CN117531380A - High-strength high-separation-performance carbon molecular sieve hollow fiber membrane and preparation method and application thereof - Google Patents
High-strength high-separation-performance carbon molecular sieve hollow fiber membrane and preparation method and application thereof Download PDFInfo
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- CN117531380A CN117531380A CN202311646179.3A CN202311646179A CN117531380A CN 117531380 A CN117531380 A CN 117531380A CN 202311646179 A CN202311646179 A CN 202311646179A CN 117531380 A CN117531380 A CN 117531380A
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- 239000012528 membrane Substances 0.000 title claims abstract description 119
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 76
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 76
- 239000002808 molecular sieve Substances 0.000 title claims abstract description 70
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 title claims abstract description 70
- 239000012510 hollow fiber Substances 0.000 title claims abstract description 64
- 238000002360 preparation method Methods 0.000 title claims abstract description 24
- 229920002301 cellulose acetate Polymers 0.000 claims abstract description 43
- 229910052734 helium Inorganic materials 0.000 claims abstract description 40
- 238000000926 separation method Methods 0.000 claims abstract description 40
- 239000001307 helium Substances 0.000 claims abstract description 39
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims abstract description 39
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 38
- 238000005266 casting Methods 0.000 claims abstract description 27
- 238000010438 heat treatment Methods 0.000 claims abstract description 27
- 238000000034 method Methods 0.000 claims abstract description 26
- 229920002678 cellulose Polymers 0.000 claims abstract description 14
- 239000001913 cellulose Substances 0.000 claims abstract description 14
- 238000003756 stirring Methods 0.000 claims abstract description 9
- 239000002608 ionic liquid Substances 0.000 claims abstract description 8
- 239000003960 organic solvent Substances 0.000 claims abstract description 8
- 238000001891 gel spinning Methods 0.000 claims abstract description 5
- 230000001681 protective effect Effects 0.000 claims abstract description 5
- 238000001035 drying Methods 0.000 claims abstract description 4
- 238000010000 carbonizing Methods 0.000 claims abstract description 3
- 238000002156 mixing Methods 0.000 claims abstract description 3
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 claims description 14
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 10
- 230000008569 process Effects 0.000 claims description 10
- ZXLOSLWIGFGPIU-UHFFFAOYSA-N 1-ethyl-3-methyl-1,2-dihydroimidazol-1-ium;acetate Chemical compound CC(O)=O.CCN1CN(C)C=C1 ZXLOSLWIGFGPIU-UHFFFAOYSA-N 0.000 claims description 7
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 6
- 229910052757 nitrogen Inorganic materials 0.000 claims description 6
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 4
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 4
- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical compound ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 claims description 4
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 claims description 4
- 238000003763 carbonization Methods 0.000 claims description 3
- 238000001816 cooling Methods 0.000 claims description 3
- IAZSXUOKBPGUMV-UHFFFAOYSA-N 1-butyl-3-methyl-1,2-dihydroimidazol-1-ium;chloride Chemical compound [Cl-].CCCC[NH+]1CN(C)C=C1 IAZSXUOKBPGUMV-UHFFFAOYSA-N 0.000 claims description 2
- PBIDWHVVZCGMAR-UHFFFAOYSA-N 1-methyl-3-prop-2-enyl-2h-imidazole Chemical compound CN1CN(CC=C)C=C1 PBIDWHVVZCGMAR-UHFFFAOYSA-N 0.000 claims description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 claims description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 2
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 claims description 2
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 2
- 229910052786 argon Inorganic materials 0.000 claims description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 2
- 239000001569 carbon dioxide Substances 0.000 claims description 2
- 230000001112 coagulating effect Effects 0.000 claims description 2
- 239000001257 hydrogen Substances 0.000 claims description 2
- 229910052739 hydrogen Inorganic materials 0.000 claims description 2
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 claims description 2
- 238000004804 winding Methods 0.000 claims description 2
- 238000005491 wire drawing Methods 0.000 claims description 2
- 239000007789 gas Substances 0.000 abstract description 32
- 239000000463 material Substances 0.000 abstract description 14
- 239000003345 natural gas Substances 0.000 abstract description 12
- 230000035699 permeability Effects 0.000 abstract description 10
- 239000002243 precursor Substances 0.000 description 30
- 230000000052 comparative effect Effects 0.000 description 17
