Ionic liquid composite supported liquid membrane as well as preparation method and application thereof

Abstract

The invention discloses an ionic liquid composite supported liquid membrane, which comprises a polymer base membrane, an ionic liquid membrane loaded on the polymer base membrane, and an active polyamide protective layer coated on the ionic liquid membrane. The invention also discloses a preparation method of the ionic liquid composite supported liquid membrane, which comprises the following steps: (1) dissolving a polyamine monomer in a water / ionic liquid cosolvent to obtain a water-phase solution; dissolving a multi-acyl chloride monomer in an organic solvent to obtain an organic phase solution; (2) loading the aqueous phase solution into a polymer basement membrane through vacuum filtration; and (3) coating the polymer base membrane with the organic phase solution, and carrying out interfacial polymerization reaction on the polyamine monomer in the water phase solution and the polyacyl chloride monomer in the organic phase solution to form an active polyamide protective layer. The invention also provides application of the ionic liquid composite supported liquid membrane in gas separation. The ionic liquid composite supported liquid membrane disclosed by the invention has relatively high gas permeability and breakdown pressure.

Description

Technical Field

[0001] The present invention relates to the technical field of membrane separation, and in particular to an ionic liquid composite supported liquid membrane and a preparation method and application thereof. Background Art

[0002] Currently, carbon dioxide (CO2) is the main anthropogenic greenhouse gas, and its concentration in the atmosphere has increased significantly since the pre-industrial era due to economic growth and increasing demand for fossil fuels (i.e., coal, oil, and natural gas) as energy. From 1750 to 2022, the atmospheric carbon dioxide concentration increased from approximately 280 ppm to 443 ppm, far exceeding the natural range of the past 650,000 years (180 to 300 ppm). Countries have adopted different approaches to reduce carbon dioxide emissions, including more efficient energy conservation, increasing the use of more efficient low-carbon fuels for energy production (natural gas, hydrogen, or nuclear power), replacing current fossil fuel energy with more environmentally friendly energy (renewable energy), etc. In addition, the capture and separation of carbon dioxide also plays a key role.

[0003] At present, the separation technology of carbon dioxide mainly includes solvent absorption, temperature and pressure swing adsorption, low-temperature distillation, etc. The above methods have some limitations in actual industrial applications. The membrane separation method has become a new gas separation technology with great application prospects due to its small equipment, convenient operation, high efficiency, low energy consumption, and small environmental impact. Gas separation membranes mainly include organic polymer membranes, inorganic membranes, composite membranes and liquid support membranes. The separation performance of organic polymer membranes and inorganic membranes is affected by the "Robeson" upper limit, that is, it is difficult to obtain high permeability and high selectivity membrane materials at the same time; composite membranes require additional buffer layers to withstand high-pressure gas separation environments; liquid support membranes are a type of membrane material prepared by using surface tension to firmly adsorb organic solvents as liquid membrane phases in the pores of porous polymer membranes. Compared with the above membrane materials, they have the characteristics of high permeability and high selectivity, showing broad development prospects in the field of gas separation.

[0004] The ionic liquid supported liquid membrane replaces the amine-containing solvent in the traditional liquid membrane with an ionic liquid with high carbon dioxide solubility. Its purpose is to combine the advantages of ionic liquid and porous polymer substrate to improve the stability of the liquid membrane and carbon dioxide selectivity. The ionic liquid supported liquid membrane is composed of an inert polymer porous substrate and a high-viscosity, low-vapor-pressure ionic liquid loaded therein. Under the action of surface tension, the ionic liquid is firmly adsorbed in the membrane pores. The ionic liquid supported liquid membrane can be prepared by coating, impregnation, pressurized filling and other methods (temperature-increasing viscosity reduction method, high-pressure carbon dioxide assisted method, etc.). Among them, the most widely used is the pressurized filling method, which has a relatively accurate calculation of the ionic liquid adsorption rate and can ensure that the skeleton is filled with ionic liquid. The permeation effect of the ionic liquid supported liquid membrane on gas also follows the dissolution-diffusion mechanism. The viscosity, moisture conditions, temperature and pressure of the ionic liquid will affect the membrane separation performance. In addition, the choice of ionic liquid will significantly affect the carbon dioxide separation performance of the ionic liquid supported liquid membrane. Among them, imidazolium cations and sulfate anions have the highest solubility in carbon dioxide.

