Flexible amino imine nickel catalyst and preparation method and application thereof

Abstract

The invention relates to the field of catalytic polymerization of olefins, in particular to a flexible amino imine nickel-based catalyst and a preparation method and application thereof, the flexible amino imine nickel-based catalyst has a structure as shown in a formula I or a formula II, and R1 and R2 are respectively and independently selected from at least one of cyclopentyl and cyclohexyl. According to the flexible amino imine nickel-based catalyst, two kinds of amino imine serve as a framework of the catalyst, two kinds of flexible naphthenic bases are introduced to the axial positions of the catalyst respectively, and the performance of the catalyst is remarkably affected by the ligand framework structure and the naphthenic base ring size; and cyclohexyl and butyl skeletons with larger volumes are beneficial to generation of products with higher molecular weights. Compared with the traditional alpha-diimine nickel catalyst, the alpha-amino imine nickel catalyst shows that the polyethylene wax generated by the alpha-amino imine nickel catalyst has higher melting point and lower molecular weight. The catalyst has good potential application value in the ethylene polymerization preparation industry.

Description

Technical Field

[0001] This application relates to the field of catalytic polymerization of olefins, specifically to a flexible amino-based imine nickel catalyst, its preparation method, and its application. Background Technology

[0002] Polyethylene wax (PE wax) is an important chemical raw material widely used in coatings, plastics, rubber, textiles, inks, lubricants, and many other fields. With industrial development and technological advancements, the application scenarios for PE wax are gradually expanding, and market demand is continuously increasing. Traditional PE wax products are mostly prepared using high-pressure polyethylene production processes, but this production method suffers from high energy consumption and high costs. Ethylene homopolymerization can be considered a cost-effective alternative for manufacturing PE wax, as it requires only one polymerization step. Traditionally, flexible α-diimide nickel catalysts exhibit high catalytic activity in ethylene homopolymerization, producing high molecular weight (up to 1022 kg / mol) and highly branched (up to 10³ / 1000 C) polyethylene materials, which limits the application areas of PE wax materials. Summary of the Invention

[0003] Therefore, it is necessary to provide a flexible amino-imine nickel-based catalyst that can catalyze the homopolymerization of ethylene to obtain a polyethylene wax with low molecular weight and low branching degree. Furthermore, a method for preparing the flexible amino-imine nickel-based catalyst and its application are also provided.

[0004] The first aspect of this application provides a flexible amino-based imine nickel catalyst having a structure as shown in Formula I or Formula II:

[0005] , ,

[0006] R1 and R2 are each independently selected from at least one of cyclopentyl and cyclohexyl.

[0007] In the aforementioned flexible amino-imine nickel-based catalysts, amino-imines are used as the catalyst framework, and flexible cycloalkyl groups are introduced at the ortho and para positions of the imine nitrogen atom, enabling the efficient preparation of low-branched, low-molecular-weight LLDPE waxes. The ligand framework and cycloalkyl group size have a significant regulatory effect on catalytic performance, providing a new strategy for customized PE wax materials. Compared with traditional α-diimine nickel catalysts, the polyethylene waxes produced by the α-amino-imine nickel system have higher melting points and lower molecular weights.

[0008] The second aspect of this application provides a method for preparing a flexible amino-based imine nickel catalyst, comprising the following steps S1 to S6.

[0009] S1. Under a protective gas atmosphere, at least one of bromocyclopentane and bromocyclohexane, a Lewis acid catalyst, and benzene are added to an inert solvent to allow at least one of bromocyclopentane and bromocyclohexane to undergo an alkylation reaction with benzene to obtain an alkyl-substituted aromatic compound A; the alkylation reaction is carried out at a temperature of -50℃ to -30℃ for 4h to 6h.

[0010] In some embodiments, the Lewis acid catalyst is anhydrous AlCl3.

[0011] In some embodiments, the inert solvent is selected from dichloromethane or toluene.

[0012] In some embodiments, the molar ratio of the total amount of bromocyclopentane and bromocyclohexane to benzene is (3.2~3.6):1. As an example, when only bromocyclopentane is added in step S1, it means that the molar ratio of bromocyclopentane to benzene is (3.2~3.6):1. When only bromocyclohexane is added in step S1, it means that the molar ratio of the total amount of bromocyclohexane to benzene is (3.2~3.6):1. Preferably, the molar ratio of the total amount of bromocyclopentane and bromocyclohexane to benzene is 3.5:1.

