A complex salt / inorganic non-metallic porous material MIL-53 (Al) hollow microsphere core-shell catalyst and a preparation method and application thereof

Abstract

This invention discloses a core-shell catalyst of hollow microspheres (@MIL-53(Al)) from a complex salt / inorganic non-metallic porous material, along with its preparation method and applications. Belonging to the field of catalyst technology, the invention includes the following steps: ultrasonic treatment of inorganic non-metallic hollow microspheres with an aluminum source and terephthalic acid in a solvent, followed by hydrothermal reaction to obtain the hollow core-shell catalyst of @MIL-53(Al); mixing the hollow core-shell catalyst of @MIL-53(Al) with a complex salt system in a solvent, followed by hydrothermal crystallization reaction to obtain the hollow core-shell catalyst of @MIL-53(Al). The catalyst provided by this invention uses readily available raw materials, exhibits high reproducibility during preparation, and demonstrates good catalytic effect on the preparation of dimethyldichlorosilane from disproportionated methyltrichlorosilane and trimethylchlorosilane, thus possessing certain industrial significance.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, and particularly relates to a core-shell catalyst of hollow microspheres made of complex salt / inorganic non-metallic porous material @MIL-53(Al), its preparation method and application. Background Technology

[0002] The most abundant elements in the Earth's crust are oxygen (49.5%) and silicon (25.7%). However, there is no free silicon in the crust; instead, it exists as silicon dioxide and metal silicates tightly bound to oxygen. This is because silicon has a high silicon-oxygen bond strength of 10. 8 The concentration of silicon is kCal / mol, so despite its high abundance, it is difficult to separate it from oxygen bonds. It is precisely this unique structure that gives it its unique properties. Organosilicon materials possess both inorganic and organic characteristics. Their complex and varied structure endows them with properties such as high pressure resistance, high temperature resistance, corrosion resistance, stain resistance, moisture resistance, hydrophobicity, and electrical insulation, making them widely applicable.

[0003] In the direct production process of organosilicon materials, M1 (methyltrichlorosilane, CH3SiCl3) accounts for approximately 10%–15% of the total product, and M3 (trimethylchlorosilane, (CH3)3SiCl) accounts for approximately 1%–3%, along with the generation of a certain amount of high-boiling-point byproducts. These byproducts have low added value and are mostly highly corrosive and easily hydrolyzed. They readily react with moisture in the air to generate hydrochloric acid mist and release a large amount of heat, causing severe corrosion to equipment and harming human skin, eyes, and respiratory mucous membranes. Furthermore, direct discharge without effective treatment leads to environmental pollution, resource waste, and increased production costs for enterprises. Among these, the high-boiling-point byproducts are rich in Si-Si and Si-C bonds, possessing high potential utilization value. Moreover, the low-boiling-point byproducts M1 and M3 can be converted into the high-value-added M2 (dimethyldichlorosilane, (CH3)2SiCl2) through disproportionation or redistribution reactions. Therefore, achieving efficient conversion between low-boiling and high-boiling substances through catalytic cracking and redistribution reactions can not only improve M2 yield and reduce by-product emissions, but also realize the resource utilization of organosilicon by-products. This is of great significance for improving the economic benefits of the organosilicon industry, reducing energy consumption, and promoting the green and sustainable development of the industry.

[0004] Existing technologies primarily utilize disproportionation reactions to convert the aforementioned high-boiling and low-boiling substances. During the disproportionation reaction, the presence of AlCl3 significantly lowers the energy barrier, allowing the reaction to proceed smoothly. However, the AlCl3 catalyst has a low sublimation temperature, making it prone to catalyst loss during the reaction, resulting in low economic efficiency and poor catalytic effectiveness. ZSM-5 molecular sieves contain Lewis and Bronsted acids within their pores, exhibiting some catalytic activity for dimethyldichlorosilane. However, as a silica-alumina material, its catalytic activity is relatively low, requiring modification with loaded active components to alter catalytic selectivity and improve stability. Furthermore, its strong surface Bronsted acid strength makes it susceptible to carbon deposition, limiting its application in the disproportionation preparation of dimethyldichlorosilane. In addition, the supports selected in existing technologies are all inorganic non-metallic supports, limiting their catalytic activity.

[0005] Therefore, how to provide a catalyst with high catalytic activity for the catalytic conversion of by-products in organosilicon is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a core-shell catalyst of a complex salt / inorganic non-metallic porous material @MIL-53(Al) hollow microspheres, its preparation method, and its application.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a core-shell catalyst of a complex salt / inorganic non-metallic porous material @MIL-53(Al) hollow microspheres includes the following steps: (1) Inorganic non-metallic hollow microspheres were ultrasonically treated with aluminum source and terephthalic acid in solvent and then subjected to hydrothermal reaction to obtain inorganic non-metallic porous material @MIL-53(Al) hollow core-shell catalyst. (2) The inorganic non-metallic porous material @MIL-53(Al) hollow core-shell catalyst and the complex salt system are mixed in a solvent and then subjected to hydrothermal crystallization reaction to obtain the complex salt / inorganic non-metallic porous material @MIL-53(Al) hollow microsphere core-shell catalyst.

[0008] Beneficial Effects: Compared with existing dual-inorganic non-metallic core-shell composite materials, this invention uses an inorganic non-metallic material as the core and grows a metal-organic framework (MOF) shell layer in situ on its surface to construct an inorganic non-metallic core@MOF shell composite material. Compared with the core-shell structure composed of two inorganic non-metallic materials, the introduction of the MOF shell in this invention allows for the regulation of the composite material's pore environment, surface functional groups, and acidic sites by changing the metal nodes, ligand types, ligand ratios, and shell growth conditions, thereby improving the designability of the material structure and surface chemical properties. The MOF shell has high porosity and numerous accessible active sites, which is beneficial for the adsorption of reactants on the material surface and their contact with the active centers, thus improving the effective utilization rate of active sites and enhancing the catalytic performance of the composite material. The heterogeneous interface formed between the inorganic non-metallic core and the MOF shell can alter the local chemical environment of the material surface, which is beneficial for regulating the electronic structure and acidic properties around the active sites, providing a suitable reaction interface for the adsorption, activation, and directional transformation of reactants.

