Na-type ZSM-5 molecular sieve, synthetic method thereof and oil catalytic cracking catalyst
By using silicon, aluminum, and alkali sources to synthesize Na-type ZSM-5 molecular sieves, the environmental pollution and cost problems caused by organic template agents have been solved, realizing efficient and low-cost molecular sieve synthesis and catalyst application.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- PETROCHINA CO LTD
- Filing Date
- 2024-11-12
- Publication Date
- 2026-05-12
AI Technical Summary
Existing methods for synthesizing ZSM-5 molecular sieves use organic templates, which lead to environmental pollution, high costs, and difficulty in large-scale industrial application. Furthermore, microwave methods use expensive equipment and pose safety hazards.
Using silicon, aluminum, alkali, and deionized water as raw materials, Na-type ZSM-5 molecular sieves are synthesized through a liquid directing agent, avoiding organic template agents and using sodium-containing alkali sources to simplify the process and reduce costs.
It achieves green and environmentally friendly molecular sieve synthesis, reduces production costs, improves crystallinity and specific surface area, and is suitable for oil catalytic cracking catalysts with high cracking activity.
Smart Images
Figure CN122010138A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of molecular sieve preparation technology, specifically relating to a Na-type ZSM-5 molecular sieve, its synthesis method, and an oil catalytic cracking catalyst. Background Technology
[0002] Low-carbon olefins (ethylene, propylene, butene, 1-3-butadiene, etc.), especially ethylene and propylene, are important basic raw materials for the production of downstream organic chemical products. Currently, the production of low-carbon olefins still mainly relies on steam cracking. However, the reaction temperature of steam cracking generally exceeds 750℃, resulting in high CO2 emissions, low yields of low-carbon olefins, poor equipment stability, and short lifespan, leading to increased production costs and high energy consumption and emissions. Among the existing technologies for producing low-carbon olefins, catalytic cracking technology has attracted increasing attention due to its lower reaction temperature, reduced CO2 emissions, controllable product distribution and selectivity, and relatively easier-to-achieve process conditions.
[0003] The core of catalytic cracking is the development of catalysts. Solid acid catalysts (such as ZSM-5 molecular sieves) have broad application prospects in catalytic cracking processes due to their advantages such as good chemical stability, unique pore structure and shape-selective properties, flexible and tunable acidity, and strong resistance to carbon deposition. Among them, the synthesis methods of ZSM-5 molecular sieves mainly include hydrothermal synthesis, non-aqueous solvothermal synthesis, microwave-assisted synthesis, and steam-assisted synthesis. At present, there are several literature and patent reports on the synthesis methods of ZSM-5, such as: the one-step synthesis of HZSM-5 molecular sieve using macroporous silica gel, aluminum nitrate, and n-propylamine as raw materials (Jing Wenjing, Zhang Yuxia. One-step green synthesis of HZSM-5 molecular sieve [J], Shanxi Chemical Industry, 2024, 200(44):22-24), the specific surface area of the synthesized molecular sieve is about 92-421 m². 2 / g, although this method uses little water and does not require subsequent ion exchange processes, the n-propylamine added during the synthesis process decomposes and produces toxic gases during calcination, which are difficult to treat and can easily cause environmental pollution; CN101041442A discloses a ZSM-5 molecular sieve synthesis method that does not use any organic template agent during the synthesis process, does not require high-temperature calcination, simplifies the production process, reduces production costs, and also solves the environmental pollution problem. However, this invention requires the use of ultrasonic technology before crystallization production, which makes it difficult to achieve large-scale industrial application; In addition, Wang et al. used the microwave method, with silica sol and aluminum sulfate octadecylhydrate as silicon source and aluminum source, respectively, to efficiently synthesize a fully crystalline ZSM-5 molecular sieve catalyst containing 100% active components (Wang Darui, Sun Hongmin, Xue Mingwei et al. Efficient synthesis of fully crystalline ZSM-5 molecular sieve catalyst by microwave method and its catalytic performance [J], Chemical Industry Progress, 2023, 42(7): 3582-3588), and the specific surface area of the synthesized ZSM-5 molecular sieve reached 419m². 2 However, this method uses a variety of organic template agents such as ammonia, ethylamine, and n-butylamine, which makes the post-processing process cumbersome and even causes environmental pollution. At the same time, the equipment required for microwave technology is relatively expensive, and the strong radiation of microwave technology poses a safety threat to operators.
[0004] Therefore, there is an urgent need to develop a new green synthesis route for ZSM-5 molecular sieves that does not use expensive and difficult-to-process organic template agents and is close to industrial production applications. Summary of the Invention
[0005] To address the aforementioned technical problems, the present invention aims to provide a Na-type ZSM-5 molecular sieve, its synthesis method, and an oil catalytic cracking catalyst. By using only four components—a silicon source, an aluminum source, an alkali source, and deionized water—a microporous ZSM-5 molecular sieve can be synthesized in a green manner, avoiding the addition of organic templates and seed crystals, and can be used as an oil catalytic cracking catalyst.
[0006] To achieve the above objectives, the present invention provides a method for synthesizing Na-type ZSM-5 molecular sieves, wherein the synthesis method includes:
[0007] (1) Dry and calcine the silicon source and aluminum source to obtain activated silicon source and activated aluminum source;
[0008] (2) Add the sodium-containing alkali source to water to obtain a sodium-containing alkali solution; grind the activated silicon source and add it to the sodium-containing alkali solution, and perform the first stirring to obtain molecular sieve gel I;
[0009] (3) Add the activated aluminum source to molecular sieve gel I and stir for the second time to obtain molecular sieve gel II;
[0010] (4) Add the liquid directing agent dropwise into molecular sieve gel II and stir for the third time to obtain molecular sieve gel III;
[0011] (5) The molecular sieve gel III was crystallized, and after cooling, filtration, washing and drying, Na-type ZSM-5 molecular sieve was obtained.
[0012] The molecular sieve gel III satisfies the molar ratio SiO2:Al2O3:Na2O:H2O = (25-50):1:(3-15):(800-2000); the molar ratio of the silicon source is SiO2, the molar ratio of the aluminum source is Al2O3, and the molar ratio of the sodium-containing alkali source is Na2O; the amount of liquid directing agent added is 5%-20% of the total weight of the silicon source added to the molecular sieve gel III.
[0013] This invention does not add organic templates or seed crystals during the synthesis process, but only a sol-based liquid directing agent. The raw material components of the liquid directing agent are highly similar to those of the molecular sieve raw materials. The final molecular sieve synthesis system contains only four components: silicon source, aluminum source, alkali source, and deionized water. Furthermore, because using potassium hydroxide as an alkali source may lead to problems such as excessive alkalinity causing framework damage, large crystal size resulting in poor catalytic cracking performance, and high economic costs, sodium-containing alkali sources are more suitable for this application compared to other inorganic alkali sources.
