Patent Application
20250177925
The invention relates to the technical field of membranes, in particular to a novel hollow fiber membrane and preparation method and use thereof.
Helium and hydrogen are gases with smaller molecules and are both very important industrial gases.
Helium is mainly prepared by purifying the associated gas during extraction of natural gas and shale gas. The processes for extracting helium from natural gas and shale gas are divided into cryogenic process and non-cryogenic process. The cryogenic process currently is a commonly used method in industrialization. Industrial processes with temperatures below-100° C. are generally classified as cryogenic processes, wherein the extraction of helium from natural gas and the liquefaction of helium are typical cryogenic processes with the lowest cryogenic separation temperature in cryogenic processes for natural gas. The cryogenic helium extraction process has high energy consumption and complex devices. Membrane separation helium purification and refining technology avoids various phase change processes and violent chemical reactions, and has low energy consumption, small devices and high safety.
Hydrogen is a clean energy carrier and is also a secondary energy source. The product of hydrogen production from fossil fuel contains N2, CO, CH4, CO2 and the like, and needs to be separated and purified. With the increasing global demand for clean and efficient energy source, the production and purification of hydrogen are also receiving more and more attention.
In order to meet the requirements for helium and hydrogen, the development of efficient, green, safe and reliable helium and hydrogen purification methods is urgently needed. The demand of membrane separation technology for key membrane materials, especially high-end membrane materials, is particularly urgent.
CN113318609A discloses a method for manufacturing a rigid network microporous hydrogen membrane with high permeability and selectivity. However, 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 preparation method and use thereof. The block copolymer constructs a proton transmission channel through the phase separation structure of the two segments since the block copolymer form a soft-hard, hydrophilic-hydrophobic phase separation structure due to the combination of soft segment of PDMS with hard segment of HBPBI and hydrophobic segment of PDMS with hydrophilic segment of HBPBI, and the hyperbranched structure of HBPBI can accommodate more phosphoric acid, and finally a high proton conductivity is obtained. However, this material is insufficient in strength and elongation at break, and cannot be used to prepare a high-pressure-resistant gas separation membrane.
US20160375410A1 discloses a method for making PBI asymmetric hollow fiber membrane and use thereof, wherein the PBI asymmetric hollow fiber membrane prepared by non-solvent induced phase separation technology in this application has a permeance of 108 GPU, a selectivity of H2/CO2 of 23.7, and a selectivity of H2/N2 of 129 at 250° C. However, the membrane is easy to generate defects during the phase inversion process, the selectivity will be greatly influenced, and the real separation effect of PBI cannot be achieved.
Therefore, the development of a membrane material which has a dense selective layer, is convenient to prepare and can exhibit the high separation effect of PBI has great significance.
The invention aims to provide a novel hollow fiber membrane and preparation method and use thereof, so as to overcome the problems that the surface of hollow fiber membrane prepared by non-solvent induced phase separation is easy to have defects or the material strength and elongation at break are insufficient and cannot be used to prepare a high-pressure-resistant gas separation membrane in the prior art. The hollow fiber membrane of present application has high selectivity and good mechanical properties.
In order to achieve above object(s), one aspect of the present application provides a hollow fiber membrane characterized in that the membrane comprises a support, a selective layer, and a transition layer between the support and the selective layer, wherein at least a portion of the transition layer is embedded in the support.
According to some embodiments, in the hollow fiber membrane of the present application, the transition layer and the selective layer comprise the same polymer; preferably, the transition layer and the selective layer comprise the same polymer and the transition layer and the selective layer are formed from the same casting solution; more preferably, the transition layer and the selective layer comprise the same polymer, the transition layer and the selective layer are formed from the same casting solution, and the transition layer and the selective layer are formed by non-solvent induced phase separation and thermally induced phase separation, respectively. According to some embodiments, the transition layer has a porous structure (porous). According to some embodiments, the transition layer is porous and the selective layer is a dense layer.
Another aspect of the invention provides a hollow fiber membrane, wherein the membrane comprises a support, a selective layer attached to the outer surface of the support and a transition layer embedded in the support; the support is a microporous hollow fiber membrane, the transition layer has a porous structure, the selective layer is made of polybenzimidazole, and the number-average molecular weight of the polybenzimidazole is 5×104-30×104.
One aspect of the present application provides a method for preparing a hollow fiber membrane, characterized in that the method comprising:
Optionally, the method for preparing hollow fiber membrane of the present invention further comprises heating to remove substantially all of the solvent after the generation of the transition layer.
A further aspect of the present invention provides a method for preparing a hollow fiber membrane, wherein the method comprises:
One aspect of the present invention provides hollow fiber membranes prepared by the aforementioned methods.
Another aspect of the invention provides the use of the hollow fiber membrane of the invention for the separation and purification of helium/nitrogen, helium/methane, hydrogen/nitrogen or hydrogen/methane.
A still further aspect of the invention provides a method for purifying helium from a helium-containing gas, the method comprising performing membrane separation using the hollow fiber membrane of the present application or the hollow fiber membrane prepared by the method of the present application.
