Hydrophobic MOF material-based mixed matrix membrane and preparation method thereof

Abstract

The application discloses a kind of based on hydrophobic MOF material mixed matrix flat membrane and its preparation method and application, preparation steps: S1, MOF material, crosslinking agent are weighed and added into solvent, sufficiently mixed uniformly, obtain A liquid;S2, after weighing organic polymer, add solvent, sufficiently mixed uniformly, obtain B liquid;S3, preparation casting solution: A liquid is mixed with B liquid, sufficiently mixed uniformly, catalyst is added, mixed uniformly, obtain casting solution;S4, take flat support and install to pulling machine, casting solution is loaded to flat support using dip-coating process, then dry, obtain mixed matrix flat membrane.The dip-coating film forming process of the application has the advantages of wide applicability, simple operation, controllable film thickness, uniformity and transparency of the film, small energy consumption, the prepared film layer is uniform, the film area is larger, can improve the permeability of the membrane while ensuring the high selectivity of the mixed matrix membrane.

Description

Technical Field

[0001] This invention relates to the field of membrane separation technology, specifically to a hydrophobic MOF material-based mixed matrix membrane and its preparation method. Background Technology

[0002] Butanol is a representative high-performance product among biofuels. Compared with ethanol, it has a higher calorific value, lower corrosivity, lower vapor pressure, and weaker hygroscopicity. It also has better miscibility with gasoline, making it easier to store and use. Biomass fermentation is one of the important routes for producing butanol; however, it suffers from product inhibition effects, resulting in lower yields and lower alcohol concentrations (generally below 5%), making subsequent product separation and recovery difficult.

[0003] Membrane separation boasts advantages such as no phase change, small footprint, high efficiency, energy saving, and environmental friendliness, and has been widely researched and applied in the fields of water environment and gas separation. Membrane separation technology utilizes materials with selective separation capabilities to achieve the separation of different components in a feed solution. Pervaporation (PV) is a type of membrane separation technology, particularly suitable for the separation of azeotropic compounds. PV utilizes the chemical potential difference between a component upstream and downstream of the membrane in the feed solution as the driving force for mass transfer, and leverages the differences in membrane affinity and mass transfer resistance to different components in the feed solution to achieve selectivity. Common applications include: recovery of organic matter in water, separation of organic-organic mixtures, and dehydration of organic solvents. Pervaporation technology uses the vapor pressure difference between components on both sides of the membrane as the driving force for mass transfer, based on the "dissolution-diffusion" or "adsorption-separation" mechanism for the separation of mixtures. The membrane material determines the membrane's performance; by selecting appropriate membrane materials and adjusting the membrane structure, the separation effect can be improved, and the cost and energy consumption of the separation process can be reduced. Therefore, the controllable preparation of membrane materials with high separation performance can reduce the cost of biobutanol, increase the production capacity of butanol, and help achieve my country's dual-carbon goals.

[0004] In past studies, pure organic membranes have often been used for the enrichment of butanol at low concentrations. However, pure organic membranes all exhibit a "trade-off" effect, meaning that the selectivity and permeability of the membrane are at odds. To overcome this "trade-off" effect, researchers have introduced porous inorganic fillers into organic matrices to obtain hybrid matrix membranes, which can further improve membrane permeability while maintaining high selectivity.

[0005] For mixed matrix membranes, the selection of inorganic fillers is crucial. MOF (Metal-Organic Framework) materials are crystalline materials assembled from metal ions and organic ligands. Therefore, MOF materials combine the advantages of both inorganic and organic materials. Their surfaces are rich in organic groups, exhibiting good compatibility with organic membrane materials and effectively avoiding interfacial defects in mixed matrix membranes. Compared to traditional porous materials, MOFs possess enormous specific surface area and porosity. Furthermore, MOF materials possess diverse topologies, and due to the abundance and modifiability of metals and ligands, selective adsorption and separation of guest molecules of different sizes, polarities, and functional groups can be achieved.

[0006] In pervaporation membrane modules, the membrane layer with separation function is synthesized on a support. Depending on the type of membrane module, the support has different shapes, such as tubular supports, flat sheet supports, and disc supports. Common support materials include α-Al₂O₃ supports, γ-Al₂O₃ supports, PAN supports, and PVDF supports. Plate-and-frame pervaporation membrane modules require flat sheet membranes, and the flat sheet membrane layer with separation function is synthesized on a flat sheet support. Currently, flat sheet membrane preparation processes include vacuum filtration, hot drop addition, spraying, and spin coating. Most reported flat sheet membranes involve loading the casting solution onto a single surface of an α-Al₂O₃ disc support via spin coating. This process can only grow a membrane on one surface of the support; the other surface cannot grow a membrane. Therefore, the surface area of ​​the separation membrane is small, and the working efficiency is low. Furthermore, since spin coating is only effective for coatings on small areas of the support, it is not suitable for large-scale production, limiting its application in research and development and large-scale production. Summary of the Invention

[0007] The purpose of this invention is to address the above-mentioned problems by providing a hybrid matrix membrane based on hydrophobic MOF materials and its preparation method.