[0014] In some specific embodiments, preferably, the molecular sieve gel III satisfies the molar ratio SiO2:Al2O3:Na2O:H2O=(35-45):1:(6-12):(1200-1600).
[0015] In some specific embodiments, preferably, the amount of liquid directing agent added is 10%-15% of the total weight of the silicon source added to the molecular sieve gel III.
[0016] According to a specific embodiment of the present invention, preferably, the silicon source includes one or more of silica, tetraethyl orthosilicate, silica gel, silica sol, and sodium silicate; more preferably, it is silica sol.
[0017] According to a specific embodiment of the present invention, preferably, the silicon source is an industrial-grade raw material, and the content of SiO2 in the dry basis of the industrial-grade raw material is above 92%, more preferably above 98%.
[0018] According to a specific embodiment of the present invention, preferably, the aluminum source includes one or more of boehmite, aluminum hydroxide, sodium aluminate, aluminum isopropoxide, aluminum sulfate, and boehmite; more preferably, it is boehmite.
[0019] According to a specific embodiment of the present invention, preferably, the liquid directing agent is obtained by dissolving a sodium-containing alkali source and the silicon source activated in step (1) in water, followed by a fourth stirring. The liquid directing agent is a pale yellow sol.
[0020] In some specific embodiments, preferably, the sodium-containing alkali source used in the preparation of molecular sieve gel I and liquid directing agent includes NaOH and / or Na2O.
[0021] According to a specific embodiment of the present invention, preferably, the molar ratio of each component in the liquid guiding agent is SiO2:Na2O:H2O=1:(0.2-2):(8-15).
[0022] According to a specific embodiment of the present invention, preferably, the calcination temperature is 500-800℃, and the calcination time is 4-8 hours. Calcination activates the silicon and aluminum sources at high temperatures and removes surface impurities.
[0023] In some specific implementations, preferably, the drying conditions in step (1) are drying at 90-120°C in an oven for 2-6 hours.
[0024] According to a specific embodiment of the present invention, preferably, the crystallization temperature is 90-175℃ (preferably 150-170℃), and the crystallization time is 24-80h (preferably 60-72h); more preferably, the crystallization method is stirred crystallization; the crystallization process is carried out in a polytetrafluoroethylene-lined reactor, and after crystallization, it is naturally cooled to room temperature, filtered and washed, and thoroughly dried at 90-120℃ to obtain Na-type ZSM-5 molecular sieve.
[0025] According to a specific embodiment of the present invention, preferably, the first stirring condition is uniform stirring at 25-75°C for 4-8 hours.
[0026] According to a specific embodiment of the present invention, preferably, the second stirring condition is stirring at 25-75°C for 1-3 hours.
[0027] According to a specific embodiment of the present invention, preferably, the third stirring condition is stirring at 25-75°C for 1-3 hours.
[0028] According to a specific embodiment of the present invention, preferably, the fourth stirring condition is uniform stirring at 40-80°C for 4-8 hours.
[0029] The present invention also provides a Na-type ZSM-5 molecular sieve, which is prepared by the above-described synthesis method.
[0030] According to a specific embodiment of the present invention, preferably, the microporous specific surface area of the Na-type ZSM-5 molecular sieve is 171-352 m². 2 / g, the micropore volume of the Na-type ZSM-5 molecular sieve is 0.07-0.13 cm³. 3 / g.
[0031] The present invention also provides an oil catalytic cracking catalyst, which is prepared using the above-mentioned Na-type ZSM-5 molecular sieve as raw material.
[0032] According to a specific embodiment of the present invention, preferably, the oil catalytic cracking catalyst comprises 5-45 parts by weight of H-type ZSM-5 molecular sieve and 55-95 parts by weight of matrix; the H-type ZSM-5 molecular sieve is obtained by ammonium exchange and calcination of the Na-type ZSM-5 molecular sieve.
[0033] In some specific embodiments, the matrix can be a material conventionally used in the preparation of catalytic cracking catalysts in the art, mainly including an inert matrix (e.g., kaolin) and a binder (e.g., aluminum sol), wherein the content of the binder can be determined according to the content of the molecular sieve; preferably, based on the mass of the matrix, the matrix contains 5%-20% binder, and the remainder is an inert matrix.
[0034] In some specific embodiments, preferably, the oil catalytic cracking catalyst is prepared by spray drying after mixing H-type ZSM-5 molecular sieve with a matrix.
[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0036] (1) The synthesis method of Na-type ZSM-5 molecular sieve provided by the present invention does not add organic template agents or seed crystals during the synthesis process, and is green and environmentally friendly. It only uses four raw materials: silicon source, aluminum source, alkali source, deionized water and self-made liquid directing agent. The synthesis method is simple and the process is convenient. At the same time, compared with the traditional method of synthesizing ZSM-5 molecular sieve by adding organic template agents, it eliminates the post-processing of organic matter, does not cause pollution to the environment, and avoids problems such as high price, complicated production, difficult post-processing, and large amount of organic waste discharge. It provides a new process route for the synthesis of ZSM-5 molecular sieve.
[0037] (2) The silicon and aluminum sources used in the synthesis method of ZSM-5 molecular sieve provided by the present invention, such as silica gel and aluminum sulfate, can be industrial-grade raw materials, which are easy to prepare and inexpensive, reducing the cost of synthesizing molecular sieves and making it easier to achieve large-scale industrial production, which is more in line with the prospects of industrial application.
[0038] (3) The ZSM-5 molecular sieve provided by this invention has a relatively high crystallinity, reaching over 90%. This ZSM-5 molecular sieve has a high specific surface area, large pore volume, and is mostly microporous, meeting the requirements of ZSM-5 molecular sieve in terms of specific surface area and pore volume. After ammonium exchange and calcination to obtain hydrogen-form ZSM-5 molecular sieve, it can be used as a catalytic cracking catalyst. The oil catalytic cracking catalyst provided by this invention has high cracking activity and a high light oil micro-reaction activity index. Attached Figure Description
[0039] Figure 1 The image shows the XRD pattern of the ZSM-5 molecular sieve synthesized in Example 1.
[0040] Figure 2 The XRD pattern of the ZSM-5 molecular sieve synthesized in Example 2 is shown.
[0041] Figure 3 The image shows the XRD pattern of the ZSM-5 molecular sieve synthesized in Example 3.
[0042] Figure 4 The image shows the XRD pattern of the ZSM-5 molecular sieve synthesized in Example 4.
[0043] Figure 5 The image shows the XRD pattern of the ZSM-5 molecular sieve synthesized in Example 5.
