Bridged compound, catalyst composition and application thereof

Abstract

The invention relates to the technical field of ethylene polymerization, and provides a bridging compound, a catalyst composition and application thereof. The bridged compound comprises a bridged ligand as shown in a formula (I) and a bridged complex as shown in a formula (II), # imgabs0, R1, R2, R3 and R4 are the same or different and are independently selected from hydrogen, alkyl, alkoxy and halogen, and R1, R2, R3 and R4 are the same or different and are independently selected from hydrogen, alkyl, alkoxy and halogen; r5 is selected from hydrogen, alkyl, cycloalkyl, alkoxy and aryl; m is selected from transition metals; x is selected from halogen, and n is an integer of 1-3; hydrogen on carbon of alkyl, cycloalkyl, alkoxy and aryl is optionally substituted by one or more substituents. The bridging type compound provided by the invention is novel in structure; the catalyst composition can effectively catalyze an ethylene polymerization reaction, and the total selectivity of 1-hexene and 1-octene in a product is high.

Description

Technical Field

[0001] The present invention relates to the technical field of ethylene polymerization, and more specifically to a bridged compound, a catalyst composition and application thereof. Background Art

[0002] 1-Hexene and 1-octene are important organic raw materials and chemical intermediates, mainly used in the production of high-quality polyethylene (PE), lubricant base oil, plasticizers, detergents and other fields. Among them, linear low-density polyethylene (LLDPE) produced by copolymerization of 1-hexene or 1-octene with ethylene can significantly improve the various properties of PE, especially the mechanical properties, optical properties, tear strength and impact strength of polyethylene. The product is very suitable for packaging films and agricultural covering films such as greenhouses and sheds. The polyolefin plastomers and polyolefin elastomers produced by copolymerization of 1-octene and ethylene currently have a large market consumption and demand. With the continuous development of the polyolefin industry, the demand for high-carbon α-olefins such as 1-hexene or 1-octene is growing rapidly worldwide.

[0003] Ethylene oligomerization is one of the most important reactions in the olefin polymerization industry. Through oligomerization, cheap small molecule ethylene can be converted into high value-added products, namely α-olefins of different length chains. Since the 1970s, the research on olefin polymerization and oligomerization catalyzed by transition metal complexes has gradually attracted the attention of scientists. People have begun to study new catalysts and improve existing catalysts to improve the activity of catalysts and the selectivity of catalytic products. Among the many explorations, the earliest, fastest-growing and most concentrated one is the nickel-based cationic catalytic system, such as the long-reported US patents US3686351A and US3676523A, and the Shell SHOP process based on the patented technology. The OP bridged ligand is involved in the Shell SHOP process, but the synthesis steps are complicated and the stability is poor. Later, many patents such as OO, PN, PP and NN type coordinated nickel catalysts were developed, such as JP11060627, WO9923096A1, CN1401666A, CN1769270A, etc. However, the catalysts obtained from the above patents generally have the disadvantage that the preparation method is relatively complicated.

[0004] Sasol's patent WO2004056478A1 discloses a PNP skeleton catalyst. In the ethylene tetramerization reaction, C 8 Component selectivity is about 66wt%, C 6The component selectivity is about 21wt%, of which the content of 1-hexene in the C6 component is only 82wt%, and the total selectivity of 1-hexene and 1-octene is about 84wt%. The US20100137669A1 patent discloses a PCCP symmetric skeleton catalyst, which is more stable than the PNP system in the ethylene tetramerization reaction, but the total selectivity of 1-hexene and 1-octene does not exceed 85wt%.

