Preparation method and application of dual-network CO2 separation membrane

Abstract

The invention relates to a preparation method and application of a dual-network CO2 separation membrane, and belongs to the field of gas separation membranes. The invention provides an innovative research thought and a preparation method. The preparation method comprises the following experimental steps: (1) molecular design and synthesis of a diamine monomer containing carboxyl and alkynyl; (2) synthesizing a TB polymer containing carboxyl and alkynyl; and (3) constructing the dual-network CO2 separation membrane by combining metal coordination and covalent bond cooperation and a gradual cross-linking strategy. The invention successfully develops a novel membrane material integrating high permeability, high selectivity and excellent aging resistance, and breaks through the traditional trade-off effect. The permeability coefficient of CO2 is larger than or equal to 150 Barrer, the selectivity coefficient of CO2 / N2 and CO2 / CH4 is larger than or equal to 50, in a 50-day aging data test, the CO2 permeability coefficient of the dual-network type CO2 separation membrane is only reduced by 2.6%, and the dual-network type CO2 separation membrane has good stability.

Description

[0001] The invention relates to a high-performance double-network CO2 separation membrane for separating CO2 and a preparation method and application thereof, belonging to the field of membrane separation. Background Art

[0003] Although CO2 separation membrane technology has shown great application potential, it still faces many challenges. As a clean and low-carbon technology, membrane CO2 separation technology has attracted widespread social attention and has shown great potential in large-scale CO2 capture.

[0004] At present, the separation and purification of CO2 can be achieved through a variety of methods, mainly adsorption, cryogenic separation technology, pressure swing adsorption (PSA), membrane permeation separation technology, etc. The adsorption method uses the selective adsorption ability of adsorbents to separate CO2. Commonly used adsorbents include activated carbon, molecular sieves, porous ceramics, and porous materials such as zeolites and alumina. The advantages of the adsorption method are simple process and low energy consumption, but the regeneration and waste treatment of the adsorbent are issues that need to be considered. Cryogenic separation technology is a low-temperature distillation method that converts CO2 into liquid or supercritical fluid, and then separates it. It requires multiple solidification separations to achieve a higher purity, so the investment and energy consumption are very high; the CO2 obtained by the PSA method is highly purified, but the adsorption capacity is limited, a large amount of adsorbent is required, and adsorption and desorption are frequent, requiring a high degree of automation. Gas membrane separation technology, relying on its principle of using the partial pressure difference of gas molecules on both sides of the membrane as mass transfer power, and the difference in the permeation rate of different gases through the membrane material to achieve component separation, shows unique technical advantages. This technology not only occupies a small area, is easy to operate and is green and environmentally friendly, but also because of its pollution-free characteristics, it has shown extremely broad application prospects and huge potential in the field of CO2 separation.

[0005] In recent years, polymer materials have exploded, and a variety of materials have provided a good foundation for membrane separation. Polymer membranes dominate the CO2 separation membrane market due to their excellent flexibility, film-forming properties, and gas separation performance. Membrane separation mainly relies on synthetic polymer materials with customizable gas transmission properties. Although polymer membranes are widely used in many fields, there are still many problems in achieving efficient separation of CO2 and other gases such as N2. The kinetic diameter and N2 and CH4 Similar, traditional polymer membranes have low selectivity for CO2, which limits their application in CO2 separation. Since CO2 is a polar gas, its special chemical properties often easily cause aging of polymer membranes and may cause plasticization of the membrane, thus affecting the stability and separation performance of the membrane material. Polyimide materials derived from aromatic dianhydrides and diamines are one of the gas separation application materials with the best comprehensive performance. Polyimide membranes have good thermal stability, chemical stability, excellent mechanical properties and high free volume, which enable them to exhibit good gas selectivity and permeability. However, the separation efficiency of key gas pairs such as CO2 / N2 and CO2 / CH4 on the current market still needs to be improved. This limitation constitutes a major challenge in its widespread promotion and application in industry. Summary of the invention

[0006] In order to solve the problems of low separation efficiency, poor selectivity, easy aging, etc. in CO2 separation membranes, the present invention provides a double network CO2 separation membrane, which has the following polymer structure:

[0007]

[0008] Wherein n is 20 to 45, the number average molecular weight of the polymer is 20,000 to 40,000 g / mol, and the spheres are metal ions.

[0009] In one embodiment, the double network type CO2 separation membrane is obtained by metal coordination and covalent cross-linking of TB polymer containing alkyne groups and carboxyl groups;

[0010] The metal coordination comprises: dissolving the TB polymer containing alkyne groups and carboxyl groups in an organic solution of metal ions to carry out metal coordination to obtain a metal coordinated CO2 separation membrane;

[0011] The covalent cross-linking is as follows: the metal coordination type CO2 separation membrane is heated to perform covalent cross-linking to obtain a double network type CO2 separation membrane.

[0012] In one embodiment, the TB polymer containing carboxyl and alkyne groups has the following structure:

[0013]

[0014] wherein n is 20 to 45, and the number average molecular weight of the polymer is 20,000 to 40,000 g / mol;

[0015] The polymer containing alkynyl and carboxyl groups is obtained by reacting a diamine monomer containing alkynyl and carboxyl groups with formaldehyde dimethyl acetal in a trifluoroacetic acid solvent.

[0016] In one embodiment, the diamine monomer containing an alkynyl group and a carboxyl group has the following structural formula:

[0017]

[0018] The invention provides an innovative polymer material, which has similarities in structure to polyimide, and at the same time, the polymer combines the rigid structure of Troger base and the unique three-dimensional structure of triptycene. This unique molecular design includes the excellent performance of polyimide, and further significantly improves the gas separation performance of the material by introducing the TB rigid structure and triptycene structure. The invention prepares a cross-linkable TB polymer by designing and synthesizing carboxyl and alkynyl diamine monomers, polymerizing the carboxyl and alkynyl diamine monomers. "Combining metal coordination and covalent bonding, step-by-step cross-linking strategy" to construct a double network type CO2 separation membrane. Each unit of the polymer chain contains a triptycene structure and a rigid V-shaped bridge, which forms a large free volume inside the polymer membrane and improves the CO2 permeability coefficient. On the other hand, the coordination network and the cross-linking network further adjust the pore size and improve the CO2 / N2 and CO2 / CH4 selectivity; the construction of a double network structure and the introduction of large volume groups work synergistically to prepare a CO2 separation membrane with a novel structure and excellent performance. Finally, the fully aromatic network polymer formed by covalent cross-linking can inhibit the spontaneous creeping and relaxation of polymer chains over time, achieving the purpose of anti-aging, and pore expansion will occur to improve gas permeability. The coordination network formed can improve gas permeability and selectivity, successfully breaking the inherent trade-off effect between gas permeability and selectivity, namely the "trade-off" effect.

