Ethylene oligomerization catalyst system and application thereof

Abstract

The invention provides an ethylene oligomerization catalyst system and application thereof. The catalyst system comprises a ligand, a transition metal compound and an activator, the ligand has a structure shown as a formula I: # imgabs0 #, R1, R2 and R3 are the same or different and are independently selected from hydrogen, alkyl, heteroatom substituted alkyl, aryl, substituted aryl and heteroaromatic ring group; r4, R5 and R6 are the same or different and are independently selected from hydrogen, alkyl, heteroatom substituted alkyl, aryl, substituted aryl, heteroaromatic ring groups and heteroatoms, at least one of R4, R5 and R6 is a heteroatom, and the heteroatom is one of oxygen, sulfur, nitrogen, silicon, fluorine, chlorine, bromine and iodine. The catalyst system is mainly used for ethylene selective oligomerization, and has the characteristics of good temperature resistance of the catalyst, high catalytic activity, low 1-butene content, high C6-C12 linear alpha-olefin selectivity and few polymer byproducts.

Description

Technical Field

[0001] The present invention belongs to the technical field of homogeneous catalysis, and particularly relates to an ethylene oligomerization catalyst system and its application. Background Art

[0002] Linear α-olefins (LAOs) are general raw materials for synthesizing olefin copolymers, plasticizers, detergents and synthetic lubricants. There are various technologies for producing LAOs industrially. For example, Overett et al. of Sasol reported that a chromium catalyst system with a PCP skeleton ligand was used to catalyze the non-selective oligomerization of ethylene, and the product composition followed the Schulz-Flory distribution (α = 0.55) (J. Mol. Catal. A: Chem, 2008, 283, 114). The most well-known catalytic system is the combination of a bidentate phosphine ligand and chromium, such as PNP, PN(C) n NP and PCCP. When another atom sulfur is used to replace the phosphorus atom, Sasol researchers found that even with a smaller amount of MAO (280 equivalents) for activation, good activity and selectivity can be obtained. The best results were obtained with the [bis-(2-decylthioethyl)-amine] chromium trichloride complex (D.S. McGuinness, P. Wasserscheid, W. Keim, D.H. Morgan, J.T. Dixon, A. Bollmann, H. Maumela, F.M. Hess, U. Englert, J. Am. Chem. Soc. 2003, 125, 5272). It is worth noting at this point that the "SCCNCCS" system developed by Sasol is the first high-selectivity and high-activity sulfur-based ethylene oligomerization catalyst. This discovery indicates that sulfur-based systems can potentially form high-performance catalysts for selective ethylene oligomerization. Although this selective oligomerization technology is currently considered to have reached the threshold of commercialization, there are still some key problems to be solved. The chromium-based catalysts with PNP and PNC structures reported by Danopoulos et al. catalyze the oligomerization of ethylene under the activation of methylaluminoxane, and the mass fraction of C 6 ~C 8 in the product reaches up to 52.28% at most (Simler, T., Braunstein, P., Danopoulos, A.A..(2016).Organometallics, 2016, 35, 4044).

[0003] The ethylene selective oligomerization process mainly produces linear α-olefins with a specific number of carbon atoms. The obtained products have a high degree of linearization, good quality, and lower separation costs. The activity of the catalyst system and the selectivity of the target product are the keys to evaluating the advancement of this technology, and the structure of the ligand in the catalyst system plays an important role in this regard. For example, the PNP ligands disclosed in Chinese patents CN1741850A (WO2004 / 056478A1) and CN1741849A (WO2004 / 056479A1), when combined with Cr and MAO to form a catalyst system for ethylene tetramerization, have high catalytic activity and long-term stability. However, this type of catalyst system has the deficiencies of relatively high contents of by-products methylcyclopentane and methylenecyclopentane, and relatively low total selectivity of C 6 ~C 12 linear α-olefins.