[0005] However, traditional ionic liquid supported liquid membranes have poor pressure resistance, are prone to leakage under pressure, and have a short service life; at the same time, the high viscosity characteristics of ionic liquids reduce the gas permeation flux of traditional ionic liquid supported liquid membranes. Summary of the invention

[0006] The present invention provides an ionic liquid composite supported liquid membrane and a preparation method and application thereof. The ionic liquid composite supported liquid membrane has high gas permeability and high breakdown pressure, which solves the problem of poor pressure resistance of traditional ionic liquid supported liquid membranes. At the same time, the ionic liquid composite supported liquid membrane has strong gas selectivity.

[0007] The technical solution of the present invention is as follows:

[0008] An ionic liquid composite support liquid membrane comprises a polymer base membrane, an ionic liquid liquid membrane loaded on the polymer base membrane, and an active polyamide protective layer coated on the ionic liquid liquid membrane.

[0009] In the ionic liquid composite supported liquid membrane of the present invention, the active polyamide protective layer improves the stability of the ionic liquid supported liquid membrane without affecting the gas permeation flux, giving the ionic liquid supported liquid membrane a higher working pressure; in addition, the amine-rich active polyamide protective layer further increases the solubility of carbon dioxide, giving the ionic liquid composite supported liquid membrane better gas separation performance.

[0010] The present invention also provides a method for preparing the ionic liquid composite supported liquid membrane, comprising:

[0011] (1) dissolving a polyamine monomer in a water / ionic liquid co-solvent to obtain an aqueous phase solution; dissolving a polyacyl chloride monomer in an organic solvent to obtain an organic phase solution;

[0012] (2) loading the aqueous phase solution into the polymer base membrane by vacuum filtration;

[0013] (3) The organic phase solution is coated on the polymer base film, and the polyamine monomers in the aqueous phase solution and the polyacyl chloride monomers in the organic phase solution undergo interfacial polymerization to form an active polyamide protective layer.

[0014] The present invention uses water / ionic liquid co-solvent to reduce the amount of ionic liquid in the ionic liquid composite support liquid membrane, reduce the effect of the viscosity of the ionic liquid on the gas permeability, and increase the gas permeability; in addition, the vacuum filtration method is used to assist in the preparation of the active polyamide separation layer, and the amine-rich branched polyethyleneimine is compounded on the ionic liquid support liquid membrane to protect the lower ionic liquid, which is not easy to leak under gas pressure conditions. In addition, the polyamide film prepared by the amine-rich polyethyleneimine has a strong solubility for specific carbon dioxide gas, thereby achieving high selectivity for carbon dioxide separation while increasing gas flux and breakdown pressure.

[0015] Preferably, the ionic liquid is at least one of 1-methyl-3-propyl imidazole tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-octyl-3-trimethylimidazolium tetrafluoroborate, 1,3-dimethylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, and 1-(2-hydroxyethyl)-3-methylimidazolium-3-ium tetrafluoroborate.

[0016] Preferably, in the water / ionic liquid co-solvent, the volume percentage of the ionic liquid is 10-100%; further, in the water / ionic liquid co-solvent, the volume percentage of the ionic liquid is 10-50%.

[0017] In water / ionic liquid co-solvent, the volume fraction of ionic liquid affects the viscosity and loading of the liquid membrane in the supported liquid membrane, thereby affecting the gas permeability, selectivity and stability of the ionic liquid supported liquid membrane. Too low volume fraction of ionic liquid will result in less ionic liquid loading in the ionic liquid supported liquid membrane, reducing the gas carrying capacity and the stability of the liquid membrane; too high volume fraction of ionic liquid will result in excessively high liquid membrane viscosity, low carrier fluidity, and reduced gas permeation flux and selectivity.

[0018] Preferably, in the aqueous solution, the mass percentage concentration of the polyamine monomer is 0.5-5wt%.

[0019] The mass percentage concentration of the polyamine monomer affects the solubility of the polyamine monomer in the water / ionic liquid co-solvent, as well as the diffusion and reaction rate at the interface, and then affects the thickness, crosslinking degree and number of surface amine groups of the polyamide layer of the composite membrane, thereby affecting the properties of the polyamide layer. If the mass percentage concentration of the polyamine monomer is too high, the thickness of the reinforcement layer will increase, which will reduce the gas flux of the composite membrane; if the mass percentage concentration of the polyamine monomer is too low, the thickness of the prepared polyamide layer will be too low or even incomplete, or the number of surface amine groups will be reduced, which will reduce the gas separation performance.

[0020] Preferably, the polyamine monomer is polyethyleneimine. The polyethyleneimine can be linear or branched.

