Method for synthesizing silver-loaded molecular sieve membrane and application thereof
By modifying the alumina substrate and preparing silver-loaded LTA-type molecular sieve membranes through hydrothermal synthesis, the problems of molecular sieve membrane density and uneven metal particle distribution were solved, achieving high-efficiency catalytic and separation performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-05
- Publication Date
- 2026-04-07
AI Technical Summary
In the existing technology, it is difficult to prepare molecular sieve membranes with good density and uniform metal particle distribution by the synthesis method of LTA type molecular sieve membrane, which limits its application in the fields of catalysts and separation membranes.
An alumina substrate was modified with aminopropyltriethoxysilane, and a hydrothermal synthesis method using organosilicon, sodium, and silver sources was used to prepare a silver-loaded LTA-type molecular sieve membrane. Ag particles were uniformly encapsulated within the molecular sieve channels through a silanization reaction.
The synthesized molecular sieve membrane has good density and uniform Ag particle distribution, making it suitable for catalysts and separation membranes, with high practical value and economic benefits.
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Figure CN118179288B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of molecular sieve membrane synthesis technology, and in particular to a method for synthesizing and applying a silver-loaded molecular sieve membrane. Background Technology
[0002] Molecular sieve membranes are thin-film materials with adjustable microporous structures. Due to their unique, well-defined channels and excellent thermal / chemical stability, they are widely used in separation, dehydration, and catalytic reactions. Introducing metal active centers into molecular sieve membranes can, on the one hand, adjust the pore size, and on the other hand, enhance their activity and selectivity in specific chemical reactions, thus significantly improving the catalytic or separation performance of the membrane. For example, in related research, a novel Pt@Y catalyst was prepared by encapsulating Ptδ+ species in Y zeolite, exhibiting good activity and selectivity in the hydrogenation of α,β-unsaturated aldehydes to unsaturated alcohols and the hydrogenation of nitroaromatics to aromatic amines.
[0003] LTA-type molecular sieve membranes have small pore sizes (approximately 0.42 nm), close to the kinetic diameter of many gas molecules. By confining the metal and adjusting the size of the introduced metal particles, the intracrystalline diffusion path of adsorbed gas molecules can be optimized to achieve efficient separation of alkenes and alkanes, showing great potential for development in current research and industry. Currently, methods for loading metals into molecular sieves are broadly divided into two types: ion exchange and in-situ encapsulation. Ion exchange involves first synthesizing a pure-phase molecular sieve powder, then replacing the existing ions in the molecular sieve with larger metal ions, narrowing the pore size and increasing the permeation resistance of certain large gas molecules to achieve selective separation. Ion exchange is the most widely used method in membrane materials due to its mature technology; for example, the synthesis of Cs-LTA molecular sieve membranes via ion exchange significantly improves the hydrogen selective separation performance of cation exchange membranes. However, this method has limitations; it can only achieve hydrogen separation by reducing the pore size, making it difficult to extend its application to the separation of other mixed gases in industry. Furthermore, it is difficult to avoid uneven distribution of metal particles. In-situ encapsulation involves the simultaneous hydrothermal synthesis of metals and molecular sieve precursor solutions. This one-step method achieves the synthesis of molecular sieves or molecular sieve membrane materials and the uniform distribution of metal particles within the pores of the molecular sieve membrane. It simplifies the synthesis process, improves metal utilization, and reduces metal agglomeration. However, a current drawback of this method is that the membrane performance is significantly affected by the composition of the synthesis solution and the surface properties of the carrier. If metal is to be encapsulated, the introduced metal source precursor will alter the composition and physicochemical properties of the synthesis solution, making it even more difficult to prepare dense and high-performance molecular sieve membranes.
[0004] Therefore, there is an urgent need to find a new method for synthesizing LTA-type molecular sieve membranes to improve the compactness of molecular sieve membranes. Summary of the Invention
[0005] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a method for synthesizing silver-loaded LTA-type molecular sieve membranes. This method is simple, rapid, and highly reproducible. The molecular sieve membranes synthesized using this method exhibit good density, with uniformly distributed and small-sized Ag particles encapsulated within the pores. It can be widely used in catalysts, separation membranes, and other fields, possessing high practical value and economic benefits.