[0009] Preferably, the inorganic non-metallic hollow microspheres in step (1) are hollow ZSM-5 molecular sieves or hollow γ-Al2O3 microspheres.

[0010] More preferably, the preparation method of the hollow ZSM-5 molecular sieve includes the following steps: A 0.1 mol / L NaOH solution was prepared, and ZSM-5 was added to the NaOH solution at a solid-liquid ratio of 1:15. The mixture was stirred uniformly at 50℃ for 30 min, and then transferred to a stainless steel hydrothermal reactor. The reactor was allowed to stand at 170℃ for 24 h after the reaction was completed. After the reaction was completed and the stainless steel hydrothermal reactor was allowed to cool naturally, the mixture was centrifuged and washed to obtain a solid product. This solid product was then dried overnight at 60℃ to obtain hollow ZSM-5 molecular sieve.

[0011] More preferably, the preparation method of the hollow γ-Al2O3 microspheres includes the following steps: 3 mL of water and 17 mL of aniline were mixed to obtain mixed solution A. 1 mL of toluene was added to 2 g of aluminum sec-butoxide and mixed thoroughly to obtain mixed solution B. Mixed solution B was slowly added dropwise to mixed solution A, and the mixture was allowed to react at 25 °C for 3 h. After the reaction was completed, the solid product was separated, washed, and dried at 60 °C to obtain the γ-AlOOH precursor. The γ-AlOOH precursor was calcined at 550 °C for 2 h to obtain hollow γ-Al₂O₃ microspheres.

[0012] Preferably, the aluminum source in step (1) is Al(NO3)3·6H2O.

[0013] Beneficial effects: Aluminum nitrate is currently the most common aluminum source, with strong water solubility and Al... 3+ The release of [aluminum chloride] is more complete, resulting in a higher yield; aluminum chloride (AlCl3) is a strong acid with a fast crystallization rate, but it contains Cl [aluminum chloride]. - This affects the judgment of subsequent double salt loading; other aluminum salts have weak hydrolytic properties.

[0014] Preferably, the ultrasonic treatment time in step (1) is 30 min.

[0015] Beneficial effects: Under the above-mentioned ultrasonic dispersion treatment time conditions, the raw materials can be more uniform, the aggregation of raw materials can be reduced, and the ligands can more easily enter the interstitial space of the core material.

[0016] Preferably, the hydrothermal reaction in step (1) is carried out at a temperature of 90°C for 20 hours.

[0017] Preferably, the complex salt system in step (2) contains the complex salt Mt. 1 Mt 2 Cl n The Mt 1 Selected from Li + Na + K + 、Rb + and Cs + Any one of them; The Mt 2 Selected from Cu 2+ Fe 2+ Al 3+ Fe 3+ and La 3+ Any one of them; The n=3 or 4.

[0018] More preferably, the Mt 2 Selected from Al 3+ Fe 3+ La 3+ When any one of the trivalent cations is present, n=4; The Mt 2 Selected from Cu 2+ Fe 2+ When n = 3, n is any one of the divalent cations in the mixture.

[0019] More preferably, the Mt 1 Mt 2 Cl n Including KAlCl4, NaAlCl4, or LiLaCl4; The complex salt system includes two of the following: KCl, AlCl3, NaCl, LiCl, and LaCl3.

[0020] Beneficial effects: This invention uses a more complete research double salt system and can comprehensively consider cost and conversion rate when selecting the type of double salt for the catalyst.

[0021] Preferably, the loading of the complex salt in step (2) is 6-12 wt.%.

[0022] Beneficial effects: Catalytic activity is affected by the double salt loading in a typical volcano-like pattern; both excessively high and low loading will reduce catalytic activity. Insufficient loading leads to too few double salts and insufficient active sites on the catalyst; high loading can cause pore blockage and reduce catalytic activity. At the loading levels specified above, the catalyst's active sites are maintained without pore blockage, effectively ensuring catalytic activity.

[0023] Preferably, the temperature of the hydrothermal crystallization reaction in step (2) is 170-190℃ and the time is 17h.

[0024] Beneficial effects: At lower temperatures, the dissolution and deprotonation of ligands are slower, resulting in fewer surface nuclei and lower crystallinity of discontinuous MOF shell products; excessively high temperatures lead to excessively rapid nucleation and growth, and the intensification of homogeneous nucleation in the liquid phase results in the formation of a large number of free MOF particles rather than core-shell structures.

[0025] Too short a time will result in discontinuous MOF shells, low surface coverage, and a severely insufficient number of MOFs, with only preliminary nucleation; too long a time will result in excessively large grain growth and agglomeration, causing blockage of catalyst pores.

[0026] A core-shell catalyst of hollow microspheres @MIL-53(Al) prepared by the above preparation method.

[0027] Application of a core-shell catalyst of a complex salt / inorganic non-metallic porous material @MIL-53(Al) hollow microspheres in the catalytic disproportionation reaction of organosilicon byproducts.

[0028] Beneficial effects: The introduction of MOF material in this invention makes the catalyst product more selective, and its application in the disproportionation reaction of organosilicon by-products can effectively improve the yield of dimethyldichlorosilane.

[0029] Preferably, the organosilicon byproduct disproportionation reaction is a disproportionation reaction of methyltrichlorosilane and trimethylchlorosilane to prepare dimethyldichlorosilane or a high-boiling-point pyrolysis disproportionation reaction.

[0030] Preferably, the reaction for preparing dimethyldichlorosilane by disproportionation of methyltrichlorosilane and trimethylchlorosilane includes the following steps: The reaction reagents for dimethyltrichlorosilane and trimethylchlorosilane were prepared. The reaction instrument was connected to a gas chromatograph. The reactants were vaporized and introduced into the reaction vessel using the injection chamber of the gas chromatograph. The reaction products were then carried into the chromatograph by the carrier gas for detection and analysis. A certain amount of complex salt / inorganic non-metallic porous material @ZSM-5 hollow microsphere core-shell catalyst was placed in a single-stage high-temperature furnace reaction tube. The reaction temperature of the high-temperature furnace was adjusted to 150-270℃, and the reaction yield of dimethyldichlorosilane was measured.