[0005] In the above reaction systems, C 6 Although the by-products such as cycloolefins and cyclized products in the product can be removed by separation and purification, it is not conducive to the economic efficiency of the entire process. Therefore, how to maintain a high 1-octene content in the reaction product while increasing the 1-hexene content in C 6 The content of the components, thereby improving the economy of the process, is of certain challenge. Summary of the invention

[0006] The object of the present invention is to provide a bridged compound and a catalyst composition to solve the technical problem in the prior art that the total selectivity of 1-hexene and 1-octene in ethylene oligomerization products is not ideal.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] In a first aspect, the present invention provides a bridged compound, comprising a bridged ligand as shown in formula (I) or a bridged complex as shown in formula (II),

[0009]

[0010] Among them, R 1 , R 2 , R 3 , R 4 are the same or different and are independently selected from hydrogen, alkyl, alkoxy, halogen; R 5 Selected from hydrogen, alkyl, cycloalkyl, alkoxy, aryl; the hydrogen on the carbon of the alkyl, cycloalkyl, alkoxy, aryl is optionally substituted by one or more substituents; M is selected from transition metals; X is selected from halogens, and n is an integer of 1 to 3.

[0011] According to some embodiments of the present invention, the alkyl group is C 1 ~C 20 Alkyl, preferably C 1 ~C 10 Alkyl, more preferably C 1 ~C 6 alkyl.

[0012] According to some embodiments of the present invention, the cycloalkyl group is C 3 ~C20 Cycloalkyl, preferably C 3 ~C 10 Cycloalkyl, more preferably C 3 ~C 6 Cycloalkyl.

[0013] According to some embodiments of the present invention, the alkoxy group is C 1 ~C 20 Alkoxy, preferably C 1 ~C 10 Alkoxy, more preferably C 1 ~C 6 Alkoxy.

[0014] According to some embodiments of the present invention, the aryl group is C 6 ~C 20 Aryl, preferably C 6 ~C 12 Aryl, more preferably C 6 ~C 8 Aryl.

[0015] According to some embodiments of the present invention, the substituent is selected from C 1 ~C 20 Alkyl, C 3 ~C 20 Cycloalkyl, C 1 ~C 20 Alkoxy, C 6 ~C 20 Aryl.

[0016] According to some embodiments of the present invention, the substituent is selected from C 1 ~C 10 Alkyl, C 3 ~C 10 Cycloalkyl, C 1 ~C 10 Alkoxy, C 6 ~C 12 Aryl.

[0017] According to some embodiments of the present invention, the substituent is selected from C 1 ~C 6 Alkyl, C 3 ~C 6 Cycloalkyl, C 1 ~C 6 Alkoxy, C 6 ~C 12 Aryl.

[0018] According to some embodiments of the invention, the substituent is selected from at least one of methyl, ethyl, propyl, butyl, isobutyl, pentyl, isopentyl, hexyl, cyclopropyl, cyclopentyl, cyclohexyl, methoxy, ethoxy, propoxy, butoxy, phenyl, tolyl, ethylphenyl, propylphenyl, biphenyl and naphthyl.

[0019] In a second aspect, the present invention provides a method for preparing the bridged compound according to the first aspect, comprising:

[0020]

[0021] S1. Compound a, n BuLi and phosphorus trichloride undergo a first reaction in a first solvent to prepare compound b;

[0022] S2. Compound b, compound c and n BuLi undergoes a second reaction in a second solvent to produce compound d;

[0023] S3. Compound d, cuprous iodide, cesium carbonate and compound e undergo a third reaction in a third solvent to obtain a bridging ligand of formula (I);

[0024] And optionally S4. The bridging ligand represented by formula (I) and the transition metal salt MX n Carrying out a coordination reaction in a fourth solvent to obtain a bridged complex represented by formula (II);

[0025] Among them, R 1 , R 2 , R 3 , R 4 are the same or different and are independently selected from hydrogen, alkyl, alkoxy, halogen; R 5 Selected from hydrogen, alkyl, cycloalkyl, alkoxy, aryl; the hydrogen on the carbon of the alkyl, cycloalkyl, alkoxy, aryl is optionally substituted by one or more substituents; M is selected from transition metals; X is selected from halogens, and n is an integer of 1 to 3.