[0021] Furthermore, the molecular weight of the polyamine monomer is 300 to 70,000 Da, and more preferably 300 to 2,000 Da.

[0022] Preferably, in the organic phase solution, the mass percentage concentration of the polyacyl chloride monomer is 0.05-0.5 wt %.

[0023] The mass percentage concentration of polyacyl chloride monomers will affect the thickness, crosslinking degree, charge and pore size of the polyamide skin layer prepared by interfacial polymerization. If the concentration of polyacyl chloride monomers is too high, the interfacial polymerization reaction will intensify, resulting in a decrease in the pore size of the polyamide layer. At the same time, the hydrolysis of excessive acyl chlorides will enhance the negative charge. If the concentration of polyacyl chloride monomers is too low, the interfacial polymerization reaction will be weakened, the pore size of the polyamide layer will be increased, and a small amount of acyl chloride hydrolysis will enhance the positive charge of the membrane.

[0024] Preferably, the polyacyl chloride monomer is at least one of trimesoyl chloride, terephthaloyl chloride, isophthaloyl chloride, phthaloyl chloride, 1,5-naphthalenedisulfonyl chloride, 1,3,6-naphthalenetrisulfonyl chloride, 1,3,5-cyclohexanetricarboxylic acid chloride and pyromellitoyl tetracarboxylic acid chloride.

[0025] Preferably, the functionality of the acyl chloride group in the polyacyl chloride monomer is 2-3.

[0026] Preferably, in the organic phase solution, the solvent is an alkane solvent (such as n-hexane, isoalkane) or toluene.

[0027] In step (2), the polymer base membrane is immersed in the aqueous solution for 1 to 10 minutes and then vacuum filtered; the vacuum filtration pressure is 0.1 to 0.15 MPa; and the vacuum filtration time is 2 to 10 minutes.

[0028] The polymer base membrane is a polysulfone, polyethersulfone, polyimide, polyamide, polyethylene, polytetrafluoroethylene, polyvinylidene fluoride, polypropylene or polyacrylonitrile microfiltration membrane.

[0029] In step (3), the organic phase solution is coated on the polymer base film, and after the interfacial polymerization reaction time is 0.5 to 30 minutes, the organic phase solution is poured out, thermally cured and dried to form an active polyamide protective layer.

[0030] Preferably, the thermal curing temperature is 50-70° C., and the thermal curing time is 1-10 min.

[0031] Preferably, the drying temperature is 50-80° C. and the drying time is 2-12 hours.

[0032] The invention also provides application of the ionic liquid composite supported liquid membrane in gas separation.

[0033] The gas separation is the separation of carbon dioxide / nitrogen and other gases.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) The ionic liquid composite supported liquid membrane provided by the present invention reduces the effect of the viscosity of the ionic liquid on the gas permeability performance and increases the gas permeability by using a water / ionic liquid co-solvent;

[0036] (2) The active polyamide separation layer is prepared by vacuum filtration. The amino-rich polyamine is compounded on the ionic liquid support liquid membrane to protect the underlying ionic liquid, which is not easy to leak under gas pressure conditions.

[0037] (3) The amine-rich polyamide film has a strong solubility in carbon dioxide gas, thereby achieving high selectivity for carbon dioxide separation while increasing gas flux and breakdown pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Surface and cross-sectional SEM images of the polyethersulfone microfiltration bottom membrane and the ionic liquid supported liquid membrane prepared in Comparative Example 1; (a) is the surface of the polyethersulfone microfiltration bottom membrane, (b) is the surface of the ionic liquid supported liquid membrane, (c) is the cross-section of the polyethersulfone microfiltration bottom membrane, and (d) is the cross-section of the ionic liquid supported liquid membrane.

[0039] Figure 2 These are infrared total reflection characterization spectra of the polyethersulfone microfiltration bottom membrane, the ionic liquid supported liquid membrane prepared in Comparative Example 1, and the polyamide thin layer composite ionic liquid supported liquid membrane prepared in Example 3.

[0040] Figure 3 This is a diagram of the loading amount of ionic liquid in the ionic liquid supported liquid membrane.

[0041] Figure 4 This is a test diagram of the gas breakdown pressure of the ionic liquid supported liquid membrane.

[0042] Figure 5 This is a test diagram of the gas permeation flux and gas selectivity performance of the ionic liquid supported liquid membrane. DETAILED DESCRIPTION

[0043] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be pointed out that the embodiments described below are intended to facilitate the understanding of the present invention and do not have any limiting effect on the present invention.

