ZSM-5 molecular sieve as well as preparation method and application thereof

Abstract

The invention provides a ZSM-5 molecular sieve and a preparation method thereof. The preparation method comprises the following steps: S1, mixing a silicon source, a pH regulator and a first solvent to obtain a first mixed solution; s2, mixing an aluminum source, a template agent and the first mixed solution to obtain a second mixed solution; s3, sequentially carrying out first crystallization treatment and second crystallization treatment on the second mixed solution to obtain a product system comprising a first crystallization product and a mother solution; s4, performing ball-milling treatment on a mixture of the first crystallization product and a second solvent to obtain a ball-milling system comprising a ball-milling product; s5, sequentially carrying out third crystallization treatment and fourth crystallization treatment on the ball-milled product in a third solvent to obtain a second crystallized product; and S6, calcining the second crystallization product to obtain the ZSM-5 molecular sieve.

Description

Technical Field

[0001] The present invention relates to the technical field of molecular sieve preparation, and in particular, to a ZSM-5 molecular sieve, a preparation method thereof, and an application thereof. Background Art

[0002] The ZSM-5 molecular sieve is a typical molecular sieve developed by Mobil Company in the United States in 1972. Its basic structural unit is a TO4 tetrahedron (T is Si or Al atom), and it has a three-dimensional pore structure with two types of pores: straight cylindrical and "Z"-shaped transverse pores. Due to its excellent properties such as controllability, ion exchangeability, and thermal stability, it is widely used in various fields such as petrochemical industry, fine chemical industry, and environmental protection. Usually, the synthesized ZSM-5 molecular sieve has a micron structure. Compared with the micron molecular sieve, the nano-ZSM-5 molecular sieve has a larger external specific surface area, active centers, and stronger adsorption capacity, provides more active sites, has short and regular pores, can shorten the diffusion path, is beneficial to the occurrence of mass transfer reactions, and improves the conversion efficiency, anti-coking ability, and stability. Therefore, in recent years, researchers have obtained nano-ZSM-5 molecular sieves through various methods, including in-situ synthesis and post-treatment methods, in order to improve its physical and chemical structure and enhance its catalytic performance.

[0003] However, the currently synthesized ZSM-5 molecular sieve has a large grain size, usually in the micron range, and a small specific surface area, and does not have the characteristics of mesopores.

[0004] In order to solve the above problems, it is necessary to research and develop a ZSM-5 molecular sieve and a preparation method thereof, which is of great significance for applications in catalytic methanol conversion to olefins, catalytic isomerization of aromatics and aromatic compounds, and catalytic aromatization reactions. Summary of the Invention

[0005] The main object of the present invention is to provide a ZSM-5 molecular sieve, a preparation method thereof, and an application thereof, so as to solve the problems that the ZSM-5 molecular sieve prepared in the prior art has a large size, a small specific surface area, and does not have mesopores.

[0006] To achieve the above object, on the one hand, the present invention provides a method for preparing ZSM-5 molecular sieve, the preparation method comprising: Step S1, mixing a silicon source, a pH regulator and a first solvent to obtain a first mixed solution; Step S2, mixing an aluminum source, a template agent and the first mixed solution to obtain a second mixed solution; Step S3, performing a first crystallization treatment and a second crystallization treatment on the second mixed solution in sequence to obtain a product system including a first crystallization product and mother liquor; wherein, the temperature of the first crystallization treatment is 100-200°C, the time is 15-60h, the temperature of the second crystallization treatment is 120-220°C, and the time is 20-72h; Step S4, performing ball milling treatment on the mixture of the first crystallization product and a second solvent to obtain a ball milling system including a ball milling product; Step S5, performing a third crystallization treatment and a fourth crystallization treatment on the ball milling product in a third solvent in sequence to obtain a second crystallization product; wherein, the temperature of the third crystallization treatment is 100-200°C, the time is 15-45h, the temperature of the fourth crystallization treatment is 120-220°C, and the time is 20-72h; Step S6, performing calcination treatment on the second crystallization product to obtain ZSM-5 molecular sieve.

[0007] Further, the molar ratio of the silicon source, the aluminum source, the template agent to the first solvent is (10-1000):1:(1.8-260):(100-2000); preferably, the pH of the first mixed solution is 7-13.

[0008] Further, the mixing process in Step S1 includes: stirring at a constant temperature of 10-90°C for 1-10h to obtain the first mixed solution, preferably stirring at a constant temperature of 20-70°C for 2-4h.

[0009] Further, the mixing process in Step S2 includes: stirring at a constant temperature of 10-90°C for 0.5-5h to obtain the second mixed solution, preferably stirring at a constant temperature of 20-60°C for 1-3h.

[0010] Further, the temperature of the first crystallization treatment is 120-160°C, and the time is 15-35h.

[0011] Further, the temperature of the second crystallization treatment is 130-170°C, and the time is 36-48h.

[0012] Further, the temperature of the third crystallization treatment is 120-160°C, and the time is 15-35h.

[0013] Further, the temperature of the fourth crystallization treatment is 130-170°C, and the time is 36-48h.

[0014] Further, between step S3 and step S4, a first solid-liquid separation treatment and a first drying treatment are also included for the product system to obtain a first crystallization product; preferably, the temperature of the first drying treatment is 10-180°C, more preferably 60-120°C, and the time is 4-24h, more preferably 4-12h.

[0015] Further, during the ball milling treatment, the weight ratio of the first crystallization product to the second solvent is (5-10):(1-5); preferably, the average particle size of the ball milling product is 10-1000nm; preferably, the rotation speed of the ball milling treatment is 200-800rpm, more preferably 400-800rpm, and the time is 1-24h, more preferably 4-24h.

[0016] Further, the second solvent and the third solvent are each independently selected from one or more of the group consisting of water, mother liquor, and sodium silicate solution; preferably, the second solvent is selected from a sodium silicate solution with a mass concentration of 10-50wt%, preferably 15-30wt%; preferably, the third solvent is selected from a sodium silicate solution with a mass concentration of 10-50wt%, preferably 15-30wt%.

[0017] Further, between step S4 and step S5, a second solid-liquid separation treatment and a second drying treatment are also included for the ball milling system to obtain a ball milling product; preferably, the temperature of the second drying treatment is 30-180°C, preferably 60-120°C, and the time is 4-48h, preferably 6-12h.

[0018] Further, the temperature of the calcination treatment is 500-900°C, the heating rate is 1-10°C / min, and the time is 2-10h; preferably, the temperature of the calcination treatment is 550-700°C, the heating rate is 2-5°C / min, and the time is 4-6h.

[0019] To achieve the above object, another aspect of the present invention also provides a ZSM-5 molecular sieve, which is prepared by using the above preparation method of the ZSM-5 molecular sieve provided in the present application.

