High-selectivity pva separation membrane, and preparation method and application thereof

Abstract

This invention relates to the field of separation membrane technology, and more specifically, to a highly selective PVA separation membrane, its preparation method, and its applications. The PVA separation membrane provided by this invention, modified with α-cyclodextrin and / or α-cyclodextrin derivatives, significantly improves the selectivity of the PVA separation membrane. It can be used to separate mixtures of organic matter and water, such as alcohol-water systems, and is suitable for the separation and preparation of high-purity products. The preparation method employed in this invention is simple and easy to operate, and does not introduce new impurities, making it applicable to the industrial production of high-purity products.

Description

Technical Field

[0001] This invention relates to the field of separation membrane technology, and more specifically, to a highly selective PVA separation membrane, its preparation method, and its application. Background Technology

[0002] Cyclodextrins (CDs) were discovered by Vellier in 1891, and their structure was characterized by Frenderg and French in 1935. Cyclodextrins are a class of cyclic oligosaccharides composed of D-pyranose glucose linked by α-1,4 glycosidic bonds. Cyclodextrins with 6, 7, or 8 glucose residues are designated as α-cyclodextrin (α-CD), β-cyclodextrin (β-CD), and γ-cyclodextrin (γ-CD), respectively. The molecular configuration of cyclodextrins is somewhat unique, exhibiting a slightly conical, hollow cylindrical, three-dimensional truncated cone structure. The top, bottom, and outer surfaces of the truncated cone are hydrophilic, while the interior is 5- Cyclodextrins contain hydrophobic cavities. Depending on the cavity size, and utilizing hydrophobic interactions, hydrogen bonds, and van der Waals forces for molecular recognition, the cavity can form different inclusion complexes with guest molecules. Based on the inclusion complexes, especially the inclusion equilibrium, which is highly sensitive to the size, structure, and hydrophilicity of the guest molecules, cyclodextrins are considered a preferred material for "molecular recognition" separation processes. Currently, this "molecular recognition" or "selective inclusion" is widely used in chemical separation, chemical analysis, pharmaceuticals, food, pesticides, and other fields.

[0003] The aforementioned properties of cyclodextrin make it suitable for use in the field of separation membranes. For example, to prevent cyclodextrin from dissolving in the feed solution, a cross-linked cyclodextrin membrane has been prepared and applied to dialysis, proving highly effective in separating various liquid mixtures (Hirai H, Komiyama M, Yamamotc H. Preparation of Cyclodextrine Membrane and its Selective Permeation J. Inclus., Phenom., 1984, 2:265). Furthermore, cyclodextrin has been introduced into polymer membranes for the separation of optical isomers of amino acids (Ishihara K, Suzuki N, Matsui K. Bull., Chem., Soc., Jpn., 1987(3):446).

[0004] Difficulties exist in alcohol-water separation, affecting its effectiveness. Conventional distillation methods cannot effectively separate alcohol-water mixtures, yielding only azeotropes or mixtures thereof. For example, industrial ethanol concentration is only 95.7 wt% because ethanol and water form an azeotrope with an azeotropic temperature of 78.15℃, very close to the boiling point of ethanol (78.30℃). To prepare high-purity, ultra-high-purity, anhydrous ethanol, further methods such as calcium oxide dehydration, adsorption distillation, pervaporation, adsorption, extractive distillation, and vacuum dehydration are needed to improve the purity of the alcohol components, resulting in complex equipment, processes, and high energy consumption. If an extraction / azeotropic distillation process is used, not only is the process complex and requires more equipment, but conventional distillation cannot obtain high-purity alcohol products. An entrainer (azeotropic agent) must be added to the alcohol-water mixture to form a new azeotrope with a component in the original system, with a boiling point at least 10℃ lower than any component or the original azeotropic point. Common entrainers include benzene, n-hexane, cyclohexane, and ethyl acetate, which can affect product quality if left in the product. Therefore, subsequent removal of these entrainers is necessary, leading to high separation energy consumption or limited product performance.

