In-situ preparation method and application of PVA / TpHz composite film

Abstract

The application relates to an in-situ preparation method and application of a PVA / TpHz composite film, relates to the technical field of high-end fine chemical processes, and is characterized in that TP is mixed with proper DMF and glacial acetic acid in a container, and the mixture is recorded as solution A; PVA is mixed with proper glycerol, and the mixture is recorded as solution B; solutions A and B are mixed, proper deionized water is added, and the mixture is uniformly mixed to obtain a mixed solution; the mixed solution is heated until completely dissolved, and then cooled to room temperature; proper hydrazine hydrate solution is added, uniformly mixed, and then degassed; an organic polymer carrier base film is placed on a smooth panel, a film is prepared by using a film preparation tool, and then placed into a preheated oven for drying and crosslinking for a period of time, so that the PVA / TpHz composite film is finally obtained. The film has a relatively flat appearance, a thin separation layer, and a uniform thickness distribution, which is beneficial to the separation factor and flux of the film; the film surface is continuous and crack-free, the surface is relatively rough, which is beneficial to the hydrophilicity of the film, and the film has good high-temperature stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fine chemicals high-end process, in particular to a method for in-situ preparation of PVA / TpHz composite membrane and application. BACKGROUND

[0002] Fine chemicals refer to those with specific application functions, technology-intensive, strong commodity, high value-added chemical products. These products are usually made by deep processing, with specific functions, specific purposes, a variety of small batch, high value-added. Many of the raw materials of fine chemicals, such as ethanol, tetrahydrofuran, isopropanol, chloroform and cyclohexane, etc. need to be purified in the process of product high-end. In reality, the separation of the mixture is usually achieved by using the property of the mixture to form azeotrope, which is called azeotropic distillation. However, in the conventional rectifying column, azeotropic distillation has the fatal defects of high energy consumption, complex operation, high cost and serious pollution, which limits its development speed in the industrial field. However, with the development of pervaporation technology and membrane separation technology, the energy consumption of azeotropic distillation is reduced by 35% and a large amount of pollution is reduced. It is imperative to promote the pervaporation membrane separation technology. In the development process of pervaporation separation membrane, many problems have been encountered, especially the practical problems of complex preparation process and high cost of separation membrane, which hinder the large-scale industrialization development.

[0003] PVA / COF composite membrane is a novel combination in membrane separation. Due to the regularity, controllability and uniformity of COF structure, PVA / COF composite membrane has excellent permeability, selectivity and high temperature stability for organic raw materials. However, the synthesis of general PVA / COF composite membrane needs to synthesize COF monomer first, then form casting solution, and then go through a series of steps such as scraping, non-solvent induced phase separation, surface segregation, soaking and drying to prepare the membrane. In the preparation process, the dispersion degree of COF monomer is the key to the performance of the membrane. The performance of PVA / COF composite membrane prepared by this method is uneven, the yield is low, and it is difficult to mass produce.

[0004] Therefore, it is of great significance to develop a new, simple, low-cost, green, energy-saving, high-performance, high-yield PVA / COF composite membrane in-situ preparation method. SUMMARY

[0005] In order to solve the problems of complex process, uneven performance, low yield and difficult mass production of current PVA / COF composite membrane, the present application provides a method for in-situ preparation of PVA / TpHz composite membrane and application, which has the advantages of low-cost process, green, energy saving, high-performance composite membrane, high yield, and meets the requirements of industrial production.

[0006] In order to achieve the above object, the technical scheme adopted by the present application is:

[0007] A method for in-situ preparation of a PVA / TpHz composite membrane is to synthesize TpHz in-situ in a PVA casting solution to prepare a composite membrane, and the specific steps are as follows:

[0008] (1) Put 1,3,5-triformylphloroglucinol (Tp) and an appropriate amount of N,N-dimethylformamide (DMF) and glacial acetic acid into a container and mix uniformly, denoted as solution A; mix polyvinyl alcohol (PVA) and an appropriate amount of glycerol uniformly, denoted as solution B; mix solutions A and B and supplement with an appropriate amount of deionized water, and mix uniformly to obtain a mixed solution;

[0009] (2) Heat the mixed solution until completely dissolved, then cool to room temperature, then add an appropriate amount of hydrazine hydrate solution (Hz·H2O), mix uniformly, and then deaerate;

[0010] (3) Place the organic polymer carrier base film on a smooth panel, use a film preparation tool to prepare a film, then place it in a preheated oven for a period of time for drying and crosslinking, and finally obtain a PVA / TpHz composite membrane.

