Separation membranes, methods of making and using the same

Abstract

The application relates to the technical field of membrane separation materials, and discloses a separation membrane and a preparation method and application thereof. The separation membrane comprises a support layer, an intermediate layer and a functional layer which are stacked in sequence; the material of the intermediate layer comprises an amino polymer. The separation membrane has high CO2 flux and high CO2 / N2 selectivity.

Description

Technical Field

[0001] This invention relates to the field of membrane separation materials technology, specifically to a separation membrane, its preparation method, and its application in CO2 separation. Background Technology

[0002] Since the Industrial Revolution, the burning of large quantities of fossil fuels has led to a nearly 50% increase in atmospheric CO2 concentration, and this is expected to continue to rise. Emissions of greenhouse gases such as CO2 are a major cause of global warming. With the increasing severity of energy and environmental problems, reducing greenhouse gas emissions and improving carbon utilization efficiency have become hot topics of international concern. Therefore, separating and recovering CO2 from emission sources and using certain methods to achieve CO2 conversion and utilization has become a key focus of scientific research both domestically and internationally. CO2 separation membrane technology has attracted widespread research interest due to its advantages such as simple equipment, low fixed investment, and low energy consumption. Currently, CO2 separation membranes prepared from single polymers often struggle to simultaneously achieve high selectivity and permeability. In contrast to homogeneous membranes, thin-layer composite membrane structures, with a porous layer providing mechanical support, can significantly reduce the thickness of the upper effective selective layer, thereby reducing overall mass transfer resistance and achieving higher flux.

[0003] To ensure low mass transfer resistance, the gas flux of the lower porous support layer should be at least 10 times that of the upper effective selective separation layer, thus ensuring that most (over 90%) of the permeate resistance is located within the separation layer. However, during the preparation of the separation layer by means of coating, deposition, or interfacial polymerization, the presence of the porous structure on the support layer surface inevitably leads to some diluted polymer solution seeping into the porous structure and clogging the pores. This not only significantly increases the effective thickness of the selective layer in the final composite membrane, reducing the membrane's permeability, but also easily causes surface defects, affecting the membrane's gas selectivity. To prevent these adverse permeation phenomena, an intermediate layer is usually added between the selective layer and the porous support layer.

[0004] Currently, the most commonly used materials for preparing the intermediate layer are rubber-like high-permeability polymers such as polydimethylsiloxane (PDMS) and poly-1-(trimethylsilyl)-1-propyne (PTMSP). The CO2 permeability of these silicone rubbers themselves can reach as high as approximately 19,000 to 37,000 barrers, but due to aging effects, the permeability of the coating decays rapidly. For example, the CO2 permeability of a PTMSP composite membrane coated on a polyacrylonitrile (PAN) carrier can decrease by 80% within 14 days ("Recent advances in multi-layer composite polymeric membranes for CO2 separation: A review" (Dai Z, Ansaloni L, Deng L. Green Energy and Environment: English Edition, 2016, 000(002), p:102-128.)). Post-crosslinking of the above coatings can improve the stability of permeation flux, but the required steps are more cumbersome. Furthermore, the preparation of silicone rubber coatings also requires the use of large amounts of organic solvents and high / low temperature conditions.

[0005] CN104428050A discloses a gas separation membrane with crosslinked dialkylsiloxane in the intermediate layer and a method for preparing the same. However, the thermal crosslinking or ultraviolet crosslinking reaction requires one or more organic solvents and the addition of initiators and catalysts. Therefore, the method is not mild and environmentally friendly, and the crosslinking will reduce the membrane's permeability.

[0006] CN113631245A discloses a membrane preparation method for separating acidic gases such as CO2 from a mixed gas. The method includes adding dispersed nanoparticles to the intermediate matrix, which can improve polymer aging. However, the compatibility between inorganic nanoparticles such as silica and the matrix is ​​poor, which is not conducive to achieving reliable membrane mechanical strength and stable operation.

[0007] Existing silicone rubber interlayers suffer from problems such as cumbersome preparation processes, solvent pollution, and unstable membrane performance. Therefore, it is of great significance to provide a separation membrane with a simple and environmentally friendly preparation method. Summary of the Invention

[0008] The purpose of this invention is to overcome the problem that existing separation membranes cannot simultaneously improve gas flux and selectivity, and to provide a separation membrane, its preparation method and application. This separation membrane has both high CO2 flux and high separation coefficients of CO2 and N2, and the preparation process is simple and environmentally friendly.

[0009] To achieve the above objectives, a first aspect of the present invention provides a separation membrane, wherein the separation membrane comprises a support layer, an intermediate layer and a functional layer stacked sequentially; wherein the material of the intermediate layer comprises an amino polymer.

[0010] A second aspect of the present invention provides a method for preparing a separation membrane, wherein the method includes:

[0011] (1) In the presence of additives, a reaction solution containing dopamine or containing dopamine and amino reactants is polymerized on the surface of the support layer to prepare an intermediate layer containing amino polymers.

[0012] (2) The separation membrane is obtained by interfacial polymerization reaction between the oil phase monomer in the oil phase solution and the aqueous phase monomer in the aqueous phase solution on the intermediate layer.

[0013] A third aspect of the present invention provides a separation membrane prepared by the aforementioned preparation method.

