Metallocene catalyst suitable for olefin polymerization and preparation method thereof

Abstract

The invention discloses a metallocene catalyst for olefin polymerization and a preparation method thereof. The metallocene catalyst comprises a metallocene compound, an organic boron compound and silica gel, and the structural formula of the metallocene compound is shown in the specification; the organic boron compound is N, N-dimethyl phenylammonium tetrakis (perfluorophenyl) borate. The preparation method comprises the following steps: mixing a solution containing a metallocene compound and an organic boron compound with smog-like silica gel to obtain a mother solution to be sprayed, and carrying out spray drying on the mother solution to be sprayed. When being used for olefin polymerization, the metallocene catalyst prepared by the method has the characteristics of high polymerization activity, good hydrogen regulation sensitivity and copolymerization performance, good polymer powder form, high stacking density and the like, and has a good application prospect in ethylene polymerization and copolymerization systems.

Description

Technical Field

[0001] This invention relates to a metallocene catalyst for preparing ethylene homopolymers or ethylene / α-olefin copolymers and its preparation method, belonging to the field of metallocene catalyst synthesis technology. Background Technology

[0002] Metallocene catalysts are a class of single-center catalysts widely used in the field of olefin polymerization. Because the olefin polymers they produce have narrow molecular weight distributions, precise and controllable chain structures, and high product purity, they are widely used in high-performance film products, high-end injection molded products, medical and health products, and high-end polyolefin elastomers.

[0003] In the existing technology, heterogeneous metallocene catalysts are mostly prepared by impregnating spherical silica gel with metallocene compounds. The co-catalysts are mostly MAO or MMAO. However, due to the high price and large consumption of MAO or MMAO co-catalysts, the catalyst cost in polymer production is high.

[0004] In terms of polymerization processes, there are mainly solution polymerization, slurry polymerization, and gas-phase polymerization. Among them, solution polymerization has a natural advantage in producing low-density polyolefin products with low melting points because the polymer is dissolved in the reaction medium, but it has the disadvantages of high energy and material consumption and difficulty in completely removing volatiles. Slurry polymerization takes place in a liquid medium, making it easier to remove the heat of reaction and reducing the risk of explosive polymerization and temperature runaway. However, it also has the disadvantage of high energy consumption due to the large amount of solvent used in the process. Gas-phase polymerization has the advantages of relatively mild reaction conditions, lower investment in production equipment, lower energy and material consumption, and lower product odor, making it the preferred production process for many metallocene products.

[0005] Studies have shown that organoboron compounds with compatible structures can activate metallocene compounds for olefin polymerization or copolymerization. However, since the matched organoborides are all solids and have low solubility in low-boiling-point alkane organic solvents such as hexane at conventional polymerization temperatures, their application has been limited to solution polymerization processes. Therefore, researching and developing a heterogeneous metallocene catalyst system using organoboron compounds as co-catalysts and applying it to slurry or gas-phase ethylene homopolymerization or ethylene / α-olefin copolymerization is of practical significance. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a highly active metallocene catalyst spherical particle using organoboron compounds as co-catalysts, so as to reduce the production cost of metallocene polyolefin products.

[0007] To address the aforementioned problems, this invention provides a metallocene catalyst for olefin polymerization, comprising a metallocene compound, an organoboron compound, and silica gel, wherein the structural formula of the metallocene compound is shown in Formula 1: Formula 1; In Formula 1, n is a natural number from 4 to 10; R1 and R2 may be the same or different, and each is independently an aryl group having 6 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms substituted with an alkyl group having 1 to 20 carbon atoms; R3 is an alkyl group having 1 to 20 carbon atoms; R4 is a tertiary amine having an alkyl group having 1 to 10 carbon atoms; A is carbon, silicon, or germanium; the two Xs may be the same or different, and each is independently a halogen or an alkyl group having 1 to 20 carbon atoms. The organoboron compound is N,N-dimethylphenylammonium tetra(perfluorophenyl)borate; The silica gel described is a fumigated silica gel with an average particle size of less than 1 μm. This type of silica gel is prepared by a gas-phase method and typically has a specific surface area of ​​200 m². 2 Approximately / g. This is an example, but not limited to, Cabot's fumigated silica gel products such as TS-530, TS-610, and TS-720.

