Pervaporation composite membranes, methods of making and using the same

Abstract

The application discloses a pervaporation composite membrane and a preparation method and application thereof, and belongs to the technical field of membrane separation. The pervaporation composite membrane comprises a porous substrate, an intermediate film layer and a separation film layer which are arranged in sequence. The average pore diameter of the porous substrate is greater than or equal to 250 nm. The average pore diameter and porosity of the intermediate film layer are both smaller than the average pore diameter and porosity of the porous substrate, and the intermediate film layer has an organic affinity characteristic. The separation film layer has a hydrophobic characteristic and an organic selective permeation characteristic. The intermediate film layer is beneficial to improving the problems of pore penetration in a solid-liquid interface preparation process, is not prone to spreading, and the thickness of the separation film layer is uncontrollable, and can ensure the defect-free preparation of the separation film layer, and is beneficial to improving the permeability of the pervaporation composite membrane to organic matters.

Description

Technical Field

[0001] This invention relates to the field of membrane separation technology, and in particular to pervaporation composite membranes, their preparation methods, and applications. Background Technology

[0002] Pervaporation technology is widely used for low-concentration ethanol concentration and high-concentration ethanol dehydration due to its advantages such as low energy consumption and easy coupling with fermentation. Generally, such pervaporation composite membranes used for ethanol treatment are called pervaporation-preferred alcohol permeation membranes.

[0003] Pervaporation-preferred alcohol permeation membranes are typically composite membranes, comprising a porous substrate and a separation membrane layer attached to the porous substrate. The porous substrate has a pore structure, which means that when the separation membrane layer is prepared on it, the polymer material corresponding to the separation membrane layer will partially permeate into the pore structure of the porous substrate. This not only causes defects in the separation membrane layer but also increases the mass transfer resistance of the pervaporation-preferred alcohol permeation membrane, thereby affecting the permeation performance of the composite membrane. Summary of the Invention

[0004] In view of this, the present invention provides a pervaporation composite membrane, its preparation method and application, which can solve the technical problems existing in related technologies.

[0005] Specifically, the following technical solutions are included:

[0006] On the one hand, a pervaporation composite membrane is provided, the pervaporation composite membrane comprising: a porous substrate (1), an intermediate membrane layer (2), and a separation membrane layer (3) arranged in sequence;

[0007] The average pore size of the porous substrate (1) is greater than or equal to 250 nm;

[0008] The average pore size and porosity of the intermediate membrane layer (2) are both smaller than those of the porous substrate, and the intermediate membrane layer has organic affinity characteristics.

[0009] The separation membrane layer (3) has hydrophobic characteristics and selective permeability to organic matter.

[0010] In some possible implementations, the intermediate film layer (2) is a polyether block amide film, and the intermediate film layer material includes at least one of polyether block amide PEBA2533, polyether block amide PEBA3533, polyether block amide PEBA4033, and polyether block amide PEBA1657.

[0011] In some possible implementations, the separation membrane layer comprises a polydimethylsiloxane membrane.

[0012] In some possible implementations, the porous substrate is selected from one of the following: polysulfone membrane, polyacrylonitrile membrane, polyvinylidene fluoride membrane, polytetrafluoroethylene membrane, polypropylene membrane, polyethylene membrane, polyethersulfone membrane, polybenzimidazole membrane, and cellulose acetate membrane.

[0013] In some possible implementations, the thickness of the porous substrate is 100µm-150µm;

[0014] The thickness of the intermediate film layer is 2µm-7µm;

[0015] The thickness of the separation membrane is 1µm-10µm.

[0016] On the other hand, a method for preparing the above-mentioned pervaporation composite membrane is provided, comprising the following steps: (a) attaching an intermediate membrane layer to a porous substrate to obtain a composite membrane intermediate;

[0017] (b) A separation membrane layer is prepared on the composite membrane intermediate, such that the separation membrane layer is attached to the intermediate membrane layer, to obtain the pervaporation composite membrane.

[0018] In some possible implementations, step (a) of attaching the intermediate membrane layer to the porous substrate to obtain a composite membrane intermediate includes:

[0019] A casting solution for the intermediate membrane layer is prepared by dropping the casting solution onto the surface of a liquid, causing the casting solution to form a film on the liquid surface, thus obtaining a wet membrane of the intermediate membrane layer. The wet membrane of the intermediate membrane layer is then removed and attached to the porous substrate, and dried to obtain the composite membrane intermediate.

[0020] In some possible implementations, the liquid is obtained from at least one of the following liquids: water, ethanol, and methanol.

[0021] In some possible implementations, step (b) of preparing a separation membrane layer on the composite membrane intermediate, such that the separation membrane layer is attached to the intermediate membrane layer, includes:

[0022] A separation membrane casting solution is prepared, which is then placed on the intermediate membrane layer of the composite membrane intermediate. A coating process is then performed to form a wet membrane of the separation membrane layer on the intermediate membrane layer. The composite membrane intermediate with the wet membrane of the separation membrane layer is dried to remove the solvent from the wet membrane of the separation membrane layer. Then, it is placed in a humid environment and left to stand for a period of time. After being dried again, the pervaporation composite membrane is obtained.

[0023] Furthermore, the present invention also provides the application of any of the above-mentioned pervaporation composite membranes in pervaporation.

