Nanocrystal packed mesoporous mfi / mel eutectic molecular sieve, and preparation method and application thereof
The hydrothermal synthesis of nanocrystalline stacked mesoporous MFI/MEL eutectic molecular sieves has solved the problems of complex and costly preparation of hierarchical porous molecular sieves, achieving a highly efficient mesoporous structure and wide catalytic applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- DALIAN INSTITUTE OF CHEMICAL PHYSICS CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2024-12-03
- Publication Date
- 2026-06-05
AI Technical Summary
The preparation process of existing multi-level porous molecular sieves is complex and costly, and the separation of nano-zeolites is difficult, making it hard to scale up production.
A combination crystallization solution containing MFI nanocrystals and a template agent for synthesizing MEL molecular sieves were used for crystallization. Nanocrystal stacked mesoporous MFI/MEL eutectic molecular sieves were prepared by hydrothermal synthesis, with mesopore sizes concentrated around 15 nm.
It achieves a mesoporous pore volume of 0.46 cm3/g, simplifies the preparation process, reduces costs, and is suitable for catalytic cracking, alcohol conversion, olefin hydration, alkylation, and isomerization reactions.
Smart Images
Figure CN122144753A_ABST
Abstract
Description
Technical Field
[0001] This application relates to a nanocrystalline stacked mesoporous MFI / MEL eutectic molecular sieve, its preparation method and application, belonging to the field of molecular sieve synthesis. Background Technology
[0002] Molecular sieve catalysts possess a regular microporous structure with a size less than 2 nm, allowing products smaller than the micropore channels to diffuse out, while larger molecules are confined within the channels or continue to react to form smaller molecules that diffuse out. Their inherent microporous structure enables them to sieve molecules, but it also leads to poor activity and easy deactivation due to the involvement of large molecules in reactions. Therefore, constructing nanomolecular sieves and introducing mesoporous structures into molecular sieves are effective methods to improve the diffusion performance of molecular sieve catalysts.
[0003] In the past decade or so, improving diffusion rates and the availability of active sites has received widespread attention. Among the many areas of research, the synthesis of nanozeolites (zeolite crystals with a grain size of less than 100 nm) has been particularly noteworthy. Reducing grain size and shortening micropores facilitates the diffusion of reactants and products, while also increasing the external surface area and the number of pore openings. However, current methods for synthesizing nanozeolites with grain sizes less than 40 nm still face challenges such as high cost and large template dosage requirements. Furthermore, the separation of nanozeolites remains a significant challenge. Nanoaggregates are formed by the aggregation of nanoparticles, which stack to form intercrystalline mesoporous or macroporous structures. These intercrystalline pores, together with the micropores of molecular sieves, constitute a hierarchical pore structure. Compared to nanocrystals, nanoaggregates are easier to separate. Nanoaggregates can be obtained through methods such as modification of the precursor mother liquor, steam-assisted conversion, synthesis in highly concentrated systems, and seed-directed crystal formation. Hu Haoquan et al. [Chem. Mater., 2008, 20, 1670] removed alcohol and some water from the precursor mother liquor during the synthesis of ZSM-12, reducing the H2O / SiO2 ratio to 8, and obtained ZSM-12 zeolite nanoaggregates after crystallization. Adding NaH2PO4 to the precursor mother liquor for the synthesis of ZSM-5 also yielded nanoaggregates. Shi Jianlin et al. [Chem. Eur. J., 2009, 15, 12949] performed steam-assisted conversion on amorphous mesoporous silica-alumina oxide TUD-1, obtaining a material with both mesoporous and microporous structures. By optimizing the steam-assisted conversion conditions (temperature, humidity, time, triethanolamine dosage, etc.), the total specific surface area, external specific surface area, micropore volume, and mesopore volume could be adjusted. Hierarchical porous ZSM-5 can be prepared by drying the zeolite precursor mother liquor without adding mesoporous template agents and then using a steam-assisted conversion method [Chem. Eur. J., 