Carrier for metallocene catalyst, preparation method of carrier, metallocene catalyst and preparation method of metallocene catalyst

Abstract

The invention provides a carrier for a metallocene catalyst, a preparation method of the carrier, the metallocene catalyst and a preparation method of the metallocene catalyst. The preparation method of the carrier for the metallocene catalyst comprises the following steps: placing silicon dioxide aerogel microspheres in a container for microwave treatment; in the microwave treatment process, hot nitrogen is introduced into the container to purge the silicon dioxide aerogel microspheres; and stopping the microwave treatment, vacuumizing the container, and then introducing normal-temperature nitrogen to purge the silicon dioxide aerogel microspheres, thereby obtaining the carrier for the metallocene catalyst. According to the invention, the silicon dioxide aerogel microspheres are used as the carrier to load the metallocene catalyst, and the silicon dioxide aerogel with high specific surface area and high porosity is used as the carrier, so that the loading capacity of the metallocene compound is improved.

Description

Metallocene catalyst supports and their preparation methods and metallocene catalysts and their preparation methods Technical Field

[0001] This invention relates to a support for a metallocene catalyst and its preparation method, as well as a metallocene catalyst and its preparation method, belonging to the field of polyolefin technology. Background Technology

[0002] Metallocene polyolefins possess good strength, transparency, and heat-sealing properties due to their narrow molecular weight distribution and uniform comonomer distribution. The core technology for producing metallocene polyolefins is the use of metallocene catalysts, which can be supported on various materials such as silica gel (silica), magnesium chloride, and alumina. Silica has abundant silanol groups on its surface, allowing for the loading of metallocene catalysts; therefore, silica is the most commonly used support for metallocene catalysts.

[0003] Silica exists in two forms: crystalline and amorphous. Silica used as a support for metallocene catalysts is usually amorphous silica, which is lightweight, porous, has a high specific surface area, good insulation, acid and alkali resistance, and high temperature resistance.

[0004] SiO2 aerogel is a porous amorphous material with an open pore structure. The main structure of silica aerogel is a continuous three-dimensional network structure formed by the aggregation of silicon-oxygen nanoparticles. It consists of over 90% network pores and less than 10% SiO2 framework, with the pores filled with a gaseous dispersion medium. Silica aerogel has many excellent properties, including a high surface area (500-1000 m²). 2 High porosity (80-99.8%), low density (0.003-0.8 g / cm³). 3 It has a low thermal conductivity (~0.02 W / m·K), among which the extremely low thermal conductivity is the most significant characteristic of silica aerogel microspheres.

[0005] Compared to ordinary silica gel (SiO2), a key characteristic of aerogel porous networks is their "open" nature and interconnectivity, allowing fluid to flow from one pore to another and eventually through the entire material. Aerogel microspheres have pore sizes of around 10 nanometers (nm) and contain numerous micropores, making them a typical nanoporous material with a continuous network structure and a relatively uniform distribution of internal network pores. Because the tiny pores of aerogel permeate the entire material, it exhibits excellent adsorption performance, resulting in adsorption efficiency superior to that of ordinary silica gel.

[0006] Silica aerogels are typically irregular, blocky materials, making them difficult to process into complex geometries and limiting their applications. However, preparing silica aerogels into porous network microspheres can broaden their application range. Post-processing SiO2 aerogel microspheres and using them as supports for metallocene catalysts can significantly increase the loading of active components in metallocene catalysts and alter their catalytic properties.

[0007] Metallocene catalyst supports (such as silica) typically require high-temperature activation before loading to remove trace amounts of water and some hydroxyl groups from the silica surface. CN1055184A discloses a supported catalyst active in the polymerization and copolymerization of olefinic unsaturated compounds. This catalyst comprises an organometallic aluminum derivative and a second component. This second component is obtained by reacting a magnesium compound and / or a titanium, vanadium, or chromium compound, and optionally at least one compound of a second metal selected from Al, V, Zr, Hf, Nd, and Mo, in the presence of one or more inorganic oxide aerogel microsphere porous supports. The support can be used directly without treatment or activated first, for example, by heating under reduced pressure at 165°C for 8 hours and then cooling in dry nitrogen. However, this method makes it difficult to effectively control the hydroxyl content on the support surface during activation, and the support is also difficult to heat uniformly, thus affecting catalyst performance. Furthermore, this method requires an extremely narrow pore diameter distribution on the aerogel support, with the difference between the maximum and minimum pore sizes not exceeding 50 angstroms, placing extremely high demands on the aerogel microspheres.

[0008] CN108970647A discloses a method for preparing a metallocene catalyst support. This method involves fluidizing SiO2 or modified SiO2 under nitrogen purging, heating to a constant temperature, and then gradually cooling to room temperature to obtain the metallocene catalyst support. For ordinary silica gel (SiO2), calcination under hot nitrogen purging ensures uniform heating of the silica gel support and sufficient exchange of atmospheres inside and outside the support, improving the activation effect. However, the stability of the SiO2 aerogel framework is slightly worse than that of ordinary silica gel, and high-temperature gas fluidization may cause damage to its framework. Therefore, SiO2 aerogel supports are not suitable for activation using this method. Summary of the Invention

[0009] To address the aforementioned technical problems, the present invention aims to provide a support for metallocene catalysts and a method for preparing the same. The support for metallocene catalysts is silica aerogel microspheres activated by microwave activation, which can increase the loading of metallocene compounds.

[0010] Another objective of this invention is to provide a metallocene catalyst and its preparation method.

[0011] To achieve the above objectives, the present invention first provides a method for preparing a support for a metallocene catalyst, which includes the following steps:

[0012] Silica aerogel microspheres were placed in a container and microwaved.

[0013] During microwave processing, hot nitrogen gas is introduced into the container to purge the silica aerogel microspheres.