The invention can provide the following beneficial effects through above technical solutions:
When polybenzimidazole is used as the polymer for preparing the casting solution, the polybenzimidazole is dissolved by an acid and optionally a volatile solvent. The resulting hollow fiber membrane adopts acid as solvent, such that the polymer is protonated during the process of dissolving the polymer, controlling the packing of molecular chains in the membrane-forming process, and inhibiting the formation of intermolecular hydrogen bonds, so as to prepare a separation membrane with both high selectivity and high permeation permeance.
The endpoints of ranges and any values disclosed herein are not limited to the precise ranges or values, but these ranges or values are to be understood to include values close to said ranges or values. For numerical ranges, the endpoint values of various ranges, the endpoint values of various ranges and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, and these new numerical ranges shall be deemed to be concretely disclosed herein.
Reference in this specification to “an embodiment” or “some embodiments” means that a feature, structure or characteristic described in connection with said embodiment(s) is included in at least one embodiment. These features, structures or characteristics can be combined in any suitable manner in one or more embodiments.
As described above, the present invention provides a hollow fiber membrane, characterized in that the membrane comprises a support, a selective layer, and a transition layer between the support and the selective layer, wherein at least a portion of the transition layer is embedded into the support.
In the present invention, the support is tubular and the tube wall of the support has pores and/or apertures. At least a portion of the transition layer is embedded in the pores and/or apertures of the tube wall of the support.
In the present invention, the transition layer and the selective layer comprise the same polymer. In some embodiments, the transition layer and the selective layer are formed by the same polymer.
In some embodiments, the polymer comprised in the transition layer and the selective layer or the polymer forming the transition layer and the selective layer is polybenzimidazole.
Preferably, in some embodiments, the transition layer and the selective layer comprise the same polymer and the transition layer and the selective layer are formed from the same casting solution. More preferably, in some embodiments, the transition layer and the selective layer comprise the same polymer, the transition layer and the selective layer are formed from the same casting solution, and the transition layer and the selective layer are formed by non-solvent induced phase separation and thermally induced phase separation, respectively.
Non-solvent induced phase separation and thermally induced phase separation are well-known in the art.
In the present invention, the selective layer is a dense layer with selectivity, and the transition layer is a layer for cohering the selective layer and the support.
In some embodiments, the present invention provides a hollow fiber membrane, wherein the membrane comprises a support, a selective layer attached to the outer surface of the support and a transition layer embedded in the support; the support is a microporous hollow fiber membrane, the transition layer has a porous structure, the selective layer is made of polybenzimidazole, and the number-average molecular weight of the polybenzimidazole is 5×104-30×104.
Polybenzimidazole (PBI) is a heterocyclic polymer with imidazole rings in main chain, and this type of polymer has good chemical stability, thermal stability, hydrolysis resistance stability and mechanical stability. As a polymer material, PBI has good processability, and PBI membrane is easy to package and the preparation cost is reasonable. PBI is particularly suitable for preparing separation membranes required for hydrogen or helium purification.
In present invention, the volatilization of solvent is promoted by adopting a high-temperature normal-pressure or reduced-pressure drying, such that the polymer selective layer such as the polybenzimidazole selective layer has a good compactness, avoiding the formation of defects, and obtaining a better separation performance. In addition, the internal support reinforcement is adopted in present invention, which improves the mechanical properties of the gas separation membrane, and the demand of a high-temperature, high-pressure and high-flow-rate gas separation system and the like on the mechanical properties of membrane can be met, expanding the applications of gas separation membranes. In present invention, the transition layer with a porous structure is obtained by non-solvent induced phase separation induced by a bore fluid, so that the selective layer is prevented from falling off.
In the case where the selective layer comprises polybenzimidazole, the present invention uses an organic acid and optionally a volatile solvent to prepare the casting solution, and the surface selective layer of the resulting hollow fiber composite membrane comprises or consists of protonated polybenzimidazole, thereby achieving a higher selectivity.
In the present invention, the transition layer is obtained by non-solvent induced phase separation of the casting solution. In a preferred embodiment, the transition layer is obtained by non-solvent induced phase separation of a polybenzimidazole-containing acid solution.
In the present invention, the selective layer and the transition layer can be formed from the same casting solution. In some embodiments, the selective layer and the transition layer are formed from the same primary film, wherein the transition layer is formed by non-solvent induced phase separation and the selective layer is formed by thermally induced phase separation.
In the present invention, the transition layer has a porous structure. In the present invention, the selective layer is a dense layer.
According to the present invention, preferably, the polymer contained in or forming the transition layer and the selective layer is polybenzimidazole. The polybenzimidazole can have a number-average molecular weight of from 5×104 to 30×104; preferably, the polybenzimidazole can have a number-average molecular weight of from 5.6×104 to 20×104 or from 8×104 to 28.7×104.
According to the present invention, preferably, the polybenzimidazole comprises one or more structural units represented by formulae (A1) to (A8);
According to the present invention, preferably, the polybenzimidazole comprises one or more of the structural units represented by formulae (A5) to (A8).