[0044] Figure 6 The XRD pattern of the ZSM-5 molecular sieve synthesized in Example 6 is shown.
[0045] Figure 7 The image shows the XRD pattern of the ZSM-5 molecular sieve synthesized in Example 7.
[0046] Figure 8 The XRD pattern of the ZSM-5 molecular sieve synthesized in Example 8 is shown.
[0047] Figure 9 The XRD pattern of the ZSM-5 molecular sieve synthesized in Example 9 is shown.
[0048] Figure 10 The XRD pattern of the ZSM-5 molecular sieve synthesized in Example 10 is shown.
[0049] Figure 11 The image shows the XRD pattern of the product synthesized in Comparative Example 1.
[0050] Figure 12 The image shows the XRD pattern of the product synthesized in Comparative Example 2.
[0051] Figure 13 The XRD pattern of the product synthesized in Comparative Example 3 is shown.
[0052] Figure 14 The XRD pattern of the product synthesized in Comparative Example 4 is shown.
[0053] Figure 15 The XRD pattern of the product synthesized in Comparative Example 5 is shown.
[0054] Figure 16 The XRD pattern of the product synthesized in Comparative Example 6 is shown.
[0055] Figure 17 The XRD pattern of the product synthesized in Comparative Example 7 is shown.
[0056] Figure 18 The XRD pattern of the product synthesized in Comparative Example 8 is shown.
[0057] Figure 19 The XRD pattern of the product synthesized in Comparative Example 9 is shown.
[0058] Figure 20 The XRD pattern of the product synthesized in Comparative Example 10. Detailed Implementation
[0059] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.
[0060] Raw material or equipment sources: silica gel (mainly coarse-pore silica gel), industrial grade, SiO2 content > 92%; aluminum sulfate, industrial grade, Al2(SO4)3 content > 75%; sodium hydroxide, analytical grade; deionized water, laboratory-made;
[0061] Evaluation and analysis methods: X-ray diffraction technique; N2- adsorption-desorption test.
[0062] Preparation Example
[0063] This preparation example provides a method for preparing a liquid directing agent, specifically including the following steps:
[0064] The coarse-pore silica gel was dried in an oven at 120°C for 4 hours; then it was calcined in a muffle furnace at 550°C for 5 hours for later use.
[0065] Take 151g of deionized water into a beaker, add 13.67g of NaOH, and stir continuously until completely dissolved; weigh 40g of calcined coarse-porous silica gel and add it to the above NaOH solution, stir at 50℃ for 5h to form a light yellow sol, and obtain a liquid directing agent.
[0066] Example 1
[0067] This embodiment provides a method for synthesizing Na-type ZSM-5 molecular sieves, specifically including the following steps:
[0068] (1) Dry coarse-pore silica gel and aluminum sulfate in an oven at 120°C for 4 hours; then calcine them in a muffle furnace at 550°C for 5 hours to serve as activated silicon and aluminum sources for later use.
[0069] (2) Molecular sieve gel III was prepared according to the molar ratio of SiO2:Al2O3:Na2O:H2O = 35:1:8:1200:
[0070] Take 120g of deionized water into a beaker, add 0.89g of NaOH, and stir continuously until completely dissolved; weigh 9g of the activated coarse-porous silica gel from step (1) and add it to the NaOH solution, stir at 30℃ for 5h to obtain molecular sieve gel I; add 1.8g of the activated aluminum sulfate from step (1), and continue stirring at 30℃ for 1h to obtain molecular sieve gel II; add 4.42g of the liquid directing agent from the preparation example, and then continue stirring at 30℃ for 1h to obtain molecular sieve gel III;
[0071] (3) Transfer the molecular sieve gel III to a crystallization kettle with a polytetrafluoroethylene liner, and let it stand at 170°C for crystallization for 72 hours. After crystallization, filter the crystallized product under reduced pressure, wash it with water until neutral, and dry it at 120°C to obtain the Na-type molecular sieve product.
[0072] Figure 1 XRD results indicate that the product is ZSM-5 molecular sieve with a relative crystallinity of 97%.
[0073] Example 2
[0074] This embodiment provides a method for synthesizing Na-type ZSM-5 molecular sieves, specifically including the following steps:
[0075] (1) Dry coarse-pore silica gel and aluminum sulfate in an oven at 120°C for 4 hours; then calcine them in a muffle furnace at 600°C for 5 hours to serve as activated silicon and aluminum sources for later use.
[0076] (2) Molecular sieve gel III was prepared according to the molar ratio of SiO2:Al2O3:Na2O:H2O = 45:1:8:1200:
[0077] Take 120g of deionized water into a beaker, add 0.89g of NaOH, and stir continuously until completely dissolved; weigh 11.58g of the activated coarse-porous silica gel from step (1) and add it to the NaOH solution, stir at 30℃ for 5h to obtain molecular sieve gel I; add 1.8g of the activated aluminum sulfate from step (1), and continue stirring at 30℃ for 1h to obtain molecular sieve gel II; add 4.42g of the liquid directing agent from the preparation example, and then continue stirring at 30℃ for 1h to obtain molecular sieve gel III;
[0078] (3) Transfer the molecular sieve gel III to a crystallization kettle with a polytetrafluoroethylene liner, and let it stand at 170°C for crystallization for 72 hours. After crystallization, filter the crystallized product under reduced pressure, wash it with water until neutral, and dry it at 120°C to obtain the Na-type molecular sieve product.
[0079] Figure 2 XRD results indicate that the product is ZSM-5 molecular sieve with a relative crystallinity of 96%.
[0080] Example 3
[0081] This embodiment provides a method for synthesizing Na-type ZSM-5 molecular sieves, specifically including the following steps:
[0082] (1) Dry coarse-pore silica gel and aluminum sulfate in an oven at 110°C for 5 hours; then calcine them in a muffle furnace at 600°C for 6 hours to serve as activated silicon and aluminum sources for later use.
[0083] (2) Molecular sieve gel III was prepared according to the molar ratio of SiO2:Al2O3:Na2O:H2O = 35:1:12:1200:
[0084] Take 120g of deionized water into a beaker, add 1.33g of NaOH, and stir continuously until completely dissolved; weigh 9g of the activated coarse-porous silica gel from step (1) and add it to the NaOH solution, stir at 30℃ for 5h to obtain molecular sieve gel I; add 1.8g of the activated aluminum sulfate from step (1), and continue stirring at 30℃ for 1h to obtain molecular sieve gel II; add 4.42g of the liquid directing agent from the preparation example, and then continue stirring at 30℃ for 1h to obtain molecular sieve gel III;
[0085] (3) Transfer the molecular sieve gel III to a crystallization kettle with a polytetrafluoroethylene liner, and let it stand at 170°C for crystallization for 72 hours. After crystallization, filter the crystallized product under reduced pressure, wash it with water until neutral, and dry it at 120°C to obtain the Na-type molecular sieve product.