[0006] The present invention also proposes an LTA-type molecular sieve membrane loaded with silver.
[0007] The present invention also proposes a method for synthesizing silver-loaded molecular sieve membranes or the application of silver-loaded LTA-type molecular sieve membranes in the preparation of catalysts or separation membranes.
[0008] A first aspect of the present invention provides a method for synthesizing a silver-loaded molecular sieve membrane, comprising the following steps:
[0009] S1. The alumina substrate was modified with aminopropyltriethoxysilane to obtain a functionalized alumina substrate.
[0010] S2. Mix the organosilicon source, sodium source, and silver source with the solvent to obtain a metal precursor solution. Then, add colloidal silica solution and aluminum foil in sequence, mix well, and obtain a molecular sieve membrane synthesis solution.
[0011] S3. The molecular sieve membrane synthesis solution is contacted with the functionalized modified alumina substrate, and the membrane is obtained after hydrothermal reaction, drying and calcination.
[0012] The synthesis method according to embodiments of the present invention has at least the following beneficial effects:
[0013] (1) This invention utilizes the silanization reaction between the 3-aminopropylsilyl group and the silanol group of APTES to attract and anchor the components of the synthesized LTA molecular sieve onto the surface of the alumina matrix, while greatly increasing the hydrophilicity of the matrix surface, accelerating the formation of crystal nuclei on the substrate surface and growing a dense and continuous LTA molecular sieve membrane.
[0014] (2) The method for synthesizing silver-loaded LTA molecular sieve membranes of the present invention is simple, fast and reproducible. The molecular sieve membranes synthesized by this method have good compactness, uniform distribution of Ag particles encapsulated in the pores and small size. They can be widely used in catalysts, separation membranes and other fields, and have high practical value and economic benefits.
[0015] In some embodiments of the present invention, step S1, the modification includes immersing the alumina substrate in an aminopropyltriethoxysilane solution. Preferably, the treatment temperature is 100°C to 120°C, and the treatment time is 1 to 4 hours.
[0016] In some embodiments of the present invention, the concentration of the aminopropyltriethoxysilane solution is 0.1~0.5mM.
[0017] In some preferred embodiments of the present invention, the concentration of the aminopropyltriethoxysilane solution is 0.15~0.25mM.
[0018] In some embodiments of the present invention, the solvent of the aminopropyltriethoxysilane solution includes at least one of toluene, acetone, chloroform and ethanol.
[0019] In some preferred embodiments of the present invention, the solvent of the aminopropyltriethoxysilane solution is toluene.
[0020] In some embodiments of the present invention, in step S2, the organosilicon source includes at least one of 3-mercaptopropyltrimethoxysilane, 3-chloropropyldimethoxymethylsilane, 3-iodopropyltrimethoxysilane, and 3-bromopropyltrimethoxysilane.
[0021] In some embodiments of the present invention, the sodium source includes at least one of sodium hydroxide and sodium oxide. Preferably, the sodium source is sodium hydroxide.
[0022] In some embodiments of the present invention, the silver source includes silver nitrate.
[0023] In some embodiments of the invention, the solvent comprises water. Deionized water is preferred.
[0024] In some embodiments of the present invention, the mass-to-volume ratio of the organosilicon source, sodium source, silver source and solvent in the metal precursor solution is 1.5~8μL:10~12g:0.0001~0.002g:20~40g.
[0025] In some embodiments of the present invention, the mass fraction of silica in the colloidal silica solution is 3-10 wt%; preferably, the mass fraction of silica in the colloidal silica solution is 3-5 wt%.
[0026] In some embodiments of the present invention, the mass ratio of the metal precursor solution, colloidal silica solution and aluminum foil in the molecular sieve membrane synthesis solution is 35~40g: 20~25g: 0.1~0.3g.
[0027] In some embodiments of the present invention, in step S2, the molar ratio of Na2O:Al2O3:SiO2:solvent in the molecular sieve membrane synthesis solution is 40~60:1:4~6:800~1200.
[0028] In some preferred embodiments of the present invention, in step S2, the molar ratio of Na2O:Al2O3:SiO2:solvent in the molecular sieve membrane synthesis solution is 45~55:1:4~6:800~1200.