According to the present invention, the support can be a fiber braided tube or a hollow fiber membrane, preferably a microporous hollow fiber membrane. The microporous hollow fiber membrane can be a microporous hollow fiber membrane prepared from a polymer material which cannot be dissolved by the acid used for preparing the casting solution by a method such as thermally induced phase separation, melt stretching and the like. The support can be one or more selected from the group consisting of a fiber braided tube, a microporous polypropylene hollow fiber membrane, a microporous polyethylene hollow fiber membrane, and a microporous inorganic hollow fiber membrane. Preferably, the microporous hollow fiber membrane is a microporous polypropylene hollow fiber membrane or a microporous polyethylene hollow fiber membrane prepared by a thermally induced phase separation method.
According to the present invention, the average thickness of the hollow fiber membrane of present invention can be 50-2000 μm or 100-2000 μm, preferably 150-1000 μm, and more preferably 180-500 μm.
According to the present invention, when the support is a microporous hollow fiber membrane, the porosity of the support can be 30 to 90%, preferably 50 to 80%. In some embodiments, the pore size of the support can be, for example, 10 nm to 20 μm. The porosity is measured by nitrogen adsorption method.
According to the present invention, the average thickness of the tube wall of the support can be 50-2000 μm or 100-2000 μm, preferably 300-1800 μm, and more preferably 500-1500 μm.
According to the present invention, the average thickness of the selective layer can be 100-50000 nm. Preferably, in some embodiments, the thickness of the selective layer can be 200-5000 nm.
According to the present invention, the average thickness of the transition layer can be 20-2000 μm, preferably 50-1500 μm, more preferably 20-1000 μm.
In the present invention, at least a portion of the transition layer is embedded into at least a portion of the support. In some embodiments, the diameter of the transition layer can be the same as the diameter of the support. In some embodiments, the transition layer can extend beyond the outer surface of the support. In some embodiments, the transition layer can extend beyond the inner surface of the support.
According to the invention, the transition layer is formed from the casting solution by non-solvent induced phase separation. In some embodiments, the transition layer is formed from a polybenzimidazole-containing acid solution by non-solvent induced phase separation.
The hollow fiber membrane of the present invention has excellent properties including, for example, breaking strength, permeance and selectivity.
According to the present invention, the breaking strength of the membrane is 10 to 500 MPa; preferably, the membrane has a breaking strength of 50 to 250 MPa; more preferably, the membrane has a breaking strength of 52 to 210 MPa.
According to the present invention, in some embodiments, the hollow fiber membrane of the present invention can have a pure helium permeance of 0.8-480 GPU, a pure hydrogen permeance of 0.8-580 GPU, a nitrogen permeance of 0.01-0.7 GPU, and/or a methane permeance of 0.01-0.7 GPU at 100° C. and 0.5 MPa test pressure; preferably, the pure helium permeance can be 3.48-477.5 GPU, the pure hydrogen permeance can be 3.03-79.6 GPU, the nitrogen permeance can be 0.016-0.68 GPU, and/or the methane permeance can be 0.0135-0.6 GPU.
According to the present invention, in some embodiments, the hollow fiber membrane of the present invention can have a selectivity of hydrogen/nitrogen of 110-300 or 110-235, and/or a selectivity of hydrogen/methane of 125-360 or 125-260 at 100° C. and 0.5 MPa test pressure; preferably, the hydrogen/nitrogen selectivity can be 110 to 234.1, and/or the hydrogen/methane selectivity can be 129.1 to 256.7.
According to the present invention, in some embodiments, the hollow fiber membrane of the invention can have a selectivity of helium/nitrogen of 140-390 or 140-190, and/or a selectivity of helium/methane of 170-500 or 170-175 at 100° C. and 0.5 MPa test pressure; preferably, the helium/nitrogen selectivity can be 141.4 to 187.5, and/or the helium/methane selectivity can be 170 to 173.8.
According to the present invention, in some embodiments, the hollow fiber membrane of the present invention can have a hydrogen/nitrogen selectivity of 200-550 and/or a hydrogen/methane selectivity of 200-860 at 25° C. and 0.5 MPa test pressure.
According to the present invention, in some embodiments, the hollow fiber membrane of the present invention can have a selectivity of helium/nitrogen of 240-900, and/or a selectivity of helium/methane of 200-2000 at 25° C. and 0.5 MPa test pressure.
The invention also provides a producing method for a hollow fiber membrane.
According to some embodiments, the method of the present invention for producing a hollow fiber membrane comprises:
Casting solutions and preparation thereof are generally known in the art. For example, a casting solution can be prepared by dissolving a polymer in a solvent. The polymer can be the polymer mentioned above with respect to the hollow fiber membrane. Preferably, the polymer is polybenzimidazole. The solvent can be selected by those skilled in the art depending on the type of the polymer or the like. The solvent can be a single solvent or can be a mixture.
Optionally, the casting solution can further comprise one or more additives. The additives can be appropriately selected as needed by those skilled in the art.
