Preparation method of supported metallocene catalyst and application of supported metallocene catalyst in ethylene polymerization

Abstract

The invention discloses a preparation method of a supported metallocene catalyst and application of the supported metallocene catalyst in ethylene polymerization, and the preparation method comprises the following steps: adding a toluene solution containing trimethylaluminum into a container, adding benzoic acid, reacting at low temperature, then heating to medium temperature for reaction, then heating to high temperature for reaction, cooling, adding n-hexane, filtering, and drying to obtain the supported metallocene catalyst. Extracting supernatant liquid, and drying to obtain an sMAO product; adding the sMAO product and a modifier into a container, then adding a toluene solution, cooling to obtain a slurry, treating the slurry with n-hexane to obtain a colorless solid precipitate, removing a supernatant, drying and separating to obtain a modified sMAO solid; and adding the modified sMAO solid and a metallocene compound into a container, adding toluene, heating, cooling to obtain an orange solid precipitate, removing the supernatant, and drying the remaining slurry to obtain the supported metallocene catalyst. The preparation method of the supported metallocene catalyst has the characteristics of simple preparation process, spherical catalyst particles, narrow particle size distribution and the like.

Description

Technical Field

[0001] The invention belongs to the field of olefin polymerization catalysts, and specifically relates to a preparation method of a supported metallocene catalyst and application of the catalyst in ethylene polymerization. Background Art

[0002] In practical applications, low molecular weight polyethylene is mainly used to replace traditional paraffin wax. However, compared with paraffin wax, low molecular weight polyethylene has the advantages of high melting point and good high temperature thermal stability, so polyethylene wax is widely used in various fields of chemical production. It is used as a dispersant, lubricant, brightener, release agent, and energy-saving agent in plastic processing; as an anti-aging agent for demoulding in rubber processing; in ink manufacturing, it can produce polishing wax and corrosion resistance; in textile processing, it is used as a softener and lubricant; in coating technology, it can be used on cardboard coatings and glass bottle coatings to improve the gloss and durability of the coating; in adhesive technology, it is used as a hot melt adhesive; polyethylene wax has the characteristics of cold resistance, excellent wear resistance, good compatibility with polyethylene, etc., and is widely used in polyethylene film modification research. Biaxially oriented polyethylene film is a type of high-performance film material produced using polyethylene resin with a special molecular structure as raw material.

[0003] Low molecular weight polyethylene hydrocarbon becomes waxy at room temperature, so it is commonly known as polyethylene wax. The average molecular weight is usually between 2000 and 8000, among which the product with a molecular weight of about 2000 is the most widely used; the molecular weight distribution is concentrated, about 2 to 5; according to its density, it is divided into low molecular weight low density polyethylene (density is 0.90) and low molecular weight high density polyethylene (density is 0.95), and the crystallinity is 50 to 80%; according to the molecular weight, its melting point varies, usually between 90 and 120°C, and its melt viscosity is low, and its melt viscosity and hardness are close to paraffin; polyethylene wax is a non-toxic, odorless, non-corrosive, white or light yellow waxy substance with excellent mechanical properties, electrical properties, dispersibility and fluidity, good demoulding performance, excellent cold resistance, heat resistance, light resistance, wear resistance and good chemical stability, and is widely used.

[0004] Abroad, polyethylene wax, as a special chemical raw material, has increasingly wide uses and applications, and demand is also on the rise. For example, the average annual growth rate of polyethylene wax in the United States from 2015 to 2019 was 3.5%; in 2019, the global annual consumption of polyolefin wax was 500,000 tons, with an annual growth rate of 3% to 4%, of which the consumption of polyethylene wax in Europe was 80,000 tons and the consumption of polyethylene wax in the United States was about 170,000 tons, of which 2 / 3 were produced by direct polymerization, and the other 1 / 3 came from by-products of polymer production; in 2019, global Fischer-Tropsch synthetic wax and polyethylene wax accounted for nearly 11% of the global wax supply, about 600,000 tons; from 2010 to 2020, global wax consumption continued to grow at an average rate of more than 2%.

[0005] Chinese patent CN 202111681460.1 proposes a non-metallocene catalyst and its preparation method and application, wherein the non-metallocene catalyst has the following formula I structure: wherein M is selected from a transition metal atom of Group IVB; L is a halogen atom; X is selected from one of O, NH and S; R-1, R-2 and R-3 are independently selected from hydrogen, a substituted or unsubstituted aliphatic hydrocarbon group having 1 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, an oxygen-containing group, a sulfur-containing group or a halogen atom, and R-2 and R-3 can also be selected from a nitrogen-containing group; or, R-3 is selected from hydrogen, a substituted or unsubstituted aliphatic hydrocarbon group having 1 to 12 carbon atoms, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 12 carbon atoms, an oxygen-containing group, a sulfur-containing group, a nitrogen-containing group or a halogen atom, and R-1 and R-2 form a ring structure, which is a substituted or unsubstituted C-4 to C-8 conjugated olefin group; n is 1 to 3. However, this method requires the use of a large amount of MAO for modification, resulting in high product cost and easy gelation.