[0029] In some embodiments of the present invention, in step S3, the contacting includes immersing the functionalized alumina substrate in the molecular sieve membrane synthesis solution.
[0030] In some embodiments of the present invention, in step S3, the temperature of the hydrothermal reaction is 55°C to 65°C; and / or, the time of the hydrothermal reaction is 10 to 36 hours.
[0031] In some embodiments of the present invention, in step S3, the calcination temperature is 250~400°C.
[0032] In some embodiments of the present invention, the roasting time is 1 to 4 hours.
[0033] In some embodiments of the present invention, the roasting atmosphere is dry air.
[0034] In a second aspect, the present invention provides a silver-loaded LTA-type molecular sieve membrane, prepared by the synthesis method described in any one of the first aspects.
[0035] The silver-loaded LTA-type molecular sieve membrane according to embodiments of the present invention has at least the following beneficial effects: the molecular sieve membrane synthesized by this method has the characteristics of good compactness, uniform distribution and small size of Ag particles encapsulated in the pores, and can be widely used in catalysts, separation membranes and other fields, with high practical value and economic benefits.
[0036] In some embodiments of the present invention, the amount of metallic silver encapsulated in the silver-loaded LTA molecular sieve membrane is 0.001~0.2%.
[0037] In some embodiments of the present invention, the amount of metallic silver encapsulated in the silver-loaded LTA-type molecular sieve membrane is 0.01~0.1%.
[0038] A third aspect of the invention provides the use of the synthesis method as described in any of the first aspects or the silver-loaded LTA-type molecular sieve membrane as described in the second aspect in the preparation of catalysts or separation membranes.
[0039] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description
[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:
[0041] Figure 1 This is a schematic diagram of the preparation process of the silver-loaded LTA molecular sieve membrane of the present invention.
[0042] Figure 2 This is an X-ray diffraction pattern of the molecular sieve membrane synthesized in Example 1 of the present invention.
[0043] Figure 3 This is a scanning electron microscope image of the surface of the molecular sieve membrane synthesized in Example 1 of the present invention.
[0044] Figure 4 This is a transmission electron microscope image of the molecular sieve membrane synthesized in Example 1 of the present invention.
[0045] Figure 5 This is a scanning electron microscope image of the surface of the molecular sieve membrane synthesized in Example 3 of the present invention.
[0046] Figure 6 This is a transmission electron microscope image of the molecular sieve membrane synthesized in Example 3 of the present invention.
[0047] Figure 7 This is a scanning electron microscope image of the surface of the molecular sieve membrane synthesized in Comparative Example 1 of this invention.
[0048] Figure 8 This is a scanning electron microscope image of the surface of the molecular sieve membrane synthesized in Comparative Example 4 of the present invention.
[0049] Figure 9 This is a scanning electron microscope image of the surface of the molecular sieve membrane synthesized in Comparative Example 5 of the present invention.
[0050] Figure 10 This is a transmission electron microscope image of the molecular sieve membrane synthesized in Comparative Example 5 of the present invention. Detailed Implementation
[0051] The following will describe the concept and technical effects of the present invention clearly and completely with reference to the embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.
[0052] The terms "preferred," "more preferably," etc., used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.
[0053] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.
[0054] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0055] Unless otherwise specified, "about" in this invention means that the allowable error is within ±2%.
[0056] Unless otherwise specified, "room temperature" in this invention means 25℃~37℃.
[0057] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.
[0058] Inventive concept
[0059] This invention provides a method for synthesizing silver-loaded LTA-type molecular sieve membranes, the synthesis flowchart of which is shown below. Figure 1 As shown, it includes: S1, modifying the alumina substrate with aminopropyltriethoxysilane;
[0060] S2. Prepare a precursor solution with an Ag encapsulation amount of 0.02~0.50% and stir at 40℃ for 24h to prepare a synthesis solution; then immerse the modified alumina substrate in the synthesis solution and synthesize at 60℃ for 6~24 hours.
[0061] S3. After synthesis, the membrane is cooled to room temperature and removed. It is washed several times with deionized water until neutral, dried, and calcined in dry air at 300°C for 2 hours to obtain Ag@LTA molecular sieve membrane.
