CPOS-based mixed matrix membrane as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of membrane separation, and particularly relates to a CPOS-based mixed matrix membrane as well as a preparation method and application thereof. According to the invention, polyethylene glycol is used as a polymer matrix, crystalline porous organic salt is used as a filler, and the crystalline porous organic salt is introduced into the polymer matrix to construct a CPOS-based mixed matrix membrane; the mass of the crystalline porous organic salt is 14-34% of the total mass of the CPOS-based mixed matrix membrane. According to the CPOS-based mixed matrix membrane, under the pressure of 1 bar, when the mass of the crystalline porous organic salt accounts for 33.33% of the total mass of the CPOS-based mixed matrix membrane, the separation coefficient for 1, 3-butadiene and n-butane can reach 4.21, the separation coefficient for 1, 3-butadiene and isobutene can reach 4.78, and good separation performance is shown.

Description

Technical Field

[0001] The invention belongs to the technical field of membrane separation, and in particular relates to a CPOS-based mixed matrix membrane and a preparation method and application thereof. Background Art

[0002] 1,3-Butadiene is an important light olefin and a key raw material for the production of synthetic rubber, synthetic resin and other chemicals. In the petrochemical industry, 1,3-Butadiene is mainly derived from petroleum cracking and coexists with other C4 hydrocarbon compounds such as n-butane, n-butene, isobutane and isobutylene. Separating 1,3-Butadiene from the C4 mixture is of great significance for improving the quality and production efficiency of downstream products.

[0003] The difficulty in separating 1,3-butadiene lies in the similarity of physical and chemical properties between C4 hydrocarbon compounds, especially their similar boiling points and molecular polarity, which makes traditional distillation methods inefficient and energy-intensive. In addition, 1,3-butadiene is extremely active at high temperatures and is prone to polymerization, which requires special attention during the distillation process to avoid losses and ensure product purity. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a CPOS-based mixed matrix membrane and a preparation method and application thereof.

[0005] In the early stage of exploring the use of mixed matrix membranes for C4 gas separation of 1,3-butadiene, the present invention studied the physicochemical properties and structure of crystalline porous organic salts; crystalline porous organic salts, the full name of which is CrystallinePorous Organic Salts, abbreviated as CPOSs in English, are a class of porous materials formed by self-assembly of organic acids and organic bases through ionic bonds, with a fixed structure and permanent porosity. The first crystalline porous organic salt, referred to as CPOS-1, as a member of the CPOS family, exhibits a series of unique physicochemical properties and potential applications. At the same time, the structural features of CPOS-1 include frameworks composed of organic salts, which are usually formed by dense stacking of ion clusters through ionic bonds. CPOS-1 exhibits a high selective adsorption capacity for specific molecules due to the abundant sulfonic acid groups and amino groups in its internal pores. The kinetic diameter of 1,3-butadiene molecule is 0.431nm, and 1,3-butadiene is a planar structure with hydrogen atoms and delocalized π electron clouds. These characteristics enhance its electrostatic interaction with the sulfonic acid groups and amino groups in the CPOS-1 channel, thereby enhancing the adsorption force between the two. The kinetic diameter of n-butene molecule is 0.446nm, and it only contains one double bond and an asymmetric structure, which makes its interaction with the functional groups in the CPOS-1 channel weaker than that of 1,3-butadiene. The kinetic diameter of n-butane molecule is 0.469nm, and it is a saturated alkane without double bonds. At the same time, its stereostructure also makes its interaction with the functional groups in the CPOS-1 channel mainly a weak van der Waals force, and lacks electron cloud overlap. The kinetic diameters of isobutylene and isobutane molecules are 0.484nm and 0.528nm, and their larger molecular size hinders their diffusion, so the adsorption force is weak.

[0006] The present invention introduces CPOS-1 as a filler into a polyethylene glycol matrix to construct a CPOS-based mixed matrix membrane, and utilizes the electrostatic interaction between the sulfonic acid groups and amino groups in the pores of CPOS-1 and the planar configuration structure of the hydrogen atoms and delocalized π electron clouds contained in 1,3-butadiene to improve the adsorption selectivity of the CPOS-based mixed matrix membrane for 1,3-butadiene, thereby improving its separation efficiency for 1,3-butadiene; and then utilizes the film-forming ability and softness of polyethylene glycol to improve the film-forming property of the CPOS-based mixed matrix membrane, thereby enhancing the mechanical stability of the CPOS-based mixed matrix membrane.

[0007] The first object of the present invention is to provide a CPOS-based mixed matrix membrane; the present invention uses polyethylene glycol as a polymer matrix and CPOS-1 as a filler, and introduces CPOS-1 into the polyethylene glycol matrix to construct a CPOS-based mixed matrix membrane.

