A method for preparing a highly dispersed thin sheet-shaped ZSM-5 molecular sieve

Abstract

The embodiment of the application provides a preparation method of high-dispersion flaky ZSM-5 molecular sieve, and relates to the field of molecular sieve preparation.S1, a seed crystal solution is prepared;S2, a tetrapropylammonium hydroxide solution, deionized water, a silicon source and the seed crystal solution prepared in the step S1 are mixed to obtain a solution B;S3, an aluminum source is added into the deionized water to dissolve the aluminum source in the deionized water;S4, the deionized water with the dissolved aluminum source is added into the clear solution in the step S2 to stir, and a white solution C is obtained;S5, an additive is added into the deionized water to dissolve the additive in the deionized water;S6, the deionized water with the dissolved additive is added into the solution C in the step S4 to stir, and then the solution is loaded into a crystallization kettle to crystallize, and a crystallized sample is obtained;S7, the crystallized sample is subjected to a drying treatment and then calcination, and a flaky ZSM-5 molecular sieve is obtained.

Description

Technical Field

[0001] This invention relates to the field of molecular sieve preparation, specifically to a method for preparing a highly dispersed thin-film ZSM-5 molecular sieve. Background Technology

[0002] ZSM-5 molecular sieve is a microporous zeolite developed by Mobil in the 1970s, possessing an MFI topology. Its unique three-dimensional channel structure, excellent physicochemical properties, and tunable silica-alumina ratio endow ZSM-5 molecular sieve with outstanding product selectivity, suitable acidity, large specific surface area and pore volume, and good hydrothermal stability. This has led to the widespread application of ZSM-5 in refining and petrochemical fields such as catalytic cracking, alkylation, isomerization, and disproportionation, greatly promoting the development of the petrochemical industry.

[0003] Despite significant progress in the synthesis and application of ZSM-5 molecular sieves over the past few decades, the diffusion limitation caused by their long micropores remains a prominent issue. This diffusion limitation not only reduces the utilization rate of the zeolite's active volume but also restricts the transport efficiency of molecules in catalysis and separation processes, particularly in reactions severely affected by diffusion. Therefore, addressing the problems of diffusion restriction, low conversion rate, poor selectivity for target products, and short catalytic lifetime in traditional ZSM-5 molecular sieves has become a key focus of current research.

[0004] To address the aforementioned challenges, researchers have conducted extensive research on preparing sheet-like ZSM-5 molecular sieves with short pore lengths. Sheet-like ZSM-5 molecular sieves combine the advantages of hierarchical porous molecular sieves and nanoporous molecular sieves, retaining the excellent catalytic, adsorption, and shape-selective properties of microporous molecular sieves while improving molecular diffusion performance by reducing pore length. This significantly enhances reactivity and stability, making it one of the materials with great research and application potential.

[0005] The main strategies for synthesizing sheet-like ZSM-5 molecular sieves are as follows: Post-processing layered zeolite precursor method: M. Choi et al. successfully prepared monolayer ZSM-5 nanosheets with a thickness of only 2 nm using post-processing techniques such as pillaring and exfoliation. However, this method is complex, has low yield, and is difficult to achieve large-scale synthesis [Reference: M. Choi, et al. Nature, 2009, 461, 246-249].

[0006] Template method: Tsapatsis et al. synthesized nanosheets with a thickness of 2 nm using a template agent. This method effectively reduces diffusion limitations, but the template agent is expensive and difficult to recycle, which limits its large-scale application [Reference: M. Tsapatsis, et al. Nature, 2017, 543, 690-694].

[0007] Chemical etching: Liu et al. successfully prepared monodisperse sheet-like molecular sieves with a thickness of 25 nm by anisotropic etching of ZSM-5 molecular sieves with TPAOH solution. Although this method is simple to operate, it is not effective for low-silicon samples and the etching conditions are relatively harsh [Reference: Y. Liu, et al. Sci. Adv., 2020, 6, eaay5993].

[0008] Additive-assisted method: Patents CN106542544A and CN105523569A describe the synthesis of sheet-like ZSM-5 molecular sieves by using bispiperidone alkyl cations and other additives, but it is difficult to control the pore length of the sample below 100 nm [Reference: CN106542544A, CN105523569A].

[0009] Low-temperature synthesis method: Patent CN108275697B reports a method for synthesizing ZSM-5 nanosheets using fluorides under low-temperature conditions, but fluorides have high toxicity and corrosiveness, which seriously limits their industrial application [Reference: CN108275697B].

[0010] In summary, current technologies for synthesizing sheet-like ZSM-5 molecular sieves still face several key challenges, including difficulty in precisely controlling thickness, the use of toxic chemicals, long synthesis cycles, and high costs. Therefore, developing green, efficient, and low-cost preparation strategies is of great significance for the large-scale industrial application of ZSM-5 molecular sieves. Summary of the Invention

[0011] According to embodiments of the present invention, a method for preparing highly dispersed sheet-like ZSM-5 molecular sieves is provided, addressing the problems raised in the background section above.

[0012] In a first aspect of the present invention, a method for preparing highly dispersed sheet-like ZSM-5 molecular sieve is provided.

[0013] The preparation method of this highly dispersed thin-film ZSM-5 molecular sieve includes: S1. Taking a 25% (w / w) tetrapropylammonium hydroxide solution, and diluting it with deionized water. Mixing the tetrapropylammonium hydroxide solution and deionized water thoroughly to obtain solution A. Adding tetraethyl orthosilicate to solution A, and stirring under water bath conditions to promote complete hydrolysis of the tetraethyl orthosilicate, and removing alcohol from the solution containing tetraethyl orthosilicate. After alcohol removal, crystallization is performed to obtain a seed crystal solution.

[0014] S2. Mix the tetrapropylammonium hydroxide solution, deionized water, silicon source and the seed solution prepared in step S1 to obtain solution B.

[0015] S3. Add the aluminum source to the deionized water to dissolve the aluminum source in the deionized water.

[0016] S4. Add the deionized water containing the dissolved aluminum source to the clarified solution in step S2 and stir to obtain a white solution C.

[0017] S5. Add the additive to the deionized water to dissolve it.

[0018] S6. Add the deionized water containing the additive to solution C in step S4 and stir. Then, put the solution into a crystallization vessel for crystallization to obtain the crystallized sample.

[0019] S7. After drying the crystallized sample, it is calcined to obtain thin sheet-like ZSM-5 molecular sieve.

[0020] Preferably, in step S1, the water bath temperature is 35°C, the alcohol removal temperature is 45°C, and the alcohol removal time is 6 hours; the crystallization temperature is 50~90°C, and the crystallization time is 36~120 hours.

[0021] Preferably, the template agent in step S2 is a 25% tetrapropylammonium hydroxide solution, n-butylamine, tetrapropylammonium bromide, or L by mass fraction; the silicon source is tetraethyl orthosilicate, silica sol, silica fume, water glass, or solid silica gel.

[0022] Preferably, the aluminum source in step S3 is aluminum chloride hexahydrate, sodium aluminate, aluminum nitrate, aluminum hydroxide, or aluminum sulfate.

[0023] Preferably, the stirring time in step S4 is 0.5~1h.

[0024] Preferably, the additive in step S5 is ammonium bicarbonate, ammonium sulfate, ammonium carbonate, ammonium bisulfate, ethylenediamine, ethylamine, ammonium chloride, urea, or ammonium nitrate.

[0025] Preferably, in step S6, the stirring time is 0.5 h, the crystallization temperature is 90~170℃, and the crystallization time is 3~72 h.

[0026] Preferably, in step S7, the drying temperature is 80°C, the drying time is 12 hours, the calcination temperature is 540°C, and the calcination time is 6 hours.

[0027] Preferably, the mass ratio of the template agent: silicon source: aluminum source: additive: seed crystal: water is (0.72~2.92): (6.3~8.0): (0.16~0.32): (0.53~0.63): (0.025~6.2): ​​60.94.

