A multi-level porous silica microsphere carrier and catalyst and preparation method

Abstract

The present invention provides a multi-level porous silica microsphere carrier, catalyst, and preparation method. The method comprises the following steps: a) using an acrylate monomer and a silicon precursor as raw materials, subjecting the acrylate monomer to a polymerization reaction to prepare polyvinyl ester microspheres loaded with a silicon precursor; b) hydrolyzing the obtained polyvinyl ester microspheres loaded with a silicon precursor to obtain polyvinyl ester / silica hybrid particles, and then calcining the polyvinyl ester / silica hybrid particles to obtain a multi-level porous silica microsphere carrier. The present invention provides a method for preparing a SiO2 carrier and its metallocene catalyst that can meet the varying requirements for catalyst carrier pore size during olefin polymerization, thereby resolving issues such as low olefin polymerization catalytic activity, high fine powder content in the polymerization product, and uneven particle size. The resulting polymer has a good particle morphology.

Description

Technical Field

[0001] The present invention relates to the field of chemical industry, and in particular to a multi-level porous structure silica microsphere carrier and catalyst and a preparation method thereof. Background Art

[0002] Currently, SiO2 supports used to support metallocene polyolefin catalysts typically have a relatively simple pore size distribution, with the majority being mesoporous SiO2 and a minority being microporous SiO2. This single-structured SiO2 support imposes certain restrictions on the mass transfer of polymerized monomer molecules within its pores, preventing molecules with chain segments larger than the pore size from efficiently contacting the catalyst centers. Even though molecules with small chain segments can effectively utilize the catalytically active centers, diffusion limitations cause the chain molecules to reside excessively long within a single pore, increasing the likelihood of side reactions and thus limiting the practical application of SiO2 supports.

[0003] Metallocene catalysts typically refer to catalytic systems composed primarily of metallocene compounds and methylaluminoxane (MAO). Compared to Ziegler-Natta catalysts, metallocene catalysts offer numerous advantages: their catalytic activity is 10-100 times greater than that of Ziegler-Natta catalysts; they can catalyze the polymerization of a wider range of monomers; their single active center facilitates the production of polymers with higher molecular weights and narrower molecular weight distributions; and the stereostructure of the polymerized product can be easily controlled by modifying the catalyst's molecular structure.

[0004] However, homogeneous metallocene catalysts also have some shortcomings: they cannot effectively control the morphology of the polymer product; they are not suitable for the gas-phase and slurry polymerization processes commonly used in the polyolefin industry; and they require large amounts of expensive MAO as a co-catalyst, which increases the cost of polymer production. Therefore, supported metallocene catalysts came into being.

[0005] In the metallocene-catalyzed ethylene polymerization process, the reaction rate is fast in the initial stages, allowing substrate diffusion to proceed easily. However, as the reaction proceeds, diffusion resistance increases, necessitating a matching of reaction and diffusion behaviors. If α-olefin comonomers with larger molecular dynamic radii are incorporated, larger pore sizes are required to ensure substrate mass transfer.

[0006] At present, the preparation of multi-level porous SiO2 materials generally adopts template method and etching method, and is mostly used in the fields of carbon dioxide adsorption separation, ion exchange, host-guest chemistry, etc. The pore size and morphology of the multi-level porous structure are mainly controlled by means of template selection, temperature, pH value, silicon source and concentration, but the ratio of pores at each level cannot be controlled. For SiO2 carriers used for metallocene olefin polymerization, in addition to obtaining a multi-level porous structure with different pore sizes, it is also necessary to consider the loading of methylaluminoxane and the anchoring of active metals. Therefore, the optimal ratio of pores at each level must be accurately controlled. In summary, how to prepare a SiO2 carrier with a microporous-mesoporous-macroporous multi-level porous structure and accurately control the ratio of pores at each level to meet the requirements of olefin polymerization: improve catalytic activity, reduce the content of fine powder in the polymerization product, ensure uniform particle size, and obtain a polymerization product with good particle morphology is a technical problem that needs to be solved at present. Summary of the Invention

[0007] One object of the present invention is to provide a method for preparing a silica microsphere carrier with a multi-level pore structure;

[0008] Another object of the present invention is to provide a silica microsphere carrier with a multi-level pore structure;

[0009] Another object of the present invention is to provide a method for preparing a metallocene catalyst;

[0010] Another object of the present invention is to provide a metallocene catalyst;

[0011] Another object of the present invention is to provide an application of a metallocene catalyst.

[0012] To achieve the above-mentioned object, the present invention provides a method for preparing a silica microsphere carrier with a hierarchical pore structure, wherein the method comprises the following steps:

[0013] a) using an acrylate monomer and a silicon precursor as raw materials, and subjecting the acrylate monomer to a polymerization reaction to prepare polyvinyl ester microspheres loaded with a silicon precursor;

[0014] b) hydrolyzing the obtained polyvinyl ester microspheres loaded with silicon precursor to obtain polyvinyl ester / silicon dioxide hybrid particles, and then calcining the polyvinyl ester / silicon dioxide hybrid particles to obtain porous silica microsphere carriers.

[0015] According to some specific embodiments of the present invention, in step a), the amount of the silicon precursor is 2-100 parts by mass based on 100 parts by mass of the acrylate monomer.

[0016] According to some specific embodiments of the present invention, in step a), the amount of the silicon precursor used is 40-120 parts by mass based on 100 parts by mass of the acrylate monomer.

[0017] According to some specific embodiments of the present invention, in step a), the amount of silicon precursor used is 40 parts by mass based on 100 parts by mass of the acrylate monomer.

[0018] According to some specific embodiments of the present invention, the polymerization reaction in step a) is carried out at 60-90° C. for 1-10 h.

[0019] According to some specific embodiments of the present invention, in step a), the acrylic ester monomer is an ester compound formed by acrylic acid or its homologues with aliphatic alcohols or aromatic alcohols; and the silicon precursor is a silicate or silicate ester compound that can form silicon dioxide through a hydrolysis / condensation process.

[0020] According to some specific embodiments of the present invention, in step a), the acrylic acid ester monomer is selected from one or more combinations of methyl acrylate, methyl 2-methacrylate, ethyl acrylate and ethyl 2-methacrylate.

[0021] According to some specific embodiments of the present invention, in step a), the silicon precursor is selected from a combination of one or more of sodium silicate, potassium silicate, methyl orthosilicate and ethyl orthosilicate.

[0022] According to some specific embodiments of the present invention, in step a), acrylate monomers and silicon precursors are used as raw materials, and the acrylate monomers are polymerized in the presence of a silane coupling agent and a polymerization initiator.

[0023] According to some specific embodiments of the present invention, in step a), based on 100 parts by mass of the acrylate monomer, the mass amount of the silane coupling agent is 0.5-10 parts; the mass amount of the polymer initiator is 0.5-10 parts.

[0024] According to some specific embodiments of the present invention, in step a), based on 100 parts by mass of the acrylate monomer, the mass amount of the silane coupling agent is 2-10 parts; the mass amount of the polymer initiator is 3-10 parts.