[0062] The synthesis method of this invention is simple, rapid, and highly reproducible. The synthesized molecular sieve membrane has good density and uniform distribution of Ag particles encapsulated in the pores. It can be widely used in catalysts, separation membranes and other fields, and has high practical value and economic benefits.
[0063] Example 1
[0064] This embodiment provides a method for synthesizing a silver-loaded LTA-type molecular sieve membrane, which specifically includes the following steps:
[0065] S1. Dissolve aminopropyltriethoxysilane (APTES) in toluene to prepare an aminopropyltriethoxysilane solution with a concentration of 0.2 mM. Then, immerse a porous alumina substrate with a diameter of about 18 mm in the aminopropyltriethoxysilane solution at 110 °C for 2 h to obtain a functionalized and modified porous alumina substrate.
[0066] S2. Dissolve 11.11 g of sodium hydroxide in 25 g of deionized water. While stirring at room temperature, add 1.6 μL of (3-mercaptopropyl)trimethoxysilane and 0.00026 g of silver nitrate to obtain a precursor solution containing metal. Then, stir 2.08 g of LUDOX AS-40 colloidal silica and 23.5 g of deionized water vigorously at 60 °C to prepare a colloidal silica suspension. Slowly add the colloidal silica suspension dropwise to the metal precursor solution that is being stirred. Stir overnight at 40 °C. Then add 0.15 g of aluminum foil and stir at room temperature for 12 h to obtain a clear solution, which is the molecular sieve membrane synthesis solution.
[0067] S3. In the reactor, the functionalized modified porous alumina substrate obtained in step S1 is completely immersed in the molecular sieve membrane synthesis solution and hydrothermally synthesized at 60°C for 24 hours. After removing the substrate, the membrane is rinsed several times with deionized water and then dried overnight in an oven at 80°C. Finally, it is calcined in dry air at 300°C for 2 hours to obtain the silver-loaded LTA type molecular sieve membrane.
[0068] The theoretical metal encapsulation amount of the silver-loaded LTA-type molecular sieve membrane prepared by the above method is 0.02%. X-ray diffraction analysis confirms that the molecular sieve membrane has an LTA-type structure (e.g., ...). Figure 2 (As shown). Further observation was performed using scanning electron microscopy and transmission electron microscopy, with the scanning electron microscopy results as follows. Figure 3 As shown, the molecular sieve membrane prepared by this method exhibits high density and no obvious defects. Transmission electron microscopy observations are as follows... Figure 4 As shown, the Ag particles are approximately 3 nm in size and are uniformly dispersed in the molecular sieve without any Ag agglomeration or precipitation.
[0069] Example 2
[0070] This embodiment provides a method for synthesizing a silver-loaded LTA-type molecular sieve membrane, which specifically includes the following steps:
[0071] S1. Dissolve aminopropyltriethoxysilane (APTES) in toluene to prepare an aminopropyltriethoxysilane solution with a concentration of 0.2 mM. Then, immerse a porous alumina substrate with a diameter of about 18 mm in the aminopropyltriethoxysilane solution at 110 °C for 2 h to obtain a functionalized and modified porous alumina substrate.
[0072] S2. Dissolve 11.11 g of sodium hydroxide in 25 g of deionized water. While stirring at room temperature, add 1.6 μL of (3-mercaptopropyl)trimethoxysilane and 0.00026 g of silver nitrate to obtain a precursor solution containing metal. Then, stir 2.08 g of LUDOX AS-40 colloidal silica and 23.5 g of deionized water vigorously at 60 °C to prepare a colloidal silica suspension. Slowly add the colloidal silica suspension dropwise to the metal precursor solution that is being stirred. Stir overnight at 40 °C. Then add 0.15 g of aluminum foil and stir at room temperature for 12 h to obtain a clear solution, which is the molecular sieve membrane synthesis solution.
[0073] S3. In the reactor, the functionalized modified porous alumina substrate obtained in step S1 is completely immersed in the molecular sieve membrane synthesis solution and hydrothermally synthesized at 60°C for 12 hours. After removing the substrate, the membrane is rinsed several times with deionized water and then dried overnight in an oven at 80°C. Finally, it is calcined in air at 300°C for 2 hours to obtain the silver-loaded LTA type molecular sieve membrane.