[0026] According to some embodiments of the present invention, in step S1, compound a, n The molar ratio of BuLi to phosphorus trichloride is 1:1-3:1-10, preferably 1:1-3:5-8, for example 1:2:5.

[0027] According to some embodiments of the invention, the first solvent comprises diethyl ether.

[0028] According to some embodiments of the present invention, in step S2, compound c, n The molar ratio of BuLi to compound b is 1:0.5-2:0.5-2, for example 1:1:1.

[0029] According to some embodiments of the invention, the second solvent comprises tetrahydrofuran (THF).

[0030] According to some embodiments of the present invention, in step S3, the molar ratio of compound d, cuprous iodide, cesium carbonate and compound e is 1:0.01-0.1:0.01-0.2:1-2, preferably 1:0.04-0.06:0.05-0.15:1-1.2, for example 1:0.05:0.1:1.1.

[0031] According to some embodiments of the present invention, the third solvent comprises N,N-dimethylformamide (DMF).

[0032] According to some embodiments of the present invention, in step S3, after the third reaction is completed, water is added, and an organic solvent is used for extraction to purify the organic phase to obtain a bridged ligand represented by formula (I).

[0033] According to some embodiments of the invention, the organic solvent comprises ethyl acetate or petroleum ether.

[0034] According to some embodiments of the present invention, in step S4, the molar ratio of the bridging ligand to the transition metal salt is 1:0.01-10, preferably 1:0.5-2, for example 1:1.

[0035] According to some embodiments of the invention, the fourth solvent comprises toluene.

[0036] In a third aspect, the present invention provides a catalyst composition, comprising the bridged compound described in the first aspect;

[0037] When the bridging compound is a bridging ligand as shown in formula (I), the catalyst composition comprises a bridging ligand as shown in formula (I), a transition metal compound and an aluminum-containing co-catalyst;

[0038] When the bridged compound is a bridged complex as shown in formula (II), the catalyst composition comprises the bridged complex as shown in formula (II) and an aluminum-containing co-catalyst.

[0039] According to some embodiments of the present invention, the aluminum-containing co-catalyst is an organic aluminum compound, preferably at least one selected from alkyl aluminum compounds, alkoxy aluminum compounds and alkyl aluminum chloride compounds, more preferably selected from at least one of methylaluminoxane, trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, diethylaluminum monochloride, ethylaluminum dichloride, ethylaluminumoxane and modified methylaluminumoxane, further preferably at least one selected from methylaluminumoxane, triethylaluminum and modified methylaluminumoxane.

[0040] According to some embodiments of the present invention, the transition metal compound is selected from at least one of compounds of chromium, molybdenum, iron, titanium, zirconium and nickel, preferably selected from at least one of chromium acetylacetonate, chromium isooctanoate, tri(tetrahydrofuran)chromium trichloride and di(tetrahydrofuran)chromium dichloride.

[0041] According to some embodiments of the present invention, the molar ratio of the transition metal compound, the bridging ligand represented by formula (I) and the aluminum-containing co-catalyst, calculated as transition metal, is 1:(0.1-10):(1-1000), preferably 1:(0.25-2):(10-700), and more preferably 1:(0.5-2):(100-500).

[0042] According to some embodiments of the present invention, in formula (II), M is selected from at least one of chromium, molybdenum, iron, titanium, zirconium and nickel.

[0043] According to some embodiments of the present invention, the molar ratio of the bridged complex represented by formula (II) to the aluminum-containing co-catalyst calculated as transition metal is 1:(1-1000), preferably 1:(10-700), and more preferably 1:(100-500).

[0044] In a fourth aspect, the present invention provides use of the catalyst composition described in the third aspect in an ethylene oligomerization reaction.

[0045] In a fifth aspect, the present invention provides a method for ethylene polymerization, comprising: in the presence of the catalyst composition described in the third aspect, continuously adding ethylene, hydrogen and an organic solvent into a reactor to carry out an ethylene polymerization reaction.