[0019] The dual-network CO2 separation membrane of the present invention has high selectivity in the application system of separating CO2 / N2 and CO2 / CH4, and also has good permeability to CO2, and the separated CO2 has high purity. In the 50-day aging data test, the CO2 permeability coefficient of the uncross-linked CO2 separation membrane dropped from 105.8 Barrer to 60.4 Barrer, and the permeability coefficient decreased by 42.9%; while the CO2 permeability coefficient of the dual-network CO2 separation membrane dropped from 158.6 Barrer to 154.4 Barrer, and the permeability coefficient decreased by 2.6%, and it has good stability.

[0020] The second object of the present invention is to provide a method for preparing a CO2 separation membrane:

[0021] Step 1, metal coordination: at 25-30°C, dissolve the TB polymer containing alkynyl and carboxyl groups in an organic solution of metal ions to obtain a casting solution, evenly apply the casting solution on the base film for coordination, and dry at 60°C to obtain a metal coordination type CO2 separation membrane;

[0022] Step 2, covalent crosslinking: Place the metal coordination CO2 separation membrane in a tubular furnace, and perform covalent crosslinking at a target temperature of 140-200°C at a heating rate of 5°C / min under a nitrogen atmosphere, and cool it to room temperature at a rate of 10°C / min to obtain a double-network CO2 separation membrane.

[0023] In one embodiment, the step 1 is specifically as follows: at room temperature, anhydrous ferric chloride is dissolved in an organic solvent to prepare a uniformly dispersed metal ion solution; TB polymer containing alkynyl and carboxyl groups is dissolved in the above metal ion solution, stirred at room temperature for 6 to 12 hours to obtain a casting solution in which the metal ions are uniformly dispersed, the selective layer is deposited on a polytetrafluoroethylene-based membrane with a pore size of 0.1 to 1 μm by coating, and dried in an oven to obtain a metal cross-linked CO2 separation membrane with a selective layer thickness of 10 to 20 μm.

[0024] In one embodiment, step 2 is specifically as follows: cut the metal cross-linked CO2 separation membrane into a rectangle of 6 cm × 4 cm and place it in a tubular furnace, use ceramic sheets to clamp the membrane to prevent deformation during the heating process, and in a nitrogen atmosphere, heat at a rate of 5°C / min, keep warm at a target temperature of 140-200°C for 30 minutes, and then cool to room temperature at a rate of 10°C / min to obtain a double-network CO2 separation membrane.

[0025] In one embodiment, the preparation method of the TB polymer containing alkynyl and carboxyl groups is:

[0026] Using trifluoroacetic acid as solvent, the diamine monomer containing alkynyl and carboxyl groups is reacted with formaldehyde dimethyl acetal at a molar ratio of 1:1-6 for 24-72 hours to generate the TB polymer containing alkynyl and carboxyl groups.

[0027] In one embodiment, the preparation steps of the diamine monomer containing alkynyl groups and carboxyl groups are:

[0028] Step 1-1, in a nitrogen atmosphere and an ice-water bath, using CHCl2 as a solvent and SnCl4 as a catalyst, triptycene and 1,1-dichlorodimethyl ether in a molar ratio of 1:1.2-1.5 are reacted to obtain 14-formyltriptycene;

[0029] Step 1-2, using pyridine and deionized water as a mixed solvent, 1,4-formyltriptycene and KMnO4 at a molar ratio of 1:2.0-4.0 are subjected to an oxidation-reduction reaction to prepare 14-carboxytriptycene;

[0030] Step 1-3, in an ice-water bath, using acetic anhydride as a solvent, 1,4-carboxytriptycene and 70% nitric acid at a molar ratio of 1:5.0-10.0 to obtain 2,6-dinitro-triptycene-1,4-carboxylic acid by nitration reaction;

[0031] Step 1-4, 2,6-dinitro-triptycene-1,4-carboxylic acid and hydrazine hydrate are reacted in a molar ratio of 1:2.0 to 4.0 to obtain 2,6-diamino-triptycene-14-carboxylic acid through a redox reaction;

[0032] In step 1-5, 2,6-diamino-triptycene-1,4-carboxylic acid and 4,4'-(ethynyl-1,2-diyl)phthalic anhydride are reacted at a molar ratio of 2.1 to 2.5:1 to obtain the diamine monomer containing alkynyl and carboxyl groups.

[0033] In one embodiment, it is characterized in that the preparation method of the diamine monomer containing alkynyl groups and carboxyl groups comprises the following specific steps:

[0034] Step 2-1, add triptycene and SnCl4 into CH2Cl2, under nitrogen atmosphere, after fully dissolving, add 1,1-dichlorodimethyl ether, stir at 0-5°C for 2-10h, quench with ice water; add dilute hydrochloric acid to acidify, extract with CHCl2; dry the organic phase over anhydrous Na2SO4, filter, concentrate, recrystallize with dichloromethane and petroleum ether, and dry to obtain 14-formyltriptycene;

[0035] Step 2-2, pyridine and deionized water are mixed evenly, 14-formyltriptycene is added, 14-formyltriptycene is fully dissolved, and a KMnO4 solution with a concentration of 2.0 to 4.0 mol / L is slowly added dropwise; the temperature is raised to 50 to 90° C., and a reflux reaction is performed for 3 to 10 hours; the mixture is cooled to room temperature, and insoluble impurities are removed; hydrochloric acid is added to the obtained clear solution to produce a white precipitate; the precipitate is collected, washed, and the precipitate is recrystallized using methanol and deionized water as solvents, and after separation and purification, it is dried to obtain 14-carboxytriptycene;