[0008] To achieve its objective, the present invention employs the following technical solution:

[0009] The first aspect of the present invention provides a method for preparing a sheet membrane based on a hydrophobic MOF material hybrid matrix, comprising the following steps:

[0010] S1. Preparation of Solution A: Weigh the MOF material and crosslinking agent, add them to the solvent, and mix thoroughly to obtain Solution A;

[0011] S2. Preparation of solution B: Weigh the organic polymer and add solvent, mix thoroughly to obtain solution B;

[0012] S3. Preparation of casting solution: Mix solution A and solution B thoroughly and evenly, add catalyst, mix well, and obtain casting solution;

[0013] S4. Preparation of mixed matrix flat sheet membrane

[0014] The flat plate support is installed on the lifting machine, and the casting solution is loaded onto the flat plate support using the dip-lifting process. Then it is dried to obtain a mixed matrix flat plate membrane.

[0015] The solvent is selected from one or more of methanol, ethanol, isooctane, n-heptane, and cyclohexane, preferably isooctane;

[0016] The MOF material is selected from ZIF-8, ZIF-L, ZIF-67, ZIF-90, ZIF-7, and ZIF-71, preferably ZIF-8, and the particle size of ZIF-8 is preferably 10-120 nm or 14-50 nm.

[0017] The organic polymer is selected from polymethylphenylsiloxane (PMPS), polydimethylsiloxane (PDMS), and polyether block amide (PEBA), preferably polymethylphenylsiloxane (PMPS);

[0018] The crosslinking agent is selected from tetraethyl orthosilicate (TEOS), methyl orthosilicate (TMOS), and methyltrimethoxysilane (MTMS), preferably tetraethyl orthosilicate (TEOS);

[0019] The catalyst is selected from dibutyltin dilaurate (DBTDL), dimethylcyclohexylamine (DMCHA), N,N-dimethylbenzylamine (DMBA), and triethylenediamine (TEDA), preferably dibutyltin dilaurate (DBTDL);

[0020] The plate support is selected from one of α-Al2O3 carrier, γ-Al2O3 carrier, PAN carrier, and PVDF carrier, preferably α-Al2O3 carrier.

[0021] In step S3, the mass ratio of catalyst, crosslinking agent, organic polymer, MOF material, and solvent in the casting solution is 1:(8-12):(90-110):(5-20):(300-1000), preferably 1:(8-12):(90-110):(5-16):(600-1000), or 1:(9-11):(95-105):(10-15):(800-1000), or 1:10:100:15:800;

[0022] In step S4, the viscosity of the casting solution is 40 cP to 65 cP or 40 cP to 50 cP.

[0023] Preferably, step S1 specifically involves: first weighing the MOF material and adding it to a solvent (preferably using ultrasonic stirring to mix) to prepare a MOF dispersion; then adding a crosslinking agent and a solvent to the MOF dispersion and mixing thoroughly to obtain liquid A; preferably, after adding the crosslinking agent and solvent to the MOF dispersion, ultrasonic mixing and magnetic stirring are used for mixing.

[0024] Preferably, an ultrasonic probe is used, with an ultrasonic amplitude of 30% to 90% and a duration of 1 to 5 minutes. More preferably, the ultrasonic probe has an ultrasonic amplitude of 60% and a duration of 5 minutes.

[0025] The magnetic stirring has a stirring rate of 200-600 rpm and a stirring time of 0.5-1 h, preferably a stirring rate of 600 rpm and a stirring time of 1 h.

[0026] Preferably, in step S2, the organic polymer is weighed and added to the solvent, and then magnetically stirred to mix thoroughly to obtain liquid B.

[0027] The magnetic stirring has a stirring rate of 200-600 rpm and a stirring time of 0.5-1 h, preferably a stirring rate of 600 rpm and a stirring time of 1 h.

[0028] Preferably, in step S3, liquid A and liquid B are mixed and thoroughly mixed using ultrasonic and magnetic stirring, then a catalyst is added and mixed to obtain a casting solution.

[0029] Preferably, an ultrasonic probe is used, with an ultrasonic amplitude of 30% to 90% and a duration of 1 to 5 minutes. More preferably, the ultrasonic probe has an ultrasonic amplitude of 60% and a duration of 5 minutes.

[0030] The magnetic stirring has a stirring rate of 200-600 rpm and a stirring time of 0.5-1 h, preferably a stirring rate of 600 rpm and a stirring time of 1 h.

