Pervaporation composite membrane

Abstract

A pervaporation composite membrane belongs to the technical field of membrane separation. The pervaporation composite membrane comprises a porous substrate, a middle membrane layer and a separation membrane layer which are sequentially stacked, the average pore size of the porous substrate is greater than or equal to 250nm; the average pore size and porosity of the middle film layer are smaller than those of the porous substrate, and the middle film layer has the organic matter affinity characteristic; the separation membrane layer has the hydrophobic characteristic and the organic matter selective permeation characteristic. The middle membrane layer is beneficial to improving the problems of seepage holes, difficulty in spreading, uncontrollable thickness of the separation membrane layer and the like in the solid-liquid interface preparation process, ensures the defect-free preparation of the separation membrane layer, and is beneficial to improving the permeability of the pervaporation composite membrane to organic matters.

Description

Technical Field

[0001] The utility model relates to the technical field of membrane separation, in particular to a pervaporation composite membrane and a preparation method and application thereof. Background Art

[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. Usually, this type of pervaporation composite membrane used for ethanol treatment is called pervaporation preferential alcohol permeation membrane.

[0003] The pervaporation preferential alcohol permeation membrane is usually in the form of a composite membrane, which includes a porous substrate and a separation membrane layer attached to the porous substrate, wherein the porous substrate includes a pore structure, so that when the separation membrane layer is prepared thereon, the polymer material corresponding to the separation membrane layer will partially penetrate into the pore structure of the porous substrate, which will not only cause defects in the separation membrane layer, but also increase the mass transfer resistance of the pervaporation preferential alcohol permeation membrane, thereby affecting the permeation performance of the composite membrane. Utility Model Content

[0004] In view of this, the utility model provides a pervaporation composite membrane, which can solve the technical problems existing in the related technology.

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

[0006] In one aspect, 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) which are sequentially stacked;

[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 the average pore size and porosity of the porous substrate, and the intermediate membrane layer has organic affinity characteristics;

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

[0010] In some possible implementations, the intermediate film layer (2) is a polyether block amide film, and the material of the intermediate film layer 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 includes a polydimethylsiloxane membrane.

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

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

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

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

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

[0017] (b) preparing a separation membrane layer on the composite membrane intermediate so that the separation membrane layer is attached to the intermediate membrane layer to obtain the pervaporation composite membrane.

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

[0019] The intermediate membrane layer casting liquid is prepared, and the intermediate membrane layer casting liquid is dripped onto the liquid surface so that the intermediate membrane layer casting liquid forms a film on the liquid surface to prepare a wet film of the intermediate membrane layer; the wet film of the intermediate membrane layer is taken out and attached to the porous substrate, and the composite membrane intermediate is prepared after drying.

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

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

[0022] A separation membrane layer casting liquid is prepared, and the separation membrane layer casting liquid is placed on the intermediate membrane layer of the composite membrane intermediate, and a wet film of the separation membrane layer is formed on the intermediate membrane layer through a coating process; the composite membrane intermediate having the wet film of the separation membrane layer is dried to remove the solvent in the wet film of the separation membrane layer, and then placed in a humid environment for a period of time, and dried again to prepare the pervaporation composite membrane.

[0023] On the other hand, the utility model also provides the use of any of the above-mentioned pervaporation composite membranes in pervaporation.

[0024] The beneficial effects of the technical solution provided by the embodiment of the utility model include at least:

[0025] The pervaporation composite membrane provided by the embodiment of the utility model is conducive to reducing the mass transfer resistance of the pervaporation composite membrane during the pervaporation process by using a porous substrate with an average pore size greater than or equal to 250nm. 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 smaller than the average pore size and porosity of the porous substrate, which is conducive to improving the easy permeability of the solid-liquid interface during the preparation process (i.e., alleviating the pore permeation phenomenon), uneven spreading of the separation layer, uncontrollable thickness of the separation membrane layer, and other problems, and is conducive to improving the spreadability of the fluid on the solid surface and ensuring the defect-free preparation of the separation membrane layer. The three-layer structure of the utility model makes the cross-sectional structure of the separation membrane layer flat and smooth, and the thickness is easy to control; on the other hand, the intermediate membrane layer has organic affinity characteristics, which is conducive to improving the permeability of the pervaporation composite membrane to organic matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 A schematic diagram of the spreading effect of the pervaporation composite membrane provided in Example 1 and Comparative Example 1;

[0028] Figure 2 This is a schematic diagram of the structure of the pervaporation composite membrane of this application.

[0029] A porous substrate (1), an intermediate membrane layer (2), and a separation membrane layer (3).

