A Si-PCCP ligand, its preparation method, an ethylene oligomerization catalyst and its application

Abstract

The present invention discloses the preparation and application of a Si-PCCP-Cr ethylene oligomerization catalyst. The catalyst includes a Si-PCCP-Cr catalyst represented by the structure of Formula I and an alkylaluminum cocatalyst. This catalytic system can be used for homogeneous catalytic ethylene oligomerization, overcoming the problem of the heterogeneous PCCP catalytic system. At the same time, it has the characteristics of a short catalyst synthesis route, high catalytic activity, high selectivity, and low polymer content.

Description

Technical Field

[0001] The present invention belongs to the technical field of ethylene oligomerization reaction, and particularly relates to a Si-PCCP ligand, a preparation method thereof, an ethylene oligomerization catalyst and an application thereof. Background Art

[0002] Linear α-olefins are important chemical raw materials and can be used in many fields such as polyolefin comonomers, PVC plasticizers, surfactants, lubricant additives, etc. Among them, the consumption of comonomers accounts for more than half of the consumption of α-olefins. Polyolefin products of 1-octene and 1-hexene have good mechanical properties and excellent processing properties, and there is a large demand in industrial production. The selectivity of 1-octene and 1-hexene in the selective oligomerization process accounts for more than 90% of the total product, with good selectivity and high conversion rate, which is suitable for industrial production. Common catalysts for selective oligomerization are chromium-based catalyst systems.

[0003] The PCCP skeleton has obvious advantages in the ethylene oligomerization system. This skeleton has strong expandability, is easy to regulate the microstructure of the catalyst by synthetic means, and performs selective polymerization of 1-C8 and 1-C6 through catalyst structure regulation. However, PCCP has obvious problems that hinder its application in the industrialization direction. PCCP-Cr metal complexes are insoluble in conventional polymerization solvents such as saturated alkanes, Isoper-E, toluene, etc. This will also lead to problems such as complex feeding systems, difficult quantification, and difficulty in ensuring catalyst uniformity.

[0004] Another well-known reason for the industrialization of ethylene oligomerization is the blockage of reaction kettles and pipelines caused by polymers. The main sites for polymer formation are on the catalyst active centers. When using heterogeneous catalysts, the polymer formation situation is more obvious. Its active centers are insoluble in solvents and are more likely to be entrapped and adsorbed by polymers for growth, aggravating the blockage situation.

[0005] Therefore, among the various technical documents disclosed so far, no homogeneous PCCP catalyst system has been proposed to dissolve the catalyst in the polymerization solution to ensure uniform catalyst feeding, stable and reliable catalytic activity, reduce polymer formation, and reduce the possibility of blockage during the polymerization process. It has the characteristics of high total selectivity of 1-octene and 1-hexene and high activity. Summary of the Invention

[0006] The purpose of the present invention is to provide a Si-PCCP ligand, a preparation method thereof, an ethylene oligomerization catalyst and an application thereof in ethylene oligomerization reaction. The ligand of the present invention can be combined with an active metal to be used as an ethylene oligomerization reaction catalyst. This catalyst is a homogeneous catalyst, with more stable catalyst performance, more uniform reaction, and more controllable feeding amount.

[0007] The present invention provides a Si-PCCP ligand, and its structural formula is as follows:

[0008]

[0009] Among them, R1 is selected from alkyl groups with 4 or more carbon atoms, trimethylsilylmethylmagnesium bromide, triethylsilylmethylmagnesium bromide, or trimethylsilylbutylmagnesium bromide; preferably n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-decyl, isobutyl, isopentyl, isoheptyl, 3-methyloctyl, 3-methylhexyl, 4-methylpentyl, 3-methylheptyl, 4-methyldecyl, 2-ethyloctyl, 4-ethylhexyl, trimethylsilylmethylmagnesium bromide, triethylsilylmethylmagnesium bromide, trimethylsilylbutylmagnesium bromide, and more preferably trimethylsilylmethylmagnesium bromide, triethylsilylmethylmagnesium bromide, or trimethylsilylbutylmagnesium bromide.

[0010] R2 and R3 can be the same or different and are independently selected from alkyl groups, aryl groups, and their derivatives. Preferably, they are selected from C10 or lower linear alkyl groups, cycloalkyl groups, phenyl groups, benzyl groups, biphenyl groups, naphthyl groups, anthracenyl groups, isopropyl groups, cyclobutyl groups, 2-methylphenyl groups, 4-methylphenyl groups, 2,4-dimethylphenyl groups, 2,6-dimethylphenyl groups, 2-ethylphenyl groups, 4-ethylphenyl groups, 2,4-diethylphenyl groups, 2,6-diethylphenyl groups, 2-isopropylphenyl groups, 4-isopropylphenyl groups, 2,4-diisopropylphenyl groups, 2,6-diisopropylphenyl groups, 2-butylphenyl groups, 4-butylphenyl groups, 2,4-dibutylphenyl groups, 2,6-dibutylphenyl groups, 4-methoxyphenyl groups, o-methoxyphenyl groups, 4-ethoxyphenyl groups, o-ethoxyphenyl groups, 2-fluorophenyl groups, 3-fluorophenyl groups, 4-fluorophenyl groups, 2-(trimethylsilyl)phenyl groups, 3-(trimethylsilyl)phenyl groups, 4-(trimethylsilyl)phenyl groups, 2-(tri-n-butylsilyl)phenyl groups, 3-(tri-n-butylsilyl)phenyl groups, 4-(tri-n-butylsilyl)phenyl groups.

[0011] The present invention also provides a preparation method of the ligand, which includes the following steps:

[0012] (1) Take an appropriate amount of ethynyl Grignard reagent, and while stirring in an ice-water bath, add substituted chlorosilane dropwise for 1 - 5 h. After the dropwise addition is completed, react at room temperature for 10 - 20 h, add water to quench the reaction, and purify the reaction solution to obtain product one, which is silylacetylene; its structure is as shown in formula a:

[0013] (2) Dissolve product one in solvent A, and while stirring in an ice-water bath, add alkyllithium reagent dropwise for 1 - 5 h. After the dropwise addition is completed, react at -10 - 0 °C for 1 - 5 h, slowly add substituted phosphine chloride, and react for 1 - 10 h. After purifying the reaction solution, product two is obtained, which is silylacetylene phosphine, and its structure is as shown in formula b:

[0014] (3) Dissolve Product II, copper(I) catalyst, inorganic base, and substituted phosphine in Solvent B, and react at 80 - 100 °C for 1 - 10 h. After purifying the reaction solution, Product III is obtained, which is the Si - PCCP ligand, and its structure is as shown in Formula c.