2016, 22, 7895]. Su Baolian et al. [Angew. Chem. Int. Ed., 2011, 50, 11156] obtained interconnected microporous-mesoporous-macroporous titanium silicate MFI zeolite via a quasi-solid phase transformation method. Karin [J. Am. Chem. Soc., 2011, 133, 5284] prepared Beta zeolite nanoaggregates by steam-assisted reforming in an extremely concentrated system. These nanoaggregates consisted of crystal domains around 20 nm in size, with intergranular pores around 13 nm in diameter, and a specific surface area of 750 m². 2 / g, with a total pore volume of 0.90cm³. 3 / g, micropore volume is 0.20cm³ 3 The Si / Al ratio can be adjusted from 10 to 33 g. David P. Serrano et al. [Chem. Mater., 2006, 18, 2462] aged the mother liquor of ZSM-5 and Beta zeolite precursors for a period of time to generate partial crystal nuclei, and then modified the mother liquor with organosilanes (PHAPTMS). After crystallization, nano-aggregates were obtained. Guo Yajun et al. [Chem. Eng. J., 2011, 166, 391] also prepared ZSM-5 nano-aggregates by adding different organosilanes. In summary, the current synthesis process of nano-aggregate molecular sieves still uses methods that are difficult to scale up, such as extremely concentrated synthesis systems, soft templates, or steam-assisted synthesis. Summary of the Invention
[0004] This application relates to a method for preparing nanocrystalline stacked mesoporous MFI / MEL eutectic molecular sieves, mainly addressing the problems of complex processes and high costs in the preparation of existing hierarchical porous molecular sieves. This application employs a combination crystallization process using a crystallization solution containing MFI nanocrystals and a template agent (tetrabutylammonium hydroxide, tetrabutylammonium bromide, or tetrabutylammonium chloride) for synthesizing MEL molecular sieves. The nanocrystalline stacked mesoporous MFI / MEL molecular sieve is obtained through hydrothermal synthesis, with mesopores concentrated at approximately 15 nm and a pore volume of 0.46 cm³. 3 / g.
[0005] According to one aspect of this application, a method for preparing nanocrystalline stacked mesoporous MFI / MEL eutectic molecular sieves is provided, comprising the following steps:
[0006] A crystallization solution containing MFI nanocrystals, a template agent containing tetrabutylammonium ions, an inorganic base, a silicon source, an aluminum source, and water are mixed and crystallized in a sealed container to obtain the nanocrystal stacked mesoporous MFI / MEL eutectic molecular sieve.
[0007] The size of the MFI nanocrystals is 10–300 nm;
[0008] In the crystallization solution containing MFI nanocrystals, the concentration of MFI nanocrystals is 0.01–20 wt%.
[0009] The solvent in the crystallization solution is selected from water and / or ethanol.
[0010] The template agent is selected from at least one of tetrabutylammonium hydroxide, tetrabutylammonium chloride, and tetrabutylammonium bromide;
[0011] The inorganic base is selected from at least one of NaOH, Na2CO3, NaHCO3, NaAlO2, KOH, K2CO3, and KHCO3;
[0012] The silicon source is selected from at least one of tetraethyl orthosilicate, silica sol, water glass, silica gel, fumed silica, and activated clay.
[0013] The aluminum source is selected from at least one of sodium aluminate, aluminum nitrate, aluminum sulfate, aluminum chloride, aluminum isopropoxide, and aluminum oxide.
[0014] The molar ratio of the silicon source to the aluminum source is 30 to 300;
[0015] The molar ratio of the inorganic base to the silicon source is 0.05 to 0.25;
[0016] The molar ratio of water to silicon source is 5 to 120;
[0017] The molar ratio of the template agent to the silicon source is 0.01 to 0.2;
[0018] Wherein, the molar amount of the silicon source is expressed as the molar amount of silicon dioxide;
[0019] The molar amount of the aluminum source is expressed as the molar amount of aluminum oxide;
[0020] The molar amount of the inorganic base is expressed as the molar amount of the alkali metal oxide corresponding to the basic substance therein.
[0021] The molar amount of the template agent is expressed as the molar amount of the tetrabutylammonium ion therein.
[0022] The crystallization temperature is 120–200°C;
[0023] The crystallization time is 4 to 96 hours.
[0024] According to another aspect of this application, a nanocrystalline stacked mesoporous MFI / MEL eutectic molecular sieve prepared by the above-described preparation method is provided.