- 239000011148 porous material Substances 0.000 description 12
- 238000000197 pyrolysis Methods 0.000 description 9
- 238000000605 extraction Methods 0.000 description 8
- 230000004907 flux Effects 0.000 description 8
- 238000012360 testing method Methods 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 238000004833 X-ray photoelectron spectroscopy Methods 0.000 description 3
- 238000005345 coagulation Methods 0.000 description 3
- 230000015271 coagulation Effects 0.000 description 3
- 239000008367 deionised water Substances 0.000 description 3
- 229910021641 deionized water Inorganic materials 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 238000001878 scanning electron micrograph Methods 0.000 description 3
- 238000009987 spinning Methods 0.000 description 3
- 229920003319 Araldite® Polymers 0.000 description 2
- 238000001237 Raman spectrum Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 238000007789 sealing Methods 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 1
- 238000001157 Fourier transform infrared spectrum Methods 0.000 description 1
- 239000004697 Polyetherimide Substances 0.000 description 1
- 239000004642 Polyimide Substances 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000000578 dry spinning Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000003822 epoxy resin Substances 0.000 description 1
- 238000005087 graphitization Methods 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 230000002209 hydrophobic effect Effects 0.000 description 1
- 230000008676 import Effects 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229920000647 polyepoxide Polymers 0.000 description 1
- 229920001601 polyetherimide Polymers 0.000 description 1
- 229920001721 polyimide Polymers 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000013557 residual solvent Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
- 238000002166 wet spinning Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/02—Inorganic material
- B01D71/021—Carbon
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
- B01D53/228—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion characterised by specific membranes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0039—Inorganic membrane manufacture
- B01D67/0067—Inorganic membrane manufacture by carbonisation or pyrolysis
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/08—Hollow fibre membranes
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B23/00—Noble gases; Compounds thereof
- C01B23/001—Purification or separation processes of noble gases
- C01B23/0036—Physical processing only
- C01B23/0042—Physical processing only by making use of membranes
- C01B23/0047—Physical processing only by making use of membranes characterised by the membrane
Abstract
The invention relates to a high-strength high-separation-performance carbon molecular sieve hollow fiber membrane and a preparation method and application thereof, wherein the preparation method comprises the following steps: (1) Mixing cellulose acetate, cellulose, an organic solvent and an ionic liquid to prepare a casting solution, and stirring and heating the casting solution; (2) Vacuumizing the casting solution to remove bubbles, and preparing the hollow fiber cellulose acetate membrane by a dry-wet spinning method; (3) Drying hollow fiber cellulose acetate membrane, and lifting under protective atmosphereAnd (3) carbonizing at a temperature to obtain the high-strength high-separation-performance carbon molecular sieve hollow fiber membrane. Compared with the prior art, the carbon molecular sieve hollow fiber membrane has good gas separation performance and high strength. The carbon molecular sieve membrane is used for He/CH 4 Separation, has higher He permeability and He/CH 4 The separation factor has good gas separation performance under high pressure, and provides a new choice for the helium stripping membrane material of natural gas.
Description
Technical Field
The invention relates to the technical field of gas separation, in particular to a high-strength high-separation-performance carbon molecular sieve hollow fiber membrane and a preparation method and application thereof.
Background
Helium is an inert gas widely applied to the fields of aerospace, military industry, advanced scientific research, medical and health and the like, and is an indispensable strategic resource for the development of high-tech industry. To date, the imported helium content of China is more than 95%, and domestic helium resources basically depend on import. Helium is found in nature primarily in air, natural gas, and geothermal water-soluble gases. Helium-containing natural gas is currently the only source of industrially extracted helium. The helium resources in China are very limited, and the ever-increasing demands cannot be met. Therefore, the recovery and utilization rate of helium gas are improved, and searching for a high-efficiency helium extraction technology becomes an urgent problem to be solved in domestic helium extraction.