[0006] Chinese patent CN 202080002414.1 provides a catalyst composition and a method for preparing an olefin polymer using the catalyst composition, wherein the catalyst composition can not only exhibit high activity in olefin polymerization reactions and thus help reduce catalyst costs, but also exhibit high copolymerizability, which can ensure excellent processability and long-term physical properties, and is therefore suitable for providing polymers for pipes. However, this method requires the use of a large amount of MAO for modification, resulting in high product costs and easy gelation.

[0007] Chinese patent CN 202111647003.0 specifically provides a supported multi-center catalyst and a preparation method thereof, wherein the catalyst comprises a carrier and an active component, wherein the active component is supported on the carrier, and the active component comprises an organic chromium active component, an inorganic chromium active component and an inorganic vanadium active component; wherein the inorganic chromium active component is obtained by loading a chromium source on the carrier, and then calcining, reducing with CO and activating with a co-catalyst; and the inorganic vanadium active component is obtained by loading a vanadium source on the carrier, and then calcining, reducing with CO and activating with a co-catalyst. The catalyst can be used to prepare polyethylene products with a wide molecular weight distribution and a trimodal or multimodal distribution. However, the process flow of this method is complicated and the reaction time is long.

[0008] Chinese patent CN 202010636498.6 proposes a catalyst for preparing low-entanglement ultra-high molecular weight polyethylene, the catalyst includes a nano-hydrotalcite carrier and a titanium active component loaded on the nano-hydrotalcite, and when the catalyst and the co-catalyst jointly catalyze polyethylene, the amount of the co-catalyst is small and the UHMWPE resin does not stick to the kettle, and the degree of entanglement is low; a preparation method of the catalyst is also provided, using the dried nano-hydrotalcite as a carrier, a Zieglar-Natta catalyst with a large spacing between active points can be obtained, the chain entanglement process is suppressed, and the viscosity of the prepared ultra-high molecular weight polyethylene is reduced and the processing performance is improved. However, this method requires the use of a large amount of MAO for modification, resulting in high product cost and easy gelation.

[0009] Chinese patent CN 201710795035.2 specifically relates to a catalyst system for olefin polymerization and a catalyst system and method for preparing low molecular weight polyethylene and low molecular weight polyethylene. The catalyst system comprises the following components: a) a fourth subgroup transition metal compound: the fourth subgroup transition metal compound contains at least one of the following ligands: substituted or unsubstituted cyclopentadienyl, substituted or unsubstituted indenyl and substituted or unsubstituted fluorenyl; b) an alkylaluminoxane; c) an organic zinc compound: the general formula of the organic zinc compound is ZnR 1 R 2 , R 1 and R 2 are the same or different and are selected from hydrogen, alkyl, alkoxy or halogen, and R 1 and R 2 The catalyst system is used to catalyze the polymerization of ethylene to produce polyethylene with a low molecular weight and a narrow molecular weight distribution. However, the process flow of this method is complicated and the reaction time is long.

[0010] Chinese patent CN 201710284399.4 discloses a method for preparing a polyethylene catalyst, which comprises the following steps: S1, a step of preparing an alkoxy magnesium solution, in which an organic oxide is added to a reactor equipped with a stirrer under nitrogen protection, and alkoxy magnesium is added with stirring turned on, and the undissolved solids at the bottom of the reactor are filtered out after standing to obtain a homogeneous solution; S3, a mixing step, in which a granular metallocene catalyst is added to the homogeneous solution obtained in step S1, and stirred to form a slurry with uniform concentration; S4, a spraying step, in which the slurry obtained in step S3 is spray-dried, and under nitrogen protection, the inlet temperature of the spray dryer is controlled to be 60-240°C and the outlet temperature is 30-180°C to obtain spherical particles; S5, a loading step, in which the spherical particles obtained in step S4 are added to a cold titanium compound, reacted, stopped stirring, and filtered out the supernatant after standing, and the solid catalyst component is obtained after washing and drying by conventional methods in the art. However, the preparation method uses an alkyl magnesium solution as a carrier, which is complicated to operate and has high toxicity. Summary of the invention

[0011] The purpose of the present invention is to provide a preparation method of a supported metallocene catalyst and application thereof in ethylene polymerization. The supported metallocene catalyst obtained by the preparation method of the present invention has good catalytic activity for ethylene polymerization and does not require modified carrier silica gel. The resin powder obtained by ethylene polymerization has good particle morphology, can control the yield, molecular weight and chain regularity of the polymer, and realizes the preparation of polyethylene wax with narrow low molecular weight distribution.

[0012] To achieve the above object, the present invention provides a method for preparing a supported metallocene catalyst, the preparation method comprising the following steps:

[0013] (1) Preparation of sMAO:

[0014] Under nitrogen protection, a toluene solution containing trimethylaluminum is added to a container, benzoic acid is added and reacted at low temperature, then heated to medium temperature for reaction, and then heated to high temperature for reaction, cooled, and n-hexane is added, a white solid precipitates out, the supernatant is extracted, filtered, separated, and dried to obtain a sMAO product;

[0015] (2) Modification of sMAO:

[0016] Add the sMAO product and the modifier into a container, then add the toluene solution, disperse and dissolve, cool to obtain a slurry, treat the slurry with n-hexane to obtain a colorless solid precipitate, remove the supernatant, dry and separate to obtain a modified sMAO solid;

[0017] (3) Preparation of supported metallocene catalyst:

[0018] The modified sMAO solid and the metallocene compound are added to a container, and then toluene is added, heated, and then cooled to obtain an orange solid precipitate. The supernatant is removed, and the remaining slurry is dried to obtain a supported metallocene catalyst.