[0004] Patent CN 201910576306.4 discloses a catalyst system with a PSiOSiP backbone. DMAO and AlEt3 are still used in combination as cocatalysts to achieve high-selectivity trimerization and tetramerization; however, the selectivity of the catalyst for 1-octene needs to be improved. Summary of the Invention

[0005] The main object of the present invention is to provide an ethylene oligomerization catalyst system and its application to overcome the defect of low selectivity of existing ethylene oligomerization catalysts.

[0006] To achieve the above object, the present invention provides an ethylene oligomerization catalyst system, comprising a ligand, a transition metal compound, and an activator; the ligand has the following structure of Formula I:

[0007]

[0008] Wherein, R 1 、R 2 、R 3 are the same or different and are independently selected from hydrogen, alkyl, heteroatom-substituted alkyl, aryl, substituted aryl, and arylheterocyclic group; R 4 、R 5 、R 6 are the same or different and are independently selected from hydrogen, alkyl, heteroatom-substituted alkyl, aryl, substituted aryl, arylheterocyclic group, and heteroatom group, and at least one of R 4 、R 5 、R 6 is a heteroatom group, and the heteroatom group is one of hydroxyl, mercapto, amino, alkylsilyl, fluorine, chlorine, bromine, and iodine.

[0009] The ethylene oligomerization catalyst system of the present invention, wherein the alkyl group has 1-10 carbon atoms, the heteroatom-substituted alkyl group has 1-10 carbon atoms, the aryl group has 6-20 carbon atoms, the substituted aryl group has 6-20 carbon atoms, and the heteroaromatic group has 3-12 carbon atoms.

[0010] The ethylene oligomerization catalyst system of the present invention, wherein the alkyl group is selected from one of methyl, ethyl, isopropyl, n-butyl, cyclopentyl, and cyclohexyl, and the heteroatom in the heteroatom-substituted alkyl group is Si or O.

[0011] The ethylene oligomerization catalyst system of the present invention, wherein the heteroaromatic group is pyrazolyl, pyrimidinyl, imidazolyl, or furyl.

[0012] The ethylene oligomerization catalyst system of the present invention, wherein the transition metal compound is a compound containing one of the metals in Group IVB, Group VB, Group VIB, Group VIIB, and Group VIII of the periodic table.

[0013] The ethylene oligomerization catalyst system of the present invention, wherein the activator is a compound containing a Group IIIA metal.

[0014] The ethylene oligomerization catalyst system of the present invention, wherein the transition metal compound is a compound containing chromium, molybdenum, tungsten, cobalt, titanium, tantalum, vanadium, zirconium, iron, nickel, or palladium.

[0015] The ethylene oligomerization catalyst system of the present invention, wherein the activator is at least one of an alkylaluminum compound, an alkylaluminoxane compound, and an organic boron compound.

[0016] The ethylene oligomerization catalyst system of the present invention, wherein the molar ratio of the ligand, the transition metal compound, and the activator is 1:0.5-100:0.1-5000.

[0017] To achieve the above object, the present invention also provides the application of the above ethylene oligomerization catalyst system in an ethylene oligomerization reaction, wherein the temperature of the ethylene oligomerization reaction is 0°C to 200°C, and the pressure is 0.1 MPa to 50 MPa.

[0018] The beneficial effects of the present invention:

[0019] The present invention provides a catalyst system for ethylene oligomerization. By changing the electronic properties and steric hindrance of the substituents of the catalyst ligand, the catalyst system has good catalytic activity. When used in the ethylene oligomerization reaction, the target products C 6 ~C 12 linear α-olefins have high selectivity, and the contents of by-products such as methylcyclopentane and methylenecyclopentane are greatly reduced. Detailed Embodiments

[0020] The technical solution of the present invention will be described in detail below. The following embodiments are implemented on the premise of the technical solution of the present invention, and the detailed implementation process is given. However, the protection scope of the present invention is not limited to the following embodiments. For the structures or experimental methods without specific conditions noted in the following embodiments, they are usually in accordance with conventional conditions.