In some embodiments, the amount of polymer is 4-18 wt %, the amount of the solvent is 77-90 wt %, and the amount of the additive is 0-5 wt %, based on the total weight of the casting solution. Preferably, in some embodiments, the amount of polymer is 8-15 wt %, the amount of the solvent is 80-90 wt %, and the amount of the additive is 1-2 wt %, based on the total weight of the casting solution.
After preparation of the casting solution, the casting solution is coated on a support. The support can be a support as described above. The coating can be conducted via various ways generally known in the art. For example, the support can be pulled through the casting solution so as to apply the casting solution to the support.
According to the present invention, the casting solution permeates into at least a portion of the support. In some embodiments, the casting solution permeates a portion of the tube wall of the tubular support, for example, the casting solution can permeate from 10% to 150% of the thickness of the tube wall of the support. In some embodiments, the casting solution can permeate 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 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. of the thickness of the tube wall of the support. The range of the permeation of the casting solution into the tube wall of the support can be appropriately determined by those skilled in the art. The method of the present invention can make the casting solution that permeates into the tube wall of the support maintain or substantially maintain the permeation depth when it is converted into the transition layer (so that the embedding depth of the resulting transition layer in the support is the same as or substantially the same as the permeation depth of the casting solution), thereby ensuring that at least a portion of the transition layer formed by the casting solution in the finally obtained finished hollow fiber membrane is embedded into the support.
After the casting solution is coated on the support, a primary film coated on the support is obtained.
The primary film can then be heated to form a selective layer. In the present invention, the heating of the primary film causes thermally induced phase separation so as to form the outermost selective layer.
The heating promotes volatilization of the solvent in the casting solution so as to form a polymer selective layer. The heating can be performed by selecting a suitable temperature by those skilled in the art according to the solvent used. Optionally, the heating can be performed under normal pressure or reduced pressure. For example, hot air can be used for heating. In some embodiments, hot air can be used to conduct volatilization of the solvent. In the present invention, the heating temperature can be, for example, from 80 to 300° C.
In the method of present invention, the thermally induced phase separation proceeds to the stage that phase separation occurs merely in the outermost portion of the primary film (thereby forming the selective layer), but no phase separation occurs in the inner portion of the primary film. In particular, the casting solution permeated into the support remains in liquid state and no thermally induced phase separation occurs.
After the primary film is heated to form the selective layer, a bore fluid can be injected into the support (i.e., into the inner tube of the tubular support), and the bore fluid causes non-solvent induced phase separation of the casting solution that has permeated into the support so as to form the transition layer. In some embodiments, for example, the bore fluid can be injected after the desired selective layer is obtained. In the present invention, the injection of the bore fluid can be performed at room temperature and normal pressure.
The bore fluid can be selected by those skilled in the art according to the composition of the casting solution, the material of the support, and the like, as long as the casting solution can undergo non-solvent induced phase separation.
In the method of the present invention, optionally, the hollow fiber membrane can be heated after the generation of the transition layer to (substantially) remove all the solvent. The heating can be carried out under normal pressure or reduced pressure. The heating can be performed by selecting a suitable temperature by those skilled in the art according to the solvent used. For example, hot air can be used for heating. In some embodiments, the same temperature as used in step (3) above can be used in this step. For example, the temperature can be 80-300° C.
In the method of the present invention, the dense selective layer and the porous transition layer are formed from the same casting solution in two different ways, which makes the selective layer and the transition layer to be integral. The method of the invention allows the transition layer to be kept in the support (i.e. embedded in the support) so as to connect firmly the selective layer to the support, avoiding the selective layer to fall off. Furthermore, the method of the present application enables the transition layer to be porous, which can further contribute to connect firmly the selective layer to the support.
The selective layer in the present application is dense, but the transition layer is porous. As will be appreciated by those skilled in the art, there may be a transitional region when transition from the dense selective layer to the porous transition layer. In the present application, the transition region (if present) is deemed as part of the transition layer.
The hollow fiber membranes produced by the method of the present invention also provide advantageous membrane properties including, for example, permeance and/or selectivity.
According to some embodiments, the method of the present invention for producing a hollow fiber membrane comprises:
According to some embodiments, the method of the present invention for producing a hollow fiber membrane comprises:
According to the present invention, preferably, the polybenzimidazole has a number average molecular weight of 5×104 to 30×104 or 5×104 to 28.7×104, more preferably the polybenzimidazole has a number average molecular weight of 8×104 to 28.7×104 or 5.6×104 to 20×104.
According to the present invention, the polybenzimidazole comprises one or more of the structural units represented by formulas (A1) to (A8);
According to the present invention, preferably, the polybenzimidazole comprises one or more of the structural units represented by formulas (A5) to (A8).
According to the present invention, the polybenzimidazole and the support can be the same as those described above with respect to the hollow fiber membrane.
Optionally, in the present invention, the support can be modified before coating. There are not particular limits to the modification methods. For example, the modification can include blending the material to be used to prepare the support, for example using a polymer blend; subjecting the support to chemical treatment, physical deposition, ultraviolet irradiation, thermal treatment, mechanical treatment, or the like.