[0020] To achieve the above object, another aspect of the present invention also provides an application of the above ZSM-5 molecular sieve provided in the present application in catalyzing the conversion of methanol to olefins, catalyzing the isomerization of aromatics and aromatic compounds, and catalyzing the aromatization reaction.

[0021] Applying the technical solution of the present invention, compared with the traditional method of directly mixing a silicon source, an aluminum source, a templating agent and a solvent, in this application, the silicon source is first dispersed, and at the same time, a pH regulator is used to adjust the acidity and alkalinity to obtain a first mixed solution. Then, the aluminum source, the templating agent and the first mixed solution are mixed, which can better play the role of the templating agent to obtain a second mixed solution. Sequentially performing a first crystallization treatment and a second crystallization treatment on the second mixed solution can improve the nucleation rate and the crystal growth rate, which is beneficial to making the subsequently prepared ZSM-5 molecular sieve have a smaller particle size and a larger specific surface area. Compared with directly calcining the crystallization product, in this application, the mixture of the first crystallization product and the second solvent is ball-milled. Through the ball-milling treatment, the first crystallization product and the second solvent increase the molecular collision probability through friction, promoting the occurrence of chemical reactions, making the obtained ball-milled product beneficial to subsequent crystal nucleation. Then, sequentially performing a third crystallization treatment and a fourth crystallization treatment on the ball-milled product in a third solvent can improve the crystal growth rate to obtain a second crystallization product; finally, the second crystallization product is calcined to carbonize and remove the contained templating agent to obtain the ZSM-5 molecular sieve.

[0022] Compared with a single crystallization treatment, this application adopts two-stage crystallization treatments twice, which can improve the nucleation rate and the crystal growth rate, thereby reducing the size of the prepared ZSM-5 molecular sieve and increasing its specific surface area.

[0023] Compared with other ranges, limiting the temperature and time of the first crystallization treatment and the second crystallization treatment within the scope of this application is beneficial to improving the nucleation rate and the crystal growth rate. At the same time, it is beneficial to improve the crystallinity of the first crystallization product. Limiting the temperature and time of the third crystallization treatment and the fourth crystallization treatment within the scope of this application is beneficial to improving the crystal growth rate, which is beneficial to reducing the size of the prepared ZSM-5 molecular sieve and increasing its specific surface area. Description of the Drawings

[0024] The specification drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0025] Figure 1 Shows the SEM image (magnification 20,000 times) of the ZSM-5 molecular sieve prepared in Example 1;

[0026] Figure 2 Shows the XRD pattern of the ZSM-5 molecular sieve prepared in Example 1;

[0027] Figure 3 Shows the SEM image (magnification 20,000 times) of the product prepared in Comparative Example 1. Detailed Embodiments

[0028] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0029] As described in the background art, the existing preparation methods of ZSM-5 molecular sieves have problems such as large size, small specific surface area and no mesopores of the obtained ZSM-5 molecular sieves. To solve the above technical problems, the present application provides a preparation method of ZSM-5 molecular sieves, and the preparation method includes: Step S1, mixing a silicon source, a pH regulator and a first solvent to obtain a first mixed solution; Step S2, mixing an aluminum source, a template agent and the first mixed solution to obtain a second mixed solution; Step S3, performing a first crystallization treatment and a second crystallization treatment on the second mixed solution in sequence to obtain a product system including a first crystallization product and a mother liquor; wherein, the temperature of the first crystallization treatment is 100-200°C, and the time is 15-60h, the temperature of the second crystallization treatment is 120-220°C, and the time is 20-72h; Step S4, performing ball milling treatment on the mixture of the first crystallization product and a second solvent to obtain a ball milling system including a ball milling product; Step S5, performing a third crystallization treatment and a fourth crystallization treatment on the ball milling product in a third solvent in sequence to obtain a second crystallization product; wherein, the temperature of the third crystallization treatment is 100-200°C, and the time is 15-45h, the temperature of the fourth crystallization treatment is 120-220°C, and the time is 20-72h; Step S6, performing calcination treatment on the second crystallization product to obtain ZSM-5 molecular sieves.

[0030] Compared with the traditional method of directly mixing a silicon source, an aluminum source, a template agent and a solvent, in the present application, the silicon source is first dispersed, and at the same time, a pH regulator is used to adjust the acidity and alkalinity to obtain a first mixed solution, and then the aluminum source, the template agent and the first mixed solution are mixed, which can better play the role of the template agent to obtain a second mixed solution. Performing the first crystallization treatment and the second crystallization treatment on the second mixed solution in sequence can improve the nucleation rate and the crystal growth rate, which is beneficial to making the subsequent obtained ZSM-5 molecular sieves have a smaller particle size and a larger specific surface area. Compared with directly performing calcination treatment on the crystallization product, in the present application, the mixture of the first crystallization product and a second solvent is subjected to ball milling treatment. Through the ball milling treatment, the first crystallization product and the second solvent increase the molecular collision probability through friction, promote the occurrence of chemical reactions, and make the obtained ball milling product beneficial to subsequent crystal nucleation. Then, performing the third crystallization treatment and the fourth crystallization treatment on the ball milling product in a third solvent in sequence can improve the crystal growth rate to obtain a second crystallization product; finally, performing calcination treatment on the second crystallization product to carbonize and remove the template agent contained therein to obtain ZSM-5 molecular sieves.

[0031] Compared with single crystallization treatment, the present application adopts two-stage two-step crystallization treatment, which can improve the nucleation rate and crystal growth rate, thereby reducing the size of the prepared ZSM-5 molecular sieve and increasing its specific surface area.

[0032] Compared with other ranges, limiting the temperatures and times of the first crystallization treatment and the second crystallization treatment within the scope of the present application is beneficial to improving the nucleation rate and crystal growth rate, and at the same time is beneficial to increasing the crystallinity of the first crystallization product. Limiting the temperatures and times of the third crystallization treatment and the fourth crystallization treatment within the scope of the present application is beneficial to improving the crystal growth rate, and is beneficial to reducing the size of the prepared ZSM-5 molecular sieve and increasing its specific surface area.

[0033] In a preferred embodiment, the molar ratio of the silicon source, aluminum source, template agent to the first solvent is (10 - 1000):1:(1.8 - 260):(100 - 2000). The molar ratio of the silicon source, pH regulator, aluminum source, template agent to the first solvent includes but is not limited to the above range. Limiting it within the above range is beneficial to controlling the obtained product to have the crystal structure of ZSM-5 molecular sieve, and at the same time is beneficial to improving the utilization rate of each raw material, and increasing the production rate and purity of ZSM-5 molecular sieve.

[0034] In a preferred embodiment, the first solvent includes but is not limited to water. Compared with other types, adopting the above type of first solvent is beneficial to improving the dispersibility of the silicon source while reducing costs.

[0035] The silicon source can provide silicon atoms for the molecular sieve. In a preferred embodiment, the silicon source includes but is not limited to one or more of the group consisting of silica sol, silicon dioxide, silica gel, and tetraethyl orthosilicate.

