A metallocene catalyst, preparation method and application thereof

Abstract

The present invention discloses a metallocene catalyst, preparation method, and application. The catalyst has a structure as shown in Formula I: The catalyst disclosed herein connects a nitrogen-containing bridge ring to cyclopentadiene via anthracene as a bridge, and then complexes the nitrogen and cyclopentadiene with a Group IV metal. The catalyst performs excellently in high-temperature solution-processed polyolefins, particularly in the copolymerization of ethylene and alpha-olefins, exhibiting outstanding high-temperature resistance and catalytic activity. The resulting polymer has a high proportion of long-chain branches.

Description

Technical Field

[0001] The present invention relates to an olefin polymerization catalyst and a preparation method thereof, as well as the application thereof in olefin polymerization, in particular to the application thereof in catalyzing the polymerization of ethylene and alpha-olefin. Background Art

[0002] Metallocene catalysts, due to their high catalytic activity and excellent ability to control polymer structure, are widely used in the production of polyolefin products. This is particularly valuable in the development and production of linear high- and low-density polyethylene, polypropylene, and polyolefin elastomers. Compared to traditional Ziegler-Natta catalysts, metallocene catalysts possess a single active catalytic site, resulting in a narrower molecular weight distribution. The polyethylene produced using these catalysts is widely used in the production of stronger plastic films. Furthermore, metallocene catalysts can regulate the polymer's microchain structure by adjusting the ligand structure, enabling the resulting polyolefins to be used in a wider range of downstream applications.

[0003] In the past 30 years, academia and industry have been vigorously developing single-site polyolefin catalysts based on pre-transition metals. From the invention of CGC catalyst by Bercaw to its application in industrial production of POE by Dow and Exxon (Organometals 1990, 9, 867–869, EP 0 416 815 A2, 1991, US 5 026 798, 1991), a large number of constrained configuration metallocene catalysts have been developed. Representative ones include phenoxy-type catalysts for the production of LLDPE developed by Sumitomo Chemicals (PHEN ICS, EP 0 842 939 B1, 1996), trivalent titanium catalysts for the production of EPDM developed by DSM (Lovacat, WO 96 / 13529, 1996), phosphocene catalysts for the production of high molecular weight LLDPE developed by Nova Chemicals (US 6 124 487,1998) etc.

[0004] The production of high-end polyolefins using metallocene catalysis requires large amounts of modified methylaluminoxane (MMAO) as an impurity remover and co-catalyst in the reaction system. This is not only costly, but also severely limited by the global shortage of MMAO production capacity, which limits the supply of high-end polyolefin products. Increasing the activity of the main catalyst can reduce the amount of MMAO used. Furthermore, while traditional CGC catalysts have high activity and comonomer insertion capabilities, their high-temperature resistance is less than ideal. To reduce production energy consumption and costs, increasing the reaction temperature and thus the solid content of the reaction solution is the most direct and effective method. Therefore, a polyolefin catalyst with high catalytic activity and good high-temperature resistance is urgently needed. Furthermore, polyolefins produced using traditional metallocene catalysts have a low proportion of long-chain branches, making it difficult to achieve high melt strength during the foaming process. Therefore, catalysts for producing polyolefins with a high proportion of long-chain branches have high application value. Summary of the Invention

[0005] In view of this, one of the objects of the present invention is to provide a metal catalyst and a preparation method thereof, which uses an anthracene ring as a bridging group, forms a ligand by connecting a nitrogen-containing bridge ring and cyclopentadiene, and forms a catalytic pocket structure consisting of a bridge ring-metal-cyclopentadiene after complexation with a metal, and has the advantages of high activity and high temperature resistance.

[0006] The present invention also aims to provide the use of the catalyst in the polymerization of ethylene and alpha olefins, which has the characteristics of high activity and thermal stability, and the prepared polyolefin has the characteristics of a high proportion of long chain branches.