The inventors of the present invention found that: preferably, polybenzimidazole is protonated in the dissolving process by using a combination of organic acid and volatile solvent, inhibiting the formation of intermolecular hydrogen bonds and increasing the flexibility of polymer molecular chains, the polymer is easy to accumulate more closely in the membrane-forming process, and the resulting hollow fiber composite membrane has a high selectivity. On the other hand, the volatilization of the solvent is promoted by using high-temperature and high-pressure film coating and high-temperature normal-pressure/reduced-pressure drying, so that the polybenzimidazole selective layer has a good compactness, avoiding the formation of defects and obtaining a better separation performance. In addition, the mechanical properties of the gas separation membrane are improved by the internal support reinforcement, and the demands of a high-temperature, high-pressure and high-flow-rate gas separation system and the like on the mechanical properties of the membrane can be met, expanding the applications of the gas separation membranes. Moreover, the transition layer with a porous structure is obtained by non-solvent induced phase separation caused by the bore fluid, and the selective layer is prevented from falling off.
According to the present invention, in some embodiments, the acid is a monoacid. Preferably, the acid is one or more selected from the group consisting of hydrochloric acid, hydrofluoric acid and methanesulfonic acid. More preferably, the acid is methanesulfonic acid. It is believed that, during the film-forming process, the organic acid induces the occurring of protonation, inhibits the formation of intermolecular hydrogen bonds between polymer molecules, reduces the rigidity of the polymer, and allows polymer molecular chains to be more closely accumulated, thereby improving the separation performance of small molecular gases such as hydrogen, helium and the like.
According to the present invention, the bore fluid can be one or more of water, ethanol, methanol, isopropanol, acetone, and tetrahydrofuran.
According to the present invention, the volatile solvent can be ethanol and/or tetrahydrofuran.
According to the present invention, the additive can be one or more selected from the group consisting of lithium nitrate, calcium chloride, sodium chloride, potassium chloride, polyethylene glycol, and polyethylene oxide. Preferably, the additive is selected from lithium nitrate and/or potassium chloride.
According to the present invention, in some embodiments, the amount of polybenzimidazole is 4-18 wt %, the amount of the acid is 77-90 wt %, the amount of the volatile solvent is 0-10 wt % and the amount of the additive is 0-5 wt %, based on the total weight of the casting solution; preferably, the amount of polybenzimidazole is 8-15 wt %, the amount of the acid is 80-90 wt %, the amount of the volatile solvent is 1-5 wt % and the amount of the additive is 1-2 wt %, based on the total weight of the casting solution. In the present invention, it should be noted that the sum of the components of polybenzimidazole, acid, volatile solvent and optional additive is 100 wt %.
In some embodiments, the casting solution can be obtained by adding polybenzimidazole into the acid and adding volatile solvent (if used) and additive (if used), and mixing. Optionally, stirring and heating can be performed during the mixing. In some embodiments, the conditions of the mixing can include: temperature 25-160° C., and time period 2-72 h; preferably, the temperature is 80-160° C. and the time period is 12-48 h. The stirring is not particularly limited and can be conventionally selected by those skilled in the art. Preferably, the stirring rate of the stirring can be 20 to 500 rpm.
After the casting solution is prepared, the casting solution is coated on the surface of the support. In some embodiments, the casting solution can be blade coated onto the surface of the support. According to the present invention, the casting solution can be blade coated onto the surface of the support at certain temperature and pressure to obtain a primary film with a certain thickness. The blade coating conditions can include: temperature 60-250° C., preferably 80-180° C. In the present invention, the blade coating pressure is not particularly limited. Preferably, the pressure can be 10-2000 KPa, and more preferably, the pressure can be 500-1200 KPa.
In the present invention, the thickness of the primary film, and in turn the thickness of the selective layer, can be controlled by controlling the distance between the doctor blade and the outer wall of the support during the blade coating process. In some embodiments, the thickness of the blade coated film (primary film) (the distance between the doctor blade and the outer wall of the support) can be 10-300 μm. Of course, the spacing distance between the doctor blade and the outer wall of the support can be adjusted by the person skilled in the art according to the desired thickness of the primary film.
In some embodiments, the casting solution is extruded into the spinneret, wherein the casting solution contacts the support inside the spinneret. The contact time is not particularly limited. For example, the contact time can be 1 to 15 seconds, and preferably, the contact time is 1 to 10 seconds. In the present invention, the pressure is not particularly limited. For example, the pressure can be 10-2000 KPa. For example, the pressure can be 0 to 0.2 MPa (gauge pressure). For example, the pressure can be 0.02 to 0.1 MPa (gauge pressure).