[0024] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following:

[0025] The pervaporation composite membrane provided in this invention, by using a porous substrate with an average pore size greater than or equal to 250 nm, helps reduce the mass transfer resistance of the pervaporation composite membrane during the pervaporation process. By adding an intermediate membrane layer between the porous substrate and the separation membrane layer, the average pore size and porosity of the intermediate membrane layer are both smaller than those of the porous substrate. This helps improve problems such as easy permeation (i.e., alleviating pore permeation), uneven spreading of the separation layer, and uncontrollable thickness of the separation membrane layer during solid-liquid interface preparation. It also improves the spreadability of the fluid on the solid surface and ensures defect-free preparation of the separation membrane layer. The three-layer structure of this invention results in a smooth and flat cross-sectional structure of the separation membrane layer with easily controllable thickness. Furthermore, the intermediate membrane layer has organic affinity characteristics, which helps improve the permeability of the pervaporation composite membrane to organic substances. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 A photograph of the pervaporation composite membrane provided in Example 1;

[0028] Figure 2 A photograph of the pervaporation composite membrane provided for Comparative Example 1;

[0029] Figure 3 A schematic diagram showing the spreading effect of the pervaporation composite membrane provided in Example 1 and Comparative Example 1;

[0030] Figure 4 SEM scan of a cross section of the pervaporation composite membrane provided in Example 1;

[0031] Figure 5 SEM scan of the cross section of the pervaporation composite membrane provided for Comparative Example 1;

[0032] Figure 6 SEM scan of the cross section of the pervaporation composite membrane provided for Comparative Example 2;

[0033] Figure 7 A planar scan image of silicon in the pervaporation composite membrane provided in Example 1;

[0034] Figure 8A planar scan image of fluorine in the pervaporation composite membrane provided in Example 1;

[0035] Figure 9 A planar scan image of silicon in the pervaporation composite membrane provided for Comparative Example 1;

[0036] Figure 10 A planar scan image of fluorine in the pervaporation composite membrane provided for Comparative Example 1.

[0037] Figure 11 The surface electron microscope scan image of the pervaporation composite membrane in Comparative Example 1 was obtained;

[0038] Figure 12 This is a schematic diagram of the pervaporation composite membrane of this application.

[0039] Porous substrate (1), intermediate membrane layer (2), separation membrane layer (3).

[0040] The accompanying drawings have illustrated specific embodiments of the invention, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0041] On one hand, embodiments of the present invention provide a pervaporation composite membrane, which includes: a porous substrate, an intermediate membrane layer, and a separation membrane layer arranged in sequence; wherein, the average pore size of the porous substrate is greater than or equal to 250 nm; the average pore size and porosity of the intermediate membrane layer are both smaller than the average pore size and porosity of the porous substrate, and the intermediate membrane layer has organic affinity characteristics; the separation membrane layer has hydrophobic characteristics and organic selective permeability characteristics.

[0042] The pervaporation composite membrane provided in this invention, by using a porous substrate with an average pore size greater than or equal to 250 nm, helps to reduce the mass transfer resistance of the pervaporation composite membrane during the pervaporation process. By adding an intermediate membrane layer between the porous substrate and the separation membrane layer, on the one hand, the average pore size and porosity of the intermediate membrane layer are both smaller than those of the porous substrate. This helps to improve problems such as easy permeation (i.e., alleviating pore permeation) and uncontrollable separation membrane thickness during the solid-liquid interface preparation process, and also helps to improve the spreadability of the fluid on the solid surface, ensuring defect-free preparation of the separation membrane layer. On the other hand, the intermediate membrane layer has organic affinity characteristics, which helps to improve the permeability of the pervaporation composite membrane to organic matter.

[0043] In some examples, the pervaporation composite membrane provided in the embodiments of the present invention can be a pervaporation-preferential alcohol permeation membrane.

[0044] In some examples, the materials suitable for the intermediate membrane layer of the pervaporation composite membrane of the present invention include at least one of polyether block amide PEBA2533, polyether block amide PEBA3533, polyether block amide PEBA4033, and polyether block amide PEBA1657.

[0045] Based on the physical properties of polyether block amide (PEBA) mentioned above, it has an affinity for organic matter and is easy to prepare into a relatively dense porous structure.

[0046] In some examples, the separation membrane layer includes a polydimethylsiloxane membrane. As a separation membrane layer, the polydimethylsiloxane membrane is hydrophobic and can provide good selectivity for the separation of water and organic matter, such as excellent selectivity for alcohols.

[0047] In some examples, the porous substrate is a hydrophobic membrane with a porous structure. The porous structure satisfies the requirement that the porous substrate can be an ultrafiltration membrane, microfiltration membrane, etc. The average pore size and porosity of the porous substrate are greater than the average pore size and porosity of the intermediate membrane layer and the separation membrane layer. It is selected from one of the following: polysulfone membrane, polyacrylonitrile membrane, polyvinylidene fluoride membrane, polytetrafluoroethylene membrane, polypropylene membrane, polyethylene membrane, polyethersulfone membrane, polybenzimidazole membrane, and cellulose acetate membrane.

[0048] In some implementations, the thickness of the porous substrate is 100um-150um, including but not limited to 100um, 105um, 110um, 115um, 120um, 125um, 130um, 135um, 140um, 145um, 150um, etc.

[0049] The thickness of the intermediate film layer is 2um-7um, including but not limited to 2um, 3um, 4um, 5um, 6um, 7um, etc. The lower thickness of the intermediate film layer is beneficial to reduce the mass transfer path and reduce resistance.

[0050] The thickness of the separation membrane layer is 1um-10um, including but not limited to 1um, 2um, 3um, 4um, 5um, 6um, 7um, 8um, 9um, 10um, etc. A lower thickness of the separation membrane layer can reduce the mass transfer path and reduce resistance.