[0044] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods; the reagents, materials, etc. used in the following examples, unless otherwise specified, can be obtained from commercial channels.

[0045] The materials used in the embodiments and comparative examples are as follows:

[0046] Supporting membrane: polyethersulfone microfiltration membrane, 0.45 μm pore size, Haiyan New Oriental Plastic Technology Co., Ltd.

[0047] Supporting membrane: polyacrylonitrile microfiltration membrane, 0.45 μm pore size, Haiyan New Oriental Plastic Technology Co., Ltd.

[0048] Supporting membrane: polypropylene microfiltration membrane, 0.45 μm pore size, Haiyan New Oriental Plastic Technology Co., Ltd.

[0049] Polyethyleneimine: PEI300, 99%, Beijing Puxitang Biotechnology Co., Ltd.;

[0050] Trimesoyl chloride: 98%, Sinopharm Chemical Reagent Co., Ltd.;

[0051] n-Hexane: 97%, Sinopharm Chemical Reagent Co., Ltd.;

[0052] 1-Butyl-3-methylimidazolium tetrafluoroborate: 97%, Shanghai Myrel Biochemical Technology Co., Ltd.

[0053] The ionic liquid supported liquid membrane with polyamide thin layer protection of the present invention comprises an ionic liquid supporting layer below and an active polyamide protective layer supported on the ionic liquid supported liquid membrane. The composite membrane is prepared by first dissolving polyamine in a water / ionic liquid co-solvent to obtain a water / ionic liquid homogeneous solution of polyamine monomers, then vacuum filtering the water / ionic liquid homogeneous solution in which the polyamine monomers are dissolved into a polymer base membrane, and then spreading an organic phase in which polyacyl chlorides are dissolved on the polymer base membrane to generate an ionic liquid supported liquid membrane protected by an active polyamide layer in a one-step process.

[0054] Example 1

[0055] The method for preparing an ionic liquid supported liquid membrane with polyamide thin layer protection comprises the following steps:

[0056] (1) The supporting base membrane (polyethersulfone microfiltration membrane) is fixed on a vacuum filtration device, and a polyamine (PEI300) water / ionic liquid solution with a mass percentage concentration of 5wt% is poured into it, wherein the volume percentage of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate is 10%. After soaking the base membrane for 1 minute, vacuum filtration is performed to prepare an ionic liquid supported liquid membrane.

[0057] (2) Pour in a 0.15 wt% polyacyl chloride (trimesoyl chloride) n-hexane solution to carry out an interfacial polymerization reaction. After reacting for 1 minute, pour out the oil phase solution, take it out and dry it.

[0058] (3) The prepared composite membrane was placed in an oven to dry out moisture and dried at 60° C. for 12 h to prepare a polyamide thin layer composite ionic liquid supported liquid membrane.

[0059] The volume fraction of the ionic liquid in the ionic liquid co-solvent is 10%, and the molecular weight of polyethyleneimine is 300 Da.

[0060] Example 2

[0061] The method for preparing an ionic liquid supported liquid membrane with polyamide thin layer protection comprises the following steps:

[0062] (1) The supporting base membrane (polyethersulfone microfiltration membrane) was fixed on a vacuum filtration device, and a polyamine (PEI) having a mass percentage concentration of 5 wt% was poured into the 300 ) water / ionic liquid solution, wherein the volume percentage of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate is 20%. After soaking the base membrane for 1 minute, vacuum filtration is performed to prepare an ionic liquid supported liquid membrane.

[0063] (2) Pour in a 0.15 wt% polyacyl chloride (trimesoyl chloride) n-hexane solution to carry out an interfacial polymerization reaction. After reacting for 1 minute, pour out the oil phase solution, take it out and dry it.

[0064] (3) The prepared composite membrane was placed in an oven to dry out moisture and dried at 60° C. for 12 h to prepare a polyamide thin layer composite ionic liquid supported liquid membrane.

[0065] The volume fraction of the ionic liquid in the ionic liquid co-solvent is 20%, and the molecular weight of polyethyleneimine is 300 Da.

[0066] Example 3

[0067] The method for preparing an ionic liquid supported liquid membrane with polyamide thin layer protection comprises the following steps:

[0068] (1) The supporting base membrane (polyethersulfone microfiltration membrane) was fixed on a vacuum filtration device, and a polyamine (PEI) having a mass percentage concentration of 5 wt% was poured into the 300) water / ionic liquid solution, wherein the volume percentage of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate is 30%. After soaking the base membrane for 1 minute, vacuum filtration is performed to prepare an ionic liquid supported liquid membrane.