[0036] Step 2-3, add 1,4-carboxytriptycene to acetic anhydride, fully dissolve, cool in an ice water bath, add 70% concentrated nitric acid dropwise within 30 minutes, react for 6 to 12 hours, add deionized water, stir vigorously for 2 to 6 hours, collect the precipitate by filtration, wash, and dry to obtain 2,6-dinitro-trimethylene-1,4-carboxylic acid;

[0037] Step 2-4, dissolving 2,6-dinitro-trimethylene-14-carboxylic acid in methanol, adding Pd / C catalyst, stirring thoroughly, adding hydrazine hydrate dropwise to the reaction system, reacting at 80-90° C. for 4-10 hours; cooling to room temperature, filtering, removing the solvent in vacuum, and drying to obtain 2,6-diaminotrimethylene-1,4-carboxylic acid;

[0038] Step 2-5, under a nitrogen atmosphere, dissolve 4,4'-(acetylene-1,2-diyl) diphthalic anhydride in N-methylpyrrolidone, add 2,6-diaminotrimethylene-14-carboxylic acid, stir at room temperature for 12 to 24 hours, add toluene as a water-carrying agent, reflux at 130°C for 1 to 3 hours, heat to 190°C and react for 6 to 12 hours, cool to room temperature, add 500 mL of deionized water and stir vigorously, precipitate a solid, wash, and dry to obtain a diamine monomer containing an alkynyl group and a carboxyl group.

[0039] In one embodiment, the method for preparing the diamine monomer containing alkynyl groups and carboxyl groups comprises the following specific steps:

[0040] Step 3-1, add 0.01 mol of triptycene and 1.75 mL of SnCl4 to 30 mL of CH2Cl2, under a nitrogen atmosphere, fully dissolve, add 1.084 mL of 1,1-dichlorodimethyl ether, stir at 0-5°C for 2-10 h, and quench with ice water; add dilute hydrochloric acid to acidify, extract with CHCl2; dry the organic phase over anhydrous Na2SO4, filter, and then concentrate to obtain a crude product; recrystallize through dichloromethane and petroleum ether, and dry in a vacuum oven at 40°C for 12-24 h to obtain 1,4-formyltriptycene;

[0041] Step 3-2, 40 mL of pyridine and 10 mL of deionized water are mixed evenly, and then 0.3 g of 1,4-formyltriptycene is added to ensure sufficient dissolution and mixing; 50 mL of a KMnO4 solution with a concentration of 2.0 to 4.0 mol / L is slowly added dropwise to the reaction system; the reaction system is heated to 50 to 90° C., and a reflux reaction is carried out within this temperature range for 3 to 10 hours; after the reaction is completed, the system is cooled to room temperature, and then centrifuged to remove insoluble impurities; hydrochloric acid is added to the obtained clear solution to produce a white precipitate; the precipitate is collected by suction filtration, and washed with deionized water to remove residual impurities; methanol and deionized water are used as solvents to recrystallize the precipitate, and after separation and purification steps, it is dried in a vacuum drying oven at 40° C. for 12 to 24 hours to obtain 1,4-carboxytriptycene;

[0042] Step 3-3, add 0.3 g of 1,4-carboxytriptycene to 15 mL of acetic anhydride, and after fully dissolving, cool in an ice water bath, add dropwise 0.4-0.6 mL of 70% concentrated nitric acid within 30 min, react for 6-12 h, add 25 mL of deionized water, stir vigorously for 2-6 h, collect the precipitate by filtration, wash with water, and dry in a vacuum drying oven at 50° C. for 12-24 h;

[0043] Step 3-4, dissolve 0.3 g of 2,6-dinitrotrimethylene-14-carboxylic acid in 30 mL of methanol, add 0.1 g of Pd / C catalyst, stir thoroughly, dropwise add 0.1 mL of hydrazine hydrate into the reaction system, and react at 80-90° C. for 4-10 h; then cool the reaction mixture to room temperature and filter through a Celite pad; remove the solvent in vacuo, and vacuum dry at 50° C. for 12 h to obtain 2,6-diaminotrimethylene-14-carboxylic acid;

[0044] Step 3-5, under a nitrogen atmosphere, dissolve 0.12 g of 4,4'-(acetylene-1,2-diyl) diphthalic anhydride in 30 mL of N-methylpyrrolidone, add 0.3 g of 2,6-diaminotrimethylene-1,4-carboxylic acid, stir at room temperature for 12 to 24 h, add 10 mL of toluene as a water-carrying agent, reflux at 130° C. for 1 to 3 h, heat to 190° C. and react for 6 to 12 h, cool to room temperature, add 500 mL of deionized water and stir vigorously, precipitate a solid, wash, and dry to obtain a diamine monomer containing an alkynyl group and a carboxyl group.

[0045] In one embodiment, in step 1, the solid content of the casting solution is: 0.5 to 5 wt.%;

[0046] The organic solvent includes at least one of N-methylpyrrolidone, tetrahydrofuran, N-ethylpyrrolidone or N,N-dimethylformamide;

[0047] The base film is tetrafluoroethylene, and the pore size of the base film is 0.1-1 μm;

[0048] The coordination time is 2 to 48 hours. The metal ions include: Cr 3+ , Cu 2+ or Fe 3+ ; In step 2, the covalent cross-linking reaction time is 10 to 120 minutes.

[0049] The third object of the present invention is to provide the use of the above separation membrane or the separation membrane prepared according to the above method in the separation of CO2 and N2, and the separation of CO2 and CH4.

[0050] The double-network CO2 separation membrane of the present invention is used to separate single gases and mixed gases of CO2 / N2 and CO2 / CH4 by a negative pressure method.

[0051] Beneficial Effects

[0052] 1. All reaction steps of the present invention are significantly simple, not only easy to operate, but also capable of achieving high-yield product generation. At the same time, compared with the traditional method, the cost of the present invention is effectively controlled, showing good economic efficiency.

[0053] 2. The double-network CO2 separation membrane prepared by the present invention has high separation selectivity and high gas permeability. The permeability coefficient of CO2 is ≥150 Barrer, and the selectivity coefficients of CO2 / N2 and CO2 / CH4 are ≥50.