[0025] According to some specific embodiments of the present invention, in step a), based on 100 parts by mass of the acrylate monomer, the amount of the silane coupling agent used is 10 parts by mass; and the amount of the polymer initiator used is 6 parts by mass.

[0026] According to some specific embodiments of the present invention, in step a), the silane coupling agent is a compound having a Y(CH2)nSiX3 structure, wherein Y is an organic functional group that reacts with the resin, X is a group that can be hydrolyzed into a silanol, and n is 0, 1, 2, 3 or 4.

[0027] According to some specific embodiments of the present invention, in step a), the silane coupling agent is a compound having a Y(CH2)nSiX3 structure, where Y is selected from vinyl, amino, thiol, epoxy or methacryloxy; and X is selected from chloro, methoxy, ethoxy or acetoxy.

[0028] According to some specific embodiments of the present invention, in step a), the silane coupling agent is chloropropyltriethoxysilane, vinylmethyldimethoxysilane, aminotrichlorosilane or methacryloxytrimethoxysilane.

[0029] According to some specific embodiments of the present invention, in step a), the polymerization initiator is an ester, alkane, or acyl substance having a peroxide group.

[0030] According to some specific embodiments of the present invention, in step a), the polymerization initiator is selected from one or more combinations of benzoyl peroxide, lauroyl peroxide, tert-butyl perbenzoate, dicumyl peroxide, tert-amyl peroxyacetate and 1,1-bis(tert-amylperoxy)cyclohexane.

[0031] According to some specific embodiments of the present invention, in step a), the acrylate monomers and silicon precursors are used as raw materials and an organic hydrocarbon solvent is used as a diluent to polymerize the acrylate monomers.

[0032] According to some specific embodiments of the present invention, step a) is to use acrylate monomers and silicon precursors as raw materials to form an oil-in-water emulsion in the presence of a surfactant, and to polymerize the acrylate monomers in the oil-in-water emulsion.

[0033] According to some specific embodiments of the present invention, step a) comprises mixing the other ingredients except the surfactant with an organic hydrocarbon solvent to obtain an oil phase, then adding water and stirring to obtain a microemulsion, and then adding a surfactant to form an oil-in-water microemulsion, so that the acrylic ester monomer undergoes a polymerization reaction in the oil-in-water microemulsion system environment.

[0034] According to some specific embodiments of the present invention, in step a), the surfactant is an anionic surfactant, a cationic surfactant, a zwitterionic surfactant or a nonionic surfactant.

[0035] According to some specific embodiments of the present invention, in step a), the surfactant is selected from one or more combinations of sorbitan fatty acid esters, partially hydrolyzed polyvinyl alcohol, polyoxyethylene fatty acid esters, polyoxyethylene ethers, polyoxyethylene amines, polyoxyethylene amides and polypropylene glycol.

[0036] According to some specific embodiments of the present invention, in step a), the amount of the surfactant is 5-11 parts by mass based on 100 parts by mass of the acrylate monomer.

[0037] According to some specific embodiments of the present invention, the weight average molecular weight of the partially hydrolyzed polyvinyl alcohol, polyoxyethylene fatty acid ester, polyoxyethylene ether, polyoxyethylene amine, polyoxyethylene amide and polypropylene glycol are independently 50,000-200,000.

[0038] According to some specific embodiments of the present invention, in step a), the amount of the organic hydrocarbon solvent is 5-200 parts by weight based on 100 parts by weight of the acrylic ester monomer.

[0039] According to some specific embodiments of the present invention, in step a), the amount of the organic hydrocarbon solvent is 40-200 parts by weight based on 100 parts by weight of the acrylic ester monomer.

[0040] According to some specific embodiments of the present invention, in step a), the amount of the organic hydrocarbon solvent used is 80 parts by mass based on 100 parts by mass of the acrylic ester monomer.

[0041] According to some specific embodiments of the present invention, step a) comprises mixing the other ingredients except the surfactant with an organic hydrocarbon solvent to obtain an oil phase, then adding water and stirring to obtain a microemulsion, and then adding the surfactant to form an oil-in-water microemulsion, and reacting the oil-in-water microemulsion at 60-90° C. for 1-10 hours.

[0042] According to some specific embodiments of the present invention, in step a), the oil-in-water microemulsion is reacted at 70-90° C. for 1-2 hours.

[0043] According to some specific embodiments of the present invention, the volume of water added in step a) is 2-15 times the volume of the oil phase.

[0044] According to some specific embodiments of the present invention, the volume of water added in step a) is 5-12 times the volume of the oil phase.

[0045] According to some specific embodiments of the present invention, the other components except the surfactant are acrylate monomers and silicon precursors.

[0046] According to some specific embodiments of the present invention, the other ingredients except the surfactant are acrylate monomers, silicon precursors, silane coupling agents and polymer initiators.

[0047] According to some specific embodiments of the present invention, in step a), the organic hydrocarbon solvent is a hydrocarbon or halogenated hydrocarbon compound that is liquid at room temperature.

[0048] According to some specific embodiments of the present invention, in step a), the organic hydrocarbon solvent is selected from one or more combinations of hexane, heptane, octane, benzene, toluene, xylene, 1,2-dichloroethane and chlorobenzene.

[0049] According to some specific embodiments of the present invention, in step a), after the polymerization reaction, the reaction solution is filtered to obtain polyvinyl ester microspheres loaded with silicon precursor; and then the obtained polyvinyl ester microspheres loaded with silicon precursor are used for hydrolysis reaction in step b).

[0050] According to some specific embodiments of the present invention, step b) is to hydrolyze the obtained polyvinyl ester microspheres loaded with silicon precursor in a hydrolysis solution consisting of acid, alcohol and water to obtain polyvinyl ester / silicon dioxide hybrid particles.

[0051] According to some specific embodiments of the present invention, in step b), the acid is an organic acid or an inorganic acid that does not dissolve silica; and the alcohol is an alkyl alcohol.

[0052] According to some specific embodiments of the present invention, in step b), the acid is selected from a combination of one or more of hydrochloric acid, nitric acid, sulfuric acid, chloric acid, formic acid, acetic acid and benzoic acid.

[0053] According to some specific embodiments of the present invention, in step b), the alcohol is selected from one or more combinations of methanol, ethanol, propanol, isopropanol, butanol, pentanol, hexanol, 2-methylpentanol, 2-ethylbutanol, heptanol, 2-ethylhexanol, octanol and decanol.

[0054] According to some specific embodiments of the present invention, in step b), the alcohol is selected from one or more combinations of ethanol, isopropanol, pentanol and heptanol.

[0055] According to some specific embodiments of the present invention, in step b), the alcohol is selected from ethanol and / or isopropanol.

[0056] According to some specific embodiments of the present invention, in step b), the mass ratio of the polyacrylate microspheres loaded with silicon precursor to the hydrolyzate is 3:(80-120).

