A method for the preparation of high valent MOF crystal films for alcohol dehydration purification

Abstract

The application discloses a preparation method of high-valence MOF crystal film for alcohol dehydration purification. The preparation method is as follows: a porous gamma-Al2O3 carrier is placed in deionized water, a gamma-AlOOH precursor layer is obtained through a hydrothermal reaction, and then the carrier modified with the precursor layer is placed in an aqueous solution containing 2,5-furan dicarboxylic acid and aluminum chloride hexahydrate, and is subjected to secondary growth. The application utilizes a hydrothermal method to modify the carrier, preplants a layer of gamma-AlOOH precursor on the surface of the porous gamma-Al2O3 carrier, and then obtains the MIL-160 crystal film through secondary growth. The prepared porous MOF film material has excellent stability and separation performance in an alcohol / water system, and is an ideal alcohol / water separation material.

Description

Technical Field

[0001] The invention relates to a method for preparing a MOF crystal membrane for alcohol / water system separation, and belongs to the field of membrane separation materials. Background Art

[0002] Pervaporation (PV) is currently a hot topic in the field of organic separation research. It offers the advantages of low energy consumption, ease of operation, and zero secondary pollution. It also overcomes the limitations of traditional distillation methods, such as those for near-boiling and constant-boiling organic mixtures, which are difficult or impossible to separate. This offers significant advantages in energy conservation, emission reduction, cost savings, and improved separation stability.

[0003] The dehydration and purification of organic chemicals through pervaporation is a key technology in the chemical industry.

[0004] The membrane material is the core material, and its structure and performance determine the separation effect of the entire pervaporation process. Compared with traditional separation materials, metal organic framework materials have many advantages such as large specific surface area, diverse topological structures, and adjustable pores, and are expected to play a role in liquid separation (V. Cristina, EJ Mater Chem. A. 2020). The vast majority of MOF materials are based on divalent metal ions, such as Zn 2+ ,Cu 2+ Numerous studies have confirmed that high-valent MOF materials, such as those with trivalent aluminum ions as metal nodes, possess superior hydrothermal stability compared to common divalent metal MOFs, meeting the stringent requirements of pervaporation separation. However, due to the constraints of coordination chemistry, the nucleation of high-valent MOF crystals is difficult, and the preparation of high-quality crystalline membranes on ceramic substrates is rare, significantly limiting the large-scale application of highly stable MOF membranes. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing a high-valent MOF crystal membrane with stable structure and excellent alcohol dehydration performance.

[0006] A method for preparing a high-valent MOF crystal membrane for alcohol dehydration purification comprises modifying a support using a hydrothermal method, wherein a porous γ-Al2O3 support is used as an inorganic aluminum source and hydrothermally reacts with deionized water to obtain a γ-AlOOH precursor film (layer); then, the support modified with the γ-AlOOH precursor layer is placed in an aqueous solution containing 2,5-furandicarboxylic acid (2,5-FDCA) and aluminum chloride hexahydrate, and secondary growth is obtained through an in-situ hydrothermal reaction; the method specifically comprises the following steps:

[0007] (1) Preparation of γ-AlOOH precursor layer

[0008] A porous γ-Al2O3 support is placed in deionized water and subjected to a solvothermal reaction under closed conditions to pre-seed a layer of γ-AlOOH nanorods on the support surface to obtain a γ-AlOOH precursor film. The reaction temperature is 130-220°C and the reaction time is 2-48 hours.

[0009] After the reaction is complete, cool to room temperature, and then wash and dry the γ-AlOOH precursor film. Specifically, cool naturally to room temperature, place the γ-AlOOH precursor film in a beaker filled with water, ultrasonically treat it at 50-400W for 5-30 seconds, then wash it by immersion in deionized water or anhydrous ethanol for 5-120 minutes. Dry the washed product in an oven at 50-80°C overnight.

[0010] Preferably, the porous Al2O3 carrier is placed horizontally in the mother liquor (reaction liquid) and reacted at 180-200°C for 4-12 hours.