[0031] In step S4, the immersion lifting process is as follows: the support is immersed in the casting solution at a speed of 60-200 mm / min. -1 (preferably 100-180 mm min) -1 Or 150-180mm min -1 The dwell time is 5–30 s (preferably 5–25 s, 5–20 s, or 5–10 s), and then the support is pulled out of the casting solution at a speed of 60–200 mm / min. -1 (Preferred 100-180 mmmin) -1 Or 150-180mm min -1 The dip-lift operation is performed once or twice (preferably once); more preferably, the immersion speed of the support in the casting solution is 180 mm / min.-1 The dwell time is 10 seconds, and then the support is pulled out of the casting solution at a speed of 60 mm / min. -1 ;

[0032] The drying process includes air-drying the support with the casting solution adhering to its surface and then baking it; preferably, it is dried at room temperature for 12-24 hours, then dried by forced air at 80-120°C for 6-12 hours, and finally dried under vacuum at 80-120°C for 6-12 hours; more preferably, it is dried at room temperature for 24 hours, dried by forced air at 100°C for 12 hours, and dried under vacuum at 100°C for 12 hours.

[0033] A second aspect of the present invention provides a hybrid matrix flat sheet membrane based on a hydrophobic MOF material, which is prepared by any of the preparation methods described above.

[0034] A third aspect of the present invention provides the application of the above-described hybrid matrix flat sheet membrane based on hydrophobic MOF material in alcohol enrichment.

[0035] Preferably, in the above application technology, the mixed matrix flat sheet membrane is used in pervaporation technology to separate and enrich alcohols; the alcohols include n-butanol, isobutanol, n-propanol, isopropanol, and ethanol;

[0036] Preferably, the alcohol is n-butanol with a concentration of 0.1-3 wt% and an enrichment temperature of 40-80°C.

[0037] The beneficial effects of this invention are:

[0038] Current circular sheet membranes can only be stretched on one side with a small effective membrane area and low separation efficiency. Furthermore, due to limitations in the preparation process, significant casting solution waste occurs, hindering process scale-up. The dip-coating membrane fabrication process adopted in this invention has the following advantages: 1. Wide applicability: The dip-coating method is suitable for the continuous preparation of large-size membranes on solid surfaces with complex geometries and chemical properties. 2. Simple operation: This method is simple to operate, easily mechanized, and suitable for uniform coating on large-area and complex-shaped supports. 3. Controllable film thickness: The film thickness and performance can be controlled by adjusting process parameters such as solution concentration, dip time, and lifting speed. 4. Uniformity and transparency: The film thickness is controlled between tens of nanometers and several micrometers, exhibiting good uniformity and transparency. 5. Low energy consumption: This method can be operated at room temperature, is simple to operate, has a short preparation time, and consumes little energy. Through extensive preliminary research, including the selection of casting solution raw materials, the selection of casting solution raw material ratios, process selection, and the exploration of process parameters, the present invention has finally obtained the process of the present invention. The prepared mixed matrix flat sheet membrane has a uniform membrane layer and a larger membrane area. After scale-up experiments, it was verified that the membrane still has good performance after scale-up, which meets the requirements of large-scale production.

[0039] Through extensive experimentation, this invention has determined that the hybridization of MOF materials and organic polymers, followed by loading onto a flat substrate using an impregnation-coating process, allows for the assembly of membrane modules for pervaporation and alcohol permeation. This approach ensures high selectivity of the hybrid matrix membrane while improving membrane permeability. Attached Figure Description

[0040] Figure 1 The results show the effect of different ZIF-8 particle sizes on the pervaporation performance of the ZIF-8 / PMPS hybrid matrix membrane.

[0041] Figure 2 The results show the effect of ZIF-8 loading on the pervaporation performance of the ZIF-8 / PMPS hybrid matrix membrane.

[0042] Figure 3 The results show the effect of casting solution viscosity on the pervaporation performance of ZIF-8 / PMPS hybrid matrix membrane.

[0043] Figure 4 The pervaporation performance of the ZIF-8 / PMPS hybrid matrix membrane (ZIF-8 loading of 13 wt.%) at different operating temperatures is shown in the figure.

[0044] Figure 5 The pervaporation performance of the ZIF-8 / PMPS hybrid matrix membrane (ZIF-8 loading of 13 wt.%) under different n-butanol / water system concentrations is shown in the figure.

[0045] Figure 6 The figure shows the long-term stability test results of the ZIF-8 / PMPS hybrid matrix membrane (ZIF-8 loading of 13 wt.%) under the pervaporation of a 1 wt.% n-butanol / water system at 40 °C.

[0046] Figure 1-6 In this case, the dimensions of the mixed matrix membrane are 3cm x 3cm (length x width) and 6mm (thickness). Detailed Implementation

[0047] The present invention will be further described below with reference to embodiments, but these embodiments are not intended to limit the scope of the invention.

[0048] Unless otherwise specified, the experimental methods described in the following examples are conventional methods.