[0005] Isopropanol is an important member of the alcohol family, a high-performance organic solvent, and a crucial organic chemical raw material. In China, the main applications of isopropanol include: pharmaceutical intermediates (23%), organic synthesis (22%), electronic cleaning (20%), pesticides (18%), inks (12%), and coatings (5%). In recent years, the government has continuously increased investment and R&D support for the semiconductor industry, leading to another boom in chemical reagents used in integrated circuits (ICs) and very large-scale integrated circuits (VLSIs). Isopropanol used as an electronic cleaning agent has experienced explosive growth. Isopropanol used as an electronic cleaning agent requires very high purity, for example, it must meet a purity requirement of at least >99.95%. Currently, industrially produced isopropanol cannot meet the performance requirements of electronic cleaning agents and requires further concentration, purification, and refinement. However, existing conventional distillation methods cannot effectively separate alcohol / water azeotropes. Further methods such as calcium oxide dehydration, adsorption distillation, pervaporation, adsorption, extractive distillation, and vacuum dehydration are needed to improve the purity of alcohol components, resulting in complex equipment and processes and high energy consumption. Even using ordinary pervaporation membranes for alcohol / water separation is difficult to achieve high-purity alcohol components.

[0006] Therefore, it is of great significance to prepare a separation membrane with high selectivity for alcohol-water mixtures. Summary of the Invention

[0007] The purpose of this invention is to provide a highly selective PVA separation membrane and its preparation method, so as to solve the technical problem that the separation effect of alcohol-water mixtures in the prior art is not ideal.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] In a first aspect, the present invention provides a highly selective PVA separation membrane, wherein the highly selective PVA separation membrane is prepared from cyclodextrin-modified PVA, wherein the cyclodextrin includes α-cyclodextrin (α-CD) and / or α-cyclodextrin derivatives (α-CD derivatives).

[0010] According to some embodiments of the present invention, the mass ratio of PVA to cyclodextrin is 100:(10-20), for example, it can be 100:10, 100:11, 100:12, 100:12.5, 100:13, 100:14, 100:14.5, 100:15, 100:16, 100:17, 100:18, 100:19, 100:20, etc.

[0011] According to some embodiments of the present invention, the mass ratio of PVA to cyclodextrin is 100:(12-15).

[0012] It should be noted that α-cyclodextrin derivatives refer to α-cyclodextrin modified products obtained by introducing substituents onto α-cyclodextrin.

[0013] According to some embodiments of the present invention, the α-cyclodextrin derivative includes at least one of allyl-α-cyclodextrin, hydroxypropyl-α-cyclodextrin, and glucosyl-α-cyclodextrin.

[0014] According to some embodiments of the present invention, the highly selective PVA separation membrane further includes a bottom membrane. The bottom membrane can provide the necessary mechanical properties, particularly strength or pressure shock resistance.

[0015] According to some embodiments of the present invention, the substrate membrane is selected from ultrafiltration membranes, preferably at least one of polyvinylidene fluoride (PVDF) ultrafiltration membranes, polyacrylonitrile (PAN) ultrafiltration membranes, and polysulfone (PSF) ultrafiltration membranes.

[0016] In a second aspect, the present invention provides a method for preparing the highly selective PVA separation membrane described in the first aspect, comprising: obtaining a mixture of PVA and cyclodextrin; forming the mixture into a membrane; and subjecting it to heat treatment to obtain the highly selective PVA separation membrane.

[0017] All commonly used polymer film-forming methods are applicable to the preparation method of the highly selective PVA separation membrane provided by this invention. This method not only facilitates mass production and reduces costs, but also allows for the molding of membranes, membrane modules, or membrane components of any configuration or shape, making it widely applicable and highly versatile.

[0018] According to some embodiments of the present invention, the film-forming method includes any one of scraping, coating, dipping, spraying, and rolling.

[0019] According to some embodiments of the present invention, the film formation is carried out at 20–40°C.

[0020] According to some embodiments of the present invention, the film thickness is 50–200 μm.

[0021] According to some embodiments of the present invention, the film thickness is 80–120 μm.