[0046] According to some embodiments of the present invention, the concentration of the catalyst composition is 0.1-10 μmol / L in terms of transition metal, based on the volume of the organic solvent. For example, when the transition metal is Cr, the concentration of the catalyst composition is 0.1-10 μmol / L in terms of Cr.

[0047] According to some embodiments of the present invention, the organic solvent comprises an aliphatic hydrocarbon compound and / or an aromatic hydrocarbon compound.

[0048] According to some embodiments of the present invention, the aliphatic hydrocarbon compound is selected from at least one of straight-chain alkanes, branched-chain alkanes and cycloalkanes; preferably at least one of pentane, heptane, hexane, cyclohexane and methylcyclohexane.

[0049] According to some embodiments of the present invention, the aromatic hydrocarbon compound is selected from at least one of benzene, toluene, xylene, monochlorobenzene, dichlorobenzene, trichlorobenzene, monochlorotoluene and derivatives thereof.

[0050] According to some embodiments of the present invention, in the above reaction, one or more of the catalyst compositions may be pre-mixed and then added to the reaction system together, or each component may be added to the reaction system separately.

[0051] According to some embodiments of the present invention, the volume ratio of hydrogen to ethylene is 1:(1-10000), preferably 1:(10-2000).

[0052] According to some embodiments of the present invention, the reaction temperature of the ethylene oligomerization reaction is 0 to 200°C, preferably 0 to 100°C, more preferably 30 to 100°C, and further preferably 40 to 75°C.

[0053] According to some embodiments of the present invention, the ethylene pressure of the ethylene oligomerization reaction is 0.1 to 20.0 MPa, preferably 0.5 to 10.0 MPa, and more preferably 2.0 to 6.0 MPa.

[0054] According to some embodiments of the present invention, the ethylene oligomerization reaction includes ethylene trimerization reaction and ethylene tetramerization reaction.

[0055] The beneficial effects of the present invention are at least:

[0056] (1) The bridged compound provided by the present invention has a novel structure, is simple to prepare and has low cost.

[0057] (2) The catalyst composition provided by the present invention includes a bridged compound, which can effectively catalyze the polymerization reaction of ethylene, has high catalyst activity, good product selectivity, and mild reaction conditions; and 6 The by-products such as cycloolefins and cyclized products in the product are significantly reduced, and the overall selectivity of 1-hexene and 1-octene is higher.

[0058] (3) The catalyst composition provided by the present invention has the characteristics of high catalytic activity and high selectivity, and has good industrial application prospects and economic value. DETAILED DESCRIPTION

[0059] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this patent in detail and do not limit the scope of protection of the present invention in any way.

[0060] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the raw materials, instruments and equipment used in the following examples, etc., can all be purchased on the market or can be obtained by existing methods; the reagent amounts, unless otherwise specified, are the reagent amounts used in conventional experimental operations; the experimental methods, unless otherwise specified, are all conventional methods.

[0061] In each embodiment and comparative example of the present invention, each performance data is tested according to the following test method:

[0062] (1) Nuclear magnetic resonance: The detection was performed using a Bruker AV400 nuclear magnetic resonance instrument; the detection conditions were: deuterated chloroform as the solvent.

[0063] (2) Room temperature test gas chromatography: Agilent 7890 chromatograph was used for detection; the detection conditions were: chromatographic column SE-54, high-purity nitrogen carrier gas, FID detector; the column temperature was raised using a two-step program.

[0064] It should be noted that, in the present invention, Bu is n-butyl, t Bu is tert-butyl, Cy is cyclohexyl, Ph is phenyl, THF is tetrahydrofuran, n BuLi is n-butyllithium, and DMF is N,N-dimethylformamide.