[0021] The present invention provides an ethylene oligomerization catalyst system, including a ligand, a transition metal compound, and an activator; the ligand has the following structural formula I:

[0022]

[0023] Wherein, R 1 , R 2 , R 3 are the same or different and are independently selected from hydrogen, alkyl, heteroatom-substituted alkyl, aryl, substituted aryl, and aryl heterocyclic group; R 4 , R 5 , R 6 are the same or different and are independently selected from hydrogen, alkyl, heteroatom-substituted alkyl, aryl, substituted aryl, aryl heterocyclic group, and heteroatom group, and at least one of R 4 , R 5 , R 6 is a heteroatom group, and the heteroatom group is one of hydroxyl, mercapto, amino, alkylsilyl, fluorine, chlorine, bromine, and iodine.

[0024] By changing the electronic properties and steric hindrance of the substituents of the catalyst ligand, the present invention enables the catalyst system to have good catalytic activity. When used in the ethylene oligomerization reaction, the target products C 6 ~C 12 linear α-olefins have high selectivity, and the contents of by-products such as methylcyclopentane and methylenecyclopentane are greatly reduced.

[0025] In one embodiment, the above alkyl has 1-10 carbon atoms. In another embodiment, the above alkyl has 1-6 carbon atoms. The above alkyl can be a straight-chain alkyl or a cycloalkyl, for example, selected from one of methyl, ethyl, isopropyl, n-butyl, cyclopentyl, cyclohexyl, and tert-butyl.

[0026] In one embodiment, the above heteroatom-substituted alkyl has 1-10 carbon atoms. In another embodiment, the above heteroatom-substituted alkyl has 1-6 carbon atoms, and the heteroatom is one of oxygen, sulfur, nitrogen, silicon, fluorine, chlorine, bromine, and iodine. In yet another embodiment, the heteroatom is Si or O. The above heteroatom-substituted alkyl is, for example, a butyl group substituted with Si or O.

[0027] In one embodiment, the above-mentioned aryl group has 6-20 carbon atoms. In another embodiment, the above-mentioned aryl group is phenyl, substituted phenyl. More specifically, the above-mentioned aryl group is phenyl, triphenylmethyl, 4-methylphenyl, p-tolyl, naphthyl, fluorenyl, substituted naphthyl, etc.

[0028] In one embodiment, the above-mentioned substituted aryl group has 6-20 carbon atoms. The substituents in the substituted aryl group are, for example, nitro, alkoxy, halogen, haloalkyl, hydrocarbon group, silyl group, etc. Specifically, the substituted aryl group is 2-nitrophenyl, 2,4-dinitrophenyl, 4-methoxyphenyl, trifluoromethylphenyl, 3,5-bis(trifluoromethyl)phenyl, 3,5-dimethyl-4-methoxyphenyl, triphenylchloromethane group, etc.

[0029] In one embodiment, the above-mentioned heteroaryl group has 3-12 carbon atoms. In another embodiment, the above-mentioned heteroaryl group has 3-6 carbon atoms. The above-mentioned heteroaryl group is, for example, pyrazolyl, pyrimidinyl, imidazolyl, furyl, oxazolyl.

[0030] In one embodiment, the heteroatom group of the present invention is one of hydroxyl, mercapto, amino, alkylsilyl, fluorine, chlorine, bromine, iodine. In another embodiment, the heteroatom is selected from hydroxyl, alkylsilyl, fluorine.

[0031] In the present invention, R 4 、R 5 、R 6 At least one of them is a heteroatom group. In one embodiment, R 5 is a heteroatom group.

[0032] In the present invention, R 1 、R 2 、R 3 、R 4 、R 5 、R 6 can be respectively connected to the ligand through a single bond, and R 1 can also form a three-membered ring, four-membered ring, five-membered ring or polycyclic ring with the S atom.