[0069] (2) Pour in a 0.15 wt% polyacyl chloride (trimesoyl chloride) n-hexane solution to carry out an interfacial polymerization reaction. After reacting for 1 minute, pour out the oil phase solution, take it out and dry it.

[0070] (3) The prepared composite membrane was placed in an oven to dry out moisture and dried at 60° C. for 12 h to prepare a polyamide thin layer composite ionic liquid supported liquid membrane.

[0071] The volume fraction of the ionic liquid in the ionic liquid co-solvent is 30%, and the molecular weight of polyethyleneimine is 300 Da.

[0072] Example 4

[0073] The method for preparing an ionic liquid supported liquid membrane with polyamide thin layer protection comprises the following steps:

[0074] (1) The supporting base membrane (polyethersulfone microfiltration membrane) was fixed on a vacuum filtration device, and a polyamine (PEI) having a mass percentage concentration of 5 wt% was poured into the 600 ) water / ionic liquid solution, wherein the volume percentage of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate is 30%. After soaking the base membrane for 1 minute, vacuum filtration is performed to prepare an ionic liquid supported liquid membrane.

[0075] (2) Pour in a 0.15 wt% polyacyl chloride (trimesoyl chloride) n-hexane solution to carry out an interfacial polymerization reaction. After reacting for 1 minute, pour out the oil phase solution, take it out and dry it.

[0076] (3) The prepared composite membrane was placed in an oven to dry out moisture and dried at 60° C. for 12 h to prepare a polyamide thin layer composite ionic liquid supported liquid membrane.

[0077] The volume fraction of the ionic liquid in the ionic liquid co-solvent is 20%, and the molecular weight of polyethyleneimine is 600 Da.

[0078] Example 5

[0079] The method for preparing an ionic liquid supported liquid membrane with polyamide thin layer protection comprises the following steps:

[0080] (1) The supporting base membrane (polyethersulfone microfiltration membrane) was fixed on a vacuum filtration device, and a polyamine (PEI) having a mass percentage concentration of 5 wt% was poured into the 1800) water / ionic liquid solution, wherein the volume percentage of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate is 30%. After soaking the base membrane for 1 minute, vacuum filtration is performed to prepare an ionic liquid supported liquid membrane.

[0081] (2) Pour in a 0.15 wt% polyacyl chloride (trimesoyl chloride) n-hexane solution to carry out an interfacial polymerization reaction. After reacting for 1 minute, pour out the oil phase solution, take it out and dry it.

[0082] (3) The prepared composite membrane was placed in an oven to dry out moisture and dried at 60° C. for 12 h to prepare a polyamide thin layer composite ionic liquid supported liquid membrane.

[0083] The volume fraction of the ionic liquid in the ionic liquid co-solvent is 30%, and the molecular weight of polyethyleneimine is 1800 Da.

[0084] Example 6

[0085] The method for preparing an ionic liquid supported liquid membrane protected by a polyamide thin layer comprises the following steps:

[0086] (1) The supporting base membrane (polyethersulfone microfiltration membrane) was fixed on a vacuum filtration device, and a polyamine (PEI) having a mass percentage concentration of 20 wt% was poured into the 300 ) water / ionic liquid solution, wherein the volume percentage of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate is 30%. After soaking the base membrane for 1 minute, vacuum filtration is performed to prepare an ionic liquid supported liquid membrane.

[0087] (2) Pour in a 0.15 wt% polyacyl chloride (trimesoyl chloride) n-hexane solution to carry out an interfacial polymerization reaction. After reacting for 1 minute, pour out the oil phase solution, take it out and dry it.

[0088] (3) The prepared composite membrane was placed in an oven to dry out moisture and dried at 60° C. for 12 h to prepare a polyamide thin layer composite ionic liquid supported liquid membrane.

[0089] The volume fraction of the ionic liquid in the ionic liquid co-solvent is 30%, and the molecular weight of polyethyleneimine is 300 Da.

[0090] Example 7

[0091] The method for preparing an ionic liquid supported liquid membrane protected by a polyamide thin layer comprises the following steps:

[0092] (1) The supporting base membrane (polyethersulfone microfiltration membrane) was fixed on a vacuum filtration device, and a polyamine (PEI) having a mass percentage concentration of 5 wt% was poured into the 300) water / ionic liquid solution, wherein the volume percentage of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate is 30%. After soaking the base membrane for 1 minute, vacuum filtration is performed to prepare an ionic liquid supported liquid membrane.

