A hybrid matrix carbon molecular sieve membrane doped with metal nanoparticles, its preparation method and application

Abstract

This invention relates to a mixed-matrix carbon molecular sieve membrane doped with metal nanoparticles, its preparation method, and its application. The method includes the following steps: adding the metal salt to be doped into a spinning solution and mixing uniformly to obtain a spinning solution doped with metal salt, wherein the metal salt is selected from Pd, Cu, and Ag salts; preparing a cellulose mixed-matrix membrane doped with metal nanoparticles using a wet-dry spinning process to induce structural rearrangement during polymer pyrolysis, and obtaining a cellulose precursor membrane doped with metal nanoparticles through pyrolysis; and carbonizing the cellulose precursor membrane under inert gas protection to obtain a carbon molecular sieve membrane. Compared with existing technologies, this invention achieves uniform dispersion of inorganic metal ions in the precursor; the obtained carbon molecular sieve membrane exhibits high permeability and selectivity, which is of great significance for the design and preparation of highly selective hydrogen separation membranes.

Description

Technical Field

[0001] This invention relates to the field of hollow fiber carbon molecular sieve membrane technology for gas separation, and in particular to a mixed matrix carbon molecular sieve membrane doped with metal nanoparticles, its preparation method, and its application. Background Technology

[0002] Hydrogen energy boasts advantages such as cleanliness, high efficiency, high calorific value, and sustainability, making it a crucial direction for future energy structure transformation. Hydrogen production, separation, purification, transportation, and storage technologies are currently hot research topics. In the field of hydrogen separation and purification, membrane separation is a simple and efficient technique. Commonly used membrane materials include polymer membranes, palladium membranes, and carbon molecular sieve membranes. Among these, carbon molecular sieve membranes (CMSMs), an inorganic membrane material formed by the high-temperature carbonization of polymer membranes, have shown great promise in hydrogen separation and purification. CMSMs possess advantages such as high-temperature resistance, good chemical stability, and tunable pore size, and have demonstrated excellent separation selectivity in H2-related separations, such as H2 / CH4 and H2 / C2H4. However, due to the strong adsorption between carbon surfaces and CO2 molecules, the H2 / CO2 separation selectivity is relatively low, severely limiting its application in hydrogen production and purification processes. Therefore, achieving precise sieving of H2 and CO2 through microstructure control of carbon molecular sieve membranes has become a key aspect of current carbon molecular sieve membrane development. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a new approach for high-selectivity hydrogen separation membranes by adding a small amount of metal ions to a carbon molecular sieve membrane to induce structural rearrangement during polymer pyrolysis.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] The first aspect of this invention provides a method for preparing a mixed-matrix carbon molecular sieve membrane doped with metal nanoparticles, comprising the following steps:

[0006] S1: Add the metal salt to be doped to the spinning solution and mix evenly to obtain a spinning solution doped with metal salt, wherein the metal salt is selected from one of Pd salt, Cu salt, and Ag salt;

[0007] S2: Based on the spinning solution doped with metal salts obtained in S1, a cellulose mixed matrix membrane doped with metal nanoparticles is prepared by dry and wet spinning process, thereby inducing structural rearrangement during polymer pyrolysis and obtaining a cellulose precursor membrane doped with metal nanoparticles through pyrolysis.

[0008] S3: Under the protection of an inert gas, the cellulose precursor membrane is carbonized to obtain a carbon molecular sieve membrane.

[0009] Furthermore, in S1, the metal salt is a Pd salt.

[0010] Furthermore, in S1, the metal salt is preferably palladium acetate.

[0011] Further, in S1, the spinning solution comprises: 8 wt% to 15 wt% microcrystalline cellulose, 20 wt% to 70 wt% organic solvent, and 20 wt% to 70 wt% ionic liquid. The percentage of each component is based on the weight of the spinning solution, and the sum of the total percentages of all components is 100 wt%.

[0012] Furthermore, in S1, the doping ratio of the metal salt is 2wt% to 5wt% of the weight of the spinning solution.