[0036] The present application uses common alkaline compounds in the art as pH regulators. In a preferred embodiment, the pH regulator includes but is not limited to one or more of the group consisting of Na2O, NaOH, KOH, and Ca(OH)2.

[0037] The aluminum source can provide aluminum atoms in the molecular sieve framework for the molecular sieve. In a preferred embodiment, the aluminum source includes but is not limited to one or more of the group consisting of aluminum sulfate, aluminum chloride, aluminum nitrate, sodium metaaluminate, and aluminum isopropoxide.

[0038] The template agent can induce the directional aggregation of the silicon source, thereby affecting the morphology and pore size of the molecular sieve. In a preferred embodiment, the template agent includes but is not limited to one or more of the group consisting of tetrabutylammonium hydroxide, tetrabutylammonium bromide, and n-butylamine.

[0039] In a preferred embodiment, the pH of the first mixed solution is 7 to 13. Compared with other ranges, limiting the pH of the first mixed solution within the above range is beneficial to improving the solubility of the silicon source, and at the same time is also beneficial to improving the crystal form purity of the ZSM-5 molecular sieve and inhibiting the formation of impurity phases.

[0040] In a preferred embodiment, the mixing process in step S1 includes: stirring at a constant temperature of 10 to 90 °C for 1 to 10 h to obtain a first mixed solution, preferably stirring at a constant temperature of 20 to 70 °C for 2 to 4 h. Mixing the silicon source, pH regulator and the first solvent in the above manner is beneficial to improving the dispersibility of the silicon source, beneficial to better exerting the role of the pH regulator in regulating acidity and alkalinity, and thus beneficial to the formation of nuclei and the growth of crystals during the crystallization process.

[0041] In a preferred embodiment, the mixing process in step S2 includes: stirring at a constant temperature of 10 to 90 °C for 0.5 to 5 h to obtain a second mixed solution, preferably stirring at a constant temperature of 20 to 60 °C for 1 to 3 h. Mixing the aluminum source, template agent and the first mixed solution in the above manner is beneficial to improving the dispersibility of the aluminum source, beneficial to better exerting the role of the template agent, and thus beneficial to improving the morphology and pore structure of the ZSM-5 molecular sieve.

[0042] In a preferred embodiment, the temperature of the first crystallization treatment is 120 to 160 °C and the time is 15 to 35 h. The temperature and time of the first crystallization treatment include but are not limited to the above range. Limiting them within the above range is beneficial to regulating the nucleation rate and crystal growth rate, beneficial to reducing the size of the prepared ZSM-5 molecular sieve and increasing its specific surface area; at the same time, it is beneficial to inhibiting the formation of impurity phases and improving its crystal form purity.

[0043] In a preferred embodiment, the temperature of the second crystallization treatment is 130 to 170 °C and the time is 36 to 48 h. The temperature and time of the second crystallization treatment include but are not limited to the above range. Limiting them within the above range is beneficial to regulating the nucleation rate and crystal growth rate, beneficial to reducing the size of the prepared ZSM-5 molecular sieve and increasing its specific surface area; at the same time, it is beneficial to inhibiting the formation of impurity phases and improving its crystal form purity.

[0044] In a preferred embodiment, the temperature of the third crystallization treatment is 120 to 160 °C and the time is 15 to 35 h. The temperature and time of the third crystallization treatment include but are not limited to the above range. Limiting them within the above range is beneficial to regulating the nucleation rate and crystal growth rate, beneficial to reducing the size of the prepared ZSM-5 molecular sieve and increasing its specific surface area; at the same time, it is beneficial to inhibiting the formation of impurity phases and improving its crystal form purity.

[0045] In a preferred embodiment, the temperature of the fourth crystallization treatment is 130 to 170 °C, and the time is 36 to 48 h. The temperature and time of the fourth crystallization treatment include but are not limited to the above ranges. Limiting them within the above ranges is beneficial to regulating the nucleation rate and crystal growth rate, beneficial to reducing the size of the prepared ZSM-5 molecular sieve, and increasing its specific surface area; at the same time, it is beneficial to inhibiting the formation of impurity phases and improving its crystal form purity.

[0046] In a preferred embodiment, between step S3 and step S4, a first solid-liquid separation treatment and a first drying treatment are further sequentially performed on the product system to obtain a first crystallization product. Performing the first solid-liquid separation treatment before the ball milling treatment can separate the first crystallization product from the mother liquor, and then performing the first drying treatment on the first crystallization product can remove the solvent components contained therein; at the same time, it is convenient for the subsequent reuse of the mother liquor.

[0047] In a preferred embodiment, the temperature of the first drying treatment is 10 to 180 °C, preferably 60 to 120 °C, and the time is 4 to 24 h, preferably 4 to 12 h. The temperature and time of the first drying treatment include but are not limited to the above ranges. Limiting them within the above ranges is beneficial to improving the removal rate of the solvent components in the first crystallization product, and at the same time is beneficial to inhibiting the influence of the drying process on the crystal form of the first crystallization product.

[0048] In a preferred embodiment, during the ball milling treatment, the weight ratio of the first crystallization product to the second solvent is (5 to 10):(1 to 5). Compared with other ranges, limiting the weight ratio of the first crystallization product to the second solvent during the ball milling process within the above ranges is beneficial to improving the ball milling effect and beneficial to reducing the size of the ball milling product.

[0049] In a preferred embodiment, preferably, the average particle size of the ball milling product is 10 to 1000 nm.

[0050] In a preferred embodiment, the rotation speed of the ball milling treatment is 200 to 800 rpm, preferably 400 to 800 rpm, and the time is 1 to 24 h, preferably 4 to 24 h. The rotation speed and time of the ball milling treatment include but are not limited to the above ranges. Limiting them within the above ranges is beneficial to making the particle size of the ball milling product more uniform and beneficial to the synthesis of ZSM-5 molecular sieve.

[0051] In a preferred embodiment, the second solvent and the third solvent each independently include but are not limited to one or more of the group consisting of water, mother liquor, and sodium silicate solution. Preferably, the second solvent includes but is not limited to a sodium silicate solution with a mass concentration of 10 to 50 wt%, preferably a sodium silicate solution with a mass concentration of 15 to 30 wt%.

[0052] To further regulate the nucleation rate and crystal growth rate, preferably, the third solvent includes, but is not limited to, a sodium silicate solution with a mass concentration of 10 to 50 wt%, preferably a sodium silicate solution with a mass concentration of 15 to 30 wt%.

[0053] In a preferred embodiment, between step S4 and step S5, a second solid-liquid separation treatment and a second drying treatment are further included for the ball-milling system to obtain a ball-milled product. Conducting the second solid-liquid separation treatment before the calcination treatment can separate the ball-milled product, and then conducting the second drying treatment can remove the solvent components therein, facilitating the subsequent calcination treatment.