[0031] Beneficial effects: The disproportionation reaction system has a window temperature of around 200℃. This invention places the reaction temperature in the range of 150-270℃, which can better find the reaction range for low-temperature and high-temperature control.

[0032] More preferably, the mass ratio of the monomethyltrichlorosilane to the trimethylchlorosilane is (1-2):(1-3).

[0033] Beneficial effects: The theoretical stoichiometric ratio of monomethyltrichlorosilane and trimethylchlorosilane should be 1:1. However, considering the different adsorption capacities of the two raw materials on the catalyst surface, the different roles of Lewis and Bronsted acid sites, and the different diffusion rates, this invention designs a feed gradient ratio to find the feed range of the catalyst, and at the same time can determine whether the reaction is limited by a certain reactant.

[0034] Preferably, the high-boiling-point pyrolysis disproportionation reaction includes the following steps: Prepare the high-boiling-point reaction reagent, connect the reaction instrument to a gas chromatograph, and use the gas chromatograph's injection chamber to vaporize the reactants and allow them to enter the reaction vessel. The reaction products are then carried by the carrier gas into the chromatograph for detection and analysis. A certain amount of Mt... 1 Mt 2 Cl n / Inorganic non-metallic porous material @ZSM-5 hollow microsphere core-shell catalyst was used in a single-stage high-temperature furnace reaction tube. The reaction temperature of the high-temperature furnace was adjusted to 150-270℃. The reaction yield of high-boiling-point cracking and the selectivity of dimethyldichlorosilane were measured.

[0035] Beneficial effects: The reaction system window temperature is around 200℃. This invention places the reaction temperature in the range of 150-270℃, which can better find the reaction range for low-temperature and high-temperature control.

[0036] More preferably, in the high-boiling-point reaction reagent, the mass ratio of high-boiling-point substance to low-boiling-point substance is (1-2):(1-3).

[0037] Beneficial effects: This invention first uses only high-boiling-point substances for pyrolysis, and then adds M1 or M3 for synergistic disproportionation to find the optimal feed range.

[0038] Compared with the prior art, the present invention has the following advantages and technical effects: This invention provides a core-shell catalyst of hollow microspheres made of complex salt / inorganic non-metallic porous material @MIL-53(Al), its preparation method, and its application. The core-shell catalyst of hollow microspheres made of complex salt / inorganic non-metallic porous material @MIL-53(Al) is prepared by hydrothermal synthesis and high-temperature and high-pressure loading method. The raw materials are readily available, the process is simple, and the reproducibility is high. It also has good catalytic effect on the preparation of dimethyldichlorosilane from disproportionation of methyltrichlorosilane and trimethylchlorosilane, which has certain industrial significance. Attached Figure Description

[0039] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 The image shows the TEM characterization of the catalyst obtained in Example 1. Figure A shows the hollow ZSM-5, and Figure B shows ZSM-5@MIL-53 (A1). Figure 2 The image shows the TEM characterization of the catalyst obtained in Example 6. Figure A shows hollow γ-Al2O3, and Figure B shows γ-Al2O3@MIL-53 (Al). Figure 3 Py-IR spectra of the catalyst prepared in Example 1 and the catalysts with different complex salt loadings obtained in Examples 4-5 and Comparative Example 3; Figure 4 Py-IR spectra of the catalyst prepared in Example 6 and the catalysts with different complex salt loadings obtained in Examples 9-10 and Comparative Example 6; Figure 5 XRD characterization diagrams of the hollow ZSM-5 molecular sieve obtained in Comparative Example 1, the MIL-53(Al) obtained in Comparative Example 7, the catalyst prepared in Example 1, and the catalysts with different complex salt loadings obtained in Examples 4-5 and Comparative Examples 2-3. Figure 6 XRD characterization diagrams of hollow γ-Al2O3 microspheres obtained in Comparative Example 4, MIL-53(Al) obtained in Comparative Example 7, catalyst prepared in Example 6, and catalysts with different complex salt loadings obtained in Examples 9-10 and Comparative Examples 5-6. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] Unless otherwise specified, all raw materials used in the embodiments of this invention were purchased through commercial channels; Unless otherwise specified, room temperature or normal temperature in the embodiments of the present invention refers to 25±3℃.

[0043] Example 1 A method for preparing a core-shell catalyst of a complex salt / inorganic non-metallic porous material @MIL-53(Al) hollow microspheres includes the following steps: (1) Prepare a 0.1 mol / L NaOH solution. Add ZSM-5 to the NaOH solution at a solid-liquid ratio of 1:15. Stir the solution uniformly at 50°C for 30 min. Then transfer the mixture to a stainless steel hydrothermal reactor and let it stand at 170°C for 24 h. After the reaction is complete, allow the stainless steel hydrothermal reactor to cool naturally. Centrifuge and wash the mixture to obtain a solid product. Dry the solid product overnight at 60°C to obtain hollow ZSM-5 molecular sieve.

[0044] (2) Take 0.5 g of terephthalic acid and 1.13 g of Al(NO3)3·6H2O, dissolve them in 65 mL of DMF solution, add 0.5 g of the hollow ZSM-5 molecular sieve obtained in step (1), sonicate for 30 minutes, and then pour the mixed solution into a stainless steel hydrothermal reactor and react at 90℃ for 20 h. After the reaction is completed, wait for the stainless steel hydrothermal reactor to cool completely, separate the obtained solid product, wash it 3 times each with DMF and ethanol, and then dry it overnight at 60℃ to obtain the ZSM-5@MIL-53(Al) hollow core-shell catalyst.

[0045] (3) Take 1 g of the ZSM-5@MIL-53(Al) hollow core-shell catalyst obtained in step (2), and select KAlCl4 system as the double salt. Weigh the corresponding mass of KCl and AlCl3 (K, Al molar ratio is 1:1) according to the loading ratio of 10wt%, and add them one by one to 20 mL of deionized water with ZSM-5@MIL-53(Al) hollow core-shell catalyst and stir evenly. After the salt is completely dissolved, put the mixed solution into a stainless steel hydrothermal reactor and crystallize it at 190℃ for 17 h. After the reaction is completed, let the stainless steel hydrothermal reactor cool naturally, and centrifuge and wash the mixed solution to obtain the solid product. Dry it overnight at 60℃ to obtain 10%KAlCl4 / ZSM-5@MIL-53(Al) hollow core-shell double salt catalyst.