[0030] The above drawings have shown clear embodiments of the present invention, which will be described in more detail below. These drawings and text descriptions are not intended to limit the scope of the present invention in any way, but to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0031] On the one hand, an embodiment of the utility model provides a pervaporation composite membrane, which comprises: 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 250nm; 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.

[0032] The pervaporation composite membrane provided by the embodiment of the utility model is conducive to reducing the mass transfer resistance of the pervaporation composite membrane during the pervaporation process by using a porous substrate with an average pore size greater than or equal to 250nm. 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 the average pore size and porosity of the porous substrate, which is conducive to improving the easy permeability (i.e., alleviating the pore permeation phenomenon) in the preparation process of the solid-liquid interface, the uncontrollable thickness of the separation membrane layer, and the like, and is conducive to improving the spreadability of the fluid on the solid surface, ensuring the defect-free preparation of the separation membrane layer. On the other hand, the intermediate membrane layer has an organic affinity characteristic, which is conducive to improving the permeability of the pervaporation composite membrane to organic matter.

[0033] In some examples, the pervaporation composite membrane provided by the embodiments of the present invention may be a pervaporation membrane that preferentially permeates alcohol.

[0034] In some examples, some materials suitable for the middle 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.

[0035] Based on the physical properties of the above-mentioned polyether block amide (PEBA), it has organic affinity characteristics and can be easily prepared to obtain a relatively dense pore structure.

[0036] In some examples, the separation membrane layer includes a polydimethylsiloxane membrane. The polydimethylsiloxane membrane is used as the separation membrane layer. The polydimethylsiloxane membrane is hydrophobic and can provide good selectivity for separation of water and organic matter, for example, it has excellent selectivity for alcohols.

[0037] In some examples, the porous substrate is a hydrophobic membrane having a porous structure, and the porous structure satisfies that the porous substrate can be an ultrafiltration membrane, a 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, and is selected from one of polysulfone membrane, polyacrylonitrile membrane, polyvinylidene fluoride membrane, polytetrafluoroethylene membrane, polypropylene membrane, polyethylene membrane, polyethersulfone membrane, polybenzimidazole membrane, and cellulose acetate membrane.

[0038] 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.

[0039] The thickness of the intermediate membrane layer is 2um-7um, which includes but is not limited to 2um, 3um, 4um, 5um, 6um, 7um, etc. The thickness of the intermediate membrane layer is within a lower range, which is conducive to reducing the mass transfer path and reducing resistance.

[0040] The thickness of the separation membrane layer is 1um-10um, which includes but is not limited to 1um, 2um, 3um, 4um, 5um, 6um, 7um, 8um, 9um, 10um, etc. The thickness of the separation membrane layer is within a lower range, which can reduce the mass transfer path and reduce resistance.

[0041] In summary, the pervaporation composite membrane provided by the embodiment of the utility model introduces an intermediate membrane layer between the porous substrate and the separation membrane layer to improve a series of problems such as the polymer corresponding to the separation membrane layer infiltrating into the porous substrate, uneven spreading resulting in uneven thickness, and uncontrollable defects. At the same time, the intermediate membrane layer uses polyether block amide, which has excellent permeability to alcohol-water systems, prevents the generation of large mass transfer resistance, and ensures the preferential alcohol permeability of the pervaporation composite membrane.

[0042] On the other hand, an embodiment of the present invention further provides a method for preparing a pervaporation composite membrane, wherein the pervaporation composite membrane is as described above.

[0043] The preparation method of the pervaporation composite membrane comprises:

[0044] Step S1, making the intermediate membrane layer adhere to the porous substrate to obtain a composite membrane intermediate.

[0045] Step S2: preparing a separation membrane layer on the composite membrane intermediate, so that the separation membrane layer is attached to the intermediate membrane layer, thereby obtaining a pervaporation composite membrane.

[0046] In some examples, in step S1, the intermediate membrane layer is attached to the porous substrate to obtain a composite membrane intermediate, including:

[0047] Step S11, preparing an intermediate film layer casting liquid, and dropping the intermediate film layer casting liquid onto the liquid surface, so that the intermediate film layer casting liquid forms a film on the water surface, thereby preparing a wet film of the intermediate film layer.

[0048] The intermediate membrane layer casting liquid includes an intermediate membrane layer raw material and a solvent. The material of the intermediate membrane layer is selected from polyether block amide PEBA2533, polyether block amide PEBA3533, polyether block amide PEBA4033, and polyether block amide PEBA1657. For example, the intermediate membrane layer 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.

[0049] For example, the polyether block amide is dissolved in a solvent with a mass ratio of n-butanol: isopropanol = 2:1 to prepare an intermediate film layer casting solution with a solute mass percentage of 7%, and stirred in a water bath at 80° C. until the polyether block amide is completely dissolved to obtain the intermediate film layer casting solution. The intermediate film layer casting solution is placed in a blast oven to remove bubbles.