[0013] Further, the organic solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, N-methylmorpholine oxide, and dimethyl sulfoxide.

[0014] Furthermore, the ionic liquid is one or more of 1-allyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, and 1-ethyl-3-methylimidazolium acetate, and the metal salt anion is kept consistent with the anion of the ionic liquid.

[0015] Furthermore, in S2, the spinning conditions include: the spinning solution temperature, core solution temperature, and coagulation bath temperature are all 15℃~30℃; the spinning solution flow rate is 1~20ml / min; the core solution flow rate is 1~10ml / min; the height of the spinning head from the water surface is 3~20cm; the drawing speed is 5~15m / min; and the winding speed is 5~30m / min.

[0016] Further, in S2, in the wet-dry spinning process: the cellulose precursor membrane is heated to 100-150°C at a heating rate of 5-10°C per minute and held for 60-120 minutes, then heated to 300-400°C at a heating rate of 5-10°C per minute and held for 60-120 minutes, and finally heated to 550-850°C at a heating rate of 5-10°C per minute and held for 60-120 minutes;

[0017] The heating atmosphere is nitrogen or argon.

[0018] A second aspect of the present invention provides a mixed matrix carbon molecular sieve membrane with doped metal nanoparticles prepared by the method described above.

[0019] A third aspect of the present invention provides an application of a mixed matrix carbon molecular sieve membrane with doped metal nanoparticles as described above in gas separation.

[0020] The present invention has the following beneficial effects:

[0021] This invention provides a method for preparing a carbon molecular sieve membrane with a mixed matrix doped with metal nanoparticles. Addressing the relatively low H2 / CO2 separation selectivity of carbon molecular sieve membranes, which severely limits their application in hydrogen production and purification processes, this invention introduces inorganic metal nanoparticles into cellulose, inducing structural rearrangement during polymer pyrolysis. A carbon molecular sieve membrane with metal nanoparticles as a precursor is obtained through high-temperature pyrolysis. By controlling the addition of the metal salt to be identical to the anion in the ionic liquid, uniform dispersion of inorganic metal ions in the precursor is achieved. The carbon molecular sieve membrane obtained by this invention exhibits high permeability and selectivity, primarily due to the simultaneous utilization of the carbon molecular sieve membrane itself and the selective adsorption of inorganic particles to achieve rapid and selective transfer of target molecules. Furthermore, the introduction of metal nanoparticles alters the local microenvironment of the carbon molecular sieve membrane, transforming the pore structure from micropores to ultramicropores. This is of significant importance for the design and preparation of highly selective hydrogen separation membranes. Attached Figure Description

[0022] Figure 1 SEM images of the carbon molecular sieve membranes prepared in Examples 1-10;

[0023] Figure 2 XPS images of C1s of the carbon molecular sieve membranes prepared in Examples 1, 3, and 5, for Comparative Example 1;

[0024] Figure 3 XPS images of Pd3d of the carbon molecular sieve membranes prepared in Examples 1, 3, and 5;

[0025] Figure 4 Raman spectra of the carbon molecular sieve membranes prepared in Examples 1, 3, and 5, for Comparative Example 1;

[0026] Figure 5 XRD curves of carbon molecular sieve membranes prepared in Examples 1, 3, and 5 are shown in Comparative Example 1.

[0027] Figure 6 The TEM and electron diffraction spectra of the carbon molecular sieve membrane prepared in Example 3 are shown.

[0028] Figure 7-8 The BET test curves for the carbon molecular sieve membranes prepared in Comparative Examples 1-2 and Examples 3-4 are shown below. Figure 7 The adsorption curve is shown. Figure 8 This is the aperture distribution curve. Detailed Implementation

[0029] The method for preparing a mixed-matrix carbon molecular sieve membrane doped with metal nanoparticles in this invention includes the following steps:

[0030] S1: Add the metal salt to be doped to the mixture of organic solvent and ionic liquid in a certain proportion and mix evenly. Then, add microcrystalline cellulose as a precursor to the mixed solution and place it in a mixer at 55-70℃ for 12-24 hours.