[0008] It should be noted that, as a filler, the sulfonic acid groups and amino groups in the pores of CPOS-1 are combined with the ether oxygen bonds of polyethylene glycol through hydrogen bonds or other non-covalent forces. The sulfonic acid groups in CPOS-1 contain hydrogen atoms, which can serve as proton donors, i.e., hydrogen bond donors; the oxygen atoms in the ether oxygen bonds of polyethylene glycol have strong negative electronegativity and can serve as hydrogen bond acceptors; hydrogen bonds are formed between the hydrogen atoms of the sulfonic acid groups of CPOS-1 and the oxygen atoms in the ether oxygen bonds of polyethylene glycol. The amino groups in CPOS-1 can also serve as hydrogen bond donors, forming hydrogen bonds with the oxygen atoms in polyethylene glycol, so that CPOS-1 and polyethylene glycol have good interaction and compatibility; preferably, the mass of the crystalline porous organic salt is 14% to 34% of the total mass of the CPOS-based mixed matrix membrane.

[0009] Polyethylene glycol is as polymer matrix, and its molecular weight is one of the key factors that affect film formation. Higher molecular weight polymer can provide better mechanical strength and more compact pore structure, which helps to improve the separation performance and stability of mixed matrix membrane. However, too high molecular weight may cause the processing difficulty of membrane to increase, and reduce the dispersibility and compatibility of filler in mixed matrix membrane. The present invention is preferred, and the molecular weight of described polymer matrix is ​​10000.

[0010] The mass ratio of CPOS-1 and polyethylene glycol is one of the key factors affecting the formation of CPOS-based mixed matrix membranes. An appropriate mass ratio can promote good interfacial bonding between the CPOS-1 filler and the polyethylene glycol matrix, which is crucial for the separation performance of gases. Too much CPOS-1 may cause filler agglomeration, while too little CPOS-1 cannot fully exert the separation performance of the CPOS-based mixed matrix membrane. Therefore, the present invention explores the effect of the mass ratio of the two on the performance of CPOS-based mixed matrix membranes. Preferably, the mass ratio of CPOS-1 and polyethylene glycol is 1:2~6. The preferred mass ratio helps to ensure that the CPOS-1 filler is evenly dispersed in the polyethylene glycol matrix, while avoiding CPOS-1 filler aggregation and reducing interface defects to improve the overall separation efficiency and mechanical stability of the CPOS-based mixed matrix membrane.

[0011] A second object of the present invention is to provide a method for preparing the above-mentioned CPOS-based mixed matrix membrane, comprising the following steps: Step 1: dissolving CPOS-1 in a solvent so that CPOS-1 as a filler is uniformly dispersed in the solvent to obtain a CPOS-1 solution.

[0012] Step 2: dissolving polyethylene glycol in water so that the polyethylene glycol as a matrix is ​​evenly dispersed in the water to obtain a polyethylene glycol solution.

[0013] Step 3: Mix the CPOS-1 solution and the polyethylene glycol solution to obtain a membrane-forming solution; then apply the membrane-forming solution to the substrate so that the sulfonic acid group and the amino group in the first crystalline porous organic salt solution are combined with the ether oxygen bond in the polyethylene glycol solution to form a dense layer, thereby obtaining a CPOS-based mixed matrix membrane.

[0014] It should be noted that in order to evenly disperse and fix the CPOS-1 filler in the polyethylene glycol matrix, so that the CPOS-1 filler and the polyethylene glycol matrix can be better combined; the present invention dissolves CPOS-1 in a solvent and mixes to form a CPOS-1 solution, dissolves polyethylene glycol in water and mixes to form a polyethylene glycol solution; then mixes the CPOS-1 solution and the polyethylene glycol solution to obtain a film-making solution; and applies the film-making solution to a substrate, which is beneficial to improving the separation performance of the CPOS-1 mixed matrix membrane prepared subsequently. This is because directly mixing CPOS-1 and polyethylene glycol may cause uneven dispersion of the filler, resulting in an interface incompatibility phenomenon between CPOS-1 and polyethylene glycol.

[0015] Preferably, the solvent is one of an aqueous solution of ammonia, an aqueous solution of sodium hydroxide and an aqueous solution of hydrochloric acid; more preferably, the solvent is an aqueous solution of ammonia. Ammonia can break the ionic bonds of CPOS-1 and easily volatilize and remove it during the film-forming and drying process. In order to better dissolve CPOS-1 in the solvent, the present invention completely dissolves CPOS-1 in the solvent under ultrasound to obtain a CPOS-1 solution. Preferably, the ultrasonic time for preparing the CPOS-1 solution is 5 min to 10 min, and the ultrasonic temperature is room temperature.