[0054] 3. The present invention introduces a triptycene structure, which can effectively inhibit the accumulation phenomenon between molecules, thereby significantly increasing the free volume in the membrane and improving gas permeability. In addition, the present invention also introduces a carboxyl group, so that the membrane can undergo a coordination reaction at room temperature, thereby forming a stable coordination cross-linked network. At the same time, the present invention also cleverly introduces an alkynyl group, which can induce a Diels-Alder addition reaction under heating conditions to generate a special network structure with fully aromatic properties. This structure can not only effectively inhibit the creep of the polymer chain, significantly improve the anti-aging properties of the membrane, thereby extending the service life of the membrane, but also achieve a pore expansion effect through covalent cross-linking, further improving the permeability and selectivity of the polymer membrane. The membrane prepared by the present invention also exhibits good mechanical properties, and has initially achieved industrial preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 The schematic diagram of the preparation principle of the double network CO2 separation membrane is constructed by "combining metal coordination and covalent bonding, and gradually cross-linking strategy". Among them: a is the reaction of polymer metal coordination, b is the reaction of covalent cross-linking, and c is the schematic diagram of the double network of the polymer.

[0056] Figure 2 It is a gas permeability performance testing device; wherein: a is a schematic diagram of the gas permeability experimental device; b is the gas diffusion coefficient and gas permeability; 1-2 is a pressure gauge, 3-9 are valves, 10 is a buffer tank, 11 is a pressure gauge, 12 is a computer, 13 is a pump, and 14 is a membrane pool.

[0057] Figure 3 Optical photos of some CO2 separation membranes. a1 is a front photo of the non-crosslinked CO2 separation membrane in Comparative Example 1, and a2 is a back photo of the non-crosslinked CO2 separation membrane in Comparative Example 1; b1 is a front photo of the metal coordination CO2 separation membrane-1 in Comparative Example 2, and b2 is a back photo of the metal coordination CO2 separation membrane-1 in Comparative Example 2; c1 is a front photo of the double network CO2 separation membrane-1 in Example 1, and c2 is a back photo of the double network CO2 separation membrane-1 in Example 1. Specific implementation plan

[0058] The scheme of the present invention is further described below by combining the implementation examples. The examples are not limitations of the present invention unless otherwise specified. The raw materials used in the examples are purchased from the market.

[0059] The test method adopted in the present invention is the constant volume variable pressure method, through the laboratory homemade gas permeability test device ( Figure 2 )Measure the gas permeability of the membrane. The test gases are: CO2, N2, CH4. The specific operation steps are as follows:

[0060] (1) According to the actual size specifications of the sample pool, the membrane sample needs to be cut to form a circular sheet of appropriate size. Subsequently, the thickness of each area of ​​the membrane sample is measured and the average thickness value is calculated. During the sample loading process, an appropriate sealing ring needs to be added to ensure the airtightness of the device, and at the same time, ensure that all interfaces are firmly tightened to prevent leakage during the experiment or use;

[0061] (2) After the vacuum environment is established inside the system, valve 4 is immediately opened, while ensuring that all other valves remain closed. Each experimental cycle is set to 1 hour, during which 0.1 MPa of raw gas is introduced into the upstream volume of the system. When conducting mixed gas experiments, all valves except valve 8 must be opened to allow argon to be scavenged on the permeable side, thereby maintaining the transmembrane pressure difference stable at 0.1 MPa. To ensure the reliability and consistency of the experimental results, the above experimental process must be repeated at least three times for each membrane sample.

[0062] (3) After the test, ensure that the gas in the device is discharged cleanly through the exhaust gas treatment device. Then turn off the power supply of the device and take out the sample after the test.

[0063] 1. The gas permeability parameter calculation method of the present invention:

[0064]

[0065] Where: P is the gas permeability coefficient (Barrer [1Barrer = 1 × 10 -10 cm 3 (STP) ×cm / (cm 2 ×s×cmHg)]); Q is the cumulative amount of gas permeation from the beginning of permeation to time t (cm 3 ); A is the area of ​​the membrane (cm 2 ), l is the membrane thickness (cm), ΔP is the pressure difference between the upstream and downstream sides (MPa).

[0066] 2. The calculation formula of the gas selectivity involved in the present invention is:

[0067]

[0068] Where: α i / j It indicates that the membrane is an ideal choice for gas components CO2, CH4 and N2; P iIndicates the permeability coefficient of CO2 (Barrer); P j Indicates the permeability coefficient (Barrer) of the gas components CH4 and N2.

[0069] Example 1 Preparation of a dual network CO2 separation membrane -1 The process is as follows:

[0070] 1. Preparation of carboxyl and alkynyl diamine monomers:

[0071] Step 1, add 2.54g of triptycene and 1.75mL of SnCl4 to 30mL of CH2Cl2, under a nitrogen atmosphere, after fully dissolving, add 1.08mL of 1,1-dichlorodimethyl ether, stir at 0-5°C for 2h, and quench with ice water. Add dilute hydrochloric acid to acidify, and extract with CHCl2. Dry the organic phase over anhydrous Na2SO4, filter, and then concentrate to obtain a crude product. Recrystallize from CH2Cl2 and petroleum ether, and dry in a vacuum oven at 40°C for 12h to obtain 14-formyltriptycene;

[0072] Step 2, mix 40mL of pyridine and 10mL of deionized water evenly, and then add 0.3g of 14-formyltriptycene to ensure sufficient dissolution and mixing. Then, slowly add 50mL of 2.0mol / L KMnO4 solution to the reaction system. Heat the reaction system to 50°C and reflux reaction within this temperature range for 3 hours. After the reaction is completed, cool the system to room temperature and then remove insoluble impurities by centrifugation. Add hydrochloric acid to the resulting clear solution to produce a white precipitate. Collect the precipitate by filtration and wash with deionized water to remove residual impurities. Finally, use methanol and deionized water as solvents to recrystallize the precipitate, and after separation and purification steps, dry it in a 40°C vacuum drying oven for 12 hours to obtain 14-carboxytriptycene;

[0073] Step 3, add 0.3 g of 14-carboxytriptycene to 15 mL of acetic anhydride, and after fully dissolving, cool in an ice water bath, add dropwise 0.4 mL of 70% concentrated nitric acid within 30 min, react for 6 h, add 25 mL of deionized water, stir vigorously for 2 h, collect the precipitate by filtration, wash with water, and dry in a vacuum drying oven at 50 ° C for 12 h;

