Low-resistance-consumption methane preferential permeation nanofiber membrane, and preparation method and application thereof

Abstract

The application provides a low-resistance-consumption methane preferential permeation nanofiber membrane and a preparation method and application thereof, and the method comprises the following steps: step S1, dissolving cellulose acetate in an acetate fiber dissolving agent to obtain a uniform cellulose acetate spinning dope; step S2, mixing beta-cyclodextrin and an alkali solution to perform activation treatment, then performing etherification modification treatment, and then mixing the cellulose acetate spinning dope obtained in step S1 to prepare a functional spinning solution; step S3, dissolving a metal salt, an organic ligand and an adjusting agent in a metal coordination promoter to react, thereby preparing MOF nanosheets; and step S4, preparing the low-resistance-consumption methane preferential permeation nanofiber membrane by spinning technology through the functional spinning solution obtained in step S2 and the MOF nanosheets obtained in step S3. The fiber membrane prepared by the application has the characteristics of excellent methane affinity, excellent breaking elongation capacity, good tensile resistance and developed specific surface area, and is a high-performance wide-range selective methane gas capturing and dust filtering purification material.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of controllable synthesis using cellulose acetate (CA) / β-cyclodextrin (β-CD) composite nanofiber membranes as templates, and in particular to a low-resistance and low-consumption methane preferential permeation nanofiber membrane, a preparation method thereof and an application thereof. BACKGROUND

[0002] Methane (CH4) is a colorless, odorless, non-toxic gas, lighter than air, and very difficult to dissolve in water. It is widely present in natural gas fields, coal seams and oil reservoirs. CH4 is a strong greenhouse gas, with a global warming potential (GWP) of about 28 times that of carbon dioxide on a 100-year time scale. Although the concentration of CH4 in the atmosphere is relatively low, due to its strong infrared absorption capacity, methane plays an important role in global climate warming. CH4 itself is non-toxic, but it is a suffocating gas. When the CH4 content in the air is too high, the oxygen content will be relatively low, causing the human body to suffocate due to lack of oxygen. When the CH4 concentration in the air reaches 25% to 30%, people may experience headaches, dizziness, shortness of breath, rapid heartbeat, and other symptoms, and in severe cases, coma and even death. Therefore, researchers have explored various methods to reduce CH4 emissions, including activated carbon adsorption, zeolite molecular sieve adsorption, inorganic membrane separation, polymer membrane separation, etc. However, due to the limitations of the above means for capturing CH4 gas, new technologies have been explored. Although CH4 is harmful to the human body to some extent, it is also a high-quality clean energy that can be recycled and converted into high-value products. For most gas streams that can produce CH4 gas, harmful particles such as dust are often produced. Therefore, for economic and environmental reasons, it is particularly important to develop high-efficiency CH4 gas capture and purification materials.

[0003] Over the decades, researchers have been exploring various materials for removing CH4, including biological materials, metal oxides, and supported catalysts. However, these materials have certain limitations that hinder their application in practical situations. For example, microbial materials are very sensitive to environmental conditions, and small changes in temperature, pH, humidity, and other environmental factors can affect their activity. In addition, they have strict requirements for substrate concentration. When the methane concentration is too low, the microorganisms may grow slowly due to lack of sufficient carbon source and energy, and cannot effectively remove methane. Metal oxides and supported catalysts have high costs and complex preparation processes, and may produce certain environmental pollution during preparation, thus also having relative limitations. These inherent limitations greatly limit their application in practical situations. Therefore, it is necessary to design new adsorbent materials with simple operation and strong CH4 adsorption capacity to overcome these inherent limitations.

[0004] Metal-organic frameworks (MOFs) are a kind of materials with unique characteristics and application potential, which are formed by self-assembly of metal ions or metal clusters and organic ligands through coordination bonds, and have the characteristics of inorganic and organic materials. MOFs can exhibit excellent adsorption performance for methane through their adjustable pore size, rich active sites and ultra-high specific surface area, and can be used for methane capture and storage.

