A three-layer composite membrane for dehydration of dipolar aprotic solvents and its preparation method

Abstract

The present invention provides a three-layer composite membrane for dehydration of a dipole aprotic solvent and a preparation method thereof, relating to the technical field of membrane materials. The present invention comprises the following steps: soaking a base membrane in pure water to remove impurities, and drying the base membrane after the impurities are removed; soaking the dried base membrane in a pore retaining agent for 3 to 5 hours, taking it out and soaking it in pure water for 10 to 20 minutes; taking out the base membrane soaked in pure water and draining it, soaking it in a monomer aqueous solution for 1 to 10 minutes, draining it after the soaking is completed, and setting it aside; soaking the treated base membrane in an organic solution containing a polyacyl chloride for 1 to 10 minutes, wherein the concentration of the polyacyl chloride is 0.05wt.%-2wt.%; taking out the treated base membrane and heat-reacting it at 50-70°C for 1 to 10 minutes to form an intermediate layer on the base membrane; spin-coating a BTESE sol on the intermediate layer; and heat-retaining the spin-coated membrane at 100-200°C for 5-30 minutes and repeating the spin-coating to obtain a three-layer composite membrane. The three-layer composite membrane of the present invention can perform pervaporation dehydration on a dipolar aprotic solvent, thereby improving dehydration efficiency, reducing energy consumption and increasing product purity.

Description

Technical Field

[0001] The invention belongs to the technical field of membrane materials, and particularly relates to a three-layer composite membrane for dehydration of a dipole aprotic solvent and a preparation method thereof. Background Art

[0002] Membrane separation technology has been widely used in various fields, including petrochemicals, pharmaceutical separation, and environmental management, due to its advantages such as low energy consumption, high efficiency, and easy operation. In these applications, composite membranes have attracted much attention due to their excellent separation performance and mechanical properties.

[0003] Composite membranes typically consist of a porous support layer and a selective separation layer. The porous support layer enhances the membrane's mechanical properties, while the selective separation layer is responsible for the actual separation process. However, existing composite membranes face several challenges during their preparation. For example, the pore structure of the porous support layer can cause the selective separation layer to grow into the support layer during membrane formation, increasing mass transfer resistance and creating surface defects, which can affect the membrane's separation performance.

[0004] In existing technologies, the support layer and the selective layer of the composite membrane are optimized separately. Moreover, the pore structure on the surface of the porous support layer is not conducive to the subsequent growth of the selective layer, making it difficult to obtain a sufficiently dense and defect-free selective layer structure. Summary of the Invention

[0005] Based on this, the present invention aims to provide a three-layer composite membrane for dehydrating dipolar aprotic solvents and a method for preparing the same. By constructing an intermediate layer between the porous support layer and the selective layer, the present invention improves the surface morphology and properties of the porous support layer, overcoming the problem of growth of the selective layer into the support layer during film formation, thereby producing a composite membrane with excellent performance. The three-layer composite membrane of the present invention is capable of pervaporation dehydration of dipolar aprotic solvents, improving dehydration efficiency, reducing energy consumption, and increasing product purity.

[0006] The present invention is achieved by adopting the following technical solutions:

[0007] A method for preparing a three-layer composite membrane for dehydration of a dipolar aprotic solvent comprises the following steps:

[0008] (1) Soak the base film in pure water to remove impurities, and then dry it; soak the dried base film in a pore retaining agent for 3 to 5 hours, and then soak it in pure water for 10 to 20 minutes;

[0009] (2) taking out the basement membrane soaked in pure water and draining it, soaking it in a monomer aqueous solution for 1 to 10 minutes, draining it after the soaking, and setting it aside; the monomer includes at least one of piperazine, methylene triphenol, and biphenol;

[0010] (3) soaking the base film treated in step (2) in an organic solution containing polyacyl chloride for 1 to 10 minutes, wherein the concentration of the polyacyl chloride is 0.05 wt.% to 2 wt.%;

[0011] (4) taking out the base film treated in step (3) and heat-retaining it at 50-70° C. for 1-10 minutes to form an intermediate layer on the base film;

[0012] (5) Spin-coating the BTESE sol on the polyamide intermediate layer; keeping the spin-coated film at 100-200° C. for 5-30 min and repeatedly spin-coating to obtain a three-layer composite film.