[0033] The ligand of the catalyst system of the present invention is a phosphine-sulfur type ligand. Under the action of the activator, the ligand coordinates with the transition metal compound to form a bidentate complex. The different substituent structures on the phosphine-sulfur change the spatial configuration of the transition metal complex and inhibit the free rotation of the C-P and C-S bonds. By adjusting R 1 、R 2 、R 3 、R 4 、R 5 、R 6The steric and electronic properties of the group can effectively regulate the chemical environment of the ligand towards the metal active center, i.e., the transition metal compound, enabling the catalyst system of the present invention to be used for the selective oligomerization of ethylene with good catalytic activity. The target product C 6 ~C 12 has a high total selectivity for linear α-olefins and low contents of by-products such as methylcyclopentane and methylenecyclopentane.

[0034] In one embodiment, the transition metal compound is a compound containing one of the metals in Group IVB, Group VB, Group VIB, Group VIIB, and Group VIII of the periodic table, serving as the central metal atom. In another embodiment, the transition metal compound is a compound containing chromium, molybdenum, tungsten, cobalt, titanium, tantalum, vanadium, zirconium, iron, nickel, or palladium. The present invention does not particularly limit the type of the compound, as long as it contains a specific transition metal.

[0035] Preferably, the transition metal compound is one of CrCl 3 (THF) 3 , CrCl 2 (THF) 2 , CoCl 3 , NiBr 2 . More preferably, the transition metal compound is a chromium-containing transition metal compound. The selectable chromium compounds include compounds represented by the general formula CrR n , where R n is an organic anion or a neutral molecule, R n usually contains 1 to 10 carbon atoms, n is an integer from 0 to 6, representing the metal valence state, and the valence state of chromium is from 0 to 6. Specifically, the R n group is an organic substance or its group containing a carboxyl group, a β-diketone group, and a hydrocarbon group. From the perspectives of easy dissolution and easy operation, more suitable chromium compounds include chromium acetate, chromium isooctanoate, chromium n-octanoate, chromium acetylacetonate, diisoprene chromium, diphenyl chromium, CrCl 3 (THF) 3 , CrCl 2 (THF) 2 , (phenyl)tricarbonyl chromium, and hexacarbonyl chromium.

[0036] In one embodiment, the activator is a compound containing a Group IIIA metal. In another embodiment, the activator is at least one of an alkylaluminum compound, an alkylaluminoxane compound, and an organic boron compound. Among them, the alkylaluminoxane compound is an alkylaluminoxane compound from which volatile components have been removed.

[0037] Specifically, the activator can be a compound containing Group IIIA metal, such as an alkylaluminum compound and an alkylaluminoxane compound. The alkylaluminum compound can be various trialkylaluminums, such as triethylaluminum (TEAL), triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum or tri-n-octylaluminum; the alkylaluminum compound can also be an alkylaluminum halide, an alkylaluminum hydride or an alkylaluminum sesquichloride, such as dichloroethylaluminum (AlEt 2 Cl) and triethylaluminum dichloride (Al 2 Et 3 Cl 3 ); the alkylaluminoxane compound can be selected from methylaluminoxane (MAO), ethylaluminoxane, isobutylaluminoxane, modified aluminoxane and methylaluminoxane with volatile components removed (DMAO), etc. The activator can be a mixture of an alkylaluminum compound and an alkylaluminoxane compound, wherein the alkylaluminum compound is TEAL and the alkylaluminoxane compound is DMAO. Preferably, the molar ratio of TEAL to DMAO is 0.01 - 100, preferably 0.1 - 10.

[0038] Among them, the alkylation ability of TEAL is relatively weak and it is more adaptable to the catalyst system proposed by the present invention; at the same time, DMAO can shield the influence of volatile components such as toluene on the catalyst complexation process, thereby improving the activity of the catalyst system. The mixture of the two can further reduce the dosage of the activator.