[0005] Polymer nanocomposites are a new type of composite materials formed by combining polymers and nanomaterials, which have many advantages and have attracted great attention from researchers. By adding carbon nanotubes, nanoclay and other nanomaterials, polymer nanocomposites can have good flexibility and extremely high strength and modulus in mechanical properties, reduce brittle fracture of materials, and withstand greater external force and stress; by adding graphene, carbon nanotubes and other nanomaterials, the thermal conductivity and stable heat resistance of the material are good in thermal performance, the heat dissipation speed is accelerated, and the use temperature range of the material is widened; by adding nanometal particles, carbon nanotubes and other conductive nanomaterials, the material has high dielectric constant and certain electrical conductivity in electrical performance.

[0006] By combining MOFs and polymer nanocomposites, the characteristics of MOFs and polymers can be combined to exhibit many advantages. For example, after combining the two, MOFs can be uniformly dispersed in the polymer matrix as a reinforcing phase, acting as a physical crosslinking point, limiting the movement of polymer chains, thereby improving the mechanical properties of the composite material such as hardness, modulus and tensile strength. SUMMARY

[0007] The main purpose of the present application is to prepare a nanofiber membrane with low resistance and methane preferential permeation, which can simultaneously capture methane gas and filter dust, in order to solve the problems of poor efficiency and poor capacity of existing dust removal and CH4 gas capture materials.

[0008] To achieve the above object, the present application provides a low resistance and low consumption methane preferential permeation nanofiber membrane and a preparation method and application thereof. According to a first aspect of the present application, a preparation method of the low resistance and low consumption methane preferential permeation nanofiber membrane is provided, comprising the following steps: Step S1, preparation of cellulose acetate spinning dope: cellulose acetate is dissolved in a cellulose acetate dissolving agent to prepare cellulose acetate spinning dope; Step S2, preparation of functional spinning solution: β-cyclodextrin is mixed with an alkali solution for activation treatment, and an etherification modification reagent is added for etherification modification treatment, and then mixed with the cellulose acetate spinning dope obtained in Step S1 to prepare a functional spinning solution; Step S3, preparation of MOF nanosheet: metal salt, organic ligand and adjusting agent are uniformly dissolved in a metal coordination promoter to form a MOF precursor solution, which is put into a reaction kettle for further reaction to prepare a MOF nanosheet; Step S4, preparation of low resistance and low consumption methane preferential permeation nanofiber membrane: the functional spinning solution obtained in Step S2 and the MOF nanosheet obtained in Step S3 are prepared into a low resistance and low consumption methane preferential permeation nanofiber membrane through a spinning technology.

[0009] Preferably, the cellulose acetate dissolving agent in Step S1 is one or more of dichloromethane, acetone, chloroform, ethyl acetate, N,N-dimethylformamide, ethanol, methanol, and triethylamine, and the concentration of the cellulose acetate in the cellulose acetate spinning dope is 1-30 wt%.

[0010] Preferably, the alkali solution used in Step S2 is one or more of sodium hydroxide aqueous solution, sodium carbonate aqueous solution, sodium bicarbonate aqueous solution, and potassium hydroxide aqueous solution, and the mass fraction of the alkali solution ranges from 5 to 20 wt%.

[0011] Preferably, the etherification modification reagent used in Step S2 is one or more of chloromethane, ethylene oxide, bromoethane, and propylene oxide, and the molar ratio of the etherification modification reagent to β-cyclodextrin is 1:5-5:2.

