A tridentate phosphine pyrrolimine ligand, a preparation method thereof, an ethylene oligomerization catalyst and application thereof

Abstract

The application discloses a tridentate phosphine pyrroline ligand, a preparation method thereof, an ethylene oligomerization catalyst and application of the catalyst. The catalyst comprises the tridentate phosphine pyrroline ligand shown in a structure of formula I, a transition metal compound and an alkyl aluminum promoter. The catalyst system can be used for homogeneously catalyzing ethylene oligomerization, and has the advantages of a short catalyst synthesis route, high catalytic activity, and selective generation of 1-octene or 1-hexene by adjusting the amount of the alkyl aluminum promoter.

Description

Technical Field

[0001] This invention belongs to the field of ethylene oligomerization technology, specifically relating to a tridentate phosphine pyrrolimide ligand and its preparation method, an ethylene oligomerization catalyst and its application. Background Technology

[0002] Since the development of PNP catalysts, selective oligomerization has been a hot research topic. New catalytic systems have been continuously developed, but the industrial application of selective oligomerization of ethylene remains unclear. Existing ethylene oligomerization catalytic systems simultaneously produce 1-octene and 1-hexene, requiring subsequent separation and purification to obtain the final product, resulting in significant production waste.

[0003] The main limitation is that highly selective 1-octene and 1-hexene cannot share a single set of equipment and processes, resulting in high production costs and high technical barriers. At the same time, due to market and technological constraints, the supply and demand relationship for 1-octene and 1-hexene fluctuates significantly, posing substantial risks to production companies. Another important factor affecting the industrialization of oligomerization is the byproduct polymer, which easily clogs reaction pipelines, preventing the unit from operating for extended periods and requiring frequent cleaning. This greatly impacts the start-up efficiency of oligomerization units.

[0004] However, none of the currently available technical literature discloses a catalyst system for ethylene oligomerization that can selectively switch between 1-octene and 1-hexene by controlling process conditions. Selective switching of products is crucial for the industrial application of ethylene oligomerization. Furthermore, no suitable solutions have been reported in the literature to address the issue of by-product polymers and reduce clogging. Summary of the Invention

[0005] The purpose of this invention is to provide a tridentate phosphine pyrrolimide ligand and its preparation method, an ethylene oligomerization catalyst, and its application in the ethylene oligomerization reaction. The catalyst of this invention can selectively generate 1-octene or 1-hexene by adjusting the amount of alkyl aluminum, achieving the generation of two products from a single catalyst system. Furthermore, when applied to ethylene oligomerization, this catalytic system produces extremely low levels of by-product polymers, ensuring long-term operation of the plant.

[0006] This invention provides a tridentate phosphine pyrrolimide ligand, the structure of which is shown in Formula I:

[0007]

[0008] Wherein, R1 is selected from aryl groups and their derivatives, preferably C6-C20 aryl groups, and more preferably, R1 is selected from phenyl, 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, and 4-fluorophenyl.

[0009] R2 is selected from hydrogen, alkyl, alkoxy, halogen, preferably hydrogen, C1-C20 alkyl, C1-C20 alkoxy, more preferably methyl, ethyl, methoxy, isopropyl, tert-butyl.

[0010] This invention also provides a method for preparing the ligand, comprising the following steps:

[0011] (1) Take 2,5-diaminopyrrole, dissolve it in an appropriate amount of solvent A, add o-bromophenylaldehyde compound, react at 75-90℃ for 1-5 h, purify the reaction solution to obtain product one, the structure of which is shown in formula a:

[0012]

[0013] The definitions of R1 and R2 are the same as in Equation I.

[0014] (2) Dissolve compound a in solvent B, and add alkyl lithium reagent dropwise under stirring in an ice-water bath for 1-5 hours. After the addition is complete, react at -5 to 0°C for 1-5 hours, then slowly add substituted phosphine chloride and react for 1-10 hours. After purification, product two is obtained, which is the tridentate phosphine pyrrolimide ligand.

[0015] Preferably, the structural formula of the o-bromophenylaldehyde compound is: R2 is defined the same as in Equation I.