[0008] Preferably, the metallocene compound is any one or more of the following structural formulas: Formula 2; Formula 3; Equation 4; Formula 5; Formula 6; Formula 7.

[0009] Preferably, the metallocene catalyst is prepared by spray drying and has an average particle size of 5-100 μm.

[0010] Preferably, the catalyst solid particles contain 0.2-10% metallocene compound, 5-50% organoboron compound, 20-80% silica gel and the balance inert solvent by mass percentage, with an average particle size of 10-60 μm.

[0011] Preferably, the catalyst solid particles contain 0.5-5% metallocene compound, 20-40% organoboron compound, 30-60% silica gel and the balance inert solvent by mass percentage, with an average particle size of 10-60 μm.

[0012] The inventors discovered that the co-catalyst N,N-dimethylphenylammonium tetra(perfluorophenyl)borate exhibits a good synergistic effect with the metallocene compound shown in Formula 1, demonstrating high activity in olefin polymerization or copolymerization. By using a spray-drying molding method, the co-catalyst N,N-dimethylphenylammonium tetra(perfluorophenyl)borate and the metallocene compound are assembled into solid metallocene catalyst particles, with both uniformly distributed within the particles. Compared to the method of separately introducing the main catalyst and co-catalyst into the reactor for contact activation, this method allows for more thorough contact between the main catalyst and co-catalyst, shortening the activation response time of the main catalyst, improving its polymerization activity, and simultaneously increasing the utilization efficiency of the co-catalyst, thus reducing its usage. Furthermore, within the solid catalyst particles, the co-catalyst N,N-dimethylphenylammonium tetra(perfluorophenyl)borate acts as a binder, significantly enhancing the strength of the metallocene catalyst solid particles, which are primarily composed of atomized silica gel.

[0013] The present invention also provides a method for preparing the above-mentioned metallocene catalyst for olefin polymerization, comprising the following steps: Step a): The metallocene compound of Formula 1 and N,N-dimethylphenylammonium tetra(perfluorophenyl)borate are completely dissolved in an inert organic solvent to obtain a homogeneous liquid. The silica gel is then mixed with the above liquid to obtain the masterbatch to be sprayed. Step b): The masterbatch obtained in step a) is spray-dried to obtain spherical metallocene catalyst particles.

[0014] In the method for preparing the solid particles of the metallocene catalyst, the inert organic solvent may be any one of those capable of dissolving the metallocene compound of Formula 1 and N,N-dimethylphenylammonium tetra(perfluorophenyl)borate, and having a boiling point not higher than 150°C. Generally, tetrahydrofuran is preferred for economic and availability reasons.

[0015] In step a), there are no special requirements for the process of dissolving the metallocene compound and organoboron compound and mixing them with silica gel to prepare the masterbatch to be sprayed. The proportion of additives is determined according to the requirements of the metallocene catalyst. There are no special requirements for the dissolution temperature and time. Any inert organic solvent can be used if it is below the reflux temperature and can dissolve the metallocene compound and organoboron compound. The amount of inert organic solvent added should be such that it can completely dissolve the metallocene compound and organoboron compound and the solid content in the subsequent masterbatch is suitable for spray drying to obtain well-shaped solid particles.

[0016] Preferably, step a) specifically involves: adding the metallocene compound and N,N-dimethylphenylammonium tetra(perfluorophenyl)borate to tetrahydrofuran, heating to 50°C-reflux temperature, stirring and dissolving for 0.5-10 hours, and after complete dissolution, adjusting the solution temperature to 20-50°C, adding silica gel, and stirring to mix evenly to obtain the masterbatch to be sprayed; the mass ratio of metallocene compound, organoboron compound, tetrahydrofuran, and silica gel is 0.2-10:5-50:200-1000:20-80.

[0017] Preferably, step a) specifically involves: adding the metallocene compound and N,N-dimethylphenylammonium tetra(perfluorophenyl)borate to tetrahydrofuran, heating to 60°C-reflux temperature, stirring and dissolving for 0.5-10 hours, and after complete dissolution, adjusting the temperature to 30-45°C, adding silica gel, and stirring to mix evenly to obtain the masterbatch to be sprayed; the mass ratio of metallocene compound, organoboron compound, tetrahydrofuran, and silica gel is 0.5-5:20-40:300-500:30-60.

