Liquid guiding agent and preparation method thereof as well as Na-type ZSM-5 molecular sieve and preparation method thereof

Abstract

The invention provides a liquid guiding agent and a preparation method thereof, and a Na-type ZSM-5 molecular sieve and a preparation method thereof. The preparation method of the liquid guiding agent comprises the following steps: sequentially carrying out first drying and roasting treatment on a first silicon source to obtain a pretreated first silicon source; the method comprises the following steps: dissolving a sodium-containing alkali source in water until the sodium-containing alkali source is completely dissolved according to a molar ratio of SiO2: Na2O: H2O of 1: (0.1-4): (8-20), adding a pretreated first silicon source, and carrying out first stirring to obtain a liquid guiding agent; the preparation method is simple, easy to implement, green and efficient, the first silicon source, the sodium-containing alkali source and the water are mixed together according to a certain proportion and stirred for a certain time, the obtained light yellow gel is added into the mother liquor of silicate species, the structure-directing effect can be achieved, continuous growth of crystals is promoted, and the preparation method is suitable for large-scale production. And the use of an organic template agent in the production process of the molecular sieve material is avoided.

Description

Technical Field

[0001] This invention belongs to the field of molecular sieve preparation technology, specifically relating to a liquid directing agent and its preparation method, and a Na-type ZSM-5 molecular sieve and its preparation method. Background Technology

[0002] Ethylene and propylene, among other low-carbon olefins, are major petrochemical products and crucial raw materials for the production of downstream organic chemicals such as polyethylene, polypropylene, dichloroethylene, and acrylonitrile. The yield and production technology of low-carbon olefins are important indicators of the development level of the petrochemical industry; therefore, vigorously developing low-carbon olefin production technologies is of great significance. Currently, low-carbon olefins such as ethylene and propylene are mainly derived from hydrocarbon steam cracking (thermal cracking) and catalytic cracking technologies. Although steam cracking technology still dominates the production of low-carbon olefins, it requires temperatures of 800℃ and above, suffers from high CO2 emissions, low yields of target products, high energy consumption, and high emissions. Catalytic cracking, on the other hand, relatively lowers the reaction temperature, increases product yield, and allows for adjustable product distribution, making it a major research direction for low-carbon olefin production technology.

[0003] The catalyst is crucial in catalytic cracking processes. Solid acid catalysts, such as ZSM-5 molecular sieves, have become important catalysts for the catalytic cracking production of low-carbon olefins due to their unique three-dimensional pore structure, shape-selective properties, tunable silica-alumina ratio, acidity, and good hydrothermal stability. Currently, the synthesis of ZSM-5 molecular sieves mainly includes: template-added systems, template-free systems, and seed-added synthesis systems. Several methods for synthesizing ZSM-5 molecular sieves have been reported, such as: hydrothermal synthesis using tetrapropylammonium hydroxide as a template agent (Zou Yangyang, Zhu Peng, Lü Xiaohuan, et al. Synthesis and optimization of hierarchical porous ZSM-5 nanocrystalline aggregate molecular sieves [J]. Modern Chemical Industry, 2024, 44(1):171-176), seed-assisted precrystallization method (Wang Hanbin, Zhang Peng, Yang Fan, et al. Synthesis of nano ZSM-5 molecular sieves by seed-assisted precrystallization method and its application in propane aromatization reaction [J], Low Carbon Chemistry and Chemical Engineering, 2024, 49(2):67-73,104), and solvent-free method using tetrapropylammonium bromide as a template agent (Wang Fupeng, Liu Jia, Guo Ziyang, et al. Solvent-free synthesis of hierarchical porous ZSM-5 molecular sieves and study on propane aromatization reaction performance [J], 2022, 19(51):23-27). It should be noted that all of the above inventions incorporate organic template agents. The addition of template agents has two main effects on the synthesis of molecular sieves: (1) template effect; (2) structure guiding effect. Although the molecular sieves synthesized with the addition of template agents can obtain higher crystallinity and smaller particle size, the use of organic template agents has the following disadvantages: (1) The production process of organic template agents is extremely complicated and it is difficult to achieve large-scale industrial production; (2) The production cost of organic template agents accounts for about 50%-70% of the molecular sieve synthesis cost, which is not conducive to reducing the production cost of molecular sieves; (3) As a classic synthesis method for molecular sieves, the hydrothermal synthesis method often has a yield of no more than 80%. The mother liquor that has not been crystallized still contains a large amount of template agent, and the template agent is not used efficiently, resulting in a waste of production costs; (4) The alkaline solution containing organic amine template agents is highly alkaline and easily forms difficult-to-treat, high-concentration ammonia nitrogen wastewater, which can easily cause environmental pollution.

[0004] Therefore, there is an urgent need to develop a green, environmentally friendly, and economically feasible synthetic route for ZSM-5 molecular sieves. Providing a method for synthesizing ZSM-5 molecular sieves that does not use organic template agents or even organic materials is of great significance. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a liquid directing agent and its preparation method, as well as a Na-type ZSM-5 molecular sieve and its preparation method. By employing a first silicon source and under appropriate proportions, a liquid directing agent can be prepared for the green synthesis of ZSM-5 molecular sieves, reducing environmental pollution.

[0006] To achieve the above objectives, the present invention provides a method for preparing a liquid directing agent, wherein the preparation method includes:

[0007] (1) The first silicon source is subjected to a first drying and calcination treatment in sequence to obtain the pretreated first silicon source;

[0008] (2) According to the molar ratio of SiO2:Na2O:H2O=1:(0.1-4):(8-20), the sodium-containing alkali source is dissolved in water until completely dissolved, and the pretreated first silicon source is added. After the first stirring, a liquid directing agent is obtained; wherein, the molar ratio of the sodium-containing alkali source is calculated as Na2O, and the molar ratio of the first silicon source is calculated as SiO2.

[0009] According to a specific embodiment of the present invention, preferably, the first silicon source includes one or a combination of two or more of sodium silicate, silica gel, silica sol, silica fume, and quartz sand; more preferably, it is silica gel, which includes one or a combination of two or more of coarse-pore silica gel (also known as type C silica gel), fine-pore silica gel, and type B silica gel. The silica gel is chemically stable, does not react with other substances except for strong alkalis and hydrofluoric acid, and has good thermal stability and high mechanical strength.

[0010] According to a specific embodiment of the present invention, preferably, the first 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%.

[0011] In some specific embodiments, preferably, based on the total dry weight of the silica gel as 100%, the content of SiO2 in the dry weight is above 98%, the content of Na2O is 0.06-0.08%, and the remainder is alkaline earth metal oxides, rare earth metal oxides, and impurities.