Membrane gas separation is a process that utilizes membrane materials to conduct gas separation for selective permeation of gas molecules. The separation of different gas molecules is realized by adjusting the pore diameter and the surface property of the membrane material based on the difference of the transfer rates of different gases on the membrane, and the separation efficiency is higher compared with that of the traditional helium extraction technology without excessive complicated operation in the process. Moreover, compared with the traditional adsorption and cryogenic gas separation technology, the membrane separation device has the advantages that the energy consumption is low, a large amount of energy sources can be saved, and the membrane separation device is simple in structure and easy to operate. Because of the adjustability of the pore size and pore structure of the membrane material, a highly selective separation of different gases is often achieved.
Carbon molecular sieve membranes are one common membrane material for membrane gas separation, and are typically manufactured by pyrolysis of polymer precursors such as polyimide, resin, cellulose, and polyetherimide. Pyrolysis reduces the precursor polymer to carbon, and some micropores are reserved in the product obtained by pyrolysis to ensure that the product has certain porosity. The carbon molecular sieve membrane thus formed can then be applied for separation of various gases. The carbon molecular sieve membrane can adjust the pore size, realize high-selectivity separation of specific molecules, and enable the carbon molecular sieve membrane to have higher efficiency and separation performance. The carbon molecular sieve membrane has a highly ordered pore structure, molecules rapidly diffuse in the carbon molecular sieve membrane to show high permeability, so that the carbon molecular sieve membrane can realize a high-flux separation process. The carbon molecular sieve membrane has higher chemical stability, can resist various solvents to corrode and severe conditions such as high temperature, and has longer service life than other membrane materials under the same separation condition.
The strength of the membrane is required in the process of extracting helium from natural gas because the gas exerts a certain pressure during helium extraction, the membrane must withstand this pressure without cracking and leakage, and the pore structure is not destroyed by too high a pressure, and good separation performance is still required at high pressure.
Disclosure of Invention
The invention aims to provide a high-strength high-separation-performance carbon molecular sieve hollow fiber membrane, and a preparation method and application thereof, and meets the requirements of industrial helium extraction on membrane materials.
The aim of the invention can be achieved by the following technical scheme: a preparation method of a high-strength high-separation-performance carbon molecular sieve hollow fiber membrane comprises the following steps:
(1) Mixing solid powder cellulose acetate, cellulose, an organic solvent and an ionic liquid to prepare a casting solution, and stirring and heating the casting solution;
(2) Vacuumizing the casting solution to remove bubbles, and preparing the hollow fiber cellulose acetate membrane by a dry-wet spinning method;
(3) Drying the hollow fiber cellulose acetate membrane, and heating and carbonizing in a protective atmosphere to obtain the high-strength high-separation-performance carbon molecular sieve hollow fiber membrane.
Preferably, the organic solvent in the step (1) is one or more of N, N-dimethylformamide, N-dimethylacetamide, tetrahydrofuran, chloroform, dimethyl sulfoxide and N-methylpyrrolidone.
Further preferably, the organic solvent in step (1) is dimethyl sulfoxide.
Preferably, the ionic liquid in the step (1) is one or more of 1-allyl-3-methylimidazole chloride, 1-butyl-3-methylimidazole chloride and 1-ethyl-3-methylimidazole acetate.
Further preferably, the ionic liquid in step (1) is 1-ethyl-3-methylimidazole acetate.
Preferably, the casting solution in the step (1) comprises 0-12 wt% of cellulose acetate, 0-15 wt% of cellulose, 15-50 wt% of ionic liquid and 50-80 wt% of organic solvent, wherein the sum of the mass of cellulose acetate and the mass of cellulose is 10-18 wt%. The percentages of the components are based on the weight of the casting solution, and the sum of the total percentages of the components is 1.