[0016] The specific preparation process of CPOS-1 of the present invention is: dissolving a strong acid tetra(4-phenylsulfonate)methane in methanol to obtain a first mixed solution; dissolving a strong base trans-1,4-cyclohexanediamine in methanol to obtain a second mixed solution; filtering the first mixed solution and the second mixed solution with a nylon filter head to obtain a first clear solution and a second clear solution; then slowly adding the first clear solution to the second clear solution, standing at room temperature for 12 hours, filtering, and obtaining light yellow crystal CPOS-1. Preferably, the molar ratio of the first mixed solution to the second mixed solution is 1:2.

[0017] It should also be noted that polyethylene glycol 10000 is a medium molecular weight polymer with good solubility in water. The solubility of polyethylene glycol 10000 in water is greater than 50%, and its solubility increases sharply with increasing temperature. At 60°C, solid polyethylene glycol of all fractions can be dissolved in water in any proportion. In addition, water is easily volatilized and removed during the film-forming and drying process. The present invention dissolves polyethylene glycol in water. In order to better dissolve polyethylene glycol in water, the present invention accelerates dissolution by stirring and ultrasound at room temperature, and the stirring time is 30min~40min, and the ultrasound time is 30min~40min.

[0018] Preferably, the total amount of the solvent and water: the amount of CPOS-1 used is 1 mL: 5 mg to 15 mg.

[0019] Preferably, the substrate is one of polyacrylonitrile, alumina sheet and polysulfone membrane. Polyacrylonitrile, also known as PAN, has an air-permeable pore structure with a pore size of about 20 nm, and has excellent mechanical properties, chemical stability and thermal stability. More preferably, the substrate is PAN. The present invention pre-treats PAN, and while removing pollutants on the surface of PAN, forms a water barrier by immersing water in the pores, thereby effectively preventing the film-making solution from penetrating into the pores of the PAN substrate. The specific operation of the pre-treatment of the present invention is to immerse the cut PAN substrate in deionized water, fix the wetted PAN on a glass plate when using it for film making, and use dust-free paper to gently wipe off the water droplets remaining on the surface of the PAN substrate to ensure that the film-making solution remains undiluted.

[0020] The number of cyclic spin coating affects the film thickness, uniformity of the film and the mechanical strength of the film, thereby affecting the separation efficiency and selectivity of the membrane. The present invention increases the number of cyclic spin coating, on the one hand, by increasing the thickness of the film to ensure that the prepared CPOS-based mixed matrix membrane can cover the substrate PAN, thereby forming a dense and continuous membrane; on the other hand, by improving the uniformity of the CPOS-based mixed matrix membrane, the membrane layer is made more compact and flat. In addition, the mechanical strength of the membrane is enhanced by a multilayer structure, and better support and stability are provided, thereby improving the separation efficiency and selectivity of the CPOS-based mixed matrix membrane.

[0021] The CPOS-based mixed matrix membrane of the present invention ensures that the membrane-forming solution remains undiluted before spin coating. The present invention adopts 10 cycles of spin coating, and the specific cycle process is: the process from adding the membrane-forming solution to completing the spin coating is considered to be one cycle, and the volume of each cycle solution is 2mL. Preferably, during the spin coating process, the rotation speed of the membrane-forming solution is 1500rpm~2000rpm, and the duration of the spin coating step is fixed at 30s~35s. The spin-coated film is dried at 40℃~50℃ for 48h and dried at 60℃~80℃ for 24h to obtain a CPOS-based mixed matrix membrane.

[0022] The third object of the present invention is to provide the use of the above CPOS-based mixed matrix membrane in separating 1,3-butadiene from C4 gas.

[0023] Compared with the prior art, the present invention has the following beneficial effects: The present invention introduces crystalline porous organic salts as fillers into the polymer matrix polyethylene glycol to construct a CPOS-based mixed matrix membrane. The sulfonic acid group in CPOS-1 contains hydrogen atoms, which can serve as proton donors, i.e., hydrogen bond donors; the oxygen atoms in the ether oxygen bonds in polyethylene glycol have strong negative electronegativity and can serve as hydrogen bond acceptors; hydrogen bonds are formed between the hydrogen atoms of the sulfonic acid group of CPOS-1 and the oxygen atoms in the ether oxygen bonds of polyethylene glycol. At the same time, the amino groups in CPOS-1 can also serve as hydrogen bond donors to form hydrogen bonds with the oxygen atoms in polyethylene glycol; thus, CPOS-1 and polyethylene glycol have good interaction and compatibility, forming a CPOS-based mixed matrix membrane. CPOS-1 has abundant sulfonic acid groups and amino groups in its internal pores, and 1,3-butadiene has a planar structure containing hydrogen atoms and delocalized π electron clouds; these characteristics enhance the electrostatic interaction between 1,3-butadiene and the sulfonic acid groups and amino groups in the pores of CPOS-1, thereby enhancing the adsorption force between the two, which can improve the adsorption selectivity of CPOS-based mixed matrix membranes for 1,3-butadiene, and thus improve the separation efficiency of CPOS-based mixed matrix membranes for 1,3-butadiene.

