CN111603945A - Ionic liquid functionalized cerium fluoride porous nanosheet, preparation method and application thereof, mixed matrix membrane, preparation method and application thereof - Google Patents
Ionic liquid functionalized cerium fluoride porous nanosheet, preparation method and application thereof, mixed matrix membrane, preparation method and application thereof Download PDFInfo
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Abstract
The invention provides an ionic liquid functionalized cerium fluoride porous nanosheet, a preparation method and application thereof, a mixed matrix membrane, a preparation method and application thereof, and belongs to the technical field of gas separation membranes. In the invention, the ionic liquid contains basic groups and has CO2Affinity, which can increase the adsorption sites of the acid gas, promote the dissolution-diffusion of the acid gas and improve the selectivity and permeability of the acid gas; the cerium fluoride porous nano-sheet has an interlayer channel, a rich nano-pore structure, a special fluorine-cerium monoatomic layer and interlayer acetate alternate stacking structure, a 0.344nm interlayer spacing is formed, gas molecules with different molecular dynamics diameters can be screened, the selectivity is improved, the transmission speed of the gas molecules is accelerated,further improving the gas permeability.
Description
Technical Field
The invention relates to the technical field of gas separation membranes, in particular to an ionic liquid functionalized cerium fluoride porous nanosheet, a preparation method and application thereof, a mixed matrix membrane, a preparation method and application thereof.
Background
A large amount of CO is generated in daily production and life2When CO is present in the air2When the content is too high, greenhouse effect is caused, and global warming and other climate problems are caused. Therefore, there is an urgent need to develop efficient CO2A trapping technique. The membrane separation technology is considered to be CO with good application prospect due to the advantages of low cost, low energy consumption, green environmental protection and the like2The trapping method, the research and development of membrane materials with good permeation and selectivity performance are the key points for improving the competitiveness of the membrane separation technology.
The membrane material in the prior art, such as the lanthanide fluoride two-dimensional porous nanosheet membrane material disclosed in CN108358233A, has the problem of poor permeability and selectivity to acidic gases.
Disclosure of Invention
In view of the above, the invention aims to provide an ionic liquid functionalized cerium fluoride porous nanosheet, a preparation method and an application thereof, a mixed matrix membrane, a preparation method and an application thereof. The ionic liquid of the ionic liquid functionalized cerium fluoride porous nanosheet contains basic groups, and has excellent permeability and selectivity on acidic gases.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides an ionic liquid functionalized cerium fluoride porous nanosheet, which comprises a cerium fluoride porous nanosheet and an ionic liquid; the cerium fluoride porous nanosheet is combined with the ionic liquid through electrostatic adsorption, and the ionic liquid contains basic groups; the cerium fluoride porous nanosheet is formed by alternately stacking and arranging fluorine-cerium monoatomic layers and interlayer acetate.
Preferably, the ionic liquid comprises one or more of 1-ethyl-3-methylimidazole thiocyanate, 1-ethyl-3-methylimidazole nitrate, and 1-butyl-3-methylimidazole thiocyanate.
Preferably, the cerium fluoride porous nanosheet is assembled by nanoparticles with diameters of 0.5-5 nm.
Preferably, the average pore diameter of the ionic liquid functionalized cerium fluoride porous nanosheet is 0.1-10 nm.
The invention also provides a preparation method of the ionic liquid functionalized cerium fluoride porous nanosheet, which comprises the following steps:
in nitrogen atmosphere, mixing water-soluble cerium salt with a sodium acetate aqueous solution to obtain a mixed solution;
mixing a fluorine-containing salt water solution with the mixed solution for precipitation reaction to obtain cerium fluoride porous nanosheets;
and mixing the aqueous solution of the cerium fluoride porous nanosheet with an ionic liquid to obtain the ionic liquid functionalized cerium fluoride porous nanosheet.
Preferably, the mass ratio of the aqueous solution of the cerium fluoride porous nanosheet to the ionic liquid is (5-20): 1, and the concentration of the aqueous solution of the cerium fluoride porous nanosheet is 0.01-0.06 mg/mL.
Preferably, the blending time is 4-72 h.
The invention also provides a mixed matrix membrane, which comprises the following components in percentage by mass: 0.5-30% of ionic liquid functionalized cerium fluoride porous nanosheet and 70-99.5% of polyoxyethylene-based polymer, wherein the ionic liquid functionalized cerium fluoride porous nanosheet is the ionic liquid functionalized cerium fluoride porous nanosheet in the technical scheme or the ionic liquid functionalized cerium fluoride porous nanosheet prepared by the preparation method in the technical scheme.