[0028] Preferably, step S2 does not include a tetrapropylammonium hydroxide solution.

[0029] One or more technical solutions provided in this application have at least the following technical effects or advantages: This invention provides a method for preparing highly dispersed sheet-like ZSM-5 molecular sieves, successfully synthesizing ZSM-5 nanosheet molecular sieves with short b-axis and controllable size. Compared with the prior art, this invention has the following advantages: First, X-ray diffraction (XRD) results showed that the synthesized sheet-like ZSM-5 molecular sieve exhibited typical MFI structural diffraction peaks, indicating high crystallinity and purity, thus demonstrating the superiority of the preparation process. Second, scanning electron microscopy (SEM) observations revealed that the molecular sieve possessed a regular and uniform sheet-like morphology with good dispersibility, providing crucial assurance for its stability in catalysis and adsorption applications. Furthermore, transmission electron microscopy (TEM) confirmed that the ZSM-5 molecular sieve possesses an ultrathin sheet-like structure, with a b-axis thickness controllable to approximately 20 nm. This ultrathin structure significantly reduces diffusion resistance, thereby enhancing the catalytic activity, selectivity, and stability of the molecular sieve in practical industrial applications.

[0030] Nitrogen physisorption experimental data further confirmed that the sheet-like ZSM-5 molecular sieve possesses a large specific surface area. High specific surface area is closely related to reactivity, significantly increasing the contact probability between reactants and active sites, thereby greatly enhancing its performance in catalytic reactions. Furthermore, combined with its ultrathin morphology, this molecular sieve exhibits superior performance in various chemical reactions and material applications.

[0031] More importantly, this preparation method eliminates the need for organic template agents, reducing preparation costs and eliminating potential environmental pollution risks, thus contributing to green and environmentally friendly industrial production.

[0032] It should be understood that the description in the Summary of the Invention is not intended to limit the key or essential features of the embodiments of the present invention, nor is it intended to restrict the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0033] The above and other features, advantages, and aspects of the various embodiments of the present invention will become more apparent from the accompanying drawings and the following detailed description. In the drawings, the same or similar reference numerals denote the same or similar elements, wherein: Figure 1 This is a TEM image of the seed solution synthesized in Example 1 of the present invention.

[0034] Figure 2 The image shows the XRD pattern of the sheet-like ZSM-5 molecular sieve synthesized in Example 1 of this invention.

[0035] Figure 3 This is a SEM image of the sheet-like ZSM-5 molecular sieve synthesized in Example 1 of the present invention.

[0036] Figure 4 This is a TEM image of the sheet-like ZSM-5 molecular sieve synthesized in Example 1 of the present invention.

[0037] Figure 5 This is the nitrogen physical adsorption-desorption isotherm of the thin-film ZSM-5 molecular sieve synthesized in Example 1 of the present invention.

[0038] Figure 6 The image shows the XRD pattern of the sheet-like ZSM-5 molecular sieve synthesized in Example 2 of this invention.

[0039] Figure 7 This is a SEM image of the sheet-like ZSM-5 molecular sieve synthesized in Example 2 of the present invention.

[0040] Figure 8 This is a SEM image of the sheet-like ZSM-5 molecular sieve synthesized in Example 3 of the present invention.

[0041] Figure 9 This is a TEM image of the seed solution synthesized in Example 7 of the present invention.

[0042] Figure 10 This is a SEM image of the sheet-like ZSM-5 molecular sieve synthesized in Example 7 of the present invention.

[0043] Figure 11 This is a SEM image of the sheet-like ZSM-5 molecular sieve synthesized in Example 12 of this invention. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Furthermore, the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0046] Example 1 A method for preparing highly dispersed sheet-like ZSM-5 molecular sieve includes the following steps: S1. Preparation of seed solution.

[0047] Take 70 g of a 25% tetrapropylammonium hydroxide solution and dilute it with 30 g of deionized water. Mix the tetrapropylammonium hydroxide solution and deionized water thoroughly to obtain solution A. Add 50 g of tetraethyl orthosilicate to solution A and maintain the mixture at 35 °C in a water bath for 6 h to promote complete hydrolysis of the tetraethyl orthosilicate, resulting in a clear and transparent solution. After complete hydrolysis of the tetraethyl orthosilicate, increase the water bath temperature to 45 °C for alcohol removal for 6 h. After alcohol removal, seal the solution and crystallize it under constant temperature conditions at 80 °C for 36 h to obtain a seed crystal solution.

[0048] The prepared seed crystals were spherical particles, as shown in the transmission electron microscope image below. Figure 1 As shown, the diameter is 20~50 nm.

[0049] S2. Mix the tetrapropylammonium hydroxide solution, deionized water, silicon source, and seed solution prepared in step S1 to obtain solution B; Take 2.92 g of 25% tetrapropylammonium hydroxide solution, dilute it with 30.94 g of deionized water, then add 8.0 g of tetraethyl orthosilicate and 6.20 g of seed solution, and stir in a water bath at 35 ℃ for 2 h to completely hydrolyze the tetraethyl orthosilicate. At this point, the solution is clear and transparent.

[0050] S3. Add the aluminum source to the deionized water to dissolve the aluminum source in the deionized water.

[0051] Dissolve 0.32 g of aluminum source in 15 g of deionized water, wherein the aluminum source is aluminum chloride hexahydrate.

[0052] S4. Add the deionized water containing the dissolved aluminum source to the clarified solution in step S2 and stir to obtain a white solution C.

[0053] The deionized water containing dissolved aluminum chloride hexahydrate was added to the clear solution in step S2 and stirred for 0.5 h to obtain a white solution C.

[0054] S5. Add the additive to the deionized water to dissolve it.

[0055] Dissolve 0.63 g of the additive in 15 g of deionized water, wherein the additive is ammonium bicarbonate.

[0056] S6. Add the deionized water containing the additive to the white solution C from step S4 and stir. Then, pour the solution into a crystallization vessel for crystallization to obtain the crystallized sample.

[0057] Deionized water containing dissolved ammonium bicarbonate was added to the white solution C from step S4 and stirred for 0.5 h. The mixture was then transferred to a 100 mL crystallization vessel and crystallized at 170 °C for 3 h to obtain the crystallized sample.

[0058] S7. After drying the crystallized sample, it is calcined to obtain thin sheet-like ZSM-5 molecular sieve.

[0059] The crystallized sample was subjected to solid-liquid separation, dried at 80 °C for 12 h, and then calcined at 540 °C for 6 h; finally, a sheet-like ZSM-5 molecular sieve with a thickness of 30 nm was obtained.

[0060] like Figures 2-5 As shown, the calcined sample was characterized by XRD, and the results are shown in the figure. Figure 2 The synthesized ZSM-5 molecular sieve exhibits typical MFI diffraction peaks, high crystallinity, and no impurity phases.

[0061] The sample was characterized by scanning electron microscopy (SEM), and the SEM images are shown below. Figure 3 As shown, the results indicate that the synthesized molecular sieve has a regular sheet-like morphology, excellent sample dispersion, and uniform size, with a length (X) of about 600 nm and a width (Y) of about 150 nm.

[0062] The sample was characterized by transmission electron microscopy (TEM) to observe its thickness Z dimension. TEM images are shown below. Figure 4 As shown in the figure, the results indicate that the thickness Z of the sample is around 20 nm.

[0063] Nitrogen physical adsorption tests were performed on the samples, such as... Figure 5 As shown, the specific surface area of ​​the sample is 427 m². 2 / g, total pore volume is 0.5 cm³ 3 / g.