[0057] According to some specific embodiments of the present invention, in step b), the mass ratio of the polyacrylate microspheres loaded with silicon precursor to the hydrolyzate is 3:100.

[0058] According to some specific embodiments of the present invention, in step b), based on the total mass of the hydrolyzed solution being 100%, the mass percentage contents of the acid, water and alcohol are 1-5%, 4-10% and the remainder respectively.

[0059] According to some specific embodiments of the present invention, in step b), based on the total mass of the hydrolyzed solution being 100%, the mass percentage contents of the acid, water and alcohol are respectively 2-4%, 6-8% and the remainder.

[0060] According to some specific embodiments of the present invention, in step b), based on the total mass of the hydrolyzed solution being 100%, the mass percentage contents of the acid, water and alcohol are 3%, 7% and 90% respectively.

[0061] According to some specific embodiments of the present invention, in step b), the hydrolysis is carried out at 0-50° C. for 2-20 h.

[0062] According to some specific embodiments of the present invention, in step b), the hydrolysis is performed at 15-35° C. for 2-20 h.

[0063] According to some specific embodiments of the present invention, in step b), the calcination comprises calcining at 400-1200° C. for 1-10 h.

[0064] According to some specific embodiments of the present invention, in step b), the calcination comprises calcining at 400-1000° C. for 1.5-3 h.

[0065] According to some specific embodiments of the present invention, step b) includes heating the poly(vinyl ester) / silicon dioxide hybrid particles obtained by hydrolysis to a calcination temperature at a rate of 1° C. / min-5° C. / min for calcination.

[0066] According to some specific embodiments of the present invention, step b) comprises heating the poly(vinyl ester) / silicon dioxide hybrid particles obtained by hydrolysis to a calcination temperature at a rate of 2° C. / min for calcination.

[0067] According to some specific embodiments of the present invention, step b) includes immersing the obtained polyvinyl ester microspheres loaded with silicon precursor in a hydrolysis solution composed of acid, alcohol and water and stirring to obtain polyvinyl ester / silica hybrid particles, and calcining for 2-10 hours to obtain porous silica microsphere carriers.

[0068] According to some specific embodiments of the present invention, the method comprises:

[0069] (1) dissolving an acrylate monomer and a silicon precursor in an organic hydrocarbon solvent to form a uniform solution;

[0070] (2) adding a silane coupling agent to the solution of step (1);

[0071] (3) adding a polymerization initiator to the solution obtained in step (2) to obtain a mixed solution as the oil phase;

[0072] (4) mixing the oil phase obtained in step (3) with water in a volume ratio of 1:2-1:6, and stirring to obtain a microemulsion;

[0073] (5) Maintaining stirring, add a surfactant to the microemulsion obtained in step (4) to form an oil-in-water microemulsion.

[0074] (6) heating the oil-in-water emulsion prepared in step (5) to 60-90° C. and maintaining the reaction for 1-10 hours to polymerize the acrylate monomer to obtain polyvinyl ester microspheres loaded with a silicon precursor;

[0075] (7) immersing the polyvinyl ester microspheres loaded with silicon precursor obtained in step (6) in a hydrolyzate solution composed of acid, alcohol and water and stirring for 2-20 hours to allow the silicon precursor to undergo a sol-gel process to generate silicon dioxide, thereby obtaining polyvinyl ester / silicon dioxide hybrid particles;

[0076] (8) calcining the polyvinyl ester / silica hybrid particles obtained in step (7) at 400-1200° C. for 2-10 hours to completely decompose the polyvinyl ester to obtain a silica microsphere carrier with a hierarchical pore structure.

[0077] The temperature for interaction of the components in steps (1) to (5) is 0°C-50°C, preferably 15°C-35°C, and the upper limit of the temperature does not exceed the boiling point of the solvent.

[0078] The dissolution time is based on complete dissolution.

[0079] On the other hand, the present invention also provides a silica microsphere carrier with a hierarchical pore structure prepared by any of the preparation methods described above.

[0080] The multi-level pore structure silica microspheres in the present invention not only have micropore (<2nm), mesopore (2-50nm), and macropore (>50nm) pore structures, but also can precisely control the proportion of each level of pore structure.

[0081] According to some specific embodiments of the present invention, the proportions of micropores, mesopores and macropores contained in the multi-level porous structure silica microsphere carrier are 5%-25%, 55%-80% and 5%-25%, respectively; the percentages are based on the total number of micropores, mesopores and macropores as 100%.

[0082] According to some specific embodiments of the present invention, the proportions of micropores, mesopores and macropores contained in the multi-level porous structure silica microsphere carrier are 7%-21%, 55%-80% and 10%-25%, respectively.

[0083] According to some specific embodiments of the present invention, the ratios of micropores, mesopores and macropores contained in the multi-level porous structure silica microsphere carrier are 8%-23%: 58%-78%: 8%-23% respectively.

[0084] According to some specific embodiments of the present invention, the ratios of micropores, mesopores and macropores contained in the multi-level porous structure silica microsphere carrier are 10%-22%: 60%-75%: 12%-20% respectively.

[0085] According to some specific embodiments of the present invention, the pore volume of the multi-level pore structure silica microsphere carrier is in the range of 0.5-10 cm 3 / g; specific surface area is 10-800m 2 / g; the average particle size range is 5-500μm.

[0086] According to some specific embodiments of the present invention, the pore volume of the multi-level pore structure silica microsphere carrier is in the range of 1-4 cm 3 / g.

[0087] According to some specific embodiments of the present invention, the pore volume of the multi-level pore structure silica microsphere carrier is in the range of 1-3 cm 3 / g.

[0088] According to some specific embodiments of the present invention, the specific surface area of ​​the multi-level porous silica microsphere carrier is 230-500m 2 / g.

[0089] According to some specific embodiments of the present invention, the specific surface area of ​​the multi-level porous silica microsphere carrier is 230-350m 2 / g.

[0090] According to some specific embodiments of the present invention, the specific surface area of ​​the multi-level porous silica microsphere carrier is 300-350m 2 / g.

[0091] According to some specific embodiments of the present invention, the average particle size of the silica microsphere carrier with a hierarchical pore structure ranges from 5 to 210 μm.

[0092] According to some specific embodiments of the present invention, the average particle size of the silica microsphere carrier with a hierarchical pore structure is in the range of 20-100 μm.

[0093] The principle of controlling the generation and proportion regulation of multi-level pores in the present invention is as follows: the multi-level structure is generated by the dynamic diffusion and self-assembly of the emulsion. It mainly includes two processes: first, the emulsification process of the emulsion, which includes the dynamic release, diffusion and consumption of the surfactant; second, the deposition and solidification process of silica, which mainly includes the hydrolysis, polymerization and self-assembly process of silane with the surfactant. The generation of multi-level porous materials is to remove the template by high-temperature treatment, and the space left behind constitutes the pores at each level. The factors affecting the emulsification of the emulsion mainly include temperature, type and concentration of surfactant; the factors affecting the deposition and solidification of silica mainly include silicon source concentration, temperature, hydrolyzing agent ratio, etc. The multi-level porous structure material can be synthesized and the pore size can be controlled by finely controlling these two processes.