[0039] Furthermore, the activator is a mixture of an alkylaluminum compound and an alkylaluminoxane compound. Among them, the alkylaluminum compound is triethylaluminum and the alkylaluminoxane compound is methylaluminoxane with volatile components removed; the molar ratio of triethylaluminum to methylaluminoxane with volatile components removed is 0.01 - 100, preferably 0.1 - 10.

[0040] In one embodiment, the molar ratio of the ligand, the transition metal compound and the activator in the present invention is 1:0.5 - 100:0.1 - 5000. In another embodiment, the molar ratio of the ligand, the transition metal compound and the activator in the present invention is 1:0.5 - 100:0.1 - 1000. In yet another embodiment, the molar ratio of the ligand, the transition metal compound and the activator in the present invention is 1:0.5 - 100:0.1 - 200. In still another embodiment, the molar ratio of the transition metal compound and the activator in the present invention is 1:1 - 500, and in yet still another embodiment, the molar ratio of the transition metal compound and the activator in the present invention is 1:1 - 200.

[0041] In an embodiment of the present invention, R in the ligand 2 is hydrogen, and the preparation method of the ligand can include the following steps:

[0042] (1) Prepare R 3 C≡CSR 1

[0043] Take a certain amount of n-BuLi, an ethereal solution of HC≡CR 3 under N 2 atmosphere, slowly drop n-BuLi into the ethereal solution of HC≡CR at -78 °C. After stirring the reaction for about 1 h, drop the ethereal solution of R 3 SCl into the above reaction and continue stirring for 4 h. After the reaction is complete, filter off the lithium salt with a sintered funnel, and distill off the solvent under reduced pressure from the solution to obtain an oily product R 1 C≡CSR 3 . 1

[0044] (2) Preparation of R 1 SHC=C(R 3 )P(PhR 4 R 5 R 6 ) 2

[0045] Take a certain amount of R 3 C≡CSR 1 , CuI and Cs 2 CO 3 and add them to an appropriate amount of N,N-dimethylformamide (DMF) for standby. Slowly drop the substituted diphenylphosphine (HP(PhR 4 R 5 R 6 )) 2 slowly into the above standby solution, heat to 90 °C, and stir the reaction for about 3 h. Then let the mixture naturally rise to room temperature and then dry it in vacuo. After further purification by distillation or column chromatography, the corresponding colorless or light yellow product R 1 SHC=C(R 3 )P(PhR 4 R 5 R 6 ) 2 .

[0046] In another embodiment of the present invention, R 3 in the ligand is hydrogen, and the preparation method of the ligand may include the following steps:

[0047] (1) Preparation of R 2 C≡CP(PhR 4 R 5 R 6 ) 2

[0048] Take a certain amount of n-BuLi, an ethereal solution of HC≡CR 2 under N 2 ​Under the condition of -78 °C, n-BuLi was slowly added dropwise to the ethereal solution of HC≡CR 2 After stirring the reaction for about 1 h, the ethereal solution of (PhR 4 R 5 R 6 ) 2 PCl was added dropwise to the above reaction, and stirring was continued for 4 h. After the reaction was complete, the lithium salt was filtered off with a sintered funnel, and the solvent was removed by distillation under reduced pressure to obtain an oily product R 2 C≡CP(PhR 4 R 5 R 6 ) 2 .

[0049] (2) Preparation of R 1 S(R 2 )C=CHP(PhR 4 R 5 R 6 ) 2

[0050] A certain amount of R 2 C≡CP(PhR 4 R 5 R 6 ) 2 ), CuI and Cs 2 CO 3 were added to an appropriate amount of N,N-dimethylformamide (DMF) for standby. HSR 1 was slowly added dropwise to the above standby solution, heated to 90 °C, and stirred for about 3 h. Then the mixture was allowed to rise to room temperature naturally and then dried in vacuo. After further purification by distillation or column chromatography, the corresponding colorless or light yellow product R 1 S(R 2 )C=CHP(PhR 4 R 5 R 6 ) 2 was obtained.