[0018] Preferably, the spray drying process involved in step b) and the equipment and conditions used in the spray drying process are not particularly limited. Any equipment and methods existing in the art that can be used for spray drying organic phase materials can be incorporated into this invention. The spray drying equipment can be a pressure spray dryer, a rotary spray dryer, or a two-fluid spray dryer. The material drying process can be completed in one step by the spray dryer, or one or more other types of drying equipment (such as fluidized bed dryers) can be connected in series after the spray dryer to continue drying until it is completely dried. In small-scale experiments, two-fluid spray dryers are often used as experimental platforms for the preparation of microspheres by spray drying due to their small size and wide adjustable particle size range. As an example, a two-fluid spray dryer is used for atomization and drying of the material to be sprayed. The spray drying process is carried out under an inert atmosphere (nitrogen), and the carrier gas is dried nitrogen. The spray drying yield is controlled by the feed flow rate of the masterbatch to be sprayed, the solvent content of the catalyst particles is adjusted by the outlet temperature, the particle size of the catalyst is adjusted by the ratio of the atomizing gas flow rate to the feed flow rate of the masterbatch to be sprayed, and the morphology of the catalyst particles is adjusted by the synergistic effect of drying temperature and masterbatch composition. The inlet temperature of the carrier gas is 120-200℃, the outlet temperature is 70-135℃, the atomizing gas is dried nitrogen, and the pressure of the atomizing gas is 3-6 bar.

[0019] The metallocene catalyst described in this invention, when applied in the polymerization process, can further introduce a small amount of alkylaluminum or alkylaluminoxane co-catalysts into the polymerization reaction system. However, it should be noted that the metallocene catalyst of this invention already includes organoboron compound co-catalysts. The alkylaluminum or alkylaluminoxane introduced into the polymerization reaction system mainly serves to remove water and other impurities from the reaction system.

[0020] This invention also provides the application of the above-mentioned metallocene catalysts for olefin polymerization in the gas-phase preparation of polyolefin elastomers.

[0021] The metallocene catalyst of the present invention has the advantages of high activity, good particle morphology, no need for co-catalysts such as MAO, and low production cost when used for olefin polymerization.

[0022] The metallocene catalyst prepared in this invention is used for olefin polymerization, resulting in resins with high ethylene content, good particle morphology, and low risk of agglomeration. The metal catalyst can achieve high catalytic activity with a small amount of co-catalyst, while other polymerization properties remain unaffected. Attached Figure Description

[0023] Figure 1 Scanning electron microscope image of the metallocene catalyst prepared in Example 1. Detailed Implementation

[0024] To make the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0025] The test methods for each embodiment and comparative example are as follows: (1) The melt index (MI) of the polymer was tested at 190℃ and 2.16kg load according to the test standard GB / T3682.1-2018.

[0026] (2) The bulk density (BD) of the polymer powder was tested according to the method specified in the test standard GB / T 1636-2008.

[0027] (3) The polymer density was tested using a densitometer (impregnation method METTLER).

[0028] Synthesis of metallocene compounds in Examples 1-6 and Comparative Examples 1-3 (1H NMR measurements were performed using a Bruker Ascend 400M nuclear magnetic resonance spectrometer): The structural formula of the metallocene compound is: .

