A nickel-based composite catalyst with core-shell structure, and a preparation method and use thereof

Abstract

The present application provides a nickel-based composite catalyst with core-shell structure, a preparation method and use thereof, the nickel-based composite catalyst with core-shell structure comprises a Ni@ZSM-5@S-1 core-shell structure and an alumina carrier, the Ni@ZSM-5@S-1 core-shell structure comprises a Ni@ZSM-5 core layer and a S-1 molecular sieve nanolayer coated outside the Ni@ZSM-5 core layer. The catalyst provided by the present application is used in the reaction of preparing chlorosilane monomer by directional catalytic cracking of organic silicon high-boiling matter, the cracking rate of high-boiling matter is more than 95%, and the selectivity of chlorosilane monomer is more than 95%.

Description

Technical Field

[0001] This invention relates to the field of organosilicon technology, and in particular to a nickel-based composite catalyst with a core-shell structure, its preparation method, and its uses. Background Technology

[0002] Currently, the preparation of chlorosilane monomers using tri-n-butylamine as a catalyst for cracking high-boiling-point compounds, despite its low operating temperature and pressure, still faces fundamental and insurmountable problems, as analyzed below: The catalyst, tri-n-butylamine, is a highly toxic chemical that must be strictly controlled throughout its use and is used as a consumable; the target product M2 has low selectivity, with the main products being low-value monomethyltrichlorosilane and monomethyldichlorosilane; the cracking rate is low, only achieving chlorine-rich Si-Si cracking; uncracked high-boiling-point compounds mix with it to form hazardous waste, further causing secondary pollution to human health and the ecological environment, and wasting resources; subsequent treatment is more complex and difficult, resulting in huge environmental costs; the homogeneous batch reaction system makes it difficult to separate the product from the catalyst and unreacted raw materials, resulting in poor product purity; the batch reaction system has limited processing capacity, and given the current rapid expansion of monomer production capacity, there is an urgent need to develop a continuous and stable catalytic reaction system.

[0003] Currently, the publicly available patent documents related to the pyrolysis of organosilicon high-boiling-point compounds to prepare dimethyldichlorosilane mainly fall into the following categories:

[0004] (1) Noble metal catalysts: CN1071927A, JP54-9228, and JP54-119417 reported the cracking of high-boiling substances using noble metals Pd and Pt as catalysts, with HCl as the cracking gas source, and requiring toluene or xylene as a solvent in the reactor. However, noble metal catalysts are expensive, difficult to recycle, and difficult to purify, making large-scale industrial application difficult.

[0005] (2) Aluminum-based catalysts: US5430168, US5321147, CN1169996A, CN1634937A, CN1634936A, CN1915999A, etc., disclose a catalyst using aluminum trichloride (AlCl3) as a catalyst and HCl as the cracking gas, in a slurry bed or fixed bed reaction. Typical process conditions: reaction temperature is 300-500℃, reaction pressure is 4-7MPa, but the M2 yield is low. During the reaction, the active component AlCl3 is easily sublimated and lost, making it difficult to regenerate and recycle the catalyst. High-pressure operation places stringent requirements on the equipment.

[0006] (3) Molecular sieve and activated carbon catalyst: Dow Corning uses LZ-Y-74 molecular sieve as catalyst to crack methylchlorosilane (Si-Si) and HCl as cracking gas. To reduce costs, the company chooses activated carbon to replace molecular sieve, but the reaction temperature is 500℃ higher and the energy consumption is higher (see "Resource Utilization of By-products in the Production of Methylchlorosilane Monomer", Li Bin, Master's Thesis of Beijing University of Chemical Technology).

[0007] CN202110874991.6 discloses a method for hydrocracking and disproportionation of high-boiling organosilicon compounds in a batch reactor on a Ni@ZSM-5 encapsulated catalyst, with an M2 selectivity >70%. On the one hand, the batch reactor has limited processing scale; on the other hand, the reaction requires a pressure of 2-5 MPa, making it difficult to determine the reaction endpoint.

[0008] CN202211395172.4 discloses a method for catalytic cracking of high-boiling organosilicon compounds, wherein the catalyst is one or more of Fe, Zn, Ni, Ti, and Mo supported on a molecular sieve, but the cracking temperature is high, exceeding 550℃.

[0009] Given the problems of low catalyst cracking rate, low target product selectivity, difficulty in recycling, and limited catalytic process in the reaction of organosilicon high-boiling-point cracking to prepare dimethyldichlorosilane, there is an urgent need to develop a new type of highly efficient and green catalyst and process for the preparation of dimethyldichlorosilane by cracking organosilicon high-boiling-point cracking. Summary of the Invention

[0010] To address the shortcomings of existing technologies, the present invention aims to provide a nickel-based composite catalyst with a core-shell structure, its preparation method, and its applications. By strengthening the protective layer of the catalytically active components, the migration and aggregation of Ni nanoparticles encapsulated inside the crystal are suppressed during the forming process, thereby ultimately improving the catalytic activity.

