Nickel-based composite catalyst with core-shell structure as well as preparation method and application of nickel-based composite catalyst

Abstract

The invention provides a nickel-based composite catalyst with a core-shell structure and a preparation method and application thereof.The nickel-based composite catalyst with the core-shell structure comprises the Ni-coated ZSM-5-coated S-1 core-shell structure and an aluminum oxide carrier, and the Ni-coated ZSM-5-coated S-1 core-shell structure comprises a Ni-coated ZSM-5 core layer and an S-1 molecular sieve nano layer wrapping the Ni-coated ZSM-5 core layer. The catalyst provided by the invention is used in a reaction for preparing a chlorosilane monomer by directional catalytic cracking of an organosilicon high-boiling residue, the cracking rate of the high-boiling residue exceeds 95%, and the selectivity of the chlorosilane monomer exceeds 95%.

Description

Technical Field

[0001] The invention relates to the technical field of organic silicon, and in particular to a nickel-based composite catalyst with a core-shell structure, a preparation method and application thereof. Background Art

[0003] At present, tri-n-butylamine is used as a catalyst to crack high-boiling products to prepare chlorosilane monomers. Although the operating temperature and pressure are low, there are still fundamental problems that are difficult to overcome. The analysis is as follows: the catalyst tri-n-butylamine is a highly toxic chemical and must be strictly controlled during its use cycle and is used as a consumable; the target product M2 has low selectivity, and the main products are low-value monomethyltrichlorosilane and monomethyldichlorosilane; the cracking rate is low, and only chlorine-rich Si-Si cracking can be achieved; the uncracked high-boiling products are mixed with them to form hazardous waste, which further causes secondary pollution to human health and the ecological environment, and wastes resources; subsequent treatment is more complicated and difficult, and the environmental protection cost is huge; in a homogeneous kettle reaction system, it is difficult to separate the product from the catalyst and unreacted raw materials, resulting in poor product purity; kettle reaction system: the processing scale is limited. Under the background of rapid expansion of monomer capacity at this stage, there is an urgent need to develop a continuous and stable catalytic reaction system.

[0004] The currently disclosed technical patent documents on the preparation of dimethyldichlorosilane by cracking high-boiling organic silicon products are mainly divided into the following methods:

[0005] (1) Precious metal catalysts: CN1071927A, JP54-9228, and JP54-119417 reported the use of precious metals Pd and Pt as catalysts to crack high boiling points, using HCl as the cracking gas source, and requiring toluene or xylene as solvent in a reactor. However, precious metal catalysts are expensive, difficult to recycle, and difficult to purify, making them difficult to apply in large-scale industrial applications.

[0006] (2) Aluminum-based catalysts: US5430168, US5321147, CN1169996A, CN1634937A, CN1634936A, CN1915999A, etc. disclose a method of using aluminum chloride (AlCl3) as a catalyst and HCl as a cracking gas to react in a slurry bed or a fixed bed. Typical process conditions: reaction temperature of 300-500°C, reaction pressure of 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, and high-pressure operation places stringent requirements on equipment.

[0007] (3) Molecular sieves and activated carbon catalysts: Dow Corning Corporation of the United States uses LZ-Y-74 molecular sieve as a catalyst to crack methylchlorodisilane (Si-Si), with HCl as the cracking gas. To reduce costs, the company chose activated carbon instead of molecular sieves, but the reaction temperature was 500°C higher and the energy consumption was high (see "Resource Utilization of By-Products in the Production of Methylchlorosilane Monomer", Li Bin, master's thesis of Beijing University of Chemical Technology).

[0008] CN202110874991.6 discloses a hydrocracking disproportionation reaction of high-boiling organic silicon products in a Ni@ZSM-5 encapsulated catalyst in a tank reactor, with an M2 selectivity of >70%. On the one hand, the scale of tank reaction is limited, and on the other hand, the reaction requires a pressure of 2 to 5 MPa, making it difficult to determine the reaction endpoint.

[0009] CN202211395172.4 discloses a method for catalytic cracking of high-boiling organic silicon products, wherein the catalyst is a molecular sieve loaded with one or more of Fe, Zn, Ni, Ti, and Mo, but the cracking temperature is high, exceeding 550°C.