The invention also provides a preparation method of the mixed matrix membrane in the technical scheme, which comprises the following steps:
mixing the solution of the ionic liquid functionalized cerium fluoride porous nanosheet with the solution of a polyoxyethylene-based polymer to obtain a membrane casting solution;
and (3) defoaming the casting solution, volatilizing the solvent and drying in vacuum in sequence to obtain the mixed matrix membrane.
The invention also provides an ionic liquid functionalized cerium fluoride porous nanosheet or an application of the mixed matrix membrane in the technical scheme in the field of gas separation.
The invention provides an ionic liquid functionalized cerium fluoride porous nanosheet, which comprises a cerium fluoride porous nanosheet and an ionic liquid; the cerium fluoride porous nanosheet is combined with the ionic liquid through electrostatic adsorption, and the ionic liquid contains basic groups; the cerium fluoride porous nanosheet is formed by alternately stacking and arranging fluorine-cerium monoatomic layers and interlayer acetate. In the invention, the ionic liquid contains basic groups and has CO2Affinity, which can increase the adsorption sites of the acid gas, promote the dissolution-diffusion of the acid gas and improve the selectivity and permeability of the acid gas; the cerium fluoride porous nanosheet is provided with an interlayer channel and a rich nanopore structure, has a special fluorine-cerium monoatomic layer and interlayer acetate alternate stacking structure, forms a 0.344nm interlayer spacing, can screen gas molecules with different molecular dynamics diameters, improves selectivity, accelerates the transmission speed of the gas molecules, and further improves gas permeability.
Furthermore, the ionic liquid comprises one or more of 1-ethyl-3-methylimidazole thiocyanate, 1-ethyl-3-methylimidazole nitrate and 1-butyl-3-methylimidazole thiocyanate, and the adsorption performance of the ionic liquid on acid gas is further improved by imidazole groups contained in the ionic liquid.
The invention also provides a preparation method of the ionic liquid functionalized cerium fluoride porous nanosheet, a template is not required to be added in the preparation process, the application range is wide, the operation process is simple and convenient, the method is green, safe and pollution-free, and the prepared cerium fluoride porous nanosheet is good in crystallinity and not damaged in the functionalization process.
The invention also provides a mixed matrix membrane, which is a polymer-inorganic mixed matrix membrane, has the advantages of a polymer membrane and an inorganic membrane, overcomes the respective defects, utilizes inorganic particles to interfere the arrangement of polymer chains in the membrane, regulates and optimizes the microstructure and the free volume of the membrane, improves the pore space and the gas permeability coefficient of the membrane, and provides a new path for the development of the separation membrane, and comprises the following components in percentage by mass: 0.5-30% of ionic liquid functionalized cerium fluoride porous nanosheet and 70-99.5% of polyoxyethylene-based polymer, wherein the ionic liquid functionalized cerium fluoride porous nanosheet is used as a dispersed phase, and a polyoxyethylene-based polymer matrix is used as a continuous phase, so that the trade-off effect in a polymer matrix film can be effectively overcome, the ionic liquid functionalized cerium fluoride porous nanosheet is used as a filler to prepare a polymer-inorganic mixed matrix film, an F element in the ionic liquid functionalized cerium fluoride porous nanosheet is easy to form a hydrogen bond with hydrogen in the polyoxyethylene-based polymer, so that the ionic liquid functionalized cerium fluoride porous nanosheet has good interface compatibility and interface bonding force, the hydrogen bond can increase the affinity between a gas molecule and the ionic liquid functionalized cerium fluoride porous nanosheet, and the transmission speed of the gas molecule in the ionic liquid functionalized cerium fluoride porous nanosheet is far higher than that in the polyoxyethylene-based polymer matrix, thereby improving the gas permeability, and the provided mixed matrix membrane not only can improve the selectivity and the permeability to acid gas, but also can improve the mechanical property of the polymer-inorganic mixed matrix membrane.
The invention also provides a preparation method of the mixed matrix membrane, the ionic liquid functionalized cerium fluoride porous nanosheet is added into the polyoxyethylene-based polymer matrix through simple physical blending, and the ionic liquid functionalized cerium fluoride porous nanosheet can play a role in size sieving in the membrane so as to improve the gas separation performance; the chain segment mobility and the phase separation structure of the polyoxyethylene-based polymer matrix can be changed, and more free volume is provided for gas transmission; the ionic liquid functionalized cerium fluoride porous nanosheet and the polyoxyethylene-based polymer have good interface compatibility and alkaline groups, and the gas permeability is improved.