[0050] In step S11, the liquid surface is obtained from at least one of the following liquids: water, ethanol, and methanol.

[0051] For example, a specific amount of the intermediate film layer casting liquid (eg, 100 μl-500 μl) is dropped onto the liquid surface, and after the film floats on the liquid surface to form a film, it is taken out to obtain a wet film of the intermediate film layer.

[0052] Step S12, taking out the wet film of the intermediate film layer and attaching it to a porous substrate, and drying it to obtain a composite film intermediate.

[0053] For example, the drying process includes a first drying process and a second drying process performed sequentially, the drying temperature of the first drying process is 30°C-50°C, and the drying temperature of the second drying process is 60°C-90°C.

[0054] For example, a composite membrane intermediate is prepared by placing the composite membrane structure consisting of a wet membrane of a porous substrate and an intermediate membrane layer in a 30°C-50°C forced air oven for drying for 10-20 hours to remove the solvent, and then placing it in a 60°C-90°C forced air oven for drying for 3-10 hours.

[0055] The embodiment of the utility model prepares an intermediate membrane layer on the surface of a porous substrate through a liquid-liquid interface water flotation method to improve the problem of uneven thickness and difficult-to-control defects caused by the polymer of the separation membrane layer penetrating into the porous substrate and spreading unevenly.

[0056] For step S2, preparing a separation membrane layer on the composite membrane intermediate so that the separation membrane layer is attached to the intermediate membrane layer comprises:

[0057] Step S21, preparing a separation membrane layer casting liquid, placing the separation membrane layer casting liquid on the intermediate membrane layer of the composite membrane intermediate, and forming a wet film of the separation membrane layer on the intermediate membrane layer through a coating process.

[0058] Exemplarily, the cross-linking viscosity of the separation membrane layer casting solution should be 3.5 mPa·s-5.5 mPa·s.

[0059] Illustratively, the coating process includes, but is not limited to, spin coating, blade coating, etc. For example, spin coating may be used to prepare a wet film of the separation membrane layer.

[0060] Taking the separation membrane layer as a polydimethylsiloxane membrane (PDMS membrane) as an example, the preparation of the separation membrane layer casting liquid 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, stirring in a water bath (e.g., 50°C-70°C) for a certain time, such as 0.5-5 hours, to prepare the separation membrane layer casting liquid.

[0061] For example, the mass ratio of polydimethylsiloxane:n-heptane:ethyl orthosilicate:dibutyltin dilaurate is 1:9:0.1:0.0025.

[0062] Taking the spin coating process for membrane preparation as an example, the separation membrane layer casting liquid (e.g. 500 μl) is dripped onto the surface of the middle membrane layer of the composite membrane intermediate, the spin coating speed is set to 500 rpm for 2 s, and then the spin coating speed is set to 3000 rpm for 60 s to form a wet film of the separation membrane layer on the middle membrane layer.

[0063] Step S22, drying the composite membrane intermediate having the wet membrane of the separation membrane layer to remove the solvent in the wet membrane of the separation membrane layer, then placing it in an environment with a preset humidity for a set time, and drying it again to prepare a pervaporation composite membrane.

[0064] The drying process involved in step S22 may be drying in a blast oven at 50° C.-80° C. for at least 3 hours. After drying, the wet film preparation and drying process of the separation membrane layer may be repeated according to actual needs to obtain a wet film of the separation membrane layer with a set thickness. For example, the above steps may be repeated twice to obtain a wet film thickness of the separation membrane layer of 600 nm.

[0065] In order to obtain a separation membrane layer with a desired membrane structure, the humidity of the environment with preset humidity can be 10% RH and can be provided by a constant humidity chamber, and the standing time in the environment with preset humidity can be 10 hours to 20 hours, for example, 12 hours.

[0066] After being placed in an environment with a preset humidity and allowed to stand for a set time, the membrane material system can be placed in a vacuum oven at 60° C.-100° C. for at least 8 hours, thereby preparing a pervaporation composite membrane.

[0067] By adjusting the fluid properties of the separation membrane layer casting solution, such as the viscosity, density, surface tension, etc. of the polydimethylsiloxane casting solution, its spreading effect on the solid surface can be improved, and the preparation effect and microstructure of the composite membrane can be adjusted. By adjusting the volume of the polydimethylsiloxane casting solution, the volume of the polyether block amide casting solution, and the porous substrates of different pore sizes and materials, the pervaporation composite membrane structure can be further optimized to achieve the purpose of adjusting its permeability and selectivity.