[0010] In view of the problems of low catalyst cracking rate, low target product selectivity, difficulty in recycling, and limited catalytic process in the reaction of cracking high-boiling silicone products to prepare dimethyldichlorosilane, there is an urgent need to develop a new type of efficient and green catalyst and process for cracking high-boiling silicone products to prepare dimethyldichlorosilane. Summary of the invention

[0011] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a nickel-based composite catalyst with a core-shell structure and a preparation method and use thereof, by strengthening the protective layer of the catalytically active component, thereby inhibiting the migration and aggregation of Ni nanoparticles encapsulated inside the crystal during the molding process, and ultimately improving the catalytic activity.

[0012] To achieve this object, the present invention adopts the following technical solutions:

[0013] In a first aspect, the present invention provides a nickel-based composite catalyst with a core-shell structure, wherein 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 on the outside of the Ni@ZSM-5 core layer.

[0014] The nickel-based composite catalyst with a core-shell structure provided by the present invention has a Ni@ZSM-5 formed by encapsulating non-precious metal nickel (Ni) nanoparticles containing a ZSM-5 molecular sieve as a core, and an S-1 all-silicon molecular sieve nanolayer with an MFI structure generated on the outer surface of the core as a shell layer, thereby preventing the agglomeration of Ni nanoparticles and ensuring the catalytic activity of the catalyst. And further compounding with an alumina carrier further improves the stability of the catalyst. Compared with other oxide carriers such as magnesium oxide, the present invention uses an alumina carrier for compounding, which has the advantage of enhancing the mechanical strength of the catalyst.

[0015] 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%, etc., but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0016] Preferably, the Ni in the Ni@ZSM-5 core layer exists in the form of nickel nanoparticles.

[0017] Preferably, the particle size range of the nickel nanoparticles in the Ni@ZSM-5 core layer is 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, and other unlisted values ​​within the range are also applicable.

[0018] 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, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0019] 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, and other unlisted values ​​within the range are also applicable.

[0020] 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, and other unlisted values ​​within this range are also applicable.

[0021] The preferred thickness of the S-1 molecular sieve nanolayer of the present invention is 50 to 200 nm. When the thickness is too thick, the cracking activity is low. When the thickness is too thin, the migration and agglomeration of Ni nanoparticles are problematic.

[0022] Preferably, the content of Ni@ZSM-5@S-1 core-shell structure in the nickel-based composite catalyst is 50-70wt%, for example, it can be 50wt%, 53wt%, 55wt%, 57wt%, 59wt%, 62wt%, 64wt%, 66wt%, 68wt% or 70wt%, etc., but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0023] Preferably, the content of the alumina carrier in the nickel-based composite catalyst is 30-50wt%, for example, it can be 30wt%, 34wt%, 37wt%, 40wt%, 44wt%, 47wt% or 50wt%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0024] The present invention preferably contains the alumina carrier in the nickel-based composite catalyst within the above range. When the carrier content is too high, the cracking activity is low, and when the carrier content is too low, the catalyst strength is poor.

[0025] In a second aspect, the present invention provides a method for preparing the nickel-based composite catalyst having a core-shell structure according to the first aspect, the preparation method comprising the following steps:

[0026] A Ni@ZSM-5 core layer, a silicon source, a structure directing agent and water are mixed to carry out a hydrothermal crystallization reaction, and the obtained reaction material is sequentially subjected to solid-liquid separation, drying and a first calcination to obtain a 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 kneading, extrusion molding, drying, a second calcination and reduction are carried out to obtain a nickel-based composite catalyst with a core-shell structure.

[0027] The present invention is preferably carried out using the above preparation method, which has better catalytic performance.

[0028] Preferably, the silicon source comprises any one of white carbon, silica sol, solid silica gel, water glass or tetraethyl orthosilicate, or a combination of at least two thereof, wherein typical but non-limiting combinations are a combination of white carbon and silica sol, a combination of solid silica gel and silica sol, a combination of white carbon 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.

[0029] Preferably, the structure directing agent comprises any one of n-butylamine, triethylamine, hexylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetramethylethyldiammonium or dimethyldiethylammonium hydroxide, or a combination of at least two thereof, wherein typical but non-limiting combinations are a combination of tetraethylammonium hydroxide and tetrapropylammonium hydroxide, a combination of tetramethylethyldiammonium and tetrapropylammonium hydroxide, a combination of tetraethylammonium hydroxide and tetramethylethyldiammonium, and a combination of dimethyldiethylammonium hydroxide and tetrapropylammonium hydroxide.