[0011] Preferably, the solvent thermal reaction is carried out under closed conditions.

[0012] Preferably, the LDH precursor film is ultrasonically treated for 10 to 30 seconds.

[0013] Preferably, the porous γ-Al2O3 carrier has a diameter of 18 mm and a pore size of 5 nm.

[0014] (2) Preparation of MIL-160 crystal film

[0015] Aluminum chloride hexahydrate, 2,5-furandicarboxylic acid, and sodium hydroxide are dissolved in water and stirred to thoroughly mix the reaction solution. The molar ratio of the four reactants (aluminum chloride hexahydrate: 2,5-furandicarboxylic acid: sodium hydroxide: water) is adjusted to 1:0.5-2:0.5-2:400-3000. The mixture is stirred at room temperature (generally 25°C) for 10 minutes to thoroughly mix the reaction solution. The γ-AlOOH precursor film is placed in the mother liquor (reaction solution) and reacted at 100-120°C for 6-72 hours, resulting in secondary growth and conversion to a porous MIL-160 crystal film.

[0016] After the reaction is complete, the membrane is washed and dried. Specifically, the membrane is placed in a beaker filled with deionized water, ultrasonically treated at 50-400W for 5-30 seconds, immersed in N,N-dimethylformamide or anhydrous ethanol for 5-120 minutes, and then dried in an oven at a drying temperature of 50-100°C overnight.

[0017] Preferably, the ratio of the four reactants is 1:0.8-1.2:0.8-1.2:600-2000.

[0018] Preferably, the γ-AlOOH precursor film is placed vertically in the mother solution (reaction solution) and reacted at 100-120° C. for 6-72 hours.

[0019] Preferably, the optimal temperature of the secondary growth step is 105-115° C., and the time is 12-24 hours.

[0020] Preferably, the membrane immersion washing step comprises immersing and washing in N,N-dimethylformamide or anhydrous ethanol at room temperature for 30 to 60 minutes.

[0021] Another object of the present invention is to provide a high-cost MOF crystal film prepared by the above method.

[0022] Another object of the present invention is to provide the application of the above-mentioned high-valent MOF crystal membrane in alcohol dehydration (i.e., alcohol / water system separation), and the alcohols include: methanol, ethanol, n-propanol, n-butanol, ethylene glycol, 1,3-propylene glycol, and glycerol.

[0023] Compared with the prior art, the advantages of the present invention are:

[0024] (1) The preparation process is fast and simple, and it is a green chemical synthesis method;

[0025] (2) The experimental strategy is ingenious. A γ-AlOOH precursor layer was prepared using a porous γ-Al2O3 carrier as an inorganic Al source via a γ-AlOOH modified support method. Subsequently, a MIL-160 crystal membrane with excellent performance and good stability was prepared using γ-AlOOH as a precursor template via in situ hydrothermal growth. This membrane has excellent separation performance for alcohol / water systems and is an ideal material for alcohol dehydration purification. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention is attached Figure 8 Size:

[0027] Figure 1 1 is the X-ray diffraction pattern of the γ-AlOOH precursor film at different reaction temperatures in Examples 1-4.

[0028] Figure 2 1 is the X-ray diffraction pattern of the MIL-160 film obtained at different reaction times in Examples 9-12 and 6.

[0029] Figure 3 1 is a scanning electron microscope image of the γ-AlOOH precursor film obtained at different reaction temperatures in Examples 1-4.

[0030] Figure 4 These are scanning electron microscope images of the MIL-160 films obtained at different reaction times in Examples 9-12 and 6.

[0031] Figure 5Graph showing the separation selectivity and permeability of the butanol / water system of the MIL-160 crystal membrane in Examples 5-8 as a function of the mother liquor concentration during the in-situ hydrothermal growth process.

[0032] Figure 6 This is the separation performance of the MIL-160 crystal membrane in Example 6 for isobutanol / water systems with different concentrations.

[0033] Figure 7 This is the separation performance of the MIL-160 crystal membrane in Example 6 for other alcohol / water systems.

