Silica gel composite carrier and preparation method thereof

Abstract

This invention provides a silica composite carrier and its preparation method. The preparation method includes the following steps: mixing organically modified montmorillonite and alcohol, then adding alkali to adjust the pH to 7-12 to obtain a mixed solution; then adding an organic precursor of silica and mixing and stirring to obtain silica-pillared modified montmorillonite / silica composite particles; mixing the composite particles with silica sol to form a gel, followed by hydrothermal aging to prepare the silica composite carrier. The carrier of this invention has a stable framework, high specific surface area, and large pore volume.

Description

Technical Field

[0001] This invention belongs to the field of polyolefins and relates to a silicone composite carrier and its preparation method. Background Technology

[0002] Compared to polyolefins produced using traditional Ziegler-Natta (ZN) catalysts, metallocene polyolefins exhibit better strength, transparency, and heat-sealing properties due to their narrow molecular weight distribution and uniform comonomer distribution. The core of metallocene polyolefin production lies in the metallocene catalyst, which is typically an organometallic complex catalyst formed by cyclopentadienyl groups and their derivatives with transition metals. While homogeneous metallocene catalysts offer many advantages, they present several challenges when used in existing polyolefin production facilities. These include poor and difficult-to-control polymer particle morphology, the need for large quantities of methylaluminoxane (MAO) leading to high costs, a tendency for residue sticking, difficulties in subsequent processing, and the requirement for a granulation step, thus limiting their further industrial application.

[0003] Currently, to overcome the shortcomings of homogeneous metallocene catalysts, they are typically supported. Among various supports, silica gel (SiO2 or modified SiO2) is the most commonly used because its surface contains abundant silanol groups, allowing it to support metallocene catalysts. Furthermore, silica gel possesses advantages such as good mechanical strength, easily controllable pore structure and specific surface area, good chemical and thermal stability, and specific surface chemical reactions.

[0004] When silica gel is used as a support, a large amount of methylaluminoxane (MAO) is required as a co-catalyst component. Due to the high cost of MAO, the cost of metallocene catalyst systems is relatively high. To overcome this drawback, much research has focused on using modified silica gel supports or composite supports to prepare catalysts that improve polymerization behavior. Silica gel composite supports can significantly alter the electronic environment of the catalyst on the support, reducing the amount of co-catalysts such as MAO and improving polymerization activity. Methods using composite supports to prepare polyolefin catalysts include silica gel-magnesium chloride, silica gel-titanium dioxide, silica gel-tungsten, silica gel-magnesium oxide, and silica gel-montmorillonite.

[0005] Layered, ultra-acidic supports such as montmorillonite can enhance the electronegativity and cation stability of the central metal, thereby increasing the content, activity, and lifetime of the active center of the catalyst. At the same time, it eliminates the need for large amounts of expensive co-catalysts such as MAO to stabilize the active center metal cation, thus reducing the production cost of the catalyst.

[0006] US patent 6559090 discloses a method for preparing a silica / montmorillonite composite carrier. This method involves wet-milling and dry-milling silica hydrogel separately, mixing them to obtain a silica slurry, then mixing it with a clay slurry to obtain a clay / silica slurry. Finally, the slurry is spray-dried to obtain the composite carrier. Patent WO\2001\025149A2 first prepares a silica slurry, then mixes an acidified cation-exchange layered silicate material with the silica slurry to prepare a mixed slurry, and finally spray-dries the mixed slurry to prepare a silica composition. The preparation methods of both US patent 6559090 and patent WO\2001\025149A2 are essentially physical mixing processes of silica and clay.

[0007] Patents CN105985458 A, CN106928379 A, ​​and CN105985462 A provide a one-step method for preparing clay / silica composite carriers. The method involves mixing and stirring clay with an inorganic acid solution to form a uniformly dispersed suspension of clay in the acid. An aqueous silicate solution is then added dropwise to the suspension to obtain a silica gel containing clay. Finally, spray drying is used to obtain the clay-containing silica composite carrier. The clay-modified silica composite carrier disclosed in CN105985462A has an average particle size of 20–100 μm, an average pore size of 10–70 nm, a pore volume between 1 and 5 g / ml, and a specific surface area of ​​150–500 m². 2 / g. This method requires acid treatment of clay to reduce metal cations in the clay, but some metal cations will still remain in the final carrier, thus affecting the olefin polymerization performance. CN106928379 A discloses that acid-modified layered clay is placed in silica sol, dispersed uniformly using an ultrasonic disperser, and spray-dried to obtain a solid acid-silica composite carrier with uniform particle morphology. The carrier is then dried at 600-800℃ for 2-10 hours under nitrogen flow and stored under an inert gas atmosphere. To ensure uniform dispersion of the layered clay, this method requires ultrasonic dispersion, increasing the energy consumption of carrier preparation.

[0008] Patents 107889472B and 107864635B disclose a green clay that has undergone intercalation, modification, and calcination, and its preparation method, and its use in preparing metallocene catalysts. A preliminary study on the synthesis conditions of porous heterogeneous montmorillonite materials (Journal of Zhejiang University of Technology, (02):3-7 (2002)) and the assembly of nano-SiO2 particles to modify montmorillonite gasoline desulfurizer (Journal of Inorganic Materials, (04):953-957 (2006)) organically modified sodium-based montmorillonite to obtain organic montmorillonite with expanded interlayer spacing. Then, the organic montmorillonite was blended with neutral amines and tetraethyl orthosilicate, etc., and tetraethyl orthosilicate hydrolyzed in the interlayer of montmorillonite to form a pillared structure. Patent CN1752113A describes a composite obtained by combining cation-exchange treated layered silicates with amine molecules and silica precursors. Mg(OH)2 is then introduced into the interlayer structure to obtain a pillared composite. This composite is then used as a Ziegler-Natta catalyst support after calcination.

[0009] Although the clay or composite supports obtained by the above-mentioned methods improve the catalyst activity, their poor particle morphology limits their application as supports for polyolefin catalysts. Summary of the Invention

[0010] The main objective of this invention is to provide a silica composite carrier and its preparation method, so as to overcome the defects of existing montmorillonite-modified silica carriers, such as poor particle morphology, weak carrier strength and stability.

[0011] To achieve the above objectives, the present invention provides a method for preparing a silicone composite carrier, comprising the following steps:

[0012] Organically modified montmorillonite and alcohol were mixed, and then alkali was added to adjust the pH value to 7-12 to obtain a mixture. Then, an organic precursor of silica was added and mixed and stirred to obtain silica-pillared modified montmorillonite / silica composite particles. The composite particles were mixed with silica sol to form a gel, and hydrothermal aging was performed to prepare a silica composite carrier.

[0013] The method for preparing the silica composite carrier of the present invention, wherein the alcohol is a fatty alcohol with 1 to 10 carbon atoms, preferably, the alcohol is one or a mixture of several of methanol, ethanol, propanol, ethylene glycol, glycerol, n-propanol, isopropanol, and n-butanol; an alkali is added to adjust the pH value to 7 to 9 to obtain a mixed solution.