According to the present invention, after the casting solution is coated (for example, blade coated) onto the support, the support to which the primary film is attached can be pulled and sent into a heating apparatus. The solvent in the outer layer of the primary film is volatilized by heating to form the polymer selective layer, such as polybenzimidazole selective layer, attached to the support. The heating can be performed by hot air, for example. The heating can be carried out under normal pressure or reduced pressure. For example, the heating can be carried out at −0.1 MPa to 0 MPa (gauge pressure). In some embodiments, conditions for facilitating solvent volatilization by heating can include: temperature 80-300° C. In some embodiments, the heating can be performed by using hot air. The heating conditions can be appropriately selected by those skilled in the art depending on the solvent used, the desired volatilization rate, and the like. In the present invention, the apparatus for heating is not particularly limited; for example, it can be an oven. In some embodiments, the heating temperature can be 100-280° C. and time period can be 2-24 h; preferably, the heating temperature is 120-150° C., and the time period is 5-12 h.
After the outermost polymer selective layer is formed by heating, a bore fluid can be injected into the support; the bore fluid induces non-solvent induced phase separation of the casting solution permeated into the support to generate a transition layer. The bore fluid is for example the bore fluid described above.
In the method of the present invention, optionally, the hollow fiber membrane can be heated after the generation of the transition layer to remove (substantially) all the solvent. The heating can be carried out under normal pressure or reduced pressure. The heating can be performed by selecting a suitable temperature by those skilled in the art according to the solvent used. For example, hot air can be used for heating. For example, the heating temperature can be 80 to 300° C.
In the present invention, optionally, the method can further include removing residual solvent from the resulting finished membrane by washing step, for example, water washing, ethanol washing, and the like.
Referring to
Referring to
The present invention also provides hollow fiber membranes prepared by the method described above. In some embodiments, the hollow fiber membrane of the present invention is prepared by the method of the present invention for producing hollow fiber membrane.
The hollow fiber membrane of the present invention can be used for gas separation. Accordingly, the present invention also provides the use of the hollow fiber membrane of the present invention for the separation of helium/nitrogen, helium/methane, hydrogen/nitrogen and/or hydrogen/methane. The hollow fiber membrane of the present invention can be used to separate gases by using operations generally known in the art.
The present invention also provides a method for purifying helium from a helium-rich gas, wherein the method comprises performing membrane separation on the gas by using the hollow fiber membrane of the present invention.
In some embodiments, the method for purifying helium from a helium-rich gas can comprise: carrying out condensation treatment through a cryogenic process, catalytic dehydrogenation treatment, membrane separation treatment and pressure swing adsorption impurity removal treatment on the helium-rich gas so as to obtain purified helium. Wherein the membrane separation treatment comprises using the hollow fiber membrane of the present invention.
In some embodiments, the method for purifying helium from a helium-rich gas can comprise: carrying out condensation treatment through a cryogenic process, catalytic dehydrogenation treatment, membrane separation treatment through helium separation membrane and pressure swing adsorption impurity removal treatment on the helium-rich gas so as to obtain purified helium; wherein the conditions of the condensation treatment include: temperature ≥−220° C. Wherein the membrane separation treatment comprises using the hollow fiber membrane of the present invention.
The method for purifying helium of present invention has the following advantages:
In some embodiments, the conditions of the condensation treatment can include a temperature of ≥−220° C. In some embodiments, the conditions of the condensation treatment can include: temperature −210° C. to −150° C., and pressure 0.2 MPa to 10 MPa; preferably, the conditions of the condensation treatment include: temperature −180° C. to −150° C., and pressure 3 MPa-10 MPa.
According to the present invention, there are no specific limitations on the helium-containing gas and there are no specific limitations on the composition of the helium-containing gas, and the method of the present invention has universal applicability. In some embodiments, the helium-containing gas can include natural gas, oilfield associated gas, or the like. In some embodiments, the helium-containing gas can comprise helium, nitrogen, methane, hydrogen, and carbon dioxide. In some embodiments, the content of helium can be 5 to 40% by volume, based on the total volume of the helium-rich gas; preferably, the content of helium can be 15 to 30 vol %.
According to the present invention, the helium-rich gas also comprises optional oxygen and water, and oxygen content is 0-8% by volume and water content is 0-2% by volume, based on the total volume of the helium-rich gas.
According to the present invention, the helium-rich gas is subjected to condensation treatment to achieve the effect of liquefying impurities such as nitrogen, methane, oxygen, light hydrocarbons and the like, and nitrogen, methane, oxygen and CO2 are removed partially to obtain a second mixed gas.
According to the present invention, the second mixed gas is subjected to catalytic dehydrogenation treatment to remove a portion of hydrogen, so as to obtain a third mixed gas.
According to the present invention, the conditions of the catalytic dehydrogenation treatment can include: temperature 60 to 120° C., preferably 60 to 110° C., more preferably 62 to 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.
According to the present invention, the third mixed gas is subjected to the membrane separation treatment of the invention to remove a portion of nitrogen, methane, oxygen and CO2, to obtain a fourth mixed gas.
According to the present invention, the membrane separation achieves the separation of helium by utilizing the difference of permeability of each component in the feed gas in the processes of dissolution, diffusion and desorption under the driving of the pressure difference at two sides of the membrane. The conditions of the membrane separation treatment can include: the membrane separation positive pressure side pressure being greater than the membrane separation permeation side pressure; wherein the membrane separation positive pressure side pressure can be 0.2-10 MPa; preferably, the membrane separation positive pressure side pressure is 0.5-10 MPa; more preferably, the membrane separation positive pressure side pressure is 3-10 MPa. The membrane separation method has the advantages of simple operation, low energy consumption and low apparatus construction and operation cost.