[0014] Stop the microwave treatment, evacuate the container, and then purge the silica aerogel microspheres with room temperature nitrogen gas to obtain the support for the metallocene catalyst.

[0015] Microwave treatment is a type of heating that occurs from within the material, enabling rapid overall temperature rise of the system within a very short time. This rapid overall heating approach overcomes the shortcomings of traditional heating methods, such as inefficiency and uneven heating due to thermal gradients. This invention utilizes microwave-assisted activation of silica aerogel microspheres to facilitate the preparation of high-performance metallocene catalyst supports.

[0016] In the above-mentioned method for preparing the support for metallocene catalysts, preferably, the silica aerogel microspheres have an average particle size of 20-200 μm and a bulk density of 0.20-0.35 g / cm³. 3 The pore volume is 1.2-3.0 cm³. 3 / g, specific surface area of ​​100-1000m² 2 / g.

[0017] In the above-mentioned method for preparing a support for a metallocene catalyst, preferably, the container is a microwave activation device, the structure of which is shown in Figure 1. The microwave activation device includes a body, a first filter screen, and a second filter screen.

[0018] The main body is spindle-shaped, with a vacuum port and a nitrogen inlet at the upper and lower ends, respectively. The nitrogen inlet is connected to a hot nitrogen pipe and a room temperature nitrogen pipe.

[0019] The first filter and the second filter are disposed in the middle of the container, with a space between them for placing silica aerogel microspheres.

[0020] Figure 2 shows a schematic diagram of how the microwave activation device is used. When in use, the silica gel microspheres to be activated are placed between the first and second filters, i.e., on the surface of the second filter. Then, the microwave activation device is placed in a microwave oven for microwave treatment.

[0021] In the above-mentioned method for preparing the support for the metallocene catalyst, preferably, the mesh count of the first filter screen is not less than 800 mesh (the sieve aperture does not exceed 18 micrometers), and / or, the mesh count of the second filter screen is not less than 800 mesh.

[0022] In the above-mentioned method for preparing the support for the metallocene catalyst, preferably, the first filter screen is made of ceramic or quartz, and / or the second filter screen is made of ceramic or quartz.

[0023] In the above-mentioned method for preparing the support for the metallocene catalyst, preferably, the microwave emission source used for the microwave treatment has a frequency of 1000-3000MHz, more preferably 2450MHz (exciting the molecules inside the material to move at 2.45 × 10⁻⁶ MHz per second). 9 The ultra-high frequency vibration and friction (repeated times) has a power of 500-1000W, preferably 850W.

[0024] In the above-mentioned method for preparing a support for a metallocene catalyst, preferably, the microwave treatment time is 1-10 minutes.

[0025] In the above-mentioned method for preparing the support for the metallocene catalyst, preferably, the temperature of the hot nitrogen gas is 70-150°C, and / or the purity of the hot nitrogen gas and the room temperature nitrogen gas is above 99.999% and the water content is not more than 5 ppm.

[0026] In the above-mentioned method for preparing the support for the metallocene catalyst, preferably, the vacuuming is performed until the pressure inside the container reaches -0.05 MPa to -0.1 MPa.

[0027] The present invention also provides a support for a metallocene catalyst, which is prepared by the above-described method for preparing a support for a metallocene catalyst.

[0028] According to a specific embodiment of the present invention, preferably, the hydroxyl content of the support for the metallocene catalyst is 2.0-5.0 mmol / g-SiO2, more preferably 2.2-3.6 mmol / g-SiO2.

[0029] The present invention also provides a metallocene catalyst, wherein the metallocene catalyst comprises the above-described metallocene catalyst support, metallocene compound and co-catalyst.

[0030] According to a specific embodiment of the present invention, preferably, the metallocene catalyst has a zirconium content of 0.2-0.5 wt% (more preferably 0.20-0.45 wt%) and an aluminum content of 10-25 wt% (more preferably 12-25 wt%) by mass percentage.

[0031] According to a specific embodiment of the present invention, preferably, the particle size of the metallocene catalyst is 25-210 μm, more preferably 35-105 μm.

[0032] According to a specific embodiment of the present invention, preferably, the bulk density of the metallocene catalyst is 0.25-0.5 g / cm³. 3 More preferably, it is 0.35-0.5 g / cm³. 3 .

[0033] According to a specific embodiment of the present invention, preferably, the metallocene compound has the general formula Cp. x MA y B z ,in:

[0034] Cp can be an unsubstituted cyclopentadienyl, a substituted cyclopentadienyl, an indenyl, a fluorenyl, an indenyl ligand in hydrogenated form, or a fluorenyl ligand in hydrogenated form.

[0035] M is a transition metal;

[0036] A and B are halogen atoms, hydrogen atoms, or alkyl groups, respectively;

[0037] x is an integer from 1 to 3, and y and z are integers from 0 to 3 respectively.

[0038] According to a specific embodiment of the present invention, preferably, in the above-mentioned metallocene compounds, when x equals 2 in the general formula, the Cp ligand can be bridged by polymethylene or dialkylsilane, such as by bridging with -Si(CH3)2-, -C(CH3)2-, -CH2-, -CH2-CH2-, etc.

[0039] According to a specific embodiment of the present invention, preferably, in the above-mentioned metallocene compound: when the substituents A and B are halogen atoms, y+z is equal to or less than 3, and x+y+z is equal to 4; when the substituents A and B in the general formula of the metallocene compound are alkyl groups, the substituents A and B are preferably straight-chain or branched alkyl groups containing 1-8 carbon atoms, such as methyl, ethyl, n-propyl, n-butyl, isobutyl or n-pentyl.