[0068] In summary, the preparation method of the pervaporation composite membrane provided in the embodiment of the utility model improves the membrane defect problem caused by the penetration of the polymer corresponding to the separation membrane layer into the porous substrate by introducing an intermediate membrane layer, and can better control the thickness of the membrane and accurately control the structure of the pervaporation composite membrane.

[0069] On the other hand, the embodiments of the present invention also provide the use of any of the above-mentioned pervaporation composite membranes in pervaporation.

[0070] That is to say, the embodiment of the utility model also provides a separation method, which includes: based on the pervaporation process, using the above-mentioned pervaporation composite membrane to separate the target substance from the liquid dispersion medium. Wherein, the liquid dispersion medium includes water, and the target substance includes alcohol organic matter, and the alcohol organic matter includes but is not limited to: methanol, ethanol, n-butanol, isopropanol, etc. The pervaporation composite membrane provided by the embodiment of the utility model shows excellent selectivity and permeability for the above-mentioned alcohol organic matter.

[0071] It can be seen that for the system composed of alcohol organic matter and water, the pervaporation composite membrane provided by the embodiment of the utility model can make the alcohol organic matter therein permeate preferentially, thereby efficiently separating the alcohol organic matter therein.

[0072] In some examples, when performing pervaporation operation using the pervaporation composite membrane provided by the embodiments of the utility model, some applicable operating parameters include but are not limited to at least one of the following: the peristaltic speed of the peristaltic pump is 80r / min-160r / min (for example, 120r / min), the feed liquid temperature is 30℃-70℃, and the pressure difference on both sides of the pervaporation composite membrane is 100Pa-300Pa.

[0073] The specific embodiments of the present invention will be described in more detail below. Although the 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 by the embodiments described here. If the specific techniques or conditions are not specified in the examples, they are carried out according to the techniques or conditions described in the literature in this area or according to the product instructions. If the manufacturers of the reagents or instruments used are not specified, they are all conventional products that can be obtained commercially. In the following examples, if not clearly stated, "%" refers to mass percentage.

[0074] Example 1

[0075] (1) 3.5 g of polyether block amide PEBA2533, 31 g of n-butanol and 15.5 g of isopropanol were mixed and stirred in a water bath at 80° C. for 5 h until the polyether block amide polymer was completely dissolved to obtain a casting solution 1. The casting solution 1 was placed in a forced air oven to remove bubbles for more than 24 h.

[0076] (2) Add 300 ml of 10°C ultrapure water to a 15 cm diameter glass culture dish and let it stand for 15 min.

[0077] 300 μl of the casting solution 1 obtained in (3) was dropped onto the water surface, and the film floated on the liquid surface and then adhered to the polytetrafluoroethylene-based substrate.

[0078] (4) The composite membrane obtained in (3) was placed in a 40°C forced air oven for 12 h to remove the solvent, and then heat treated in an 80°C forced air oven for 5 h to obtain composite membrane A.

[0079] (5) 2 g of polydimethylsiloxane was dissolved in 18 g of n-heptane, and the mixture was stirred for 12 h. Then, 0.2 g of ethyl orthosilicate and 0.005 g of dibutyltin dilaurate were added, and the mixture was stirred in a 60° C. water bath for 1.5 h to obtain a casting solution 2.

[0080] (6) Take 500 μl of the casting solution 2 obtained in (5) and drop it onto the upper surface of composite film A. Set the spin coating speed to 500 rpm for 2 s; then set the spin coating speed to 3000 rpm for 60 s. Composite film B is obtained.

[0081] (7) The film obtained in (6) was placed in a 60°C forced air oven for 3 h.

[0082] (8) Steps (6) and (7) are repeated once in sequence to prepare composite membrane C.

[0083] (9) The composite membrane C was placed in a 10% RH constant humidity chamber for 12 h, and then placed in a 80°C vacuum oven for 8 h to prepare a pervaporation composite membrane.

[0084] The pervaporation composite membrane prepared in Example 1 was used for the pervaporation separation of butanol / water. The feed liquid was a 1 wt % butanol / water solution. The vacuum degree on the downstream side of the membrane was less than 600 Pa. The feed liquid temperature was 60°C. The flux and separation factor for the butanol / water mixture were 2.7 kg·m -2 ·h -1 and 25.6.

[0085] Example 2

[0086] (1) 3.5 g of polyether block amide PEBA2533, 31 g of n-butanol and 15.5 g of isopropanol were mixed and stirred in a water bath at 80° C. for 5 h until the polyether block amide polymer was completely dissolved to obtain a casting solution 1. The casting solution 1 was placed in a forced air oven to remove bubbles for more than 24 h.