[0030] Preferably, the temperature of the hydrothermal crystallization reaction is 120-170°C, for example, it can be 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, and other unlisted values ​​within the range are also applicable.

[0031] 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, and other unlisted values ​​within the range are also applicable.

[0032] Preferably, the temperature of the first calcination is 400-600°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, and other unlisted values ​​within the range are also applicable.

[0033] Preferably, the first calcination time is 4 to 12 h, for example, 4 h, 4.9 h, 5.8 h, 6.7 h, 7.6 h, 8.5 h, 9.4 h, 10.3 h, 11.2 h or 12 h, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0034] Preferably, the alumina source comprises any one of dry glue powder, SB powder, aluminum sol or pseudo-boehmite, or a combination of at least two of them, wherein typical but non-limiting combinations are a combination of dry glue powder and SB powder, a combination of aluminum sol and SB powder, a combination of dry glue powder and aluminum sol, a combination of pseudo-boehmite and SB powder, and a combination of dry glue powder and pseudo-boehmite.

[0035] Preferably, the temperature of the second calcination is 500-700°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, and other unlisted values ​​within the range are also applicable.

[0036] Preferably, the second calcination time is 4 to 10 h, for example, 4 h, 4.7 h, 5.4 h, 6 h, 6.7 h, 7.4 h, 8 h, 8.7 h, 9.4 h or 10 h, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0037] Preferably, the reduction temperature is 400-600°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, and other unlisted values ​​within the range are also applicable.

[0038] Preferably, the reduction time is 10 to 20 h, for example, 10 h, 11.2 h, 12.3 h, 13.4 h, 14.5 h, 15.6 h, 16.7 h, 17.8 h, 18.9 h or 20 h, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0039] Preferably, the Ni@ZSM-5 core layer can be prepared by a method disclosed in the art, for example, the preparation method disclosed in CN109731608B and / or CN202110874991.6.

[0040] Preferably, the Ni@ZSM-5@S-1 core-shell catalytic active component has a hydrocracking function and an acid-catalyzed disproportionation function.

[0041] In a third aspect, the present invention provides a use of the nickel-based composite catalyst with a core-shell structure described in the first aspect in the disproportionation cracking of organic silicon.

[0042] The present invention in situ grows a 50-200nm S-1 all-silicon molecular sieve nanolayer outside the Ni@ZSM-5 crystal to inhibit the migration and aggregation of Ni nanoparticles during the molding process, thereby ensuring the efficient cracking rate and high selectivity of high-boiling organic silicon. In addition, the fixed bed catalytic process of the present invention has mild reaction conditions and a reaction pressure of 0.1-1.5MPa, which is significantly lower than the pressure of the kettle reactor (3-7MPa), greatly reducing the equipment investment cost. The catalyst of the present invention has no loss or addition during use, is green and environmentally friendly, has efficient cracking, and is easy to scale.

[0043] In the present invention, the high boiling organic silicon products include Si-Si, Si-CH2-Si, Si-C n (n>4) A mixture of equal bonds.

[0044] Preferably, the use includes: a cracking and disproportionation reaction of high-boiling organosilicon products and cracked gas under the action of a nickel-based composite catalyst having a core-shell structure.

[0045] Preferably, the cracked gas comprises any one of hydrogen, hydrogen chloride or methyl chloride or a combination of at least two of them, wherein typical but non-limiting combinations are a combination of hydrogen and hydrogen chloride, a combination of methyl chloride and hydrogen chloride, a combination of hydrogen and methyl chloride, and a combination of methyl chloride, hydrogen and hydrogen chloride.

[0046] Preferably, the temperature of the cracking disproportionation reaction is 250-450°C, for example, it can be 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, and other unlisted values ​​within the range are also applicable.

[0047] Preferably, the pressure of the cracking disproportionation reaction is 0.1-1.5 MPa, for example, 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, and other values ​​not listed within the range are also applicable.

[0048] Preferably, the mass space velocity of high boiling products of organosilicon in the cracking and disproportionation reaction is 0.05 to 3.0 h -1 , for example, it can 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 The above values ​​are not limited to the above values, and other values ​​not listed in the above values ​​are also applicable.