[0051] In summary, the pervaporation composite membrane provided in this invention improves upon a series of problems, such as polymer seepage into the porous substrate, uneven spreading leading to uneven thickness, and uncontrollable defects, by introducing an intermediate membrane layer between the porous substrate and the separation membrane layer. Furthermore, the intermediate membrane layer is made of polyether block amide, which exhibits excellent permeability to alcohol-water systems, preventing significant mass transfer resistance and ensuring the preferential alcohol permeation performance of the pervaporation composite membrane.

[0052] On the other hand, embodiments of the present invention also provide a method for preparing a pervaporation composite membrane, wherein the pervaporation composite membrane is as described in any of the above descriptions.

[0053] The preparation method of this pervaporation composite membrane includes:

[0054] Step S1: Attach the intermediate membrane layer to the porous substrate to obtain the composite membrane intermediate.

[0055] Step S2: Prepare a separation membrane layer on the composite membrane intermediate, so that the separation membrane layer is attached to the intermediate membrane layer to obtain a pervaporation composite membrane.

[0056] In some examples, in step S1, the intermediate membrane layer is attached to a porous substrate to obtain a composite membrane intermediate, including:

[0057] Step S11: Prepare intermediate film casting solution by dropping the intermediate film casting solution onto the liquid surface, so that the intermediate film casting solution forms a film on the water surface, and a wet film of intermediate film layer is obtained.

[0058] The intermediate film casting solution includes intermediate film raw materials and solvents. Taking the intermediate film material selected from polyether block amide PEBA2533, polyether block amide PEBA3533, polyether block amide PEBA4033, and polyether block amide PEBA1657 as an example, the intermediate film raw material is polyether block amide, and the solvent used can be a mixture of n-butanol and isopropanol. For example, the mass ratio of n-butanol to isopropanol can be 2:1.

[0059] For example, a polyether block amide is dissolved in a solvent with a mass ratio of n-butanol:isopropanol = 2:1 to prepare an intermediate film casting solution with a solute mass percentage of 7%. The solution is stirred in a water bath at 80°C until the polyether block amide is completely dissolved, yielding the intermediate film casting solution. The intermediate film casting solution is then allowed to stand in a forced-air drying oven to remove bubbles.

[0060] In step S11, the liquid surface is obtained by at least one of the following liquids: water, ethanol, and methanol.

[0061] For example, a specific amount of intermediate film casting solution (e.g., 100 μL-500 μL) is dropped onto the liquid surface. After the film floats on the liquid surface and forms a film, it can be removed to obtain a wet film of the intermediate film.

[0062] Step S12: Take out the wet membrane of the intermediate membrane layer and attach it to the porous substrate. After drying, the composite membrane intermediate is prepared.

[0063] For example, the drying process includes a first drying process and a second drying process performed sequentially, wherein the drying temperature of the first drying process is 30℃-50℃ and the drying temperature of the second drying process is 60℃-90℃.

[0064] For example, a composite membrane intermediate is prepared by drying the composite membrane structure, which consists of a porous substrate and a wet membrane of an intermediate layer, in a forced-air oven at 30°C-50°C for 10-20 hours to remove the solvent, and then drying it in a forced-air oven at 60°C-90°C for 3-10 hours.

[0065] In this embodiment of the invention, an intermediate membrane layer is prepared on the surface of a porous substrate by a liquid-liquid interface water flotation method, so as to improve the problem of uneven thickness and difficulty in controlling defects caused by polymer seepage into the porous substrate and uneven spreading of the separation membrane layer.

[0066] For step S2, preparing a separation membrane layer on the composite membrane intermediate, such that the separation membrane layer is attached to the intermediate membrane layer, includes:

[0067] Step S21: Prepare the separation membrane casting solution. Place the separation membrane casting solution on the intermediate membrane layer of the composite membrane intermediate, and form a wet membrane of the separation membrane layer on the intermediate membrane layer through a coating process.

[0068] For example, the crosslinking viscosity of the casting solution for separating the membrane layer should be 3.5 mPa·s-5.5 mPa·s.

[0069] For example, the coating process includes, but is not limited to, spin coating, blade coating, etc. For instance, spin coating can be used to prepare a wet film with a separation layer.

[0070] Taking a polydimethylsiloxane (PDMS) membrane as an example, the preparation of the casting solution for the separation membrane includes: dissolving polydimethylsiloxane in a solvent, such as n-heptane, stirring for a certain time, such as 12 hours, then adding tetraethyl orthosilicate and dibutyltin dilaurate, and stirring in a water bath (such as 50℃-70℃) for a certain time, such as 0.5-5 hours, to prepare the casting solution for the separation membrane.

[0071] For example, the mass ratio of polydimethylsiloxane: n-heptane: tetraethyl orthosilicate: dibutyltin dilaurate is 1:9:0.1:0.0025.

[0072] Taking spin coating as an example, the separation membrane casting solution (e.g., 500 μL) is dropped onto the surface of the intermediate membrane layer of the composite membrane intermediate. The spin coating speed is set to 500 rpm and the time is 2 s. Then the spin coating speed is set to 3000 rpm and the time is 60 s, forming a wet membrane of the separation membrane layer on the intermediate membrane layer.

[0073] Step S22: The composite membrane intermediate with a wet membrane having a separation membrane layer is dried to remove the solvent from the wet membrane of the separation membrane layer. Then it is placed in an environment with a preset humidity for a set time and dried again to prepare a pervaporation composite membrane.