[0012] Preferably, the metal salt in Step S3 is one or more of zinc nitrate hexahydrate, cadmium nitrate, cadmium sulfate, cadmium chloride, zinc nitrate, zinc acetate, aluminum nitrate, aluminum trichloride, and aluminum sulfate, the organic ligand is one or more of triphenylmethane tricarboxylic acid, terephthalic acid, 4,4',4''-benzenetriol tribenzoic acid, triethylamine, 4,4',4'',4''',4'''',4'''''-(9,10-dihydro-9,10-(1,2)benzanthracene-2,3,6,7,14,15-hexyl)hexabenzoic acid-2 (H6PET-2), and 1,4-benzenedicarboxylic acid, and the molar ratio of the organic ligand to the metal salt is 1:1-1:6.

[0013] Preferably, the adjusting agent in step S3 is one or more of benzoic acid, methanol, ethanol, phenylacetic acid, p-toluenic acid, salicylic acid, and the molar ratio of the adjusting agent to the metal salt is 1:1-1:5.

[0014] Preferably, the metal coordination promoter in step S3 is one or more of N,N-dimethylformamide, methanol, anhydrous methanol, dimethyl sulfoxide, acetone, ethanol, acetonitrile, diethylformamide, and the volume ratio of the adjusting agent to the metal coordination promoter is 1:1-1:7.

[0015] Preferably, the reaction conditions for preparing the MOF nanosheet in step S3 are that the reaction temperature is 100-150°C and the reaction time is 12-24 h.

[0016] Preferably, the average thickness of the MOF nanosheet obtained in step S3 is 100-500 nm.

[0017] Preferably, the spinning technique in step S4 is one or more of parallel electrospinning, coaxial electrospinning, wet spinning, centrifugal spinning, and melt spinning.

[0018] To achieve the above-mentioned purpose, according to a second aspect of the present application, the present application further provides a nanofiber membrane obtained by the above-mentioned preparation method.

[0019] Preferably, the average diameter of the nanofiber membrane is 169-298 nm, the specific surface area is 198 m 2 / g-339 m 2 / g, and the elongation at break is 14.3%-20%.

[0020] To achieve the above-mentioned purpose, according to a third aspect of the present application, the present application further provides an application of the above-mentioned nanofiber membrane in a purification material for simultaneously selectively capturing methane gas and filtering dust.

[0021] The present application has the following beneficial effects: (1) The preparation method of the low-resistance methane preferential permeation nanofiber membrane of the present application uses a cellulose acetate / β-cyclodextrin composite nanofiber membrane as a template-induced controllable synthesis technology, introduces MOF nanosheets having an adsorption effect on methane, and performs functional modification to obtain a nanofiber membrane with excellent mechanical properties and containing multiple functions. (2) The interaction between the β-cyclodextrin and the cellulose acetate molecular chain through hydrogen bonds and the like makes the binding ability between the molecular chains stronger, improves the tensile strength and other mechanical properties of the composite system, and improves the flexibility and durability of the membrane. (3) The introduction of the MOF nanosheet as a functional component increases the selective adsorption capacity of the membrane for methane and improves the comprehensive performance of the composite membrane. (4) The various components synergize with each other to obtain excellent filtration performance (PM0.3 and PM 2.5 The low-resistance methane preferential permeation nanofiber membrane has high filtration efficiency (higher than 96.6%) and good mechanical properties, and has excellent methane gas capturing capacity (CH4 adsorption capacity is higher than 4.8 mmol / g), and can ideally solve the problems of synergistic capture of methane and dust filtration, and is a high-performance wide-range purification material.

[0022] The low-resistance methane preferential permeation nanofiber membrane has high filtration efficiency (higher than 96.6%) and good mechanical properties, and has excellent methane gas capturing capacity (CH4 adsorption capacity is higher than 4.8 mmol / g), and can ideally solve the problems of synergistic capture of methane and dust filtration, and is a high-performance wide-range purification material. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0024] Figure 1 is a process flowchart of the method of the present application.

[0025] Figure 2 is a scanning electron microscope image of the low-resistance methane preferential permeation nanofiber membrane in Example 1. DETAILED DESCRIPTION

[0026] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions of the present application will be described in detail below. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. The present application will be described in detail below in combination with the embodiments.

