A method for rapid hydrothermal synthesis of Sn-Beta molecular sieves using aerosol-assisted synthesis in a fluorine-free system
By preparing mesoporous silicon-tin composite oxides through spray drying and controlling the dissolution rate of tin species, nanoscale Sn-Beta molecular sieves with high framework tin content were efficiently synthesized in a fluorine-free system, solving the problems of environmental pollution and low synthesis efficiency, and improving catalytic performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- LIAONING UNIVERSITY OF TECHNOLOGY
- Filing Date
- 2026-05-21
- Publication Date
- 2026-07-31
AI Technical Summary
Existing technologies cannot rapidly synthesize Sn-Beta molecular sieves with high framework tin content while maintaining nanoscale and high crystallinity under fluorine-free conditions, and also pose environmental pollution and high cost problems.
Mesoporous silicon-tin composite oxides with recessed hollow structures were prepared using a spray dryer as silicon and tin sources. Nanoscale Sn-Beta molecular sieves were rapidly synthesized in a fluorine-free system by combining them with a specific template agent. The dissolution and release rates of tin species were controlled to allow them to enter the molecular sieve framework.
A high-skeletal-Sn-Beta molecular sieve with high Sn content was synthesized efficiently under fluorine-free conditions, solving the environmental pollution problem, improving the synthesis efficiency, and exhibiting excellent catalytic performance.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of molecular sieve material preparation, and more specifically relates to a method for rapidly synthesizing nanoscale Sn-Beta molecular sieves with high framework Sn content using mesoporous silicon-tin composite oxides in a fluorine-free system. Background Technology
[0002] Sn-Beta molecular sieves are important solid Lewis acid catalysts that have shown great potential in green chemistry processes such as biomass conversion. Their catalytic activity depends on the successful entry of tin atoms into the molecular sieve framework, but this process is inherently difficult due to the mismatch between the ionic radii of tin and silicon.
[0003] While Sn-Beta molecular sieves synthesized via the traditional hydrothermal method exhibit high crystallinity and catalytic activity, this method uses fluorides as mineralizers, which not only causes severe equipment corrosion and environmental damage but also requires several weeks to complete crystallization, resulting in high energy consumption and low efficiency. Furthermore, this synthesis method struggles to produce products with high skeletal Sn content, with the silicon-tin ratio generally limited to above 100 (i.e., SiO2 / SnO2 molar ratio ≥ 100, corresponding to Sn content ≤ 0.01). This directly restricts the improvement of the catalyst's active site density, thereby limiting its performance ceiling.
[0004] To overcome the hazards of fluorides in traditional synthesis methods and the limitation of not being able to further increase the Sn content, researchers have developed a variety of fluorine-free synthesis routes. For example, modifying high-silica Beta zeolite through post-treatment can increase the tin loading to some extent, but it often introduces a large number of skeletal defects, leading to increased hydrophilicity of the material (see J. Phys. Chem. C2011, 115, 3663-3670). Some researchers have also used Na ions instead of F ions as mineralizing agents and successfully synthesized Sn-Beta in a fluorine-free system using specific template agents, but the template agents used in this method have complex structures and are expensive (see Inorg. Chem. Front. 2018, 5, 2763-2771).
[0005] In recent years, progress has been made in the synthesis of nanoscale Sn-Beta molecular sieves under fluorine-free systems. For example, Chinese patent application CN110422857A (publication date: November 8, 2019) discloses a method for preparing nanoscale Sn-Beta molecular sieves under fluorine-free conditions. However, the amount of tin added in this method is limited, and the molar ratio of SiO2 to SnO2 in the final mixture is only 1:0.007 (corresponding to a Sn content of 0.007), which cannot further increase the skeletal tin content.