[0086] Figure 3 XRD results indicate that the product is ZSM-5 molecular sieve with a relative crystallinity of 96%.
[0087] Example 4
[0088] This embodiment provides a method for synthesizing Na-type ZSM-5 molecular sieves, specifically including the following steps:
[0089] (1) Dry coarse-pore silica gel and aluminum sulfate in an oven at 120°C for 4 hours; then calcine them in a muffle furnace at 550°C for 5 hours to serve as activated silicon and aluminum sources for later use.
[0090] (2) Molecular sieve gel III was prepared according to the molar ratio of SiO2:Al2O3:Na2O:H2O = 35:1:8:1800:
[0091] Take 180g of deionized water into a beaker, add 0.89g of NaOH, and stir continuously until completely dissolved; weigh 9g of the activated coarse-porous silica gel from step (1) and add it to the NaOH solution, stir at 30℃ for 5h to obtain molecular sieve gel I; add 1.8g of the activated aluminum sulfate from step (1), and continue stirring at 30℃ for 1h to obtain molecular sieve gel II; add 4.42g of the liquid directing agent from the preparation example, and then continue stirring at 30℃ for 1h to obtain molecular sieve gel III;
[0092] (3) Transfer the molecular sieve gel III to a crystallization kettle with a polytetrafluoroethylene liner, and let it stand at 170°C for crystallization for 72 hours. After crystallization, filter the crystallized product under reduced pressure, wash it with water until neutral, and dry it at 120°C to obtain the Na-type molecular sieve product.
[0093] Figure 4 XRD results indicate that the product is ZSM-5 molecular sieve with a relative crystallinity of 95%.
[0094] Example 5
[0095] This embodiment provides a method for synthesizing Na-type ZSM-5 molecular sieves, specifically including the following steps:
[0096] (1) Dry coarse-pore silica gel and aluminum sulfate in an oven at 120°C for 6 hours; then calcine them in a muffle furnace at 650°C for 5 hours to serve as activated silicon and aluminum sources for later use.
[0097] (2) Molecular sieve gel III was prepared according to the molar ratio of SiO2:Al2O3:Na2O:H2O = 35:1:8:1800:
[0098] Take 180g of deionized water into a beaker, add 0.89g of NaOH, and stir continuously until completely dissolved; weigh 9g of the activated coarse-porous silica gel from step (1) and add it to the NaOH solution, stir at 30℃ for 5h to obtain molecular sieve gel I; add 1.8g of the activated aluminum sulfate from step (1), and continue stirring at 30℃ for 1h to obtain molecular sieve gel II; add 4.42g of the liquid directing agent from the preparation example, and then continue stirring at 30℃ for 1h to obtain molecular sieve gel III;
[0099] (3) Transfer the molecular sieve gel III to a crystallization kettle with a polytetrafluoroethylene liner, and let it stand at 150°C for crystallization for 72 hours. After crystallization, filter the crystallized product under reduced pressure, wash it with water until neutral, and dry it at 120°C to obtain the Na-type molecular sieve product.
[0100] Figure 5 XRD results indicate that the product is ZSM-5 molecular sieve with a relative crystallinity of 96%.
[0101] Example 6
[0102] This embodiment provides a method for synthesizing Na-type ZSM-5 molecular sieves, specifically including the following steps:
[0103] (1) Dry coarse-pore silica gel and aluminum sulfate in an oven at 120°C for 5 hours; then calcine them in a muffle furnace at 650°C for 6 hours to serve as activated silicon and aluminum sources for later use.
[0104] (2) Molecular sieve gel III was prepared according to the molar ratio of SiO2:Al2O3:Na2O:H2O = 35:1:8:1800:
[0105] Take 180g of deionized water into a beaker, add 0.89g of NaOH, and stir continuously until completely dissolved; weigh 9g of the activated coarse-porous silica gel from step (1) and add it to the NaOH solution, stir at 30℃ for 5h to obtain molecular sieve gel I; add 1.8g of the activated aluminum sulfate from step (1), and continue stirring at 30℃ for 1h to obtain molecular sieve gel II; add 4.42g of the liquid directing agent from the preparation example, and then continue stirring at 30℃ for 1h to obtain molecular sieve gel III;
[0106] (3) Transfer the molecular sieve gel III to a crystallization kettle with a polytetrafluoroethylene liner, and let it stand at 120°C for crystallization for 72 hours. After crystallization, filter the crystallized product under reduced pressure, wash it with water until neutral, and dry it at 120°C to obtain the Na-type molecular sieve product.
[0107] Figure 6 XRD results indicate that the product is ZSM-5 molecular sieve with a relative crystallinity of 90%.
[0108] Example 7
[0109] This embodiment provides a method for synthesizing Na-type ZSM-5 molecular sieves, specifically including the following steps:
[0110] (1) Dry coarse-pore silica gel and aluminum sulfate in an oven at 120°C for 5 hours; then calcine them in a muffle furnace at 650°C for 6 hours to serve as activated silicon and aluminum sources for later use.
[0111] (2) Molecular sieve gel III was prepared according to the molar ratio of SiO2:Al2O3:Na2O:H2O = 35:1:8:1800:
[0112] Take 180g of deionized water into a beaker, add 0.89g of NaOH, and stir continuously until completely dissolved; weigh 9g of the activated coarse-porous silica gel from step (1) and add it to the NaOH solution, stir at 30℃ for 5h to obtain molecular sieve gel I; add 1.8g of the activated aluminum sulfate from step (1), and continue stirring at 30℃ for 1h to obtain molecular sieve gel II; add 4.42g of the liquid directing agent from the preparation example, and then continue stirring at 30℃ for 1h to obtain molecular sieve gel III;
[0113] (3) Transfer the molecular sieve gel III to a crystallization kettle with a polytetrafluoroethylene liner, and let it stand at 160°C for crystallization for 24 hours. After crystallization, filter the crystallized product under reduced pressure, wash it with water until neutral, and dry it at 120°C to obtain the Na-type molecular sieve product.
[0114] Figure 7 XRD results indicate that the product is ZSM-5 molecular sieve with a relative crystallinity of 90%.
[0115] Example 8
[0116] This embodiment provides a method for synthesizing Na-type ZSM-5 molecular sieves, specifically including the following steps:
[0117] (1) Dry coarse-pore silica gel and aluminum sulfate in an oven at 120°C for 5 hours; then calcine them in a muffle furnace at 650°C for 6 hours to serve as activated silicon and aluminum sources for later use.