[0014] A fourth aspect of the present invention provides an application of the aforementioned separation membrane in CO2 separation.

[0015] Through the above technical solution, the present invention has the following beneficial effects:

[0016] (1) In this invention, non-covalent interactions make the support layer, intermediate layer and functional layer stacked in sequence adhere tightly to each other, which increases the gas flux of the separation membrane and enables selective separation of CO2; specific amino polymers further promote the selective transfer of CO2, increase the rate at which CO2 permeates through the membrane relative to other gases, and achieve selective separation of CO2.

[0017] (2) The preparation method of the present invention first prepares an intermediate layer on the support layer, and then prepares a functional layer on the intermediate layer; the specific preparation method enables the prepared support layer, intermediate layer and functional layer to be connected in pairs by van der Waals forces; furthermore, the specific method prepares an intermediate layer that is smooth and flat, which provides an excellent site for preparing the functional layer, which is conducive to the interfacial polymerization reaction and improves the reaction rate.

[0018] (3) The process of the present invention is simple, green and environmentally friendly, and can be mass-produced. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the separation membrane in Embodiment 1 of the present invention;

[0020] Figure 2 This is an electron microscope image of the cross-section of the separation membrane in Example 1. Detailed Implementation

[0021] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] The first aspect of the present invention provides a separation membrane, wherein the separation membrane comprises a support layer, an intermediate layer and a functional layer stacked sequentially;

[0023] The intermediate layer is made of an amino polymer.

[0024] In this invention, the inventors discovered that the intermediate layer contains an amino polymer, which enables the separation membrane to selectively pass through gases that have an affinity interaction with amino groups, thereby achieving gas screening and improving gas selectivity. The separation membrane of this invention can selectively separate CO2 and N2 gases.

[0025] In this invention, the intermediate layer is relatively smooth, which is conducive to the preparation of functional layers on its surface. The layers are stacked tightly to ensure that the separation membrane has a higher gas flux.

[0026] According to the present invention, the nitrogen content in the amino polymer is 3-45 wt%.

[0027] In this invention, the nitrogen content in the amino polymer is measured by X-ray photoelectron spectroscopy. When the nitrogen content meets the above-mentioned range, it can effectively promote gas transfer and increase CO2 flux.

[0028] Furthermore, the nitrogen content in the amino polymer is 6-12 wt%.

[0029] According to the present invention, the theoretical weight-average molecular weight of the amino polymer is 300-50000 Da, preferably 400-10000 Da.

[0030] According to the present invention, the amino polymer is selected from homopolymers and / or copolymers of dopamine.

[0031] In this invention, the homopolymer and / or copolymer of dopamine have a high nitrogen content, which can effectively promote CO2 transport and improve CO2 flux and gas selectivity.

[0032] According to the present invention, the amino polymer is selected from at least one of polydopamine, dopamine-ethylenediamine copolymer, dopamine-diethylenetriamine copolymer, dopamine-triethylenetetramine copolymer, dopamine-tetraethylenepentamine copolymer, dopamine-polyethyleneimine copolymer, dopamine-ethylenediamine-polyethyleneimine copolymer, dopamine-diethylenetriamine-polyethyleneimine copolymer, dopamine-triethylenetetramine-polyethyleneimine copolymer, and dopamine-tetraethylenepentamine-polyethyleneimine copolymer; preferably at least one of polydopamine, dopamine-polyethyleneimine copolymer, and dopamine-triethylenetetramine copolymer.

[0033] According to the present invention, the material constituting the support layer is selected from at least one of polysulfone, polyethersulfone, polyacrylonitrile, and polyvinylidene fluoride.

[0034] According to the present invention, the weight-average molecular weight of the material constituting the support layer is 1,000-500,000 Da, preferably 2,500-150,000 Da.

[0035] According to the present invention, the support layer has a porous structure.

[0036] According to the present invention, the porosity of the support layer is >10%.

[0037] According to the present invention, the average pore size of the support layer is 1-10000 nm.

[0038] In this invention, the porosity of the support layer is tested by measuring it with a scanning electron microscope and dividing the area of ​​the pores in the field of view by the total surface area; the average pore diameter of the support layer is tested by measuring the diameter of all visible pores in the field of view with a scanning electron microscope and calculating the average value.

[0039] In this invention, the support layer that meets the above-mentioned specific range of porosity and average pore size allows gas to pass through, and the surface of the generated support layer is relatively smooth, which is beneficial for preparing an intermediate layer on the surface and improving the adhesion of the film.

[0040] Furthermore, the porosity of the support layer is 25-75%.

[0041] Furthermore, the average pore size of the support layer is 5-500 nm.

[0042] According to the present invention, the thickness of the support layer is 20-500 μm, the thickness of the intermediate layer is 10-500 nm, and the thickness of the functional layer is 10-1100 nm.

[0043] In this invention, the separation membrane that meets the above-mentioned thickness range has both high gas flux and gas selectivity.

[0044] Furthermore, the thickness of the support layer is 60-150 μm, the thickness of the intermediate layer is 50-300 nm, and the thickness of the functional layer is 50-400 nm.

[0045] According to the present invention, the average pore size of the separation membrane is 0.1-1 nm.