[0040] According to a specific embodiment of the present invention, preferably, suitable metallocene compounds that can be used in the present invention include one or more combinations of bis(cyclopentadienyl) metal dihalides, bis(cyclopentadienyl) metal monoalkyl monohalides, bis(cyclopentadienyl) metal dialkyl compounds and bis(indenyl) metal dihalides, wherein the metal (M) is a group IVB metal, including titanium, zirconium or hafnium metal, usually zirconium or hafnium, the halogen group can be chlorine, and the alkyl group can be an alkyl group containing 1-6 carbon atoms.

[0041] The following description uses examples to illustrate the metallocene compounds used in this invention, but is not intended to limit the invention. These metallocene compounds include di(cyclopentadienyl)zirconia dichloride, di(cyclopentadienyl)hafnium dichloride, di(cyclopentadienyl)dimethylzirconia, di(cyclopentadienyl)dimethylhafnium, di(n-butylcyclopentadienyl)zirconia dichloride, di(n-butylcyclopentadienyl)hafnium dichloride, di(n-butylcyclopentadienyl)dimethylzirconia, di(n-butylcyclopentadienyl)dimethylzirconia, di(n-butylcyclopentadienyl)zilium chloride ... (di(dimethylcyclopentadienyl)dimethylhafnium, bis(dimethylcyclopentadienyl)dimethylzirconium, bis(tetramethylcyclopentadienyl)dimethylhafnium, diindylzirconium dichloride, methylene-bridged diindylzirconium dichloride and bis(4,5,6,7-tetrahydro-1-indyl)zirconium dichloride, ethylidene-bridged di(indyl)zirconium dichloride, diindylhafnium dichloride, methylene-bridged diindylhafnium dichloride and bis(4,5,6,7-tetrahydro-1-indyl)zirconium dichloride, ethylidene-bridged di( Hafnium dichloride (indenyl), ethylene-bridged bis(indenyl)titanium dichloride, bis(4,5,6,7-tetrahydro-1-indenyl)titanium dichloride, bis(n-butylcyclopentadienyl)titanium dichloride, bis(cyclopentadienyl)titanium dichloride, dimethylsilyl-bridged bis(2-methyl-4-phenylindenyl)zirconium dichloride, dimethylsilyl-bridged bis(2-methyl-4-phenylindenyl)hafnium dichloride, dimethylsilyl-bridged bis(2-methyl-4-phenylindenyl)dimethylzirconium, dimethyl The following are examples of methylsilicon-bridged bis(2-methylindene)zirconium dichloride, bis(2-methylindene)hafnium dichloride, bis(2-methyl-benzoindene)zirconium dichloride, bis(2-methyl-benzoindene)hafnium dichloride, bis(2-methyl-benzoindene)dimethylzirconium dichloride, bis(2-methyl-benzoindene)dimethylzirconium dichloride, and methylsilicon-bridged bis(2-methyl-4-phenylindene)dimethylzirconium dichloride.

[0042] According to a specific embodiment of the present invention, preferably, the co-catalyst is selected from alkylaluminoxane compounds. The alkylaluminoxane compounds include, but are not limited to, methylaluminoxane, ethylaluminoxane, isobutylaluminoxane, butylaluminoxane, pentylaluminoxane, decylaluminoxane, modified methylaluminoxane, etc.

[0043] The present invention also provides a method for preparing the above-mentioned metallocene catalyst, which includes the following steps:

[0044] The metallocene catalyst is reacted by mixing a support with a solution of alkylaluminoxane as a co-catalyst.

[0045] After washing the solid product of the reaction, a solvent was added, followed by the addition of a metallocene compound for loading.

[0046] The loaded product was washed and desolventized to obtain the metallocene catalyst.

[0047] The reaction formulas for silanol groups with MAO and cyclohexane compounds are as follows:

[0048]

[0049] In the above-mentioned method for preparing metallocene catalysts, preferably, the temperature of the mixing reaction is -20°C to 60°C, and the time is 1-8 hours.

[0050] In the above-mentioned method for preparing metallocene catalysts, preferably, the loading temperature is 30-70℃ and the loading time is 1-10 hours.

[0051] In the above-mentioned method for preparing metallocene catalysts, preferably, the solvent is an alkane solvent and / or an aromatic solvent, wherein the alkane solvent can be butane, hexane, heptane, cyclohexane, etc., and the aromatic solvent can be benzene, xylene, toluene, etc.

[0052] In the preparation of metallocene catalysts using silica aerogel microspheres, metallocene compounds and the co-catalyst methylaluminoxane (MAO) are primarily loaded onto the support through interaction with silanol groups on and within the aerogel surface. The type and quantity of silanol groups significantly influence the metal loading of the metallocene catalyst; excessive or insufficient hydroxyl content is detrimental to metallocene loading and ultimately affects catalyst performance. Since the silica aerogel microsphere content is mainly controlled through the activation process, achieving appropriate hydroxyl content control during silica aerogel activation while avoiding damage to its framework structure presents a crucial technical challenge.

[0053] This invention employs microwave treatment combined with vacuuming and hot nitrogen purging to enable activated silica aerogel microspheres to have an appropriate hydroxyl content, thereby facilitating the loading of metallocene compounds in metallocene catalysts and resulting in highly active metallocene catalysts.

[0054] This invention utilizes silica aerogel microspheres as a support for loading metallocene catalysts. The high specific surface area and high porosity of silica aerogel as a support (compared to ordinary silica gel supports) increases the loading capacity of metallocene compounds, allowing ethylene monomers to polymerize on the surface and within the pores of the silica aerogel. This results in improved polymerization activity of the metallocene catalyst, stable catalyst release, improved polymer morphology, significantly increased bulk density, and higher molecular weight.

[0055] The beneficial effects of this invention are:

[0056] (1) Compared with metallocene catalysts supported on traditional silica gel supports, the silica aerogel support has a higher specific surface area and pore volume, which can increase the loading of metallocene catalysts and thus greatly improve the activity of metallocene catalysts.