[0049] Example 1: Effect of different parameters on the performance of hybrid matrix flat sheet membranes

[0050] I. Preparation method of hybrid matrix flat sheet membrane based on MOF material

[0051] A method for preparing a hybrid matrix flat sheet membrane based on MOF materials, comprising the following steps (taking the preparation of a hybrid matrix flat sheet membrane with a ZIF-8 loading of 13 wt.% as an example):

[0052] S1. Preparation of solution A:

[0053] 0.75g of ZIF-8 was added to 14.25g of isooctane (CAS No.: 540-84-1) to prepare a ZIF-8 dispersion. 0.5g of crosslinking agent TEOS (tetraethyl orthosilicate, CAS No.: 562-90-3) and 5.75g of isooctane were added to the ZIF-8 dispersion and ultrasonically mixed using a probe under an ice-water bath. The ultrasonic conditions were: probe ultrasonic amplitude: 60%, ultrasonic time: 5min; then magnetic stirring was performed under the following conditions: rotation speed: 600rpm, stirring time: 1h, to obtain solution A.

[0054] S2. Preparation of solution B:

[0055] Take 5g of organic PMPS (polymethylphenylsiloxane, CAS No.: 9004-73-3) and add it to 20g of isooctane. Stir magnetically for 1h at a stirring speed of 600rpm to mix evenly and obtain solution B.

[0056] S3. Preparation of casting solution

[0057] Pour solution A into solution B, and then ultrasonically mix the mixture under an ice-water bath using a probe. The ultrasonic conditions are: probe amplitude: 60%, ultrasonic time: 5 min. Then, magnetic stirring is performed using a rotation speed of 600 rpm for 1 h. Next, the catalyst DBTDL (dibutyltin dilaurate, CAS No.: 77-58-7) is added, and the mixture is stirred until homogeneous (magnetic stirring conditions: rotation speed: 400 rpm, stirring time: 10 s) to form a uniform and stable casting solution.

[0058] S4. Preparation of mixed matrix flat sheet membrane

[0059] Pour the casting solution into the casting solution tank. Secure the thoroughly cleaned and dried α-Al₂O₃ flat plate support (3cm x 3cm, 6mm thickness) onto the automatic lifting machine using the membrane assembly. Adjust the immersion speed of the support in the casting solution (viscosity 40-50cP) to 180 mm / min. -1 The dwell time is 10 seconds, and then the support is pulled out of the casting solution at a speed of 60 mm / min. -1 The support with casting solution adhering to its surface was air-dried at 25°C for 24 hours, then placed in a forced-air drying oven at 100°C for 12 hours, and finally placed in a vacuum drying oven at 100°C for 12 hours to obtain a stable ZIF-8 / PMPS hybrid matrix flat sheet membrane.

[0060] II. Investigating the Influence of Different MOF Materials on Sheet Films

[0061] In this experiment, MOF-PMPS hybrid matrix membranes were prepared using the following MOF materials according to the method described in section "I" above: ZIF-8 (2-methylimidazolium zinc salt, CAS No.: 59061-53-9), ZIF-L, and ZIF-67 (2-methylimidazolium cobalt salt, CAS No.: 46201-07-4).

[0062] The mass ratio of catalyst / crosslinking agent / PMPS / MOF material / solvent in the casting solution is 1:10:100:15:800.

[0063] The prepared hybrid matrix membrane was placed in a feed solution tank and subjected to pervaporation tests in a 1 wt.% n-butanol solution at 40°C. The results are shown in Table 1: When ZIF-8 was selected as the MOF material, the pervaporation flux of the synthesized ZIF-8 / PMPS hybrid matrix flat sheet membrane reached 925.86 gm. -2 h -1 The n-BuOH / H2O separation factor reached 37.65, which is higher than that of ZIF-L / PMPS and ZIF-67 / PMPS mixed matrix flat sheet membranes, indicating that ZIF-8 / PMPS has a better butanol separation effect compared with mixed matrix membranes synthesized from other MOF materials.

[0064] Table 1

[0065] Hybrid matrix membrane <![CDATA[Flux (gm -2 h -1 )]]> <![CDATA[n-BuOH / H2O separation factor]]> ZIF-8 / PMPS hybrid matrix membrane 925.86 37.65 ZIF-L / PMPS hybrid matrix membrane 871.05 24.07 ZIF-67 / PMPS hybrid matrix membrane 580.06 18.56

[0066] III. Investigating the effect of different ZIF-8 particle sizes on the membrane.

[0067] ZIF-8 / PMPS hybrid matrix membranes were prepared using ZIF-8 with different particle sizes (14nm, 50nm, 120nm) according to the method in section "I" above. The mass ratio of catalyst / crosslinking agent / PMPS / ZIF-8 / solvent in the casting solution was 1:10:100:15:800 (i.e., the ZIF-8 loading was 13.0 wt.%).