[0013] In some embodiments, after the alkylation reaction in step S1 is completed, the following steps are further included:

[0014] Hydrochloric acid was added to the reaction solution after alkylation to quench the reaction; then water was added, and the organic phase containing the reaction product was separated by water extraction; the organic phase was dried with anhydrous magnesium sulfate to remove residual water; the inert solvent in the dried organic phase was removed by vacuum concentration; ethanol was added to precipitate the solid, and then the solid was filtered and vacuum dried in sequence to obtain alkyl-substituted aromatic compound A.

[0015] Preferably, the pressure during vacuum concentration is 80~200 mbar and the temperature is 40℃~50℃;

[0016] S2. The alkyl-substituted aromatic compound A is mixed with acetic anhydride, acetic acid and an inert solvent, cooled to -10℃ to -5℃, and a nitrating agent is added to carry out a nitration reaction to obtain nitroalkylbenzene compound B; wherein the temperature of the nitration reaction is -5℃ to 5℃ and the time is 4h to 6h; the nitrating agent is nitric acid.

[0017] Preferably, the nitration reaction is carried out at a temperature of 0°C for 5 hours.

[0018] In some embodiments, the molar ratio of alkyl-substituted aromatic compound A to nitrating agent is 1:(4.2~4.5).

[0019] In some embodiments, in step S2, the mass-to-volume ratio of the added alkyl-substituted aromatic compound A, acetic anhydride, and acetic acid is (10g~12g):(40mL~45mL):(20mL~25mL).

[0020] In some embodiments, after the nitration reaction in step S2 is completed, the following steps are further included:

[0021] The reaction solution after nitration is quenched by adding NaHCO3 solution, followed by the addition of water and extraction to separate the organic phase containing the reaction products. The organic phase is then dried with anhydrous magnesium sulfate to remove residual water. Part of the inert solvent in the dried organic phase is removed by vacuum concentration. Ethanol is then added to precipitate a solid, which is then filtered and dried to obtain nitroalkylbenzene compound B. Preferably, the vacuum concentration is performed at a pressure of 80–200 mbar and a temperature of 40–50°C.

[0022] S3. Dissolve nitroalkylbenzene compound B in ethyl acetate, add zinc powder, and then add hydrochloric acid until no bubbles are generated in the solution. Then carry out a reduction reaction at 55℃~70℃ for 1h~1.5h to reduce the nitro group in nitroalkylbenzene compound B to amino group to obtain aminoalkylbenzene compound C.

[0023] In some embodiments, the reduction reaction is carried out at a temperature of 60°C for 1 hour.

[0024] In some embodiments, the molar ratio of nitroalkylbenzene compound B to zinc powder is 1:(10~14).

[0025] In some embodiments, in step S3, nitroalkylbenzene compound B is dissolved in a solution formed by ethyl acetate, and the amount of nitroalkylbenzene compound B added is 9 g to 10 g; the amount of ethyl acetate added is 30 mL to 40 mL.

[0026] In some embodiments, after the reduction reaction in step S3 is completed, the following steps are further included:

[0027] The reaction solution after reduction is quenched by adding NaHCO3 solution, followed by the addition of water and extraction to separate the organic phase containing the reaction products. The organic phase is then dried with anhydrous magnesium sulfate to remove residual water. Part of the ethyl acetate solvent in the dried organic phase is removed by vacuum concentration. Ethanol is then added to precipitate a solid, which is then filtered and dried to obtain aminoalkylbenzene compound C. Preferably, the pressure during vacuum concentration is 80–200 mbar and the temperature is 50–60°C.

[0028] S4. The aminoalkylbenzene compound C is condensed with 2,3-butanedione in a mixed solution of toluene and p-toluenesulfonic acid to form a catalyst ligand intermediate with the structure of formula III. The condensation reaction is carried out at a temperature of 110℃~130℃ for 45h~55h.

[0029] ,

[0030] R1 is selected from at least one of cyclopentyl and cyclohexyl.

[0031] In some embodiments, the molar ratio of aminoalkylbenzene compound C to 2,3-butanedione is (2~2.1):1; preferably, the molar ratio of aminoalkylbenzene compound C to 2,3-butanedione is (2.05~2.1):1.