[0074] The theoretical metal encapsulation amount of the silver-loaded LTA-type molecular sieve membrane prepared by the above method is 0.02%, and the molecular sieve membrane is confirmed to be an LTA-type structure by X-ray diffraction. Further observation by scanning electron microscopy and transmission electron microscopy showed that the molecular sieve membrane was smooth and continuous, without obvious agglomeration.
[0075] Example 3
[0076] This embodiment provides a method for synthesizing a silver-loaded LTA-type molecular sieve membrane, which specifically includes the following steps:
[0077] S1. Dissolve aminopropyltriethoxysilane (APTES) in toluene to prepare an aminopropyltriethoxysilane solution with a concentration of 0.2 mM. Then, immerse a porous alumina substrate with a diameter of about 18 mm in the aminopropyltriethoxysilane solution at 110 °C for 2 h to obtain a functionalized and modified porous alumina substrate.
[0078] S2. Dissolve 11.11 g of sodium hydroxide in 25 g of deionized water. While stirring at room temperature, add 8 μL of (3-mercaptopropyl)trimethoxysilane and 0.0013 g of silver nitrate to obtain a precursor solution containing metal. Then, add 2.08 g of LUDOX AS-40 colloidal silica and 23.5 g of deionized water at 60 °C and stir vigorously to prepare a colloidal silica suspension. Slowly add the colloidal silica suspension dropwise to the metal precursor solution that is being stirred. Stir overnight at 40 °C. Then add 0.15 g of aluminum foil and stir at room temperature for 12 h to obtain a clear solution, which is the molecular sieve membrane synthesis solution.
[0079] S3. In the reactor, the functionalized modified porous alumina substrate obtained in step S1 is completely immersed in the molecular sieve membrane synthesis solution and hydrothermally synthesized at 60°C for 24 hours. After removing the substrate, the membrane is rinsed several times with deionized water and then dried overnight in an oven at 80°C. Finally, it is calcined in dry air at 300°C for 2 hours to obtain the silver-loaded LTA type molecular sieve membrane.
[0080] The theoretical metal encapsulation amount of the silver-loaded LTA-type molecular sieve membrane prepared by the above method is 0.10%, and the molecular sieve membrane is confirmed to be an LTA-type structure by X-ray diffraction. Further observation using scanning electron microscopy and transmission electron microscopy yielded the following results: Figure 5 and Figure 6 As shown, the morphology of the molecular sieve membrane has changed, with a small amount of amorphous products growing, but the overall structure is smooth and continuous. Furthermore, the transmission electron microscope image shows that the Ag particles are larger in size, approximately 10 nm, after the encapsulation amount is increased.
[0081] Comparative Example 1
[0082] This comparative example provides a method for synthesizing a silver-loaded LTA-type molecular sieve membrane, which differs from Example 1 in that the porous alumina substrate is not modified, while all other conditions remain unchanged. The synthesis method specifically includes the following steps:
[0083] S1. Dissolve 11.11 g of sodium hydroxide in 25 g of deionized water. While stirring at room temperature, add 1.6 μL of (3-mercaptopropyl)trimethoxysilane and 0.00026 g of silver nitrate to obtain a precursor solution containing metal. Then, add 2.08 g of LUDOX AS-40 colloidal silica and 23.5 g of deionized water at 60 °C and stir vigorously to prepare a colloidal silica suspension. Slowly add the colloidal silica suspension dropwise to the metal precursor solution that is being stirred. Stir overnight at 40 °C. Then add 0.15 g of aluminum foil and stir at room temperature for 12 h to obtain a clear solution, which is the molecular sieve membrane synthesis solution.
[0084] S2. In the reactor, the porous alumina substrate is completely immersed in the molecular sieve membrane synthesis solution and hydrothermally synthesized at 60°C for 24 hours. After removing the substrate, the membrane is rinsed several times with deionized water and then dried overnight in an oven at 80°C. Finally, it is calcined in air at 300°C for 2 hours to obtain the silver-loaded LTA type molecular sieve membrane.