[0027] As Figure 1 shown, the present application provides a preparation method of a low-resistance methane preferential permeation nanofiber membrane, which comprises the following steps:

[0028] Step S11, preparation of cellulose acetate spinning dope: cellulose acetate is dissolved in acetone (the concentration of cellulose acetate in the cellulose acetate spinning dope is 5 wt%) to prepare cellulose acetate spinning dope;

[0029] Step S12, preparation of a functional spinning solution: β-cyclodextrin is mixed with an aqueous sodium hydroxide solution for activation treatment (the mass fraction of the aqueous sodium hydroxide solution is 10 wt%), and chloromethane, an etherification modification reagent, is added for etherification modification treatment and separation and purification (the molar ratio of chloromethane to β-cyclodextrin is 1:5), and then mixed with the cellulose acetate spinning dope obtained in step S1 to prepare a functional spinning solution;

[0030] Step S13, preparation of MOF nanosheets: MOF nanosheet precursor solution is prepared (the molar ratio of zinc nitrate to triphenylmethane tricarboxylic acid is 1:1, the molar ratio of methanol to zinc nitrate is 1:1, and the volume ratio of N,N-dimethylformamide to methanol is 5:1), centrifuged and dried after being treated at 120℃ for 12 h in a high-pressure reaction kettle to obtain MOF-177 nanosheets (with an average thickness of 500 nm);

[0031] Step S14, preparation of a low-resistance methane preferential permeation nanofiber membrane: the functional spinning solution obtained in step S12 and the MOF nanosheets obtained in step S13 are synthesized and modified by parallel electrospinning (flow rate 5 mL / h, temperature 25±5℃, voltage 30 KV), and dried to obtain a low-resistance methane preferential permeation nanofiber membrane (with a specific surface area of 339 m 2 / g, an average fiber diameter of 169 nm, and an elongation at break of 20%).

[0032] The embodiment 2 of the present application provides a preparation method of a low-resistance methane preferential permeation nanofiber membrane, including the following steps:

[0033] Step S21, preparation of a cellulose acetate spinning dope: cellulose acetate is dissolved in dichloromethane, a cellulose acetate dissolving agent (the concentration of cellulose acetate in the cellulose acetate spinning dope is 5 wt%) to prepare a cellulose acetate spinning dope;

[0034] Step S22, preparation of a functional spinning solution: β-cyclodextrin is mixed with an aqueous sodium hydroxide solution for activation treatment (the mass fraction of the aqueous sodium hydroxide solution is 10 wt%), and ethylene oxide, an etherification modification reagent, is added for etherification modification treatment and separation and purification (the molar ratio of ethylene oxide to β-cyclodextrin is 2:1), and then mixed with the cellulose acetate spinning dope obtained in step S1 to prepare a functional spinning solution;

[0035] Step S23, preparation of MOF nanosheets: MOF nanosheet precursor solution is prepared (the molar ratio of terephthalic acid to zinc nitrate hexahydrate is 1:2, the molar ratio of methanol to zinc nitrate hexahydrate is 1:1, and the volume ratio of N,N-dimethylformamide to methanol is 1:1), centrifuged and dried after being treated at 100℃ for 24 h in a stainless steel reaction kettle to obtain MOF-5 nanosheets (with an average thickness of 200 nm);

[0036] Step S24, preparation of low resistance and low consumption methane preferential permeation nanofiber membrane: the functional spinning solution obtained in step S22 and the MOF nanosheet obtained in step S23 are synthesized and modified by coaxial electrospinning (core layer flow rate 0.5 mL / h, shell layer flow rate 2 mL / h, voltage 20 KV), and dried to obtain a low resistance and low consumption methane preferential permeation nanofiber membrane (specific surface area 286 m 2 / g, average fiber diameter 233 nm, elongation at break 18.5%).