[0019] The preparation method of the supported metallocene catalyst of the present invention, the general formula of the metallocene compound is Cp* 2 (Z)MX n Wherein, Cp* is a substituted or unsubstituted cyclopentadienyl, indenyl or fluorenyl, and the substituent is selected from C 1 -C 20 alkyl, alkoxy, silyl, aralkyloxy or halogen; Z is a linking unit connecting two cyclopentadienyl rings; if the general formula is a non-bridged metallocene complex, Z does not represent any element; if the general formula is a bridged metallocene complex, Z is selected from SiR* 2 , CR* 2 、SiR* 2 SiR* 2 , CR* 2 CR* 2 , CR*=CR*, or CR* 2 SiR* 2 , wherein R* is hydrogen or an alkyl, aryl, silyl, halogenated alkyl or halogenated aryl group having less than 20 carbon atoms; M is a transition metal of Group 4 or Group 5 in the periodic table; X is the same or different and is selected from one of halogen, hydrocarbon, hydrocarbonoxy, acid radical and amine; and n is an integer satisfying the valence state of M.

[0020] The invention discloses a method for preparing a supported metallocene catalyst. In the general formula of the metallocene compound, X is selected from halogen, hydrocarbon group, allyl group, cyclopentadienyl group, alkoxy group and aromatic hydrocarbon group, and n=2.

[0021] The invention discloses a method for preparing a supported metallocene catalyst, wherein in the general formula of the metallocene catalyst, M is zirconium or titanium.

[0022] The preparation method of the supported metallocene catalyst of the present invention comprises the following components: per gram of sMAO, the content of MAO is 0.01-10g, and the content of the metallocene compound is 0.002-10g.

[0023] The preparation method of the supported metallocene catalyst of the present invention comprises the following steps: the aluminum content in the supported metallocene catalyst is 0.1-30wt%, and the metal M content is 0.01-5wt%.

[0024] The method for preparing a supported metallocene catalyst of the present invention, wherein the modifier is a perfluoroalkyl carboxylic acid, selected from at least one of perfluorobutyric acid, perfluoropentanoic acid, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluoroundecanoic acid and perfluorododecanoic acid.

[0025] The preparation method of the supported metallocene catalyst of the present invention comprises the following steps: the low temperature reaction temperature is -20-20°C, and the reaction time is 0.5-5 hours; the medium temperature reaction temperature is 30-70°C, and the reaction time is 6-30 hours; the high temperature reaction temperature is 70-100°C, and the reaction time is 6-24 hours.

[0026] The present invention also provides an application of the supported metallocene catalyst obtained by the preparation method in ethylene polymerization.

[0027] The preparation method of the supported metallocene catalyst of the present invention has the characteristics of simple preparation process, spherical catalyst particles, narrow particle size distribution, etc. The supported metallocene catalyst obtained by the preparation method of the present invention can be used to produce ethylene polymers. By optimizing the design of the catalyst and the ligand, the yield, molecular weight and chain regularity of the ethylene polymer are controlled to achieve the preparation of polyethylene wax with narrow low molecular weight distribution, high crystallinity, good crystallization performance and high melting point. The preparation method of the supported metallocene catalyst of the present invention greatly reduces the amount of MAO added, the experimental design is more green and environmentally friendly, and is very suitable for low molecular weight polyethylene polymerization process. DETAILED DESCRIPTION

[0028] The following examples are provided to illustrate the present invention in more detail, but the present invention is not limited to these examples.

[0029] Evaluation and analysis methods:

[0030] 1. ICP (Inductively Coupled Plasma Atomic Emission Spectroscopy) Characterization: Quantitative determination of the weight percentage of metals in the supported catalyst. The instrument used is the P1000 ICP-AES plasma emission spectrometer produced by PE Company of the United States.

[0031] 2. Characterization of polymer molecular weight and molecular weight distribution: The molecular weight and its distribution were determined by gel permeation chromatography (GPC) using Agilent PL220, 1,2,4-trichlorobenzene as solvent, sample concentration of 1 mg / mL, solvent flow rate of 1.0 mL / min, and measurement temperature of 150°C. Each sample was measured twice.

[0032] 3. Characterization of crystallinity: Thermal performance test was performed using a differential scanning calorimeter. Test conditions: nitrogen (analytical grade), flow rate: 50 mL / min (1 ± 10%), sample size 5 mg to 10 mg, press seal. The melting point Tc and heat of fusion H of the polymer were directly read from the curve, and the crystallinity was calculated using the heat of fusion. Polyethylene crystallinity = H / H 0 , where H 0 =278.

