WO2023160073A1 - 中空纤维分离膜及其制备方法及应用 - Google Patents

中空纤维分离膜及其制备方法及应用 Download PDF

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Publication number
WO2023160073A1
WO2023160073A1 PCT/CN2022/134854 CN2022134854W WO2023160073A1 WO 2023160073 A1 WO2023160073 A1 WO 2023160073A1 CN 2022134854 W CN2022134854 W CN 2022134854W WO 2023160073 A1 WO2023160073 A1 WO 2023160073A1
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Prior art keywords
membrane
hollow fiber
separation
support body
polybenzimidazole
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PCT/CN2022/134854
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English (en)
French (fr)
Inventor
吴长江
魏昕
刘轶群
丁黎明
郦和生
徐一潇
郗仁杰
王玉杰
唐安琪
邹琦
Original Assignee
中国石油化工股份有限公司
中石化(北京)化工研究院有限公司
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Priority claimed from CN202210166344.4A external-priority patent/CN116675191A/zh
Priority claimed from CN202210857961.9A external-priority patent/CN117463165A/zh
Application filed by 中国石油化工股份有限公司, 中石化(北京)化工研究院有限公司 filed Critical 中国石油化工股份有限公司
Priority to AU2022443634A priority Critical patent/AU2022443634A1/en
Publication of WO2023160073A1 publication Critical patent/WO2023160073A1/zh

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    • 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
    • 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
    • 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

Definitions

  • the invention relates to the field of membrane technology, in particular to a novel hollow fiber separation membrane and its preparation method and application.
  • Helium and hydrogen are gases with small molecules, and both are very important industrial gases.
  • Helium is mainly obtained from the purification of associated gas during the exploitation of natural gas and shale gas.
  • Natural gas and shale gas helium extraction processes are divided into cryogenic process and non-cryogenic process.
  • the cryogenic process is a commonly used method in industrialization. Generally, industrial processes with temperatures lower than -100°C are classified as cryogenic processing. Among them, the extraction of helium from natural gas and the liquefaction of helium are typical cryogenic processes with the lowest refrigeration separation temperature in natural gas cryogenic processing.
  • the cryogenic helium extraction process has high energy consumption and complex equipment.
  • Membrane separation helium purification and refining technology avoids various phase transition processes and violent chemical reactions, has low energy consumption, small equipment, and high safety.
  • Hydrogen is a clean energy carrier and a secondary energy source.
  • the products of hydrogen production from fossil fuels contain N 2 , CO, CH 4 , CO 2 and other gases, which need to be separated and purified.
  • N 2 , CO, CH 4 , CO 2 and other gases which need to be separated and purified.
  • Membrane separation technology has a particularly urgent demand for core membrane materials, especially high-end membrane materials.
  • CN113318609A discloses a method for manufacturing a rigid network microporous hydrogen separation membrane with high permeability and selectivity.
  • the membrane of this application has limited selectivity for hydrogen, and cannot produce high-purity hydrogen or helium products.
  • CN112142980B discloses a hyperbranched polybenzimidazole-polysiloxane block copolymer and its preparation method and application.
  • the block copolymer is due to the combination of the soft segment of PDMS and the hard segment of HBPBI, and the hydrophobic segment of PDMS and the hydrophilic segment of HBPBI to form a soft-hard, hydrophilic-phobic phase separation structure, through the phase separation of the two segments.
  • the separation structure constructs the proton transport channel, and the hyperbranched structure of HBPBI can accommodate more phosphoric acid, and finally obtain high proton conductivity, but the strength and elongation at break of the material are insufficient, and the high-pressure resistant gas separation membrane cannot be prepared.
  • US20160375410A1 discloses a preparation method and application of a PBI asymmetric hollow fiber membrane.
  • the patent uses a non-solvent-induced phase separation technology to prepare a PBI asymmetric hollow fiber membrane.
  • the flux at 250°C is 108GPU, H 2 /CO
  • the separation factor for 2 is 23.7, and the separation factor for H 2 /N 2 is 129.
  • the membrane is prone to defects during the phase inversion process, the selectivity will be greatly affected, and the real separation effect of PBI cannot be exerted.
  • the purpose of the present invention is to overcome the problem that the surface of the hollow fiber membrane prepared by non-solvent-induced phase separation is prone to defects, or the material strength and elongation at break are insufficient, and the high-pressure resistant gas separation membrane cannot be prepared, and to provide a A novel hollow fiber separation membrane and its preparation method and application.
  • the hollow fiber separation membrane of the present application has a high separation coefficient and good mechanical properties.
  • one aspect of the present application provides a hollow fiber separation membrane, characterized in that the separation membrane includes a support, a functional layer, and a connecting layer between the support and the functional layer, wherein the At least a part of the connection layer is embedded in the support body.
  • connection layer and the functional layer contain the same polymer; preferably, the connection layer and the functional layer contain the same polymer and the The tie layer and the functional layer are formed from the same casting solution; more preferably, the tie layer and the functional layer comprise the same polymer, the tie layer and the functional layer are formed from the same casting solution , and the connection layer and the functional layer are formed by non-solvent-induced phase separation and thermal-induced phase separation, respectively.
  • the connection layer has a porous structure (porous).
  • the tie layer is porous and the functional layer is dense.
  • the separation membrane includes a support, a functional layer attached to the outer surface of the support, and a connecting layer embedded in the support;
  • the support is hollow
  • the connection layer has a porous structure, the material of the functional layer is polybenzimidazole, and the number average molecular weight of the polybenzimidazole is 50,000-300,000.
  • One aspect of the present application provides a kind of preparation method of hollow fiber separation membrane, it is characterized in that, described method comprises:
  • the method for preparing the hollow fiber separation membrane of the present invention further includes heating to remove substantially all the solvent after forming the tie layer.
  • Another aspect of the present invention provides a method for preparing a hollow fiber separation membrane, wherein the method includes:
  • One aspect of the present invention provides a hollow fiber separation membrane prepared by the aforementioned method.
  • Still another aspect of the present invention provides the use of the hollow fiber separation membrane of the present invention in separating and purifying helium/nitrogen, helium/methane, hydrogen/nitrogen or hydrogen/methane.
  • Another aspect of the present invention provides a method for purifying helium from a gas containing helium, the method comprising performing membrane separation using the hollow fiber separation membrane of the present application or the hollow fiber separation membrane prepared by the method of the present application.
  • the present invention can provide the following beneficial effects:
  • phase transformation of the polybenzimidazole material is realized by the volatilization of the solvent in the coating layer to prepare an outer functional layer with separation performance
  • the thickness of the outer functional layer can be controlled by means of the present invention.
  • the polybenzimidazole When polybenzimidazole is used as the polymer for preparing the casting solution, the polybenzimidazole is dissolved with an acid and optionally a volatile solvent.
  • the resulting hollow fiber membrane uses acid as a solvent to protonate the polymer during the dissolution process to control the accumulation of molecular chains during the membrane formation process while inhibiting the formation of intermolecular hydrogen bonds.
  • the preparation has high separation coefficient and permeation flux at the same time. separation membrane.
  • Fig. 1 is the structural representation of a kind of spinneret that the present invention prepares nascent film and tie-up used;
  • Fig. 2 is the schematic diagram of the process that the present invention uses the spinneret of Fig. 1 to prepare nascent film and connecting layer;
  • Fig. 3 is a cross-sectional full-view electron micrograph of the hollow fiber separation membrane prepared in Example 1 of the present invention.
  • Fig. 4 is the cross-sectional electron micrograph of the functional layer of the hollow fiber separation membrane prepared in Example 1 of the present invention.
  • Figure 5 is an electron micrograph of the cross-section of the inner surface of the hollow fiber separation membrane prepared in Example 1 of the present invention.
  • Figure 6 is an electron microscope image of the outer surface of the hollow fiber separation membrane prepared in Example 1 of the present invention.
  • Figure 7 is an electron micrograph of the inner surface of the hollow fiber separation membrane prepared in Example 1 of the present invention.
  • Figure 8 is an electron micrograph of the hollow fiber separation membrane prepared in Example 4 of the present invention.
  • Fig. 9 is an electron micrograph of the hollow fiber separation membrane prepared in Example 5 of the present invention.
  • Fig. 10 is the electron micrograph of the hollow fiber separation membrane prepared in comparative example 1;
  • Fig. 11 is a schematic diagram of a method for purifying helium from a helium-rich gas according to the present invention.
  • references to “one embodiment” or “some embodiments” means that a described feature, structure, or characteristic in connection with said embodiment is included in at least one embodiment. In one or more embodiments, the features, structures or characteristics may be combined in any suitable manner.
  • the present invention provides a hollow fiber separation membrane, which is characterized in that the separation membrane includes a support, a functional layer, and a connecting layer between the support and the functional layer, wherein the At least a portion of the tie layer is embedded in the support body.
  • the support body is tubular and the tube wall of the support body has holes and/or slits. At least a part of the connecting layer is embedded in the holes and/or gaps of the tube wall of the support body.
  • the tie layer and the functional layer comprise the same polymer. In some embodiments, the tie layer and the functional layer are formed from the same polymer.
  • the polymer comprising or forming the tie layer and the functional layer is polybenzimidazole.
  • the tie layer and the functional layer comprise the same polymer and the tie layer and the functional layer are formed from the same casting solution. More preferably, in some embodiments, the connection layer and the functional layer comprise the same polymer, the connection layer and the functional layer are formed from the same casting solution, and the connection layer and the The functional layers are formed by non-solvent induced phase separation and thermally induced phase separation, respectively.
  • Nonsolvent induced phase separation and thermally induced phase separation are known in the art.
  • the functional layer is a selectively dense layer
  • the tie layer is a layer for connecting the functional layer with the support.
  • the present invention provides a hollow fiber separation membrane, wherein the separation membrane includes a support, a functional layer attached to the outer surface of the support, and a connecting layer embedded in the support; the support
  • the body is a hollow fiber microporous membrane, the connecting layer has a porous structure, the material of the functional layer is polybenzimidazole, and the number average molecular weight of the polybenzimidazole is 50,000-300,000.
  • Polybenzimidazole (Polybenzimidazole, PBI) is a class of heterocyclic polymers whose main chain contains imidazole rings. This type of polymer has good chemical stability, thermal stability, hydrolytic stability and mechanical stability. As a polymer material, PBI has good processability, and the PBI film is easy to encapsulate, and the preparation cost is reasonable. PBI is especially suitable for the preparation of separation membranes for hydrogen or helium purification.
  • the volatilization of the solvent is promoted by means of high temperature, normal pressure or reduced pressure drying, so that the polymer functional layer such as polybenzimidazole functional layer has a good density, avoids the formation of defects, and obtains better separation performance .
  • the internal support reinforcement method is adopted to improve the mechanical properties of the gas separation membrane, which can meet the requirements of high temperature, high pressure, and high flow rate gas separation systems on the mechanical properties of the membrane filaments, and expand the application range of the gas separation membrane.
  • the non-solvent-induced phase separation is induced by the core fluid to obtain a connection layer with a porous structure, which avoids the shedding of the functional layer.
  • the present invention uses an organic acid and optionally a volatile solvent to prepare a casting solution, and the surface functional layer of the resulting hollow fiber composite membrane comprises protonated polybenzimidazole Or it is composed of protonated polybenzimidazole, so as to obtain a higher separation factor.
  • connection layer is obtained by non-solvent-induced phase separation of the casting solution.
  • tie layer is obtained by non-solvent-induced phase separation of an acid solution containing polybenzimidazole.
  • the functional layer and the connection layer may be formed from the same casting solution.
  • the functional layer and tie layer are formed from the same nascent film, wherein the tie layer is formed by non-solvent-induced phase separation and the functional layer is formed by thermally-induced phase separation.
  • connection layer has a porous structure.
  • functional layer is dense.
  • the polymer contained in the connection layer and the functional layer or the polymer forming the connection layer and the functional layer is polybenzimidazole.
  • the number average molecular weight of the polybenzimidazole can be 50,000-300,000; preferably, the number average molecular weight of the polybenzimidazole can be 56,000-200,000 or 80,000-287,000.
  • the polybenzimidazole includes one or more of the structural units represented by formulas (A1) to (A8);
  • the polybenzimidazole includes one or more structural units represented by formulas (A5) to (A8).
  • the support body may be a fiber braided tube or a hollow fiber membrane, preferably a hollow fiber microporous membrane.
  • the hollow fiber microporous membrane can be a hollow fiber microporous membrane prepared by thermally induced phase separation, melt stretching and other methods from a polymer material that cannot be dissolved by the acid used to prepare the casting solution.
  • the support body may be one or more selected from fiber braided tubes, polypropylene hollow microporous membranes, polyethylene hollow microporous membranes and inorganic hollow microporous membranes.
  • the hollow fiber microporous membrane is a polypropylene hollow microporous membrane or a polyethylene hollow microporous membrane prepared by a thermally induced phase separation method.
  • the average thickness of the hollow fiber separation membrane may be 50-2000 ⁇ m or 100-2000 ⁇ m, preferably 150-1000 ⁇ m, more preferably 180-500 ⁇ m.
  • the porosity of the support when the support is a hollow fiber microporous membrane, the porosity of the support may be 30-90%, preferably 50-80%. In some embodiments, the pore size of the support may be, for example, 10 nanometers to 20 micrometers. The porosity is measured by nitrogen adsorption method.
  • the average thickness of the tube wall of the support body may be 50-2000 ⁇ m or 100-2000 ⁇ m, preferably 300-1800 ⁇ m, more preferably 500-1500 ⁇ m.
  • the average thickness of the functional layer may be 100-50000 nm.
  • the thickness of the functional layer may be 200-5000 nm.
  • the average thickness of the connecting layer may be 20-2000 ⁇ m, preferably 50-1500 ⁇ m, more preferably 20-1000 ⁇ m.
  • connection layer is embedded in at least a part of the support body.
  • the tie layer may have the same diameter as the support.
  • the tie layer can span the outer surface of the support.
  • the tie layer can span the inner surface of the support.
  • the connecting layer is formed from the casting solution through non-solvent-induced phase separation.
  • the tie layer is formed by non-solvent-induced phase separation from an acid solution containing polybenzimidazole.
  • the hollow fiber separation membrane of the present invention has excellent properties including, for example, breaking strength, flux, and separation coefficient.
  • the breaking strength of the separation membrane is 10-500MPa; preferably, the breaking strength of the separation membrane is 50-250MPa; more preferably, the breaking strength of the separation membrane is 52-210MPa.
  • the hollow fiber separation membrane of the present invention is under the test pressure of 0.5MPa at 100°C
  • the flux of pure helium can be 0.8-480GPU
  • the flux of pure hydrogen can be 0.8-580GPU
  • the flux of nitrogen gas can be 0.8-580GPU.
  • the amount can be 0.01-0.7GPU, and/or the flux of methane can be 0.01-0.7GPU; preferably, the flux of pure helium can be 3.48-477.5GPU
  • the flux of pure hydrogen can be 3.03-79.6GPU, and the flux of nitrogen can be 3.03-79.6GPU
  • methane flux can be 0.0135-0.6 GPU.
  • the hollow fiber separation membrane of the present invention has a hydrogen/nitrogen separation coefficient of 110-300 or 110-235 at 100° C. and a test pressure of 0.5 MPa, and/or hydrogen/methane separation coefficient
  • the separation coefficient may be 125-360 or 125-260; preferably, the hydrogen/nitrogen separation coefficient may be 110-234.1, and/or the hydrogen/methane separation coefficient may be 129.1-256.7.