[0049] Preferably, the reactor for the cracking and disproportionation reaction comprises any one of a fixed bed, a moving bed, a fluidized bed or a slurry bed.

[0050] The present invention has no special limitation on the solid-liquid separation in the above process. Any device and method for solid-liquid separation known to those skilled in the art can be used, and can also be adjusted according to the actual process, such as filtration, centrifugation or sedimentation separation, or a combination of different methods.

[0051] The present invention has no particular limitation on the drying in the above process. Any drying device and method known to those skilled in the art can be used, and can also be adjusted 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.

[0052] Compared with the prior art, the present invention has at least the following beneficial effects:

[0053] (1) The preparation method of the nickel-based composite catalyst with a core-shell structure provided by the present invention uses Ni@ZSM-5 synthesized by the encapsulation method as the core, adds a silicon source and a structure-directing agent, and undergoes hydrothermal treatment to grow an S-1 all-silicon molecular sieve nanoshell on the outer surface of the core, and then mixes with an alumina carrier, field sesbania powder, etc., extrudes into strips, and calcines and reduces to obtain a Ni@ZSM-5@S-1 / Al2O3 catalyst, which not only protects the particle size and distribution of the encapsulated Ni nanoparticles, effectively inhibits the migration, agglomeration and loss of the nickel nanoparticles in the encapsulated catalytic active component Ni@ZSM-5 due to the alumina carrier during the molding process, but also improves the mechanical strength of the overall catalyst, meeting the requirements for its mechanical strength in the fixed bed catalytic process. In the cracking and disproportionation reaction of high-boiling substances in organosilicon, it exhibits a higher high-boiling substance cracking rate, target product dimethyldichlorosilane selectivity, and catalyst service life;

[0054] (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 high-boiling organic silicon products, with a cracking rate of ≥95% and a chlorosilane monomer selectivity of ≥95%;

[0055] (3) The present invention adopts a fixed bed reactor. On the catalyst, the high-boiling organic silicon product and the cracking gas flow through the catalyst bed to carry out a gas-solid phase continuous catalytic reaction. The Si, CH3, and Cl functional groups in the chlorosilane monomer formed by the cracking of the high-boiling product are directional disproportionately rearranged, which significantly improves the selectivity of the target product dimethyldichlorosilane. Under preferred conditions, the catalyst has a higher high-boiling product cracking rate (≥95%) and a higher chlorosilane selectivity (≥95%), wherein the dimethyldichlorosilane selectivity exceeds 50%, and has better catalytic stability. In the life test experiment, the catalyst stably operates for more than 1000h in the laboratory test. During the whole process, the cracking rate and dimethyldichlorosilane selectivity do not change significantly. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0057] Figure 2 This is a TEM image of the Ni@ZSM-5@S-1 core-shell structure prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0058] For the convenience of understanding the present invention, the present invention lists the following embodiments. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0059] It should be understood that, in the description of the present invention, the terms "first", "second", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0060] Example 1

[0061] This embodiment provides a method for preparing a nickel-based composite catalyst having a core-shell structure, the preparation method comprising:

[0062] (1) Synthesis of Ni@ZSM-5 core layer: The method disclosed in Example 1 of CN109731608B was used as reference. The SiO2:Al2O3 ratio of the Ni@ZSM-5 core layer was 240:1, the particle size of the nickel nanoparticles was in the range of 2 to 5 nm, and the Ni content was 5.2 wt%.

[0063] (2) Preparation of Ni@ZSM-5@S-1 core-shell structure: The Ni@ZSM-5 core layer obtained in step (1), silicon source (white carbon black), structure directing agent (TPAOH) and water were mixed evenly (TPAOH / SiO2=0.3:1, H2O / SiO2=50:1), transferred to a hydrothermal crystallization reactor for hydrothermal crystallization at 150°C for 12 h, filtered, dried, and first calcined at 500°C for 10 h to obtain a Ni@ZSM-5@S-1 core-shell structure; HRTEM analysis showed that the shell thickness was about 67 nm, as shown in FIG. Figure 1 shown.

