A hollow fiber composite substrate, a hollow fiber composite substrate loaded with a zinc-containing organic framework membrane, and a method of preparation

Abstract

The present application relates to a kind of hollow fiber composite matrix, hollow fiber composite matrix of zinc-containing organic framework membrane and preparation method for supporting, hollow fiber composite matrix includes hollow fiber ceramic matrix and the coating attached to the inner surface of hollow fiber ceramic matrix;Hollow fiber ceramic matrix contains zinc oxide;Coating includes coupling agent and zinc oxide.Hollow fiber composite matrix of zinc-containing organic framework membrane for supporting includes zinc-containing organic framework membrane and the above-mentioned hollow fiber composite matrix, zinc-containing organic framework membrane is attached to coating.The present application directly introduces nano zinc oxide in the preparation process of hollow fiber ceramic matrix, and a layer of coating is coated in the inner cavity of hollow fiber ceramic matrix, forms hollow fiber composite matrix, zinc-containing organic framework membrane is attached to coating, the protection of outer hollow fiber ceramic matrix is played, can avoid damage in loading and unloading process, both can simplify the membrane preparation step of zinc-containing organic framework membrane, also have great practical significance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramic membrane, in particular to a hollow fiber composite substrate, a hollow fiber composite substrate loaded with a zinc-containing organic framework membrane and a preparation method. BACKGROUND

[0002] In petrochemical industry, energy consumption for separation and purification accounts for half of the total energy consumption. As a potential gas membrane separation technology that can replace traditional cryogenic rectification, phase transition does not occur in the separation process, and the gas does not need to be liquefied at low temperature, which can greatly reduce energy consumption and cost.

[0003] Zeolitic imidazolate framework (ZIFs) is a new type of metal organic framework material, which has good thermal stability and regular pore structure, inherits and develops the traditional advantages of inorganic molecular sieve, and has great potential in gas separation and other aspects. Among them, ZIFs membrane containing zinc has the widest application and the most research, but the mechanical strength of the membrane is low, and it is easy to be damaged in practical application. Hollow fiber ceramic substrate has large specific surface area, thin wall, high flux and small floor area, and is an excellent carrier for membranes. There are many methods for preparing metal organic framework membranes on hollow fiber ceramic substrate, including in-situ growth method, secondary seed method, coupling agent method, reaction seed method and metal oxide induction method. The in-situ method is to form a composite coating on the surface of the carrier by directly introducing the seed of the organic framework membrane, which has a simple preparation process, but lacks nucleation centers, making it difficult to form a continuous MOF membrane layer. The secondary seed method relies on the chemical bond or physical adhesion of amino silane coupling agent to introduce the seed layer to the surface of the porous substrate. The membrane prepared by this method can grow continuously, but the preparation process is complex, and the metal organic framework membrane prepared on the surface of the substrate is easy to fall off. The metal oxide induction method introduces a homologous oxide modification layer on the outer surface of the ceramic substrate, and then induces the growth of the corresponding ZIFs membrane. The membrane prepared by this method is not easy to fall off, but the continuity is poor.

[0004] Therefore, solving the problem of the combination of the seed layer and the substrate and constructing a high-performance and stable metal organic framework membrane system are the keys to this technology. The current literature reports that the solving strategies focus on the membrane preparation process, while ignoring the characteristics of the substrate itself.

[0005] In the prior art, the zinc-containing ZIFs membrane is prepared in a complicated process, the seed layer and the carrier have insufficient bonding force, and the membrane is easy to be damaged in actual use. How to design and prepare a hollow fiber composite substrate suitable for introducing a zinc-containing metal organic framework membrane to enhance the bonding force between the framework membrane and the hollow fiber composite substrate, while avoiding or reducing damage to the framework membrane during loading and unloading is a technical problem to be solved at present. SUMMARY

[0006] The present application provides a hollow fiber composite matrix, a hollow fiber composite matrix loaded with a zinc-containing organic framework membrane and a preparation method, so as to enhance the binding force between the zinc-containing organic framework membrane and the hollow fiber composite matrix, while avoiding or reducing damage to the framework membrane during loading and unloading.

[0007] In a first aspect, the present application relates to a hollow fiber composite matrix, comprising a hollow fiber ceramic matrix and a coating attached to the inner surface of the hollow fiber ceramic matrix; the hollow fiber ceramic matrix contains zinc oxide; and the coating comprises a coupling agent and zinc oxide.

[0008] Optionally, the hollow fiber composite matrix is a single-tube hollow fiber composite matrix or a multi-channel hollow fiber composite matrix; the hollow fiber ceramic matrix contains the zinc oxide in a mass fraction of 0.1-12.5%, based on the mass of the hollow fiber ceramic matrix.

[0009] In a second aspect, the present application relates to a hollow fiber composite matrix loaded with a zinc-containing organic framework membrane, comprising a zinc-containing organic framework membrane and the above-mentioned hollow fiber composite matrix, wherein the zinc-containing organic framework membrane is attached to the coating.

[0010] Optionally, the zinc-containing organic framework membrane is selected from one of ZIF-7, ZIF-8, ZIF-11 and ZIF-71.