[0054] In a preferred embodiment, the temperature of the second drying treatment is 30 to 180 °C, preferably 60 to 120 °C, and the time is 4 to 48 h, preferably 6 to 12 h. The temperature and time of the second drying treatment include, but are not limited to, the above ranges. Limiting them within the above ranges is beneficial to improving the removal rate of solvent components in the second crystallization product and is also beneficial to suppressing the influence of the drying process on the crystal form of the second crystallization product.

[0055] In a preferred embodiment, the temperature of the calcination treatment is 500 to 900 °C, the heating rate is 1 to 10 °C / min, and the time is 2 to 10 h. Compared with other ranges, limiting the temperature, heating rate, and time of the calcination treatment within the above ranges is beneficial to improving the crystallinity and crystal form purity of the ZSM-5 molecular sieve and is beneficial to suppressing the formation of impurity phases.

[0056] To further improve the crystallinity and crystal form purity of the ZSM-5 molecular sieve and further suppress the formation of impurity phases, preferably, the temperature of the calcination treatment is 550 to 700 °C, the heating rate is 2 to 5 °C / min, and the time is 4 to 6 h.

[0057] In a preferred embodiment, between the fourth crystallization treatment and the calcination treatment, it further includes: performing a third drying treatment on the second crystallization product to obtain a material to be calcined. Performing a third drying treatment on the second crystallization product facilitates the subsequent calcination treatment.

[0058] To further improve the calcination treatment efficiency, preferably, the temperature of the third drying treatment is 100 to 140 °C, and the time is 4 to 24 h.

[0059] The second aspect of the present application also provides a ZSM-5 molecular sieve, which is prepared by using the above-mentioned preparation method of the ZSM-5 molecular sieve provided by the present application. The ZSM-5 molecular sieve provided by the present application has the characteristics of small size and large specific surface area.

[0060] The third aspect of the present application also provides an application of the above-mentioned ZSM-5 molecular sieve provided by the present application in catalyzing the conversion of methanol to olefins, catalyzing the isomerization of aromatics and aromatic compounds, and catalyzing the aromatization reaction.

[0061] The following further describes the present application in detail with specific examples, and these examples should not be construed as limiting the scope claimed by the present application.

[0062] Example 1

[0063] A preparation method of ZSM-5 molecular sieve includes:

[0064] (1) Add 90 g of silica sol (mass fraction of silicon dioxide is 40%) and 2.3 g of sodium hydroxide to 20 g of deionized water and stir. Keep stirring at a constant temperature of 30 °C for 2 h to obtain a first mixed solution, and the pH of the first mixed solution is 10;

[0065] (2) Add 2.1 g of aluminum sulfate and 30 g of n-butylamine to the first mixed solution in sequence, and stir at 40 °C for 2 h to obtain a second mixed solution;

[0066] (3) Transfer the second mixed solution to a crystallization kettle with a polytetrafluoroethylene inner lining and conduct the first crystallization treatment and the second crystallization treatment in sequence. Among them, the temperature of the first crystallization treatment is 150 °C and the time is 24 h, the temperature of the second crystallization treatment is 160 °C and the time is 48 h. After cooling, filter to obtain a first crystallization product and mother liquor; dry the first crystallization product at 100 °C for 12 h;

[0067] (4) Mix 32 g of the dried first crystallization product with 32 g of the mother liquor prepared above, conduct ball milling treatment at a rotation speed of 400 rpm for 4 h, and obtain a ball milling product after centrifugal separation; dry the ball milling product at 120 °C for 6 h;

[0068] (5) Mix the remaining mother liquor with the dried ball milling product, stir at 30 °C for 12 h, then transfer to a high-pressure crystallization kettle with a polytetrafluoroethylene inner lining and conduct the third crystallization treatment and the fourth crystallization treatment in sequence. Among them, the temperature of the third crystallization treatment is 150 °C and the time is 24 h, the temperature of the fourth crystallization treatment is 160 °C and the time is 48 h; filter the product and wash it to neutral, then dry it at 100 °C, and obtain a second crystallization product after drying for 14 h;

[0069] (6) Heat the above-mentioned second crystallization product to 550 °C at a heating rate of 5 °C / min for calcination, and obtain a nano-mesoporous ZSM-5 molecular sieve after calcination for 8 h, denoted as sample 1.

[0070] As Figure 1 shown, the crystal grain size of sample 1 is 90 nm, and through analysis and testing, the specific surface area is 362 m2 / g, the mesoporous volume is 0.72 m 3 / g.

[0071] The XRD of Sample 1 is as Figure 2 shown. It can be seen from the figure that the prepared molecular sieve has the characteristic peaks of ZSM-5 molecular sieve, that is, obvious characteristic diffraction peaks appear at 2θ = 7.2 ± 0.5°, 8.5 ± 0.5°, 22.2 ± 0.5°, 22.8 ± 0.5°, 23.2 ± 0.5°, 45.8 ± 0.5° and 46.2 ± 0.5°, indicating that the synthesized molecular sieve is ZSM-5 molecular sieve.

[0072] Example 2

[0073] A preparation method of ZSM-5 molecular sieve, comprising:

[0074] (1) Add 30 g of silica gel and 1.5 g of potassium hydroxide to 40 g of deionized water and stir. Stir at a constant temperature of 50 °C for 3 h to obtain a first mixed solution; the pH of the first mixed solution is 11;

[0075] (2) Add 1.2 g of aluminum sulfate, 1.5 g of sodium aluminate and 25 g of tetrabutylammonium bromide to the first mixed solution in sequence, and stir at 30 °C for 3 h to obtain a second mixed solution;

[0076] (3) Transfer the second mixed solution to a crystallization kettle with a polytetrafluoroethylene lining and carry out the first crystallization treatment and the second crystallization treatment in sequence. Among them, the temperature of the first crystallization treatment is 100 °C and the time is 36 h, and the temperature of the second crystallization treatment is 165 °C and the time is 36 h. After cooling, filter to obtain the first crystallization product and the mother liquor; dry the first crystallization product at 80 °C for 10 h;

[0077] (4) Mix 16 g of the dried first crystallization product obtained above with 16 g of the mother liquor prepared above, carry out ball milling treatment at a rotation speed of 450 rpm for 4.5 h, and obtain a ball milling product after centrifugal separation; dry the ball milling product at 120 °C for 8 h;

[0078] (5) Mix the remaining mother liquor with the dried ball milling product obtained above, stir at 40 °C for 8 h and then transfer to a high-pressure crystallization kettle with a polytetrafluoroethylene lining and carry out the third crystallization treatment and the fourth crystallization treatment in sequence. Among them, the temperature of the third crystallization treatment is 100 °C and the time is 36 h, and the temperature of the fourth crystallization treatment is 165 °C and the time is 36 h; filter the product and wash it to neutral, and then dry it at 120 °C. After drying for 6 h, obtain the second crystallization product;

[0079] (6) Heat the second crystallization product obtained above to 540 °C at a heating rate of 5 °C / min for calcination. After calcination for 6 h, obtain the nano-multi-level pore ZSM-5 molecular sieve, denoted as Sample 2.