[0046] Example 2 A method for preparing a core-shell catalyst of a complex salt / inorganic non-metallic porous material @MIL-53(Al) hollow microspheres includes the following steps: Steps (1)-(2) are the same as in Example 1; (3) Take 1 g of the ZSM-5@MIL-53(Al) hollow core-shell catalyst obtained in step (2), and select the NaAlCl4 system as the double salt. Weigh the corresponding mass of NaCl and AlCl3 (the molar ratio of Na to Al is 1:1) according to the loading ratio of 8wt%, and add them one by one to 20 mL of deionized water with the ZSM-5@MIL-53(Al) hollow core-shell catalyst and stir evenly. After the salt is completely dissolved, put the mixed solution into a stainless steel hydrothermal reactor and crystallize it at 190℃ for 17 h. After the reaction is completed, let the stainless steel hydrothermal reactor cool naturally, and centrifuge and wash the mixed solution to obtain the solid product. Dry it overnight at 60℃ to obtain the NaAlCl4 / ZSM-5@MIL-53(Al) hollow core-shell double salt catalyst.

[0047] Example 3 A method for preparing a core-shell catalyst of a complex salt / inorganic non-metallic porous material @MIL-53(Al) hollow microspheres includes the following steps: Steps (1)-(2) are the same as in Example 1; (3) Take 1 g of the ZSM-5@MIL-53(Al) hollow core-shell catalyst obtained in step (2), and simultaneously select the NaAlCl4 system as the double salt. Weigh the corresponding mass of NaCl and AlCl3 (the molar ratio of Na to Al is 1:1) according to the loading ratio of 10wt.%, and add them one by one to 20 mL of deionized water with the ZSM-5@MIL-53(Al) hollow core-shell catalyst and stir evenly. After the salt is completely dissolved, put the mixed solution into a stainless steel hydrothermal reactor and crystallize it at 190℃ for 17 h. After the reaction is completed, let the stainless steel hydrothermal reactor cool naturally, and centrifuge and wash the mixed solution to obtain the solid product. Dry it overnight at 60℃ to obtain the NaAlCl4 / ZSM-5@MIL-53(Al) hollow core-shell double salt catalyst.

[0048] Example 4 The difference from Example 1 is that the loading ratio of the complex salt in step (3) is 6 wt%, which specifically includes the following steps: Steps (1)-(2) are the same as in Example 1; (3) Take 1 g of the ZSM-5@MIL-53(Al) hollow core-shell catalyst obtained in step (1), and select KAlCl4 system as the double salt. Weigh the corresponding mass of KCl and AlCl3 (K, Al molar ratio of 1:1) according to the loading ratio of 6wt.%, and add them one by one to 20 mL of deionized water with the ZSM-5@MIL-53(Al) hollow core-shell catalyst and stir evenly. After the salt is completely dissolved, put the mixed solution into a stainless steel hydrothermal reactor and crystallize it at 190℃ for 17 h. After the reaction is completed, let the stainless steel hydrothermal reactor cool naturally, and centrifuge and wash the mixed solution to obtain the solid product. Dry it overnight at 60℃ to obtain the 6%KAlCl4 / ZSM-5@MIL-53(Al) hollow core-shell double salt catalyst.

[0049] Example 5 The difference from Example 1 is that the loading ratio of the complex salt in step (3) is 8 wt%, which specifically includes the following steps: Steps (1)-(2) are the same as in Example 1; (3) Take 1 g of the ZSM-5@MIL-53(Al) hollow core-shell catalyst obtained in step (1), and select KAlCl4 system as the double salt. Weigh the corresponding mass of KCl and AlCl3 (K, Al molar ratio of 1:1) according to the loading ratio of 8wt.%, and add them one by one to 20 mL of deionized water with the ZSM-5@MIL-53(Al) hollow core-shell catalyst and stir evenly. After the salt is completely dissolved, put the mixed solution into a stainless steel hydrothermal reactor and crystallize it at 190℃ for 17 h. After the reaction is completed, let the stainless steel hydrothermal reactor cool naturally, and centrifuge and wash the mixed solution to obtain the solid product. Dry it overnight at 60℃ to obtain the 8%KAlCl4 / ZSM-5@MIL-53(Al) hollow core-shell double salt catalyst.

[0050] Example 6 A method for preparing a core-shell catalyst of a complex salt / inorganic non-metallic porous material @MIL-53(Al) hollow microspheres includes the following steps: (1) Mix 3 mL of water and 17 mL of aniline to obtain mixed solution A; add 1 mL of toluene to 2 g of aluminum sec-butoxide and mix well to obtain mixed solution B. Slowly add mixed solution B dropwise to mixed solution A, and let it stand at 25 °C for 3 h. After the reaction is complete, the solid product is separated, washed, and dried at 60 °C to obtain the γ-AlOOH precursor. Calcinate the γ-AlOOH precursor at 550 °C for 2 h to obtain hollow γ-Al2O3 microspheres.

[0051] (2) Take 0.5 g of terephthalic acid and 1.13 g of Al(NO3)3·6H2O, dissolve them in 65 mL of DMF solution, add 0.5 g of the hollow γ-Al2O3 microspheres obtained in step (1), sonicate for 30 minutes, and then pour the mixed solution into a stainless steel hydrothermal reactor and react at 90℃ for 20 h. After the reaction is completed, wait for the stainless steel hydrothermal reactor to cool completely, separate the obtained solid product, wash it 3 times each with DMF and ethanol, and then dry it overnight at 60℃ to obtain the γ-Al2O3@MIL-53(Al) hollow core-shell catalyst.

[0052] (3) Take 1 g of the γ-Al2O3@MIL-53(Al) hollow core-shell catalyst obtained in step (2), and select KAlCl4 system as the double salt. Weigh the corresponding mass of KCl and AlCl3 (K, Al molar ratio is 1:1) according to the loading ratio of 10wt.%, and add them one by one to 20 mL of deionized water with ZSM-5@MIL-53(Al) hollow core-shell catalyst and stir evenly. After the salt is completely dissolved, put the mixed solution into a stainless steel hydrothermal reactor and crystallize it at 170℃ for 17 h. After the reaction is completed, let the stainless steel hydrothermal reactor cool naturally, and centrifuge and wash the mixed solution to obtain the solid product. Dry it overnight at 60℃ to obtain 10%KAlCl4 / γ-Al2O3@MIL-53(Al) hollow core-shell double salt catalyst.