[0014] The method for preparing the silica composite carrier according to the present invention includes the steps of mixing composite particles with silica sol to form a gel and hydrothermal aging:

[0015] Step a: Mix the silicate solution with the surfactant, heat, and adjust the pH to 9-11 to produce a sol;

[0016] Step b: Mix the silica-pillared modified montmorillonite / silica composite particles with the mixture obtained in step a, adjust the pH value to 5-8 to gel the system, add an aging accelerator, and heat to react.

[0017] Step c: Add inorganic acid to the reaction system of step b, and age to obtain silica composite carrier.

[0018] The method for preparing the silica composite carrier according to the present invention includes a silicate solution that is a sodium silicate solution and / or a potassium silicate solution; and a surfactant selected from one or more of hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, and dodecyltrimethylammonium chloride.

[0019] The method for preparing the silica composite carrier of the present invention includes the following: the mass ratio of the silica-pillared modified montmorillonite / silica composite particles to SiO2 in step b is 0.1–10; the heating reaction temperature in step b is 60–80°C; the aging accelerator is a mixed solution of silicate ester compound and water, wherein the silicate ester compound is selected from one or more of methyl orthosilicate, ethyl orthosilicate, and butyl orthosilicate, and the volume ratio of silicate ester compound to water is 1:2–1:10.

[0020] The method for preparing the silicone composite carrier according to the present invention includes step c, which further includes an activation step of the silicone composite carrier: activating the silicone composite carrier at 450-800°C for 2-8 hours.

[0021] The method for preparing the silica composite carrier according to the present invention, wherein the organically modified montmorillonite is alkylamine-modified montmorillonite with 6-20 carbon atoms, has a volatile content of less than 3 wt%, and a density of 1-2 g / cm³. 3 The interlayer spacing is 2–100 nm, and the average particle size is 1–50 μm.

[0022] The method for preparing the silicone composite carrier of the present invention, wherein the mixing ratio of organic modified montmorillonite and alcohol is: 20-250 ml of alcohol per gram of organic modified montmorillonite, preferably 50-100 ml of alcohol per gram of organic modified montmorillonite.

[0023] The method for preparing the silica composite carrier of the present invention includes the following: the alkali is selected from sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate, and organic amine; the organic precursor of silica is an alkoxysilane with 4 to 48 carbon atoms, preferably, the organic precursor of silica is at least one of methyl orthosilicate, ethyl orthosilicate, and butyl orthosilicate; after adding the organic precursor of silica, the concentration of the organic precursor of silica in the system is 0.1 to 1 mol / L.

[0024] To achieve the above objectives, the present invention also provides a silica composite carrier prepared by the above-described preparation method, wherein the silica composite carrier has an average particle size of 10–120 μm and a specific surface area of ​​250–500 m². 2 / g, with an average pore size of 10-50nm, a pore volume of 1-5ml / g, a bulk density of 0.25-0.35, and a SiO2 content of not less than 98wt%.

[0025] The beneficial effects of this invention are:

[0026] 1. This invention modifies organomontmorillonite in alcohol. In addition to modifying the organomontmorillonite with silica pillars, this method also obtains nano-silica particles, which are then uniformly dispersed in the silica gel structure, stabilizing the silica gel skeleton and reducing the damage to the gel network during drying. This allows the resulting carrier to maintain a high specific surface area while obtaining a large pore volume.

[0027] 2. The organo-montmorillonite-modified silica composite carrier prepared in this invention achieves uniform dispersion of montmorillonite in silica gel through further modification of the organo-modified montmorillonite, resulting in a silica composite carrier of uniform quality and good particle morphology. The average particle size of the carrier is adjustable from 10 to 120 μm, the average pore size is from 10 to 50 nm, the pore volume is from 1 to 5 ml / g, and the specific surface area is from 250 to 500 m². 2 / g, bulk density of 0.25-0.35, and SiO2 content of not less than 98%. Detailed Implementation

[0028] The technical solution of the present invention will be described in detail below. The following embodiments are implemented under the premise of the technical solution of the present invention and a detailed implementation process is given. However, the protection scope of the present invention is not limited to the following embodiments. Structures or experimental methods that do not specify specific conditions in the following embodiments are generally performed under conventional conditions.

[0029] This invention provides a method for preparing a silica composite support, utilizing the surface acidity and layered structure of montmorillonite to modify the surface properties of silica and improve catalyst activity. By modifying organically modified montmorillonite with silica pillars in an alcohol solution, the interlayer spacing of montmorillonite is further expanded, stabilizing the silica gel framework. Furthermore, by adding pillar-modified montmorillonite during the sol-gel process of traditional silica support preparation, uniform dispersion and efficient intercalation of montmorillonite in silica are achieved. The pillar-modified montmorillonite is added before the silica sol gels, and the pH and temperature of the system are adjusted to induce gelation. After acidification of the gel product, it is washed and dried to obtain the composite support.

[0030] In one embodiment, the method for preparing the silica composite carrier of the present invention includes two main steps: modification of organomontmorillonite with silica pillars and the use of the modified composite particles in the preparation of the montmorillonite / silica composite carrier. Specifically, it includes the following steps:

[0031] Organically modified montmorillonite and alcohol were mixed, and then alkali was added to adjust the pH value to 7-12 to obtain a mixture. Then, an organic precursor of silica was added and mixed and stirred to obtain silica-pillared modified montmorillonite / silica composite particles. The composite particles were mixed with silica sol to form a gel, and hydrothermal aging was performed to prepare a silica composite carrier.

[0032] This invention modifies organomontmorillonite in alcohol. In addition to modifying the silica pillar of montmorillonite, this method also obtains nano-silica particles, which are then uniformly dispersed in the silica gel structure, stabilizing the silica gel skeleton and reducing the damage to the gel network during drying. This allows the resulting carrier to maintain a high specific surface area while obtaining a large pore volume.

[0033] In one embodiment, the organically modified montmorillonite can be commercially available organically modified montmorillonite or can be prepared by organically modifying montmorillonite according to publicly available reports. The organically modified montmorillonite of this invention is a high-purity montmorillonite modified with alkylamines having 6-20 carbon atoms, with a volatile matter content of less than 3 wt% and a density of 1-2 g / cm³. 3 The interlayer spacing is In this invention, the content of the modifier in the organically modified montmorillonite is not particularly limited, for example, it is 25-35% of the mass of the organically modified montmorillonite. In another embodiment, the average particle size of the organically modified montmorillonite is 1-50 μm; preferably, the particle size of the organically modified montmorillonite is 15-30 μm; furthermore, the purity of the organically modified montmorillonite is preferably above 99%.

[0034] In one embodiment, the alcohol is a fatty alcohol with 1 to 10 carbon atoms, preferably one or a mixture of several of methanol, ethanol, propanol, ethylene glycol, glycerol, n-propanol, isopropanol, and n-butanol; the alcohol is added, for example, in the form of an alcohol solution, which is an aqueous solution of alcohol, and the volume ratio of alcohol to water is 1 to 25, preferably 3 to 10.

