Polyolefin catalyst, preparation method thereof and olefin polymerization method

Abstract

The invention discloses a polyolefin catalyst, a preparation method thereof and an olefin polymerization method. R1 and R8 are selected from hydrogen atoms and respectively meet the following conditions: 6.0 ppm < = delta1 < = 6.8 ppm, 6.0 ppm < = delta8 < = 6.8 ppm, and delta1 and delta8 are respectively chemical shifts of R1 and R8 in hydrogen spectrum nuclear magnetism of the catalyst. The catalyst can catalyze copolymerization of ethylene / alpha-olefin with high activity.

Description

Technical Field

[0001] The invention belongs to the field of polyolefins, and in particular relates to a polyolefin catalyst. Background Art

[0002] Polyolefin materials are widely used in packaging, automobiles, construction, electronics and other fields. In polyolefin production, catalysts are the core elements and greatly affect production efficiency and product performance. High-efficiency catalysts can improve polymerization activity and produce more polyolefin products per unit of catalyst, thereby achieving the purpose of cost reduction. At the same time, polymer performance indicators such as molecular weight, melting point, etc. should be precisely controlled to meet different application scenarios.

[0003] Patent CN118930572A discloses a series of sulfide-amine coordinated titanium zirconium hafnium metal catalysts for high-temperature solution polymerization of olefins, and successfully synthesized polyolefin elastomer POE. The catalyst has good polymerization activity at 160°C.

[0004] Patent CN1121079A discloses a supported catalyst for producing polyolefins by gas phase process or slurry process, which reduces the amount of solvent used, but involves a complicated loading process and high production cost.

[0005] It is necessary to develop a highly active catalyst to reduce the production cost of polyolefins and improve the market competitiveness of products. Summary of the invention

[0006] The invention provides a polyolefin catalyst and a preparation method thereof, and an olefin polymerization method. The catalyst has high activity and can reduce the production cost of polyolefin.

[0007] In one aspect, the present invention provides a polyolefin catalyst, the chemical structure of which comprises a fluorenyl ligand, a cyclopentadienyl ligand, a bridging structure and a metal part.

[0008] As a preferred embodiment, the polyolefin catalyst has the general structural formula shown in Formula I,

[0009]

[0010] Among them, R 1 and R 8 All are selected from hydrogen atoms and meet the following conditions: 6.0ppm≤δ 1 ≤6.8ppm,6.0ppm≤δ 8 ≤6.8ppm,δ 1 and δ 8 R 1 , R 8 Chemical shifts in the catalyst's H NMR spectrum;

[0011] R 2 , R3 , R 4 , R 5 , R 6 , R 7 , R 9 , R 10 , R 11 , R 12 , R 13 and R 14 are independently selected from hydrogen atoms, halogens, C 1 ~C 20 Alkyl, C 6 ~C 20 Aryl, C 1 ~C 20 Alkyl substituted C 6 ~C 20 Aryl, C 6 ~C 20 Aryl substituted C 1 ~C 20 Alkyl, C 1 ~C 20 Alkoxy, C 6 ~C 20 Aryloxy, C 1 ~C 20 Silane group;

[0012] L is selected from atoms C, Si, Ge;

[0013] M is selected from titanium, zirconium, and hafnium;

[0014] X is selected from halogen, C 1 ~C 20 Alkyl, C 6 ~C 20 Aryl substituted C 1 ~C 10 alkyl.

[0015] As a scheme, in Formula I, R 2 , R 3 , R 4 , R 5 , R 6 and R 7 Any two or more groups may be linked to form a ring.

[0016] As a preferred embodiment, the polyolefin catalyst of the present invention comprises one or more of the following compounds:

[0017]

[0018] In an optional embodiment, the hydrogen spectrum nuclear magnetic resonance testing method is to dissolve the polyolefin catalyst in anhydrous deuterated benzene, and then encapsulate it in a nuclear magnetic resonance tube, and perform hydrogen spectrum testing using a nuclear magnetic resonance spectrometer, the instrument brand is BrukerAVANCE III 400M.