[0093] (2) Pour in a 0.35 wt% polyacyl chloride (trimesoyl chloride) n-hexane solution to carry out an interfacial polymerization reaction. After reacting for 1 minute, pour out the oil phase solution, take it out and dry it.

[0094] (3) The prepared composite membrane was placed in an oven to dry out moisture and dried at 60° C. for 12 h to prepare a polyamide thin layer composite ionic liquid supported liquid membrane.

[0095] The volume fraction of the ionic liquid in the ionic liquid co-solvent is 30%, and the molecular weight of polyethyleneimine is 300 Da.

[0096] Example 8

[0097] The method for preparing an ionic liquid supported liquid membrane protected by a polyamide thin layer comprises the following steps:

[0098] (1) The supporting base membrane (polyethersulfone microfiltration membrane) was fixed on a vacuum filtration device, and a polyamine (PEI) having a mass percentage concentration of 5 wt% was poured into the 600 ) water / ionic liquid solution, wherein the volume percentage of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate is 30%. After soaking the base membrane for 1 minute, vacuum filtration is performed to prepare an ionic liquid supported liquid membrane.

[0099] (2) Pour in a 0.15 wt% polyacyl chloride (trimesoyl chloride) n-hexane solution to carry out interfacial polymerization reaction. After reacting for 10 minutes, pour out the oil phase solution, take it out and dry it.

[0100] (3) The prepared composite membrane was placed in an oven to dry out moisture and dried at 60° C. for 12 h to prepare a polyamide thin layer composite ionic liquid supported liquid membrane.

[0101] The volume fraction of the ionic liquid in the ionic liquid co-solvent is 30%, and the molecular weight of polyethyleneimine is 600 Da.

[0102] Example 9

[0103] The method for preparing an ionic liquid supported liquid membrane protected by a polyamide thin layer comprises the following steps:

[0104] (1) The supporting base membrane (polyethersulfone microfiltration membrane) was fixed on a vacuum filtration device, and a polyamine (PEI) having a mass percentage concentration of 5 wt% was poured into the 300) water / ionic liquid solution, wherein the volume percentage of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate is 50%. After soaking the base membrane for 1 minute, vacuum filtration is performed to prepare an ionic liquid supported liquid membrane.

[0105] (2) Pour in a 0.15 wt% polyacyl chloride (trimesoyl chloride) n-hexane solution to carry out an interfacial polymerization reaction. After reacting for 1 minute, pour out the oil phase solution, take it out and dry it.

[0106] (3) The prepared composite membrane was placed in an oven to dry out moisture and dried at 60° C. for 12 h to prepare a polyamide thin layer composite ionic liquid supported liquid membrane.

[0107] The volume fraction of the ionic liquid in the ionic liquid co-solvent is 50%, and the molecular weight of polyethyleneimine is 300 Da.

[0108] Comparative Example 1

[0109] This comparative example provides a traditional ionic liquid supported liquid membrane, which is prepared by vacuum filtration. The ionic liquid is 1-butyl-3-methyl-imidazole tetrafluoroborate.

[0110] The preparation method comprises the following steps:

[0111] (1) The supporting base membrane (polyethersulfone microfiltration membrane) was fixed on a vacuum filtration device, and the ionic liquid was poured into the supporting base membrane. After soaking the supporting base membrane for 1 min, the supporting base membrane was vacuum filtered to prepare the ionic liquid supporting liquid membrane.

[0112] (2) Control the filtration pressure to 0.1 MPa and the filtration time to 5 min. After the filtration is completed, take it out and dry it.

[0113] (3) The prepared ionic liquid supported liquid membrane was placed in an oven for drying at 60° C. for 12 h to obtain an ionic liquid supported liquid membrane.

[0114] Figure 1 The surface and cross-sectional electron microscope scanning images of the pure polyethersulfone microfiltration bottom membrane and the ionic liquid supported liquid membrane prepared in Comparative Example 1. Compared with the pure polyethersulfone microfiltration bottom membrane, the bottom membrane pores in the ionic liquid supported liquid membrane are filled with ionic liquid to form a dense and uneven structure.

[0115] Figure 2 The infrared total reflection characterization spectra of the pure polyethersulfone microfiltration bottom membrane, the ionic liquid supported liquid membrane prepared in Comparative Example 1, and the polyamide thin layer composite ionic liquid supported liquid membrane prepared in Example 3. -1 、2950cm -1 The wave number position is the stretching vibration peak of the methyl and methylene groups on the imidazole ring of the ionic liquid, indicating the successful preparation of the ionic liquid supported liquid membrane; 1650cm -1The wave number position is the stretching vibration peak of the carbonyl group on the amide bond, which can be used to determine the successful preparation of the polyamide thin layer; 3300cm -1 The stretching vibration peak of the amine group appeared at the wavenumber position, proving the successful preparation of the amino-rich polyamide layer.