[0085] The theoretical metal encapsulation amount of the silver-loaded LTA-type molecular sieve membrane prepared by the above method is 0.02%, and the molecular sieve membrane is confirmed to be an LTA-type structure by X-ray diffraction. Further scanning electron microscopy analysis yielded the following results: Figure 7 As shown, the crystals are loosely arranged and the film has obvious defects, indicating poor compactness.
[0086] Therefore, it can be seen that the silanization reaction between the 3-aminopropylsilyl group and the silanol group of APTES is beneficial to attract and anchor the components of the synthesized LTA molecular sieve onto the support surface, thereby accelerating the formation of crystal nuclei on the substrate surface and growing a dense and continuous LTA molecular sieve membrane.
[0087] Comparative Example 2
[0088] This comparative example provides a method for synthesizing a silver-loaded LTA-type molecular sieve membrane, which differs from Example 1 in that the substrate modification type is adjusted while other conditions remain unchanged. The synthesis method specifically includes the following steps:
[0089] S1. Dissolve 3-chloropropyltrimethoxysilane in toluene to prepare a 0.2 mM 3-chloropropyltrimethoxysilane solution. Then, immerse a porous alumina substrate with a diameter of about 18 mm in the 3-chloropropyltrimethoxysilane solution at 110 °C for 2 h to obtain a functionalized and modified porous alumina substrate.
[0090] S2. Dissolve 11.11 g of sodium hydroxide in 25 g of deionized water. While stirring at room temperature, add 1.6 μL of (3-mercaptopropyl)trimethoxysilane and 0.00026 g of silver nitrate to obtain a precursor solution containing metal. Then, stir 2.08 g of LUDOX AS-40 colloidal silica and 23.5 g of deionized water vigorously at 60 °C to prepare a colloidal silica suspension. Slowly add the colloidal silica suspension dropwise to the metal precursor solution that is being stirred. Stir overnight at 40 °C. Then add 0.15 g of aluminum foil and stir at room temperature for 12 h to obtain a clear solution, which is the molecular sieve membrane synthesis solution.
[0091] S3. In the reactor, the functionalized modified porous alumina substrate obtained in step S1 is completely immersed in the molecular sieve membrane synthesis solution and hydrothermally synthesized at 60°C for 6 hours. After removing the substrate, the membrane is rinsed several times with deionized water and then dried overnight in an oven at 80°C. Finally, it is calcined in air at 300°C for 2 hours to obtain the silver-loaded LTA type molecular sieve membrane.
[0092] The theoretical metal encapsulation amount of the silver-loaded LTA-type molecular sieve membrane prepared by the above method is 0.02%, and the molecular sieve membrane is confirmed to be an LTA-type structure by X-ray diffraction. Further scanning electron microscopy observation showed that the compactness of the molecular sieve membrane was significantly reduced, which is presumably related to the decrease in the hydrophilicity of the substrate surface.
[0093] Comparative Example 3
[0094] This comparative example provides a method for synthesizing a silver-loaded LTA-type molecular sieve membrane, which differs from Example 1 in that the hydrothermal synthesis time in step S3 is adjusted to 6 hours, while the other conditions remain unchanged. The synthesis method specifically includes the following steps:
[0095] S1. Dissolve aminopropyltriethoxysilane (APTES) in toluene to prepare an aminopropyltriethoxysilane solution with a concentration of 0.2 mM. Then, immerse a porous alumina substrate with a diameter of about 18 mm in the aminopropyltriethoxysilane solution at 110 °C for 2 h to obtain a functionalized and modified porous alumina substrate.
[0096] S2. Dissolve 11.11 g of sodium hydroxide in 25 g of deionized water. While stirring at room temperature, add 1.6 μL of (3-mercaptopropyl)trimethoxysilane and 0.00026 g of silver nitrate to obtain a precursor solution containing metal. Then, stir 2.08 g of LUDOX AS-40 colloidal silica and 23.5 g of deionized water vigorously at 60 °C to prepare a colloidal silica suspension. Slowly add the colloidal silica suspension dropwise to the metal precursor solution that is being stirred. Stir overnight at 40 °C. Then add 0.15 g of aluminum foil and stir at room temperature for 12 h to obtain a clear solution, which is the molecular sieve membrane synthesis solution.