[0046] The average pore size of the separation membrane is tested according to the standard GB / T 42269-2022 "Separation Membrane Pore Size Test Method Gas Permeation Method"; at the same time, the support layer, intermediate layer and functional layer have different pore sizes, and the smallest pore size is defined as the average pore size of the separation membrane; different pore sizes can sieve gas molecules of different sizes, so as to achieve selective gas separation.

[0047] Furthermore, the average pore size of the separation membrane is 0.2-0.5 nm.

[0048] According to the present invention, the material constituting the functional layer is selected from at least one of polyamide and polyester.

[0049] In this invention, the material constituting the functional layer is a conventional material in the art and need not be limited, as long as it can achieve the technical effect of this invention. The unreacted -NH2 and -OH in the amino polymer on the intermediate layer are connected to the -NH2 and -O- in the material of the functional layer through non-covalent bonds such as hydrogen bonds and electrostatic interactions.

[0050] In this invention, the polymer material in the above-mentioned functional layer has a high gas flux and a separation coefficient between CO2 and N2, making it suitable for CO2 gas separation.

[0051] According to the present invention, the CO2 flux of the separation membrane is ≥300 GPU.

[0052] According to the present invention, the separation selectivity of the separation membrane for CO2 and N2 is ≥20.

[0053] The separation membrane of the present invention can simultaneously achieve both high CO2 flux and high selectivity, and is suitable for the separation of CO2 and N2 gases.

[0054] Furthermore, the CO2 flux of the separation membrane is ≥400 GPU.

[0055] Furthermore, the separation selectivity of the separation membrane for CO2 and N2 is ≥30.

[0056] A second aspect of the present invention provides a method for preparing a separation membrane, wherein the method includes:

[0057] (1) In the presence of additives, a reaction solution containing dopamine or containing dopamine and amino reactants is polymerized on the surface of the support layer to prepare an intermediate layer containing amino polymers.

[0058] (2) The separation membrane is obtained by interfacial polymerization reaction between the oil phase monomer in the oil phase solution and the aqueous phase monomer in the aqueous phase solution on the intermediate layer.

[0059] In this invention, the "amino-containing reactant" does not include dopamine.

[0060] The preparation method of the present invention first prepares an intermediate layer on a support layer, and then prepares a functional layer on the intermediate layer; the specific preparation method enables the prepared support layer, intermediate layer and functional layer to be connected to each other through non-covalent interactions; furthermore, the specific method prepares a smooth and flat intermediate layer, which provides an excellent site for the preparation of the functional layer, which is conducive to the interfacial polymerization reaction and improves the reaction rate.

[0061] Meanwhile, the inventors unexpectedly discovered that dopamine contains a large number of amino groups, which can promote CO2 transfer, resulting in a high CO2 flux in the prepared separation membrane. At the same time, the polymerization reaction of dopamine is mild and the reaction conditions are simple, which is conducive to industrial promotion. When dopamine undergoes polymerization with reactants containing amino groups, it can increase the amino content in the intermediate layer, thereby enhancing the separation membrane's ability to promote CO2 transfer, thus improving the CO2 flux and selectivity relative to other gases (such as N2).

[0062] According to the present invention, in step (1), an additive is added to adjust the pH to 7.5-10.

[0063] In this invention, adjusting the pH to the above-mentioned range ensures the smooth progress of the intermediate layer preparation reaction and avoids defects in the obtained intermediate layer.

[0064] Furthermore, the pH is 8.5-10.

[0065] According to the present invention, the additive includes additive A, or additive A and additive B, wherein additive A is selected from sodium hydroxide and / or tris(hydroxymethyl)aminomethane, and additive B is selected from at least one of hydrochloric acid, sodium dihydrogen phosphate and potassium dihydrogen phosphate.

[0066] According to the present invention, the amino-containing reactants are selected from amino-containing monomers and / or amino-containing polymers.

[0067] According to the present invention, the amino-containing monomer is selected from at least one of ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

[0068] According to the present invention, the amino-containing polymer is selected from polyethyleneimine.

[0069] According to the present invention, the weight-average molecular weight of the polyethyleneimine is 500-2000 Da, preferably 600-1800 Da.

[0070] In this invention, polyethyleneimine has a relatively small molecular weight, and when it is polymerized with dopamine, the reaction mechanism is similar to that of dopamine with amino-containing monomers.

[0071] According to the present invention, the concentration of dopamine in the reaction solution is 0.1 wt%-5 wt%.

[0072] According to the present invention, the concentration of the amino-containing reactant in the reaction solution is 0 wt%-5 wt%.

[0073] In this invention, the concentration of the amino reactant in the reaction solution is 0 wt%, and the product obtained is a homopolymer of dopamine.

[0074] In this invention, when the concentrations of dopamine and amino-containing reactants meet the above-mentioned range, the prepared intermediate layer can be made smooth and flat, which helps to prepare a functional layer on it. At the same time, the high amino content in the prepared intermediate layer promotes CO2 transfer, so that the separation membrane has both high CO2 flux and gas selectivity for CO2 and N2.

[0075] Furthermore, the concentration of dopamine in the reaction solution is 0.5wt%-2wt%.

[0076] Furthermore, in the reaction solution, the concentration of the amino-containing reactant is 0.2 wt%-2 wt%.

[0077] According to the present invention, when dopamine undergoes a polymerization reaction with an amino-containing reactant, the weight ratio of the dopamine to the amino-containing reactant is 1:10 or less.