[0011] To achieve this objective, the present invention adopts the following technical solution:

[0012] In a first aspect, the present invention provides a nickel-based composite catalyst with a core-shell structure, the nickel-based composite catalyst comprising a Ni@ZSM-5@S-1 core-shell structure and an alumina support, the Ni@ZSM-5@S-1 core-shell structure comprising a Ni@ZSM-5 core layer and an S-1 molecular sieve nanolayer covering the outside of the Ni@ZSM-5 core layer.

[0013] The core-shell structured nickel-based composite catalyst provided by this invention uses Ni@ZSM-5, formed by encapsulating non-noble metal nickel (Ni) nanoparticles with ZSM-5 molecular sieve, as the core, and an S-1 all-silica molecular sieve nanolayer with an MFI structure formed on the outer surface of the core as the shell. This prevents the aggregation of Ni nanoparticles and ensures the catalytic activity of the catalyst. Furthermore, the composite with an alumina support further improves the stability of the catalyst. Compared with other oxide supports such as magnesium oxide, the use of an alumina support in this invention has the advantage of enhancing the mechanical strength of the catalyst.

[0014] Preferably, the Ni content in the Ni@ZSM-5 core layer is 1.0 to 8.0 wt%, for example, it can be 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5.0 wt%, 6.0 wt%, 7.0 wt%, or 8.0 wt%, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0015] Preferably, Ni in the Ni@ZSM-5 core layer exists in the form of nickel nanoparticles.

[0016] Preferably, the particle size of the nickel nanoparticles in the Ni@ZSM-5 core layer is in the range of 1 to 8 nm, for example, it can be 1 nm, 1.8 nm, 2.6 nm, 3.4 nm, 4.2 nm, 4.9 nm, 5.7 nm, 6.5 nm, 7.3 nm or 8 nm, but is not limited to the listed values. Other unlisted values ​​in this range are also applicable.

[0017] Preferably, the silicon-aluminum molar ratio (SiO2 / Al2O3) of the ZSM-5 molecular sieve in the Ni@ZSM-5 core layer is 50 to 500:1, for example, it can be 50:1, 100:1, 150:1, 200:1, 250:1, 300:1, 350:1, 400:1, 450:1 or 500:1, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0018] Preferably, the diameter of the Ni@ZSM-5 core layer is 0.3 to 3 μm, for example, it can be 0.3 μm, 0.6 μm, 0.9 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2.1 μm, 2.4 μm, 2.7 μm or 3 μm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] Preferably, the thickness of the S-1 molecular sieve nanolayer is 50 to 200 nm, for example, it can be 50 nm, 67 nm, 84 nm, 100 nm, 117 nm, 134 nm, 150 nm, 167 nm, 184 nm or 200 nm, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0020] The preferred thickness of the S-1 molecular sieve nanolayer in this invention is 50-200 nm. When the thickness is too thick, there is a problem of low pyrolysis activity; when the thickness is too thin, there is a problem of Ni nanoparticle migration and agglomeration.

[0021] Preferably, the content of Ni@ZSM-5@S-1 core-shell structure in the nickel-based composite catalyst is 50-70 wt%, for example, it can be 50 wt%, 53 wt%, 55 wt%, 57 wt%, 59 wt%, 62 wt%, 64 wt%, 66 wt%, 68 wt%, or 70 wt%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0022] Preferably, the content of alumina support in the nickel-based composite catalyst is 30-50 wt%, for example, it can be 30 wt%, 34 wt%, 37 wt%, 40 wt%, 44 wt%, 47 wt%, or 50 wt%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0023] In this invention, the content of alumina support in the nickel-based composite catalyst is preferably within the above-mentioned range. When the content of the support is too high, there is a problem of low cracking activity; when the content of the support is too low, there is a problem of poor catalyst strength.

[0024] In a second aspect, the present invention provides a method for preparing the nickel-based composite catalyst with a core-shell structure as described in the first aspect, the method comprising the following steps:

[0025] A hydrothermal crystallization reaction was carried out by mixing Ni@ZSM-5 core layer, silicon source, structure directing agent and water. The resulting reaction material was then subjected to solid-liquid separation, drying and first calcination to obtain Ni@ZSM-5@S-1 core-shell structure. The Ni@ZSM-5@S-1 core-shell structure, alumina source and water were mixed and then kneaded, extruded, dried, second calcined and reduced to obtain nickel-based composite catalyst with core-shell structure.

[0026] The present invention preferably uses the above preparation method, which has better catalytic performance.

[0027] Preferably, the silicon source includes any one or a combination of at least two of silica, silica sol, solid silica gel, water glass, or tetraethyl orthosilicate, wherein typical but non-limiting combinations are a combination of silica and silica sol, a combination of solid silica gel and silica sol, a combination of silica and solid silica gel, a combination of water glass and silica sol, a combination of water glass and tetraethyl orthosilicate, and a combination of tetraethyl orthosilicate and silica sol.