[0015] Preferably, in step (1), the ethynyl Grignard reagent is selected from magnesium ethynyl bromide,

[0016] Preferably, in step (1), the structural formula of the substituted chlorosilane is: (R1)3SiCl, where the definition of R1 is the same as the above definition.

[0017] Preferably, in step (1), the molar ratio of the ethynyl Grignard reagent to the alkyl chlorosilane is 1:0.8 - 1; preferably, in step (2), the structure of the substituted phosphorus chloride is: P(R2)2Cl, where the definition of R2 is the same as the above definition.

[0018] Preferably, in step (2), the molar ratio of the silylacetylene to the substituted phosphorus chloride is 1:1 - 1.2, and Solvent A is one or more of tetrahydrofuran, dioxane, ether, 2 - methyltetrahydrofuran.

[0019] Preferably, in step (2), the addition amount of alkyllithium and the molar ratio of Product I is 1:1 - 1.2.

[0020] Preferably, in step (3), the structure of the substituted phosphine is: P(R3)2H, where the definition of R3 is the same as the above definition.

[0021] Preferably, in step (3), the copper(I) catalyst is one or more of copper iodide, iron chloride, cuprous oxide. The inorganic base is one or more of cesium carbonate, potassium carbonate, sodium hydroxide.

[0022] In step (3), the molar ratio of Product II, copper(I) catalyst, inorganic base, and substituted phosphine is 1:0.1 - 0.2:0.1 - 0.2:1 - 1.2, and Solvent B is selected from one or more of N,N - dimethylformamide, N,N - dimethylacetamide.

[0023] The chemical reaction route in step (1) is as follows:

[0024]

[0025] The chemical reaction route in step (2) is as follows:

[0026]

[0027] The reaction route in step (3) is as follows:

[0028]

[0029] In the present invention, the reaction solution in steps (1)-(3) can be purified by column chromatography to obtain the target product and the target product is recrystallized. The column height-diameter ratio of the column chromatography purification is 5-10, the residence time is 10-60 min, and the solvent used for recrystallization is a mixed solvent of ethanol and ethyl acetate.

[0030] The present invention also provides an ethylene oligomerization catalyst, which catalyst comprises the ligand and the active component chromium described in the present invention.

[0031] The ethylene oligomerization catalyst is prepared by the following method: adding the ligand described in the present invention into a solvent, then adding a chromium source (such as chromium chloride in tetrahydrofuran), reacting at 20-30 °C for 1-10 h, and purifying the reaction solution to obtain product four, namely the Si-PCCP-Cr catalyst.

[0032] The molar ratio of the ligand to chromium in the chromium source is 0.8-1:1.

[0033] The reaction route of the catalyst is schematically shown as follows:

[0034]

[0035] Preferably, the catalyst further comprises an alkylaluminum or an alkylaluminoxane cocatalyst.

[0036] The cocatalyst described in the present invention is selected from one or more of trimethylaluminum, triethylaluminum, triisobutylaluminum, diethylethoxyaluminum, monochlorodiethylaluminum, dichloroethylaluminum, sesquialter ethyl aluminum chloride, trioctylaluminum, methylaluminoxane (MAO), modified methylaluminoxane (MMAO) or ethylaluminoxane.

[0037] In the catalyst described in the present invention, the molar ratio of the cocatalyst to chromium in the catalyst is 50-2000:1, preferably 90-800:1.

[0038] The present invention also provides the application of the above catalyst, which is used for ethylene oligomerization reaction.

[0039] In some preferred embodiments of the present invention, the method for the ethylene oligomerization reaction is as follows: before the reaction, the reaction kettle needs to be heated to 110-160 °C, evacuated for 1-4 h, replaced with nitrogen, and after the temperature is cooled to room temperature, replaced with ethylene. First, add solvent C and the cocatalyst, then add the catalyst. After the temperature reaches the reaction temperature, 0-0.8 Mpa of hydrogen and 2 MPa-7 MPa of ethylene are sequentially introduced to start the reaction. The reaction temperature is 35-90 °C, preferably 40-70 °C, and the reaction time is 10 min-240 min, preferably 20 min-100 min.

[0040] The ethylene oligomerization reaction solvent C is selected from one or more of n-butane, isobutane, n-pentane, cyclopentane, methylcyclopentane, methylenecyclopentane, n-hexane, cyclohexane, methylcyclohexane, n-heptane, n-octane, n-nonane, benzene, toluene, and xylene.

[0041] In a more specific embodiment, the polymerization method of the catalyst composition of the present invention is as follows: Polymerization is carried out in a high-pressure reactor, and refined alkane is used as solvent C. Before the reaction, the reactor is heated to 120 °C - 140 °C, evacuated for 1 - 3 h, and replaced with nitrogen three times. After cooling to room temperature, ethylene is replaced twice. First, dehydrated and deoxygenated solvent C and a quantitative alkylaluminum cocatalyst are added, then a transition metal compound and a PCPN ligand are added. When the temperature is constant at the reaction temperature, 0.2 - 0.7 Mpa of hydrogen and 2 MPa - 7 MPa of ethylene are sequentially introduced to start the reaction. The reaction temperature is 35 - 90 °C, preferably 40 - 70 °C, and the reaction time is 10 min - 240 min, preferably 20 min - 100 min. After the reaction, the ethylene inlet valve is closed, and the temperature is rapidly decreased using an ice-water bath or liquid nitrogen, and the pressure is slowly released to unload the reactor to obtain the ethylene oligomerization product.

[0042] The addition amount of the catalyst is such that the molar concentration of the added transition metal chromium in the ethylene oligomerization reaction system is 10 - 25 μmol / L (solvent), preferably 15 - 20 μmol / L (solvent).

[0043] Compared with the prior art, by introducing a silyl chain, the PCCP system catalyst with extremely poor solubility can be very easily dissolved in the reaction solution. The homogeneous catalytic feeding solves problems such as abnormal fluctuations in polymerization activity and catalyst deactivation caused by uneven stirring and catalyst sedimentation. It has very important significance for industrial production.

[0044] By introducing a homogeneous PCCP catalyst, while improving the activity, the generation sites of polymer by-products are reduced, the growth of polymers is inhibited, which is beneficial to reducing the blockage of the polymerization kettle and significantly reducing the frequency of kettle cleaning.