[0012] In some specific embodiments, preferably, the sodium-containing alkali source includes NaOH and / or Na2O.

[0013] According to a specific embodiment of the present invention, preferably, the calcination temperature is 500-800°C, and the calcination time is 2-6 hours. Calcination activates the first silicon source at high temperature and removes impurities.

[0014] According to a specific embodiment of the present invention, preferably, the first stirring is carried out in a water bath at a temperature of 35-80°C for 4-20 hours. More preferably, the first stirring is carried out in a water bath at 50°C for 8 hours.

[0015] According to a specific embodiment of the present invention, preferably, the molar ratio of the sodium-containing alkali source to the first silicon source is (0.2-4):1. More preferably, the molar ratio of the raw materials of the liquid directing agent is SiO2:Na2O:H2O = 1:(0.2-2):(8-15).

[0016] In some specific embodiments, preferably, the first drying condition is to dry in an oven at a temperature of 90-120°C until constant weight is achieved.

[0017] The present invention also provides a liquid directing agent, which is prepared by the above-described preparation method. The liquid directing agent is an active, pale yellow gel.

[0018] According to a specific embodiment of the present invention, preferably, the viscosity of the liquid directing agent is 45cp-200cp.

[0019] This invention also provides a method for preparing Na-type ZSM-5 molecular sieves, wherein the preparation method includes:

[0020] The above-mentioned liquid directing agent was added to the ZSM-5 synthetic gel, and a second stirring aging process was performed to obtain an aged gel. After crystallization, cooling, filtration, washing, and a second drying process, Na-type ZSM-5 molecular sieve was obtained. The molar ratio of the components in the aged gel was SiO2:Al2O3:Na2O:H2O = (25-50):1:(3-15):(800-2000). The calculation of the molar ratio in the aged gel included the liquid directing agent.

[0021] In some specific implementations, preferably, the second stirring aging time is 1-3 hours.

[0022] According to a specific embodiment of the present invention, preferably, the ZSM-5 synthetic gel is obtained by mixing and stirring a second silicon source, an aluminum source, a second sodium-containing alkali source and water; the molar ratio of the second silicon source is SiO2, the molar ratio of the aluminum source is Al2O3, and the molar ratio of the second sodium-containing alkali source is Na2O.

[0023] According to a specific embodiment of the present invention, preferably, the amount of liquid directing agent added is 5%-20% of the total weight of the first silicon source and the second silicon source added to the aging gel.

[0024] According to a specific embodiment of the present invention, preferably, the second silicon source includes one or more combinations of tetraethyl orthosilicate, silica gel, silica sol, silica fume, and quartz sand; and / or, the aluminum source includes one or more combinations of sodium aluminate, aluminum isopropoxide, aluminum sulfate, boehmite, and boehmite. The silica gel includes one or more combinations of coarse-pore silica gel (also known as type C silica gel), fine-pore silica gel, and type B silica gel.

[0025] In some specific embodiments, preferably, the second sodium-containing alkali source includes NaOH and / or Na2O.

[0026] According to a specific embodiment of the present invention, preferably, the crystallization temperature is 120-170℃, and the crystallization time is 48-96 hours. The crystallization process is carried out in a polytetrafluoroethylene-lined reactor. After crystallization, the reactor is naturally cooled to room temperature, filtered and washed, and dried overnight at 110℃ to obtain Na-type ZSM-5 molecular sieve.

[0027] The present invention also provides a Na-type ZSM-5 molecular sieve, which is prepared by the above preparation method.

[0028] According to a specific embodiment of the present invention, preferably, the microporous specific surface area of ​​the Na-type ZSM-5 molecular sieve is 310-353 m². 2 / g, the micropore volume of the Na-type ZSM-5 molecular sieve is 0.07-0.14 cm³. 3 / g.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] (1) The preparation method of the liquid guiding agent provided by the present invention is simple, easy, green and efficient. It only requires mixing the first silicon source, sodium-containing alkali source and water together in a certain ratio and stirring for a certain time. The resulting light yellow gel can be added to the mother liquor of silicate species to play a structural guiding role and promote the continuous growth of crystals.

[0031] (2) The liquid directing agent provided by the present invention has low production cost and is economically feasible. The industrial-grade first silicon source raw material used has relatively stable chemical properties, and its production cost is low and its sources are wide, which is closer to the industrial application of molecular sieve synthesis.

[0032] (3) The raw materials of the liquid directing agent provided by the present invention can be the same as the silicon source in the molecular sieve synthesis system using the liquid directing agent, so that in the final synthesis system of the liquid directing agent, there are only four types of raw materials: silicon source, aluminum source, alkali source and deionized water. This simplifies the types of raw materials in the molecular sieve synthesis system, makes it easier to explore the synthesis mechanism of molecular sieve crystals, and avoids the use of organic template agents in the production process of molecular sieve materials. Attached Figure Description

[0033] Figure 1 The image shows the XRD pattern of the ZSM-5 molecular sieve synthesized in Example 1.

[0034] Figure 2 The XRD pattern of the ZSM-5 molecular sieve synthesized in Example 2 is shown.

[0035] Figure 3 The image shows the XRD pattern of the ZSM-5 molecular sieve synthesized in Example 3.

[0036] Figure 4 The image shows the XRD pattern of the ZSM-5 molecular sieve synthesized in Example 4.

[0037] Figure 5 The image shows the XRD pattern of the ZSM-5 molecular sieve synthesized in Example 5.

[0038] Figure 6 The XRD pattern of the ZSM-5 molecular sieve synthesized in Example 6 is shown.

[0039] Figure 7 The image shows the XRD pattern of the ZSM-5 molecular sieve synthesized in Example 7.

[0040] Figure 8 The XRD pattern of the ZSM-5 molecular sieve synthesized in Example 8 is shown.

[0041] Figure 9 The XRD pattern of the ZSM-5 molecular sieve synthesized in Example 9 is shown.

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

[0043] Figure 11 The image shows the XRD pattern of the ZSM-5 molecular sieve synthesized in Example 11.

[0044] Figure 12 The XRD pattern of the ZSM-5 molecular sieve synthesized in Example 12 is shown.

[0045] Figure 13 The XRD pattern of the ZSM-5 molecular sieve synthesized in Example 13 is shown.

[0046] Figure 14 The image shows the XRD pattern of the product synthesized in Comparative Example 1.

[0047] Figure 15 The image shows the XRD pattern of the product synthesized in Comparative Example 2.

[0048] Figure 16 The XRD pattern of the product synthesized in Comparative Example 3 is shown.

[0049] Figure 17 The image shows the XRD pattern of the product synthesized in Comparative Example 4.