[0094] The higher the polyacrylate synthesis temperature and the higher the acid content in the hydrolyzate, the greater the ratio of micropores to macroporous silica in the resulting hierarchical porous structure, and the greater the proportion of micropores in the resulting pore distribution. Simultaneously, the mesopore size decreases slightly, and the mesopore wall thickness increases, which has a certain effect on improving the strength of the silica material. The proportion of the hierarchical porous structure can be controlled by carefully controlling the acrylate polymerization conditions and the hydrolysis process.

[0095] In another aspect, the present invention further provides a method for preparing a metallocene catalyst, wherein the method comprises loading a metallocene compound on the multi-level porous silica microsphere carrier described in any one of the present invention as a carrier, thereby obtaining the metallocene catalyst.

[0096] According to some specific embodiments of the present invention, the method comprises using the multi-level porous silica microsphere carrier according to any one of the present invention as a carrier, loading the metallocene compound onto the carrier through reaction at 25-80°C, and the added mass ratio of the metallocene compound to the carrier is 0.01-0.1.

[0097] According to some specific embodiments of the present invention, the metallocene compound has the structural formula: Cp2ZrR n X 2-n ; wherein Cp is selected from C 1-4 Alkyl substituted or unsubstituted cyclopentadienyl, indenyl or fluorenyl; two Cp groups are bridged or unbridged; R is C 1-8 alkyl; X is halogen; n is selected from 0, 1 or 2.

[0098] According to some specific embodiments of the present invention, X is selected from fluorine, chlorine, bromine or iodine.

[0099] According to some specific embodiments of the present invention, the metallocene compound is selected from one or more combinations of bis-n-butylcyclopentadienyl zirconium dichloride, difluorenyl zirconium dichloride, vinyl-bridged bis-indenylethyl zirconium dichloride, bis-cyclopentadienyl zirconium dichloride, diindenyl zirconium dichloride, dimethylindenyl zirconium dichloride and vinyl-bridged bis-cyclopentadienyl zirconium dichloride.

[0100] According to some specific embodiments of the present invention, the metallocene compound is selected from one or more combinations of bis-indenyl zirconium dichloride, di-n-butylcyclopentadienyl zirconium dichloride and vinyl-bridged bis-cyclopentadienyl zirconium dichloride.

[0101] According to some specific embodiments of the present invention, the method comprises first loading methylaluminoxane onto the hierarchical porous silica microsphere carrier according to any one of the present invention; and then loading the metallocene compound onto the carrier.

[0102] According to some specific embodiments of the present invention, the methylaluminoxane is produced by the reaction of trimethylaluminum and water.

[0103] According to some specific embodiments of the present invention, the molar ratio of aluminum in methylaluminoxane to zirconium in the metallocene compound is (2000:1)-(5:1).

[0104] According to some specific embodiments of the present invention, the molar ratio of aluminum in methylaluminoxane to zirconium in the metallocene compound is (500:1)-(10:1).

[0105] According to some specific embodiments of the present invention, the molar ratio of aluminum in methylaluminoxane to zirconium in the metallocene compound is (200:1)-(20:1).

[0106] According to some specific embodiments of the present invention, the method comprises mixing the hierarchical porous silica microsphere carrier and methylaluminoxane, and stirring at 25-80° C. for 1-10 hours, thereby loading the methylaluminoxane onto the hierarchical porous silica microsphere carrier.

[0107] According to some specific embodiments of the present invention, the method comprises mixing the silica microsphere carrier with a hierarchical porous structure and methylaluminoxane, and stirring the mixture at 65-70° C. for 4-5 hours.

[0108] According to some specific embodiments of the present invention, the method comprises adding the hierarchical porous silica microsphere carrier and methylaluminoxane to a reaction solvent, stirring at 25-80°C for 1-10 hours, thereby obtaining hierarchical porous silica microspheres loaded with methylaluminoxane; then adding the hierarchical porous silica microspheres loaded with methylaluminoxane to the reaction solvent, adding the metallocene compound solution dropwise to the reaction solution, and stirring at 25-80°C for 0.3-2 hours to obtain the metallocene catalyst.

[0109] According to some specific embodiments of the present invention, the method comprises dropwise adding a metallocene compound solution into a reaction solution, and stirring at 65-70° C. for 1-2 hours to obtain the metallocene catalyst.

[0110] According to some specific embodiments of the present invention, the method comprises mixing the hierarchical porous silica microsphere carrier and methylaluminoxane, stirring at 25-80° C. for 1-10 hours, and washing to obtain hierarchical porous silica microspheres loaded with methylaluminoxane; under nitrogen protection, adding the hierarchical porous silica microspheres loaded with methylaluminoxane to a reactor, adding a reaction solvent, and stirring to form a slurry; dissolving a metallocene compound in the reaction solvent in a container pre-substituted with nitrogen to form a solution; slowly adding the metallocene compound solution dropwise to the reaction solution under stirring; filtering the obtained solid after the reaction, washing it with toluene and hexane, and then drying it with nitrogen to obtain a loaded metallocene catalyst.

[0111] According to some specific embodiments of the present invention, the metallocene compound solution is slowly added dropwise to the reaction solution at a rate of 0.5-2 mL / min.

[0112] According to some specific embodiments of the present invention, the water content of the reaction solvent is less than or equal to 5 ppm.

[0113] According to some specific embodiments of the present invention, the reaction solvent is toluene.

[0114] According to some specific embodiments of the present invention, the method comprises:

[0115] (1) placing a hierarchical porous silica microsphere carrier in a reactor fully purged with nitrogen, adding purified toluene and methylaluminoxane, stirring at 25-80° C. for 1-10 hours, filtering to obtain a solid, washing the solid with hexane, and finally drying the solid with nitrogen to obtain a hierarchical porous silica microsphere loaded with methylaluminoxane;

[0116] (2) Under nitrogen protection, the hierarchical porous silica microspheres loaded with methylaluminoxane are added to a reactor, and refined toluene is added and stirred to form a slurry; the metallocene compound is dissolved in a container pre-displaced with nitrogen to form a solution, and the metallocene compound solution is slowly added dropwise to the reactor under stirring conditions of 25-80° C., and the reaction is stirred for 0.3-2 hours. After the reaction is completed, the reaction is allowed to stand, the liquid is filtered out, washed with toluene and hexane, and blown dry with nitrogen to obtain a loaded metallocene catalyst.

[0117] In another aspect, the present invention provides a metallocene catalyst prepared by any of the above preparation methods.

[0118] The metallocene catalyst of the present invention has the characteristics of adjustable particle size and narrow particle size distribution, simple process and mild preparation conditions, high catalytic activity, and the obtained polymer has good particle morphology.

