Three-layer structure composite membrane for dipole aprotic solvent dehydration and preparation method of three-layer structure composite membrane

Abstract

The invention provides a three-layer structure composite membrane for dipole aprotic solvent dehydration and a preparation method of the three-layer structure composite membrane, and relates to the technical field of membrane materials. The preparation method comprises the following steps: soaking a base membrane in pure water for impurity removal, and drying after impurity removal; soaking the dried base membrane in a pore protecting agent for 3-5 hours, taking out the base membrane, and soaking the base membrane in pure water for 10-20 minutes; taking out and draining the base membrane soaked in the pure water, soaking the base membrane in a monomer aqueous solution for 1-10 minutes, and draining the base membrane for later use after soaking is finished; the treated base membrane is soaked in an organic solution containing multi-element acyl chloride for 1-10 min, and the concentration of the multi-element acyl chloride is 0.05 wt.%-2 wt.%; the treated base film is taken out and subjected to a heat preservation reaction for 1-10 min at the temperature of 50-70 DEG C, and a middle layer is formed on the base film; the intermediate layer is coated with BTESE sol in a spin coating mode; and keeping the temperature of the spin-coated film at 100-200 DEG C for 5-30 minutes, and repeatedly spin-coating to obtain the composite film with a three-layer structure. The composite membrane with the three-layer structure can perform pervaporation dehydration on the dipole aprotic solvent, so that the dehydration efficiency is improved, the energy consumption is reduced, and the product purity is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of membrane materials, and in particular 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 many fields such as petrochemical industry, drug separation, environmental management, etc. due to its advantages of low energy consumption, high efficiency and convenient operation. In these applications, composite membranes have attracted much attention due to their excellent separation performance and mechanical properties.

[0003] Composite membranes are usually composed of a porous support layer and a separation selective layer, where the porous support layer is used to enhance the mechanical properties of the membrane, while the separation selective layer is responsible for the actual separation effect. However, there are some challenges in the preparation process of existing composite membranes. For example, the pore structure on the surface of the porous support layer may cause the selective layer to grow into the support layer during the membrane formation process, thereby increasing the mass transfer resistance and generating surface defects, affecting the separation performance of the membrane.

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

[0005] Based on this, the purpose of the present invention is to provide a three-layer composite membrane for dehydration of a dipole aprotic solvent and a preparation method thereof. The present invention improves the surface morphology and properties of the porous support layer by constructing an intermediate layer between the porous support layer and the selective layer, overcomes the growth problem of the selective layer into the support layer during the film formation process, and thus prepares a composite membrane with excellent performance. The three-layer composite membrane of the present invention can dehydrate a dipole aprotic solvent by pervaporation, improves the dehydration efficiency, reduces energy consumption and improves the purity of the product.

[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 dipole aprotic solvent comprises the following steps:

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

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

[0010] (3) soaking the base film treated in step (2) in an organic solution containing polyacid chloride for 1 to 10 minutes, wherein the concentration of the polyacid 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; heat-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 polyetheretherketone, polyamide-imide ultrafiltration membrane, or polytetrafluoroethylene that is resistant to organic solvents. Preferably, the present invention is to soak the base membrane in pure water first to remove the preservative on the membrane surface; then soak it in a pore retaining agent after drying, and then soak it in pure water again to remove the pore retaining agent on the membrane surface. The drying temperature is preferably 40°C to 50°C.

[0014] Preferably, the pore retaining agent is glycerol.

[0015] Preferably, the concentration of the aqueous monomer 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 0.5wt.%-10wt.%.

[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 structure composite membrane to perform dehydration treatment on the dipole aprotic solvent, thereby effectively improving the dehydration efficiency, reducing energy consumption, and improving the purity of the product.