[0068] The prepared mixed matrix membrane was subjected to pervaporation tests at 40°C using a 1 wt.% n-butanol / water solution. The results are as follows: Figure 1 As shown, the 14nm-ZIF-8 / PMPS hybrid matrix membrane exhibited the best separation performance, with a pervaporation flux reaching 925.86 gm³. -2 h -1The n-BuOH / H2O separation factor reached 37.65, exhibiting better pervaporation performance compared to the 50nm-ZIF-8 / PMPS hybrid matrix membranes synthesized with larger ZIF-8 particles, indicating better compatibility between smaller ZIF-8 nanoparticles and the PMPS matrix. Future research will focus on the 14nm-ZIF-8 / PMPS hybrid matrix membrane.

[0069] IV. Investigating the effect of ZIF-8 particle loading on the membrane

[0070] Casting solutions with different 14nm-ZIF-8 loadings were prepared using the method described in section "I" above: 14nm-ZIF-8 / PMPS hybrid matrix films with 14nm-ZIF-8 loadings of 0 wt.%, 4.8 wt.%, 9.1 wt.%, 13.0 wt.%, and 16.7 wt.% were prepared, respectively. The ZIF-8 loading was calculated using the mass of the raw materials ZIF-8 and PMPS.

[0071] ZIF-8 load capacity = Mass of ZIF-8 / (Sum of the masses of ZIF-8 and PMPS)

[0072] The 14nm-ZIF-8 / PMPS mixed matrix membranes with 14nm-ZIF-8 loadings of 0wt.%, 4.8wt.%, 9.1wt.%, 13.0wt.%, and 16.7wt.% had the following mass ratios in the casting solution of catalyst / crosslinking agent / PMPS / ZIF-8 / solvent: 1:10:100:0:800, 1:10:100:5:800, 1:10:100:10:800, 1:10:100:15:800, and 1:10:100:20:800.

[0073] The prepared mixed matrix membrane was subjected to pervaporation tests at 40°C using a 1 wt.% n-butanol / water solution. The results are as follows: Figure 2 As shown, the 14nm-ZIF-8 / PMPS hybrid matrix membrane with a loading of 13wt.% achieved the best separation performance, with a pervaporation flux of 925.86 gm³. -2 h -1The n-BuOH / H2O separation factor reached 37.65. Before the loading reached 13.0 wt.%, the pervaporation performance of the mixed matrix membrane gradually increased. After the loading reached 13.0 wt.%, the n-BuOH / H2O separation factor during pervaporation decreased sharply at a loading of 16.7 wt.%, indicating that excessively high loading created a non-selective space, leading to a significant increase in flux and a significant decrease in selectivity. Future research will focus on a 14 nm-ZIF-8 / PMPS mixed matrix membrane with a loading of 13 wt.%.

[0074] V. Investigate the effect of casting solution viscosity on the membrane.

[0075] A 14nm-ZIF-8 / PMPS hybrid matrix membrane with a loading of 13wt.% was prepared using the method described in section "I" above. Since the viscosity of the casting solution increases over time, different thicknesses of the hybrid matrix membrane will be prepared by pulling the casting solution under different viscosities, which will affect the final pervaporation performance of the hybrid matrix membrane. Therefore, a viscometer was used to accurately detect the target viscosity of the casting solution, and the pulling operation was performed when the target viscosity was reached.

[0076] The prepared mixed matrix membranes with different viscosities were subjected to pervaporation tests at 40°C using a 1 wt.% n-butanol / water solution. The results are as follows: Figure 3 As shown: The mixed matrix membrane synthesized at a casting solution viscosity of 45 cP exhibits good pervaporation performance, with a pervaporation flux reaching 744.06 gm³. -2 h -1 The n-BuOH / H2O separation factor reached 38.03, and the pervaporation performance of the mixed matrix membrane synthesized at casting solution viscosities of 40 cP and 50 cP was also at a high level. Subsequently, as the casting solution viscosity continued to increase, the pervaporation performance of the mixed matrix membrane began to decline. It can be seen that the optimal casting solution viscosity range for C-coating is 40 cP to 50 cP. Future research will focus on C-coating mixed matrix membranes synthesized within the casting solution viscosity range of 40 cP to 50 cP.

[0077] VI. Investigating the effect of casting solution raw material ratio on the membrane

[0078] Casting solutions with different isooctane contents were prepared using the method described in section "I" above: 14nm ZIF-8 / PMPS mixed matrix membranes were prepared with mass ratios of catalyst / crosslinking agent / organic polymer / ZIF-8 / solvent of 1:10:100:15:600, 1:10:100:15:800, and 1:10:100:15:1000. The prepared mixed matrix membranes were subjected to pervaporation tests at 40℃ using a 1wt.% n-butanol / water solution. The results are shown in Table 2.