[0074] Step 4, dissolve 0.3 g of 2,6-dinitrotrimethylene-14-carboxylic acid in 30 mL of methanol, add 0.1 g of Pd / C catalyst, stir thoroughly, then drop 0.1 mL of hydrazine hydrate into the reaction system, and react at 80-90°C for 4 h. Then cool the reaction mixture to room temperature and filter through a Celite pad. Remove the solvent in vacuo, and vacuum dry at 50°C for 12 h to obtain 2,6-diaminotrimethylene-14-carboxylic acid;

[0075] Step 5, under a nitrogen atmosphere, dissolve 0.12 g of 4,4'-(acetylene-1,2-diyl) diphthalic anhydride in 30 mL of N-methylpyrrolidone, add 0.3 g of 2,6-diaminotrimethylene-14-carboxylic acid, stir at room temperature for 12 h, add 10 mL of toluene as a water-carrying agent, reflux at 130 ° C for 1 h, heat to 190 ° C for 6 h, cool to room temperature, add 500 mL of deionized water and stir vigorously, precipitate a solid, wash and dry to obtain a diamine monomer containing an alkynyl group and a carboxyl group.

[0076] The structure of the diamine monomer containing alkynyl and carboxyl groups is as follows:

[0077]

[0078] 2. Synthesis of TB polymer:

[0079] 0.3 g of a carboxyl- and alkynyl-containing diamine monomer was placed in an ice-water bath, 0.3 mL of formaldehyde dimethyl acetal was added to the system, and 2.4 mL of trifluoroacetic acid was added dropwise at a rate of 1 drop / second. After reacting for 1 hour, the ice-water bath was removed, and after reacting at room temperature for 24 hours, a 2.5% ammonia solution was used to terminate the reaction, and the TB polymer containing carboxyl and alkynyl groups was obtained by washing and drying;

[0080] The structure of TB polymer containing carboxyl and alkyne groups is as follows:

[0081]

[0082] Wherein, n is 23, and the number average molecular weight of the polymer is 22894 g / mol.

[0083] 3. Preparation of double network CO2 separation membrane by combining metal coordination and covalent bonding, step-by-step cross-linking strategy:

[0084] Step 1: Dissolve FeCl3 in NMP at room temperature to prepare a uniformly dispersed solution with a concentration of 1.5×10 -8 mol / L metal ion solution. Dissolve the TB polymer in the metal ion solution, stir for 6 hours at room temperature to obtain a casting solution with uniform metal ion dispersion, deposit it on a polytetrafluoroethylene membrane with a pore size of 0.1 to 1 μm by coating, and dry it in a 60°C oven for 48 to 72 hours to obtain a metal cross-linked CO2 separation membrane with a selective layer thickness of 10 μm;

[0085] Step 2: Cut the metal cross-linked CO2 separation membrane into a rectangle of 6 cm × 4 cm and place it in a tubular furnace. Use ceramic sheets to clamp the membrane to prevent deformation during the heating process. In a nitrogen atmosphere, heat at a rate of 5°C / min and keep at 160°C for 30 minutes. Then cool to room temperature at a rate of 10°C / min to obtain a double-network CO2 separation membrane.

[0086] The polymer structure of the double network CO2 separation membrane is as follows:

[0087]

[0088] Among them, n is 23, the number average molecular weight of the polymer is 22894g / mol, and the sphere is Fe 3+ ion.

[0089] Example 2 Preparation of a dual network CO2 separation membrane -2 process is as follows:

[0090] 1. Preparation of carboxyl and alkynyl diamine monomers:

[0091] Step 1, add 2.54g of triptycene and 1.75mL of SnCl4 to 30mL of CH2Cl2, under a nitrogen atmosphere, after fully dissolving, add 1.08mL of 1,1-dichlorodimethyl ether, stir at 0-5°C for 2h, and quench with ice water. Add dilute hydrochloric acid to acidify, and extract with CHCl2. Dry the organic phase over anhydrous Na2SO4, filter, and then concentrate to obtain a crude product. Recrystallize from CH2Cl2 and petroleum ether, and dry in a vacuum oven at 40°C for 12h to obtain 14-formyltriptycene;

[0092] Step 2, mix 40mL of pyridine and 10mL of deionized water evenly, and then add 0.3g of 14-formyltriptycene to ensure sufficient dissolution and mixing. Then, slowly add 50mL of 2.0mol / L KMnO4 solution to the reaction system. Heat the reaction system to 50°C and reflux reaction within this temperature range for 3 hours. After the reaction is completed, cool the system to room temperature and then centrifuge to remove insoluble impurities. Add hydrochloric acid to the resulting clear solution to produce a white precipitate. Collect the precipitate by suction and wash with deionized water to remove residual impurities. Finally, use methanol and deionized water as solvents to recrystallize the precipitate. After separation and purification steps, dry it in a vacuum drying oven at 40°C for 12 hours to obtain 14-carboxytriptycene;

[0093] Step 3, add 0.3 g of 14-carboxytriptycene to 15 mL of acetic anhydride, and after fully dissolving, cool in an ice water bath, add dropwise 0.4 mL of 70% concentrated nitric acid within 30 min, react for 4 h, add 25 mL of deionized water, stir vigorously for 2 h, collect the precipitate by filtration, wash with water, and dry in a vacuum drying oven at 50 ° C for 12 h;

[0094] Step 4, dissolve 0.3 g of 2,6-dinitrotrimethylene-14-carboxylic acid in 30 mL of methanol, add 0.1 g of Pd / C catalyst, stir thoroughly, then drop 0.1 mL of hydrazine hydrate into the reaction system, and react at 90°C for 5 h. Then cool the reaction mixture to room temperature and filter through a Celite pad. Remove the solvent in vacuo, and vacuum dry at 50°C for 12 h to obtain 2,6-diaminotrimethylene-14-carboxylic acid;

[0095] Step 5, under a nitrogen atmosphere, dissolve 0.12 g of 4,4'-(acetylene-1,2-diyl) diphthalic anhydride in 30 mL of N-methylpyrrolidone, add 0.3 g of 2,6-diaminotrimethylene-14-carboxylic acid, stir at room temperature for 12 h, add 10 mL of toluene as a water-carrying agent, reflux at 130 ° C for 3 h, heat to 160 ° C for 8 h, cool to room temperature, add 500 mL of deionized water and stir vigorously, precipitate a solid, wash and dry to obtain a diamine monomer containing an alkynyl group and a carboxyl group.