[0064] The above results confirm that the method of this invention can successfully prepare highly dispersed sheet-like ZSM-5 molecular sieves with a thickness of only 20 nm. These sieves possess excellent physical structural properties such as large specific surface area, high pore volume, and short diffusion length, which can greatly improve the accessibility between reactants and active centers, thereby enhancing reaction performance. Furthermore, compared to conventional ZSM-5 synthesis, ZSM-5 nanosheets can complete crystallization in just 3 hours, significantly reducing energy consumption and time costs. More importantly, this invention confirms that ammonium bicarbonate, as an additive, can successfully prepare highly dispersed sheet-like ZSM-5 molecular sieves, a feat not previously reported.

[0065] Example 2 A method for preparing highly dispersed sheet-like ZSM-5 molecular sieve includes the following steps: S1. Preparation of seed solution.

[0066] Specifically, 70 g of a 25% tetrapropylammonium hydroxide solution was taken, and 30 g of deionized water was added to dilute it. The tetrapropylammonium hydroxide solution and deionized water were mixed thoroughly to obtain solution A. 50 g of tetraethyl orthosilicate was added to solution A, and the mixture was stirred at 35 °C in a water bath for 6 hours to promote complete hydrolysis of the tetraethyl orthosilicate, resulting in a clear and transparent solution. After complete hydrolysis of the tetraethyl orthosilicate, the water bath temperature was increased to 45 °C for alcohol removal, which took 6 hours. After alcohol removal, the solution was sealed and crystallized under constant temperature conditions at 80 °C for 36 hours to obtain a seed crystal solution.

[0067] S2. Mix the tetrapropylammonium hydroxide solution, deionized water, silicon source, and seed solution prepared in step S1 to obtain solution B; Take 2.92 g of 25% tetrapropylammonium hydroxide solution, dilute it with 30.94 g of deionized water, then add 8.0 g of tetraethyl orthosilicate and 6.20 g of seed solution, and stir in a water bath at 35 ℃ for 2 h to completely hydrolyze the tetraethyl orthosilicate. At this point, the solution is clear and transparent.

[0068] S3. Add the aluminum source to the deionized water to dissolve the aluminum source in the deionized water.

[0069] Dissolve 0.32 g of aluminum source in 15 g of deionized water, wherein the aluminum source is aluminum chloride hexahydrate.

[0070] S4. Add the deionized water containing the dissolved aluminum source to the clarified solution in step S2 and stir to obtain a white solution C.

[0071] The deionized water containing dissolved aluminum chloride hexahydrate was added to the clear solution in step S2 and stirred for 0.5 h to obtain a white solution C.

[0072] S5. Add the additive to the deionized water to dissolve it.

[0073] Dissolve 0.63 g of the additive in 15 g of deionized water, wherein the additive is ammonium bicarbonate.

[0074] S6. Add the deionized water containing the additive to the white solution C from step S4 and stir. Then, pour the solution into a crystallization vessel for crystallization to obtain the crystallized sample.

[0075] Deionized water containing dissolved ammonium bicarbonate was added to the white solution C from step S4 and stirred for 0.5 h. The mixture was then transferred to a 100 mL crystallization vessel and crystallized at 90 °C for 72 h to obtain the crystallized sample.

[0076] S7. After drying the crystallized sample, it is calcined to obtain thin sheet-like ZSM-5 molecular sieve.

[0077] The crystallized sample was subjected to solid-liquid separation, dried at 80 °C for 12 h, and then calcined at 540 °C for 6 h; finally, a sheet-like ZSM-5 molecular sieve with a thickness of 30 nm was obtained.

[0078] like Figure 6 As shown, the obtained ZSM-5 nanosheets were characterized by X-ray diffraction (XRD) as pure-phase ZSM-5 molecular sieves with good crystallinity; Figure 7 As shown, scanning electron microscopy characterization confirmed that the sample had a sheet-like morphology, good dispersion, and uniform size.

[0079] The advantage of this embodiment is that it can achieve the synthesis of sheet-like ZSM-5 molecular sieves at a low temperature of 90 °C, whereas the synthesis of ZSM-5 molecular sieves usually requires a temperature of 150-180 °C, which helps to reduce synthesis energy consumption. In addition, since the saturated vapor pressure of water at 90 °C is <0.1 MPa, the pressure resistance requirements of the crystallization equipment are lower, and containers such as plastics can be used for crystallization, thus expanding the versatility of the equipment.

[0080] Example 3 A method for preparing highly dispersed sheet-like ZSM-5 molecular sieve includes the following steps: S1. Preparation of seed solution.

[0081] Specifically, 70 g of a 25% tetrapropylammonium hydroxide solution was taken, and 30 g of deionized water was added to dilute it. The tetrapropylammonium hydroxide solution and deionized water were mixed thoroughly to obtain solution A. 50 g of tetraethyl orthosilicate was added to solution A, and the mixture was stirred at 35 °C in a water bath for 6 hours to promote complete hydrolysis of the tetraethyl orthosilicate, resulting in a clear and transparent solution. After complete hydrolysis of the tetraethyl orthosilicate, the water bath temperature was increased to 45 °C for alcohol removal, which took 6 hours. After alcohol removal, the solution was sealed and crystallized under constant temperature conditions at 80 °C for 36 hours to obtain a seed crystal solution.

[0082] S2. Mix the tetrapropylammonium hydroxide solution, deionized water, silicon source, and seed solution prepared in step S1 to obtain solution B; Take 2.92 g of a 25% tetrapropylammonium hydroxide solution, dilute it with 30.94 g of deionized water, then add 8.0 g of tetraethyl orthosilicate and 0.025 g of seed solution, and stir in a water bath at 35 ℃ for 2 h to completely hydrolyze the tetraethyl orthosilicate. At this point, the solution is clear and transparent.

[0083] S3. Add the aluminum source to the deionized water to dissolve the aluminum source in the deionized water.

[0084] Dissolve 0.32 g of aluminum source in 15 g of deionized water, wherein the aluminum source is aluminum chloride hexahydrate.

[0085] S4. Add the deionized water containing the dissolved aluminum source to the clarified solution in step S2 and stir to obtain a white solution C.

[0086] The deionized water containing dissolved aluminum chloride hexahydrate was added to the clear solution in step S2 and stirred for 0.5 h to obtain a white solution C.

[0087] S5. Add the additive to the deionized water to dissolve it.

[0088] Dissolve 0.63 g of the additive in 15 g of deionized water, wherein the additive is ammonium bicarbonate.

[0089] S6. Add the deionized water containing the additive to the white solution C from step S4 and stir. Then, pour the solution into a crystallization vessel for crystallization to obtain the crystallized sample.

[0090] Deionized water containing dissolved ammonium bicarbonate was added to the white solution C from step S4 and stirred for 0.5 h. The mixture was then transferred to a 100 mL crystallization vessel and crystallized at 170 °C for 12 h to obtain the crystallized sample.

[0091] S7. After drying the crystallized sample, it is calcined to obtain thin sheet-like ZSM-5 molecular sieve.

[0092] The crystallized sample was subjected to solid-liquid separation, dried at 80 °C for 12 h, and then calcined at 540 °C for 6 h; finally, a sheet-like ZSM-5 molecular sieve with a thickness of 90 nm was obtained.

[0093] The sample was characterized by scanning electron microscopy (SEM), and the SEM images are shown below. Figure 8 As shown, the results indicate that the synthesized molecular sieve has a regular sheet-like morphology, excellent sample dispersion, and uniform size, with a length (X) of about 500 nm, a width (Y) of about 200 nm, and a thickness (Z) of about 90 nm.

[0094] This embodiment achieves the synthesis of ZSM-5 nanosheets by adjusting the amount of seed crystals added from 50 wt.% in Example 1 to 0.2 wt.%, with the advantage of being able to adjust the thickness of the ZSM-5 nanosheets. Since the thickness direction of ZSM-5 is its straight channel direction, the controllable adjustment of the straight channel length is beneficial for realizing a variety of reaction applications.

[0095] Example 4 A method for preparing highly dispersed sheet-like ZSM-5 molecular sieve includes the following steps: S1. Preparation of seed solution.