[0035] In one embodiment, the mixing ratio of organically modified montmorillonite to alcohol is 20-250 ml of alcohol per gram of organically modified montmorillonite, preferably 50-100 ml of alcohol per gram of organically modified montmorillonite. In another embodiment, the organically modified montmorillonite and alcohol are mixed and stirred at 10°C to 40°C for, for example, 0.5-2 hours, to form a uniformly dispersed suspension.

[0036] In one embodiment, the alkali is selected from sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate, and organic amines; preferably, the alkaline catalyst is ammonia or organic amines. In another embodiment, the amount of alkali added should adjust the pH of the mixture from step 1 to 7-12, preferably to 7-9.

[0037] In one embodiment, the organic precursor of silica is first mixed and stirred evenly with an organic alcohol, and then added to the modified mixture of the above-mentioned organic modified montmorillonite, and stirred at 10-60°C for 4-10 hours. Then, the mixture is washed and dried to obtain silica-pillared modified montmorillonite / silica composite particles containing silica-pillared modified montmorillonite and nano-silica particles.

[0038] In one embodiment, the organic precursor of silicon dioxide is an alkoxysilane with 4 to 48 carbon atoms, preferably methyl orthosilicate, ethyl orthosilicate, or butyl orthosilicate; the concentration of the silicon precursor in the reaction system in step 2 is 0.1 to 1 mol / L.

[0039] The present invention does not impose any particular limitation on the above-mentioned drying method, such as ordinary drying oven drying, freeze drying, or any other available drying method.

[0040] In one specific embodiment, the steps of preparing a silica composite carrier by mixing composite particles with silica sol to form a gel and then hydrothermally aging the gel include:

[0041] Step a: Mix the silicate solution with the surfactant, heat, and adjust the pH to 9-11 to produce a sol;

[0042] Step b: Mix the silica-pillared modified montmorillonite / silica composite particles with the mixture obtained in step a, adjust the pH value to 5-8 to gel the system, add an aging accelerator, and heat to react.

[0043] Step c: Add inorganic acid to the reaction system of step b, and age to obtain silica composite carrier.

[0044] In step a, the silicate is selected from one or a mixture of two of sodium silicate and potassium silicate. The surfactant is selected from one or more of hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, and dodecyltrimethylammonium chloride. The heating temperature is 20–80°C, preferably 30–50°C. The amount of surfactant used is 0.1 wt%–1 wt% of the silicate solution.

[0045] In one embodiment, an inorganic acid is used to adjust the pH value of the system in step a. The inorganic acid is selected from one or more of sulfuric acid, hydrochloric acid, and nitric acid. The concentration of the inorganic acid is 1.0 mol / L. The inorganic acid is preferably added by dropping, and the dropping rate is 1 to 20 ml / min.

[0046] In one embodiment, in step b, the ratio of the mass of the silica-pillared modified montmorillonite / silica composite particles to the mass of SiO2 in the reaction system (i.e., the mass of silicate in the silicate solution as silica) is 0.1–10, preferably 0.5–1. In another embodiment, the reaction temperature in step b is 50–90°C, and the reaction time is 2–10 hours; preferably, the reaction temperature is 50–90°C, and the reaction time is 2–10 hours.

[0047] In one embodiment, the aging accelerator is a mixed solution of silicate compound and water, wherein the silicate compound may be one or more of methyl orthosilicate, ethyl orthosilicate and butyl orthosilicate, the volume ratio of silicate compound to deionized water is 1:2 to 1:10, and the amount of aging accelerator added is 1% to 10% of the volume of the reaction system.

[0048] Step c is as follows: Inorganic acid is added to the reaction system in step b, and the mixture is aged for 3 to 8 hours. The reaction product is then washed, dried, and activated to obtain the silica composite carrier.

[0049] In one embodiment, after adding the inorganic acid in step c, the pH value of the system can be 2-4. In step c, the drying method can be a conventional drying oven, spray drying, or any other available drying method, preferably centrifugal spray drying. The activation method can be as follows: activate the montmorillonite-modified silica gel composite carrier in a muffle furnace or under nitrogen flow at 450-800°C for 2-8 hours, and store it under an inert gas atmosphere for later use.

[0050] The montmorillonite-modified silica composite carrier obtained by this invention has an average particle size of 10–120 μm and a specific surface area of ​​250–500 m². 2 / g, with an average pore size of 10-50nm, a pore volume of 1-5ml / g, a bulk density of 0.25-0.35, and a SiO2 content of not less than 98%.

[0051] The silica composite support of this invention, after loading a metallocene catalyst, can be used in ethylene gas-phase polymerization or slurry polymerization processes; more specifically, it can be used for homogeneous polymerization of ethylene, or for the polymerization of ethylene with C3-C4 catalysts. 20 Copolymerization of one or more of the α-olefins.

[0052] Therefore, this invention provides a montmorillonite-modified silica composite carrier and its preparation method, which can utilize the surface acidity and layered structure of montmorillonite to modify the surface properties of silica and improve the activity of the catalyst. By modifying the organomontmorillonite with silica pillars, the interlayer spacing of montmorillonite is further expanded, and then introduced into the preparation process of the silica carrier, so as to achieve uniform dispersion and efficient composite of montmorillonite in silica.

[0053] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0054] 1) This invention discloses a montmorillonite-modified silica composite carrier and its preparation method. First, a suspension of organically modified montmorillonite is prepared. Part of the silicon precursor hydrolyzes and condenses between the montmorillonite layers to form SiO2-pillared modified montmorillonite, further expanding the interlayer spacing of the organically modified montmorillonite. During the silica carrier preparation process, the SiO2-pillared modified montmorillonite is added after sol and before gelation, eliminating the need for ultrasonic dispersion or other methods. It is uniformly dispersed in situ in the silica via intercalation. Compared to directly using organically modified montmorillonite without silicon precursor modification, this invention improves the dispersion performance of montmorillonite in the composite silica carrier, thereby significantly improving the polymerization performance of the metallocene catalyst.

[0055] 2) While obtaining SiO2-pillared modified montmorillonite, nano-silica particles are also generated. The nano-sized silica particles are also uniformly dispersed in the silica gel structure, which plays a role in stabilizing the silica gel skeleton and reducing the damage to the gel network during the drying process, so that it can obtain large pore volume while maintaining a high specific surface area.

[0056] 3) The intercalation of montmorillonite into silica gel can effectively increase the acidity of the silica gel surface, improve the catalytic efficiency of metallocene catalysts, reduce the amount of MAO co-catalyst, and improve the microenvironment of the composite support surface, thereby improving the copolymerization activity of the supported metallocene catalyst and enhancing the performance of the copolymer.