[0033] Embodiment 1:

[0034] (1) Preparation of sMAO:

[0035] Under nitrogen protection, pour 500mL of trimethylaluminum toluene solution into a three-necked flask and cool to zero degrees. Add 1.24mmol of benzoic acid. When the mixture starts to bubble, heat it to 20°C. After half an hour, the mixture becomes clear and transparent. Continue heating at 70°C for 28h, at which time the mixture solution is still colorless. Heat to 100°C and heat for 14h. After the reaction is completed, wait for the liquid to cool to room temperature, add n-hexane, and a white solid precipitates. Draw out the supernatant, filter, separate, and dry to obtain the sMAO product.

[0036] (2) Modification of sMAO:

[0037] 45 g of sMAO product and 120 mL of perfluorobutyric acid were added to a three-necked flask, 20 mL of toluene solution was added, and the mixture was ultrasonically dispersed and dissolved at 45 ° C for 1 hour. After cooling to room temperature, the synthesized slurry was treated with n-hexane to extract by-products and promote the precipitation of colorless solids. After precipitation, the supernatant was removed, and the solid sample was vacuum dried and separated to obtain a modified sMAO solid.

[0038] (3) Preparation of supported metallocene catalyst:

[0039] Toluene was added to a three-necked flask containing 50 g of modified sMAO solid and 1.2 g of bis(1-butyl-3-methylcyclopentadienyl)zirconium dichloride, and the resulting orange dispersion was heated at 70 °C for 2 h at a speed of 500 rmin. -1 The mixture was cooled to room temperature, an orange solid precipitated under the colorless supernatant, the supernatant was removed by decantation, and the remaining slurry was dried overnight in vacuum to obtain a supported metallocene catalyst A. According to ICP characterization, in catalyst A, the weight content of aluminum was 15.38%, and the weight content of zirconium was 0.93%.

[0040] (4) Ethylene polymerization:

[0041] Ethylene polymerization: A 2L stainless steel polymerization reactor was fully replaced with high-purity nitrogen, and then 1.0L of hexane and 1.0mL of 1.0M triethylaluminum were added. The accurately weighed catalyst A prepared above was added with a syringe. The temperature was raised to 80°C, and hydrogen and ethylene were introduced so that the total pressure in the reactor reached 0.93MPa (gauge pressure). The volume ratio of hydrogen to ethylene was 6.5. Polymerization was carried out at 85°C for 2 hours to obtain a polyethylene product. The polymerization results are shown in Table 1.

[0042] Embodiment 2:

[0043] (1) Preparation of sMAO:

[0044] Under nitrogen protection, pour 500mL of trimethylaluminum toluene solution into a three-necked flask and cool to zero degrees. Add 1.24mmol of benzoic acid. When the mixture starts to bubble, lower the temperature to -10°C. After three hours, the mixture becomes clear and transparent. Continue heating at 70°C for 28h. At this time, the mixture solution is still colorless. Heat to 100°C and heat for 14h. After the reaction is completed, wait for the liquid to cool to room temperature, add n-hexane, and a white solid precipitates. Draw out the supernatant, filter, separate, and dry to obtain the sMAO product.

[0045] (2) Modification of sMAO:

[0046] 45 g of sMAO product and 120 mL of perfluorobutyric acid were added to a three-necked flask, 20 mL of toluene solution was added, and the mixture was ultrasonically dispersed and dissolved at 45 ° C for 1 hour. After cooling to room temperature, the synthesized slurry was treated with n-hexane to extract by-products and promote the precipitation of colorless solids. After precipitation, the supernatant was removed, and the solid sample was vacuum dried and separated to obtain a modified sMAO solid.

[0047] (3) Preparation of supported metallocene catalyst:

[0048] Toluene was added to a three-necked flask containing 50 g of modified sMAO solid and 1.2 g of bis(1-butyl-3-methylcyclopentadienyl)zirconium dichloride, and the resulting orange dispersion was heated at 80 °C for 2 h at a speed of 500 rmin. -1 The mixture was cooled to room temperature, an orange solid precipitated under the colorless supernatant, the supernatant was removed by decantation, and the remaining slurry was dried overnight in a vacuum to obtain a supported metallocene catalyst B. According to ICP characterization, in catalyst B, the weight content of aluminum was 17.68%, and the weight content of zirconium was 0.31%.

[0049] (4) Ethylene polymerization:

[0050] Ethylene polymerization: A 2L stainless steel polymerization reactor was fully replaced with high-purity nitrogen, and then 1.0L of hexane and 1.0mL of 1.0M triethylaluminum were added. The accurately weighed catalyst B prepared above was added with a syringe. The temperature was raised to 80°C, and hydrogen and ethylene were introduced so that the total pressure in the reactor reached 0.93MPa (gauge pressure). The volume ratio of hydrogen to ethylene was 6.5. Polymerization was carried out at 85°C for 2 hours to obtain a polyethylene product. The polymerization results are shown in Table 1.

[0051] Embodiment 3:

[0052] (1) Preparation of sMAO:

[0053] Under nitrogen protection, pour 500mL of trimethylaluminum toluene solution into a three-necked flask and cool to zero degrees. Add 1.24mmol of benzoic acid. When the mixture starts to bubble, heat it to 20°C. After half an hour, the mixture becomes clear and transparent. Continue heating at 50°C for 20h, at which time the mixture solution is still colorless. Heat to 100°C and heat for 14h. After the reaction is completed, wait for the liquid to cool to room temperature, add n-hexane, and a white solid precipitates. Draw out the supernatant, filter, separate, and dry to obtain the sMAO product.