[0057] (2) The high porosity and pore volume of silica aerogel support are conducive to the stable release of the activity of metallocene catalyst during polymerization, the catalyst activity decay rate is slower, and the polymer morphology is improved and the polymer bulk density is increased.

[0058] (3) By using microwave-assisted activation of the support, the support can be heated efficiently and uniformly, preventing the destruction of the support skeleton structure of silica aerogel microspheres at high temperature or in fluidized state, thereby obtaining high-performance metallocene catalysts. Attached Figure Description

[0059] Figure 1 is a schematic diagram of the microwave activation device used in the embodiments and comparative examples.

[0060] Figure 2 is a schematic diagram of how the microwave activation device is used. Detailed Implementation

[0061] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0062] The evaluation and analysis methods for some parameters involved in the examples and comparative examples are as follows:

[0063] (1) The particle size of the support and catalyst was determined using a Mastersizer 2000 Malvern particle size analyzer.

[0064] (2) Specific surface area, pore structure and porosity were tested using a Microneritics TriStar IIPlus 3.02 specific surface area and porosity analyzer by N2 adsorption method.

[0065] (3) The bulk density was tested using an HT1001 multi-functional powder physical property tester.

[0066] (4) The content of metal elements in the catalyst was determined using an Avio 500 inductively coupled plasma atomic emission spectrometer.

[0067] (5) The hydroxyl content of the carrier was determined using an sSDT Q600 (TA company) thermogravimetric analyzer.

[0068] (5) The molecular weight and molecular weight distribution of the polymer were tested using a Polymer Char high-temperature gel permeation chromatograph.

[0069] The structure of the microwave activation device used in the embodiments and comparative examples is shown in Figure 1. The microwave activation device includes a body 1, a first filter 2, and a second filter 3.

[0070] The main body 1 is spindle-shaped, with a vacuum port 4 at the top and a nitrogen inlet at the bottom. The nitrogen inlet is connected to a hot nitrogen pipe 5 and a room temperature nitrogen pipe 6 respectively.

[0071] The first filter 2 and the second filter 3 are disposed in the middle of the body 1, and there is a space between them for placing silica aerogel microspheres; the first filter 2 has a mesh size of 800 mesh, and the second filter 3 has a mesh size of 800 mesh; the first filter is made of ceramic or quartz, and the second filter is made of ceramic or quartz.

[0072] Figure 2 shows a schematic diagram of how the microwave activation device is used.

[0073] Example 1

[0074] This embodiment provides a metallocene catalyst, the preparation method of which includes the following steps:

[0075] (1) Preparation of SiO2 aerogel microspheres, specifically including the following steps:

[0076] ① Preparation of silica sol: At room temperature, 23.3g of tetraethyl orthosilicate (TEOS), 28.4g of ethanol and 6.1g of water are stirred and mixed at 400r / min for 5 minutes. Then, 0.53g of 0.01mol / L glycolic acid solution is added dropwise and stirred for 10 minutes. At this time, the pH value of the solution is 6.2. Let it stand for 3 hours to carry out the hydrolysis reaction. Then, 2.94g of 0.3mol / L ethanol ammonia solution is added dropwise and stirred for 10 minutes. At this time, the pH value of the solution is 8.2, thus forming silica sol.

[0077] ② At room temperature, 100 mL of soybean oil and 0.57 g of octylphenol polyoxyethylene ether-10 (op-10) were mixed in a 50 mL three-necked flask to prepare an oil phase. The mixture was stirred at 300 r / min until homogeneous. Then, 20 mL of the above silica sol was added and stirred at 800 r / min until gelation occurred, thus obtaining an emulsion system.

[0078] ③ Add 100 mL of ethanol to the above emulsion system, stir and mix at 800 r / min for 10 minutes, let stand and separate the layers, and then perform solid-liquid separation (after stopping stirring and standing, the entire emulsion system is divided into three layers, from top to bottom: ethanol, alcohol gel microspheres, and oil phase, and then use a separatory funnel to separate the alcohol gel microspheres). Wash the alcohol gel microspheres once with an ethanol-water solution (ethanol and water volume ratio of 1:2), wash them three times with ethanol, and then soak them in ethanol for aging for 20 hours to obtain aged alcohol gel microspheres.

[0079] ④ The aged alcohol aerogel microspheres are subjected to supercritical drying. The supercritical drying temperature reaches 50-270℃ within 5 hours, the supercritical drying pressure is 10-18MPa, and after reaching 250-270℃, it is held for 10 minutes. Then the pressure is released, nitrogen is purged, and the material is cooled to below 50℃ before being discharged. The obtained silica aerogel microspheres are sieved using sieves of different mesh sizes to obtain silica aerogel microspheres of specific particle sizes.

[0080] From the preparation of silica aerogel microspheres, some microspheres were screened out, and the average particle size was measured to be 30 μm and the bulk density was 0.30 g / cm³. 3 Specific surface area is 500m² 2 / g, pore volume 2.0cm 3 / g.

[0081] (2) Activation of SiO2 aerogel microspheres: 10g of silica aerogel microspheres were placed between the two filters of a microwave activation device. The microwave oven was turned on, with a microwave emission frequency of 2450MHz and a power of 850W. The activation device was purged with hot nitrogen gas preheated to 100℃ for 10 minutes. Then the microwave oven was turned off, the hot nitrogen gas was stopped, and the activation device was evacuated to -0.05MPa through the vacuum port. The device was then purged with room temperature nitrogen gas for 30 minutes. The activation was then completed. The activated carrier was stored under nitrogen protection for later use. The hydroxyl content of the carrier before and after activation is shown in Table 1.