[0007] In order to achieve the above technical effects, the present invention adopts the following technical solutions:

[0008] The present invention provides a metallocene catalyst, the structure of which is shown in Formula I:

[0009]

[0010] In the formula, M is selected from titanium, zirconium or hafnium, preferably zirconium; X is selected from Cl, Br, methyl, benzyl or dimethylamino, preferably Cl or methyl, more preferably Cl; R1-R4 are each independently selected from hydrogen or C1-C10 alkyl, preferably methyl, and R1-R4 are the same or different; R5 and R6 are each independently selected from F, methyl, ethyl, isopropyl, tert-butyl or trifluoromethyl, preferably methyl or tert-butyl, and R5 and R6 are the same or different.

[0011] The metallocene catalyst of the present invention is preferably one or more compounds having the structures shown in the following formula AC:

[0012]

[0013] The present invention also provides a method for preparing the above-mentioned metallocene catalyst, comprising the following steps:

[0014] Under nitrogen protection, in tetrahydrofuran solvent, the compound represented by formula II is reacted with n-butyl lithium at -78-30°C, preferably -30-0°C, for 1-10 hours, preferably 1-6 hours, and then the metal halide M is added and complexed at -78-30°C, preferably -30-0°C, for 1-10 hours, preferably 1-6 hours to prepare the metallocene catalyst represented by formula I;

[0015] Wherein, the compound structure shown in formula II is wherein R1-R6 are the same as R1-R6 in formula I.

[0016] In the present invention, the molar ratio of the compound represented by formula II to n-butyl lithium and M metal halide is 1:(1-2):(1-2), preferably 1:(1-1.5):(1-1.5).

[0017] In the present invention, the M metal halide is selected from halides of titanium, zirconium or hafnium, and is preferably chloride of zirconium or hafnium.

[0018] In the present invention, the concentration of the compound represented by formula II in tetrahydrofuran is 0.01-1 mol / L, preferably 0.05-0.2 mol / L.

[0019] In the present invention, after the reaction is completed, post-processing processes such as desolvation and washing (n-hexane) are also included, which are conventional operations in the field and are not specifically limited in the present invention.

[0020] The compound represented by Formula II of the present invention is not specifically limited in its source. For example, it can be prepared by the following method, which comprises the following steps:

[0021] 1) Under nitrogen protection, compound 1 is reacted with n-butyl lithium and compound 2 to obtain compound 3;

[0022] 2) Under nitrogen protection, compound 3 is reacted with n-butyl lithium and compound 4 to obtain compound 5, i.e., the compound represented by formula II;

[0023] The reaction formula of the preparation process is as follows:

[0024]

[0025] wherein R1-R6 are the same as R1-R6 in formula I.

[0026] In step 1) of the present invention, the molar ratio of compound 1 to n-butyl lithium and compound 2 is 1:(1-1.5):(1-2), preferably 1:(1-1.2):(1-1.2), for example 1:1:1.

[0027] In step 1), the reaction can be carried out in a solvent environment, wherein the solvent is selected from at least one of toluene, diethyl ether, THF, etc., preferably THF or diethyl ether;

[0028] The concentration of compound 1 in the solvent is 0.01-1 mol / L, preferably 0.05-0.2 mol / L;

[0029] In step 1) of the present invention, the reaction temperature is -78-25°C, preferably -30-0°C, and the reaction time is 1-10h, preferably 1-4h;

[0030] Preferably, the reaction is carried out in two stages, firstly, compound 1 is reacted with n-butyl lithium for 1-2 hours, and then compound 2 is added and the reaction is continued for 1-6 hours.

[0031] In step 1) of the present invention, after the reaction is completed, post-treatment processes such as desolvation and crystallization (preferably crystallization in n-hexane) are also included, which are conventional operations in the field and are not specifically limited in the present invention.

[0032] In step 2) of the present invention, the molar ratio of compound 3 to n-butyl lithium and compound 4 is 1:(1-2):(1-2), preferably 1:(1-1.2):(1-1.2), for example 1:1:1.

[0033] In step 2), the reaction can be carried out in a solvent environment, wherein the solvent is selected from at least one of toluene, diethyl ether, THF, etc., preferably THF or diethyl ether;

[0034] The concentration of compound 3 in the solvent is 0.01-1 mol / L, preferably 0.05-0.2 mol / L;

[0035] In step 2) of the present invention, the reaction temperature is -78-30°C, preferably -30-0°C, and the reaction time is 1-10h, preferably 1-4h;

[0036] Preferably, the reaction is carried out in two stages, firstly reacting compound 3 with n-butyl lithium for 1-2 hours, and then adding compound 4 and continuing the reaction for 1-6 hours.

