High-selectivity PVA (Polyvinyl Alcohol) separation membrane as well as preparation method and application thereof

Abstract

The invention relates to the technical field of separation membranes, in particular to a high-selectivity PVA separation membrane as well as a preparation method and application thereof. The PVA separation membrane provided by the invention is modified by adopting the alpha-cyclodextrin and / or the alpha-cyclodextrin derivative, so that the selectivity of the PVA separation membrane is obviously improved, and the PVA separation membrane can be used for separating a mixture of water and organic matters in an alcohol-water system and the like, and is suitable for separating and preparing a high-purity product. The preparation method is simple and easy to operate, does not introduce new impurities, and can be applied to industrial production of high-purity products.

Description

Technical Field

[0001] The present invention relates to the technical field of separation membranes, and more specifically to a high-selectivity PVA separation membrane and a preparation method and application thereof. Background Art

[0002] Cyclodextrin (CD) was discovered by Vellier in 1891, and its structure was characterized by Freundg and French in 1935. Cyclodextrin is a type of cyclic oligosaccharide composed of D-pyranose glucose linked by α-1,4 glycosidic bonds. The number of glucose residues is 6, 7, and 8, respectively called α-cyclodextrin (α-CD), β-cyclodextrin (β-CD), and γ-cyclodextrin (γ-CD). The molecular configuration of cyclodextrin is quite special, with a slightly conical, hollow cylindrical, three-dimensional annular truncated cone structure. The top, bottom, and outside of the truncated cone are all hydrophilic surfaces, but the inside is a 5- The hydrophobic cavity of the molecule. Depending on the size of the cavity, the cavity can form different inclusion complexes with the guest molecule by utilizing hydrophobic interactions, hydrogen bonds, and van der Waals forces for molecular recognition. Based on the fact that the inclusion complex, especially the inclusion equilibrium, is very sensitive to the size, structure, and hydrophilicity of the guest molecule, cyclodextrin is considered to be a preferred material for "molecular recognition" separation and processing. At present, this "molecular recognition" or "selective inclusion" has been widely used in chemical separation, chemical analysis, medicine, food, pesticides and other fields.

[0003] The above-mentioned performance characteristics of cyclodextrin make it applicable to the field of separation membranes. For example, in order to prevent cyclodextrin from dissolving into the feed liquid, people prepared a cross-linked cyclodextrin membrane and applied it to dialysis, which is very effective for separating various liquid mixtures (Hirai H, Komiyama M, Yamamotc H. Preparation of Cyclodextrine Membrane and its Selective Permeation J. Inclus., Phenom., 1984, 2: 265). In addition, some people introduced cyclodextrin into polymer membranes for separating the optical isomers of amino acids (Ishihara K, Suzuki N, Matsui K. Bull., Chem., Soc., Jpn., 1987 (3): 446).

[0004] There are difficulties in the alcohol-water separation process, which causes the alcohol-water separation effect to be affected. If conventional distillation methods are used, the alcohol-water mixture cannot be effectively separated, and only alcohol-water azeotropes or their mixtures can be obtained. For example, the industrial ethanol concentration is only 95.7wt%, because ethanol and water form an azeotrope, and the azeotropic temperature of this azeotrope is 78.15°C, which is very close to the boiling point of ethanol (78.30°C). If you want to prepare high-purity, ultra-high-purity, anhydrous ethanol, it is necessary to further use methods such as calcium oxide dehydration, adsorption distillation, pervaporation, adsorption, extraction distillation and vacuum dehydration to improve the purity of alcohol components, resulting in equipment and process complexity, and high energy consumption. If extraction / boiling distillation technology is used, not only the process is complicated, the equipment used is more, and conventional distillation cannot obtain high-purity alcohol products, and entrainer (boiling agent) needs to be added to the alcohol-water mixture to form a new azeotrope with a certain component in the original system, which is more than 10°C lower than the boiling point of any component in the system or the original azeotropic point. Common entrainers include benzene, n-hexane, cyclohexane, ethyl acetate, etc., which will affect product quality if left in the product. Therefore, the entrainer needs to be removed later, resulting in high separation energy consumption or limited product performance.

[0005] Isopropyl alcohol is an important member of the alcohol product family. It is an organic solvent with excellent performance and an important organic chemical raw material. The application fields of isopropyl alcohol in China mainly include: pharmaceutical intermediates (23%), organic synthesis (22%), electronic cleaning (20%), pesticides (18%), inks (12%) and coatings (5%). In recent years, the country has continued to increase investment and R&D support for the semiconductor industry. Chemical reagents for integrated circuits IC or very large-scale integrated circuits VLSI have ushered in another opportunity for vigorous development. Isopropyl alcohol used as an electronic cleaning agent has entered an explosive growth. Isopropyl alcohol used as an electronic cleaning agent has very high requirements for product purity. For example, it must meet the performance index requirement of purity>99.95% at least. The industrial isopropyl alcohol currently produced is difficult to meet the performance requirements of electronic cleaning agents, and it needs to be further concentrated, purified and purified. However, the existing conventional distillation method cannot effectively separate the alcohol / water azeotrope, and needs to be further combined with calcium oxide dehydration, adsorption distillation, pervaporation, adsorption, extraction distillation and vacuum dehydration to improve the purity of the alcohol component, resulting in complex equipment and processes and high energy consumption. It is also difficult to separate high-purity alcohol components using ordinary pervaporation membranes for alcohol / water separation.