[0011] In a third aspect, the present application relates to a method for preparing the above-mentioned hollow fiber composite matrix, comprising the following steps: (1) dissolving an organic polymer and a dispersing agent in a first solvent to obtain a polymer solution; dispersing nano-zinc oxide and α-alumina powder in the polymer solution and then ball milling to obtain a casting solution; (2) successively performing spinning, straightening, drying and calcining on the casting solution obtained in step (1) to obtain a hollow fiber ceramic matrix; (3) mixing a zinc salt, an alkali source, a coupling agent and a second solvent to obtain a coating sol; and forming a coating on the inner surface of the hollow fiber ceramic matrix obtained in step (2) by using the coating sol, thereby obtaining a hollow fiber composite matrix.

[0012] Optionally, in step (1), the particle size of the nano-zinc oxide is 20-50 nanometers.

[0013] Optionally, in step (1), the content of the organic polymer is 5-10%, the content of the dispersing agent is 0.1-0.3%, the content of the first solvent is 20-50%, the content of the nano-zinc oxide is 0.1-5%, and the content of the α-alumina powder is 35-70%, based on the weight of the casting solution.

[0014] Optionally, in step (1), the organic polymer is polyether sulfone or polysulfone, the dispersing agent is polyvinylpyrrolidone, and the first solvent is N-methyl-2-pyrrolidone.

[0015] Optionally, in step (2), the spinning comprises: vacuumizing the casting solution, and then placing the casting solution in a spinning device tank, extruding the casting solution through a spinneret into an outer coagulation liquid for immersion condensation, while an inner coagulation liquid flows out of the inner cavity of the hollow fiber ceramic substrate through the spinneret.

[0016] Optionally, the inner coagulation liquid and the outer coagulation liquid are both water, an air gap of 2-20 cm high exists between the spinneret and the liquid surface of the outer coagulation liquid, the pressure of the casting solution extruded through the spinneret is 0.2-0.5 Mpa, and the outflow speed of the inner coagulation liquid is 5-20 ml / min.

[0017] Optionally, in step (2), the calcining comprises: raising the temperature from room temperature to a first temperature at a first temperature raising rate, raising the temperature from the first temperature to a second temperature at a second temperature raising rate, raising the temperature from the second temperature to a third temperature at a third temperature raising rate, and keeping the temperature at the third temperature for 4-6 h, and then cooling to room temperature; the first temperature raising rate is 5-10 ℃ / min, the second temperature raising rate is 0.5-5 ℃ / min, and the third temperature raising rate is 5-10 ℃ / min; the first temperature is 200-400 ℃, the second temperature is 500-800 ℃, and the third temperature is 1400-1600 ℃.

[0018] Optionally, in step (3), the zinc salt is selected from one of zinc chloride, zinc acetate, and zinc acetate dihydrate; the alkali source is selected from sodium hydroxide or ethanolamine; the coupling agent is an amino silane coupling agent selected from one or more of 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, and 3-aminopropyltriethoxysilane; and the second solvent is selected from one or more of ethylene glycol, ethanol, and ethylene glycol methyl ether.

[0019] Optionally, in step (3), in the coating sol, the molar concentration of the zinc salt is 0.5-1.5 mol / L, the molar ratio of the zinc salt to the alkali source is 1:(1-3), and the molar ratio of the coupling agent to the zinc salt is 1:(5-20).

[0020] Optionally, in step (3), forming the coating on the inner surface of the hollow fiber ceramic substrate obtained from step (2) by the coating sol comprises: injecting the coating sol into the inner cavity of the hollow fiber ceramic substrate, and staying for 10-300 s, and then discharging.

[0021] Fourthly, the present invention relates to a method for preparing the above-mentioned hollow fiber composite matrix loaded with a zinc-containing organic framework membrane, comprising the following steps: S1. mixing an organic framework membrane ligand and a third solvent to obtain an activation solution; circulating the activation solution through the inner cavity of the hollow fiber composite matrix to obtain an activated hollow fiber composite matrix; S2. injecting a zinc-containing organic framework membrane synthesis solution into the inner cavity of the activated hollow fiber composite matrix obtained from step S1, crystallizing, rinsing and drying.

[0022] Optionally, the organic framework membrane ligand in step S1 is selected from one of 2-methylimidazole, 4,5-dichloroimidazole and 2-nitroimidazole.

[0023] Beneficial effects:

[0024] This invention directly introduces nano-zinc oxide during the preparation of hollow fiber ceramic matrix and coats a layer of coating on the inner cavity of the hollow fiber ceramic matrix to form a hollow fiber composite matrix. The zinc-containing organic framework membrane is attached to the coating, and the outer hollow fiber ceramic matrix plays a protective role, which can avoid damage during loading and unloading. This invention simplifies the membrane preparation steps of the zinc-containing organic framework membrane and has great practical significance. Attached Figure Description

[0025] Figure 1 This is a microscope image of the hollow fiber ceramic tube obtained in step (1) of Embodiment 1 of the present invention.

[0026] Figure 2 This is an SEM image of the cross-section of the hollow fiber ceramic tube obtained in step (1) of Embodiment 1 of the present invention.

[0027] Figure 3 This is an SEM image of the inner surface of the hollow fiber ceramic tube obtained in step (1) of Embodiment 1 of the present invention.

[0028] Figure 4 SEM image of the inner surface of the hollow fiber ceramic composite matrix obtained in step (2) of Example 1 of the present invention.