[0119] In another aspect, the present invention provides use of the metallocene catalyst in catalyzing ethylene homopolymerization or ethylene and α-olefin copolymerization.

[0120] According to some specific embodiments of the present invention, the α-olefin has a structural formula of CH2=CHR, wherein R is hydrogen, an alkyl group of 1 to 6 carbon atoms, or a phenyl group.

[0121] According to some specific embodiments of the present invention, R is H, methyl, ethyl, propyl, butyl, pentyl or hexyl.

[0122] According to some specific embodiments of the present invention, the temperature of the copolymerization reaction is 0-150°C.

[0123] According to some specific embodiments of the present invention, the temperature of the copolymerization reaction is 60-100°C.

[0124] According to some embodiments of the present invention, the copolymerization reaction is carried out in liquid phase monomers, or in a solution of monomers dissolved in an inert solvent, or in gas phase, or by a combined polymerization process in gas and liquid phases.

[0125] According to some specific embodiments of the present invention, the pressure of the copolymerization reaction is normal pressure or higher.

[0126] It is understood that, under the premise of no contradiction, the specific embodiments of the present invention can be arbitrarily combined with each other.

[0127] In summary, the present invention provides a multi-level porous silica microsphere carrier and catalyst and a preparation method. The technical solution of the present invention has the following advantages:

[0128] The present invention utilizes an emulsification system to obtain a metallocene catalyst with a hierarchical porous structure and a silica-based carrier, and its preparation method. By controlling the water / oil phase volume ratio in an oil-in-water emulsion, the polymerization of acrylate monomers, and the sol-gel process, a SiO2 carrier with a hierarchical porous structure is prepared. The pore size and ratio of the hierarchical pores can also be precisely controlled. The SiO2 carrier and its metallocene catalyst preparation method provided by the present invention can meet the varying requirements for catalyst carrier pore size during olefin polymerization, thereby resolving issues such as low olefin polymerization catalytic activity, high fine powder content in the polymerized product, and uneven particle size. The resulting polymer exhibits a favorable particle morphology. BRIEF DESCRIPTION OF THE DRAWINGS

[0129] Figure 1 Schematic diagram of the preparation method of Example 1;

[0130] Figure 2 This is a morphology image of the multi-level pore structure silica support of Example 5;

[0131] Figure 3 The pore size distribution diagram of the multi-level pore structure silica carrier of Example 5 and Comparative Example 1; DETAILED DESCRIPTION

[0132] The following describes in detail the implementation process of the present invention and the beneficial effects produced by specific embodiments, which is intended to help readers better understand the essence and characteristics of the present invention and is not intended to limit the scope of implementation of this case.

[0133] Example 1

[0134] Preparation method Figure 1 As shown, including:

[0135] 1. Preparation of SiO2 microsphere carrier:

[0136] 1) 100 g of ethyl acrylate (EA), 200 g of benzene (diluent), 100 g of TEOS (precursor), 8 g of chloropropyltriethoxysilane (coupling agent), and 1 g of dicumyl peroxide (initiator) were mixed and uniformly stirred at 500 rpm to form the oil phase.

[0137] 2) The oil phase was added to 1000 mL of deionized water and stirred to form suspended microemulsion droplets. 10.5 g of partially hydrolyzed polyvinyl alcohol with a weight average molecular weight of 50,000 was added as a surfactant.

[0138] 3) reacting at 70° C. for 60 minutes to obtain polymethyl methacrylate (PMMA) polymer particles containing TEOS.

[0139] 4) The PMMA particles containing TEOS are immersed in a hydrochloric acid / isopropyl alcohol mixed aqueous solution with a mass ratio of hydrogen chloride: water: isopropyl alcohol of 3:7:90, so that the TEOS forms silicon dioxide through a sol-gel reaction.

[0140] 5) The hexane was removed by vacuum drying and the product was calcined in a muffle furnace at a temperature of 10°C / min to 400°C and maintained at 400°C for 2 hours to obtain silica microspheres with a hierarchical pore structure. The microsphere pore structure and particle size data are shown in Table 1.

[0141] 2. Metallocene catalyst loading

[0142] 1) Transfer 1 gram of hierarchically porous silica microspheres to a reactor thoroughly purged with nitrogen, add 6 ml of purified toluene, and stir to form a suspension. Add a 10% (mass fraction) methylaluminoxane (MAO) toluene solution to the suspension, stir at 65°C for 4 hours, and then wash with hexane. Finally, blow dry the solid with nitrogen to obtain MAO-loaded hierarchically porous silica microspheres.

[0143] 2) Under nitrogen, 1 gram of MAO-loaded hierarchically porous silica microspheres was added to a reactor, followed by 10 milliliters of purified toluene and stirred to form a slurry. In a container previously purged with nitrogen, 40 milligrams of di-n-butylcyclopentadienyl zirconium dichloride (n-BuCp)2ZrCl2 was dissolved in 10 milliliters of toluene to form a solution. The metallocene compound solution was slowly added dropwise to the reactor under stirring at 65°C. The reaction was stirred for 1 hour. After the reaction was completed, the mixture was allowed to stand, the liquid was filtered, washed with toluene and hexane, and blown dry with nitrogen to obtain a supported metallocene catalyst. The catalyst morphology and pore size distribution were similar to those in Example 5.

[0144] 3. Ethylene homopolymerization:

[0145] After fully purging the atmosphere with nitrogen, a 5-liter stainless steel autoclave was charged with 40 mg of the aforementioned solid catalyst, 12.0 mmol of triisobutylaluminum, and 2.5 L of n-hexane as solvent. Ethylene was introduced to a pressure of 1.0 MPa. The autoclave was heated to 80°C and polymerization was continued at 80°C for 2 hours. The polymerization results are shown in Table 2, and the screening results of the polymer product are shown in Table 3.

[0146] Example 2

[0147] 1. Preparation of SiO2 microsphere carrier:

[0148] 1) 150 g of methyl acrylate (MA), 120 g of heptane (diluent), 60 g of tetraethyl orthosilicate (TEOS), 15 g of vinylmethyldimethoxysilane (coupling agent), and 9 g of benzoyl peroxide (initiator) were mixed and uniformly stirred at 500 rpm to form the oil phase;

[0149] 2) The oil phase was added to 800 mL of deionized water and stirred to form suspended microemulsion droplets. 10.5 g of partially hydrolyzed polyvinyl alcohol with a weight-average molecular weight of 125,000 was added as a surfactant.

[0150] 3) reacting at 70° C. for 60 minutes to obtain polymethyl methacrylate (PMMA) polymer particles containing TEOS.

[0151] 4) The PMMA particles containing TEOS are immersed in a hydrochloric acid / isopropyl alcohol mixed aqueous solution with a mass ratio of hydrogen chloride: water: isopropyl alcohol of 3:7:90, so that the TEOS forms silicon dioxide through a sol-gel reaction.

[0152] 5) Vacuum drying to remove hexane, and calcining in a muffle furnace at 400°C for 2 hours to obtain silica microspheres with a hierarchical pore structure. The microsphere pore structure and particle size data are shown in Table 1.