[0024] The present invention utilizes a CPOS-based mixed matrix membrane to selectively adsorb 1,3-butadiene in C4 gas, thereby achieving separation of 1,3-butadiene in C4 gas, avoiding the prior art of separating C4 gas at high temperature, causing polymerization reaction of 1,3-butadiene at high temperature, resulting in low separation efficiency.

[0025] The CPOS-based mixed matrix membrane of the present invention, under a pressure of 1 bar, when the mass of the crystalline porous organic salt is 33.33% of the total mass of the CPOS-based mixed matrix membrane, the separation factor for 1,3-butadiene and n-butane can reach 4.21, and the separation factor for 1,3-butadiene and isobutylene can reach 4.78, showing good separation performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the XRD pattern of CPOS-1 prepared in Comparative Example 1.

[0027] Figure 2 XRD patterns of the CPOS-based mixed matrix membranes prepared in Examples 1 to 3 and CPOS-1 prepared in Comparative Example 1.

[0028] Figure 3The scanning electron microscope image of the CPOS-based mixed matrix membrane prepared in Example 1; wherein (a) is a surface morphology image, and (b) is a cross-sectional image.

[0029] Figure 4 The scanning electron microscope image of the CPOS-based mixed matrix membrane prepared in Example 2; wherein (a) is a surface morphology image, and (b) is a cross-sectional image.

[0030] Figure 5 The scanning electron microscope image of the CPOS-based mixed matrix membrane prepared in Example 3; wherein (a) is a surface morphology image, and (b) is a cross-sectional image.

[0031] Figure 6 This is the isothermal physical adsorption curve of the CPOS-1 prepared in Comparative Example 1 for the adsorption performance of C4 gas at 298K.

[0032] Figure 7 The theoretical diagram of the ideal adsorption solution of C4 gas of CPOS-1 prepared in Comparative Example 1 at 298K; wherein (a) C4 gas is 1,3-butadiene and n-butane, and (b) C4 gas is 1,3-butadiene and isobutylene. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand that the technical solution of the present invention can be implemented, the present invention is further described below in conjunction with specific embodiments and drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] In the description of the present invention, unless otherwise specified, all reagents used are commercially available and all methods used are conventional techniques in the art.

[0035] The invention is further described below through specific examples.

[0036] Example 1 This embodiment provides a CPOS-based mixed matrix membrane.

[0037] In this embodiment, polyethylene glycol is used as a polymer matrix and a crystalline porous organic salt is used as a filler. The crystalline porous organic salt is introduced into the polymer matrix to construct a CPOS-based mixed matrix membrane; the mass of the crystalline porous organic salt is 14.29% of the total mass of the CPOS-based mixed matrix membrane.

[0038] The CPOS-based mixed matrix membrane of the present embodiment is prepared by the following steps: Step 1, preparation of CPOS-1 solution: (1.1) Dissolve 42.8 mg of tetrakis(4-sulfonatophenyl)methane in 6.0 mL of methanol to obtain a first mixed solution; dissolve 11.4 mg of trans-1,4-cyclohexanediamine in 6.0 mL of methanol to obtain a second mixed solution; filter the first mixed solution and the second mixed solution with nylon filter heads to obtain a first clear solution and a second clear solution, respectively; then, slowly add the first clear solution to the second clear solution, let stand at room temperature for 12 h, and filter to obtain light yellow crystals of CPOS-1.

[0039] (1.2) Add 10 mg of CPOS-1 to 40 μL of ammonia water and 1 mL of distilled water and ultrasonicate at 25 °C for 5 min to obtain a CPOS-1 solution.

[0040] Step 2, preparing polyethylene glycol solution: 60 mg of polyethylene glycol with a molecular weight of 10,000 was added to 0.96 mL of distilled water, stirred at room temperature for 30 min, and ultrasonicated at 25° C. for 30 min to obtain a polyethylene glycol solution.

[0041] Step 3: Preparation of CPOS-based mixed matrix membrane: (3.1) The CPOS-1 solution and the polyethylene glycol solution were mixed, stirred at room temperature for 10 min, and ultrasonicated for 5 min to obtain a membrane-forming solution.