[0034] Figure 8 This is the test result of the separation stability of the MIL-160 crystal membrane in Example 6 for the isobutanol / water system. DETAILED DESCRIPTION

[0035] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0036] Example 1. Preparation of γ-AlOOH-1 precursor film

[0037] Transfer 20 ml of deionized water to a 25 ml polytetrafluoroethylene-lined reactor. Place a disc-shaped porous γ-Al2O3 support with an 18 mm diameter and 5 nm pore size horizontally in the aqueous solution. The lined reactor is then sealed in a stainless steel autoclave and heated to 135°C in an oven. Maintain the temperature and allow the reaction to proceed for 4 hours.

[0038] After the reaction is completed, it is naturally cooled to room temperature, the inner lined reactor is opened and the supernatant liquid is poured out, the γ-AlOOH precursor film is first placed in water, ultrasonically treated with 300w for 20s, and then immersed and washed with deionized water for 60min, and then placed in a 60℃ oven to dry overnight to obtain a γ-AlOOH-1 precursor film.

[0039] Example 2. Preparation of γ-AlOOH-2 precursor film

[0040] Transfer 20 ml of deionized water to a 25 ml polytetrafluoroethylene-lined reactor. Place a disc-shaped porous γ-Al2O3 support with an 18 mm diameter and 5 nm pore size horizontally in the aqueous solution. The lined reactor is then sealed in a stainless steel autoclave and heated to 150°C in an oven. Maintain the temperature and allow the reaction to proceed for 4 hours.

[0041] After the reaction is completed, it is naturally cooled to room temperature, the inner-lined reactor is opened and the supernatant liquid is poured out. The γ-AlOOH precursor film is first placed in water, ultrasonically treated with 300w for 20s, and then immersed and washed with deionized water for 60min, and then placed in a 60℃ oven to dry overnight to obtain a γ-AlOOH-2 precursor film.

[0042] Example 3. Preparation of γ-AlOOH-3 precursor film

[0043] Transfer 20 ml of deionized water to a 25 ml polytetrafluoroethylene-lined reactor. Place a disc-shaped porous γ-Al2O3 support with an 18 mm diameter and 5 nm pore size horizontally in the aqueous solution. The lined reactor is then sealed in a stainless steel autoclave and heated to 180°C in an oven. Maintain the temperature and allow the reaction to proceed for 4 hours.

[0044] After the reaction is completed, it is naturally cooled to room temperature, the lined reactor is opened and the supernatant liquid is poured out, the γ-AlOOH precursor film is first placed in water, ultrasonically treated with 300w for 20s, and then immersed and washed with deionized water for 60min, and placed in a 60℃ oven to dry overnight to obtain a γ-AlOOH-3 precursor film.

[0045] Example 4. Preparation of γ-AlOOH-4 precursor film

[0046] Transfer 20 ml of deionized water to a 25 ml polytetrafluoroethylene-lined reactor. Place a disc-shaped porous γ-Al2O3 support with an 18 mm diameter and 5 nm pore size horizontally in the aqueous solution. The lined reactor is then sealed in a stainless steel autoclave and heated to 220°C in an oven. Maintain the temperature and allow the reaction to proceed for 4 hours.

[0047] After the reaction is completed, it is naturally cooled to room temperature, the lined reactor is opened and the supernatant liquid is poured out, the γ-AlOOH precursor film is first placed in water, ultrasonically treated with 300w for 20s, and then immersed and washed with deionized water for 60min, and then placed in a 60℃ oven to dry overnight to obtain a γ-AlOOH-4 precursor film.

[0048] Example 5. Preparation of MIL-160-1 crystal film

[0049] Similar to Example 3, a γ-AlOOH precursor film was prepared using the same method.

[0050] Weigh 0.120g of aluminum chloride hexahydrate, 0.078g of 2,5-furandicarboxylic acid, and 0.2g of sodium hydroxide and dissolve them in 25ml of water. Stir the mixture at room temperature for 10 minutes, then transfer the mixture to a 100ml polytetrafluoroethylene-lined reactor. Place the γ-AlOOH precursor film vertically in the mother liquor. The lined reactor is then sealed in a stainless steel autoclave and heated to 120°C in an oven. Maintain the temperature and allow the reaction to proceed for 24 hours.