[0078] In this invention, when the weight ratio of the dopamine to the amino-containing reactant meets the above-mentioned range, the prepared intermediate layer can be made smooth and flat, while improving the CO2 flux and the CO2 and N2 selectivity.

[0079] Furthermore, when dopamine undergoes a polymerization reaction with an amino-containing reactant, the weight ratio of dopamine to the amino-containing reactant is 1:1.5 or less.

[0080] According to the present invention, the reaction time of the polymerization reaction is 2-48 h, and the reaction temperature of the polymerization reaction is 0-50 °C.

[0081] In this invention, when the above-mentioned time and temperature conditions for polymerization reaction are met, the resulting intermediate layer is smooth and flat, which is beneficial for modifying functional layers on its surface. At the same time, the reaction conditions are relatively mild, which can be promoted on a large scale for industrial application.

[0082] Furthermore, the polymerization reaction takes 5-24 hours and the polymerization reaction takes 20-35°C.

[0083] According to the present invention, the concentration of the aqueous monomer in the aqueous solution is 1 wt%-4 wt%.

[0084] According to the present invention, the concentration of the oil phase monomer in the oil phase solution is 0.05wt%-0.5wt%.

[0085] In this invention, aqueous and oil-phase monomers that meet the above-mentioned ranges can make the prepared functional layer thinner and denser, resulting in a higher CO2 flux and better CO2 and N2 gas separation properties.

[0086] Furthermore, in the aqueous solution, the concentration of the aqueous monomer is 2wt%-4wt%.

[0087] Furthermore, in the oil phase solution, the concentration of the oil phase monomer is 0.05wt%-0.15wt%.

[0088] According to the present invention, the weight ratio of the aqueous phase monomer to the oil phase monomer is 2-40:1.

[0089] In this invention, the aqueous monomer and oil monomer that meet the above weight ratio can make the reaction proceed more smoothly, and the aforementioned functional layer is obtained without wasting raw materials. The prepared functional layer enables the separation membrane to have high gas flux and gas selectivity.

[0090] Furthermore, the weight ratio of the aqueous phase monomer to the oil phase monomer is 5-15:1.

[0091] According to the present invention, the oil phase monomer is selected from at least one of pyromellitic methyl chloride, isophthaloyl chloride, 1,4-dichlorobenzyl chloride and 3,3,4,4-biphenyltetrachloroyl chloride; preferably pyromellitic methyl chloride.

[0092] According to the present invention, the aqueous monomer is selected from amino compounds and / or hydroxy compounds.

[0093] According to the present invention, the amino compound is selected from at least one of m-phenylenediamine, piperazine, ethylenediamine, triethylenetetramine, tetraethylenepentamine, 1,4-cyclohexanediamine, 1,3-diamino-2-methylpropane, bis(2-aminoethyl) ether, ethylene glycol bis(2-aminoethyl) ether, diethylene glycol di(3-aminopropyl) ether, 1,4-butanediol bis(3-aminopropyl) ether, and 1,4-bis(3-aminopropyl)piperazine, preferably selected from m-phenylenediamine and / or piperazine.

[0094] According to the present invention, the hydroxyl compound is selected from at least one of α-cyclodextrin, β-cyclodextrin and γ-cyclodextrin, preferably β-cyclodextrin.

[0095] According to the present invention, the oil phase solution further includes an oil phase solvent, wherein the oil phase solvent is selected from at least one of n-hexane, n-heptane, and isoalkanes.

[0096] According to the present invention, the isoparaffin is selected from Iospar G and / or Isopar E, both of which are solvent oil products of ExxonMobil.

[0097] According to the present invention, the interfacial polymerization reaction takes 0.5-60 min and the temperature is 15-50℃.

[0098] In this invention, the interfacial polymerization reaction that meets the above-mentioned range has a faster reaction rate, milder reaction conditions, simpler process, and produces a thinner and defect-free functional layer, which facilitates gas passage and increases gas throughput.

[0099] Furthermore, the interfacial polymerization reaction takes 0.5-3 minutes and is carried out at a temperature of 25-50°C.

[0100] According to the present invention, step (1) further includes: washing the obtained amine polymer intermediate layer with water.

[0101] In this invention, the water cleaning method is not specifically limited and can be any common cleaning method in the art, preferably soaking, shaking, and ultrasonic cleaning, as long as it can clean the unreacted reactants on the surface.

[0102] In this invention, the purpose of cleaning the intermediate layer is to remove polymers that are not attached to the surface, thereby making the intermediate layer smooth and free of impurities.

[0103] According to the present invention, the cleaning time is ≥5h, preferably ≥12h.

[0104] In this invention, the ratio of the dopamine-containing solution or the reaction solution containing dopamine and an amino-containing reactant to the membrane area of ​​the support layer is 0.5-5 g / cm². 2 .

[0105] In this invention, the ratio of the oil phase solution to the membrane area of ​​the intermediate layer of the separation membrane is 0.05-0.35 g / cm². 2 .

[0106] In this invention, the ratio of the area of ​​the aqueous solution to the area of ​​the intermediate membrane of the separation membrane is 0.05-0.35 g / cm². 2 .

[0107] A third aspect of the present invention provides a separation membrane prepared by the aforementioned preparation method.

[0108] A fourth aspect of the present invention provides an application of the aforementioned separation membrane in CO2 separation.