[0006] In summary, existing technologies fail to achieve a good balance in multiple dimensions, including environmental friendliness, synthesis efficiency, product quality (high crystallinity and high framework tin content), and economic cost. In particular, there is a lack of a simple method to directly synthesize Sn-Beta molecular sieves with high framework tin content while maintaining nanoscale and high crystallinity under fluorine-free conditions. Therefore, developing a simple, rapid, and efficient universal method to directly synthesize high framework tin content, high crystallinity, and nanoscale Sn-Beta molecular sieves under fluorine-free conditions has become a key technical challenge that urgently needs to be overcome in this field. Summary of the Invention
[0007] To address the aforementioned problems and overcome the shortcomings of existing technologies, this invention provides a method for rapidly synthesizing nanoscale Sn-Beta molecular sieves with high framework Sn content by preparing silicon-tin composite oxides with recessed hollow structures using a spray dryer in a fluorine-free system, providing silicon and tin sources.
[0008] The specific technical solution of this invention to solve the above-mentioned technical problems is as follows: a method for rapidly synthesizing nanoscale Sn-Beta molecular sieves with high framework Sn content using mesoporous silicon-tin composite oxides in a fluorine-free system, the specific steps of which are as follows: (1) Industrial grade molecular sieves were placed in nitric acid solution for dealumination. After the treatment was completed, the resulting solid was washed, dried and calcined at 550°C for 4 hours to obtain β-seed, which was used as seed crystal for the synthesis of nano-sized Sn-Beta molecular sieves. (2) According to the molar ratio of 1SiO2:0.008-0.017SnO2:0.05-0.2CTAB:0.2HCl:40H2O, weigh tetraethyl orthosilicate (as SiO2), tin tetrachloride (as SnO2), hexadecyltrimethylammonium bromide (CTAB, pore-forming agent), hydrochloric acid (mass fraction 36%~38%, as HCl) and deionized water and mix them; stir the mixture at 70°C for 30 minutes, and then use a spray drying device to quickly evaporate the water at 220°C to obtain a white powder; The white powder was dried overnight at 100°C, and then calcined in air at 550°C for 4 hours to finally obtain a mesoporous silicon-tin composite oxide, such as... Figure 1 As shown in (a), the morphology of the mesoporous silicon-tin composite oxide prepared in this step is a hollow microsphere with surface depressions. (3) Weigh out the mesoporous silicon-tin composite oxide (calculated as SiO2), tetraethylammonium hydroxide aqueous solution (mass fraction 35%, calculated as TEAOH), tetraethylammonium chloride, sodium chloride, deionized water and β-seed (calculated as SiO2) prepared in step (2) according to the molar ratio of 1SiO2:0.35TEAOH:0.1TEACl:0.175NaCl:7H2O:10wt%β-seed, according to the ... The liner was then placed in a stainless steel reactor, which was then placed in a homogeneous reactor for rotational crystallization at 140°C for 6-144 hours. After crystallization, the mixture was cooled to room temperature. The resulting solid was filtered, washed until neutral, and then dried overnight in a 100°C oven. Finally, it was calcined in a muffle furnace at 550°C for 4 hours to obtain nanoscale Sn-Beta molecular sieves. Figure 1 As shown in (b); The obtained nanoscale Sn-Beta molecular sieve has a particle size of approximately 100 nm.