[0087] (2) Add 300 ml of 10°C ultrapure water to a 15 cm diameter glass culture dish and let it stand for 15 min.

[0088] (3) 100 μl of the casting solution 1 obtained in (1) is dropped onto the water surface. The film floats on the liquid surface and then adheres to the polytetrafluoroethylene-based substrate.

[0089] (4) The composite membrane obtained in (3) was placed in a 40°C forced air oven for 12 h to remove the solvent, and then heat treated in an 80°C forced air oven for 5 h to obtain composite membrane A.

[0090] (5) 2 g of polydimethylsiloxane was dissolved in 18 g of n-heptane, and the mixture was stirred for 12 h. Then, 0.2 g of ethyl orthosilicate and 0.005 g of dibutyltin dilaurate were added, and the mixture was stirred in a 60° C. water bath for 1.5 h to obtain a casting solution 2.

[0091] (6) Take 500 μl of the casting solution 2 obtained in (5) and drop it onto the upper surface of composite film A. Set the spin coating speed to 500 rpm for 2 s; then set the spin coating speed to 3000 rpm for 60 s. Composite film B is obtained.

[0092] (7) The film obtained in (6) was placed in a 60°C forced air oven for 3 h. Composite film C was obtained.

[0093] (8) The composite film C was placed in a 10% RH constant humidity chamber for 12 h, and then placed in a 80°C vacuum oven for 8 h.

[0094] The prepared pervaporation composite membrane was used for the pervaporation separation of butanol / water. The feed liquid 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 liquid temperature was 60 °C. The flux and separation factor for the butanol / water mixture were 3.4 kg·m -2 ·h -1 and 18.6.

[0095] Example 3

[0096] (1) 3.5 g of polyether block amide PEBA2533, 31 g of n-butanol and 15.5 g of isopropanol were mixed and stirred in a water bath at 80° C. for 5 h until the polyether block amide polymer was completely dissolved to obtain a casting solution 1. The casting solution 1 was placed in a forced air oven to remove bubbles for more than 24 h.

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

[0098] (3) 200 μl of the casting solution 1 obtained in (1) is dropped onto the water surface. The film floats on the liquid surface and adheres to the polytetrafluoroethylene-based substrate.

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

[0100] (5) 2 g of polydimethylsiloxane was dissolved in 18 g of n-heptane, and the mixture was stirred for 12 h. Then, 0.2 g of ethyl orthosilicate and 0.005 g of dibutyltin dilaurate were added, and the mixture was stirred in a 60° C. water bath for 1.5 h to obtain a casting solution 2.

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

[0102] (7) The film obtained in (6) was placed in a 60°C forced air oven for 3 h.

[0103] (8) Repeat steps (6) and (7) once to obtain composite membrane C.

[0104] (9) The composite film C was placed in a 10% RH constant humidity chamber for 12 h, and then placed in a 80°C vacuum oven for 8 h.

[0105] The prepared pervaporation composite membrane was used for the pervaporation separation of butanol / water. The feed liquid 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 liquid temperature was 60 °C. The flux and separation factor for the butanol / water mixture were 2.9 kg·m -2 ·h -1 and 20.9.

[0106] Example 4

[0107] (1) 3.5 g of polyether block amide PEBA2533, 31 g of n-butanol and 15.5 g of isopropanol were mixed and stirred in a water bath at 80° C. for 5 h until the polyether block amide polymer was completely dissolved to obtain a casting solution 1. The casting solution 1 was placed in a forced air oven to remove bubbles for more than 24 h.

[0108] (2) Add 300 ml of 10°C ultrapure water to a 15 cm diameter glass culture dish and let it stand for 15 min.

[0109] (3) 400 μl of the casting solution 1 obtained in step (1) is dropped onto the water surface. The film floats on the liquid surface and adheres to the polytetrafluoroethylene-based substrate.

[0110] (4) The composite membrane obtained in (3) was placed in a 40°C forced air oven for 12 h to remove the solvent, and then heat treated in an 80°C forced air oven for 5 h to obtain composite membrane A.

[0111] (5) 2 g of polydimethylsiloxane was dissolved in 18 g of n-heptane, and the mixture was stirred for 12 h. Then, 0.2 g of ethyl orthosilicate and 0.005 g of dibutyltin dilaurate were added, and the mixture was stirred in a 60° C. water bath for 1.5 h to obtain a casting solution 2.

[0112] (6) Take 500 μl of the casting solution 2 obtained in (5) and drop it onto the upper surface of composite film A. Set the spin coating speed to 500 rpm for 2 s; then set the spin coating speed to 3000 rpm for 60 s. Composite film B is obtained.