Preferably, in the step (1), the casting solution is mechanically stirred and heated, the stirring speed is 10-60 r/min, and the heating temperature is 40-80 ℃.
Preferably, the parameters set by the dry and wet spinning method in the step (2) are that the temperature of the casting solution is 25-40 ℃, the temperature of the core solution and the coagulation bath temperature are 15-35 ℃, the flow rate of the casting solution is 2-10 ml/min, the flow rate of the core solution is 0.5-20 ml/min, and the wire drawing and winding rates are 4-20 m/min.
Further preferably, the core liquid is deionized water and the coagulation bath is water.
Preferably, the vacuum degree of the vacuumizing and bubble removing in the step (2) is 0.08-0.12 MPa, and the time is 20-30 h.
Preferably, the hollow fiber cellulose acetate membrane of step (2) contains 0.5 to 3wt% of cellulose acetate.
Preferably, the drying of step (3) is performed at room temperature.
Preferably, the protective atmosphere in the step (3) is one or more of nitrogen, argon and helium.
Preferably, the carbonization process of step (3) comprises the steps of:
1) Heating to 110-130 ℃ at the room temperature, wherein the heating rate is 3-15 ℃/min, and staying for 1.5-2.5 h;
2) Continuously heating to 290-350 ℃, heating at a speed of 3-15 ℃/min, and staying for 0.5-1.5 h;
3) Then continue to heat up to T max Heating rate is 3-15 ℃/min, T max Stay for 1.5-2.5 h, T max Heat preservation and cooling to room temperature to obtain the high-strength and high-separation performanceA carbon molecular sieve hollow fiber membrane;
the T is max The range of (2) is 500-800 ℃.
A high-strength high-separation-performance carbon molecular sieve hollow fiber membrane is prepared by adopting the preparation method.
The application of the high-strength high-separation-performance carbon molecular sieve hollow fiber membrane is that the high-strength high-separation-performance carbon molecular sieve hollow fiber membrane is used for separating helium from methane, hydrogen from methane, carbon dioxide from methane, and helium from nitrogen.
Preferably, the high strength high separation performance carbon molecular sieve hollow fiber membrane is used for natural gas helium stripping. The film material is used for He, CH 4 Solves the problems of insufficient strength and low permeability of the conventional hollow fiber carbon film.
The high strength membrane can withstand higher pressures so that the operating pressure can be increased to a higher level, improving helium extraction efficiency. In the helium stripping process of natural gas, the membrane can be subjected to pressure and abrasion of particles, and the membrane with high strength can better resist the action of external force, so that the service life of the membrane is prolonged. The carbon molecular sieve membrane has higher separation selectivity under high pressure, and the high-selectivity membrane can separate helium gas from other gas components more effectively, so that non-helium components can be filtered more efficiently by the membrane with lower selectivity compared with the helium extraction process, and the efficiency is greatly improved. Because the helium content of the natural gas in China is low, the loss of helium can be reduced by using the high-selectivity membrane, and the resource utilization rate is ensured. The carbon molecular sieve membrane is applied to natural gas helium stripping, and has excellent chemical stability, good mechanical strength and excellent separation performance under high pressure, so that the carbon molecular sieve membrane becomes a membrane material with excellent natural gas helium stripping.
The carbon molecular sieve hollow fiber membrane prepared by adding cellulose acetate into the membrane casting solution has high permeability and the strength of the membrane is improved from 91.32MPa to 223.68MPa.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention provides a high-strength high-separation-performance carbon molecular sieve hollow fiber membrane and a preparation method thereof, which can solve the problems of insufficient strength and low permeability of the conventional carbon molecular sieve hollow fiber membrane, and more accords with the requirements of industrial helium extraction on membrane materials;
2. according to the invention, cellulose acetate is added into a conventional cellulose membrane system, so that the gas flux of He is improved, and the tensile strength of the carbon membrane is improved, and a strategy is provided for further practical application of the carbon membrane;
3. the carbon molecular sieve hollow fiber membrane has low cost, easy preparation, large flux and high strength, and the carbon molecular sieve membrane is used for He/CH 4 Separation, has higher He permeability and He/CH 4 Separating the factors;
4. the carbon molecular sieve hollow fiber membrane has good gas separation performance and high strength, has good gas separation performance under high pressure, and provides a new choice for natural gas helium stripping membrane materials.