[0009] The beneficial effects that this invention can produce include: (1) The entire synthesis route of this invention completely eliminates fluorides, fundamentally solving the environmental problem of fluorine pollution in traditional methods, and the process is safe and clean; (2) Mesoporous silicon-tin composite oxide with a concave hollow structure was prepared by doping hexadecyltrimethylammonium bromide (CTAB) as a pore-forming agent, and nanoscale Sn-Beta molecular sieve with high framework Sn content was prepared. While ensuring the excellent performance of the product, the synthesis efficiency was greatly improved, which has important practical production value. This preparation method has the advantages of fast crystallization speed, high product crystallinity, and environmental friendliness. Furthermore, the Sn-Beta molecular sieve prepared by this method exhibits excellent catalytic performance in the Baeter-Villiger redox of 2-adamantanone. Attached Figure Description
[0010] Figure 1 (a) is a SEM image of the mesoporous silicon-tin composite oxide prepared in step (2) of Example 1; (b) is a SEM image of Sn-Beta prepared in step (3) of Example 1. Figure 2 The UV-Vis spectra of Sn-Beta prepared in Example 1 and Comparative Example 1 are shown. Figure 3 The UV-Vis spectra of Sn-Beta prepared in Example 1 and Comparative Example 2 are shown below. Figure 4 The pore size distribution diagrams are shown for the silicon-tin composite oxides prepared in step (2) of Examples 1, 2, and 3. Figure 5 (a) is a SEM image of the mesoporous silicon-tin composite oxide prepared in step (2) of Comparative Example 3; (b) is a SEM image of Sn-Beta prepared in step (3) of Comparative Example 3. Figure 6 (a) is a SEM image of the mesoporous silicon-tin composite oxide prepared in step (2) of Example 4; (b) is a SEM image of Sn-Beta prepared in step (3) of Example 4. Figure 7 The UV-Vis spectra of Sn-Beta prepared in Example 4 and Comparative Example 4 are shown. Detailed Implementation
[0011] Specific embodiments of the present invention: To better understand the present invention, specific embodiments are described. It is worth emphasizing that the effects of these embodiments are not substantially different from those of the various embodiments within the scope of protection of the present invention, including their respective reagents and reagent content ratios. All of them can achieve the effects described in the present invention and solve the above-mentioned problems. Other combinations are not described here. Example 1
[0012] A method for rapidly synthesizing nanoscale Sn-Beta molecular sieves with high framework Sn content using mesoporous silicon-tin composite oxides in a fluorine-free system is disclosed, with the following specific steps: (1) Industrial grade molecular sieve with a silicon-aluminum molar ratio of 25 was placed in nitric acid solution for dealumination treatment. After treatment, the obtained solid was washed, dried, and calcined at 550°C for 4 hours to obtain β-seed, which was used as seed crystal for the synthesis of nanoscale Sn-Beta molecular sieve. (2) According to the molar ratio of 1SiO2:0.008SnO2:0.05CTAB:0.2HCl:40H2O, weigh tetraethyl orthosilicate (as SiO2), tin tetrachloride (as SnO2), hexadecyltrimethylammonium bromide (CTAB, pore-forming agent), hydrochloric acid (mass fraction 36~38%, as HCl) and deionized water and mix them; stir the mixture at 70℃ for 30 minutes, and then use a spray drying device to quickly evaporate the water at 220℃ to obtain a white powder; dry the white powder at 100℃ overnight, and then calcine it in air at 550℃ for 4 hours to finally obtain mesoporous silicon-tin composite oxide, such as Figure 1 As shown in (a), the morphology of the mesoporous silicon-tin composite oxide prepared in this step is a hollow microsphere with surface depressions. (3) According to the molar ratio of 1SiO2:0.35TEAOH:0.1TEACl:0.175NaCl:7H2O:10wt%β-seed, weigh the mesoporous silicon-tin composite oxide (calculated as SiO2), tetraethylammonium hydroxide aqueous solution (mass fraction 35%, calculated as TEAOH), tetraethylammonium chloride, sodium chloride, deionized water and β-seed (calculated as SiO2) prepared in step (2), and add them sequentially to the polytetrafluoroethylene liner. Stir at room temperature for 30 minutes to form a homogeneous suspension. Then place the liner in a stainless steel reactor, and then place the stainless steel reactor in a homogeneous reactor. Rotate and crystallize at 140℃ for 48 hours. After crystallization, cool to room temperature. After the solid is filtered and washed until neutral, dry it overnight in a constant temperature oven at 100℃. Finally, calcine it in a muffle furnace at 550℃ for 4 hours to obtain nano-sized Sn-Beta molecular sieves, such as Figure 1 As shown in (b), the particle size of the prepared nanoscale Sn-Beta molecular sieve is approximately 100 nm. Example 2
[0013] The difference between this embodiment and embodiment 1 is that in step (2), the molar ratio of each raw material is adjusted to 1SiO2:0.008SnO2:0.1CTAB:0.2HCl:40H2O, and the rest is the same as in embodiment 1. Example 3
[0014] The difference between this embodiment and embodiment 1 is that in step (2), the molar ratio of each raw material is adjusted to 1SiO2:0.008SnO2:0.2CTAB:0.2HCl:40H2O, and the rest is the same as in embodiment 1.