[0045] Moreover, the ethylene oligomerization catalyst system of the present invention has an activity for ethylene oligomerization of more than 1,500,000 g / (gCr·h). Most significantly, the total selectivity of 1-hexene and 1-octene can reach 91.5%, and the PE selectivity is less than 0.05 wt%. Detailed implementation mode

[0046] The following specific examples only illustrate the present invention, but these examples are only part of the content of the present invention and do not limit the application of the present invention in other fields.

[0047] The raw materials used in the examples are all conventional raw materials in the art, and the purity specifications used are analytical pure or chemically pure.

[0048] Raw material source information:

[0049] Ethynylmagnesium bromide: Beijing Innochem Science & Technology Co., Ltd.

[0050] Tributylchlorosilane, Trioctylchlorosilane: Beijing Innochem Science & Technology Co., Ltd.

[0051] Copper(I) iodide, Cesium carbonate: Beijing Innochem Science & Technology Co., Ltd.

[0052] Diphenylphosphine: 98%, J&K Scientific Ltd.

[0053] N,N-Dimethylformamide: 99%, Shanghai Merck Chemical Technology Co., Ltd.

[0054] N,N-Dimethylacetamide: 99%, Shanghai Merck Chemical Technology Co., Ltd.

[0055] Tetrahydrofuran: Beijing Innochem Science & Technology Co., Ltd.

[0056] Diethyl ether: 99%, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0057] 1,4-Dioxane: 99%, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0058] Diphenylphosphinous chloride: 97%, Alfa Aesar (China) Chemicals Co., Ltd.

[0059] p-tert-Butyldiphenylphosphinous chloride, 98%, Beijing Innochem Co., Ltd.

[0060] p-Methoxydiphenylphosphinous chloride, 98%, Aladdin Reagent Co., Ltd.

[0061] m-Methoxydiphenylphosphinous chloride, 98%, Beijing Innochem Co., Ltd.

[0062] p-Methyldiphenylphosphine, 98%, Beijing Innochem Co., Ltd.

[0063] Ethyl acetate: 99.9%, J&K Scientific Ltd.

[0064] Ethanol: Analytical reagent grade, Sinopharm Chemical Reagent Co., Ltd.

[0065] Butyllithium: 1.6 M in hexane, Aladdin Reagent Co., Ltd.

[0066] Di-p-tolyphosphinous chloride Shanghai Merck Chemical Technology Co., Ltd.

[0067] Tris(trimethylsilylmethyl)chlorosilane: 98%, Shanghai Wuxi Apptec Co., Ltd., CAS No.: 18077-32-2

[0068] Tris(triethylsilylmethyl)chlorosilane: 98%, Shanghai Wuxi AppTec Co., Ltd., CAS No.: 30432-47-4

[0069] The catalytic activity of the oligomerization reaction was analyzed qualitatively and quantitatively for each component in the reaction solution. The conditions of the GC analysis instrument used were as follows:

[0070] Instrument model: Shimadzu GC2010

[0071] Chromatographic column: DB-5 (30m 0.25mm 0.25μm)

[0072] Column temperature program: First, hold at 35°C for 10 min, then raise the temperature to 250°C at a rate of 10°C / min and hold at this temperature for 10 min.

[0073] Detector temperature: 300°C

[0074] Carrier gas: 1 bar

[0075] Air: 0.3 bar

[0076] Fuel gas (H2): 0.3 bar

[0077] The sample mass analysis was carried out using the internal standard method. There should be:

[0078]

[0079] Where m1 is the mass of a certain product, m is the mass of the internal standard, a1 is the peak area detected for this product in the gas chromatography, and a is the peak area of the internal standard. k is a correction factor related to the substance to be measured and the detection conditions.

[0080] Example 1

[0081] Preparation of catalyst C1: The relevant solvents were dehydrated and deoxygenated before use.

[0082] Preparation of tributylsilylacetylene: Take 16.1 mmol of ethynylmagnesium bromide, cool to 0°C, and slowly add 13.4 mmol of tributylchlorosilane dropwise. After the addition is complete, raise the temperature to 25°C and react for 12 h. Add an appropriate amount of water to quench the reaction, extract the reaction solution with n-hexane, filter to remove insoluble substances, and dry the filtrate to obtain tributylsilylacetylene.

[0083] Preparation of tributylsilylacetylenephosphine: Under anhydrous and anaerobic conditions, take 2.27 mmol of tributylsilylacetylene, dissolve it in 10 ml of tetrahydrofuran, cool to 0°C, slowly add 1.6 ml of butyllithium dropwise, maintain the reaction at 0°C for 1 h, add 2.27 mol of diphenylphosphine chloride, and react for 2 h. After the reaction is complete, add an appropriate amount of water to quench the reaction, extract the reaction solution with n-hexane, filter to remove insoluble substances, and obtain tributylsilylacetylenephosphine by column chromatography separation.

[0084] Preparation of Si-PCCP ligand: Under anhydrous and anaerobic conditions, 1.02 mmol of tributylsilylacetylene phosphine, 0.12 mmol of copper iodide, 0.1 mmol of cesium carbonate, 1.02 mmol of diphenylphosphine, and 6 ml of N,N-dimethylformamide were added, and the mixture was heated to 90 °C and reacted for 6 h. After the reaction was completed, an appropriate amount of water was added to quench the reaction, and the reaction solution was extracted with n-hexane. The insoluble substances were removed by filtration, and the tributylsilyl PCCP ligand was obtained by column chromatography separation. 1 H NMR (400 MHz, CDCl3) δ 7.71–7.60 (m, 12H), 7.40–7.32 (m, 8H), 5.5 (s, 1H), 1.46–1.36 (m, 12H), 0.93 (t, J = 7.0 Hz, 9H), 0.75–0.67 (m, 6H).

[0085] Preparation of catalyst C1: Under anhydrous and anaerobic conditions, 0.5 mmol of Si-PCCP ligand was dissolved in 10 ml of dichloromethane, 0.5 mmol of chromium chloride in tetrahydrofuran was added, and the reaction was carried out at 25 °C for 2 h. The solvent was removed under vacuum, the solid was extracted with n-hexane, the insoluble substances were removed by filtration, and the solvent was dried under vacuum to obtain the catalyst.

[0086]

[0087] Ethylene oligomerization:

[0088] Before the reaction, the 300 ml reaction kettle was heated to 150 °C, evacuated for 3 h, and replaced with nitrogen three times. After the temperature was cooled to room temperature, ethylene was replaced twice. First, 100 ml of dehydrated and deoxygenated solvent methylcyclohexane and 1 ml of (Al / Cr = 500) MMAO-3a (7 wt% Al, n-heptane) were added, and then 3.5 μmol of Si-PCCP-Cr catalyst was added. When the temperature was constant at 45 °C, 0.5 Mpa of hydrogen and 5 MPa of ethylene were sequentially introduced to start the reaction. The reaction temperature was 45 °C, and the reaction time was 60 min. After the reaction was completed, the ethylene inlet valve was closed, and the temperature was rapidly cooled to below 5 °C with an ice-water bath, and the pressure was slowly released to unload the kettle to obtain the ethylene oligomerization product.