[0153] 2. Metallocene catalyst loading

[0154] 1) Transfer 1 gram of hierarchically porous silica microspheres to a reactor thoroughly purged with nitrogen, add 6 ml of purified toluene, and stir to form a suspension. Add a 10% (mass fraction) methylaluminoxane (MAO) toluene solution to the suspension, stir at 65°C for 4 hours, and then wash with hexane. Finally, blow dry the solid with nitrogen to obtain MAO-loaded hierarchically porous silica microspheres.

[0155] 2) Under nitrogen, 1 gram of MAO-loaded hierarchically porous silica microspheres was added to a reactor, followed by 10 milliliters of purified toluene and stirred to form a slurry. In a container previously purged with nitrogen, 20 milligrams of bis-n-butylcyclopentadienyl zirconium dichloride (n-BuCp)2ZrCl2 was dissolved in 10 milliliters of toluene to form a solution. The metallocene compound solution was slowly added dropwise to the reactor under stirring at 65°C. The reaction was stirred for 1 hour. After the reaction was completed, the mixture was allowed to stand, the liquid was filtered, washed with toluene and hexane, and blown dry with nitrogen to obtain a supported metallocene catalyst. The catalyst morphology and pore size distribution were similar to those in Example 5.

[0156] 3. Ethylene homopolymerization:

[0157] Same as Example 1, the polymerization results are shown in Table 2, and the polyethylene product screening results are shown in Table 3.

[0158] Example 3

[0159] 1. Preparation of SiO2 microsphere carrier:

[0160] 1) 200 g of 2-methyl methacrylate (MMA) monomer, 90 g of hexane diluent, 120 g of tetraethyl orthosilicate (TEOS) precursor, 10 g of aminotrichlorosilane coupling agent, and 20 g of lauroyl peroxide initiator were mixed and uniformly stirred at 500 rpm to form the oil phase;

[0161] 2) Add the oil phase to 1000 mL of deionized water and stir to form suspended microemulsion droplets. Add 10.5 g of partially hydrolyzed polyvinyl alcohol with a weight-average molecular weight of 200,000 as a surfactant.

[0162] 3) reacting at 70° C. for 60 minutes to obtain polymethyl methacrylate (PMMA) polymer particles containing TEOS.

[0163] 4) The PMMA particles containing TEOS were immersed in a hydrochloric acid / isopropyl alcohol mixed solution with a mass ratio of hydrogen chloride: water: isopropyl alcohol of 3:7:90, so that the TEOS formed silicon dioxide through a sol-gel reaction.

[0164] 5) Vacuum drying to remove hexane, and calcining in a muffle furnace at 400°C for 2 hours to obtain silica microspheres with a hierarchical pore structure. The microsphere pore structure and particle size data are shown in Table 1.

[0165] 2. Metallocene catalyst loading

[0166] 1) Transfer 1 gram of hierarchically porous silica microspheres to a reactor thoroughly purged with nitrogen, add 6 ml of purified toluene, and stir to form a suspension. Add a 10% (mass fraction) methylaluminoxane (MAO) toluene solution to the suspension, stir at 65°C for 4 hours, and then wash with hexane. Finally, blow dry the solid with nitrogen to obtain MAO-loaded hierarchically porous silica microspheres.

[0167] 2) Under nitrogen, 1 gram of MAO-loaded hierarchically porous silica microspheres was added to a reactor, followed by 10 milliliters of purified toluene and stirred to form a slurry. In a container previously purged with nitrogen, 80 milligrams of bis-n-butylcyclopentadienyl zirconium dichloride (n-BuCp)2ZrCl2 was dissolved in 10 milliliters of toluene to form a solution. The metallocene compound solution was slowly added dropwise to the reactor under stirring at 65°C. The reaction was stirred for 1 hour. After the reaction was completed, the mixture was allowed to stand, the liquid was filtered, washed with toluene and hexane, and blown dry with nitrogen to obtain a supported metallocene catalyst. The catalyst morphology and pore size distribution were similar to those in Example 5.

[0168] 3. Ethylene homopolymerization:

[0169] Same as Example 1, the polymerization results are shown in Table 2, and the polyethylene product screening results are shown in Table 3.

[0170] Example 4

[0171] 1. Preparation of SiO2 microsphere carrier:

[0172] 1) 150 g of methyl methacrylate (MMA), 60 g of hexane (diluent), 90 g of tetraethyl orthosilicate (TEOS), 3 g of methacryloyloxytrimethoxysilane (coupling agent), and 4.5 g of lauroyl peroxide (initiator) were mixed and uniformly stirred at 500 rpm to form the oil phase.

[0173] 2) Add the oil phase to 700 mL of deionized water and stir to form suspended microemulsion droplets. Add 10.5 g of partially hydrolyzed polyvinyl alcohol (MW 125,000) as a surfactant.

[0174] 3) reacting at 70° C. for 60 minutes to obtain polymethyl methacrylate (PMMA) polymer particles containing TEOS;

[0175] 4) Immerse the PMMA particles containing TEOS in a hydrochloric acid / isopropanol mixture (hydrogen chloride: water:isopropanol) at a mass ratio of 3:7:90 to allow the TEOS to form silica via a sol-gel reaction. Vacuum dry the particles to remove the hexane, yielding a SiO2 / PMMA template.

[0176] 5) The SiO2 / PMMA template was calcined in a muffle furnace at 400°C for 2 hours to obtain silica microspheres with a hierarchical pore structure. The microsphere pore structure and particle size data are shown in Table 1.

[0177] 2. Metallocene catalyst loading

[0178] 1) Transfer 1 gram of hierarchically porous silica microspheres to a reactor thoroughly purged with nitrogen, add 6 mL of purified toluene, and stir to form a suspension. Add 6 mL of a 10% (mass fraction) methylaluminoxane (MAO) toluene solution to the suspension, stir at 65°C for 4 hours, and then wash with hexane. Finally, blow dry the solid with nitrogen to obtain MAO-loaded hierarchically porous silica microspheres.

[0179] 2) Under nitrogen, 1 gram of MAO-loaded hierarchically porous silica microspheres was added to a reactor, followed by 10 milliliters of purified toluene and stirred to form a slurry. In a container previously purged with nitrogen, 40 milligrams of di-n-butylcyclopentadienyl zirconium dichloride (n-BuCp)2ZrCl2 was dissolved in 10 milliliters of toluene to form a solution. The metallocene compound solution was slowly added dropwise to the reactor under stirring at 65°C. The reaction was stirred for 1 hour. After the reaction was completed, the mixture was allowed to stand, the liquid was filtered, washed with toluene and hexane, and blown dry with nitrogen to obtain a supported metallocene catalyst. The catalyst morphology and pore size distribution were similar to those in Example 5.

[0180] 3. Ethylene homopolymerization:

[0181] Same as Example 1, the polymerization results are shown in Table 2, and the polyethylene product screening results are shown in Table 3.