[0031] S2: Prepare a cellulose mixed matrix membrane doped with metal nanoparticles by using the spinning solution through a dry and wet spinning process.

[0032] S3: After drying and cutting the cellulose precursor membrane, place it in a tube furnace and purge it with an inert gas for protection. Heat it from room temperature to 550-850℃ at a certain heating rate curve and hold for 60-120 minutes. Then allow it to cool naturally to obtain a carbon molecular sieve membrane with metal nanoparticles doped with cellulose as the precursor.

[0033] In S1, the spinning solution contains 8% to 15% by weight of microcrystalline cellulose, 20% to 70% by weight of organic solvent, and 20% to 70% by weight of ionic liquid. The weight percentages of each are based on the total weight of the spinning solution and are equal to 100% by weight when added together as the spinning solution.

[0034] In S1, the metal salt to be doped is 1% to 10% by weight of the precursor microcrystalline cellulose.

[0035] In S1, the organic solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, N-methylmorpholine oxide, and dimethyl sulfoxide.

[0036] In S1, the ionic liquid is one or more of 1-allyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, and 1-ethyl-3-methylimidazolium acetate.

[0037] In S2, the combination of spinning conditions includes spinning solution temperature, core solution temperature, and coagulation bath temperature all being 15°C to 30°C, spinning solution flow rate being 1 to 20 ml / min, core solution flow rate being 1 to 10 ml / min, spinning head height from water surface being 3 to 20 cm, drawing speed being 5 to 15 m / min, and winding speed being 5 to 30 m / min.

[0038] In step S3, the carbonization treatment of the cellulose precursor membrane specifically involves heating the polycellulose precursor membrane to 100-150°C at a heating rate of 5-10°C per minute and holding it for 60-120 minutes, then heating it to 300-400°C at a heating rate of 5-10°C per minute and holding it for 60-120 minutes, and finally heating it to 550-850°C at a heating rate of 5-10°C per minute and holding it for 60-120 minutes. The pyrolysis atmosphere is an inert gas such as nitrogen or argon.

[0039] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Any preparation methods, materials, structures, or compositional ratios not explicitly described in this technical solution are considered common technical features disclosed in the prior art.

[0040] To further understand the present invention, the present invention will be described below with reference to embodiments. These descriptions are only for further explaining the features and advantages of the present invention and are not intended to limit the claims of the present invention.

[0041] Any percentage content not explicitly stated can be considered as a percentage by mass.

[0042] The following examples illustrate a method for preparing carbon molecular sieve membranes using microcrystalline cellulose, dimethyl sulfoxide, and 1-ethyl-3-methylimidazolium acetate as spinning solutions, including the following steps:

[0043] (1) Preparation of spinning solution: Add 300g of dimethyl sulfoxide and 100g of 1-ethyl-3-methylimidazolium acetate successively, followed by metal acetate, the mass of which is 1%-10% of the mass of the precursor cellulose to be added. Stir magnetically at room temperature for 2-8 hours. After stirring evenly, add 54.54g of microcrystalline cellulose in 6 portions to the above solution gradually, stirring simultaneously to prevent cellulose agglomeration. Then place the above solution in a mixer and maintain at 55-70℃ for 12-24 hours.

[0044] (2) Precursor membrane preparation: The spinning solution is placed in the spinning machine's storage tank, and the internal temperature is controlled at 50-55℃ for 10-16 hours using an externally wound thermocouple. Simultaneously, a vacuum is drawn to remove air bubbles from the solution. After the internal liquid cools to room temperature, a dry-jet wet spinning process is used to manufacture the hollow fiber membrane. The spinning conditions are as follows: deionized water is used as the non-solvent for the core solution; the spinning solution temperature, core solution temperature, and coagulation bath temperature are 15℃ to 30℃; the spinning solution flow rate is 2 to 5 ml / min; the core solution flow rate is 1.5 to 3 ml / min; the height of the spinning head from the water surface is 3 to 10 cm; the drawing rate is 8 to 12 m / min; and the winding rate is 8 to 15 m / min. After spinning, the fiber membrane is soaked in water for 3 days, with the water changed every 24 hours to remove residual solvent from the membrane surface.