[0057] 4) The montmorillonite-modified silica composite carrier prepared in this invention has an adjustable average particle size of 10–120 μm, an average pore size of 10–50 nm, a pore volume of 1–5 ml / g, and a specific surface area of ​​250–500 m². 2 The composite support prepared by this invention has excellent physical properties and surface microenvironment, resulting in superior ethylene-α-olefin copolymerization activity of the supported metallocene catalyst and improved copolymer performance. The bulk density is 0.25–0.35 g / g.

[0058] This invention does not specifically limit the method of preparing catalysts using silica composite supports; conventional methods in the field can be used.

[0059] To further understand the present invention, preferred embodiments are described below in conjunction with examples, but these are not intended to limit the scope of the invention. The following examples and comparative examples use the same amount of zirconium dichloroethylene raw material, but due to differences in the specific surface area and pore volume of the prepared carriers, the zirconium loading after loading differs.

[0060] Test methods

[0061] The carrier was analyzed using a surface area and porosity analyzer and a Malvern particle size analyzer, while the polymer was analyzed using a gel permeation chromatography system.

[0062] (1) Particle size and particle size distribution analysis: Mastersizer 2000 Malvern particle size analyzer.

[0063] (2) Specific surface area and pore structure analysis: The specific surface area and porosity were tested by N2 adsorption method using a TriStar II Plus 3.02 specific surface area and porosity analyzer from Microneritics, USA.

[0064] (3) Bulk density: HT1001 multi-functional powder physical property tester.

[0065] (4) SiO2 content determination: Accurately weigh a certain amount of silica gel sample into a platinum crucible, add concentrated nitric acid to completely wet the sample, add 10-15 ml of hydrofluoric acid, let stand for a moment, heat on an electric furnace until the sample is completely dissolved, and evaporate to dryness. Repeat once. Place the platinum crucible in a muffle furnace and ignite at 950℃ for 0.5 hours, then place it in a desiccator to cool for 0.5 hours, and weigh it.

[0066] (5) Molecular weight and distribution analysis: Polymer Char high-temperature gel permeation chromatography.

[0067] (6) Melting point test: German Netzsch differential scanning calorimeter (DSC 214).

[0068] (7) Zirconium loading in catalyst: The zirconium (Zr) content in metallocene catalyst was determined using a Lamber 25 UV / Vis spectrophotometer manufactured by Perkin Elmer, USA.

[0069] Example 1

[0070] Preparation of nano-silica / SiO2 pillar-modified montmorillonite composite particles: (1) At 10℃, 10g of organically modified montmorillonite (modified with octadecylamine, modifier content 28wt%, volatile matter 2wt%, density 1.2g / cm³) with an average particle size of 15μm from Nanocor, USA, was mixed. 3 The interlayer spacing is (1) Add 500 ml of ethanol solution (ethanol to water volume ratio of 3) to the reaction vessel, and then add 5 mol / L ammonia water to the reaction vessel to adjust the pH value of the solution to about 7.0; (2) Mix 16 ml of tetraethyl orthosilicate and 250 ml of ethanol, and then add the mixed solution to the reaction vessel and react at 10°C for 4 hours; (3) Wash and filter the reaction product, and then dry it in an oven for 3 hours to obtain composite particles.

[0071] Preparation of montmorillonite / silica composite carrier: (1) Place 50 ml of dilute sodium silicate aqueous solution with pH value of 12 in a reaction vessel, add 1 g of hexadecyltrimethylammonium bromide, stir and heat to 30°C, slowly add 1 mol / L dilute sulfuric acid to the reaction vessel at a rate of 1 ml / min until the pH of the reaction solution reaches 9; (2) After a large amount of sol appears in the reaction vessel, add 5 g of nano silica / SiO2 pillar-modified montmorillonite composite particles to the reaction vessel, add dilute sulfuric acid until the pH of the system is 5, and add 8 ml of aging accelerator (ethyl orthosilicate). (3) After washing and filtering the reaction product, a centrifugal spray dryer was used to spray dry the montmorillonite / silica composite carrier with uniform particle morphology at 1500 rpm, 0.5 MPa, and 90 ℃. The dried montmorillonite / silica composite carrier was placed in a muffle furnace and activated at 600 ℃ for 4 hours. It was then stored in a nitrogen atmosphere for later use. The average particle size of the obtained montmorillonite / silica composite carrier was 68 μm and the specific surface area was 302 m². 2 / g, pore volume is 2.1ml / g, average pore size is 15nm, bulk density is 0.28, and SiO2 content is 98%.

[0072] Catalyst preparation: The catalyst preparation method is based on CN 108976326 B. Under anhydrous and oxygen-free conditions, 1 g of the pre-treated montmorillonite / silica gel composite support was accurately weighed and added to 30 mL of toluene to form a suspension. Then, 25 mmol of MAO solution was added, and the mixture was stirred at 50 °C for 2 h. The solid portion was then washed three times with 30 mL of toluene to obtain the MAO-modified composite support. Next, 30 mL of toluene was added, followed by a certain amount of Cp₂ZrCl₂. The mixture was stirred at room temperature for 2 h, and the solid portion was washed three times with 30 mL of toluene. The mixture was then vacuum-sealed at 40 °C for 4 h. After removing the toluene, a catalyst with good flowability was obtained.

[0073] Polymerization Evaluation: Polymerization was conducted using a 10L slurry C2H4 polymerization evaluation apparatus. 5L of n-hexane and 10mL of a triethylaluminum solution in n-hexane were added to the polymerization reactor. After stirring for 15 minutes, 60mg of catalyst was added, the temperature was raised to 80℃, and C2H4 was introduced. The reaction pressure was 1MPa. After polymerization for 1 hour, the C2H4 feed was stopped, and the product was discharged after cooling to room temperature. Polyethylene was separated from hexane, dried, and weighed. Polymerization activity was expressed as the total amount of polymer produced per gram of catalyst per hour (g.PE / g cat.h). The polymerization results are shown in Table 1.

[0074] Example 2

[0075] Preparation of nano-silica / SiO2 pillar-modified montmorillonite composite particles: (1) At 40℃, 10g of organically modified montmorillonite (modified with octadecylamine, modifier content 29wt%, volatile matter 2wt%, density 1.6g / cm³) with an average particle size of 30μm from Nanocor, USA, was mixed. 3 The interlayer spacing is (1) Add 500 ml of ethanol solution (ethanol to water volume ratio of 10) to the reaction vessel, and then add 5 mol / L ammonia water to the reaction vessel to adjust the pH value of the solution to about 9.0; (2) Mix 160 ml of tetraethyl orthosilicate and 250 ml of ethanol, and then add the mixed solution to the reaction vessel and react at 60°C for 10 hours; (3) Wash and filter the reaction product, and then dry it in an oven for 3 hours to obtain composite particles.