[0050] Figure 18 The XRD pattern of the product synthesized in Comparative Example 5 is shown.

[0051] Figure 19 The XRD pattern of the product synthesized in Comparative Example 6 is shown.

[0052] Figure 20 The XRD pattern of the product synthesized in Comparative Example 7 is shown.

[0053] Figure 21 The XRD pattern of the product synthesized in Comparative Example 8 is shown.

[0054] Figure 22 The XRD pattern of the product synthesized in Comparative Example 9 is shown.

[0055] Figure 23 The XRD pattern of the product synthesized in Comparative Example 10.

[0056] Figure 24 The XRD pattern of the product synthesized in Comparative Example 11. Detailed Implementation

[0057] 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.

[0058] Sources of raw materials or equipment: Coarse-pore silica gel, industrial grade, SiO2 content > 99%; Type B silica gel, industrial grade, SiO2 content > 99%; Fine-pore silica gel, industrial grade, SiO2 content > 92%; Sodium hydroxide, analytical grade; Deionized water, prepared in the laboratory.

[0059] Evaluation and analysis methods: X-ray fluorescence spectroscopy; X-ray diffraction; scanning electron microscopy; N2- adsorption-desorption technique.

[0060] Example 1

[0061] This embodiment provides a method for preparing a liquid directing agent and a Na-type ZSM-5 molecular sieve, specifically including the following steps:

[0062] (1) Place a sufficient amount of coarse-pore silica gel in an oven and dry it at 120°C until constant weight. Then place it in a muffle furnace at 600°C and calcine for 2 hours to activate it at high temperature and remove impurities.

[0063] (2) At room temperature, according to the molar ratio SiO2:Na2O:H2O=1:0.25:10, first add 11.67g NaOH to 105g deionized water until dissolved, then add 38.19g coarse-porous silica gel, stir vigorously with a glass rod until uniform, and finally heat and stir in a 45℃ water bath for 6h to form a light yellow gel, thus obtaining a liquid directing agent;

[0064] (3) Add appropriate amounts of coarse-pore silica gel, aluminum sulfate, sodium hydroxide and deionized water to the container, stir at room temperature for 5 hours to obtain ZSM-5 synthetic gel, then add 1.96g of the above liquid directing agent, and stir for 1 hour to obtain an aged gel with a molar ratio of SiO2:Al2O3:Na2O:H2O=40:1:15:1800; transfer the aged gel to a crystallization kettle and crystallize at 170℃ for 70 hours; after crystallization, wash with water, filter and dry to obtain Na-type molecular sieve product;

[0065] Figure 1 XRD results indicate that the product is a ZSM-5 molecular sieve with a relative crystallinity of 95% and a specific surface area of ​​391.19 m² based on BET analysis. 2 / g.

[0066] Example 2

[0067] This embodiment provides a method for preparing a liquid directing agent and a Na-type ZSM-5 molecular sieve, specifically including the following steps:

[0068] (1) Place a sufficient amount of coarse-pore silica gel in an oven and dry it at 120°C until constant weight. Then place it in a muffle furnace at 600°C and calcine for 4 hours to activate it at high temperature and remove impurities.

[0069] (2) At room temperature, according to the molar ratio SiO2:Na2O:H2O=1:0.5:10, first add 23.34g NaOH to 105g deionized water until dissolved, then add 38.19g coarse-porous silica gel, stir vigorously with a glass rod until uniform, and finally heat and stir in a 45℃ water bath for 8h to form a light yellow gel, thus obtaining a liquid directing agent;

[0070] (3) Add appropriate amounts of coarse-pore silica gel, aluminum sulfate, sodium hydroxide and deionized water to the container, stir at room temperature for 5 hours to obtain ZSM-5 synthetic gel, then add 1.96g of the above liquid directing agent, and stir for 1 hour to obtain an aged gel with a molar ratio of SiO2:Al2O3:Na2O:H2O=40:1:15:1800; transfer the aged gel to a crystallization kettle and crystallize at 170℃ for 70 hours; after crystallization, wash with water, filter and dry to obtain Na-type molecular sieve product;

[0071] Figure 2 XRD results indicate that the product is ZSM-5 molecular sieve with a relative crystallinity of 90% and a specific surface area of ​​372.99 m² / g based on BET analysis. 2 / g.

[0072] Example 3

[0073] This embodiment provides a method for preparing a liquid directing agent and a Na-type ZSM-5 molecular sieve, specifically including the following steps:

[0074] (1) Place a sufficient amount of coarse-pore silica gel in an oven and dry it at 120°C until constant weight. Then place it in a muffle furnace at 550°C and calcine for 6 hours to activate it at high temperature and remove impurities.

[0075] (2) At room temperature, according to the molar ratio SiO2:Na2O:H2O=1:1:10, first add 35.01g NaOH to 105g deionized water until dissolved, then add 38.19g coarse-porous silica gel, stir vigorously with a glass rod until uniform, and finally heat and stir in a 45℃ water bath for 10h to form a light yellow gel, thus obtaining a liquid directing agent;

[0076] (3) Add appropriate amounts of coarse-pore silica gel, aluminum sulfate, sodium hydroxide and deionized water to the container, stir at room temperature for 5 hours to obtain ZSM-5 synthetic gel, then add 1.96g of the above liquid directing agent, and stir for 1 hour to obtain an aged gel with a molar ratio of SiO2:Al2O3:Na2O:H2O=40:1:15:1800; transfer the aged gel to a crystallization kettle and crystallize at 170℃ for 70 hours; after crystallization, wash with water, filter and dry to obtain Na-type molecular sieve product;

[0077] Figure 3 XRD results indicate that the product is ZSM-5 molecular sieve with a relative crystallinity of 92% and a specific surface area of ​​364.46 m² based on BET analysis. 2 / g.

[0078] Example 4

[0079] This embodiment provides a method for preparing a liquid directing agent and a Na-type ZSM-5 molecular sieve, specifically including the following steps:

[0080] (1) Place a sufficient amount of coarse-pore silica gel in an oven and dry it at 120°C until constant weight. Then place it in a muffle furnace at 600°C and calcine for 2 hours to activate it at high temperature and remove impurities.