[0015] This comparative example prepared Sn-Beta molecular sieves according to the method disclosed in Example 1 of Chinese Patent Application CN110422857A (publication date: November 8, 2019). The specific steps are as follows: 0.17 g of tin tetrachloride was mixed with 4.21 g of tetraethylammonium hydroxide aqueous solution (35% by mass) and stirred at 500 r / min for 12 hours. The mixture was then dried at 70 °C for 120 minutes to obtain a mixed solution. This mixed solution was then mixed with 4.8 g of silica to obtain a mixture. The mixture was transferred into a polytetrafluoroethylene liner of a small reactor, and then the liner was transferred into the liner of a large reactor containing 2 mL of water. The liner was then placed in the large reactor, and the reactor was placed in a constant temperature oven at 160 °C for 20 hours to crystallize. After crystallization, the mixture was cooled to room temperature, and the resulting solid was filtered, washed until neutral, dried overnight in a constant temperature oven at 100 °C, and finally calcined in a muffle furnace at 580 °C for 12 hours to obtain nano-sized Sn-Beta molecular sieves.
[0016] This comparative example provides a method for rapidly synthesizing nanoscale Sn-Beta molecular sieves with high framework tin content using non-porous silicon-tin composite oxide in a fluorine-free system; the method is carried out according to the method in Example 1, except that CTAB is not added in step (2) (i.e., no pore-forming agent is used), and the rest is the same as in Example 1.
[0017] This comparative example provides a method for rapidly synthesizing Sn-Beta molecular sieves with high framework tin content using mesoporous silicon-tin composite oxides in a fluorine-free system; the method is carried out according to the method in Example 1, except that the pore-forming agent in step (2) is replaced with 3-aminopropyltrimethoxysilane.
[0018] The analytical method used in this application is as follows: The morphology and grain size of the molecular sieve samples were characterized using a Hitachi S-4800 scanning electron microscope (SEM). Before testing, the samples were sputtered with gold to ensure good conductivity and imaging effect. The test voltage was set to 3kV.
[0019] The coordination state of tin was analyzed using a Jasco UV-550 UV-Vis spectrophotometer, with barium sulfate (BaSO4) powder used as a reference sample.
[0020] The pore size distribution of silicon-tin composite oxides was characterized using an ASAP2020 nitrogen physical adsorption (BET) instrument from Micron Technology, Inc. 100 mg of sample was weighed and degassed under vacuum at 473 K for 4 h, followed by detection and analysis in liquid nitrogen at 77 K.
[0021] The Sn-Beta molecular sieve samples prepared in Examples 1-4 and Comparative Examples 1-6 were used to catalyze the Baeyer-Villiger oxidation reaction of 2-adamantanone with hydrogen peroxide to evaluate their catalytic performance.
[0022] The specific reaction steps are as follows: In chlorobenzene (10 mL), 2-adamantanone (2 mmol), 50% hydrogen peroxide aqueous solution (2 mmol, calculated as H2O2), 1,4-dioxane (2 mmol) and the Sn-Beta molecular sieve to be tested (0.1 g) are added sequentially. After mixing evenly, the mixture is stirred at 90 °C for 4 hours. After the reaction is completed, the reaction solution is quantitatively analyzed by gas chromatography (GC) or high performance liquid chromatography (HPLC) to calculate the conversion rate of 2-adamantanone.
[0023] The evaluation results of the catalytic performance of each sample are shown in Table 1 (low tin feed system) and Table 2 (high tin feed system).