[0096] 2. Synthesis of TB polymer:

[0097] 0.3 g of a carboxyl and alkynyl diamine monomer was placed in an ice-water bath, 0.3 mL of formaldehyde dimethyl acetal was added to the system, and 2.4 mL of trifluoroacetic acid was added dropwise at a rate of 1 drop / second. After reacting for 1 hour, the ice-water bath was removed, and after reacting at room temperature for 36 hours, a 2.5% ammonia solution was used to terminate the reaction, and the TB polymer containing carboxyl and alkynyl groups was obtained by washing and drying;

[0098] The structure of TB polymer containing carboxyl and alkyne groups is as follows:

[0099]

[0100] Wherein, n is 32, and the number average molecular weight of the polymer is 31254 g / mol.

[0101] 3. Preparation of double network CO2 separation membrane by combining metal coordination and covalent bonding, step-by-step cross-linking strategy:

[0102] Step 1: Dissolve CrCl3 in NMP at room temperature to prepare a uniformly dispersed solution with a concentration of 1.5×10 -8mol / L metal ion solution. Dissolve the TB polymer in the metal ion solution, stir at room temperature for 12 hours to obtain a casting solution with uniform metal ion dispersion, deposit it on a polytetrafluoroethylene-based membrane with a pore size of 0.1 to 1 μm by coating, and dry it in an oven for 72 hours to obtain a metal coordination CO2 separation membrane with a selective layer thickness of about 10 μm;

[0103] Step 2: Cut the metal cross-linked CO2 separation membrane into a rectangle of 6 cm × 4 cm and place it in a tubular furnace. Use ceramic sheets to clamp the membrane to prevent deformation during the heating process. In a nitrogen atmosphere, heat at a rate of 5°C / min and keep at 160°C for 30 minutes. Then cool to room temperature at a rate of 10°C / min to obtain a double-network CO2 separation membrane.

[0104] The polymer structure of the double network CO2 separation membrane is as follows:

[0105]

[0106] Among them, n is 32, the number average molecular weight of the polymer is 31254g / mol, and the sphere is Cr 3+ ion.

[0107] Example 3 Preparation of a dual network CO2 separation membrane -3 process is as follows:

[0108] 1. Preparation of carboxyl and alkynyl diamine monomers:

[0109] Step 1, add 2.54g of triptycene and 1.75mL of SnCl4 to 30mL of CH2Cl2, under a nitrogen atmosphere, after fully dissolving, add 1.08mL of 1,1-dichlorodimethyl ether, stir at 0-5°C for 3h, and quench with ice water. Add dilute hydrochloric acid to acidify, and extract with CHCl2. Dry the organic phase over anhydrous Na2SO4, filter, and then concentrate to obtain a crude product. Recrystallize from CH2Cl2 and petroleum ether, and dry in a vacuum oven at 40°C for 24h to obtain 14-formyltriptycene;

[0110] Step 2, mix 40mL of pyridine and 10mL of deionized water evenly, and then add 0.3g of 14-formyltriptycene to ensure sufficient dissolution and mixing. Then, slowly drop 50mL of KMnO4 solution with a concentration of 2.0-4.0mol / L into the reaction system. Heat the reaction system to 70°C and reflux the reaction within this temperature range for 6 hours. After the reaction is completed, cool the system to room temperature and then remove insoluble impurities by centrifugation. Add hydrochloric acid to the resulting clear solution to produce a white precipitate. Collect the precipitate by suction and wash it with deionized water to remove residual impurities. Finally, use methanol and deionized water as solvents to recrystallize the precipitate, and after separation and purification steps, dry it in a vacuum drying oven at 40°C for 24 hours to obtain 14-carboxytriptycene;

[0111] Step 3, add 0.3 g of 14-carboxytriptycene to 15 mL of acetic anhydride, and after fully dissolving, cool in an ice water bath, add dropwise 0.6 mL of 70% concentrated nitric acid within 30 min, react for 10 h, add 25 mL of deionized water, stir vigorously for 5 h, collect the precipitate by filtration, wash with water, and dry in a vacuum drying oven at 50 ° C for 24 h;

[0112] Step 4, dissolve 0.3 g of 2,6-dinitrotrimethylene-14-carboxylic acid in 30 mL of methanol, add 0.1 g of Pd / C catalyst, stir thoroughly, then drop 0.1 mL of hydrazine hydrate into the reaction system, and react at 80°C for 7 h. Then cool the reaction mixture to room temperature and filter through a Celite pad. Remove the solvent in vacuo, and vacuum dry at 50°C for 12 h to obtain 2,6-diaminotrimethylene-14-carboxylic acid;

[0113] Step 5, under a nitrogen atmosphere, dissolve 0.12 g of 4,4'-(acetylene-1,2-diyl) diphthalic anhydride in 30 mL of N-methylpyrrolidone, add 0.3 g of 2,6-diaminotrimethylene-14-carboxylic acid, stir at room temperature for 16 h, add 10 mL of toluene as a water-carrying agent, reflux at 130° C. for 2 h, heat to 190° C. for 10 h, cool to room temperature, add 500 mL of deionized water and stir vigorously, precipitate a solid, wash and dry to obtain a diamine monomer containing an alkynyl group and a carboxyl group;

[0114] 2. Synthesis of TB polymer:

[0115] 0.3 g of a carboxyl and alkynyl diamine monomer was placed in an ice-water bath, 0.3 mL of formaldehyde dimethyl acetal was added to the system, and 2.4 mL of trifluoroacetic acid was added dropwise at a rate of 1 drop / second. After reacting for 1 hour, the ice-water bath was removed, and after reacting at room temperature for 48 hours, a 2.5% ammonia solution was used to terminate the reaction, and the TB polymer containing carboxyl and alkynyl groups was obtained by washing and drying.

[0116] The structure of the TB polymer containing carboxyl and alkyne groups is as follows:

[0117]

[0118] Wherein, n is 39 and the number average molecular weight of the polymer is 38521 g / mol.