[0080] Example 3

[0081] A preparation method of ZSM-5 molecular sieve, comprising:

[0082] (1) Add 50 g of silica and 3.0 g of sodium hydroxide to 30 g of deionized water and stir. Stir at a constant temperature of 30 °C for 3 h to obtain a first mixed solution; the pH of the first mixed solution is 12;

[0083] (2) Add 1.6 g of aluminum chloride and 40 g of n-butylamine to the first mixed solution in sequence, and stir at 40 °C for 3 h to obtain a second mixed solution;

[0084] (3) Transfer the second mixed solution to a crystallization kettle with a polytetrafluoroethylene inner lining and perform a first crystallization treatment and a second crystallization treatment in sequence. Among them, the temperature of the first crystallization treatment is 160 °C and the time is 12 h, the temperature of the second crystallization treatment is 140 °C and the time is 24 h. After cooling, filter to obtain a first crystallization product and mother liquor; dry the first crystallization product at 60 °C for 5 h;

[0085] (4) Mix 45 g of the dried first crystallization product with the mother liquor prepared above, perform ball milling treatment at a rotation speed of 300 rpm for 4 h, and obtain a ball-milled product after centrifugal separation; dry the ball-milled product at 100 °C for 8 h;

[0086] (5) Mix the remaining mother liquor with the dried ball-milled product above, stir at 20 °C for 6 h, then transfer to a high-pressure crystallization kettle with a polytetrafluoroethylene inner lining and perform a third crystallization treatment and a fourth crystallization treatment in sequence. Among them, the temperature of the third crystallization treatment is 120 °C and the time is 40 h, the temperature of the fourth crystallization treatment is 180 °C and the time is 24 h; filter the product and wash it to neutrality, then dry it at 100 °C. After drying for 14 h, obtain a second crystallization product;

[0087] (6) Heat the above second crystallization product to 600 °C at a heating rate of 2 °C / min for calcination. After calcination for 6 h, obtain a nano-mesoporous ZSM-5 molecular sieve, denoted as sample 3.

[0088] Example 4

[0089] A preparation method of ZSM-5 molecular sieve, comprising:

[0090] (1) Add 180 g of silica sol (mass fraction of silica is 40%) and 4.1 g of sodium hydroxide to 90 g of deionized water and stir. Stir at a constant temperature of 80 °C for 5 h to obtain a first mixed solution; the pH of the first mixed solution is 12;

[0091] (2) 3.2 g of aluminum sulfate and 100 g of tetrapropylammonium bromide were successively added to the first mixed solution, and stirred at 60 °C for 3 h to obtain a second mixed solution;

[0092] (3) The second mixed solution was transferred to a crystallization kettle with a polytetrafluoroethylene lining and subjected to a first crystallization treatment and a second crystallization treatment in sequence. Among them, the temperature of the first crystallization treatment was 145 °C and the time was 36 h, the temperature of the second crystallization treatment was 180 °C and the time was 24 h. After cooling, filtration was carried out to obtain a first crystallization product and mother liquor; the first crystallization product was dried at 120 °C for 6 h;

[0093] (4) 72 g of the dried first crystallization product was mixed with 9.5 g of the mother liquor prepared above, and ball-milled at a rotation speed of 600 rpm for 4 h. After centrifugal separation, a ball-milled product was obtained; the ball-milled product was dried at 120 °C for 10 h;

[0094] (5) The remaining mother liquor was mixed with the dried ball-milled product prepared above, stirred at 30 °C for 6 h, and then transferred to a high-pressure crystallization kettle with a polytetrafluoroethylene lining and subjected to a third crystallization treatment and a fourth crystallization treatment in sequence. Among them, the temperature of the third crystallization treatment was 145 °C and the time was 36 h, the temperature of the fourth crystallization treatment was 180 °C and the time was 24 h; the filtered product was washed until neutral and then dried at 120 °C. After drying for 10 h, a second crystallization product was obtained;

[0095] (6) The above second crystallization product was heated to 560 °C at a heating rate of 4 °C / min for calcination. After calcination for 5 h, a nano-multi-pore ZSM-5 molecular sieve was obtained, denoted as sample 4.

[0096] Example 5

[0097] A preparation method of ZSM-5 molecular sieve, comprising:

[0098] (1) 100 g of tetraethyl orthosilicate and 2.5 g of sodium hydroxide were added to 100 g of deionized water and stirred. Stirring was carried out at a constant temperature of 20 °C for 6 h to obtain a first mixed solution; the pH of the first mixed solution was 10;

[0099] (2) 3.3 g of sodium aluminate and 50 g of n-butylamine were successively added to the first mixed solution, and stirred at 60 °C for 1 h to obtain a second mixed solution;

[0100] (3) The second mixed solution was transferred to a crystallization kettle with a polytetrafluoroethylene lining and subjected to a first crystallization treatment and a second crystallization treatment in sequence. Among them, the temperature of the first crystallization treatment was 130 °C and the time was 24 h, the temperature of the second crystallization treatment was 180 °C and the time was 42 h. After cooling, filtration was carried out to obtain a first crystallization product and mother liquor; the first crystallization product was dried at 100 °C for 4 h;

[0101] (4) Mix the above 64 g of the dried first crystallization product with the above-prepared 15 g of mother liquor, perform ball milling treatment at a rotation speed of 450 rpm for 4 h, and obtain a ball-milled product after centrifugal separation; dry the ball-milled product at 90 °C for 12 h;

[0102] (5) Mix the remaining mother liquor with the above-dried ball-milled product, stir at 40 °C for 3 h, then transfer it to a high-pressure crystallization kettle with a polytetrafluoroethylene lining and perform third crystallization treatment and fourth crystallization treatment in sequence. Among them, the temperature of the third crystallization treatment is 130 °C and the time is 24 h, and the temperature of the fourth crystallization treatment is 180 °C and the time is 42 h; filter the product, wash it until neutral, and then dry it at 120 °C. After drying for 6 h, obtain the second crystallization product;

[0103] (6) Heat the above second crystallization product to 700 °C at a heating rate of 4 °C / min for calcination. After calcination for 5 h, obtain the nano-mesoporous ZSM-5 molecular sieve, denoted as sample 5.