[0109] The present invention will be described in detail below through embodiments.

[0110] In the following examples and comparative examples,

[0111] The CO2 flux was determined by the differential pressure method, and the specific method of the differential pressure method was in accordance with GB / T 1038.1-2022 "Test methods for gas permeability of plastic films and sheets - Part 1: Differential pressure method";

[0112] The formula for calculating the separation coefficient between CO2 and N2 is: CO2 separation coefficient = CO2 flux / N2 flux;

[0113] The method for detecting the thickness of each layer in the separation membrane is as follows: the thickness of the support layer is measured using a micrometer in the dry state, with 5 points measured and the average value calculated, accurate to 1 μm; the thickness of the intermediate layer is measured at the transition portion in the SEM image (as shown in the attached image). Figure 1 The average value of the range marked by the white line in the middle is calculated to the nearest 1 nm. The thickness of the functional layer is the distance from the top surface of the entire film to the boundary of the support layer in the SEM image minus the thickness of the intermediate layer, accurate to 1 nm.

[0114] The average pore size of the separation membrane is determined according to the standard GB / T 42269-2022 "Separation Membrane Pore Size Test Method - Gas Permeation Method".

[0115] Polysulfone, with a weight-average molecular weight of 3500 Da, was purchased from Solvay.

[0116] Dopamine, acquired by Sigma-Aldrich;

[0117] Polyethyleneimine, with a weight-average molecular weight of 600 Da, was purchased from Sigma-Aldrich.

[0118] Triethylenetetramine, m-phenylenediamine, and pyromellitic trichloroethylene were acquired by Anaiji Chemical.

[0119] Sodium hydroxide was purchased from Sinopharm Reagent.

[0120] The support layer is polysulfone. The preparation method is to add 400g of polysulfone to 1600g of dimethylacetamide to prepare a 20wt% solution, heat it to 75℃, and after the solution is uniform, coat it on a non-woven fabric substrate. The polysulfone support layer is obtained by phase inversion method. The weight average molecular weight of polysulfone is 3600Da.

[0121] Example 1

[0122] (1) At 25℃, add tris(hydroxymethyl)aminomethane aqueous solution, 0.5 mol / L sodium hydroxide aqueous solution and 0.5 mol / L hydrochloric acid aqueous solution, and adjust the pH to 8.5 by titration, so that the total mass of the aqueous solution is 200 g. Add 2 g of dopamine and pour 324 cm 2 The polysulfone support layer is spread out in a container and completely immersed in the mixed solution for polymerization reaction. The reaction time is 24 hours. After the reaction, the residual liquid is drained and the mixture is thoroughly washed with water to obtain the membrane A1 with the intermediate layer stacked on the support layer.

[0123] (2) At 25°C, 2g of m-phenylenediamine was added to 98g of water, and 0.15g of trimesoyl chloride was added to 99.85g of n-hexane. The mixture was then heated to 324cm³. 2 Interfacial polymerization was carried out on membrane A1 for 3 minutes. After the reaction, the residual solvent was thoroughly washed with water to obtain separation membrane B1.

[0124] Electron microscopy was performed on the cross-section of the membrane in Example 1, as follows: Figure 2 As shown in the electron microscope image, the intermediate layer is smooth and flat, and there is no clear boundary between the intermediate layer and the functional layer, which proves that the intermediate layer and the functional layer are closely bonded.

[0125] Example 2

[0126] (1) At 25℃, add tris(hydroxymethyl)aminomethane aqueous solution, 0.5 mol / L sodium hydroxide aqueous solution and 0.5 mol / L hydrochloric acid aqueous solution, and adjust the pH to 10 by titration, so that the total mass of the aqueous solution is 200 g. Add 2 g of dopamine and pour 324 cm 2 The polysulfone support layer is spread out in a container and completely immersed in the mixed solution for polymerization reaction. The reaction time is 5 hours. After the reaction, the residual liquid is drained and the mixture is thoroughly washed with water to obtain the membrane A2 with the intermediate layer stacked on the support layer.

[0127] (2) At 25°C, 2g of m-phenylenediamine was added to 98g of water, and 0.15g of trimesoyl chloride was added to 99.85g of n-hexane. The above membrane was then subjected to a curvature of 324cm. 2 Interfacial polymerization was carried out on A2 for 3 minutes. After the reaction, the residual solvent was thoroughly washed with water to obtain separation membrane B2.

[0128] Example 3

[0129] (1) At 25℃, add tris(hydroxymethyl)aminomethane aqueous solution, 0.5 mol / L sodium hydroxide aqueous solution and 0.5 mol / L hydrochloric acid aqueous solution, and adjust the pH to 8.5 by titration, so that the total mass of the aqueous solution is 200 g. Add 2 g of dopamine and 3 g of polyethyleneimine, and pour 324 cm³ of water into a container. 2The polysulfone support layer is spread out in a container and completely immersed in the mixed solution for polymerization reaction. The reaction time is 24 hours. After the reaction, the residual liquid is drained and the mixture is thoroughly washed with water to obtain the film A3 with the intermediate layer stacked on the support layer.

[0130] (2) At 25°C, 2g of m-phenylenediamine was added to 98g of water, and 0.15g of trimesoyl chloride was added to 99.85g of n-hexane. The mixture was then heated to 324cm³. 2 Interfacial polymerization was carried out on membrane A3 for 3 minutes. After the reaction, the residual solvent was thoroughly washed with water to obtain separation membrane B3.