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

[0023] The present invention can significantly improve the selectivity and permeability of the polymer membrane by introducing an intermediate layer into the composite membrane, thereby improving the efficiency of dipole aprotic dehydration. The intermediate layer of the composite membrane of the present invention can act as a buffer to reduce the adverse effect of the pores of the support layer on the selection layer, making the selection layer more uniform and dense, and reducing mass transfer resistance. The introduction of the intermediate layer of the present invention can enhance the overall mechanical properties of the membrane and improve 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 The surface and cross-sectional SEM images of the PEEK-PA-BTESE-4 membrane prepared in Example 3;

[0028] Figure 5 The 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] In order to make the purpose, technical scheme and advantages of the present invention clearer, the preferred embodiments of the present invention are further described in detail in conjunction with the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without 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) drying the membrane in an oven at 40° C. and placing it in a glycerol pore retainer for 4 hours, then soaking the membrane surface 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, immersing the membrane in a piperazine aqueous solution having a piperazine concentration of 0.4 wt.% at 25° C. for 3 min, removing the residual aqueous solution on the surface of the membrane 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 min;

[0036] (5) The film after the reaction in step (4) is placed in an oven at 60° C. and heated for 10 minutes 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 as follows: 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, the steps are as follows:

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

[0041] (2) drying the membrane in an oven at 40° C. and placing it in a glycerol pore retainer for 4 hours, then soaking the membrane surface in pure water for 20 minutes to remove the pore retainer on the membrane surface;

[0042] (3) removing water droplets on the surface of the membrane with a rubber roller, immersing the membrane in an aqueous solution with a piperazine concentration of 0.4 wt.% at 25° C. for 3 min, removing the residual aqueous solution on the surface of the membrane with a rubber roller, and setting 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 min;

[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 min to form a polyamide intermediate layer on the polyetheretherketone ultrafiltration membrane, thereby obtaining four types of PEEK-PA membranes.

[0045] The prepared PEEK-PA membrane was tested for separation performance. Figure 2The results show that the methanol flux of the membrane (Example 1) heat-treated at 60°C is 4.3LMH / bar, and the rejection rate of methyl orange (MO, MW=327Da) is 96.9%. The dye concentration is 50ppm methanol solution, the test pressure is 6bar, and the test is performed after pre-pressing at 25°C for 1 hour. The flux unit is LMH / bar (liter / square meter / hour / bar).

[0046] Example 3

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

[0048] The PEEK-PA membrane prepared in Example 1 was cut into a suitable size and fixed flat on a glass sheet with a 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 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 Figure 2, as the number of spin coating cycles increases from 2 to 4, the permeation flux of these membranes increases 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 The surface and cross-sectional SEM images of the PEEK-PA-BTESE-4 composite film prepared by spin coating four times are shown.

[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 described with reference to Example 1, except that methylenetriphenol is used to replace piperazine, and other parameters remain unchanged.

[0053] Example 5

[0054] A composite membrane with a three-layer structure for dehydration of a dipolar aprotic solvent is described with reference to Example 1, except that biphenol is used to replace piperazine, and 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 hours 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, and 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 the spin coating, the film was thermally cured at 150°C for 15 min and then taken out. This process was repeated 4 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 part of the embodiments of the present invention, rather than all of the embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are 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) soaking the base film in pure water to remove impurities, and drying after removing impurities; soaking the dried base film in a pore retaining agent for 3 to 5 hours, and then soaking it in pure water for 10 to 20 minutes; (2) taking out the base film soaked in pure water and draining it, soaking it in a monomer aqueous solution for 1 to 10 minutes, draining it after soaking, and setting it aside; the monomer comprises at least one of piperazine, methylene triphenol, and biphenol; (3) soaking the base film treated in step (2) in an organic solution containing polyacid chloride for 1 to 10 minutes, wherein the concentration of the polyacid 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; heat the spin-coated film at 100-200° C. for 5-30 min and repeat the 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 dipole 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 dipole aprotic solvent according to claim 1, characterized in that: The organic solvent is one of n-hexane and isoalkane.

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

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