[0019] The present invention provides a method for preparing the polyolefin catalyst, comprising the following steps:

[0020]

[0021] 1) Dissolve compound 1 in an organic solvent and set the temperature to T 1 ; Slowly add the lithium reagent dropwise, the reaction time is t 1 , obtain a lithium salt solution; T 1 At a temperature of T, compound 2 is slowly added dropwise to the lithium salt solution, and then the temperature is adjusted to T 2 , reaction time t 2 ; After treatment, an alcohol solvent is added to the solution, and the mixture is stirred thoroughly to obtain a powder suspension, which is filtered and washed to obtain compound 3;

[0022] 2) Dissolve compound 3 in an organic solvent and set the temperature to T 3 ; Slowly add the lithium reagent dropwise, the reaction time is t 3 , and obtain a dilithium salt solution; T 3 At a temperature of T, add compound M to the dilithium salt solution, and then adjust the temperature to T 4 , reaction time t 4 , to obtain a powder suspension; after post-treatment, filtering and washing, the catalyst of formula I is obtained.

[0023] In an optional embodiment, the organic solvent is selected from one or more of tetrahydrofuran, diethyl ether, propyl ether, butyl ether, toluene and xylene.

[0024] In an optional embodiment, the lithiation agent is selected from one or more of methyllithium, ethyllithium, n-butyllithium, and phenyllithium.

[0025] In an optional embodiment, the M compound is selected from one or more of titanium tetrachloride, zirconium tetrachloride, hafnium tetrachloride, dimethyl titanium dichloride, dimethyl zirconium dichloride, dimethyl hafnium dichloride, tetrabenzyl titanium, tetrabenzyl zirconium, tetrabenzyl hafnium, tetrahydrofuran titanium tetrachloride, tetrahydrofuran zirconium tetrachloride, and tetrahydrofuran hafnium tetrachloride.

[0026] In an optional embodiment, the alcohol solvent is selected from one or more of methanol, ethanol, and isopropanol.

[0027] In an optional embodiment, the T 1The range is -20~60℃, T 2 The range is -20~60℃, T 3 The range is -20~80℃, T 4 The range is -20~60℃.

[0028] In an optional embodiment, the t 1 The range is 0.5~18h, t 2 The range is 0.5~10h, t 3 The range is 0.5~36h, t 4 The range is 0.5~18h.

[0029] In another aspect, the present invention provides use of the polyolefin catalyst in olefin polymerization.

[0030] In an optional embodiment, a method for olefin polymerization comprises the following steps: allowing olefin monomers to undergo polymerization reaction in an organic solvent in the presence of the polyolefin catalyst and co-catalyst described in the present invention.

[0031] In an optional embodiment, the co-catalyst is selected from one or more of an organic aluminum co-catalyst or a boron co-catalyst.

[0032] In an optional embodiment, the organic aluminum auxiliary agent is selected from at least one of aluminoxane, alkyl aluminum, and alkyl aluminum chloride.

[0033] In an optional embodiment, the aluminoxane includes one or more of methylaluminoxane, modified methylaluminoxane, ethylaluminoxane, n-propylaluminoxane, isopropylaluminoxane, n-butylaluminoxane, isobutylaluminoxane, neopentylaluminoxane, n-hexylaluminoxane, and n-octylaluminoxane.

[0034] In an optional embodiment, the modified methylaluminoxane includes one or more of ethylaluminum-modified methylaluminoxane, butylaluminum-modified methylaluminoxane, and octylaluminum-modified methylaluminoxane.

[0035] In an optional embodiment, the alkylaluminum includes one or more of trimethylaluminum, triethylaluminum, tri-n-propylaluminum, triisopropylaluminum, tri-n-butylaluminum, triisobutylaluminum, tri-n-hexylaluminum, triisohexylaluminum, tri-n-octylaluminum, and triisooctylaluminum.