[0042] (3.2) Soak the PAN substrate in distilled water, fix the wetted PAN substrate on a glass plate, use dust-free paper to gently wipe off the water droplets remaining on the surface of the PAN substrate, fix the glass plate of the PAN substrate on the pressure plate of the spin coater, and spin coat the film-forming liquid dropwise onto the PAN substrate at a rotation speed of 1500 rpm. The duration of the spin coating step is fixed at 30 s, and the spin coating is repeated 10 times. The volume of the film-forming liquid in each cycle is 2 mL. The spin-coated film is dried at 40 ° C for 48 h and at 60 ° C for 24 h to obtain a CPOS-based mixed matrix film.

[0043] Example 2 This embodiment provides a CPOS-based mixed matrix membrane.

[0044] In this embodiment, polyethylene glycol is used as a polymer matrix and a crystalline porous organic salt is used as a filler. The crystalline porous organic salt is introduced into the polymer matrix to construct a CPOS-based mixed matrix membrane; the mass of the crystalline porous organic salt is 25.00% of the total mass of the CPOS-based mixed matrix membrane.

[0045] The CPOS-based mixed matrix membrane of the present embodiment is prepared by the following steps: Step 1, preparation of CPOS-1 solution: (1.1) Dissolve 42.8 mg of tetrakis(4-sulfonatophenyl)methane in 6.0 mL of methanol to obtain a first mixed solution; dissolve 11.4 mg of trans-1,4-cyclohexanediamine in 6.0 mL of methanol to obtain a second mixed solution; filter the first mixed solution and the second mixed solution with nylon filter heads to obtain a first clear solution and a second clear solution, respectively; then, slowly add the first clear solution to the second clear solution, let stand at room temperature for 12 h, and filter to obtain light yellow crystals of CPOS-1.

[0046] (1.2) Add 20 mg of CPOS-1 to 80 μL of ammonia water and 0.96 mL of distilled water and ultrasonicate at 25 °C for 5 min to obtain a CPOS-1 solution.

[0047] Step 2, preparing polyethylene glycol solution: 60 mg of polyethylene glycol with a molecular weight of 10,000 was added to 0.96 mL of distilled water, stirred at room temperature for 30 min, and ultrasonicated at 25° C. for 30 min to obtain a polyethylene glycol solution.

[0048] Step 3: Preparation of CPOS-based mixed matrix membrane: (3.1) The CPOS-1 solution and the polyethylene glycol solution were mixed, stirred at room temperature for 10 min, and ultrasonicated for 5 min to obtain a membrane-forming solution.

[0049] (3.2) Soak the PAN substrate in distilled water, fix the wetted PAN substrate on a glass plate, use dust-free paper to gently wipe off the water droplets remaining on the surface of the PAN substrate, fix the glass plate of the PAN substrate on the pressure plate of the spin coater, and spin coat the film-forming liquid dropwise onto the PAN substrate at a rotation speed of 1500 rpm. The duration of the spin coating step is fixed at 30 s, and the spin coating is repeated 10 times. The volume of the film-forming liquid in each cycle is 2 mL. The spin-coated film is dried at 40 ° C for 48 h and at 60 ° C for 24 h to obtain a CPOS-based mixed matrix film.

[0050] The difference between this embodiment and embodiment 1 is: In this example, the mass of CPOS-1 is 25.00% of the total mass of the CPOS-based mixed matrix membrane.

[0051] Example 3 This embodiment provides a CPOS-based mixed matrix membrane.

[0052] In this embodiment, polyethylene glycol is used as a polymer matrix and a crystalline porous organic salt is used as a filler. The crystalline porous organic salt is introduced into the polymer matrix to construct a CPOS-based mixed matrix membrane; the mass of the crystalline porous organic salt is 33.33% of the total mass of the CPOS-based mixed matrix membrane.

[0053] The CPOS-based mixed matrix membrane of the present embodiment is prepared by the following steps: Step 1, preparation of CPOS-1 solution: (1.1) Dissolve 42.8 mg of tetrakis(4-sulfonatophenyl)methane in 6.0 mL of methanol to obtain a first mixed solution; dissolve 11.4 mg of trans-1,4-cyclohexanediamine in 6.0 mL of methanol to obtain a second mixed solution; filter the first mixed solution and the second mixed solution with nylon filter heads to obtain a first clear solution and a second clear solution, respectively; then, slowly add the first clear solution to the second clear solution, let stand at room temperature for 12 h, and filter to obtain light yellow crystals of CPOS-1.

[0054] (1.2) Add 30 mg of CPOS-1 to 120 μL of ammonia water and 0.92 mL of distilled water and ultrasonicate at 25 °C for 5 min to obtain a CPOS-1 solution.

[0055] Step 2, preparing polyethylene glycol solution: 60 mg of polyethylene glycol with a molecular weight of 10,000 was added to 0.96 mL of distilled water, stirred at room temperature for 30 min, and ultrasonicated at 25° C. for 30 min to obtain a polyethylene glycol solution.