[0065] Preparation Example 1

[0066] Preparation of bridging ligand I 1 (R 1 =R 2 =R 3 =R 4 =H, R 5 = t Bu)

[0067] 2,2'-Bisbromobisbenzene (2.49 g, 7.98 mmol) and diethyl ether (50 mL) were added to a dry 100 mL Schlenk tube filled with nitrogen, cooled to 0°C, and added dropwise n BuLi (16.0 mmol, 6.4 mL n The mixture was stirred at room temperature for 1 h, cooled to -196 °C with liquid nitrogen, and the solution in the bottle was frozen. Phosphorus trichloride (5.0 mL, 57.2 mmol) was added dropwise, and the mixture was slowly heated to room temperature. After the frozen solution in the bottle melted, it was stirred vigorously. After it was heated to room temperature, it was stirred for 15 min. The volatile substances were removed in vacuo, and toluene was added for extraction (15 mL × 2). The solvent was removed in vacuo to obtain a crude product of compound 1a, which was directly used in the next step.

[0068] Tert-butylacetylene (1.2 mL, 10.0 mmol) was placed in a dry 50 mL Schlenk tube filled with nitrogen, 10 mL of THF was added thereto to dissolve it, and then the solution was cooled to 0°C and added dropwise n BuLi (10.0 mmol, 4.0 mL n After the addition was completed, the mixture was reacted at 0°C for 30 minutes, 1a (10 mmol, 20 wt% THF solution) was added dropwise, and after the addition was completed, the mixture was transferred to room temperature and reacted at room temperature for 2 hours. After the reaction was completed, the solvent was removed in vacuo, and the compound 1b was separated and purified by silica gel column to obtain compound 1b, which was directly used in the next step reaction.

[0069] 1b (3.5 mmol), cuprous iodide (34 mg, 0.18 mmol) and cesium carbonate (114 mg, 0.35 mmol) were added to a dry 50 mL Schlenk tube filled with nitrogen in sequence, and then DMF (15 mL) was added thereto to disperse the mixture, and diphenylphosphine (0.73 g, 3.9 mmol) was added thereto dropwise under stirring. After the addition was completed, the mixture was heated to 90°C and stirred for 6 hours. After the reaction was completed, it was cooled to room temperature, 20 mL of water was added thereto and stirred for 5 minutes, and then ethyl acetate (15 mL×3) was used to extract the mixture, and the organic phases were combined, dried with anhydrous magnesium sulfate, filtered, and the solvent was removed under pressure to obtain a crude product. The crude product was further separated and purified using silica gel column chromatography to obtain a bridged ligand I 1 (62%, 976.9 mg).

[0070] 1 H NMR (400 MHz, CDCl 3 )δ7.91-7.70(m,6H), 7.46(m,4H), 7.38(t,J=7.7Hz,4H), 7.25-7.16(m,2H ), 7.13 (dd, J=7.3, 4.2Hz, 2H), 6.26 (dd, J=17.7, 4.2Hz, 1H), 1.20 (s, 9H).

[0071] Preparation Example 2

[0072] Preparation of bridging ligand I 2 (R 1 =R 2 =R 3 =R 4 =H, R 5 =Cy)

[0073] The preparation method is the same as that of Preparation Example 1, except that tert-butylacetylene is replaced by cyclohexylacetylene.

[0074] Preparation Example 3

[0075] Preparation of bridging ligand I 3 (R 1 =R 2 =2-F, R 3 =R 4 =H, R 5 =Ph)

[0076] The preparation method is the same as that of Preparation Example 1, except that tert-butylacetylene is replaced by cyclohexylacetylene, and diphenylphosphine is replaced by di(2-F-phenyl)phosphine.

[0077] Preparation Example 4

[0078] Preparation of bridging ligand I 4 (R 1 =R 2 =3-Me, R 3 =R 4 =H, R 5 =4-OMe-Ph)

[0079] The preparation method is the same as that of Preparation Example 1, except that tert-butylacetylene is replaced by 4-methoxyphenylacetylene, and diphenylphosphine is replaced by di(3-methyl-phenyl)phosphine.