[0053] Example 7 A method for preparing a core-shell catalyst of a complex salt / inorganic non-metallic porous material @MIL-53(Al) hollow microspheres includes the following steps: Steps (1)-(2) are the same as in Example 6; (3) Take 1 g of the γ-Al2O3@MIL-53(Al) hollow core-shell catalyst obtained in step (2), and simultaneously select the LiLaCl4 system as the double salt. Weigh the corresponding mass of LiCl and LaCl3 (the molar ratio of Li to La is 1:1) according to the loading ratio of 10wt.%, and add them one by one to 20 mL of deionized water with the γ-Al2O3@MIL-53(Al) hollow core-shell catalyst and stir evenly. After the salt is completely dissolved, put the mixed solution into a stainless steel hydrothermal reactor and crystallize it at 170℃ for 17 h. After the reaction is completed, let the stainless steel hydrothermal reactor cool naturally, and centrifuge and wash the mixed solution to obtain the solid product. Dry it overnight at 60℃ to obtain the LiLaCl4 / γ-Al2O3@MIL-53(Al) hollow core-shell double salt catalyst.

[0054] Example 8 A method for preparing a core-shell catalyst of a complex salt / inorganic non-metallic porous material @MIL-53(Al) hollow microspheres includes the following steps: Steps (1)-(2) are the same as in Example 6; (3) Take 1 g of the γ-Al2O3@MIL-53(Al) hollow core-shell catalyst obtained in step (2), and simultaneously select the NaAlCl4 system as the double salt. Weigh the corresponding mass of NaCl and AlCl3 (the molar ratio of Na to Al is 1:1) according to the loading ratio of 10wt.%, and add them one by one to 20 mL of deionized water with the γ-Al2O3@MIL-53(Al) hollow core-shell catalyst and stir evenly. After the salt is completely dissolved, put the mixed solution into a stainless steel hydrothermal reactor and crystallize it at 170℃ for 17 h. After the reaction is completed, let the stainless steel hydrothermal reactor cool naturally, and centrifuge and wash the mixed solution to obtain the solid product. Dry it overnight at 60℃ to obtain the NaAlCl4 / γ-Al2O3@MIL-53(Al) hollow core-shell double salt catalyst.

[0055] Example 9 The difference from Example 6 is that the loading ratio of the complex salt in step (3) is 6 wt%, specifically including the following steps: Steps (1)-(2) are the same as in Example 6; (3) Take 1 g of the γ-Al2O3@MIL-53(Al) hollow core-shell catalyst obtained in step (2), and select KAlCl4 system as the double salt. Weigh the corresponding mass of KCl and AlCl3 (K, Al molar ratio is 1:1) according to the loading ratio of 6wt.%, and add them one by one to 20 mL of deionized water with the γ-Al2O3@MIL-53(Al) hollow core-shell catalyst and stir evenly. After the salt is completely dissolved, put the mixed solution into a stainless steel hydrothermal reactor and crystallize it at 170℃ for 17 h. After the reaction is completed, let the stainless steel hydrothermal reactor cool naturally, and centrifuge and wash the mixed solution to obtain the solid product. Dry it overnight at 60℃ to obtain the 6%KAlCl4 / γ-Al2O3@MIL-53(Al) hollow core-shell double salt catalyst.

[0056] Example 10 The difference from Example 6 is that the loading ratio of the complex salt in step (3) is 8 wt%, specifically including the following steps: Steps (1)-(2) are the same as in Example 6; (3) Take 1 g of the γ-Al2O3@MIL-53(Al) hollow core-shell catalyst obtained in step (2), and select KAlCl4 system as the double salt. Weigh the corresponding mass of KCl and AlCl3 (the molar ratio of K and Al is 1:1) according to the loading ratio of 8wt.%, and add them one by one to 20 mL of deionized water with the γ-Al2O3@MIL-53(Al) hollow core-shell catalyst and stir evenly. After the salt is completely dissolved, put the mixed solution into a stainless steel hydrothermal reactor and crystallize it at 170℃ for 17 h. After the reaction is completed, let the stainless steel hydrothermal reactor cool naturally, and centrifuge and wash the mixed solution to obtain the solid product. Dry it overnight at 60℃ to obtain the 8%KAlCl4 / γ-Al2O3@MIL-53(Al) hollow core-shell double salt catalyst.

[0057] Comparative Example 1 The difference from Example 1 is that the loading of MOF material and complex salt in steps (2) and (3) is not included. Specifically, the following steps are included: A 0.1 mol / L NaOH solution was prepared, and ZSM-5 was added to the NaOH solution at a solid-liquid ratio of 1:15. The mixture was stirred uniformly at 50℃ for 30 min, and then transferred to a stainless steel hydrothermal reactor. The reactor was allowed to stand at 170℃ for 24 h after the reaction was completed. After the reaction was completed and the stainless steel hydrothermal reactor was allowed to cool naturally, the mixture was centrifuged and washed to obtain a solid product. This solid product was then dried overnight at 60℃ to obtain hollow ZSM-5 molecular sieve.

[0058] Comparative Example 2 The difference from Example 1 is that the loading of the double salt in step (3) is not included, and the specific steps include: (1) Prepare a 0.1 mol / L NaOH solution. Add ZSM-5 to the NaOH solution at a solid-liquid ratio of 1:15. Stir the solution uniformly at 50°C for 30 min. Then transfer the mixture to a stainless steel hydrothermal reactor and let it stand at 170°C for 24 h. After the reaction is complete, allow the stainless steel hydrothermal reactor to cool naturally. Centrifuge and wash the mixture to obtain a solid product. Dry the solid product overnight at 60°C to obtain hollow ZSM-5 molecular sieve.