[0089] The product was analyzed by GC, with an activity of 1523 kg / gCr·h, a selectivity of (1-hexene + 1-octene) of 82.5 wt%, and a polymer selectivity of 0.12 wt%.

[0090] Example 2

[0091] Preparation of catalyst C2: Take 16.1 mmol of ethynylmagnesium bromide, cool it to 0 °C, and slowly add dropwise 13.4 mmol of trioctylchlorosilane. After the addition is complete, raise the temperature to 25 °C and react for 12 h. Add an appropriate amount of water to quench the reaction, extract the reaction solution with n-hexane, filter to remove the insoluble substances, and dry the filtrate by suction to obtain trioctylsilylacetylene.

[0092] Preparation of trioctylsilylacetylene phosphine: Under anhydrous and anaerobic conditions, take 2.27 mmol of trioctylsilylacetylene, dissolve it in 10 ml of dioxane, cool it to -10 °C, slowly add dropwise 1.45 ml of butyllithium, maintain the reaction at 0 °C for 1 h, add 2.27 mol of diphenylphosphine chloride, and react for 2 h. After the reaction is complete, add an appropriate amount of water to quench the reaction, extract the reaction solution with n-hexane, filter to remove the insoluble substances, and obtain trioctylsilylacetylene phosphine by column chromatography separation.

[0093] Preparation of Si-PCCP ligand: Under anhydrous and anaerobic conditions, add 1.02 mmol of trioctylsilylacetylene phosphine, 0.1 mmol of copper iodide, 0.12 mmol of cesium carbonate, 1.02 mmol of bis(4-methoxyphenyl)phosphine, and 6 ml of N,N-dimethylformamide, heat to 90 °C, and react for 6 h. After the reaction is complete, add an appropriate amount of water to quench the reaction, extract the reaction solution with n-hexane, filter to remove the insoluble substances, and obtain the trioctylsilyl PCCP ligand by column chromatography separation. 1 H NMR (400 MHz, CDCl3) δ 7.65–7.61 (m, 10H), 7.30–7.22 (m, 8H), 5.5 (s, 1H), 3.05 (s, 6H), 1.40–1.31 (m, 36H), 0.92 (t, J = 7.0 Hz, 9H), 0.70–0.67 (m, 6H).

[0094] Preparation of Si-PCCP-Cr catalyst: Under anhydrous and anaerobic conditions, add 0.5 mmol of Si-PCCP ligand, dissolve it in 10 ml of dichloromethane, add 0.5 mmol of chromium tetrahydrofuran chloride, react at 25 °C for 2 h, remove the solvent under vacuum, extract the solid with n-hexane, filter to remove the insoluble substances, and dry the solvent by vacuum suction to obtain the catalyst.

[0095]

[0096] Ethylene oligomerization:

[0097] Before the reaction, heat a 500 ml reactor to 160 °C, evacuate it for 1.5 h, and replace the gas with nitrogen three times. After the temperature cools to room temperature, replace the gas with ethylene twice. First, add 200 ml of dehydrated and deoxygenated solvent methylcyclohexane and 1.4 ml of MMAO-3a (7 wt% Al, n-heptane) with Al / Cr = 600, and then add 3 μmol of Si-PCCP-Cr catalyst. When the temperature is constant at 55 °C, sequentially introduce 0.4 Mpa of hydrogen and 4.5 MPa of ethylene to start the reaction. The reaction temperature is 55 °C, and the reaction time is 40 min. After the reaction is completed, close the ethylene inlet valve, quickly cool it to below 5 °C with an ice-water bath, slowly relieve the pressure, and unload the reactor to obtain the ethylene oligomerization product.

[0098] Analyze the product by GC. The activity is 1785 kg / gCr·h, the selectivity of (1-hexene + 1-octene) is 88.3 wt%, and the selectivity of the polymer is 0.07 wt%.

[0099] Example 3

[0100] Preparation of catalyst C3: Take 16.1 mmol of ethynylmagnesium bromide, cool it to 0 °C, slowly add 13.4 mmol of tris(trimethylsilylmethyl)chlorosilane dropwise. After the addition is complete, raise the temperature to 25 °C and react for 12 h. Add an appropriate amount of water to quench the reaction, extract the reaction solution with n-hexane, filter to remove insoluble substances, and dry the filtrate to obtain tris(trimethylsilylmethyl)silylacetylene.

[0101] Preparation of tris(trimethylsilylmethyl)silylacetylene phosphine: Under anhydrous and anaerobic conditions, take 2.27 mmol of tris(trimethylsilylmethyl)silylacetylene, dissolve it in 10 ml of diethyl ether, cool it to 0 °C, slowly add 1.6 ml of butyllithium dropwise, maintain the reaction at 0 °C for 1 h, add 2.27 mol of bis(4-methylphenyl)chlorophosphine and ditolylchlorophosphine, and react for 2 h. After the reaction is completed, add an appropriate amount of water to quench the reaction, extract the reaction solution with n-hexane, filter to remove insoluble substances, and obtain tris(trimethylsilylmethyl)silylacetylene phosphine by column chromatography separation.

[0102] Preparation of Si-PCCP ligand: Under anhydrous and anaerobic conditions, add 1.02 mmol of tris(trimethylsilylmethyl)silylacetylene phosphine, 0.15 mmol of copper iodide, 0.1 mmol of cesium carbonate, 1.2 mmol of bis(4-methylphenyl)chlorophosphine, and 6 ml of N,N-dimethylformamide, heat to 80 °C, and react for 6 h. After the reaction is completed, add an appropriate amount of water to quench the reaction, extract the reaction solution with n-hexane, filter to remove insoluble substances, and obtain tris(trimethylsilylmethyl)silyl PCCP ligand by column chromatography separation. 1 H NMR (400 MHz, CDCl3) δ 7.30–7.22 (m, 16H), 5.5 (s, 1H), 2.1 (s, 12H), 0.21 (s, 27H), 0.01 (s, 6H).

[0103] Preparation of Si-PCCP-Cr catalyst: Under anhydrous and anaerobic conditions, 0.5 mmol of Si-PCCP ligand was added and dissolved in 10 ml of dichloromethane. Then 0.5 mmol of chromium(III) chloride tetrahydrofuran complex was added, and the reaction was carried out at 20 °C for 2 h. The solvent was removed under vacuum, and the solid was extracted with n-hexane. The insoluble substances were removed by filtration, and the solvent was dried under vacuum to obtain the catalyst.