[0064] (3) Preparation of Ni@ZSM-5@S-1 / Al2O3 catalyst: Ni@ZSM-5@S-1 core-shell structure, carrier dry rubber powder, appropriate amount of water and nitric acid with a concentration of 66% were mixed evenly, extruded into strips, and then dried, second calcined at 600°C for 5h, and reduced at 500°C in a hydrogen atmosphere for 15h to obtain the nickel-based composite catalyst with a core-shell structure. The mass ratio of Ni@ZSM-5@S-1 core-shell structure to alumina carrier was 50:50.

[0065] Example 2

[0066] This embodiment provides a method for preparing a nickel-based composite catalyst having a core-shell structure, the preparation method comprising:

[0067] (1) Synthesis of Ni@ZSM-5 core layer: The method disclosed in Example 1 of CN109731608B was used as reference. The SiO2:Al2O3 ratio in the final Ni@ZSM-5 core layer was 100:1, the particle size of the nickel nanoparticles was in the range of 2 to 5 nm, and the Ni content was 5.2 wt%.

[0068] (2) Preparation of Ni@ZSM-5@S-1 core-shell structure: The Ni@ZSM-5 core layer obtained in step (1), silicon source (white carbon black), structure directing agent (TPAOH) and water were mixed evenly (wherein: TPAOH / SiO2=0.1:1, H2O / SiO2=45:1), transferred into a hydrothermal crystallization reactor for hydrothermal crystallization treatment at 170°C for 4 h, filtered, dried, and first calcined at 600°C for 4 h to obtain the Ni@ZSM-5@S-1 core-shell structure; HRTEM analysis showed that the shell thickness was about 50 nm.

[0069] (3) Preparation of Ni@ZSM-5@S-1 / Al2O3 catalyst: Ni@ZSM-5@S-1 core-shell structure, carrier dry rubber powder, appropriate amount of water and nitric acid with a concentration of 66% were mixed evenly, extruded into strips, and then dried, second calcined at 700°C for 4 hours, and reduced at 600°C in a hydrogen atmosphere for 10 hours to obtain the nickel-based composite catalyst with a core-shell structure. The mass ratio of Ni@ZSM-5@S-1 core-shell structure to alumina carrier was 60:40.

[0070] Example 3

[0071] This embodiment provides a method for preparing a nickel-based composite catalyst having a core-shell structure, the preparation method comprising:

[0072] (1) Synthesis of Ni@ZSM-5 core layer: The method disclosed in Example 1 of CN109731608B was used as reference. The SiO2:Al2O3 ratio of the final Ni@ZSM-5 core layer was 130:1, the particle size of the nickel nanoparticles was in the range of 2 to 5 nm, and the Ni content was 4.8 wt%.

[0073] (2) Preparation of Ni@ZSM-5@S-1 core-shell structure: The Ni@ZSM-5 core layer obtained in step (1), silicon source (white carbon black), structure directing agent (TPAOH) and water were mixed evenly (wherein: TPAOH / SiO2=0.3:1, H2O / SiO2=25:1), transferred into a hydrothermal crystallization reactor for hydrothermal crystallization treatment at 170°C for 12 h, filtered, dried, and first calcined at 400°C for 12 h to obtain the Ni@ZSM-5@S-1 core-shell structure; HRTEM analysis showed that the shell thickness was about 115 nm.

[0074] (3) Preparation of Ni@ZSM-5@S-1 / Al2O3 catalyst: Ni@ZSM-5@S-1 core-shell structure, carrier dry rubber powder, appropriate amount of water and nitric acid with a concentration of 66% were mixed evenly, extruded into strips, and then dried, second calcined at 500°C for 10 hours, and reduced at 400°C in a hydrogen atmosphere for 20 hours to obtain the nickel-based composite catalyst with a core-shell structure. The mass ratio of Ni@ZSM-5@S-1 core-shell structure to alumina carrier was 70:30.

[0075] Example 4

[0076] The present embodiment provides a method for preparing a nickel-based composite catalyst with a core-shell structure. The preparation method is the same as that in Example 1, except that the content of Al2O3 in the Ni@ZSM-5@S-1 / Al2O3 catalyst is 55wt%, and will not be described again.

[0077] Example 5

[0078] The present embodiment provides a method for preparing a nickel-based composite catalyst with a core-shell structure. The preparation method is the same as that in Example 1, except that the content of Al2O3 in the Ni@ZSM-5@S-1 / Al2O3 catalyst is 15wt%, and will not be described again.