[0013] Preferably, the base membrane is an organic solvent-resistant polyetheretherketone, polyamide-imide ultrafiltration membrane, or polytetrafluoroethylene. Preferably, the present invention involves first soaking the base membrane in pure water to remove preservatives from the membrane surface; drying the base membrane, then soaking it in a pore-preserving agent for treatment, and then soaking it in pure water again to remove the pore-preserving agent from the membrane surface. The drying temperature is preferably 40°C to 50°C.

[0014] Preferably, the pore-preserving agent is glycerol.

[0015] Preferably, the concentration of the monomer aqueous solution is 0.15 wt.%-2 wt.%.

[0016] Preferably, the organic solvent is one of n-hexane and isoparaffin. Preferably, the polyacid chloride of the present invention is trimesoyl chloride.

[0017] Preferably, the concentration of BTESE in the BTESE sol is 0.5 wt.%-10 wt.%.

[0018] Preferably, the BTESE sol is obtained by dissolving BTESE in an alcohol solvent, adding deionized water and a hydrochloric acid catalyst under continuous stirring, and heating in a water bath for 1 to 2 hours, wherein the alcohol solvent is one of methanol, ethanol, isopropanol, and n-propanol; and the molar ratio of the hydrochloric acid catalyst to BTESE is 0.01:1.

[0019] Preferably, the spin coating speed in step (5) is 500-6000 r / min and the acceleration is 50-1000 m / s 2 , the spin coating time is 5-60s.

[0020] Preferably, the amount of BTESE sol spin-coated each time in step (5) is 0.5-5 mL.

[0021] The present invention uses the prepared three-layer composite membrane to perform dehydration treatment on a dipolar aprotic solvent, thereby effectively improving dehydration efficiency, reducing energy consumption, and improving product purity.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] By introducing an intermediate layer into the composite membrane, the present invention significantly improves the selectivity and permeability of polymer membranes, thereby enhancing the efficiency of dipolar aprotic dehydration. The intermediate layer in the composite membrane acts as a buffer, reducing the adverse effects of the support layer's pores on the selective layer, making the selective layer more uniform and dense, and reducing mass transfer resistance. The introduction of the intermediate layer enhances the membrane's overall mechanical properties, improving its durability in industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Surface and cross-sectional SEM images of the PEEK-PA membrane prepared in Example 1;

[0025] Figure 2 The separation performance results of the PEEK-PA membrane after heat treatment in Example 2;

[0026] Figure 3 The pervaporation dehydration performance of the PEEK-PA-BTESE-n membrane prepared by multiple spin coating cycles in Example 3;

[0027] Figure 4 Surface and cross-sectional SEM images of the PEEK-PA-BTESE-4 membrane prepared in Example 3;

[0028] Figure 5 Pervaporation dehydration performance of the PEEK-PA-BTESE-4 membrane prepared in Example 3 and the PEEK-BTESE-4 prepared in Comparative Example 1; DETAILED DESCRIPTION

[0029] To make the purpose, technical solutions and advantages of the present invention more clear, the preferred embodiments of the present invention are further described in detail below with reference to the examples. Based on the examples in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0030] Example 1

[0031] A method for preparing a polyamide interlayer (PEEK-PA) membrane comprises the following steps:

[0032] (1) Soak the polyetheretherketone ultrafiltration membrane in pure water for two hours to remove the preservative on the membrane surface;

[0033] (2) The membrane was dried in an oven at 40°C and placed in a glycerol pore retainer for 4 hours. The membrane surface was then immersed in pure water for 15 minutes to remove the pore retainer on the membrane surface.

[0034] (3) removing water droplets from the surface of the membrane with a rubber roller, and immersing the membrane in a piperazine aqueous solution having a piperazine concentration of 0.4 wt.% at 25° C. for 3 min, and removing the remaining aqueous solution from the membrane surface with a rubber roller, and setting aside;

[0035] (4) Soaking the polyetheretherketone ultrafiltration membrane treated in step (3) in a n-hexane solution having a trimesoyl chloride concentration of 0.15 wt.% at 25° C. for 2 minutes;

[0036] (5) The film after the reaction in step (4) was placed in an oven at 60° C. and heated for 10 min to obtain a polyamide interlayer (PEEK-PA) film.