Drawings
FIG. 1 is a low power TEM image of ionic liquid functionalized cerium fluoride porous nanosheets prepared in example 1;
FIG. 2 is a high-power TEM image of ionic liquid functionalized cerium fluoride porous nanosheets prepared in example 1;
FIG. 3 is X-ray diffraction patterns of ionic liquid functionalized cerium fluoride porous nanosheets and cerium fluoride porous nanosheets prepared in example 1;
FIG. 4 is a Fourier infrared spectrum of the ionic liquid functionalized cerium fluoride porous nanosheet prepared in example 1;
FIG. 5 is a pore size distribution diagram of an ionic liquid functionalized cerium fluoride porous nanosheet prepared in example 1;
FIG. 6 is a sectional partial SEM photograph of a polyoxyethylene-based polymer pure film obtained in comparative example 1;
FIG. 7 is a sectional partial SEM photograph of the mixed matrix membrane obtained in example 6.
Detailed Description
The invention provides an ionic liquid functionalized cerium fluoride porous nanosheet (F-F-Ce), which comprises a cerium fluoride porous nanosheet (F-Ce) and Ionic Liquid (ILs); the cerium fluoride porous nanosheet is combined with the ionic liquid through electrostatic adsorption, and the ionic liquid contains basic groups; the cerium fluoride porous nanosheet is formed by alternately stacking and arranging fluorine-cerium monoatomic layers and interlayer acetate.
In the present invention, the ionic liquid preferably comprises one or more of 1-ethyl-3-methylimidazole thiocyanate, 1-ethyl-3-methylimidazole nitrate and 1-butyl-3-methylimidazole thiocyanate. The source of the ionic liquid is not particularly limited in the present invention, and the ionic liquid can be prepared by a preparation method well known to those skilled in the art or can be commercially available.
In the invention, the cerium fluoride porous nanosheet is preferably assembled by nanoparticles with diameters of 0.5-5 nm.
In the invention, the average pore diameter of the ionic liquid functionalized cerium fluoride porous nanosheet is preferably 0.1-10 nm, and more preferably 3.057 nm. In the present invention, the interlayer spacing of the ionic liquid functionalized cerium fluoride porous nanosheets is preferably 0.344 nm.
The invention also provides a preparation method of the ionic liquid functionalized cerium fluoride porous nanosheet, which comprises the following steps:
in nitrogen atmosphere, mixing water-soluble cerium salt with a sodium acetate aqueous solution to obtain a mixed solution;
mixing a fluorine-containing salt water solution with the mixed solution for precipitation reaction to obtain cerium fluoride porous nanosheets;
and mixing the aqueous solution of the cerium fluoride porous nanosheet with an ionic liquid to obtain the ionic liquid functionalized cerium fluoride porous nanosheet.
In the invention, water-soluble cerium salt and sodium acetate aqueous solution are mixed in nitrogen atmosphere to obtain mixed solution. In the invention, the water-soluble cerium salt is preferably cerium nitrate, the concentration of the cerium nitrate in the mixed solution is preferably 5-100 mg/mL, and the molar ratio of the cerium nitrate to sodium acetate is preferably 1 (1-10). In the invention, the mixing time is preferably 12-72 h, and the mixing temperature is preferably 7-50 ℃.
After the mixed solution is obtained, the fluorine-containing salt water solution and the mixed solution are mixed for precipitation reaction to obtain the cerium fluoride porous nanosheet. In the present invention, the concentration of the fluorine-containing salt aqueous solution is preferably 5 to 100mg/mL, and the fluorine-containing salt aqueous solution and the mixed solution are preferably mixed so that the molar ratio of fluorine element to cerium element is (0.1 to 10): 1. In the present invention, the fluorine-containing salt in the aqueous fluorine-containing salt solution preferably includes one or more of ammonium fluoride, sodium fluoride, potassium fluoroborate, potassium fluorosilicate, and tetrabutylammonium fluoride.
In the invention, the temperature of the precipitation reaction is preferably 15-25 ℃, and the time is preferably 0.5-24 h.
After the cerium fluoride porous nanosheet is obtained, the aqueous solution of the cerium fluoride porous nanosheet is mixed with the ionic liquid to obtain the ionic liquid functionalized cerium fluoride porous nanosheet.
In the invention, the mass ratio of the aqueous solution of the cerium fluoride porous nanosheet to the ionic liquid is preferably (5-20): 1, and the concentration of the aqueous solution of the cerium fluoride porous nanosheet is preferably 0.01-0.06 mg/mL.
In the invention, the blending time is preferably 4-72 h, more preferably 8h, and the blending temperature is preferably 7-50 ℃.