[0037] In step 2) of the present invention, after the reaction is completed, post-processing processes such as desolvation and column chromatography separation are also included, which are conventional operations in the field and are not specifically limited in the present invention.

[0038] The catalyst of the present invention is suitable for catalyzing the polymerization of α-olefins, wherein the α-olefins are selected from C2-C20 α-olefins, preferably C2, C4, C6, C8 and other α-olefins.

[0039] Preferably, the present invention provides an olefin polymerization method, wherein the method comprises catalyzing the polymerization reaction of ethylene and α-olefin under the combined action of the above-mentioned metallocene catalyst and co-catalyst to produce a polyolefin product.

[0040] In the present invention, the cocatalyst is selected from methylaluminoxane or trioctylaluminum-modified methylaluminoxane;

[0041] The molar ratio of the metallocene catalyst to the co-catalyst is 1:(1-10000), preferably 1:(100-1000), for example 1:500.

[0042] In the present invention, the amount of the metallocene catalyst is 10% of the molar amount of the α-olefin. -7 -10 -3 %.

[0043] In the present invention, the polymerization reaction can be carried out in a solvent or non-solvent environment. The solvent is selected from n-hexane, toluene, etc., which is a conventional operation in the field. The present invention does not specifically limit its type and amount.

[0044] In the present invention, the polymerization reaction temperature is 100-250°C, preferably 120-200°C, more preferably 160-180°C, and the time is 0.05-1h, preferably 0.05-0.1h;

[0045] The pressure of the ethylene introduced is 1-5 MPa, preferably 2-4 MPa, such as 3 MPa.

[0046] The polyolefin product prepared by the catalyst of the present invention has an Mw of 50,000-150,000 g / mol and a long chain branch content (I10 / I2) of 10-50.

[0047] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0048] The present invention uses an anthracene ring as a bridging group, connects a nitrogen-containing bridge ring and cyclopentadiene to form a ligand, and then forms a pocket-structured catalyst consisting of a bridge ring-metal-cyclopentadiene after complexation with a metal. The catalyst has outstanding high-temperature resistance and catalytic activity, and performs excellently in a high-temperature solution polyolefin process, especially in the copolymerization of ethylene and alpha olefins. The steric hindrance of the metal center is determined by the space between the bridge ring and cyclopentadiene. By regulating the substituents, a high proportion of insertion of longer chain segments containing terminal double bonds is achieved. DETAILED DESCRIPTION

[0049] The specific embodiments of the present method will be further described below with reference to examples. However, the present invention is not limited to the examples listed, but also includes any other known changes within the scope of the claimed invention.

[0050] In the examples and comparative examples of the present invention, the sources of the main raw materials are as follows. Unless otherwise specified, other raw materials and reagents were purchased from common commercial sources:

[0051] Compound 1 (2,7-dimethylanthracene, 2,7-di-tert-butylanthracene), n-butyllithium, compound 2 (cyclopentenone, tetramethylcyclopentenone), and zirconium tetrachloride were purchased from Inotech Technology Co., Ltd.

[0052] MMAO-7 was purchased from Nouryon.

[0053] The main performance of the embodiment of the present invention is tested by the following method:

[0054] The compounds in the following examples were characterized by nuclear magnetic resonance (NMR) spectrometer (Brucker ARX-400);

[0055] Molecular weight and molecular weight distribution of the polymer: measured by PL-GPC220 at 150°C using 1,2,4-trichlorobenzene as the solvent.

[0056] The polymerization activity of the polymer is calculated according to the following formula:

[0057] Polymerization activity = polymer mass / (catalyst dosage·polymerization time).

[0058] Long chain branch content: characterized by the melt index ratio (I 10 / I 2) under different weights.