[0079] Table 2

[0080] Product Number Casting solution raw material ratio <![CDATA[Flux (gm -2 h -1 )]]> <![CDATA[n-BuOH / H2O separation factor]]> A1 1:10:100:15:600 545.34 28.12 A2 1:10:100:15:800 925.86 37.65 A3 1:10:100:15:1000 773.25 23.17

[0081] As can be seen from the results in Table 2, the ZIF-8 / PMPS mixed matrix membrane synthesized when the raw material ratio of the casting solution is 1:10:100:15:800 has the highest pervaporation performance.

[0082] VII. Investigate the effect of dwell time during the lifting process on the membrane.

[0083] A 14 nm ZIF-8 / PMPS mixed matrix membrane (ZIF-8 loading of 13.0 wt.%) with different residence times in the casting solution during the lifting process was prepared according to the method described in section "I" above. The mass ratio of catalyst / crosslinking agent / polymer / ZIF-8 / solvent in the casting solution was 1:10:100:15:800, and the immersion rate was 180 mm / min. -1 The lifting speed is 60mm / min. -1 The prepared mixed matrix membrane was subjected to pervaporation tests at 40°C using a 1 wt.% n-butanol / water solution. The results are shown in Table 3.

[0084] Table 3

[0085] Product Number Duration during lifting <![CDATA[Flux (gm -2 h -1 )]]> <![CDATA[n-BuOH / H2O separation factor]]> B1 5s 1239.45 17.87 B2 10s 925.86 37.65 B3 20s 672.67 28.03

[0086] As can be seen from the results in Table 3, the synthesized ZIF-8 / PMPS hybrid matrix membrane exhibits the highest pervaporation performance when the residence time of the flat plate support in the casting solution during the lifting process is 10 s.

[0087] 8. Investigate the effect of immersion speed / lifting speed on the membrane during the lifting process.

[0088] A 14nm ZIF-8 / PMPS mixed matrix membrane with a loading of 13.0 wt.% at different immersion / lifting speeds in the casting solution was prepared according to the method described in section "I" above. The mass ratio of catalyst / crosslinking agent / polymer / ZIF-8 / solvent in the casting solution was 1:10:100:15:800, and the residence time in the casting solution was 10 s. The prepared mixed matrix membrane was subjected to pervaporation tests in a 1 wt.% n-butanol / water solution at 40 °C. The results are shown in Table 4.

[0089] Table 4

[0090] Product Number Immersion speed / Lifting speed <![CDATA[Flux (gm -2 h -1 )]]> <![CDATA[n-BuOH / H2O separation factor]]> C1 <![CDATA[180mmmin -1 / 180mmmin -1 ]]> 1023.87 21.23 C2 <![CDATA[180mmmin -1 / 60mmmin -1 ]]> 925.86 37.65 C3 <![CDATA[60mmmin -1 / 60mmmin -1 ]]> 798.59 30.09

[0091] As shown in Table 4, the immersion speed of the flat plate support during the lifting process was 180 mm / min. -1The lifting speed is 60mm / min. -1 At that time, the synthesized ZIF-8 / PMPS hybrid matrix membrane exhibited the highest pervaporation performance.

[0092] IX. Investigate the effect of the number of lifting cycles on the membrane during the lifting process.

[0093] The effect of different immersion-lifting cycles in the casting solution on the performance of a 14nm ZIF-8 / PMPS hybrid matrix membrane (ZIF-8 loading of 13.0 wt.%) during the preparation process according to the method in section "I" above was as follows: The mass ratio of catalyst / crosslinking agent / polymer / ZIF-8 / solvent in the casting solution was 1:10:100:15:800, the residence time in the casting solution was 10 s, and the immersion rate was 180 mm / min. -1 The lifting speed is 60mm / min. -1 The prepared mixed matrix membrane was subjected to pervaporation tests at 40°C using a 1 wt.% n-butanol / water solution. The results are shown in Table 5.

[0094] Table 5

[0095] Product Number Number of dips and lifts <![CDATA[Flux (gm -2 h -1 )]]> <![CDATA[n-BuOH / H2O separation factor]]> D1 1 925.86 37.65 D2 2 505.86 38.95 D3 3 334.87 39.09

[0096] As shown in Table 5, the synthesized ZIF-8 / PMPS hybrid matrix membrane exhibits the highest pervaporation performance when the dip-coating process is performed only once. Repeating the dip-coating process two or three times results in a decrease in membrane performance due to the increased membrane thickness.