[0113] (7) The film obtained in (6) was placed in a 60°C forced air oven for 3 h.

[0114] (8) Repeat steps (6) and (7) once to obtain composite membrane C.

[0115] (9) The composite film C was placed in a 10% RH constant humidity chamber for 12 h, and then placed in a 80°C vacuum oven for 8 h.

[0116] The prepared pervaporation composite membrane was used for the pervaporation separation of butanol / water. The feed liquid was a 1 wt% butanol / water solution, the vacuum degree on the downstream side of the membrane was less than 600 Pa, the feed liquid temperature was 60 °C, and the flux and separation factor for the butanol / water mixture were 2.2 kg·m -2 ·h -1 and 26.3.

[0117] Example 5

[0118] (1) 3.5 g of polyether block amide PEBA2533, 31 g of n-butanol and 15.5 g of isopropanol were mixed and stirred in a water bath at 80° C. for 5 h until the polyether block amide polymer was completely dissolved to obtain a casting solution 1. The casting solution 1 was placed in a forced air oven to remove bubbles for more than 24 h.

[0119] (2) Add 300 ml of 10°C ultrapure water to a 15 cm diameter glass culture dish and let it stand for 15 min.

[0120] (3) 500 μl of the casting solution 1 obtained in (1) is dropped onto the water surface. The film floats on the liquid surface and then adheres to the polytetrafluoroethylene-based substrate.

[0121] (4) The composite membrane obtained in (3) was placed in a 40°C forced air oven for 12 h to remove the solvent, and then heat treated in an 80°C forced air oven for 5 h to obtain composite membrane A.

[0122] (5) 2 g of polydimethylsiloxane was dissolved in 18 g of n-heptane, and the mixture was stirred for 12 h. Then, 0.2 g of ethyl orthosilicate and 0.005 g of dibutyltin dilaurate were added, and the mixture was stirred in a 60° C. water bath for 1.5 h to obtain a casting solution 2.

[0123] (6) Take 500 μl of the casting solution 2 obtained in (5) and drop it onto the upper surface of composite film A. Set the spin coating speed to 500 rpm for 2 s; then set the spin coating speed to 3000 rpm for 60 s. Composite film B is obtained.

[0124] (7) The film obtained in (6) was placed in a 60°C forced air oven for 3 h.

[0125] (8) Repeat steps (6) and (7) once to obtain composite membrane C.

[0126] (9) The composite film C was placed in a 10% RH constant humidity chamber for 12 h, and then placed in a 80°C vacuum oven for 8 h.

[0127] The prepared pervaporation composite membrane was used for the pervaporation separation of butanol / water. The feed liquid was a 1 wt% butanol / water solution, the vacuum degree on the downstream side of the membrane was less than 600 Pa, the feed liquid temperature was 60 °C, and the flux and separation factor for the butanol / water mixture were 2.6 kg·m -2 ·h -1 and 20.0.

[0128] Example 6

[0129] (1) 3.5 g of polyether block amide PEBA2533, 31 g of n-butanol and 15.5 g of isopropanol were mixed and stirred in a water bath at 80° C. for 5 h until the polyether block amide polymer was completely dissolved to obtain a casting solution 1. The casting solution 1 was placed in a forced air oven to remove bubbles for more than 24 h.

[0130] (2) Add 300 ml of 10°C ultrapure water to a 15 cm diameter glass culture dish and let it stand for 15 min.

[0131] (3) 300 μl of the casting solution 1 obtained in (1) is dropped onto the water surface. The film floats on the liquid surface and adheres to the polytetrafluoroethylene-based substrate.

[0132] (4) The composite membrane obtained in (3) was placed in a 40°C forced air oven for 12 h to remove the solvent, and then heat treated in an 80°C forced air oven for 5 h to obtain composite membrane A.

[0133] (5) 2 g of polydimethylsiloxane was dissolved in 18 g of n-heptane, and the mixture was stirred for 12 h. Then, 0.2 g of ethyl orthosilicate and 0.005 g of dibutyltin dilaurate were added, and the mixture was stirred in a 60° C. water bath for 1.5 h to obtain a casting solution 2.

[0134] (6) Take 500 μl of the casting solution 2 obtained in (5) and drop it onto the upper surface of composite film A. Set the spin coating speed to 500 rpm for 2 s; then set the spin coating speed to 3000 rpm for 60 s. Composite film B is obtained.

[0135] (7) The film obtained in (6) was placed in a 60°C forced air oven for 3 h.

[0136] (8) Repeat (6) and (7) twice in sequence to obtain composite membrane C.

[0137] (9) The composite film C was placed in a 10% RH constant humidity chamber for 12 h, and then placed in a 80°C vacuum oven for 8 h.