[0059] Example 1

[0060] The catalyst of the structure shown in formula A is prepared by the following steps:

[0061]

[0062] 1) Under nitrogen protection, 2.1 g (10 mmol) of compound 1 (2,7-dimethylanthracene) was dissolved in 30 ml of THF, the temperature was lowered to 0°C, and then 5 ml (10 mmol) of n-butyl lithium was added. After reacting for 1 hour, 0.8 g (10 mmol) of compound 2 (cyclopentenone) was added, and the reaction was continued at 0°C for 2 hours. After the solvent was dried, the mixture was crystallized in n-hexane to obtain compound 3;

[0063] NMR characterization data of compound 3: 1 HNMR(CDC l3 400MHz)δ,2.66(s,3H),2.68(s,3H),2.94(d,J=8.2Hz,2H),6.43-6.57(m,3H),7.42-7.58(m,2H),7.75-7.68(m,3H),8.23(s,1H),8.35(s,1H)

[0064] 2) Under nitrogen protection, 1.3 g (5 mmol) of compound 3 was dissolved in 20 ml of THF. The reaction temperature was lowered to 0°C and 2.5 ml (5 mmol) of n-butyl lithium was added. After reacting for 1 hour, 0.95 g (5 mmol) of compound 4 was added and reacted at 0°C for 2 hours. The solvent was then drained and the mixture was separated by silica gel column chromatography to obtain compound 5, which is the compound represented by Formula II.

[0065] NMR characterization data of compound 5: 1 HNMR(CDC l3 400MHz)δ,1.56-1.78(m,7H),2.21-2.35(m,4H),2.69(s,3H),2.72(s,3H),2.92(d,J=8.2Hz,2H) ,3.63(m,2H),6.38-6.47(m,3H),7.35-7.45(m,2H),7.65-7.76(m,2H),8.21(s,1H),8.29(s,1H)

[0066] 3) Under nitrogen protection, 0.38 g (1 mmol) of compound 5 was dissolved in 5 ml of tetrahydrofuran, and then the temperature was lowered to 0°C and 0.5 ml (1 mmol) of n-butyl lithium was added. After reacting for 1 hour, 0.23 g (1 mmol) of zirconium tetrachloride was added and the complex reaction was carried out at 0°C for 1 hour. After that, the solvent was drained and the mixture was washed with n-hexane to obtain the compound represented by Formula A;

[0067] NMR characterization data of compound A: 1 HNMR(CDC l3 400MHz)δ,1.66-1.87(m,7H),2.18-2.32(m,4H),2.69(s,3H),2.77(s,3H),3.68(m,2 H),5.98-6.23(m,4H),6.88-6.97(m,2H),7.21-7.32(m,2H),8.24(s,1H),8.31(s,1H)

[0068] Example 2

[0069] The catalyst of the structure shown in formula B is prepared by the following steps:

[0070]

[0071] 1) Under nitrogen protection, 4.2 g (20 mmol) of compound 1 (2,7-dimethylanthracene) was dissolved in 50 ml of THF, the temperature was lowered to 0°C, and then 12 ml (24 mmol) of n-butyl lithium was added. After reacting for 1 hour, 3.3 g (24 mmol) of compound 2 (tetramethylcyclopentenone) was added, and the reaction was continued at 0°C for 2 hours. After the solvent was drained, the mixture was crystallized in n-hexane to obtain compound 3;

[0072] NMR characterization data of compound 3: 1 HNMR(CDC l3 400MHz)δ,1.79(s,6H),2.12(s,6H)2.64(s,3H),2.69(s,3H),2.99(d,J=8.2Hz,1H) ,6.52-6.64(m,3H),7.21-7.27(m,2H),7.67-7.77(m,3H),8.19(s,1H),8.28(s,1H)

[0073] 2) Under nitrogen protection, 3.2 g (10 mmol) of compound 3 was dissolved in 50 ml of THF. The reaction temperature was lowered to 0°C and 6 ml (12 mmol) of n-butyl lithium was added. After reacting for 1 hour, 1.9 g (10 mmol) of compound 4 was added and reacted at 0°C for 2 hours. The solvent was then drained and the product was separated by silica gel column chromatography to obtain compound 5, which is the compound of Formula II.