[0022] According to some embodiments of the present invention, the heat treatment includes first drying at 50-60°C; then heating to 120-160°C and holding at that temperature for 5-120 minutes.

[0023] In the preparation method of the highly selective PVA separation membrane provided by the present invention, the above-mentioned heat treatment method is used to heat treat the membrane, which not only helps to improve the separation effect of the PVA separation membrane, but also prevents the separation effect of the PVA separation membrane from decreasing significantly after long-term use.

[0024] According to some embodiments of the present invention, the drying time is 12 to 24 hours.

[0025] Thirdly, the present invention provides the application of the highly selective PVA separation membrane described in the first aspect or the highly selective PVA separation membrane prepared by the preparation method described in the second aspect in the field of pervaporation.

[0026] According to some embodiments of the present invention, the application is an application in the dehydration of alcohols, especially in the dehydration of ethanol or isopropanol.

[0027] According to some embodiments of the present invention, the purity of the dehydrated ethanol or isopropanol is >99.95%.

[0028] Fourthly, the present invention provides a separation device, the separation device including a membrane separation module, the membrane separation module including the highly selective PVA separation membrane described in the first aspect or the highly selective PVA separation membrane prepared by the preparation method described in the second aspect.

[0029] Depending on the actual application requirements, the membrane separation module can be equipped with one high-selectivity PVA separation membrane or multiple high-selectivity PVA separation membranes sequentially, so that the mixture to be separated undergoes one membrane separation process or multiple membrane separation processes sequentially. Passing the mixture to be separated through multiple membrane separation processes sequentially can further improve the purity of the product obtained after separation.

[0030] The beneficial effects of this invention are at least as follows:

[0031] The PVA separation membrane provided by this invention, modified with α-cyclodextrin and / or α-cyclodextrin derivatives, significantly improves the selectivity of the PVA separation membrane. It can be used to separate mixtures of organic matter and water, such as alcohol-water systems, and is suitable for the separation and preparation of high-purity products. The preparation method used in this invention is simple and easy to operate, and does not introduce new impurities, making it applicable to the industrial production of high-purity products. Detailed Implementation

[0032] To make the technical problem to be solved, the technical solution, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely for illustrating this patent and do not limit the scope of protection of this invention in any way.

[0033] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art. Unless otherwise specified, the reagents used in the following embodiments are conventional biochemical reagents; the raw materials, instruments, and equipment used in the following embodiments can all be obtained commercially or by existing methods; unless otherwise specified, the reagent dosages are those used in routine experimental operations; unless otherwise specified, the experimental methods are conventional methods.

[0034] The 1 part (by weight) mentioned in the various embodiments and comparative examples of the present invention can be any weight such as 10g, 100g, 1000g, or 10kg.

[0035] Example 1

[0036] 1) Weigh 10 parts of PVA 1788 and dissolve them in 80 parts of water, thoroughly wet them for 3 hours, then heat while stirring to complete the swelling, infinite swelling, and complete dissolution at 80℃, then cool to room temperature to obtain a PVA solution; weigh 1.5 parts of α-CD and dissolve them in 20 parts of water to obtain an α-CD solution;

[0037] 2) Slowly add the α-CD solution to the PVA solution and stir at 30°C until the mixture is homogeneous to obtain the film-forming solution; the film-forming solution is then used to form a film by a blade coating method, specifically by using a 100μm scalpel to form a 100μm thick wet film on a commercially available PVDF base film with a nominal pore size of 0.05μm.

[0038] 3) Dry the wet membrane at 50℃ for 24h, and then heat it at 130℃ for 2h by slowly increasing the temperature at 0.5℃ / min to obtain the α-CD modified PVA separation membrane.

[0039] Example 2

[0040] 1) Weigh 10 parts of PVA 1799 and dissolve them in 80 parts of water, thoroughly wet them for 3 hours, then heat while stirring, successively complete swelling, infinite swelling, until fully dissolved at 90℃, then cool to room temperature to obtain a PVA solution; weigh 1.3 parts of α-CD and dissolve them in 20 parts of water to obtain an α-CD solution;

[0041] 2) Slowly add the α-CD solution to the PVA solution and stir at 35°C until the mixture is homogeneous to obtain the film-forming solution; the film-forming solution is used to form a film by roller pressing, specifically by using a 100μm roller gap on a commercially available PAN base film with a nominal pore size of 0.08μm to form a 100μm thick wet film.