[0131] Example 4

[0132] (1) At 25℃, add tris(hydroxymethyl)aminomethane aqueous solution, 0.5 mol / L sodium hydroxide aqueous solution and 0.5 mol / L hydrochloric acid aqueous solution, and adjust the pH to 8.5 by titration, so that the total mass of the aqueous solution is 200 g. Add 2 g of dopamine and 0.4 g of triethylenetetramine, and then add 324 cm³ of water. 2 The polysulfone support layer is spread out in a container and completely immersed in the mixed solution for polymerization reaction. The reaction time is 5 hours. After the reaction, the residual liquid is drained and the mixture is thoroughly washed with water to obtain the film A4 with the intermediate layer stacked on the support layer.

[0133] (2) At 25°C, 2g of m-phenylenediamine was added to 98g of water, and 0.15g of trimesoyl chloride was added to 99.85g of n-hexane. The mixture was then heated to 324cm³. 2 Interfacial polymerization was carried out on membrane A4 for 3 minutes. After the reaction, the residual solvent was thoroughly washed with water to obtain separation membrane B4.

[0134] Example 5

[0135] (1) At 25℃, add tris(hydroxymethyl)aminomethane aqueous solution, 0.5 mol / L sodium hydroxide aqueous solution and 0.5 mol / L hydrochloric acid aqueous solution, and adjust the pH to 8.5 by titration, so that the total mass of the aqueous solution is 200 g. Add 2 g of dopamine and 0.4 g of ethylenediamine, and pour 324 cm 2 The polysulfone support layer is spread out in a container and completely immersed in the mixed solution for polymerization reaction. The reaction time is 24 hours. After the reaction, the residual liquid is drained and the mixture is thoroughly washed with water to obtain the membrane A5 with the intermediate layer stacked on the support layer.

[0136] (2) At 25°C, 2g of m-phenylenediamine was added to 98g of water, and 0.15g of trimesoyl chloride was added to 99.85g of n-hexane. The mixture was then heated to 324cm³. 2 Interfacial polymerization was carried out on membrane A5 for 3 minutes. After the reaction, the residual solvent was thoroughly washed with water to obtain separation membrane B5.

[0137] Example 6

[0138] (1) At 25℃, potassium dihydrogen phosphate buffer solution, 0.5 mol / L sodium hydroxide aqueous solution, and 0.5 mol / L hydrochloric acid aqueous solution were added and the pH was adjusted to 7.4 by titration, so that the total mass of the aqueous solution was 200 g. 2 g of dopamine was added, and 324 cm 2 The polysulfone support layer is spread out in a container and completely immersed in the mixed solution for polymerization reaction. The reaction time is 24 hours. After the reaction, the residual liquid is drained and the mixture is thoroughly washed with water to obtain the membrane A6 with the intermediate layer stacked on the support layer.

[0139] (2) At 25°C, 2g of m-phenylenediamine was added to 98g of water, and 0.15g of trimesoyl chloride was added to 99.85g of n-hexane. The mixture was then heated to 324cm³. 2 Interfacial polymerization was carried out on membrane A6 for 3 minutes. After the reaction, the residual solvent was thoroughly washed with water to obtain separation membrane B6.

[0140] Example 7

[0141] (1) Step (1) is carried out in accordance with the method of Example 1, except that “adding 0.4g of dopamine” is used instead of “adding 2g of dopamine” to obtain separation membrane B7.

[0142] Example 8

[0143] (1) Step (1) is carried out in accordance with the method of Example 1, except that “polymerization reaction is carried out for 3 hours” is used instead of “polymerization reaction is carried out for 24 hours” to obtain separation membrane B8.

[0144] Comparative Example 1

[0145] The implementation was carried out in accordance with Example 1, but unlike Example 1, there was no support layer, and it was impossible to obtain a complete membrane with self-supporting mechanical strength.

[0146] Comparative Example 2

[0147] The procedure was carried out in accordance with Example 1, except that step (1) was omitted, and the separation membrane D2 was obtained.

[0148] Comparative Example 3

[0149] The procedure was carried out in accordance with Example 1, except that step (2) was omitted, and the separation membrane D3 was obtained.

[0150] The performance parameters of the separation membrane obtained from the test are shown in Table 1.

[0151] Table 1

[0152]

[0153] The results of testing the CO2 flux and the separation coefficient of CO2 and N2 of the separation membrane under the conditions of 25℃ and 0.1MPa are shown in Table 2.

[0154] Table 2

[0155] serial number <![CDATA[CO2 flux (GPU)]]> <![CDATA[Separation coefficient of CO2 and N2]]> B1 423 44 B2 572 27 B3 720 68 B4 680 54 B5 600 55 B6 319 20 B7 554 23 B8 503 31 D1 - - D2 286 17 D3 6159 2.3

[0156] As can be seen from the results in Tables 1 and 2, the separation membrane of the present invention has a superior CO2 flux and a higher selectivity for separating CO2 and N2.