[0080] Preparation Example 5

[0081] Preparation of bridging ligand I 4 (R 1 =R 2 =4-Bu, R 3 =R 4 =H, R 5 =OMe)

[0082] The preparation method is the same as that of Preparation Example 1, except that tert-butylacetylene is replaced by methoxyacetylene, and diphenylphosphine is replaced by di(4-butyl-phenyl)phosphine.

[0083] Preparation Example 6

[0084] Preparation of bridged complex II 1 (R 1 =R 2 =R 3 =R 4 =H, R 5 = t Bu, M=Cr, Xn=Cl 2 )

[0085] The preparation method is as follows: 5 mmol of bridging ligand I 1and 5 mmol chromium chloride were transferred to a Schlenk tube, 50 mL toluene solution was added, and then the temperature was raised to 80°C and stirred for 8 hours. The reaction solution was cooled to room temperature and filtered, and the obtained solid was washed with toluene and n-hexane respectively, and vacuum dried to obtain the corresponding bridged complex II 1 .

[0086] Example 1

[0087] A 300 mL stainless steel polymerization autoclave was used. The autoclave was heated to 80°C, evacuated and replaced with nitrogen several times, then filled with ethylene for replacement, and then cooled to the set temperature. Methylcyclohexane was then added at 40°C, along with 0.5 μmol of chromium acetylacetonate and 0.5 μmol of bridging ligand I. 1 and co-catalyst modified methylaluminoxane (MMAO), the total volume of the mixed solution is 100 mL, wherein chromium acetylacetonate, bridging ligand I 1 The molar ratio of ethylene to MMAO is 1:1:1000, the reaction pressure is controlled at 4MPa, a mixed gas of ethylene and hydrogen (the volume ratio of hydrogen to ethylene is 1:1000) is introduced, and ethylene polymerization is carried out at 40°C.

[0088] After half an hour, the reaction was completed, the system was cooled to room temperature, the gas phase product was collected in a gas metering tank, the liquid phase product was collected in a conical flask, and 1 mL of ethanol was added as a terminator to terminate the reaction. The gas and liquid phase products were measured and analyzed by gas chromatography. The data results are shown in Table 1.

[0089] Example 2

[0090] The preparation method is similar to that of Example 1, except that the bridging ligand I 1 Replaced with bridging ligand I 2 The data results are shown in Table 1.

[0091] Example 3

[0092] The preparation method is similar to that of Example 1, except that the bridging ligand I 1 Replaced with bridging ligand I 3 The data results are shown in Table 1.

[0093] Example 4

[0094] The preparation method is similar to that of Example 1, except that the bridging ligand I 1 Replaced with bridging ligand I 4 The data results are shown in Table 1.

[0095] Example 5

[0096] The preparation method is similar to that of Example 1, except that the bridging ligand I 1Replaced with bridging ligand I 5 The data results are shown in Table 1.

[0097] Example 6

[0098] A 300 mL stainless steel polymerization autoclave was used. The autoclave was heated to 80°C, evacuated and replaced with nitrogen several times, then filled with ethylene for replacement, and then cooled to the set temperature. Methylcyclohexane was then added at 50°C, and 0.5 μmol of the bridged complex II was added at the same time. 1 and co-catalyst modified methylaluminoxane (MMAO), the total volume of the mixed solution is 100 mL, of which the bridged complex II 1 The molar ratio of the catalyst to the co-catalyst is 1:800, the reaction pressure is controlled at 5MPa, a mixed gas of ethylene and hydrogen (the volume ratio of hydrogen to ethylene is 1:1000) is introduced, and ethylene polymerization is carried out at 50°C.

[0099] After half an hour, the reaction was completed, the system was cooled to room temperature, the gas phase product was collected in a gas metering tank, the liquid phase product was collected in a conical flask, and 1 mL of ethanol was added as a terminator to terminate the reaction. The gas and liquid phase products were measured and analyzed by gas chromatography. The data results are shown in Table 1.