According to the present invention, the membrane separation can adopt one-stage or multi-stage membrane separation to purify helium. In the membrane separation, the multi-stage membrane separation means that the permeation side gas is pressurized and is used as feed gas again to undergo membrane separation, and the process can be 1 to 5 stages.
According to the present invention, the fourth mixed gas is subjected to adsorption impurity removal treatment to remove a portion of nitrogen, methane, oxygen, hydrogen and CO2, so as to obtain the purified helium; wherein the content of helium can be 99.986-99.996% by volume, based on the total volume of purified helium.
According to the present invention, the conditions of the pressure swing adsorption impurity removal treatment can include: adsorption pressure 0.2-15 MPa, preferably 10-15 MPa. In the present invention, the adsorbent used in the adsorption impurity removal treatment can be one or more selected from activated carbon, molecular sieve, metal organic framework material MOF, and activated alumina.
In the present application, the pressures are gauge pressures unless otherwise specified.
The present invention will be described in detail below by way of Examples.
In the following Examples and comparative Examples:
Polybenzimidazoles were purchased from Shanghai Shengjun Polymer Co., Ltd; other reagents/agents were purchased from Beijing InnoChem Science & Technology Co., Ltd. Wherein, ethanol 99.9%; hydrochloric acid 12 mol/L; methanesulfonic acid 99.0%; and tetrahydrofuran 99.9%.
Permeance (unit GPU) test method: the gas flow rate per unit membrane area per unit time at a specific pressure difference at a specific temperature is measured. Wherein 1 GPU=10−6 cm3 (STP)/(cm2·s·cmHg).
Selectivity α, dimensionless, is used to characterize the selective permeability of a gas component in a membrane. The selectivity is the ratio of the permeances of two gases in the membrane.
Breaking strength is tested with Instron 3342 according to Standard ASTMD882.
This example provided a hollow fiber membrane prepared using the method of the present invention.
The thickness of the selective layer of the produced hollow fiber membrane is about 27-29 μm; referring to
The breaking strength of the hollow fiber membrane prepared in Example 1 is 160 MPa; under the test pressure of 0.5 MPa and at 100° C., the pure helium permeance is 3.48GPU, the pure hydrogen permeance is 3.03GPU, and the nitrogen permeance and the methane permeance are respectively 0.016GPU and 0.0135 GPU; the hydrogen/nitrogen and hydrogen/methane selectivities are 189 and 224, respectively.
This example provided a hollow fiber membrane prepared using the method of the present invention.
The average thickness of the produced hollow fiber membrane is about 200 μm; the thickness of the selective layer is about 2-5 μm; and the transition layer is embedded into the support and has a thickness of about 200 μm.
The breaking strength of the hollow fiber membrane prepared is 155 MPa; under the test pressure of 0.5 MPa and at 100° C., the pure helium permeance is 7.5GPU, the pure hydrogen permeance is 6.8GPU, and the nitrogen permeance and the methane permeance are respectively 0.04GPU and 0.04GPU; the helium/nitrogen and helium/methane selectivities are 187.5 and 170, respectively.
This example provided a hollow fiber membrane prepared using the method of the present invention.
The thickness of the selective layer of the produced hollow fiber membrane is about 45˜50 μm; and the transition layer is embedded into the support and has a thickness of about 450 μm.
The breaking strength of the hollow fiber membrane prepared is 206 MPa; under the test pressure of 0.5 MPa and at 100° C., the pure helium permeance is 0.87GPU, the pure hydrogen permeance is 0.81GPU, and the nitrogen permeance and the methane permeance are respectively 0.005GPU and 0.004GPU; the hydrogen/nitrogen and hydrogen/methane selectivities are 162 and 202.5, respectively.
This example provided a hollow fiber membrane prepared using the method of the present invention.
The thickness of the selective layer of the produced hollow fiber membrane is 400˜600 nm, with a relatively obvious transitional region; and the transition layer is embedded into the support and has a thickness of 200-400 μm, with some parts extending through the support.
The breaking strength of the hollow fiber membrane prepared is 161 MPa; under the test pressure of 0.5 MPa and at 100° C., the pure helium permeance is 107GPU, the pure hydrogen permeance is 95GPU, and the nitrogen permeance and the methane permeance are respectively 0.45GPU and 0.41GPU; the hydrogen/nitrogen and hydrogen/methane selectivities are 211 and 231.7, respectively.
This example provided a hollow fiber membrane prepared using the method of the present invention.
The average thickness of the produced hollow fiber membrane is about 350 μm; the average thickness of the selective layer is about 1.2-2.0 μm; and the transition layer is embedded into the support and has a thickness of about 30 μm.