[0051] After the reaction, the membrane was transferred to a beaker filled with deionized water, ultrasonically treated for 15 seconds using a 200W ultrasonic cleaner, immersed and washed with DMF for 30 minutes, and then dried in a 60°C oven overnight to obtain a MIL-160-1 crystal membrane.

[0052] Example 6. Preparation of MIL-160-2 Crystal Film

[0053] Similar to Example 3, a γ-AlOOH precursor film was prepared using the same method.

[0054] Weigh 0.241g of aluminum chloride hexahydrate, 0.156g of 2,5-furandicarboxylic acid, and 0.4g of sodium hydroxide and dissolve them in 25ml of water. Stir the mixture at room temperature for 10 minutes, then transfer the mixture to a 100ml polytetrafluoroethylene-lined reactor. Place the γ-AlOOH precursor film vertically in the mother liquor. The lined reactor is then sealed in a stainless steel autoclave and heated to 120°C in an oven. Maintain the temperature and allow the reaction to proceed for 24 hours.

[0055] After the reaction, the membrane was transferred to a beaker filled with deionized water, ultrasonically treated for 15 seconds using a 200W ultrasonic cleaner, immersed and washed with DMF for 30 minutes, and then dried in a 60°C oven overnight to obtain a MIL-160-2 crystal membrane.

[0056] Example 7. Preparation of MIL-160-3 crystal film

[0057] Similar to Example 3, a γ-AlOOH precursor film was prepared using the same method.

[0058] Weigh 0.361g of aluminum chloride hexahydrate, 0.234g of 2,5-furandicarboxylic acid, and 0.6g of sodium hydroxide and dissolve them in 25ml of water. Stir the mixture at room temperature for 10 minutes, then transfer the mixture to a 100ml polytetrafluoroethylene-lined reactor. Place the γ-AlOOH precursor film vertically in the mother liquor. The lined reactor is then sealed in a stainless steel autoclave and heated to 120°C in an oven. Maintain the temperature and allow the reaction to proceed for 24 hours.

[0059] After the reaction, the membrane was transferred to a beaker filled with deionized water, ultrasonically treated for 15 seconds using a 200W ultrasonic cleaner, immersed and washed with DMF for 30 minutes, and then dried in a 60°C oven overnight to obtain a MIL-160-3 crystal membrane.

[0060] Example 8. Preparation of MIL-160-4 Crystal Film

[0061] Similar to Example 3, a γ-AlOOH precursor film was prepared using the same method.

[0062] Weigh 0.482g of aluminum chloride hexahydrate, 0.312g of 2,5-furandicarboxylic acid, and 0.8g of sodium hydroxide and dissolve them in 25ml of water. Stir the mixture at room temperature for 10 minutes, then transfer the mixture to a 100ml polytetrafluoroethylene-lined reactor. Place the γ-AlOOH precursor film vertically in the mother liquor. The lined reactor is then sealed in a stainless steel autoclave and heated to 120°C in an oven. Maintain the temperature and allow the reaction to proceed for 24 hours.

[0063] After the reaction, the membrane was transferred to a beaker filled with deionized water, ultrasonically treated for 15 seconds using a 200W ultrasonic cleaner, immersed and washed with DMF for 30 minutes, and then dried in a 60°C oven overnight to obtain a MIL-160-4 crystal membrane.

[0064] Example 9. Preparation of MIL-160-5 Crystalline Film

[0065] Similar to Example 3, a γ-AlOOH precursor film was prepared using the same method.

[0066] Weigh 0.241g of aluminum chloride hexahydrate, 0.156g of 2,5-furandicarboxylic acid, and 0.4g of sodium hydroxide and dissolve them in 25ml of water. Stir the mixture at room temperature for 10 minutes, then transfer the mixture to a 100ml polytetrafluoroethylene-lined reactor. Place the γ-AlOOH precursor film vertically in the mother liquor. The lined reactor is then sealed in a stainless steel autoclave and heated to 120°C in an oven. Maintain the temperature and allow the reaction to proceed for 1 hour.