[0100] Table 1

[0101]

[0102]

[0103] From the data in Table 1, it can be seen that the catalytic activity of the catalyst composition provided by the present invention can reach up to 5.5×10 8 g·mol(Cr) -1 ·h -1 , and the total selectivity of 1-hexene and 1-octene exceeds 92wt%. Compared with the existing PNP ligand or PCCP ligand, the catalyst composition including the bridged compound provided by the present invention greatly improves the selectivity of 1-hexene in C 6 The content of C 6 The byproducts are significantly reduced, indicating that the catalyst composition provided by the present invention has better performance. The change in the catalyst ligand structure affects the coordination ability and electronic effect of the ligand, and the complex formed with the metal is more suitable for ethylene polymerization reaction, thus having a very obvious effect on the catalytic performance and effect.

[0104] It can be seen from the above test results that the catalyst composition provided by the present invention is used for ethylene oligomerization reaction, and the selectivity of 1-octene and 1-hexene in the product is very high. 8-LLDPE, PAO and other new materials are in urgent need of copolymer-grade high-purity 1-octene or 1-hexene; therefore, process technology with higher selectivity for 1-octene and 1-hexene can improve the efficiency of atomic utilization and has obvious economic benefits and social value.

[0105] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A bridged compound comprising a bridged ligand as shown in formula (I) or a bridged complex as shown in formula (II), in, R1, R2, R3, and R4 are the same or different and are independently selected from hydrogen, alkyl, alkoxy, and halogen; R5 is selected from hydrogen, alkyl, cycloalkyl, alkoxy, and aryl; the hydrogen on the carbon of the alkyl, cycloalkyl, alkoxy, and aryl is optionally substituted by one or more substituents; M is selected from transition metals; X is selected from halogen, and n is an integer of 1 to 3.

2. The bridged compound according to claim 1, characterized in that The alkyl group is C1~C 20 Alkyl, preferably C1~C 10 Alkyl, more preferably C1-C6 alkyl; And / or, the cycloalkyl group is C3 to C 20 Cycloalkyl, preferably C3~C 10 Cycloalkyl, more preferably C3-C6 cycloalkyl; And / or, the alkoxy group is C1~C 20 Alkoxy, preferably C1-C 10 Alkoxy, more preferably C1-C6 alkoxy; And / or, the aryl group is C6~C 20 Aryl, preferably C6~C 12 Aryl, more preferably C6-C8 aryl; And / or, the substituent is selected from C1 to C 20 Alkyl, C3~C 20 Cycloalkyl, C1~C 20 Alkoxy, C6~C 20 Aryl; preferably selected from C1 to C 10 Alkyl, C3~C 10 Cycloalkyl, C1~C 10 Alkoxy, C6~C 12 Aryl; more preferably selected from C1~C6 alkyl, C3~C6 cycloalkyl, C1~C6 alkoxy, C6~C 12 Aryl; further selected from at least one of methyl, ethyl, propyl, butyl, isobutyl, pentyl, isopentyl, hexyl, cyclopropyl, cyclopentyl, cyclohexyl, methoxy, ethoxy, propoxy, butoxy, phenyl, tolyl, ethylphenyl, propylphenyl, biphenyl, and naphthyl.

3. The method for preparing the bridged compound according to claim 1 or 2, characterized in that: include: S1. Compound a, n BuLi and phosphorus trichloride undergo a first reaction in a first solvent to prepare compound b; S2. Compound b, compound c and n BuLi undergoes a second reaction in a second solvent to produce compound d; S3. Compound d, cuprous iodide, cesium carbonate, and compound e undergo a third reaction in a third solvent to obtain a bridging ligand of formula (I); And optionally S4. The bridging ligand represented by formula (I) and the transition metal salt MX n Carrying out a coordination reaction in a fourth solvent to obtain a bridged complex represented by formula (II); Wherein, R1, R2, R3, and R4 are the same or different and are independently selected from hydrogen, alkyl, alkoxy, and halogen; R5 is selected from hydrogen, alkyl, cycloalkyl, alkoxy, and aryl; the hydrogen on the carbon of the alkyl, cycloalkyl, alkoxy, and aryl is optionally substituted by one or more substituents; M is selected from transition metals; X is selected from halogen, and n is an integer of 1 to 3.