[0119] 3. Preparation of double network CO2 separation membrane by combining metal coordination and covalent bonding, step-by-step cross-linking strategy:

[0120] Step 1: Dissolve CuCl2 in NMP at room temperature to prepare a uniformly dispersed solution with a concentration of 1.5×10 -8 mol / L metal ion solution. Dissolve the TB polymer in the metal ion solution, stir at room temperature for 12 hours to obtain a casting solution with uniform metal ion dispersion, deposit it on a polytetrafluoroethylene membrane with a pore size of 0.1 to 1 μm by coating, and dry it in a 60°C oven for 72 hours to obtain a metal coordination CO2 separation membrane with a selective layer thickness of about 10 μm;

[0121] Step 2: Cut the metal cross-linked CO2 separation membrane into a rectangle of 6 cm × 4 cm and place it in a tubular furnace. Use ceramic sheets to clamp the membrane to prevent deformation during the heating process. In a nitrogen atmosphere, heat at a rate of 5°C / min and keep at 160°C for 30 minutes. Then cool to room temperature at a rate of 10°C / min to obtain a double-network CO2 separation membrane.

[0122] The polymer structure of the double network CO2 separation membrane is as follows:

[0123]

[0124] Among them, n is 39, the number average molecular weight of the polymer is 38521g / mol, and the sphere is Cu 2+ ion.

[0125] Comparative Example 1 Preparation of uncrosslinked CO2 separation membrane

[0126] 1. Preparation of carboxyl and alkynyl diamine monomers:

[0127] Same as Example 1.

[0128] 2. Synthesis of TB polymer:

[0129] Same as Example 1.

[0130] 3. Preparation of uncrosslinked CO2 separation membrane:

[0131] TB polymer was dissolved in NMP with a solid content of 5 wt.%, insoluble matter was removed by centrifugation, coated on a PTFE base membrane with a pore size of 1 μm by a casting method, and dried in a vacuum oven at 60°C for 24 h to obtain a composite membrane with a selective layer thickness of about 10 μm.

[0132] Comparative Example 2 Preparation of Metal Coordination Type CO2 Separation Membrane

[0133] 1. Preparation of carboxyl and alkynyl diamine monomers:

[0134] Same as Example 1.

[0135] 2. Synthesis of TB polymer:

[0136] Same as Example 1.

[0137] 3. Metal coordination CO2 separation membrane:

[0138] At room temperature, FeCl3 was dissolved in NMP to prepare a uniformly dispersed solution with a concentration of 1.5×10 -8 mol / L metal ion solution. The TB polymer was dissolved in the above metal ion solution and stirred at room temperature for 6 hours to obtain a casting solution with uniform metal ion dispersion, which was deposited on a polytetrafluoroethylene-based membrane with a pore size of 0.1 to 1 μm by coating, and dried in an oven for 48 hours to obtain a metal coordination CO2 separation membrane with a selective layer thickness of about 10 μm.

[0139] Comparative Example 3 Preparation of covalently cross-linked CO2 separation membrane:

[0140] 1. Preparation of carboxyl and alkynyl diamine monomers:

[0141] Same as Example 1.

[0142] 2. Synthesis of TB polymer:

[0143] Same as Example 1.

[0144] 3. Covalently cross-linked CO2 separation membrane:

[0145] The composite membrane was cut into a rectangle of 6 cm × 4 cm and placed in a tubular furnace. Under nitrogen protection, the temperature was increased at a rate of 5 °C / min and kept at 160 °C for 30 minutes. Then the temperature was lowered to room temperature at a rate of 10 °C / min to obtain a covalently cross-linked polymer membrane.

[0146] Results Analysis

[0147] according to Figure 3 The optical photographs of the separation membranes show that the surface of the uncrosslinked CO2 separation membrane is smooth and has no obvious defects, and its color is light yellow. The surface of the metal coordination CO2 separation membrane is smooth and flat. 3+The presence of , the color of the membrane surface deepens; after heat treatment of the metal coordination CO2 separation membrane, a double network CO2 separation membrane is obtained, the surface is still relatively smooth and flat, and the surface color of the membrane is further deepened, which can be inferred that the reaction has been completed. It can be seen from Table 1 that compared with Comparative Example 1, the covalent cross-linked CO2 separation membrane and the metal coordination CO2 separation membrane have higher CO2 / N2, CO2 / CH4 selectivity, breaking the "trade-off" effect, while increasing the gas permeability coefficient and maintaining a high selectivity. Compared with Comparative Examples 2 and 3, the importance of coupling covalent crosslinking and metal coordination strategies is illustrated. The dual network structure synergistically enhances the CO2 mass transfer separation and resistance to physical aging. It can be seen from the long-term stability test data in Table 2 that in the 50-day aging data test, the CO2 permeability coefficient of the uncrosslinked CO2 membrane decreased from 105.8 Barrer to 60.4 Barrer, and the permeability coefficient decreased by 42.9%; the CO2 permeability coefficient of the covalently crosslinked CO2 separation membrane decreased from 125.6 Barrer to 118.3 Barrer, and the permeability coefficient decreased by 5.8%; the CO2 permeability coefficient of the metal coordination CO2 separation membrane decreased from 130.8 Barrer to 104.1 Barrer, and the permeability coefficient decreased by 20.4%; and the CO2 permeability coefficient of the dual network separation membrane decreased from 158.6 Barrer to 154.4 Barrer, and the permeability coefficient decreased by 2.6%, which has good stability.

[0148] Table 1: Single component gas permeability performance data

[0149]

[0150] Table 2: Aging data

[0151]

[0152]

Claims

1. A double network type CO2 separation membrane, characterized in that: The dual network type CO2 separation membrane has the following polymer structure: Wherein n is 20-45, the number average molecular weight of the polymer is 20000-40000 g / mol, and the spheres are metal ions.

2. A double network type CO2 separation membrane according to claim 1, characterized in that: The double network type CO2 separation membrane is obtained by metal coordination and covalent cross-linking of TB polymer containing alkyne and carboxyl groups; The metal coordination comprises: dissolving the TB polymer containing alkyne groups and carboxyl groups in an organic solution of metal ions to carry out metal coordination to obtain a metal coordinated CO2 separation membrane; The covalent cross-linking is as follows: the metal coordination type CO2 separation membrane is heated to perform covalent cross-linking to obtain a double network type CO2 separation membrane.

3. A double network type CO2 separation membrane according to claim 2, characterized in that: The structure of the TB polymer containing carboxyl and alkyne groups is as follows: wherein n is 20 to 45, and the number average molecular weight of the polymer is 20,000 to 40,000 g / mol; The TB polymer containing alkynyl and carboxyl groups is obtained by reacting a diamine monomer containing alkynyl and carboxyl groups with formaldehyde dimethyl acetal in a trifluoroacetic acid solvent.