[0096] Specifically, 70 g of a 25% tetrapropylammonium hydroxide solution was taken, and 30 g of deionized water was added to dilute it. The tetrapropylammonium hydroxide solution and deionized water were mixed thoroughly to obtain solution A. 50 g of tetraethyl orthosilicate was added to solution A, and the mixture was stirred at 35 °C in a water bath for 6 hours to promote complete hydrolysis of the tetraethyl orthosilicate, resulting in a clear and transparent solution. After complete hydrolysis of the tetraethyl orthosilicate, the water bath temperature was increased to 45 °C for alcohol removal, which took 6 hours. After alcohol removal, the solution was sealed and crystallized under constant temperature conditions at 80 °C for 36 hours to obtain a seed crystal solution.

[0097] S2. Mix deionized water, silicon source and seed solution prepared in step S1 to obtain solution B; Take 30.94 g of deionized water, then add 8.0 g of tetraethyl orthosilicate and 6.20 g of seed solution, and stir in a water bath at 35 ℃ for 2 h to completely hydrolyze the tetraethyl orthosilicate. At this point, the solution is clear and transparent.

[0098] S3. Add the aluminum source to the deionized water to dissolve the aluminum source in the deionized water.

[0099] Dissolve 0.32 g of aluminum source in 15 g of deionized water, wherein the aluminum source is aluminum chloride hexahydrate.

[0100] S4. Add the deionized water containing the dissolved aluminum source to the clarified solution in step S2 and stir to obtain a white solution C.

[0101] The deionized water containing dissolved aluminum chloride hexahydrate was added to the clear solution in step S2 and stirred for 0.5 h to obtain a white solution C.

[0102] S5. Add the additive to the deionized water to dissolve it.

[0103] Dissolve 0.63 g of the additive in 15 g of deionized water, wherein the additive is ammonium bicarbonate.

[0104] S6. Add the deionized water containing the additive to the white solution C from step S4 and stir. Then, pour the solution into a crystallization vessel for crystallization to obtain the crystallized sample.

[0105] Deionized water containing dissolved ammonium bicarbonate was added to the white solution C from step S4 and stirred for 0.5 h. The mixture was then transferred to a 100 mL crystallization vessel and crystallized at 170 °C for 12 h to obtain the crystallized sample.

[0106] S7. After drying the crystallized sample, it is calcined to obtain thin sheet-like ZSM-5 molecular sieve.

[0107] The crystallized sample was subjected to solid-liquid separation, dried at 80 °C for 12 h, and then calcined at 540 °C for 6 h; finally, a sheet-like ZSM-5 molecular sieve with a thickness of 30 nm was obtained.

[0108] The obtained ZSM-5 nanosheets were characterized by X-ray diffraction (XRD) as pure-phase ZSM-5 molecular sieves. Scanning electron microscopy showed that the samples had good crystallization, thin sheet morphology, good dispersibility, and uniform size.

[0109] The advantage of this embodiment is that no organic template agent is introduced during the preparation process. The template-free synthesis of sheet-like ZSM-5 molecular sieves is achieved by adding seed crystal solution. Usually, the synthesis of ZSM-5 molecular sieves requires a large amount of organic template agent. This helps to reduce the preparation cost and reduce environmental pollution problems.

[0110] Example 5 S1. Preparation of seed solution.

[0111] Specifically, 70 g of a 25% tetrapropylammonium hydroxide solution was taken, and 30 g of deionized water was added to dilute it. The tetrapropylammonium hydroxide solution and deionized water were mixed thoroughly to obtain solution A. 50 g of tetraethyl orthosilicate was added to solution A, and the mixture was stirred at 35 °C in a water bath for 6 hours to promote complete hydrolysis of the tetraethyl orthosilicate, resulting in a clear and transparent solution. After complete hydrolysis of the tetraethyl orthosilicate, the water bath temperature was increased to 45 °C for alcohol removal, which took 6 hours. After alcohol removal, the solution was sealed and crystallized under constant temperature conditions at 80 °C for 36 hours to obtain a seed crystal solution.

[0112] S2. Mix the tetrapropylammonium hydroxide solution, deionized water, silicon source, and seed solution prepared in step S1 to obtain solution B; Take 0.96 g of tetrapropylammonium bromide, add 25.56 g of deionized water to dissolve it, then add 7.68 g of silica sol and 2.48 g of seed solution, and stir in a water bath at 35 ℃ for 2 h. At this time, it is a clear and transparent solution.

[0113] S3. Add the aluminum source to the deionized water to dissolve the aluminum source in the deionized water.

[0114] Dissolve 0.32 g of aluminum source in 15 g of deionized water, wherein the aluminum source is aluminum chloride hexahydrate.

[0115] S4. Add the deionized water containing the dissolved aluminum source to the clarified solution in step S2 and stir to obtain a white solution C.

[0116] The deionized water containing dissolved aluminum chloride hexahydrate was added to the clear solution in step S2 and stirred for 0.5 h to obtain a white solution C.

[0117] S5. Add the additive to the deionized water to dissolve it.

[0118] Take 0.60g of the additive and dilute it in 15g of deionized water. The additive is ethylamine.

[0119] S6. Add deionized water containing additives to the white solution C in step S4 and stir. Then, put the solution into a crystallization kettle for crystallization to obtain the crystallized sample.

[0120] Deionized water containing ethylamine was added to the white solution C from step S4 and stirred for 0.5 h. The mixture was then transferred to a 100 mL crystallization vessel and crystallized at 170 °C for 12 h to obtain the crystallized sample.

[0121] S7. After drying the crystallized sample, it is calcined to obtain thin sheet-like ZSM-5 molecular sieve.

[0122] The crystallized sample was subjected to solid-liquid separation, dried at 80 °C for 12 h, and then calcined at 540 °C for 6 h; finally, a sheet-like ZSM-5 molecular sieve with a thickness of 30 nm was obtained.

[0123] The obtained ZSM-5 nanosheets were characterized by X-ray diffraction (XRD) as pure-phase ZSM-5 molecular sieves. Scanning electron microscopy showed that the samples had good crystallization, thin sheet morphology, good dispersibility, and uniform size.

[0124] The advantage of this embodiment is that it utilizes inexpensive silica sol instead of tetraethyl orthosilicate to synthesize ZSM-5 nanosheets, which helps reduce preparation costs. However, it requires changing the template agent to tetrapropylammonium bromide and the additive to ethylamine to control nanosheet growth while providing an alkaline environment.

[0125] Example 6 A method for preparing highly dispersed sheet-like ZSM-5 molecular sieve includes the following steps: S1. Preparation of seed solution.

[0126] Specifically, 70 g of a 25% tetrapropylammonium hydroxide solution was taken, and 30 g of deionized water was added to dilute it. The tetrapropylammonium hydroxide solution and deionized water were mixed thoroughly to obtain solution A. 50 g of tetraethyl orthosilicate was added to solution A, and the mixture was stirred at 35 °C in a water bath for 6 hours to promote complete hydrolysis of the tetraethyl orthosilicate, resulting in a clear and transparent solution. After complete hydrolysis of the tetraethyl orthosilicate, the water bath temperature was increased to 45 °C for alcohol removal, which took 6 hours. After alcohol removal, the solution was sealed and crystallized under constant temperature conditions at 80 °C for 36 hours to obtain a seed crystal solution.

[0127] S2. Mix the tetrapropylammonium hydroxide solution, deionized water, silicon source, and seed solution prepared in step S1 to obtain solution B; Take 2.92 g of 25% tetrapropylammonium hydroxide solution, dilute it with 30.94 g of deionized water, then add 8.0 g of tetraethyl orthosilicate and 6.20 g of seed solution, and stir in a water bath at 35 ℃ for 2 h to completely hydrolyze the tetraethyl orthosilicate. At this point, the solution is clear and transparent.