  • the hollow fiber separation membrane of the present invention can have a separation coefficient of helium/nitrogen of 140-390 or 140-190 at 100°C and a test pressure of 0.5 MPa, and/or helium/nitrogen
  • the methane separation factor may be 170-500 or 170-175; preferably, the helium/nitrogen separation factor may be 141.4-187.5, and/or the helium/methane separation factor may be 170-173.8.
  • the hollow fiber separation membrane of the present invention has a separation coefficient of hydrogen/nitrogen of 200-550 at 25°C and a test pressure of 0.5 MPa, and/or a separation coefficient of hydrogen/methane of 200-860.
  • the hollow fiber separation membrane of the present invention has a separation coefficient of helium/nitrogen of 240-900 at 25°C and a test pressure of 0.5 MPa, and/or a separation coefficient of helium/methane It can be 200-2000.
  • the invention also provides a preparation method of the hollow fiber separation membrane.
  • the preparation method of the hollow fiber separation membrane of the present invention comprises:
  • casting solutions and their preparation are generally known in the art.
  • casting solutions can be prepared by dissolving a polymer in a solvent.
  • the polymer may be the polymers mentioned above with respect to the hollow fiber separation membrane.
  • the polymer is polybenzimidazole.
  • Those skilled in the art can select the solvent according to the kind of polymer and the like.
  • the solvent may be a single solvent or may be a mixture.
  • the casting solution may also contain one or more additives. Those skilled in the art can properly select additives as needed.
  • the polymer is used in an amount of 4-18 wt%, the solvent is used in an amount of 77-90 wt%, and the additive is used in an amount of 0-5 wt%.
  • the polymer is used in an amount of 8-15 wt%, the solvent in an amount of 80-90 wt%, and the additive in an amount of 1 -2wt%.
  • the casting solution is applied to the support.
  • the support may be the one described above. Coating can be performed in various ways generally known in the art. For example, a support may be drawn through the casting solution to coat the casting solution onto the support.
  • the casting solution penetrates into at least a part of the support body.
  • the casting solution permeates a part of the tube wall of the tubular support, for example, it can penetrate 10% to 150% of the tube wall thickness of the support.
  • the casting solution can penetrate greater than or equal to 10%, greater than or equal to 15%, greater than or equal to 20%, greater than or equal to 25%, greater than or equal to 30%, greater than or equal to or equal to 35%, greater than or equal to 40%, greater than or equal to 45%, greater than or equal to 50%, greater than or equal to 60%, greater than or equal to 70%, greater than or equal to 80%, greater than or equal to 90%, greater than or equal to 100%, greater than or equal to 110%, etc.
  • the method of the present invention can make the casting solution permeated into the support body tube wall substantially maintain or maintain the penetration depth when it is converted into a connecting layer (making the embedded depth of the connecting layer obtained in the support body the same as the penetration depth of the casting solution or substantially the same), so as to ensure that at least a part of the connection layer formed by the casting solution in the final product hollow fiber separation membrane is embedded in the support body.
  • the nascent film may then be heated to form a functional layer.
  • heating of the nascent film results in thermally induced phase separation, thereby forming the outermost functional layer.
  • the heating promotes the volatilization of the solvent in the casting solution to form the polymer functional layer.
  • Those skilled in the art can select an appropriate temperature for heating according to the solvent used. Alternatively, heating can be performed under normal pressure or reduced pressure.
  • hot air can be used for heating. In some embodiments, hot air can be used to effect evaporation of the solvent.
  • the heating temperature may be 80-300°C.
  • the thermally induced phase separation proceeds until only the outermost portion of the nascent film is phase-separated (thereby forming a functional layer), but the interior of the nascent film does not phase-separate.
  • the casting solution permeated into the support remains in a liquid state, and no thermally induced phase separation occurs.
  • a core liquid can be injected into the support body (i.e., the tube of the tubular support body), and the core liquid causes non-solvent phase induction of the casting liquid that penetrates into the support body. Separation generates connected layers.
  • the core fluid can be injected after obtaining the desired functional layer.
  • the introduction of the core fluid can be performed at room temperature and normal pressure.
  • the hollow fiber separation membrane may be heated to remove (substantially) all of the solvent after forming the tie layer.
  • the heating can be performed under normal pressure or reduced pressure.
  • Those skilled in the art can select an appropriate temperature for heating according to the solvent used.
  • hot air can be used for heating.
  • the same temperature as used in step (3) above may be used in this step.
  • the temperature may be 80-300°C.
  • the dense functional layer and the porous connecting layer are formed from the same casting solution in two different ways, which makes the functional layer and connecting layer integral.
  • the method of the present invention can keep the connection layer in the support body (that is, be embedded in the support body) so as to firmly connect the functional layer to the support body and prevent the functional layer from falling off.
  • the method of the present application enables the connection layer to be kept porous, which may further contribute to firmly connecting the functional layer to the support.
  • the functional layer in the present invention is dense, but the connecting layer is porous.
  • transition regions may exist when going from a dense functional layer to a porous tie layer.
  • the transition zone if present is considered to be part of the connecting layer.
  • the hollow fiber separation membranes prepared by the method of the present invention also provide advantageous membrane properties including, for example, flux and/or separation coefficients.
  • the preparation method of the hollow fiber separation membrane of the present invention comprises:
  • polybenzimidazole, acid, optional volatile solvent and optional additives are mixed to prepare a casting solution containing polymer
  • the preparation method of the hollow fiber separation membrane of the present invention comprises:
  • the extruded casting solution enters the spinneret, and scrape the casting solution on the support body with a scraper, while the support body is drawn from bottom to top Traction through the spinneret to obtain a nascent film attached to the support, and part of the casting solution penetrates into the support;
  • the number average molecular weight of the polybenzimidazole is 50,000 to 300,000 or 50,000-287,000, more preferably, the number average molecular weight of the polybenzimidazole is 80,000 to 28.7 Ten thousand or 56,000-200,000.
  • the polybenzimidazole includes one or more of the structural units represented by formulas (A1) to (A8);
  • the polybenzimidazole includes one or more of the structural units represented by formulas (A5) to (A8).
  • the polybenzimidazole and the support may be the same as those described above regarding the hollow fiber separation membrane.
  • the support may be modified before coating.
  • the modification method is not particularly limited.
  • the modification may include blending the materials used to prepare the support, such as using blended polymers; performing chemical treatment, physical deposition, ultraviolet irradiation, heat treatment or mechanical treatment on the support, and the like.
  • the inventors of the present invention found that: preferably, by compounding organic acid and volatile solvent, polybenzimidazole is protonated during the dissolution process, which inhibits the formation of intermolecular hydrogen bonds and increases the flexibility of polymer molecular chains.
  • the polymer tends to pack more closely during the membrane forming process, and the resulting hollow fiber composite membrane has a high separation coefficient.
  • the method of high temperature and high pressure scraping film and high temperature normal pressure/reduced pressure drying can promote the volatilization of solvent, so that the polybenzimidazole functional layer can get a good density, avoid the formation of defects, and obtain better separation performance .
  • the internal support reinforcement method is adopted to improve the mechanical properties of the gas separation membrane, which can meet the requirements of high temperature, high pressure, and high flow rate gas separation systems on the mechanical properties of the membrane filaments, and expand the application range of the gas separation membrane.
  • the non-solvent-induced phase separation was induced by the core fluid to obtain a connection layer with a porous structure, which avoided the exfoliation of the functional layer.
  • the acid is a monobasic acid.
  • the acid is one or more selected from hydrochloric acid, hydrofluoric acid and methanesulfonic acid. More preferably, the acid is methanesulfonic acid. It is believed that during the film formation process, the organic acid induces protonation, inhibits the formation of hydrogen bonds between polymer molecules, reduces the rigidity of the polymer, and enables the polymer molecular chains to pack more tightly to improve the resistance to hydrogen, helium, and helium. Separation performance of small molecule gases such as gas.
  • the core fluid may be one or more of water, ethanol, methanol, isopropanol, acetone and tetrahydrofuran.
  • the volatile solvent may be ethanol and/or tetrahydrofuran.
  • the additive may be one or more selected from lithium nitrate, calcium chloride, sodium chloride, potassium chloride, polyethylene glycol and polyethylene oxide.
  • the additive is selected from lithium nitrate and/or potassium chloride.
  • the amount of polybenzimidazole is 4-18wt%, the amount of acid is 77-90wt%, and the volatile solvent
  • the consumption of polybenzimidazole is 0-10wt%, and the consumption of described additive is 0-5wt%;
  • the consumption of polybenzimidazole is 8-15wt%, and the consumption of described acid
  • the usage amount is 80-90wt%, the usage amount of the volatile solvent is 1-5wt%, and the usage amount of the additive is 1-2wt%.
  • the sum of the components of polybenzimidazole, acid, volatile solvent and optional additives is 100wt%.
  • polybenzimidazole can be added to the acid and mixed with volatile solvents (if used) and additives (if used) to obtain a casting solution.
  • stirring and heating may be used during mixing.
  • the mixing conditions may include: the temperature is 25-160° C., and the time is 2-72 hours; preferably, the temperature is 80-160° C., and the time is 12-48 hours.
  • the agitation is not particularly limited, and can be routinely selected by those skilled in the art.
  • the stirring speed of the stirring may be 20-500 rpm.
  • the casting solution is applied to the surface of the support.
  • the casting solution may be knife-coated onto the surface of the support.
  • the film-casting solution can be scraped onto the surface of the support at a certain temperature and pressure to obtain a primary film with a certain thickness.
  • the blade coating conditions may include: the temperature is 60-250°C, preferably, the temperature is 80-180°C.
  • the doctor blade pressure is not particularly limited.
  • the pressure may be 10-2000KPa, more preferably, the pressure may be 500-1200KPa.
  • the thickness of the nascent film can be controlled by controlling the distance between the scraper and the outer wall of the support, and thus the thickness of the functional layer can be controlled.
  • the scraper film (nascent film) thickness (the distance between the scraper blade and the outer wall of the support body) may be 10-300 ⁇ m.
  • those skilled in the art can adjust the distance between the scraper and the outer wall of the support body according to the required primary film thickness.
  • the casting solution is extruded into a spinneret, wherein the casting solution contacts the support inside the spinneret.
  • the contact time is not particularly limited.
  • the contact time may be 1-15s, preferably, the contact time is 1-10s.
  • the pressure is not particularly limited.
  • the pressure may be 10-2000KPa.
  • the pressure may be 0 to 0.2 MPa (gauge pressure).
  • the pressure may be 0.02-0.1 MPa (gauge pressure).
  • the support body with the nascent film attached can be pulled and sent into the heating device.
  • the solvent in the outer layer of the nascent film is volatilized by heating to form a polymer functional layer attached to the support, such as a polybenzimidazole functional layer.
  • the heating can be performed, for example, by means of hot air. Heating can be performed under normal pressure or reduced pressure. For example, heating can be performed at -0.1 to 0 MPa (gauge pressure).
  • the conditions for promoting solvent volatilization by heating may include: the temperature is 80-300°C. In some embodiments, hot air may be used for heating.
  • the device for heating is not specifically limited; for example, it may be an oven.
  • the heating temperature may be 100-280° C. for 2-24 hours; preferably, the heating temperature is 120-150° C. for 5-12 hours.
  • a core liquid can be injected into the support body; the core liquid causes non-solvent-induced phase separation of the casting liquid permeating into the support body to form a connection layer.
  • the core fluid is, for example, the core fluid described above.
  • the hollow fiber separation membrane may be heated to remove (substantially) all of the solvent after forming the tie layer.
  • the heating can be performed under normal pressure or reduced pressure.
  • Those skilled in the art can select an appropriate temperature for heating according to the solvent used.
  • hot air can be used for heating.
  • the heating temperature may be 80-300°C.
  • the method may further include removing residual solvents by washing the prepared finished film, such as washing with water, washing with ethanol, and the like.
  • Fig. 1 is a schematic structural view of a spinneret used for preparing a nascent film and a tie layer in the present invention.
  • Fig. 2 is a schematic diagram of the process of preparing a nascent film and a tie layer by using the spinneret shown in Fig. 1 according to the present invention.
  • the spinneret includes a support body positioner, an annular scraper and a core tube.
  • the support body positioner surrounds the support body and is located at one end of the casting solution cavity for containing the casting solution.
  • a casting solution inlet and a casting solution outlet are provided on the casting solution chamber.
  • the casting solution outlet is higher than the casting solution inlet.
  • the support body positioner is arranged at one end of the casting solution cavity to form a closed end, and the other end of the casting solution cavity is provided with the annular scraper.
  • the diameter of the annular scraper is larger than the width of the support body positioner, and the gap formed by the difference between the two can be used to form the nascent film. Also shown in FIG.
  • FIG. 1 is a support holder for holding and pulling the support through the casting chamber. Also shown in Figure 1 is a core tube.
  • the core tube can be inserted into the support body, and injected with core fluid to form a core fluid channel inside the support body. After the core liquid is injected through the core tube, the core liquid induces non-solvent-induced phase separation to obtain a connection layer with a porous structure, which avoids the falling off of the functional layer.
  • FIG. 2 the process of preparing a nascent membrane and a tie layer by using the spinneret described in FIG. 1 is described.
  • the casting solution extruded from the twin-screw extruder or the gear pump is injected into the casting solution cavity through the casting solution inlet.
  • the support is pulled through the casting solution chamber from bottom to top and scraped with a ring scraper; part of the casting solution penetrates into the support.
  • a nascent film attached to the support was obtained after leaving the ring scraper. Excess casting solution flows out through the casting solution outlet.
  • the support with the primary film attached is pulled, and enters the heating device, so that the outer layer of the primary film is heated (for example, heated by hot air) to promote the volatilization of the solvent, forming a layer attached to the surface of the support.
  • Polymer functional layer such as polybenzimidazole functional layer.
  • the core tube is placed inside the support body, the core liquid is injected into the inside of the support body through the core tube, and the non-solvent-induced phase separation is induced by the core liquid from the casting liquid that penetrates into the support body.
  • a tie layer with a porous structure is obtained.
  • the connection layer is embedded in the support body and integrated with the functional layer, which prevents the functional layer from falling off.
  • the present invention also provides the hollow fiber separation membrane prepared by the above method.
  • the hollow fiber separation membrane of the present invention is produced by the method for producing a hollow fiber separation membrane of the present invention.
  • the hollow fiber separation membrane of the present invention can be used for gas separation. Therefore, the present invention also provides the use of the hollow fiber separation membrane of the present invention for separating helium/nitrogen, helium/methane, hydrogen/nitrogen and/or hydrogen/methane. Gases can be separated using the hollow fiber separation membrane of the present invention using operations generally known in the art.
  • the present invention also provides a method for purifying helium from a helium-rich gas, the method comprising performing membrane separation on the gas by using the hollow fiber separation membrane of the present invention.
  • the method for purifying helium from a helium-rich gas may include: subjecting the helium-rich gas to condensation treatment, catalytic dehydrogenation treatment, membrane separation treatment and pressure swing through a cryogenic process Adsorption and impurity removal treatment to obtain purified helium.
  • the membrane separation treatment includes using the hollow fiber separation membrane of the present invention.
  • the method for purifying helium from a gas rich in helium may include: condensing the gas rich in helium through a cryogenic process, through catalytic dehydrogenation, through a helium separation membrane Perform membrane separation treatment and pressure swing adsorption treatment to remove impurities to obtain purified helium; wherein, the conditions of the condensation treatment include: temperature ⁇ -220°C.