[0082] (3) Preparation of metallocene catalyst: Under anhydrous and oxygen-free conditions, 1 g of the above-treated silica aerogel microsphere carrier was accurately weighed, 30 mL of toluene was added to form a suspension, 10 mL of toluene solution containing 25 mmol MAO was added, and the mixture was stirred at 60 °C for 1 hour; the solid part was separated and washed 3 times with 30 mL of toluene, then 30 mL of toluene was added, and then 0.05 g of di(cyclopentadienyl)zirconium dichloride (Cp2ZrCl2) was added, and the mixture was stirred at 30 °C for 10 h, the solid part was separated and washed 3 times with 30 mL of toluene, and the mixture was vacuumed for 2 h. After the toluene was dried, a catalyst with good flowability was obtained.

[0083] The obtained catalyst has an average particle size of 35 μm, an aluminum content of 25 wt%, and a zirconium content of 0.35 wt%.

[0084] (4) Ethylene polymerization: Polymerization was carried out using a 10L slurry C2H4 polymerization evaluation device. 5L of n-hexane and 10mL of triethylaluminum n-hexane solution (the mass fraction of triethylaluminum in the n-hexane solution was 10wt%) were added to the polymerization vessel. After stirring for 15 minutes, 200mg of polyethylene catalyst obtained in step (3) was added. The temperature was raised to 80℃, ethylene was introduced, and the reaction pressure was maintained at 1MPa for slurry polymerization. After 1h of polymerization, the ethylene feed was stopped, the temperature was lowered to room temperature, polyethylene was separated from the reactor, washed with hexane, dried and weighed.

[0085] Then, following the same polymerization method, polymerization was carried out for 2 hours to obtain the 2-hour polymerization activity. The ratio of the 2-hour polymerization activity to the 1-hour polymerization activity (Act) was used. 2h / Act 1h () represents the rate of activity decay.

[0086] The polymerization results and polymerization properties are shown in Table 2.

[0087] Example 2

[0088] This embodiment provides a metallocene catalyst, the preparation method of which includes the following steps:

[0089] (1) Preparation of SiO2 aerogel microspheres: The preparation method is the same as in Example 1. From the prepared silica aerogel microspheres, some microspheres were screened out, and then the following were measured: the average particle size was 100 μm and the bulk density was 0.20 g / cm³. 3 Specific surface area is 1000 m² 2 / g, pore volume 1.5cm 3 / g.

[0090] (2) Activation of SiO2 aerogel microspheres: 10g of silica aerogel microspheres were placed between the two filters of a microwave activation device. The microwave oven was turned on, with a microwave emission frequency of 2450MHz and a power of 850W. The activation device was purged with preheated nitrogen gas at 150℃ for 1 minute. Then the microwave oven was turned off, the hot nitrogen gas was stopped, and the activation device was evacuated to -0.1MPa through the vacuum port. The device was then purged with room temperature nitrogen gas for 30 minutes. The activation was then completed. The activated carrier was stored under nitrogen protection for later use. The hydroxyl content of the carrier before and after activation is shown in Table 1.

[0091] (3) Preparation of metallocene catalyst: Under anhydrous and oxygen-free conditions, 1 g of the above-treated silica aerogel microsphere carrier was accurately weighed, 30 mL of toluene was added to form a suspension, 10 mL of toluene solution containing 25 mmol MAO was added, and the mixture was stirred at 60 °C for 8 hours; the solid part was washed 3 times with 30 mL of toluene, then 30 mL of toluene was added, and 0.05 g of bis(cyclopentadienyl)zirconium dichloride (Cp2ZrCl2) was added, and the mixture was stirred at 70 °C for 5 hours. The solid part was washed 3 times with 30 mL of toluene, and the mixture was vacuumed for 2 hours. After the toluene was dried, a catalyst with good flowability was obtained.

[0092] The obtained catalyst has an average particle size of 105 μm, an aluminum content of 20.1 wt%, and a zirconium content of 0.50 wt%.

[0093] (4) Ethylene polymerization: Same as in Example 1. The polymerization results and polymerization properties are shown in Table 2.

[0094] Example 3

[0095] This embodiment provides a metallocene catalyst, the preparation method of which includes the following steps:

[0096] (1) Preparation of SiO2 aerogel microspheres: The preparation method is the same as in Example 1. From the prepared silica aerogel microspheres, some microspheres were screened out, and then the following were measured: the average particle size was 50 μm and the bulk density was 0.26 g / cm³. 3 Specific surface area is 300m² 2 / g, pore volume 3.0cm 3 / g.

[0097] (2) Activation of SiO2 aerogel microspheres: 10g of silica aerogel microspheres were placed between the two filters of a microwave activation device. The microwave oven was turned on, with a microwave emission frequency of 2450MHz and a power of 850W. The activation device was purged with preheated nitrogen gas at 70℃ for 5 minutes. Then the microwave oven was turned off, the hot nitrogen gas was stopped, and the activation device was evacuated to -0.08MPa through the vacuum port. The device was then purged with room temperature nitrogen gas for 30 minutes. The activation was then completed. The activated carrier was stored under nitrogen protection for later use. The hydroxyl content of the carrier before and after activation is shown in Table 1.

[0098] (3) Preparation of metallocene catalyst: Under anhydrous and oxygen-free conditions, 1 g of the above-treated silica aerogel microsphere carrier was accurately weighed, 30 mL of toluene was added to form a suspension, 10 mL of toluene solution containing 25 mmol MAO was added, and the mixture was stirred at -20 °C for 8 hours; the solid part was washed 3 times with 30 mL of toluene, then 30 mL of toluene was added, and 0.05 g of bis(cyclopentadienyl)zirconium dichloride (Cp2ZrCl2) was added, and the mixture was stirred at 30 °C for 1 h, and the solid part was washed 3 times with 30 mL of toluene; the mixture was then vacuumed for 2 h, and the toluene was dried to obtain a catalyst with good flowability.