[0045] (3) Preparation of carbon molecular sieve membrane: The fiber membrane is removed from the water and suspended in the air to dry the moisture inside the membrane. A weight is attached to the other end to prevent the membrane from curling. The cellulose precursor membrane is then heated to 100-150℃ at a heating rate of 5-10℃ per minute and held for 60-120 minutes. Next, it is heated to 300-400℃ at a heating rate of 5-10℃ per minute and held for 60-120 minutes. Finally, it is heated to 550-850℃ at a heating rate of 5-10℃ per minute and held for 60-120 minutes. The membrane is then allowed to cool naturally. The pyrolysis atmosphere is an inert gas such as nitrogen or argon to obtain the carbon molecular sieve membrane.

[0046] The gas permeation characteristics of a membrane can be determined using gas permeation experiments. Two intrinsic properties can be used to evaluate the separation performance of a membrane: its "permeability," i.e., a measure of the membrane's intrinsic productivity; and its "selectivity," i.e., a measure of the membrane's separation efficiency. These properties are typically determined using Barrer (1 Barrer = 10⁻⁶). -10 [cm 3 (STP)] / [cm 2 The "permeability" of the s cmHg meter can be calculated as flux (n i Divide by the partial pressure difference between the upstream and downstream of the membrane (Δp) i And multiply by the thickness of the film (l).

[0047]

[0048] Another term, “permeance,” is defined in this application as the productivity of hollow fiber membranes and is typically expressed in gas permeation units (GPUs) (1 GPU = 10^6). -6 [cm 3 (STP)] / [cm 2 [s cmHg], which is determined by dividing the permeability by the effective membrane separation layer thickness.

[0049]

[0050] Finally, "selectivity" in this application is defined as the ability of a gas to permeate through a membrane or the permeability relative to another gas of the same nature. It is measured as a dimensionless ratio.

[0051]

[0052] Comparative Example 1

[0053] Preparation of pure cellulose carbon molecular sieve membranes

[0054] (1) Preparation of spinning solution

[0055] First, add 300g of dimethyl sulfoxide. Then, gradually add 54.54g of microcrystalline cellulose to the above solution in 6 portions, stirring simultaneously to prevent cellulose agglomeration. After the addition is complete, add 100g of 1-ethyl-3-methylimidazolium acetate. Finally, place the above solution in a mixer and maintain it at 60°C for 12 hours.

[0056] (2) Preparation of precursor membrane

[0057] The spinning solution was placed in the spinning machine's storage tank, and the internal temperature was maintained at 50-55℃ for 12 hours using an externally wound thermocouple. Simultaneously, a vacuum was drawn to remove air bubbles from the solution. After the internal liquid cooled to room temperature, hollow fiber membranes were manufactured using a dry-jet wet spinning process. Spinning conditions included: deionized water as the non-solvent for the core solution; spinning solution temperature, core solution temperature, and coagulation bath temperature all at 20℃; spinning solution flow rate of 3.5 ml / min; core solution flow rate of 2.5 ml / min; spinning head height above the water surface of 5 cm; drawing speed of 8.5 m / min; and winding speed of 9.35 m / min. After spinning, the fiber membrane was soaked in water for 3 days, with the water changed every 24 hours to remove residual solvent from the membrane surface.

[0058] (3) Preparation of CMS-600℃ membrane

[0059] The fiber membrane was removed from the water and suspended in the air to dry the moisture inside. A weight was attached to the other end to prevent the membrane from curling. The precursor membrane was cut and placed in a tube furnace, evacuated for 2 hours, and then purged with nitrogen for 30 minutes at a flow rate of 60-70 mL / min. The cellulose precursor membrane was then heated to 120°C at a rate of 5°C per minute and held for 120 minutes, followed by a rate of 10°C per minute to 340°C and held for 60 minutes, and finally heated to 600°C at a rate of 5°C per minute and held for 120 minutes. After natural cooling, the CMS-600°C carbon molecular sieve membrane was obtained.