[0081] (2) At room temperature, according to the molar ratio SiO2:Na2O:H2O=1:0.25:10, first add 11.67g NaOH to 105g deionized water until dissolved, then add 38.19g coarse-porous silica gel, stir vigorously with a glass rod until uniform, and finally heat and stir in a 60℃ water bath for 8h to form a light yellow gel, thus obtaining a liquid directing agent;

[0082] (3) Add appropriate amounts of coarse-pore silica gel, aluminum sulfate, sodium hydroxide and deionized water to the container, stir at room temperature for 5 hours to obtain ZSM-5 synthetic gel, then add 1.96g of the above liquid directing agent, and stir for 1 hour to obtain an aged gel with a molar ratio of SiO2:Al2O3:Na2O:H2O=40:1:15:1800; transfer the aged gel to a crystallization kettle and crystallize at 170℃ for 70 hours; after crystallization, wash with water, filter and dry to obtain Na-type molecular sieve product;

[0083] Figure 4 XRD results indicate that the product is ZSM-5 molecular sieve with a relative crystallinity of 95% and a specific surface area of ​​359.83 m² / g based on BET analysis. 2 / g.

[0084] Example 5

[0085] This embodiment provides a method for preparing a liquid directing agent and a Na-type ZSM-5 molecular sieve, specifically including the following steps:

[0086] (1) Place a sufficient amount of coarse-pore silica gel in an oven and dry it at 120°C until constant weight. Then place it in a muffle furnace at 600°C and calcine for 5 hours to activate it at high temperature and remove impurities.

[0087] (2) At room temperature, according to the molar ratio SiO2:Na2O:H2O=1:0.25:10, first add 11.67g NaOH to 105g deionized water until dissolved, then add 38.19g coarse-porous silica gel, stir vigorously with a glass rod until uniform, and finally heat and stir in a 70℃ water bath for 8h to form a light yellow gel, thus obtaining a liquid directing agent;

[0088] (3) Add appropriate amounts of coarse-pore silica gel, aluminum sulfate, sodium hydroxide and deionized water to the container, stir at room temperature for 5 hours to obtain ZSM-5 synthetic gel, then add 1.96g of the above liquid directing agent, and stir for 1 hour to obtain an aged gel with a molar ratio of SiO2:Al2O3:Na2O:H2O=40:1:15:1800; transfer the aged gel to a crystallization kettle and crystallize at 170℃ for 70 hours; after crystallization, wash with water, filter and dry to obtain Na-type molecular sieve product;

[0089] Figure 5 XRD results indicate that the product is ZSM-5 molecular sieve with a relative crystallinity of 93% and a specific surface area of ​​377.05 m² / g based on BET analysis. 2 / g.

[0090] Example 6

[0091] This embodiment provides a method for preparing a liquid directing agent and a Na-type ZSM-5 molecular sieve, specifically including the following steps:

[0092] (1) Place a sufficient amount of coarse-pore silica gel in an oven and dry it at 120°C until constant weight. Then place it in a muffle furnace at 600°C and calcine for 4 hours to activate it at high temperature and remove impurities.

[0093] (2) At room temperature, according to the molar ratio SiO2:Na2O:H2O=1:0.25:18, first add 11.67g NaOH to 189g deionized water until dissolved, then add 38.19g coarse-porous silica gel, stir vigorously with a glass rod until uniform, and finally heat and stir in a 60℃ water bath for 8h to form a light yellow gel, thus obtaining a liquid directing agent;

[0094] (3) Add appropriate amounts of coarse-pore silica gel, aluminum sulfate, sodium hydroxide and deionized water to the container, stir at room temperature for 5 hours to obtain ZSM-5 synthetic gel, then add 1.96g of the above liquid directing agent, and stir for 1 hour to obtain an aged gel with a molar ratio of SiO2:Al2O3:Na2O:H2O=40:1:15:1800; transfer the aged gel to a crystallization kettle and crystallize at 170℃ for 70 hours; after crystallization, wash with water, filter and dry to obtain Na-type molecular sieve product;

[0095] Figure 6 XRD results indicate that the product is ZSM-5 molecular sieve with a relative crystallinity of 88% and a specific surface area of ​​396.96 m² based on BET analysis. 2 / g.

[0096] Example 7

[0097] This embodiment provides a method for preparing a liquid directing agent and a Na-type ZSM-5 molecular sieve, specifically including the following steps:

[0098] (1) Place sufficient silica in an oven and dry it at 120°C until constant weight. Then place it in a muffle furnace at 700°C and calcine for 2 hours to activate it at high temperature and remove impurities.

[0099] (2) At room temperature, according to the molar ratio SiO2:Na2O:H2O=1:0.2:10, first add 9.34g NaOH to 105g deionized water until dissolved, then add 28.98g white carbon black, stir vigorously with a glass rod until uniform, and finally put it into a 60℃ water bath for heating and stirring for 6h to form a light yellow gel, thus obtaining a liquid directing agent;

[0100] (3) Add appropriate amounts of silica, aluminum sulfate, sodium hydroxide and deionized water to the container, stir at room temperature for 5 hours to obtain ZSM-5 synthetic gel, then add 1.96g of the above liquid directing agent, and stir for 1 hour to obtain an aged gel with a molar ratio of SiO2:Al2O3:Na2O:H2O=40:1:15:1800; transfer the aged gel to a crystallization kettle and crystallize at 170℃ for 70 hours; after crystallization, wash with water, filter and dry to obtain Na-type molecular sieve product;

[0101] Figure 7 XRD results indicate that the product is ZSM-5 molecular sieve with a relative crystallinity of 95% and a specific surface area of ​​357.43 m² / g based on BET analysis. 2 / g.

[0102] Example 8

[0103] This embodiment provides a method for preparing a liquid directing agent and a Na-type ZSM-5 molecular sieve, specifically including the following steps:

[0104] (1) Place a sufficient amount of coarse-pore silica gel in an oven and dry it at 120°C until constant weight. Then place it in a muffle furnace at 800°C and calcine for 3 hours to activate it at high temperature and remove impurities.

[0105] (2) At room temperature, according to the molar ratio SiO2:Na2O:H2O=1:0.5:10, first add 23.34g NaOH to 105g deionized water until dissolved, then add 28.98g white carbon black, stir vigorously with a glass rod until uniform, and finally heat and stir in a 60℃ water bath for 12h to form a light yellow gel, thus obtaining a liquid directing agent;

[0106] (3) Add appropriate amounts of coarse-pore silica gel, sodium aluminate, sodium hydroxide, and deionized water to the container. Stir at room temperature for 5 hours to obtain ZSM-5 synthetic gel. Then add 1.96g of the above liquid directing agent and stir for 1 hour to obtain an aged gel with a molar ratio of SiO2:Al2O3:Na2O:H2O=40:1:15:1800. Transfer the aged gel to a crystallization kettle and crystallize at 170℃ for 70 hours. After crystallization, wash with water, filter, and dry to obtain Na-type molecular sieve product.

[0107] Figure 8 XRD results indicate that the product is ZSM-5 molecular sieve with a relative crystallinity of 97% and a specific surface area of ​​368.32 m² / g based on BET analysis. 2 / g.