[0079] Example 6

[0080] This embodiment provides a method for preparing a nickel-based composite catalyst with a core-shell structure. The preparation method is the same as that of Embodiment 1 except that the thickness of the S-1 molecular sieve nanolayer is 40 nm, and will not be described in detail here.

[0081] Compared with the catalyst prepared in Example 1, the Ni nanoparticles of the catalyst prepared in this example are larger, and some particles are larger than 10 nm. Under the same high-boiling-substance cracking reaction conditions, the cracking activity of the catalyst prepared in this example is low.

[0082] Example 7

[0083] This embodiment provides a method for preparing a nickel-based composite catalyst with a core-shell structure. The preparation method is the same as that of Embodiment 1 except that the thickness of the S-1 molecular sieve nanolayer is 220 nm, and will not be described in detail here.

[0084] The shell thickness of the catalyst S-1 prepared in this example is significantly increased compared with the catalyst prepared in Example 1. Under the same high-boiling-substance cracking reaction conditions, the cracking activity of the catalyst prepared in this example is low.

[0085] Comparative Example 1

[0086] This comparative example provides a method for preparing a nickel-based composite catalyst. The preparation method is the same as Example 1 except that step (2) is not performed and step (3) is performed directly using the Ni@ZSM-5 core layer, and the details are not repeated here.

[0087] Compared with the catalyst prepared in Example 1, the Ni nanoparticles of the catalyst prepared in this example are larger, and some particles are larger than 10 nm. Under the same high-boiling-substance cracking reaction conditions, the cracking activity of the catalyst prepared in this example is low.

[0088] Comparative Example 2

[0089] This comparative example provides a method for preparing a nickel-based composite catalyst. The preparation method is the same as Example 1 except that step (3) is not performed and the Ni@ZSM-5@S-1 core-shell structure is directly used as the catalyst, and the rest is not repeated here.

[0090] Compared with the catalyst prepared in Example 1, the catalyst prepared in this example has poor strength and is easily pulverized during the high-boiling material cracking reaction, resulting in bed blockage.

[0091] Comparative Example 3

[0092] This comparative example provides a method for preparing a nickel-based composite catalyst. The preparation method is the same as that of Example 1 except that the carrier dry rubber powder in step (3) is replaced by magnesium oxide, and the details are not described again.

[0093] Compared with the catalyst prepared in Example 1, under the same high-boiling-substance cracking reaction conditions, the cracking activity of the catalyst prepared in this example is lower than 95%.

[0094] Comparative Example 4

[0095] This comparative example provides a method for preparing a nickel-based composite catalyst. The preparation method is the same as Example 1 except that step (3) is not performed and magnesium nitrate is added in step (2), and the details are not repeated here.

[0096] Compared with the catalyst prepared in Example 1, under the same high-boiling-substance cracking reaction conditions, the cracking activity of the catalyst prepared in this example is lower than 95%.

[0097] 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 composition and content of the catalyst in the above embodiments and comparative examples are shown in Table 1.

[0098] Table 1

[0099]

[0100] Application Example 1-1

[0101] This application example provides a method for cracking and disproportionating high-boiling organic silicon products, the method comprising:

[0102] A fixed bed reactor was used to introduce high boiling organosilicon products (composed of 25% methyl-rich disilane, 40% trichlorotrimethyldisilane, and 35% chloro-rich disilane) and hydrogen into a catalyst prepared in Example 1 at a temperature of 300° C., a pressure of 0.3 MPa, and a mass space velocity of 0.1 h / min. -1 The cracking reaction is carried out under the conditions of , to obtain a reaction material containing chlorosilane monomer.

[0103] Application Example 1-2

[0104] This application example provides a method for cracking and disproportionating high-boiling organic silicon products. The method is different from application example 1-1 only in that the cracking reaction temperature is 450°C, the pressure is 0.5 MPa, and the feed mass space velocity of the high-boiling organic silicon products is 0.5 h -1 .