[0060] Comparative Example 2

[0061] (1) The preparation of the spinning solution is the same as step (1) in Example 1.

[0062] (2) The preparation of the precursor membrane is the same as step (2) in Example 1.

[0063] (3) Preparation of CMS-700℃ membrane

[0064] The fiber membrane was removed from the water and suspended in the air to dry the moisture inside. A weight was attached to the other end to prevent the membrane from curling. The precursor membrane was cut and placed in a tube furnace, evacuated for 2 hours, and then purged with nitrogen for 30 minutes at a flow rate of 60-70 mL / min. The cellulose precursor membrane was then heated to 120°C at a rate of 5°C per minute and held for 120 minutes, followed by a rate of 10°C per minute to 340°C and held for 60 minutes, and finally heated to 700°C at a rate of 5°C per minute and held for 120 minutes. After natural cooling, the CMS-700°C carbon molecular sieve membrane was obtained.

[0065] Example 1

[0066] (1) Preparation of spinning solution with 2% palladium acetate doping

[0067] 300g of dimethyl sulfoxide and 100g of 1-ethyl-3-methylimidazolium acetate were added sequentially, followed by palladium acetate, with the mass of palladium acetate being 2% of the mass of the precursor cellulose to be added. The mixture was magnetically stirred at room temperature for 4 hours until homogeneous. Then, 54.54g of microcrystalline cellulose was added to the solution in six portions, stirring continuously during the addition process to prevent cellulose agglomeration. The solution was then placed in a homogenizer and maintained at 60°C for 12 hours.

[0068] (2) Preparation of precursor membrane

[0069] The spinning solution was placed in the spinning machine's storage tank, and the internal temperature was maintained at 50-55℃ for 12 hours using an externally wound thermocouple. Simultaneously, a vacuum was drawn to remove air bubbles from the solution. After the internal liquid cooled to room temperature, hollow fiber membranes were manufactured using a dry-jet wet spinning process. Spinning conditions included: deionized water as the non-solvent for the core solution; spinning solution temperature, core solution temperature, and coagulation bath temperature all at 20℃; spinning solution flow rate at 3.5 ml / min; core solution flow rate at 2.5 ml / min; spinneret height above the water surface at 5 cm; drawing speed at 8.5 m / min; and winding speed at 9.35 m / min. After spinning, the fiber membrane was soaked in water for 3 days, with the water changed every 24 hours to remove residual solvent from the membrane surface.

[0070] (3) Preparation of CMS-600℃ membrane

[0071] The fiber membrane was removed from the water and suspended in the air to dry the moisture inside. A weight was attached to the other end to prevent the membrane from curling. The precursor membrane was cut and placed in a tube furnace, evacuated for 2 hours, and then purged with nitrogen for 30 minutes at a flow rate of 60-70 mL / min. The cellulose precursor membrane was then heated to 120°C at a rate of 5°C per minute and held for 120 minutes, followed by a rate of 10°C per minute to 340°C and held for 60 minutes, and finally heated to 600°C at a rate of 5°C per minute and held for 120 minutes. After natural cooling, the CMS-600°C carbon molecular sieve membrane was obtained.

[0072] Example 2

[0073] (1) The spinning solution with 2% palladium acetate doping was prepared in the same way as step (1) in Example 1.

[0074] (2) The preparation of the precursor membrane is the same as step (2) in Example 1.

[0075] (3) Preparation of CMS-700℃ membrane

[0076] The fiber membrane was removed from the water and suspended in the air to dry the moisture inside. A weight was attached to the other end to prevent the membrane from curling. The precursor membrane was cut and placed in a tube furnace, evacuated for 2 hours, and then purged with nitrogen for 30 minutes at a flow rate of 60-70 mL / min. The cellulose precursor membrane was then heated to 120°C at a rate of 5°C per minute and held for 120 minutes, followed by a rate of 10°C per minute to 340°C and held for 60 minutes, and finally heated to 700°C at a rate of 5°C per minute and held for 120 minutes. After natural cooling, the CMS-700°C carbon molecular sieve membrane was obtained.