[0099] The obtained catalyst has an average particle size of 52 μm, an aluminum content of 12.0 wt%, and a zirconium content of 0.45 wt%.

[0100] (4) Ethylene polymerization: Same as in Example 1. The polymerization results and polymerization properties are shown in Table 2.

[0101] Example 4

[0102] This embodiment provides a metallocene catalyst, the preparation method of which includes the following steps:

[0103] (1) Preparation of SiO2 aerogel microspheres: The preparation method is the same as in Example 1. From the prepared silica aerogel microspheres, some microspheres were screened out, and then the following were measured: the average particle size was 43 μm and the bulk density was 0.22 g / cm³. 3 Specific surface area is 560m² 2 / g, pore volume 2.3cm 3 / g.

[0104] (2) Activation of SiO2 aerogel microspheres: 10g of silica aerogel microspheres were placed between the two filters of a microwave activation device. The microwave oven was turned on, with a microwave emission frequency of 2450MHz and a power of 850W. The activation device was purged with hot nitrogen gas preheated to 105℃ for 8 minutes. Then the microwave oven was turned off, the hot nitrogen gas was stopped, and the activation device was evacuated to -0.1MPa through the vacuum port. The device was then purged with room temperature nitrogen gas for 30 minutes. The activation was then completed. The activated carrier was stored under nitrogen protection for later use. The hydroxyl content of the carrier before and after activation is shown in Table 1.

[0105] (3) Preparation of metallocene catalyst: Under anhydrous and oxygen-free conditions, 1 g of the above-treated silica aerogel microsphere carrier was accurately weighed, 30 mL of toluene was added to form a suspension, 10 mL of toluene solution containing 25 mmol MAO was added, and the mixture was stirred at 10 °C for 6 hours; the solid part was washed 3 times with 30 mL of toluene, and then 30 mL of toluene was added, along with 0.05 g of bis(cyclopentadienyl)zirconium dichloride (Cp2ZrCl2), and the mixture was stirred at 55 °C for 8 hours. The solid part was washed 3 times with 30 mL of toluene; the mixture was then vacuumed for 2 hours, and after the toluene was dried, a catalyst with good flowability was obtained.

[0106] The obtained catalyst has an average particle size of 45 μm, an aluminum content of 18.4 wt%, and a zirconium content of 0.30 wt%.

[0107] (4) Ethylene polymerization: Same as in Example 1. The polymerization results and polymerization properties are shown in Table 2.

[0108] Example 5

[0109] This embodiment provides a metallocene catalyst, the preparation method of which includes the following steps:

[0110] (1) Preparation of SiO2 aerogel microspheres: The preparation method is the same as in Example 1. From the prepared silica aerogel microspheres, some microspheres were screened out, and then the following were measured: the average particle size was 65 μm and the bulk density was 0.28 g / cm³. 3 Specific surface area is 700m² 2 / g, pore volume 1.9cm 3 / g.

[0111] (2) Activation of SiO2 aerogel microspheres: 10g of silica aerogel microspheres were placed between the two filters of a microwave activation device. The microwave oven was turned on, with a microwave emission frequency of 2450MHz and a power of 850W. The activation device was purged with preheated nitrogen gas at 90℃ for 10 minutes. Then the microwave oven was turned off, the hot nitrogen gas was stopped, and the activation device was evacuated to -0.1MPa through the vacuum port. The device was then purged with room temperature nitrogen gas for 30 minutes. The activation was then completed. The activated carrier was stored under nitrogen protection for later use. The hydroxyl content of the carrier before and after activation is shown in Table 1.

[0112] (3) Preparation of metallocene catalyst: Under anhydrous and oxygen-free conditions, 1 g of the above-treated silica aerogel microsphere carrier was accurately weighed, 30 mL of toluene was added to form a suspension, 10 mL of toluene solution containing 25 mmol MAO was added, and the mixture was stirred at 30 °C for 5 hours; the solid part was washed 3 times with 30 mL of toluene, then 30 mL of toluene was added, and 0.05 g of bis(cyclopentadienyl)zirconium dichloride (Cp2ZrCl2) was added, and the mixture was stirred at 65 °C for 4 hours, and the solid part was washed 3 times with 30 mL of toluene; the mixture was then vacuumed for 2 hours, and the toluene was dried to obtain a catalyst with good flowability.

[0113] The obtained catalyst has an average particle size of 69 μm, an aluminum content of 24.5 wt%, and a zirconium content of 0.44 wt%.

[0114] (4) Ethylene polymerization: Same as in Example 1. The polymerization results and polymerization properties are shown in Table 2.

[0115] Example 6

[0116] This embodiment provides a metallocene catalyst, the preparation method of which includes the following steps:

[0117] (1) Preparation of SiO2 aerogel microspheres: The preparation method is the same as in Example 1. From the prepared silica aerogel microspheres, some microspheres were screened out, and then the following were measured: the average particle size was 65 μm and the bulk density was 0.28 g / cm³. 3 Specific surface area is 300m² 2 / g, pore volume 1.9cm 3 / g.

[0118] (2) Activation of SiO2 aerogel microspheres, preparation of metallocene catalyst and ethylene polymerization (Example 5); The average particle size of the obtained catalyst was 71 μm, the aluminum content in the catalyst was 21.5 wt%, and the zirconium content in the catalyst was 0.40 wt%.

[0119] The polymerization results and polymerization properties are shown in Table 2.

[0120] Example 7

[0121] This embodiment provides a metallocene catalyst, the preparation method of which includes the following steps:

[0122] (1) Preparation of SiO2 aerogel microspheres: The preparation method is the same as in Example 1. From the prepared silica aerogel microspheres, some microspheres were screened out, and then the following were measured: the average particle size was 65 μm and the bulk density was 0.28 g / cm³. 3 Specific surface area is 100m² 2 / g, pore volume 1.9cm 3 / g.