[0108] Example 9

[0109] This embodiment provides a method for preparing a liquid directing agent and a Na-type ZSM-5 molecular sieve, specifically including the following steps:

[0110] (1) Place sufficient silica sol in an oven and dry it at 120°C until constant weight. Then place it in a muffle furnace at 700°C and calcine for 5 hours to activate it at high temperature and remove impurities.

[0111] (2) At room temperature, according to the molar ratio SiO2:Na2O:H2O=1:0.6:20, first add 37.34g NaOH to 210g deionized water until dissolved, then add 28.98g silica sol, stir vigorously with a glass rod until uniform, and finally heat and stir in a 50℃ water bath for 8h to form a light yellow gel, thus obtaining a liquid directing agent;

[0112] (3) Add appropriate amounts of silica sol, sodium aluminate, sodium hydroxide, and deionized water to the container. Stir at room temperature for 5 hours to obtain ZSM-5 synthetic gel. Then add 1.96g of the above liquid directing agent and stir for 1 hour to obtain an aged gel with a molar ratio of SiO2:Al2O3:Na2O:H2O=40:1:15:1800. Transfer the aged gel to a crystallization kettle and crystallize at 170℃ for 70 hours. After crystallization, wash with water, filter, and dry to obtain Na-type molecular sieve product.

[0113] Figure 9 XRD results indicate that the product is ZSM-5 molecular sieve with a relative crystallinity of 96% and a specific surface area of ​​384.23 m² based on BET analysis. 2 / g.

[0114] Example 10

[0115] This embodiment provides a method for preparing a liquid directing agent and a Na-type ZSM-5 molecular sieve, specifically including the following steps:

[0116] (1) Place a sufficient amount of coarse-pore silica gel in an oven and dry it at 120°C until constant weight. Then place it in a muffle furnace at 600°C and calcine for 4 hours to activate it at high temperature and remove impurities.

[0117] (2) At room temperature, according to the molar ratio SiO2:Na2O:H2O=1:0.25:10, first add 11.67g NaOH to 105g deionized water until dissolved, then add 38.19g coarse-porous silica gel, stir vigorously with a glass rod until uniform, and finally heat and stir in a 45℃ water bath for 8h to form a light yellow gel, thus obtaining a liquid directing agent;

[0118] (3) Add appropriate amounts of coarse-pore silica gel, aluminum sulfate, sodium hydroxide and deionized water to the container, stir at room temperature for 5 hours to obtain ZSM-5 synthetic gel, then add 7.72g of the above liquid directing agent, and stir for 1 hour to obtain an aged gel with a molar ratio of SiO2:Al2O3:Na2O:H2O=40:1:15:1800; transfer the aged gel to a crystallization kettle and crystallize at 170℃ for 70 hours; after crystallization, wash with water, filter and dry to obtain Na-type molecular sieve product;

[0119] XRD results indicate that the product is a ZSM-5 molecular sieve with a relative crystallinity of 99% and a specific surface area of ​​389.16 m² based on BET measurements. 2 / g. Figure 10 The SEM images show the morphology of the ZSM-5 molecular sieve prepared in this embodiment.

[0120] Example 11

[0121] This embodiment provides a method for preparing a liquid directing agent and a Na-type ZSM-5 molecular sieve, specifically including the following steps:

[0122] (1) Place sufficient quartz sand in an oven and dry it at 120°C until constant weight. Then place it in a muffle furnace at 600°C and calcine for 4 hours to activate it at high temperature and remove impurities.

[0123] (2) At room temperature, according to the molar ratio SiO2:Na2O:H2O=1:0.25:10, first add 11.67g NaOH to 105g deionized water until dissolved, then add 30.29g quartz sand, stir vigorously with a glass rod until uniform, and finally heat and stir in a 45℃ water bath for 8h to form a light yellow gel, thus obtaining a liquid directing agent;

[0124] (3) Add appropriate amounts of quartz sand, aluminum sulfate, sodium hydroxide, and deionized water to the container. Stir at room temperature for 5 hours to obtain ZSM-5 synthetic gel. Then add 7.72g of the above liquid directing agent and stir for 1 hour to obtain an aged gel with a molar ratio of SiO2:Al2O3:Na2O:H2O=40:1:15:1800. Transfer the aged gel to a crystallization kettle and crystallize at 170℃ for 70 hours. After crystallization, wash with water, filter, and dry to obtain Na-type molecular sieve product.

[0125] Figure 11 XRD results indicate that the product is ZSM-5 molecular sieve with a relative crystallinity of 101% and a specific surface area of ​​405.28 m² based on BET analysis. 2 / g.

[0126] Example 12

[0127] This embodiment provides a method for preparing a liquid directing agent and a Na-type ZSM-5 molecular sieve, specifically including the following steps:

[0128] (1) Place a sufficient amount of type B silicone in an oven and dry it at 120°C until constant weight. Then place it in a muffle furnace at 600°C and calcine for 4 hours to activate it at high temperature and remove impurities.

[0129] (2) At room temperature, according to the molar ratio SiO2:Na2O:H2O=1:0.25:10, first add 11.67g NaOH to 105g deionized water until dissolved, then add 42.64g type B silica gel, stir vigorously with a glass rod until uniform, and finally heat and stir in a 45℃ water bath for 7h to form a light yellow gel, thus obtaining a liquid directing agent;

[0130] (3) Add appropriate amounts of type B silica gel, aluminum sulfate, sodium hydroxide and deionized water to the container, stir at room temperature for 5 hours to obtain ZSM-5 synthetic gel, then add 7.72g of the above liquid directing agent, and stir for 1 hour to obtain an aged gel with a molar ratio of SiO2:Al2O3:Na2O:H2O=40:1:15:1800; transfer the aged gel to a crystallization kettle and crystallize at 170℃ for 70 hours; after crystallization, wash with water, filter and dry to obtain Na-type molecular sieve product;

[0131] Figure 12 XRD results indicate that the product is ZSM-5 molecular sieve with a relative crystallinity of 100% and a specific surface area of ​​400.96 m² / g based on BET analysis. 2 / g.

[0132] Example 13

[0133] This embodiment provides a method for preparing a liquid directing agent and a Na-type ZSM-5 molecular sieve, specifically including the following steps:

[0134] (1) Place a sufficient amount of fine-pore silica gel in an oven and dry it at 120°C until constant weight. Then place it in a muffle furnace at 550°C and calcine for 4 hours to activate it at high temperature and remove impurities.