[0029] Figure 5 This is a SEM image of the ZIF-8 membrane loaded on the inner surface of the hollow fiber ceramic composite matrix in step (3) of embodiment 1 of the present invention. Detailed Implementation

[0030] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. Through these descriptions, the features and advantages of the present application will become clearer and more apparent.

[0031] The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations. Although various aspects of implementations can be presented in terms of methods, one should appreciate that such implementations can also be implemented as appropriate with any number of computer-readable storage media storing instructions for execution on a computer or other processing device, and that the execution of such instructions can produce the operations illustrated in the corresponding flow diagrams.

[0032] Moreover, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as there is no conflict.

[0033] In a first aspect, the present application relates to a hollow fiber composite substrate, comprising a hollow fiber ceramic substrate and a coating attached to the inner surface of the hollow fiber ceramic substrate; the hollow fiber ceramic substrate contains zinc oxide; the coating comprises a coupling agent and zinc oxide.

[0034] It should be noted that the main material of the hollow fiber ceramic substrate is alumina, and it also contains trace amounts of zinc oxide. Alumina and zinc oxide together constitute the hollow fiber ceramic substrate. The thickness of the coating can be 50-500 nm. The length of the hollow fiber ceramic substrate can be 10-50 cm, the diameter can be 1-5 mm, and the wall thickness can be 0.1-0.5 mm.

[0035] It should be noted that, first, in the hollow fiber composite substrate of the present application, nano-zinc oxide is introduced into the raw material of the hollow fiber ceramic substrate, so that the hollow fiber ceramic substrate contains zinc oxide, which can improve the connection between the hollow fiber ceramic substrate and the coating containing zinc oxide to a certain extent, and make the coating more stably attached to the inner surface of the hollow fiber ceramic substrate. Second, the coating is attached to the inner surface of the hollow fiber ceramic substrate, and then the introduction of the zinc-containing organic framework membrane can make the zinc-containing organic framework membrane located inside the hollow fiber ceramic substrate, which can effectively avoid or reduce the damage to the zinc-containing organic framework membrane during loading and unloading, and improve the safety and stability of the zinc-containing organic framework membrane.

[0036] Based on one embodiment of the hollow fiber composite substrate, the hollow fiber composite substrate is a single-tube hollow fiber composite substrate or a multi-channel hollow fiber composite substrate; the hollow fiber ceramic substrate contains the zinc oxide, and the mass fraction of the zinc oxide is 0.1-12.5% based on the mass of the hollow fiber ceramic substrate. The balance is alumina. The multi-channel hollow fiber composite substrate can be a two-channel, three-channel, and four-channel multi-channel hollow fiber composite substrate.

[0037] It should be noted that the hollow fiber composite substrate of the present application can simplify the membrane preparation steps of the zinc-containing metal organic framework membrane, and solve the problem of the combination of the seed layer and the carrier. The hollow fiber composite substrate of the present application is suitable for the stable and continuous growth of the zinc-containing ZIFs membrane, and the addition of a certain amount of nano-zinc oxide in the substrate can also reduce the calcination temperature of the hollow fiber substrate and save energy.

[0038] In a second aspect, the present application relates to a hollow fiber composite substrate loaded with a zinc-containing organic framework membrane, comprising a zinc-containing organic framework membrane and the above-mentioned hollow fiber composite substrate, wherein the zinc-containing organic framework membrane is attached to the coating.

[0039] It should be noted that in the hollow fiber composite substrate loaded with a zinc-containing organic framework membrane of the present application, the zinc-containing organic framework membrane is attached to the coating, and the coating is loaded on the inner surface of the hollow fiber ceramic substrate, so that the zinc-containing organic framework membrane is located in the inner cavity of the hollow fiber ceramic substrate. In this way, the hollow fiber ceramic substrate can protect the coating and the zinc-containing organic framework membrane to some extent, so as to avoid damage to the coating and the zinc-containing organic framework membrane during loading and unloading, thereby improving the stability of the hollow fiber composite substrate loaded with the zinc-containing organic framework membrane.

[0040] Based on one embodiment of the hollow fiber composite substrate loaded with a zinc-containing organic framework membrane, the zinc-containing organic framework membrane is selected from one of ZIF-7, ZIF-8, ZIF-11 and ZIF-71.

[0041] It should be noted that in the hollow fiber composite substrate of the present application, a certain amount of nano-zinc oxide is introduced into the hollow fiber ceramic substrate, and a coating containing zinc oxide is loaded on the inner surface of the hollow fiber ceramic substrate, thereby enabling the ZIF-7, ZIF-8, ZIF-11 and ZIF-71 zinc-containing organic framework membranes to grow stably and continuously on the coating. The connection between the zinc-containing organic framework membrane and the hollow fiber composite substrate is better. The zinc-containing organic framework membrane in the hollow fiber composite substrate loaded with a zinc-containing organic framework membrane of the present application is not limited to the ZIF-7, ZIF-8, ZIF-11 and ZIF-71, and other zinc-containing organic framework membranes can be selectively matched for use.