[0042] 3) Dry the wet membrane at 60℃ for 20h, and then heat it at 140℃ for 1h by slowly increasing the temperature at 0.5℃ / min to obtain the α-CD modified PVA separation membrane.

[0043] Example 3

[0044] 1) Weigh 10 parts of PVA 1788 and dissolve them in 120 parts of water, thoroughly wet them for 3 hours, then heat while stirring to complete the swelling, infinite swelling, and complete dissolution at 80℃, then cool to room temperature to obtain a PVA solution; weigh 1.2 parts of α-CD and dissolve them in 40 parts of water to obtain an α-CD solution;

[0045] 2) Slowly add the α-CD solution to the PVA solution and stir at 30°C until the mixture is homogeneous to obtain the film-forming liquid; the film-forming liquid is then applied to a commercially available PAN base film with a nominal pore size of 0.08μm to form a wet film with a thickness of about 100μm.

[0046] 3) Dry the wet membrane at 50℃ for 24h, and then heat it at 130℃ for 2h by slowly increasing the temperature at 0.5℃ / min to obtain the α-CD modified PVA separation membrane.

[0047] Example 4

[0048] The preparation method of the PVA separation membrane is the same as in Example 1, except that the amount of α-CD is changed from 1.5 parts to 1 part.

[0049] Example 5

[0050] The preparation method of the PVA separation membrane is the same as in Example 1, except that the amount of α-CD is changed from 1.5 parts to 2 parts.

[0051] Example 6

[0052] The preparation method of the PVA separation membrane is the same as in Example 1, except that α-CD is replaced with an equal mass of glucose-α-CD (Shanghai Jinpan Biotechnology Co., Ltd.).

[0053] Example 7

[0054] The preparation method of the PVA separation membrane is the same as in Example 1, except that α-CD is replaced with an equal mass of allyl-α-CD (Shanghai Jinpan Biotechnology Co., Ltd.).

[0055] Example 8

[0056] 1) Weigh 10 parts of PVA 1788 and dissolve them in 80 parts of water, thoroughly wet them for 3 hours, then heat while stirring to complete the swelling, infinite swelling, and complete dissolution at 80℃, then cool to room temperature to obtain a PVA solution; weigh 1.5 parts of α-CD and dissolve them in 20 parts of water to obtain an α-CD solution;

[0057] 2) Slowly add the α-CD solution to the PVA solution and stir at 30°C until the mixture is homogeneous to obtain the film-forming solution; the film-forming solution is then used to form a film by a blade coating method, specifically by using a 100μm scalpel to form a 100μm thick wet film on a commercially available PVDF base film with a nominal pore size of 0.05μm.

[0058] 3) Dry the wet membrane at 50℃ for 24 hours to obtain the α-CD modified PVA separation membrane.

[0059] Comparative Example 1

[0060] The preparation method of the PVA separation membrane is the same as in Example 1, except that α-CD is replaced with an equal mass of β-CD.

[0061] Comparative Example 2

[0062] The preparation method of the PVA separation membrane is the same as in Example 1, except that α-CD is replaced with an equal mass of γ-CD.

[0063] Comparative Example 3

[0064] 1) Weigh 10 parts of PVA 1788 and dissolve it in 100 parts of water. Wet the solution thoroughly for 3 hours. Then, while stirring, heat the solution to complete the swelling, infinite swelling, and complete dissolution at 80°C. Then cool the solution to room temperature to obtain a PVA solution.

[0065] 2) The PVA solution is coated to form a film using a blade coating method. Specifically, a 100μm scalpel is used to coat the film onto a commercially available PVDF base film with a nominal pore size of 0.05μm to form a wet film with a thickness of 100μm.