[0135] (2) At room temperature, according to the molar ratio SiO2:Na2O:H2O=1:0.25:10, first add 11.67g NaOH to 105g deionized water until dissolved, then add 36.35g fine-pore silica gel, stir vigorously with a glass rod until uniform, and finally heat and stir in a 45℃ water bath for 6h to form a light yellow gel, thus obtaining a liquid directing agent;

[0136] (3) Add appropriate amounts of fine-pore silica gel, aluminum sulfate, sodium hydroxide and deionized water to the container, stir at room temperature for 5 hours to obtain ZSM-5 synthetic gel, then add 1.96g of the above liquid directing agent, and stir for 1 hour to obtain an aged gel with a molar ratio of SiO2:Al2O3:Na2O:H2O=40:1:15:1800; transfer the aged gel to a crystallization kettle and crystallize at 170℃ for 70 hours; after crystallization, wash with water, filter and dry to obtain Na-type molecular sieve product;

[0137] Figure 13 XRD results indicate that the product is ZSM-5 molecular sieve with a relative crystallinity of 100% and a specific surface area of ​​399.48 m² / g based on BET analysis. 2 / g.

[0138] Comparative Example 1

[0139] This comparative example provides a method for preparing a material, specifically including the following steps:

[0140] (1) Place a sufficient amount of coarse-pore silica gel in an oven and dry it at 120°C until constant weight. Then place it in a muffle furnace at 600°C and calcine for 2 hours to activate it at high temperature and remove impurities.

[0141] (2) At room temperature, according to the molar ratio SiO2:Na2O:H2O=1:0.05:10, first add 2.33g NaOH to 105g deionized water until dissolved, then add 38.19g coarse-porous silica gel, stir vigorously with a glass rod until uniform, and finally heat and stir in a 45℃ water bath for 6h to form a light yellow gel, thus obtaining a liquid directing agent;

[0142] (3) Add appropriate amounts of coarse-pore silica gel, aluminum sulfate, sodium hydroxide, and deionized water to the container. Stir at room temperature for 5 hours to obtain ZSM-5 synthetic gel. Then add 1.96g of the above liquid directing agent and stir for 1 hour to obtain an aged gel with a molar ratio of SiO2:Al2O3:Na2O:H2O=40:1:15:1800. Transfer the aged gel to a crystallization kettle and crystallize at 170℃ for 70 hours. After crystallization, wash with water, filter, and dry to obtain the product.

[0143] Figure 14 The XRD results showed that no ZSM-5 crystalline phase was formed. This comparative example, Example 1, illustrates that ZSM-5 molecular sieves cannot be prepared when the directing agent ratio is not within the requirements of this invention.

[0144] Comparative Example 2

[0145] This comparative example provides a method for preparing a material, specifically including the following steps:

[0146] (1) Place a sufficient amount of coarse-pore silica gel in an oven and dry it at 120°C until constant weight. Then place it in a muffle furnace at 600°C and calcine for 2 hours to activate it at high temperature and remove impurities.

[0147] (2) At room temperature, according to the molar ratio SiO2:Na2O:H2O=1:5:10, first add 233.4g NaOH to 105g deionized water until dissolved, then add 38.19g coarse-porous silica gel, stir vigorously with a glass rod until uniform, and finally heat and stir in a 45℃ water bath for 6h to form a light yellow gel, thus obtaining a liquid directing agent;

[0148] (3) Add appropriate amounts of coarse-pore silica gel, aluminum sulfate, sodium hydroxide, and deionized water to the container. Stir at room temperature for 5 hours to obtain ZSM-5 synthetic gel. Then add 1.96g of the above liquid directing agent and stir for 1 hour to obtain an aged gel with a molar ratio of SiO2:Al2O3:Na2O:H2O=40:1:15:1800. Transfer the aged gel to a crystallization kettle and crystallize at 170℃ for 70 hours. After crystallization, wash with water, filter, and dry to obtain the product.

[0149] Figure 15 The XRD results showed that no ZSM-5 crystalline phase was formed. This comparative example, Example 1, illustrates that ZSM-5 molecular sieves cannot be prepared when the directing agent ratio is not within the requirements of this invention.

[0150] Comparative Example 3

[0151] This comparative example provides a method for preparing a material, specifically including the following steps:

[0152] (1) Place a sufficient amount of coarse-pore silica gel in an oven and dry it at 120°C until constant weight. Then place it in a muffle furnace at 600°C and calcine for 2 hours to activate it at high temperature and remove impurities.

[0153] (2) At room temperature, according to the molar ratio SiO2:Na2O:H2O=1:0.25:10, first add 11.67g NaOH to 105g deionized water until dissolved, then add 38.19g coarse-porous silica gel, stir vigorously with a glass rod until uniform, and finally heat and stir in a 25℃ water bath for 6h to form a light yellow gel, thus obtaining a liquid directing agent;

[0154] (3) Add appropriate amounts of coarse-pore silica gel, aluminum sulfate, sodium hydroxide, and deionized water to the container. Stir at room temperature for 5 hours to obtain ZSM-5 synthetic gel. Then add 1.96g of the above liquid directing agent and stir for 1 hour to obtain an aged gel with a molar ratio of SiO2:Al2O3:Na2O:H2O=40:1:15:1800. Transfer the aged gel to a crystallization kettle and crystallize at 170℃ for 70 hours. After crystallization, wash with water, filter, and dry to obtain the product.

[0155] Figure 16 The XRD results showed that no ZSM-5 crystalline phase was formed. This comparative example, Example 1, demonstrates that ZSM-5 molecular sieves cannot be prepared when the reaction temperature of the directing agent is outside the required range of this invention.

[0156] Comparative Example 4

[0157] This comparative example provides a method for preparing a material, specifically including the following steps:

[0158] (1) Place a sufficient amount of coarse-pore silica gel in an oven and dry it at 120°C until constant weight. Then place it in a muffle furnace at 600°C and calcine for 4 hours to activate it at high temperature and remove impurities.

[0159] (2) At room temperature, according to the molar ratio SiO2:Na2O:H2O=1:0.5:25, first add 23.34g NaOH to 262.5g deionized water until dissolved, then add 38.19g coarse-porous silica gel, stir vigorously with a glass rod until uniform, and finally heat and stir in a 45℃ water bath for 6h to form a light yellow gel, thus obtaining a liquid directing agent;

[0160] (3) Add appropriate amounts of coarse-pore silica gel, aluminum sulfate, sodium hydroxide, and deionized water to the container. Stir at room temperature for 5 hours to obtain ZSM-5 synthetic gel. Then add 1.96g of the above liquid directing agent and stir for 1 hour to obtain an aged gel with a molar ratio of SiO2:Al2O3:Na2O:H2O=40:1:15:1800. Transfer the aged gel to a crystallization kettle and crystallize at 170℃ for 70 hours. After crystallization, wash with water, filter, and dry to obtain the product.