The invention also provides a mixed matrix membrane, which comprises the following components in percentage by mass: 0.5-30% of ionic liquid functionalized cerium fluoride porous nanosheet and 70-99.5% of polyoxyethylene-based polymer, wherein the ionic liquid functionalized cerium fluoride porous nanosheet is the ionic liquid functionalized cerium fluoride porous nanosheet in the technical scheme or the ionic liquid functionalized cerium fluoride porous nanosheet prepared by the preparation method in the technical scheme.
In the invention, the mass fraction of the ionic liquid functionalized cerium fluoride porous nanosheet is preferably 4-30%, and more preferably 10-20%.
In the present invention, the polyoxyethylene-based polymer is preferably Pebax 1657.
In the present invention, the thickness of the mixed matrix film is preferably 80 to 200 μm.
The invention also provides a preparation method of the mixed matrix membrane in the technical scheme, which comprises the following steps:
mixing the solution of the ionic liquid functionalized cerium fluoride porous nanosheet with the solution of a polyoxyethylene-based polymer to obtain a membrane casting solution;
and (3) defoaming the casting solution, volatilizing the solvent and drying in vacuum in sequence to obtain the mixed matrix membrane.
According to the invention, preferably, ionic liquid functionalized cerium fluoride porous nanosheets are added into a composite solvent for ultrasonic dispersion to obtain a solution of the ionic liquid functionalized cerium fluoride porous nanosheets, and a polyoxyethylene-based polymer is added into the composite solvent to obtain a solution of the polyoxyethylene-based polymer. The invention can make the ionic liquid functionalized cerium fluoride porous nanosheet have better dispersibility in the membrane casting solution by mixing in times.
In the present invention, the polyoxyethylene-based polymer solution is preferably obtained by stirring under reflux at 80 ℃ for 1 to 3 hours.
In the invention, the composite solvent is preferably formed by mixing ethanol and water according to a mass ratio of 7: 3.
In the invention, the mass fraction of the solution of the ionic liquid functionalized cerium fluoride porous nanosheet is preferably 0.05-0.1%; the mass fraction of the polyoxyethylene-based polymer solution is preferably 3% to 15%.
In the invention, the casting solution is preferably defoamed and poured into a clean polytetrafluoroethylene culture dish, and the mixed matrix membrane is obtained after the solvent is volatilized and dried in vacuum. In the invention, the temperature for volatilizing the solvent is preferably 15-25 ℃, and the time is preferably 24-72 h; the temperature of the vacuum drying is preferably 40-60 ℃, and the time is preferably 24-48 h.
The invention also provides an ionic liquid functionalized cerium fluoride porous nanosheet or an application of the mixed matrix membrane in the technical scheme in the field of gas separation.
In the present invention, said application preferably comprises CO2And CH4，O2And N2，H2And N2，H2And CH4，CO2And N2，H2And CO2Separation of (4).
In order to further illustrate the invention, the ionic liquid functionalized cerium fluoride porous nanosheet and the preparation method and application thereof, the mixed matrix membrane and the preparation method and application thereof provided by the invention are described in detail below with reference to examples, but the ionic liquid functionalized cerium fluoride porous nanosheet and the preparation method and application thereof cannot be construed as limiting the scope of the invention.
Example 1
Preparing 1-ethyl-3-methylimidazole thiocyanate ionic liquid functionalized cerium fluoride porous nanosheets:
(a) adding 300mL of pure water into a three-neck flask, blowing nitrogen for 20min, and then sequentially adding 3.6mmol of cerium nitrate and 3.6mmol of sodium acetate solid powder, wherein the molar ratio of the cerium nitrate to the sodium acetate is 1:1, and stirring and dissolving at 25 ℃ to obtain a mixed solution;
(b) adding 20mL of 5mg/mL ammonium fluoride aqueous solution into the mixed solution, stirring and reacting for 2h at room temperature, and centrifuging, freezing and drying to obtain cerium fluoride porous nanosheets;
(c) and (c) fully blending the aqueous solution of the cerium fluoride porous nanosheet obtained in the step (b) and 1-ethyl-3-methylimidazol thiocyanate ionic liquid for 8 hours in a mass ratio of 10:1 to obtain the ionic liquid functionalized cerium fluoride porous nanosheet.
Example 2
Same as example 1 except that "fully blended 48 h" in step (c) was modified to "fully blended 72 h".
Example 3
Same as example 1 except that "thoroughly blending at a mass ratio of 10: 1" in step (c) was modified to "thoroughly blending at a mass ratio of 5: 1".
Example 4
Same as example 1 except that "1-ethyl-3-methylimidazolium thiocyanate ionic liquid" was modified to "1-ethyl-3-methylimidazolium nitrate" in step (c).