[0104] Example 6

[0105] A preparation method of ZSM-5 molecular sieve, comprising:

[0106] (1) Add 100 g of tetraethyl orthosilicate and 2.5 g of sodium hydroxide to 100 g of deionized water and stir. Keep stirring at 20 °C for 6 h to obtain a first mixed solution; the pH of the first mixed solution is 10;

[0107] (2) Add 3.3 g of sodium aluminate and 50 g of n-butylamine to the first mixed solution in sequence, and stir at 30 °C for 2 h to obtain a second mixed solution;

[0108] (3) Transfer the second mixed solution to a crystallization kettle with a polytetrafluoroethylene lining and perform first crystallization treatment and second crystallization treatment in sequence. Among them, the temperature of the first crystallization treatment is 120 °C and the time is 30 h, and the temperature of the second crystallization treatment is 170 °C and the time is 24 h. After cooling, filter to obtain the first crystallization product and mother liquor; dry the first crystallization product at 70 °C for 6 h;

[0109] (4) Mix the above 65 g of the dried first crystallization product with 50 g of a sodium silicate solution with a mass concentration of 25%, perform ball milling treatment at a rotation speed of 400 rpm for 8 h, and obtain a ball-milled product after centrifugal separation; dry the ball-milled product at 60 °C for 24 h;

[0110] (5) Mix 80 g of sodium silicate solution with a mass concentration of 25% with the above-mentioned dried ball-milled product, stir at 60 °C for 4 h, and then transfer it to a high-pressure crystallization kettle with a polytetrafluoroethylene lining for the third crystallization treatment and the fourth crystallization treatment in sequence. Among them, the temperature of the third crystallization treatment is 130 °C and the time is 24 h, and the temperature of the fourth crystallization treatment is 180 °C and the time is 42 h; filter the product, wash it until neutral, and then dry it at 140 °C. After drying for 4 h, a second crystallization product is obtained;

[0111] (6) Heat the above-mentioned second crystallization product to 550 °C at a heating rate of 5 °C / min for calcination. After calcination for 6 h, a nano-mesoporous ZSM-5 molecular sieve is obtained, denoted as sample 6.

[0112] Example 7

[0113] A preparation method of ZSM-5 molecular sieve, comprising:

[0114] (1) Add 50 g of silica sol (mass fraction of silicon dioxide is 40%) and 3.2 g of sodium hydroxide to 50 g of deionized water and stir. Keep stirring at 30 °C for 2 h to obtain a first mixed solution; the pH of this first mixed solution is 11;

[0115] (2) Add 4.1 g of aluminum sulfate and 70 g of n-butylamine to the first mixed solution in sequence, and stir at 50 °C for 3 h to obtain a second mixed solution;

[0116] (3) Transfer the second mixed solution to a crystallization kettle with a polytetrafluoroethylene lining for the first crystallization treatment and the second crystallization treatment in sequence. Among them, the temperature of the first crystallization treatment is 180 °C and the time is 15 h, and the temperature of the second crystallization treatment is 180 °C and the time is 27 h. After cooling, filter to obtain a first crystallization product and mother liquor; dry the first crystallization product at 100 °C for 6 h;

[0117] (4) Mix 20 g of the above-mentioned dried first crystallization product with 20 g of sodium silicate solution with a mass concentration of 30%, perform ball-milling treatment at a rotation speed of 500 rpm for 6 h, and obtain a ball-milled product after centrifugal separation; dry the ball-milled product at 120 °C for 7 h;

[0118] (5) Mix all the mother liquor obtained in step (3) with the above-mentioned dried ball-milled product, stir at 30 °C for 6 h, and then transfer it to a high-pressure crystallization kettle with a polytetrafluoroethylene lining for the third crystallization treatment and the fourth crystallization treatment in sequence. Among them, the temperature of the third crystallization treatment is 180 °C and the time is 20 h, and the temperature of the fourth crystallization treatment is 180 °C and the time is 27 h; filter the product, wash it until neutral, and then dry it at 120 °C. After drying for 12 h, a second crystallization product is obtained;

[0119] (6) Heat the above second crystallization product to 650 °C at a heating rate of 5 °C / min for calcination. After calcination for 8 h, a nano - hierarchical pore ZSM - 5 molecular sieve is obtained, denoted as Sample 7.

[0120] Example 8

[0121] A preparation method of ZSM - 5 molecular sieve, comprising:

[0122] (1) Add 80 g of silica sol (mass fraction of silicon dioxide is 40%) and 1.5 g of sodium hydroxide to 180 g of deionized water and stir. Stir at a constant temperature of 40 °C for 4 h to obtain a first mixed solution; the pH of this first mixed solution is 9;

[0123] (2) Add 0.8 g of aluminum chloride and 120 g of tetrabutylammonium bromide to the first mixed solution in sequence, and stir at 60 °C for 2 h to obtain a second mixed solution;

[0124] (3) Transfer the second mixed solution to a crystallization kettle with a polytetrafluoroethylene lining and carry out the first crystallization treatment and the second crystallization treatment in sequence. Among them, the temperature of the first crystallization treatment is 150 °C and the time is 48 h, the temperature of the second crystallization treatment is 150 °C and the time is 48 h. After cooling, filter to obtain the first crystallization product and the mother liquor; dry the first crystallization product at 100 °C for 6 h;

[0125] (4) Mix 30 g of the above - dried first crystallization product, 5 g of the above - prepared mother liquor and 6 g of sodium silicate solution with a mass concentration of 30%, carry out ball - milling treatment at a rotation speed of 400 rpm for 8 h, and obtain a ball - milled product after centrifugal separation; dry the ball - milled product at 100 °C for 12 h;

[0126] (5) Mix the remaining mother liquor, 60 g of sodium silicate solution with a mass concentration of 30% and the above - dried ball - milled product, stir at 50 °C for 8 h, then transfer to a high - pressure crystallization kettle with a polytetrafluoroethylene lining and carry out the third crystallization treatment and the fourth crystallization treatment in sequence. Among them, the temperature of the third crystallization treatment is 150 °C and the time is 48 h, the temperature of the fourth crystallization treatment is 150 °C and the time is 48 h; filter the product, wash it to neutral, and then dry it at 100 °C. After drying for 10 h, a second crystallization product is obtained;

[0127] (6) Heat the above second crystallization product to 580 °C at a heating rate of 4 °C / min for calcination. After calcination for 7 h, a nano - hierarchical pore ZSM - 5 molecular sieve is obtained, denoted as Sample 8.