[0161] Figure 17 The XRD results showed that no ZSM-5 crystalline phase was formed. This comparative example, Example 2, illustrates that ZSM-5 molecular sieves cannot be prepared when the water-to-silica ratio in the directing agent is not within the range required by this invention.

[0162] Comparative Example 5

[0163] This comparative example provides a method for preparing a material, specifically including the following steps:

[0164] (1) Place a sufficient amount of coarse-pore silica gel in an oven and dry it at 120°C until constant weight. Then place it in a muffle furnace at 600°C and calcine for 2 hours to activate it at high temperature and remove impurities.

[0165] (2) At room temperature, according to the molar ratio SiO2:Na2O:H2O=1:0.25:10, first add 11.67g NaOH to 105g deionized water until dissolved, then add 38.19g coarse-porous silica gel, stir vigorously with a glass rod until uniform, and finally put it into a 60℃ water bath for heating and stirring for 1h to form a gel and obtain a liquid directing agent.

[0166] (3) Add appropriate amounts of coarse-pore silica gel, aluminum sulfate, sodium hydroxide, and deionized water to the container. Stir at room temperature for 5 hours to obtain ZSM-5 synthetic gel. Then add 1.96g of the above liquid directing agent and stir for 1 hour to obtain an aged gel with a molar ratio of SiO2:Al2O3:Na2O:H2O=40:1:15:1800. Transfer the aged gel to a crystallization kettle and crystallize at 170℃ for 70 hours. After crystallization, wash with water, filter, and dry to obtain the product.

[0167] Figure 18 Although the XRD results show that the product has the crystal phase structure of ZSM-5 molecular sieve, its relative crystallinity is poor, with a relative crystallinity of only 45%. This comparative example, Example 4, illustrates that when the stirring time of the raw materials in the directing agent is not within the range required by the present invention, it is difficult to synthesize ZSM-5 molecular sieve with a complete crystal phase structure.

[0168] Comparative Example 6

[0169] This comparative example provides a method for preparing a material, specifically including the following steps:

[0170] (1) Place a sufficient amount of coarse-pore silica gel in an oven and dry it at 120°C until constant weight. Then place it in a muffle furnace at 600°C and calcine for 5 hours to activate it at high temperature and remove impurities.

[0171] (2) At room temperature, according to the molar ratio SiO2:Na2O:H2O=1:0.25:10, first add 11.67g NaOH to 105g deionized water until dissolved, then add 38.19g coarse-porous silica gel, stir vigorously with a glass rod until uniform, and finally heat and stir in a 90℃ water bath for 8h to form a gel and obtain a liquid directing agent.

[0172] (3) Add appropriate amounts of coarse-pore silica gel, aluminum sulfate, sodium hydroxide, and deionized water to the container. Stir at room temperature for 5 hours to obtain ZSM-5 synthetic gel. Then add 1.96g of the above liquid directing agent and stir for 1 hour to obtain an aged gel with a molar ratio of SiO2:Al2O3:Na2O:H2O=40:1:15:1800. Transfer the aged gel to a crystallization kettle and crystallize at 170℃ for 70 hours. After crystallization, wash with water, filter, and dry to obtain the product.

[0173] Figure 19 Although the XRD results show that the product has the crystal phase structure of ZSM-5 molecular sieve, the relative crystallinity is poor, with a relative crystallinity of only 40%. This comparative example, Example 5, illustrates that when the stirring temperature in the directing agent is not within the required range of the present invention, it is difficult to synthesize ZSM-5 molecular sieve with a complete crystal phase structure.

[0174] Comparative Example 7

[0175] This comparative example provides a method for preparing a material, specifically including the following steps:

[0176] According to the molar ratio of SiO2:Al2O3:Na2O:H2O=40:1:15:1800, appropriate amounts of coarse-pore silica gel, aluminum sulfate, sodium hydroxide, and deionized water were added to the container. After stirring at room temperature for 5 hours, without adding a guiding agent, the mixture was stirred for another hour. The mixture was then transferred to a crystallization kettle and crystallized at 170℃ for 70 hours. After crystallization, the product was obtained by washing with water, filtration, and drying.

[0177] Figure 20 XRD results showed that no ZSM-5 crystalline phase was formed. This comparative example, Example 10, demonstrates that ZSM-5 molecular sieves cannot be prepared without the addition of a liquid-phase directing agent.

[0178] Comparative Example 8

[0179] This comparative example provides a method for preparing a material, specifically including the following steps:

[0180] According to the molar ratio of SiO2:Al2O3:Na2O:H2O=40:1:15:1800, appropriate amounts of quartz sand, aluminum sulfate, sodium hydroxide, and deionized water were added to the container. After stirring at room temperature for 5 hours, without adding a directing agent, the mixture was stirred for another hour. The mixture was then transferred to a crystallization kettle and crystallized at 170℃ for 70 hours. After crystallization, the product was obtained by washing with water, filtration, and drying.

[0181] Figure 21 The XRD results showed that no ZSM-5 crystalline phase was formed. This comparative example, Example 11, demonstrates that ZSM-5 molecular sieves cannot be prepared without the addition of a liquid phase directing agent.

[0182] Comparative Example 9

[0183] This comparative example provides a method for preparing a material, specifically including the following steps:

[0184] (1) Place a sufficient amount of fine-pore silica gel in an oven and dry it at 120°C until constant weight. Then place it in a muffle furnace at 600°C and calcine for 2 hours to activate it at high temperature and remove impurities.

[0185] (2) At room temperature, according to the molar ratio SiO2:Na2O:H2O=0.1:0.25:10, first add 11.67g NaOH to 105g deionized water until dissolved, then add 3.82g fine-pore silica gel, stir vigorously with a glass rod until uniform, and finally heat and stir in a 45℃ water bath for 6h to form a light yellow gel, thus obtaining a liquid directing agent;

[0186] (3) Add appropriate amounts of coarse-pore silica gel, aluminum sulfate, sodium hydroxide, and deionized water to the container. Stir at room temperature for 5 hours to obtain ZSM-5 synthetic gel. Then add 1.96g of the above liquid directing agent and stir for 1 hour to obtain an aged gel with a molar ratio of SiO2:Al2O3:Na2O:H2O=40:1:15:1800. Transfer the aged gel to a crystallization kettle and crystallize at 170℃ for 70 hours. After crystallization, wash with water, filter, and dry to obtain the product.

[0187] Figure 22 The XRD results showed that no ZSM-5 crystalline phase was formed. This comparative example, Example 13, illustrates that ZSM-5 molecular sieves cannot be prepared when the directing agent ratio is not within the requirements of this invention.