[0028] Preferably, the structure-directing agent comprises any one or a combination of at least two of n-butylamine, triethylamine, hexylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetramethylethyldiammonium, or dimethyldiethylammonium hydroxide, wherein typical but non-limiting combinations are the combination of tetraethylammonium hydroxide and tetrapropylammonium hydroxide, the combination of tetramethylethyldiammonium and tetrapropylammonium hydroxide, the combination of tetraethylammonium hydroxide and tetramethylethyldiammonium, or the combination of dimethyldiethylammonium hydroxide and tetrapropylammonium hydroxide.

[0029] Preferably, the temperature of the hydrothermal crystallization reaction is 120-170°C, for example, 120°C, 126°C, 132°C, 137°C, 143°C, 148°C, 154°C, 159°C, 165°C or 170°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0030] Preferably, the hydrothermal crystallization reaction time is 12 to 72 hours, for example, it can be 12 hours, 19 hours, 26 hours, 32 hours, 39 hours, 46 hours, 52 hours, 59 hours, 66 hours or 72 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] Preferably, the temperature of the first roasting is 400 to 600°C, for example, it can be 400°C, 423°C, 445°C, 467°C, 489°C, 512°C, 534°C, 556°C, 578°C or 600°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0032] Preferably, the first roasting time is 4 to 12 hours, for example, it can be 4 hours, 4.9 hours, 5.8 hours, 6.7 hours, 7.6 hours, 8.5 hours, 9.4 hours, 10.3 hours, 11.2 hours or 12 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0033] Preferably, the alumina source includes any one or a combination of at least two of the following: dry adhesive powder, SB powder, alumina sol, or boehmite. Typical but non-limiting combinations include the combination of dry adhesive powder and SB powder, the combination of alumina sol and SB powder, the combination of dry adhesive powder and alumina sol, the combination of boehmite and SB powder, and the combination of dry adhesive powder and boehmite.

[0034] Preferably, the second roasting temperature is 500 to 700°C, for example, it can be 500°C, 523°C, 545°C, 567°C, 589°C, 612°C, 634°C, 656°C, 678°C or 700°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0035] Preferably, the second roasting time is 4 to 10 hours, for example, it can be 4 hours, 4.7 hours, 5.4 hours, 6 hours, 6.7 hours, 7.4 hours, 8 hours, 8.7 hours, 9.4 hours or 10 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0036] Preferably, the reduction temperature is 400 to 600°C, for example, 400°C, 423°C, 445°C, 467°C, 489°C, 512°C, 534°C, 556°C, 578°C or 600°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0037] Preferably, the reduction time is 10 to 20 hours, for example, it can be 10 hours, 11.2 hours, 12.3 hours, 13.4 hours, 14.5 hours, 15.6 hours, 16.7 hours, 17.8 hours, 18.9 hours or 20 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0038] Preferably, the Ni@ZSM-5 core layer can be prepared using methods already disclosed in the art, such as the preparation methods disclosed in CN109731608B and / or CN202110874991.6.

[0039] Preferably, the Ni@ZSM-5@S-1 core-shell catalytic active component has hydrogenation cracking function and acid catalytic disproportionation function.

[0040] Thirdly, the present invention provides the use of the nickel-based composite catalyst with a core-shell structure described in the first aspect in the disproportionation pyrolysis of organosilicon.

[0041] This invention achieves high efficiency and selectivity in the pyrolysis of organosilicon high-boiling-point compounds by in-situ growing a 50-200 nm S-1 all-silica molecular sieve nanolayer outside Ni@ZSM-5 crystals, thereby suppressing the migration and aggregation of Ni nanoparticles during the forming process. Furthermore, the fixed-bed catalytic process described in this invention features mild reaction conditions and a reaction pressure of 0.1-1.5 MPa, significantly lower than the pressure of a batch reactor (3-7 MPa), greatly reducing equipment investment costs. The catalyst described in this invention is lossless and additive-free during use, environmentally friendly, highly efficient in pyrolysis, and easily scalable.

[0042] In this invention, the high-boiling-point organosilicon compounds include Si-Si, Si-CH2-Si, and Si-C. n A mixture composed of (n>4) equal bonds.

[0043] Preferably, the application includes: the high-boiling-point organosilicon compound and the cracked gas undergoing a cracking disproportionation reaction under the action of a nickel-based composite catalyst with a core-shell structure.

[0044] Preferably, the pyrolysis gas includes any one or a combination of at least two of hydrogen, hydrogen chloride, or chloromethane, wherein typical but non-limiting combinations are a combination of hydrogen and hydrogen chloride, a combination of chloromethane and hydrogen chloride, a combination of hydrogen and chloromethane, or a combination of chloromethane, hydrogen, and hydrogen chloride.

[0045] Preferably, the temperature of the pyrolysis disproportionation reaction is 250–450°C, for example, 250°C, 260°C, 280°C, 300°C, 320°C, 340°C, 360°C, 380°C, 400°C, 420°C, 440°C, or 450°C, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0046] Preferably, the pressure of the pyrolysis disproportionation reaction is 0.1 to 1.5 MPa, for example, it can be 0.1 MPa, 0.5 MPa, 0.8 MPa, 1.1 MPa, 1.4 MPa or 1.5 MPa, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0047] Preferably, the mass hourly space velocity (MSV) of the organosilicon high-boiling-point compound in the pyrolysis disproportionation reaction is 0.05–3.0 h⁻¹. -1 For example, it could be 0.05h -1 0.38h -1 0.71h -1 1.04h -1 1.37h -1 1.69h -1 2.02h -1 2.35h -1 2.68h -1 or 3.0h -1 This includes, but is not limited to, the listed values; other unlisted values ​​within this range also apply.

