of the Invention

[0005] To address some shortcomings in existing technologies, this invention provides an electrostatically gated CD@HZ composite material, its preparation method, and its application in carbon capture. This invention combines CD and HZ to obtain an electrostatically gated CD@HZ composite material, which is then used as a filler to physically blend with a Pebax matrix to form a mixed matrix membrane. In this mixed matrix membrane, CD selectively recognizes CO2 and CH4 through electrostatic interaction, while HZ provides a rapid CO2 transport channel. The mixed matrix membrane exhibits excellent selectivity for CO2 / CH4, enabling efficient separation of CO2 / CH4 and demonstrating promising applications in carbon capture.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention first provides a method for preparing an electrostatically gated CD@HZ composite material, the method comprising: HZ was dispersed into activated CD, and the mixture was stirred and reacted at a certain temperature. After the reaction was completed, the mixture was collected by centrifugation, washed, and dried to obtain a white solid, which is the electrostatically gated CD@HZ composite material.

[0007] Preferably, the preparation steps of HZ include: A methanol solution of 2-methylimidazole and an aqueous solution of histidine (L-His) were thoroughly mixed, and then triethylamine (TEA) was added. After stirring and mixing evenly, a methanol solution of zinc sulfate heptahydrate (ZnSO4·7H2O) was added and stirred to react. After the reaction was completed, the mixture was washed, centrifuged, and dried to obtain HZ.

[0008] Preferably, the ratio of 2-methylimidazole, histidine, triethylamine and zinc sulfate heptahydrate is 575 mg: 155 mg: 200 µL: 1.15 g; The conditions for the stirring and mixing reaction are: stirring at 20~35℃ for 6~12h.

[0009] Preferably, carboxymethyl cyclodextrin (CD) and TEA are dissolved in H2O, and then 1-ethyl(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) are added to the solution. The reaction is carried out under stirring conditions, and activated CD is obtained after the reaction is completed.

[0010] Preferably, the dosage ratio of CD, TEA, EDC, and NHS is 10~50 mg: 10µL: 50 mg: 50 mg; The reaction conditions are: stirring at 20~35℃ for 2~5 hours.

[0011] Preferably, the dosage ratio of HZ to CD is 50~120mg:10~50mg; The conditions for the stirring reaction are: stirring at 20~35℃ for 24~36 hours.

[0012] The present invention also provides an electrostatically gated CD@HZ composite material prepared by the above preparation method, wherein the HZ composite material belongs to a core-shell heterostructure and exhibits a spherical morphology.

[0013] The present invention also provides a hybrid matrix membrane prepared based on the above-mentioned CD@HZ composite material, wherein the hybrid matrix membrane is formed by physical blending of filler CD@HZ composite material and polymer matrix polyether polyimide block Pebax at room temperature.

[0014] Preferably, in the mixed matrix membrane, the filler accounts for 1-7 wt.% of the mass percentage of the mixed matrix membrane. The thickness of the hybrid matrix membrane is 130-142 µm.

[0015] The present invention also provides the application of the above-mentioned hybrid matrix membrane in carbon capture.

[0016] Preferably, the application includes the separation of CO2 / CH4.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention combines CD and HZ to prepare an electrostatically gated CD@HZ composite material. In this composite material, CD acts as a gatekeeper, selectively recognizing CO2 and CH4 through its negatively charged microenvironment, while HZ provides a rapid CO2 transport channel. This invention also uses the CD@HZ composite material as a filler and physically blends it with a Pebax matrix to form a hybrid matrix membrane. The CD@HZ in the hybrid matrix membrane constructs electrostatically gated hierarchical transport channels, which can enhance CO2 transport within the membrane. The preparation method of the hybrid matrix membrane is simple, the reaction is controllable, and the raw materials are inexpensive and readily available.

[0018] The hybrid matrix membrane of this invention first separates CO2 / CH4 outside the pores based on the difference in positive electrostatic potential, and then rapidly transfers the selectively passing CO2. Considering the significant difference in positive potential between CO2 and CO4 molecules (CO2 has a much higher positive potential than methane), this difference provides an opportunity for selective CO2 separation through electrostatic gating. Conversely, because the positive potential of CH4 molecules is very low, they cannot effectively interact with the formed negatively charged microenvironment, thus hindering their entry into the pores of the composite material, thereby achieving CO2 / CH4 separation.