[0118] (2) Molecular sieve gel III was prepared according to the molar ratio of SiO2:Al2O3:Na2O:H2O = 35:1:8:1800:
[0119] Take 180g of deionized water into a beaker, add 0.89g of NaOH, and stir continuously until completely dissolved; weigh 9g of the activated coarse-porous silica gel from step (1) and add it to the NaOH solution, stir at 30℃ for 5h to obtain molecular sieve gel I; add 1.8g of the activated aluminum sulfate from step (1), and continue stirring at 30℃ for 1h to obtain molecular sieve gel II; add 4.42g of the liquid directing agent from the preparation example, and then continue stirring at 30℃ for 1h to obtain molecular sieve gel III;
[0120] (3) Transfer the molecular sieve gel III to a crystallization kettle with a polytetrafluoroethylene liner, and let it stand at 160°C for crystallization for 48 hours. After crystallization, filter the crystallized product under reduced pressure, wash it with water until neutral, and dry it at 120°C to obtain the Na-type molecular sieve product.
[0121] Figure 8 XRD results indicate that the product is ZSM-5 molecular sieve with a relative crystallinity of 92%.
[0122] Example 9
[0123] This embodiment provides a method for synthesizing Na-type ZSM-5 molecular sieves, specifically including the following steps:
[0124] (1) Dry coarse-pore silica gel and aluminum sulfate in an oven at 120°C for 5 hours; then calcine them in a muffle furnace at 650°C for 6 hours to serve as activated silicon and aluminum sources for later use.
[0125] (2) Molecular sieve gel III was prepared according to the molar ratio of SiO2:Al2O3:Na2O:H2O = 35:1:8:1800:
[0126] Take 180g of deionized water into a beaker, add 0.89g of NaOH, and stir continuously until completely dissolved; weigh 9g of the activated coarse-porous silica gel from step (1) and add it to the NaOH solution, stir at 30℃ for 5h to obtain molecular sieve gel I; add 1.8g of the activated aluminum sulfate from step (1), and continue stirring at 30℃ for 1h to obtain molecular sieve gel II; add 4.42g of the liquid directing agent from the preparation example, and then continue stirring at 30℃ for 1h to obtain molecular sieve gel III;
[0127] (3) Transfer the molecular sieve gel III to a crystallization kettle with a polytetrafluoroethylene liner, and let it stand at 160°C for 60 hours to crystallize. After crystallization, filter the crystallized product under reduced pressure, wash it with water until it is neutral, and dry it at 120°C to obtain the Na-type molecular sieve product.
[0128] Figure 9 XRD results indicate that the product is ZSM-5 molecular sieve with a relative crystallinity of 94%.
[0129] Example 10
[0130] This embodiment provides a method for synthesizing Na-type ZSM-5 molecular sieves, specifically including the following steps:
[0131] (1) Dry coarse-pore silica gel and aluminum sulfate in an oven at 120°C for 4 hours; then calcine them in a muffle furnace at 550°C for 5 hours to serve as activated silicon and aluminum sources for later use.
[0132] (2) Molecular sieve gel III was prepared according to the molar ratio of SiO2:Al2O3:Na2O:H2O = 35:1:8:1200:
[0133] Take 120g of deionized water into a beaker, add 0.89g of NaOH, and stir continuously until completely dissolved; weigh 9g of the activated coarse-porous silica gel from step (1) and add it to the NaOH solution, stir at 30℃ for 5h to obtain molecular sieve gel I; add 1.8g of the activated aluminum sulfate from step (1), and continue stirring at 30℃ for 1h to obtain molecular sieve gel II; add 7.72g of the liquid directing agent from the preparation example, and then continue stirring at 30℃ for 1h to obtain molecular sieve gel III;
[0134] (3) Transfer the molecular sieve gel III to a crystallization kettle with a polytetrafluoroethylene liner, and let it stand at 170°C for crystallization for 72 hours. After crystallization, filter the crystallized product under reduced pressure, wash it with water until neutral, and dry it at 120°C to obtain the Na-type molecular sieve product.
[0135] Figure 10 XRD results indicate that the product is ZSM-5 molecular sieve with a relative crystallinity of 98%.
[0136] Comparative Example 1
[0137] This comparative example provides a method for preparing a material, which includes the following steps:
[0138] (1) Dry coarse-pore silica gel and aluminum sulfate in an oven at 120°C for 4 hours; then calcine them in a muffle furnace at 550°C for 5 hours to serve as activated silicon and aluminum sources for later use.
[0139] (2) Molecular sieve gel III was prepared according to the molar ratio of SiO2:Al2O3:Na2O:H2O = 35:1:8:1200:
[0140] Take 120g of deionized water into a beaker, add 0.89g of NaOH, and stir continuously until completely dissolved; weigh 9g of the activated coarse-porous silica gel from step (1) and add it to the NaOH solution, stir at 30℃ for 5h to obtain molecular sieve gel I; add 1.8g of the activated aluminum sulfate from step (1), and continue stirring at 30℃ for 1h to obtain molecular sieve gel II; add 4.42g of the liquid directing agent from the preparation example, and then continue stirring at 30℃ for 1h to obtain molecular sieve gel III;
[0141] (3) Transfer molecular sieve gel III to a crystallization kettle with a polytetrafluoroethylene liner, let it stand at 80°C for crystallization, and crystallize for 72 hours. After crystallization, filter the crystallized product under reduced pressure, wash it with water until neutral, and dry it at 120°C to obtain the product.
[0142] Figure 11 XRD results showed that the product did not exhibit the crystalline phase structure of ZSM-5 molecular sieve. This comparative example, Example 1, demonstrates that ZSM-5 molecular sieve cannot be synthesized when the crystallization temperature is outside the range required by this invention.
[0143] Comparative Example 2
[0144] This comparative example provides a method for preparing a material, which includes the following steps:
[0145] (1) Dry coarse-pore silica gel and aluminum sulfate in an oven at 120°C for 6 hours; then calcine them in a muffle furnace at 650°C for 5 hours to serve as activated silicon and aluminum sources for later use.
[0146] (2) Molecular sieve gel III was prepared according to the molar ratio of SiO2:Al2O3:Na2O:H2O = 35:1:8:1800:
[0147] Take 180g of deionized water into a beaker, add 0.89g of NaOH, and stir continuously until completely dissolved; weigh 9g of the activated coarse-porous silica gel from step (1) and add it to the NaOH solution, stir at 30℃ for 5h to obtain molecular sieve gel I; add 1.8g of the activated aluminum sulfate from step (1), and continue stirring at 30℃ for 1h to obtain molecular sieve gel II; add 4.42g of the liquid directing agent from the preparation example, and then continue stirring at 30℃ for 1h to obtain molecular sieve gel III;
[0148] (3) Transfer the molecular sieve gel III to a crystallization kettle with a polytetrafluoroethylene liner, let it stand at 150°C for crystallization, and let it crystallize for 20 hours. After crystallization, filter the crystallized product under reduced pressure, wash it with water until it is neutral, and dry it at 120°C to obtain the product.