Example 5
Same as example 1 except that "1-ethyl-3-methylimidazolium thiocyanate ionic liquid" in step (c) was modified to "1-butyl-3-methylimidazolium thiocyanate".
Example 6
A preparation method of a mixed matrix membrane specifically comprises the following steps:
(1) 0.036g of the ionic liquid functionalized cerium fluoride porous nanosheet prepared in example 1 is added into 4mL of a composite solvent (the composite solvent is prepared by mixing ethanol and water according to a mass ratio of 7: 3), and ultrasonic dispersion is carried out for 3 hours, so as to obtain a functionalized cerium fluoride porous nanosheet solution.
(2) 0.9g of polyoxyethylene-based polymer is added into a composite solvent of ethanol and water, which is prepared by 15.75g of ethanol and 6.75g of water, and the mixture is refluxed and stirred for 2 hours at 80 ℃ to obtain a 4 wt% transparent solution of the polyoxyethylene-based polymer.
(3) Adding the ionic liquid functionalized cerium fluoride porous nanosheet solution into a polyoxyethylene-based polymer solution, and stirring for 2 hours to obtain a membrane casting solution; and (3) defoaming the casting solution, pouring the casting solution onto a clean polytetrafluoroethylene culture dish, volatilizing the solvent at room temperature for 24 hours, and then performing vacuum drying at 45 ℃ for 24 hours to obtain a polyoxyethylene-based polymer mixed matrix membrane filled with the ionic liquid functionalized cerium fluoride porous nanosheets with the thickness of 91 mu m, wherein the mass fraction of the ionic liquid functionalized cerium fluoride porous nanosheets is 4%.
Example 7
A preparation method of a mixed matrix membrane specifically comprises the following steps:
(1) 0.09g of the ionic liquid functionalized cerium fluoride porous nanosheet prepared in the embodiment 1 is added into 4mL of a composite solvent (the composite solvent is prepared by mixing ethanol and water according to a mass ratio of 7: 3), and ultrasonic dispersion is carried out for 3 hours, so that a functionalized cerium fluoride porous nanosheet solution is obtained.
(2) 0.9g of polyoxyethylene-based polymer is added into a composite solvent of ethanol and water, which is prepared by 15.75g of ethanol and 6.75g of water, and the mixture is refluxed and stirred for 2 hours at 80 ℃ to obtain a 4 wt% transparent solution of the polyoxyethylene-based polymer.
(3) Adding the ionic liquid functionalized cerium fluoride porous nanosheet solution into a polyoxyethylene-based polymer solution, and stirring for 2 hours to obtain a membrane casting solution; and (3) defoaming the casting solution, pouring the casting solution onto a clean polytetrafluoroethylene culture dish, volatilizing the solvent at room temperature for 24 hours, and then performing vacuum drying at 45 ℃ for 24 hours to obtain a polyoxyethylene-based polymer mixed matrix membrane filled with the ionic liquid functionalized cerium fluoride porous nanosheets with the thickness of 91 mu m, wherein the mass fraction of the ionic liquid functionalized cerium fluoride porous nanosheets is 10%.
Example 8
The same as example 7, except that "take 0.09g of the prepared ionic liquid functionalized cerium fluoride porous nanosheet" in step (1) was modified to "take 0.18g of the prepared ionic liquid functionalized cerium fluoride porous nanosheet", to prepare a polyoxyethylene-ionic liquid functionalized cerium fluoride porous nanosheet mixed matrix membrane having a thickness of 93 μm, wherein the mass fraction of the ionic liquid functionalized cerium fluoride porous nanosheet in the membrane is 20%.
Example 9
The same as example 7, except that the "taking 0.09g of the functionalized cerium fluoride porous nanosheet prepared above" in the step (1) was modified to "taking 0.267g of the ionic liquid functionalized cerium fluoride porous nanosheet prepared above", to prepare a polyoxyethylene-ionic liquid functionalized cerium fluoride porous nanosheet mixed matrix membrane with a thickness of 95 μm, wherein the mass fraction of the ionic liquid functionalized cerium fluoride porous nanosheet is 30%.
Example 10
A method for preparing a mixed matrix membrane comprises the following steps:
(1) preparing a functionalized cerium fluoride porous nanosheet:
(a) adding 300mL of pure water into a three-neck flask, blowing nitrogen for 20min, sequentially adding 3.6mmol of cerium nitrate and 3.6mmol of sodium acetate solid powder, wherein the molar ratio of the cerium nitrate to the sodium acetate is 1:1, and stirring at room temperature to dissolve the cerium nitrate and the sodium acetate to obtain a mixed solution;
(b) adding 20mL of 5mg/mL ammonium fluoride aqueous solution into the mixed solution, stirring at room temperature and normal pressure for reaction for 2 hours, and centrifuging, freezing and drying to obtain cerium fluoride porous nanosheets;
(c) and (c) fully blending the aqueous solution of the cerium fluoride porous nanosheet obtained in the step (b) and 1-ethyl-3-methylimidazol thiocyanate ionic liquid in a mass ratio of 10:1 for 48 hours to obtain an ionic liquid functionalized cerium fluoride porous nanosheet.