[0097] Example 2: Performance of a mixed matrix membrane for pervaporation enrichment of butanol in the temperature range of 40–80°C

[0098] The pervaporation enrichment performance of the 14nm-ZIF-8 / PMPS mixed matrix membrane prepared in Example 1 with a loading of 13 wt.% was investigated within a temperature range of 40–80 °C. The operating temperature was tested with an increasing trend. After each operating temperature test, the water bath temperature was adjusted until the feed solution (1.0 wt.% n-butanol / aqueous solution) reached the target temperature. A 20-minute pre-vaporization process was performed before testing at the target operating temperature. After pre-vaporization, the permeate was collected for flux calculation and component analysis using chromatography to calculate the selectivity at this operating temperature.

[0099] As attached Figure 4As shown, during the pervaporation test, the operating temperatures were set at 40℃, 50℃, 60℃, 70℃, and 80℃. The total permeation flux of the mixed matrix membrane increased significantly with increasing pervaporation feed liquid temperature, and the n-BuOH / H2O separation factor also increased with increasing temperature. When the temperature increased from 40℃ to 80℃, the pervaporation flux increased from 744.06 gm³ / h. - 2 h -1 Increased to 2356.85gm -2 h -1 The n-BuOH / H2O separation factor increased to 43.27.

[0100] Example 3: Investigating the pervaporation enrichment performance of butanol by a mixed matrix membrane with different feed liquid concentrations.

[0101] The pervaporation performance of a 14nm-ZIF-8 / PMPS hybrid matrix membrane with a 13wt.% loading of 14nm-ZIF-8 prepared in Example 1 was investigated at 40°C for feed solutions of different concentrations. After each feed solution concentration test, the feed solution concentration was adjusted to the target concentration, and a 20-minute pre-vaporization process was performed before testing at the target feed solution concentration. After the pre-vaporization, the permeate was collected for flux calculation and component analysis using chromatography to calculate the selectivity at this feed solution concentration.

[0102] As attached Figure 5 As shown, during the pervaporation test, the concentrations of the n-butanol / water system were set to 0.1 wt.%, 0.5 wt.%, 1.0 wt.%, 2.0 wt.%, 2.5 wt.%, and 3.0 wt.%. The total permeation flux of the ZIF-8 / PMPS hybrid matrix membrane increased with increasing pervaporation feed concentration. As the n-butanol content in the feed solution increased, the total permeation flux decreased from 625.20 g·m³. -2 ·h -1 It rose to 1272.33 g·m -2 ·h -1 The n-BuOH / H2O separation factor also fluctuated within the range of 33.07 to 38.17.

[0103] Example 4: Investigating the long-term stability of the ZIF-8 / PMPS hybrid matrix membrane

[0104] This embodiment investigated the long-term stability of the 14nm-ZIF-8 / PMPS hybrid matrix film prepared in Example 1 with a 13wt.% loading of 14nm-ZIF-8 in a 1wt.% n-butanol / water system at 40°C. Figure 6 As shown, a stability test was conducted for 600 hours, and the average flux was found to be 872.19 g·m⁻². -2 ·h -1The average selectivity was 35.83, indicating that the mixed matrix membrane has good long-term stability in the n-butanol separation system.

[0105] Example 5, Scale-up Experiment

[0106] A mixed-matrix flat sheet membrane (ZIF-8 loading of 13 wt.%) was prepared using a flat sheet support with dimensions of 10 cm × 10 cm (thickness of 6 mm) according to the method described in Example 1. Its pervaporation performance at 40°C in a 1 wt.% n-butanol / water solution was tested, and the flux of the 10 cm × 10 cm mixed-matrix flat sheet membrane was found to be 728.40 gm³. -2 h -1 The n-BuOH / H2O separation factor is 19.09, indicating that even after scale-up, flat sheet membranes suitable for industrial applications can be successfully prepared.

[0107] Existing membrane preparation processes are difficult to scale up, and scaled-up membranes often fail to meet performance standards. Issues include uneven and ineffective membrane loading on the support, resulting in very low n-BuOH / H2O separation factors, or even a complete lack of separation performance. Compared to existing technologies, the process of this invention not only improves membrane permeability while maintaining high selectivity in the mixed matrix membrane, but also produces qualified products during scale-up production, making it suitable for large-scale industrial production.