[0016] Preferably, in step (1), the molar ratio of 2,5-diaminopyrrole to o-bromophenylaldehyde is 1:2-2.2;

[0017] Preferably, in step (1), solvent A is one or more of ethanol, methanol, and isopropanol.

[0018] Preferably, in step (2), the molar ratio of compound a to alkyl lithium reagent is 1:3-3.3.

[0019] Preferably, solvent B in step (2) is one or more of tetrahydrofuran, dioxane, diethyl ether, and 2-methyltetrahydrofuran.

[0020] Preferably, the substituted phosphine chloride in step (2) has the structural formula CIPR1, where R1 is defined as in formula I. Preferably, the molar ratio of compound a to the substituted phosphine chloride in step (2) is 1:3-3.3.

[0021] The chemical reaction pathway in step (1) is as follows:

[0022]

[0023] The chemical reaction pathway in step (2) is as follows:

[0024]

[0025] The present invention also provides an ethylene oligomerization catalyst, comprising the ligands described in the present invention and metallic chromium.

[0026] The ethylene oligomerization catalyst can be generated in situ in the reaction system, or it can be prepared as a complex before being added to the reaction system.

[0027] The catalyst is prepared by dissolving compound c in dichloromethane and adding a chromium source (such as tetrahydrofuran chromium chloride), reacting at 20-30℃ for 1-10 hours, and then purifying the reaction solution to obtain the product, which is the tridentate phosphine pyrrole imine chromium catalyst.

[0028] Preferably, the molar ratio of the chromium source to compound C is 1:0.8-1.2.

[0029] The present invention also provides the application of the catalyst in the ethylene oligomerization reaction.

[0030] An ethylene oligomerization reaction using the catalyst and alkylaluminum co-catalyst described in this invention;

[0031] The alkylaluminum cocatalyst is selected from one or more of trimethylaluminum, triethylaluminum, triisobutylaluminum, diethylethoxyaluminum, diethylaluminum chloride, diethylaluminum chloride, sesquiethylaluminum chloride, trioctylaluminum, methylaluminoxane, modified methylaluminoxane, or ethylaluminoxane.

[0032] The molar ratio of alkylaluminum co-catalyst to chromium is 50-2000:1, preferably 90-800:1.

[0033] The amount of catalyst added is such that the molar concentration of chromium in the oligomerization reaction system is 10-60 μmol / L, preferably 20-50 μmol / L.

[0034] In some preferred embodiments of the present invention, the method for the ethylene oligomerization reaction is as follows: before the reaction, the reactor needs to be heated to 110-160°C, evacuated for 1-4 hours, and purged with nitrogen. After the temperature is cooled to room temperature, ethylene is purged. Solvent C and alkylaluminum co-catalyst are added first, followed by the addition of catalyst. After the temperature reaches the reaction temperature, hydrogen gas at 0-0.8 MPa and ethylene gas at 2 MPa-7 MPa are introduced sequentially 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.

[0035] The solvent C for the ethylene oligomerization reaction is selected from one or more of the following: n-butane, isobutane, n-pentane, cyclopentane, methylcyclopentane, methylenecyclopentane, n-hexane, cyclohexane, methylcyclohexane, n-heptane, n-octane, n-nonane, benzene, toluene, and xylene.

[0036] 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 300 mL high-pressure reactor using purified alkane as solvent C. Before the reaction, the reactor is heated to 130°C, evacuated for 1-3 hours, and purged with nitrogen three times. After cooling to room temperature, ethylene is purged twice. First, dehydrated and deoxygenated solvent C and a measured amount of alkylaluminum co-catalyst are added, followed by a chromium source and tridentate phosphine imine pyrrole ligand. Once the temperature is constant at the reaction temperature, hydrogen gas at 0.2-0.7 MPa and ethylene gas at 2 MPa-7 MPa are introduced sequentially to initiate the reaction. The reaction temperature is 35-90°C, preferably 40-70°C, and the reaction time is 10-240 min, preferably 20-100 min. After the reaction is completed, the ethylene inlet valve is closed, and the reactor is rapidly cooled using an ice-water bath or liquid nitrogen. The pressure is slowly released, and the reactor is unloaded to obtain the ethylene oligomer product.