[0076] Preparation of montmorillonite / silica composite carrier: (1) Place 50 ml of dilute sodium silicate aqueous solution with pH value of 12 in a reaction vessel, add 1 g of hexadecyltrimethylammonium bromide, stir and heat to 50°C, slowly add 1 mol / L dilute sulfuric acid to the reaction vessel at a dropping rate of 20 ml / min until the pH of the reaction solution reaches 11; (2) After a large amount of sol appears in the reaction vessel, add 20 g of nano silica / SiO2 pillar-modified montmorillonite composite particles to the reaction vessel, add dilute sulfuric acid until the pH of the system is 8, and add 10 ml of aging accelerator (butadiene silicate). (2) The volume ratio of ester to deionized water is 1:10. After reacting at 80°C for 8 hours, dilute sulfuric acid is added to adjust the pH of the reaction system to 4, and the system is aged for 8 hours. (3) After washing and filtering the reaction product, a centrifugal spray drying device is used to spray dry the montmorillonite / silica composite carrier with uniform particle morphology at 1500 rpm, 0.5 MPa, and 90°C. The dried montmorillonite / silica composite carrier is placed in a muffle furnace and activated at 600°C for 4 hours. It is then stored in a nitrogen atmosphere for later use. The average particle size of the obtained montmorillonite / silica composite carrier is 60 μm, and the specific surface area is 342 m². 2 / g, pore volume is 2.5ml / g, average pore size is 18nm, bulk density is 0.29, and SiO2 content is 98%.

[0077] The catalyst preparation and polymerization evaluation were the same as in Example 1, and the polymerization results are shown in Table 1.

[0078] Example 3

[0079] Preparation of nano-silica / SiO2 pillar-modified montmorillonite composite particles: (1) At 30℃, 10g of organically modified montmorillonite (modified with octadecylamine, modifier content 32wt%, volatile matter 1.9wt%, density 1.7g / cm³) with an average particle size of 25μm from Nanocor, USA, was mixed. 3 The interlayer spacing is (1) Add 500ml of ethanol solution (ethanol to water volume ratio of 7) to the reaction vessel, and then add 1mol / L sodium hydroxide solution to the reaction vessel to adjust the pH value of the solution to about 8.0; (2) Mix 150ml of tetraethyl orthosilicate and 200ml of ethanol, and then add the mixed solution to the reaction vessel and react at 45℃ for 8 hours; (3) Wash and filter the reaction product, and then dry it in an oven for 3 hours to obtain composite particles.

[0080] Preparation of montmorillonite / silica composite carrier: (1) Place 50 ml of dilute potassium silicate aqueous solution with pH value of 12 in a reaction vessel, add 1 g of dodecyltrimethylammonium bromide, stir and heat to 40°C, slowly add 1 mol / L dilute sulfuric acid to the reaction vessel at a dropping rate of 5 ml / min until the pH of the reaction solution reaches 9.5; (2) After a large amount of sol appears in the reaction vessel, add 5 g of nano silica / SiO2 pillar-modified montmorillonite composite particles to the reaction vessel, add dilute sulfuric acid until the pH of the system is 7, and add 10 ml of aging accelerator (ethyl orthosilicate). (3) After washing and filtering the reaction product, a centrifugal spray dryer was used to spray dry the montmorillonite / silica composite carrier with uniform particle morphology at 2100 rpm, 0.5 MPa, and 90 ℃. The dried montmorillonite / silica composite carrier was placed in a fluoropolymer furnace and activated at 650 ℃ for 4 hours. It was then stored in a nitrogen atmosphere for later use. The average particle size of the obtained montmorillonite / silica composite carrier was 49 μm and the specific surface area was 413 m². 2 / g, pore volume is 2.3ml / g, average pore size is 17nm, bulk density is 0.29, and SiO2 content is 99%.

[0081] The catalyst preparation and polymerization evaluation were the same as in Example 1, and the polymerization results are shown in Table 1.

[0082] Example 4

[0083] The preparation method of nano-silica / SiO2 pillar-modified montmorillonite composite particles is the same as in Example 1.

[0084] Preparation of montmorillonite / silica composite carrier: (1) Place 50 ml of dilute sodium silicate aqueous solution with pH value of 12 in a reaction vessel, add 1.5 g of cetyltrimethylammonium bromide, stir and heat to 45°C, slowly add 1 mol / L dilute sulfuric acid to the reaction vessel at a rate of 8 ml / min until the pH of the reaction solution reaches 9.5; (2) After a large amount of sol appears in the reaction vessel, add 7 g of nano silica / SiO2 pillar-supported modified montmorillonite composite particles to the reaction vessel, add dilute sulfuric acid until the pH of the system is 7, and add 12 ml of aging accelerator (methyl orthosilicate). (2) The volume ratio of ester to deionized water is 1:5. After reacting at 65°C for 6 hours, dilute sulfuric acid is added to adjust the pH of the reaction system to 2.5 and the system is aged for 6 hours. (3) After washing and filtering the reaction product, a centrifugal spray dryer is used to spray dry the montmorillonite / silica composite carrier with uniform particle morphology at 2500 rpm, 0.5 MPa and 90°C. The dried montmorillonite / silica composite carrier is placed in a fluoropolymer furnace and activated at 650°C for 4 hours. It is then stored in a nitrogen atmosphere for later use. The average particle size of the obtained montmorillonite / silica composite carrier is 41 μm and the specific surface area is 389 m². 2 / g, pore volume is 2.9ml / g, average pore size is 21nm, bulk density is 0.28, and SiO2 content is 98%.

[0085] The catalyst preparation and polymerization evaluation were the same as in Example 1, and the polymerization results are shown in Table 1.

[0086] Example 5

[0087] The preparation method of nano-silica / SiO2 pillar-modified montmorillonite composite particles is the same as in Example 2.

[0088] Preparation of montmorillonite / silica composite carrier: (1) Place 60 ml of dilute sodium silicate aqueous solution with pH value of 12 in a reaction vessel, add 1.2 g of dodecyltrimethylammonium bromide, stir and heat to 45°C, slowly add 1 mol / L dilute sulfuric acid to the reaction vessel at a dropping rate of 3 ml / min until the pH of the reaction solution reaches 10; (2) After a large amount of sol appears in the reaction vessel, add 9 g of nano silica / SiO2 pillar-modified montmorillonite composite particles to the reaction vessel, add dilute sulfuric acid until the pH of the system is 8.5, and add 20 ml of aging accelerator (orthosilicic acid). (2) The volume ratio of ethyl ester to deionized water is 1:8. After reacting at 60°C for 7 hours, dilute sulfuric acid is added to adjust the pH of the reaction system to 3.5, and the mixture is aged for 3 hours. (3) After washing and filtering the reaction product, a centrifugal spray dryer is used to spray dry the product at 3500 rpm, 0.5 MPa, and 90°C to obtain a montmorillonite / silica composite carrier with uniform particle morphology. The dried montmorillonite / silica composite carrier is placed in a fluoropolymer furnace and activated at 650°C for 4 hours. It is then stored in a nitrogen atmosphere for later use. The average particle size of the obtained montmorillonite / silica composite carrier is 35 μm, and the specific surface area is 291 m². 2 / g, pore volume is 1.9ml / g, average pore size is 28nm, bulk density is 0.30, and SiO2 content is 98%.

[0089] The catalyst preparation and polymerization evaluation were the same as in Example 1, and the polymerization results are shown in Table 1.