[0011] As a further preferred technical scheme of the present application, in the preparation method:

[0012] In steps (1) and (2), the mixing method includes mechanical stirring, ultrasonic, shaking or manual stirring.

[0013] In step (2), the heating and dissolving temperature is 50-150℃. The cooling method includes natural cooling, air cooling, liquid cooling or circulating cooling. One of ultrasonic, shaking, centrifugation, vacuum deaeration and heating is used for deaeration.

[0014] In step (3), the organic polymer carrier base film is selected from polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE). A doctor blade or a table-top film applicator is used for film preparation. The drying and crosslinking temperature is 50-200℃, and the time is 0.1-12h.

[0015] The PVA / TpHz composite membrane prepared by the present application can be applied in organic-water solution pervaporation separation, and can be used for membrane separation treatment of a mixed system of ethanol, tetrahydrofuran, isopropyl alcohol, chloroform, cyclohexane and the like and water.

[0016] Compared with the prior art, the present application has the following beneficial effects:

[0017] (1) The present application can avoid the product performance difference caused by uneven dispersion of COF structure monomers (Tp, Hz) by synthesizing TpHz in-situ in a PVA casting solution to prepare a composite membrane, and the yield is high.

[0018] (2) The PVA / TpHz composite membrane prepared by the application has a relatively flat morphology, a thin separation layer, and a uniform thickness distribution, which is beneficial to its separation factor and flux, and the continuous surface of the membrane without cracks and the relatively rough surface are beneficial to its hydrophilicity, and the composite membrane has good high-temperature stability.

[0019] (3) The PVA / TpHz composite membrane prepared by the application can be used for membrane separation treatment of an organic-water mixed system such as an ethanol, tetrahydrofuran, isopropanol, chloroform and cyclohexane system, has high permeation capacity and high selectivity for water molecules, and has good high-temperature stability.

[0020] (4) The PVA / TpHz composite membrane prepared by the application is used in the field of pervaporation membrane separation of high-end fine chemical processes, can greatly reduce the energy consumption of azeotropic distillation in industrial production, and greatly reduces the environmental pollution degree of a rectifying column in industrial production.

[0021] (5) The raw material used in the preparation method has a moderate price, the reaction is simple and easy to control, and the method is easy to industrialize. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 X-ray powder diffraction pattern of the PVA / TpHz composite membrane prepared in Example 1.

[0023] Figure 2 Fourier transform infrared spectrum of the PVA / TpHz composite membrane prepared in Example 1.

[0024] Figure 3 Thermogravimetric analysis diagram of the PVA / TpHz composite membrane prepared in Example 1.

[0025] Figure 4 Scanning electron microscope images of the surface of the PVA / TpHz composite membrane prepared in Example 1, wherein a and b represent high and low magnifications, respectively.

[0026] Figure 5 Scanning electron microscope images of the cross section of the PVA / TpHz composite membrane prepared in Example 1, wherein a and b represent high and low magnifications, respectively.

[0027] Figure 6 Pervaporation performance diagram of the PVA / TpHz composite membrane prepared in Example 1 in an organic-water solution system.

[0028] Figure 7 Long-time pervaporation performance diagram of the PVA / TpHz composite membrane prepared in Example 1 in an ethanol-water solution system. DETAILED DESCRIPTION

[0029] The application provides an in-situ preparation method of a PVA / TpHz composite film.

[0030] (1) 50-1000 mg 1,3,5-triformylphloroglucinol (Tp) is mixed with 1-10 mL N,N-dimethylformamide (DMF) and 0.1-2 mL glacial acetic acid in a container, and the mixture is uniformly mixed, and the mixture is recorded as solution A; 1-10 g polyvinyl alcohol (PVA) is mixed with 0.1-1 mL glycerol, and the mixture is uniformly mixed, and the mixture is recorded as solution B; the solutions A and B are mixed, and deionized water is added to a total weight of 50-500 g, and the mixture is uniformly mixed to obtain a mixed solution.

[0031] (2) The mixed solution is heated until completely dissolved, and then cooled to room temperature; then 30-1000 μL of hydrazine hydrate solution (Hz·H2O) is added, and the mixture is uniformly mixed and degassed.