[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 object of the present invention is to provide a high-selectivity PVA separation membrane and a preparation method thereof, so as to solve the technical problem that the separation effect of alcohol-water mixture in the prior art is not ideal.

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

[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 PVA modified with cyclodextrin, 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 the α-cyclodextrin derivative refers to a modified α-cyclodextrin obtained by introducing a substituent into 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 high-selectivity PVA separation membrane further comprises a bottom membrane. The bottom membrane can provide necessary mechanical properties, especially strength or pressure shock performance.

[0015] According to some embodiments of the present invention, the bottom 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 mixed solution of PVA and cyclodextrin; forming a membrane from the mixed solution; and performing heat treatment to obtain the highly selective PVA separation membrane.

[0017] Existing commonly used polymer film-forming methods are all applicable to the preparation method of the highly selective PVA separation membrane provided by the present invention, which not only facilitates mass production and reduces costs, but also can form membranes, membrane assemblies or membrane components of any configuration or shape, with a wide range of applicable scenarios and strong universality.

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

[0019] According to some embodiments of the present invention, the film forming is performed at 20-40°C.

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

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

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

[0023] In the preparation method of the highly selective PVA separation membrane provided by the present invention, the membrane is heat treated by the above-mentioned heat treatment method, which is not only beneficial to improving the separation effect of the PVA separation membrane, but also can prevent the separation effect of the PVA separation membrane from being significantly reduced after long-term use.

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

[0025] In a third aspect, the present invention provides the use of the high-selectivity PVA separation membrane described in the first aspect or the high-selectivity 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 application in alcohol dehydration, especially application in ethanol or isopropanol dehydration.

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

[0028] In a fourth aspect, the present invention provides a separation device, comprising a membrane separation module, wherein the membrane separation module comprises the high-selectivity PVA separation membrane described in the first aspect or the high-selectivity PVA separation membrane prepared by the preparation method described in the second aspect.

[0029] According to actual use needs, a high-selectivity PVA separation membrane or multiple high-selectivity PVA separation membranes can be set in the membrane separation module, so that the mixture to be separated undergoes a single membrane separation treatment or undergoes multiple membrane separation treatments in sequence. The purity of the product obtained after separation can be further improved by subjecting the mixture to be separated to multiple membrane separation treatments in sequence.

[0030] The beneficial effects of the present invention are at least:

[0031] The PVA separation membrane provided by the present invention is modified by using α-cyclodextrin and / or α-cyclodextrin derivatives, which significantly improves the selectivity of the PVA separation membrane, can be used for separation of mixtures of organic matter and water such as alcohol-water systems, and is suitable for separation and preparation of high-purity products. The preparation method adopted by the present invention is simple and easy to operate, and does not introduce new impurities, and can be applied to the industrial production of high-purity products. DETAILED DESCRIPTION

[0032] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this patent in detail and do not limit the scope of protection of the present invention in any way.

[0033] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the raw materials, instruments and equipment used in the following examples, etc., can all be purchased on the market or can be obtained by existing methods; the reagent amounts, unless otherwise specified, are the reagent amounts used in conventional experimental operations; the experimental methods, unless otherwise specified, are all conventional methods.

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

[0035] Example 1

[0036] 1) Weigh 10 parts of PVA 1788 and dissolve them in 80 parts of water, fully wet for 3 hours, then heat while stirring, complete swelling, unlimited swelling, until fully dissolved at 80°C, and 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 adding the α-CD solution to the PVA solution, stirring at 30° C. until the mixture is uniformly mixed, to obtain a film-forming solution; forming a film with the film-forming solution by a doctor blade method, specifically, forming a film on a commercially available PVDF base film with a nominal pore size of 0.05 μm using a 100 μm scalpel, to form a 100 μm thick wet film;

[0038] 3) The wet membrane was dried at 50°C for 24 h, and then slowly heated to 130°C at a rate of 0.5°C / min for 2 h to obtain an 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, fully wet for 3 hours, then heat while stirring, complete swelling, unlimited swelling, until fully dissolved at 90°C, and 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 adding the α-CD solution to the PVA solution, stirring at 35° C. until the mixture is uniformly mixed, to obtain a film-forming solution; forming a film with the film-forming solution by a roller pressing method, specifically, forming a film on a commercially available PAN-based film with a nominal pore size of 0.08 μm using a roller gap of 100 μm to form a 100 μm thick wet film;

[0042] 3) The wet membrane was dried at 60°C for 20 h, and then slowly heated to 140°C at 0.5°C / min for 1 h to obtain an 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, fully wet for 3 hours, then heat while stirring, complete swelling, unlimited swelling, until fully dissolved at 80°C, and 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 adding the α-CD solution to the PVA solution, stirring at 30° C. until the mixture is uniform, to obtain a film-forming solution; forming a film by spraying the film-forming solution, specifically, spraying the film-forming solution on a commercially available PAN-based film with a nominal pore size of 0.08 μm, to form a wet film of about 100 μm thick;

[0046] 3) The wet membrane was dried at 50°C for 24 h, and then slowly heated to 130°C at a rate of 0.5°C / min for 2 h to obtain an α-CD modified PVA separation membrane.