[0054] (2) Modification of sMAO:

[0055] 45 g of sMAO product and 120 mL of perfluoropentanoic acid were added to a three-necked flask, 20 mL of toluene solution was added, and the mixture was ultrasonically dispersed and dissolved at 45 ° C for 1 hour. After cooling to room temperature, the synthesized slurry was treated with n-hexane to extract by-products and promote the precipitation of colorless solids. After precipitation, the supernatant was removed, and the solid sample was vacuum dried and separated to obtain a modified sMAO solid.

[0056] (3) Preparation of supported metallocene catalyst:

[0057] Toluene was added to a three-necked flask containing 50 g of modified sMAO solid and 1.2 g of bis(1-butyl-3-methylcyclopentadienyl)zirconium dichloride, and the resulting orange dispersion was heated at 80 °C for 2 h at a speed of 500 rmin. -1 The mixture was cooled to room temperature, an orange solid precipitated under the colorless supernatant, the supernatant was removed by decantation, and the remaining slurry was dried overnight in vacuum to obtain a supported metallocene catalyst C. According to ICP characterization, in catalyst C, the aluminum weight content was 25.08%, and the zirconium weight content was 0.93%.

[0058] (4) Ethylene polymerization:

[0059] Ethylene polymerization: A 2L stainless steel polymerization reactor was fully replaced with high-purity nitrogen, and then 1.0L of hexane and 1.0mL of 1.0M triethylaluminum were added. The accurately weighed catalyst C prepared above was added with a syringe. The temperature was raised to 80°C, and hydrogen and ethylene were introduced so that the total pressure in the reactor reached 0.93MPa (gauge pressure). The volume ratio of hydrogen to ethylene was 6.5. Polymerization was carried out at 85°C for 2 hours to obtain a polyethylene product. The polymerization results are shown in Table 1.

[0060] Embodiment 4:

[0061] (1) Preparation of sMAO:

[0062] Under nitrogen protection, pour 100mL of trimethylaluminum toluene solution into a three-necked flask and cool to zero degrees. Add 1.24mmol of benzoic acid. When the mixture starts to bubble, heat it to 20°C. After half an hour, the mixture becomes clear and transparent. Continue heating at 70°C for 28h. At this time, the mixture solution is still colorless. Heat to 80°C and heat for 18h. After the reaction is completed, wait for the liquid to cool to room temperature, add n-hexane dropwise, and a white solid precipitates. Draw out the supernatant, filter, separate, and dry to obtain the sMAO product.

[0063] (2) Modification of sMAO:

[0064] 45 g of sMAO product and 120 mL of perfluoropentanoic acid were added to a three-necked flask, 20 mL of toluene solution was added, and the mixture was ultrasonically dispersed and dissolved at 45 ° C for 1 hour. After cooling to room temperature, the synthesized slurry was treated with n-hexane to extract by-products and promote the precipitation of colorless solids. After precipitation, the supernatant was removed, and the solid sample was vacuum dried and separated to obtain a modified sMAO solid.

[0065] (3) Preparation of supported metallocene catalyst:

[0066] Toluene was added to a three-necked flask containing 50 g of modified sMAO solid and 1.2 g of bis(1-butyl-3-methylcyclopentadienyl)zirconium dichloride, and the resulting orange dispersion was heated at 70 °C for 2 h at a speed of 500 rmin. -1 The mixture was cooled to room temperature, an orange solid precipitated under the colorless supernatant, the supernatant was removed by decantation, and the remaining slurry was dried overnight in vacuum to obtain a supported metallocene catalyst D. According to ICP characterization, in catalyst D, the weight content of aluminum was 2.47%, and the weight content of zirconium was 0.84%.

[0067] (4) Ethylene polymerization:

[0068] Ethylene polymerization: A 2L stainless steel polymerization reactor was fully replaced with high-purity nitrogen, and then 1.0L of hexane and 1.0mL of 1.0M triethylaluminum were added. The accurately weighed catalyst D prepared above was added with a syringe. The temperature was raised to 80°C, and hydrogen and ethylene were introduced so that the total pressure in the reactor reached 0.93MPa (gauge pressure). The volume ratio of hydrogen to ethylene was 6.5. Polymerization was carried out at 85°C for 2 hours to obtain a polyethylene product. The polymerization results are shown in Table 1.

[0069] Embodiment 5:

[0070] (1) Preparation of sMAO:

[0071] Under nitrogen protection, pour 500mL of trimethylaluminum toluene solution into a three-necked flask and cool to zero degrees. Add 1.24mmol of benzoic acid. When the mixture starts to bubble, heat it to 20°C. After half an hour, the mixture becomes clear and transparent. Continue heating at 70°C for 28h, at which time the mixture solution is still colorless. Heat to 100°C and heat for 14h. After the reaction is completed, wait for the liquid to cool to room temperature, add n-hexane, and a white solid precipitates. Draw out the supernatant, filter, separate, and dry to obtain the sMAO product.