[0074] The drying process in step S22 can be performed by drying in a forced-air oven at 50℃-80℃ for at least 3 hours. After drying, the wet film preparation and drying process of the separation film layer can be repeated according to actual needs to obtain a wet film of the separation film layer with a set thickness. For example, the above steps can be repeated twice to make the thickness of the wet film of the separation film layer 600nm.

[0075] To obtain a separation membrane layer with the desired membrane structure, the humidity of the environment with preset humidity can be 10% RH, which can be provided by a humidity chamber. The settling time in the environment with preset humidity can be 10-20 hours, for example, 12 hours.

[0076] After being placed in an environment with preset humidity for a set time, the membrane material system can be placed in a vacuum oven at 60℃-100℃ for at least 8 hours to prepare a pervaporation composite membrane.

[0077] By adjusting the fluid properties of the casting solution used to separate the membrane layers, such as the viscosity, density, and surface tension of the polydimethylsiloxane casting solution, its spreading effect on solid surfaces can be improved, thereby adjusting the preparation effect and microstructure of the composite membrane. Furthermore, by adjusting the volume of the polydimethylsiloxane casting solution, the volume of the polyether block amide casting solution, and porous substrates with different pore sizes and materials, the structure of the pervaporation composite membrane can be further optimized, achieving the goal of adjusting its permeability and selectivity.

[0078] In summary, the method for preparing the pervaporation composite membrane provided in this embodiment of the invention improves the membrane defect problem caused by the permeation of the polymer corresponding to the separation membrane layer into the porous substrate by introducing an intermediate membrane layer, thereby better controlling the membrane thickness and accurately controlling the structure of the pervaporation composite membrane.

[0079] Furthermore, embodiments of the present invention also provide the application of any of the above-mentioned pervaporation composite membranes in pervaporation.

[0080] In other words, this invention also provides a separation method, which includes: based on a pervaporation process, using the aforementioned pervaporation composite membrane to separate the target substance from the liquid dispersion medium. The liquid dispersion medium includes water, and the target substance includes alcoholic organic compounds, including but not limited to methanol, ethanol, n-butanol, and isopropanol. The pervaporation composite membrane provided in this invention exhibits excellent selectivity and permeability for the aforementioned alcoholic organic compounds.

[0081] It is evident that, for systems composed of alcohols and water, the pervaporation composite membrane provided in this embodiment of the invention enables preferential permeation of alcohols, thereby achieving efficient separation of the alcohols.

[0082] In some examples, when performing pervaporation operation using the pervaporation composite membrane provided in the embodiments of the present invention, some applicable operating parameters include, but are not limited to, at least one of the following: the peristaltic pump peristaltic speed is 80 r / min-160 r / min (e.g., 120 r / min), the feed liquid temperature is 30℃-70℃, and the pressure difference across the pervaporation composite membrane is 100 Pa-300 Pa.

[0083] The specific embodiments of the present invention will now be described in more detail. While specific embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with the techniques or conditions described in the literature in the art or according to the product instructions. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be obtained commercially. In the following embodiments, unless otherwise specified, "%" refers to mass percentage.

[0084] Example 1

[0085] (1) Mix 3.5g of polyether block amide PEBA2533, 31g of n-butanol and 15.5g of isopropanol, and stir in an 80℃ water bath for 5h until the polyether block amide polymer is completely dissolved to obtain casting solution 1. Let casting solution 1 stand in a forced-air drying oven to remove bubbles for more than 24h.

[0086] (2) Add 300ml of 10℃ ultrapure water to a glass petri dish with a diameter of 15cm and let it stand for 15min.

[0087] (3) 300 μL of the casting solution 1 obtained in the process was dropped onto the water surface. After floating on the liquid surface to form a film, it was attached to the polytetrafluoroethylene substrate.

[0088] (4) The composite membrane obtained in (3) is placed in a 40°C forced-air oven for 12 hours to remove the solvent, and then heat-treated in an 80°C forced-air oven for 5 hours to obtain composite membrane A.

[0089] (5) Dissolve 2g of polydimethylsiloxane in 18g of n-heptane, stir for 12h, then add 0.2g of tetraethyl orthosilicate and 0.005g of dibutyltin dilaurate, and stir in a 60℃ water bath for 1.5h to obtain casting solution 2.

[0090] (6) Take 500 μL of the casting solution 2 obtained in (5) and drop it onto the surface of the composite membrane A. Set the spin coating speed to 500 rpm and the time to 2 s; then set the spin coating speed to 3000 rpm and the time to 60 s. The composite membrane B is obtained.

[0091] (7) Place the membrane obtained in (6) in a 60°C forced-air drying oven for 3 hours.

[0092] (8) Repeat steps (6) and (7) once in sequence to prepare composite membrane C.

[0093] (9) The composite membrane C was placed in a 10% RH constant humidity chamber for 12 hours, and then placed in an 80℃ vacuum oven for 8 hours to prepare the pervaporation composite membrane.

[0094] The pervaporation composite membrane prepared in Example 1 was used for the pervaporation separation of butanol / water. The feed solution was a 1 wt% butanol / water solution. The vacuum degree on the downstream side of the membrane was less than 600 Pa, and the feed solution temperature was 60 °C. The flux and separation factor for the butanol / water mixture were 2.7 kg·m³. -2 ·h -1 And 25.6.

[0095] Example 2

[0096] (1) Mix 3.5g of polyether block amide PEBA2533, 31g of n-butanol and 15.5g of isopropanol, and stir in an 80℃ water bath for 5h until the polyether block amide polymer is completely dissolved to obtain casting solution 1. Let casting solution 1 stand in a forced-air drying oven to remove bubbles for more than 24h.