  • the membrane separation treatment includes using the hollow fiber separation membrane of the present invention.
  • the prepared helium can be of high purity, for example reaching 4N level (99.99%) or even higher; and can greatly improve the efficiency of helium extraction;
  • the cryogenic process has a high temperature and reduces energy consumption.
  • the conditions of the condensation treatment may include a temperature ⁇ -220°C. In some embodiments, the conditions of the condensation treatment may include: a temperature of -210°C to -150°C, and a pressure of 0.2-10MPa; preferably, the conditions of the condensation treatment include: a temperature of -180°C to -150°C , pressure 3-10MPa.
  • the helium-containing gas may include natural gas, oilfield associated gas, and the like.
  • the helium-containing gas may include helium, nitrogen, methane, hydrogen, and carbon dioxide.
  • the content of helium may be 5-40% by volume; preferably, the content of helium may be 15-30% by volume.
  • the gas rich in helium also contains optional oxygen and water, and based on the total volume of the gas rich in helium, the content of oxygen is 0-8% by volume, and the content of water 0-2% by volume.
  • the helium-rich gas is condensed to achieve the effect of liquefying impurities such as nitrogen, methane, oxygen, and light hydrocarbons, and part of the nitrogen, methane, oxygen, and CO 2 is removed to obtain the second mixed gas.
  • the second mixed gas is subjected to catalytic dehydrogenation treatment to remove part of the hydrogen to obtain the third mixed gas.
  • the conditions of the catalytic dehydrogenation treatment may include: the temperature is 60-120°C, preferably 60-110°C, more preferably 62-106°C.
  • the catalytic dehydrogenation treatment is carried out in the presence of oxygen and a catalyst, wherein the catalyst is a noble metal catalyst, preferably, the catalyst is selected from Pt, Pb, Rh, Ru or Au; more preferably, the catalyst is selected from Pt, Pb or Au.
  • the third mixed gas is subjected to the membrane separation treatment of the present invention to remove part of nitrogen, methane, oxygen and CO 2 to obtain the fourth mixed gas.
  • the membrane separation is driven by the pressure difference on both sides of the membrane, utilizing the difference in permeability of each component in the raw material gas during the process of dissolution, diffusion and desorption to realize helium separation.
  • the conditions of the membrane separation treatment may include: membrane separation positive pressure side pressure > membrane separation permeation side pressure; wherein, the membrane separation positive pressure side pressure may be 0.2-10MPa; preferably, the membrane separation positive pressure side The pressure is 0.5-10MPa; more preferably, the positive pressure side of the membrane separation is 3-10MPa.
  • the membrane separation method has the advantages of simple operation, low energy consumption, and low device construction and operation costs.
  • membrane separation can adopt one-stage or multi-stage membrane separation to purify helium.
  • multi-stage membrane separation means that the gas on the permeate side is pressurized and then used as an inlet for separation using membranes. This process can be 1-5 stages.
  • the fourth mixed gas is subjected to adsorption and impurity removal treatment to remove part of nitrogen, methane, oxygen, hydrogen and CO 2 to obtain purified helium; wherein, based on the total volume of purified helium, the content of helium can be It is 99.986-99.996% by volume.
  • possible conditions for the pressure swing adsorption impurity removal treatment include: the adsorption pressure is 0.2-15 MPa, preferably 10-15 MPa.
  • the adsorbent used in the adsorption and impurity removal treatment may be selected from one or more of activated carbon, molecular sieve, metal organic framework material MOF, and activated alumina.
  • pressures are gauge pressures unless otherwise indicated.
  • Polybenzimidazole was purchased from Shanghai Shengjun Plastic Technology Co., Ltd.; other reagents were purchased from Beijing Yinuokai Technology Co., Ltd. Among them, ethanol 99.9%; hydrochloric acid 12mol/L; methanesulfonic acid 99.0%; tetrahydrofuran 99.9%.
  • test method of permeation rate (unit GPU): measure the gas flow per unit time per unit membrane area under a specific pressure difference at a specific temperature.
  • 1GPU 10 -6 cm 3 (STP)/(cm 2 ⁇ s ⁇ cmHg).
  • the separation coefficient ⁇ is used to characterize the selective permeation ability of gas components in the membrane.
  • the separation factor is the ratio of the permeation rates of two gases through the membrane.
  • the breaking strength is tested by Instron 3342 according to the standard ASTMD882.
  • This example provides the hollow fiber separation membrane prepared by the method of the present invention.
  • polybenzimidazole A5 The structural unit of polybenzimidazole A5 is as follows:
  • the number average molecular weight of the polybenzimidazole A5 is 56,000;
  • the thickness of the functional layer of the prepared hollow fiber separation membrane is about 27-29 ⁇ m; please refer to FIG. 4 , which is a cross-sectional electron microscope image of the functional layer of the hollow fiber separation membrane prepared in Example 1 of the present invention.
  • the connection layer is embedded into the support body with a thickness of about 380 ⁇ m (in Example 1, the connection layer also extends inward from the inner surface of the support body, so the support body is slightly thicker), and the thickness of the embedded layer exceeds the wall thickness of the support body.
  • the breaking strength of the hollow fiber separation membrane prepared in Example 1 is 160MPa; under the test pressure of 100°C and 0.5MPa, the flux of pure helium is 3.48GPU, the flux of pure hydrogen is 3.03GPU, and the fluxes of nitrogen and methane are respectively are 0.016GPU and 0.0135GPU; the separation coefficients of hydrogen/nitrogen and hydrogen/methane are 189 and 224, respectively.
  • Figure 3 is an electron microscopic view of the cross-section of the hollow fiber separation membrane prepared in Example 1 of the present invention; it can be seen from Figure 3 that the functional layer is on the outer surface of the membrane, and the connecting layer is embedded in the support and tightly combined with the PBI membrane.
  • Fig. 5 is a cross-sectional electron microscope image of the inner surface of the hollow fiber separation membrane prepared in Example 1 of the present invention; it can be seen from Fig. 5 that the support body is embedded in the connecting layer, and the inner surface of the connecting layer has a microporous structure.
  • Fig. 6 is an electron microscope image of the outer surface of the hollow fiber separation membrane prepared in Example 1 of the present invention; it can be seen from Fig. 6 that the outer surface is a dense structure.
  • Fig. 7 is an electron microscope image of the inner surface of the novel hollow fiber separation membrane prepared in Example 1 of the present invention; it can be seen from Fig. 7 that the inner surface is a connecting layer with a microporous structure.
  • This example provides the hollow fiber separation membrane prepared by the method of the present invention.
  • the structural unit of the polybenzimidazole A6 is as follows:
  • the number average molecular weight of the polybenzimidazole A6 is 72,000;
  • the support is a polypropylene microporous membrane made by thermally induced phase separation;
  • the concentric circle compound spinning technology makes the cast film contact with the polypropylene microporous membrane in the spinneret (the spinneret cavity height is 10cm), the contact time is 10s, and the contact pressure is 0.4MPa; It is drawn upwards through the inside of the spinneret, and then passes through the ring scraper and controls the thickness of the polybenzimidazole primary film to be 100 ⁇ m to obtain the polybenzimidazole primary film attached to the support; the excess casting solution Flow out through the outlet of the casting solution, and part of the casting solution penetrates into the support body;
  • the average thickness of the prepared hollow fiber separation membrane is about 200 ⁇ m; the thickness of the functional layer is about 2-5 ⁇ m; the connecting layer is embedded in the support body, and the thickness is about 200 ⁇ m.
  • the fracture strength of the prepared hollow fiber separation membrane is 155MPa; under the test pressure of 100°C and 0.5MPa, the flux of pure helium is 7.5GPU, the flux of pure hydrogen is 6.8GPU, and the flux of nitrogen and methane is 0.04GPU and 0.04GPU respectively. 0.04GPU; separation factors for helium/nitrogen and helium/methane are 187.5 and 170, respectively.
  • This example provides the hollow fiber separation membrane prepared by the method of the present invention.
  • the structural unit of the polybenzimidazole A4 is as follows:
  • the number average molecular weight of the polybenzimidazole A4 is 68,000;
  • the mixture liquid is heated to 100° C. and extruded into a spinneret through a gear pump, using a spinneret as shown in Figure 1;
  • the support body is a polypropylene microporous membrane (made by thermally induced phase separation); Adopt the concentric circle composite spinning technology, make the cast film contact with the support in the spinneret (the spinneret cavity height is 10cm), the contact time of the cast film and the braided tube is 2s, and the contact pressure is 0.5MPa;
  • the support is pulled through the inside of the spinneret from bottom to top, and the thickness of the polybenzimidazole primary film is controlled to be 100 ⁇ m through an annular scraper to obtain a polybenzimidazole primary film attached to the support body;
  • the membrane solution flows out through the outlet of the casting solution, and part of the casting solution penetrates into the support;
  • the thickness of the prepared hollow fiber separation membrane functional layer is about 45-50 ⁇ m; the connection layer is embedded in the support body, and the thickness is about 450 ⁇ m.
  • the fracture strength of the prepared hollow fiber separation membrane is 206MPa; under the test pressure of 100°C and 0.5MPa, the flux of pure helium is 0.87GPU, the flux of pure hydrogen is 0.81GPU, and the flux of nitrogen and methane are 0.005GPU and 0.005GPU respectively. 0.004GPU; the separation coefficients of hydrogen/nitrogen and hydrogen/methane reach 162 and 202.5 respectively.
  • This example provides the hollow fiber separation membrane prepared by the method of the present invention.
  • polybenzimidazole A8 ethanol and methanesulfonic acid, stir at 60°C and normal pressure for 24 hours and mix evenly; wherein the mass fraction is composed of: polybenzimidazole 4wt%, ethanol 10wt%, methanesulfonic acid 86wt %, the mixture liquid (casting solution) is prepared; the structural unit of the polybenzimidazole A8 is as follows:
  • the number average molecular weight of the polybenzimidazole A8 is 97,000;
  • the support body is a polypropylene fiber braided tube, which is obtained by weaving polypropylene fibers ;Adopt the concentric circle compound spinning technology, make casting liquid contact with support in spinneret (spinneret cavity height 10cm) casting liquid and braided tube contact time 10s, contact pressure 0.05MPa; Described support
  • the body is pulled through the inside of the spinneret from bottom to top, and the thickness of the polybenzimidazole primary film is controlled to be 100 ⁇ m through an annular scraper to obtain a polybenzimidazole primary film attached to the support body;
  • the membrane solution flows out through the outlet of the casting solution, and part of the casting solution penetrates into the support;
  • the thickness of the prepared hollow fiber separation membrane functional layer is 400-600nm, and there is a relatively obvious transition layer; the connection layer is embedded in the support body, with a thickness of 200-400 ⁇ m, and some of them penetrate the support body.
  • the fracture strength of the prepared hollow fiber separation membrane is 161MPa; at 100°C and 0.5MPa test pressure, the flux of pure helium is 107GPU, the flux of pure hydrogen is 95GPU, and the flux of nitrogen and methane are 0.45GPU and 0.41GPU respectively ; The separation coefficients of hydrogen/nitrogen and hydrogen/methane reach 211 and 231.7 respectively.
  • Fig. 8 shows the electron micrograph of the hollow fiber separation membrane prepared in Example 4; from left to right and from top to bottom are the overall section, functional layer and connecting layer, enlarged functional layer and connecting layer, outer surface, inner surface (the tie layer is porous) and a diagram of the cross-section of the support.
  • This example provides the hollow fiber separation membrane prepared by the method of the present invention.
  • the structural unit of the polybenzimidazole A7 is as follows:
  • the number average molecular weight of the polybenzimidazole A7 is 287,000;
  • the mixture liquid is heated to 80 DEG C and extruded into the spinneret through a gear pump, using a spinneret as shown in Figure 1;
  • the support body is a polypropylene hollow fiber microporous membrane (average pore size is 0.01 ⁇ m, The porosity is 65%, and the contact angle of the outer surface is 75°C; its preparation method is as follows: the mass fraction is 25% polypropylene resin, 0.5% maleic anhydride grafted polypropylene, 0.5% polyvinylpyrrolidone and 74% soybean oil at 185°C Stir and heat to obtain a homogeneous casting film; after vacuum degassing and filtration, it is transported to the hollow spinneret with soybean oil as the inner core liquid, and enters the soybean oil to cool and solidify; after extraction with acetone and natural air drying, the polypropylene hollow fiber microporous membrane); using concentric circle composite spinning technology, the casting liquid is in contact with the polypropylene microporous membrane (made by thermal
  • the average thickness of the prepared hollow fiber separation membrane is about 350 ⁇ m; the average thickness of the functional layer is about 1.2-2.0 ⁇ m; the connecting layer is embedded in the support body with a thickness of about 30 ⁇ m.
  • the fracture strength of the prepared hollow fiber separation membrane is 63MPa; under the test pressure of 100°C and 0.5MPa, the flux of pure helium is 88.9GPU, the flux of pure hydrogen is 76.1GPU, and the flux of nitrogen and methane are 0.66GPU and 0.66GPU respectively. 0.52GPU; the separation coefficients of hydrogen/nitrogen and hydrogen/methane are 134.7 and 170.9 respectively.
  • Fig. 9 shows the electron micrograph of the hollow fiber separation membrane prepared in Example 5; from left to right from top to bottom are the overall section, functional layer and connecting layer, enlarged functional layer and connecting layer, outer surface, inner surface and a diagram of the cross-section of the support body.
  • This example provides the hollow fiber separation membrane prepared by the method of the present invention.
  • the structural unit of the polybenzimidazole A1 is as follows:
  • the number average molecular weight of the polybenzimidazole A1 is 87,000;
  • the support body is a polyethylene microporous membrane (made by melt-spinning stretching method; 1-10 microns, porosity 65%-80%); using concentric composite spinning technology, the casting solution is in contact with the polyethylene microporous membrane in the spinneret (spinneret cavity height 10cm), contact The time is 10s, and the contact pressure is 0.2MPa; the support is drawn from bottom to top through the inside of the spinneret, passes through the ring scraper and controls the thickness of the polybenzimidazole primary film to be 80 ⁇ m, and is attached to the support. The polybenzimidazole primary film on the top; the excess casting solution flows out through the casting solution outlet, and part of the casting solution penetrates into the support;
  • the thickness of the prepared hollow fiber separation membrane functional layer is about 2000nm; the connection layer is embedded in the support body, and the thickness is about 180-190 ⁇ m (the average thickness is about 185 ⁇ m).
  • the fracture strength of the prepared hollow fiber separation membrane is 52MPa; under the test pressure of 100°C and 0.5MPa, the flux of pure helium is 82.2GPU, the flux of pure hydrogen is 79.6GPU, and the flux of nitrogen and methane is 0.68GPU and 0.68GPU respectively. 0.55GPU; the separation coefficients of hydrogen/nitrogen and hydrogen/methane reach 120.61 and 144.7 respectively.
  • This example provides the hollow fiber separation membrane prepared by the method of the present invention.
  • the structural unit of the polybenzimidazole A7 is as follows:
  • the number average molecular weight of the polybenzimidazole A7 is 126,000;
  • the support body is polyethylene hydrophobic micropores with a porosity of 60%-80% Membrane (produced by melt-spinning stretching method); using concentric composite spinning technology, the casting liquid is in contact with the polyethylene hydrophobic microporous membrane in the spinneret (the spinneret cavity height is 10cm), and the contact time is 10s , the contact pressure is controlled at 0.1MPa; the support body is pulled through the inside of the spinneret from bottom to top, passes through the ring scraper and controls the thickness of the polybenzimidazole primary film to be 80 ⁇ m, and is attached to the support body The nascent polybenzimidazole membrane; the excess casting solution flows out through the casting solution outlet, and part of the casting solution penetrates into the support;
  • the thickness of the prepared hollow fiber separation membrane functional layer is about 10-12 ⁇ m; the connection layer is embedded in the support body, and the thickness is about 300 ⁇ m.