[0138] The prepared pervaporation composite membrane was used for the pervaporation separation of butanol / water. The feed liquid 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 liquid temperature was 60 °C. The flux and separation factor for the butanol / water mixture were 3.1 kg·m -2 ·h -1 and 21.

[0139] Example 7

[0140] (1) 3.5 g of polyether block amide PEBA2533, 31 g of n-butanol and 15.5 g of isopropanol were mixed and stirred in a water bath at 80° C. for 5 h until the polyether block amide polymer was completely dissolved to obtain a casting solution 1. The casting solution 1 was placed in a forced air oven to remove bubbles for more than 24 h.

[0141] (2) Add 300 ml of 10°C ultrapure water to a 15 cm diameter glass culture dish and let it stand for 15 min.

[0142] (3) 300 μl of the casting solution 1 obtained in (1) is dropped onto the water surface. The film floats on the liquid surface and adheres to the polytetrafluoroethylene-based substrate.

[0143] (4) The composite membrane obtained in (3) was placed in a 40°C forced air oven for 12 h to remove the solvent, and then heat treated in an 80°C forced air oven for 5 h to obtain composite membrane A.

[0144] (5) 2 g of polydimethylsiloxane was dissolved in 18 g of n-heptane, and the mixture was stirred for 12 h. Then, 0.2 g of ethyl orthosilicate and 0.005 g of dibutyltin dilaurate were added, and the mixture was stirred in a 60° C. water bath for 1.5 h to obtain a casting solution 2.

[0145] (6) Take 500 μl of the casting solution 2 obtained in (5) and drop it onto the upper surface of composite film A. Set the spin coating speed to 500 rpm for 2 s; then set the spin coating speed to 3000 rpm for 60 s. Composite film B is obtained.

[0146] (7) The film obtained in (6) was placed in a forced air oven at 60°C for 3 h to obtain composite film C.

[0147] (8) The composite film C was placed in a 10% RH constant humidity chamber for 12 h, and then placed in a 80°C vacuum oven for 8 h.

[0148] The prepared pervaporation composite membrane was used for the pervaporation separation of butanol / water. The feed liquid was a 1 wt% butanol / water solution, the vacuum degree on the downstream side of the membrane was less than 600 Pa, the feed liquid temperature was 60 °C, and the flux and separation factor for the butanol / water mixture were 6.2 kg·m -2 ·h -1 and 16.3.

[0149] Comparative Example 1

[0150] (1) 2 g of polydimethylsiloxane was dissolved in 18 g of n-heptane, and the mixture was stirred for 12 h. Then, 0.2 g of ethyl orthosilicate and 0.005 g of dibutyltin dilaurate were added, and the mixture was stirred in a 60° C. water bath for 1.5 h to obtain a casting solution 1.

[0151] (2) Take 500 μl of the casting solution 2 obtained in (1) and drop it onto the upper surface of the polytetrafluoroethylene-based substrate. Set the spin coating speed to 500 rpm for 2 s; then set the spin coating speed to 3000 rpm for 60 s. A composite composite membrane A is obtained.

[0152] (3) The film obtained in (2) was placed in a forced air oven at 60°C for 3 h.

[0153] (4) Repeat (2) and (3) twice in sequence to obtain composite membrane C.

[0154] (5) The composite film C was placed in a 10% RH constant humidity chamber for 12 h, and then placed in a 80°C vacuum oven for 8 h.

[0155] The prepared pervaporation composite membrane was used for the pervaporation separation of butanol / water. The feed liquid 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 liquid temperature was 60 °C. The flux and separation factor for the butanol / water mixture were 10.7 kg·m -2 ·h -1 and 12.3.

[0156] Comparative Example 2

[0157] (1) 3.5 g of polyether block amide PEBA2533, 31 g of n-butanol and 15.5 g of isopropanol were mixed and stirred in a water bath at 80° C. for 5 h until the polyether block amide polymer was completely dissolved to obtain a casting solution 1. The casting solution 1 was placed in a forced air oven to remove bubbles for more than 24 h.

[0158] (2) Add 300 ml of 10°C ultrapure water to a 15 cm diameter glass culture dish and let it stand for 15 min.

[0159] (3) 300 μl of the casting solution 1 obtained in (1) is dropped onto the water surface. The film floats on the liquid surface and adheres to the polytetrafluoroethylene-based substrate.

[0160] (4) The composite membrane obtained in (3) was placed in a 40°C forced air oven for 12 h to remove the solvent, and then heat treated in an 80°C forced air oven for 5 h to obtain composite membrane A.