[0149] Figure 12 The XRD results showed that the product did not exhibit the crystalline phase structure of ZSM-5 molecular sieve; this comparative example, Example 5, demonstrates that ZSM-5 molecular sieve cannot be synthesized when the crystallization time is outside the range required by this invention.
[0150] Comparative Example 3
[0151] This comparative example provides a method for preparing a material, which includes the following steps:
[0152] (1) Dry coarse-pore silica gel and aluminum sulfate in an oven at 120°C for 4 hours; then calcine them in a muffle furnace at 600°C for 5 hours to serve as activated silicon and aluminum sources for later use.
[0153] (2) Molecular sieve gel III was prepared according to the molar ratio of SiO2:Al2O3:Na2O:H2O = 70:1:8:1200:
[0154] Take 120g of deionized water into a beaker, add 0.89g of NaOH, and stir continuously until completely dissolved; weigh 18.01g of the activated coarse-porous silica gel from step (1) and add it to the NaOH solution, stir at 30℃ for 5h to obtain molecular sieve gel I; add 1.8g of the activated aluminum sulfate from step (1), and continue stirring at 30℃ for 1h to obtain molecular sieve gel II; add 4.42g of the liquid directing agent from the preparation example, and then continue stirring at 30℃ for 1h to obtain molecular sieve gel III;
[0155] (3) Transfer the molecular sieve gel III to a crystallization kettle with a polytetrafluoroethylene liner, and let it stand at 170°C for crystallization for 72 hours. After crystallization, filter the crystallized product under reduced pressure, wash it with water until it is neutral, and dry it at 120°C to obtain the product.
[0156] Figure 13 The XRD results showed that the product did not exhibit the crystalline phase structure of ZSM-5 molecular sieve; this comparative example, Example 2, demonstrates that when the silica-alumina ratio of molecular sieve gel III is higher than the range required by this invention, ZSM-5 molecular sieve cannot be synthesized.
[0157] Comparative Example 4
[0158] This comparative example provides a method for preparing a material, which includes the following steps:
[0159] (1) Dry coarse-pore silica gel and aluminum sulfate in an oven at 110°C for 5 hours; then calcine them in a muffle furnace at 600°C for 6 hours to serve as activated silicon and aluminum sources for later use.
[0160] (2) Molecular sieve gel III was prepared according to the molar ratio of SiO2:Al2O3:Na2O:H2O = 35:1:20:1200:
[0161] Take 120g of deionized water into a beaker, add 3.33g of NaOH, and stir continuously until completely dissolved; weigh 9g of the activated coarse-porous silica gel from step (1) and add it to the NaOH solution, stir at 30℃ for 5h to obtain molecular sieve gel I; add 1.8g of the activated aluminum sulfate from step (1), and continue stirring at 30℃ for 1h to obtain molecular sieve gel II; add 4.42g of the liquid directing agent from the preparation example, and then continue stirring at 30℃ for 1h to obtain molecular sieve gel III;
[0162] (3) Transfer the molecular sieve gel III to a crystallization kettle with a polytetrafluoroethylene liner, and let it stand at 170°C for crystallization for 72 hours. After crystallization, filter the crystallized product under reduced pressure, wash it with water until it is neutral, and dry it at 120°C to obtain the product.
[0163] Figure 14The XRD results showed that the product did not exhibit the crystalline phase structure of ZSM-5 molecular sieve; this comparative example, Example 3, demonstrates that ZSM-5 molecular sieve cannot be synthesized when the alkali-silicon ratio of molecular sieve gel III is higher than the range required by this invention.
[0164] Comparative Example 5
[0165] This comparative example provides a method for preparing a material, which includes the following steps:
[0166] (1) Dry coarse-pore silica gel and aluminum sulfate in an oven at 120°C for 4 hours; then calcine them in a muffle furnace at 550°C for 5 hours to serve as activated silicon and aluminum sources for later use.
[0167] (2) Molecular sieve gel III was prepared according to the molar ratio of SiO2:Al2O3:Na2O:H2O = 35:1:8:2300:
[0168] Take 230g of deionized water into a beaker, add 0.89g of NaOH, and stir continuously until completely dissolved; weigh 9g of the activated coarse-porous silica gel from step (1) and add it to the NaOH solution, stir at 30℃ for 5h to obtain molecular sieve gel I; add 1.8g of the activated aluminum sulfate from step (1), and continue stirring at 30℃ for 1h to obtain molecular sieve gel II; add 4.42g of the liquid directing agent from the preparation example, and then continue stirring at 30℃ for 1h to obtain molecular sieve gel III;
[0169] (3) Transfer the molecular sieve gel III to a crystallization kettle with a polytetrafluoroethylene liner, and let it stand at 170°C for crystallization for 72 hours. After crystallization, filter the crystallized product under reduced pressure, wash it with water until it is neutral, and dry it at 120°C to obtain the product.
[0170] Figure 15 XRD results showed that the product did not exhibit the crystalline structure of ZSM-5 molecular sieve. This comparative example, Example 4, demonstrates that ZSM-5 molecular sieve cannot be synthesized when the water-to-silica ratio of molecular sieve gel III is outside the range required by this invention.
[0171] Comparative Example 6
[0172] This comparative example provides a method for preparing a material, which includes the following steps:
[0173] (1) Dry coarse-pore silica gel and aluminum sulfate in an oven at 120°C for 4 hours; then calcine them in a muffle furnace at 600°C for 5 hours to serve as activated silicon and aluminum sources for later use.
[0174] (2) Molecular sieve gel III was prepared according to the molar ratio of SiO2:Al2O3:Na2O:H2O = 20:1:8:1200:
[0175] Take 120g of deionized water into a beaker, add 0.89g of NaOH, and stir continuously until completely dissolved; weigh 5.15g of the activated coarse-porous silica gel from step (1) and add it to the NaOH solution, stir at 30℃ for 5h to obtain molecular sieve gel I; add 1.8g of the activated aluminum sulfate from step (1), and continue stirring at 30℃ for 1h to obtain molecular sieve gel II; add 4.42g of the liquid directing agent from the preparation example, and then continue stirring at 30℃ for 1h to obtain molecular sieve gel III;
[0176] (3) Transfer the molecular sieve gel III to a crystallization kettle with a polytetrafluoroethylene liner, and let it stand at 170°C for crystallization for 72 hours. After crystallization, filter the crystallized product under reduced pressure, wash it with water until it is neutral, and dry it at 120°C to obtain the product.