[0128] S3. Add the aluminum source to the deionized water to dissolve the aluminum source in the deionized water.

[0129] Dissolve 0.32g of aluminum source in 15g of deionized water, wherein the aluminum source is aluminum chloride hexahydrate.

[0130] S4. Add the deionized water containing the dissolved aluminum source to the clarified solution in step S2 and stir to obtain a white solution C.

[0131] The deionized water containing dissolved aluminum chloride hexahydrate was added to the clear solution in step S2 and stirred for 0.5 h to obtain a white solution C.

[0132] S5. Add the additive to the deionized water to dissolve it.

[0133] Dissolve 0.53g of the additive in 15g of deionized water. The additive consists of ammonium sulfate and ammonium chloride.

[0134] S6. Add the deionized water containing the additive to the white solution C from step S4 and stir. Then, pour the solution into a crystallization vessel for crystallization to obtain the crystallized sample.

[0135] Deionized water containing dissolved ammonium sulfate and ammonium chloride was added to the white solution C from step S4 and stirred for 0.5 h. The mixture was then transferred to a 100 mL crystallization vessel and crystallized at 170 °C for 12 h to obtain the crystallized sample.

[0136] S7. After drying the crystallized sample, it is calcined to obtain thin sheet-like ZSM-5 molecular sieve.

[0137] The crystallized sample was subjected to solid-liquid separation, dried at 80℃ for 12 hours, and then calcined at 540℃ for 6 hours; finally, a sheet-like ZSM-5 molecular sieve with a thickness of 20 nm was obtained.

[0138] The obtained ZSM-5 nanosheets were characterized by X-ray diffraction (XRD) as pure-phase ZSM-5 molecular sieves. Scanning electron microscopy showed that the samples had good crystallization, thin sheet morphology, good dispersibility, and uniform size.

[0139] This embodiment utilizes ammonium sulfate and ammonium chloride instead of ammonium bicarbonate solution to synthesize ZSM-5 nanosheets, thus expanding the synthesis range.

[0140] Example 7 A method for preparing highly dispersed sheet-like ZSM-5 molecular sieve includes the following steps: S1. Preparation of seed solution.

[0141] Specifically, 70 g of a 25% tetrapropylammonium hydroxide solution was taken, and 30 g of deionized water was added to dilute it. The tetrapropylammonium hydroxide solution and deionized water were mixed thoroughly to obtain solution A. 50 g of tetraethyl orthosilicate was added to solution A, and the mixture was stirred at 35 °C in a water bath for 6 hours to promote complete hydrolysis of the tetraethyl orthosilicate, resulting in a clear and transparent solution. After complete hydrolysis of the tetraethyl orthosilicate, the water bath temperature was increased to 45 °C for alcohol removal, which took 6 hours. After alcohol removal, the solution was sealed and crystallized under constant temperature conditions at 60 °C for 120 hours to obtain a seed crystal solution.

[0142] The prepared seed crystals were spherical particles, as shown in the transmission electron microscope image below. Figure 9 As shown, the diameter is 20~30 nm.

[0143] S2. Mix the tetrapropylammonium hydroxide solution, deionized water, silicon source, and seed solution prepared in step S1 to obtain solution B; Take 2.92 g of 25% tetrapropylammonium hydroxide solution, dilute it with 30.94 g of deionized water, then add 8.0 g of tetraethyl orthosilicate and 6.20 g of seed solution, and stir in a water bath at 35 ℃ for 2 h to completely hydrolyze the tetraethyl orthosilicate. At this point, the solution is clear and transparent.

[0144] S3. Add the aluminum source to the deionized water to dissolve the aluminum source in the deionized water.

[0145] Dissolve 0.32 g of aluminum source in 15 g of deionized water, wherein the aluminum source is aluminum chloride hexahydrate.

[0146] S4. Add the deionized water containing the dissolved aluminum source to the clarified solution in step S2 and stir to obtain a white solution C.

[0147] The deionized water containing dissolved aluminum chloride hexahydrate was added to the clear solution in step S2 and stirred for 0.5 h to obtain a white solution C.

[0148] S5. Add the additive to the deionized water to dissolve it.

[0149] Dissolve 0.63 g of the additive in 15 g of deionized water, wherein the additive is ammonium bicarbonate.

[0150] S6. Add the deionized water containing the additive to the white solution C from step S4 and stir. Then, pour the solution into a crystallization vessel for crystallization to obtain the crystallized sample.

[0151] Deionized water containing dissolved ammonium bicarbonate was added to the white solution C from step S4 and stirred for 0.5 h. The mixture was then transferred to a 100 mL crystallization vessel and crystallized at 170 °C for 12 h to obtain the crystallized sample.

[0152] S7. After drying the crystallized sample, it is calcined to obtain thin sheet-like ZSM-5 molecular sieve.

[0153] The crystallized sample was subjected to solid-liquid separation, dried at 80 °C for 12 h, and then calcined at 540 °C for 6 h; finally, a sheet-like ZSM-5 molecular sieve with a thickness of 30 nm was obtained.

[0154] The sample was characterized by scanning electron microscopy (SEM), and the SEM images are shown below. Figure 10 As shown, the results indicate that the synthesized molecular sieve has a regular sheet-like morphology, excellent sample dispersion, and uniform size, with a length (X) of about 400 nm, a width (Y) of about 200 nm, and a thickness (Z) of about 30 nm.

[0155] This embodiment controls the crystal size of ZSM-5 nanosheets by changing the crystallization temperature and time of the seed solution. This method is simpler, faster, and more efficient in crystal control.

[0156] Example 8 A method for preparing highly dispersed sheet-like ZSM-5 molecular sieve includes the following steps: S1. Preparation of seed solution.

[0157] Specifically, 70 g of a 25% tetrapropylammonium hydroxide solution was taken and diluted with 30 g of deionized water. The tetrapropylammonium hydroxide solution and deionized water were mixed thoroughly to obtain solution A. 50 g of tetraethyl orthosilicate was added to solution A, and the mixture was stirred at 35 °C in a water bath for 6 hours to promote complete hydrolysis of the tetraethyl orthosilicate, resulting in a clear and transparent solution. After complete hydrolysis of the tetraethyl orthosilicate, the water bath temperature was increased to 45 °C for alcohol removal, which took 6 hours. After alcohol removal, the solution was sealed and crystallized under constant temperature conditions at 90 °C for 24 hours to obtain a seed crystal solution.

[0158] S2. Mix the tetrapropylammonium hydroxide solution, deionized water, silicon source, and seed solution prepared in step S1 to obtain solution B; Take 4.37 g of 25% tetrapropylammonium hydroxide solution, dilute it with 30.94 g of deionized water, then add 8.0 g of tetraethyl orthosilicate and 6.20 g of seed solution, and stir in a water bath at 35 ℃ for 2 h to completely hydrolyze the tetraethyl orthosilicate. At this point, the solution is clear and transparent.

[0159] S3. Add the aluminum source to the deionized water to dissolve the aluminum source in the deionized water.

[0160] Dissolve 0.96 g of aluminum source in 15 g of deionized water, wherein the aluminum source is aluminum chloride hexahydrate.

[0161] S4. Add the deionized water containing the dissolved aluminum source to the clarified solution in step S2 and stir to obtain a white solution C.

[0162] The deionized water containing dissolved aluminum chloride hexahydrate was added to the clear solution in step S2 and stirred for 0.5 h to obtain a white solution C.

[0163] S5. Add the additive to the deionized water to dissolve it.

[0164] Dissolve 0.63 g of the additive in 15 g of deionized water, wherein the additive is ammonium bicarbonate.

[0165] S6. Add the deionized water containing the additive to the white solution C from step S4 and stir. Then, pour the solution into a crystallization vessel for crystallization to obtain the crystallized sample.