[0037] Embodiment 3 of the present application provides a preparation method of a low resistance and low consumption methane preferential permeation nanofiber membrane, comprising the following steps:

[0038] Step S31, preparation of cellulose acetate spinning solution: cellulose acetate is dissolved in chloroform (the concentration of cellulose acetate in the cellulose acetate spinning solution is 5 wt%) to prepare a cellulose acetate spinning solution;

[0039] Step S32, preparation of functional spinning solution: β-cyclodextrin is mixed with sodium bicarbonate aqueous solution for activation treatment (the mass fraction of sodium bicarbonate aqueous solution is 10 wt%), etherification modification reagent bromoethane is added for etherification modification treatment and separation and purification (the molar ratio of bromoethane to β-cyclodextrin is 1:2), and then mixed with the cellulose acetate spinning solution obtained in step S1 to prepare a functional spinning solution;

[0040] Step S33, preparation of MOF nanosheet: MOF nanosheet precursor solution is prepared (the molar ratio of H6PET-2 to aluminum chloride hexahydrate is 1:3, the molar ratio of methanol to aluminum chloride hexahydrate is 1:1, and the volume ratio of N,N-dimethylformamide to methanol is 1:1), centrifuged and dried after being treated at 150℃ for 24 h in a stainless steel reaction kettle with a polytetrafluoroethylene liner to obtain NU-1501 nanosheet (average thickness 300 nm);

[0041] Step S34, preparation of low resistance and low consumption methane preferential permeation nanofiber membrane: the functional spinning solution obtained in step S32 and the MOF nanosheet obtained in step S33 are synthesized and modified by wet spinning (flow rate 0.5 m / s, stretching speed 10 m / min, coagulation bath temperature 20℃), and dried to obtain a low resistance and low consumption methane preferential permeation nanofiber membrane (specific surface area 231 m 2 / g, average fiber diameter 279 nm, elongation at break 16.7%).

[0042] Embodiment 4 of the present application provides a preparation method of a low resistance and low consumption methane preferential permeation nanofiber membrane, comprising the following steps:

[0043] Step S41, preparation of cellulose acetate spinning dope: cellulose acetate was dissolved in ethyl acetate (the concentration of cellulose acetate in the cellulose acetate spinning dope was 5 wt%) to prepare the cellulose acetate spinning dope;

[0044] Step S42, preparation of functional spinning solution: β-cyclodextrin was mixed with sodium bicarbonate aqueous solution for activation treatment (the mass fraction of sodium bicarbonate aqueous solution was 10 wt%), and etherification modifier propylene oxide was added for etherification modification treatment and separation and purification (the molar ratio of propylene oxide to β-cyclodextrin was 5:2), and then mixed with the cellulose acetate spinning dope obtained in step S1 to prepare the functional spinning solution;

[0045] Step S43, preparation of MOF nanosheet: MOF nanosheet precursor solution was prepared (the mass ratio of zinc nitrate hexahydrate to 1,4-benzenedicarboxylic acid was 3:1, the molar ratio of methanol to zinc nitrate hexahydrate was 1:5, and the volume ratio of diethylformamide to methanol was 2:1), and was placed in a glass jar with a Teflon lining and treated at 105℃ for 12.5 h to obtain SNU-70 nanosheet (the average thickness was 400 nm);

[0046] Step S44, preparation of low-resistance methane preferential permeation nanofiber membrane: the functional spinning solution obtained in step S42 and the MOF nanosheet obtained in step S43 were synthesized and modified by centrifugal spinning (centrifugal speed 1000 rpm / min, receiving distance 15 cm, temperature 25±5℃), and were dried to obtain the low-resistance methane preferential permeation nanofiber membrane (the specific surface area was 198 m 2 / g, the average fiber diameter was 298 nm, and the elongation at break was 14.3%).