[0056] Step 3: Preparation of CPOS-based mixed matrix membrane: (3.1) The CPOS-1 solution and the polyethylene glycol solution were mixed, stirred at room temperature for 10 min, and ultrasonicated for 5 min to obtain a membrane-forming solution.

[0057] (3.2) Soak the PAN substrate in distilled water, fix the wetted PAN substrate on a glass plate, use dust-free paper to gently wipe off the water droplets remaining on the surface of the PAN substrate, fix the glass plate of the PAN substrate on the pressure plate of the spin coater, and spin coat the film-forming liquid dropwise onto the PAN substrate at a rotation speed of 1500 rpm. The duration of the spin coating step is fixed at 30 s, and the spin coating is repeated 10 times. The volume of the film-forming liquid in each cycle is 2 mL. The spin-coated film is dried at 40 ° C for 48 h and at 60 ° C for 24 h to obtain a CPOS-based mixed matrix film.

[0058] The difference between this embodiment and embodiment 1 is: In this example, the mass of CPOS-1 is 33.33% of the total mass of the CPOS-based mixed matrix membrane.

[0059] Comparative Example 1 This comparative example provides a method for preparing CPOS-1.

[0060] Dissolve 42.8 mg of tetrakis(4-sulfonatephenyl)methane in 6.0 mL of methanol to obtain a first mixed solution; dissolve 11.4 mg of trans-1,4-cyclohexanediamine in 6.0 mL of methanol to obtain a second mixed solution; filter the first mixed solution and the second mixed solution with a nylon filter head to obtain a first clear solution and a second clear solution, respectively; then, slowly add the first clear solution to the second clear solution, let stand at room temperature for 12 hours, and filter to obtain light yellow crystals of CPOS-1.

[0061] Examples 1 to 3 of the present invention all prepare mixed matrix membranes for separating 1,3-butadiene from C4 gas. The following is a study using Examples 1 to 3 and Comparative Example 1 as examples. The specific research methods and results are as follows: 1. Structural Characterization from Figure 1 It can be seen that CPOS-1 has good crystallinity.

[0062] from Figure 2 It can be seen that the characteristic peaks of CPOS-1 exist in the mixed matrix membrane, and CPOS-1 still maintains its crystallinity, indicating that the dissolution regeneration strategy is feasible. In addition, with the increase of filler content, the peak intensity of CPOS-1 in the mixed matrix membrane gradually increases.

[0063] 2. Surface morphology characterization The CPOS-based mixed matrix membranes prepared in Examples 1 to 3 were subjected to SEM testing. The results are as follows: Figure 3~Figure 5 shown.

[0064] from Figure 3~Figure 5 As can be seen from (a) in the figure, the CPOS-based mixed matrix membranes prepared in Examples 1 to 3 have smooth surfaces, no obvious filler aggregation, and good interfacial compatibility; Figure 3~Figure 5 As can be seen from (b) in the figure, the cross-sectional thickness of the CPOS-based mixed matrix membranes prepared in Examples 1 to 3 is 200 nm, which indicates that the present invention can realize the preparation of ultra-thin mixed matrix membranes.

[0065] 3. Adsorption test The CPOS-1 prepared in Comparative Example 1 was activated at 150°C for 8 hours in a nitrogen atmosphere and subjected to adsorption tests. The tests were all completed under standard atmospheric pressure. The results are shown in Tables 1 and Figure 6 shown.

[0066] Table 1 Adsorption performance data of CPOS-1 prepared in comparative example 1 for C4 gas at 298K

[0067] from Figure 6It can be seen from the table that as the pressure increases, the adsorption of 1,3-butadiene, n-butane and isobutylene by CPOS-1 gradually increases. At the same time, Table 1 shows the adsorption performance data of CPOS-1 prepared in Comparative Example 1 for C4 gas at 298K. It can be seen from Table 1 that at 298K, the adsorption of 1,3-butadiene by CPOS-1 is the largest.

[0068] from Figure 7 It can be seen from (a) that for an equimolar gas mixture of 1,3-butadiene and n-butane, the ideal selectivity of 1,3-butadiene to n-butane is 7.07; Figure 7 As can be seen in (b), for an equimolar gas mixture of 1,3-butadiene and isobutylene, the ideal selectivity of 1,3-butadiene to isobutylene is 43.74. This indicates that the CPOS-1 prepared by the present invention has a significant affinity for 1,3-butadiene and confirms its potential in the application of separating C4 gas.

[0069] 4. Gas separation test The gas separation device is partly made in the laboratory and is used in conjunction with a gas chromatograph. The gas chromatograph is mainly used to determine the concentration and content of each component in the mixed gas, and the carrier gas used is high-purity Ar with a purity of 99.999%.