[0104]

[0105] Ethylene oligomerization:

[0106] Before the reaction, a 500 ml autoclave was heated to 160 °C and evacuated for 1.5 h, and then purged with nitrogen three times. After the temperature was cooled to room temperature, it was purged with ethylene twice. First, 200 ml of dehydrated and deoxygenated solvent methylcyclohexane and 1.4 ml of MMAO-3a (7 wt% Al, in n-heptane) with Al / Cr = 600 were added, and then 3 μmol of Si-PCCP-Cr catalyst was added. When the temperature was kept constant at 55 °C, 0.4 MPa of hydrogen and 4.5 MPa of ethylene were sequentially introduced to start the reaction. The reaction temperature was 55 °C and the reaction time was 40 min. After the reaction, the ethylene inlet valve was closed, and the temperature was rapidly cooled to below 5 °C by ice-water bath, and the pressure was slowly released. The autoclave was unloaded to obtain the ethylene oligomerization product.

[0107] The product was analyzed by GC. The activity was 3398 kg / gCr·h, the selectivity of (1-hexene + 1-octene) was 93.2 wt%, and the selectivity of polymer was 0.05 wt%.

[0108] Example 4

[0109] Preparation of catalyst C4: 16.1 mmol of ethynylmagnesium bromide was taken and cooled to 0 °C. 13.4 mmol of tris(trimethylsilylmethyl)chlorosilane was slowly added dropwise. After the addition was completed, the temperature was raised to 25 °C and the reaction was carried out for 12 h. An appropriate amount of water was added to quench the reaction, and the reaction solution was extracted with n-hexane. The insoluble substances were removed by filtration, and the filtrate was dried to obtain tris(trimethylsilylmethyl)silylacetylene.

[0110] Preparation of tris(trimethylsilylmethyl)silylacetylene phosphine: Under anhydrous and anaerobic conditions, 2.27 mmol of tris(trimethylsilylmethyl)silylacetylene was taken and dissolved in 10 ml of tetrahydrofuran. It was cooled to 0 °C, and 1.6 ml of butyllithium was slowly added dropwise. The reaction was carried out at 0 °C for 1 h, and then 2.27 mmol of bis(4-methoxyphenyl)phosphinous chloride was added and the reaction was carried out for 2 h. After the reaction was completed, an appropriate amount of water was added to quench the reaction, and the reaction solution was extracted with n-hexane. The insoluble substances were removed by filtration, and tris(trimethylsilylmethyl)silylacetylene phosphine was obtained by column chromatography separation.

[0111] Preparation of Si-PCCP ligand: Under anhydrous and anaerobic conditions, 1.02 mmol of tris(trimethylsilylmethyl)silylacetylene phosphine, 0.1 mmol of copper iodide, 0.15 mmol of cesium carbonate, 1.02 mmol of bis(4-methoxyphenyl)phosphine, and 6 ml of N,N-dimethylformamide were added, and the mixture was heated to 90 °C and reacted for 6 h. After the reaction was completed, an appropriate amount of water was added to quench the reaction, and the reaction solution was extracted with n-hexane. The insoluble substances were removed by filtration, and the tris(trimethylsilylmethyl)silyl PCCP ligand was obtained by column chromatography separation. 1 H NMR (400 MHz, CDCl3) δ 7.30–7.22 (m, 16H), 5.5 (s, 1H), 3.5 (s, 12H), 0.21 (s, 27H), 0.01 (s, 6H).

[0112] Preparation of Si-PCCP-Cr catalyst: Under anhydrous and anaerobic conditions, 0.5 mmol of Si-PCCP ligand was dissolved in 10 ml of dichloromethane, 0.5 mmol of chromium chloride tetrahydrofuran was added, and the reaction was carried out at 25 °C for 2 h. The solvent was removed under vacuum, the solid was extracted with n-hexane, the insoluble substances were removed by filtration, and the solvent was dried under vacuum to obtain the catalyst.

[0113]

[0114] Ethylene oligomerization:

[0115] Before the reaction, a 500 ml reaction kettle was heated to 160 °C, evacuated for 1.5 h, and replaced with nitrogen three times. After the temperature was cooled to room temperature, ethylene was replaced twice. First, 200 ml of dehydrated and deoxygenated solvent methylcyclohexane and 1.4 ml of (Al / Cr = 600) MMAO-3a (7 wt% Al, n-heptane) were added, and then 3 μmol of Si-PCCP-Cr catalyst was added. When the temperature was constant at 55 °C, 0.4 Mpa of hydrogen and 4.5 MPa of ethylene were sequentially introduced to start the reaction. The reaction temperature was 55 °C, and the reaction time was 40 min. After the reaction was completed, the ethylene inlet valve was closed, and the temperature was quickly cooled to below 5 °C with an ice-water bath, and the pressure was slowly released to unload the kettle to obtain the ethylene oligomerization product.

[0116] The product was analyzed by GC, with an activity of 3250 kg / gCr·h, a selectivity of (1-hexene + 1-octene) of 89.8 wt%, and a polymer selectivity of 0.08 wt%.

[0117] Example 5

[0118] Preparation of Catalyst C5: Take 16.1 mmol of ethynylmagnesium bromide, cool it to 0 °C, and slowly add dropwise 12.9 mmol of tris(triethylsilylmethyl)chlorosilane. After the addition is complete, warm the temperature to 25 °C and react for 12 h. Add an appropriate amount of water to quench the reaction, extract the reaction solution with n-hexane, filter to remove the insoluble substances, and dry the filtrate by suction to obtain tris(triethylsilylmethyl)silylacetylene.

[0119] Preparation of tris(triethylsilylmethyl)silylacetylene phosphine: Under anhydrous and anaerobic conditions, take 2.16 mmol of tris(triethylsilylmethyl)silylacetylene, dissolve it in 10 ml of 2-methyltetrahydrofuran, cool it to 0 °C, slowly add dropwise 1.6 ml of butyllithium, maintain the reaction at 0 °C for 1 h, add 2.27 mmol of bis(4-tert-butylphenyl)chlorophosphine, and react for 2 h. After the reaction is complete, add an appropriate amount of water to quench the reaction, extract the reaction solution with n-hexane, filter to remove the insoluble substances, and obtain tris(triethylsilylmethyl)silylacetylene phosphine by column chromatography separation.