[0037] The surface and cross-sectional SEM images of the PEEK-PA membrane prepared in Example 1 are shown in FIG. Figure 1 .from Figure 1 It can be seen that the polyamide intermediate layer was successfully prepared on the polyetheretherketone ultrafiltration membrane.

[0038] Example 2

[0039] A method for preparing a polyamide interlayer (PEEK-PA) membrane comprises the following steps:

[0040] (1) Soak the polyetheretherketone ultrafiltration membrane in pure water for two hours to remove the preservative on the membrane surface;

[0041] (2) The membrane was dried in an oven at 40°C and placed in a glycerol pore retainer for 4 hours. The membrane surface was then immersed in pure water for 20 minutes to remove the pore retainer on the membrane surface.

[0042] (3) Remove water droplets from the surface of the membrane with a rubber roller, soak in an aqueous solution with a piperazine concentration of 0.4 wt.% at 25°C for 3 minutes, and remove the remaining aqueous solution on the surface of the membrane with a rubber roller, and set aside;

[0043] (4) Soaking the polyetheretherketone ultrafiltration membrane treated in step (3) in a n-hexane solution having a trimesoyl chloride concentration of 0.15 wt.% at 25° C. for 2 minutes;

[0044] (5) The membrane after the reaction in step (4) was placed in an oven at 60°C, 100°C, 150°C, and 200°C, respectively, and heated for 10 minutes to form a polyamide intermediate layer on the polyetheretherketone ultrafiltration membrane, thereby obtaining four PEEK-PA membranes.

[0045] The separation performance of the prepared PEEK-PA membrane was tested as follows Figure 2The membrane heat-treated at 60°C (Example 1) showed a methanol flux of 4.3 LMH / bar and a methyl orange (MO, MW = 327 Da) rejection of 96.9%. The dye concentration was 50 ppm in methanol, tested at a pressure of 6 bar, and after a one-hour pre-press at 25°C. Flux is measured in LMH / bar (liters / square meter / hour / bar).

[0046] Example 3

[0047] A method for preparing a three-layer composite membrane (PEEK-PA-BTESE membrane) for dehydration of a dipolar aprotic solvent, comprising the following steps:

[0048] The PEEK-PA membrane prepared in Example 1 was cut to a suitable size and fixed flatly on a glass slide with transparent tape. 2 ml of 4.0 wt.% organosilicone sol was dripped onto the membrane surface with a dropper until the membrane was completely covered. The membrane was maintained at a speed of 4000 r / min for 30 s and an acceleration of 500 m / s. 2 After the spin coating, the film was thermally cured at 150°C for 15 min and then taken out. This process was repeated n times to obtain a PEEK-PA-BTESE-n film.

[0049] At the same time, the pervaporation dehydration performance of the PEEK-PA-BTESE-n membrane prepared by multiple spin coating cycles was evaluated using NMP / water solution (90 wt.% NMP). Figure 3 As shown in the figure, with the increase of the number of spin coating cycles from 2 to 4, the permeation flux of these membranes increased from 0.46 kg / (m 2 h) gradually decreased to 0.39kg / (m 2 h), while the separation factor of NMP / water increased sharply from the initial 3500 to about 10,000. Figure 4 Shows the surface and cross-sectional SEM images of the PEEK-PA-BTESE-4 composite film prepared by spin coating four times.

[0050] The pervaporation dehydration performance of the PEEK-PA-BTESE-4 membrane prepared by four spin-coating cycles was evaluated using NMP / water solution (90 wt.% NMP). Figure 5 As shown, the flux is 0.39 kg / (m 2 h), while the separation factor of NMP / water is about 10,000.

[0051] Example 4

[0052] A composite membrane with a three-layer structure for dehydration of a dipolar aprotic solvent is prepared with reference to Example 1, except that methylenetriphenol is used instead of piperazine, and other parameters remain unchanged.

[0053] Example 5

[0054] A composite membrane with a three-layer structure for dehydration of dipolar aprotic solvents is prepared with reference to Example 1, except that diphenol is used instead of piperazine, while other parameters remain unchanged.