[0116] Comparative Example 2

[0117] This comparative example provides a polyamide thin layer composite membrane, which is prepared by interfacial polymerization. The active polyamide separation layer includes an interfacial polymerization product of polyamine and polyacyl chloride.

[0118] The preparation method comprises the following steps:

[0119] (1) The supporting base membrane (polyethersulfone microfiltration membrane) was fixed on a vacuum filtration device, and a polyamine (PEI) having a mass percentage concentration of 5 wt% was poured into the 300 ) aqueous solution, soak the base film for 1 minute, then vacuum filter, then pour in a 0.15wt% polyacyl chloride (trimesoyl chloride) n-hexane solution to carry out interfacial polymerization. After reacting for 1 minute, pour out the oil phase solution, take it out and dry it.

[0120] (2) The prepared composite membrane is washed three times with deionized water until the ionic liquid is completely washed away, and then placed in an oven for drying to obtain a polyamide thin layer composite membrane.

[0121] Performance Testing

[0122] Test Example 1: Ionic Liquid Absorption

[0123] The amount of ionic liquid absorbed by the microfiltration bottom membrane can be expressed by the liquid absorption amount, as shown in formula (1):

[0124] Absorbance=(Δm / ρ) / (S*H) (1)

[0125] Where Absorbance represents the amount of liquid absorbed, Δm represents the difference in membrane weight before and after absorption (g); ρ represents the density of the ionic liquid (g / cm 3 ); S*H represents the volume of polyethersulfone microfiltration membrane (cm 3 ).

[0126] The polyamide thin layer composite ionic liquid supported liquid membranes with different ionic liquid contents were thermally cured at 60°C and weighed on a balance. The liquid absorption of the ionic liquid supported liquid membranes under different conditions was calculated using formula (1).

[0127] like Figure 3As shown, the loading amount of ionic liquid in the ionic liquid supported liquid membrane increases with the increase of the ionic liquid co-solvent content, and the loading amount of ionic liquid in the pure ionic liquid supported liquid membrane is 7%. In Examples 1, 2, 3, 9, and Comparative Example 1, the loading amounts of ionic liquid in the ionic liquid supported liquid membrane are 0.8%, 1.6%, 2.4%, 3.7%, and 7%, respectively.

[0128] This indicates that as the volume fraction of ionic liquid in the water / ionic liquid co-solvent increases, the loading amount of ionic liquid in the ionic liquid supported liquid membrane prepared by vacuum filtration also increases.

[0129] Test Example 2: Breakdown Pressure Test

[0130] The breakdown pressure refers to the critical pressure at which the prepared polyamide thin layer composite ionic liquid supported liquid membrane is broken through by gas, i.e. the membrane is destroyed. The breakdown pressure can reflect the pressure resistance and stability of the membrane.

[0131] The prepared membrane is fixed in the membrane pool of the gas separation device with the polyamide skin layer facing the upstream side of gas separation. A soap film flowmeter is connected to one side of the membrane pool, and the end of the flowmeter is connected to the atmosphere. A positive pressure is applied to the other side. The pressure increases step by step with time, and the critical pressure at which bubbles appear in the flowmeter is measured. This pressure is the breakdown pressure of the membrane.

[0132] The breakdown pressure of Comparative Example 2, Example 1, Example 2, Example 3, Example 9, and Comparative Example 1 was tested. The test gas was N2. The test method was to increase the pressure on the membrane by 0.02 MPa every five minutes until the membrane was punctured, and the breakdown pressure at this time was recorded.

[0133] like Figure 4 As shown, the breakdown pressure in Comparative Example 2 is 0.02 MPa, indicating that the pore size of the polyamide cortex is too large to block N2; the breakdown pressure in Comparative Example 1 is 0.1 MPa, indicating that the traditional ionic liquid supported liquid membrane has a blocking effect on gas, but the pressure resistance and stability are not high; the breakdown pressure in Example 3 is about 0.15 MPa, indicating that compared with the traditional ionic liquid supported liquid membrane, the polyamide thin layer composite ionic liquid supported liquid membrane has higher pressure resistance and stability.