[0120] Preparation of Si-PCCP ligand: Under anhydrous and anaerobic conditions, add 1.02 mmol of tris(triethylsilylmethyl)silylacetylene phosphine, 0.1 mmol of copper iodide, 0.1 mmol of cesium carbonate, 1.02 mmol of diphenylphosphine, and 6 ml of N,N-dimethylformamide, heat to 90 °C, and react for 6 h. After the reaction is complete, add an appropriate amount of water to quench the reaction, extract the reaction solution with n-hexane, filter to remove the insoluble substances, and obtain the tris(triethylsilylmethyl)silyl PCCP ligand by column chromatography separation. 1H NMR (400 MHz, CDCl3) δ 7.30–7.22 (m, 18H), 5.5 (s, 1H), 1.3 (s, 18H), 0.91 (s, 27H), 0.11 (m, 18H), 0.01 (s, 6H).

[0121] Preparation of Si-PCCP-Cr catalyst: Under anhydrous and anaerobic conditions, add 0.5 mmol of Si-PCCP ligand, dissolve it in 10 ml of dichloromethane, add 0.5 mmol of chromium tetrahydrofuran chloride, react at 25 °C for 2 h, remove the solvent under vacuum, extract the solid with n-hexane, filter to remove the insoluble substances, and dry the solvent by vacuum suction to obtain the catalyst.

[0122]

[0123] Oligomerization of ethylene:

[0124] Before the reaction, heat a 500 ml reactor to 160 °C, evacuate it for 1.5 h, and replace the gas with nitrogen three times. After the temperature cools to room temperature, replace the gas with ethylene twice. First, add 200 ml of dehydrated and deoxygenated solvent methylcyclohexane and 0.21 ml of MMAO-3a (7 wt% Al, n-heptane) with Al / Cr = 90, and then add 3 μmol of Si-PCCP-Cr catalyst. When the temperature is constant at 55 °C, sequentially introduce 0.4 Mpa of hydrogen and 4.5 MPa of ethylene to start the reaction. The reaction temperature is 55 °C and the reaction time is 40 min. After the reaction is completed, close the ethylene inlet valve, quickly cool it to below 5 °C with an ice-water bath, slowly release the pressure, and unload the reactor to obtain the ethylene oligomerization product.

[0125] The product was analyzed by GC. The activity was 3422 kg / gCr·h, the selectivity of (1-hexene + 1-octene) was 88.8 wt%, and the selectivity of the polymer was 0.07 wt%.

[0126] Example 6

[0127] Preparation of catalyst C6: Take 16.1 mmol of ethynylmagnesium bromide, cool it to 0 °C, and slowly add dropwise 16.1 mmol of trimethylchlorosilane. After the addition is complete, warm it up to 25 °C and react for 12 h. Add an appropriate amount of water to quench the reaction, extract the reaction solution with n-hexane, filter to remove insoluble substances, and dry the filtrate to obtain trimethylsilylacetylene.

[0128] Preparation of trimethylsilylacetylene phosphine: Under anhydrous and anaerobic conditions, take 2.27 mmol of trimethylsilylacetylene, dissolve it in 10 ml of diethyl ether, cool it to -5 °C, slowly add dropwise 1.75 ml of butyllithium, maintain the reaction at 0 °C for 1 h, add 2.27 mol of bis(3-methoxyphenyl)phosphine chloride, and react for 2 h. After the reaction is completed, add an appropriate amount of water to quench the reaction, extract the reaction solution with n-hexane, filter to remove insoluble substances, and obtain trimethylsilylacetylene phosphine by column chromatography separation.

[0129] Preparation of Si-PCCP ligand: Under anhydrous and anaerobic conditions, add 1.02 mmol of trimethylsilylacetylene phosphine, 0.1 mmol of copper iodide, 0.1 mmol of cesium carbonate, 1.02 mmol of diphenylphosphine, and 6 ml of N,N-dimethylformamide, heat to 90 °C, and react for 6 h. After the reaction is completed, add an appropriate amount of water to quench the reaction, extract the reaction solution with n-hexane, filter to remove insoluble substances, and obtain the trimethylsilyl PCCP ligand by column chromatography separation. 1 H NMR (400 MHz, CDCl3) δ 7.30–7.22 (m, 18H), 5.5 (s, 1H), 3.7 (s, 6H), 0.01 (s, 9H).

[0130] Preparation of Si-PCCP-Cr catalyst: Under anhydrous and anaerobic conditions, 0.5 mmol of Si-PCCP ligand was added and dissolved in 10 ml of dichloromethane. Then 0.5 mmol of chromium(III) chloride tetrahydrofuran complex was added, and the reaction was carried out at 25 °C for 2 h. The solvent was removed under vacuum, and the solid was extracted with n-hexane. The insoluble matter was removed by filtration, and the solvent was dried under vacuum to obtain the catalyst.

[0131]

[0132] Ethylene oligomerization:

[0133] Before the reaction, a 500 ml autoclave was heated to 160 °C and evacuated for 1.5 h, and then purged with nitrogen three times. After the temperature was cooled to room temperature, the autoclave was purged with ethylene twice. First, 200 ml of dehydrated and deoxygenated solvent methylcyclohexane and 1.9 ml of MMAO-3a (7 wt% Al, in n-heptane) with Al / Cr = 800 were added, and then 3 μmol of Si-PCCP-Cr catalyst was added. When the temperature was kept constant at 55 °C, 0.4 MPa of hydrogen and 4.5 MPa of ethylene were introduced successively to start the reaction. The reaction temperature was 55 °C and the reaction time was 40 min. After the reaction was completed, the ethylene inlet valve was closed, and the temperature was quickly cooled to below 5 °C by an ice-water bath, and the pressure was slowly released. The ethylene oligomerization product was obtained by discharging the autoclave.

[0134] The product was analyzed by GC. The activity was 1833 kg / gCr·h, the selectivity of (1-hexene + 1-octene) was 89.7 wt%, and the selectivity of polymer was 0.11 wt%.

[0135] Example 7

[0136] Preparation of catalyst C7: 16.1 mmol of ethynylmagnesium bromide was taken and cooled to 0 °C. 16.1 mmol of triisobutylchlorosilane was slowly added dropwise. After the addition was completed, the temperature was raised to 25 °C and the reaction was carried out for 12 h. An appropriate amount of water was added to quench the reaction, and the reaction solution was extracted with n-hexane. The insoluble matter was removed by filtration, and the filtrate was dried to obtain triisobutylsilylacetylene.