[0166] Deionized water containing dissolved ammonium bicarbonate was added to the white solution C from step S4 and stirred for 0.5 h. The mixture was then transferred to a 100 mL crystallization vessel and crystallized at 170 °C for 48 h to obtain the crystallized sample.

[0167] S7. After drying the crystallized sample, it is calcined to obtain thin sheet-like ZSM-5 molecular sieve.

[0168] The crystallized sample was subjected to solid-liquid separation, dried at 80 °C for 12 h, and then calcined at 540 °C for 6 h; finally, a sheet-like ZSM-5 molecular sieve with a thickness of 30 nm was obtained.

[0169] The obtained ZSM-5 nanosheets were characterized by X-ray diffraction (XRD) as pure-phase ZSM-5 molecular sieves. Scanning electron microscopy showed that the samples had good crystallization, thin sheet morphology, good dispersibility, and uniform size.

[0170] This embodiment achieves the synthesis of ZSM-5 nanosheets with a low silicon-to-aluminum ratio by adjusting the amount of template agent and aluminum source added.

[0171] Example 9 A method for preparing highly dispersed sheet-like ZSM-5 molecular sieve includes the following steps: S1. Preparation of seed solution.

[0172] Specifically, 70 g of a 25% tetrapropylammonium hydroxide solution was taken, and 30 g of deionized water was added to dilute it. The tetrapropylammonium hydroxide solution and deionized water were mixed thoroughly to obtain solution A. 50 g of tetraethyl orthosilicate was added to solution A, and the mixture was stirred at 35 °C in a water bath for 6 hours to promote complete hydrolysis of the tetraethyl orthosilicate, resulting in a clear and transparent solution. After complete hydrolysis of the tetraethyl orthosilicate, the water bath temperature was increased to 45 °C for alcohol removal, which took 6 hours. After alcohol removal, the solution was sealed and crystallized under constant temperature conditions at 80 °C for 36 hours to obtain a seed crystal solution.

[0173] S2. Mix the tetrapropylammonium hydroxide solution, deionized water, silicon source, and seed solution prepared in step S1 to obtain solution B; Take 2.92 g of 25% tetrapropylammonium hydroxide solution, dilute it with 30.94 g of deionized water, then add 8.0 g of tetraethyl orthosilicate and 6.20 g of seed solution, and stir in a water bath at 35 ℃ for 2 h to completely hydrolyze the tetraethyl orthosilicate. At this point, the solution is clear and transparent.

[0174] S3. Add the aluminum source to the deionized water to dissolve the aluminum source in the deionized water.

[0175] Dissolve 0.21 g of aluminum source in 15 g of deionized water, wherein the aluminum source is sodium aluminate and aluminum hydroxide.

[0176] S4. Add the deionized water containing the dissolved aluminum source to the clarified solution in step S2 and stir to obtain a white solution C.

[0177] Deionized water containing dissolved sodium aluminate and aluminum hydroxide was added to the clear solution in step S2 and stirred for 0.5 h to obtain a white solution C.

[0178] S5. Add the additive to the deionized water to dissolve it.

[0179] Dissolve 0.63 g of the additive in 15 g of deionized water, wherein the additive is ammonium bicarbonate.

[0180] S6. Add the deionized water containing the additive to the white solution C from step S4 and stir. Then, pour the solution into a crystallization vessel for crystallization to obtain the crystallized sample.

[0181] Deionized water containing dissolved ammonium bicarbonate was added to the white solution C from step S4 and stirred for 0.5 h. The mixture was then transferred to a 100 mL crystallization vessel and crystallized at 170 °C for 12 h to obtain the crystallized sample.

[0182] S7. After drying the crystallized sample, it is calcined to obtain thin sheet-like ZSM-5 molecular sieve.

[0183] The crystallized sample was subjected to solid-liquid separation, dried at 80 °C for 12 h, and then calcined at 540 °C for 6 h; finally, a sheet-like ZSM-5 molecular sieve with a thickness of 30 nm was obtained.

[0184] The obtained ZSM-5 nanosheets were characterized by X-ray diffraction (XRD) as pure-phase ZSM-5 molecular sieves. Scanning electron microscopy showed that the samples had good crystallization, thin sheet morphology, good dispersibility, and uniform size.

[0185] This embodiment utilizes sodium aluminate and aluminum hydroxide to replace aluminum chloride in the synthesis of ZSM-5 nanosheets, which has the advantage of reducing the corrosion of equipment by chloride ions in the solution.

[0186] Example 10 A method for preparing highly dispersed sheet-like ZSM-5 molecular sieve includes the following steps: S1. Preparation of seed solution.

[0187] Specifically, 70 g of a 25% tetrapropylammonium hydroxide solution was taken, and 30 g of deionized water was added to dilute it. The tetrapropylammonium hydroxide solution and deionized water were mixed thoroughly to obtain solution A. 50 g of tetraethyl orthosilicate was added to solution A, and the mixture was stirred at 35 °C in a water bath for 6 hours to promote complete hydrolysis of the tetraethyl orthosilicate, resulting in a clear and transparent solution. After complete hydrolysis of the tetraethyl orthosilicate, the water bath temperature was increased to 45 °C for alcohol removal, which took 6 hours. After alcohol removal, the solution was sealed and crystallized under constant temperature conditions at 80 °C for 36 hours to obtain a seed crystal solution.

[0188] S2. Mix the tetrapropylammonium hydroxide solution, deionized water, silicon source, and seed solution prepared in step S1 to obtain solution B; Take 0.45 g of 1,6-hexanediamine, add 30.94 g of deionized water to dissolve and dilute it, then add 8.0 g of tetraethyl orthosilicate and 2.48 g of seed solution, and stir in a water bath at 35 ℃ for 2 h to completely hydrolyze the tetraethyl orthosilicate. At this point, the solution is clear and transparent.

[0189] S3. Add the aluminum source to the deionized water to dissolve the aluminum source in the deionized water.

[0190] Dissolve 0.16 g of aluminum source in 15 g of deionized water, wherein the aluminum source is aluminum nitrate nonahydrate.

[0191] S4. Add the deionized water containing the dissolved aluminum source to the clarified solution in step S2 and stir to obtain a white solution C.

[0192] The deionized water containing dissolved aluminum nitrate nonahydrate was added to the clear solution in step S2 and stirred for 0.5 h to obtain a white solution C.

[0193] S5. Add the additive to the deionized water to dissolve it.

[0194] Dissolve 0.61 g of the additive in 15 g of deionized water, wherein the additive is ammonium nitrate.

[0195] S6. Add the deionized water containing the additive to the white solution C from step S4 and stir. Then, pour the solution into a crystallization vessel for crystallization to obtain the crystallized sample.

[0196] Deionized water containing dissolved ammonium nitrate was added to the white solution C from step S4 and stirred for 0.5 h. The mixture was then transferred to a 100 mL crystallization vessel and crystallized at 170 °C for 48 h to obtain the crystallized sample.

[0197] S7. After drying the crystallized sample, it is calcined to obtain thin sheet-like ZSM-5 molecular sieve.

[0198] The crystallized sample was subjected to solid-liquid separation, dried at 80 °C for 12 h, and then calcined at 540 °C for 6 h; finally, a sheet-like ZSM-5 molecular sieve with a thickness of 30 nm was obtained.

[0199] The obtained ZSM-5 nanosheets were characterized by X-ray diffraction (XRD) as pure-phase ZSM-5 molecular sieves. Scanning electron microscopy showed that the samples had good crystallization, thin sheet morphology, good dispersibility, and uniform size.

[0200] In this embodiment, 1,6-hexanediamine was used instead of tetrapropylammonium hydroxide as the organic template agent to prepare ZSM-5 nanosheets. Because the ZSM-5 molecular sieve synthesized with 1,6-hexanediamine has a uniform aluminum distribution, the positions of acidic sites on the ZSM-5 nanosheets could be controlled.

[0201] Example 11 A method for preparing highly dispersed sheet-like ZSM-5 molecular sieve includes the following steps: S1. Preparation of seed solution.