[0074] NMR characterization data of compound 5: 1 HNMR(CDC l3 400MHz)δ,1.52-1.71(m,7H),1.81(s,6H),1.98(s,6H),2.25-2.38(m,4H),2.69(s,3H),2.74(s,3H),2.90(d, J=8.2Hz,1H),3.62(m,2H),6.32-6.45(m,3H),7.35-7.43(m,2H),7.66-7.76(m,2H),8.15(s,1H),8.26(s,1H)

[0075] 3) Under nitrogen protection, 0.87 g (2 mmol) of compound 5 was dissolved in 10 ml of tetrahydrofuran, and then the temperature was lowered to 0°C and 1.2 ml (2.4 mmol) of n-butyl lithium was added. After reacting for 1 hour, 0.46 g (2 mmol) of zirconium tetrachloride was added and the complex reaction was carried out at 0°C for 1 hour. After that, the solvent was drained and the mixture was washed with n-hexane to obtain the compound represented by formula B;

[0076] NMR characterization data of compound B: 1 HNMR(CDC l3 400MHz)δ,1.58-1.69(m,7H),1.71(s,6H),1.92(s,6H)2.12-2.27(m,4H),2.66(s,3H),2.74(s,3H) ),3.56(m,2H),5.88-6.12(m,3H),6.76-6.87(m,2H),7.16-7.28(m,2H),8.19(s,1H),8.27(s,1H)

[0077] Example 3

[0078] The catalyst of the structure shown in formula C is prepared by the following steps:

[0079]

[0080] 1) Under nitrogen protection, 4.2 g (20 mmol) of compound 1 (2,7-di-tert-butylanthracene) was dissolved in 50 ml of THF, the temperature was lowered to 0°C, and then 12 ml (24 mmol) of n-butyllithium was added. After reacting for 1 hour, 3.3 g (24 mmol) of compound 2 (tetramethylcyclopentenone) was added. After reacting at 0°C for 2 hours, the solvent was drained and the mixture was crystallized in n-hexane to obtain compound 3;

[0081] NMR characterization data of compound 3: 1 HNMR(CDC l3 400MHz)δ,1.52(s,9H),1.59(s,9H),2.75(d,J=8.4Hz,2H),6.42-6.51(m,3H),7.36-7.48(m,2H),7.68-7.79(m,3H),8.18(s,1H),8.29(s,1H)

[0082] 2) Under nitrogen protection, 1.8 g (5 mmol) of compound 3 was dissolved in 30 ml of THF. The reaction temperature was lowered to 0°C and 2.5 ml (5 mmol) of n-butyl lithium was added. After reacting for 1 hour, 0.95 g (5 mmol) of compound 4 was added and reacted at 0°C for 2 hours. The solvent was then drained and the mixture was separated by silica gel column chromatography to obtain compound 5, which is the compound represented by Formula II.

[0083] NMR characterization data of compound 5: 1 HNMR(CDC l3 400MHz)δ,1.49(s,9H),1.56(s,9H),1.59-1.79(m,7H),2.21-2.35(m,4H),2.89(d,J=8.4Hz,2H) ,3.58(m,2H),6.42-6.51(m,3H),7.42-7.48(m,2H),7.67-7.78(m,2H),8.15(s,1H),8.34(s,1H)

[0084] 3) Under nitrogen protection, 0.92 g (2 mmol) of compound 5 was dissolved in 15 ml of tetrahydrofuran, and then the temperature was lowered to 0°C and 1.1 ml (2.2 mmol) of n-butyl lithium was added. After reacting for 1 hour, 0.48 g (2.2 mmol) of zirconium tetrachloride was added and the complex reaction was carried out at 0°C for 1 hour. After that, the solvent was drained and the mixture was washed with n-hexane to obtain the compound represented by Formula C;

[0085] NMR characterization data of compound C:1 HNMR(CDC l3 400MHz)δ,1.52(s,9H),1.58(s,9H),1.63-1.72(m,7H),2.25-2.39(m,4H),3.58(m,2 H),5.92-6.15(m,4H),6.79-6.87(m,2H),7.18-7.26(m,2H),8.16(s,1H),8.25(s,1H)

[0086] The metallocene catalyst prepared in Examples 1-3 above was used to catalyze the polymerization of ethylene and 1-octene in the following manner:

[0087] 0.5 μmol of catalyst was encapsulated in an ampoule and pre-loaded into a 1L high-pressure polymerization reactor. After drying at 120°C for 1 hour, the reaction mixture was cooled to 100°C and 260 ml of n-hexane and 140 ml (0.88 mol) of 1-octene were added, followed by 2 ml (2 mmol) of MMAO-7. The reaction system was heated to the set temperature, ethylene was introduced, and the pressure was set to 3 MPa. The ampoule was broken, and the polymerization reaction began. The reaction pressure and temperature were maintained constant throughout the reaction. The reaction was terminated after 5 minutes. The ethylene in the reactor was replaced with nitrogen, and the temperature was lowered to 100°C. The reaction solution was then discharged through the lower discharge port into a beaker containing 500 ml of ethanol. After discharge, the solid polymer was filtered and dried.

[0088] The molecular weight, molecular weight distribution, polymerization activity, long chain branch content (I 10 / I 2 ) and other performance data of the tested polymers are shown in Table 1.

[0089] Comparative Example 1

[0090] The polymerization of ethylene and 1-octene was carried out by the above method, except that catalyst X (structure as follows) was used. The synthesis method of catalyst X is described in WO2004044018A2.

[0091]

[0092] Table 1:

[0093]

[0094] As can be seen from Table 1, catalysts A, B, and C have higher polymerization activity under high temperature polymerization conditions than catalyst X in the comparative example. 10 From the data comparison of / I2, it can be seen that the obtained polymer has obvious shear thinning characteristics, which means that the polymer prepared by the invention contains a high proportion of long chain branches.

Claims

1. A metallocene catalyst having a structure as shown in Formula I: In the formula, M is selected from titanium, zirconium or hafnium; X is selected from Cl, Br, methyl, benzyl or dimethylamino; R1-R4 are each independently selected from hydrogen or C1-C10 alkyl, and R1-R4 are the same or different; R5 and R6 are each independently selected from F, methyl, ethyl, isopropyl, tert-butyl or trifluoromethyl, and R5 and R6 are the same or different.

2. The metallocene catalyst according to claim 1, characterized in that M is zirconium; X is Cl or methyl; R1-R4 are methyl; R5 and R6 are each independently methyl or tert-butyl, and R5 and R6 are the same or different.

3. The metallocene catalyst according to claim 1, characterized in that One or more compounds having the structures shown in the following formula AC:

4. A method for preparing the metallocene catalyst according to claim 1 or 2, characterized in that: The following steps are involved: Under nitrogen protection, in tetrahydrofuran solvent, the compound represented by formula II is reacted with n-butyl lithium at -78-30°C for 1-10 hours, and then a metal halide M is added and complexed at -78-30°C for 1-10 hours to prepare the metallocene catalyst represented by formula I; Wherein, the compound structure shown in formula II is wherein R1-R6 are the same as R1-R6 in formula I.

5. The preparation method according to claim 4, characterized in that The method comprises the following steps: under nitrogen protection, in tetrahydrofuran solvent, reacting the compound represented by formula II with n-butyl lithium at -30-0°C for 1-6 hours, then adding M metal halide and carrying out complex reaction at -30-0°C for 1-6 hours to prepare the metallocene catalyst represented by formula I.

6. The preparation method according to claim 4, characterized in that The molar ratio of the compound represented by formula II to n-butyl lithium and M metal halide is 1:(1-2):(1-2); The M metal halide is selected from the halide of titanium, zirconium or hafnium; The concentration of the compound represented by formula II in tetrahydrofuran is 0.01-1 mol / L.

7. The preparation method according to claim 6, characterized in that The molar ratio of the compound represented by formula II to n-butyl lithium and M metal halide is 1:(1-1.5):(1-1.5).

8. The preparation method according to claim 6, characterized in that The M metal halide is selected from zirconium or hafnium chloride.

9. The preparation method according to claim 6, characterized in that The concentration of the compound represented by formula II in tetrahydrofuran is 0.05-0.2 mol / L.