[0128] Example 9

[0129] A preparation method of ZSM - 5 molecular sieve, comprising:

[0130] (1) Add 80 g of silica and 2 g of sodium hydroxide to 260 g of deionized water and stir. Stir at a constant temperature of 30 °C for 8 h to obtain a first mixed solution; the pH of the first mixed solution is 10;

[0131] (2) Add 2.3 g of aluminum isopropoxide and 150 g of tetrapropylammonium bromide to the first mixed solution in sequence, and stir at 70 °C for 1.5 h to obtain a second mixed solution;

[0132] (3) Transfer the second mixed solution to a crystallization kettle with a polytetrafluoroethylene lining and carry out the first crystallization treatment and the second crystallization treatment in sequence. Among them, the temperature of the first crystallization treatment is 190 °C and the time is 24 h, and the temperature of the second crystallization treatment is 150 °C and the time is 36 h. After cooling, filter to obtain a first crystallization product and mother liquor; dry the first crystallization product at 110 °C for 4 h;

[0133] (4) Mix 72 g of the dried first crystallization product above with 35 g of deionized water, and carry out ball milling treatment at a rotation speed of 700 rpm for 5 h. After centrifugal separation, obtain a ball-milled product; dry the ball-milled product at 120 °C for 8 h;

[0134] (5) Mix 50 g of deionized water with the dried ball-milled product above, stir at 30 °C for 5 h, and then transfer it to a high-pressure crystallization kettle with a polytetrafluoroethylene lining and carry out the third crystallization treatment and the fourth crystallization treatment in sequence. Among them, the temperature of the third crystallization treatment is 190 °C and the time is 24 h, and the temperature of the fourth crystallization treatment is 150 °C and the time is 36 h; filter the product and wash it until neutral, and then dry it at 110 °C. After drying for 11 h, obtain a second crystallization product;

[0135] (6) Heat the above second crystallization product to 550 °C at a heating rate of 3 °C / min for calcination. After calcination for 5 h, obtain a nano-mesoporous ZSM-5 molecular sieve, denoted as sample 9.

[0136] Example 10

[0137] A preparation method of ZSM-5 molecular sieve, comprising:

[0138] (1) Add 90 g of tetraethyl orthosilicate and 1.7 g of sodium hydroxide to 260 g of deionized water and stir. Stir at a constant temperature of 60 °C for 4 h to obtain a first mixed solution; the pH of the first mixed solution is 11;

[0139] (2) Add 4.5 g of aluminum isopropoxide and 54 g of n-butylamine to the first mixed solution in sequence, and stir at 40 °C for 5 h to obtain a second mixed solution;

[0140] (3) Transfer the second mixture into a crystallization kettle with a polytetrafluoroethylene lining and conduct the first crystallization treatment and the second crystallization treatment in sequence. Among them, the temperature of the first crystallization treatment is 170 °C, the time is 18 h, the temperature of the second crystallization treatment is 150 °C, and the time is 27 h. After cooling, filter to obtain the first crystallization product and the mother liquor; dry the first crystallization product at 90 °C for 7 h;

[0141] (4) Mix the above 45 g of dried first crystallization product with 10 g of deionized water, conduct ball milling treatment at a rotation speed of 650 rpm for 4 h, and obtain the ball-milled product after centrifugal separation; dry the ball-milled product at 100 °C for 8 h;

[0142] (5) Mix 100 g of a sodium silicate solution with a mass concentration of 15% with the above dried ball-milled product, stir at 40 °C for 8 h, and then transfer it to a high-pressure crystallization kettle with a polytetrafluoroethylene lining to conduct the third crystallization treatment and the fourth crystallization treatment in sequence. Among them, the temperature of the third crystallization treatment is 140 °C, the time is 20 h, the temperature of the fourth crystallization treatment is 155 °C, and the time is 72 h; filter the product, wash it until neutral, and then dry it at 100 °C. After drying for 24 h, obtain the second crystallization product;

[0143] (6) Heat the above second crystallization product to 550 °C at a heating rate of 4 °C / min for calcination. After calcination for 7 h, obtain the nano-mesoporous ZSM-5 molecular sieve, denoted as sample 10.

[0144] Comparative Example 1

[0145] The difference from Example 1 is that steps (4) and (5) are omitted, and directly conduct calcination treatment on the dried first crystallization product obtained in step (3) to obtain Comparative Example sample 1.

[0146] The SEM image of the sample prepared in Comparative Example 1 is as Figure 3 shown. It can be seen from the figure that the prepared sample has larger crystal grains. Compared with Figure 1 , the morphology is irregular, and there are a small amount of small particulate substances attached to the surface. This may be due to the insufficient reaction in the nucleation stage.

[0147] Comparative Example 2

[0148] The difference from Example 1 is that steps (3) and (4) are omitted, and directly conduct the third crystallization treatment, the fourth crystallization treatment in step (5) and the operation in step (6) on the mixture obtained in step (2) to obtain Comparative Example sample 2.

[0149] Comparative Example 3

[0150] The difference from Example 1 is that the temperature of the first crystallization treatment is 80 °C and the time is 10 h, and the remaining steps are the same as those in Example 1 to obtain Comparative Example sample 3.

[0151] Comparative Example 4

[0152] The difference from Example 1 is that the temperature of the second crystallization treatment is 100 °C and the time is 96 h, and the remaining steps are the same as those in Example 1, obtaining Comparative Example Sample 4.

[0153] Comparative Example 5

[0154] The difference from Example 1 is that the second crystallization treatment is omitted, and the remaining steps are the same as those in Example 1, obtaining Comparative Example Sample 5.

[0155] Comparative Example 6

[0156] The difference from Example 1 is that the temperature of the third crystallization treatment is 80 °C and the time is 36 h, and the remaining steps are the same as those in Example 1, obtaining Comparative Example Sample 6.

[0157] Comparative Example 7

[0158] The difference from Example 1 is that the temperature of the fourth crystallization treatment is 100 °C and the time is 14 h, and the remaining steps are the same as those in Example 1, obtaining Comparative Example Sample 7.

[0159] Comparative Example 8

[0160] The difference from Example 1 is that the fourth crystallization treatment is omitted, and the remaining steps are the same as those in Example 1, obtaining Comparative Example Sample 8.

[0161] The test results of the grain size, specific surface area and mesopore volume of the samples prepared in all the above examples and comparative examples of the present application are summarized in Table 1.

[0162] Table 1

[0163] Grain size <![CDATA[Specific surface area (m 2 / g)]]> <![CDATA[Mesopore volume (m 3 / g)]]> Example 1 90nm 362 0.72 Example 2 60nm 380 0.63 Example 3 10nm 350 0.51 Example 4 50nm 420 0.84 Example 5 5nm 330 0.32 Example 6 120nm 300 0.22 Example 7 20nm 450 0.78 Example 8 6nm 440 0.74 Example 9 60nm 396 0.65 Example 10 10nm 316 0.25 Comparative Example 1 24μm 196 0.09 Comparative Example 2 12μm 230 0.11 Comparative Example 3 8μm 245 0.10 Comparative Example 4 17μm 198 0.09 Comparative Example 5 16μm 156 0.08 Comparative Example 6 25μm 187 0.08 Comparative Example 7 16μm 201 0.07 Comparative Example 8 12μm 157 0.05

[0164] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects: Compared with the traditional method of directly mixing a silicon source, an aluminum source, a templating agent and a solvent, in the present application, the silicon source is first dispersed, and a pH regulator is used to adjust the acidity and alkalinity to obtain a first mixed solution. Then, the aluminum source, the templating agent and the first mixed solution are mixed, which can better exert the role of the templating agent to obtain a second mixed solution. Sequentially performing a first crystallization treatment and a second crystallization treatment on the second mixed solution can improve the nucleation rate and the crystal growth rate, which is beneficial to making the subsequently prepared ZSM-5 molecular sieve have a smaller particle size and a larger specific surface area. Compared with directly calcining the crystallization product, in the present application, a ball milling treatment is performed on the mixture of the crystallization product and a second solvent. Through the ball milling treatment, the first crystallization product and the second solvent increase the molecular collision probability through friction, promote the occurrence of chemical reactions, and make the obtained ball milling product beneficial to subsequent crystal nucleation. Then, sequentially performing a third crystallization treatment and a fourth crystallization treatment on the ball milling product in a third solvent can improve the crystal growth rate to obtain a second crystallization product; finally, the second crystallization product is calcined to carbonize and remove the templating agent contained therein to obtain the ZSM-5 molecular sieve.

