Carbon-titanium-based two-dimensional layered composite gas separation membrane as well as preparation method and application thereof

Abstract

The invention relates to the technical field of gas separation membranes, in particular to a carbon-titanium-based two-dimensional layered composite gas separation membrane as well as a preparation method and application thereof. The preparation method comprises the following steps: ultrasonically dispersing the titanium carbide nanosheets and the Hf-MOF nanosheets in ionized water to obtain mixed dispersion liquid, pouring the mixed dispersion liquid into a sand core cup with a filter membrane for suction filtration, and drying to obtain the carbon-titanium-based two-dimensional layered composite gas separation membrane. The two-dimensional layered Ti3C2 nanosheets and the Hf-MOF nanosheets are compounded, the advantages of the two materials are combined, the specific surface area and the pore structure of the membrane are improved, the mechanical strength and the chemical stability of the membrane are enhanced, the CO2 separation efficiency is remarkably improved, the membrane stability is enhanced, the specific surface area is high, the pore structure is optimized, and the hydrophilicity is good; the gas permeation rate is effectively improved. The prepared carbon-titanium-based two-dimensional layered composite gas separation membrane has an excellent separation effect on CO2 / N2.

Description

Technical Field

[0001] The present invention relates to the technical field of gas separation membranes, and in particular to a carbon-titanium-based two-dimensional layered composite gas separation membrane, a preparation method thereof, and applications thereof. Background Art

[0002] Compared to traditional carbon capture and storage technologies, gas membrane separation technology offers advantages such as low cost, low energy consumption, high efficiency, simple operation, a small equipment footprint, and environmental friendliness. CO2 membrane separation technology, driven by a pressure differential, captures CO2 based on the differences in solubility or diffusion rates of different gas components on either side of a separation membrane. It has garnered widespread attention in recent years and is considered one of the most significant technological advances in the separation field. The membrane is crucial in membrane separation, and its performance determines the performance of CO2 separation.

[0003] Currently, widely used separation membranes are primarily made of polymer materials, which are easy to process and have low production costs. However, the thickness of polymer separation membranes typically ranges from tens of nanometers to several micrometers, which results in a long CO2 permeation time, severely limiting their separation efficiency. Furthermore, the thermal and chemical stability of polymer separation membranes needs to be improved. Inorganic membranes, including porous and non-porous membranes, offer advantages such as high-temperature and high-pressure stability, high mechanical strength, and good chemical stability. However, the complex preparation process and high cost of inorganic membranes limit their large-scale application. Inorganic membranes also have poor plasticity, are easily damaged, and are difficult to process. Some inorganic membranes, such as silicon oxide membranes, exhibit poor selectivity for CO2. Summary of the Invention

[0004] The purpose of the present invention is to address the above-mentioned deficiencies in the prior art and to provide a carbon-titanium based two-dimensional layered composite gas separation membrane and its preparation method and application.

[0005] The first object of the present invention is to provide a method for preparing a carbon-titanium-based two-dimensional layered composite gas separation membrane, comprising ultrasonically dispersing titanium carbide nanosheets and Hf-MOF nanosheets in ionized water to obtain a mixed dispersion, pouring the mixed dispersion into a sand core cup with a filter membrane for suction filtration, and drying to obtain an Hf-MOF / Ti3C2 thin film, i.e., a carbon-titanium-based two-dimensional layered composite gas separation membrane; Among them, Hf-MOF nanosheets are prepared by the following method: Hafnium tetrachloride and 1,3,5-tris(4-carboxyphenyl)benzene are dissolved in an organic solvent to form a mixed solution, which is then ultrasonically mixed with formic acid and ultrapure water, followed by heating for reaction, centrifugal washing, and drying to obtain Hf-MOF nanosheets.

[0006] Furthermore, the mass ratio of the titanium carbide nanosheets to the Hf-MOF nanosheets is 10-15:1.

[0007] Furthermore, the thickness of the film is 2-11 μm.

[0008] Furthermore, the organic solvent is N,N-dimethylformamide.

[0009] Furthermore, the heating reaction is performed at 120-180° C. for 36-48 hours.

[0010] Furthermore, the centrifugal washing is first performed by washing with N,N-dimethylformamide three times to remove unreacted raw materials and solvent, and then washing again with ethanol three times to further purify the product.