[0067] After the reaction, the membrane was transferred to a beaker filled with deionized water, ultrasonically treated for 15 seconds using a 200W ultrasonic cleaner, immersed and washed with DMF for 30 minutes, and then dried in a 60°C oven overnight to obtain a MIL-160-5 crystal membrane.

[0068] Example 10. Preparation of MIL-160-6 Crystal Film

[0069] Similar to Example 3, a γ-AlOOH precursor film was prepared using the same method.

[0070] Example 10. MIL-160-6 crystal film preparation

[0071] After the reaction was completed, the film was transferred to a beaker containing deionized water, and was treated with a 200w ultrasonic cleaner for 15s. After being immersed in DMF for 30min, the film was dried in a 60°C oven overnight to obtain a MIL-160-6 crystal film.

[0072] Example 11. MIL-160-7 crystal film preparation

[0073] A γ-AlOOH precursor film was prepared in the same manner as in Example 3.

[0074] A solution was prepared by dissolving 0.241g of aluminum chloride hexahydrate, 0.156g of 2,5-furan dicarboxylic acid, and 0.4g of sodium hydroxide in 25ml of water. After stirring at room temperature for 10min, the solution was transferred to a 100ml polytetrafluoroethylene-lined reaction kettle. The γ-AlOOH precursor film was placed vertically in the solution, and then the lined reaction kettle was sealed in a stainless steel autoclave, which was placed in an oven and heated to 120°C for 12h.

[0075] After the reaction was completed, the film was transferred to a beaker containing deionized water, and was treated with a 200w ultrasonic cleaner for 15s. After being immersed in DMF for 30min, the film was dried in a 60°C oven overnight to obtain a MIL-160-7 crystal film.

[0076] Example 12. MIL-160-8 crystal film preparation

[0077] A γ-AlOOH precursor film was prepared in the same manner as in Example 3.

[0078] A solution was prepared by dissolving 0.241g of aluminum chloride hexahydrate, 0.156g of 2,5-furan dicarboxylic acid, and 0.4g of sodium hydroxide in 25ml of water. After stirring at room temperature for 10min, the solution was transferred to a 100ml polytetrafluoroethylene-lined reaction kettle. The γ-AlOOH precursor film was placed vertically in the solution, and then the lined reaction kettle was sealed in a stainless steel autoclave, which was placed in an oven and heated to 120°C for 18h.

[0079] After the reaction, the membrane was transferred to a beaker filled with deionized water, ultrasonically treated for 15 seconds using a 200W ultrasonic cleaner, immersed and washed with DMF for 30 minutes, and then dried in a 60°C oven overnight to obtain a MIL-160-8 crystal membrane.

[0080] The structure of the MIL-160 crystal membrane was characterized using X-ray diffractometer (XRD) and scanning electron microscopy (SEM). The separation performance of the crystal membrane for a butanol / water system was tested using a pervaporation apparatus. The morphology and butanol / water separation performance of the MIL-160 crystal membrane prepared in the present invention are as follows:

[0081] Figure 1 The X-ray diffraction patterns of the γ-AlOOH precursor films at different reaction temperatures in Examples 1-4 are given. A characteristic peak of the γ-AlOOH layer can be observed at 14.4°, and the higher the reaction temperature, the stronger the characteristic peak intensity, indicating that the γ-Al2O3 surface is converted into a γ-AlOOH precursor layer.

[0082] Figure 2 The X-ray diffraction patterns of the MIL-160 films at different reaction times in Examples 9-12 and 6 are given, indicating that as the reaction time increases, characteristic peaks of MIL-160 appear on the surface of the film layer, proving the formation of the MIL-160 film layer.