[0072] (2) Modification of sMAO:

[0073] 45 g of sMAO product and 120 mL of perfluorobutyric acid were added to a three-necked flask, 20 mL of toluene solution was added, and the mixture was ultrasonically dispersed and dissolved at 45 ° C for 1 hour. After cooling to room temperature, the synthesized slurry was treated with n-hexane to extract by-products and promote the precipitation of colorless solids. After precipitation, the supernatant was removed, and the solid sample was vacuum dried and separated to obtain a modified sMAO solid.

[0074] (3) Preparation of supported metallocene catalyst:

[0075] Toluene was added to a three-necked flask containing 50 g of modified sMAO solid and 120 g of bis(n-butylcyclopentadienyl)zirconium dichloride, and the resulting orange dispersion was heated at 70 °C for 2 h at a speed of 500 rmin. -1 The mixture was cooled to room temperature, an orange solid precipitated under the colorless supernatant, the supernatant was removed by decantation, and the remaining slurry was dried overnight in vacuum to obtain supported metallocene catalyst E. According to ICP characterization, in catalyst E, the weight content of aluminum was 25.08%, and the weight content of zirconium was 4.3%.

[0076] (4) Ethylene polymerization:

[0077] Ethylene polymerization: A 2L stainless steel polymerization reactor was fully replaced with high-purity nitrogen, and then 1.0L of hexane and 1.0mL of 1.0M triethylaluminum were added. The accurately weighed catalyst E prepared above was added with a syringe. The temperature was raised to 80°C, and hydrogen and ethylene were introduced so that the total pressure in the reactor reached 0.93MPa (gauge pressure). The volume ratio of hydrogen to ethylene was 6.5. Polymerization was carried out at 85°C for 2 hours to obtain a polyethylene product. The polymerization results are shown in Table 1.

[0078] Embodiment 6:

[0079] (1) Preparation of sMAO:

[0080] Under nitrogen protection, pour 500mL of trimethylaluminum toluene solution into a three-necked flask and cool to zero degrees. Add 1.24mmol of benzoic acid. When the mixture starts to bubble, heat it to 20°C. After half an hour, the mixture becomes clear and transparent. Continue heating at 70°C for 28h. At this time, the mixture solution is still colorless. Heat to 100°C and heat for 24h. After the reaction is completed, wait for the liquid to cool to room temperature, add n-hexane, and a white solid precipitates. Draw out the supernatant, filter, separate, and dry to obtain the sMAO product.

[0081] (2) Modification of sMAO:

[0082] 45 g of sMAO product and 120 mL of perfluorobutyric acid were added to a three-necked flask, 20 mL of toluene solution was added, and the mixture was ultrasonically dispersed and dissolved at 45 ° C for 1 hour. After cooling to room temperature, the synthesized slurry was treated with n-hexane to extract by-products and promote the precipitation of colorless solids. After precipitation, the supernatant was removed, and the solid sample was vacuum dried and separated to obtain a modified sMAO solid.

[0083] (3) Preparation of supported metallocene catalyst:

[0084] Toluene was added to a three-necked flask containing 50 g of sMAO solid and 1.2 g of bis(n-butylcyclopentadienyl)zirconium dichloride, and the resulting orange dispersion was heated at 70 °C for 2 h at a speed of 500 rmin. -1 The mixture was cooled to room temperature, an orange solid precipitated under the colorless supernatant, the supernatant was removed by decantation, and the remaining slurry was dried overnight in vacuum to obtain a supported metallocene catalyst F. According to ICP characterization, in catalyst F, the weight content of aluminum was 27.08%, and the weight content of zirconium was 3.31%.

[0085] (4) Ethylene polymerization:

[0086] Ethylene polymerization: A 2L stainless steel polymerization reactor was fully replaced with high-purity nitrogen, and then 1.0L of hexane and 1.0mL of 1.0M triethylaluminum were added. The accurately weighed catalyst F prepared above was added with a syringe. The temperature was raised to 80°C, and hydrogen and ethylene were introduced so that the total pressure in the reactor reached 0.93MPa (gauge pressure). The volume ratio of hydrogen to ethylene was 6.5. Polymerization was carried out at 85°C for 2 hours to obtain a polyethylene product. The polymerization results are shown in Table 1.

[0087] Embodiment 7:

[0088] (1) Preparation of sMAO:

[0089] Under nitrogen protection, pour 500mL of trimethylaluminum toluene solution into a three-necked flask and cool to zero degrees. Add 1.24mmol of benzoic acid. When the mixture starts to bubble, heat it to -20°C. After three hours, the mixture becomes clear and transparent. Continue heating at 70°C for 28h, at which time the mixture solution is still colorless. Heat to 100°C and heat for 14h. After the reaction is completed, wait for the liquid to cool to room temperature, add n-hexane, and a white solid precipitates. Draw out the supernatant, filter, separate, and dry to obtain the sMAO product.

[0090] (2) Modification of sMAO:

[0091] 45 g of sMAO product and 120 mL of perfluorobutyric acid were added to a three-necked flask, 20 mL of toluene solution was added, and the mixture was ultrasonically dispersed and dissolved at 45 ° C for 1 hour. After cooling to room temperature, the synthesized slurry was treated with n-hexane to extract by-products and promote the precipitation of colorless solids. After precipitation, the supernatant was removed, and the solid sample was vacuum dried and separated to obtain a modified sMAO solid.