[0019] This invention combines the advantages of CD and HZ fillers to achieve a synergistic effect. The preparation process of the mixed matrix membrane is simple, the reaction is controllable, the raw materials are inexpensive and readily available, and the conditions are mild, which can promote the complementary advantages of inorganic fillers and polymeric matrices. The results show that the present invention has the highest CO2 flux of 878.1 ± 9.1 Barrer and CO2 / CH4 selectivity of 33.1 ± 0.6 for CO2 / CH4 mixed gases. Attached Figure Description

[0020] Figure 1 The image shows the XRD pattern of the CD@HZ composite material prepared in Example 1.

[0021] Figure 2 This is a scanning electron microscope image of the CD@HZ composite material prepared in Example 1.

[0022] Figure 3 This is a scanning electron microscope cross-sectional image of the Pebax / CD@HZ (1%) hybrid matrix film prepared in Example 1.

[0023] Figure 4 This is a scanning electron microscope cross-sectional image of the Pebax / CD@HZ (3%) hybrid matrix film prepared in Example 2.

[0024] Figure 5 This is a scanning electron microscope cross-sectional image of the Pebax / CD@HZ (5%) hybrid matrix film prepared in Example 3.

[0025] Figure 6 This is a scanning electron microscope cross-sectional image of the Pebax / CD@HZ (7%) hybrid matrix film prepared in Example 4.

[0026] Figure 7 This is a scanning electron microscope cross-sectional image of the Pebax film prepared in Comparative Example 1.

[0027] Figure 8 This is a scanning electron microscope cross-sectional image of the Pebax / HZ (5%) mixed matrix film prepared in Comparative Example 2. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto. Example 1: Preparation of CD@HZ

[0029] (1) Dissolve 574.7 mg of 2-methylimidazole in 20 mL of methanol to obtain a methanol solution of 2-methylimidazole; dissolve 155.1 mg of histidine in 10 mL of water to obtain an aqueous solution of histidine; dissolve 575.1 mg of ZnSO4·7H2O in 10 mL of methanol under sonication to obtain a methanol solution of ZnSO4·7H2O for later use.

[0030] The methanol solution of 2-methylimidazole was thoroughly mixed with an aqueous solution of histidine. Then, 200 µL of triethylamine was added and the mixture was stirred for several minutes to obtain a homogeneous mixture. Next, a methanol solution of ZnSO4·7H2O was added to the mixture, and the reaction was continued with stirring for 6 h. After the reaction was complete, the product was washed with methanol and centrifuged to obtain a white solid product. Finally, the white solid product was dried in a vacuum oven at 60 °C for 12 h and named HZ.

[0031] 20 mg CD and 10 µL TEA were dissolved in 10 mL H2O. 30 mg EDC and 50 mg NHS were added to the solution to activate the carboxyl groups in CD. The mixture was stirred at room temperature for 4 hours to obtain activated CD.

[0032] 100 mg of HZ was dispersed in 30 mg of activated CD, and the mixture was stirred vigorously at room temperature for 12 hours. After the reaction was completed, the mixture was collected by centrifugation and washed with ethanol. Finally, it was dried in a vacuum drying oven at 60 °C to obtain a white solid CD@HZ.

[0033] Figure 1 The XRD pattern is shown at CD@HZ. Figure 1 As can be seen, all diffraction peaks of HZ and CD appear on the CD@HZ composite material. This indicates that the CD@HZ composite material was successfully synthesized.

[0034] Figure 2 This is a SEM test image for CD@HZ. From... Figure 2 It can be seen that CD is coated on HZ, exhibiting a spherical core-shell heterostructure, indicating the synthesis of CD@HZ composite material.

[0035] Example 2: Preparation of Pebax / CD@HZ (1%) hybrid matrix membrane Weigh 0.537 g of Pebax® 1657 and dissolve it in 10 mL of a 7:3 mixture of ethanol and water. Heat and stir in an 80 °C water bath for 4 h to ensure that all Pebax particles are dissolved, thus preparing a 6 wt.% Pebax matrix solution.

[0036] 0.005 g of CD@HZ prepared in Example 1 was physically blended with the Pebax matrix solution and stirred at room temperature for 8 h to obtain a casting solution. The casting solution was poured onto a clean petri dish for casting and then dried at room temperature (25°C) for 48 h. After drying, the mixture was vacuum dried at 40°C in a vacuum drying oven to remove residual solvent from the surface of the mixed matrix membrane, resulting in a Pebax / CD@HZ mixed matrix membrane with a thickness of 140 µm. Since the weight percentage of CD@HZ in the Pebax / CD@HZ (1%) mixed matrix membrane is 1%, it is named the Pebax / CD@HZ (1%) mixed matrix membrane.