[0090] Example 6

[0091] The preparation method of nano-silica / SiO2 pillar-modified montmorillonite composite particles is the same as in Example 3.

[0092] The preparation method of the montmorillonite / silica gel composite carrier is the same as in Example 5. The obtained montmorillonite / silica gel composite carrier has an average particle size of 36 μm and a specific surface area of ​​314 m². 2 / g, pore volume is 1.6ml / g, average pore size is 27nm, bulk density is 0.30, and SiO2 content is 98%.

[0093] Catalyst preparation: Under anhydrous and oxygen-free conditions, 1 g of the above-treated montmorillonite / silica composite support was accurately weighed, and 30 mL of toluene was added to form a suspension. The suspension was stirred at 50 °C for 2 h, and then a certain amount of Cp2ZrCl2 was added. The suspension was stirred at room temperature for 2 h, and the solid part was washed three times with 30 mL of toluene. The suspension was then evacuated at 40 °C under vacuum for 4 h. After the toluene was dried, a catalyst with good flowability was obtained.

[0094] The ethylene polymerization method was the same as in Example 1, and the polymerization results are shown in Table 1.

[0095] Example 7

[0096] The preparation method of nano-silica / SiO2 pillar-modified montmorillonite composite particles is the same as in Example 3.

[0097] The montmorillonite / silica gel composite carrier was prepared using the same method as in Example 1, and the resulting montmorillonite / silica gel composite carrier had an average particle size of 60 μm and a specific surface area of ​​293 m². 2 The catalyst has a pore volume of 2.1 ml / g, an average pore size of 16 nm, a bulk density of 0.30, and a SiO2 content of 98%. The catalyst preparation and polymerization evaluation were the same as in Example 1, and the polymerization results are shown in Table 1.

[0098] Example 8

[0099] The preparation method of nano-silica / SiO2 pillar-modified montmorillonite composite particles is the same as in Example 3.

[0100] The preparation method of the montmorillonite / silica gel composite carrier is the same as in Example 2. The average particle size of the obtained montmorillonite / silica gel composite carrier is 58 μm, and the specific surface area is 374 m². 2 The catalyst has a pore volume of 2.5 ml / g, an average pore size of 19 nm, a bulk density of 0.29, and a SiO2 content of 99%. The catalyst preparation and polymerization evaluation were the same as in Example 1, and the polymerization results are shown in Table 1.

[0101] Example 9

[0102] Preparation of nano-silica / SiO2 pillar-supported modified montmorillonite composite particles: (1) At 30℃, 10g of organically modified montmorillonite (modified with octadecylamine, modifier content 30wt%, volatile matter 1.2wt%, density 2.0g / cm³) with an average particle size of 25μm from Nanocor, USA, was mixed. 3 The interlayer spacing is (1) Add 500ml of ethanol solution (ethanol to water volume ratio of 7) to the reaction vessel, and then add 15g of hexadecaneamine to the reaction vessel to adjust the pH value of the solution to about 8.0; (2) Mix 150ml of tetraethyl orthosilicate and 200ml of ethanol, and then add the mixed solution to the reaction vessel and react at 45℃ for 8 hours; (3) Wash and filter the reaction product, and then dry it in an oven for 3 hours to obtain composite particles.

[0103] The montmorillonite / silica gel composite carrier was prepared in the same manner as in Example 3, and the resulting montmorillonite / silica gel composite carrier had an average particle size of 51 μm and a specific surface area of ​​347 m². 2 The catalyst has a pore volume of 3.1 ml / g, an average pore size of 17 nm, a bulk density of 0.31, and a SiO2 content of 98%. The catalyst preparation and polymerization evaluation were the same as in Example 3, and the polymerization results are shown in Table 1.

[0104] Example 10

[0105] The preparation method of nano-silica / SiO2 pillar-modified montmorillonite composite particles is the same as in Example 9, the preparation of montmorillonite / silica composite carrier is the same as in Example 3, the catalyst preparation and polymerization evaluation are the same as in Example 6, and the polymerization results are shown in Table 1.

[0106] Example 11

[0107] The preparation method of nano-silica / SiO2 pillar-modified montmorillonite composite particles is the same as in Example 1, and the preparation of montmorillonite / silica composite support and catalyst is the same as in Example 1.

[0108] Polymerization Evaluation: Polymerization was conducted using a 10L slurry C2H4 polymerization evaluation apparatus. 5L of n-hexane and 10mL of a triethylaluminum solution in n-hexane were added to the polymerization reactor. After stirring for 15 min, 60mg of catalyst was added, the temperature was raised to 80℃, ethylene was introduced, and the reaction pressure was 1MPa. 55mL of hexene-1 was added, and polymerization was carried out for 1 h. The feed was then stopped, and the mixture was allowed to cool to room temperature before being discharged. The copolymer was separated from the hexane, dried, and weighed. Polymerization activity was expressed as the total amount of polymer produced per gram of catalyst per hour (g.PE / gcat.h). The polymerization results are shown in Table 1.

[0109] Example 12

[0110] The preparation of nano-silica / SiO2 pillar-supported modified montmorillonite composite particles, the preparation of montmorillonite / silica composite carrier, and the preparation of catalyst are the same as in Example 1.

[0111] Polymerization Evaluation: Polymerization was conducted using a 10L slurry C2H4 polymerization evaluation apparatus. 5L of n-hexane and 10mL of a triethylaluminum solution in n-hexane were added to the polymerization reactor. After stirring for 15 min, 60mg of catalyst was added, the temperature was raised to 80℃, ethylene was introduced, the reaction pressure was 1MPa, and 50mL of octene-1 was added. After polymerization for 1 h, the feed was stopped, and the mixture was discharged after cooling to room temperature. The copolymer was separated from the hexane, dried, and weighed. Polymerization activity was expressed as the total amount of polymer produced per gram of catalyst per hour (g.PE / gcat.h). The polymerization results are shown in Table 1.

[0112] Example 13

[0113] Preparation of nano-silica / SiO2 pillared modified montmorillonite composite particles: same as in Example 1.

[0114] Preparation of montmorillonite / silica composite carrier: (1) Place 50 ml of dilute sodium silicate aqueous solution with pH value of 12 in a reaction vessel, stir and heat to 30°C, slowly add 1 mol / L dilute sulfuric acid to the reaction vessel at a rate of 1 ml / min until the pH of the reaction solution reaches 9; (2) After a large amount of sol appears in the reaction vessel, add 5 g of nano silica / SiO2 pillar-modified montmorillonite composite particles to the reaction vessel, add dilute sulfuric acid to the pH value of the system to 5, heat to 60°C and react for 5 hours, then add dilute sulfuric acid to adjust the pH value of the reaction system to 2, and age for 3 hours; (3) After washing and filtering the reaction product, use a centrifugal spray drying device to spray dry at 1500 rpm, 0.5 MPa and 90°C to obtain montmorillonite / silica composite carrier with uniform particle morphology, put the dried montmorillonite / silica composite carrier into a muffle furnace, activate at 600°C for 4 hours, and store in a nitrogen atmosphere for later use. The obtained montmorillonite / silica composite carrier had an average particle size of 59 μm and a specific surface area of ​​278 m². 2 / g, pore volume is 1.3ml / g, average pore size is 14nm, bulk density is 0.26, and SiO2 content is 98%.