[0092] (3) Preparation of supported metallocene catalyst:

[0093] Toluene was added to a three-necked flask containing 50 g of sMAO solid and 1.2 g of bis(n-butylcyclopentadienyl)zirconium dichloride, and the resulting orange dispersion was heated at 70 °C for 2 h at a speed of 500 rmin. -1 The mixture was cooled to room temperature, an orange solid precipitated under the colorless supernatant, the supernatant was removed by decantation, and the remaining slurry was dried overnight in vacuum to obtain the supported metallocene catalyst G. According to ICP characterization, in the catalyst G, the weight content of aluminum was 25.08%, and the weight content of zirconium was 2.31%.

[0094] (4) Ethylene polymerization:

[0095] Ethylene polymerization: A 2L stainless steel polymerization reactor was fully replaced with high-purity nitrogen, and then 1.0L of hexane and 1.0mL of 1.0M triethylaluminum were added. The accurately weighed catalyst G prepared above was added with a syringe. The temperature was raised to 80°C, and hydrogen and ethylene were introduced so that the total pressure in the reactor reached 0.93MPa (gauge pressure). The volume ratio of hydrogen to ethylene was 6.5. Polymerization was carried out at 85°C for 2 hours to obtain a polyethylene product. The polymerization results are shown in Table 1.

[0096] Embodiment 8:

[0097] (1) Preparation of sMAO:

[0098] Under nitrogen protection, pour 500mL of trimethylaluminum toluene solution into a three-necked flask and cool to zero degrees. Add 1.24mmol of benzoic acid. When the mixture starts to bubble, heat it to 20°C. After half an hour, the mixture becomes clear and transparent. Continue heating at 50°C for 20h, at which time the mixture solution is still colorless. Heat to 80°C and heat for 18h. After the reaction is completed, wait for the liquid to cool to room temperature, add n-hexane, and a white solid precipitates. Draw out the supernatant, filter, separate, and dry to obtain the sMAO product.

[0099] (2) Modification of sMAO:

[0100] 45 g of sMAO product and 120 mL of perfluorobutyric acid were added to a three-necked flask, 20 mL of toluene solution was added, and the mixture was ultrasonically dispersed and dissolved at 45 ° C for 1 hour. After cooling to room temperature, the synthesized slurry was treated with n-hexane to extract by-products and promote the precipitation of colorless solids. After precipitation, the supernatant was removed, and the solid sample was vacuum dried and separated to obtain a modified sMAO solid.

[0101] (3) Preparation of supported metallocene catalyst:

[0102] Toluene was added to a three-necked flask containing 50 g of modified sMAO solid and 1.2 g of bis(1-butyl-3-methylcyclopentadienyl)zirconium dichloride, and the resulting orange dispersion was heated at 70 °C for 2 h at a speed of 500 rmin. -1 The mixture was cooled to room temperature, an orange solid precipitated under the colorless supernatant, the supernatant was removed by decantation, and the remaining slurry was dried overnight in vacuum to obtain the supported metallocene catalyst H. According to ICP characterization, in the catalyst H, the aluminum weight content was 12.47%, and the zirconium weight content was 0.84%.

[0103] (4) Ethylene polymerization:

[0104] Ethylene polymerization: A 2L stainless steel polymerization reactor was fully replaced with high-purity nitrogen, and then 1.0L of hexane and 1.0mL of 1.0M triethylaluminum were added. The accurately weighed catalyst H prepared above was added with a syringe. The temperature was raised to 80°C, and hydrogen and ethylene were introduced so that the total pressure in the reactor reached 0.93MPa (gauge pressure). The volume ratio of hydrogen to ethylene was 6.5. Polymerization was carried out at 85°C for 2 hours to obtain a polyethylene product. The polymerization results are shown in Table 1.

[0105] Comparative Example 1:

[0106] The difference from Example 1 is that sMAO was not modified.

[0107] (1) Preparation of sMAO:

[0108] Same steps as in Example 1.

[0109] (2) Preparation of supported metallocene catalysts:

[0110] Instead of adding "modified sMAO solid", "sMAO solid" was added, and the rest was the same as in Example 1 to obtain supported metallocene catalyst I.

[0111] (3) Ethylene polymerization:

[0112] Ethylene polymerization: A 2L stainless steel polymerization reactor was fully replaced with high-purity nitrogen, and then 1.0L of hexane and 1.0mL of 1.0M triethylaluminum were added. The accurately weighed catalyst I prepared above was added with a syringe. The temperature was raised to 80°C, and hydrogen and ethylene were introduced so that the total pressure in the reactor reached 0.93MPa (gauge pressure). The volume ratio of hydrogen to ethylene was 6.5. Polymerization was carried out at 85°C for 2 hours to obtain a polyethylene product. The polymerization results are shown in Table 1.

[0113] Comparative Example 2:

[0114] The difference from Example 2 is that sMAO was not modified.

[0115] (1) Preparation of sMAO:

[0116] Same steps as Example 2.

[0117] (2) Preparation of supported metallocene catalysts:

[0118] Instead of adding "modified sMAO solid", "sMAO solid" was added, and the rest was the same as in Example 2 to obtain supported metallocene catalyst J.