[0042] In a third aspect, the present application relates to a method for preparing the above-mentioned hollow fiber composite substrate, comprising the following steps:

[0043] (1) dissolving an organic polymer and a dispersant in a first solvent to obtain a polymer solution; dispersing nano-zinc oxide and α-alumina powder in the polymer solution and then ball milling to obtain a casting solution;

[0044] (2) performing spinning, straightening, drying and calcining on the casting solution obtained from step (1) in sequence to obtain a hollow fiber ceramic substrate;

[0045] (3) mixing a zinc salt, an alkali source, a coupling agent and a second solvent to obtain a coating sol; forming a coating on the inner surface of the hollow fiber ceramic substrate obtained from step (2) by using the coating sol, thereby obtaining a hollow fiber composite substrate.

[0046] It should be noted that, as a preferred embodiment, in step (1), the nano-zinc oxide is first uniformly dispersed in the ceramic powder (α-alumina powder), and the uniformly mixed powder is slowly added into the polymer solution, and a casting solution is obtained by using a planetary ball mill. The ball milling time is 24-48 hours. In this way, the nano-zinc oxide in the hollow fiber ceramic matrix obtained after step (2) is very uniformly dispersed.

[0047] It should be noted that the temperature of the calcination in step (2) can be 1450°C. In step (3), the zinc salt is dissolved in the second solvent as a precursor, and the coupling agent is used to modify the nano-zinc oxide during the formation of the nano-zinc oxide, so as to obtain a near-transparent coating sol.

[0048] Based on one embodiment, in step (1), the particle size of the nano-zinc oxide is 20-50 nm.

[0049] Based on one embodiment, in step (1), the content of the organic polymer is 5-10%, the content of the dispersant is 0.1-0.3%, the content of the first solvent is 20-50%, the content of the nano-zinc oxide is 0.1-5%, and the content of the α-alumina powder is 35-70%, based on the weight of the casting solution.

[0050] It should be noted that the sum of the weight contents of the organic polymer, the dispersant, the first solvent, the nano-zinc oxide, and the α-alumina powder is 100%.

[0051] It should be noted that, in the method for preparing the above-mentioned hollow fiber composite matrix, in step (1), the casting solution contains an organic polymer, a dispersant, a first solvent, nano-zinc oxide, and α-alumina powder, and the hollow fiber ceramic matrix obtained after the drying and calcination steps in step (2) is composed of a main material α-alumina and a small amount of zinc oxide. The organic polymer, the dispersant, and the first solvent have been removed after drying and calcination.

[0052] Based on one embodiment, in step (1), the organic polymer is polyether sulfone or polysulfone, the dispersant is polyvinylpyrrolidone, and the first solvent is N-methyl-2-pyrrolidone.

[0053] It should be noted that, in step (1), the nano-zinc oxide with the above-mentioned particle size is selected, and the specific selection and amount control of each raw material substance can obtain a hollow fiber ceramic matrix with good performance after the spinning step in step (2), so as to better attach the coating to the inner surface of the hollow fiber ceramic matrix.

[0054] Based on one embodiment, in step (2), the spinning includes: vacuumizing the casting solution and then placing it in a spinning device tank, extruding the casting solution through a spinneret into an outer coagulation liquid for immersion condensation, while an inner coagulation liquid flows out of the inner cavity of the hollow fiber ceramic matrix through the spinneret.

[0055] It should be noted that in step (2), the casting solution contacts the inner coagulation liquid through the spinneret and is spun into the outer coagulation liquid for immersion, and under the joint action of the inner and outer coagulation liquids, a hollow fiber ceramic precursor is obtained through phase inversion and solidification. The hollow fiber ceramic precursor is straightened and dried, and then is calcined in a high-temperature furnace to obtain a hollow fiber ceramic matrix.

[0056] Based on one embodiment, the inner coagulation liquid and the outer coagulation liquid are both water, there is an air gap of 2-20 cm high between the spinneret and the liquid surface of the outer coagulation liquid, the pressure of the casting solution extruded through the spinneret is 0.2-0.5 Mpa, and the outflow speed of the inner coagulation liquid is 5-20 ml / min.

[0057] It should be noted that the casting solution obtained in step (1) of the present application is not limited to the above-mentioned spinning method, and wet spinning, dry spinning, phase separation spinning, flash spinning, spray coagulation spinning, jet spinning, electrospinning, etc. can be selectively used in matching.

[0058] As a preferred embodiment, in step (2), the calcining includes: heating from room temperature to a first temperature at a first heating rate, heating from the first temperature to a second temperature at a second heating rate, heating from the second temperature to a third temperature at a third heating rate, and keeping the third temperature for 4-6 h, and then cooling to room temperature; the first heating rate is 5-10 ℃ / min, the second heating rate is 0.5-5 ℃ / min, and the third heating rate is 5-10 ℃ / min; the first temperature is 200-400 ℃, the second temperature is 500-800 ℃, and the third temperature is 1400-1600 ℃. Preferably, the first heating rate is 5-8 ℃ / min, the second heating rate is 0.5-2 ℃ / min, and the third heating rate is 5-8 ℃ / min; the first temperature is 250-350 ℃, the second temperature is 600-700 ℃, and the third temperature is 1450-1500 ℃.

[0059] It should be noted that in this embodiment, the heating and calcining are carried out according to the above-mentioned heating mode, which achieves better results.

[0060] According to one embodiment, in step (3), the zinc salt is selected from the group consisting of zinc chloride, zinc acetate and zinc acetate dihydrate; the alkali source is selected from the group consisting of sodium hydroxide and ethanolamine; the coupling agent is an aminosilane coupling agent selected from the group consisting of one or more of 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane and 3-aminopropyltriethoxysilane; and the second solvent is selected from the group consisting of one or more of ethylene glycol, ethanol and ethylene glycol methyl ether.