[0048] Preferably, the reactor for the pyrolysis disproportionation reaction includes any one of a fixed bed, a moving bed, a fluidized bed, or a slurry bed.

[0049] The present invention does not impose any special restrictions on the solid-liquid separation in the above process. Any device and method known to those skilled in the art for solid-liquid separation can be used. It can also be adjusted according to the actual process. For example, it can be filtration, centrifugation or sedimentation separation, or a combination of different methods.

[0050] The present invention does not impose any special restrictions on the drying process described above. Any device and method known to those skilled in the art for drying can be used. Adjustments can also be made according to the actual process. For example, it can be air drying, vacuum drying, oven drying, or freeze drying, or a combination of different methods.

[0051] Compared with the prior art, the present invention has at least the following beneficial effects:

[0052] (1) The method for preparing the core-shell structured nickel-based composite catalyst provided by this invention uses Ni@ZSM-5 synthesized by encapsulation as the core, adds a silicon source and a structure directing agent, and performs hydrothermal treatment to grow an S-1 all-silica molecular sieve nanoshell on the outer surface of the core. Then, it is mixed with an alumina support, guar gum powder, etc., extruded, and calcined to obtain the Ni@ZSM-5@S-1 / Al2O3 catalyst. This method not only protects the particle size and distribution of the encapsulated Ni nanoparticles, but also effectively inhibits the migration, agglomeration, and loss of the nickel nanoparticles in the encapsulated catalytic active component Ni@ZSM-5 due to the alumina support during the forming process, and improves the overall mechanical strength of the catalyst, meeting the mechanical strength requirements of the fixed-bed catalytic process. In the high-boiling-point cracking and disproportionation reaction of organosilicon, it exhibits higher high-boiling-point cracking rate, selectivity for the target product dimethyldichlorosilane, and catalyst lifespan.

[0053] (2) The nickel-based composite catalyst with a core-shell structure provided by the present invention is used to catalyze the production of chlorosilane monomers from organosilicon high-boiling substances, with a cracking rate of ≥95% and a chlorosilane monomer selectivity of ≥95%.

[0054] (3) This invention employs a fixed-bed reactor. On the catalyst, high-boiling-point organosilicon compounds and the cracked gas stream undergo a continuous gas-solid phase catalytic reaction. The Si, CH3, and Cl functional groups in the chlorosilane monomers formed by the cracking of the high-boiling-point compounds undergo directional disproportionation and rearrangement, significantly improving the selectivity of the target product, dimethyldichlorosilane. Under preferred conditions, this catalyst exhibits a higher high-boiling-point cracking rate (≥95%) and a higher chlorosilane selectivity (≥95%), with the dimethyldichlorosilane selectivity exceeding 50%, demonstrating superior catalytic stability. In lifetime testing experiments, this catalyst operated stably for over 1000 hours in laboratory trials, with no significant changes in cracking rate or dimethyldichlorosilane selectivity throughout the process. Attached Figure Description

[0055] Figure 1This is a TEM image of the Ni@ZSM-5@S-1 core-shell structure prepared in Example 1 of this invention.

[0056] Figure 2 This is a TEM image of the Ni@ZSM-5@S-1 core-shell structure prepared in Example 3 of this invention. Detailed Implementation

[0057] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0058] It should be understood that in the description of this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0059] Example 1

[0060] This embodiment provides a method for preparing a nickel-based composite catalyst with a core-shell structure, the preparation method comprising:

[0061] (1) Synthesis of Ni@ZSM-5 core layer: The method disclosed in Example 1 of CN109731608B was followed. The final Ni@ZSM-5 core layer had a SiO2:Al2O3 ratio of 240:1, a nickel nanoparticle size range of 2-5 nm, and a Ni content of 5.2 wt%.

[0062] (2) Preparation of Ni@ZSM-5@S-1 core-shell structure: The Ni@ZSM-5 core layer obtained in step (1), silicon source (silica), structure directing agent (TPAOH), and water were mixed evenly (where TPAOH / SiO2 = 0.3:1, H2O / SiO2 = 50:1), transferred to a hydrothermal crystallization kettle, and hydrothermally crystallized at 150℃ for 12h. After filtration, drying, and first calcination at 500℃ for 10h, the Ni@ZSM-5@S-1 core-shell structure was obtained. HRTEM analysis showed that the shell thickness was approximately 67nm. Figure 1 As shown.