0.3375g of the prepared ionic liquid functionalized cerium fluoride porous nanosheet is added into 4mL of composite solvent (the composite solvent is prepared by mixing ethanol and water according to the mass ratio of 7: 3), and ultrasonic dispersion is carried out for 3 hours, so as to obtain an ionic liquid functionalized cerium fluoride porous nanosheet solution.
(2) 3.375g of polyoxyethylene-based polymer is added into a composite solvent of ethanol and water, which is prepared by 15.75g of ethanol and 6.75g of water, and the mixture is refluxed and stirred for 2 hours at 80 ℃ to obtain a 15 wt% transparent solution of the polyoxyethylene-based polymer.
(3) Adding the ionic liquid functionalized cerium fluoride porous nanosheet solution into a polyoxyethylene-based polymer solution, and stirring for 2 hours to obtain a membrane casting solution; and (3) defoaming the casting solution, pouring the casting solution onto a clean polytetrafluoroethylene culture dish, volatilizing the solvent at room temperature for 24 hours, and then performing vacuum drying at 45 ℃ for 24 hours to obtain a polyoxyethylene-based polymer mixed matrix membrane filled with ionic liquid functionalized cerium fluoride porous nanosheets with the thickness of about 80 microns, wherein the mass fraction of the ionic liquid functionalized cerium fluoride porous nanosheets is 10%.
Comparative example 1
A preparation method of a polyoxyethylene-based polymer film comprises the following steps:
firstly, 0.9g of polyoxyethylene-based polymer is added into a solution of ethanol and water prepared from 15.75g of ethanol and 6.75g of water, and the mixture is refluxed and stirred for 2 hours at the temperature of 80 ℃ to obtain a 4 wt% transparent solution of the polyoxyethylene-based polymer; then, the mixture was stirred for 2 hours. And finally, defoaming the casting solution, pouring the casting solution on a clean polytetrafluoroethylene culture dish, volatilizing the solvent at room temperature for 24 hours, and then carrying out vacuum drying at 45 ℃ for 24 hours to obtain the pure polyoxyethylene-based high-molecular polymer membrane.
Comparative example 2
A preparation method of a mixed matrix membrane specifically comprises the following steps:
(1) preparing cerium fluoride porous nanosheets:
(a) adding 300mL of pure water into a three-neck flask, blowing nitrogen for 20min, and then sequentially adding 3.6mmol of cerium nitrate and 3.6mmol of sodium acetate solid powder, wherein the molar ratio of the cerium nitrate to the sodium acetate is 1:1, and stirring and dissolving at 25 ℃ to obtain a mixed solution;
(b) and adding 20mL of ammonium fluoride aqueous solution and 5mg/mL of ammonium fluoride aqueous solution into the mixed solution, stirring and reacting for 2 hours at room temperature, and centrifuging, freezing and drying to obtain the cerium fluoride porous nanosheet.
0.036g of the prepared cerium fluoride porous nanosheet is added into 4mL of a composite solvent (the composite solvent is obtained by mixing ethanol and water according to a mass ratio of 7: 3), and ultrasonic dispersion is carried out for 3 hours, so as to obtain a cerium fluoride porous nanosheet solution.
(2) 0.9g of polyoxyethylene-based polymer is added into a composite solvent of ethanol and water, which is prepared by 15.75g of ethanol and 6.75g of water, and the mixture is refluxed and stirred for 2 hours at 80 ℃ to obtain a 4 wt% transparent solution of the polyoxyethylene-based polymer.
(3) Adding the cerium fluoride porous nanosheet solution into a polyoxyethylene-based polymer solution, and stirring for 2 hours to obtain a membrane casting solution; and (3) defoaming the casting solution, pouring the casting solution onto a clean polytetrafluoroethylene culture dish, volatilizing the solvent at room temperature for 24 hours, and then performing vacuum drying at 45 ℃ for 24 hours to obtain a polyoxyethylene-based polymer mixed matrix membrane filled with cerium fluoride porous nanosheets with the thickness of 91 mu m, wherein the mass fraction of the cerium fluoride porous nanosheets is 4%.