[0047] The low resistance and low consumption methane preferential permeation nanofiber membrane was prepared by the method of Example 1. The difference is that the etherification modification of β-cyclodextrin is not used in this example, and β-cyclodextrin is directly added to the cellulose acetate spinning solution to prepare a functional spinning solution. Specifically, the cellulose acetate is dissolved in the cellulose acetate solvent acetone (the concentration of cellulose acetate in the cellulose acetate spinning solution is 5 wt%), to prepare a cellulose acetate spinning solution; β-cyclodextrin is added to the cellulose acetate spinning solution obtained in the preceding step to prepare a functional spinning solution; a MOF nanosheet precursor solution (the molar ratio of zinc nitrate to triphenylmethane tricarboxylic acid is 1:1, the molar ratio of methanol to zinc nitrate is 1:1~1:5, and the volume ratio of N,N-dimethylformamide to methanol is 5:1) is prepared, and after being treated at 120°C for 12 h in a high-pressure reaction kettle and centrifuged and dried, MOF-177 nanosheets (with an average thickness of 500 nm) are obtained; the obtained functional spinning solution and the obtained MOF nanosheets are synthesized and modified by parallel electrospinning (flow rate 5 mL / h, temperature 25±5°C, voltage 30 KV), and dried to obtain a low resistance and low consumption methane preferential permeation nanofiber membrane (the specific surface area is 58 m 2 / g, the average fiber diameter is 264 nm, and the elongation at break is 6.8%).

[0048] The low resistance and low consumption methane preferential permeation nanofiber membrane was prepared by the method of Example 1. The difference is that the etherification modification of β-cyclodextrin is not used in this example, and β-cyclodextrin is directly added to the cellulose acetate spinning solution to prepare a functional spinning solution. Specifically, the cellulose acetate is dissolved in the cellulose acetate solvent acetone (the concentration of cellulose acetate in the cellulose acetate spinning solution is 5 wt%), to prepare a cellulose acetate spinning solution; β-cyclodextrin is added to the cellulose acetate spinning solution obtained in the preceding step to prepare a functional spinning solution; a MOF nanosheet precursor solution (the molar ratio of zinc nitrate to triphenylmethane tricarboxylic acid is 1:1, the molar ratio of methanol to zinc nitrate is 1:1~1:5, and the volume ratio of N,N-dimethylformamide to methanol is 5:1) is prepared, and after being treated at 120°C for 12 h in a high-pressure reaction kettle and centrifuged and dried, MOF-177 nanosheets (with an average thickness of 500 nm) are obtained; the obtained functional spinning solution and the obtained MOF nanosheets are synthesized and modified by parallel electrospinning (flow rate 5 mL / h, temperature 25±5°C, voltage 30 KV), and dried to obtain a low resistance and low consumption methane preferential permeation nanofiber membrane (the specific surface area is 58 m 2 / g, the average fiber diameter is 264 nm, and the elongation at break is 6.8%).

[0049] Example 3. Preparation of low resistance methane preferential permeation nanofiber membrane. The low resistance methane preferential permeation nanofiber membrane was prepared by using the method of Example 3. The difference is that the β-cyclodextrin was not used in this example. Specifically, the cellulose acetate spinning dope was prepared by dissolving cellulose acetate in acetone (the concentration of cellulose acetate in the cellulose acetate spinning dope was 5%); the MOF nanosheet precursor solution was prepared (the molar ratio of zinc nitrate to triphenylmethane tricarboxylic acid was 1:1, the molar ratio of methanol to aluminum chloride hexahydrate was 1:1, and the volume ratio of N,N-dimethylformamide to methanol was 5:1), which was placed in a high-pressure reaction kettle and treated at 120°C for 12 h, then centrifuged and dried to obtain MOF-177 nanosheets (the average thickness was 500 nm); the functional spinning dope obtained in step S12 and the MOF nanosheets obtained in step S13 were synthesized and modified by parallel electrospinning (flow rate 5 mL / h, temperature 25±5°C, voltage 30 KV), and then dried to obtain a low resistance methane preferential permeation nanofiber membrane (the specific surface area was 57 m 2 / g, the average fiber diameter was 302 nm, and the elongation at break was 5.9%).