[0063] (3) Preparation of Ni@ZSM-5@S-1 / Al2O3 catalyst: Ni@ZSM-5@S-1 core-shell structure, dry support powder, appropriate amount of water and 66% nitric acid are mixed evenly, extruded into strips, and then successively dried, calcined at 600℃ for 5h, and reduced at 500℃ for 15h in a hydrogen atmosphere to obtain the nickel-based composite catalyst with core-shell structure. The mass ratio of Ni@ZSM-5@S-1 core-shell structure to alumina support is 50:50.

[0064] Example 2

[0065] This embodiment provides a method for preparing a nickel-based composite catalyst with a core-shell structure, the preparation method comprising:

[0066] (1) Synthesis of Ni@ZSM-5 core layer: The method disclosed in Example 1 of CN109731608B was followed. The final Ni@ZSM-5 core layer had a SiO2:Al2O3 ratio of 100:1, a nickel nanoparticle size range of 2-5 nm, and a Ni content of 5.2 wt%.

[0067] (2) Preparation of Ni@ZSM-5@S-1 core-shell structure: The Ni@ZSM-5 core layer obtained in step (1), silicon source (silica), structure directing agent (TPAOH) and water were mixed evenly (where TPAOH / SiO2=0.1:1, H2O / SiO2=45:1), and transferred into a hydrothermal crystallization kettle for hydrothermal crystallization treatment at 170℃ for 4h. After filtration, drying and first calcination at 600℃ for 4h, the Ni@ZSM-5@S-1 core-shell structure was obtained. HRTEM analysis showed that the shell thickness was about 50nm.

[0068] (3) Preparation of Ni@ZSM-5@S-1 / Al2O3 catalyst: Ni@ZSM-5@S-1 core-shell structure, dry support powder, appropriate amount of water and 66% nitric acid were mixed evenly, extruded into strips, and successively dried, calcined at 700℃ for 4 hours, and reduced at 600℃ for 10 hours in a hydrogen atmosphere to obtain the nickel-based composite catalyst with core-shell structure. The mass ratio of Ni@ZSM-5@S-1 core-shell structure to alumina support is 60:40.

[0069] Example 3

[0070] This embodiment provides a method for preparing a nickel-based composite catalyst with a core-shell structure, the preparation method comprising:

[0071] (1) Synthesis of Ni@ZSM-5 core layer: The method disclosed in Example 1 of CN109731608B was followed. The final Ni@ZSM-5 core layer had a SiO2:Al2O3 ratio of 130:1, a nickel nanoparticle size range of 2-5 nm, and a Ni content of 4.8 wt%.

[0072] (2) Preparation of Ni@ZSM-5@S-1 core-shell structure: The Ni@ZSM-5 core layer obtained in step (1), silicon source (silica), structure directing agent (TPAOH) and water were mixed evenly (where TPAOH / SiO2=0.3:1, H2O / SiO2=25:1), and transferred to a hydrothermal crystallization kettle for hydrothermal crystallization treatment at 170℃ for 12h. After filtration, drying and first calcination at 400℃ for 12h, the Ni@ZSM-5@S-1 core-shell structure was obtained. HRTEM analysis showed that the shell thickness was approximately 115nm.

[0073] (3) Preparation of Ni@ZSM-5@S-1 / Al2O3 catalyst: Ni@ZSM-5@S-1 core-shell structure, dry gel powder of support, appropriate amount of water and 66% nitric acid are mixed evenly, extruded into strips, and successively dried, calcined at 500℃ for 10h, and reduced at 400℃ for 20h in a hydrogen atmosphere to obtain the nickel-based composite catalyst with core-shell structure. The mass ratio of Ni@ZSM-5@S-1 core-shell structure to alumina support is 70:30.

[0074] Example 4

[0075] This embodiment provides a method for preparing a nickel-based composite catalyst with a core-shell structure. The preparation method is the same as in Example 1, except that the content of Al2O3 in the Ni@ZSM-5@S-1 / Al2O3 catalyst is 55wt%, and will not be repeated here.

[0076] Example 5

[0077] This embodiment provides a method for preparing a nickel-based composite catalyst with a core-shell structure. The preparation method is the same as in Example 1, except that the content of Al2O3 in the Ni@ZSM-5@S-1 / Al2O3 catalyst is 15wt%, and will not be repeated here.

[0078] Example 6

[0079] This embodiment provides a method for preparing a nickel-based composite catalyst with a core-shell structure. Except for the thickness of the S-1 molecular sieve nanolayer being 40 nm, the preparation method is the same as in Example 1, and will not be repeated here.

[0080] Compared to the catalyst prepared in Example 1, the Ni nanoparticles in the catalyst prepared in this example are larger, with some particles exceeding 10 nm. Under the same high-boiling-point pyrolysis reaction conditions, the catalyst prepared in this example exhibits lower pyrolysis activity.

[0081] Example 7

[0082] This embodiment provides a method for preparing a nickel-based composite catalyst with a core-shell structure. Except for the thickness of the S-1 molecular sieve nanolayer being 220 nm, the preparation method is the same as in Example 1, and will not be repeated here.

[0083] Compared with the catalyst prepared in Example 1, the catalyst S-1 prepared in this example has a significantly increased shell thickness. Under the same high-boiling-point cracking reaction conditions, the catalyst prepared in this example has low cracking activity.