[0157] Comparing Example 1 with Comparative Example 1, it can be seen that a separation membrane without a support layer cannot exist. Comparing Example 1 with Comparative Example 2, it can be seen that a separation membrane without an intermediate layer has low CO2 flux and poor separation selectivity between CO2 and N2. Comparing Example 1 with Comparative Example 3, it can be seen that a separation membrane without a functional layer can have a sharp increase in CO2 flux, but the separation selectivity between CO2 and N2 is very poor and cannot meet the requirements of practical applications.

[0158] Furthermore, comparing Example 1 with Examples 3-5, it can be seen that when the amino polymer is a dopamine copolymer, the CO2 flux and the separation coefficient of CO2 and N2 are both better than when the amino polymer is a dopamine homopolymer. Comparing Example 1 with Example 7, it can be seen that the amount of dopamine will affect the CO2 flux and the gas selectivity of CO2 and N2 of the separation membrane. Comparing Example 1 with Example 8, it can be seen that specific polymerization reaction conditions can produce a smooth and flat intermediate layer, which is beneficial for modifying the functional layer on its upper surface. The resulting separation membrane can have both high CO2 flux and high separation selectivity of CO2 and N2.

[0159] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A CO2-N2 separation membrane, characterized in that, The separation membrane comprises a support layer, an intermediate layer, and a functional layer stacked sequentially. The material constituting the intermediate layer is an amino polymer; The amino polymer is selected from homopolymers and / or copolymers of dopamine.

2. The separation membrane according to claim 1, wherein, Based on the total amount of the amino polymer, the nitrogen content in the amino polymer is 3-45 wt%.

3. The separation membrane according to claim 2, wherein, The amino polymer contains 6-12 wt% nitrogen.

4. The separation membrane according to claim 3, wherein, The theoretical weight-average molecular weight of the amino polymer is 300-50000 Da.

5. The separation membrane according to claim 4, wherein, The theoretical weight-average molecular weight of the amino polymer is 400-10000 Da.

6. The separation membrane according to claim 1, wherein, The amino polymer is selected from at least one of polydopamine, dopamine-ethylenediamine copolymer, dopamine-diethylenetriamine copolymer, dopamine-triethylenetetramine copolymer, dopamine-tetraethylenepentamine copolymer, dopamine-polyethyleneimine copolymer, dopamine-ethylenediamine-polyethyleneimine copolymer, dopamine-diethylenetriamine-polyethyleneimine copolymer, dopamine-triethylenetetramine-polyethyleneimine copolymer, and dopamine-tetraethylenepentamine-polyethyleneimine copolymer.

7. The separation membrane according to claim 6, wherein, The amino polymer is selected from at least one of polydopamine, dopamine-polyethyleneimine copolymer, and dopamine-triethylenetetramine copolymer.

8. The separation membrane according to claim 1, wherein, The material constituting the support layer is selected from at least one of polysulfone, polyethersulfone, polyacrylonitrile, and polyvinylidene fluoride.

9. The separation membrane according to claim 8, wherein, The weight-average molecular weight of the material constituting the support layer is 1,000-500,000 Da.

10. The separation membrane according to claim 9, wherein, The weight-average molecular weight of the material constituting the support layer is 2500-150000 Da.

11. The separation membrane according to claim 1, wherein, The support layer has a porous structure.

12. The separation membrane according to claim 11, wherein, The porosity of the support layer is >10%.

13. The separation membrane according to claim 12, wherein, The porosity of the support layer is 25-75%.

14. The separation membrane according to claim 11, wherein, The average pore size of the support layer is 1-10000 nm.

15. The separation membrane according to claim 14, wherein, The average pore size of the support layer is 5-500 nm.

16. The separation membrane according to claim 1, wherein, The thickness of the support layer is 20-500 μm, the thickness of the intermediate layer is 10-500 nm, and the thickness of the functional layer is 10-1100 nm.

17. The separation membrane according to claim 16, wherein, The thickness of the support layer is 60-150 μm, the thickness of the intermediate layer is 50-300 nm, and the thickness of the functional layer is 50-400 nm.

18. The separation membrane according to claim 1, wherein, The average pore size of the separation membrane is 0.1-1 nm.

19. The separation membrane according to claim 18, wherein, The average pore size of the separation membrane is 0.2-0.5 nm.

20. The separation membrane according to claim 1, wherein, The material constituting the functional layer is selected from at least one of polyamide and polyester.

21. The separation membrane according to any one of claims 1-20, wherein, The CO2 flux of the separation membrane is ≥300 GPU.

22. The separation membrane according to claim 21, wherein, The CO2 flux of the separation membrane is ≥400 GPU.

23. The separation membrane according to any one of claims 1-20, wherein, The separation selectivity of the separation membrane for CO2 and N2 is ≥20.

24. The separation membrane according to claim 23, wherein, The separation selectivity of the separation membrane for CO2 and N2 is ≥30.

25. A method for preparing a CO2-N2 separation membrane, characterized in that, The preparation method includes: (1) In the presence of additives, a reaction solution containing dopamine or containing dopamine and amino reactants is polymerized on the surface of the support layer to prepare an intermediate layer containing amino polymers. (2) The separation membrane is obtained by interfacial polymerization reaction between the oil phase monomer in the oil phase solution and the aqueous phase monomer in the aqueous phase solution on the intermediate layer.

26. The preparation method according to claim 25, wherein, In step (1), additives are added to adjust the pH of the polymerization reaction to 7.5-10.

27. The preparation method according to claim 26, wherein, In step (1), additives are added to adjust the pH of the polymerization reaction to 8.5-10.