[0097] (2) Add 300ml of 10℃ ultrapure water to a glass petri dish with a diameter of 15cm and let it stand for 15min.

[0098] (3) Take 100 μL of the casting solution 1 obtained in (1) and drop it onto the water surface. After floating on the liquid surface to form a film, it adheres to the polytetrafluoroethylene substrate.

[0099] (4) The composite membrane obtained in (3) is placed in a 40°C forced-air oven for 12 hours to remove the solvent, and then heat-treated in an 80°C forced-air oven for 5 hours to obtain composite membrane A.

[0100] (5) Dissolve 2g of polydimethylsiloxane in 18g of n-heptane, stir for 12h, then add 0.2g of tetraethyl orthosilicate and 0.005g of dibutyltin dilaurate, and stir in a 60℃ water bath for 1.5h to obtain casting solution 2.

[0101] (6) Take 500 μL of the casting solution 2 obtained in (5) and drop it onto the surface of the composite membrane A. Set the spin coating speed to 500 rpm and the time to 2 s; then set the spin coating speed to 3000 rpm and the time to 60 s. The composite membrane B is obtained.

[0102] (7) Place the membrane obtained in (6) in a 60°C forced-air drying oven for 3 hours. The composite membrane C is obtained.

[0103] (8) Place the composite membrane C in a 10% RH constant humidity chamber for 12 hours, and then place it in an 80℃ vacuum oven for 8 hours.

[0104] The fabricated pervaporation composite membrane was used for the pervaporation separation of butanol / water. The feed solution was a 1 wt% butanol / water solution. The vacuum degree on the downstream side of the membrane was less than 600 Pa, and the feed solution temperature was 60 °C. The flux and separation factor for the butanol / water mixture were 3.4 kg·m³. -2 ·h -1 And 18.6.

[0105] Example 3

[0106] (1) Mix 3.5g of polyether block amide PEBA2533, 31g of n-butanol and 15.5g of isopropanol, and stir in an 80℃ water bath for 5h until the polyether block amide polymer is completely dissolved to obtain casting solution 1. Let casting solution 1 stand in a forced-air drying oven to remove bubbles for more than 24h.

[0107] (2) Add 300ml of 10℃ ultrapure water to a glass petri dish with a diameter of 15cm and let it stand for 15min.

[0108] (3) Take 200 microliters of the casting solution 1 obtained in (1) and drop it onto the water surface. After floating on the liquid surface to form a film, it adheres to the polytetrafluoroethylene substrate.

[0109] (4) The composite membrane obtained in (3) is placed in a 40°C forced-air oven for 12 hours to remove the solvent, and then heat-treated in an 80°C forced-air oven for 5 hours to obtain composite membrane A.

[0110] (5) Dissolve 2g of polydimethylsiloxane in 18g of n-heptane, stir for 12h, then add 0.2g of tetraethyl orthosilicate and 0.005g of dibutyltin dilaurate, and stir in a 60℃ water bath for 1.5h to obtain casting solution 2.

[0111] (6) Take 500 μL of the casting solution 2 obtained in (5) and drop it onto the surface of the composite membrane A. Set the spin coating speed to 500 rpm and the time to 2 s; then set the spin coating speed to 3000 rpm and the time to 60 s. The composite membrane B is obtained.

[0112] (7) Place the membrane obtained in (6) in a 60°C forced-air drying oven for 3 hours.

[0113] (8) Repeat steps (6) and (7) once to obtain composite membrane C.

[0114] (9) Place the composite membrane C in a 10% RH constant humidity chamber for 12 hours, and then place it in an 80℃ vacuum oven for 8 hours.

[0115] The prepared pervaporation composite membrane was used for the pervaporation separation of butanol / water. The feed solution was a 1 wt% butanol / water solution. The vacuum degree on the downstream side of the membrane was less than 600 Pa, and the feed solution temperature was 60℃. The flux and separation factor for the butanol / water mixture were 2.9 kg·m³. -2 ·h -1 And 20.9.

[0116] Example 4

[0117] (1) Mix 3.5g of polyether block amide PEBA2533, 31g of n-butanol and 15.5g of isopropanol, and stir in an 80℃ water bath for 5h until the polyether block amide polymer is completely dissolved to obtain casting solution 1. Let casting solution 1 stand in a forced-air drying oven to remove bubbles for more than 24h.

[0118] (2) Add 300ml of 10℃ ultrapure water to a glass petri dish with a diameter of 15cm and let it stand for 15min.

[0119] (3) Take 400 μL of the casting solution 1 obtained in (1) and drop it onto the water surface. After floating on the liquid surface to form a film, it adheres to the polytetrafluoroethylene substrate.

[0120] (4) The composite membrane obtained in (3) is placed in a 40°C forced-air oven for 12 hours to remove the solvent, and then heat-treated in an 80°C forced-air oven for 5 hours to obtain composite membrane A.

[0121] (5) Dissolve 2g of polydimethylsiloxane in 18g of n-heptane, stir for 12h, then add 0.2g of tetraethyl orthosilicate and 0.005g of dibutyltin dilaurate, and stir in a 60℃ water bath for 1.5h to obtain casting solution 2.

[0122] (6) Take 500 μL of the casting solution 2 obtained in (5) and drop it onto the surface of the composite membrane A. Set the spin coating speed to 500 rpm and the time to 2 s; then set the spin coating speed to 3000 rpm and the time to 60 s. The composite membrane B is obtained.

[0123] (7) Place the membrane obtained in (6) in a 60°C forced-air drying oven for 3 hours.

[0124] (8) Repeat steps (6) and (7) once to obtain composite membrane C.