[0036] In an optional embodiment, the alkylaluminum chloride includes one or more of methylaluminum dichloride, ethylaluminum dichloride, dimethylaluminum monochloride, diethylaluminum monochloride, di-n-butylaluminum monochloride, diisobutylaluminum monochloride, n-butylaluminum dichloride, isobutylaluminum dichloride, sesqui-n-butylaluminum chloride, sesquiethylaluminum chloride, sesquimethylaluminum chloride, and sesquiisobutylaluminum chloride.

[0037] In an optional embodiment, the boron auxiliary agent is selected from one or more of tris(pentafluorophenyl)boron, trityltetrakis(pentafluorophenyl)borate, triphenylmethyltetrakis(pentafluorophenyl)borate, triphenylformiumtetrakis(pentafluorophenyl)borate, tetrakis(pentafluorophenyl)boric acid-methyldi-(octadecyl)ammonium salt, N,N-dioctadecylmethylaminotetrakis(pentafluorophenyl)borate, N,N-dimethylaniliniumtetrakis(pentafluorophenyl)borate, dioctadecylmethyltertiaryammoniumtetrakis(pentafluorophenyl)borate, and dihydrogenated tallow methyltertiaryammoniumtetrakis(pentafluorophenyl)borate.

[0038] In an optional embodiment, the molar ratio of the Al element in the organoaluminum additive to the M element in the polyolefin catalyst is 3 to 2000. Further optionally, the molar ratio of the Al element in the organoaluminum to the M element in the polyolefin catalyst is 100 to 1000.

[0039] In an optional embodiment, the molar ratio of the B element in the boron adjuvant to the M element in the polyolefin catalyst is 0 to 200. Further optionally, the molar ratio of the B element in the organic boron to the M element in the polyolefin catalyst is 0 to 100.

[0040] In an optional embodiment, the olefin monomers include ethylene and α-olefins. The α-olefins are selected from one or more of propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, cyclopentene, cyclohexene, norbornene, phenylnorbornene, and styrene.

[0041] In an optional embodiment, the polymerization reaction temperature is 20-260° C., and the polymerization reaction pressure is 0.1-50 MPa.

[0042] Beneficial effects of the present invention: The polyolefin catalyst provided by the present invention comprises a fluorene group, a cyclopentadienyl group and a bridging structure connecting them. 1 and R 8 The chemical shift in hydrogen nuclear magnetic resonance can produce catalysts with excellent performance, which are applied to olefin polymerization, especially ethylene / α-olefin copolymerization, and show high activity characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is the NMR spectrum of the catalyst obtained in Example 1;

[0044] Figure 2 is the NMR spectrum of the catalyst obtained in Example 2;

[0045] Figure 3This is the NMR spectrum of the catalyst obtained in Example 3;

[0046] Figure 4 This is the NMR spectrum of the catalyst obtained in Comparative Example 1;

[0047] Figure 5 This is the NMR spectrum of the catalyst obtained in Comparative Example 2. DETAILED DESCRIPTION

[0048] The present invention is further described below by means of specific examples. The examples described in the present invention are only used to illustrate the present invention and do not limit the scope of the present invention.

[0049] The materials and reagents used in the following examples were purchased from commercial sources, including:

[0050] THF: AR, aladdin;

[0051] Ethanol: AR, aladdin;

[0052] n-Hexane: AR, aladdin;

[0053] n-Butyl lithium: AR, Innochem;

[0054] Dimethyldichlorosilane: AR, Innochem;

[0055] Zirconium tetrachloride: AR, Innochem;

[0056] Deuterated benzene: AR, Innochem;

[0057] Modified methylaluminoxane (MMAO): Albemarle;

[0058] Trityl tetrakis(pentafluorophenyl)borate: AR, Aladdin;

[0059] Ethylene: 99.9%, Beijing Yanshan Petrochemical Company;

[0060] 1-Octene: 98%, Beijing Yanshan Petrochemical Company;

[0061] 1-Hexene: 98%, Beijing Yanshan Petrochemical Company;

[0062] Isopar E: ExxonMobil Corporation.