[0032] (3) An organic polymer carrier base film is placed on a smooth panel, a film is prepared by using a film preparation tool, and then the film is placed in a preheated oven for drying and crosslinking for a period of time, and finally a PVA / TpHz composite film is obtained.

[0033] The application is further described in detail in combination with the embodiments and the drawings.

[0034] Example 1

[0035] An in-situ preparation method of a PVA / TpHz composite film:

[0036] (1) 100 mg 1,3,5-triformylphloroglucinol (Tp), 5 mL N,N-dimethylformamide (DMF) and 1 mL glacial acetic acid are placed in a container and ultrasonically treated, and the mixture is recorded as solution A. 3 g of polyvinyl alcohol (PVA) and 0.19 mL of glycerol are uniformly mixed, and the mixture is recorded as solution B. The solutions A and B are uniformly stirred, and deionized water is added to a total weight of 50 g.

[0037] (2) The mixed solution is placed in a heating device at 98℃ until completely dissolved, and then cooled to room temperature. 30 μL of hydrazine hydrate solution (Hz·H2O) is added to the above solution, and the mixture is uniformly stirred and ultrasonically degassed.

[0038] (3) A polyvinylidene fluoride (PVDF) base film is placed on a smooth panel, a film is prepared by using a doctor blade, and then the film is placed in a preheated oven at 150℃, dried and crosslinked for 6 min, and a PVA / TpHz composite film is obtained.

[0039] As Figure 1As shown in the figure, the small-angle diffraction peak of PVA / TpHz at about 2.5° and the diffraction peak at 20° completely correspond to those of TpHz monomer, confirming the successful synthesis of PVA / TpHz composite film.

[0040] like Figure 2 As shown in the Fourier transform infrared spectrum of TpHz powder, 679 cm -1 、977cm -1 、1180cm -1 、1272cm -1 、1443cm -1 、1585cm -1 The diamond marks are marked at the same positions, which are exactly consistent with the diamond marks of PVA / TpHz in the figure, proving the existence of TpHz in the membrane. Figure 1 The results echoed each other and confirmed the successful synthesis of PVA / TpHz composite membrane.

[0041] like Figure 3 As shown in the figure, at around 230°C, the weight change of the PVA / TpHz composite membrane is probably due to the evaporation of water and organic matter in the membrane, while the weight change of the membrane itself is very small, which proves its excellent high temperature resistance.

[0042] like Figure 4 、 Figure 5 As shown in the figure, its morphology is relatively flat, the separation layer is thin, and the thickness distribution is uniform, which is conducive to improving its separation factor and flux. Under high magnification scanning electron microscopy, the membrane surface is continuous and crack-free, while under low magnification scanning electron microscopy, the surface is relatively rough, which is conducive to its hydrophilicity.

[0043] Example 2

[0044] An in-situ preparation method of PVA / TpHz composite membrane:

[0045] (1) Place 500 mg of 1,3,5-triformylphloroglucinol (Tp), 10 mL of N,N-dimethylformamide (DMF), and 2 mL of glacial acetic acid in a container and ultrasonically treat. This is referred to as solution A. Mix 10 g of polyvinyl alcohol (PVA) and 1 mL of glycerol. This is referred to as solution B. Ultrasonicate solutions A and B, and add deionized water to a total weight of 300 g.

[0046] (2) Place the mixed solution in a heating device at 70°C until completely dissolved, then cool to room temperature. Add 1000 μL of hydrazine hydrate solution (Hz·H2O) to the above solution, shake it evenly, and perform vacuum degassing.

[0047] (3) Put the polytetrafluoroethylene (PTFE) base film on the smooth panel, use the table type uniform glue machine to make the film, after the film is made, put it into the oven preheated to 50℃, dry and crosslink for 12h, to obtain the PVA / TpHz composite film.