4. A double network type CO2 separation membrane according to claim 3, characterized in that: The structural formula of the diamine monomer containing alkynyl and carboxyl is as follows:

5. A method for preparing a double-network CO2 separation membrane according to any one of claims 1 to 4, characterized in that: The preparation method of the separation membrane is as follows: Step 1, metal coordination: at 25-30°C, dissolve the TB polymer containing alkynyl and carboxyl groups in an organic solution of metal ions to obtain a casting solution, evenly apply the casting solution on the base film for coordination, and dry at 60°C to obtain a metal coordination type CO2 separation membrane; Step 2, covalent crosslinking: Place the metal coordination CO2 separation membrane in a tubular furnace, and perform covalent crosslinking at a target temperature of 140-200°C at a heating rate of 5°C / min under a nitrogen atmosphere, and cool it to room temperature at a rate of 10°C / min to obtain a double-network CO2 separation membrane.

6. The method for preparing a double-network CO2 separation membrane according to claim 5, characterized in that: The preparation method of the TB polymer containing alkynyl and carboxyl groups is as follows: Using trifluoroacetic acid as solvent, the diamine monomer containing alkynyl and carboxyl groups is reacted with formaldehyde dimethyl acetal at a molar ratio of 1:1-6 for 24-72 hours to generate the TB polymer containing alkynyl and carboxyl groups.

7. The method for preparing a double-network CO2 separation membrane according to claim 6, characterized in that: The preparation steps of the diamine monomer containing alkynyl and carboxyl groups are as follows: Step 1-1, in a nitrogen atmosphere and an ice-water bath, using CHCl2 as a solvent and SnCl4 as a catalyst, triptycene and 1,1-dichlorodimethyl ether in a molar ratio of 1:1.2-1.5 are reacted to obtain 14-formyltriptycene; Step 1-2, using pyridine and deionized water as a mixed solvent, 14-formyltriptycene and KMnO4 at a molar ratio of 1:2.0-4.0 through an oxidation-reduction reaction to prepare 14-carboxytriptycene; Step 1-3, in an ice-water bath, using acetic anhydride as a solvent, 14-carboxytriptycene and 70% nitric acid at a molar ratio of 1:5.0-10.0 to obtain 2,6-dinitro-triptycene-14-carboxylic acid by nitration reaction; Step 1-4, 2,6-dinitro-triptycene-14-carboxylic acid and hydrazine hydrate are reacted in a molar ratio of 1:2.0 to 4.0 to obtain 2,6-diamino-triptycene-14-carboxylic acid through a redox reaction; In step 1-5, 2,6-diamino-triptycene-14-carboxylic acid and 4,4'-(ethynyl-1,2-diyl)phthalic anhydride are reacted at a molar ratio of 2.1 to 2.5:1 to obtain the diamine monomer containing alkynyl and carboxyl groups.

8. A method for preparing a double-network CO2 separation membrane according to claim 6 or 7, characterized in that: The method for preparing the diamine monomer containing alkynyl groups and carboxyl groups comprises the following specific steps: Step 2-1, add triptycene and SnCl4 into CH2Cl2, under nitrogen atmosphere, after fully dissolving, add 1,1-dichlorodimethyl ether, stir at 0-5°C for 2-10h, quench with ice water; add dilute hydrochloric acid to acidify, extract with CHCl2; dry the organic phase over anhydrous Na2SO4, filter, concentrate, recrystallize with dichloromethane and petroleum ether, and dry to obtain 14-formyltriptycene; Step 2-2, mix pyridine and deionized water evenly, add 14-formyltriptycene and fully dissolve it. Slowly drop a KMnO4 solution with a concentration of 2.0-4.0 mol / L; heat to 50-90°C and reflux for 3-10 hours; cool to room temperature and remove insoluble impurities; add hydrochloric acid to the resulting clear solution to produce a white precipitate; The precipitate is collected, washed, and recrystallized using methanol and deionized water. After separation and purification, the precipitate is dried to obtain 14-carboxytriptycene; Step 2-3, add 14-carboxytriptycene to acetic anhydride, fully dissolve, cool in an ice water bath, add 70% concentrated nitric acid dropwise within 30 minutes, react for 6 to 12 hours, add deionized water, stir vigorously for 2 to 6 hours, collect the precipitate by filtration, wash, and dry to obtain 2,6-dinitro-trimethylene-14-carboxylic acid; Step 2-4, dissolve 2,6-dinitrotrimethylene-14-carboxylic acid in methanol, add Pd / C catalyst, stir thoroughly, add hydrazine hydrate dropwise to the reaction system, react at 80-90°C for 4-10 hours. Cool to room temperature, filter, remove the solvent in vacuo, and dry to obtain 2,6-diaminotrimethylene-14-carboxylic acid; Step 2-5, under a nitrogen atmosphere, dissolve 4,4'-(acetylene-1,2-diyl) diphthalic anhydride in N-methylpyrrolidone, add 2,6-diaminotrimethylene-14-carboxylic acid, stir at room temperature for 12 to 24 hours, add toluene as a water-carrying agent, reflux at 130°C for 1 to 3 hours, heat to 190°C for reaction for 6 to 12 hours, cool to room temperature, add deionized water, stir vigorously, precipitate solid, wash, purify and dry to obtain a diamine monomer containing alkynyl and carboxyl groups.

9. The method for preparing a double network CO2 separation membrane according to claim 5, characterized in that In the step 1, the solid content of the casting solution is: 0.5-5wt.%; The organic solvent includes at least one of N-methylpyrrolidone, tetrahydrofuran, N-ethylpyrrolidone or N,N-dimethylformamide; The base film is tetrafluoroethylene, and the pore size of the base film is 0.1-1 μm; The metal coordination time is 2 to 48 hours. The metal ions include: Cr 3+ , Cu 2+ or Fe 3+ ; In step 2, the covalent cross-linking reaction time is 10 to 120 minutes.

10. The separation membrane according to claims 1-4 or the separation membrane prepared according to the method of claims 5-9 is suitable for separation of CO2 and N2, and separation of CO2 and CH4.

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