[0077] Example 3

[0078] (1) Preparation of spinning solution with 3.5% palladium acetate doping

[0079] 300g of dimethyl sulfoxide and 100g of 1-ethyl-3-methylimidazolium acetate were added sequentially, followed by palladium acetate, the mass of which was 3.5% of the mass of the precursor cellulose to be added. The mixture was magnetically stirred at room temperature for 4 hours until homogeneous. Then, 54.54g of microcrystalline cellulose was added to the solution in six portions, stirring continuously during the addition to prevent cellulose agglomeration. The solution was then placed in a homogenizer and maintained at 60°C for 12 hours.

[0080] (2) The preparation of the precursor membrane is the same as step (2) in Example 1.

[0081] (3) The preparation of CMS-600℃ membrane is the same as step (3) in Example 1.

[0082] Example 4

[0083] (1) The spinning solution with 3.5% palladium acetate doping was prepared in the same way as step (1) in Example 3.

[0084] (2) The preparation of the precursor membrane is the same as step (2) in Example 1.

[0085] (3) The preparation of the CMS-700℃ membrane is the same as step (3) in Example 2.

[0086] Example 5

[0087] (1) Preparation of spinning solution with 5% palladium acetate doping

[0088] 300g of dimethyl sulfoxide and 100g of 1-ethyl-3-methylimidazolium acetate were added sequentially, followed by palladium acetate, the mass of which was 5% of the mass of the precursor cellulose to be added. The mixture was magnetically stirred at room temperature for 4 hours until homogeneous. Then, 54.54g of microcrystalline cellulose was added to the solution in six portions, stirring continuously during the addition to prevent cellulose agglomeration. The solution was then placed in a homogenizer and maintained at 60°C for 12 hours.

[0089] (2) The preparation of the precursor membrane is the same as step (2) in Example 1.

[0090] (3) The preparation of CMS-600℃ membrane is the same as step (3) in Example 1.

[0091] Example 6

[0092] (1) The spinning solution with 5% palladium acetate doping was prepared in the same way as step (1) in Example 5.

[0093] (2) The preparation of the precursor membrane is the same as step (2) in Example 1.

[0094] (3) The preparation of the CMS-700℃ membrane is the same as step (3) in Example 2.

[0095] Example 7

[0096] (1) Preparation of spinning solution with 2.57% silver acetate doping

[0097] 300g of dimethyl sulfoxide and 100g of 1-ethyl-3-methylimidazolium acetate were added sequentially, followed by silver acetate. The mass of silver acetate was 2.57% of the mass of the precursor cellulose to be added, in order to control the amount of silver ions added to be the same as the amount of palladium acetate ions added when 3.5% of the precursor cellulose mass was added. The mixture was magnetically stirred at room temperature for 4 hours. After homogenization, 54.54g of microcrystalline cellulose was gradually added to the above solution in 6 portions, with stirring during the addition process to prevent cellulose agglomeration. The solution was then placed in a mixer and kept at 60°C for 12 hours.

[0098] (2) The preparation of the precursor membrane is the same as step (2) in Example 1.

[0099] (3) The preparation of CMS-600℃ membrane is the same as step (3) in Example 1.

[0100] Example 8

[0101] (1) The spinning solution with 2.57% silver acetate doping was prepared in the same way as step (1) in Example 7.

[0102] (2) The preparation of the precursor membrane is the same as step (2) in Example 1.

[0103] (3) The preparation of the CMS-700℃ membrane is the same as step (3) in Example 2.