[0105] Application Example 2-1

[0106] This application example provides a method for cracking and disproportionating high-boiling organic silicon products, the method comprising:

[0107] A fixed bed reactor was used to introduce high boiling organosilicon products (composed of 25% methyl-rich disilane, 5% Si-CH2-Si, 50% trimethyltrichlorodisilane, and 20% chloro-rich disilane) and hydrogen into a catalyst prepared in Example 2, and the reaction mixture was heated at a temperature of 300°C, a pressure of 0.3 MPa, and a mass space velocity of 0.1 h / min.-1 The cracking reaction is carried out under the conditions of , to obtain a reaction material containing chlorosilane monomer.

[0108] Application Example 2-2

[0109] This application example provides a method for cracking and disproportionating high-boiling organic silicon products. The method is different from application example 2-1 only in that the cracking reaction temperature is 450°C, the pressure is 1.5 MPa, and the feed mass space velocity of the high-boiling organic silicon products is 0.5 h -1 .

[0110] Application Example 3-1

[0111] This application example provides a method for cracking and disproportionating high-boiling organic silicon products, the method comprising:

[0112] A fixed bed reactor was used to introduce high boiling organosilicon products (composed of 10% methyl-rich disilane, 5% Si-CH2-Si, 5% Si-O-Si, 40% trimethyltrichlorodisilane and 40% chloro-rich disilane) and hydrogen into a catalyst prepared in Example 3 at a temperature of 350°C, a pressure of 0.3 MPa and a mass space velocity of 0.06 h / min. -1 The cracking reaction is carried out under the conditions of , to obtain a reaction material containing chlorosilane monomer.

[0113] Application Example 3-2

[0114] This application example provides a method for cracking and disproportionating high-boiling organic silicon products. The method is different from application example 3-1 only in that the cracking reaction temperature is 450°C, the pressure is 1.0 MPa, and the feed mass space velocity of the high-boiling organic silicon products is 0.3 h -1 .

[0115] Application Examples 4 to 7 and Comparative Application Examples 1 to 4

[0116] Application Examples 4 to 7 and Application Comparative Examples 1 to 4 provide a method for cracking and disproportionating a high-boiling-point organic silicon product. The method for cracking and disproportionating a high-boiling-point organic silicon product is the same as Application Example 1-1 except that the catalysts in Examples 4 to 7 and Comparative Examples 1 to 4 are used respectively, and will not be described in detail here.

[0117] Application Comparative Example 1-2

[0118] This comparative example provides a method for cracking and disproportionating high-boiling organic silicon products. The method is different from comparative example 1 in that the cracking reaction temperature is 350°C, the pressure is 0.3 MPa, and the feed mass space velocity of the high-boiling organic silicon products is 0.06 h -1 .

[0119] Application Comparative Examples 1-3

[0120] This comparative example provides a method for cracking and disproportionating high-boiling organic silicon products. The method is different from comparative example 1 in that the cracking reaction temperature is 450°C, the pressure is 1.0 MPa, and the feed mass space velocity of the high-boiling organic silicon products is 0.3 h -1 .

[0121] Application Comparative Examples 1-4

[0122] This application comparative example provides a method for cracking and disproportionating high-boiling organic silicon products. The method is different from application comparative examples 1-3 only in that the temperature of the cracking reaction is 550°C.

[0123] The reaction materials in the above application examples and application comparison examples were subjected to gas chromatography analysis. The test results of the above application examples and application comparison examples are shown in Table 2.

[0124] Table 2

[0125]

[0126] “ / ” in Tables 1 and 2 indicates that there is no relevant data.

[0127] From Table 1 and Table 2, we can see the following points:

[0128] (1) Comprehensive application examples 1 to 3 show that the particle size of nickel in the nickel-based composite catalyst with a core-shell structure provided by the present invention can be controlled within the range of 1 to 8 nm, and the strength is above 85N. The catalyst is used in the cracking and disproportionation reaction of high-boiling organic silicon products, and the high-boiling product cracking rate is above 95.7%, the chlorosilane monomer selectivity is above 93.1%, and the dimethyldichlorosilane selectivity is above 60.3%;

[0129] (2) It can be seen from the combined application examples 1-1 and application examples 4 to 5 that the cracking activity of the catalyst in application example 4 is less than 95%, only 88.1%. The Al2O3 content in application example 5 is low, and the strength of the prepared catalyst is poor. It is easy to pulverize during the high-boiling material cracking reaction, resulting in bed blockage, and it is difficult to operate continuously for 1000 hours. This shows that the present invention preferably controls the content of aluminum oxide in the catalyst within a reasonable range, which can significantly improve the catalytic activity and catalytic stability of the catalyst.