[0025] According to another aspect of this application, an application of the above-mentioned nanocrystalline stacked mesoporous MFI / MEL eutectic molecular sieve is provided for catalytic cracking reactions, alcohol conversion reactions, olefin hydration reactions, alkylation reactions, and isomerization reactions.
[0026] The beneficial effects that this application can produce include:
[0027] This application relates to a method for preparing nanocrystalline stacked mesoporous MFI / MEL eutectic molecular sieves, mainly addressing the problems of complex processes and high costs in the preparation of existing hierarchical porous molecular sieves. This application employs a combination crystallization process using a crystallization solution containing MFI nanocrystals and a template agent (tetrabutylammonium hydroxide, tetrabutylammonium bromide, or tetrabutylammonium chloride) for synthesizing MEL molecular sieves. The nanocrystalline stacked mesoporous MFI / MEL molecular sieve is obtained through hydrothermal synthesis, with mesopores concentrated at approximately 15 nm and a pore volume of 0.46 cm³. 3 / g. Attached Figure Description
[0028] Figure 1 The image shown is a transmission electron microscope (TEM) image of the sample from Example 1, at a scale of 100 nm.
[0029] Figure 2 The image shows the XRD pattern of the sample from Example 1.
[0030] Figure 3 The nitrogen physical adsorption curve is shown for the sample in Example 1.
[0031] Figure 4 The image shows the XRD pattern of the sample from Example 2.
[0032] Figure 5 The nitrogen physical adsorption curve is shown for the sample in Example 2. Detailed Implementation
[0033] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.
[0034] Unless otherwise specified, the raw materials and reagents used in the embodiments of this application were all purchased commercially.
[0035] Example 1:
[0036] A crystallization solution containing Silicalite-1 seed crystals with a size of less than 80 nm (1 wt% of seed crystals) was mixed evenly with silica sol, deionized water, sodium hydroxide, tetrabutylammonium hydroxide, and aluminum trichloride hexahydrate. The mixture was then placed in a reactor for rotary crystallization at 140 °C for 48 h. The molar ratio of each component was 1 SiO2:0.0125 Al2O3:15 H2O:0.12 Na2O:0.04 TBAOH.
[0037] Appendix Figure 1 Transmission electron microscopy results showed that the prepared sample was a mesoporous molecular sieve with nanocrystal stacking;
[0038] Appendix Figure 2 XRD results show that it is an MFI / MEL eutectic molecular sieve;
[0039] Appendix Figure 3Physical adsorption results show that it has a hierarchical porous structure with a specific surface area of 485 m². 2 / g, micropore volume is 0.130cm³ 3 / g, with mesopores distributed at around 15nm and a pore volume of 0.462cm³. 3 / g.
[0040] Example 2:
[0041] A crystallization solution containing Silicalite-1 seed crystals (3 wt%) with a size of less than 40 nm was mixed thoroughly with silica sol, deionized water, sodium hydroxide, tetrabutylammonium hydroxide, and aluminum trichloride hexahydrate. The mixture was then placed in a reactor for rotary crystallization at 140 °C for 48 h. The molar ratio of each component was 1 SiO2:0.0125 Al2O3:15 H2O:0.12 Na2O:0.025 TBAOH.
[0042] Appendix Figure 4 XRD results show that it is an MFI / MEL eutectic molecular sieve;
[0043] Appendix Figure 5 Physical adsorption results show that it has a hierarchical porous structure with a specific surface area of 456 m². 2 / g, micropore volume is 0.131cm³ 3 / g, with mesopores distributed at approximately 12nm and a pore volume of 0.339cm³. 3 / g.
[0044] Example 3
[0045] A crystallization solution containing Silicalite-1 seed crystals with a size of less than 150 nm (5 wt% of seed crystals) was mixed evenly with silica sol, deionized water, sodium hydroxide, tetrabutylammonium bromide, and aluminum trichloride hexahydrate. The mixture was then placed in a reactor for rotary crystallization at 130 °C for 96 h. The molar ratio of each component was 1 SiO2:0.0125 Al2O3:15 H2O:0.15 Na2O:0.08 TBABr.