[0137] Preparation of triisobutylsilylacetylene phosphine: Under anhydrous and anaerobic conditions, 2.27 mmol of triisobutylsilylacetylene was taken and dissolved in 10 ml of diethyl ether. It was cooled to 0 °C, and 1.6 ml of butyllithium was slowly added dropwise. The reaction was carried out at 0 °C for 1 h, and then 2.27 mmol of dimethylphosphinous chloride was added, and the reaction was carried out for 2 h. After the reaction was completed, an appropriate amount of water was added to quench the reaction, and the reaction solution was extracted with n-hexane. The insoluble matter was removed by filtration, and triisobutylsilylacetylene phosphine was obtained by column chromatography separation.

[0138] Preparation of Si-PCCP ligand: Under anhydrous and anaerobic conditions, 1.02 mmol of triisobutylsilylacetylene phosphine, 0.1 mmol of copper iodide, 0.1 mmol of cesium carbonate, 1.02 mmol of diphenylphosphine, and 6 ml of N,N-dimethylformamide were added, and the mixture was heated to 100 °C and reacted for 6 h. After the reaction was completed, an appropriate amount of water was added to quench the reaction, and the reaction solution was extracted with n-hexane. The insoluble substances were removed by filtration, and the triisobutylsilyl PCCP ligand was obtained by column chromatography separation. 1 H NMR (400 MHz, CDCl3) δ 7.71–7.59 (m, 10H), 5.4 (s, 1H), 1.6 (m, 3H), 0.98 (m, 6H), 0.92 (m, 18H), 0.55 (m, 6H).

[0139] Preparation of Si-PCCP-Cr catalyst: Under anhydrous and anaerobic conditions, 0.5 mmol of Si-PCCP ligand was dissolved in 10 ml of dichloromethane, 0.5 mmol of chromium chloride tetrahydrofuran was added, and the mixture was reacted at 30 °C for 2 h. The solvent was removed under vacuum, the solid was extracted with n-hexane, the insoluble substances were removed by filtration, and the solvent was dried under vacuum to obtain the catalyst.

[0140]

[0141] Ethylene oligomerization:

[0142] Before the reaction, a 500 ml reaction kettle was heated to 160 °C, evacuated for 1.5 h, and replaced with nitrogen three times. After the temperature was cooled to room temperature, ethylene was replaced twice. First, 200 ml of dehydrated and deoxygenated solvent methylcyclohexane and 1.4 ml of (Al / Cr = 600) MMAO-3a (7 wt% Al, n-heptane) were added, and then 3 μmol of Si-PCCP-Cr catalyst was added. When the temperature was constant at 55 °C, 0.4 Mpa of hydrogen and 4.5 MPa of ethylene were sequentially introduced to start the reaction. The reaction temperature was 55 °C, and the reaction time was 40 min. After the reaction was completed, the ethylene inlet valve was closed, and the temperature was quickly cooled to below 5 °C with an ice-water bath or rapidly, and the pressure was slowly released, and the reaction kettle was unloaded to obtain the ethylene oligomerization product.

[0143] The product was analyzed by GC, with an activity of 1859 kg / gCr·h, a selectivity of (1-hexene + 1-octene) of 83.7 wt%, and a polymer selectivity of 0.06 wt%.

[0144] Comparative Example 1

[0145] Preparation of catalyst C8:

[0146] Preparation of isopropylacetylene phosphine: Under anhydrous and anaerobic conditions, 2.27 mmol of isopropylacetylene was taken and dissolved in 10 ml of ether. It was cooled to 0 °C, and 1.6 ml of butyllithium was slowly added dropwise. The reaction was maintained at 0 °C for 1 h, and then 2.27 mol of diphenylphosphine chloride was added, and the reaction was carried out for 2 h. After the reaction was completed, an appropriate amount of water was added to quench the reaction. The reaction solution was extracted with n-hexane, and the insoluble substances were removed by filtration. Isopropylacetylene phosphine was obtained by column chromatography separation.

[0147] Preparation of PCCP ligand: Under anhydrous and anaerobic conditions, 1.02 mmol of isopropylacetylene phosphine, 0.1 mmol of copper iodide, 0.1 mmol of cesium carbonate, 1.02 mmol of diphenylphosphine, and 6 ml of N,N-dimethylformamide were added. The mixture was heated to 80 °C and reacted for 6 h. After the reaction was completed, an appropriate amount of water was added to quench the reaction. The reaction solution was extracted with n-hexane, and the insoluble substances were removed by filtration. Isopropyl PCCP ligand was obtained by column chromatography separation. 1 H NMR(400MHz,CDCl3)δ7.30–7.02(m,20H),5.5(s,1H),2.31(m,1H),1.36(d,6H)

[0148] Preparation of PCCP-Cr catalyst: Under anhydrous and anaerobic conditions, 0.5 mmol of PCCP ligand was added and dissolved in 10 ml of dichloromethane. Then 0.5 mmol of chromium tetrahydrofuran chloride was added, and the reaction was carried out at 20 °C for 2 h. The solvent was removed under vacuum. The solid was extracted with n-hexane, and the insoluble substances were removed by filtration. The solvent was dried under vacuum to obtain the catalyst.

[0149]

[0150] Ethylene oligomerization:

[0151] Before the reaction, a 500 ml reaction kettle was heated to 160 °C and evacuated for 1.5 h, and then replaced with nitrogen three times. After the temperature was cooled to room temperature, it was replaced with ethylene twice. First, 200 ml of dehydrated and deoxygenated solvent methylcyclohexane and 1.4 ml of (Al / Cr = 600) MMAO-3a (7 wt% Al, n-heptane) were added, and then 3 μmol of PCCP-Cr catalyst was added. When the temperature was constant at 55 °C, 0.4 Mpa of hydrogen and 4.5 MPa of ethylene were sequentially introduced to start the reaction. The reaction temperature was 55 °C, and the reaction time was 40 min. After the reaction was completed, the ethylene inlet valve was closed, and the temperature was quickly cooled to below 5 °C with an ice-water bath, and the pressure was slowly released. The reaction kettle was unloaded to obtain the ethylene oligomerization product.

[0152] The product was analyzed by GC. The activity was 1192 kg / gCr.h, the selectivity of (1-hexene + 1-octene) was 87.8 wt%, and the selectivity of the polymer was 0.5 wt%.