Drawings
FIG. 1 is a cross-sectional, surface SEM image of a carbon molecular sieve membrane produced in example 1;
FIG. 2 is a Fourier transform infrared spectrum of the precursor films prepared in comparative example 1 and examples 1 to 3;
FIG. 3 is a schematic structural diagram of the carbon molecular sieve hollow fiber membrane modules prepared in comparative example 1 and examples 1 to 3;
FIG. 4 is a graph showing the single gas flux performance of the carbon molecular sieve hollow fiber membranes prepared in comparative example 1 and examples 1 to 3;
FIG. 5 is a graph showing the He/X selectivity performance of the carbon molecular sieve hollow fiber membranes prepared in comparative example 1 and examples 1 to 3;
FIG. 6 is an X-ray photoelectron spectroscopy (XPS) C1s chart of the carbon molecular sieve hollow fiber membranes prepared in comparative example 1 and examples 1 to 3;
FIG. 7 is an SEM image and a Raman spectrum image of the surfaces of the hollow fiber membranes of the carbon molecular sieves prepared in comparative example 1 and examples 1 to 3;
FIG. 8 is a graph showing pore size distribution of hollow fiber membranes of carbon molecular sieves prepared in comparative example 1 and example 1;
FIG. 9 is a graph showing the high pressure separation performance of the hollow fiber membrane of carbon molecular sieve prepared in example 1;
FIG. 10 is a drawing showing tensile strength test of carbon molecular sieve hollow fiber membranes prepared in comparative example 1, example 1 and example 2;
fig. 11 is a cross-sectional SEM image and a cross-sectional pore distribution diagram of comparative example 1 and example 1.
Detailed Description
The invention will now be described in detail with reference to the drawings and specific examples. The present embodiment is implemented on the premise of the technical scheme of the present invention, and a detailed implementation manner and a specific operation process are given, but the protection scope of the present invention is not limited to the following examples.
Comparative example 1
(1) Preparation of casting solution
Firstly, 300g of dimethyl sulfoxide is weighed, 54.54g of cellulose is added for three times, and shaking is carried out uniformly; 100g of 1-ethyl-3-methylimidazole acetate were then added. Heating to 60deg.C, and mechanically stirring at 30r/min for 24 hr.
(2) Preparation of the precursor
And (3) vacuumizing the uniformly mixed casting solution at room temperature to remove bubbles for 24 hours, and preparing the cellulose acetate-free film by using a dry-wet spinning method. And (3) introducing the hollow fiber membrane manufactured by the spinning machine into cold water for solidification, performing solvent exchange through a water washing tank, and finally collecting the hollow fiber membrane on a rotating wheel. In the spinning process, the core liquid temperature, the casting solution temperature and the coagulating bath temperature are all set to 25 ℃, and the spinning solution and the core liquid flow rate are respectively set to 3.5mLmin -1 And 2.5mLmin -1 . The linear velocity roll of the collecting wheel of the hollow fiber membrane is kept at 8m/min, finally the hollow fiber membrane is cut into 1.8m, and is soaked in deionized water, and the deionized water is replaced every 24 hours, so that residual solvent is completely washed off, and the precursor membrane containing 0wt% of cellulose acetate is obtained.