The breaking strength of the hollow fiber membrane prepared is 63 MPa; under the test pressure of 0.5 MPa and at 100° C., the pure helium permeance is 88.9GPU, the pure hydrogen permeance is 76.1GPU, and the nitrogen permeance and the methane permeance are respectively 0.66GPU and 0.52GPU; the hydrogen/nitrogen and hydrogen/methane selectivities are 134.7 and 170.9, respectively.
This example provided a hollow fiber membrane prepared using the method of the present invention.
The thickness of the selective layer of the produced hollow fiber membrane is about 2000 nm; and the transition layer is embedded into the support and has a thickness of about 180-190 μm (average thickness about 185 μm).
The breaking strength of the hollow fiber membrane prepared is 52 MPa; under the test pressure of 0.5 MPa and at 100° C., the pure helium permeance is 82.2GPU, the pure hydrogen permeance is 79.6GPU, and the nitrogen permeance and the methane permeance are respectively 0.68GPU and 0.55GPU; the hydrogen/nitrogen and hydrogen/methane selectivities are 120.61 and 144.7, respectively.
This example provided a hollow fiber membrane prepared using the method of the present invention.
The thickness of the selective layer of the produced hollow fiber membrane is about 10-12 μm; and the transition layer is embedded into the support and has a thickness of about 300 μm.
The breaking strength of the hollow fiber membrane prepared is 52 MPa; under the test pressure of 0.5 MPa and at 100° C., the pure helium permeance is 22.6GPU, the pure hydrogen permeance is 22.1GPU, and the nitrogen permeance and the methane permeance are respectively 0.16GPU and 0.13GPU; the helium/nitrogen and helium/methane selectivities are 141.4 and 173.8, respectively.
The selective layer of the produced hollow fiber membrane is thick; there is no porous transition layer, and the selective layer is directly attached to the support on the outer surface of the support. The membrane has poor binding between the selective layer and the support due to the absent of transition layer, so that the selective layer is easy to fall off and the service life is shortened. When the internal pressure exceeds 0.04 MPa, the selective layer is damaged; when external pressure operation is adopted, the service life is only 2000-5000 hours after multiple times of pressure change.
The breaking strength of the hollow fiber membrane prepared is 166 MPa; under the test pressure of 0.5 MPa and at 100° C., the pure helium permeance is 12.8GPU, the pure hydrogen permeance is 11.6GPU, and the nitrogen permeance and the methane permeance are respectively 0.11GPU and 0.10GPU; the hydrogen/nitrogen and hydrogen/methane selectivities are 105 and 116, respectively.
The average thickness of the produced hollow fiber membrane is about 600 μm; the thickness of the selective layer is about 500 nm; the outer diameter of the support is 1400 μm; the membrane has poor binding between the selective layer and the support, so that the selective layer is easy to fall off and the service life is shortened. When the internal pressure exceeds 0.05 MPa, the selective layer is damaged.
In addition, the breaking strength of the hollow fiber membrane prepared is 166 MPa; under the test pressure of 0.5 MPa and at 100° C., the pure helium permeance is 28.5GPU, the pure hydrogen permeance is 27.6GPU, and the nitrogen permeance and the methane permeance are respectively 0.33GPU and 0.27GPU; the hydrogen/nitrogen and hydrogen/methane selectivities are 83.7 and 102.2, respectively.
The thickness of the selective layer of the prepared hollow fiber membrane is about 200 nm, and the structure of the membrane is not dense, and the selectivity is low; when the internal pressure exceeds 0.1 MPa, the selective layer is damaged.
In addition, the breaking strength of the hollow fiber membrane prepared is 165 MPa; under the test pressure of 0.5 MPa and at 100° C., the pure helium permeance is 107GPU, the pure hydrogen permeance is 89.5GPU, and the nitrogen permeance and the methane permeance are respectively 12.9GPU and 11.4GPU; the hydrogen/nitrogen and hydrogen/methane selectivities are 6.94 and 7.85, respectively.
The feed gas-helium-rich gas comprises: volume fraction of helium volume %, volume fraction of methane 17 volume %, volume fraction of nitrogen 60 volume %, volume fraction of hydrogen 1 volume %, volume fraction of carbon dioxide 0.5 volume % and volume fraction of oxygen 1.5 volume %.
The helium-rich gas was purified, as shown in
Wherein the gas composition at each stage of the helium purification process is shown in Table 1.
Based on above table, it can be seen clearly that in present invention, helium concentration can be significantly increased by cryogenic process; the hydrogen which is difficult to separate from helium in mixed gas is effectively removed by catalytic oxidation section; the gas is further purified intensely through membrane separation to obtain crude helium gas having a concentration of 99.75%; and the crude helium gas is further treated by pressure swing adsorption, such that the helium concentration of the product obtained can reach 99.995%, meeting the 4N-grade standard.
The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Many simple modifications can be made to the technical solutions of the present invention within the scopes of the technical concepts of the present invention, including the combinations of various technical features in any other suitable manners. These simple modifications and combinations should also be deemed as the disclosures of the present invention, and all of them are covered by the protection scopes of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202210166344.4 | Feb 2022 | CN | national |
| 202210857961.9 | Jul 2022 | CN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2022/134854 | 11/29/2022 | WO |