[0029] Step 1-1: Synthesis of 4-(6-(dichloro(methyl)silyl)hexyl)-N,N-dimethylaniline In a flask, 4-(6-bromohexyl)-N,N-dimethylaniline (5.00 g, 25 mmol) and Mg (1.22 g, 50.2 mmol) were added to THF (25 mL), and the mixture was stirred at 70 °C for 4 hours. In another flask, MeSiCl3 (7.47 g, 50.0 mmol) was dissolved in THF (75 mL), and the mixture was slowly added dropwise at 0 °C for 1 hour. The mixture was then stirred overnight at room temperature, and saturated NaHCO3 was added. Water was removed with anhydrous MgSO4, and the resulting solution was concentrated under reduced pressure to obtain a white solid, 4-(6-(dichloro(methyl)silyl)hexyl)-N,N-dimethylaniline (4.80 g, 82%). The 1H NMR is as follows: 1H NMR(500MHz, CDCl3,7.24ppm): 0.99(3H,s),3.01(6H,s),6.75(2H,d),7.57(2H,d) Steps 1-2: Synthesis of 4-(6-(bis(4-(4-(tert-butyl)phenyl)-2-methyl-1H-inden-1-yl)(methyl)silyl)hexyl)-N,N-dimethylaniline 4-(4-(tert-butyl)phenyl)-2-methyl-1H-indene (10.3 g, 39.3 mmol) and CuCN (176 mg, 1.97 mmol) were dissolved in toluene (90 mL) and THF (12 mL) under argon (Ar) atmosphere. The solution was cooled to -30 °C, and n-butyllithium (2.5 M hexane solution, 16.5 mL) was slowly added. The mixture was stirred at this temperature for about 10 minutes, and then heated to room temperature for 2 hours. The resulting 4-(6-(dichloro(methyl)silyl)hexyl)-N,N-dimethylaniline (4.80 g, 20.5 mmol) in toluene (30 mL) was added to the solution, and the mixture was stirred overnight at room temperature. After the reaction was complete, MTBE and water were added, and the organic layer was separated. The obtained organic layer was dried over anhydrous MgSO4 and concentrated to give 4-(6-(bis(4-(4-(tert-butyl)phenyl)-2-methyl-1H-inden-1-yl)(methyl)silyl)hexyl)-N,N-dimethylaniline (13.8 g, 100%), as a white solid. The 1H NMR is as follows: 1H NMR (500MHz, CDCl3, 7.24ppm): 0.00-0.07(3H,m),1.49-1.52(18H,m),2.46-2.49(6H,m),3.00(3H,s),3.02(3H,s),4.23-4.39(2H,m),6.50-7.52(20H,m) Steps 1-3: Synthesis of [4-(6-(bis(4-(4-(tert-butyl)phenyl)-2-methyl-1H-inden-1-yl)(methyl)silyl)hexyl)-N,N-dimethylaniline]zirconium dichloride Under argon (Ar) atmosphere, 6.74 g (9.83 mmol) of 4-(6-(bis(4-(4-(tert-butyl)phenyl)-2-methyl-1H-inden-1-yl)(methyl)silyl)hexyl)-N,N-dimethylaniline was added to a 50 mL Schlenk flask and dissolved in diethyl ether (8.2 mL). The temperature was lowered to -78 °C, and 8.1 mL (2.5 M in hexane) of n-butyllithium was added, followed by stirring at room temperature for 2 hours. At -78 °C, 2.29 g (9.83 mmol) of ZrCl4 in a Tol / diethyl ether (24.6 mL / 8.2 mL) slurry was slowly added to the ligand solution, the temperature was raised to room temperature, and the mixture was stirred overnight. The solvent was distilled under reduced pressure to dissolve the ligand in CH2Cl2, and the solution was filtered to remove LiCl. The filtrate was concentrated, and the resulting crude product was saturated with CH₂Cl₂. Two volumes of hexane were added, and the mixture was recrystallized at -20°C for 15 hours. Subsequently, when a yellow solid formed, it was filtered and washed twice with hexane to obtain [4-(6-(bis(4-(4-(tert-butyl)phenyl)-2-methyl-1H-inden-1-yl)(methyl)silyl)hexyl)-N,N-dimethylaniline]zirconium dichloride (225 mg, 30%, r / m > 20 / 1). The 1H NMR is as follows: 1H NMR(500MHz, CDCl3,7.24ppm): 1.30–1.40(21H,m),2.00(3H,s),2.33(3H,s),3.10(6H,s),6.85–7.94(18H,m) Example 1 (1) Catalyst preparation Preparation of metallocene compound solution: Under nitrogen protection, accurately weigh 500 mg of the synthesized metallocene compound [4-(6-(bis(4-(4-(tert-butyl)phenyl)-2-methyl-1H-inden-1-yl)(methyl)silyl)hexyl)-N,N-dimethylaniline]zirconium dichloride and 3 g of N,N-dimethylphenylammonium tetra(perfluorophenyl)borate (commercially available) and transfer them to a glass reactor that has been fully purged with nitrogen. Add 80 mL of dehydrated and purified tetrahydrofuran, start stirring, heat to 70 °C, react for 30 min and stir until completely dissolved, then cool to 40 °C and wait for the material to dissolve. Preparation of masterbatch to be sprayed: Accurately weigh 10g of fumigated silica gel TS-610, transfer it to a glass reactor, and fully replace the air carried in the system with nitrogen; transfer the previously obtained solution to the glass reactor and stir and mix it with the fumigated silica gel for 30min to obtain the masterbatch to be sprayed; Spray drying: The masterbatch obtained in the previous step was spray-dried using a Buchi B290 spray dryer to obtain solid microspheres. The spraying conditions were: carrier gas inlet temperature 150℃, outlet temperature 105℃, masterbatch feed pump opening 30%, and atomizing gas flow rate 600 L / h. 13.5 g of spherical metallocene catalyst particles were collected in the product collection tank, with an average particle size D50 of 20.2 μm. The morphology is shown in the scanning electron microscope image below. Figure 1 As shown.