[0037] At 30 ℃ and 2 bar, the Pebax / CD@HZ (1%) mixed matrix membrane was used for the separation of CO2 / CH4 mixed gas with a CO2 volume fraction of 20%. The test results are as follows: Figure 3 As shown in the figure, the CO2 flux of Pebax / CD@HZ (1%) is 684.0 ± 7.6 Barrer, and the CO2 / CH4 selectivity is 22.7 ± 0.8.

[0038] Example 3: Preparation of Pebax / CD@HZ (3%) hybrid matrix membrane In this embodiment, a Pebax / CD@HZ (3%) hybrid matrix membrane was prepared. The preparation method was basically the same as in Example 2, with the only difference being that 0.005 g of CD@HZ was changed to 0.016 g of CD@HZ, and the mass ratio of Pebax to CD@HZ was 0.97:0.03. The thickness of the prepared Pebax / CD@HZ (3%) hybrid matrix membrane was 130 µm.

[0039] At 30 ℃ and 2 bar, the Pebax / CD@HZ (3%) mixed matrix membrane was used for the separation of CO2 / CH4 mixed gas with a CO2 volume fraction of 20%. The test results are as follows: Figure 4 As shown in the figure, the CO2 flux of Pebax / CD@HZ (3%) is 741.4 ± 3.9 Barrer, and the CO2 / CH4 selectivity is 25.5 ± 1.3.

[0040] Example 4: Preparation of Pebax / CD@HZ (5%) hybrid matrix membrane In this embodiment, a Pebax / CD@HZ (5%) hybrid matrix membrane was prepared. The preparation method was basically the same as in Example 2, with the only difference being that 0.005 g of CD@HZ was changed to 0.027 g of CD@HZ, and the mass ratio of Pebax to CD@HZ was 0.95:0.05. The thickness of the prepared Pebax / CD@HZ (5%) hybrid matrix membrane was 142 µm.

[0041] At 30 ℃ and 2 bar, the Pebax / CD@HZ (5%) mixed matrix membrane was used for the separation of CO2 / CH4 mixed gas with a CO2 volume fraction of 20%. The test results are as follows: Figure 5 As shown in the figure, the CO2 flux of Pebax / CD@HZ (5%) is 878.1 ± 9.1 Barrer, and the CO2 / CH4 selectivity is 33.1 ± 0.6.

[0042] Example 5: Preparation of Pebax / CD@HZ (7%) hybrid matrix membrane In this embodiment, a Pebax / CD@HZ (7%) hybrid matrix membrane was prepared. The preparation method was basically the same as in Example 2, with the only difference being that 0.005 g of CD@HZ was changed to 0.038 g of CD@HZ, and the mass ratio of Pebax to CD@HZ was 0.93:0.07. The thickness of the prepared Pebax / CD@HZ (7%) hybrid matrix membrane was 136 µm.

[0043] The Pebax / CD@HZ (7%) hybrid matrix membrane was used for the separation of a CO2 / CH4 mixed gas with a CO2 volume fraction of 20% at 30 ℃ and 2 bar. The test results are as follows. Figure 6 As shown in the figure, the CO2 flux of Pebax / CD@HZ (7%) is 578.1 ± 9.2 Barrer, and the CO2 / CH4 selectivity is 18.3 ± 1.0.

[0044] Comparative Example 1: In this comparative example, a Pebax membrane was prepared, and the specific steps included: Weigh 0.537 g of Pebax® 1657 and dissolve it in 10 mL of a 7:3 mixture of ethanol and water. Heat and stir in an 80 °C water bath for 4 h to ensure that all Pebax particles are dissolved. Pour the resulting casting solution onto a clean ultraflat petri dish and cast it. Dry it at room temperature (25 °C) for 48 h, and then place it in a 40 °C vacuum oven for 24 h to remove residual solvent, resulting in a Pebax film with a thickness of 133 μm.

[0045] At 30 °C and 2 bar, the Pebax membrane was used for the separation of a CO2 / CH4 mixture with a CO2 volume fraction of 20% (CO2 to CH4 volume ratio of 2:8). The test results are as follows: Figure 7 As shown in the figure, the CO2 flux of the Pebax membrane is 244.8 ± 4.4 Barrer, and the CO2 / CH4 selectivity is 18.3 ± 1.0.