[0097] S3. In the reactor, the functionalized modified porous alumina substrate obtained in step S1 is completely immersed in the molecular sieve membrane synthesis solution and hydrothermally synthesized at 60°C for 6 hours. After removing the substrate, the membrane is rinsed several times with deionized water and then dried overnight in an oven at 80°C. Finally, it is calcined in air at 300°C for 2 hours to obtain the silver-loaded LTA type molecular sieve membrane.
[0098] The theoretical metal encapsulation amount of the silver-loaded LTA-type molecular sieve membrane prepared by the above method is 0.02%, and the molecular sieve membrane is confirmed to be an LTA-type structure by X-ray diffraction. Further scanning electron microscopy observation showed that the compactness of the molecular sieve membrane was significantly reduced.
[0099] Comparative Example 4
[0100] This comparative example provides a method for synthesizing a silver-loaded molecular sieve membrane, which differs from Example 1 in that the type of aluminum source in the synthesis solution is changed, while other conditions remain the same. The synthesis method specifically includes the following steps:
[0101] S1. Dissolve aminopropyltriethoxysilane (APTES) in toluene to prepare an aminopropyltriethoxysilane solution with a concentration of 0.2 mM. Then, immerse a porous alumina substrate with a diameter of about 18 mm in the aminopropyltriethoxysilane solution at 110 °C for 2 h to obtain a functionalized and modified porous alumina substrate.
[0102] S2. Dissolve 11.11 g of sodium hydroxide in 25 g of deionized water. While stirring at room temperature, add 1.6 μL of (3-mercaptopropyl)trimethoxysilane and 0.00026 g of silver nitrate to obtain a precursor solution containing metal. Then, stir 2.08 g of LUDOX AS-40 colloidal silica and 23.5 g of deionized water vigorously at 60 °C to prepare a colloidal silica suspension. Slowly add the colloidal silica suspension dropwise to the metal precursor solution that is being stirred. Stir overnight at 40 °C. Then add 0.15 g of sodium aluminate and stir at room temperature for 12 h to obtain a clear solution, which is the molecular sieve membrane synthesis solution.
[0103] S3. In the reactor, the functionalized and modified porous alumina substrate obtained in step S1 is completely immersed in the molecular sieve membrane synthesis solution and hydrothermally synthesized at 60°C for 24 hours. After removing the substrate, the membrane is rinsed several times with deionized water and then dried overnight in an oven at 80°C. Finally, it is calcined in air at 300°C for 2 hours to obtain the silver-loaded molecular sieve membrane.
[0104] The theoretical metal encapsulation amount of the silver-loaded molecular sieve membrane prepared by the above method is 0.02%. X-ray diffraction analysis confirmed that the molecular sieve membrane has an amorphous structure. Further scanning electron microscopy observation revealed the following results: Figure 8 As shown, the molecular sieve membrane exhibits poor compactness, and no clear molecular sieve membrane structure was observed.
[0105] Comparative Example 5
[0106] This comparative example provides a method for synthesizing a silver-loaded molecular sieve membrane, which differs from Example 1 in that the amount of Ag metal encapsulation is adjusted, while other conditions remain unchanged. The synthesis method specifically includes the following steps:
[0107] S1. Dissolve aminopropyltriethoxysilane (APTES) in toluene to prepare an aminopropyltriethoxysilane solution with a concentration of 0.2 mM. Then, immerse a porous alumina substrate with a diameter of about 18 mm in the aminopropyltriethoxysilane solution at 110 °C for 2 h to obtain a functionalized and modified porous alumina substrate.
[0108] S2. Dissolve 11.11 g of sodium hydroxide in 25 g of deionized water. While stirring at room temperature, add 40 μL of (3-mercaptopropyl)trimethoxysilane and 0.0065 g of silver nitrate to obtain a precursor solution containing metal. Then, add 2.08 g of LUDOX AS-40 colloidal silica and 23.5 g of deionized water at 60 °C and stir vigorously to prepare a colloidal silica suspension. Slowly add the colloidal silica suspension dropwise to the metal precursor solution that is being stirred. Stir overnight at 40 °C. Then add 0.15 g of aluminum foil and stir at room temperature for 12 h to obtain a clear solution, which is the molecular sieve membrane synthesis solution.