[0083] Figure 3 The scanning electron microscope images of the γ-AlOOH precursor films obtained at different reaction temperatures in Examples 1-4 show that after the reaction at 135-220° C., a nanorod-shaped γ-AlOOH precursor layer is formed on the surface of the support.

[0084] Figure 4 The scanning electron microscope images of the MIL-160 films obtained at different reaction times in Examples 9-12 and 6 show that as the reaction time is extended to 24 h, the MIL-160 film obtained on the carrier surface becomes uniform and dense.

[0085] Figure 5 The separation selectivity and permeability of the butanol / water system of the MIL-160 crystal membrane in Examples 5-8 vary with the mother liquor concentration during the in situ hydrothermal growth process. As the benzoic acid concentration increases during the in situ hydrothermal growth process, the selectivity of the membrane increases first and then decreases. The separation factor can reach up to 1265, indicating that the membrane has excellent isobutanol / water separation performance.

[0086] Figure 6 This is the separation performance of the MIL-160 crystal membrane in Example 6 for isobutanol / water systems with different concentrations, indicating that the MIL-160 membrane can achieve efficient separation of isobutanol / water solutions with different compositions.

[0087] Figure 7 The separation performance of the MIL-160 crystal membrane for other alcohol / water systems in Example 6 indicates that the MIL-160 crystal membrane can achieve efficient separation of a variety of alcohol / water systems.

[0088] Figure 8 The results of the separation stability test of the MIL-160 crystal membrane for the isobutanol / water system in Example 6 are shown. During the 120-hour pervaporation test, the total permeation and separation factor of the crystal membrane remained stable, indicating that the crystal membrane has excellent stability.

Claims

1. A method for preparing a high-priced MOF crystal film, characterized in that: The steps include: (1) Preparation of γ-AlOOH drive layer The porous γ-Al2O3 support was placed in deionized water and subjected to a solvothermal reaction under closed conditions to obtain a rod-shaped γ-AlOOH precursor layer. Wherein, the reaction temperature is 130-220°C, and the reaction time is 2-48h; (2) Preparation of high-cost MOF crystal films Aluminum chloride hexahydrate, 2,5-furandicarboxylic acid, and sodium hydroxide are dissolved in water and stirred to fully mix the reaction solution; a γ-AlOOH precursor film is placed in the reaction solution and reacted at 100-120°C for 6-72 hours to obtain a porous MOF crystal film; The molar ratio of aluminum chloride hexahydrate, 2,5-furandicarboxylic acid, sodium hydroxide and water is 1:0.5-2:0.5-2:400-3000.

2. The method for preparing a high-priced MOF crystal film according to claim 1, wherein: In step (1), after the reaction is completed, the γ-AlOOH precursor film is washed and dried.

3. The method for preparing a high-priced MOF crystal film according to claim 2, wherein: The washing step is as follows: firstly placing the γ-AlOOH precursor film in water, subjecting it to ultrasonic treatment at 50-400W for 5-30s, and then immersing and washing it in deionized water or anhydrous ethanol for 5-120min; and drying it at a temperature of 50-80°C overnight.

4. The method for preparing a high-priced MOF crystal film according to claim 1, wherein: In step (2), the γ-AlOOH precursor film is placed vertically in the reaction solution.

5. The method for preparing a high-priced MOF crystal film according to claim 1, wherein: In step (2), after the reaction is completed, the crystal film is washed and dried.

6. The method for preparing a high-priced MOF crystal film according to claim 5, characterized in that: The washing step is as follows: firstly, the crystal membrane is placed in water, ultrasonically treated with 50-400W for 5-30s, and then immersed in N,N-dimethylformamide or anhydrous ethanol for 5-120min; the drying temperature is 50-100°C, and the membrane is dried overnight.

7. A high-valent MOF crystal film prepared by the method according to any one of claims 1 to 6.

8. Use of the high-valent MOF crystal membrane according to claim 7 in alcohol / water system separation.

9. The use according to claim 8, characterized in that The alcohol is methanol, ethanol, n-propanol, n-butanol, ethylene glycol, 1,3-propylene glycol or glycerol.

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