[0037] Compared with the prior art, the catalytic system of the present invention has the controllability of 1-octene and 1-hexene. Under the condition that the molar ratio of alkylaluminum co-catalyst to chromium is less than or equal to 200:1, preferably 50-200:1, the selectivity of 1-hexene is high, which can be greater than 85%. Under the condition that the molar ratio of alkylaluminum co-catalyst to chromium is greater than or equal to 500:1, preferably 500-1000:1, the selectivity for generating 1-octene is greater than 85%.

[0038] Moreover, the ethylene oligomerization catalyst system of the present invention has high activity for ethylene oligomerization and low PE selectivity. Detailed Implementation

[0039] The following specific embodiments are only for illustrating 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.

[0040] All raw materials used in the examples are conventional raw materials in the art, and the purity specifications used are analytical grade or chemically pure.

[0041] Raw material source information:

[0042] 2,5-Diaminopyrrole: Beijing Inokay Technology Co., Ltd.

[0043] o-Bromobenzaldehyde: Beijing Innocare Technology Co., Ltd.

[0044] 4-Methoxy-2-bromobenzaldehyde: Shanghai BIDE Pharmaceutical Technology Co., Ltd.

[0045] Tetrahydrofuran Chromium Chloride: Bailingwei Technology Co., Ltd.

[0046] Diphenylphosphine chloride: Beijing Inokai Technology Co., Ltd.

[0047] 5-tert-Butyl-2-bromobenzaldehyde: Shanghai Ruisheng Chemical Technology Co., Ltd.

[0048] Bis(4-methoxyphenyl)phosphine chloride: Beijing Innocare Technology Co., Ltd.

[0049] Bis(3,5-di-tert-butyl-4-methoxyphenyl)phosphine chloride: Beijing Innocare Technology Co., Ltd.

[0050] Dioxane: Beijing Inocare Technology Co., Ltd.

[0051] 2-Methyltetrahydrofuran: Beijing Innocare Technology Co., Ltd.

[0052] The catalyst activity of the oligomerization reaction was determined by qualitative and quantitative analysis of the components in the reaction solution. The conditions of the GC analytical instrument used were as follows:

[0053] Instrument Model: Shimadzu GC2010

[0054] Column: DB-5 (30m 0.25mm 0.25μm)

[0055] Column temperature program: First, maintain at 35℃ for 10 min, then increase to 250℃ at a rate of 10℃ / min, and maintain at this temperature for 10 min.

[0056] Detector temperature: 300℃

[0057] Carrier gas: 1 bar

[0058] Air: 0.3 bar

[0059] Gas (H2): 0.3 bar

[0060] Sample quality analysis was performed using the internal standard method. It should include:

[0061]

[0062] In the formula, m1 is the mass of a certain product, m is the mass of the internal standard, a1 is the peak area of ​​the product detected in gas chromatography, and a is the peak area of ​​the internal standard. k is a correction coefficient related to the analyte and detection conditions.

[0063] Example 1

[0064] Preparation of tridentate phosphine pyrrolimide: Remove water and oxygen from the relevant solvents before use.

[0065] Preparation of 2-bromoimine pyrrole ligand: Take 10.3 mmol of 2,5-diaminopyrrole, add 15 ml of ethanol, add 20.6 mmol of o-bromobenzaldehyde, heat to 75 °C, react for 1 h. After the reaction is complete, filter, wash the mother liquor with ethanol, and remove the solvent under vacuum to obtain the product 2-bromoimine ligand.

[0066] Preparation of tridentate phosphineimine pyrrole: Under anhydrous and oxygen-free conditions, 7.2 mmol of 2-bromoimine pyrrole was dissolved in 30 mL of tetrahydrofuran. The solution was cooled to 0 °C, and 21.6 mmol of butyllithium was slowly added dropwise. The reaction was maintained at 0 °C for 1 h. Then, 21.6 mmol of diphenylphosphine chloride was added, and the reaction was allowed to proceed for 2 h. After the reaction was complete, an appropriate amount of water was added to quench the reaction. The reaction solution was extracted with n-hexane, and the insoluble matter was removed by filtration. The tridentate phosphineimine pyrrole was obtained by column chromatography. ¹H NMR (400 MHz, CDCl₃) δ 8.91 (s, 2H), 7.82–7.02 (m, 38H), 6.82 (d, 2H).