Performance characterization
Performance characterization of ionic liquid functionalized cerium fluoride porous nanosheet
(1) The ionic liquid functionalized cerium fluoride porous nanosheet prepared in example 1 is observed by a high power transmission electron microscope, and the model is Hitachi H7650 transmission electron microscope (Fei, Netherlands). And (3) carrying out ultrasonic oscillation on the sample by taking ethanol as a dispersion liquid for 30min until the sample is fully dispersed, dripping a small amount of the sample on the front surface of a copper mesh, and drying the sample to obtain the sample for TEM test. And (3) testing (XRD) by adopting an X-ray diffractometer, and detecting the ionic liquid functionalized cerium fluoride porous nanosheet and a diffraction spectrogram of the cerium fluoride porous nanosheet by using a model D8 DISCOVER X-ray diffractometer within the range of 5-40 degrees. Fourier infrared spectroscopy (FT-IR) test adopts BRUKER Vertex 70 infrared spectroscopy (Bruker, USA) to detect the chemical structure of the nanosheet, and the scanning range of the spectral region is 400-4000 cm-1Resolution of 4cm-1. In the experiment, infrared spectra of samples are collected by a transmission method. The test results are shown in FIGS. 1-4, wherein FIG. 1 is a low-power TEM image of the ionic liquid functionalized cerium fluoride porous nanosheet prepared in example 1; FIG. 2 is a high-power TEM image of ionic liquid functionalized cerium fluoride porous nanosheets prepared in example 1; FIG. 3 is X-ray diffraction patterns of ionic liquid functionalized cerium fluoride porous nanosheets and cerium fluoride porous nanosheets prepared in example 1; fig. 4 is a fourier infrared spectrum of the ionic liquid functionalized cerium fluoride porous nanosheet prepared in example 1.
As can be seen from the analysis of FIGS. 1 to 4, the ionic liquid functionalized cerium fluoride in the TEM image has low background contrast, which proves that the prepared material is a nano material, and a small area on the nano sheet has low background contrast, thus the nano sheet is a porous nano sheet. The sectional test result and XRD test result of a single nano sheet by combining a high-power TEM image show that the functionalized cerium fluoride porous nano sheet modified by the ionic liquid has no change in crystal structure, good crystallinity and 0.344nm of interlayer spacing. The test results of FT-IR showed successful loading of basic groups.
(2) The ionic liquid functionalized cerium fluoride porous nanosheet prepared in example 1 is subjected to full-automatic physical chemical absorption instrument test, and a NOVA 1000 type gas absorption analyzer of Congta corporation in America is adopted to perform test characterization on a sample at room temperature. The obtained result is shown in fig. 5, and the result shows that the average pore diameter of the ionic liquid functionalized cerium fluoride porous nanosheet is 3.057 nm. The result is consistent with that reflected by a TEM picture, and the F-Ce nanosheet is further proved to be a porous nanosheet.
Performance representation of polyoxyethylene-based polymer-ionic liquid functionalized cerium fluoride porous nanosheet mixed matrix membrane
(1) SEM characteristics of the polyoxyethylene-based polymer-ionic liquid functionalized cerium fluoride porous nanosheet mixed matrix membrane prepared in example 6 of the invention and the polyoxyethylene-based polymer membrane prepared in comparative example 1 were carried out by using a scanning electron microscope of Hitachi S-4800 type Japan. During testing, a dried sample is adhered to a sample table through conductive adhesive, and the sample table is placed into equipment for observation after gold spraying.
The results are shown in fig. 6 to 7, fig. 6 is a sectional local SEM image of the polyoxyethylene-based polymer pure film prepared in comparative example 1, fig. 7 is a sectional local SEM image of the polyoxyethylene-based polymer-ionic liquid functionalized cerium fluoride porous nanosheet mixed matrix film prepared in example 6, and combined observation of SEM test results shows that the ionic liquid functionalized cerium fluoride porous nanosheet has good dispersibility and interface compatibility in the polyoxyethylene-based polymer matrix.
(2) The films prepared in examples 6-9 and comparative examples 1-2 are respectively taken, a film sample with a certain area is cut, and the permeability and the selectivity of the film sample are measured to obtain the gas separation performance.
And (3) permeability measurement:
Barrer(1barrer＝10-10cm3(STP)cm/(cm2s · cmHg)) as a unit of gas permeability.