[0070] Test blank sample fitting standard curve: Test the peak areas of 1,3-butadiene, n-butane and isobutylene in gas chromatography when the concentrations are 0.001, 0.005, 0.01, 0.02, 0.03, 0.04 and 0.05 respectively as raw gas and carrier gas, and each concentration corresponds to a peak area. Keep all test conditions unchanged, and obtain 7 sets of data corresponding to the concentration of 1,3-butadiene, 7 sets of data corresponding to the concentration of n-butane and 7 sets of data corresponding to the concentration of isobutylene, and perform linear fitting on them to obtain the corresponding relationship between concentration and peak area, that is, the standard curve of 1,3-butadiene, n-butane and isobutylene gas. Among them, the test conditions are: Ar is the purge gas and carrier gas, high-purity 1,3-butadiene, n-butane and isobutylene are raw gas, the pressure at both ends of the membrane is kept at 1 bar, and the temperature is room temperature.

[0071] The gas standard curve is the standard for calculating gas concentration and content by peak area in gas separation test. Its accuracy directly affects the calculation of gas permeation flux and separation coefficient. Therefore, the R corresponding to the fitted standard curve is required. 2 The value is above 0.9999. 2 The R value, also known as the coefficient of determination, is a statistical indicator in regression analysis that measures how well the model fits the data. 2 The value range is between 0 and 1. 2A value of 1 means that the model fits the data perfectly, with all data points falling on the regression line; R 2 A value of 0 means that the model does not provide any ability to explain the data. 2 The closer it is to 1, the better the model fit is.

[0072] Gas separation test: When conducting a two-component gas separation experiment, high-purity Ar was used as the purge gas and carrier gas, and high-purity 1,3-butadiene, n-butane and isobutylene were used as the raw gas. The CPOS-based mixed matrix membranes prepared in Example 1, Example 2 and Example 3 were respectively immobilized on the membrane assembly, and the gas flow rate was adjusted using a soap bubble flowmeter. The Ar flow rate as the purge gas was adjusted to 7.5 mL min -1 The inlet is a mixture of two raw materials with a volume ratio of 1:1, and the flow rate of each raw gas is 10 mL min -1 Before the separation experiment, the purge gas and the raw gas need to be processed and stabilized for at least 3 hours. The mixed gas enters from the air inlet end of the mold (the front of the membrane), and the purge gas is used to blow the permeated gas into the gas chromatograph at the permeation end of the membrane. The gas composition that permeates the membrane is analyzed to obtain the peak area of ​​the two gases. The concentration of each gas in the purge gas is obtained using the standard curve and converted into gas permeation flux. p represents the permeation flux, the unit is mol·m -2 s -1 pa -1 The results are shown in Table 2~Table 3.

[0073] Table 2 shows the separation test results of the CPOS-based mixed matrix membranes prepared in Examples 1 to 3 of the present invention for the mixed gas of n-butane and 1,3-butadiene. It should be noted that the pure polymer membrane is impermeable. As can be seen from Table 2, at a pressure of 1 bar, for the separation of 1,3-butadiene and n-butane, when the filler content is 14.29%, the permeation of 1,3-butadiene is 3.63E -08 , the permeation of n-butane is 1.36E -08 , the selectivity of 1,3-butadiene and n-butane is 2.67; when the filler content is 25.00%, the permeation of 1,3-butadiene is 4.60E -08 , the permeation of n-butane is 1.42E -08 , the selectivity of 1,3-butadiene and n-butane is 3.24; when the filler content is 33.33%, the permeation of 1,3-butadiene is 6.36E -08 , the permeation of n-butane is 1.51E -08, the selectivity of 1,3-butadiene and n-butane is 4.21. With the increase of filler content in the mixed matrix membrane, CPOS-1 plays a significant separation role, the permeation of 1,3-butadiene increases, the selectivity of mixed gas improves, and the mixed matrix membrane has a separation effect.

[0074] Table 2 Separation test results of CPOS-based mixed matrix membranes prepared in Examples 1 to 3 for mixed gases of n-butane and 1,3-butadiene