[0067]

[0068] Preparation of tridentate phosphine imine pyrrole-chromium catalyst: Under anhydrous and oxygen-free conditions, 0.5 mmol of tridentate phosphine imine pyrrole ligand was added and dissolved in 10 ml of dichloromethane. 0.5 mmol of tetrahydrofuran chromium chloride was added and reacted at 25 °C for 2 h. The solvent was removed under vacuum, 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.

[0069] Ethylene oligomerization 1-1:

[0070] Before the reaction, the 300ml reactor was heated to 150℃ and evacuated for 3 hours, with nitrogen purging three times. After cooling to room temperature, ethylene was purged twice. First, 100ml of dehydrated and deoxygenated solvent methylcyclohexane and 1ml of (Al / Cr=500)MMAO-3a (7wt% Al, n-heptane) were added, followed by 3.5μmol of the catalyst prepared in Example 1. Once the temperature was constant at 45℃, 0.5MPa hydrogen and 5MPa ethylene were introduced sequentially to initiate the reaction. The reaction temperature was 45℃, and the reaction time was 60min. After the reaction was completed, the ethylene inlet valve was closed, and the reactor was cooled to below 5℃ using an ice-water bath or rapidly. The pressure was slowly released, and the reactor was unloaded to obtain the ethylene oligomer.

[0071] The product was analyzed by GC, showing an activity of 3202 kg / gCr·h, a 1-octene selectivity of 85.3 wt%, and a polymer selectivity of 0.09 wt%.

[0072] Ethylene oligomerization 1-2

[0073] The experimental conditions were the same as those for ethylene oligomerization 1-1, except for 0.1 ml of (Al / Cr = 50) MMAO-3a. The product was analyzed by GC, with an activity of 3002 kg / gCr·h, a 1-hexene selectivity of 92.3 wt%, and a polymer selectivity of 0.05 wt%.

[0074] Example 2

[0075] Preparation of tridentate phosphine pyrrolimide: Remove water and oxygen from the relevant solvents before use.

[0076] Preparation of 2-bromoimine pyrrole ligand: Take 10.3 mmol of 2,5-diaminopyrrole, add 15 ml of isopropanol, add 22.7 mmol of o-bromobenzaldehyde, heat to 90 °C, react for 1 h. After the reaction is complete, filter, wash the mother liquor with ethanol, and remove the solvent under vacuum to obtain the product 2-bromoimine ligand.

[0077] Preparation of tridentate phosphineimine pyrrole: Under anhydrous and oxygen-free conditions, 7.2 mmol of 2-bromoimine pyrrole was dissolved in 30 mL of tetrahydrofuran, cooled to 0 °C, and 21.6 mmol of butyllithium was slowly added dropwise. The reaction was maintained at 0 °C for 1 h, followed by the addition of 21.6 mmol of bis(4-methoxyphenyl)phosphine chloride, and the reaction was allowed to proceed for 2 h. After the reaction was complete, an appropriate amount of water was added to quench the reaction, the reaction solution was extracted with n-hexane, and the insoluble matter was removed by filtration. Tridentate phosphineimine pyrrole was obtained by column chromatography. ¹H NMR (400 MHz, CDCl₃) δ 8.91 (s, 2H), 7.82–7.02 (m, 32H), 6.82 (d, 2H), 3.82 (s, 18H).

[0078]

[0079] Preparation of tridentate phosphine imine pyrrole-chromium catalyst: Under anhydrous and oxygen-free conditions, 0.5 mmol of tridentate phosphine imine pyrrole ligand was added and dissolved in 10 ml of dichloromethane. 0.5 mmol of tetrahydrofuran chromium chloride was added and reacted at 25 °C for 2 h. The solvent was removed under vacuum, 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.

[0080] Ethylene oligomerization 2-1:

[0081] Before the reaction, the 300ml reactor was heated to 150℃ and evacuated for 3 hours, with nitrogen purging three times. After cooling to room temperature, ethylene was purged twice. First, 100ml of dehydrated and deoxygenated solvent methylcyclohexane and 2ml of (Al / Cr = 1000)MMAO-3a (7wt% Al, n-heptane) were added, followed by 3.5μmol of catalyst. Once the temperature was constant at 45℃, 0.5MPa hydrogen and 5MPa ethylene were introduced sequentially to initiate the reaction. The reaction temperature was 45℃, and the reaction time was 60min. After the reaction was complete, the ethylene inlet valve was closed, and the reactor was cooled to below 5℃ using an ice-water bath or rapidly. The pressure was slowly released, and the reactor was unloaded to obtain the ethylene oligomer.