[0030] (2) Aggregation Under nitrogen protection, 1L of hexane, 0.5mL of 1mol / L triethylaluminum solution and 0.05g of the metallocene catalyst prepared in step (1) were added to a 2L stainless steel stirred tank. The temperature of the polymerization tank was then raised to 85℃, and 0.28MPa of hydrogen gas was introduced at once. Then, ethylene was used to maintain the total pressure of the system at 1.03MPa for polymerization. After 2 hours of polymerization, the addition of ethylene was stopped, the temperature was lowered, and the pressure was released. The resulting polyethylene powder was vacuum dried at 50℃ for 4 hours, and the activity of the catalyst was calculated by weighing.

[0031] Example 2 (1) Catalyst preparation Preparation of metallocene compound solution: Under nitrogen protection, accurately weigh 1g of the above-synthesized metallocene compound [4-(6-(bis(4-(4-(tert-butyl)phenyl)-2-methyl-1H-inden-1-yl)(methyl)silyl)hexyl)-N,N-dimethylaniline]zirconium dichloride and 3g of N,N-dimethylphenylammonium tetra(perfluorophenyl)borate (commercially available) and transfer them to a glass reactor that has been fully purged with nitrogen. Add 80mL of dehydrated and purified tetrahydrofuran, start stirring, heat to 70℃, react for 30min and stir until completely dissolved, then cool to 40℃ and wait for the material to dissolve. Preparation of masterbatch to be sprayed: Accurately weigh 10g of fumigated silica gel TS-610, transfer it to a glass reactor, and fully replace the air carried in the system with nitrogen; transfer the previously obtained solution to the glass reactor and stir and mix it with the fumigated silica gel for 30min to obtain the masterbatch to be sprayed; Spray drying: The masterbatch obtained in the previous step was spray-dried using a spray dryer (Buchi B290) to obtain solid microsphere particles. The spraying conditions were: carrier gas inlet temperature 160℃, outlet temperature 108℃, masterbatch feed pump opening 30%, and atomizing gas flow rate 600L / h. 12.8g of spherical metallocene catalyst particles were collected in the product collection tank, with an average particle size D50 of 21.3μm.

[0032] (2) Aggregation Same as Example 1.

[0033] Example 3 (1) Catalyst preparation Preparation of metallocene compound solution: Except for the addition of 4.5g of N,N-dimethylphenylammonium tetra(perfluorophenyl)borate, the rest is the same as in Example 1.

[0034] Preparation of masterbatch to be sprayed: Same as in Example 1.

[0035] Spray drying: The masterbatch obtained in the previous step was spray dried using a spray dryer (Buchi B290) to obtain solid microsphere particles. The spraying conditions were: carrier gas inlet temperature 160℃, outlet temperature 112℃, masterbatch feed pump opening 35%, and atomizing gas flow rate 600L / h. 14.1g of spherical metallocene catalyst particles were collected in the product collection tank, with an average particle size D50 of 24.3μm.

[0036] (2) Aggregation Same as Example 1.

[0037] Example 4 (1) Catalyst preparation Same as Example 1.