[0115] The catalyst preparation and polymerization evaluation were the same as in Example 1, and the polymerization results are shown in Table 1.

[0116] Comparative Example 1

[0117] Preparation of montmorillonite / silica gel composite carrier: (1) Place 60 ml of dilute sodium silicate aqueous solution with pH value of 12 in a reaction vessel, add 1.2 g of dodecyltrimethylammonium bromide, stir and heat to 45 °C, slowly add 1 mol / L dilute sulfuric acid to the reaction vessel at a rate of 3 ml / min until the pH of the reaction solution reaches 10; (2) After a large amount of sol appears in the reaction vessel, add 9 g of commercially available montmorillonite with a particle size of 25 μm (unmodified organically, with a volatile content of 2.8 wt% and a density of 1.6 g / cm³) to the reaction vessel. 3 The interlayer spacing is Add dilute sulfuric acid to adjust the pH of the system to 8.5, add 20 ml of aging accelerator (ethyl orthosilicate to deionized water volume ratio = 1:8), heat to 60℃ and react for 7 hours, then add dilute sulfuric acid to adjust the pH of the reaction system to 3.5 and age for 3 hours; (3) After washing and filtering the reaction product, use a centrifugal spray drying device to spray dry at 3500 rpm, 0.5 MPa and 90℃ to obtain montmorillonite / silica composite carrier with uniform particle morphology. Put the dried montmorillonite / silica composite carrier into a fluoropolymer furnace and activate it at 650℃ for 4 hours, and store it under a nitrogen atmosphere for later use. The average particle size of the obtained montmorillonite / silica composite carrier is 32 μm and the specific surface area is 263 m². 2 / g, pore volume is 1.2ml / g, average pore size is 12nm, bulk density is 0.28, and SiO2 content is 95%.

[0118] The catalyst preparation and ethylene polymerization method were the same as in Example 1, and the polymerization results are shown in Table 1.

[0119] Comparative Example 2

[0120] The preparation of the montmorillonite / silica composite support and the catalyst were carried out according to Comparative Example 1, and the polymerization was carried out according to Example 12. The polymerization results are shown in Table 1.

[0121] Comparative Example 3

[0122] The preparation method of the montmorillonite / silica composite support is the same as that of Comparative Example 1, the preparation method of the catalyst is the same as that of Example 6, the ethylene polymerization method is the same as that of Example 1, and the polymerization results are shown in Table 1.

[0123] Comparative Example 4

[0124] Preparation of silica gel carrier: (1) 60 ml of dilute sodium silicate aqueous solution with pH value of 12 was placed in a reaction vessel, stirred and heated to 45°C. Dilute sulfuric acid with a concentration of 1 mol / L was slowly added dropwise to the reaction vessel at a rate of 3 ml / min until the pH of the reaction solution reached 10; (2) After a large amount of sol appeared in the reaction vessel, dilute sulfuric acid was added until the pH of the system reached 8.5. After reacting at 60°C for 7 hours, dilute sulfuric acid was added to adjust the pH of the reaction system to 3.5; (3) After washing and filtering the reaction product, the silica gel carrier with uniform particle morphology was obtained by spray drying using a centrifugal spray drying device at a speed of 3500 rpm, 0.5 MPa, and 90°C. The dried silica gel carrier was placed in a muffle furnace and activated at 650°C for 4 hours, and then stored under a nitrogen atmosphere for later use. The average particle size of the obtained silica gel carrier was 36 μm and the specific surface area was 254 m². 2 / g, pore volume is 1.1ml / g, average pore size is 12nm, bulk density is 0.28, and SiO2 content is 97%.

[0125] The catalyst preparation and ethylene polymerization method were the same as in Example 1, and the polymerization results are shown in Table 1.

[0126] Comparative Example 5

[0127] The preparation method of the silica support is the same as that of Comparative Example 4, the preparation method of the catalyst is the same as that of Example 6, the ethylene polymerization method is the same as that of Example 1, and the polymerization results are shown in Table 1.

[0128] Comparative Example 6

[0129] The preparation method of the silica support was the same as that of Comparative Example 4, the preparation method of the catalyst was the same as that of Example 1, and the polymerization was carried out according to Example 12. The polymerization results are shown in Table 1.

[0130] Comparative Example 7

[0131] Divason 955 silica gel was used as a support, and the catalyst preparation process and ethylene polymerization method of Example 1 were followed. The polymerization results are shown in Table 1.

[0132] Comparative Example 8

[0133] Divason 955 silica gel was used as a support, and the catalyst preparation process and ethylene polymerization method of Example 6 were followed. The polymerization results are shown in Table 1.

[0134] Comparative Example 9

[0135] Preparation of SiO2 pillar-modified montmorillonite: The preparation was carried out in accordance with the literature “Preliminary study on the synthesis conditions of porous heterogeneous materials of montmorillonite (Journal of Zhejiang University of Technology, (02):3-7 (2002))”. (1) At 30℃, 10g of organic modified montmorillonite (modified with octadecylamine, modifier content 30wt%, volatile matter 1.2wt%, density 2.0g / cm³) with an average particle size of 25μm from Nanocor Company of the United States was prepared. 3 The interlayer spacing is (1) Add 15g of hexadecaneamine to the reaction vessel and adjust the pH of the solution to about 8.0; (2) Add 150ml of tetraethyl orthosilicate to the reaction vessel and react at 45℃ for 8 hours; (3) Wash and filter the reaction product and dry it in an oven for 3 hours to obtain SiO2 pillar-modified montmorillonite.

[0136] The montmorillonite / silica gel composite carrier was prepared in the same manner as in Example 3, and the resulting montmorillonite / silica gel composite carrier had an average particle size of 55 μm and a specific surface area of ​​304 m². 2 The catalyst has a pore volume of 1.9 ml / g, an average pore size of 15 nm, a bulk density of 0.30, and a SiO2 content of 96%. The catalyst preparation and polymerization evaluation were the same as in Example 3, and the polymerization results are shown in Table 1.