  • the fracture strength of the prepared hollow fiber separation membrane is 52MPa; under the test pressure of 100°C and 0.5MPa, the flux of pure helium is 22.6GPU, the flux of pure hydrogen is 22.1GPU, and the flux of nitrogen and methane are 0.16GPU and 0.16GPU respectively. 0.13GPU; the separation coefficients of helium/nitrogen and helium/methane reach 141.4 and 173.8 respectively.
  • the polybenzimidazole A1 includes the following structural units:
  • the number average molecular weight of the polybenzimidazole A1 is 68,000;
  • the functional layer of the prepared hollow fiber separation membrane is very thick; there is no porous connection layer, and the functional layer is directly attached to the support body on the outer surface of the support body. Since the film has no connection layer, the binding between the functional layer and the support body is poor, the functional layer is easy to fall off, and the service life is reduced. When the internal pressure exceeds 0.04MPa, the functional layer is damaged; when the external pressure is used, the service life is only 2000-5000 hours after repeated pressure changes.
  • the fracture strength of the prepared hollow fiber separation membrane is 166MPa; under the test pressure of 100°C and 0.5MPa, the flux of pure helium is 12.8GPU, the flux of pure hydrogen is 11.6GPU, and the flux of nitrogen and methane is 0.11GPU and 0.11GPU respectively. 0.10GPU, the separation coefficients of hydrogen/nitrogen and hydrogen/methane reach 105 and 116 respectively.
  • Fig. 10 shows the electron micrograph of the hollow fiber separation membrane prepared in comparative example 1; from left to right from top to bottom are the diagrams of the overall section, functional layer, enlarged functional layer, outer surface, inner surface and support body section respectively .
  • the structural unit of the polybenzimidazole A7 is as follows:
  • the number average molecular weight of the polybenzimidazole A7 is 126,000;
  • the average thickness of the prepared hollow fiber separation membrane is about 600 ⁇ m; the thickness of the functional layer is about 500 nm; the outer diameter of the support is 1400 ⁇ m; the functional layer of the membrane is poorly bonded to the support, the functional layer is easy to fall off, and the service life is reduced.
  • the internal pressure exceeds 0.05 MPa, the functional layer is damaged.
  • the fracture strength of the prepared hollow fiber separation membrane is 166MPa.
  • the flux of pure helium is 28.5GPU
  • the flux of pure hydrogen is 27.6GPU
  • the flux of nitrogen and methane are 0.33
  • the separation coefficients of hydrogen/nitrogen and hydrogen/methane reach 83.7 and 102.2, respectively.
  • the structural unit of the polybenzimidazole A7 is as follows:
  • the number average molecular weight of the polybenzimidazole A7 is 126,000;
  • the thickness of the functional layer of the prepared hollow fiber separation membrane is about 200nm, the structure of the membrane is not dense, and the selectivity is low; when the internal pressure exceeds 0.1MPa, the functional layer is damaged.
  • the fracture strength of the prepared hollow fiber separation membrane is 165MPa.
  • the flux of pure helium is 107GPU
  • the flux of pure hydrogen is 89.5GPU
  • the flux of nitrogen and methane is 12.9GPU respectively.
  • 11.4GPU the separation coefficients of hydrogen/nitrogen and hydrogen/methane reached 6.94 and 7.85 respectively.
  • the raw material gas helium-rich gas includes: the volume fraction of helium is 20% by volume, the volume fraction of methane is 17% by volume, the volume fraction of nitrogen is 60% by volume, the volume fraction of hydrogen is 1% by volume, and the volume fraction of carbon dioxide is 0.5% The volume % and the volume fraction of oxygen are 1.5 volume %.
  • the helium-enriched gas is refined, as shown in Figure 11:
  • Raw material gas 1# first enters the cryogenic unit, where the temperature is -180°C and the pressure is 4MPa;
  • step (2) The tower top gas 2# obtained by step (1) enters the catalytic dehydrogenation unit, and a small amount of pure oxygen is introduced as a combustion-supporting gas during the combustion process to ensure the smooth operation of the catalytic reaction.
  • the catalyst is Pt and the temperature is 98 ° C;
  • (3) 3# enters the membrane unit after the gas after combustion is dried, passes through the membrane module prepared by the hollow fiber membrane of embodiment 4 of the present application to carry out primary and secondary membrane separation operations, and the operating pressure of the membrane separation positive pressure side is respectively 3MPa, 3MPa;
  • the helium-poor gas on the retentate side flows back to the cryogenic unit, and the crude helium product 4# on the permeate side enters the adsorption and impurity removal unit for pressure swing adsorption operation, in which 5A molecular sieve, coconut shell activated carbon and activated alumina are used for adsorption agent, and the adsorption pressure is 10MPa to obtain refined helium 5#.
  • the present invention can significantly increase the concentration of helium through the cryogenic process, and effectively remove the hydrogen that is difficult to separate from the helium in the mixed gas through the catalytic oxidation section, and then perform membrane separation.
  • the crude helium gas concentration obtained is 99.75%, and then through pressure swing adsorption, the product helium concentration can reach 99.995%, reaching the 4N level standard.

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Abstract

本发明涉及膜分离技术领域，并公开了一种中空纤维分离膜及其制备方法及应用。所述中空纤维分离膜包括支撑体、功能层以及位于所述支撑体和所述功能层之间的连接层，其中所述连接层的至少一部分嵌入所述支撑体中。所述中空纤维分离膜的分离系数高以及具有较好的力学性能。

Description

中空纤维分离膜及其制备方法及应用 技术领域
本发明涉及膜技术领域，具体地，涉及一种新型中空纤维分离膜及其制备方法及应用。
背景技术
氦气和氢气是分子较小的气体，并且都是非常重要的工业气体。
氦气主要是从天然气、页岩气开采时的伴生气进行提纯制得。天然气、页岩气提氦工艺分为深冷工艺和非深冷工艺。深冷工艺是目前工业化常用的方法。一般将温度低于-100℃的工业过程归于深冷加工的范畴，其中，天然气提氦与氦的液化属于天然气深冷加工中制冷分离温度最低的典型深冷过程。深冷提氦工艺能耗高、装置复杂。膜分离氦气提纯和精制技术避免各种相变过程和剧烈化学反应，能耗低、装置小、安全性高。
氢气是一种清洁能源的载体同时还是一种二次能源。化石燃料制氢的产物中含有N 2、CO、CH 4、CO 2等气体，需经过分离、纯化处理。随着全球对清洁、高效能源的需求日益增长，氢气的生产、精制也越来越受重视。
为了满足对氦气和氢气的需求，急需开发高效、绿色、安全、可靠的氦气和氢气提纯方法。膜分离技术对核心膜材料、尤其是高端膜材料的需求尤其迫切。
CN113318609A公开了具有高渗透性及选择性的刚性网络微孔氢气分离膜制造方法。但是该申请的膜对于氢气的选择性有限，无法制备高纯氢气或者氦气产品。
CN112142980B公开了一种超支化聚苯并咪唑-聚硅氧烷嵌段共聚物及其制备方法与应用。所述嵌段共聚物由于是PDMS的软段与HBPBI的硬段、PDMS的疏水段与HBPBI的亲水段结合从而形成软-硬、亲-疏的相分离结构，通过两种链段的相分离结构构筑质子传输通道，HBPBI的超支化结构能够容纳更多的磷酸，最终获得高质子电导率，但是该材料强度和断裂伸长率不足，不能制备耐高压气体分离膜。