(3) Preparation of carbon molecular sieve hollow fiber membrane
The prepared precursor film is dried for 24 hours at room temperature, then is placed in a tube furnace, air in the tube furnace is pumped out by a vacuum pump, and is pyrolyzed under the condition of continuous flow of nitrogen (100 ml/min), wherein the specific pyrolysis conditions are as follows:
1) Heating from room temperature to 120 ℃, heating rate of 5 ℃/min, and staying at 120 ℃ for 2h;
2) Heating from 120 ℃ to 340 ℃, wherein the heating rate is 5 ℃/min, and staying at 340 ℃ for 1h;
3) Heating from 340 ℃ to 600 ℃, keeping the temperature at a heating rate of 5 ℃/min, keeping the temperature at 600 ℃ for 2 hours, and cooling the temperature at 600 ℃ to room temperature to obtain the high-strength high-separation-performance carbon molecular sieve hollow fiber membrane with the precursor containing no cellulose acetate, which is marked as CMSM-0wt%.
Example 1
(1) Preparation of casting solution
Firstly, 300g of dimethyl sulfoxide is weighed, 40.91g of cellulose is added for three times, and shaking is carried out uniformly; adding 13.64g of cellulose acetate for three times, and shaking uniformly; 100g of 1-ethyl-3-methylimidazole acetate were then added. Heating to 60deg.C, and mechanically stirring at 30r/min for 24 hr.
(2) Preparation of the precursor
As in step (2) of comparative example 1, a precursor film containing 3% by weight of cellulose acetate was obtained.
(3) Preparation of carbon molecular sieve hollow fiber membrane
The specific pyrolysis process is the same as the step (3) in the comparative example, thus obtaining the carbon molecular sieve hollow fiber membrane with high strength and high separation performance, the precursor of which contains 3wt% of cellulose acetate, which is marked as CMSM-3wt%.
Example 2
(1) Preparation of casting solution
Firstly, 300g of dimethyl sulfoxide is weighed, 49.995g of cellulose is added for three times, and the mixture is uniformly shaken; adding 4.545g of cellulose acetate three times, and shaking uniformly; 100g of 1-ethyl-3-methylimidazole acetate were then added. Heating to 60deg.C, and mechanically stirring at 30r/min for 24 hr.
(2) Preparation of the precursor
As in step (2) of comparative example 1, a precursor film containing 1% by weight of cellulose acetate was obtained.
(3) Preparation of carbon molecular sieve hollow fiber membrane
The specific pyrolysis process is the same as the step (3) in the comparative example, thus obtaining the carbon molecular sieve hollow fiber membrane with high strength and high separation performance, the precursor of which contains 1wt% of cellulose acetate, which is marked as CMSM-1wt%.
Example 3
(1) Preparation of casting solution
Firstly, 300g of dimethyl sulfoxide is weighed, 52.2675g of cellulose is added for three times, and shaking is carried out uniformly; adding 2.2725g of cellulose acetate three times, and shaking uniformly; 100g of 1-ethyl-3-methylimidazole acetate were then added. Heating to 60deg.C, and mechanically stirring at 30r/min for 24 hr.
(2) Preparation of the precursor
As in step (2) of comparative example 1, a precursor film containing 0.5% by weight of cellulose acetate was obtained.
(3) Preparation of carbon molecular sieve hollow fiber membrane
The specific pyrolysis process is the same as in step (3) in the comparative example, thus obtaining the high-strength high-separation-performance carbon molecular sieve hollow fiber membrane with 0.5wt% of cellulose acetate as the precursor, which is marked as CMSM-0.5wt%.
As can be seen from fig. 2, the precursor films prepared by adding different amounts of cellulose acetate showed that characteristic peaks with different intensities of c=o in the fourier transform infrared spectrogram represent successful introduction of cellulose acetate into the precursor.
The method comprises the steps of placing a hollow fiber carbon molecular sieve gas separation membrane prepared from cellulose acetate with different precursor contents in a hollow metal tube with a left end connected with a three-way joint, sealing the right end of the membrane by using an epoxy resin adhesive Araldite 2012, sealing the left end of the three-way joint by using the Araldite 2012, and finally connecting the left end of the three-way joint with the right side of the metal tube by using a plug to prepare a membrane assembly, wherein the membrane assembly is used for testing gas separation performance as shown in fig. 3.