[0038] (2) Aggregation Under nitrogen protection, 1L of hexane, 0.5mL of 1mol / L triethylaluminum solution and 0.05g of the metallocene catalyst prepared in step (1) were added to a 2L stainless steel stirred tank. The temperature of the polymerization tank was then raised to 85℃, 10mL of hexene was added, and 0.28MPa of hydrogen gas was introduced at once. Then, ethylene was used to maintain the total pressure of the system at 1.03MPa for polymerization reaction. After 2 hours of polymerization reaction, the addition of ethylene was stopped, the temperature was lowered, and the pressure was released. The resulting polyethylene powder was vacuum dried at 50℃ for 4 hours, and the activity of the catalyst was calculated by weighing.

[0039] Example 5 (1) Catalyst preparation Same as Example 1.

[0040] (2) Aggregation Except for the amount of hexene added, which is 20 mL, everything else is the same as in Example 4. Example 6 (1) Catalyst preparation Same as Example 1.

[0041] (2) Aggregation Except for the amount of hydrogen added being 0.75 MPa, everything else is the same as in Example 1.

[0042] Comparative Example 1 (1) Catalyst preparation Preparation of metallocene compound solution: except for the absence of N,N-dimethylphenylammonium tetra(perfluorophenyl)borate, the preparation is the same as in Example 1.

[0043] Preparation of masterbatch to be sprayed: Accurately weigh 10g of fumigated silica gel TS-610, transfer it to a glass reactor, and fully replace the air carried in the system with nitrogen; transfer the previously obtained solution to the glass reactor and stir and mix it with the fumigated silica gel for 30min to obtain the masterbatch to be sprayed; Spray drying: The masterbatch obtained in the previous step was spray-dried using a spray dryer (Buchi B290) to obtain solid microspheres. The spraying conditions were: carrier gas inlet temperature 150℃, outlet temperature 105℃, masterbatch feed pump opening 30%, and atomizing gas flow rate 600L / h. During the drying process, the atomized droplets were difficult to form high-strength particles, resulting in a small amount of unformed product collected, most of which was carried away by the exhaust gas from the cyclone separator.

[0044] Comparative Example 2 (1) Catalyst preparation Under nitrogen protection, accurately weigh 10g of pretreated silica gel carrier (Grace955) and transfer it to a glass reactor that has been fully purged with nitrogen. Add 100mL of dehydrated and purified toluene. Stir to disperse it evenly, then add 20mL of methylaluminoxane (1.5M toluene solution) and stir at 30℃ for 20min to obtain chemically activated silica gel carrier.

[0045] Under nitrogen protection, 500 mg of the synthesized metallocene compound [4-(6-(bis(4-(4-(tert-butyl)phenyl)-2-methyl-1H-inden-1-yl)(methyl)silyl)hexyl)-N,N-dimethylaniline]zirconium dichloride was accurately weighed and added to a chemically activated silica gel / toluene suspension. The mixture was stirred at 30 °C for 60 min. After the reaction was completed, the mixture was allowed to stand for 30 min, and after separation, the liquid was filtered off. The liquid was washed twice with 100 mL of dehydrated toluene and then twice with 100 mL of dehydrated hexane. The obtained solid was dried under vacuum at room temperature for 2 hours to obtain the supported metallocene catalyst.

[0046] (2) Aggregation Under nitrogen protection, 1L of toluene, 0.5mL of 1mol / L triethylaluminum solution, 0.05g of the metallocene catalyst prepared in step (1) and 0.05g of N,N-dimethylphenylammonium tetra(perfluorophenyl)borate were added to a 2L stainless steel stirred tank. The temperature of the polymerization tank was then raised to 85℃, and 0.28MPa of hydrogen gas was introduced at once. Then, ethylene was used to maintain the total pressure of the system at 1.03MPa for polymerization. After 2 hours of polymerization, the addition of ethylene was stopped, the temperature was lowered, and the pressure was released. The resulting polyethylene powder was washed once with 1L of hexane and then vacuum dried at 50℃ for 4 hours. The activity of the catalyst was calculated by weighing.

[0047] Comparative Example 3 (1) Catalyst preparation Same as Comparative Example 2.

[0048] (2) Aggregation Except for the addition of 0.1g N,N-dimethylphenylammonium tetra(perfluorophenyl)borate, the same as comparative example 2.

[0049] The experimental data of the above embodiments and comparative examples are shown in Table 1.