Claims

1. A Si-PCCP ligand, characterized in that, Its structural formula is as follows: Among them, R1 is selected from alkyl groups with 4 to 20 carbon atoms; R2 and R3 are the same or different and are independently selected from lower chain alkyl groups with 10 or fewer carbon atoms, phenyl, benzyl, biphenyl, naphthyl, anthracenyl, cyclobutyl, 2-methylphenyl, 4-methylphenyl, 2,4-dimethylphenyl, 2,6-dimethylphenyl, 2-ethylphenyl, 4-ethylphenyl, 2,4-diethylphenyl, 2,6-diethylphenyl, 2-isopropylphenyl, 4-isopropylphenyl, 2,4-diisopropylphenyl, 2,6-diisopropylphenyl, 2-butylphenyl, 4-butylphenyl, 2,4-dibutylphenyl, 2,6-dibutylphenyl, 4-methoxyphenyl, o-methoxyphenyl, 4-ethoxyphenyl, o-ethoxyphenyl, 2-fluorophenyl, 3-fluorophenyl, 4-fluorophenyl, 2-(trimethylsilyl)phenyl, 3-(trimethylsilyl)phenyl, 4-(trimethylsilyl)phenyl, 2-(tri-n-butylsilyl)phenyl, 3-(tri-n-butylsilyl)phenyl, 4-(tri-n-butylsilyl)phenyl.

2. The ligand according to claim 1, wherein R1 is selected from n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-decyl, isobutyl, isopentyl, isoheptyl, 3-methyloctyl, 3-methylhexyl, 4-methylpentyl, 3-methylheptyl, 4-methyldecyl, 2-ethyloctyl, 4-ethylhexyl.

3. The preparation method of the ligand according to claim 1, comprising the following steps: (1) Take an appropriate amount of ethynyl Grignard reagent, and while stirring in an ice-water bath, add substituted chlorosilane dropwise for 1 - 5 h. After the dropwise addition is completed, react at room temperature for 10 - 20 h, add water to quench the reaction, and purify the reaction solution to obtain Product 1, which is silylacetylene; (2) Dissolve Product 1 in Solvent A, and while stirring in an ice-water bath, add an alkyllithium reagent dropwise for 1 - 5 h. After the dropwise addition is completed, react at -10 - 0 °C for 1 - 5 h, slowly add substituted phosphinous chloride, and react for 1 - 10 h. After purifying the reaction solution, obtain Product 2, which is silylacetylene phosphine; (3) Dissolve Product 2, a copper(I) catalyst or iron(III) chloride, an inorganic base, and a substituted phosphine in Solvent B, and react at 80 - 100 °C for 1 - 10 h. After purifying the reaction solution, obtain Product 3, which is the Si-PCCP ligand; In step (1), the structural formula of the substituted chlorosilane is: (R1)3SiCl, where the definition of R1 is the same as the above definition; The structure of the substituted phosphinous chloride in step (2) is: P(R2)2Cl, where the definition of R2 is the same as the above definition; The copper(I) catalyst in step (3) is one or more of copper(I) iodide and copper(I) oxide.

4. According to the preparation method of claim 3, the ethynyl Grignard reagent in step (1) is selected from ethynylmagnesium bromide.

5. According to the preparation method of claim 3, in step (1), the molar ratio of the ethynyl Grignard reagent to the substituted chlorosilane is 1:0.8 - 1.

6. According to the preparation method of claim 3, wherein, In the step (2), the molar ratio of silicon-based acetylene to substituted phosphine chloride is 1:1 - 1.2, and the solvent A is one or more of tetrahydrofuran, dioxane, ether, and 2-methyltetrahydrofuran; In the step (2), the addition amount of alkyllithium and the molar ratio of the product I is 1:1 - 1.

2.

7. According to the preparation method described in claim 3, The inorganic base is one or more of cesium carbonate, potassium carbonate, and sodium hydroxide.

8. According to the preparation method described in claim 3, in the step (3), the molar ratio of the product II, copper(I) catalyst or ferric chloride, inorganic base, and substituted phosphine is 1:0.1 - 0.2:0.1 - 0.2:1 - 1.2, and the solvent B is selected from one or more of N,N-dimethylformamide and N,N-dimethylacetamide.

9. An ethylene oligomerization catalyst, which comprises the ligand described in any one of claims 1 - 2 or the ligand prepared by the preparation method described in any one of claims 3 - 8 and the active component chromium.

10. According to the catalyst described in claim 9, add the ligand to the solvent, then add the chromium source, react at 20 - 30 °C for 1 - 10 h, and obtain the product IV by purifying the reaction solution, which is the Si-PCCP-Cr catalyst.

11. According to the catalyst described in claim 10, the molar ratio of the ligand to chromium in the chromium source is 0.8 - 1:

1.

12. According to the catalyst described in claim 9, the catalyst further comprises an alkylaluminum or an alkylaluminoxane cocatalyst.

13. According to the catalyst described in claim 12, the cocatalyst is selected from one or more of trimethylaluminum, triethylaluminum, triisobutylaluminum, diethyl ethoxyaluminum, chloro diethylaluminum, dichloroethylaluminum, sesquiethyl aluminum chloride, trioctylaluminum, methylaluminoxane, modified methylaluminoxane, or ethylaluminoxane.

14. According to the catalyst described in claim 12, the molar ratio of the cocatalyst to chromium in the catalyst is 50 - 2000:

1.

15. According to the catalyst described in claim 14, the molar ratio of the cocatalyst to chromium in the catalyst is 90 - 800:

1.

16. An application of the catalyst described in any one of claims 9 - 15, which is used for ethylene oligomerization reaction.

17. According to the application described in claim 16, the method for the ethylene oligomerization reaction is as follows: before the reaction, the reaction kettle needs to be heated to 110 - 160 °C, evacuated for 1 - 4 h, replaced with nitrogen, and after the temperature is cooled to room temperature, replaced with ethylene. First, add the solvent C and the cocatalyst, then add the catalyst. After the temperature reaches the reaction temperature, 0 - 0.8 Mpa of hydrogen and 2 MPa - 7 MPa of ethylene are sequentially introduced to start the reaction. The reaction temperature is 35 - 90 °C, and the reaction time is 10 min - 240 min.

18. According to the application described in claim 17, the ethylene oligomerization reaction solvent C is selected from one or more of n-butane, isobutane, n-pentane, cyclopentane, methylcyclopentane, methylene cyclopentane, n-hexane, cyclohexane, methylcyclohexane, n-heptane, n-octane, n-nonane, benzene, toluene, and xylene.

19. The application according to claim 16, wherein the addition amount of the catalyst is such that the molar concentration of the added chromium in the ethylene oligomerization reaction system is 10 - 25 μmol / L of the solvent.

20. The application according to claim 19, wherein the addition amount of the catalyst is such that the molar concentration of the added chromium in the ethylene oligomerization reaction system is 15 - 20 μmol / L of the solvent.

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