The method comprises the steps of performing gas separation performance test on all sample membrane materials by a gas permeameter according to national standard GB/T1083 by using a differential pressure method, placing a carbon molecular sieve membrane module into the test, wherein the single gas feeding pressure is 2bar, the measurement temperature is room temperature, pumping the lower part of a sample pool to below 30Pa by using a vacuum pump during the test, finishing the test after the permeation quantity of the gas to be tested is stable for about 2 hours, repeating the test for three times, and calculating the permeation rate and separation factor by using the following formula:
wherein P is i ，P j The permeabilities of the gases i, j, respectively, α represents the separation factor, Q (cm) 3 (STP)s -1 ) Represents the volumetric flow rate of the gas at the outlet, l (cm) is the thickness of the membrane, A represents the membrane area (cm) 2 ) Δp (cmHg) represents the pressure differential of the gas i across the membrane. 1 barrer=10 -10 cm 3 (STP)cm(cm 2 scmHg) -1 。
The gas properties of the carbon films obtained in comparative example 1 and examples 1 to 3 are shown in fig. 4 and 5.
The He permeability of the carbon molecular sieve membrane prepared in the above example increased from 0wt% to 3wt% with precursor cellulose acetate content, and the helium flux increased from 9.7GPU to 24.09GPU, with a helium permeability increase of 148%, he/CH 4 The separation factor is reduced from 253.7 to 155.5 by 39%.
As can be seen from FIG. 6, as the cellulose acetate content in the precursor film increases from 0wt% to 3wt%, sp 2 /sp 3 From 1.89 to 1.53. As the content of cellulose acetate is increased, the precursor film is induced to generate a porous structure after pyrolysis, as shown in figure 11, the defects of the carbon film generated by pyrolysis are increased, the graphitization degree is reduced, and the gas flux is increased, but if the content of cellulose acetate is further increased, the casting solution becomes quite hydrophobic, so that the film cannot be formed by the coagulation tank. FIG. 7 shows Raman spectrum to obtain the same conclusion as XPS, I D /I G The ratio increases from 0wt% to 3wt% with the cellulose acetate content in the precursor film, and increases from 0.7 to 0.81, which proves that the cellulose acetate in the precursor is pyrolyzed to leave a porous structure for the carbon molecular sieve hollow fiber film, resulting in an increase in flux. The pore size distribution of figure 8 also demonstrates that the pore size becomes large,the 0.2488nm size pores of the carbon molecular sieve membrane prepared by the precursor containing 3wt% of cellulose acetate disappear, and the proportion of 0.4973nm size pores is increased from 0.62 to 0.82.
Carbon molecular sieve membrane prepared by precursor containing 3wt% of cellulose acetate is used for simulating helium stripping performance test of lean helium natural gas, and the feed composition is 0.13% He and 90.87% CH 4 And 9% N 2 The performance is shown in FIG. 9, in which helium flux stabilized around 20GPU and methane flux decreased from 0.179 to 0.1GPU, he/CH, as feed pressure increased from 7bar to 35bar 4 The selectivity rises from 117 to 218.
The introduction of the precursor cellulose acetate also enhances the tensile strength of the carbonized carbon molecular sieve hollow fiber membrane, as shown in figure 10, the precursor does not contain cellulose acetate, the maximum tensile load of the precursor is only 91.32MPa, and after the introduction of the cellulose acetate, the maximum tensile load reaches 223.68MPa, and the strength is improved by 144.9%.
Aiming at the defects of low strength, easy breakage and difficult further application of the conventional hollow fiber carbon molecular sieve membrane after carbonization, the invention adds cellulose acetate into a precursor material. The obtained carbon molecular sieve membrane has high He permeability and high strength, greatly increases the practical usability of separation in a natural gas helium stripping system, and provides a thinking for industrial application of high-performance membrane materials.
The previous description of the embodiments is provided to facilitate a person of ordinary skill in the art in order to make and use the present invention. It will be apparent to those skilled in the art that various modifications can be readily made to these embodiments and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above-described embodiments, and those skilled in the art, based on the present disclosure, should make improvements and modifications without departing from the scope of the present invention.