[0104] Example 9

[0105] (1) Preparation of spinning solution with 4.74% copper acetate doping

[0106] 300g of dimethyl sulfoxide and 100g of 1-ethyl-3-methylimidazolium acetate were added sequentially, followed by copper acetate. The mass of copper acetate was 4.74% of the mass of the precursor cellulose to be added, in order to control the amount of copper ions added to be the same as the amount of palladium acetate ions added when 3.5% of the precursor cellulose mass was added. The mixture was magnetically stirred at room temperature for 4 hours. After homogenization, 54.54g of microcrystalline cellulose was gradually added to the above solution in 6 portions, with stirring during the addition process to prevent cellulose agglomeration. The solution was then placed in a mixer and kept at 60°C for 12 hours.

[0107] (2) The preparation of the precursor membrane is the same as step (2) in Example 1.

[0108] (3) The preparation of CMS-600℃ membrane is the same as step (3) in Example 1.

[0109] Example 10

[0110] (1) The spinning solution with 4.74% copper acetate doping was prepared in the same way as step (1) in Example 7.

[0111] (2) The preparation of the precursor membrane is the same as step (2) in Example 1.

[0112] (3) The preparation of the CMS-700℃ membrane is the same as step (3) in Example 2.

[0113] Verification Example 1

[0114] The following results were achieved through various characterization methods:

[0115] Figure 1 These are SEM images of the carbon molecular sieve membranes prepared in Examples 1-10 of this invention;

[0116] Figure 2 XPS plots of C1s of the carbon molecular sieve membranes prepared in Comparative Example 1, Examples 1, 3, and 5 of this invention. 2 / sp 3 The hybrid carbon ratio decreased from 2.125 in the pure film to 2.012 with 3.5% palladium acetate doping, and then increased to 2.065 with increasing doping concentration. The gradual addition of palladium nanoparticles induced a localized structural rearrangement of the carbon molecular sieve film, confining the palladium nanoparticles around the carbon and transforming them towards graphitic carbon, resulting in a denser film structure and gradually increased selectivity. However, excessive doping led to a decrease in the amount of graphitic carbon, thus causing a decline in selectivity.

[0117] Figure 3 These are XPS images of Pd3d of the carbon molecular sieve membranes prepared in Examples 1, 3, and 5 of this invention. 0 At 340.6 eV, it corresponds to Pd3d 3 / 2 The orbital corresponds to Pd3d at 335.2 eV. 5 / 2 Track; Pd 2+ At 342.9 eV, it corresponds to Pd3d 3 / 2 The orbital corresponds to Pd3d at 336.8 eV. 5 / 2 track.

[0118] Figure 4 Raman spectra of the carbon molecular sieve membranes prepared in Comparative Example 1, Examples 1, 3, and 5. When the temperature is increased to 600°C, the Raman spectrum at 1340 cm⁻¹... -1 (D belt) and 1590cm -1 A new Raman scattering peak appeared at the (G band) position, indicating the presence of defective graphitic carbon in the membrane material, i.e., the gradual formation of a carbon molecular sieve membrane. D / l G The ratio also shows a trend of first decreasing and then increasing, consistent with the XPS data, proving that the addition of palladium can promote the transformation of amorphous carbon into graphitic carbon.

[0119] Figure 5 The XRD curves of the carbon molecular sieve membranes prepared in Examples 1, 3, and 5 are shown for Comparative Example 1. A new diffraction peak appears at a 2θ position of 21-23°, corresponding to the (002) plane of graphite. With the addition of palladium, the diffraction angle first increases and then decreases, while the interlayer spacing decreases and then increases. Similarly, the interlayer spacing is smallest at 3.5% doping concentration, at which point the selectivity is best. This demonstrates that the addition of inorganic metal nanoparticles can transform the radial micropores of the carbon molecular sieve membrane.

[0120] Figure 6The figures show the TEM and electron diffraction spectra of the carbon molecular sieve membrane prepared in Example 3. As can be seen from the figures, the crystal form of palladium can be clearly observed, and the carbon around the palladium also develops towards short-range order. The appearance of the ordered carbon layer structure lengthens the diffusion path of the gas during the transport process, which is beneficial to the improvement of selectivity.