[0125] (9) Place the composite membrane C in a 10% RH constant humidity chamber for 12 hours, and then place it in an 80℃ vacuum oven for 8 hours.

[0126] The fabricated pervaporation composite membrane was used for the pervaporation separation of butanol / water. The feed solution was a 1 wt% butanol / water solution. The vacuum degree downstream of the membrane was less than 600 Pa, and the feed solution temperature was 60 °C. The flux and separation factor for the butanol / water mixture were 2.2 kg·m³. -2 ·h -1 And 26.3.

[0127] Example 5

[0128] (1) Mix 3.5g of polyether block amide PEBA2533, 31g of n-butanol and 15.5g of isopropanol, and stir in an 80℃ water bath for 5h until the polyether block amide polymer is completely dissolved to obtain casting solution 1. Let casting solution 1 stand in a forced-air drying oven to remove bubbles for more than 24h.

[0129] (2) Add 300ml of 10℃ ultrapure water to a glass petri dish with a diameter of 15cm and let it stand for 15min.

[0130] (3) Take 500 μL of the casting solution 1 obtained in (1) and drop it onto the water surface. After floating on the liquid surface to form a film, it adheres to the polytetrafluoroethylene substrate.

[0131] (4) The composite membrane obtained in (3) is placed in a 40°C forced-air oven for 12 hours to remove the solvent, and then heat-treated in an 80°C forced-air oven for 5 hours to obtain composite membrane A.

[0132] (5) Dissolve 2g of polydimethylsiloxane in 18g of n-heptane, stir for 12h, then add 0.2g of tetraethyl orthosilicate and 0.005g of dibutyltin dilaurate, and stir in a 60℃ water bath for 1.5h to obtain casting solution 2.

[0133] (6) Take 500 μL of the casting solution 2 obtained in (5) and drop it onto the surface of the composite membrane A. Set the spin coating speed to 500 rpm and the time to 2 s; then set the spin coating speed to 3000 rpm and the time to 60 s. The composite membrane B is obtained.

[0134] (7) Place the membrane obtained in (6) in a 60°C forced-air drying oven for 3 hours.

[0135] (8) Repeat steps (6) and (7) once to obtain composite membrane C.

[0136] (9) Place the composite membrane C in a 10% RH constant humidity chamber for 12 hours, and then place it in an 80℃ vacuum oven for 8 hours.

[0137] The fabricated pervaporation composite membrane was used for the pervaporation separation of butanol / water. The feed solution was a 1 wt% butanol / water solution. The vacuum degree on the downstream side of the membrane was less than 600 Pa, and the feed solution temperature was 60 °C. The flux and separation factor for the butanol / water mixture were 2.6 kg·m³. -2 ·h -1 And 20.0.

[0138] Example 6

[0139] (1) Mix 3.5g of polyether block amide PEBA2533, 31g of n-butanol and 15.5g of isopropanol, and stir in an 80℃ water bath for 5h until the polyether block amide polymer is completely dissolved to obtain casting solution 1. Let casting solution 1 stand in a forced-air drying oven to remove bubbles for more than 24h.

[0140] (2) Add 300ml of 10℃ ultrapure water to a glass petri dish with a diameter of 15cm and let it stand for 15min.

[0141] (3) Take 300 microliters of the casting solution 1 obtained in (1) and drop it onto the water surface. After floating on the liquid surface to form a film, it adheres to the polytetrafluoroethylene substrate.

[0142] (4) The composite membrane obtained in (3) is placed in a 40°C forced-air oven for 12 hours to remove the solvent, and then heat-treated in an 80°C forced-air oven for 5 hours to obtain composite membrane A.

[0143] (5) Dissolve 2g of polydimethylsiloxane in 18g of n-heptane, stir for 12h, then add 0.2g of tetraethyl orthosilicate and 0.005g of dibutyltin dilaurate, and stir in a 60℃ water bath for 1.5h to obtain casting solution 2.

[0144] (6) Take 500 μL of the casting solution 2 obtained in (5) and drop it onto the surface of the composite membrane A. Set the spin coating speed to 500 rpm and the time to 2 s; then set the spin coating speed to 3000 rpm and the time to 60 s. The composite membrane B is obtained.

[0145] (7) Place the membrane obtained in (6) in a 60°C forced-air drying oven for 3 hours.

[0146] (8) Repeat (6) and (7) twice to obtain composite membrane C.

[0147] (9) Place the composite membrane C in a 10% RH constant humidity chamber for 12 hours, and then place it in an 80℃ vacuum oven for 8 hours.

[0148] The fabricated pervaporation composite membrane was used for the pervaporation separation of butanol / water. The feed solution was a 1 wt% butanol / water solution. The vacuum degree on the downstream side of the membrane was less than 600 Pa, and the feed solution temperature was 60 °C. The flux and separation factor for the butanol / water mixture were 3.1 kg·m³.-2 ·h -1 And 21.

[0149] Example 7

[0150] (1) Mix 3.5g of polyether block amide PEBA2533, 31g of n-butanol and 15.5g of isopropanol, and stir in an 80℃ water bath for 5h until the polyether block amide polymer is completely dissolved to obtain casting solution 1. Let casting solution 1 stand in a forced-air drying oven to remove bubbles for more than 24h.

[0151] (2) Add 300ml of 10℃ ultrapure water to a glass petri dish with a diameter of 15cm and let it stand for 15min.

[0152] (3) Take 300 microliters of the casting solution 1 obtained in (1) and drop it onto the water surface. After floating on the liquid surface to form a film, it adheres to the polytetrafluoroethylene substrate.