[0063] Unless otherwise specified, the experimental methods used in the following examples and comparative examples are conventional methods.

[0064] Unless otherwise specified, the concentrations in the following examples and comparative examples are molar concentrations.

[0065] In the following examples and comparative examples, "eq" means molar equivalent.

[0066] The polymerization activities of the polymers described in the following examples and comparative examples are calculated according to the following formula: polymerization activity = polymer mass / (metal content in catalyst×polymerization time).

[0067] In all the following examples and comparative examples, the chemical reactions involved were carried out after nitrogen substitution.

[0068] [Example 1]

[0069] Preparation of Catalyst 1:

[0070]

[0071] 1) Dissolve 2 g of compound 1 (1 eq) in 100 ml of anhydrous tetrahydrofuran, replace with nitrogen three times, and cool to 0°C; slowly add 1.62 ml of n-butyl lithium (2.5 M, 1 eq) dropwise, and continue stirring for 3 h to obtain a lithium salt solution; at 0°C, slowly add 1.18 g of compound 2 (1 eq) dropwise to the lithium salt solution, then heat to 25°C and continue stirring for 16 h; post-treatment, add 10 ml of ethanol to the solution, stir for 5 h, and obtain a powder suspension, which is filtered and washed with 50 ml of ethanol to obtain compound 3.

[0072] 2) Dissolve 0.8 g of compound 3 (1 eq) in 50 ml of anhydrous tetrahydrofuran, replace with nitrogen three times, and set the temperature to 50° C.; slowly add 0.82 ml of n-butyl lithium (2.5 M, 2 eq) dropwise, and continue stirring for 8 h to obtain a dilithium salt solution; add 0.24 g of zirconium tetrachloride (1 eq) to the dilithium salt solution at 25° C., and then continue stirring at 25° C. for 16 h to obtain a powder suspension; post-treat, filter, and wash with 50 ml of n-hexane to obtain catalyst 1.

[0073] 3) NMR characterization: 15 mg of the catalyst was dissolved in 0.5 ml of anhydrous deuterated benzene and subjected to H NMR testing using a Bruker AVANCE III400M. The analysis results were: δ 1 =δ 8 =6.19.

[0074] [Example 2]

[0075] Preparation of Catalyst 2:

[0076]

[0077] 1) Dissolve 2 g of compound 1 (1 eq) in 100 ml of anhydrous tetrahydrofuran, replace with nitrogen three times, and cool to 0°C; slowly drop 4.12 ml of n-butyl lithium (2.5 M, 1 eq), continue stirring for 3 h to obtain a lithium salt solution; at 0°C, slowly drop 3 g of compound 2 (1 eq) into the lithium salt solution, then raise the temperature to 25°C and continue stirring for 16 h; post-treatment, add 10 ml of ethanol to the solution, stir for 5 h to obtain a powder suspension, filter, and wash with 50 ml of ethanol to obtain compound 3.

[0078] 2) Dissolve 1 g of compound 3 (1 eq) in 50 ml of anhydrous tetrahydrofuran, replace with nitrogen three times, and cool to 0°C; slowly drop 1.65 ml of n-butyl lithium (2.5 M, 2 eq) and continue stirring for 16 h to obtain a dilithium salt solution; add 0.48 g of zirconium tetrachloride (1 eq) to the dilithium salt solution at 0°C, then raise the temperature to 25°C and continue stirring for 16 h to obtain a powder suspension; post-treat, filter, and wash with 50 ml of n-hexane to obtain catalyst 2.

[0079] 3) NMR characterization: 15 mg of the catalyst was dissolved in 0.5 ml of anhydrous deuterated benzene and subjected to H NMR testing using a Bruker AVANCE III400M. The analysis results were: δ 1 =δ 8 =6.41.