US20160375410A1公开了一种PBI非对称中空纤维膜的制备方法及其应用，该专利采用非溶剂致相分离技术制备的PBI非对称中空纤维膜，在250℃时的通量为108GPU，H 2/CO 2的分离系数为23.7，H 2/N 2的分离系数为129。但是该膜在相转化过程中容易产生缺陷，选择性会受到很大影响，无法发挥出PBI真实的分离效果。
因此，开发具有致密功能层、方便制备、能够体现出PBI的高分离效果的膜材料具有重要意义。
发明内容
本发明的目的是为了克服现有技术中非溶剂诱导相分离制备的中空纤维膜表面容易出现缺陷，或者是材料强度和断裂伸长率不足、不能制备耐高压气体分离膜的问题，而提供一种新型中空纤维分离膜及其制备方法及应用。本申请的中空纤维分离膜的分离系数高，并且具有良好的力学性能。
为了实现上述目的，本申请的一个方面提供了中空纤维分离膜，其特征在于，所述分离膜包括支撑体、功能层以及位于所述支撑体和所述功能层之间的连接层，其中所述连接层的至少一部分嵌入所述支撑体中。
根据一些实施方案，在本申请的中空纤维分离膜中，所述连接层和所述功能层包含相同的聚合物；优选地，所述连接层和所述功能层包含相同的聚合物并且所述连接层和所述功能层由相同的铸膜液形成；更优选地，所述连接层和所述功能层包含相同的聚合物，所述连接层和所述功能层由相同的铸膜液形成，并且所述连接层和所述功能层分别通过非溶剂致相分离和热致相分离形成。根据一些实施方案，所述连接层具有多孔结构(多孔的)。根据一些实施方案，所述连接层是多孔的而所述功能层是致密的。
本发明另一方面提供了一种中空纤维分离膜，其中，所述分离膜包括支撑体、附着在所述支撑体外表面的功能层以及嵌入所述支撑体的连接层；所述支撑体为中空纤维微孔膜，所述连接层具有多孔结构，所述功能层的材质为聚苯并咪唑，且所述聚苯并咪唑的数均分子量为5万-30万。
本申请的一个方面提供了一种中空纤维分离膜的制备方法，其特 征在于，所述方法包括：
(1)制备包含聚合物的铸膜液；
(2)将所述铸膜液涂覆在支撑体上，其中所述铸膜液的一部分渗透到所述支撑体中，得到涂覆在所述支撑体上的初生膜；
(3)将所述初生膜进行加热以形成功能层；和
(4)在所述支撑体内注入芯液，使渗透到所述支撑体中的铸膜液发生非溶剂诱导相分离生成连接层。
任选地，本发明的中空纤维分离膜的制备方法还包括在生成连接层之后进行加热以基本上除去所有溶剂。
本发明又一个方面提供了一种中空纤维分离膜的制备方法，其中，所述的方法包括：
(1)将聚苯并咪唑、酸(溶剂)、可选的易挥发溶剂和可选的添加剂进行混合，得到铸膜液；所述聚苯并咪唑的数均分子量为5万-30万；
(2)将所述铸膜液挤出，挤出的铸膜液进入喷丝头，并采用刮刀将所述铸膜液刮涂在支撑体上，同时所述支撑体由下向上被牵引通过所述喷丝头内部，得到附着在所述支撑体上的初生膜，以及有部分铸膜液渗透到所述支撑体内；
(3)将所述初生膜进行加热处理，形成具有致密结构的聚苯并咪唑功能层；并且在所述支撑体内通过中芯管注入非溶剂作为芯液，促使所述支撑体内渗入的所述部分铸膜液发生非溶剂诱导相分离生成多孔结构的连接层；然后进行充分干燥，得到中空纤维分离膜。
本发明的一个方面提供了一种由前述的方法制备得到的中空纤维分离膜。
本发明的又一个方面提供了本发明的中空纤维分离膜在分离和纯化氦气/氮气、氦气/甲烷、氢气/氮气或者氢气/甲烷方面的用途。
本发明的再一个方面提供了从含有氦气的气体中提纯氦气的方法，所述方法包括使用本申请的中空纤维分离膜或本申请的方法制备的中空纤维分离膜进行膜分离。
通过上述技术方案，本发明可以提供以下有益效果：
(1)通过涂覆层中溶剂挥发实现聚苯并咪唑材料相转化制备出具有分离性能的外功能层；
(2)采用内支撑增强，改进了气体分离膜的力学性能，可满足高温、高压、高流速气体分离系统等对膜丝力学性能的要求，扩大了气体分离膜的应用范围；
(3)实现铸膜液渗透到支撑体，并通过芯液诱导非溶剂致相分离获得了具有多孔结构的连接层，避免了功能层的脱落；
(4)纺丝过程中可以通过本发明所述的方式控制外部功能层厚度。
当采用聚苯并咪唑作为用于制备铸膜液的聚合物时，采用酸和任选地易挥发溶剂溶解聚苯并咪唑。所得中空纤维膜采用酸为溶剂，在聚合物溶解过程中对其进行质子化，控制成膜过程中分子链的堆积，同时抑制分子间氢键的形成，制备同时具有高分离系数和渗透通量的分离膜。
附图说明
图1是本发明制备初生膜和连接层所用的一种喷丝头的结构示意图；
图2是本发明使用图1的喷丝头制备初生膜和连接层的过程的示意图；
图3是本发明实施例1制备的中空纤维分离膜的横截面全貌电镜图；
图4是本发明实施例1制备的中空纤维分离膜的功能层横截面电镜图；
图5是本发明实施例1制备的中空纤维分离膜的内表面横截面电镜图；
图6是本发明实施例1制备的中空纤维分离膜的外表面电镜图；
图7是本发明实施例1制备的中空纤维分离膜的内表面电镜图；
图8是本发明实施例4制备的中空纤维分离膜的电镜图；
图9是本发明实施例5制备的中空纤维分离膜的电镜图；
图10是对比例1制备的中空纤维分离膜的电镜图；和
图11是本发明的一种从富含氦气的气体中提纯氦气的方法的示意图。
具体实施方式
在本文中所披露的范围的端点和任何值都不限于该精确的范围或值，这些范围或值应当理解为包含接近这些范围或值的值。对于数值范围来说，各个范围的端点值之间、各个范围的端点值和单独的点值之间，以及单独的点值之间可以彼此组合而得到一个或多个新的数值范围，这些数值范围应被视为在本文中具体公开。
在本说明书中，提及“一个实施方案”或“一些实施方案”是指与所述实施方案有关所描述的特征、结构或特性包括在至少一个实施方案中。在一个或多个实施方案中，这些特征、结构或特性能够以任何适合的方式进行组合。
如前所述，本发明提供了一种中空纤维分离膜，其特征在于，所述分离膜包括支撑体、功能层以及位于所述支撑体和所述功能层之间的连接层，其中所述连接层的至少一部分嵌入所述支撑体中。
在本发明中，所述支撑体是管状的并且支撑体的管壁具有孔和/或缝隙。所述连接层的至少一部分嵌入支撑体的管壁的孔和/或缝隙中。
在本发明中，所述连接层和所述功能层包含相同的聚合物。在一些实施方案中，所述连接层和所述功能层由相同的聚合物形成。
在一些实施方案中，所述连接层和所述功能层包含的聚合物或者形成所述连接层和所述功能层的聚合物是聚苯并咪唑。
优选地，在一些实施方案中，所述连接层和所述功能层包含相同的聚合物并且所述连接层和所述功能层由相同的铸膜液形成。更优选地，在一些实施方案中，所述连接层和所述功能层包含相同的聚合物，所述连接层和所述功能层由相同的铸膜液形成，并且所述连接层和所述功能层分别通过非溶剂致相分离和热致相分离形成。
非溶剂致相分离和热致相分离是本领域中已知的。
在本发明中，功能层是具有选择性的致密层，和连接层是用于将功能层与支撑体连接起来的层。
在一些实施方案中，本发明提供了一种中空纤维分离膜，其中，所述分离膜包括支撑体、附着在所述支撑体外表面的功能层以及嵌入所述支撑体的连接层；所述支撑体为中空纤维微孔膜，所述连接层具有多孔结构，所述功能层的材质为聚苯并咪唑，且所述聚苯并咪唑的数均分子量为5万-30万。
聚苯并咪唑(Polybenzimidazole，PBI)是一类主链含有咪唑环的杂环聚合物，这类聚合物具有良好的化学稳定性、热稳定性、耐水解稳定性和机械稳定性。作为一种聚合物材料，PBI具有良好加工性，PBI膜易于封装，制备成本合理。PBI特别适合于制备用于氢气或者氦气提纯所需的分离膜。
在本发明中，采用高温常压或减压干燥的方式促进溶剂的挥发，使得聚合物功能层例如聚苯并咪唑功能层具有很好的致密度，避免缺陷的形成，获得更好的分离性能。另外，在本发明中采用内支撑增强方式，改进了气体分离膜的力学性能，可满足高温、高压、高流速气体分离系统等对膜丝力学性能的要求，扩大了气体分离膜的应用范围。在本发明中，通过芯液诱导非溶剂致相分离获得了具有多孔结构的连接层，避免了功能层的脱落。
在所述功能层包含聚苯并咪唑的情况中，本发明使用有机酸和任选地易挥发溶剂来制备铸膜液，所得中空纤维复合膜的表面功能层包含由质子化的聚苯并咪唑或由质子化的聚苯并咪唑构成，从而得到较高的分离系数。
在本发明中，所述连接层通过铸膜液的非溶剂诱导相分离得到。在优选的实施方案中，所述连接层通过含有聚苯并咪唑的酸溶液的非溶剂诱导相分离得到。
在本发明中，所述功能层和连接层可以是由相同的铸膜液形成。在一些实施方案中，所述功能层和连接层由同一初生膜形成，其中所述连接层通过非溶剂致相分离形成和所述功能层通过热致相分离形成。
在本发明中，所述连接层具有多孔结构。在本发明中，所述功能层是致密的。
根据本发明，优选地，所述连接层和所述功能层包含的聚合物或者形成所述连接层和所述功能层的聚合物是聚苯并咪唑。所述聚苯并咪唑的数均分子量可以为5万-30万；优选地，所述聚苯并咪唑的数均分子量可以为5.6万-20万或8-28.7万。
根据本发明，优选地，所述聚苯并咪唑包括式(A1)至(A8)所示的结构单元中的一种或多种；
Figure PCTCN2022134854-appb-000001
根据本发明，优选地，所述聚苯并咪唑包括式(A5)至(A8)所示的结构单元中的一种或多种。
根据本发明，所述支撑体可以是纤维编织管或者中空纤维膜，优选中空纤维微孔膜。所述中空纤维微孔膜可以是由不能被用于制备铸膜液的酸所溶解的聚合物材料通过热致相分离、熔融拉伸等方法制备 的中空纤维微孔膜。所述支撑体可以是选自纤维编织管、聚丙烯中空微孔膜、聚乙烯中空微孔膜和无机中空微孔膜中的一种或多种。优选地，所述中空纤维微孔膜为通过热致相分离法制备的聚丙烯中空微孔膜或聚乙烯中空微孔膜。
根据本发明，所述中空纤维分离膜的平均厚度可以为50-2000μm或100-2000μm，优选为150-1000μm，更优选为180-500μm。
根据本发明，当所述支撑体是中空纤维微孔膜时，所述支撑体的孔隙率可以为30-90％，优选为50-80％。在一些实施方案中，支撑体的孔径可以例如是10纳米-20微米。所述孔隙率由氮气吸附法测得。
根据本发明，所述支撑体的管壁的平均厚度可以为50-2000μm或100-2000μm，优选为300-1800μm，更优选为500-1500μm。
根据本发明，所述功能层的平均厚度可以为100-50000nm。优选地，在一些实施方案中，所述功能层的厚度可以为200-5000nm。
根据本发明，所述连接层的平均厚度可以为20-2000μm，优选为50-1500μm，更优选为20-1000μm。
在本发明中，所述连接层的至少一部分嵌入所述支撑体的至少一部分中。在一些实施方案中，所述连接层的直径可以与所述支撑体的直径相同。在一些实施方案中，所述连接层可以跨越支撑体外表面。在一些实施方案中，所述连接层可以跨越支撑体的内表面。
根据本发明，所述连接层由铸膜液通过非溶剂致相分离形成。在一些实施方案中，所述连接层由含有聚苯并咪唑的酸溶液通过非溶剂诱导相分离形成。
本发明的中空纤维分离膜具有优异的性能，包括例如断裂强度、通量和分离系数。
根据本发明，所述分离膜的断裂强度为10-500MPa；优选地，所述分离膜的断裂强度为50-250MPa；更优选地，所述分离膜的断裂强度为52-210MPa。
根据本发明，在一些实施方案中，本发明的中空纤维分离膜在100℃、0.5MPa测试压力下，纯氦气通量可以为0.8-480GPU，纯氢气通量可以为0.8-580GPU，氮气通量可以为0.01-0.7GPU，和/或甲烷通量可以为0.01-0.7GPU；优选地，纯氦气通量可以为3.48-477.5GPU，纯氢气通量可以为3.03-79.6GPU，氮气通量可以为0.016-0.68GPU，和/或 甲烷通量可以为0.0135-0.6GPU。
根据本发明，在一些实施方案中，本发明的中空纤维分离膜在100℃、0.5MPa测试压力下，氢气/氮气的分离系数可以为110-300或110-235，和/或氢气/甲烷的分离系数可以为125-360或125-260；优选地，氢气/氮气的分离系数可以为110-234.1，和/或氢气/甲烷的分离系数可以为129.1-256.7。
根据本发明，在一些实施方案中，本发明的中空纤维分离膜在100℃、0.5MPa测试压力下，氦气/氮气的分离系数可以为140-390或140-190，和/或氦气/甲烷的分离系数可以为170-500或170-175；优选地，氦气/氮气的分离系数可以为141.4-187.5，和/或氦气/甲烷的分离系数可以为170-173.8。
根据本发明，在一些实施方案中，本发明的中空纤维分离膜在25℃、0.5MPa测试压力下，氢气/氮气的分离系数可以为200-550，和/或氢气/甲烷的分离系数可以为200-860。
根据本发明，在一些实施方案中，本发明的中空纤维分离膜在25℃、0.5MPa测试压力下，氦气/氮气的分离系数可以为240-900，和/或氦气/甲烷的分离系数可以为200-2000。
本发明还提供了中空纤维分离膜的制备方法。
根据一些实施方案，本发明的中空纤维分离膜的制备方法包括：
(1)制备包含聚合物的铸膜液；
(2)将所述铸膜液涂覆在支撑体上，其中所述铸膜液的一部分渗透到所述支撑体中，得到涂覆在所述支撑体上的初生膜；
(3)将所述初生膜进行加热以形成功能层；和
(4)在所述支撑体内注入芯液，使渗透到所述支撑体中的铸膜液发生非溶剂诱导相分离生成连接层。
铸膜液及其制备是本领域中通常已知的。例如铸膜液可以通过将聚合物溶解在溶剂中制备。所述聚合物可以是以上关于中空纤维分离膜所提及的聚合物。优选地，所述聚合物是聚苯并咪唑。本领域技术人员可以根据聚合物的种类等等来选择溶剂。所述溶剂可以是单一一种溶剂或者可以是混合物。
可选地，所述铸膜液还可以包含一种或多种添加剂。本领域技术人员可以根据需要合适地选择添加剂。
在一些实施方案中，以所述铸膜液的总重量为基准，聚合物的用量为4-18wt％，溶剂的用量为77-90wt％，和所述添加剂的用量为0-5wt％。优选地，在一些实施方案中，以所述铸膜液的总重量为基准，聚合物的用量为8-15wt％，所述溶剂的用量为80-90wt％，和所述添加剂的用量为1-2wt％。
在制备铸膜液之后，将所述铸膜液涂覆到支撑体上。支撑体可以是上文中描述的支撑体。可以采用本领域中通常已知的各种方式来实施涂覆。例如，可以将支撑体牵引通过所述铸膜液以将铸膜液涂覆到所述支撑体上。
根据本发明，所述铸膜液渗透到所述支撑体的至少一部分中。在一些实施方案中，所述铸膜液渗透管状支撑体的管壁的一部分，例如可以渗透支撑体管壁厚度的10％至150％。在一些实施方案中，所述铸膜液可以渗透支撑体管壁厚度的大于或等于10％、大于或等于15％、大于或等于20％、大于或等于25％、大于或等于30％、大于或等于35％、大于或等于40％、大于或等于45％、大于或等于50％、大于或等于60％、大于或等于70％、大于或等于80％、大于或等于90％、大于或等于100％、大于或等于110％等。本领域技术人员可以合理地确定铸膜液在支撑体管壁中的渗入范围。本发明的方法可以使渗透到支撑体管壁中的铸膜液在转变为连接层时基本保持或保持渗透深度(使得得到的连接层在支撑体中的嵌入深度与铸膜液的渗透深度相同或基本相同)，从而保证最终得到的成品中空纤维分离膜中由铸膜液形成的连接层的至少一部分嵌入所述支撑体中。
在将所述铸膜液涂覆到所述支撑体上之后，得到涂覆在所述支撑体上的初生膜。