[0061] According to one embodiment, in step (3), the molar concentration of the zinc salt in the coating sol is 0.5-1.5 mol / L, and the molar ratio of the zinc salt to the alkali source is 1:(1-3), and the molar ratio of the coupling agent to the zinc salt is 1:(5-20).

[0062] According to one embodiment, in step (3), forming the coating on the inner surface of the hollow fiber ceramic substrate from the coating sol obtained in step (2) comprises:

[0063] According to one embodiment, in step (3), the coating sol is injected into the inner cavity of the hollow fiber ceramic substrate and left to stay for 10-300 seconds, and then discharged. After being discharged, the coating sol can be dried for standby use. After being dried, the formed coating comprises the coupling agent and zinc oxide, and the alkali source and the second solvent have been converted into components of the zinc oxide or removed.

[0064] It is to be noted that the injection of the coating sol into the inner cavity of the hollow fiber ceramic substrate can be performed by a circulating pump.

[0065] It is to be noted that the mixing in step (3) can comprise the following steps: first, dissolving the zinc salt in the second solvent to obtain a milky white suspension, then adding the alkali source and continuing to stir at room temperature to obtain a nano-zinc oxide colloid, then slowly adding the aminosilane coupling agent to the nano-zinc oxide colloid and stirring overnight at room temperature to obtain the coupling agent / zinc oxide sol, i.e. the coating sol.

[0066] In a fourth aspect, the present application relates to a method for preparing the hollow fiber composite substrate loaded with the zinc-containing organic framework membrane, comprising the following steps:

[0067] S1. mixing the organic framework membrane ligand and the third solvent to obtain an activation liquid; and circulating the activation liquid through the inner cavity of the hollow fiber composite substrate to obtain an activated hollow fiber composite substrate;

[0068] S2. injecting the zinc-containing organic framework membrane synthesis liquid into the inner cavity of the activated hollow fiber composite substrate obtained in step S1, crystallizing, rinsing and drying.

[0069] It should be noted that the third solvent can be an alcohol solvent such as methanol or ethanol, the activation solution can be circulated through the inner cavity of the hollow fiber composite substrate at a temperature of 50℃ and a flow rate of 2ml / min, and the activation time (circulation time) can be 4 hours. The circulation of the activation solution through the inner cavity of the hollow fiber composite substrate or the injection of the zinc-containing organic framework membrane synthesis solution into the inner cavity of the activated hollow fiber composite substrate can be performed by a circulating pump. The flushing in step S2 includes flushing the surface and the inner surface of the substrate.

[0070] According to an embodiment, the organic framework membrane ligand in step S1 is selected from one of 2-methylimidazole, 4,5-dichloroimidazole and 2-nitroimidazole.

[0071] It should be noted that the zinc-containing organic framework membrane synthesis solution can contain sodium formate, 2-methylimidazole, methanol and zinc chloride, and the ratio of each component can be a conventional ratio for preparing a zinc-containing organic framework membrane. The zinc-containing organic framework membrane prepared according to the method of the present application is stable, continuous and dense. In step S2, the flushing can be performed with methanol or ethanol, and the drying temperature can be 80℃ and the time can be 24h. The selection and mass relationship of each component in the zinc-containing organic framework membrane synthesis solution can use the conventional ratio in the art.

[0072] The present application provides a simple hollow fiber composite substrate suitable for the growth of zinc-containing metal organic framework membranes and a preparation method thereof, which can simultaneously solve the problems of the binding force of the membrane and the carrier and the nucleation induction, and is beneficial to the formation of high-quality membranes. It also solves the technical difficulty that the composite coating is easily damaged during handling and unloading. The method has universality and good guiding significance for the large-scale preparation of zinc-containing metal organic framework membranes.

[0073] The present application will be further described in detail by the following examples.

[0074] Example 1

[0075] In this embodiment, the method of the present application is used to prepare a ZIF-8 membrane on the inner surface of a single-tube hollow fiber composite substrate.

[0076] (1) Preparation of a hollow fiber ceramic tube containing nano-zinc oxide

[0077] 0.53g of polyvinylpyrrolidone was dissolved in 40g of N-methyl-2-pyrrolidone, 10.9g of polyether sulfone was added and stirred uniformly to obtain an organic solution (i.e. a polymer solution); 5.0g of nano-zinc oxide powder was slowly added to the organic solution under rapid stirring and uniformly dispersed; and then 120g of α-alumina powder was added. After ball milling for 48 hours, a uniform organic-inorganic system, i.e. a casting solution, was obtained.

[0078] The casting solution is vacuum degassed for 1-2 hours, the vacuum degree is kept at 0.05 MPa, after degassing, 0.4 MPa nitrogen pressure is used for extrusion, the internal coagulation liquid (tap water) is opened, the casting solution forms a hollow fiber shape through the spinneret, enters the external coagulation liquid (tap water), and the hollow fiber blank is kept immersed in the external coagulation liquid for 10-20 hours, so that the solvent-non-solvent is fully exchanged. Then, it is dried at room temperature after being straightened; the dried hollow fiber substrate is placed in a high-temperature calcination furnace, the temperature is raised at a rate of 5 ℃ / min from room temperature to 300 ℃, the temperature is slowly raised at a rate of 1 ℃ / min from 300 ℃ to 600 ℃, then the temperature is raised at a rate of 5 ℃ / min to 1450 ℃, and kept for 4 hours, and finally cooled to room temperature with the furnace.