[0080] [Example 3]

[0081] Preparation of Catalyst 3:

[0082]

[0083] 1) Dissolve 2 g of compound 1 (1 eq) in 100 ml of anhydrous tetrahydrofuran, replace with nitrogen three times, and cool to 0°C; slowly add 1.47 ml of n-butyl lithium (2.5 M, 1 eq) dropwise, and continue stirring for 3 h to obtain a lithium salt solution; at 0°C, slowly add 0.85 g of compound 2 (1 eq) dropwise to the lithium salt solution, then heat to 25°C and continue stirring for 16 h; post-treatment, add 10 ml of ethanol to the solution, stir for 5 h, and obtain a powder suspension, which is filtered and washed with 50 ml of ethanol to obtain compound 3.

[0084] 2) Dissolve 0.6 g of compound 3 (1 eq) in 50 ml of anhydrous tetrahydrofuran, replace with nitrogen three times, and set the temperature to 35°C; slowly add 0.62 ml of n-butyl lithium (2.5 M, 2 eq) dropwise, and continue stirring for 10 hours to obtain a dilithium salt solution; add 0.18 g of zirconium tetrachloride (1 eq) to the dilithium salt solution at 35°C, and then continue stirring at 35°C for 10 hours to obtain a powder suspension; post-treat, filter, and wash with 50 ml of n-hexane to obtain catalyst 3.

[0085] 3) NMR characterization: 15 mg of the catalyst was dissolved in 0.5 ml of anhydrous deuterated benzene and subjected to H NMR testing using a Bruker AVANCE III400M. The analysis results were: δ 1 =δ 8 =6.71.

[0086] [Example 4]

[0087] A method for preparing an ethylene / 1-octene copolymer comprises the following steps:

[0088] To 500 mL of Isopar E solvent, 2 μmol of the polyolefin catalyst Catalyst 1 prepared in Example 1, 150 ml of 1-octene and MMAO at a molar ratio of Al / Zr=800 were added, the temperature was raised to 140° C., 3 MPa of ethylene gas was introduced, and the polymerization reaction was carried out for 5 minutes. After the reaction was completed, the ethylene was vented and replaced with nitrogen three times. The reaction solution was discharged into ethanol, and the precipitate was collected and dried to obtain an ethylene / 1-octene copolymer.

[0089] [Example 5]

[0090] Ethylene / 1-octene copolymer was prepared according to the method provided in Example 4, except that MMAO was added at a molar ratio of Al / Zr=100, and trityltetrakis(pentafluorophenyl)borate was added at a molar ratio of B / Zr=100.

[0091] [Example 6]

[0092] Ethylene / 1-octene copolymer was prepared according to the method provided in Example 4, except that the polyolefin catalyst Catalyst 2 prepared in Example 2 was used, and Al / Zr=500, and the ethylene gas pressure was 5 MPa.

[0093] [Example 7]

[0094] The copolymer was prepared according to the method provided in Example 4, except that the polyolefin catalyst Catalyst 2 prepared in Example 2 was used, 1-octene was replaced by 1-hexene, and the polymerization temperature was 160°C.

[0095] [Example 8]

[0096] Ethylene / 1-octene copolymer was prepared according to the method provided in Example 4, except that the polyolefin catalyst Catalyst 2 prepared in Example 2 was used, and the molar ratio of Al / Zr=1000.

[0097] [Example 9]

[0098] Ethylene / 1-octene copolymer was prepared according to the method provided in Example 4, except that the polyolefin catalyst Catalyst 3 prepared in Example 3 was used, and the molar ratio of Al / Zr was 1500.

[0099] [Example 10]

[0100] Ethylene / 1-octene copolymer was prepared according to the method provided in Example 4, except that the polyolefin catalyst Catalyst 3 prepared in Example 3 was used and the polymerization temperature was 80°C.