4. The preparation method according to claim 3, characterized in that: In the step S1, compound a, n The molar ratio of BuLi to phosphorus trichloride is 1:1-3:1-10; and / or, the first solvent comprises diethyl ether; And / or, in step S2, compound c, n The molar ratio of BuLi to compound b is 1:0.5~2:0.5~2; and / or, the second solvent comprises tetrahydrofuran; And / or, in step S3, the molar ratio of compound d, cuprous iodide, cesium carbonate and compound e is 1:0.01-0.1:0.01-0.2:1-2; and / or, the third solvent comprises N,N-dimethylformamide; And / or, in the step S3, after the third reaction is completed, water is added, and an organic solvent is used for extraction to purify the organic phase to obtain a bridged ligand represented by formula (I); preferably, the organic solvent includes ethyl acetate or petroleum ether; And / or, in step S4, the molar ratio of the bridging ligand to the transition metal salt is 1:0.01-10; And / or, the fourth solvent comprises toluene.

5. A catalyst composition, characterized in that Comprising the bridged compound according to claim 1 or 2; When the bridging compound is a bridging ligand as shown in formula (I), the catalyst composition comprises a bridging ligand as shown in formula (I), a transition metal compound and an aluminum-containing co-catalyst; When the bridged compound is a bridged complex as shown in formula (II), the catalyst composition comprises the bridged complex as shown in formula (II) and an aluminum-containing co-catalyst.

6. The catalyst composition according to claim 5, characterized in that The aluminum-containing co-catalyst is an organic aluminum compound, preferably at least one selected from an alkyl aluminum compound, an alkoxy aluminum compound and an alkyl aluminum chloride compound, more preferably at least one selected from methylaluminoxane, trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, diethylaluminum monochloride, ethylaluminum dichloride, ethylaluminumoxane and modified methylaluminumoxane, further preferably at least one selected from methylaluminumoxane, triethylaluminum and modified methylaluminumoxane.

7. The catalyst composition according to claim 5 or 6, characterized in that The transition metal compound is selected from at least one of compounds of chromium, molybdenum, iron, titanium, zirconium and nickel, preferably selected from at least one of chromium acetylacetonate, chromium isooctanoate, tri(tetrahydrofuran)chromium trichloride and di(tetrahydrofuran)chromium dichloride; And / or, the molar ratio of the transition metal compound, the bridging ligand represented by formula (I) and the aluminum-containing co-catalyst, calculated as transition metal, is 1:(0.1-10):(1-1000), preferably 1:(0.25-2):(10-700), and more preferably 1:(0.5-2):(100-500).

8. The catalyst composition according to claim 5 or 6, characterized in that In formula (II), M is selected from at least one of chromium, molybdenum, iron, titanium, zirconium and nickel; And / or, the molar ratio of the bridged complex represented by formula (II) to the aluminum-containing co-catalyst, calculated as transition metal, is 1:(1-1000), preferably 1:(10-700), and more preferably 1:(100-500).

9. Use of the catalyst composition according to any one of claims 5 to 8 in ethylene oligomerization reaction.

10. A method for the polymerization of ethylene, comprising: In the presence of the catalyst composition according to any one of claims 5 to 8, ethylene, hydrogen and an organic solvent are continuously added into a reactor to carry out an ethylene oligomerization reaction.

11. The method for ethylene oligomerization according to claim 10, characterized in that The ethylene oligomerization reaction includes ethylene trimerization and ethylene tetramerization; And / or, the volume ratio of hydrogen to ethylene is 1:(1-10000), preferably 1:(10-2000).

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