[0051] In an embodiment of the present invention, the preparation method of the catalyst system may include the following steps:

[0052] The ligand, transition metal compound, and activator are pre-mixed or directly added to the reaction system for in-situ synthesis. That is to say, the preparation of the catalyst is to pre-mix the ligand, transition metal compound, and activator; or the ligand, transition metal compound, and activator can be directly added to the reaction system for in-situ synthesis.

[0053] The reaction modes of the ligand, transition metal compound and activator of Formula I can be carried out by liquid-phase reaction, such as reacting under the action of a solvent. Optional solvents include toluene, benzene and its derivatives, etc.; it can also be carried out by solid-phase reaction; it can also be carried out by in-situ reaction during the oligomerization reaction to generate a catalyst. The reaction here can be a reaction between one, two or three of the above-mentioned ligand, transition metal compound and activator. The process of this reaction is also the aging (pre-complexation) process of the catalyst.

[0054] The above-mentioned ethylene oligomerization catalyst system of the present invention can be used for ethylene oligomerization reaction. The temperature of the ethylene oligomerization reaction is, for example, 0°C to 200°C, preferably 80°C to 100°C, and the pressure is, for example, 0.1 MPa to 50 MPa, preferably 1.0 MPa to 10 MPa. Here, ethylene oligomerization can include ethylene selective trimerization, tetramerization, etc. The ethylene selective oligomerization reaction is carried out in a solvent, and the solvent can be one or more of alkanes, aromatics, olefins or ionic liquids. Typical solvents include but are not limited to benzene, toluene, xylene, cumene, n-heptane, n-hexane, methylcyclohexane, cyclohexane, 1-hexene, 1-octene, ionic liquids, etc., and methylcyclohexane is preferred. In this reaction system, the concentration of the catalyst is 0.01 μmol metal / L to 1000 μmol metal / L, preferably 0.1 μmol metal / L to 10 μmol metal / L. The metal here refers to the transition metal in the transition metal compound.

[0055] The catalyst system of the present invention is used for ethylene oligomerization, and C 6 ~C 12 linear α-olefins can be obtained.

[0056] The content of the present invention will be further illustrated below in conjunction with specific examples, but the content of the present invention is not limited to the following examples. It should be noted that "C 6 ~C 12 total selectivity" refers to the mass ratio of the total amount of C 6 ~C 12 linear α-olefins in the total product (all linear α-olefins and by-products).

[0057] Example 1

[0058] 1. Preparation of ligand [(Z)-(2-bis(3-fluorophenyl)phosphino)(3-methyl-1-(triphenylmethylthio))-1-butene (L1)]:

[0059]

[0060] The ethereal solution of n-BuLi (0.23 g, 3.62 mmol) was slowly added dropwise to the ethereal solution of 3-methyl-1-butyne (0.29 g, 4.26 mmol) at -78 °C. After stirring for about 1 h, a small amount of ethereal solution-diluted triphenylsulfur chloride (1 g, 3.21 mmol) was added dropwise, and the mixture was stirred for 2 h. After the reaction was complete, the lithium salt was filtered off through a fritted funnel, and the solvent was removed by distillation under reduced pressure to obtain the oily product 3-methyl-1-(triphenylmethylthio)-1-butyne. Take 3-methyl-1-(triphenylmethylthio)-1-butyne (1 g, 2.92 mmol), CuI (0.028 g, 0.14 mmol) and Cs 2 CO 3 (0.095 g, 0.29 mmol) and dissolve them in an appropriate amount of N,N-dimethylformamide (DMF) for standby. Then, HP(Ph-mF) 2 (0.78 g, 3.50 mmol) was slowly added dropwise to the above-mentioned standby solution, heated to 90 °C, and stirred for about 5 h. After that, the mixture was allowed to rise to room temperature naturally, and then dried in vacuo. After further purification by column chromatography, a colorless oily product was obtained.