Claims

1. A method for preparing a flat sheet membrane based on a hydrophobic MOF material hybrid matrix, characterized in that, Includes the following steps: S1. Preparation of Solution A: Weigh the MOF material and crosslinking agent, add them to the solvent, and mix thoroughly to obtain Solution A; the MOF material is selected from ZIF-8, ZIF-L or ZIF-67, and the crosslinking agent is selected from tetraethyl orthosilicate (TEOS), methyl orthosilicate (TMOS) or methyltrimethoxysilane (MTMS). S2. Preparation of Solution B: Weigh the organic polymer polymethylphenylsiloxane (PMPS) and add it to the solvent, mix thoroughly to obtain Solution B; the solvent is selected from one or more of methanol, ethanol, isooctane, n-heptane, and cyclohexane; S3. Preparation of casting solution: Mix solution A and solution B thoroughly and evenly, add catalyst, and mix well to obtain casting solution; the catalyst is selected from dibutyltin dilaurate (DBTDL), dimethylcyclohexylamine (DMCHA), N,N-dimethylbenzylamine (DMBA) or triethylenediamine (TEDA); the mass ratio of catalyst, crosslinking agent, organic polymer, MOF material and solvent in casting solution is 1 : (8~12) : (90~110) : (5~16) : (600~1000); the viscosity of casting solution is 40 cP~50 cP; S4. Preparation of mixed matrix flat sheet membrane A flat plate support is installed on a lifting machine, and the casting solution is loaded onto the flat plate support using an immersion lifting process. Then, it is dried to obtain a mixed matrix flat plate membrane. The flat plate support is selected from one of α-Al2O3 carrier, γ-Al2O3 carrier, PAN carrier, and PVDF carrier. The dip-coating process is as follows: the support is immersed in the casting solution at a speed of 60~180 mm / min. -1 The dwell time is 5-20 seconds, and then the support is pulled out of the casting solution at a speed of 60-180 mm / min. -1 The immersion-lifting operation can be performed once or twice.

2. The preparation method according to claim 1, characterized in that: The solvent is isooctane; The MOF material is ZIF-8, and the particle size of ZIF-8 is 10~120 nm or 14~50 nm. The crosslinking agent is tetraethyl orthosilicate (TEOS). The catalyst is dibutyltin dilaurate (DBTDL). The plate support is an α-Al2O3 carrier.

3. The preparation method according to claim 1, characterized in that: In step S3, the mass ratio of catalyst, crosslinking agent, organic polymer, MOF material and solvent in the casting solution is 1 : (9~11) : (95~105) : (10~15) : (800~1000).

4. The preparation method according to claim 1, characterized in that: Step S1 is as follows: First, weigh the MOF material and add it to the solvent to prepare a MOF dispersion. Then, add the crosslinking agent and solvent to the MOF dispersion and mix thoroughly to obtain solution A.

5. The preparation method according to claim 4, characterized in that: Step S1 is as follows: First, weigh the MOF material and add it to the solvent. Then, mix it with ultrasonic stirring to prepare a MOF dispersion. After adding the crosslinking agent and solvent to the MOF dispersion, mix it with ultrasonic mixing and magnetic stirring to obtain liquid A. The ultrasound is conducted using a probe, with an amplitude of 30% to 90% and a duration of 1 to 5 minutes. The magnetic stirring speed is 200~600 rpm, and the stirring time is 0.5~1 h.

6. The preparation method according to claim 1, characterized in that: In step S2, the organic polymer is weighed and added to the solvent, and then magnetically stirred to mix thoroughly to obtain solution B. The magnetic stirring speed is 200~600 rpm, and the stirring time is 0.5~1 h.

7. The preparation method according to claim 1, characterized in that: In step S3, liquid A and liquid B are mixed and thoroughly mixed using ultrasonic and magnetic stirring. Then, a catalyst is added and mixed to obtain the casting solution.

8. The preparation method according to claim 7, characterized in that: The ultrasound is a probe-based ultrasound with an amplitude of 30% to 90% and a duration of 1 to 5 minutes. The magnetic stirring speed is 200~600 rpm, and the stirring time is 0.5~1 h.

9. The preparation method according to claim 1, characterized in that: In step S4, the immersion lifting process is as follows: the speed at which the support is immersed in the casting solution is 100~180 mm / min. -1 The dwell time is 5-10 seconds, and then the support is pulled out of the casting solution at a speed of 100-180 mm / min. -1 The immersion-lifting operation is performed once; The drying process includes air-drying the support with casting solution adhering to its surface and then baking it.

10. The preparation method according to claim 9, characterized in that: In step S4, the immersion lifting process is as follows: the support is immersed in the casting liquid at a speed of 180 mm / min. -1 The residence time is 10 s, and then the support is pulled out of the casting solution at a speed of 60 mm / min. -1 ; The drying process involves first drying at room temperature for 12-24 hours, then drying in a forced-air environment at 80-120°C for 6-12 hours, and finally drying under vacuum at 80-120°C for 6-12 hours.

11. A hybrid matrix flat sheet membrane based on hydrophobic MOF material, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 10.

12. The application of the hybrid matrix flat sheet membrane based on hydrophobic MOF material as described in claim 11 in alcohol enrichment.

13. The application according to claim 12, characterized in that: Mixed matrix flat sheet membranes are used in pervaporation technology for the separation and enrichment of alcohols; The alcohols include n-butanol, isobutanol, n-propanol, isopropanol, and ethanol.

14. The application according to claim 13, characterized in that: The alcohol is n-butanol with a concentration of 0.1-3 wt% and an enrichment temperature of 40-80 °C.

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