The permeability of a gas is measured by the volumetric transformation method, applying a certain pressure of the gas on one side of the membrane. While on the other side, the permeate side, the pressure change over time was recorded. Specifically, the pure gas permeability of the membrane is tested by a constant volume variable pressure method in a dry state, the pressure of raw material gas is 2bar, the temperature is 35 ℃, the gas permeability coefficient and the separation coefficient of the membrane are in an equal knotAs shown in table 1. From the results in table 1, it can be seen that the gas permeability of the membrane tends to increase first and then decrease as the filling amount of the ionic liquid functionalized cerium fluoride porous nanosheet increases. Compared with the polyoxyethylene-based polymer film, the CO of the polyoxyethylene-based polymer-ionic liquid functionalized cerium fluoride porous nanosheet mixed matrix film with the filling amount of 10 percent2Permeability coefficient increased from 95.4Barrer to 145.5Barrer, CO2/CH4The pure gas separation coefficient increased from 12.2 to 22.7. Compared with the polyoxyethylene-polymer-cerium fluoride porous nanosheet mixed matrix membrane with the same filling amount of 4 percent, the CO is2Permeability coefficient increased from 97.7Barrer to 126.7Barrer, CO2/CH4The pure gas separation coefficient is increased from 15.8 to 16.5, which shows that the gas permeability and the selectivity of the carbon dioxide methane mixed gas are improved compared with the mixed matrix membrane prepared by the nano sheet which is not modified by the ionic liquid and has the same addition amount.
Gas permeability was calculated by the following formula:
pure gas separation coefficient αA/BObtained by the following equation:
αA/B＝PA/PB
PAand PBRepresenting the permeability coefficients of gases a and B, respectively.
TABLE 1 gas separation Performance of the films prepared in examples 6-10 and comparative examples 1-2
The foregoing is merely a preferred embodiment of the invention and is not intended to limit the invention in any manner. It should be noted that, for those skilled in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be construed as the protection scope of the present invention.
Claims (10)
1. An ionic liquid functionalized cerium fluoride porous nanosheet is characterized by comprising a cerium fluoride porous nanosheet and an ionic liquid; the cerium fluoride porous nanosheet is combined with the ionic liquid through electrostatic adsorption, and the ionic liquid contains basic groups; the cerium fluoride porous nanosheet is formed by alternately stacking and arranging fluorine-cerium monoatomic layers and interlayer acetate.
2. Porous nanoplatelets functionalized with ionic liquid according to claim 1 wherein said ionic liquid comprises one or more of 1-ethyl-3-methylimidazolium thiocyanate, 1-ethyl-3-methylimidazolium nitrate and 1-butyl-3-methylimidazolium thiocyanate.
3. The ionic liquid functionalized cerium fluoride porous nanosheet of claim 1, wherein the cerium fluoride porous nanosheet is assembled from nanoparticles having a diameter of 0.5-5 nm.
4. The ionic liquid functionalized cerium fluoride porous nanosheet of claim 1 or 3, wherein the ionic liquid functionalized cerium fluoride porous nanosheet has an average pore size of 0.1-10 nm.
5. The preparation method of ionic liquid functionalized cerium fluoride porous nanosheets according to any one of claims 1 to 4, comprising the steps of:
in nitrogen atmosphere, mixing water-soluble cerium salt with a sodium acetate aqueous solution to obtain a mixed solution;
mixing a fluorine-containing salt water solution with the mixed solution for precipitation reaction to obtain cerium fluoride porous nanosheets;
and mixing the aqueous solution of the cerium fluoride porous nanosheet with an ionic liquid to obtain the ionic liquid functionalized cerium fluoride porous nanosheet.
6. The preparation method according to claim 5, wherein the mass ratio of the aqueous solution of the cerium fluoride porous nanosheets to the ionic liquid is (5-20): 1, and the concentration of the aqueous solution of the cerium fluoride porous nanosheets is 0.01-0.06 mg/mL.
7. The preparation method according to claim 5, wherein the blending time is 4-72 h.
8. A mixed matrix membrane is characterized by comprising the following components in percentage by mass: 0.5-30% of ionic liquid functionalized cerium fluoride porous nanosheet and 70-99.5% of polyoxyethylene-based polymer, wherein the ionic liquid functionalized cerium fluoride porous nanosheet is the ionic liquid functionalized cerium fluoride porous nanosheet as defined in any one of claims 1-4 or the ionic liquid functionalized cerium fluoride porous nanosheet prepared by the preparation method as defined in any one of claims 5-7.
9. The method for preparing a mixed matrix membrane according to claim 8, comprising the steps of:
mixing the solution of the ionic liquid functionalized cerium fluoride porous nanosheet with the solution of a polyoxyethylene-based polymer to obtain a membrane casting solution;
and (3) defoaming the casting solution, volatilizing the solvent and drying in vacuum in sequence to obtain the mixed matrix membrane.
10. Use of the ionic liquid functionalized cerium fluoride porous nanosheets of any one of claims 1 to 4 or the mixed matrix membrane of claim 8 in the field of gas separation.
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