[0046] Example 4
[0047] A crystallization solution containing Silicalite-1 seed crystals with a size of less than 150 nm (5 wt% of seed crystals) was mixed evenly with silica sol, deionized water, sodium hydroxide, tetrabutylammonium hydroxide, and aluminum trichloride hexahydrate. The mixture was then placed in a reactor for rotary crystallization at 140 °C for 72 h. The molar ratio of each component was 1 SiO2:0.01667 Al2O3:15 H2O:0.135 Na2O:0.015 TBAOH.
[0048] Example 5
[0049] A crystallization solution containing Silicalite-1 seed crystals with a size of less than 80 nm (1 wt% of seed crystals) was mixed evenly with silica sol, deionized water, sodium hydroxide, tetrabutylammonium hydroxide, and aluminum trichloride hexahydrate. The mixture was then placed in a reactor for rotary crystallization at 140 °C for 48 h. The molar ratio of each component was 1 SiO2:0.00833 Al2O3:15 H2O:0.15 Na2O:0.04 TBAOH.
[0050] Example 6
[0051] A crystallization solution containing Silicalite-1 seed crystals (size less than 40 nm) (1 wt% of seed crystals) was mixed thoroughly with silica sol, deionized water, sodium hydroxide, tetrabutylammonium hydroxide, and aluminum trichloride hexahydrate. The mixture was then placed in a reactor for rotary crystallization at 140 °C for 48 h. The molar ratio of each component was 1 SiO2:0.003333 Al2O3:15 H2O:0.10 Na2O:0.04 TBAOH.
[0052] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. A method for preparing a nanocrystalline stacked mesoporous MFI / MEL eutectic molecular sieve, characterized in that, Includes the following steps: A crystallization solution containing MFI nanocrystals, a template agent containing tetrabutylammonium ions, an inorganic base, a silicon source, an aluminum source, and water are mixed and crystallized in a sealed container to obtain the nanocrystal stacked mesoporous MFI / MEL eutectic molecular sieve.
2. The preparation method according to claim 1, characterized in that, The size of the MFI nanocrystals is 10–300 nm; In the crystallization solution containing MFI nanocrystals, the concentration of MFI nanocrystals is 0.01–20 wt%. The solvent in the crystallization solution is selected from water and / or ethanol.
3. The preparation method according to claim 1, characterized in that, The template agent is selected from at least one of tetrabutylammonium hydroxide, tetrabutylammonium chloride, and tetrabutylammonium bromide; The inorganic base is selected from at least one of NaOH, Na2CO3, NaHCO3, NaAlO2, KOH, K2CO3, and KHCO3; The silicon source is selected from at least one of tetraethyl orthosilicate, silica sol, water glass, silica gel, fumed silica, and activated clay. The aluminum source is selected from at least one of sodium aluminate, aluminum nitrate, aluminum sulfate, aluminum chloride, aluminum isopropoxide, and aluminum oxide.
4. The preparation method according to claim 1, characterized in that, The molar ratio of the silicon source to the aluminum source is 30 to 300; The molar ratio of the inorganic base to the silicon source is 0.05 to 0.25; The molar ratio of water to silicon source is 5 to 120; The molar ratio of the template agent to the silicon source is 0.01 to 0.2; Wherein, the molar amount of the silicon source is expressed as the molar amount of silicon dioxide; The molar amount of the aluminum source is expressed as the molar amount of aluminum oxide; The molar amount of the inorganic base is expressed as the molar amount of the alkali metal oxide corresponding to the basic substance therein. The molar amount of the template agent is expressed as the molar amount of the tetrabutylammonium ion therein.
5. The preparation method according to claim 1, characterized in that, The crystallization temperature is 120–200°C; The crystallization time is 4 to 96 hours.
6. A nanocrystalline stacked mesoporous MFI / MEL eutectic molecular sieve prepared by the preparation method according to any one of claims 1 to 5.
7. An application of the nanocrystalline stacked mesoporous MFI / MEL eutectic molecular sieve according to claim 6, characterized in that, It is used for catalytic cracking reactions, alcohol conversion reactions, olefin hydration reactions, alkylation reactions, and isomerization reactions.