[0059] (2) Take 0.5 g of terephthalic acid and 1.13 g of Al(NO3)3·6H2O, dissolve them in 65 mL of DMF solution, add 0.5 g of the hollow ZSM-5 molecular sieve obtained in step (1), sonicate for 30 minutes, and then pour the mixed solution into a stainless steel hydrothermal reactor and react at 90℃ for 20 h. After the reaction is completed, wait for the stainless steel hydrothermal reactor to cool completely, separate the obtained solid product, wash it 3 times each with DMF and ethanol, and then dry it overnight at 60℃ to obtain the ZSM-5@MIL-53(Al) hollow core-shell catalyst.

[0060] Comparative Example 3 The difference from Example 1 is that the loading ratio of the complex salt in step (3) is 12 wt%, which specifically includes the following steps: Steps (1)-(2) are the same as in Example 1; (3) Take 1 g of the ZSM-5@MIL-53(Al) hollow core-shell catalyst obtained in step (1), and select KAlCl4 system as the double salt. Weigh the corresponding mass of KCl and AlCl3 (K, Al molar ratio is 1:1) according to the loading ratio of 12wt.%, and add them one by one to 20 mL of deionized water with the ZSM-5@MIL-53(Al) hollow core-shell catalyst and stir evenly. After the salt is completely dissolved, put the mixed solution into a stainless steel hydrothermal reactor and crystallize it at 190℃ for 17 h. After the reaction is completed, let the stainless steel hydrothermal reactor cool naturally, and centrifuge and wash the mixed solution to obtain the solid product. Dry it overnight at 60℃ to obtain the 12%KAlCl4 / ZSM-5@MIL-53(Al) hollow core-shell double salt catalyst.

[0061] Comparative Example 4 The difference from Example 6 is that the loading of MOF material and complex salt in steps (2) and (3) is not included. Specifically, the following steps are included: 3 mL of water and 17 mL of aniline were mixed to obtain mixed solution A. 1 mL of toluene was added to 2 g of aluminum sec-butoxide and mixed thoroughly to obtain mixed solution B. Mixed solution B was slowly added dropwise to mixed solution A, and the mixture was allowed to react at 25 °C for 3 h. After the reaction was completed, the solid product was separated, washed, and dried at 60 °C to obtain the γ-AlOOH precursor. The γ-AlOOH precursor was calcined at 550 °C for 2 h to obtain hollow γ-Al₂O₃ microspheres.

[0062] Comparative Example 5 The difference from Example 6 is that the loading of the double salt in step (3) is not included, and the specific steps include: (1) Mix 3 mL of water and 17 mL of aniline to obtain mixed solution A; add 1 mL of toluene to 2 g of aluminum sec-butoxide and mix well to obtain mixed solution B. Slowly add mixed solution B dropwise to mixed solution A, and let it stand at 25 °C for 3 h. After the reaction is complete, the solid product is separated, washed, and dried at 60 °C to obtain the γ-AlOOH precursor. Calcinate the γ-AlOOH precursor at 550 °C for 2 h to obtain hollow γ-Al2O3 microspheres.

[0063] (2) Take 0.5 g of terephthalic acid and 1.13 g of Al(NO3)3·6H2O, dissolve them in 65 mL of DMF solution, add 0.5 g of the hollow γ-Al2O3 microspheres obtained in step (1), sonicate for 30 minutes, and then pour the mixed solution into a stainless steel hydrothermal reactor and react at 90℃ for 20 h. After the reaction is completed, wait for the stainless steel hydrothermal reactor to cool completely, separate the obtained solid product, wash it 3 times each with DMF and ethanol, and then dry it overnight at 60℃ to obtain the γ-Al2O3@MIL-53(Al) hollow core-shell catalyst.

[0064] Comparative Example 6 The difference from Example 6 is that the loading ratio of the complex salt in step (3) is 12 wt%, which specifically includes the following steps: Steps (1)-(2) are the same as in Example 6; (3) Take 1 g of the γ-Al2O3@MIL-53(Al) hollow core-shell catalyst obtained in step (2), and select KAlCl4 system as the double salt. Weigh the corresponding mass of KCl and AlCl3 (K, Al molar ratio is 1:1) according to the loading ratio of 12wt.%, and add them one by one to 20 mL of deionized water with ZSM-5@MIL-53(Al) hollow core-shell catalyst and stir evenly. After the salt is completely dissolved, put the mixed solution into a stainless steel hydrothermal reactor and crystallize it at 170℃ for 17 h. After the reaction is completed, let the stainless steel hydrothermal reactor cool naturally, and centrifuge and wash the mixed solution to obtain the solid product. Dry it overnight at 60℃ to obtain 12%KAlCl4 / γ-Al2O3@MIL-53(Al) hollow core-shell double salt catalyst.

[0065] Comparative Example 7 The preparation of MIL-53(Al) includes the following steps: 0.5 g of terephthalic acid and 1.13 g of 6H₂O·Al(NO₃)₃ were dissolved in 65 ml of DMF solution. After sonicating the solution for 30 minutes, the mixture was poured into a stainless steel hydrothermal reactor and reacted at 170 °C for 24 h. After the stainless steel hydrothermal reactor had completely cooled, the solid product in the mixture was separated and washed three times each with DMF and ethanol. The solid product was dried overnight at 60 °C to obtain the MIL-53(Al) hollow core-shell catalyst.

[0066] Technical effects: 1. Performance Characterization Figure 1 The images show TEM characterization of the catalyst prepared in Example 1. TEM was used to analyze the surface morphology and elemental composition distribution of the prepared core-shell double salt catalyst. In Figure (A), the internal portion of ZSM-5 appears transparent. This is because the internal portion of ZSM-5 was etched by the alkaline solution, forming cavities, further indicating the successful preparation of hollow ZSM-5 molecular sieves. In Figure (B), oat-like MIL-53(Al) coats ZSM-5, further indicating the successful preparation of ZSM-5@MIL-53(Al) core-shell catalyst support. When KAlCl4 is loaded, the abundant pores of the ZSM-5@MIL-53(Al) support allow KAlCl4 molecules to enter the pores of the support through these pores. At high temperatures, a uniform layer of crystals forms on the support, filling a large number of pores, thus appearing opaque in the TEM image.