[0066] 3) Dry the wet membrane at 50℃ for 24 hours, and then heat it at 130℃ for 2 hours by slowly increasing the temperature at 0.5℃ / min to obtain the PVA separation membrane.

[0067] Performance evaluation of PVA separation membrane

[0068] The PVA separation membranes provided in the various examples and comparative examples were applied to an aqueous solution containing 95.1 wt% isopropanol (IPA) for dehydration tests. Specific conditions were: operating temperature 25°C, and membrane area 12.57 cm². 2 .

[0069] The performance test results of the PVA separation membrane are shown in Table 1.

[0070] Table 1 Performance Evaluation of PVA Separation Membrane

[0071]

[0072] Note: A separation coefficient >100 after 500 hours indicates that the PVA separation membrane still has a relatively ideal separation effect after long-term use, and the PVA separation membrane has good durability.

[0073] The test results above show that the PVA separation membrane provided by the present invention, by modifying it with α-cyclodextrin and α-cyclodextrin derivatives, can significantly improve the selectivity of the PVA separation membrane. It can be used for further purification of high-concentration isopropanol-water mixtures to obtain high-purity alcohol products.

[0074] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A highly selective PVA separation membrane, characterized in that, The highly selective PVA separation membrane is prepared from cyclodextrin-modified PVA, wherein the cyclodextrin includes α -Cyclodextrin and / or α - Cyclodextrin derivatives; The method for preparing the highly selective PVA separation membrane includes: obtaining a mixture of PVA and cyclodextrin; forming the mixture into a membrane; and subjecting it to heat treatment to obtain the highly selective PVA separation membrane. The heat treatment includes first drying at 50-60°C; then heating to 120-160°C and holding at that temperature for 5-120 minutes.

2. The highly selective PVA separation membrane according to claim 1, characterized in that, The mass ratio of PVA to cyclodextrin is 100:(10-20).

3. The highly selective PVA separation membrane according to claim 1, characterized in that, The mass ratio of PVA to cyclodextrin is 100:(12-15).

4. The highly selective PVA separation membrane according to any one of claims 1-3, characterized in that, The α -Cyclodextrin derivatives include allyl- α -Cyclodextrin, hydroxypropyl- α -Cyclodextrin, glucose- α - At least one of the cyclodextrins.

5. The highly selective PVA separation membrane according to any one of claims 1-3, characterized in that, The highly selective PVA separation membrane also includes a bottom membrane.

6. The highly selective PVA separation membrane according to claim 5, characterized in that, The substrate membrane is selected from ultrafiltration membranes.

7. The highly selective PVA separation membrane according to claim 5, characterized in that, The substrate membrane is selected from at least one of polyvinylidene fluoride ultrafiltration membrane, polyacrylonitrile ultrafiltration membrane, and polysulfone ultrafiltration membrane.

8. The method for preparing the highly selective PVA separation membrane according to any one of claims 1-7, characterized in that, include: A mixture of PVA and cyclodextrin is obtained; the mixture is formed into a film; and heat treatment is performed to obtain the highly selective PVA separation membrane. The heat treatment includes first drying at 50-60°C; then heating to 120-160°C and holding at that temperature for 5-120 minutes.

9. The preparation method according to claim 8, characterized in that, The film-forming method includes any one of the following: scraping, coating, dipping, spraying, and rolling.

10. The preparation method according to claim 8 or 9, characterized in that, The film formation is carried out at 20–40°C.

11. The application of the highly selective PVA separation membrane according to any one of claims 1-7 or the highly selective PVA separation membrane prepared by the preparation method according to any one of claims 8-10 in the field of pervaporation.

12. The application according to claim 11, characterized in that, The application is in the dehydration of alcohol.

13. The application according to claim 11, characterized in that, The application is in the dehydration of ethanol or isopropanol.

14. The application according to claim 13, characterized in that, The purity of the dehydrated ethanol or isopropanol is >99.95%.

15. A separation device, characterized in that, The separation device includes a membrane separation module, which includes a highly selective PVA separation membrane according to any one of claims 1-7 or a highly selective PVA separation membrane prepared by the preparation method according to any one of claims 8-10.

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