[0153] (4) The composite membrane obtained in (3) is placed in a 40°C forced-air oven for 12 hours to remove the solvent, and then heat-treated in an 80°C forced-air oven for 5 hours to obtain composite membrane A.

[0154] (5) Dissolve 2g of polydimethylsiloxane in 18g of n-heptane, stir for 12h, then add 0.2g of tetraethyl orthosilicate and 0.005g of dibutyltin dilaurate, and stir in a 60℃ water bath for 1.5h to obtain casting solution 2.

[0155] (6) Take 500 μL of the casting solution 2 obtained in (5) and drop it onto the surface of the composite membrane A. Set the spin coating speed to 500 rpm and the time to 2 s; then set the spin coating speed to 3000 rpm and the time to 60 s. The composite membrane B is obtained.

[0156] (7) Place the membrane obtained in (6) in a 60°C forced-air drying oven for 3 hours. The composite membrane C is obtained.

[0157] (8) Place the composite membrane C in a 10% RH constant humidity chamber for 12 hours, and then place it in an 80℃ vacuum oven for 8 hours.

[0158] The fabricated pervaporation composite membrane was used for the pervaporation separation of butanol / water. The feed solution was a 1 wt% butanol / water solution. The vacuum degree on the downstream side of the membrane was less than 600 Pa, and the feed solution temperature was 60 °C. The flux and separation factor for the butanol / water mixture were 6.2 kg·m³. -2 ·h -1 And 16.3.

[0159] Comparative Example 1

[0160] (1) Dissolve 2g of polydimethylsiloxane in 18g of n-heptane, stir for 12h, then add 0.2g of tetraethyl orthosilicate and 0.005g of dibutyltin dilaurate, and stir in a 60℃ water bath for 1.5h to obtain casting solution 1.

[0161] (2) Take 500 μL of the casting solution 2 obtained in (1) and drop it onto the upper surface of the polytetrafluoroethylene substrate. Set the spin coating speed to 500 rpm and the time to 2 s; then set the spin coating speed to 3000 rpm and the time to 60 s. The composite film A is obtained.

[0162] (3) Place the membrane obtained in (2) in a 60°C forced-air drying oven for 3 hours.

[0163] (4) Repeat (2) and (3) twice to obtain composite membrane C.

[0164] (5) Place the composite membrane C in a 10% RH constant humidity chamber for 12 hours, and then place it in an 80℃ vacuum oven for 8 hours.

[0165] The fabricated pervaporation composite membrane was used for the pervaporation separation of butanol / water. The feed solution was a 1 wt% butanol / water solution. The vacuum degree on the downstream side of the membrane was less than 600 Pa, and the feed solution temperature was 60 °C. The flux and separation factor for the butanol / water mixture were 10.7 kg·m³. -2 ·h -1 And 12.3.

[0166] Comparative Example 2

[0167] (1) Mix 3.5g of polyether block amide PEBA2533, 31g of n-butanol and 15.5g of isopropanol, and stir in an 80℃ water bath for 5h until the polyether block amide polymer is completely dissolved to obtain casting solution 1. Let casting solution 1 stand in a forced-air drying oven to remove bubbles for more than 24h.

[0168] (2) Add 300ml of 10℃ ultrapure water to a glass petri dish with a diameter of 15cm and let it stand for 15min.

[0169] (3) Take 300 microliters of the casting solution 1 obtained in (1) and drop it onto the water surface. After floating on the liquid surface to form a film, it adheres to the polytetrafluoroethylene substrate.

[0170] (4) The composite membrane obtained in (3) is placed in a 40°C forced-air oven for 12 hours to remove the solvent, and then heat-treated in an 80°C forced-air oven for 5 hours to obtain composite membrane A.

[0171] The fabricated pervaporation composite membrane was used for the pervaporation separation of butanol / water. The feed solution was a 1 wt% butanol / water solution. The vacuum degree on the downstream side of the membrane was less than 600 Pa, and the feed solution temperature was 60 °C. The flux and separation factor for the butanol / water mixture were 6.9 kg·m³.-2 ·h -1 And 16.6.

[0172] Test Example 1

[0173] This test example photographs the spin-coating effect of the pervaporation composite membranes provided in Example 1 and Comparative Example 1. The resulting photographs are shown in the attached images. Figure 1 , Figure 2

[0174] The pervaporation composite membrane provided in Example 1 is a bilayer composite membrane containing an intermediate PEBA layer, on which PDMS is spin-coated. Figure 1 As shown, the pervaporation composite membrane provided in Example 1 has a uniform PDMS spin coating on its surface, with a comprehensive and smooth spin coating effect and good spreading effect.

[0175] Comparative Example 1 provides a pervaporation composite membrane, which is a composite membrane obtained by spin-coating PDMS onto a PTFE substrate support layer without containing an intermediate PEBA layer. Figure 2 As shown, the pervaporation composite membrane provided in Comparative Example 1 has uneven PDMS spin coating on its surface, and the spin coating effect is an incomplete spiral shape with poor spreading effect.

[0176] This test example also tested the spreading effect of the pervaporation composite membranes provided in Example 1 and Comparative Example 1. See the photographs obtained. Figure 3 The left side shows the spreading effect of PDMS on a PEBA interlayer double-layer composite film in Example 1; the right side shows the spreading effect of PDMS on a PTFE substrate support layer without a PEBA interlayer. Figure 3 It can be clearly seen that in Comparative Example 1, PDMS mostly penetrates into the support layer, while this situation is significantly improved in Example 1.