[0050] Table 1

[0051] As can be seen from the polymerization data in Table 1, the metallocene catalyst of this invention uses organoboron compounds as co-catalysts, and can complete catalyst activation without the presence of MAO or MMAO co-catalysts, with low consumption of organoboron compounds. In polymerization, the metallocene catalyst of this invention exhibits high polymerization activity, superior hydrogen regulation sensitivity and copolymerization performance, and the polymer powder has good morphology and high bulk density, showing promising application prospects in slurry or gas-phase ethylene polymerization and copolymerization systems.

Claims

1. A metallocene catalyst for olefin polymerization, characterized in that, The compounds include metallocene compounds, organoboron compounds, and silica gel, wherein the structural formula of the metallocene compounds is shown in Formula 1: Formula 1; In Formula 1, n is a natural number from 4 to 10; R1 and R2 may be the same or different, and each is independently an aryl group having 6 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms substituted with an alkyl group having 1 to 20 carbon atoms; R3 is an alkyl group having 1 to 20 carbon atoms; R4 is a tertiary amine having an alkyl group having 1 to 10 carbon atoms; A is carbon, silicon, or germanium; the two Xs may be the same or different, and each is independently a halogen or an alkyl group having 1 to 20 carbon atoms. The organoboron compound is N,N-dimethylphenylammonium tetra(perfluorophenyl)borate; The silica gel is a fumigated silica gel with an average particle size of less than 1 μm.

2. The metallocene catalyst for olefin polymerization as described in claim 1, characterized in that, The metallocene compound is any one or more of the following structural formulas: Formula 2; Formula 3; Equation 4; Formula 5; Formula 6; Formula 7.

3. The metallocene catalyst for olefin polymerization as described in claim 1, characterized in that, It was prepared by spray drying, with an average particle size of 5-100 μm.

4. The metallocene catalyst for olefin polymerization as described in claim 1 or 3, characterized in that, The catalyst solid particles contain 0.2-10% metallocene compounds, 5-50% organoboron compounds, 20-80% silica gel, and the balance inert solvent by mass percentage, with an average particle size of 10-60 μm.

5. The metallocene catalyst for olefin polymerization as described in claim 1 or 3, characterized in that, The catalyst solid particles contain 0.5-5% metallocene compounds, 20-40% organoboron compounds, 30-60% silica gel, and the balance inert solvent by mass percentage, with an average particle size of 10-60 μm.

6. The method for preparing the metallocene catalyst for olefin polymerization according to any one of claims 1-5, characterized in that, Includes the following steps: Step a): The metallocene compound of Formula 1 and N,N-dimethylphenylammonium tetra(perfluorophenyl)borate are completely dissolved in an inert organic solvent to obtain a homogeneous liquid. The silica gel is mixed with the above liquid to obtain the masterbatch to be sprayed. Step b): The masterbatch obtained in step a) is spray-dried to obtain spherical metallocene catalyst particles.

7. The method for preparing the metallocene catalyst for olefin polymerization as described in claim 6, characterized in that, Step a) specifically involves: adding the metallocene compound and N,N-dimethylphenylammonium tetra(perfluorophenyl)borate to tetrahydrofuran, heating to 50°C-reflux temperature, stirring and dissolving for 0.5-10 hours, and after complete dissolution, adjusting the solution temperature to 20-50°C, adding silica gel, and stirring to mix evenly to obtain the masterbatch to be sprayed; the mass ratio of metallocene compound, organoboron compound, tetrahydrofuran, and silica gel is 0.2-10:5-50:200-1000:20-80.

8. The method for preparing the metallocene catalyst for olefin polymerization as described in claim 6, characterized in that, Step a) specifically involves: adding the metallocene compound and N,N-dimethylphenylammonium tetra(perfluorophenyl)borate to tetrahydrofuran, heating to 60°C-reflux temperature, stirring and dissolving for 0.5-10 hours, and after complete dissolution, adjusting the temperature to 30-45°C, adding silica gel, and stirring to mix evenly to obtain the masterbatch to be sprayed; the mass ratio of metallocene compound, organoboron compound, tetrahydrofuran, and silica gel is 0.5-5:20-40:300-500:30-60.

9. The use of the metallocene catalyst for olefin polymerization according to any one of claims 1-5 in olefin polymerization.

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