[0011] Furthermore, titanium carbide nanosheets are prepared by the following method: S1. Pour lithium fluoride into a hydrochloric acid solution and stir to obtain a solution; S2, immersing the Ti3AlC2 powder in the solution of step S1, heating and stirring, washing with deionized water, and centrifuging to obtain a precipitate; S3. Ultrasonic treatment is performed on the precipitate in step S2 with deionized water, and the supernatant is removed and then dried to obtain a Ti3C2 two-dimensional nanosheet material.

[0012] Furthermore, in step S1, the concentration of the hydrochloric acid solution is 9 to 12 M; in step S1, the mass volume ratio of lithium fluoride to hydrochloric acid solution is 1 to 2 g: 10 to 30 mL; in step S1, the stirring is performed at room temperature for 30 to 60 minutes.

[0013] Furthermore, in step S2, the mass ratio of the Ti3AlC2 powder to lithium fluoride is 1 to 2:2; in step S2, the heating and stirring is stirring at 35°C for 24 hours; in step S2, the precipitate is centrifuged and washed with deionized water until it is neutral.

[0014] The second object of the present invention is to provide a carbon-titanium based two-dimensional layered composite gas separation membrane prepared by the above-mentioned preparation method.

[0015] The second object of the present invention is to provide an application of a carbon-titanium based two-dimensional layered composite gas separation membrane for separating CO2.

[0016] Single Ti3C2 easily self-stacks during the film formation process, affecting gas transmission channels and leading to performance degradation. The two-dimensional Hf-MOF (metal-organic framework) with its unique regular pore structure, high specific surface area, and chemical stability is combined with Hf-MOF nanosheets and Ti3C2 two-dimensional nanosheets. By stacking them layer by layer, the resulting two-dimensional layered gas separation membrane not only inherits the high mechanical strength and conductivity of Ti3C2 but also significantly improves the membrane's gas separation performance. The regular pore structure of Hf-MOF provides precise screening channels for gas molecules, enabling efficient separation of different gas molecules; while its high specific surface area increases the adsorption sites on the membrane surface, improving the capture and transmission efficiency of gas molecules. Furthermore, the chemical stability of Hf-MOF ensures that the membrane maintains stable separation performance during long-term use and is not easily affected by environmental factors. Therefore, the present invention prepares a composite membrane material that combines the advantages of Hf-MOF and Ti3C2, improving the membrane's specific surface area and pore structure while enhancing its mechanical strength and chemical stability. The resulting carbon-titanium-based two-dimensional layered composite gas separation membrane exhibits excellent CO2 / N2 separation efficiency. It can be used in industrial waste gas treatment, natural gas purification, and other fields, playing a significant role in reducing greenhouse gas emissions and improving energy efficiency. It possesses excellent performance and broad application prospects in the field of gas separation.

[0017] The present invention uses vacuum filtration equipment to prepare a carbon-titanium-based two-dimensional layered composite gas separation membrane Hf-MOF / Ti3C2 through a layer-by-layer stacking self-assembly process. The composite membrane significantly improves CO2 separation efficiency and enhances membrane stability through the uniform combination of Ti3C2 and Hf-MOF nanosheets. Its high specific surface area, optimized pore structure, and good hydrophilicity effectively enhance gas permeation rate. The specific mechanism is as follows: High specific surface area: The uniform dispersion and compounding of Ti3C2 nanosheets and Hf-MOF nanosheets results in a composite membrane with a surface area of ​​up to 426 m² / g, much larger than that of pure Ti3C2. The high specific surface area provides more adsorption sites, facilitating the selective adsorption of CO2. Optimized pore structure: The introduction of Hf-MOF not only increases the number of pores but also optimizes the pore size distribution. The larger molecular size of N2 enhances the size screening effect, which enhances the composite membrane's adsorption capacity for CO2 while reducing N2 permeation, thereby improving separation efficiency. Enhanced membrane stability and durability: Ti3C2, as a two-dimensional transition metal carbide, has excellent mechanical strength and chemical stability. This structure acts as a skeleton in the composite membrane, enhancing the mechanical strength of the membrane and improving its stability and durability during use. Hf-MOF itself has excellent chemical stability and can maintain its structural integrity under various environments, further enhancing the stability of the composite membrane. Increase gas permeation rate: Good hydrophilicity: Both Ti3C2 and Hf-MOF have good hydrophilicity, which makes it easy for a water layer to form on the surface of the composite membrane. The water layer is conducive to the dissolution of CO2. CO2 has a certain solubility in water, which makes it easier to capture CO2 and facilitates its dissolution and diffusion. N2 is insoluble in water, which hinders its transmission; thereby improving the selectivity and permeation rate of CO2. Optimized membrane structure: The composite membrane prepared by vacuum filtration has a uniform and dense membrane structure, which reduces the permeation resistance of gas molecules and further improves the gas permeation rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the preparation of a titanium carbide-based two-dimensional layered composite gas separation membrane; Figure 2 is a cross-sectional SEM image of the prepared titanium carbide-based two-dimensional layered composite gas separation membrane; Figure 3 is the N2 adsorption-desorption curve of the prepared titanium carbide-based two-dimensional layered composite gas separation membrane; Figure 4 The permeation flux of two gases under different pressures of 7μm titanium carbide-based two-dimensional layered composite gas separation membrane; Figure 5 Gas selectivity of titanium carbide-based two-dimensional layered composite gas separation membrane under different membrane thicknesses. DETAILED DESCRIPTION