[0061] 2. Preparation of the catalyst

[0062] In an N 2 environment, (Z)-(2-bis(3-fluorophenyl)phosphino)(3-methyl-1-(triphenylmethylthio))-1-butene (L1) (1.42 mg, 2.52 μmol) was dissolved in dichloromethane (20 mL) for standby. Then, a dichloromethane solution of CrCl 3 ·(THF) 3 (0.89 mg, 2.40 μmol) was added dropwise to the above-mentioned standby solution. After reacting at room temperature for 8 h, the solvent was dried by suction. The obtained catalyst was washed with n-hexane and then filtered and dried by suction.

[0063] 3. Ethylene oligomerization reaction

[0064] A 100 mL reaction kettle was heated and evacuated for 20 min, then purged with nitrogen several times and filled with ethylene. The temperature was raised to the predetermined temperature, and dehydrated methylcyclohexane (20 mL), 0.87 mL of MMAO and the above catalyst were added. The oligomerization reaction was carried out at 50 °C and an ethylene pressure of 1 MPa. After reacting for 30 min, the temperature was lowered with an ice bath and the pressure was released, and the reaction was terminated with 10% acidified ethanol by mass fraction. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activity are shown in Table 2.

[0065] Example 2

[0066] Same as Example 1. The difference lies in the R of the ligand 1is 2-nitrophenyl. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activities are shown in Table 2.

[0067] Example 3

[0068] Same as Example 1. The difference lies in that R of the ligand 1 is 2,4-dinitrophenyl. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activities are shown in Table 2.

[0069] Example 4

[0070] Same as Example 1. The difference lies in that R of the ligand 1 is (3-triethoxysilyl)propyl, R 2 is isopropyl, R 3 is hydrogen. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activities are shown in Table 2.

[0071] Example 5

[0072] Same as Example 4. The difference lies in that R of the ligand 1 is imidazolyl. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activities are shown in Table 2.

[0073] Example 6

[0074] Same as Example 4. The difference lies in that R of the ligand 1 is 4,6-dimethylpyrimidinyl. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activities are shown in Table 2.

[0075] Example 7

[0076] Same as Example 4. The difference lies in that R of the ligand 1 is benzimidazolyl. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activities are shown in Table 2.

[0077] Example 8

[0078] Same as Example 4. The difference lies in that R of the ligand 1 is benzoxazolyl. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activities are shown in Table 2.

[0079] Example 9

[0080] Same as Example 4. The difference lies in that R of the ligand 1 is benzothiazolyl. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activities are shown in Table 2.

[0081] Example 10

[0082] Same as Example 4. The difference lies in that R of the ligand 1It is 3-methylfuranyl. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activities are shown in Table 2.

[0083] Example 11

[0084] Same as Example 1. The difference is that the pressure of the oligomerization reaction is 5.0 MPa and the reactor is 500 ml. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activities are shown in Table 2.

[0085] Example 12

[0086] Same as Example 6. The difference is that the pressure of the oligomerization reaction is 5.0 MPa and the reactor is 500 ml. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activities are shown in Table 2.

[0087] Example 13

[0088]