[0048] Example 3

[0049] PVA / TpHz composite film in organic-water solution system pervaporation performance test:

[0050] 95wt% ethanol aqueous solution, 70wt% tetrahydrofuran aqueous solution, 90wt% isopropanol aqueous solution, 84wt% acetonitrile aqueous solution are respectively configured, and the separation membrane performance test device is used to test the permeation performance and separation factor of PVA / TpHz composite film for dehydration of organic-water solution system. The organic-water solution feed liquid is placed on the upstream of the membrane, the flow rate of the feed side is adjusted to 20L·h -1 The feed liquid is circulated, the feed liquid is kept at 55℃ by using a hydrothermal heating device, and the change of the feed liquid temperature on the feed side is monitored by using a K-type thermocouple. In the performance test, 0.1MPa vacuum pressure is used for organic-water solution system pervaporation test, the vacuum pump is used to apply pressure on the permeation side, and the obtained permeate is collected in a liquid nitrogen cold trap. After starting the pervaporation device, the flow rate and temperature of the feed liquid are adjusted to ensure stable operation of the device. The performance test is carried out after reaching the stable state, and one group of pervaporation experiments is designed to be carried out for 3h.

[0051] As Figure 6 shown, in the four organic-water solution systems, compared with the industrial benchmark, PVA / TpHz composite film has good permeation performance. This shows that the PVA / TpHz composite film prepared by this method has good development potential in the field of pervaporation organic dehydration.

[0052] Example 4

[0053] PVA / TpHz composite film in ethanol-water solution system long-time pervaporation performance test:

[0054] 95wt% ethanol aqueous solution is configured, and the separation membrane performance test device is used to test the permeation performance and separation factor of PVA / TpHz composite film for dehydration of ethanol-water solution system. The ethanol aqueous solution feed liquid is placed on the upstream of the membrane, the flow rate of the feed side is adjusted to make the feed liquid circulate, the feed liquid is kept at 55℃ by using a hydrothermal heating device, and the change of the feed liquid temperature on the feed side is monitored by using a K-type thermocouple. In the performance test, 0.1MPa vacuum pressure is used for ethanol-water mixture pervaporation test, the vacuum pump is used to apply pressure on the permeation side, and the obtained permeate is collected in a liquid nitrogen cold trap. After starting the pervaporation device, the flow rate and temperature of the feed liquid are adjusted to ensure stable operation of the device.

[0055] AsFigure 7 As shown, the water flux and water content of the composite membrane in the permeation solution at 55 DEG C are relatively stable throughout the entire 100h pervaporation test, and the composite membrane has excellent long-term stable separation capacity.

[0056] The above is only an example and illustration of the concept of the present application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace, as long as the concept of the present application is not deviated or the scope defined by the present application is not exceeded, which shall belong to the protection scope of the present application.

Claims

1. An in-situ preparation method of a PVA / TpHz composite membrane, characterized in that: The composite membrane was prepared by in-situ synthesis of TpHz in PVA casting solution. The specific steps are as follows: (1) 1,3,5-triformylphloroglucinol (Tp) was mixed evenly with an appropriate amount of N,N-dimethylformamide (DMF) and glacial acetic acid in a container, which was recorded as solution A; polyvinyl alcohol (PVA) was mixed evenly with an appropriate amount of glycerol, which was recorded as solution B; solutions A and B were mixed and supplemented with an appropriate amount of deionized water, and mixed evenly to obtain a mixed solution; (2) Heat the mixed solution until it is completely dissolved, cool it to room temperature, then add an appropriate amount of hydrazine hydrate solution (Hz·H2O), mix well, and degas; (3) Place the organic polymer carrier base film on a smooth panel, use a film-making tool to prepare a film, and then place it in a preheated oven for drying and cross-linking for 0.1-12 hours to finally obtain a PVA / TpHz composite film.

2. The in-situ preparation method according to claim 1, wherein The addition ratios of 1,3,5-triformylphloroglucinol (Tp), polyvinyl alcohol (PVA) in step (1) and hydrazine hydrate solution (Hz·H2O) in step (2) are: 50-1000 mg, 1-10 g, and 30-1000 μL, respectively.

3. The in-situ preparation method according to claim 1, wherein The heating and dissolving temperature in step (2) is 50-150°C.

4. The in-situ preparation method according to claim 1, wherein In step (2), degassing is performed by one of ultrasonic, oscillation, centrifugation, vacuum degassing and heating.

5. The in-situ preparation method according to claim 1, wherein The organic polymer carrier base membrane in step (3) is selected from polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE).

6. The in-situ preparation method according to claim 1, wherein In step (3), a scraper or a table-top coating machine is used to form the film.

7. The in-situ preparation method according to claim 1, wherein The drying and cross-linking temperature in step (3) is 50-200°C.

8. Use of the PVA / TpHz composite membrane prepared by the method according to any one of claims 1 to 7 in organic-aqueous solution pervaporation separation.

Images