[0202] Specifically, 70 g of a 25% tetrapropylammonium hydroxide solution was taken, and 30 g of deionized water was added to dilute it. The tetrapropylammonium hydroxide solution and deionized water were mixed thoroughly to obtain solution A. 50 g of tetraethyl orthosilicate was added to solution A, and the mixture was stirred at 35 °C in a water bath for 6 hours to promote complete hydrolysis of the tetraethyl orthosilicate, resulting in a clear and transparent solution. After complete hydrolysis of the tetraethyl orthosilicate, the water bath temperature was increased to 45 °C for alcohol removal, which took 6 hours. After alcohol removal, the solution was sealed and crystallized under constant temperature conditions at 80 °C for 36 hours to obtain a seed crystal solution.

[0203] S2. Mix the tetrapropylammonium hydroxide solution, deionized water, silicon source, and seed solution prepared in step S1 to obtain solution B; Take 0.72 g of n-butylamine, dilute it with 30.94 g of deionized water, then add 6.3 g of water glass, 1.2 g of silica and 6.20 g of seed solution, and stir in a water bath at 35 ℃ for 2 h to make the solution uniform.

[0204] S3. Add the aluminum source to the deionized water to dissolve the aluminum source in the deionized water.

[0205] Dissolve 0.32 g of aluminum source in 15 g of deionized water, wherein the aluminum source is aluminum chloride hexahydrate.

[0206] S4. Add the deionized water containing the dissolved aluminum source to the solution in step S2 and stir to obtain a white solution C.

[0207] The deionized water containing dissolved aluminum chloride hexahydrate was added to the clear solution in step S2 and stirred for 0.5 h to obtain a white solution C.

[0208] S5. Add the additive to the deionized water to dissolve it.

[0209] Dissolve 0.63 g of the additive in 15 g of deionized water, wherein the additive is ammonium bicarbonate.

[0210] S6. Add the deionized water containing the additive to the white solution C from step S4 and stir. Then, pour the solution into a crystallization vessel for crystallization to obtain the crystallized sample.

[0211] Deionized water containing dissolved ammonium bicarbonate was added to the white solution C from step S4 and stirred for 0.5 h. The mixture was then transferred to a 100 mL crystallization vessel and crystallized at 170 °C for 48 h to obtain the crystallized sample.

[0212] S7. After drying the crystallized sample, it is calcined to obtain thin sheet-like ZSM-5 molecular sieve.

[0213] The crystallized sample was subjected to solid-liquid separation, dried at 80℃ for 12 h, and then calcined at 540℃ for 6 h; finally, a sheet-like ZSM-5 molecular sieve with a thickness of 30 nm was obtained.

[0214] The obtained ZSM-5 nanosheets were characterized by X-ray diffraction (XRD) as pure-phase ZSM-5 molecular sieves. Scanning electron microscopy showed that the samples had good crystallization, thin sheet morphology, good dispersibility, and uniform size.

[0215] The advantage of this embodiment lies in using n-butylamine instead of tetrapropylammonium hydroxide as the organic template agent, and using water glass and precipitated silica instead of tetraethyl orthosilicate as the silicon source. Since n-butylamine, water glass, and precipitated silica are relatively inexpensive, and n-butylamine is easily recyclable, the preparation cost can be effectively reduced.

[0216] Example 12 A method for preparing highly dispersed sheet-like ZSM-5 molecular sieve includes the following steps: S1. Preparation of seed solution.

[0217] Specifically, 140 kg of a 25% tetrapropylammonium hydroxide solution was taken, and 60 kg of deionized water was added to dilute it. The tetrapropylammonium hydroxide solution and deionized water were mixed thoroughly to obtain solution A. 100 kg of tetraethyl orthosilicate was added to solution A, and the mixture was stirred at 35 °C for 6 h to promote complete hydrolysis of the tetraethyl orthosilicate, resulting in a clear and transparent solution. After complete hydrolysis of the tetraethyl orthosilicate, the solution was sealed and crystallized under constant temperature conditions; the crystallization temperature was 80 °C, and the crystallization time was 36 h, yielding a seed crystal solution.

[0218] S2. Mix the tetrapropylammonium hydroxide solution, deionized water, silicon source, and seed solution prepared in step S1 to obtain solution B; Take 328.0 kg of a 25% tetrapropylammonium hydroxide solution, dilute it with 1827.9 kg of deionized water, then add 1200.0 kg of tetraethyl orthosilicate and 190.0 kg of seed solution, and stir at 35 °C for 2 h to completely hydrolyze the tetraethyl orthosilicate. At this point, the solution is clear and transparent.

[0219] S3. Add the aluminum source to the deionized water to dissolve the aluminum source in the deionized water.

[0220] Take 21.1 kg of aluminum source and dissolve it in 1037.0 kg of deionized water, wherein the aluminum source is aluminum sulfate.

[0221] S4. Add the deionized water containing the dissolved aluminum source to the clarified solution in step S2 and stir to obtain a white solution C.

[0222] The deionized water in which aluminum sulfate is dissolved is added to the clear solution in step S2 and stirred for 2 hours to obtain a white solution C.

[0223] S5. Add the additive to the deionized water to dissolve it.

[0224] Dissolve 69.1 kg of the additive in 600.0 kg of deionized water, wherein the additive is urea.

[0225] S6. Add the deionized water containing the additive to the white solution C from step S4 and stir. Then, pour the solution into a crystallization vessel for crystallization to obtain the crystallized sample.

[0226] Deionized water containing dissolved urea was added to the white solution C from step S4 and stirred for 2 hours, followed by stirring at 8 m. 3 The sample was crystallized in an industrial crystallization vessel at 170 °C for 72 h to obtain the crystallized sample.

[0227] S7. After washing, filtering, and drying the crystallized sample, it is calcined to obtain thin-film ZSM-5 molecular sieve.

[0228] The crystallized sample was subjected to solid-liquid separation, dried at 80 °C for 12 h, and then calcined at 540 °C for 6 h; finally, a sheet-like ZSM-5 molecular sieve with a thickness of about 30 nm was obtained.

[0229] The obtained ZSM-5 nanosheets were characterized by X-ray diffraction (XRD) as pure-phase ZSM-5 molecular sieves. Scanning electron microscopy (SEM) was performed on the samples, and the SEM images are shown below. Figure 11 As shown, the results indicate that the synthesized molecular sieve has a regular sheet-like morphology, excellent sample dispersion, and uniform size, with a length (X) of about 400 nm, a width (Y) of about 150 nm, and a thickness (Z) of about 33 nm.

[0230] This embodiment utilizes an industrial 8m 3 The large-scale synthesis of ZSM-5 nanosheets was achieved using a crystallization reactor, demonstrating the feasibility of this synthesis strategy in industrial-scale synthesis and laying the foundation for its further application in industrial-scale catalytic reactions and adsorption separation.

[0231] Example 13 A method for preparing highly dispersed sheet-like ZSM-5 molecular sieve includes the following steps: S1. Preparation of seed solution.

[0232] Take 70 g of a 25% tetrapropylammonium hydroxide solution and dilute it with 30 g of deionized water. Mix the tetrapropylammonium hydroxide solution and deionized water thoroughly to obtain solution A. Add 50 g of tetraethyl orthosilicate to solution A and maintain the mixture at 35 °C in a water bath for 6 h to promote complete hydrolysis of the tetraethyl orthosilicate, resulting in a clear and transparent solution. After complete hydrolysis of the tetraethyl orthosilicate, increase the water bath temperature to 45 °C for alcohol removal for 6 h. After alcohol removal, seal the solution and crystallize it under constant temperature conditions at 80 °C for 36 h to obtain a seed crystal solution.

[0233] The prepared seed crystals were spherical particles, as shown in the transmission electron microscope image below. Figure 1 As shown, the diameter is 20~50 nm.