[0055] Comparative Example 1

[0056] A method for preparing an organosilicon composite film is as follows:

[0057] (1) Soak the polyetheretherketone ultrafiltration membrane in pure water for 2 h to remove the preservatives in the membrane;

[0058] (2) The polyetheretherketone ultrafiltration membrane was taken out, dried in an oven at 40°C, immersed in a glycerol pore retainer for 4 hours, and then the surface was immersed in pure water for 15 minutes to remove the pore retainer on the surface.

[0059] (3) The membrane was fixed flat on a glass slide with transparent tape. 2 ml of 4.0 wt.% organic silicon sol was dripped onto the membrane surface with a dropper until the PEEK-PA membrane was completely covered. The speed was maintained at 4000 r / min for 30 s and the acceleration was 500 m / s. 2 After spin coating, the film was thermally cured at 150°C for 15 minutes and then removed. This process was repeated four times to obtain a PEEK-BTESE-4 film.

[0060] The pervaporation NMP dehydration test of the prepared composite membrane showed that the total flux was 0.26 kg / m 2 h, the separation factor is 6650.

[0061] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

Claims

1. A method for preparing a three-layer composite membrane for dehydration of a dipolar aprotic solvent, characterized in that: The following steps are involved: (1) Soak the base film in pure water to remove impurities, and then dry it; soak the dried base film in a pore retaining agent for 3 to 5 hours, and then soak it in pure water for 10 to 20 minutes; (2) taking out the basement membrane soaked in pure water and draining it, soaking it in a monomer aqueous solution for 1 to 10 minutes, draining it after the soaking, and setting it aside; the monomer includes at least one of piperazine, methylene triphenol, and biphenol; (3) soaking the base film treated in step (2) in an organic solvent containing polyacyl chloride for 1 to 10 minutes, wherein the concentration of the polyacyl chloride is 0.05 wt.% to 2 wt.%; (4) taking out the base film treated in step (3) and heat-retaining it at 50-70° C. for 1-10 minutes to form an intermediate layer on the base film; (5) Spin-coating the BTESE sol on the intermediate layer; keeping the spin-coated film at 100-200° C. for 5-30 min and repeatedly spin-coating to obtain a three-layer composite film.

2. The method for preparing a three-layer composite membrane for dehydration of a dipolar aprotic solvent according to claim 1, characterized in that: The base membrane is polyetheretherketone, polyamide-imide ultrafiltration membrane, or polytetrafluoroethylene.

3. The method for preparing a three-layer composite membrane for dehydration of a dipolar aprotic solvent according to claim 1, characterized in that: The pore retaining agent is glycerol.

4. The method for preparing a three-layer composite membrane for dehydration of a dipolar aprotic solvent according to claim 1, characterized in that: The concentration of the monomer aqueous solution is 0.15 wt.%-2 wt.%.

5. The method for preparing a three-layer composite membrane for dehydration of a dipolar aprotic solvent according to claim 1, characterized in that: The organic solvent is one of n-hexane and isoparaffin.

6. The method for preparing a three-layer composite membrane for dehydration of a dipolar aprotic solvent according to claim 1, characterized in that: The concentration of BTESE in the BTESE sol is 0.5 wt.%-10 wt.%.

7. The method for preparing a three-layer composite membrane for dehydration of a dipolar aprotic solvent according to claim 1, characterized in that: The BTESE sol is prepared by dissolving BTESE in an alcohol solvent, adding deionized water and a hydrochloric acid catalyst under continuous stirring, and heating in a water bath for 1 to 2 hours. The alcohol solvent is one of methanol, ethanol, isopropanol, and n-propanol. The molar ratio of the hydrochloric acid catalyst to the BTESE is 0.01:

1.

8. The method for preparing a three-layer composite membrane for dehydration of a dipolar aprotic solvent according to claim 1, characterized in that: Step (5) Spin coating speed is 500-6000r / min, acceleration is 50-1000m / s 2 , the spin coating time is 5-60s.

9. The method for preparing a three-layer composite membrane for dehydration of a dipolar aprotic solvent according to claim 1, characterized in that: In step (5), the amount of BTESE sol spin-coated each time is 0.5-5 mL.

10. A three-layer composite membrane for dehydration of a dipolar aprotic solvent, characterized in that: The method is prepared by any one of claims 1 to 9.

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