[0101] [Comparative Example 1]

[0102] Preparation of Compound 1:

[0103]

[0104] 1) Dissolve 2 g of compound 1 (1 eq) in 100 ml of anhydrous tetrahydrofuran, replace with nitrogen three times, and cool to 0°C; slowly add 2.12 ml of n-butyl lithium (2.5 M, 1 eq) dropwise, and continue stirring for 3 h to obtain a lithium salt solution; at 0°C, take 1.4 g of compound 2 (1 eq) and slowly add dropwise to the lithium salt solution, then raise the temperature to 25°C and continue stirring for 16 h; post-treatment, add 10 ml of ethanol to the solution, stir for 5 h, and obtain a powder suspension, which is filtered and washed with 50 ml of ethanol to obtain compound 3.

[0105] 2) Dissolve 0.6 g of compound 3 (1 eq) in 50 ml of anhydrous tetrahydrofuran, replace with nitrogen three times, and cool to 0°C; slowly add 0.79 ml of n-butyl lithium (2.5 M, 2 eq) dropwise, and continue stirring for 16 h to obtain a dilithium salt solution; add 0.23 g of zirconium tetrachloride (1 eq) to the dilithium salt solution at 0°C, then raise the temperature to 25°C and continue stirring for 16 h to obtain a powder suspension; post-treat, filter, and wash with 50 ml of n-hexane to obtain the catalyst compound 1.

[0106] 3) NMR characterization: 15 mg of the catalyst was dissolved in 0.5 ml of anhydrous deuterated benzene and subjected to H NMR testing using a Bruker AVANCE III400M. The analysis results were: δ 1 =δ 8 =5.68.

[0107] An ethylene / 1-octene copolymer was prepared according to the method provided in Example 4, except that the catalyst Compound 1 was used.

[0108] [Comparative Example 2]

[0109] Preparation of Compound 2:

[0110]

[0111] 1) Dissolve 2 g of compound 1 (1 eq) in 50 ml of anhydrous THF, and slowly drop 3.16 ml of n-butyl lithium (2.5 M, 1.1 eq) under an ice-water bath; after the addition, continue stirring at low temperature for 3 h, then add 0.51 g (0.5 eq) of dimethyldichlorosilane and stir for 6 h; quench with water to separate the phases, concentrate, slurry and purify to obtain compound 2.

[0112] 2) Take 0.6g of compound 2 (1eq) and add it to 20ml of anhydrous toluene. Slowly add 0.86ml of n-butyl lithium (2.2eq, 2.5M) dropwise under an ice-water bath. After the addition is completed, remove the ice-water bath, return to 25°C, and continue stirring for 3h. Add 20ml of ultra-dry n-hexane to the reaction solution, stir well, filter and dry to obtain compound 3.

[0113] 3) Disperse 0.6 g of compound 3 in 20 ml of toluene and stir thoroughly; add 0.22 g of zirconium tetrachloride (1 eq) at 25°C and stir for 3 h; filter the solution, wash with n-hexane, and dry to obtain compound 2.

[0114] 4) NMR characterization: 15 mg of the catalyst was dissolved in 0.5 ml of anhydrous deuterated benzene and subjected to H NMR testing using a Bruker AVANCE III400M. The analysis results were: δ 1 =δ 8 =7.76.

[0115] An ethylene / 1-octene copolymer was prepared according to the method provided in Example 4, except that the catalyst Compound 2 was used.

[0116] The polyolefin materials prepared in the examples and comparative examples were subjected to polymerization evaluation, and the results are shown in the following table:

[0117] Table 1 Experimental results

[0118]

[0119]

[0120] It can be seen from the above table that the catalyst prepared in the example has higher polymerization activity, indicating that through the regulation of chemical shift, the catalyst provided by the present invention can catalyze the copolymerization of ethylene / α-olefin with high activity, which is beneficial to reducing the production cost of polyolefins and is suitable for industrial production.