[0084] Comparative Example 1

[0085] This comparative example provides a method for preparing a nickel-based composite catalyst. The preparation method is the same as in Example 1 except that step (2) is omitted and step (3) is performed directly using the Ni@ZSM-5 core layer. It will not be repeated here.

[0086] Compared to the catalyst prepared in Example 1, the Ni nanoparticles in the catalyst prepared in this example are larger, with some particles exceeding 10 nm. Under the same high-boiling-point pyrolysis reaction conditions, the catalyst prepared in this example exhibits lower pyrolysis activity.

[0087] Comparative Example 2

[0088] This comparative example provides a method for preparing a nickel-based composite catalyst. The preparation method is the same as in Example 1 except that step (3) is omitted and the Ni@ZSM-5@S-1 core-shell structure is directly used as the catalyst. It will not be described again here.

[0089] Compared with the catalyst prepared in Example 1, the catalyst prepared in this example has poor strength and is prone to pulverization during the high-boiling-point cracking reaction, leading to bed blockage.

[0090] Comparative Example 3

[0091] This comparative example provides a method for preparing a nickel-based composite catalyst. The preparation method is the same as in Example 1 except that the dry adhesive powder of the support is replaced with magnesium oxide in step (3), and will not be repeated here.

[0092] Compared with the catalyst prepared in Example 1, the catalyst prepared in this example has a cracking activity of less than 95% under the same high-boiling-point cracking reaction conditions.

[0093] Comparative Example 4

[0094] This comparative example provides a method for preparing a nickel-based composite catalyst. The preparation method is the same as that in Example 1 except that step (3) is omitted and magnesium nitrate is added in step (2). It will not be described again here.

[0095] Compared with the catalyst prepared in Example 1, the catalyst prepared in this example has a cracking activity of less than 95% under the same high-boiling-point cracking reaction conditions.

[0096] HRTEM was used to detect the particle size in the catalyst, XRF was used to detect the composition in the catalyst, and a strength tester was used to test the strength of the catalyst. The main components and contents of the catalysts in the above examples and comparative examples are shown in Table 1.

[0097] Table 1

[0098]

[0099] Application Example 1-1

[0100] This application example provides a method for the pyrolysis and disproportionation reaction of organosilicon high-boiling-point compounds, the method comprising:

[0101] A fixed-bed reactor was used to pass a high-boiling-point organosilicon compound (composed of 25% methylsilane-rich, 40% trichlorotrimethylsilane, and 35% chlorosilane-rich) and hydrogen into a catalyst packed with the catalyst prepared in Example 1. The reactor was operated at a temperature of 300°C, a pressure of 0.3 MPa, and a feed mass hourly space velocity (WHSV) of 0.1 h⁻¹ for the high-boiling-point organosilicon compound. -1 Under certain conditions, a pyrolysis reaction is carried out to obtain reactants containing chlorosilane monomers.

[0102] Application Example 1-2

[0103] This application example provides a method for the pyrolysis and disproportionation reaction of organosilicon high-boiling-point compounds. The only difference between this method and Application Example 1-1 is that the pyrolysis reaction temperature is 450°C, the pressure is 0.5 MPa, and the feed mass hourly space velocity (WHSV) of the organosilicon high-boiling-point compounds is 0.5 h⁻¹. -1 .

[0104] Application Example 2-1

[0105] This application example provides a method for the pyrolysis and disproportionation reaction of organosilicon high-boiling-point compounds, the method comprising:

[0106] A fixed-bed reactor was used to pass a high-boiling-point organosilicon compound (composed of 25% methylsilane-rich, 5% Si-CH2-Si, 50% trimethyltrichlorosilane, and 20% chlorosilane-rich) and hydrogen into a catalyst packed with the catalyst prepared in Example 2. The reactor was operated at a temperature of 300°C, a pressure of 0.3 MPa, and a feed mass hourly space velocity (WHSV) of 0.1 h⁻¹ for the high-boiling-point organosilicon compound.-1 Under certain conditions, a pyrolysis reaction is carried out to obtain reactants containing chlorosilane monomers.

[0107] Application Example 2-2

[0108] This application example provides a method for the pyrolysis and disproportionation reaction of organosilicon high-boiling-point compounds. The only difference between this method and Application Example 2-1 is that the pyrolysis reaction temperature is 450°C, the pressure is 1.5 MPa, and the feed mass hourly space velocity (WHSV) of the organosilicon high-boiling-point compounds is 0.5 h⁻¹. -1 .

[0109] Application Example 3-1

[0110] This application example provides a method for the pyrolysis and disproportionation reaction of organosilicon high-boiling-point compounds, the method comprising:

[0111] A fixed-bed reactor was used to introduce a high-boiling-point organosilicon compound (composed of 10% methylsilane-rich, 5% Si-CH2-Si, 5% Si-O-Si, 40% trimethyltrichlorosilane, and 40% chlorosilane-rich) and hydrogen into a catalyst packed with the catalyst prepared in Example 3. The reactor was operated at a temperature of 350°C, a pressure of 0.3 MPa, and a feed mass hourly space velocity (WHSV) of 0.06 h⁻¹ for the high-boiling-point organosilicon compound. -1 Under certain conditions, a pyrolysis reaction is carried out to obtain reactants containing chlorosilane monomers.