[0119] (3) Ethylene polymerization:

[0120] Ethylene polymerization: A 2L stainless steel polymerization reactor was fully replaced with high-purity nitrogen, and then 1.0L of hexane and 1.0mL of 1.0M triethylaluminum were added. The accurately weighed catalyst J prepared above was added with a syringe. The temperature was raised to 80°C, and hydrogen and ethylene were introduced so that the total pressure in the reactor reached 0.93MPa (gauge pressure). The volume ratio of hydrogen to ethylene was 6.5. Polymerization was carried out at 85°C for 2 hours to obtain a polyethylene product. The polymerization results are shown in Table 1.

[0121] Table 1 Polymerization results of supported metallocene catalysts

[0122]

[0123]

[0124] It can be seen from the results in Table 1 that the supported metallocene catalyst obtained by the preparation method of the present invention can be used to produce ethylene polymers. By optimizing the design of the catalyst and the ligand, the yield, molecular weight and chain regularity of the ethylene polymer can be controlled to achieve a narrow low molecular weight distribution, high crystallinity and good crystallization performance.

[0125] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and deformations based on the present invention, but these corresponding changes and deformations should all fall within the scope of protection of the present invention.

Claims

1. A preparation method of a supported metallocene catalyst, characterized in that, it comprises the following steps: (1) Preparation of sMAO: Under nitrogen protection, a toluene solution containing trimethylaluminum is added to a container, benzoic acid is added and the reaction is carried out at low temperature, then heated to medium temperature for reaction, and then heated to high temperature for reaction. After cooling, n-hexane is added, and a white solid precipitate appears. The upper clear liquid is drawn out, filtered, separated, and dried to obtain the sMAO product; (2) Modification of sMAO: The sMAO product and the modifier are added to a container, and then a toluene solution is added, dispersed and dissolved, cooled to obtain a slurry. The slurry is treated with n-hexane to obtain a precipitate of a colorless solid. The supernatant is removed, dried and separated to obtain the modified sMAO solid; (3) Preparation of the supported metallocene catalyst: The modified sMAO solid and the metallocene compound are added to a container, and then toluene is added, heated, and then cooled to obtain an orange solid precipitate. The supernatant is removed, and the remaining slurry is dried to obtain the supported metallocene catalyst.

2. The preparation method of the supported metallocene catalyst according to claim 1, characterized in that, The general formula of the metallocene compound is Cp* 2 (Z)MX n ; wherein, Cp* is a substituted or unsubstituted cyclopentadienyl, indenyl or fluorenyl, and the substituent is selected from C 1 -C 20 alkyl, alkoxy, silyl, aralkoxy or halogen; Z is a linking unit connecting two metallocene rings; if the general formula is a non-bridged metallocene complex, then Z does not represent any element; if the general formula is a bridged metallocene complex, then Z is selected from SiR* 2 , CR* 2 , SiR* 2 SiR* 2 , CR* 2 CR* 2 , CR*=CR*, or CR* 2 SiR* 2 , wherein R* is hydrogen or an alkyl, aryl, silyl, haloalkyl or haloaryl having less than 20 carbon atoms; M is a transition metal of Group 4 or Group 5 in the periodic table; X is the same or different and is selected from one of halogen, hydrocarbon group, hydrocarbonoxy group, acid radical, amino group; n is an integer satisfying the valence state of M.

3. The preparation method of the supported metallocene catalyst according to claim 2, characterized in that, In the general formula of the metallocene compound, X is selected from halogen, hydrocarbon group, allyl group, cyclopentadienyl group, alkoxy group, arylalkoxy group, and n = 2.

4. The preparation method of the supported metallocene catalyst according to claim 2, characterized in that, In the general formula of the metallocene catalyst, M is zirconium or titanium.

5. The preparation method of the supported metallocene catalyst according to claim 1, characterized in that, The proportion of each component in the supported metallocene catalyst is: based on every gram of sMAO, the content of MAO is 0.01 - 10 g, and the content of the metallocene compound is 0.002 - 10 g.

6. The preparation method of the supported metallocene catalyst according to claim 1, characterized in that, The aluminum content in the supported metallocene catalyst is 0.1 - 30 wt%, and the content of metal M is 0.01 - 5 wt%.

7. The preparation method of the supported metallocene catalyst according to claim 1, characterized in that, The modifier is a perfluoroalkyl carboxylic acid.

8. The preparation method of the supported metallocene catalyst according to claim 7, characterized in that, The modifier is at least one of perfluorobutyric acid, perfluorovaleric acid, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorooctanoic acid, perfluoroundecanoic acid, and perfluorododecanoic acid.

9. The preparation method of the supported metallocene catalyst according to claim 1, characterized in that, The reaction temperature at low temperature is -20 - 20 °C, and the reaction time is 0.5 - 5 hours; the reaction temperature at medium temperature is 30 - 70 °C, and the reaction time is 6 - 30 hours; the reaction temperature at high temperature is 70 - 100 °C, and the reaction time is 6 - 24 hours.

10. Application of the supported metallocene catalyst obtained by the preparation method according to any one of claims 1 - 9 in ethylene polymerization.

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