然后，可以对所述初生膜进行加热以形成功能层。在本发明中，对初生膜的加热导致热致相分离，从而形成在最外部的功能层。
所述加热促进铸膜液中溶剂的挥发以形成聚合物功能层。本领域技术人员可以根据所使用的溶剂选择合适的温度来进行加热。可选地，可在常压或减压下进行加热。例如，可以使用热空气进行加热。在一些实施方案中，可以采用热空气来进行溶剂的挥发。在本发明中，例如，加热温度可以为80-300℃。
在本发明的方法中，所述热致相分离进行到仅所述初生膜的最外 部发生相分离(从而形成功能层)，但是初生膜的内部并没有发生相分离。特别地，渗透到所述支撑体中的铸膜液仍然保持为液体状态，并没有发生热致相分离。
在对初生膜进行加热形成功能层之后，可以在所述支撑体内(即管状支撑体的管内)注入芯液，所述芯液使渗透到所述支撑体中的铸膜液发生非溶剂致相分离生成连接层。在一些实施方案中，例如可以在得到所需的功能层之后就注入所述芯液。在本发明中，芯液的通入可以在室温和常压下进行。
本领域技术人员可以根据铸膜液的组成、支撑体的材料等来选择芯液，只要能够使所述铸膜液发生非溶剂致相分离。
在本发明的方法中，任选地，在生成连接层之后可以对中空纤维分离膜进行加热以(基本上)除去所有溶剂。所述加热可以在常压或减压下进行。本领域技术人员可以根据所使用的溶剂选择合适的温度来进行加热。例如，可以使用热空气进行加热。在一些实施方案中，本步骤中可以使用与以上步骤(3)中使用的温度相同的温度。例如，温度可以为80-300℃。
在本发明的方法中，以两种不同的方式由同一铸膜液形成致密的功能层和多孔的连接层，这使得所述功能层和连接层是一体的。本发明的方法可以使连接层保持在支撑体中(即嵌在支撑体中)从而将功能层牢固地连接到支撑体，避免功能层的脱落。此外，本申请的方法能够使连接层保持为是多孔的，这可以进一步有助于将功能层牢固地连接到支撑体。
本发明中的功能层是致密的，但连接层是多孔的。如本领域技术人员所理解的那样，在从致密的功能层转变到多孔的连接层时，可能会存在过渡区域。在本申请中，将过渡区域(如果存在)视为连接层的一部分。
本发明的方法制备的中空纤维分离膜还提供有利的膜性能，包括例如通量和/或分离系数。
根据一些实施方案，本发明的中空纤维分离膜的制备方法包括：
(1)将聚苯并咪唑、酸、可选的易挥发溶剂和可选的添加剂进行混合制备包含聚合物的铸膜液；
(2)将所述铸膜液涂覆在支撑体上，其中所述铸膜液的一部分渗 透到所述支撑体的至少一部分中，得到涂覆在所述支撑体上的初生膜；
(3)将所述初生膜进行加热以形成功能层；和
(4)在所述支撑体内注入芯液，使渗透到所述支撑体中的铸膜液发生非溶剂诱导相分离生成连接层。
根据一些实施方案，本发明的中空纤维分离膜的制备方法包括：
(1)将聚苯并咪唑、酸、可选的易挥发溶剂和可选的添加剂进行混合，得到铸膜液；所述聚苯并咪唑的数均分子量为5万-30万；
(2)采用制备初生膜和连接层用喷丝头；采用中空纤维微孔膜作为支撑体；
(3)将所述铸膜液挤出，挤出的铸膜液进入喷丝头，并采用刮刀将所述铸膜液刮涂在所述支撑体上，同时所述支撑体由下向上被牵引通过所述喷丝头内，得到附着在所述支撑体上的初生膜，以及有部分铸膜液渗透到所述支撑体内部；
(4)将所述初生膜进行加热处理，形成具有致密结构的聚苯并咪唑功能层；并且在所述支撑体内通过中心管注入非溶剂作为芯液，促使所述支撑体内渗入的所述部分铸膜液发生非溶剂诱导相分离生成多孔结构的连接层；然后经加热除溶剂处理，得到中空纤维分离膜。
根据本发明，优选地，所述聚苯并咪唑的数均分子量为5万至30万或5万-28.7万，更优选情况下，所述聚苯并咪唑的数均分子量为8万至28.7万或5.6万-20万。
根据本发明，所述聚苯并咪唑包括式(A1)至(A8)所示的结构单元中的一种或多种；
Figure PCTCN2022134854-appb-000002
Figure PCTCN2022134854-appb-000003
根据本发明，优选情况下，所述聚苯并咪唑包括式(A5)至(A8)所示的结构单元中的一种或多种。
根据本发明，所述聚苯并咪唑以及所述支撑体可以与以上关于中空纤维分离膜所描述的那些相同。
可选地，在本发明中，在涂覆之前还可以对所述支撑体进行改性。对改性方法没有特别限定。例如所述改性可以包括对用于制备支撑体的材料进行共混，例如使用共混聚合物；对支撑体进行化学处理、物理沉积、紫外照射、热处理或者力学处理等等。
本发明的发明人发现：优选地，采用有机酸和易挥发溶剂复配，聚苯并咪唑在溶解的过程中发生质子化，抑制分子间氢键的形成，增加聚合物分子链的柔顺性，聚合物在成膜过程中容易更加紧密堆积，所得中空纤维复合膜具有高分离系数。另一方面，采用高温高压刮膜和高温常压/减压干燥的方式，促进溶剂的挥发，使得聚苯并咪唑功能 层得到很好的致密度，避免缺陷的形成，获得更好的分离性能。另外，采用内支撑增强方式，改进了气体分离膜的力学性能，可满足高温、高压、高流速气体分离系统等对膜丝力学性能的要求，扩大了气体分离膜的应用范围。此外，通过芯液诱导非溶剂致相分离获得了具有多孔结构的连接层，避免了功能层的脱落。
根据本发明，在一些实施方案中，所述酸为一元酸。优选地，所述酸是选自盐酸、氢氟酸和甲磺酸中的一种或多种。更优选地，所述酸为甲磺酸。据信，在成膜过程之中，有机酸诱导发生质子化作用，抑制聚合物分子间氢键的形成，减小聚合物刚性，使聚合物分子链能够更加紧密的堆积从而提高对氢气、氦气等小分子气体的分离性能。
根据本发明，所述芯液可以为水、乙醇、甲醇、异丙醇、丙酮和四氢呋喃中的一种或多种。
根据本发明，所述易挥发溶剂可以为乙醇和/或四氢呋喃。
根据本发明，所述添加剂可以为选自硝酸锂、氯化钙、氯化钠、氯化钾、聚乙二醇和聚氧化乙烯中的一种或多种。优选地，所述添加剂选自硝酸锂和/或氯化钾。
根据本发明，在一些实施方案中，以所述铸膜液的总重量为基准，聚苯并咪唑的用量为4-18wt％，所述酸的用量为77-90wt％，所述易挥发溶剂的用量为0-10wt％，所述添加剂的用量为0-5wt％；优选地，以所述铸膜液的总重量为基准，聚苯并咪唑的用量为8-15wt％，所述酸的用量为80-90wt％，所述易挥发溶剂的用量为1-5wt％，所述添加剂的用量为1-2wt％。在本发明中，需要说明的是：聚苯并咪唑、酸、易挥发溶剂和可选的添加剂各组分之和为100wt％。
在一些实施方案中，可以将聚苯并咪唑加入酸中并加入易挥发溶剂(如果使用)、添加剂(如果使用)进行混合得到铸膜液。可选地，混合过程中可以进行搅拌和加热。在一些实施方案中，所述混合的条件可以包括：温度为25-160℃，时间为2-72h；优选地，温度为80-160℃，时间为12-48h。对所述搅拌没有特别限定，并且可以由本领域技术人员常规地选择。优选地，所述搅拌的搅拌速率可以为20-500rpm。
在制备铸膜液之后，将铸膜液涂覆到支撑体表面上。在一些实施方案中，可以将铸膜液刮涂到支撑体的表面上。根据本发明，可以以一定温度和压力将铸膜液刮涂到支撑体的表面，获得具有一定厚度的 初生膜。所述刮涂的条件可以包括：温度为60-250℃，优选地，温度为80-180℃。在本发明中，对刮涂压力没有特定限定。优选地，所述压力可以为10-2000KPa，更优选地，压力可以为500-1200KPa。
在本发明中，在刮涂过程中，可以通过控制刮刀和支撑体外壁之间的间距来控制初生膜的厚度，并进而可以控制功能层的厚度。在一些实施方案中，刮膜(初生膜)厚度(刮刀与支撑体外壁的间距)可以是10-300μm。当然，本领域技术人员可以根据所需要的初生膜厚度来调节刮刀与支撑体外壁之间的间距。
在一些实施方案中，将铸膜液挤出进入喷丝头，其中，所述铸膜液在所述喷丝头内部与所述支撑体进行接触。接触的时间没有特别限定。例如接触的时间可以为1-15s，优选地，接触的时间为1-10s。在本发明中，对压力没有特定限定。例如，压力可以为10-2000KPa。例如压力可以为0到0.2MPa(表压)。例如压力可以为0.02-0.1MPa(表压)。
根据本发明，在将铸膜液涂覆到支撑体上(例如刮膜)之后，可以将附着有初生膜的支撑体进行牵引并送入加热装置。通过加热使初生膜的外层中的溶剂挥发，形成附着于支撑体的聚合物功能层，例如聚苯并咪唑功能层。所述加热例如可以通过热空气进行加热。加热可以在常压或减压下进行。例如加热可以在-0.1～0MPa(表压)下进行。在一些实施方案中，采用加热促进溶剂挥发的条件可以包括：温度为80-300℃。在一些实施方案中，可以采用热空气进行加热。本领域技术人员可以根据使用的溶剂、希望的挥发速度等等合适地选择加热条件。在本发明中，对用于加热的装置没有具体限定；例如可以为烘箱。在一些实施方案中，加热温度可以为100-280℃，时间为2-24h；优选地，加热温度为120-150℃，时间为5-12h。
在通过加热形成位于最外面的聚合物功能层之后，可以在所述支撑体内注入芯液；所述芯液使渗透到所述支撑体中的所述铸膜液发生非溶剂诱导相分离生成连接层。所述芯液例如是上文中描述的芯液。
在本发明的方法中，任选地，在生成连接层之后可以对中空纤维分离膜进行加热以(基本上)除去所有溶剂。所述加热可以在常压或减压下进行。本领域技术人员可以根据所使用的溶剂选择合适的温度来进行加热。例如，可以使用热空气进行加热。例如，加热温度可以 为80-300℃。
在本发明中，任选地，所述方法还可以包括对制备得到的成品膜通过洗涤例如水洗涤、乙醇洗涤等步骤清除残余的溶剂。
图1是本发明制备初生膜和连接层所用的一种喷丝头的结构示意图。图2是本发明使用图1的喷丝头制备初生膜和连接层的过程的示意图。
参考图1和图2，所述喷丝头包括支撑体定位器、环状刮刀和中芯管。所述支撑体定位器围绕着所述支撑体，并且位于用于容纳铸膜液的铸膜液腔的一端。在所述铸膜液腔上设有铸膜液入口和铸膜液出口。优选地，所述铸膜液出口高于所述铸膜液入口。所述支撑体定位器设置在所述铸膜液腔的一端并形成密闭端，所述铸膜液腔的另一端设置有所述环状刮刀。所述环状刮刀的直径大于所述支撑体定位器的宽度，二者的差形成的缝隙可用于形成初生膜。图1中还示出了支撑体夹持器，其用于夹持支撑体并将支撑体牵引通过铸膜液腔。图1中还示出了中芯管。所述中芯管可以插入所述支撑体的内部，并注入芯液从而在所述支撑体内部形成芯液流道。通过所述中芯管注入芯液后，芯液诱导非溶剂致相分离获得了具有多孔结构的连接层，避免了功能层的脱落。
参考图2，描述采用图1所述的喷丝头制备初生膜和连接层的过程。首先，选择支撑体，并采用支撑体定位器将支撑体固定。将从双螺杆挤出机或者齿轮泵挤出的铸膜液通过铸膜液入口注入铸膜液腔。将所述支撑体由下向上牵引通过所述铸膜液腔并用环状刮刀刮涂；有部分铸膜液渗透到支撑体中。离开环状刮刀后得到附着在所述支撑体上的初生膜。多余的铸膜液通过铸膜液出口流出。在离开环状刮刀之后，对附着有初生膜的支撑体进行牵引，并进入加热装置，使初生膜的外层通过加热(例如热空气加热)而促进溶剂的挥发，形成附着于支撑体表面的聚合物功能层，例如聚苯并咪唑功能层。然后将所述中芯管置于所述支撑体的内部，通过所述中芯管注入芯液至支撑体的内部，通过芯液诱导非溶剂致相分离从渗透到支撑体中的铸膜液获得了具有多孔结构的连接层。所述连接层嵌入在所述支撑体中并且与所述功能层是一体的，这避免了功能层的脱落。
本发明还提供了由以上所述的方法制备得到的中空纤维分离膜。 在一些实施方案中，通过本发明的制备中空纤维分离膜的方法制备了本发明的中空纤维分离膜。
本发明的中空纤维分离膜可用于气体分离。因此，本发明还提供了本发明的中空纤维分离膜用于分离氦气/氮气、氦气/甲烷、氢气/氮气和/或氢气/甲烷的用途。可以使用本领域中通常已知的操作来使用本发明的中空纤维分离膜来分离气体。
本发明还提供了一种从富含氦气的气体中提纯氦气的方法，所述方法包括使用本发明的中空纤维分离膜对气体进行膜分离。
在一些实施方案中，所述从富含氦气的气体中提纯氦气的方法可以包括：将富含氦气的气体通过深冷工艺进行冷凝处理、催化脱氢处理、膜分离处理和变压吸附除杂处理，得到提纯氦气。其中，所述膜分离处理包括使用本发明的中空纤维分离膜。
在一些实施方案中，所述从富含氦气的气体中提纯氦气的方法可以包括：将富含氦气的气体经深冷工艺进行冷凝处理、经催化脱氢处理、经氦气分离膜进行膜分离处理和经变压吸附除杂处理，得到提纯氦气；其中，所述冷凝处理的条件包括：温度≥-220℃。其中，所述膜分离处理包括使用本发明的中空纤维分离膜。
本发明的提纯氦气的方法具有如下优点：
(1)制备出的氦气可以具有高纯度，例如达到4N级(99.99％)甚至更高；并且可以大幅度提升提氦效率；
(2)深冷工艺温度高，降低能耗。
在一些实施方案中，所述冷凝处理的条件可以包括温度为≥-220℃。在一些实施方案中，所述冷凝处理的条件可以包括：温度为-210℃至-150℃，压力0.2-10MPa；优选地，所述冷凝处理的条件包括：温度为-180℃至-150℃，压力3-10MPa。
根据本发明，对于所述包含氦气的气体没有具体限定并且对于所述包含氦气的气体的组成也没有具体限定，本发明的方法具有普适性。在一些实施方案中，所述包含氦气的气体可以包括天然气、油田伴生气等。在一些实施方案中，所述包含氦气的气体可以包含氦气、氮气、甲烷、氢气和二氧化碳。在一些实施方案中，以所述富含氦气的气体的总体积为基准，氦气的含量可以为5-40体积％；优选地，氦气的含量可以为15-30体积％。
根据本发明，所述富含氦气的气体还含有可选的氧气和水，且以所述富含氦气的气体的总体积为基准，氧气的含量为0-8体积％，水的含量为0-2体积％。
根据本发明，所述富含氦气的气体经冷凝处理达到氮气、甲烷、氧气、轻烃等杂质液化的效果，除去部分氮气、甲烷、氧气和CO 2，得到第二混合气。
根据本发明，所述第二混合气经催化脱氢处理后除去部分氢气，得到第三混合气。
根据本发明，所述催化脱氢处理的条件可以包括：温度为60-120℃，优选为60-110℃，更优选为62-106℃。所述催化脱氢处理在氧气和催化剂存在下进行，其中，所述催化剂为贵金属催化剂，优选地，所述催化剂选自Pt、Pb、Rh、Ru或Au；更优选地，所述催化剂选自Pt、Pb或Au。
根据本发明，所述第三混合气经本发明的膜分离处理除去部分氮气、甲烷、氧气和CO 2，得到第四混合气。
根据本发明，膜分离是在膜两侧压差的推动下，利用原料气中各组分在溶解、扩散、解吸过程中渗透性能的差异，实现氦气分离。所述膜分离处理的条件可以包括：膜分离正压侧压力＞膜分离透过侧压力；其中，所述膜分离正压侧压力可以为0.2-10MPa；优选地，所述膜分离正压侧压力为0.5-10MPa；更优选地，所述膜分离正压侧压力为3-10MPa。膜分离法具有操作简单、能耗低、装置建设和运行成本低的优点。
根据本发明，膜分离可以采用一级或多级膜分离对氦气进行提纯。在膜分离中，多级膜分离是指，透过侧气体经过加压后再次作为进气采用膜进行分离，该过程可以是1-5级。
根据本发明，所述第四混合气经吸附除杂处理除去部分氮气、甲烷、氧气、氢气和CO 2，得到提纯氦气；其中，以提纯氦气的总体积为基准，氦气的含量可以为99.986-99.996体积％。
根据本发明，所述变压吸附除杂处理的可以条件包括：吸附压力为0.2-15MPa，优选为10-15MPa。在本发明中，所述吸附除杂处理中采用的吸附剂可以选自活性炭、分子筛、金属有机框架材料MOF、活性氧化铝中的一种或多种。
在本申请中，压力都是表压，除非另有说明。