[0067] Figure 2 The image shows the TEM characterization of the catalyst prepared in Example 6. TEM was used to analyze the surface morphology and elemental composition distribution of the prepared core-shell complex salt catalyst. As shown in Figure (A), the γ-Al₂O₃ is filled with voids, further indicating that the prepared γ-Al₂O₃ is filled with channels, successfully preparing hollow porous γ-Al₂O₃. As shown in Figure (B), the γ-Al₂O₃ is uniformly coated with MIL-53(Al), further indicating the successful preparation of the γ-Al₂O₃@MIL-53(Al) core-shell catalyst support. When KAlCl₄ is loaded, the abundant channels of the γ-Al₂O₃@MIL-53(Al) support allow KAlCl₄ molecules to enter the voids in the support through these channels. At high temperatures, a uniform layer of crystals forms on the support, filling a large number of channels, thus appearing as opaque in the TEM image.

[0068] Figure 3The images show the Py-IR spectra of the catalyst prepared in Example 1, and the catalysts with different complex salt loadings obtained in Examples 4-5 and Comparative Example 3. Py-IR was used to analyze the acid type and acid content of the prepared core-shell catalysts. Figure 3 It can be seen that it is distributed at 1540 cm. -1 The characteristic peak at 1450 cm⁻¹ indicates the pyridine adsorption peak of Brønsted (B acid) in the sample. -1 The characteristic peak at 1490 cm⁻¹ indicates the pyridine adsorption peak of Lewis acid in the sample, while the peak at 1490 cm⁻¹ is a characteristic peak of Lewis acid adsorption. -1 The characteristic peak at the position belongs to the total pyridine adsorption peak at the L acid and Brønsted acid sites, indicating that the prepared catalyst is mainly composed of L acid and supplemented by Brønsted acid.

[0069] Figure 4 The images show the Py-IR spectra of the catalyst prepared in Example 6, and the catalysts with different complex salt loadings obtained in Examples 9-10 and Comparative Example 6. It can be seen that at 3446 cm⁻¹... -1 The vibrational peak at 1098 cm⁻¹ is related to the stretching vibration of the -OH bond, while at 1098 cm⁻¹... -1 The vibrational peak at 1417 cm⁻¹ indicates that Al and O atoms have formed Al-O bonds within the framework. It can be seen that this peak gradually decreases with increasing complex salt loading, indicating that complex salt loading can replace the original Al-OH active sites with Al-O-Al-Cl active sites, which matches previous theoretical calculations. -1 1508cm -1 1610cm -1 1670cm -1 The characteristic peak at γ-Al₂O₃ belongs to the C=C benzene ring. However, after adding MIL-53(Al), a significant enhancement of this characteristic peak is observed, indicating a π-π interaction between γ-Al₂O₃ and MIL-53(Al). Terephthalic acid (H₂BDC) provides an additional benzene ring to this framework, which facilitates stronger π-π interactions, demonstrating the successful binding of γ-Al₂O₃ and MIL-53(Al). Figures (c)-(f) show samples with different complex salt ratios. After loading the complex salt, a weakening of the C=C characteristic peak is observed, indicating successful loading of the complex salt into the core-shell catalyst. Furthermore, a peak at 480 cm⁻¹ is observed... -1 The enhanced vibrational peak at the point indicates that the KAlCl4 double salt has formed Al-Cl bonds.

[0070] Figure 5 XRD characterization images of the hollow ZSM-5 molecular sieve obtained in Comparative Example 1, the MIL-53(Al) obtained in Comparative Example 7, the catalyst prepared in Example 1, and the catalysts with different double salt loadings obtained in Examples 4-5 and Comparative Examples 2-3 are shown. The crystal structure of the prepared core-shell double salt catalysts was characterized by XRD, and the results are as follows. Figure 4 As shown in the figure. Figure (a) shows the diffraction peaks of hollow ZSM-5 molecular sieve. Compared with its standard PDF card, typical MFI structure diffraction peaks appear near 2θ of 23.1°, 23.8° and 24.4°, indicating that the crystal structure of hollow ZSM-5 molecular sieve was not destroyed after alkali treatment. Typical MFI structure diffraction peaks were also found in subsequent samples, indicating that hollow ZSM-5 molecular sieve was successfully prepared. Figure (b) shows the diffraction peaks of MIL-53(Al) obtained in Comparative Example 7. It is almost identical to that in the reference (Ma X, Tan J, Li Z, et al. Fabrication of StableMIL-53(Al) for Excellent Removal of Rhodamine B [J]. Langmuir, 2022, 38(3):1158-69.). The same MIL-53(Al) diffraction peaks were also found in subsequent samples, indicating that MIL-53(Al) was successfully prepared. Figure (c) shows the characteristic peaks of ZSM-5 and MIL-53(Al), indicating that ZSM-5 and MIL-53(Al) were successfully combined. Figures (d)-(g) show samples with different complex salt ratios. Compared with the KAlCl4 standard PDF card, some peak positions are close to the characteristic peaks of the KAlCl4 standard card, but the crystallinity is lower and the characteristic peak intensity is weaker due to the difference in complex salt ratio. Combined with subsequent EDS analysis, it shows that the complex salt KAlCl4 was successfully loaded onto the catalyst support, and it can also be observed that the characteristic peak intensity of KAlCl4 gradually increases with the increase of the loading ratio.

[0071] Figure 6The figures show the XRD characterization of the hollow γ-Al₂O₃ microspheres obtained in Comparative Example 4, the MIL-53(Al) obtained in Comparative Example 7, the catalyst prepared in Example 6, and the catalysts with different complex salt loadings obtained in Examples 9-10 and Comparative Examples 5-6. Figure (a) shows the diffraction peaks of γ-Al₂O₃ obtained in Comparative Example 4. Compared with its standard PDF card, it has typical γ-Al₂O₃ characteristic peaks, and γ-Al₂O₃ characteristic peaks were also found in subsequent samples, indicating that hollow γ-Al₂O₃ microspheres were successfully prepared. Figure (b) shows the diffraction peaks of the prepared sample MIL-53(Al), which are almost identical to those in the reference Ma X, Tan J, Li Z, et al. Fabrication of Stable MIL-53(Al) for Excellent Removal of Rhodamine B [J]. Langmuir, 2022,38(3): 1158-69. The same MIL-53(Al) diffraction peaks were also found in subsequent samples, indicating that MIL-53(Al) was successfully prepared. Figure (c) shows the characteristic peaks of γ-Al2O3 and MIL-53(Al), indicating that γ-Al2O3 and MIL-53(Al) were successfully combined. Figures (d)-(g) show samples with different complex salt ratios. Compared with the KAlCl4 standard PDF card, some peak positions are close to the characteristic peaks of the KAlCl4 standard card. However, due to the difference in complex salt ratio, the crystallinity is lower and the characteristic peak intensity is weaker. Combined with subsequent EDS analysis, it shows that the complex salt KAlCl4 was successfully loaded onto the catalyst support. It can also be observed that the characteristic peak intensity of KAlCl4 gradually increases with the increase of the loading ratio.