[0109] S3. In the reactor, the functionalized and modified porous alumina substrate obtained in step S1 is completely immersed in the molecular sieve membrane synthesis solution and hydrothermally synthesized at 60°C for 24 hours. After removing the substrate, the membrane is rinsed several times with deionized water and then dried overnight in an oven at 80°C. Finally, it is calcined in air at 300°C for 2 hours to obtain the silver-loaded molecular sieve membrane.
[0110] The theoretical metal encapsulation amount of the silver-loaded molecular sieve membrane prepared by the above method is 0.50%. X-ray diffraction analysis confirmed that the molecular sieve membrane has an amorphous structure. Further observation using scanning electron microscopy and transmission electron microscopy was performed. The results of the scanning electron microscopy are as follows: Figure 9 As shown, the morphology of the molecular sieve membrane has changed, with a large amount of amorphous products growing. Transmission electron microscopy observations are as follows... Figure 10 As shown, the Ag particle size is larger after the encapsulation amount is increased, about 10nm, and there is a lot of agglomeration of large Ag particles.
[0111] In summary, this invention provides a method for synthesizing silver-loaded LTA-type molecular sieve membranes. The main steps include: first, preparing a precursor solution with an Ag encapsulation amount of 0.02-0.50%, and stirring at 40°C for 24 hours to prepare a synthesis solution; then, immersing a modified alumina substrate in the synthesis solution and synthesizing at 60°C for 6-24 hours; after synthesis, cooling to room temperature and removing the membrane, washing repeatedly with deionized water until neutral, drying, and calcining in dry air at 300°C for 2 hours to obtain the Ag@LTA molecular sieve membrane. The synthesis method of this invention is simple, rapid, and highly reproducible. The synthesized molecular sieve membrane exhibits good density and uniform distribution of encapsulated Ag particles within the pores, making it widely applicable in catalysts, separation membranes, and other fields, demonstrating high practical value and economic benefits.
[0112] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.
Claims
1. A method for synthesizing a silver-loaded molecular sieve membrane, characterized in that, Includes the following steps: S1. The alumina substrate was modified with aminopropyltriethoxysilane to obtain a functionalized alumina substrate. S2. Mix the organosilicon source, sodium source, and silver source with the solvent to obtain a metal precursor solution. Then, add colloidal silica solution and aluminum foil in sequence, mix well, and obtain a molecular sieve membrane synthesis solution. The organosilicon source is selected from any one of 3-mercaptopropyltrimethoxysilane, 3-chloropropyldimethoxymethylsilane, 3-iodopropyltrimethoxysilane, and 3-bromopropyltrimethoxysilane; the sodium source is sodium hydroxide or sodium oxide; the silver source is silver nitrate; the mass-volume ratio of the organosilicon source, sodium source, silver source, and solvent is 1.5–8 μL: 10–12 g: 0.0001–0.00026 g: 20–40 g; the mass ratio of the metal precursor solution, colloidal silica solution, and aluminum foil is 35–40 g: 20–25 g: 0.1–0.3 g; the mass fraction of silica in the colloidal silica solution is 3–10 wt%. S3. The molecular sieve membrane synthesis solution is contacted with the functionalized modified alumina substrate, and the mixture is subjected to hydrothermal reaction, drying and calcination to obtain the final product; wherein the hydrothermal reaction time is 10~36h; the calcination temperature is 250~400℃, the time is 1~4h, and the atmosphere is dry air.
2. The synthesis method according to claim 1, characterized in that, In step S1, the modification includes immersing the alumina substrate in an aminopropyltriethoxysilane solution.
3. The synthesis method according to claim 2, characterized in that, The concentration of the aminopropyltriethoxysilane solution is 0.1~0.5mM.
4. The synthesis method according to claim 1, characterized in that, In step S3, the contacting process includes immersing the functionalized alumina substrate in the molecular sieve membrane synthesis solution.
5. The synthesis method according to claim 1, characterized in that, In step S3, the temperature of the hydrothermal reaction is 55℃~65℃.
6. A silver-loaded LTA-type molecular sieve membrane, characterized in that, It is prepared by the synthesis method described in any one of claims 1 to 5.
7. The application of the silver-loaded LTA molecular sieve membrane as described in claim 6 in the preparation of catalysts or separation membranes.