[0082] The product was analyzed by GC, showing an activity of 2980 kg / gCr·h, a 1-octene selectivity of 85.2 wt%, and a polymer selectivity of 0.09 wt%.

[0083] Ethylene oligomerization 2-2

[0084] The experimental conditions were the same as those for ethylene oligomerization 1-1, except that 0.4 ml of (Al / Cr = 200) MMAO-3a was analyzed by GC. The activity was 3120 kg / gCr·h, the 1-hexene selectivity was 87.5 wt%, and the polymer selectivity was 0.08 wt%.

[0085] Example 3

[0086] Preparation of tridentate phosphine pyrrolimide: Remove water and oxygen from the relevant solvents before use.

[0087] Preparation of 2-bromoimine pyrrole ligand: Take 10.3 mmol of 2,5-diaminopyrrole, add 15 ml of methanol, add 22.7 mmol of 5-tert-butyl-2-bromobenzaldehyde, heat to 75 °C, react for 1 h. After the reaction is complete, filter, wash the mother liquor with ethanol, and remove the solvent under vacuum to obtain the product 2-bromoimine ligand.

[0088] Preparation of tridentate phosphineimine pyrrole: Under anhydrous and oxygen-free conditions, 7.2 mmol of 2-bromoimine pyrrole was dissolved in 30 mL of 2-methyltetrahydrofuran. The solution was cooled to 0 °C, and 22.7 mmol of butyllithium was slowly added dropwise. The reaction was maintained at 0 °C for 1 h. Then, 21.6 mmol of diphenylphosphine chloride was added, and the reaction was allowed to proceed for 2 h. After the reaction was complete, an appropriate amount of water was added to quench the reaction. The reaction solution was extracted with n-hexane, and the insoluble matter was removed by filtration. Tridentate phosphineimine pyrrole was obtained by column chromatography. ¹H NMR (400 MHz, CDCl₃) δ 8.91 (s, 2H), 7.82–7.02 (m, 36H), 6.82 (d, 2H), 2.21 (s, 18H).

[0089]

[0090] Preparation of tridentate phosphine imine pyrrole-chromium catalyst: Under anhydrous and oxygen-free conditions, 0.5 mmol of tridentate phosphine imine pyrrole ligand was added and dissolved in 10 ml of dichloromethane. 0.5 mmol of tetrahydrofuran chromium chloride was added and reacted at 25 °C for 2 h. The solvent was removed under vacuum, 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.

[0091] Ethylene oligomerization 3-1:

[0092] Before the reaction, the 300ml reactor was heated to 150℃ and evacuated for 3 hours, with nitrogen purging three times. After cooling to room temperature, ethylene was purged twice. First, 100ml of dehydrated and deoxygenated solvent methylcyclohexane and 1.6ml of (Al / Cr = 800)MMAO-3a (7wt% Al, n-heptane) were added, followed by 3.5mol of Si-PCCP-Cr catalyst. Once the temperature was constant at 45℃, 0.5MPa hydrogen and 5MPa ethylene were introduced sequentially to initiate the reaction. The reaction temperature was 45℃, and the reaction time was 60min. After the reaction was complete, the ethylene inlet valve was closed, and the reactor was cooled to below 5℃ using an ice-water bath or rapidly. The pressure was slowly released, and the reactor was unloaded to obtain the ethylene oligomer.

[0093] The product was analyzed by GC, with an activity of 3005 kg / gCr·h, a 1-octene selectivity of 86.2 wt%, and a polymer selectivity of 0.10 wt%.

[0094] Ethylene oligomerization 3-2

[0095] The experimental conditions were the same as those for ethylene oligomerization 1-1, except that 0.3 ml of (Al / Cr = 150) MMAO-3a was analyzed by GC. The activity was 2908 kg / gCr·h, the 1-hexene selectivity was 85.5 wt%, and the polymer selectivity was 0.05 wt%.