[0019] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0020] Preparation method of carbon-titanium based two-dimensional layered composite gas separation membrane The solution was pretreated using a reaction between hydrochloric acid and lithium fluoride to ensure a suitable reaction environment. Next, carbon-aluminum-titanium (Ti3AlC2) powder was slowly and portionwise added to the beaker containing the pretreated solution and stirred continuously at a constant temperature for 24 hours to allow for sufficient etching reaction and generate the desired two-dimensional layered structure. After the reaction, the precipitate was separated by centrifugation and subjected to multiple centrifugal washes and ultrasonic treatments to remove residual impurities and further purify the product. Finally, the precipitate was dried in a vacuum oven to yield pure and stable two-dimensional layered Ti3C2 nanosheets.

[0021] In the presence of anhydrous formic acid, hafnium tetrachloride reacts with 1,3,5-tris(4-carboxyphenyl)benzene in N,N-dimethylformamide (DMF) solvent and water. Heating and ultrasonic treatment are used to ensure that the reaction proceeds fully to generate Hf-MOF nanosheets.

[0022] like Figure 1 As shown, the prepared titanium carbide nanosheets and Hf-MOF nanosheets were dispersed in deionized water and thoroughly mixed by ultrasonic treatment. The mixed dispersion was then deposited onto a hydrophilic polypropylene membrane using vacuum filtration, forming a uniform thin film through layer-by-layer self-assembly. Finally, the film was dried in a vacuum oven to obtain a flexible, independent, and structurally stable Hf-MOF / Ti3C2 composite film. This film combines the advantages of both materials and exhibits excellent gas separation performance.

[0023] Example 1 Preparation of MXene titanium carbide nanosheets First, measure 10 mL of 9 mol / L hydrochloric acid solution and pour it into a clean Teflon beaker. Next, weigh 1 g of lithium fluoride (LiF) powder and slowly and evenly add it to the Teflon beaker containing the hydrochloric acid to avoid localized high concentrations. Turn on the stirring device and continue stirring for 30 minutes to ensure that the LiF powder is fully dissolved and evenly dispersed in the hydrochloric acid.

[0024] 1 g of titanium-aluminum-carbon (Ti3AlC2) powder was slowly added to the beaker in portions, stirring gently after each addition to minimize the initial temperature rise of the solution due to the exothermic reaction. The entire mixed solution was transferred to an oil bath preheated to 35°C. Stirring was continued at this temperature for 24 hours to ensure the reaction proceeded fully and the desired two-dimensional layered structure was generated.

[0025] After the reaction, the mixed solution was centrifuged to obtain a precipitate. To remove residual hydrochloric acid and other impurities, the precipitate was centrifuged and washed several times with deionized water until the washing solution was neutral. The precipitate was then ultrasonically treated in an ultrasonic cleaner at 180 W for 1 hour to further disperse and purify the product.

[0026] Finally, the supernatant was removed and the resulting precipitate was placed in a vacuum drying oven and dried at 70°C for 15 hours. This step aims to completely remove water and volatile impurities from the product, thereby obtaining pure and stable two-dimensional layered Ti3C2 nanosheets.

[0027] Preparation of Hf-MOF nanosheets Measure 1.113 g of anhydrous formic acid (HCOOH) and add it to a 20 mL upright vial. Ensure the vial is tightly capped and set aside.