[0050] Structural characterization and performance test

[0051] Scanning electron microscope observation: the microstructure of the low resistance methane preferential permeation nanofiber membrane was observed by a field emission scanning electron microscope (model JSM-7900F, Japan Electron). Figure 2 .

[0052] Mechanical property test: the obtained low resistance methane preferential permeation nanofiber membrane was cut to obtain a tensile sample, and the mechanical properties of the composite material were tested by using a universal testing machine (model 5982, Instron Corporation, USA) according to the plastic tensile property test standard in ASTM D638-2003 of the American Society for Testing Materials. At least 3 parallel test samples were guaranteed for each group, and the average value was taken as the result.

[0053] Filtering performance test: the air filtering performance of the fiber membrane (area 25 cm 2 ) was tested by using a CLJ-3016 type laser dust particle counter (Shenzhen Huashengchang Machinery Experiment Co., Ltd.), and the gas flow rate was set to 85 L / min. At least 3 different positions of the filter membrane were tested for each group, and the average value was taken as the result.

[0054] Methane adsorption performance test: CH4 was adsorbed by using a gas adsorption instrument (ASAP 2020, Micromeritics Corporation, USA). High-purity gas CH4 (99.999%) was used for adsorption measurement, and helium (99.999%) was used for free space measurement. Isothermal adsorption was carried out at 273 K (ice water bath) and 298 K (water bath).

[0055] Experimental results:Figure 1 The technical roadmap of the low resistance and methane preferential permeation nanofiber membrane obtained in Example 1 is shown.

[0056] Figure 2 The scanning electron microscope image of the low resistance and methane preferential permeation nanofiber membrane in Example 1 is shown, and it can be seen that the MOF is dispersed on the composite fiber membrane, and the target product is ideal.

[0057] Table 1 compares the specific surface area, average fiber diameter, elongation at break, tensile strength, methane adsorption capacity and filtration efficiency of the low resistance and methane preferential permeation nanofiber membranes obtained in the examples and comparative examples.

[0058] Table 1

[0059]

[0060] Examples 1-4 have a higher specific surface area (198 m 2 / g~339 m 2 / g) and a finer fiber diameter (169 nm~298 nm), because the cellulose acetate is modified with β-cyclodextrin to obtain the permeation nanofiber membrane; the specific surface area of Comparative Example 1 is only 58 m 2 / g, and the fiber diameter is 264 nm, because the cellulose acetate is not modified with β-cyclodextrin, and the permeation nanofiber membrane is directly prepared.

[0061] The dust filtration and methane gas capture capacity of the low resistance and methane preferential permeation nanofiber membrane are closely related to its specific surface area, fiber size and mechanical properties, and the dust (PM 0.3 and PM 2.5 ) filtration efficiency of the nanofiber permeation membrane of Examples 1-4 with a larger specific surface area, higher gas permeability and good tensile properties is all above 96.6%, and the methane gas (CH4) adsorption capacity is all above 4.8 mmol / g, showing good dust and methane gas filtration capacity. Among them, Example 1 with the largest specific surface area and the smallest fiber size performs extremely well in performance testing, and the filtration efficiency of PM 0.3 and PM 2.5 is 99.6% and 99.8% respectively, and the CH4 adsorption capacity is 6.0 mmol / g, which is much higher than that of Comparative Examples 1-3 with low specific surface area and coarse fiber diameter (CH4 adsorption capacity is less than 4.8 mmol / g).

[0062] The above merely describes specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims. In addition, it should be noted that, in the above specific embodiments, various specific technical features can be combined in any appropriate manner without contradiction, in order to avoid unnecessary repetition, the present application will not further describe various possible combinations. Furthermore, various different embodiments of the present application can also be combined in any manner, as long as it does not violate the idea of the present application, it should also be considered as disclosed by the present application.