[0024] Table 1:
[0025] As can be seen from Table 1 and the attached figure: (1) Compared with the product obtained in Example 1 of the present invention, the ultraviolet-visible diffuse reflectance spectrum (UV-Vis) of the product of Comparative Example 1 shows a broader absorption peak at about ~300 nm (e.g. Figure 2 As shown in the figure, this indicates the presence of a large number of non-skeleton tin species; This may be because the comparative method did not use the spray drying step to prepare silicon-tin composite oxide, resulting in tin species mainly existing in the liquid phase during crystallization. Some tin species formed clusters due to local supersaturation and failed to effectively enter the molecular sieve framework. Under the same catalytic conditions, the lactone conversion rate of the Sn-Beta molecular sieve obtained in Comparative Example 1 was 38%, while the conversion rate of the product obtained in Example 1 of the present invention was 52%. This comparative result further illustrates that the mesoporous silicon-tin composite oxide constructed by spray drying coupled with the pore-forming agent CTAB in the present invention is more conducive to the high dispersion of tin and the insertion of the framework.
[0026] (2) For example Figure 3 As shown, compared with Example 1 of the present invention, the nanoscale Sn-Beta molecular sieve prepared in Comparative Example 2 also contains more non-framework Sn. Although Comparative Example 2, compared to the Example, used spray drying to form a solid silicon-tin composite oxide, which could slow down the Sn content in the liquid phase during crystallization and thus reduce Sn agglomeration in the liquid phase, it lacked mesopores ( Figure 4 This results in the dissolution rate of Sn not keeping up with the crystallization rate, which in turn causes some Sn to not have time to enter the Si framework and thus exist in the Sn-Beta channels in the form of clusters; its catalytic performance is also worse than that of the catalyst prepared in Example 1 (Table 1).
[0027] (3) The scanning electron microscope image of the non-porous silicon-tin composite oxide obtained in step (2) of Comparative Example 3 is shown below. Figure 5 As shown in (a); Compared with the hollow microspheres with surface depressions in Example 1 ( Figure 1 (a) is different; the composite oxide in Comparative Example 3 is a solid microsphere with a smooth surface. The scanning electron microscope image of the Sn-Beta molecular sieve product obtained in step (3) of this Comparative Example is as follows: Figure 5 As shown in (b), its average particle size is about 1 μm, which is significantly larger than the particle size of the product of Example 1 (about 100 nm). Under the same catalytic reaction conditions as in Example 1, the conversion rate of 2-adamantanone of the Sn-Beta molecular sieve prepared in this comparative example in the BV reaction is only 35% (as shown in Table 1), which is much lower than the 52% of Example 1.
[0028] Therefore, the above results indicate that not all mesoporous template agents can achieve the technical effects of this invention; although 3-aminopropyltrimethoxysilane can also form mesoporous structures ( Figure 4 However, its molecular ends contain amino groups, which may interact strongly with silicon-tin precursors, altering the self-assembly behavior in the sol-gel process and resulting in the formation of smooth, solid microspheres instead of the recessed hollow structure unique to this invention. This solid structure is not conducive to the controllable release of silicon-tin species during subsequent crystallization, thereby leading to increased product particle size and decreased catalytic performance.
[0029] Example 4 The difference between this embodiment and embodiment 1 is that in step (2), the molar ratio of each raw material is adjusted to 1SiO2:0.017SnO2:0.05CTAB:0.2HCl:40H2O (that is, the molar amount of SnO2 is increased from 0.008 in embodiment 1 to 0.017), and the rest is the same as in embodiment 1.
[0030] Comparative Example 4 The difference between this comparative example and comparative example 1 is that the amount of tin tetrachloride added is increased to 0.47 g (that is, the molar amount of SnO2 is increased from 0.008 in comparative example 1 to 0.017), and the rest is the same as comparative example 1.