[0161] The prepared pervaporation composite membrane was used for the pervaporation separation of butanol / water. The feed liquid was a 1 wt% butanol / water solution, the vacuum degree on the downstream side of the membrane was less than 600 Pa, the feed liquid temperature was 60 °C, and the flux and separation factor for the butanol / water mixture were 6.9 kg·m -2 ·h -1 and 16.6.

[0162] Test Example 1

[0163] In this test example, photographs were taken on the spin coating effects of the pervaporation composite membranes provided in Example 1 and Comparative Example 1.

[0164] The pervaporation composite membrane provided in Example 1 is a double-layer composite membrane containing an intermediate layer of PEBA, on which PDMS is spin-coated. The pervaporation composite membrane provided in Example 1 has a surface that is evenly spin-coated with PDMS, a comprehensive and smooth spin-coating effect, and a good spreading effect.

[0165] The pervaporation composite membrane provided in Comparative Example 1 does not contain an intermediate layer of PEBA, and is obtained by spin coating PDMS on a PTFE substrate support layer. The pervaporation composite membrane provided in Comparative Example 1 has an uneven surface coating of PDMS, an incomplete spiral effect of the spin coating, and a poor spreading effect.

[0166] This test example also tests the spreading effect of the pervaporation composite membrane provided in Example 1 and Comparative Example 1. Figure 1 The left side shows the spreading effect of PDMS on the double-layer composite membrane containing the middle layer of PEBA in Example 1; the right side shows the spreading effect of PDMS on the PTFE base support layer without the middle layer of PEBA. Figure 1 It can be clearly seen that in Comparative Example 1, most of the PDMS penetrates into the support layer, and this situation is significantly improved in Example 1.

[0167] Test Example 2

[0168] In this test example, SEM electron microscope scanning was performed on the cross-section of the pervaporation composite membrane provided in Example 1, Comparative Example 1 and Comparative Example 2.

[0169] The pervaporation composite membrane provided in Example 1 is a PDMS-PEBA / PTFE double-layer membrane structure. The pervaporation composite membrane provided in Example 1 has an example showing a membrane thickness of 3.4 μm and a flat and smooth membrane cross-sectional structure.

[0170] The pervaporation composite membrane provided in Comparative Example 1 is a PDMS / PTFE composite membrane structure. The pervaporation composite membrane provided in Comparative Example 1 has a membrane thickness of 10 μm, and a flat membrane cross-section structure but with obvious pore structures.

[0171] The pervaporation composite membrane provided in Comparative Example 2 is a PEBA / PTFE composite membrane structure. The pervaporation composite membrane provided in Comparative Example 2 has a membrane thickness of 2.8 μm and a flat and smooth membrane cross-sectional structure.

[0172] In Example 1, the two materials PDMS and PTFE are clearly separated and have a distinct boundary. Analysis shows that the boundary area between the two is PEBA material.

[0173] In Comparative Example 1, PDMS and PTFE are mixed with each other, resulting in serious permeation.

[0174] This test example also performed SEM surface electron microscope scanning on the pervaporation composite membrane provided in Comparative Example 1. The pervaporation composite membrane provided in Comparative Example 1, that is, the spin-coated PDMS on the PTFE substrate support layer without the intermediate layer, had obvious holes on the surface, and it was not a dense structure. This may be caused by the occurrence of permeation.

[0175] The above description is only for the purpose of facilitating the technical solution of the present invention to be understood by those skilled in the art, and is not intended to limit the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A pervaporation composite membrane, characterized in that: The pervaporation composite membrane comprises: a porous substrate (1), an intermediate membrane layer (2) and a separation membrane layer (3) which are stacked 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 average pore size of the porous substrate (1) is greater than or equal to 250 nm; The intermediate film layer (2) has organic matter affinity characteristics; The separation membrane layer (3) has hydrophobic characteristics and organic matter selective permeation characteristics.

2. A pervaporation composite membrane according to claim 1, characterized in that: The intermediate film layer (2) is a polyether block amide film, and the material of the intermediate film layer is one of polyether block amide PEBA2533, polyether block amide PEBA3533, polyether block amide PEBA4033, and polyether block amide PEBA1657; The separation membrane layer (3) is a polydimethylsiloxane membrane; The porous substrate (1) is selected from one of polysulfone membrane, polyacrylonitrile membrane, polyvinylidene fluoride membrane, polytetrafluoroethylene membrane, polypropylene membrane, polyethylene membrane, polyethersulfone membrane, polybenzimidazole membrane and cellulose acetate membrane.

3. A pervaporation composite membrane according to claim 1, characterized in that: The thickness of the porous substrate is 100um-150um; The thickness of the intermediate film layer is 2um-7um; The thickness of the separation membrane layer is 1um-10um.

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