[0182] Example 5

[0183] 1. Preparation of SiO2 microsphere carriers: The same as Example 1 except that the volume ratio of water phase to oil phase in the preparation of oil-in-water emulsion was increased to 17:3.

[0184] 2. Catalyst synthesis: The same as Example 1 except that 10 mg of di-n-butylcyclopentadienyl zirconium dichloride (n-BuCp) 2ZrCl2 was added. The morphology of the catalyst is shown in the electron microscope image. Figure 2 As shown, the pore size distribution is Figure 3 shown.

[0185] 3. Polymerization: Same as Example 1. The polymerization results are shown in Table 2, and the polyethylene product screening results are shown in Table 3.

[0186] Example 6

[0187] 1. Preparation of SiO2 microsphere carriers: The same as Example 1 except that the oil-in-water emulsion is maintained at 90°C for 2 hours.

[0188] 2. Catalyst synthesis: Same as Example 1. The catalyst morphology and pore size distribution are similar to those in Example 5.

[0189] 3. Polymerization: Same as Example 1. The polymerization results are shown in Table 2, and the polyethylene product screening results are shown in Table 3.

[0190] Example 7

[0191] 1. Preparation of SiO2 microsphere carriers: The same as Example 1 except that the polymer microspheres containing TEOS are immersed in a hydrolysis solution composed of acetic acid / ethanol.

[0192] 2. Catalyst synthesis: Same as Example 1. The catalyst morphology and pore size distribution are similar to those in Example 5.

[0193] 3. Polymerization: Same as Example 1. The polymerization results are shown in Table 2, and the polyethylene product screening results are shown in Table 3.

[0194] Example 8

[0195] 1. Preparation of SiO2 microsphere carrier: The same as Example 1 except that the calcination conditions of the SiO2 / PMMA template in the muffle furnace were changed to a temperature of 1000°C and a time of 1.5 hours.

[0196] 2. Catalyst synthesis: The same process as in Example 1 was used except that the metallocene compound used was difluorenyl zirconium dichloride. The catalyst morphology and pore size distribution were similar to those in Example 5.

[0197] 3. Polymerization: Same as Example 1. The polymerization results are shown in Table 2, and the polyethylene product screening results are shown in Table 3.

[0198] Example 9

[0199] 1. Preparation of SiO2 microsphere carrier: same as Example 1.

[0200] 2. Catalyst synthesis: The same process as in Example 1 was performed except that 12 mL of 10% by mass MAO toluene solution was added. The catalyst morphology and pore size distribution were similar to those in Example 5.

[0201] 3. Polymerization: Same as Example 1. The polymerization results are shown in Table 2, and the polyethylene product screening results are shown in Table 3.

[0202] Example 10

[0203] 1. Preparation of SiO2 microsphere carrier: same as Example 1.

[0204] 2. Catalyst synthesis: The same as Example 1 except that the metallocene compound used was diindenyl zirconium dichloride. The catalyst morphology and pore size distribution were similar to those of Example 5.

[0205] 3. Polymerization: Same as Example 1. The polymerization results are shown in Table 2, and the polyethylene product screening results are shown in Table 3.

[0206] Example 11

[0207] 1. Preparation of SiO2 microsphere carrier: same as Example 1.

[0208] 2. Catalyst synthesis: The same process as in Example 1 was performed except that the metallocene compound added was vinyl-bridged bis-indenylethyl zirconium dichloride. The catalyst morphology and pore size distribution were similar to those in Example 5.

[0209] 3. Polymerization: Same as Example 1. The polymerization results are shown in Table 2, and the polyethylene product screening results are shown in Table 3.

[0210] Example 12

[0211] 1. Preparation of SiO2 microsphere carrier: same as Example 1.

[0212] 2. Catalyst synthesis: Same as Example 1. The catalyst morphology and pore size distribution are similar to those in Example 5.

[0213] 3. Ethylene / 1-hexene copolymerization:

[0214] After fully purging the atmosphere with nitrogen, a 5-liter stainless steel autoclave was charged with 40 mg of the solid catalyst, 12.0 mmol of triisobutylaluminum, and 50 mL of 1-hexene. 2.5 L of n-hexane was added as solvent. The temperature was raised to 80°C, and polymerization was carried out at 80°C for 2 hours. The polymerization results are shown in Table 2, and the screening results of the polymer product are shown in Table 3.

[0215] Comparative Example 1

[0216] 1. Carrier preparation:

[0217] 90 grams of tetraethyl orthosilicate (TEOS) precursor was added to 700 mL of deionized water, followed by a hydrochloric acid / isopropyl alcohol mixture. This allowed the TEOS to form silica via a sol-gel reaction. After vacuum drying, the SiO2 was calcined in a muffle furnace at 400°C for 2 hours to obtain silica microspheres prepared by the sol-gel method. The microsphere pore structure and particle size data are shown in Table 1.

[0218] 2. Catalyst synthesis: same as in Example 1.

[0219] 3. Polymerization: Same as Example 1. The polymerization results are shown in Table 2, and the polyethylene product screening results are shown in Table 3.

[0220] Comparative Example 2

[0221] 1. Carrier Preparation: Grace 955 silica microspheres were used as carriers. The microsphere pore structure and particle size data are shown in Table 1.

[0222] 2. Catalyst synthesis: same as in Example 1.

[0223] 3. Polymerization: Same as Example 1. The polymerization results are shown in Table 2, and the polyethylene product screening results are shown in Table 3.

[0224] Comparative Example 3

[0225] 1. Carrier Preparation: SBA-15 molecular sieve microspheres were prepared as carriers according to the method described in the literature "Xie Huanling et al., Preparation and Characterization of SBA-15 Microspheres, Journal of Chongqing Institute of Technology (Natural Science Edition), 2008, 22(11): 57-61." The pore structure and particle size data of the microspheres are shown in Table 1.

[0226] 2. Catalyst synthesis: same as in Example 1.

[0227] 3. Polymerization: Same as Example 1. The polymerization results are shown in Table 2, and the polyethylene product screening results are shown in Table 3.

[0228] Comparative Example 4

[0229] 1. Carrier preparation: ZSM-5 molecular sieve microspheres were prepared as carriers according to the method in patent 201210073742.8

[0230] 2. Catalyst synthesis: same as in Example 1.

[0231] 3. Polymerization: Same as Example 1. The polymerization results are shown in Table 2, and the polyethylene product screening results are shown in Table 3.

[0232] Effect Example 1

[0233] The structural parameters of the catalysts prepared in the above examples and comparative examples are shown in Table 1 below:

[0234] Table 1. Structural parameters of the catalysts

[0235]

[0236] Effect Example 2

[0237] The catalysts prepared in the above examples and comparative examples were used to carry out olefin polymerization reactions, and the evaluation and analysis methods were as follows:

[0238] (1) The polymerization activity was calculated by the following method:

[0239]

[0240] The unit of polymerization activity is kgPE / gcat.