[0031] Comparative Example 5 The difference between this embodiment and Comparative Example 2 is that in step (2), the molar ratio of each raw material is adjusted to 1SiO2:0.017SnO2:0.05CTAB:0.2HCl:40H2O (that is, the molar amount of SnO2 is increased from 0.008 in Comparative Example 2 to 0.017), and the rest is the same as Comparative Example 2.
[0032] Comparative Example 6 The difference between this embodiment and Comparative Example 3 is that in step (2), the molar ratio of each raw material is adjusted to 1SiO2:0.017SnO2:0.05CTAB:0.2HCl:40H2O (that is, the molar amount of SnO2 is increased from 0.008 in Comparative Example 3 to 0.017), and the rest is the same as Comparative Example 3.
[0033] Table 2
[0034] As can be seen from Table 2 and the attached figure: (4) Scanning electron microscope image of the mesoporous silicon-tin composite oxide prepared in step (2) of Example 4 is shown below. Figure 6 As shown in (a), its morphology is still that of hollow microspheres with surface depressions, similar to Example 1 ( Figure 1 (a) is basically the same; The scanning electron microscope image of the nanoscale Sn-Beta molecular sieve prepared in step (3) is shown below. Figure 6 As shown in (b), its average particle size is still approximately 100 nm, similar to Example 1 ( Figure 1 (b) is basically the same; The results indicate that increasing the tin content in the synthesis system does not significantly affect the morphology of the mesoporous silicon-tin composite oxide or the final particle size of the Sn-Beta molecular sieve. The obtained Sn-Beta molecular sieve was characterized by ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis), and the results are as follows: Figure 7 As shown, no obvious non-framework tin characteristic absorption peaks were observed, indicating that even with an increase in the tin content in the initial feed, tin species can still effectively enter the molecular sieve framework.
[0035] This is thanks to the mesoporous silicon-tin composite oxide prepared by spray drying technology in this invention: the composite oxide has a unique recessed hollow mesoporous structure, which can effectively regulate the dissolution and release rate of tin species during crystallization, so that tin species are continuously supplied at an appropriate rate, thereby avoiding the formation of tin clusters due to local supersaturation and promoting more tin species to enter the framework sites of Beta molecular sieves.
[0036] The Sn-Beta molecular sieve obtained in this example was used to catalyze the Baeyer-Villiger oxidation reaction with 2-adamantanone as the substrate. Due to the increased Sn content at the active site, the conversion rate reached 65% (Table 2).
[0037] (5) The Sn-Beta molecular sieve obtained in Example 4 was characterized by ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis), and the results are as follows: Figure 7 As shown; Compared with the spectrum of the Sn-Beta molecular sieve prepared in Example 4, Sn-Beta in Comparative Example 4 showed a significant non-framework tin characteristic absorption peak at about 300 nm, while the intensity of the framework tin characteristic absorption peak at about 200 nm was significantly reduced. This result indicates that, in the absence of the controlled release mechanism of the spray-dried mesoporous composite oxide of the present invention, simply increasing the amount of tin feed will lead to supersaturation of tin species in the crystallization system. A large number of tin species will form tin oxide clusters because they do not have time to enter the framework, which will reduce the loading of framework tin. In the BV reaction, the conversion rate of 2-adamantanone decreased significantly (17%, Table 2).
[0038] (6) The conversion rate of 2-adamantanone by the Sn-Beta molecular sieve obtained in Comparative Example 5 was not significantly improved compared with that in Comparative Example 2 (see Table 2). This result indicates that in the absence of a mesoporous structure, even if the amount of tin fed and the spray drying technology are used, it is not possible to effectively improve the skeletal tin loading and catalytic performance.
[0039] (7) The conversion rate of 2-adamantanone by the Sn-Beta molecular sieve obtained in Comparative Example 6 was not significantly improved compared with that in Comparative Example 3 (see Table 2). This result indicates that even if the amount of tin is increased, the performance improvement shown in Example 4 cannot be achieved by using other pore-forming agents to replace CTAB.
[0040] In summary: (1) The entire synthesis route of this invention completely eliminates fluorides, fundamentally solving the environmental problem of fluorine pollution in traditional methods, and the process is safe and clean.