[0112] Application Example 3-2

[0113] This application example provides a method for the pyrolysis and disproportionation reaction of organosilicon high-boiling-point compounds. The only difference between this method and Application Example 3-1 is that the pyrolysis reaction temperature is 450°C, the pressure is 1.0 MPa, and the feed mass hourly space velocity (WHSV) of the organosilicon high-boiling-point compounds is 0.3 h⁻¹. -1 .

[0114] Application Examples 4-7 and Comparative Examples 1-4

[0115] Application Examples 4-7 and Comparative Examples 1-4 provide a method for the pyrolysis and disproportionation reaction of organosilicon high-boiling-point compounds. Except for the use of the catalysts in Examples 4-7 and Comparative Examples 1-4, the method for the pyrolysis and disproportionation reaction of organosilicon high-boiling-point compounds is the same as that in Application Example 1-1, and will not be described again here.

[0116] Application Comparative Example 1-2

[0117] This application provides a method for the pyrolysis and disproportionation reaction of high-boiling-point organosilicon compounds. The only difference between this method and Application Comparative Example 1 is that the pyrolysis reaction temperature is 350℃, the pressure is 0.3MPa, and the feed mass hourly space velocity (WHSV) of the high-boiling-point organosilicon compounds is 0.06 h⁻¹. -1 .

[0118] Application Comparative Examples 1-3

[0119] This application comparative example provides a method for the pyrolysis and disproportionation reaction of organosilicon high-boiling-point compounds. The only difference between this method and application comparative example 1 is that the pyrolysis reaction temperature is 450℃, the pressure is 1.0 MPa, and the feed mass hourly space velocity of the organosilicon high-boiling-point compounds is 0.3 h⁻¹. -1 .

[0120] Application Comparative Examples 1-4

[0121] This application comparative example provides a method for the pyrolysis and disproportionation reaction of organosilicon high-boiling-point compounds. The only difference between this method and application comparative examples 1-3 is that the pyrolysis reaction temperature is 550℃.

[0122] Gas chromatography analysis was performed on the reactants in the above application examples and comparative examples. The test results of the above application examples and comparative examples are shown in Table 2.

[0123] Table 2

[0124]

[0125] In Tables 1 and 2, " / " indicates that there is no relevant data.

[0126] The following points can be observed from Tables 1 and 2:

[0127] (1) As can be seen from the comprehensive application examples 1 to 3, the nickel particle size in the nickel-based composite catalyst with core-shell structure provided by the present invention can be controlled within the range of 1 to 8 nm, and the strength is above 85 N. When the catalyst is applied to the cracking and disproportionation reaction of organosilicon high-boiling substances, the cracking rate of high-boiling substances is above 95.7%, the selectivity of chlorosilane monomers is above 93.1%, and the selectivity of dimethyldichlorosilane is above 60.3%.

[0128] (2) It can be seen from the combined application examples 1-1 and 4-5 that the cracking activity of the catalyst in application example 4 is less than 95%, only 88.1%, and the content of Al2O3 in application example 5 is too low, resulting in poor catalyst strength. It is easy to pulverize during the cracking reaction of high boiling point substances, leading to bed blockage and making it difficult to operate continuously for 1000 hours. This shows that the present invention preferably controls the content of alumina in the catalyst within a reasonable range, which can significantly improve the catalytic activity and catalytic stability of the catalyst.

[0129] (3) As can be seen from the combined application examples 1-1 and 6-7, the present invention preferably controls the thickness of the S-1 molecular sieve nanolayer within a reasonable range, which can better improve the cracking activity of the catalyst.

[0130] (4) As can be seen from the combined application examples 1 and 1-4, the preparation method provided by the present invention can significantly improve the catalytic activity and catalytic stability of the catalyst by coating the outer surface of the Ni@ZSM-5 core layer with an S-1 structure and mixing it with the alumina support.

[0131] The present invention has been illustrated with the above embodiments to illustrate its detailed features, but the present invention is not limited to the above detailed features, that is, it does not mean that the present invention must rely on the above detailed features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the selected technical features, additions of auxiliary technical features, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A nickel-based composite catalyst having a core-shell structure, characterized in that, The nickel-based composite catalyst comprises a Ni@ZSM-5@S-1 core-shell structure and an alumina carrier, wherein the Ni@ZSM-5@S-1 core-shell structure comprises a Ni@ZSM-5 core layer and an S-1 molecular sieve nanolayer coated outside the Ni@ZSM-5 core layer. The Ni@ZSM-5 core layer is formed by encapsulating non-noble metal Ni nanoparticles with ZSM-5 through an encapsulation method. The particle size of the nickel nanoparticles in the Ni@ZSM-5 core layer ranges from 1 to 8 nm. The preparation method of the nickel-based composite catalyst comprises the following steps: The Ni@ZSM-5 core layer, a silicon source, a structure directing agent and water are mixed for a hydrothermal crystallization reaction, and the obtained post-reaction material is sequentially subjected to solid-liquid separation, drying and first calcination to obtain the Ni@ZSM-5@S-1 core-shell structure; The Ni@ZSM-5@S-1 core-shell structure, an alumina source and water are mixed and subjected to kneading, extrusion molding, drying, second calcination and reduction to obtain the nickel-based composite catalyst with a core-shell structure.