[0075] Table 3 shows the separation test results of the CPOS-based mixed matrix membranes prepared in Examples 1 to 3 of the present invention for the mixed gas of isobutylene and 1,3-butadiene. It should be noted that the pure polymer membrane is impermeable. As can be seen from Table 3, at a pressure of 1 bar, for the separation of 1,3-butadiene and isobutylene, when the filler content is 14.29%, the permeation of 1,3-butadiene is 3.48E -08 , the permeation of isobutylene is 1.27E -08 , the selectivity of 1,3-butadiene and isobutylene is 2.74; when the filler content is 25.00%, the permeation of 1,3-butadiene is 4.32E -08 , the permeation of isobutylene is 1.23E -08 , the selectivity of 1,3-butadiene and isobutylene is 3.51; when the filler content is 33.33%, the permeation of 1,3-butadiene is 5.78E -08 , the permeation of isobutylene is 1.21E -08 , the selectivity of 1,3-butadiene and isobutylene is 4.78. With the increase of filler content in the mixed matrix membrane, CPOS-1 plays a significant separation role, the permeation of 1,3-butadiene increases, the selectivity of the mixed gas improves, and the mixed matrix membrane has a separation effect. And because the molecular dynamics diameter of isobutylene is larger than that of n-butane, for mixed matrix membranes with the same filler content, when the diffusion effect is dominant, isobutylene is more hindered by diffusion, so the separation selectivity of 1,3-butadiene and isobutylene is higher.

[0076] Table 3 Separation test results of CPOS-based mixed matrix membranes prepared in Examples 1 to 3 for mixed gases of isobutylene and 1,3-butadiene

[0077] Selectivity is one of the key performance indicators of gas membrane separation technology. An ideal gas separation membrane should have good separation performance, excellent thermal and chemical stability, and high mechanical strength. High selectivity means that the membrane can separate the target gas more effectively, thereby improving separation efficiency and product purity.

[0078] In the field of gas separation, the Knudsen coefficient is used to describe the flow pattern of gas molecules through a porous membrane. When the Knudsen coefficient is large, the gas molecules mainly pass through the membrane pores by Knudsen diffusion. In this case, the separation process is related to the size and shape of the molecules. The Knudsen diffusion coefficient is inversely proportional to the square root of the molecular mass, which means that gas molecules with smaller molecular mass can pass through the porous membrane more easily.

[0079] It should be noted that when the present invention involves a numerical range, it should be understood that the two endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes a preferred embodiment. Although the preferred embodiments of the present invention have been described, once those skilled in the art know the basic creative concept, they can make other changes and modifications to these embodiments, and these changes and modifications all fall within the scope of the present invention.

[0080] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. If these modifications and variations of the present invention fall within the scope of the equivalent technology of the present invention, the present invention is also intended to include these modifications and variations.

Claims

1. A CPOS-based mixed matrix membrane, characterized in that: Using polyethylene glycol as a polymer matrix and a first crystalline porous organic salt as a filler, introducing the first crystalline porous organic salt into the polymer matrix to construct a CPOS-based mixed matrix membrane; The mass of the first crystalline porous organic salt is 14% to 34% of the total mass of the CPOS-based mixed matrix membrane.

2. A method for preparing a CPOS-based mixed matrix membrane according to claim 1, characterized in that: The following steps are involved: dissolving the first crystalline porous organic salt in a solvent so that the first crystalline porous organic salt is uniformly dispersed in the solvent as a filler to obtain a first crystalline porous organic salt solution; Dissolving polyethylene glycol in water so that the polyethylene glycol as a matrix is ​​evenly dispersed in the water to obtain a polyethylene glycol solution; mixing the first crystalline porous organic salt solution and the polyethylene glycol solution to obtain a membrane-forming solution; The membrane-making solution is then coated on the substrate so that the sulfonic acid groups and amino groups in the first crystalline porous organic salt solution are combined with the ether oxygen bonds in the polyethylene glycol solution to form a dense layer, thereby obtaining a CPOS-based mixed matrix membrane.

3. The method for preparing a CPOS-based mixed matrix membrane according to claim 2, characterized in that: The mass ratio of the first crystalline porous organic salt to polyethylene glycol is 1:2-6.

4. The method for preparing a CPOS-based mixed matrix membrane according to claim 2, characterized in that: The solvent is one of an aqueous solution of ammonia water, an aqueous solution of sodium hydroxide and an aqueous solution of hydrochloric acid.

5. The method for preparing a CPOS-based mixed matrix membrane according to claim 2, characterized in that: The total amount of the solvent and water: the amount of CPOS-1 used is 1 mL: 5 mg to 15 mg.

6. An application of the CPOS-based mixed matrix membrane according to claim 1, characterized in that: The CPOS-based mixed matrix membrane is used for separation of 1,3-butadiene from C4 gas.

7. The use of the CPOS-based mixed matrix membrane according to claim 6, characterized in that: The CPOS-based mixed matrix membrane separates 1,3-butadiene from C4 gas by the following steps: The C4 gas is infiltrated from the CPOS-based mixed matrix membrane, and the CPOS-based mixed matrix membrane adsorbs 1,3-butadiene in the C4 gas, thereby achieving separation of 1,3-butadiene in the C4 gas.

8. The use of the CPOS-based mixed matrix membrane according to claim 7, characterized in that: The C4 gas is a mixed gas of normal butane, normal butene, isobutane, isobutene and 1,3-butadiene.

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