[0041] (2) Mesoporous silicon-tin composite oxide with a concave hollow structure was prepared by doping hexadecyltrimethylammonium bromide (CTAB) as a pore-forming agent, and nanoscale Sn-Beta molecular sieve with high framework Sn content was prepared. While ensuring the excellent performance of the product, the synthesis efficiency was greatly improved, which has important practical production value.
[0042] (3) This preparation method has the advantages of fast crystallization speed, high product crystallinity and environmental friendliness. The Sn-Beta molecular sieve prepared by this method shows excellent catalytic performance in the Baeter-Villiger redox of 2-adamantanone.
Claims
1. A method for rapid hydrothermal synthesis of Sn-Beta molecular sieves using aerosol-assisted synthesis in a fluorine-free system, characterized in that, Includes the following steps: (1) Weigh tetraethyl orthosilicate, tin tetrachloride, pore-forming agent, hydrochloric acid and deionized water and mix them; stir the mixture at 70°C for 30 minutes, and then use a spray drying device to quickly evaporate the water at 220°C to obtain a white powder; (2) The white powder was dried at 100°C overnight and then calcined in air at 550°C for 4 hours to finally obtain mesoporous silicon-tin composite oxide; (3) Weigh the mesoporous silicon-tin composite oxide, tetraethylammonium hydroxide aqueous solution, tetraethylammonium chloride, sodium chloride, deionized water and β-seed prepared in step (2), add them to the polytetrafluoroethylene liner in sequence, stir at room temperature for 30 minutes to form a uniform suspension; (4) Crystallize at 140℃ for 6-144 hours by rotation; after crystallization, cool to room temperature, filter and wash the obtained solid until neutral, dry it overnight in a constant temperature oven at 100℃, and finally calcine it in a muffle furnace at 550℃ for 4 hours to obtain nano-sized Sn-Beta molecular sieve.
2. The method for rapid hydrothermal synthesis of Sn-Beta molecular sieves using aerosol-assisted hydrothermal synthesis in a fluorine-free system according to claim 1, characterized in that... The pore-forming agent is CTAB.
3. The method for rapid hydrothermal synthesis of Sn-Beta molecular sieves using aerosol-assisted hydrothermal synthesis in a fluorine-free system according to claim 2, characterized in that: In step (2), tetraethyl orthosilicate, tin tetrachloride, pore-forming agent, hydrochloric acid, and deionized water are mixed in the following molar ratio: 1SiO2:0.008-0.017SnO2:0.05-0.2CTAB:0.2HCl:40H2O.
4. The method for rapid hydrothermal synthesis of Sn-Beta molecular sieves using aerosol-assisted hydrothermal synthesis in a fluorine-free system according to claim 2, characterized in that: In step (3), The amounts of mesoporous silicon-tin composite oxide (based on SiO2), tetraethylammonium hydroxide aqueous solution, tetraethylammonium chloride, sodium chloride, deionized water, and β-seed added are as follows: The molar ratio is 1SiO2:0.35TEAOH:0.1TEACl:0.175NaCl:7H2O:10wt%β-seed.
5. The method for rapid hydrothermal synthesis of Sn-Beta molecular sieves using aerosol-assisted hydrothermal system in a fluorine-free system according to any one of claims 1-4, characterized in that... The preparation method of nanoscale Sn-Beta molecular sieve seeds includes: placing industrial-grade molecular sieve in nitric acid solution for dealumination treatment, washing and drying the obtained solid after treatment, and calcining it at 550℃ for 4 hours to obtain β-seed.
6. The method for rapid hydrothermal synthesis of Sn-Beta molecular sieves using aerosol-assisted hydrothermal synthesis in a fluorine-free system according to claim 5, characterized in that... Step (4) Rotation crystallization is as follows: place the liner in a stainless steel reactor, then place the stainless steel reactor in a homogeneous reactor, and rotate crystallize at 140°C for 6-144 hours.