[0241] (2) Apparent density is tested in accordance with GB / T1636.

[0242] The results are shown in Tables 2 and 3 below.

[0243] Table 2. Aggregation results

[0244]

[0245] Table 3. Screening results of polymer powder

[0246]

[0247]

[0248] As can be seen from the above examples and comparative examples, the metallocene catalyst obtained by using the multi-level porous silica prepared by the present invention as a carrier has high polymerization yield and polymerization activity, high apparent density of the polymer powder, and narrow molecular weight distribution. This is because: the multi-level porous silica contains a certain proportion of micropores, mesopores, and macropores, and the proportion of macropores is reasonably regulated so that molecules with chain segments larger than the pore size can efficiently contact the catalyst center, thereby significantly improving the activity of the olefin polymerization catalyst (see Example 1 and Comparative Example 1); adjusting the micropore ratio shortens the residence time of small molecules within the micropore channels, reducing the probability of side reactions, and suppressing the formation of fine powder with a particle size greater than 120 mesh. The polymer product has a high apparent density, low fine powder content, and a more excellent product particle morphology (see Example 5 and Comparative Example 2).

Claims

1. A method for preparing a silica microsphere carrier with a multi-level pore structure, wherein: The method comprises the following steps: a) using acrylate monomers and silicon precursors as raw materials, in the presence of a silane coupling agent and a polymerization initiator, and in the presence of a surfactant to form an oil-in-water emulsion, and polymerizing the acrylate monomers in the oil-in-water emulsion to prepare polyvinyl ester microspheres loaded with a silicon precursor, wherein the polymerization reaction in step a) is carried out at 60-90° C. for 1-10 hours, and the amount of the silicon precursor is 2-100 parts by weight based on 100 parts by weight of the acrylate monomers, the amount of the silane coupling agent is 0.5-10 parts by weight based on 100 parts by weight of the acrylate monomers, and the amount of the polymerization initiator is 0.5-10 parts by weight; b) hydrolyzing the obtained polyvinyl ester microspheres loaded with silicon precursor to obtain polyvinyl ester / silica hybrid particles, and then calcining the polyvinyl ester / silica hybrid particles to obtain porous silica microsphere carriers, wherein the hydrolysis is performed at 0-50° C. for 2-20 hours, and the calcination comprises calcining at 400-1200° C. for 1-10 hours; The proportions of micropores, mesopores and macropores in the multi-level porous silica microsphere carrier are 5%-25%, 55%-80% and 5%-25% respectively; the percentages are based on the total number of micropores, mesopores and macropores being 100%.

2. The preparation method according to claim 1, wherein In step a), the acrylic acid ester monomer is an ester compound formed by acrylic acid or its homologues with aliphatic alcohol or aromatic alcohol; the silicon precursor is a silicate or silicate ester compound that can form silicon dioxide through a hydrolysis / condensation process.

3. The preparation method according to claim 1, wherein In step a), acrylate monomers and silicon precursors are used as raw materials and organic hydrocarbon solvents are used as diluents to polymerize the acrylate monomers.

4. The preparation method according to claim 1, wherein Step a) comprises mixing the other ingredients except the surfactant with an organic hydrocarbon solvent to obtain an oil phase, then adding water and stirring to obtain a microemulsion, and then adding the surfactant to form an oil-in-water microemulsion, and polymerizing the acrylic ester monomer in the oil-in-water microemulsion system environment.

5. The preparation method according to claim 1, wherein Step b) is to hydrolyze the obtained polyurethane microspheres loaded with silicon precursor in a hydrolysis solution consisting of acid, alcohol and water to obtain polyurethane / silicon dioxide hybrid particles.

6. The preparation method according to claim 5, wherein In step b), the acid is an organic acid or an inorganic acid that does not dissolve silica; and the alcohol is an alkyl alcohol.

7. A silica microsphere carrier with a hierarchical pore structure prepared by the preparation method according to any one of claims 1 to 6.

8. The multi-level pore structure silica microsphere carrier according to claim 7, wherein: The pore volume of the multi-level pore structure silica microsphere carrier ranges from 0.5 to 10 cm 3 / g; specific surface area is 10-800m 2 / g; the average particle size range is 5-500μm.

9. A method for preparing a metallocene catalyst, wherein: The method comprises using the multi-level porous silica microsphere carrier according to claim 7 or 8 as a carrier to load the metallocene compound, thereby obtaining the metallocene catalyst.

10. The preparation method according to claim 9, wherein The method comprises using the multi-level porous silica microsphere carrier according to claim 7 or 8 as a carrier, loading the metallocene compound onto the carrier through reaction at 25-80° C., and the added mass ratio of the metallocene compound to the carrier is 0.01-0.

1.

11. The preparation method according to claim 9, wherein The structural formula of the metallocene compound is: Cp2ZrR n X 2-n ; wherein Cp is selected from C 1-4 Alkyl substituted or unsubstituted cyclopentadienyl, indenyl or fluorenyl; two Cp groups are bridged or unbridged; R is C 1-8 alkyl; X is halogen; n is selected from 0, 1 or 2.

12. The preparation method according to claim 9, wherein The metallocene compound is selected from one or more combinations of bis-n-butylcyclopentadienyl zirconium dichloride, difluorenyl zirconium dichloride, vinyl-bridged bis-indenylethyl zirconium dichloride, bis-cyclopentadienyl zirconium dichloride, diindenyl zirconium dichloride, dimethylindenyl zirconium dichloride and vinyl-bridged bis-cyclopentadienyl zirconium dichloride.

13. The preparation method according to claim 9, wherein The method comprises first loading methylaluminoxane onto the multi-level porous structure silica microsphere carrier according to claim 7 or 8; and then loading the metallocene compound onto the carrier.

14. The preparation method according to claim 13, wherein The molar ratio of aluminum in methylaluminoxane to zirconium in the metallocene compound is (2000:1)-(5:1).

15. The preparation method according to claim 13 or 14, wherein The method comprises mixing the multi-level porous structure silica microsphere carrier and methylaluminoxane, and stirring at 25-80° C. for 1-10 hours, thereby loading the methylaluminoxane onto the multi-level porous structure silica microsphere carrier.

16. The preparation method according to claim 13 or 14, wherein The method comprises adding the hierarchical porous silica microsphere carrier and methylaluminoxane into a reaction solvent, stirring at 25-80° C. for 1-10 hours, thereby obtaining the hierarchical porous silica microspheres loaded with methylaluminoxane; then adding the hierarchical porous silica microspheres loaded with methylaluminoxane into the reaction solvent, dropwise adding a metallocene compound solution into the reaction solution, and stirring at 25-80° C. for 0.3-2 hours, thereby obtaining the metallocene catalyst.

17. The metallocene catalyst prepared by the preparation method according to any one of claims 9 to 16.

18. Use of the metallocene catalyst according to claim 17 in catalyzing ethylene homopolymerization or ethylene and alpha-olefin copolymerization.

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