[0134] Test Example 3: Gas Separation Performance Test

[0135] Gas separation performance refers to the performance of selective separation of a specific gas component using a membrane under ideal gas conditions. In the test, the separation performance of a specific gas component is calculated based on the different permeation rates of different gas components through the membrane. Gas separation performance is measured by separation degree, and the separation degree calculation formula is as follows:

[0136] α=P(A) / P(B)

[0137] Where α represents the separation degree, P(A) represents the ideal gas permeability of component A (GPU, 10 -6 cm 3 cm -2 ·s -1 cmHg -1 ), P(B) represents the ideal gas permeability of component B (GPU, 10 -6 cm 3 cm -2 ·s -1 cmHg -1 ).

[0138] The gas separation performance of polyamide thin layer composite ionic liquid supported liquid membrane prepared with different ionic liquid co-solvent contents was tested, and the permeability of different gas components was calculated by the pressure gauge readings through the constant volume variable pressure gas separation performance test device. Figure 5 As shown, the separation selectivity of comparative example 2 for carbon dioxide / nitrogen is not high, about 1.43; the selectivity of example 1 for carbon dioxide / nitrogen is slightly improved, reaching about 14.3, because the content of ionic liquid is small and the separation is not high; examples 2 and 3 have higher selectivity for carbon dioxide / nitrogen, reaching 195.1 and 210.5. The reason is that the IL content is further increased, and the amine-rich polyamide layer and the complete ionic liquid support liquid membrane greatly improve the solubility of carbon dioxide; the pure ionic liquid support liquid membrane has separation performance for carbon dioxide / nitrogen but not so high, because the lack of polyamide skin layer reduces the dissolution of carbon dioxide. In addition, the high viscosity of the ionic liquid hinders the passage of gas and reduces the separation degree.

[0139] The embodiments described above provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements and equivalent substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An ionic liquid composite supported liquid membrane, characterized in that: The invention comprises a polymer base film, an ionic liquid membrane loaded on the polymer base film, and an active polyamide protective layer coated on the ionic liquid membrane.

2. A method for preparing the ionic liquid composite supported liquid membrane according to claim 1, characterized in that: include: (1) dissolving a polyamine monomer in a water / ionic liquid co-solvent to obtain an aqueous phase solution; dissolving a polyacyl chloride monomer in an organic solvent to obtain an organic phase solution; (2) loading the aqueous phase solution into the polymer base membrane by vacuum filtration; (3) The organic phase solution is coated on the polymer base film, and the polyamine monomers in the aqueous phase solution and the polyacyl chloride monomers in the organic phase solution undergo interfacial polymerization to form an active polyamide protective layer.

3. The method for preparing the ionic liquid composite supported liquid membrane according to claim 2, characterized in that: The ionic liquid is at least one of 1-methyl-3-propyl imidazole tetrafluoroborate, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-octyl-3-trimethylimidazolium tetrafluoroborate, 1,3-dimethylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, and 1-(2-hydroxyethyl)-3-methylimidazolium-3-ium tetrafluoroborate.

4. The method for preparing the ionic liquid composite supported liquid membrane according to claim 2, characterized in that: In the water / ionic liquid co-solvent, the volume percentage of the ionic liquid is 10-100%.

5. The method for preparing the ionic liquid composite supported liquid membrane according to claim 2, characterized in that: In the aqueous solution, the mass percentage concentration of the polyamine monomer is 0.5-5wt%.

6. The method for preparing the ionic liquid composite supported liquid membrane according to claim 2 or 5, characterized in that: The polyamine monomer is polyethyleneimine; the molecular weight of the polyamine monomer is 300-70000Da.

7. The method for preparing the ionic liquid composite supported liquid membrane according to claim 2, characterized in that: In the organic phase solution, the mass percentage concentration of the polyacyl chloride monomer is 0.05-0.5wt%.

8. The method for preparing the ionic liquid composite supported liquid membrane according to claim 2, characterized in that: In step (2), the polymer base membrane is immersed in the aqueous solution for 1 to 10 minutes and then vacuum filtered; the vacuum filtration pressure is 0.1 to 0.15 MPa; and the vacuum filtration time is 2 to 10 minutes.

9. The method for preparing an ionic liquid composite supported liquid membrane according to claim 2, characterized in that: In step (3), the organic phase solution is coated on the polymer base film, and after the interfacial polymerization reaction time is 0.5 to 30 minutes, the organic phase solution is poured out, thermally cured and dried to form an active polyamide protective layer.

10. Use of the ionic liquid composite supported liquid membrane according to claim 1 in gas separation.

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