[0028] In a 100 mL beaker, weigh 0.0434 mmol (14 mg) of hafnium tetrachloride (HfCl4). Then, add 5 mL of N,N-dimethylformamide (DMF) to the beaker. Ultrasonicate at room temperature to fully dissolve the hafnium tetrachloride in DMF until a clear solution forms.

[0029] Accurately weigh 0.0285 mmol (12.5 mg) of 1,3,5-tris(4-carboxyphenyl)benzene (H3BTB) and add it to the above solution. Ensure that the H3BTB is completely dissolved in the clear solution by gently stirring or sonicating again.

[0030] Carefully transfer the HfCl4 and H3BTB solution to the previously prepared upright vial containing formic acid. Next, add 120 µL of ultrapure water to the vial and mix again using an ultrasonic device to ensure uniform dispersion of all components.

[0031] After mixing is complete, seal the upright vial and place it in a forced-air drying oven. Set the heating temperature to 120 °C and maintain it for 48 hours to ensure sufficient reaction. After the reaction is complete, remove the material from the vial and centrifuge it for washing. First, wash it three times with N,N-dimethylformamide (DMF) to remove unreacted starting material and solvent. Then, wash it again three times with ethanol to further purify the product.

[0032] The washed material was transferred to a blast drying oven and dried at a heating temperature of 50 °C to obtain Hf-MOF nanosheets.

[0033] Preparation of Titanium Carbide-Based Two-Dimensional Layered Composite Membranes The titanium carbide-based two-dimensional layered composite membrane was prepared using a vacuum filtration device. 1 g of titanium carbide nanosheets was weighed and added to 500 ml of deionized water. Ultrasonication was performed for more than 2 hours to uniformly disperse the titanium carbide nanosheets. Then 0.1 g of Hf-MOF nanosheets was added and ultrasonication was continued for 2 hours to fully mix the two to obtain a mixed dispersion.

[0034] A hydrophilic polypropylene membrane was placed in a suction and filtration device. After being secured with a clamp, the mixed dispersion was poured into a sand core cup. The oil pump was turned on to filter until all the mixed dispersion was filtered. The Hf-MOF / Ti3C2 thin film prepared on the polypropylene membrane was removed and further dried in a vacuum oven at 80°C to obtain a flexible, independent Hf-MOF / Ti3C2 mixed film.

[0035] Figure 2 This is a cross-sectional SEM image of the prepared titanium carbide-based two-dimensional layered composite gas separation membrane. As can be seen, the titanium carbide-based two-dimensional layered composite gas separation membrane prepared by the present invention has a sheet-by-sheet stacking structure, achieving efficient separation of CO2 and N2. This principle primarily relies on the regular, controllable transmission channels and abundant surface functional groups formed by the two-dimensional nanosheet material. These properties enable the membrane material to effectively screen molecules of different sizes. During the gas separation process, CO2 and N2 molecules experience varying degrees of hindrance as they pass through the membrane material due to their differences in size and polarity, thus achieving separation. The advantage of this membrane material lies in its combination of the high permeability of Ti3C2 two-dimensional nanosheets and the excellent selectivity of Hf-MOF nanosheets, ensuring high gas separation efficiency while also possessing excellent mechanical strength and thermal stability. Furthermore, the sheet-by-sheet stacking structure simplifies the preparation process, reduces costs, and facilitates large-scale production, offering broad prospects for industrial applications.

[0036] Figure 3 The following is the N2 adsorption-desorption curve for the prepared titanium carbide-based two-dimensional layered composite gas separation membrane. The titanium carbide-based Hf-MOF / Ti3C2 composite membrane has a high specific surface area of ​​426 m² / g, which is greater than that of pure Ti3C2. This increased specific surface area provides more active sites and adsorption sites on the composite membrane surface. These sites play a key role in the separation process by more effectively capturing and adsorbing the target gas molecules, namely CO2. Since CO2 molecules have higher polarity and adsorbability than N2 molecules, the increased specific surface area enhances the composite membrane's selective adsorption capacity for CO2.

[0037] Secondly, the introduction of Hf-MOF further enhances the performance of the composite membrane. Hf-MOF, with its regular pore structure and excellent chemical stability, effectively complements the Ti3C2 two-dimensional material. This complementarity not only enhances the mechanical strength of the composite membrane but also optimizes its pore structure, making the diffusion and separation of gas molecules within the membrane more efficient.