[0121] Figure 7-8 The BET test curves for the carbon molecular sieve membranes prepared in Comparative Examples 1-2 and Examples 3-4 are shown below. Figure 7 The adsorption curve is shown. Figure 8 The figure shows the pore size distribution curve. It can be seen that with the addition of palladium, the adsorption of carbon dioxide and methane by the carbon molecular sieve membrane is reduced, and the pore size distribution changes from micropores to ultramicropores.

[0122] Tables 1 and 2 show the gas separation performance of the carbon molecular sieve membranes prepared in Comparative Examples 1-2 and Examples 1-6 of this invention:

[0123] Table 1 shows the gas permeation performance and selectivity of the 600°C carbon carbide molecular sieve membrane.

[0124]

[0125]

[0126] Table 2 shows the gas permeation performance and selectivity of the 600°C carbon carbide molecular sieve membrane.

[0127]

[0128] As shown in Tables 1 and 2, doping the precursor with inorganic palladium nanoparticles significantly improves the selectivity of the carbon molecular sieve membrane. The selectivity increases substantially with increasing carbonization temperature. This is mainly because it utilizes both the carbon molecular sieve membrane itself and the selective adsorption of inorganic particles to achieve rapid selective transport of target molecules. Furthermore, the introduction of metal nanoparticles alters the local microenvironment of the carbon molecular sieve membrane, transforming the pore structure from micropores to ultramicropores.

[0129] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a mixed matrix carbon molecular sieve membrane doped with metal nanoparticles, characterized in that, Includes the following steps: S1: The metal salt to be doped is added to the spinning solution and mixed evenly to obtain a spinning solution doped with metal salt, wherein the metal salt is a Pd salt; the doping ratio of the metal salt is 2wt% to 5wt% of the weight of the spinning solution; the spinning solution contains an ionic liquid, and the metal salt anion is kept consistent with the ionic liquid anion. S2: Based on the spinning solution doped with metal salts obtained in S1, a cellulose mixed matrix membrane doped with metal nanoparticles is prepared by dry and wet spinning process, thereby inducing structural rearrangement during polymer pyrolysis and obtaining a cellulose precursor membrane doped with metal nanoparticles through pyrolysis. S3: Under the protection of an inert gas, the cellulose precursor membrane is carbonized to obtain a carbon molecular sieve membrane.

2. The preparation method according to claim 1, characterized in that, In S1, the spinning solution contains: 8wt% to 15wt% microcrystalline cellulose, 20wt% to 70wt% organic solvent, and 20wt% to 70wt% ionic liquid. The percentage of each component is based on the weight of the spinning solution, and the sum of the percentages of all components is 100wt%.

3. The preparation method according to claim 2, characterized in that, The organic solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, N-methylmorpholine oxide, and dimethyl sulfoxide.

4. The preparation method according to claim 2, characterized in that, The ionic liquid is one or more of 1-allyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, and 1-ethyl-3-methylimidazolium acetate.

5. The preparation method according to claim 1, characterized in that, In S2, the spinning conditions include: the spinning solution temperature, core solution temperature, and coagulation bath temperature are all 15°C to 30°C; the spinning solution flow rate is 1 to 20 ml / min; the core solution flow rate is 1 to 10 ml / min; the height of the spinning head from the water surface is 3 to 20 cm; the drawing speed is 5 to 15 m / min; and the winding speed is 5 to 30 m / min.

6. The preparation method according to claim 1, characterized in that, In S2, during the wet-dry spinning process: the cellulose precursor membrane is heated to 100-150°C at a heating rate of 5-10°C per minute and held for 60-120 minutes, then heated to 300-400°C at a heating rate of 5-10°C per minute and held for 60-120 minutes, and finally heated to 550-850°C at a heating rate of 5-10°C per minute and held for 60-120 minutes; the heating atmosphere is nitrogen or argon.

7. A mixed matrix carbon molecular sieve membrane with doped metal nanoparticles prepared by the method according to any one of claims 1 to 6.

8. The application of a hybrid matrix carbon molecular sieve membrane doped with metal nanoparticles as described in claim 7 in gas separation.

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