[0096] Example 4

[0097] Preparation of tridentate phosphine pyrrolimide: Remove water and oxygen from the relevant solvents before use.

[0098] Preparation of 2-bromoimine pyrrole ligand: Take 10.3 mmol of 2,5-diaminopyrrole, add 15 ml of ethanol, add 21.6 mmol of o-bromobenzaldehyde, heat to 75 °C, react for 1 h. After the reaction is complete, filter, wash the mother liquor with ethanol, and remove the solvent under vacuum to obtain the product 2-bromoimine ligand.

[0099] Preparation of tridentate phosphineimine pyrrole: Under anhydrous and oxygen-free conditions, 7.2 mmol of 2-bromoimine pyrrole was dissolved in 30 mL of diethyl ether, cooled to 0 °C, and 21.6 mmol of butyllithium was slowly added dropwise. The reaction was maintained at 0 °C for 1 h. Then, 21.6 mmol of bis(3,5-di-tert-butyl-4-methoxyphenyl)phosphine chloride was added, and the reaction was allowed to proceed for 2 h. After the reaction was complete, an appropriate amount of water was added to quench the reaction, the reaction solution was extracted with n-hexane, and the insoluble matter was removed by filtration. The tridentate phosphineimine pyrrole was obtained by column chromatography. ¹H NMR (400 MHz, CDCl₃) δ 8.91 (s, 2H), 7.82–7.02 (m, 20H), 6.82 (d, 2H), 3.21 (s, 18H), 1.35 (s, 10⁸H).

[0100]

[0101] Preparation of tridentate phosphine imine pyrrole-chromium catalyst: Under anhydrous and oxygen-free conditions, 0.5 mmol of tridentate phosphine imine pyrrole ligand was added and dissolved in 10 ml of dichloromethane. 0.5 mmol of tetrahydrofuran chromium chloride was added and reacted at 25 °C for 2 h. The solvent was removed under vacuum, 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.

[0102] Ethylene oligomerization 4-1:

[0103] Before the reaction, the 300ml reactor was heated to 150℃ and evacuated for 3 hours, with nitrogen purging three times. After cooling to room temperature, ethylene was purged twice. First, 100ml of dehydrated and deoxygenated solvent methylcyclohexane and 1.6ml of (Al / Cr = 800)MMAO-3a (7wt% Al, n-heptane) were added, followed by 3.5mol of Si-PCCP-Cr catalyst. Once the temperature was constant at 45℃, 0.5MPa hydrogen and 5MPa ethylene were introduced sequentially to initiate the reaction. The reaction temperature was 45℃, and the reaction time was 60min. After the reaction was complete, the ethylene inlet valve was closed, and the reactor was cooled to below 5℃ using an ice-water bath or rapidly. The pressure was slowly released, and the reactor was unloaded to obtain the ethylene oligomer.

[0104] The product was analyzed by GC, showing an activity of 3110 kg / gCr·h, a 1-octene selectivity of 85.5 wt%, and a polymer selectivity of 0.07 wt%.

[0105] Ethylene oligomerization 4-2

[0106] The experimental conditions were the same as those for ethylene oligomerization 1-1, except that 0.3 ml of (Al / Cr = 150) MMAO-3a was analyzed by GC, with an activity of 2990 kg / gCr·h, a 1-hexene selectivity of 90.5 wt%, and a polymer selectivity of 0.05 wt%.

[0107] Example 5

[0108] Preparation of tridentate phosphine pyrrolimide: Remove water and oxygen from the relevant solvents before use.

[0109] Preparation of 2-bromoimine pyrrole ligand: Take 10.3 mmol of 2,5-diaminopyrrole, add 15 ml of ethanol, add 21.6 mmol of 4-methoxy-2-bromobenzaldehyde, heat to 75 °C, react for 1 h. After the reaction is complete, filter, wash the mother liquor with ethanol, remove the solvent under vacuum, and the product 2-bromoimine ligand is obtained.