10. The preparation method according to claim 4, characterized in that The compound represented by formula II is prepared by the following method, which comprises the following steps: 1) Under nitrogen protection, compound 1 is reacted with n-butyl lithium and compound 2 to obtain compound 3; 2) Under nitrogen protection, compound 3 is reacted with n-butyl lithium and compound 4 to obtain compound 5, i.e., the compound represented by formula II; The reaction formula of the preparation process is as follows: wherein R1-R6 are the same as R1-R6 in formula I.

11. The preparation method according to claim 10, characterized in that: In step 1), the molar ratio of compound 1 to n-butyl lithium and compound 2 is 1:(1-1.5):(1-2); In step 1), the reaction can be carried out in a solvent environment, wherein the solvent is selected from at least one of toluene, diethyl ether, and THF; The concentration of compound 1 in the solvent is 0.01-1 mol / L; In step 1), the reaction temperature is -78-25°C and the reaction time is 1-10 hours.

12. The preparation method according to claim 11, characterized in that The molar ratio of the compound 1 to n-butyl lithium and the compound 2 is 1:(1-1.2):(1-1.2).

13. The preparation method according to claim 11, characterized in that The concentration of the compound 1 in the solvent is 0.05-0.2 mol / L.

14. The preparation method according to claim 11, characterized in that The reaction in step 1) is carried out at a temperature of -30-0°C for 1-4 hours.

15. The preparation method according to claim 11, characterized in that The reaction is carried out in two stages. First, compound 1 is reacted with n-butyl lithium for 1-2 hours, and then compound 2 is added and the reaction is continued for 1-6 hours.

16. The preparation method according to claim 10, characterized in that In step 2), the molar ratio of compound 3 to n-butyl lithium and compound 4 is 1:(1-2):(1-2); In step 2), the reaction can be carried out in a solvent environment, wherein the solvent is selected from at least one of toluene, diethyl ether, and THF; The concentration of compound 3 in the solvent is 0.01-1 mol / L; In step 2), the reaction temperature is -78-30°C and the reaction time is 1-10 hours.

17. The preparation method according to claim 16, characterized in that The molar ratio of the compound 3 to n-butyl lithium and the compound 4 is 1:(1-1.2):(1-1.2).

18. The preparation method according to claim 16, characterized in that The concentration of the compound 3 in the solvent is 0.05-0.2 mol / L.

19. The preparation method according to claim 16, characterized in that Step 2) The reaction temperature is -30-0°C and the reaction time is 1-4 hours.

20. The preparation method according to claim 16, characterized in that The reaction is carried out in two stages. First, compound 3 is reacted with n-butyl lithium for 1-2 hours, and then compound 4 is added and the reaction is continued for 1-6 hours.

21. The metallocene catalyst according to any one of claims 1 to 3 or the metallocene catalyst prepared by the preparation method according to any one of claims 4 to 20 is suitable for catalyzing the polymerization of α-olefins, wherein the α-olefin is selected from C2-C20 α-olefins.

22. The metallocene catalyst according to claim 21 is suitable for C2, C4, C6, and C8 α-olefins.

23. A method for olefin polymerization, characterized in that: The method comprises the following steps: catalyzing the polymerization reaction of ethylene and α-olefin to prepare a polyolefin product under the combined action of the metallocene catalyst described in any one of claims 1 to 3 or the metallocene catalyst prepared by the preparation method described in any one of claims 4 to 20 and a co-catalyst.

24. The olefin polymerization method according to claim 23, characterized in that The co-catalyst is selected from methylaluminoxane or trioctyl aluminum modified methylaluminoxane; The molar ratio of the metallocene catalyst to the co-catalyst is 1:(1-10000); The amount of the metallocene catalyst is 10% of the molar amount of the α-olefin -7 -10 -3 %; The polymerization reaction temperature is 100-250°C and the time is 0.05-1h; The pressure of the ethylene feed is 1-5 MPa.

25. The olefin polymerization method according to claim 24, characterized in that The molar ratio of the metallocene catalyst to the co-catalyst is 1:(100-1000).

26. The olefin polymerization method according to claim 24, characterized in that The polymerization reaction temperature is 120-200° C. and the time is 0.05-0.1 h.

27. The olefin polymerization method according to claim 24, characterized in that The pressure of the ethylene feed is 2-4 MPa.

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