[0234] S2. Mix the tetrapropylammonium hydroxide solution, deionized water, silicon source, and seed solution prepared in step S1 to obtain solution B; Take 2.92 g of a 25% tetrapropylammonium hydroxide solution, dilute it with 30.94 g of deionized water, then add 8.0 g of tetraethyl orthosilicate and 6.20 g of seed solution. Stir in a water bath at 35 °C for 2 h to allow the tetraethyl orthosilicate to completely hydrolyze, resulting in a clear and transparent solution. Tetraethyl orthosilicate can be replaced with silica sol, silica gel, water glass, or solid silica gel.

[0235] S3. Add the aluminum source to the deionized water to dissolve the aluminum source in the deionized water.

[0236] Dissolve 0.32 g of aluminum source in 15 g of deionized water, wherein the aluminum source is aluminum chloride hexahydrate.

[0237] S4. Add the deionized water containing the dissolved aluminum source to the clarified solution in step S2 and stir to obtain a white solution C.

[0238] The deionized water in which aluminum chloride hexahydrate is dissolved is added to the clear solution in step S2 and stirred for 1 hour to obtain a white solution C.

[0239] S5. Add the additive to the deionized water to dissolve it.

[0240] Dissolve 0.63 g of the additive in 15 g of deionized water, wherein the additive is ammonium bicarbonate.

[0241] S6. Add the deionized water containing the additive to the white solution C from step S4 and stir. Then, pour the solution into a crystallization vessel for crystallization to obtain the crystallized sample.

[0242] Deionized water containing dissolved ammonium bicarbonate was added to the white solution C from step S4 and stirred for 0.5 h. The mixture was then transferred to a 100 mL crystallization vessel and crystallized at 170 °C for 3 h to obtain the crystallized sample.

[0243] S7. After drying the crystallized sample, it is calcined to obtain thin sheet-like ZSM-5 molecular sieve.

[0244] The crystallized sample was subjected to solid-liquid separation, dried at 80 °C for 12 h, and then calcined at 540 °C for 6 h; finally, a sheet-like ZSM-5 molecular sieve with a thickness of 30 nm was obtained.

[0245] Example 14 A method for preparing highly dispersed sheet-like ZSM-5 molecular sieve includes the following steps: S1. Preparation of seed solution.

[0246] Take 70 g of a 25% tetrapropylammonium hydroxide solution and dilute it with 30 g of deionized water. Mix the tetrapropylammonium hydroxide solution and deionized water thoroughly to obtain solution A. Add 50 g of tetraethyl orthosilicate to solution A and maintain the mixture at 35 °C in a water bath for 6 h to promote complete hydrolysis of the tetraethyl orthosilicate, resulting in a clear and transparent solution. After complete hydrolysis of the tetraethyl orthosilicate, raise the water bath temperature to 45 °C to remove alcohol for 6 h. After alcohol removal, seal the solution and crystallize it under constant temperature conditions at 80 °C for 48 h to obtain a seed crystal solution.

[0247] The prepared seed crystals were spherical particles, as shown in the transmission electron microscope image below. Figure 1 As shown, the diameter is 20~50 nm.

[0248] S2. Mix the tetrapropylammonium hydroxide solution, deionized water, silicon source, and seed solution prepared in step S1 to obtain solution B; Take 2.92 g of 25% tetrapropylammonium hydroxide solution, dilute it with 30.94 g of deionized water, then add 8.0 g of tetraethyl orthosilicate and 6.20 g of seed solution, and stir in a water bath at 35 ℃ for 2 h to completely hydrolyze the tetraethyl orthosilicate. At this point, the solution is clear and transparent.

[0249] S3. Add the aluminum source to the deionized water to dissolve the aluminum source in the deionized water.

[0250] Dissolve 0.32 g of aluminum source in 15 g of deionized water, wherein the aluminum source is aluminum chloride hexahydrate.

[0251] S4. Add the deionized water containing the dissolved aluminum source to the clarified solution in step S2 and stir to obtain a white solution C.

[0252] The deionized water containing dissolved aluminum chloride hexahydrate was added to the clear solution in step S2 and stirred for 0.7 h to obtain a white solution C.

[0253] S5. Add the additive to the deionized water to dissolve it.

[0254] Dissolve 0.63 g of the additive in 15 g of deionized water. The additive is ammonium bicarbonate, ammonium sulfate, ammonium carbonate, ammonium bisulfate, ethylenediamine, ethylamine, ammonium chloride, urea, or ammonium nitrate.

[0255] S6. Add the deionized water containing the additive to the white solution C from step S4 and stir. Then, pour the solution into a crystallization vessel for crystallization to obtain the crystallized sample.

[0256] Deionized water containing dissolved ammonium bicarbonate was added to the white solution C from step S4 and stirred for 0.5 h. The mixture was then transferred to a 100 mL crystallization vessel and crystallized at 170 °C for 12 h to obtain the crystallized sample.

[0257] S7. After drying the crystallized sample, it is calcined to obtain thin sheet-like ZSM-5 molecular sieve.

[0258] The crystallized sample was subjected to solid-liquid separation, dried at 80 °C for 12 h, and then calcined at 540 °C for 6 h; finally, a sheet-like ZSM-5 molecular sieve with a thickness of 30 nm was obtained.

[0259] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for preparing highly dispersed thin-film ZSM-5 molecular sieve, characterized in that, Includes the following steps: S1. Take a 25% tetrapropylammonium hydroxide solution and dilute it with deionized water. Mix the tetrapropylammonium hydroxide solution and deionized water evenly to obtain solution A. Add tetraethyl orthosilicate to solution A and stir under water bath conditions to promote the complete hydrolysis of tetraethyl orthosilicate. Crystallize solution A containing tetraethyl orthosilicate to obtain seed crystal solution. S2. Mix deionized water, silicon source and seed solution prepared in step S1 to obtain solution B; S3. Add the aluminum source to the deionized water to dissolve the aluminum source in the deionized water; S4. Add the deionized water containing the dissolved aluminum source to the clear solution in step S2 and stir to obtain a white solution C; S5. Add the additive to the deionized water to dissolve it. S6. Add the deionized water containing the additive to the white solution C from step S4 and stir. Then, put the solution into a crystallization vessel for crystallization to obtain the crystallized sample. S7. The crystallized sample is washed, separated, dried and then calcined to obtain a thin sheet ZSM-5 molecular sieve with a thickness of 20nm~30nm. In step S1, before crystallization, the solution A containing tetraethyl orthosilicate is subjected to alcohol removal at a temperature of 45°C for 6 hours. In step S1, the water bath temperature is 35°C, the crystallization temperature is 50-90°C, and the crystallization time is 36-120 hours. The additives in step S5 are ammonium bicarbonate, ammonium sulfate, ammonium carbonate, ammonium bisulfate, ethylenediamine, ethylamine, ammonium chloride, urea, or ammonium nitrate. The silicon source is tetraethyl orthosilicate, silica sol, silica fume, water glass, and solid silica gel; The preparation method of this highly dispersed sheet-like ZSM-5 molecular sieve does not introduce organic template agents during the preparation process. The template agent-free synthesis of sheet-like ZSM-5 molecular sieve is achieved by adding seed crystal solution.

2. The method for preparing highly dispersed sheet-like ZSM-5 molecular sieve according to claim 1, characterized in that, The stirring time in step S4 is 0.5~1h.

3. The method for preparing highly dispersed sheet-like ZSM-5 molecular sieve according to claim 1, characterized in that, In step S6, the stirring time is 0.5 h, the crystallization temperature is 90~170℃, and the crystallization time is 3~72 h.

4. The method for preparing highly dispersed sheet-like ZSM-5 molecular sieve according to claim 1, characterized in that, In step S7, the drying temperature is 80℃ and the drying time is 12h, and the calcination temperature is 540℃ and the calcination time is 6h.

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