[0123] (2) Activation of SiO2 aerogel microspheres, preparation of metallocene catalysts and ethylene polymerization (Example 5). The average particle size of the obtained catalyst was 70 μm, the aluminum content in the catalyst was 18.2 wt%, and the zirconium content in the catalyst was 0.33 wt%.

[0124] The polymerization results and polymerization properties are shown in Table 2.

[0125] Example 8

[0126] This embodiment provides a metallocene catalyst, the preparation method of which includes the following steps:

[0127] (1) Preparation of SiO2 aerogel microspheres: Same as in Example 5.

[0128] (2) Activation of SiO2 aerogel microspheres: 10g of silica aerogel microspheres were placed between the two filters of a microwave activation device. The microwave oven was turned on, with a microwave emission source frequency of 2450MHz and a microwave oven power of 850W. The activation device was purged with hot nitrogen gas preheated to 90℃ for 5 minutes. Then the microwave oven was turned off, the hot nitrogen gas was stopped, and the activation device was evacuated to -0.1MPa through the vacuum port. The device was then purged with room temperature nitrogen gas for 30 minutes. The activation was then completed. The activated carrier was stored under nitrogen protection for later use. The hydroxyl content of the carrier before and after activation is shown in Table 1.

[0129] (3) Preparation of metallocene catalyst: Same as in Example 5.

[0130] The average particle size of the obtained catalyst was 68 μm, the aluminum content in the catalyst was 20.3 wt%, and the zirconium content in the catalyst was 0.35 wt%.

[0131] (4) Ethylene polymerization: Same as in Example 5. The polymerization results and polymerization properties are shown in Table 2.

[0132] Example 9

[0133] This embodiment provides a metallocene catalyst, the preparation method of which includes the following steps:

[0134] (1) Preparation of SiO2 aerogel microspheres: Same as in Example 5.

[0135] (2) Activation of SiO2 aerogel microspheres: 10g of silica aerogel microspheres were placed between the two filters of a microwave activation device. The microwave oven was turned on, with a microwave emission frequency of 2450MHz and a power of 850W. The activation device was purged with hot nitrogen gas preheated to 90℃ for 15 minutes. Then the microwave oven was turned off, the hot nitrogen gas was stopped, and the activation device was evacuated to -0.1MPa through the vacuum port. It was then purged with room temperature nitrogen gas for 30 minutes to complete the activation. The activated carrier was stored under nitrogen protection for later use. The hydroxyl content of the carrier before and after activation is shown in Table 1.

[0136] (3) Preparation of metallocene catalyst: Same as in Example 5.

[0137] The obtained catalyst has an average particle size of 68 μm, an aluminum content of 18.2 wt%, and a zirconium content of 0.31 wt%.

[0138] (4) Ethylene polymerization: Same as in Example 5. The polymerization results and polymerization properties are shown in Table 2.

[0139] Comparative Example 1

[0140] This comparative example provides a metallocene catalyst, the preparation method of which includes the following steps:

[0141] (1) SiO2 aerogel microspheres: The preparation method is the same as in Example 1.

[0142] (2) Activation of SiO2 aerogel microspheres: 10g of silica aerogel microspheres were placed between the two filters of a microwave activation device. The device was purged with hot nitrogen gas preheated to 100℃ for 10 minutes. The hot nitrogen gas was then stopped, and the device was evacuated to -0.05MPa through the vacuum port. The device was then purged with room temperature nitrogen gas for 30 minutes to complete the activation. The activated carrier was stored under nitrogen protection for later use. The hydroxyl content of the carrier before and after activation is shown in Table 1.

[0143] (3) Preparation of metallocene catalyst: Same as in Example 1.

[0144] The obtained catalyst has an average particle size of 34 μm, an aluminum content of 16.3 wt%, and a zirconium content of 0.28 wt%.

[0145] (4) Ethylene polymerization: Same as in Example 1. The polymerization results and polymerization properties are shown in Table 2.

[0146] Comparative Example 2

[0147] This comparative example provides a metallocene catalyst, the preparation method of which includes the following steps:

[0148] (1) SiO2 aerogel microspheres: The preparation method is the same as in Example 1.

[0149] (2) Activation of SiO2 aerogel microspheres: Referring to CN1055184A, 10g of silica aerogel microspheres were heated at 165℃ under reduced pressure to -0.02MPa for 8 hours, and then cooled in nitrogen for later use. The hydroxyl content of the carrier before and after activation is shown in Table 1.

[0150] (3) Preparation of metallocene catalyst: Same as in Example 1.

[0151] The obtained catalyst has an average particle size of 34 μm, an aluminum content of 14.1 wt%, and a zirconium content of 0.29 wt%.

[0152] (4) Ethylene polymerization: Same as in Example 1. The polymerization results and polymerization properties are shown in Table 2.

[0153] Comparative Example 3

[0154] This comparative example provides a metallocene catalyst, the preparation method of which includes the following steps:

[0155] (1) SiO2 aerogel microspheres: The preparation method is the same as in Example 1.

[0156] (2) Activation of SiO2 aerogel microspheres: Referring to CN 108970647 A, silica aerogel microspheres were placed in an activator, and nitrogen gas was introduced to fluidize the silica aerogel microspheres; the activator was heated to 200℃ and held at that temperature for 2 hours; then heated to 600℃ and held at that temperature for 2 hours; the temperature was then lowered to 300℃ within 2 hours, and then lowered to room temperature (20℃) for another 2 hours before being discharged for use. The hydroxyl content of the carrier before and after activation is shown in Table 1.

[0157] (3) Preparation of metallocene catalyst: Same as in Example 1.

[0158] The obtained catalyst has an average particle size of 26 μm, an aluminum content of 15.5 wt%, and a zirconium content of 0.30 wt%.