[0137] Table 1 Catalyst performance evaluation results

[0138] Zirconium loading (wt%) Activity (gP / g cat.h) Molecular weight distribution Melting point (°C) Example 1 0.42 4013 1.7 133.2 Example 2 0.43 4215 1.9 132.5 Example 3 0.49 4503 1.6 133.4 Example 4 0.43 4310 2.1 132.4 Example 5 0.36 3852 1.8 133.1 Example 6 0.37 3267 1.7 132.2 Example 7 0.35 3761 2.2 131.8 Example 8 0.38 3801 2.0 132.6 Example 9 0.39 3954 1.9 133.4 Example 10 0.38 3198 2.1 132.1 Example 11 0.40 4676 3.1 97.2 Example 12 0.41 4332 3.8 90.4 Example 13 0.37 3271 1.7 133.1 Comparative Example 1 0.33 3056 1.9 132.8 Comparative Example 2 0.32 2875 4.3 104.2 Comparative Example 3 0.33 2643 2.1 131.8 Comparative Example 4 0.28 2135 1.8 132.0 Comparative Example 5 0.25 1403 1.8 131.8 Comparative Example 6 0.26 1893 3.8 113.6 Comparative Example 7 0.29 2354 2.1 132.4 Comparative Example 8 0.28 1583 2.3 130.9 Comparative Example 9 0.35 3167 2.4 132.5

[0139] As shown in Table 1, Examples 1-10 prepared nano-silica / SiO2 pillar-modified montmorillonite composite particles and composite supports under different conditions. Metallocene catalysts were then prepared using these composite supports, and their ethylene polymerization activity was evaluated. In Examples 6 and 10, no MAO treatment was added during the preparation of the metallocene catalysts using the composite supports, resulting in a slight decrease in the ethylene polymerization activity of the catalysts, but the decrease was minimal. Comparative Examples 1-3 directly added inorganic montmorillonite during support preparation, while Comparative Examples 4-6 used pure silica gel supports during catalyst preparation. Comparative Example 1 directly used inorganic montmorillonite to prepare the composite support, and the resulting metallocene catalyst showed a significant decrease in zirconium loading and polymerization activity compared to Example 5. Comparative Examples 3 and 5 did not add MAO during catalyst preparation, therefore the activity of the resulting catalysts decreased significantly. Therefore, the method of intercalating montmorillonite into silica gel in this invention can effectively increase the acidity of the silica gel surface, improve the catalytic efficiency of the metallocene catalyst, and reduce the amount of MAO co-catalyst required.

[0140] Examples 11 and 12 used composite supports to prepare catalysts, and ethylene-hexene copolymerization and ethylene-octene copolymerization were performed, respectively. Compared with the copolymerization behavior of Comparative Examples 2 and 6, the catalysts of Examples 11 and 12 showed higher copolymerization activity and lower melting points of the resulting copolymers. This indicates that the improved surface microenvironment of the composite support in this invention enhances the copolymerization activity of the supported metallocene catalyst and improves the copolymer performance.

[0141] Comparative Example 9 involved modifying montmorillonite with silica pillars in a non-organic alcohol solution system, based on existing literature. Other processes were the same as in Example 9. Compared to Example 9, the catalyst prepared in Comparative Example 9 exhibited lower polymerization activity and a slightly wider polymer molecular weight distribution. Example 13 did not involve the addition of surfactants or aging agents during support preparation; other processes were the same as in Example 1. Compared to Example 1, the composite support of Example 13 had a lower specific surface area and pore volume, resulting in a catalyst with lower zirconium loading and polymerization activity.

[0142] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a silicone composite carrier, characterized in that, Includes the following steps: Organically modified montmorillonite and alcohol were mixed, and then alkali was added to adjust the pH value to 7-12 to obtain a mixture. Then, an organic precursor of silica was added and mixed and stirred to obtain silica-pillared modified montmorillonite / silica composite particles. The composite particles were mixed with silica sol to form a gel, and hydrothermal aging was performed to prepare a silica composite carrier.

2. The method for preparing the silicone composite carrier according to claim 1, characterized in that, The alcohol is a fatty alcohol with 1 to 10 carbon atoms; an alkali is added to adjust the pH to 7 to 9 to obtain a mixed solution.

3. The method for preparing the silicone composite carrier according to claim 1, characterized in that, The alcohol is one or a mixture of several of methanol, ethanol, ethylene glycol, glycerol, n-propanol, isopropanol, and n-butanol.

4. The method for preparing the silicone composite carrier according to claim 1, characterized in that, The steps of mixing composite particles with silica sol to form a gel and hydrothermal aging include: Step a: Mix the silicate solution with the surfactant, heat, and adjust the pH to 9-11 to produce a sol; Step b: Mix the silica-pillared modified montmorillonite / silica composite particles with the mixture obtained in step a, adjust the pH value to 5-8 to gel the system, add an aging accelerator, and heat to react; Step c: Add inorganic acid to the reaction system of step b, and age to obtain silica composite carrier.

5. The method for preparing the silicone composite carrier according to claim 4, characterized in that, The silicate solution is a sodium silicate solution and / or a potassium silicate solution; the surfactant is selected from one or more of hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, dodecyltrimethylammonium bromide, and dodecyltrimethylammonium chloride.

6. The method for preparing the silicone composite carrier according to claim 4, characterized in that, The mass ratio of the silica-pillared modified montmorillonite / silica composite particles to the silicate solution in step a, calculated as SiO2, is 0.1~10; the heating reaction temperature in step b is 60~80℃; the aging accelerator is a mixed solution of silicate ester compound and water, wherein the silicate ester compound is selected from one or more of methyl orthosilicate, ethyl orthosilicate and butyl orthosilicate, and the volume ratio of silicate ester compound to water is 1:2~1:

10.

7. The method for preparing the silicone composite carrier according to claim 4, characterized in that, Step c is followed by an activation step for the silica composite carrier: the silica composite carrier is activated at 450~800℃ for 2~8h.

8. The method for preparing the silicone composite carrier according to claim 1, characterized in that, The organically modified montmorillonite is alkylamine-modified montmorillonite with 6-20 carbon atoms, has a volatile content of less than 3 wt%, a density of 1-2 g / cm³, an interlayer spacing of 2-100 nm, and an average particle size of 1-50 μm.

9. The method for preparing the silicone composite carrier according to claim 1, characterized in that, The mixing ratio of organically modified montmorillonite and alcohol is: 20-250 ml of alcohol per gram of organically modified montmorillonite.

10. The method for preparing the silicone composite carrier according to claim 1, characterized in that, The mixing ratio of organically modified montmorillonite and alcohol is: 50-100 ml of alcohol per gram of organically modified montmorillonite.

11. The method for preparing the silicone composite carrier according to claim 1, characterized in that, The alkali is selected from one of sodium hydroxide, potassium hydroxide, ammonia, sodium carbonate, and organic amine; the organic precursor of the silica is an alkoxysilane with 4 to 48 carbon atoms; after adding the organic precursor of the silica, the concentration of the organic precursor of the silica in the system is 0.1 to 1 mol / L.

12. The method for preparing the silicone composite carrier according to claim 1, characterized in that, The organic precursor of the silica is at least one of methyl orthosilicate, ethyl orthosilicate, and butyl orthosilicate.

13. The silicone composite carrier prepared by the preparation method according to any one of claims 1-12, characterized in that, The silica composite carrier has an average particle size of 10~120μm and a specific surface area of ​​250~500m². 2 / g, with an average pore size of 10~50nm, a pore volume of 1~5ml / g, a bulk density of 0.25~0.35, and a SiO2 content of not less than 98wt%.