2. The nickel-based composite catalyst having a core-shell structure according to claim 1, characterized in that, The content of Ni in the Ni@ZSM-5 core layer ranges from 1.0 to 8.0 wt%.

3. The nickel-based composite catalyst having a core-shell structure according to claim 1, wherein the core-shell structure is formed by coating the nickel-based catalyst with the metal oxide. The SiO2 / Al2O3 molar ratio of the ZSM-5 molecular sieve in the Ni@ZSM-5 core layer ranges from 50 to 500:

1.

4. The nickel-based composite catalyst having a core-shell structure according to claim 1 or 2, characterized in that, The diameter of the Ni@ZSM-5 core layer ranges from 0.3 to 3.0 μm.

5. The nickel-based composite catalyst with a core-shell structure according to claim 1, characterized in that, The thickness of the S-1 molecular sieve nanolayer ranges from 50 to 200 nm.

6. The nickel-based composite catalyst with a core-shell structure according to claim 1, characterized in that, The content of the Ni@ZSM-5@S-1 core-shell structure in the nickel-based composite catalyst ranges from 50 to 70 wt%.

7. The nickel-based composite catalyst with a core-shell structure according to claim 1, characterized in that, The content of the alumina carrier in the nickel-based composite catalyst ranges from 30 to 50 wt%.

8. A method for preparing the nickel-based composite catalyst having a core-shell structure according to any one of claims 1 to 7, characterized by, The preparation method comprises the following steps: The Ni@ZSM-5 core layer, a silicon source, a structure directing agent and water are mixed for a hydrothermal crystallization reaction, and the obtained post-reaction material is sequentially subjected to solid-liquid separation, drying and first calcination to obtain the Ni@ZSM-5@S-1 core-shell structure; The Ni@ZSM-5@S-1 core-shell structure, an alumina source and water are mixed and subjected to kneading, extrusion molding, drying, second calcination and reduction to obtain the nickel-based composite catalyst with a core-shell structure.

9. The preparation method according to claim 8, characterized in that, The silicon source comprises any one or a combination of at least two of white carbon black, silica sol, solid silica gel, water glass or tetraethyl orthosilicate.

10. The preparation method according to claim 8, characterized in that, The structure directing agent comprises any one or a combination of at least two of n-butylamine, triethylamine, hexylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetramethylethyldiammonium or dimethyldiethylammonium hydroxide.

11. The preparation method according to claim 8, characterized in that, The temperature of the hydrothermal crystallization reaction ranges from 120 to 170 ℃.

12. The preparation method according to claim 8, characterized in that, The time of the hydrothermal crystallization reaction ranges from 12 to 72 h.

13. The preparation method according to claim 8, characterized in that, The temperature of the first calcination ranges from 400 to 600 ℃.

14. The preparation method according to claim 8, characterized in that, The time of the first calcination ranges from 4 to 12 h.

15. The preparation method according to claim 8, characterized in that, The alumina source comprises any one or a combination of at least two of dry gel powder, SB powder, aluminum sol or pseudo-boehmite.

16. The preparation method according to claim 8, characterized in that, The temperature of the second calcination ranges from 500 to 700 ℃.

17. The method of claim 8, wherein the method further comprises, The time of the second calcination ranges from 4 to 10 h.

18. The method of claim 8, wherein, The temperature of the reduction ranges from 400 to 600 ℃.

19. The method of claim 8, wherein, The time of the reduction ranges from 10 to 20 h.

20. Use of the nickel-based composite catalyst with core-shell structure according to any one of claims 1-7 in the disproportionation cracking of organosilicon.

21. Use according to claim 20, characterized in that, The use comprises: organosilicon high-boiling substances and cracking gas are subjected to a disproportionation cracking reaction under the action of the nickel-based composite catalyst with core-shell structure.

22. The use according to claim 21, characterized in that, The cracking gas comprises any one or a combination of at least two of hydrogen, hydrogen chloride or chloromethane.

23. The use according to claim 21, characterized in that, The temperature of the disproportionation cracking reaction is 250-450°C.

24. The use according to claim 21, characterized in that, The pressure of the disproportionation cracking reaction is 0.1-1.5 MPa.

25. The use according to claim 21, characterized in that, The mass space velocity of the organic silicon high-boiling residue in the cleavage disproportionation reaction is 0.05-3.0 h -1 .

26. The use according to claim 21, characterized in that, The reactor for the disproportionation cracking reaction comprises any one of a fixed bed, a moving bed, a fluidized bed or a slurry bed.

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