[0159] (4) Ethylene polymerization: Same as in Example 1, the polymerization results and polymerization properties are shown in Table 2.

[0160] Comparative Example 4

[0161] This comparative example provides a metallocene catalyst, the preparation method of which includes the following steps:

[0162] (1) Catalyst: Commercial silica gel support was selected, with an average particle size of 45 μm and a bulk density of 0.25 g / cm³. 3 Specific surface area 310m² 2 / g, pore volume 1.6cm 3 / g.

[0163] (2) The activation of the support, preparation of the metallocene catalyst and the ethylene polymerization method are the same as in Example 1.

[0164] The obtained catalyst had an average particle size of 48 μm, an aluminum content of 12.1 wt%, and a zirconium content of 0.28 wt%. The polymerization results and polymerization properties are shown in Table 2.

[0165] Table 1. Changes in hydroxyl content before and after activation of the silica carrier.

[0166]

[0167]

[0168] Note: The SiO2 aerogel microspheres in Examples 1 and Comparative Examples 1-3 were prepared using the same method, but were not from the same batch. The difference in hydroxyl content before carrier activation is due to testing error.

[0169] Table 2 Catalyst Metal Content and Polymerization Performance

[0170]

[0171] A comparison of Example 1 and Comparative Example 1 shows that by using microwave-activated silica aerogel microspheres as a carrier, a higher loading of metallocene compounds and higher polymerization activity can be obtained.

[0172] The comparison between Example 1 and Comparative Examples 2 and 3 shows that the catalytic activity obtained by using the microwave activation method provided by the present invention is significantly better than that obtained by other activation methods.

[0173] A comparison of Example 1 and Comparative Example 4 shows that the metallocene catalyst obtained by using microwave-activated silica aerogel microspheres as a support provided by the present invention has significantly higher catalytic activity than existing commercially available catalysts made with silica supports, with a slower activity decay rate and higher polymer molecular weight and wider molecular weight distribution.

Claims

1. A method for preparing a support for a metallocene catalyst, comprising the following steps: Silica aerogel microspheres were placed in a container and microwaved. During microwave treatment, hot nitrogen gas is introduced into the container to purge the silica aerogel microspheres; after stopping the microwave treatment, the container is evacuated, and then room temperature nitrogen gas is introduced to purge the silica aerogel microspheres to obtain the support for the metallocene catalyst.

2. The method for preparing the support for the metallocene catalyst according to claim 1, wherein, The silica aerogel microspheres have an average particle size of 20-200 μm and a bulk density of 0.20-0.35 g / cm³. 3 The pore volume is 1.2-3.0 cm³. 3 / g, specific surface area of ​​100-1000m² 2 / g.

3. The method for preparing a support for a metallocene catalyst according to claim 1, wherein, The container is a microwave activation device, which includes a body, a first filter, and a second filter. The body is spindle-shaped, with a vacuum port at the top and a nitrogen inlet at the bottom. The nitrogen inlet is connected to a hot nitrogen pipe and a room-temperature nitrogen pipe, respectively. The first filter and the second filter are located in the middle of the container, with a space between them for placing silica aerogel microspheres.

4. The method for preparing a support for a metallocene catalyst according to claim 3, wherein, The first filter screen has a mesh count of not less than 800 mesh, and / or the second filter screen has a mesh count of not less than 800 mesh.

5. The method for preparing a support for a metallocene catalyst according to claim 3, wherein, The first filter screen is made of ceramic or quartz, and / or the second filter screen is made of ceramic or quartz.

6. The method for preparing a support for a metallocene catalyst according to claim 1, wherein, The microwave processing uses a microwave emission source with a frequency of 1000-3000MHz and a power of 500-1000W.

7. The method for preparing a support for a metallocene catalyst according to claim 1, wherein, The microwave treatment time is 1-10 minutes.

8. The method for preparing a support for a metallocene catalyst according to claim 1, wherein, The temperature of the hot nitrogen gas is 70-150℃, and / or the purity of the hot nitrogen gas and the room temperature nitrogen gas is above 99.999% and the water content is not more than 5ppm.

9. The method for preparing a support for a metallocene catalyst according to claim 1, wherein, The vacuuming process involves evacuating the container until the pressure reaches -0.05 MPa to -0.1 MPa.

10. A support for a metallocene catalyst, which is prepared by the method for preparing a support for a metallocene catalyst according to any one of claims 1-9.

11. The support for the metallocene catalyst according to claim 10, wherein, The hydroxyl content of the support used for this metallocene catalyst is 2.0-5.0 mmol / g-SiO2.

12. A metallocene catalyst, wherein, The metallocene catalyst comprises the metallocene catalyst support, metallocene compound, and co-catalyst as described in claim 10 or 11.

13. The metallocene catalyst according to claim 12, wherein, The metallocene catalyst contains 0.2-0.5 wt% zirconium and 10-25 wt% aluminum by mass percentage.

14. The metallocene catalyst according to claim 12, wherein, The particle size of this metallocene catalyst is 25-210 μm.

15. The metallocene catalyst according to claim 12, wherein, The bulk density of this metallocene catalyst is 0.25-0.5 g / cm³. 3 .

16. A method for preparing a metallocene catalyst according to any one of claims 12-15, comprising the following steps: The metallocene catalyst was reacted by mixing a support with a solution of an alkylaluminoxane cocatalyst; the solid product of the reaction was washed and then a solvent was added, followed by the addition of a metallocene compound for loading; the loaded product was washed and desolventized to obtain the metallocene catalyst.

17. The preparation method according to claim 16, wherein, The mixing reaction is carried out at a temperature of -20°C to 60°C for 1-8 hours.

18. The preparation method according to claim 16, wherein, The temperature of the load is 30-70℃, and the time is 1-10 hours.

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