28. The preparation method according to claim 25, wherein, The additive includes additive A, or additive A and additive B, wherein additive A is selected from sodium hydroxide and / or tris(hydroxymethyl)aminomethane, and additive B is selected from at least one of hydrochloric acid, sodium dihydrogen phosphate, and potassium dihydrogen phosphate.

29. The preparation method according to claim 25, wherein, The amino-containing reactants are selected from amino-containing monomers and / or amino-containing polymers.

30. The preparation method according to claim 29, wherein, The amino-containing monomer is selected from at least one of ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

31. The preparation method according to claim 29, wherein, The amino-containing polymer is selected from polyethyleneimine.

32. The preparation method according to claim 31, wherein, The weight-average molecular weight of the polyethyleneimine is 500-2000 Da.

33. The preparation method according to claim 32, wherein, The weight-average molecular weight of the polyethyleneimine is 600-1800 Da.

34. The preparation method according to claim 25, wherein, In the reaction solution, the concentration of dopamine is 0.1wt%-5wt%.

35. The preparation method according to claim 34, wherein, In the reaction solution, the concentration of dopamine is 0.5wt%-2wt%.

36. The preparation method according to claim 25, wherein, In the reaction solution, the concentration of the amino-containing reactant is 0-5 wt%.

37. The preparation method according to claim 36, wherein, In the reaction solution, the concentration of the amino-containing reactant is 0.2wt%-2wt%.

38. The preparation method according to claim 25, wherein, When dopamine undergoes a polymerization reaction with an amino-containing reactant, the weight ratio of dopamine to the amino-containing reactant is less than 1:

10.

39. The preparation method according to claim 38, wherein, The weight ratio of dopamine to the amino-containing reactant is less than 1:1.

5.

40. The preparation method according to claim 25, wherein, The polymerization reaction takes 2-48 hours and is carried out at a temperature of 0-50°C.

41. The preparation method according to claim 40, wherein, The polymerization reaction takes 5-24 hours and is carried out at a temperature of 20-35°C.

42. The preparation method according to claim 25, wherein, In step (2), the concentration of the aqueous monomer in the aqueous solution is 1wt%-4wt%.

43. The preparation method according to claim 42, wherein, The concentration of the aqueous monomer is 2wt%-4wt%.

44. The preparation method according to claim 25, wherein, In the oil phase solution, the concentration of the oil phase monomer is 0.05wt%-0.5wt%.

45. The preparation method according to claim 44, wherein, The concentration of the oil phase monomer is 0.05wt%-0.15wt%.

46. ​​The preparation method according to claim 25, wherein, The weight ratio of the aqueous phase monomer to the oil phase monomer is 2-40:

1.

47. The preparation method according to claim 46, wherein, The weight ratio of the aqueous phase monomer to the oil phase monomer is 5-15:

1.

48. The preparation method according to claim 25, wherein, The oil phase monomer is selected from at least one of pyromellitic methyl chloride, isophthaloyl chloride, 1,4-dichlorobenzyl chloride and 3,3,4,4-biphenyltetrachlorochloride.

49. The preparation method according to claim 48, wherein, The oil phase monomer is pyromellitic acid chloride.

50. The preparation method according to claim 25, wherein, The aqueous monomers are selected from amino compounds and / or hydroxy compounds.

51. The preparation method according to claim 50, wherein, The amino compound is selected from at least one of m-phenylenediamine, piperazine, ethylenediamine, triethylenetetramine, tetraethylenepentamine, 1,4-cyclohexanediamine, 1,3-diamino-2-methylpropane, bis(2-aminoethyl) ether, ethylene glycol bis(2-aminoethyl) ether, diethylene glycol di(3-aminopropyl) ether, 1,4-butanediol bis(3-aminopropyl) ether, and 1,4-bis(3-aminopropyl)piperazine.

52. The preparation method according to claim 51, wherein, The amino compound is selected from m-phenylenediamine and / or piperazine.

53. The preparation method according to claim 50, wherein, The hydroxyl compound is selected from at least one of α-cyclodextrin, β-cyclodextrin, and γ-cyclodextrin.

54. The preparation method according to claim 53, wherein, The hydroxyl compound is β-cyclodextrin.

55. The preparation method according to claim 25, wherein, The oil phase solution also includes an oil phase solvent, which is selected from at least one of n-hexane, n-heptane, and isoalkanes.

56. The preparation method according to claim 55, wherein, The isoalkanes are selected from Iospar G and / or Isopar E.

57. The preparation method according to claim 25, wherein, The interfacial polymerization reaction takes 0.5-60 min and is carried out at a temperature of 15-50°C.

58. The preparation method according to claim 57, wherein, The interfacial polymerization reaction takes 0.5-3 minutes and is carried out at a temperature of 25-50°C.

59. The preparation method according to any one of claims 25-58, wherein, Step (1) also includes: washing the obtained intermediate layer containing amino polymer with water.

60. The preparation method according to claim 59, wherein, The cleaning time is ≥5 hours.

61. The preparation method according to claim 60, wherein, The cleaning time is ≥12 hours.

62. The CO2-N2 separation membrane prepared by the preparation method according to any one of claims 25-61.

63. The application of the CO2-N2 separation membrane according to any one of claims 1-24 in CO2 separation.

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