Claims (10)
1. The preparation method of the carbon molecular sieve hollow fiber membrane with high strength and high separation performance is characterized by comprising the following steps:
(1) Mixing cellulose acetate, cellulose, an organic solvent and an ionic liquid to prepare a casting solution, and stirring and heating the casting solution;
(2) Vacuumizing the casting solution to remove bubbles, and preparing the hollow fiber cellulose acetate membrane by a dry-wet spinning method;
(3) Drying the hollow fiber cellulose acetate membrane, and heating and carbonizing in a protective atmosphere to obtain the high-strength high-separation-performance carbon molecular sieve hollow fiber membrane.
2. The method for preparing a high-strength and high-separation-performance carbon molecular sieve hollow fiber membrane according to claim 1, wherein the organic solvent in the step (1) is one or more of N, N-dimethylformamide, N-dimethylacetamide, tetrahydrofuran, chloroform, dimethylsulfoxide and N-methylpyrrolidone.
3. The method for preparing the high-strength and high-separation-performance carbon molecular sieve hollow fiber membrane according to claim 1, wherein the ionic liquid in the step (1) is one or more of 1-allyl-3-methylimidazole chloride, 1-butyl-3-methylimidazole chloride and 1-ethyl-3-methylimidazole acetate.
4. The method for preparing the high-strength high-separation-performance carbon molecular sieve hollow fiber membrane according to claim 1, wherein the casting solution in the step (1) comprises 0-12 wt% of cellulose acetate, 0-15 wt% of cellulose, 15-50 wt% of ionic liquid and 50-80 wt% of organic solvent, the sum of the mass of cellulose acetate and the mass of cellulose is 10-18 wt%, the percentages of all components are based on the weight of the casting solution, and the sum of the total percentages of all components is 1.
5. The method for preparing a high-strength high-separation-performance carbon molecular sieve hollow fiber membrane according to claim 1, wherein in the step (1), the casting solution is mechanically stirred and heated, the stirring speed is 10-60 r/min, and the heating temperature is 40-80 ℃.
6. The method for preparing a high-strength high-separation-performance carbon molecular sieve hollow fiber membrane according to claim 1, wherein parameters set by the dry-wet spinning method in the step (2) are that the temperature of a casting solution is 25-40 ℃, the temperature of a core solution and the temperature of a coagulating bath are 15-35 ℃, the flow rate of the casting solution is 2-10 ml/min, the flow rate of the core solution is 0.5-20 ml/min, and the wire drawing and winding rates are 4-20 m/min.
7. The method for preparing a high-strength high-separation-performance carbon molecular sieve hollow fiber membrane according to claim 1, wherein the protective atmosphere in the step (3) is one or more of nitrogen, argon and helium.
8. The method for preparing a high-strength high-separation-performance carbon molecular sieve hollow fiber membrane according to claim 1, wherein the carbonization process of step (3) comprises the steps of:
1) Heating to 110-130 ℃ at the room temperature, wherein the heating rate is 3-15 ℃/min, and staying for 1.5-2.5 h;
2) Continuously heating to 290-350 ℃, heating at a speed of 3-15 ℃/min, and staying for 0.5-1.5 h;
3) Then continue to heat up to T max Heating rate is 3-15 ℃/min, T max Stay for 1.5-2.5 h, T max Keeping the temperature and cooling to room temperature to obtain the high-strength high-separation-performance carbon molecular sieve hollow fiber membrane;
the T is max The range of (2) is 500-800 ℃.
9. A high-strength high-separation-performance carbon molecular sieve hollow fiber membrane, which is characterized in that the hollow fiber membrane is prepared by the preparation method of any one of claims 1 to 8.
10. Use of the high strength high separation performance carbon molecular sieve hollow fiber membrane of claim 9 for the separation of helium and methane, hydrogen and methane, carbon dioxide and methane, helium and nitrogen.
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