[0177] Figure 16 XRD results showed that the product did not exhibit the crystalline structure of ZSM-5 molecular sieve. This comparative example, Example 2, demonstrates that ZSM-5 molecular sieve cannot be synthesized when the silica-alumina ratio of molecular sieve gel III is below the range required by this invention.
[0178] Comparative Example 7
[0179] This comparative example provides a method for preparing a material, which includes the following steps:
[0180] (1) Dry coarse-pore silica gel and aluminum sulfate in an oven at 110°C for 5 hours; then calcine them in a muffle furnace at 600°C for 6 hours to serve as activated silicon and aluminum sources for later use.
[0181] (2) Molecular sieve gel III was prepared according to the molar ratio of SiO2:Al2O3:Na2O:H2O = 35:1:2:1200:
[0182] Take 120g of deionized water into a beaker, add 0.22g of NaOH, and stir continuously until completely dissolved; weigh 9g of the activated coarse-porous silica gel from step (1) and add it to the NaOH solution, stir at 30℃ for 5h to obtain molecular sieve gel I; add 1.8g of the activated aluminum sulfate from step (1), and continue stirring at 30℃ for 1h to obtain molecular sieve gel II; add 4.42g of the liquid directing agent from the preparation example, and then continue stirring at 30℃ for 1h to obtain molecular sieve gel III;
[0183] (3) Transfer the molecular sieve gel III to a crystallization kettle with a polytetrafluoroethylene liner, and let it stand at 170°C for crystallization for 72 hours. After crystallization, filter the crystallized product under reduced pressure, wash it with water until it is neutral, and dry it at 120°C to obtain the product.
[0184] Figure 17The XRD results showed that the product did not exhibit the crystalline phase structure of ZSM-5 molecular sieve; this comparative example, Example 3, demonstrates that ZSM-5 molecular sieve cannot be synthesized when the alkali-silicon ratio of molecular sieve gel III is below the range required by this invention.
[0185] Comparative Example 8
[0186] This comparative example provides a method for preparing a material, which includes the following steps:
[0187] (1) Dry coarse-pore silica gel and aluminum sulfate in an oven at 120°C for 4 hours; then calcine them in a muffle furnace at 550°C for 5 hours to serve as activated silicon and aluminum sources for later use.
[0188] (2) Molecular sieve gel III was prepared according to the molar ratio of SiO2:Al2O3:Na2O:H2O = 35:1:8:1200:
[0189] Take 120g of deionized water into a beaker, add 0.89g of NaOH, and stir continuously until completely dissolved; weigh 9g of the activated coarse-porous silica gel from step (1) and add it to the NaOH solution, stir at 30℃ for 5h to obtain molecular sieve gel I; add 1.8g of the activated aluminum sulfate from step (1), and continue stirring at 30℃ for 1h to obtain molecular sieve gel II; add 0.96g of the liquid directing agent from the preparation example, and then continue stirring at 30℃ for 1h to obtain molecular sieve gel III;
[0190] (3) Transfer the molecular sieve gel III to a crystallization kettle with a polytetrafluoroethylene liner, and let it stand at 170°C for crystallization for 72 hours. After crystallization, filter the crystallized product under reduced pressure, wash it with water until it is neutral, and dry it at 120°C to obtain the product.
[0191] Figure 18 The XRD results showed that the product was ZSM-5 molecular sieve, but the relative crystallinity was only 50%. This comparative example, Example 10, illustrates that when the liquid directing agent content of molecular sieve gel III is lower than the range required by this invention, it is difficult to synthesize ZSM-5 molecular sieve with high relative crystallinity.
[0192] Comparative Example 9
[0193] This comparative example provides a method for preparing a material, which includes the following steps:
[0194] (1) Dry coarse-pore silica gel and aluminum sulfate in an oven at 120°C for 4 hours; then calcine them in a muffle furnace at 550°C for 5 hours to serve as activated silicon and aluminum sources for later use.
[0195] (2) Molecular sieve gel III was prepared according to the molar ratio of SiO2:Al2O3:Na2O:H2O = 35:1:8:1200:
[0196] Take 120g of deionized water into a beaker, add 0.89g of NaOH, and stir continuously until completely dissolved; weigh 9g of the activated coarse-porous silica gel from step (1) and add it to the NaOH solution, stir at 30℃ for 5h to obtain molecular sieve gel I; add 1.8g of the activated aluminum sulfate from step (1), and continue stirring at 30℃ for 1h to obtain molecular sieve gel II. Without using a liquid directing agent, it is directly regarded as obtaining molecular sieve gel III;
[0197] (3) Transfer the molecular sieve gel III to a crystallization kettle with a polytetrafluoroethylene liner, and let it stand at 170°C for crystallization for 72 hours. After crystallization, filter the crystallized product under reduced pressure, wash it with water until it is neutral, and dry it at 120°C to obtain the product.
[0198] Figure 19 XRD results showed that the product did not exhibit the crystalline phase structure of ZSM-5 molecular sieve crystals. This comparative example, Example 10, demonstrates that without the addition of a liquid directing agent to molecular sieve gel III, it is difficult to synthesize ZSM-5 molecular sieves with relatively high crystallinity.
[0199] Comparative Example 10
[0200] This comparative example provides a method for preparing a material, which includes the following steps:
[0201] (1) Dry coarse-pore silica gel and aluminum sulfate in an oven at 120°C for 4 hours; then calcine them in a muffle furnace at 550°C for 5 hours to serve as activated silicon and aluminum sources for later use.
[0202] (2) Molecular sieve gel III was prepared according to the molar ratio of SiO2:Al2O3:Na2O:H2O = 35:1:8:1200:
[0203] Take 120g of deionized water into a beaker, add 0.89g of NaOH, and stir continuously until completely dissolved; weigh 9g of the activated coarse-porous silica gel from step (1) and add it to the NaOH solution, stir at 30℃ for 5h to obtain molecular sieve gel I; add 1.8g of the activated aluminum sulfate from step (1), and continue stirring at 30℃ for 1h to obtain molecular sieve gel II; add 5.92g of the liquid directing agent from the preparation example, and then continue stirring at 30℃ for 1h to obtain molecular sieve gel III;
[0204] (3) Transfer the molecular sieve gel III to a crystallization kettle with a polytetrafluoroethylene liner, and let it stand at 170°C for crystallization for 72 hours. After crystallization, filter the crystallized product under reduced pressure, wash it with water until it is neutral, and dry it at 120°C to obtain the product.