[0046] Comparative Example 2: In this comparative example, a Pebax / HZ (5%) mixed matrix membrane was prepared. The preparation method was basically the same as that in Example 4, except for the following difference: instead of weighing 0.027 g CD@HZ, 0.027 g HZ was weighed, and a mixed matrix membrane with a thickness of 130 µm was finally obtained.

[0047] At 30 °C and 2 bar, the Pebax membrane was used for the separation of a CO2 / CH4 mixture with a CO2 volume fraction of 20% (CO2 to CH4 volume ratio of 2:8). The test results are as follows: Figure 8 As shown in the figure, when the Pebax / HZ (5%) mixed matrix membrane was used for the separation test of CO2 / CH4 mixed gas with a CO2 volume fraction of 20%, the CO2 flux was 660.7 ± 7.2 Barrer and the CO2 / CH4 selectivity was 23.0 ± 0.8.

[0048] In summary, this invention combines CD and HZ to obtain an electrostatically gated CD@HZ composite material, which is then used as a filler to physically blend with a Pebax matrix to form a hybrid matrix membrane. In the hybrid matrix membrane, CD selectively recognizes CO2 and CH4 through electrostatic interaction, while HZ provides a fast CO2 transport channel. The hybrid matrix membrane exhibits excellent selectivity for CO2 / CH4 and can efficiently separate CO2 / CH4, making it well-suited for carbon capture.

[0049] The embodiments described above are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing an electrostatically gated CD@HZ composite material, characterized in that, The preparation method includes: HZ was dispersed into activated CD, and the mixture was stirred and reacted at a certain temperature. After the reaction was completed, the mixture was collected by centrifugation, washed, and dried to obtain a white solid, which is the electrostatically gated CD@HZ composite material.

2. The method for preparing the electrostatically gated CD@HZ composite material according to claim 1, characterized in that, The preparation steps of the HZ include: A methanol solution of 2-methylimidazole and an aqueous solution of histidine (L-His) were thoroughly mixed, and then triethylamine (TEA) was added. After stirring and mixing evenly, a methanol solution of zinc sulfate heptahydrate (ZnSO4·7H2O) was added and stirred to react. After the reaction was completed, the mixture was washed, centrifuged, and dried to obtain HZ.

3. The method for preparing the electrostatically gated CD@HZ composite material according to claim 2, characterized in that, The ratio of 2-methylimidazole, histidine, triethylamine, and zinc sulfate heptahydrate is 575 mg: 155 mg: 200 µL: 1.15 g; The conditions for the stirring and mixing reaction are: stirring at 20~35℃ for 6~12h.

4. The method for preparing the electrostatically gated CD@HZ composite material according to claim 1, characterized in that, Carboxymethyl cyclodextrin (CD) and TEA were dissolved in H2O, and then 1-ethyl(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) were added to the solution. The reaction was carried out under stirring conditions, and the activated CD was obtained after the reaction was completed.

5. The method for preparing the electrostatically gated CD@HZ composite material according to claim 4, characterized in that, The dosage ratio of CD, TEA, EDC, and NHS is 10~50 mg: 10µL: 50 mg: 50 mg; The reaction conditions are: stirring at 20~35℃ for 2~5 hours.

6. The method for preparing the electrostatically gated CD@HZ composite material according to claim 1, characterized in that, The dosage ratio of HZ to CD is 50~120mg:10~50mg; The conditions for the stirring reaction are: stirring at 20~35℃ for 24~36 hours.

7. The electrostatically gated CD@HZ composite material prepared by the preparation method according to any one of claims 1-6, characterized in that, The HZ composite material has a core-shell heterostructure and exhibits a spherical morphology.

8. The hybrid matrix membrane prepared from the CD@HZ composite material according to claim 7, characterized in that, The hybrid matrix membrane is formed by physical blending of filler CD@HZ composite material and polymer matrix polyether polyimide block Pebax at room temperature; In the hybrid matrix membrane, the filler accounts for 1-7 wt.% of the mass percentage of the hybrid matrix membrane. The thickness of the hybrid matrix membrane is 130-142 µm.

9. The application of the hybrid matrix membrane according to claim 8 in carbon capture.

10. The application according to claim 9, characterized in that, The application includes the separation of CO2 / CH4.

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