[0072] 2. Preparation of dimethyldichlorosilane by disproportionation The reaction instrument was connected to a gas chromatograph. Using the gas chromatograph's injection chamber, the vaporized reactants were introduced into the reaction vessel. The resulting product, carried by a carrier, entered the chromatograph for detection and analysis. A reaction solution of dimethyltrichlorosilane and trimethylchlorosilane in a volume ratio of 1:2 was prepared. 0.5 g of the catalysts obtained in Examples 1-10 and Comparative Examples 1-6 were loaded into the reaction tubes of a single-stage high-temperature furnace. The furnace temperature was adjusted to 210°C, and the reaction was carried out for 0.5 h. The yield of dimethyldichlorosilane was then measured. The yield results for the disproportionation preparation of dimethyldichlorosilane are shown in Table 1. Table 1 As can be seen from Table 1, Example 6 has the highest yield of the target product (dimethyldichlorosilane M2) at a feed ratio of 1:2 at 210°C; The yield of Comparative Example 3 was only 73.57%, which was significantly lower than that of Example 1. This is because the catalyst obtained in Comparative Example 3 had only a thick layer of KAlCl4 double salt active component attached to its surface, which simultaneously invaded the pores and reduced the specific surface area. During the catalytic process, the catalytically active acidic sites and acid strength that could be provided were limited.

[0073] 3. Catalytic cracking of high-boiling-point substances 1.0 g of the catalysts prepared in Examples 1-10 and Comparative Examples 1-6 were respectively loaded into a fixed-bed reactor. A 1:1 mixture of high-boiling and low-boiling organosilicon compounds was introduced, and a disproportionation reaction was carried out at a reaction temperature of 200 °C and atmospheric pressure for 0.5 h. The resulting products were analyzed by gas chromatography. The conversion rate of the high-boiling compounds and the selectivity of the target product (dimethyldichlorosilane M2) are shown in Table 2. Table 2 The results show that, using the catalyst obtained in Example 1, the conversion rate of high-boiling substances can reach 87.43%, and the selectivity of the target product (dimethyldichlorosilane M2) can reach 38.72%; using the catalyst obtained in Example 6, the conversion rate of high-boiling substances can reach 89.24%, and the selectivity of the target product (dimethyldichlorosilane M2) can reach 40.32%. Both catalysts show good catalytic activity and promising prospects for industrial application.

[0074] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing a core-shell catalyst of a complex salt / inorganic non-metallic porous material @MIL-53(Al) hollow microspheres, characterized in that, Includes the following steps: (1) Inorganic non-metallic hollow microspheres were ultrasonically treated with aluminum source and terephthalic acid in solvent and then subjected to hydrothermal reaction to obtain inorganic non-metallic porous material @MIL-53(Al) hollow core-shell catalyst. (2) The inorganic non-metallic porous material @MIL-53(Al) hollow core-shell catalyst and the complex salt system are mixed in a solvent and then subjected to hydrothermal crystallization reaction to obtain the complex salt / inorganic non-metallic porous material @MIL-53(Al) hollow microsphere core-shell catalyst.

2. The preparation method of a core-shell catalyst for a complex salt / inorganic non-metallic porous material @MIL-53(Al) hollow microspheres according to claim 1, characterized in that, The inorganic non-metallic hollow microspheres mentioned in step (1) are hollow ZSM-5 molecular sieves or hollow γ-Al2O3 microspheres.

3. The preparation method of a core-shell catalyst for a complex salt / inorganic non-metallic porous material @MIL-53(Al) hollow microspheres according to claim 1, characterized in that, The aluminum source mentioned in step (1) is Al(NO3)3·6H2O.

4. The preparation method of a core-shell catalyst for a complex salt / inorganic non-metallic porous material @MIL-53(Al) hollow microspheres according to claim 1, characterized in that, The ultrasonic treatment time in step (1) is 30 minutes.

5. The method for preparing a core-shell catalyst of a complex salt / inorganic non-metallic porous material @MIL-53(Al) hollow microspheres according to claim 1, characterized in that, The hydrothermal reaction in step (1) is carried out at a temperature of 90°C for 20 hours.

6. The method for preparing a core-shell catalyst of a complex salt / inorganic non-metallic porous material @MIL-53(Al) hollow microspheres according to claim 1, characterized in that, The complex salt system described in step (2) contains the complex salt Mt. 1 Mt 2 Cl n The Mt 1 Selected from Li + Na + K + 、Rb + and Cs + Any one of them; The Mt 2 Selected from Cu 2+ Fe 2+ Al 3+ Fe 3+ and La 3+ Any one of them; The n=3 or 4.

7. The preparation method of a core-shell catalyst for a complex salt / inorganic non-metallic porous material @MIL-53(Al) hollow microspheres according to claim 1, characterized in that, The loading of the complex salt in step (2) is 6-12 wt.%.

8. The method for preparing a core-shell catalyst of a complex salt / inorganic non-metallic porous material @MIL-53(Al) hollow microspheres according to claim 1, characterized in that, The temperature of the hydrothermal crystallization reaction in step (2) is 170-190℃ and the time is 17h.

9. A core-shell catalyst of hollow microspheres of a complex salt / inorganic non-metallic porous material @MIL-53(Al) prepared by the preparation method according to any one of claims 1-8.

10. The application of the core-shell catalyst of the complex salt / inorganic non-metallic porous material @MIL-53(Al) hollow microspheres as described in claim 9 in the disproportionation reaction of organosilicon byproducts.

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