[0089] The ethereal solution of n-BuLi (0.23 g, 3.62 mmol) was slowly added dropwise to the ethereal solution of 3-methyl-1-butyne (0.29 g, 4.26 mmol) at -78 °C. After stirring the reaction for about 1 h, a small amount of bis[4-(triethylsilyl)phenyl]phosphonium chloride (1.44 g, 3.21 mmol) diluted with ether was added dropwise and stirred for 2 h. After the reaction was complete, the lithium salt was filtered off through a sintered funnel, and the solvent was removed by distillation under reduced pressure to obtain an oily product, 3-methyl-1-(bis[4-(triethylsilyl)phenyl]phosphino)-1-butyne. Take 3-methyl-1-(bis[4-(triethylsilyl)phenyl]phosphino)-1-butyne (1.31 g, 2.92 mmol), CuI (0.028 g, 0.14 mmol) and Cs 2 CO 3 (0.095 g, 0.29 mmol) were added to an appropriate amount of N,N-dimethylformamide (DMF) for dissolution and standby. Then, 2-mercaptopyridine (0.39 g, 3.50 mmol) was slowly added dropwise to the above standby solution, heated to 90 °C, and stirred for about 5 h. After that, the mixture was allowed to rise to room temperature naturally and then dried in vacuo. After further purification by column chromatography, a colorless oily product was obtained. The preparation of the catalyst and the oligomerization reaction conditions were the same as those in Example 11.

[0090] Comparative Example 1

[0091] Same as Example 1. The difference is that the structure of the ligand is different, and the ligand is as follows:

[0092]

[0093] The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activities are shown in Table 2.

[0094]

[0095]

[0096] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should fall within the protection scope of the claims of the present invention.

Claims

1. An ethylene oligomerization catalyst system, characterized in that: It includes a ligand, a transition metal compound and an activator; the ligand has the following formula I structure: Among them, R 1 , R 2 , R 3 are the same or different and are independently selected from hydrogen, alkyl, heteroatom-substituted alkyl, aryl, substituted aryl and aromatic heterocyclic group; R 4 , R 5 , R 6 are the same or different and are independently selected from hydrogen, alkyl, heteroatom-substituted alkyl, aryl, substituted aryl, aromatic heterocyclic group and heteroatom group, and R 4 , R 5 , R 6 At least one of them is a heteroatom group, and the heteroatom group is one of hydroxyl, mercapto, amino, alkylsilyl, fluorine, chlorine, bromine and iodine.

2. The ethylene oligomerization catalyst system according to claim 1, characterized in that The alkyl group has 1 to 10 carbon atoms, the heteroatom-substituted alkyl group has 1 to 10 carbon atoms, the aryl group has 6 to 20 carbon atoms, the substituted aryl group has 6 to 20 carbon atoms, and the aromatic heterocyclic group has 3 to 12 carbon atoms.

3. The ethylene oligomerization catalyst system according to claim 2, characterized in that The alkyl group is selected from one of methyl, ethyl, isopropyl, n-butyl, cyclopentyl and cyclohexyl, and the heteroatom in the heteroatom-substituted alkyl group is Si or O.

4. The ethylene oligomerization catalyst system according to claim 2, characterized in that The aromatic heterocyclic group is pyrazolyl, pyrimidinyl, imidazolyl, or furyl.

5. The ethylene oligomerization catalyst system according to claim 1, characterized in that The transition metal compound is a compound containing one of the metals of Group IVB, Group VB, Group VIB, Group VIIB and Group VIII.

6. The ethylene oligomerization catalyst system according to claim 1, characterized in that The activator is a compound containing a Group IIIA metal.

7. The ethylene oligomerization catalyst system according to claim 5, characterized in that The transition metal compound is a compound containing chromium, molybdenum, tungsten, cobalt, titanium, tantalum, vanadium, zirconium, iron, nickel or palladium.

8. The ethylene oligomerization catalyst system according to claim 6, characterized in that The activator is at least one of an alkyl aluminum compound, an alkyl aluminoxane compound, and an organic boron compound.

9. The ethylene oligomerization catalyst system according to claim 1, characterized in that The molar ratio of the ligand, the transition metal compound and the activator is 1:0.5-100:0.1-5000.

10. Use of the ethylene oligomerization catalyst system according to any one of claims 1 to 9 in ethylene oligomerization reaction, characterized in that: The temperature of the ethylene polymerization reaction is 0°C to 200°C, and the pressure is 0.1MPa to 50MPa.

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