[0110] Preparation of tridentate phosphineimine pyrrole: Under anhydrous and oxygen-free conditions, 7.2 mmol of 2-bromoimine pyrrole was dissolved in 30 mL of dioxane, cooled to 0 °C, and 21.6 mmol of butyllithium was slowly added dropwise. The reaction was maintained at 0 °C for 1 h, followed by the addition of 21.6 mmol of diphenylphosphine chloride, and the reaction was allowed to proceed for 2 h. After the reaction was complete, an appropriate amount of water was added to quench the reaction, the reaction solution was extracted with n-hexane, and the insoluble matter was removed by filtration. Tridentate phosphineimine pyrrole was obtained by column chromatography. ¹H NMR (400 MHz, CDCl₃) δ 8.89 (s, 2H), 7.80–7.02 (m, 36H), 6.81 (d, 2H), 3.82 (s, 6H).

[0111]

[0112] Preparation of tridentate phosphine imine pyrrole-chromium catalyst: Under anhydrous and oxygen-free conditions, 0.5 mmol of tridentate phosphine imine pyrrole ligand was added and dissolved in 10 ml of dichloromethane. 0.5 mmol of tetrahydrofuran chromium chloride was added and reacted at 25 °C for 2 h. The solvent was removed under vacuum, 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.

[0113] Ethylene oligomerization 5-1:

[0114] Before the reaction, the 300ml reactor was heated to 150℃ and evacuated for 3 hours, with nitrogen purging three times. After cooling to room temperature, ethylene was purged twice. First, 100ml of dehydrated and deoxygenated solvent methylcyclohexane and 1.6ml of (Al / Cr = 800)MMAO-3a (7wt% Al, n-heptane) were added, followed by 3.5mol of Si-PCCP-Cr catalyst. Once the temperature was constant at 45℃, 0.5MPa hydrogen and 5MPa ethylene were introduced sequentially to initiate the reaction. The reaction temperature was 45℃, and the reaction time was 60min. After the reaction was complete, the ethylene inlet valve was closed, and the reactor was cooled to below 5℃ using an ice-water bath or rapidly. The pressure was slowly released, and the reactor was unloaded to obtain the ethylene oligomer.

[0115] The product was analyzed by GC, showing an activity of 3305 kg / gCr·h, a 1-octene selectivity of 88.3 wt%, and a polymer selectivity of 0.07 wt%.

[0116] Ethylene oligomerization 5-2

[0117] The experimental conditions were the same as those for ethylene oligomerization 1-1, except that 0.3 ml of (Al / Cr = 150) MMAO-3a was analyzed by GC. The activity was 3108 kg / gCr·h, the 1-hexene selectivity was 89.5 wt%, and the polymer selectivity was 0.09 wt%.

Claims

1. A tridentate phosphine pyrrolimide ligand, characterized in that, The structure is shown in formula I: Wherein, R1 is selected from C6-C20 aryl; R2 is selected from hydrogen, C1-C20 alkyl, C1-C20 alkoxy.

2. The ligand of claim 1, wherein R1 is selected from phenyl, 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; R2 is selected from methyl, ethyl, methoxy, isopropyl, tert-butyl.

3. A process for the preparation of a ligand according to claim 1 or 2, characterized in that, The method comprises the following steps: (1) 2,5-diaminopyrrole is dissolved in a proper amount of solvent A, o-bromophenyl aldehyde compound is added, and reaction is carried out at 75-90℃ for 1-5h, and the reaction solution is purified and treated to obtain product one, the structure of which is shown in formula a: Wherein, R1 and R2 are defined as the same as formula I; (2) Compound a is dissolved in solvent B, and alkyl lithium reagent is added dropwise under ice water bath stirring for 1-5h; after the addition is completed, reaction is carried out at-5-0℃ for 1-5h, substituted phosphine chloride is slowly added, and reaction is carried out for 1-10h, and the reaction solution is purified and treated to obtain product two, which is a tridentate phosphine pyrrole imine ligand; The structural formula of the ortho-bromophenyl aldehyde compound is: R2 is defined the same as formula I.

4. The production method according to claim 3, characterized by, In step (1), the molar ratio of 2,5-diaminopyrrole to o-bromophenyl aldehyde compound is 1:2-2.

2.

5. The preparation method according to claim 3, characterized in that, In step (1), the solvent A is one or more of ethanol, methanol, isopropanol.