[0047] Example 4

[0048] The preparation method of the PVA separation membrane refers to that of 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 refers to that of 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 refers to Example 1, with the only difference being that α-CD is replaced with an equal mass of glucosyl-α-CD (Shanghai Jinpan Biotechnology Co., Ltd.).

[0053] Example 7

[0054] The preparation method of the PVA separation membrane refers to Example 1, with the only difference being 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, fully wet for 3 hours, then heat while stirring, complete swelling, unlimited swelling, until fully dissolved at 80°C, and 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 adding the α-CD solution to the PVA solution, stirring at 30° C. until the mixture is uniformly mixed, to obtain a film-forming solution; forming a film with the film-forming solution by a doctor blade method, specifically, forming a film on a commercially available PVDF base film with a nominal pore size of 0.05 μm using a 100 μm scalpel, to form a 100 μm thick wet film;

[0058] 3) Dry the wet membrane at 50° C. for 24 h to obtain an α-CD modified PVA separation membrane.

[0059] Comparative Example 1

[0060] The preparation method of the PVA separation membrane is similar to that of 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 similar to that of 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 them in 100 parts of water, fully wet for 3 hours, then heat while stirring, complete swelling, unlimited swelling, until fully dissolved at 80°C, and then cool to room temperature to obtain a PVA solution;

[0065] 2) forming a film of the PVA solution by a doctor blade method, specifically, forming a film on a commercially available PVDF base film with a nominal pore size of 0.05 μm using a 100 μm scalpel to form a 100 μm thick wet film;

[0066] 3) The wet film was dried at 50°C for 24 h, and then slowly heated to 130°C at 0.5°C / min for 2 h to obtain a PVA separation membrane.

[0067] Performance evaluation of PVA separation membrane

[0068] The PVA separation membranes provided in the examples and comparative examples were applied to an aqueous solution containing 95.1 wt% isopropyl alcohol (IPA) to conduct a dehydration test. The specific conditions were: operating temperature was 25°C, the separation membrane area was 12.57 cm 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: The separation factor > 100 after 500 hours indicates that the separation effect of the PVA separation membrane is still relatively ideal after long-term use, and the durability of the PVA separation membrane is good.

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

[0074] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to 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 words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A highly selective PVA separation membrane, characterized in that: The high-selectivity PVA separation membrane is prepared from PVA modified by cyclodextrin, and the cyclodextrin includes α-cyclodextrin and / or α-cyclodextrin derivatives.

2. The highly selective PVA separation membrane according to claim 1, characterized in that: The mass ratio of the PVA to cyclodextrin is 100:(10-20), preferably 100:(12-15).

3. The highly selective PVA separation membrane according to claim 1 or 2, characterized in that: The α-cyclodextrin derivative includes at least one of allyl-α-cyclodextrin, hydroxypropyl-α-cyclodextrin, and glucosyl-α-cyclodextrin.

4. The highly selective PVA separation membrane according to any one of claims 1 to 3, characterized in that: The highly selective PVA separation membrane also includes a bottom membrane; Preferably, the bottom membrane is selected from ultrafiltration membranes, preferably at least one of polyvinylidene fluoride ultrafiltration membranes, polyacrylonitrile ultrafiltration membranes, and polysulfone ultrafiltration membranes.

5. The method for preparing a highly selective PVA separation membrane according to any one of claims 1 to 4, characterized in that: include: Obtaining a mixed solution of PVA and cyclodextrin; forming the mixed solution into a film; The high-selectivity PVA separation membrane is prepared by heat treatment.

6. The preparation method according to claim 5, characterized in that: The film forming method includes any one of scraping, painting, dipping, spraying and rolling.

7. The preparation method according to claim 6, characterized in that: The film formation is carried out at 20-40°C.

8. The preparation method according to any one of claims 5 to 7, characterized in that: The heat treatment comprises drying at 50-60° C. first, heating to 120-160° C., and keeping the temperature for 5-120 minutes.

9. Application of the highly selective PVA separation membrane according to any one of claims 1 to 4 or the highly selective PVA separation membrane prepared by the preparation method according to any one of claims 5 to 8 in the field of pervaporation; Preferably, the application is in alcohol dehydration, especially in ethanol or isopropanol dehydration; More preferably, the purity of the dehydrated ethanol or isopropanol is >99.95%.

10. A separation device, characterized in that: The separation device comprises a membrane separation module, and the membrane separation module comprises the high-selectivity PVA separation membrane described in any one of claims 1 to 4 or the high-selectivity PVA separation membrane prepared by the preparation method described in any one of claims 5 to 8.

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