Claims

1. A method for preparing a low resistance methane preferential permeation nanofiber membrane, characterized in that, The method comprises the following steps: Step S1, dissolving cellulose acetate in a cellulose acetate solvent to prepare a cellulose acetate spinning solution; Step S2, mixing β-cyclodextrin with an alkali solution for activation treatment, adding an etherification modification reagent for etherification modification treatment, and then mixing with the cellulose acetate spinning solution obtained in step S1 to prepare a functional spinning solution; Step S3, dissolving a metal salt, an organic ligand and a regulator in a metal coordination promoter to react and prepare MOF nanosheets; Step S4, preparing a low-resistance methane preferential permeation nanofiber membrane by spinning technology through the functional spinning solution obtained in step S2 and the MOF nanosheets obtained in step S3.

2. The method of claim 1, wherein the low resistance loss methane preferential permeation nanofiber membrane is prepared by the steps of: The cellulose acetate solvent in step S1 is one or more of dichloromethane, acetone, chloroform, ethyl acetate, N,N-dimethylformamide, ethanol, methanol, and triethylamine, and the concentration of the cellulose acetate in the cellulose acetate spinning solution is 1-30 wt%.

3. The method of claim 1, wherein the low resistance loss methane preferential permeation nanofiber membrane is prepared by the steps of: The alkali solution in step S2 is one or more of sodium hydroxide aqueous solution, sodium carbonate aqueous solution, sodium bicarbonate aqueous solution, and potassium hydroxide aqueous solution, and the mass fraction of the alkali solution is 5-20 wt%.

4. The method of claim 1, wherein the low methanol permeation preferential nanofiber membrane is prepared by the steps of: The etherification modification reagent in step S2 is one or more of chloromethane, ethylene oxide, bromoethane, and propylene oxide, and the molar ratio of the etherification modification reagent to β-cyclodextrin is 1:5-5:

2.

5. The method of claim 1, wherein the low methanol permeation preferential nanofiber membrane is prepared by the steps of: The metal salt in step S3 is one or more of zinc nitrate hexahydrate, cadmium nitrate, cadmium sulfate, cadmium chloride, zinc nitrate, zinc acetate, aluminum nitrate, aluminum trichloride, and aluminum sulfate; the organic ligand is one or more of triphenylmethane tricarboxylic acid, terephthalic acid, 4,4',4''-benzenetriol tricarboxylic acid, triethylamine, H6PET-2, and 1,4-benzenedicarboxylic acid; and the molar ratio of the organic ligand to the metal salt is 1:1-1:

6.

6. The method of producing a low draw methane preferring nanofiber membrane according to claim 1, wherein, The regulator in step S3 is one or more of benzoic acid, methanol, ethanol, phenylacetic acid, p-methylbenzoic acid, and salicylic acid, and the molar ratio of the regulator to the metal salt is 1:1-1:

5.

7. The method of claim 1, wherein the low methanol permeation preferential nanofiber membrane is prepared by the steps of: The metal coordination promoter in step S3 is one or more of N,N-dimethylformamide, methanol, anhydrous methanol, dimethyl sulfoxide, acetone, ethanol, acetonitrile, and diethylformamide, and the volume ratio of the regulator to the metal coordination promoter is 1:1-1:7; and the reaction conditions in step S3 are that the reaction temperature is 100-150℃ and the reaction time is 12-24 h.

8. The method of claim 1, wherein the low methanol permeation preferential nanofiber membrane is prepared by the steps of: The spinning technology in step S4 is one or more of parallel electrospinning, coaxial electrospinning, wet spinning, centrifugal spinning, and melt spinning.

9. A nanofiber membrane prepared by the method of claim 1-8.

10. The application of the nanofiber membrane of claim 9 in a purification material for simultaneously selectively capturing methane gas and filtering dust.

Images