[0177] Test Example 2

[0178] In this test example, cross-sections of the pervaporation composite membranes provided in Example 1, Comparative Example 1, and Comparative Example 2 were scanned using SEM. The obtained SEM images are shown in [reference 1]. Figure 4 , Figure 5 , Figure 6 .

[0179] The pervaporation composite membrane provided in Example 1 has a PDMS-PEBA / PTFE bilayer membrane structure. Figure 4 As can be seen, the pervaporation composite membrane provided in Example 1 has a membrane thickness of 3.4 μm and a smooth and flat cross-sectional structure.

[0180] The pervaporation composite membrane provided in Comparative Example 1 has a PDMS / PTFE composite membrane structure. (The remaining text appears to be incomplete and requires further context.) Figure 5As can be seen, the pervaporation composite membrane provided in Comparative Example 1 has a membrane thickness of 10 μm, a smooth cross-sectional structure, and obvious pore structure.

[0181] The pervaporation composite membrane provided in Comparative Example 2 has a PEBA / PTFE composite membrane structure. (The remaining text appears to be incomplete and requires further context.) Figure 6 As can be seen, the pervaporation composite membrane provided in Comparative Example 2 has a membrane thickness of 2.8 μm and a smooth and flat cross-sectional structure.

[0182] In this test example 2, EDX elemental scanning was also performed on the pervaporation composite membranes provided in Example 1 and Comparative Example 1. The obtained scan images are shown below. Figure 7 , Figure 8 , Figure 9 , Figure 10 . Figure 7 A planar scan image of silicon (i.e., characteristic elements of PDMS material) in the pervaporation composite membrane provided in Example 1. Figure 8 A planar scan image of the fluorine element (i.e., the characteristic element of PTFE material) in the pervaporation composite membrane provided in Example 1. Figure 9 A planar scan image of silicon (i.e., characteristic element of PDMS material) in the pervaporation composite membrane provided for Comparative Example 1. Figure 10 A planar scan image of the fluorine element (i.e., a characteristic element of PTFE material) in the pervaporation composite membrane provided for Comparative Example 1.

[0183] Depend on Figure 7 and Figure 8 It can be seen that in Example 1, the two materials PDMS and PTFE are clearly separated into layers with a clear boundary. The boundary region between the two materials is analyzed to be PEBA material.

[0184] Depend on Figure 9 and Figure 10 It can be seen that in Comparative Example 1, the two materials PDMS and PTFE are mutually doped, resulting in relatively severe porosity.

[0185] This test case also included surface electron microscopy (SEM) scanning of the pervaporation composite membrane provided in Comparative Example 1. The resulting images are shown below. Figure 11 .Depend on Figure 11 It can be seen that the pervaporation composite membrane provided in Comparative Example 1, i.e., spin-coated PDMS, has obvious pores on the surface of the PTFE substrate support layer without an intermediate layer, and it is not a dense structure. This may be due to the occurrence of percolation.

[0186] The above description is merely for the purpose of enabling those skilled in the art to understand the technical solutions of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An application of a pervaporation composite membrane, characterized in that, For the separation of butanol / water, the pervaporation composite membrane comprises: a porous substrate (1), an intermediate membrane layer (2), and a separation membrane layer (3) arranged in sequence; the average pore size and porosity of the porous substrate are both greater than the average pore size and porosity of the intermediate membrane layer and the separation membrane layer; The preparation method of the pervaporation composite membrane includes the following steps: (a) The intermediate membrane layer is attached to a porous substrate to obtain a composite membrane intermediate; (b) A separation membrane layer is prepared on the composite membrane intermediate, such that the separation membrane layer is attached to the intermediate membrane layer, to obtain the pervaporation composite membrane; Step (a) involves attaching the intermediate membrane layer to the porous substrate to obtain a composite membrane intermediate, comprising: The intermediate film material includes at least one of polyether block amide PEBA2533, polyether block amide PEBA3533, polyether block amide PEBA4033, and polyether block amide PEBA1657; The average pore size of the porous substrate (1) is greater than or equal to 250 nm; The thickness of the porous substrate is 100um-150um; The thickness of the intermediate film layer is 2µm-7µm; The thickness of the separation membrane layer is 1µm-10µm; The porous substrate (1) is selected from one of the following: polysulfone membrane, polyacrylonitrile membrane, polyvinylidene fluoride membrane, polytetrafluoroethylene membrane, polypropylene membrane, polyethylene membrane, polyethersulfone membrane, polybenzimidazole membrane, and cellulose acetate membrane. Step (a) involves attaching an intermediate membrane layer to a porous substrate to obtain a composite membrane intermediate, comprising: preparing an intermediate membrane layer casting solution; dropping the intermediate membrane layer casting solution onto a liquid surface to form a film on the liquid surface, thereby obtaining a wet membrane of the intermediate membrane layer; removing the wet membrane of the intermediate membrane layer and attaching it to the porous substrate, followed by drying to obtain the composite membrane intermediate; the intermediate membrane layer casting solution includes intermediate membrane layer raw materials and a solvent; Step (b) of preparing a separation membrane layer on the composite membrane intermediate, such that the separation membrane layer is attached to the intermediate membrane layer, includes: A separation membrane casting solution is prepared, which is then placed on the intermediate membrane layer of the composite membrane intermediate. A coating process is then performed to form a wet membrane of the separation membrane layer on the intermediate membrane layer. The composite membrane intermediate with the wet membrane of the separation membrane layer is dried to remove the solvent from the wet membrane of the separation membrane layer. Then, it is placed in a humid environment and left to stand for a period of time. After being dried again, the pervaporation composite membrane is obtained.

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