[0079] (2) Hollow fiber ceramic composite substrate with silane / zinc oxide coating

[0080] 6.6 g of zinc acetate dihydrate is dissolved in 30 ml of anhydrous ethanol, a milky white suspension is obtained by continuously stirring at 70 ℃, then 2.4 g of sodium hydroxide is added, and the stirring is continued at room temperature for 2 hours to obtain a nano-zinc oxide colloid, then 0.5 g of 3-aminopropyl triethoxysilane is slowly added to the nano-zinc oxide colloid, and the stirring is continued at room temperature overnight to obtain a silane / zinc oxide sol. The silane / zinc oxide sol is injected into the hollow fiber lumen by using a circulating pump, and the solution is discharged after staying for 30 s, and then dried for standby use.

[0081] (3) Preparation of ZIF-8 membrane

[0082] 2-methylimidazole 4.1 g is dissolved in methanol 100 ml to prepare an activation solution with a concentration of 0.5 mol / L, the activation solution is circulated through the inner surface of the hollow fiber substrate at a flow rate of 2 ml / min and a temperature of 50 ℃ by using a circulating pump, and the activation time is 4 hours.

[0083] Sodium formate, 2-methylimidazole, methanol, and zinc chloride are used as raw materials to prepare a synthesis solution with a molar ratio of sodium formate: zinc chloride: 2-methylimidazole: methanol of 1:1:1.5:250, the synthesis solution is introduced into the inner surface of the activated hollow fiber carrier by using a circulating pump at a flow rate of 5 ml / min and a temperature of 100 ℃, and the crystallization is carried out for 5 hours, then the substrate surface and the inner surface are washed with methanol, and placed in an oven for drying at 80 ℃ for 24 hours.

[0084] Example 2

[0085] In this example, the method of the application is used to prepare a ZIF-71 membrane on the inner surface of a single-tube hollow fiber composite substrate.

[0086] (1) Preparation of hollow fiber ceramic tube containing nano-zinc oxide

[0087] 0.53 g of polyvinylpyrrolidone was dissolved in 40 g of N-methyl-2-pyrrolidone, 10.9 g of polyethersulfone was added, stirred uniformly to obtain an organic solution (polymer solution); under the condition of rapid stirring, 5.0 g of nano-zinc oxide powder was slowly added into the organic solution, uniformly dispersed; then 120 g of alpha-alumina powder was added. After ball milling for 48 hours, a uniform organic-inorganic system, i.e. a casting solution, was obtained;

[0088] The above casting solution was vacuum degassed for 1-2 hours, the vacuum degree was kept at 0.05 MPa, after degassing, 0.4 MPa nitrogen pressure was used for extrusion, the inner coagulation liquid (tap water) was opened, the casting solution passed through the spinneret to form a hollow fiber shape, entered the outer coagulation liquid (tap water), and the hollow fiber blank was kept immersed in the outer coagulation liquid for 10-20 hours to allow sufficient exchange between the solvent and the non-solvent. Then, it was straightened and air-dried at room temperature; the air-dried hollow fiber matrix was placed in a high-temperature calcination furnace, the heating rate was 5 ℃ / min from room temperature to 300 ℃, the temperature was slowly increased to 600 ℃ at 1 ℃ / min from 300 ℃, then the temperature was increased to 1450 ℃ at 5 ℃ / min, and kept for 4 hours, and finally cooled to room temperature with the furnace.

[0089] (2) Hollow fiber ceramic composite matrix with silane / zinc oxide coating

[0090] 6.6 g of zinc acetate dihydrate was dissolved in 30 ml of anhydrous ethanol, stirred at 70 ℃ to obtain a milky white suspension, then 2.4 g of sodium hydroxide was added, and the stirring was continued at room temperature for 2 hours to obtain a nano-zinc oxide colloid, then 1.0 g of 3-aminopropyl triethoxysilane was slowly added into the nano-zinc oxide colloid, and the stirring was continued at room temperature overnight to obtain a silane / zinc oxide sol. The silane / zinc oxide sol was injected into the inner cavity of the hollow fiber by using a circulating pump, and the solution was discharged after staying for 30 s, and then dried for standby use.

[0091] (3) Preparation of ZIF-71 membrane

[0092] 4,5-dichloroimidazole 6.85 g was dissolved in 100 ml of methanol to prepare an activation solution with a concentration of 0.5 mol / L, the activation solution was circulated through the inner surface of the hollow fiber matrix at a flow rate of 2 ml / min and a temperature of 50 ℃ by using a circulating pump, and the activation time was 4 hours.

[0093] Then, 4,5-dichloroimidazole, methanol, and zinc acetate were used as raw materials to prepare a synthesis solution with a molar ratio of zinc acetate:4,5-dichloroimidazole:methanol of 1:1:250, the synthesis solution was introduced into the inner surface of the activated hollow fiber carrier by using a circulating pump at a flow rate of 5 ml / min and a temperature of 100 ℃, and the crystallization was carried out for 5 hours, then the matrix surface and the inner surface were washed with methanol, and then placed in an oven for drying at 80 ℃ for 24 hours.