[0130] (3) It can be seen from the combined application examples 1-1 and application examples 6 to 7 that 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.

[0131] (4) It can be seen from the comprehensive application example 1 and the application comparison examples 1 to 4 that the preparation method provided by the present invention can significantly improve the catalytic activity and catalytic stability of the catalyst by coating a layer of S-1 structure on the outer surface of the Ni@ZSM-5 core layer and mixing it with an alumina carrier.

[0132] The present invention illustrates the detailed features of the present invention through the above embodiments, 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 improvement to the present invention, equivalent replacement of the technical features selected by the present invention, addition of auxiliary technical features, 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. 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.

2. The nickel-based composite catalyst with a core-shell structure according to claim 1, characterized in that: The Ni content in the Ni@ZSM-5 core layer is 1.0-8.0wt%; Preferably, the Ni in the Ni@ZSM-5 core layer exists in the form of nickel nanoparticles; Preferably, the particle size of the nickel nanoparticles in the Ni@ZSM-5 core layer is in the range of 1 to 8 nm; 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.

3. The nickel-based composite catalyst with a core-shell structure according to claim 1 or 2, characterized in that: The diameter of the Ni@ZSM-5 core layer is 0.3-3.0 μm; Preferably, the thickness of the S-1 molecular sieve nanolayer is 50 to 200 nm; Preferably, the content of Ni@ZSM-5@S-1 core-shell structure in the nickel-based composite catalyst is 50-70wt%; Preferably, the content of the alumina carrier in the nickel-based composite catalyst is 30 to 50 wt%.

4. A method for preparing a nickel-based composite catalyst having a core-shell structure according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: The Ni@ZSM-5 core layer, silicon source, structure directing agent and water are mixed to perform hydrothermal crystallization reaction, and the obtained reaction material is sequentially subjected to solid-liquid separation, drying and first calcination to obtain a 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 kneaded, extruded, dried, second calcined and reduced to obtain a nickel-based composite catalyst with a core-shell structure.

5. The preparation method according to claim 4, characterized in that: The silicon source includes any one of white carbon black, silica sol, solid silica gel, water glass or ethyl orthosilicate, or a combination of at least two thereof; Preferably, the structure directing agent includes any one of n-butylamine, triethylamine, hexylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetramethylethyldiammonium or dimethyldiethylammonium hydroxide, or a combination of at least two thereof.

6. The preparation method according to claim 4 or 5, characterized in that: The temperature of the hydrothermal crystallization reaction is 120-170°C; Preferably, the hydrothermal crystallization reaction time is 12 to 72 hours; Preferably, the temperature of the first calcination is 400-600°C; Preferably, the first calcination time is 4 to 12 hours.

7. The preparation method according to any one of claims 4 to 6, characterized in that: The alumina source includes any one of dry rubber powder, SB powder, aluminum sol or pseudo-boehmite, or a combination of at least two of them.

8. The preparation method according to any one of claims 4 to 7, characterized in that: The second calcination temperature is 500-700°C; Preferably, the second calcination time is 4 to 10 hours; Preferably, the reduction temperature is 400-600°C; Preferably, the reduction time is 10 to 20 hours.

9. Use of the nickel-based composite catalyst with a core-shell structure as claimed in any one of claims 1 to 3 in the disproportionation cracking of organosilicon.

10. The use according to claim 9, characterized in that The use includes: performing cracking and disproportionation reaction of high-boiling organic silicon products and cracked gas under the action of a nickel-based composite catalyst with a core-shell structure; Preferably, the cracked gas comprises any one of hydrogen, hydrogen chloride or methyl chloride, or a combination of at least two thereof; Preferably, the temperature of the cracking disproportionation reaction is 250-450°C; Preferably, the pressure of the cracking disproportionation reaction is 0.1-1.5 MPa; Preferably, the mass space velocity of high boiling products of organosilicon in the cracking and disproportionation reaction is 0.05 to 3.0 h -1 ; Preferably, the reactor for the cracking and disproportionation reaction comprises any one of a fixed bed, a moving bed, a fluidized bed or a slurry bed.

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