6. The preparation method according to claim 3, characterized in that, In step (2), the molar ratio of compound a to alkyl lithium reagent is 1:3-3.

3.

7. The preparation method according to claim 3, characterized in that, In step (2), the solvent B is one or more of tetrahydrofuran, dioxane, diethyl ether, 2-methyltetrahydrofuran.

8. The preparation method according to claim 3, characterized in that, In step (2), the structure of substituted phosphine chloride is ClPR1, wherein R1 is defined as the same as formula I.

9. The preparation method according to claim 3, characterized in that, In step (2), the molar ratio of compound a to substituted phosphine chloride is 1:3-3.

3.

10. An ethylene oligomerization catalyst comprising the ligand of claim 1 or 2 and the ligand prepared by the preparation method of any one of claims 3-9 and metal chromium.

11. The ethylene oligomerization catalyst of claim 10, wherein, The ethylene oligomerization catalyst is generated in situ in a reaction system or is prepared into a complex and then added into a reaction system.

12. The ethylene oligomerization catalyst of claim 10, wherein, The preparation method of the catalyst is that compound c is dissolved in dichloromethane, a chromium source is added, reaction is carried out at 20-30℃ for 1-10h, and the reaction solution is purified and treated to obtain product, which is a tridentate phosphine pyrrole imine chromium catalyst.

13. The ethylene oligomerization catalyst of claim 10, wherein, The molar ratio of the amount of the chromium source added to the molar amount of compound c is 1:0.8-1.

2.

14. The catalyst of claim 10 is applied in ethylene oligomerization reaction.

15. An ethylene oligomerization reaction characterized by, The catalyst of claim 10 and an alkyl aluminum cocatalyst are used.

16. The ethylene oligomerization reaction of claim 15, wherein, The alkyl aluminum cocatalyst is selected from one or more of trimethyl aluminum, triethyl aluminum, triisobutyl aluminum, diethyl ethoxy aluminum, monochlorodiethyl aluminum, dichloroethyl aluminum, ethyl aluminum sesquichloride, trioctyl aluminum, methylaluminoxane, modified methylaluminoxane, or ethylaluminoxane.

17. The ethylene oligomerization reaction of claim 15, wherein, The molar ratio of the alkyl aluminum cocatalyst to chromium is 50-2000:

1.

18. The ethylene oligomerization reaction of claim 17, wherein, The molar ratio of the alkyl aluminum cocatalyst to chromium is 90-800:

1.

19. The ethylene oligomerization reaction of claim 15, wherein, The catalyst is added in an amount such that the molar concentration of chromium in the oligomerization reaction system is 10-60 μmol / L.

20. The ethylene oligomerization reaction of claim 19, wherein, The catalyst is added in an amount such that the molar concentration of chromium in the oligomerization reaction system is 20-50 μmol / L.

21. The ethylene oligomerization reaction of claim 15, wherein, The method for the ethylene oligomerization reaction is as follows: the reactor is heated to 110-160 ℃, vacuumed for 1-4 h, replaced with nitrogen, cooled to room temperature, replaced with ethylene, the solvent C and the alkyl aluminum cocatalyst are added first, then the catalyst is added, 0-0.8 MPa hydrogen and 2 MPa-7 MPa ethylene are introduced in sequence to start the reaction, the reaction temperature is 35-90 ℃, and the reaction time is 10 min-240 min.

22. The ethylene oligomerization reaction of claim 21 wherein, The reaction temperature is 40-70 ℃, and the reaction time is 20 min-100 min.

23. The ethylene oligomerization reaction of claim 21 wherein, 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.

24. The ethylene oligomerization reaction of claim 15, wherein, When the molar ratio of the alkyl aluminum cocatalyst to chromium is less than or equal to 200:1, the selectivity of 1-hexene is high, and when the molar ratio of the alkyl aluminum cocatalyst to chromium is greater than or equal to 500:1, the selectivity of 1-octene is high.

25. The ethylene oligomerization reaction of claim 24, wherein, When the molar ratio of the alkyl aluminum cocatalyst to chromium is 50-200:1, the selectivity of 1-hexene is high, and when the molar ratio of the alkyl aluminum cocatalyst to chromium is 500-1000:1, the selectivity of 1-octene is high.

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