[0094] Example 3

[0095] This example employs the method of the present application to prepare a ZIF-8 membrane on the inner surface of a single tube hollow fiber composite substrate.

[0096] Example 3 is substantially the same as Example 1 except that the preparation of the composite sol coating in step (2) is different. The preparation is as follows: 10.0 g of zinc acetate dihydrate is added to 50.0 g of ethylene glycol methyl ether with constant stirring at 70 °C to obtain a milky white suspension; then 2.88 g of ethanolamine is added dropwise until the suspension is clear, slowly reduced to room temperature and slowly added with 1.0 g of 3- aminopropyltriethoxysilane, continue stirring at room temperature overnight to obtain the silane / zinc oxide sol, store at low temperature and wait for use.

[0097] Example 4

[0098] This example employs the method of the present application to prepare a ZIF-8 membrane on the inner surface of a single tube hollow fiber composite substrate.

[0099] Example 4 is substantially the same as Example 1 except that 7.2 g of nano zinc oxide powder is added in the preparation of the casting solution in step (1).

[0100] Example 5

[0101] This example employs the method of the present application to prepare a ZIF-8 membrane on the inner surface of a four-channel hollow fiber composite substrate.

[0102] Example 5 is substantially the same as Example 1 except that the hollow fiber composite substrate is a four-channel hollow fiber composite substrate.

[0103] Test Example 1

[0104] The hollow fiber ceramic tube prepared in step (1) of Example 1 is observed by Toupcam microscope and a photo is taken at 4x5 magnification as shown in Figure 1 .

[0105] The cross section of the hollow fiber ceramic tube prepared in step (1) of Example 1 is observed by scanning electron microscope and the SEM photo of the cross section of the hollow fiber ceramic tube is as shown in Figure 2 . The inner surface of the hollow fiber ceramic tube prepared in step (1) of Example 1 is observed by scanning electron microscope and the SEM photo of the inner surface of the hollow fiber ceramic tube is as shown in Figure 3 . The inner surface of the hollow fiber ceramic composite substrate prepared in step (2) of Example 1 is observed by scanning electron microscope and the SEM photo of the inner surface of the hollow fiber ceramic composite substrate is as shown in Figure 4 . The SEM photo of the ZIF-8 membrane loaded on the inner surface of the hollow fiber ceramic composite substrate in step (3) of Example 1 is observed by scanning electron microscope and the SEM photo of the ZIF-8 membrane is as shown in Figure 5as shown.

[0106] By Figure 1 It can be seen that the hollow fiber ceramic substrate (hollow fiber ceramic tube) is a single-hole tubular structure, and the diameter is 3.5 mm and the wall thickness is 0.25 mm measured by a vernier caliper. Figure 2 It can be seen that the hollow fiber ceramic tube has a finger-like pore structure, Figure 3 It can be seen that the inner surface of the hollow fiber ceramic tube is consistent with the structure reported in the related literature. Figure 4 It can be seen that the inner surface of the hollow fiber ceramic composite substrate is covered with a layer of silane / zinc oxide sol. Figure 5 It can be seen that the ZIF-8 membrane grown on the inner surface of the hollow fiber ceramic composite substrate has uniform morphology.

[0107] Test Example 2

[0108] The ZIF-8 membrane loaded hollow fiber composite substrate prepared in Example 1 was subjected to single-component gas permeation characterization, which was detected under the conditions of a pressure of 0.1 MPa and a temperature of 30℃, and the H2 permeation rate was measured to be 41.5 x 10 - 8 mol·m -2 ·s -1 ·Pa -1 , and the N2 permeation rate was 5.4 x 10 -8 mol·m -2 ·s -1 ·Pa -1 .

[0109] The H2 / N2 separation factor is 7.69 by calculating the ratio of the H2 permeation rate and the N2 permeation rate, which is greater than the Knudsen diffusion value of H2 / N2 of 3.7, indicating that the prepared membrane is complete and defect-free, and has good gas permeation performance and gas separation capacity.

[0110] In the description of the present application, it should be explained that the terms "upper", "lower", "inner", "outer", "front", "back", "left", "right" and the like indicate the orientation or positional relationship based on the working state of the present application, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as limiting the present application. The device or element must have a specific orientation, be constructed and operated in a specific orientation.

[0111] In the description of the present application, it should be explained that the terms "installation", "connection", "connection" should be understood in a broad sense, unless otherwise specified and limited. For ordinary skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0112] The application has been described above with reference to preferred embodiments. However, these embodiments are merely exemplary and are presented for purposes of illustration only. Variations and modifications to the application can be made based on what is described herein by a person of ordinary skill in the art. Such variations and modifications are considered to be within the scope of the application.