[0038] In addition, the adsorption-desorption isotherm shows that the adsorption amount continues to increase before the relative pressure P / P0=0.4, and there is a slight hysteresis in the desorption process. This phenomenon indicates that there are some mesopores and macropores in the titanium carbide-based Hf-MOF / Ti3C2 composite membrane. These pore structures not only provide more adsorption sites for gas molecules, but also facilitate the diffusion and transmission of gas molecules within the material.

[0039] Figure 4 The permeation flux of two gases of 7μm titanium carbide based two-dimensional layered composite gas separation membrane at different pressures. Figure 4 It can be seen that under different test pressures, the CO2 gas permeation flux of the titanium carbide-based Hf-MOF / Ti3C2 composite membrane is much higher than that of N2.

[0040] Figure 5 The gas selectivity of titanium carbide based two-dimensional layered composite gas separation membrane under different membrane thickness conditions. Figure 5 It can be seen that at different membrane thicknesses, the carbon-titanium-based two-dimensional layered composite gas separation membrane has excellent gas separation selectivity.

[0041] Any matters not mentioned above shall be subject to the existing technology.

[0042] Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are for illustration only and are not intended to limit the scope of the present invention. Those skilled in the art of the present invention may make various modifications or additions to the described specific embodiments or replace them in similar ways, but they will not deviate from the direction of the present invention or exceed the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent replacements, improvements, etc. made to the above embodiments based on the technical essence of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a carbon-titanium based two-dimensional layered composite gas separation membrane, characterized in that: Titanium carbide nanosheets and Hf-MOF nanosheets are ultrasonically dispersed in ionized water to obtain a mixed dispersion, the mixed dispersion is poured into a sand core cup with a filter membrane for suction filtration, and dried to obtain an Hf-MOF / Ti3C2 thin film, i.e., a carbon-titanium-based two-dimensional layered composite gas separation membrane; Among them, Hf-MOF nanosheets are prepared by the following method: Hafnium tetrachloride and 1,3,5-tris(4-carboxyphenyl)benzene are dissolved in an organic solvent to form a mixed solution, which is then ultrasonically mixed with formic acid and ultrapure water, followed by heating for reaction, centrifugal washing, and drying to obtain Hf-MOF nanosheets.

2. The preparation method according to claim 1, wherein: The mass ratio of titanium carbide nanosheets to Hf-MOF nanosheets is 10-15:

1.

3. The preparation method according to claim 1, wherein: The thickness of the film is 2-11 μm.

4. The preparation method according to claim 1, wherein: The organic solvent is N,N-dimethylformamide, and the centrifugal washing is first washed with N,N-dimethylformamide three times to remove unreacted raw materials and solvent, and then washed again with ethanol three times to further purify the product.

5. The preparation method according to claim 1, wherein: Heat the reaction at 120-180°C for 36-48 hours.

6. The preparation method according to claim 1, wherein: Titanium carbide nanosheets were prepared by the following method: S1. Pour lithium fluoride into a hydrochloric acid solution and stir to obtain a solution; S2, immersing the Ti3AlC2 powder in the solution of step S1, heating and stirring, washing with deionized water, and centrifuging to obtain a precipitate; S3. Ultrasonic treatment is performed on the precipitate in step S2 with deionized water, and the supernatant is removed and then dried to obtain a Ti3C2 two-dimensional nanosheet material.

7. The preparation method according to claim 6, wherein: In step S1, the concentration of the hydrochloric acid solution is 9-12M; in step S1, the mass volume ratio of lithium fluoride to hydrochloric acid solution is 1-2 g: 10-30 mL; in step S1, stirring is performed at room temperature for 30-60 minutes.

8. The preparation method according to claim 6, characterized in that In step S2, the mass ratio of the Ti3AlC2 powder to lithium fluoride is 1 to 2:2; in step S2, the heating and stirring is stirring at 35°C for 24 hours; in step S2, the precipitate is centrifuged and washed with deionized water until it is neutral.

9. A carbon-titanium based two-dimensional layered composite gas separation membrane prepared by the preparation method according to any one of claims 1 to 8.

10. A use of the carbon-titanium based two-dimensional layered composite gas separation membrane according to claim 1, characterized in that: Used to separate CO2.

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