以下将通过实施例对本发明进行详细描述。
以下实施例和对比例中：
聚苯并咪唑购自上海盛钧塑胶科技有限公司；其它试剂均购自北京伊诺凯科技有限公司。其中，乙醇99.9％；盐酸12mol/L；甲磺酸99.0％；四氢呋喃99.9％。
渗透速率(单位GPU)的测试方法：在特定温度下，测量特定压力差下，单位时间内透过单位膜面积的气体流量。其中，1GPU＝10 -6cm 3(STP)/(cm 2·s·cmHg)。
分离系数α，无量纲，用于表征气体组分在膜中的选择透过能力。分离系数为两种气体在膜中的渗透速率之比。
断裂强度采用Instron 3342根据标准ASTMD882进行测试。
实施例1
本实施例提供采用本发明的方法制备得到的中空纤维分离膜。
(1)将聚苯并咪唑A5、乙醇、盐酸加入甲磺酸中，在70℃、0MPa(表压)搅拌24h混合均匀，制备得到混合料液(铸膜液)；其中质量分数为：聚苯并咪唑10wt％，乙醇3wt％，盐酸3wt％，甲磺酸84wt％；
聚苯并咪唑A5的结构单元如下所示：
Figure PCTCN2022134854-appb-000004
其中，所述聚苯并咪唑A5的数均分子量为5.6万；
(2)将混合料液加热至240℃并经双螺杆挤出机挤出进入喷丝头，使用如图1所示的喷丝头；支撑体是聚酯纤维编织管；采用同心圆复合纺丝技术，使铸膜液在喷丝头内与编织管进行接触(喷丝头空腔高度10cm)，接触时间为10s，压力0.1MPa；所述支撑体由下向上被牵引通过所述喷丝头内部，随后经过环状刮刀并控制聚苯并咪唑初生膜的厚度为200μm，得到附着在所述支撑体上的聚苯并咪唑初生膜；多余的铸膜液通过铸膜液出口流出，并且有部分铸膜液渗透到支撑体中；
(3)将所述聚苯并咪唑初生膜在100℃的空气浴中牵引100cm长后截断、并继续置于100℃的空气浴中50分钟，形成具有致密结构的聚苯并咪唑功能层；
(4)通过中芯管在支撑体内管中通入乙醇，诱导发生相分离，促使所述支撑体内渗入的所述部分铸膜液发生非溶剂诱导相分离生成多孔结构的连接层；随后在110℃烘箱之中使初生膜内的溶剂完全挥发，制备得到成品膜-中空纤维分离膜。
制备的中空纤维分离膜功能层的厚度为约27-29μm；请见图4，图4是本发明实施例1制备的中空纤维分离膜的功能层横截面电镜图。连接层嵌入到支撑体内，厚度为约380μm(在实施例1中，连接层还从支撑体的内表面向内延伸，因此，支撑体稍厚)，嵌入层厚度超过了支撑体壁厚。
本实施例1制备的中空纤维分离膜的断裂强度为160MPa；在100℃、0.5MPa测试压力下，纯氦气通量为3.48GPU，纯氢气通量为3.03GPU，氮气、甲烷的通量分别为0.016GPU和0.0135GPU；氢气/氮气、氢气/甲烷的分离系数分别为189和224。
图3是本发明实施例1制备的中空纤维分离膜横截面全貌电镜图；从图3能够看出：功能层在膜的外表面，连接层嵌入到支撑体中，并与PBI膜结合紧密。
图5是本发明实施例1制备的中空纤维分离膜内表面横截面电镜图；从图5能够看出：支撑体嵌入到连接层内部，而连接层内表面为微孔结构。
图6是本发明实施例1制备的中空纤维分离膜外表面电镜图；从图6能够看出：外表面为致密结构。
图7是本发明实施例1制备的新型中空纤维分离膜内表面电镜图；从图7能够看出：内表面为微孔结构的连接层。
实施例2
本实施例提供采用本发明的方法制备得到的中空纤维分离膜。
(1)将聚苯并咪唑A6、乙醇、四氢呋喃与甲磺酸混合，在80℃、0.5MPa压力下搅拌24h混合均匀，制备得到混合料液(铸膜液)；其中质量分数为：聚苯并咪唑10wt％，乙醇2wt％，四氢呋喃2wt％，甲 磺酸86wt％；
所述聚苯并咪唑A6的结构单元如下所示：
Figure PCTCN2022134854-appb-000005
其中，所述聚苯并咪唑A6的数均分子量为7.2万；
(2)将混合料液加热至180℃并经齿轮泵挤出进入喷丝头，使用如图1所示的喷丝头；支撑体为热致相分离制得的聚丙烯微孔膜；采用同心圆复合纺丝技术，使铸膜液在喷丝头内与聚丙烯微孔膜进行接触(喷丝头空腔高度10cm)，接触时间为10s，接触压力0.4MPa；所述支撑体由下向上被牵引通过所述喷丝头内部，随后经过环状刮刀并控制聚苯并咪唑初生膜的厚度为100μm，得到附着在所述支撑体上的聚苯并咪唑初生膜；多余的铸膜液通过铸膜液出口流出，并且有部分铸膜液渗透到支撑体中；
(3)将所述聚苯并咪唑初生膜在100℃的空气浴中牵引200cm后截断、并继续置于100℃的空气浴40分钟后，形成具有致密结构的聚苯并咪唑功能层；
(4)通过中芯管在支撑体内管中通入乙醇，诱导发生相分离，促使所述支撑体内渗入的所述部分铸膜液发生非溶剂乙醇诱导相分离生成多孔结构的连接层；随后在100℃烘箱之中使初生膜内的溶剂完全挥发；结果制备得到成品膜-中空纤维分离膜。
制备的中空纤维分离膜的平均厚度为约200μm；功能层的厚度为约2-5μm；连接层嵌入到支撑体内，厚度为约200μm。
制备的中空纤维分离膜的断裂强度为155MPa；在100℃、0.5MPa测试压力下，纯氦气通量为7.5GPU，纯氢气通量为6.8GPU，氮气、甲烷的通量分别为0.04GPU和0.04GPU；氦气/氮气、氦气/甲烷的分离系数分别为187.5和170。
实施例3
本实施例提供采用本发明的方法制备得到的中空纤维分离膜。
(1)将聚苯并咪唑A4与甲磺酸混合，在150℃、1.0MPa压力下搅拌24h混合均匀，制备得到混合料液(铸膜液)；其中质量分数组 成为：聚苯并咪唑18wt％，甲磺酸82wt％；
所述聚苯并咪唑A4的结构单元如下所示：
Figure PCTCN2022134854-appb-000006
其中，所述聚苯并咪唑A4的数均分子量为6.8万；
(2)将混合料液加热至100℃并经齿轮泵挤出进入喷丝头，使用如图1所示的喷丝头；支撑体是聚丙烯微孔膜(热致相分离制得)；采用同心圆复合纺丝技术，使铸膜液在喷丝头内与支撑体进行接触(喷丝头空腔高度10cm)，铸膜液与编织管接触时间2s，接触压力0.5MPa；所述支撑体由下向上被牵引通过所述喷丝头内部，经过环状刮刀并控制聚苯并咪唑初生膜的厚度为100μm，得到附着在所述支撑体上的聚苯并咪唑初生膜；多余的铸膜液通过铸膜液出口流出，并且有部分铸膜液渗透到支撑体中；
(3)将所述聚苯并咪唑初生膜在150℃的空气浴中牵引200cm后截断，并继续置于150℃的空气浴中继续保持50min，形成具有致密结构的聚苯并咪唑功能层；
(4)通过中芯管在支撑体内管中通入水，诱导仍未分相的初生膜发生非溶剂诱导相分离，促使所述支撑体内渗入的所述部分铸膜液发生非溶剂诱导相分离生成多孔结构的连接层；随后在120℃烘箱之中使初生膜内的溶剂完全挥发；制备得到成品膜-中空纤维分离膜。
制备的中空纤维分离膜功能层的厚度为约45～50μm；连接层嵌入到支撑体内，厚度为约450μm。
制备的中空纤维分离膜的断裂强度为206MPa；在100℃、0.5MPa测试压力下，纯氦气通量为0.87GPU，纯氢气通量为0.81GPU，氮气、甲烷的通量分别为0.005GPU和0.004GPU；氢气/氮气、氢气/甲烷的分离系数分别达到162和202.5。
实施例4
本实施例提供采用本发明的方法制备得到的中空纤维分离膜。
(1)将聚苯并咪唑A8、乙醇与甲磺酸混合，在60℃、常压下搅 拌24h混合均匀；其中质量分数组成为：聚苯并咪唑4wt％，乙醇10wt％，甲磺酸86wt％，制备得到混合料液(铸膜液)；所述聚苯并咪唑A8的结构单元如下所示：
Figure PCTCN2022134854-appb-000007
其中，所述聚苯并咪唑A8的数均分子量为9.7万；
(2)将混合料液加热至80℃并经齿轮泵挤出进入喷丝头，使用如图1所示的喷丝头；支撑体是聚丙烯纤维编织管，其由聚丙烯纤维经过编织得到；采用同心圆复合纺丝技术，使铸膜液在喷丝头内与支撑体进行接触(喷丝头空腔高度10cm)铸膜液与编织管接触时间10s，接触压力0.05MPa；所述支撑体由下向上被牵引通过所述喷丝头内部，经过环状刮刀并控制聚苯并咪唑初生膜的厚度为100μm，得到附着在所述支撑体上的聚苯并咪唑初生膜；多余的铸膜液通过铸膜液出口流出，并且有部分铸膜液渗透到支撑体中；
(3)当所述聚苯并咪唑初生膜长度达到200cm后截断，移入到150℃的空气浴中干燥10min，形成具有致密结构的聚苯并咪唑功能层；
(4)随后通过中芯管在支撑体内管中通入乙醇，诱导发生相分离，促使所述支撑体内渗入的所述部分铸膜液发生非溶剂诱导相分离生成多孔结构的连接层；然后继续在110℃烘箱之中使初生膜内的溶剂完全挥发；制备得到成品膜-中空纤维分离膜。
制备的中空纤维分离膜功能层的厚度为400～600nm，有比较明显的过渡层；连接层嵌入到支撑体内，厚度为200-400μm，有些贯穿支撑体。
制备的中空纤维分离膜的断裂强度为161MPa；在100℃、0.5MPa测试压力下，纯氦气通量为107GPU，纯氢气通量为95GPU，氮气、甲烷的通量分别为0.45GPU和0.41GPU；氢气/氮气、氢气/甲烷的分离系数分别达到211和231.7。
图8示出了实施例4制备的中空纤维分离膜的电镜图；由左至右由上到下分别是整体断面、功能层和连接层、放大的功能层和连接层、外表面、内表面(连接层是多孔的)和支撑体断面的图。
实施例5
本实施例提供采用本发明的方法制备得到的中空纤维分离膜。
(1)将聚苯并咪唑A7、乙醇与甲磺酸混合，在60℃、常压下搅拌72h混合均匀，制备得到混合料液(铸膜液)；其中质量分数组成为：聚苯并咪唑4wt％，乙醇1wt％，甲磺酸95wt％；
所述聚苯并咪唑A7的结构单元如下所示：
Figure PCTCN2022134854-appb-000008
其中，所述聚苯并咪唑A7的数均分子量为28.7万；
(2)将混合料液加热至80℃并经齿轮泵挤出进入喷丝头，使用如图1所示的喷丝头；支撑体是聚丙烯中空纤维微孔膜(平均孔径为0.01μm，孔隙率为65％，外表面接触角75℃；其制备方法如下：将质量分数为25％聚丙烯树脂、0.5％马来酸酐接枝聚丙烯、0.5％聚乙烯基吡咯烷酮以及74％豆油在185℃搅拌加热，得到均相的铸膜液；经真空脱泡、过滤，输送至由豆油作为内芯液的中空喷丝头，进入豆油中降温固化；经丙酮萃取、空气自然干燥后得到聚丙烯中空纤维微孔膜)；采用同心圆复合纺丝技术，使铸膜液在喷丝头内与聚丙烯微孔膜(热致相分离制得)进行接触(喷丝头空腔高度10cm)，铸膜液与支撑体接触时间10s，接触压力0.1MPa；所述支撑体由下向上被牵引通过所述喷丝头内部，经过环状刮刀并控制聚苯并咪唑初生膜的厚度为100μm，得到附着在所述支撑体上的聚苯并咪唑初生膜；多余的铸膜液通过铸膜液出口流出，并且有部分铸膜液渗透到支撑体中；
(3)当所述聚苯并咪唑初生膜在150℃的空气浴内牵引100cm后截断，并继续在150℃的空气浴内，干燥100分钟，形成具有致密结构的聚苯并咪唑功能层；
(4)通过中芯管在支撑体内管中通入乙醇，诱导发生相分离，促使所述支撑体内渗入的所述部分铸膜液发生非溶剂诱导相分离生成多孔结构的连接层；随后在110℃烘箱之中使初生膜内的溶剂完全挥发；制备得到成品膜-中空纤维分离膜。
制备的中空纤维分离膜的平均厚度为约350μm；功能层的平均厚度为约1.2～2.0μm；连接层嵌入到支撑体内，厚度为约30μm。
制备的中空纤维分离膜的断裂强度为63MPa；在100℃、0.5MPa测试压力下，纯氦气通量为88.9GPU，纯氢气通量为76.1GPU，氮气、甲烷的通量分别为0.66GPU和0.52GPU；氢气/氮气、氢气/甲烷的分离系数分别达到134.7和170.9。
图9示出了实施例5制备的中空纤维分离膜的电镜图；由左至右由上到下分别是整体断面、功能层和连接层、放大的功能层和连接层、外表面、内表面和支撑体断面的图。
实施例6
本实施例提供采用本发明的方法制备得到的中空纤维分离膜。
(1)将聚苯并咪唑A1、四氢呋喃与甲磺酸混合，在60℃、常压下搅拌72h混合均匀，制备得到混合料液(铸膜液)；其中质量分数为：聚苯并咪唑8wt％，四氢呋喃2wt％，甲磺酸90wt％；
所述聚苯并咪唑A1的结构单元如下所示：
Figure PCTCN2022134854-appb-000009
其中，所述聚苯并咪唑A1的数均分子量为8.7万；
(2)将混合料液加热至80℃并经齿轮泵挤出进入喷丝头，使用如图1所示的喷丝头；支撑体是聚乙烯微孔膜(熔纺拉伸法制得；孔径1-10微米，孔隙率65％-80％)；采用同心圆复合纺丝技术，使铸膜液在喷丝头内与聚乙烯微孔膜进行接触(喷丝头空腔高度10cm)，接触时间为10s，接触压力0.2MPa；所述支撑体由下向上被牵引通过所述喷丝头内部，经过环状刮刀并控制聚苯并咪唑初生膜的厚度为80μm，得到附着在所述支撑体上的聚苯并咪唑初生膜；多余的铸膜液通过铸膜液出口流出，并且有部分铸膜液渗透到支撑体中；
(3)当所述聚苯并咪唑初生膜在150℃的空气浴中牵引100cm后截断，并置于150℃的空气浴内，干燥100分钟，待形成具有致密结构的聚苯并咪唑功能层；
(4)通过中芯管在支撑体内管中通入四氢呋喃，诱导发生相分离，促使所述支撑体内渗入的所述部分铸膜液发生非溶剂四氢呋喃诱导相 分离生成多孔结构的连接层；随后在110℃烘箱之中使初生膜内的溶剂完全挥发；制备得到成品膜-中空纤维分离膜。
制备的中空纤维分离膜功能层的厚度为约2000nm；连接层嵌入到支撑体内，厚度为约180-190μm(平均厚度为约185μm)。
制备的中空纤维分离膜的断裂强度为52MPa；在100℃、0.5MPa测试压力下，纯氦气通量为82.2GPU，纯氢气通量为79.6GPU，氮气、甲烷的通量分别为0.68GPU和0.55GPU；氢气/氮气、氢气/甲烷的分离系数分别达到120.61和144.7。
实施例7
本实施例提供采用本发明的方法制备得到的中空纤维分离膜。
(1)将聚苯并咪唑A7、四氢呋喃与甲磺酸混合，在60℃、常压下搅拌24h混合均匀，制备得到混合料液(铸膜液)；其中质量分数组成为：聚苯并咪唑8wt％，四氢呋喃2wt％，甲磺酸90wt％；
所述聚苯并咪唑A7的结构单元如下所示：
Figure PCTCN2022134854-appb-000010
其中，所述聚苯并咪唑A7的数均分子量为12.6万；
(2)将混合料液加热至80℃并经齿轮泵挤出进入喷丝头，使用如图1所示的喷丝头；支撑体为孔隙率为60％-80％的聚乙烯疏水微孔膜(熔纺拉伸法制得)；采用同心圆复合纺丝技术，使铸膜液在喷丝头内与聚乙烯疏水微孔膜进行接触(喷丝头空腔高度10cm)，接触时间为10s，接触压力控制在0.1MPa；所述支撑体由下向上被牵引通过所述喷丝头内部，经过环状刮刀并控制聚苯并咪唑初生膜的厚度为80μm，得到附着在所述支撑体上的初生态聚苯并咪唑膜；多余的铸膜液通过铸膜液出口流出，并且有部分铸膜液渗透到支撑体中；
(3)当所述聚苯并咪唑初生膜在150℃的空气浴中牵引100cm后截断，并置于150℃的空气浴内干燥100分钟，待形成具有致密结构的聚苯并咪唑功能层；
(4)通过中芯管在支撑体内管中通入四氢呋喃，诱导发生相分离，促使所述支撑体内渗入的所述部分铸膜液发生非溶剂四氢呋喃诱导相 分离生成多孔结构的连接层；随后在110℃烘箱之中使初生膜内的溶剂完全挥发；制备得到成品膜-中空纤维分离膜。
制备的中空纤维分离膜功能层的厚度为约10～12μm；连接层嵌入到支撑体内，厚度为约300μm。