Claims

1. A hollow fiber composite substrate loaded with a zinc-containing organic framework membrane, characterized in that, The hollow fiber composite substrate comprises a hollow fiber ceramic substrate and a coating attached to the inner surface of the hollow fiber ceramic substrate; The zinc-containing organic framework membrane is attached to the coating; The hollow fiber ceramic substrate contains zinc oxide; the coating comprises a coupling agent and zinc oxide; The hollow fiber ceramic substrate contains the zinc oxide in a mass fraction of 0.1-12.5% based on the mass of the hollow fiber ceramic substrate, The hollow fiber composite substrate is prepared by a method comprising the following steps: (1) dissolving an organic polymer and a dispersant in a first solvent to obtain a polymer solution; dispersing nano-zinc oxide and α-alumina powder in the polymer solution and then ball milling to obtain a casting solution; (2) spinning, straightening, drying and calcining the casting solution obtained in step (1) in sequence to obtain a hollow fiber ceramic substrate; (3) mixing a zinc salt, an alkali source, a coupling agent and a second solvent to obtain a coating sol; forming the coating sol into a coating on the inner surface of the hollow fiber ceramic substrate obtained in step (2) to obtain a hollow fiber composite substrate. The hollow fiber composite substrate is a single-tube hollow fiber composite substrate or a multi-channel hollow fiber composite substrate.

2. The hollow fiber composite substrate loaded with a zinc-containing organic framework film according to claim 1, wherein, The zinc-containing organic framework membrane is selected from one of ZIF-7, ZIF-8, ZIF-11 and ZIF-71.

3. The hollow fiber composite substrate loaded with a zinc-containing organic framework film according to claim 1 or 2, characterized in that, In step (1), the particle size of the nano-zinc oxide is 20-50 nm.

4. The hollow fiber composite substrate loaded with a zinc-containing organic framework film of claim 1, wherein, In step (1), the content of the organic polymer is 5-10%, the content of the dispersant is 0.1-0.3%, the content of the first solvent is 20-50%, the content of the nano-zinc oxide is 0.1-5%, and the content of the α-alumina powder is 35-70% based on the weight of the casting solution.

5. The hollow fiber composite substrate loaded with a zinc-containing organic framework film according to claim 1, wherein, In step (1), the organic polymer is polyether sulfone or polysulfone, the dispersant is polyvinylpyrrolidone, and the first solvent is N-methyl-2-pyrrolidone.

6. The hollow fiber composite substrate loaded with a zinc-containing organic framework film of claim 1, wherein, In step (2), the spinning comprises: vacuumizing the casting solution and then placing it in a spinning equipment tank, extruding the casting solution through a spinneret into an external coagulation liquid for immersion and condensation, while an internal coagulation liquid flows out of the inner cavity of the hollow fiber ceramic substrate through the spinneret.

7. The hollow fiber composite substrate loaded with a zinc-containing organic framework film of claim 1, wherein, The internal coagulation liquid and the external coagulation liquid are both water, there is an air gap of 2-20 cm high between the spinneret and the liquid level of the external coagulation liquid, the pressure of the casting solution extruded through the spinneret is 0.2-0.5 MPa, and the outflow speed of the internal coagulation liquid is 5-20 ml / min.

8. The hollow fiber composite substrate loaded with a zinc-containing organic framework film of claim 7, wherein, The calcining in step (2) comprises: heating from room temperature to a first temperature at a first heating rate, heating from the first temperature to a second temperature at a second heating rate, heating from the second temperature to a third temperature at a third heating rate, and then maintaining the third temperature for 4-6 h before cooling to room temperature; 9. The hollow fiber composite substrate loaded with a zinc-containing organic framework film of claim 1, wherein, ​ The first temperature raising rate is 5-10℃ / min, the second temperature raising rate is 0.5-5℃ / min, and the third temperature raising rate is 5-10℃ / min; the first temperature is 200-400℃, the second temperature is 500-800℃, and the third temperature is 1400-1600℃.

10. The hollow fiber composite substrate loaded with a zinc-containing organic framework film of claim 1, wherein, In step (3), the zinc salt is selected from one of zinc chloride, zinc acetate and zinc acetate dihydrate; the alkali source is selected from sodium hydroxide or ethanolamine; the coupling agent is an amino silane coupling agent selected from one or more of 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane and 3-aminopropyltriethoxysilane; and the second solvent is selected from one or more of ethylene glycol, ethanol and ethylene glycol methyl ether.

11. The hollow fiber composite substrate loaded with a zinc-containing organic framework film of claim 1, wherein, In step (3), in the coating sol, the molar concentration of the zinc salt is 0.5-1.5 mol / L, the molar ratio of the zinc salt to the alkali source is 1:(1-3), and the molar ratio of the coupling agent to the zinc salt is 1:(5-20).

12. The hollow fiber composite substrate loaded with a zinc-containing organic framework film of claim 1, wherein, In step (3), forming a coating on the inner surface of the hollow fiber ceramic substrate from step (2) by the coating sol comprises: Injecting the coating sol into the inner cavity of the hollow fiber ceramic substrate and allowing it to stay for 10-300s before being discharged.

13. A method of making the hollow fiber composite substrate loaded with a zinc- containing organic framework film according to any one of claims 1-12, characterized in that, The method comprises the following steps: S1. mixing an organic framework membrane ligand and a third solvent to obtain an activation liquid; and circulating the activation liquid through the inner cavity of the hollow fiber composite substrate to obtain an activated hollow fiber composite substrate; S2. injecting a zinc-containing organic framework membrane synthesis liquid into the inner cavity of the activated hollow fiber composite substrate from step S1, crystallizing, rinsing and drying.

14. The method of claim 13, wherein, The organic framework membrane ligand in step S1 is selected from one of 2-methylimidazole, 4,5-dichloroimidazole and 2-nitroimidazole.

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