[0165] Compared with a single crystallization treatment, the present application adopts two-stage crystallization treatments, which can improve the nucleation rate and the crystal growth rate, thereby reducing the size of the prepared ZSM-5 molecular sieve and increasing its specific surface area.

[0166] Compared with other ranges, limiting the temperature and time of the first crystallization treatment and the second crystallization treatment within the ranges of the present application is beneficial to improving the nucleation rate and the crystal growth rate, and is also beneficial to increasing the crystallinity of the first crystallization product. Limiting the temperature and time of the third crystallization treatment and the fourth crystallization treatment within the ranges of the present application is beneficial to improving the crystal growth rate, and is beneficial to reducing the size of the prepared ZSM-5 molecular sieve and increasing its specific surface area.

[0167] It should be noted that the terms "first", "second", etc. in the description and claims of the present application are used to distinguish similar objects, and do not necessarily need to describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances so that the embodiments of the present application described herein can be implemented in an order other than those described herein.

[0168] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of ZSM-5 molecular sieve, characterized in that, The preparation method includes: Step S1: Mix a silicon source, a pH regulator, and a first solvent to obtain a first mixture; Step S2: Mix an aluminum source, a template agent, and the first mixture to obtain a second mixture; Step S3: Perform a first crystallization treatment and a second crystallization treatment on the second mixture in sequence to obtain a product system including a first crystallization product and mother liquor; wherein, the temperature of the first crystallization treatment is 100 - 200 °C, and the time is 15 - 60 h, and the temperature of the second crystallization treatment is 120 - 220 °C, and the time is 20 - 72 h; Step S4: Perform ball milling on a mixture of the first crystallization product and a second solvent to obtain a ball milling system including a ball milling product; Step S5: Perform a third crystallization treatment and a fourth crystallization treatment on the ball milling product in a third solvent in sequence to obtain a second crystallization product; wherein, the temperature of the third crystallization treatment is 100 - 200 °C, and the time is 15 - 45 h, and the temperature of the fourth crystallization treatment is 120 - 220 °C, and the time is 20 - 72 h; Step S6: Perform a calcination treatment on the second crystallization product to obtain the ZSM-5 molecular sieve.

2. The preparation method of the ZSM-5 molecular sieve according to claim 1, characterized in that, The molar ratio of the silicon source, the aluminum source, the template agent, and the first solvent is (10 - 1000):1:(1.8 - 260):(100 - 2000); Preferably, the pH of the first mixture is 7 - 13.

3. The preparation method of the ZSM-5 molecular sieve according to claim 1 or 2, characterized in that, The mixing process in Step S1 includes: stirring at a constant temperature of 10 - 90 °C for 1 - 10 h to obtain the first mixture, preferably stirring at a constant temperature of 20 - 70 °C for 2 - 4 h; and / or, The mixing process in Step S2 includes: stirring at a constant temperature of 10 - 90 °C for 0.5 - 5 h to obtain the second mixture, preferably stirring at a constant temperature of 20 - 60 °C for 1 - 3 h.

4. The preparation method of the ZSM-5 molecular sieve according to any one of claims 1 to 3, characterized in that, The temperature of the first crystallization treatment is 120 - 160 °C, and the time is 15 - 35 h; and / or, The temperature of the second crystallization treatment is 130 - 170 °C, and the time is 36 - 48 h; and / or, The temperature of the third crystallization treatment is 120 - 160 °C, and the time is 15 - 35 h; and / or, The temperature of the fourth crystallization treatment is 130 - 170 °C, and the time is 36 - 48 h.

5. The preparation method of the ZSM-5 molecular sieve according to claim 4, characterized in that, Between Step S3 and Step S4, a first solid-liquid separation treatment and a first drying treatment are further included on the product system to obtain the first crystallization product; Preferably, the temperature of the first drying treatment is 10 - 180 °C, more preferably 60 - 120 °C, and the time is 4 - 24 h, more preferably 4 - 12 h.

6. The preparation method of the ZSM-5 molecular sieve according to any one of claims 1 to 5, characterized in that, During the ball milling process, the weight ratio of the first crystallization product to the second solvent is (5 - 10):(1 - 5); Preferably, the average particle size of the ball milling product is 10 - 1000 nm; Preferably, the rotation speed of the ball milling is 200 - 800 rpm, more preferably 400 - 800 rpm, and the time is 1 - 24 h, more preferably 4 - 24 h.

7. The preparation method of the ZSM-5 molecular sieve according to claim 6, characterized in that, The second solvent and the third solvent are each independently selected from one or more of the group consisting of water, mother liquor, and sodium silicate solution; Preferably, the second solvent is selected from sodium silicate solutions with a mass concentration of 10-50 wt%, preferably sodium silicate solutions with a mass concentration of 15-30 wt%; Preferably, the third solvent is selected from sodium silicate solutions with a mass concentration of 10-50 wt%, preferably sodium silicate solutions with a mass concentration of 15-30 wt%.

8. The preparation method of the ZSM-5 molecular sieve according to claim 7, wherein, Between the step S4 and the step S5, a second solid-liquid separation treatment and a second drying treatment are further included for the ball milling system to obtain the ball milling product; Preferably, the temperature of the second drying treatment is 30-180 °C, preferably 60-120 °C, and the time is 4-48 h, preferably 6-12 h.

9. The preparation method of the ZSM-5 molecular sieve according to any one of claims 1 to 8, characterized in that, The temperature of the calcination treatment is 500-900 °C, the heating rate is 1-10 °C / min, and the time is 2-10 h; preferably, the temperature of the calcination treatment is 550-700 °C, the heating rate is 2-5 °C / min, and the time is 4-6 h.

10. A ZSM-5 molecular sieve, characterized in that, The ZSM-5 molecular sieve is prepared by the preparation method of the ZSM-5 molecular sieve according to any one of claims 1 to 9.

11. Use of the ZSM-5 molecular sieve according to claim 10 in the catalytic conversion of methanol to olefins, the catalytic isomerization of aromatics and aromatic compounds, and the catalytic aromatization reaction.

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