[0205] Figure 20XRD results showed that the product's crystal structure contained other impurities that did not belong to the ZSM-5 molecular sieve crystals. This comparative example, Example 10, demonstrates that when the liquid directing agent content of molecular sieve gel III exceeds the range required by this invention, it is difficult to synthesize ZSM-5 molecular sieves with relatively high crystallinity and stable crystal structure.
[0206] In this invention, the specific surface area and pore properties of the ZSM-5 molecular sieves prepared in Examples 1-10 are summarized in Table 1, and the specific surface area and pore properties of the products prepared in Comparative Examples 1-10 are summarized in Table 2.
[0207] Table 1. Specific surface area and pore properties of ZSM-5 molecular sieves synthesized in Examples 1-10
[0208]
[0209]
[0210] Table 2. Specific surface area and pore properties of the products synthesized in Comparative Examples 1-10
[0211]
[0212] As can be seen from Tables 1 and 2, the synthesis method of Na-type ZSM-5 molecular sieve provided by this invention can successfully prepare ZSM-5 molecular sieves with more microporous structures by relying solely on self-made liquid directing agents without using organic template agents or adding seed crystals. Compared with the comparative example, it has higher micropore specific surface area and micropore volume. Moreover, the raw material composition of the self-made liquid directing agent is highly similar to that of the molecular sieve raw material, avoiding complicated post-processing steps and reducing wastewater pollution and production costs.
[0213] Furthermore, the application of the products from Examples 1-2, 10 and Comparative Examples 4, 8, and 10 in the catalytic cracking of oil products was investigated. The products from the above examples and comparative examples were prepared as catalytic cracking catalysts for oil products, and their cracking capacity was tested. The specific evaluation test methods and results are as follows:
[0214] Evaluation test method: Using the products in the above examples and comparative examples as raw materials, H-type ZSM-5 molecular sieve was obtained after ammonium exchange and roasting. 10 parts by mass of H-type ZSM-5 molecular sieve were mixed with 90 parts by mass of matrix (based on the mass of matrix as 100%, the matrix contains 15% aluminum sol and 85% kaolin). After spray drying, the oil catalytic cracking catalyst was obtained. The oil was subjected to cracking reaction at 550℃, and the light oil micro-reaction activity evaluation experiment (MAT method) was carried out. The experimental results are shown in Table 3.
[0215] Table 3. Experimental results of light oil microreactor activity evaluation of catalysts prepared from products of some examples and comparative examples.
[0216] raw material Oil yield / g Gasoline content (%) MAT Example 1 0.95 45.3 66.7 Example 2 0.85 46.5 70.8 Example 10 0.93 49 69.6 Comparative Example 4 1.14 13.8 37.0 Comparative Example 8 1.13 15.1 38.5 Comparative Example 10 1.10 12.8 38.5
[0217] The Micro-Reaction Activity Index (MAT) of light oil can represent the cracking ability of a catalyst for real oil products. The higher the cracking activity of the catalyst, the higher the MAT value. As can be seen from Table 3, the catalysts prepared by mixing the ZSM-5 molecular sieves from Examples 1-2 and 10 with the matrix after ammonium exchange and calcination to obtain hydrogen-form ZSM-5 molecular sieves have better cracking ability for oil products, and the measured MAT values are all higher than those of the comparative examples.
Claims
1. A method for synthesizing Na-type ZSM-5 molecular sieves, wherein, The synthesis method includes: (1) Dry and calcine the silicon source and aluminum source to obtain activated silicon source and activated aluminum source; (2) Add the sodium-containing alkali source to water to obtain a sodium-containing alkali solution; grind the activated silicon source and add it to the sodium-containing alkali solution, and perform the first stirring to obtain molecular sieve gel I; (3) Add the activated aluminum source to molecular sieve gel I and stir for the second time to obtain molecular sieve gel II; (4) Add the liquid directing agent dropwise into molecular sieve gel II and stir for the third time to obtain molecular sieve gel III; (5) The molecular sieve gel III was crystallized, and after cooling, filtration, washing and drying, Na-type ZSM-5 molecular sieve was obtained. The molecular sieve gel III satisfies the molar ratio SiO2:Al2O3:Na2O:H2O=(25-50):1:(3-15):(800-2000); the molar ratio of the silicon source is SiO2, the molar ratio of the aluminum source is Al2O3, and the molar ratio of the sodium-containing alkali source is Na2O. The amount of the liquid directing agent added is 5%-20% of the total weight of the silicon source added to the molecular sieve gel III.
2. The synthesis method according to claim 1, wherein, The silicon source includes one or more of the following: silica, tetraethyl orthosilicate, silica gel, silica sol, and sodium silicate.
3. The synthesis method according to claim 2, wherein, The silicon source is an industrial-grade raw material, and the SiO2 content in the dry basis of the industrial-grade raw material is above 92%.
4. The synthesis method according to claim 1, wherein, The aluminum source includes one or more of boehmite, aluminum hydroxide, sodium aluminate, aluminum isopropoxide, aluminum sulfate, and boehmite.
5. The synthesis method according to claim 1, wherein, The liquid directing agent is obtained by dissolving a sodium-containing alkaline source and the silicon source activated in step (1) in water, followed by a fourth stirring process. The molar ratio of each component in the liquid guiding agent is SiO2:Na2O:H2O = 1:(0.2-2):(8-15).
6. The synthesis method according to claim 1, wherein, The roasting temperature is 500-800℃, and the roasting time is 4-8 hours.
7. The synthesis method according to claim 1, wherein, The crystallization temperature is 90-175℃, and the crystallization time is 24-80h.
8. The synthesis method according to claim 1 or 5, wherein, The first stirring condition is to stir at a uniform speed at 25-75℃ for 4-8 hours; The second stirring condition is stirring at 25-75℃ for 1-3 hours; The third stirring condition is stirring at 25-75℃ for 1-3 hours; The fourth stirring condition is to stir at a uniform speed at 40-80℃ for 4-8 hours.
9. A Na-type ZSM-5 molecular sieve, which is prepared by the synthesis method according to any one of claims 1-8.
10. The Na-type ZSM-5 molecular sieve according to claim 9, wherein, The specific surface area of the micropores in the Na-type ZSM-5 molecular sieve is 171-352 m². 2 / g, the micropore volume of the Na-type ZSM-5 molecular sieve is 0.07-0.13 cm³. 3 / g.
11. An oil catalytic cracking catalyst, which is prepared using the Na-type ZSM-5 molecular sieve as described in claim 9 or 10 as a raw material; The oil catalytic cracking catalyst comprises 5-45 parts by weight of H-type ZSM-5 molecular sieve and 55-95 parts by weight of matrix; The H-type ZSM-5 molecular sieve is obtained by ammonium exchange and calcination of the Na-type ZSM-5 molecular sieve.