[0188] Comparative Example 10

[0189] This comparative example provides a method for preparing a material, specifically including the following steps:

[0190] (1) Place a sufficient amount of type B silicone in an oven and dry it at 120°C until constant weight. Then place it in a muffle furnace at 600°C and calcine for 4 hours to activate it at high temperature and remove impurities.

[0191] (2) At room temperature, according to the molar ratio SiO2:Na2O:H2O=1:0.25:6, first add 11.67g NaOH to 63g deionized water until dissolved, then add 42.64g type B silica gel, stir vigorously with a glass rod until uniform, and finally heat and stir in a 45℃ water bath for 7h to form a light yellow gel, thus obtaining a liquid directing agent;

[0192] (3) Add appropriate amounts of type B silica gel, aluminum sulfate, sodium hydroxide and deionized water to the container, stir at room temperature for 5 hours to obtain ZSM-5 synthetic gel, then add 7.72g of the above liquid directing agent, and stir for 1 hour to obtain an aged gel with a molar ratio of SiO2:Al2O3:Na2O:H2O=40:1:15:1800; transfer the aged gel to a crystallization kettle and crystallize at 170℃ for 70 hours; after crystallization, wash with water, filter and dry to obtain the product;

[0193] Figure 23 The XRD results showed that no ZSM-5 crystalline phase was formed. This comparative example, Example 12, demonstrates that ZSM-5 molecular sieves cannot be prepared when the water-to-silica ratio of the directing agent is outside the range required by this invention.

[0194] Comparative Example 11

[0195] This comparative example provides a method for preparing a material, specifically including the following steps:

[0196] (1) Place a sufficient amount of coarse-pore silica gel in an oven and dry it at 120°C until constant weight. Then place it in a muffle furnace at 600°C and calcine for 4 hours to activate it at high temperature and remove impurities.

[0197] (2) According to the molar ratio of SiO2:Al2O3:Na2O:H2O:TPAOH=40:1:15:1800:4, add appropriate amounts of coarse-pore silica gel, aluminum sulfate, sodium hydroxide, deionized water and tetrapropylammonium hydroxide into the container, stir at room temperature for 5 hours, then stir for another hour, transfer to a crystallization kettle and crystallize at 170℃ for 70 hours; after crystallization, wash with water, filter and dry to obtain the product;

[0198] Figure 24 XRD results indicate that the product has a ZSM-5 molecular sieve crystal structure with a relative crystallinity of 89% and a specific surface area of ​​364.28 m² as determined by BET analysis. 2 / g. This comparative example, Example 1, demonstrates that the crystallinity and specific surface area of ​​the ZSM-5 molecular sieve synthesized using the conventional organic template agent tetrapropylammonium hydroxide both failed to exceed those of the ZSM-5 molecular sieve synthesized using the directing agent prepared in this invention.

[0199] In this invention, the specific surface area and pore properties of the ZSM-5 molecular sieves prepared in Examples 1-13 are summarized in Table 1, and the specific surface area and pore properties of the products prepared in Comparative Examples 1-11 are summarized in Table 2.

[0200] Table 1. Specific surface area and pore properties of ZSM-5 molecular sieves synthesized in Examples 1-13

[0201]

[0202] Table 2. Specific surface area and pore properties of the products synthesized in Comparative Examples 1-11

[0203]

[0204]

[0205] As can be seen from Tables 1 and 2, the liquid directing agent prepared by the method provided by the present invention can be used for green synthesis of molecular sieves. Compared with the comparative example, it achieves successful synthesis of ZSM-5 molecular sieves without the use of organic template agents, and has higher micropore specific surface area and micropore volume, avoiding complicated post-processing steps and reducing wastewater pollution and production costs.

Claims

1. A method for preparing a liquid directing agent, wherein, The preparation method includes: (1) The first silicon source is subjected to a first drying and calcination treatment in sequence to obtain the pretreated first silicon source; (2) Dissolve the sodium-containing alkaline source in water until completely dissolved according to the molar ratio of SiO2:Na2O:H2O=1:(0.1-4):(8-20), add the pretreated first silicon source, and stir for the first time to obtain a liquid directing agent; The molar ratio of the sodium-containing alkali source is calculated as Na2O, and the molar ratio of the first silicon source is calculated as SiO2.

2. The preparation method according to claim 1, wherein, The first silicon source includes one or more of sodium silicate, silica gel, silica sol, silica fume, and quartz sand.

3. The preparation method according to claim 2, wherein, The first 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 preparation method according to claim 1, wherein, The roasting temperature is 500-800℃, and the roasting time is 2-6 hours.

5. The preparation method according to claim 1, wherein, The molar ratio of the sodium-containing alkaline source to the first silicon source is (0.2-4):

1.

6. A liquid directing agent, which is prepared by the preparation method according to any one of claims 1-5.

7. The liquid directing agent according to claim 6, wherein, The viscosity of the liquid directing agent is 45cp-200cp.

8. A method for preparing Na-type ZSM-5 molecular sieve, wherein, The preparation method includes: The liquid directing agent described in claim 6 or 7 is added to the ZSM-5 synthetic gel, and a second stirring and aging process is carried out to obtain an aged gel; then crystallization treatment is performed, followed by cooling, filtration and washing, and a second drying process to obtain Na-type ZSM-5 molecular sieve. The molar ratio of each component in the aging gel is SiO2:Al2O3:Na2O:H2O=(25-50):1:(3-15):(800-2000).

9. The preparation method according to claim 8, wherein, The ZSM-5 synthetic gel is obtained by mixing and stirring a second silicon source, an aluminum source, a second sodium-containing alkali source, and water; the molar ratio of the second silicon source is SiO2, the molar ratio of the aluminum source is Al2O3, and the molar ratio of the second sodium-containing alkali source is Na2O. The amount of the liquid directing agent added is 5%-20% of the total weight of the first and second silicon sources added to the aging gel.

10. The preparation method according to claim 9, wherein, The second silicon source includes one or more of tetraethyl orthosilicate, silica gel, silica sol, silica fume, and quartz sand; And / or, the aluminum source includes one or more of sodium aluminate, aluminum isopropoxide, aluminum sulfate, boehmite, and boehmite.

11. The preparation method according to claim 8, wherein, The crystallization temperature is 120-170℃, and the crystallization time is 48-96h.

12. A Na-type ZSM-5 molecular sieve, which is prepared by the preparation method according to any one of claims 8-11.

13. The Na-type ZSM-5 molecular sieve according to claim 12, wherein, The specific surface area of ​​the micropores in the Na-type ZSM-5 molecular sieve is 310-353 m². 2 / g, the micropore volume of the Na-type ZSM-5 molecular sieve is 0.07-0.14 cm³. 3 / g.

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