制备的中空纤维分离膜的断裂强度为52MPa；在100℃、0.5MPa测试压力下，纯氦气通量为22.6GPU，纯氢气通量为22.1GPU，氮气、甲烷的通量分别为0.16GPU和0.13GPU；氦气/氮气、氦气/甲烷的分离系数分别达到141.4和173.8。
对比例1
(1)将聚苯并咪唑A1与甲磺酸混合，在150℃、1.0MPa压力下搅拌24h混合均匀，制备得到混合料液(铸膜液)；其中质量分数组成为：聚苯并咪唑10wt％，甲磺酸90wt％；
所述聚苯并咪唑A1包括如下的结构单元：
Figure PCTCN2022134854-appb-000011
其中，所述聚苯并咪唑A1的数均分子量为6.8万；
(2)将混合料液加热至140℃并经齿轮泵挤出进入喷丝头，使用如图1所示的喷丝头；采用同心圆复合纺丝技术，使铸膜液在喷丝头内与聚酯纤维编织管进行接触(喷丝头空腔高度10cm)，在140℃下纺丝，铸膜液与编织管接触时间2s，接触压力0.05MPa；所述支撑体由下向上被牵引通过所述喷丝头内部，经过环状刮刀并控制聚苯并咪唑初生膜的厚度为100μm，得到附着在所述支撑体上的聚苯并咪唑初生膜；多余的铸膜液通过铸膜液出口流出，并且有部分铸膜液渗透到支撑体中；当所述聚苯并咪唑初生膜达到200cm长度后，移入烘箱；
(3)直接在200℃烘箱之中使聚苯并咪唑初生膜内的溶剂完全挥发，再通过水洗、乙醇清洗步骤清除残余的溶剂，形成成品膜-中空纤维分离膜。
制备的中空纤维分离膜功能层很厚；不存在多孔连接层，功能层在支撑体外表面与支撑体直接附着。该膜由于没有连接层，功能层与 支撑体结合性差，功能层容易脱落，寿命下降。内压超过0.04MPa时，功能层损坏；当采用外压操作时，经过多次压力变化，寿命仅有2000-5000小时。
制备的中空纤维分离膜的断裂强度为166MPa；在100℃、0.5MPa测试压力下，纯氦气通量为12.8GPU，纯氢气通量为11.6GPU，氮气、甲烷的通量分别为0.11GPU和0.10GPU，氢气/氮气、氢气/甲烷的分离系数分别达到105和116。
图10示出了对比例1制备的中空纤维分离膜的电镜图；由左至右由上到下分别是整体断面、功能层、放大的功能层、外表面、内表面和支撑体断面的图。
对比例2
(1)将聚苯并咪唑A7与甲磺酸混合，在150℃，1.0MPa压力下搅拌24h混合均匀，制备得到混合料液(铸膜液)；其中质量分数组成为：聚苯并咪唑10wt％，甲磺酸90wt％；
所述聚苯并咪唑A7的结构单元如下：
Figure PCTCN2022134854-appb-000012
其中，所述聚苯并咪唑A7的数均分子量为12.6万；
(2)将混合料液经齿轮泵挤出，使用如图1所示的喷丝头，采用同心圆复合纺丝技术，使铸膜液在喷丝头内与尼龙编织管进行接触(喷丝头空腔高度10cm)，在140℃下纺丝，铸膜液与编织管接触时间2s，接触压力0.1MPa，经过环状刮刀控制初生态聚苯并咪唑膜的厚度为30μm，经200cm长度、进入纯水凝固浴，以5cm/min卷绕速度进行卷绕；
(3)随后在纯水之中使初生膜内的溶剂向水中转移，再通过水洗、乙醇清洗步骤清除残余的溶剂，形成成品膜-中空纤维分离膜。
制备的中空纤维分离膜的平均厚度为约600μm；功能层的厚度为约500nm；支撑体的外径为1400μm；该膜功能层与支撑体结合性差，功能层容易脱落，寿命下降。内压超过0.05MPa时，功能层损坏。
另外，制备的中空纤维分离膜的断裂强度为166MPa，在100℃、 0.5MPa测试压力下，纯氦气通量为28.5GPU，纯氢气通量为27.6GPU，氮气、甲烷的通量分别为0.33GPU和0.27GPU，氢气/氮气、氢气/甲烷的分离系数分别达到83.7和102.2。
对比例3
(1)将聚苯并咪唑A7与N-甲基吡咯烷酮(NMP)混合，在50℃、常压下搅拌24h混合均匀，制备得到混合料液(铸膜液)；其中质量分数组成为：聚苯并咪唑10wt％，NMP 90wt％；
所述聚苯并咪唑A7的结构单元如下：
Figure PCTCN2022134854-appb-000013
其中，所述聚苯并咪唑A7的数均分子量为12.6万；
(2)将混合料液经齿轮泵挤出，使用如图1所示的喷丝头，采用同心圆复合纺丝技术，使铸膜液在喷丝头内与尼龙编织管进行接触(喷丝头空腔高度10cm)，在60℃下纺丝，铸膜液与编织管接触时间2s，接触压力0.05MPa，经过环状刮刀控制初生态聚苯并咪唑膜的厚度为30μm，经200cm长度、进入纯水凝固浴，以5cm/min卷绕速度进行卷绕；
(3)随后在纯水之中使初生膜内的溶剂向水中转移，形成成品膜；再通过水洗、乙醇清洗步骤清除残余的溶剂。
制备的中空纤维分离膜功能层的厚度为约200nm，膜的结构不致密，选择性较低；内压超过0.1MPa时，功能层损坏。
另外，制备的中空纤维分离膜的断裂强度为165MPa，在100℃、0.5MPa测试压力下，纯氦气通量为107GPU，纯氢气通量为89.5GPU，氮气、甲烷的通量分别为12.9GPU和11.4GPU，氢气/氮气、氢气/甲烷的分离系数分别达到6.94和7.85。
提纯氦气实施例
原料气富氦气体包括：氦气的体积分数为20体积％，甲烷的体积分数为17体积％，氮气的体积分数为60体积％，氢气的体积分数为1体积％，二氧化碳的体积分数为0.5体积％以及氧气的体积分数为1.5 体积％。
对该富氦气体进行精制，如图11所示：
(1)原料气1#首先进入深冷单元，其中温度-180℃，压力4MPa；
(2)经步骤(1)得到的塔顶气2#进入催化脱氢单元，燃烧过程中通入少量纯氧作为助燃气体，保证催化反应平稳运行，催化剂为Pt，温度98℃；
(3)燃烧后的气体经过干燥后3#进入膜单元，通入本申请实施例4的中空纤维膜制备的膜组件进行一级、二级膜分离操作，膜分离正压侧操作压力分别为3MPa、3MPa；
(4)渗余侧贫氦气体回流至深冷单元，渗透侧粗氦产品4#进入吸附除杂单元，进行变压吸附操作，其中使用5A分子筛、椰壳活性炭、活性氧化铝复配的吸附剂，吸附压力10MPa，得到精制氦气5#。
其中，氦气提纯方法的各阶段气体组成如表1所示。
表1
编号\组成％ 氦气 氮气 甲烷 氧气 氢气 CO 2 水
原料气1# 20 60 17 1.5 1 0.5 0
深冷分离2# 73.35 22.96 0.01 0.02 3.66 0 0
催化脱氢3# 75.32 23.57 0.01 1.07 0.02 0 0.01
一级膜 95.865 3.931 0.001 0.179 0.023 0 0.001
二级膜4# 99.75 0.217 0 0.01 0.023 0 0
产品5# 99.995 0.005 0 0 0 0 0
根据上表可以清晰的看到，本发明通过深冷工艺能够显著提高氦气浓度，并通过催化氧化工段有效的将混合气中难以与氦气进行分离的氢气进行脱除，再通过膜分离进行深度提纯，得到的粗氦气体浓度为99.75％，再通过变压吸附，得到的产品氦气浓度可以达到99.995％，达到4N级标准。
以上详细描述了本发明的优选实施方式，但是，本发明并不限于此。在本发明的技术构思范围内，可以对本发明的技术方案进行多种简单变型，包括各个技术特征以任何其它的合适方式进行组合，这些简单变型和组合同样应当视为本发明所公开的内容，均属于本发明的保护范围。

Claims (20)

  1. 一种中空纤维分离膜，其特征在于，所述中空纤维分离膜包括支撑体、功能层以及位于所述支撑体和所述功能层之间的连接层，其中所述连接层的至少一部分嵌入所述支撑体中。
  2. 根据权利要求1所述的中空纤维分离膜，其中，所述连接层和所述功能层包含相同的聚合物；优选地，所述连接层和所述功能层包含相同的聚合物并且所述连接层和所述功能层由相同的铸膜液形成；更优选地，所述连接层和所述功能层包含相同的聚合物，所述连接层和所述功能层由相同的铸膜液形成，并且所述连接层和所述功能层分别通过非溶剂致相分离和热致相分离形成。
  3. 根据权利要求1-2中任一项所述的中空纤维分离膜，其中，所述连接层和所述功能层都包含聚苯并咪唑；优选地，所述聚苯并咪唑的数均分子量为5万-30万，更优选地所述聚苯并咪唑的数均分子量为5.6万-28.7万。
  4. 根据权利要求3所述的中空纤维分离膜，其中，所述聚苯并咪唑包括式(A1)至(A8)所示的结构单元中的一种或多种；
    Figure PCTCN2022134854-appb-100001
    Figure PCTCN2022134854-appb-100002
    优选地，所述聚苯并咪唑包括式(A5)至(A8)所示的结构单元中的一种或多种。
  5. 根据权利要求1-4中任一项所述的中空纤维分离膜，其中，所述支撑体为纤维编织管或中空纤维膜，优选中空纤维微孔膜，更优选地所述支撑体是选自纤维编织管、聚丙烯中空微孔膜、聚乙烯中空微孔膜和无机中空微孔膜中的一种或多种；和/或
    所述连接层具有多孔结构；和/或
    所述连接层通过铸膜液的非溶剂诱导相分离得到，优选地所述连接层通过含有聚苯并咪唑的酸溶液的非溶剂诱导相分离得到。
  6. 根据权利要求1-5中任意一项所述的分离膜，其中所述中空纤维分离膜的平均厚度为100-2000μm；
    和/或，所述支撑体的管壁的平均厚度为50-2000μm；
    和/或，所述功能层的平均厚度为100-50000nm；
    和/或，所述连接层的平均厚度为20-2000μm；
    和/或，所述分离膜的断裂强度为10-500MPa；
    和/或，在100℃、0.5MPa测试压力下，氢气/氮气的分离系数为110-300，氢气/甲烷的分离系数为125-360；
    和/或，在100℃、0.5MPa测试压力下，氦气/氮气的分离系数为140-390，氦气/甲烷的分离系数为170-500；
    和/或，在25℃、0.5MPa测试压力下，氢气/氮气的分离系数为200-550，氢气/甲烷的分离系数为200-860；
    和/或，在25℃、0.5MPa测试压力下，氦气/氮气的分离系数为240-900，氦气/甲烷的分离系数为200-2000。
  7. 一种中空纤维分离膜的制备方法，其特征在于，所述方法包括：
    (1)制备包含聚合物的铸膜液；
    (2)将所述铸膜液涂覆在支撑体上，其中所述铸膜液的一部分渗透到支撑体中，得到涂覆在所述支撑体上的初生膜；
    (3)将所述初生膜进行加热以形成功能层；
    (4)在所述支撑体内注入芯液，使渗透到所述支撑体中的铸膜液发生非溶剂诱导相分离生成连接层；和
    (5)任选地，在生成连接层之后进行加热以基本上除去所有溶剂。
  8. 根据权利要求7所述的方法，其中，采用刮刀、优选环状刮刀将所述铸膜液涂覆在所述支撑体上；和/或
    所述支撑体被牵引通过所述铸膜液，优选地所述支撑体被由下向上牵引通过所述铸膜液；和/或
    所述支撑体为纤维编织管或中空纤维膜，优选中空纤维微孔膜，更优选地所述支撑体是选自纤维编织管、聚丙烯中空微孔膜、聚乙烯中空微孔膜和无机中空微孔膜中的一种或多种。
  9. 根据权利要求7或8所述的方法，其中，通过将所述聚合物、酸、可选的易挥发溶剂和可选的添加剂混合得到铸膜液；优选地，所述混合的条件包括：温度为25-160℃，时间为2-72h。
  10. 根据权利要求7-9任一项所述的方法，其中，所述聚合物为聚苯并咪唑；优选地，所述聚苯并咪唑的数均分子量为5万-30万，更优选地所述聚苯并咪唑的数均分子量为5.6万-28.7万。
  11. 根据权利要10所述的方法，其中，所述聚苯并咪唑包括式(A1)至(A8)所示的结构单元中的一种或多种；
    Figure PCTCN2022134854-appb-100003
    Figure PCTCN2022134854-appb-100004
    优选地，所述聚苯并咪唑包括式(A5)至(A8)所示的结构单元中的一种或多种。
  12. 根据权利要求10所述的方法，其中所述酸为一元酸；优选地，所述酸选自盐酸、氢氟酸、甲磺酸或它们的混合物；
    和/或，所述易挥发溶剂选自甲醇、乙醇、四氢呋喃或它们的混合物；
    和/或，所述添加剂选自硝酸锂、氯化钙、氯化钠、氯化钾、聚乙二醇、聚氧化乙烯或它们的混合物；
    和/或，所述芯液选自水、乙醇、甲醇、异丙醇、丙酮、四氢呋喃 或它们的混合物；
    和/或，以所述铸膜液的总重量为基准，聚苯并咪唑的用量为4-18wt％，所述酸的用量为77-90wt％，所述易挥发溶剂的用量为0-10wt％，和所述添加剂的用量为0-5wt％。
  13. 根据权利要求10所述的方法，其中所述涂覆的条件包括：温度为20-240℃；
    和/或，步骤(3)中所述加热的条件包括：温度100-280℃；
    和/或，所述铸膜液与所述支撑体接触的时间为1-15秒。
  14. 根据权利要求7-13任一项所述的方法，其中，步骤(2)中的涂覆使用喷丝头实施，所述喷丝头包括支撑体定位器、环状刮刀、和中芯管；
    所述支撑体定位器围绕着所述支撑体形成空腔；所述空腔用于储备铸膜液，并在所述空腔上设有铸膜液入口和铸膜液出口；且所述空腔的一端与所述支撑体定位器相连接形成密闭端，所述空腔的另一端设置有所述环状刮刀，所述环状刮刀的直径大于所述支撑体定位器的宽度；
    所述中芯管内置于所述支撑体的内部。
  15. 根据权利要求7所述的方法，其中所述中空纤维分离膜是权利要求1所述的中空纤维分离膜。
  16. 一种由权利要求7-14中任意一项所述的方法制备得到的中空纤维分离膜。
  17. 一种权利要求1-6和16中任意一项所述的中空纤维分离膜用于分离氦气/氮气、氦气/甲烷、氢气/氮气或者氢气/甲烷的用途。
  18. 一种从含有氦气的气体中提纯氦气的方法，其特征在于，所述方法包括使用权利要求1-6和16中任意一项所述的中空纤维分离膜进行膜分离。
  19. 根据权利要求18所述的方法，其中，所述方法包括：将含有氦气的气体通过深冷工艺进行冷凝处理、催化脱氢处理、膜分离处理和变压吸附除杂处理，得到提纯氦气。
  20. 根据权利要求19所述的方法，其中，所述冷凝处理的条件包括：温度≥-220℃；优选地，所述冷凝处理的条件包括：温度为-210℃至-150℃，压力0.2-10MPa；更优选地，所述冷凝处理的条件包括： 温度为-180℃至-150℃，压力3-10MPa；和/或
    其中，所述催化脱氢处理的条件包括：温度为60-120℃，优选为60-110℃；和/或
    其中，所述催化脱氢处理在氧气和催化剂存在下进行，其中，所述催化剂为贵金属催化剂；优选地，所述催化剂选自Pt、Pb、Rh、Ru或Au；更优选地，所述催化剂选自Pt、Pb或Au；和/或
    其中，所述膜分离处理的条件包括：膜分离正压侧压力＞膜分离透过侧压力；优选地，所述膜分离正压侧压力为0.2-10MPa，更优选地，所述膜分离正压侧压力为0.5-10MPa；和/或
    其中，所述变压吸附除杂处理的条件包括：吸附压力为0.2-15MPa，优选为10-15MPa；
    和/或，所述吸附除杂处理中采用的吸附剂选自活性炭、分子筛、金属有机框架材料MOF、活性氧化铝中的一种或多种。
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