[0121] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A polyolefin catalyst having the general structural formula shown in Formula I, in, R1 and R8 are both hydrogen atoms and satisfy the following conditions: 6.0ppm≤δ1≤6.8ppm, 6.0ppm≤δ8≤6.8ppm, δ1 and δ8 are the chemical shifts of R1 and R8 in the catalyst hydrogen spectrum nuclear magnetic resonance respectively; R2, R3, R4, R5, R6, R7, R9, R 10 , R 11 , R 12 , R 13 and R 14 Each independently selected from hydrogen atom, halogen, C1-C 20 Alkyl, C6~C 20 Aryl, C1~C 20 Alkyl substituted C6~C 20 Aryl, C6~C 20 Aryl substituted C1~C 20 Alkyl, C1~C 20 Alkoxy, C6~C 20 Aryloxy, C1~C 20 Silane group; L is selected from atoms C, Si, Ge; M is selected from titanium, zirconium, and hafnium; X is selected from halogen, C1~C 20 Alkyl, C6~C 20 Aryl substituted C1~C 10 alkyl.

2. The polyolefin catalyst according to claim 1, characterized in that Any two or more groups of R2, R3, R4, R5, R6 and R7 are connected to form a ring.

3. The polyolefin catalyst according to claim 1, characterized in that The polyolefin catalyst comprises one or more of the following compounds:

4. A method for preparing a polyolefin catalyst according to any one of claims 1 to 3, comprising the following steps: 1) Compound 1 Dissolve in an organic solvent and set the temperature to T1; slowly add the lithium reagent dropwise for a reaction time of t1 to obtain a lithium salt solution; at the temperature of T1, take compound 2 Slowly add it dropwise to the lithium salt solution, then adjust the temperature to T2, and the reaction time is t2; post-treatment, add an alcohol solvent to the solution, stir it thoroughly to obtain a powder suspension, filter and wash it to obtain compound 3 2) dissolving compound 3 in an organic solvent and setting the temperature to T3; slowly dropping a lithiation reagent for a reaction time of t3 to obtain a dilithium salt solution; adding compound M to the dilithium salt solution at temperature T3, and then adjusting the temperature to T4 for a reaction time of t4 to obtain a powder suspension; post-processing, filtering, and washing to obtain a catalyst of formula I.

5. The method according to claim 4, characterized in that The lithium reagent is selected from one or more of methyl lithium, ethyl lithium, n-butyl lithium, and phenyl lithium.

6. The method according to claim 4, characterized in that The range of T1 is -20 to 60°C, the range of T2 is -20 to 60°C, the range of T3 is -20 to 80°C, and the range of T4 is -20°C to 60°C.

7. The method according to claim 4, characterized in that The range of t1 is 0.5 to 18 hours, the range of t2 is 0.5 to 10 hours, the range of t3 is 0.5 to 36 hours, and the range of t4 is 0.5 to 18 hours.

8. The method according to claim 4, characterized in that The M compound is selected from one or more of titanium tetrachloride, zirconium tetrachloride, hafnium tetrachloride, dimethyl titanium dichloride, dimethyl zirconium dichloride, dimethyl hafnium dichloride, tetrabenzyl titanium, tetrabenzyl zirconium, tetrabenzyl hafnium, tetrahydrofuran titanium tetrachloride, tetrahydrofuran zirconium tetrachloride, and tetrahydrofuran hafnium tetrachloride.

9. A method for olefin polymerization comprising the steps of: In the presence of the polyolefin catalyst and the co-catalyst according to any one of claims 1 to 3, olefin monomers are polymerized in an organic solvent.

10. The method according to claim 9, characterized in that The co-catalyst is selected from one or more of an organic aluminum promoter or a boron promoter; and / or, the olefin monomer includes ethylene and an α-olefin; the α-olefin is selected from one or more of propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, cyclopentene, cyclohexene, norbornene, phenylnorbornene, and styrene.

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