[0032] In some embodiments, the condensation reaction in step S4 is carried out at a temperature of 120°C for 48 hours.

[0033] In some embodiments, after the condensation reaction in step S4 is completed, the precipitate is filtered to separate it, and then washed with methanol and vacuum dried to obtain a catalyst ligand intermediate having the structure of Formula III.

[0034] S5. Under protective gas conditions, the catalyst ligand intermediate with the structure of formula III and trimethylaluminum are dissolved in toluene, and then reacted at 90℃~110℃ for 2.5h~3.5h to obtain the catalyst ligand with the structure of formula IV.

[0035] ,

[0036] R1 is selected from at least one of cyclopentyl and cyclohexyl.

[0037] In some embodiments, in step S5, the molar ratio of the catalyst ligand intermediate having the structure of Formula III to trimethylaluminum is (3.5~4.5):1.

[0038] In some embodiments, after the reaction is complete, step S5 further includes the following steps:

[0039] The reaction solution is quenched by adding NaOH solution; dichloromethane is added to separate the reaction solution into layers; water is then added to wash the dichloromethane organic layer, and the organic phase containing the reaction products is separated; the organic phase is dried with anhydrous magnesium sulfate to remove residual water; most of the toluene and dichloromethane solvent in the dried organic phase is removed by vacuum concentration; ethanol is then added to precipitate a solid, which is filtered and dried to obtain a catalyst ligand with formula IV. Preferably, the pressure during vacuum concentration is 80~200 mbar and the temperature is 50℃~60℃.

[0040] S6. Under protective gas and room temperature conditions, a catalyst ligand with the structure of formula IV is subjected to a coordination reaction with NiBr2 activated by ethylene glycol dimethyl ether in an inert solvent to obtain a catalyst with the structure of formula I.

[0041] In some embodiments, the molar ratio of the catalyst ligand having the structure of Formula IV to NiBr2 activated by ethylene glycol dimethyl ether is (1~1.1):1.

[0042] In some embodiments, the method for activating NiBr2 with ethylene glycol dimethyl ether includes the following steps:

[0043] Nickel bromide trihydrate and triethyl orthoformate were dissolved in methanol solution and stirred under reflux at 85°C for 12 h to obtain a dark green quicksand-like solid. Excess solvent was removed by vacuum evaporation, and ethylene glycol dimethyl ether was added. The mixture was stirred under reflux at 90°C for 12 h, filtered while hot, and the precipitate was dried to obtain nickel bromide activated by ethylene glycol dimethyl ether.

[0044] The third aspect of this application provides a method for preparing a flexible amino-based imine nickel catalyst, comprising the following steps S1' to S6'.

[0045] The preparation steps of S1'~S3' are completely the same as the preparation steps of S1~S3 described above, and will not be repeated here.

[0046] S4'. Mix aminoalkylbenzene compound C with acenaphthene and acetonitrile, and then add acetic acid dropwise. After the addition is complete, carry out an acid-catalyzed condensation reaction at 85℃~95℃ to obtain a catalyst ligand intermediate with the structure of formula VI. The acid-catalyzed condensation reaction time is 2.5h~3.5h.

[0047] ,

[0048] R2 is selected from at least one of cyclopentyl and cyclohexyl.

[0049] In some embodiments, the acid-catalyzed condensation reaction is carried out at a temperature of 90°C for 3 hours.

[0050] In some embodiments, in step S4', the molar ratio of aminoalkylbenzene compound C to acenaphthoquinone is (2~2.1):1; preferably, the molar ratio of aminoalkylbenzene compound C to acenaphthoquinone is (2.05~2.1):1.

[0051] In some embodiments, after the acid-catalyzed condensation reaction in step S4' is completed, the precipitate is separated by filtration, then washed with methanol and vacuum dried to obtain a catalyst ligand intermediate having a structure of formula VI.

[0052] S5' Under protective gas conditions, the catalyst ligand intermediate with the structure of formula VI is dissolved in toluene solvent with trimethylaluminum, and then reacted at 90℃~110℃ for 2.5h~3.5h to obtain the catalyst ligand with the structure of formula VII.

[0053] ,

[0054] R2 is selected from at least one of cyclopentyl and cyclohexyl.

[0055] In some embodiments, the molar ratio of the catalyst ligand intermediate having the structure of formula VI to trimethylaluminum is (3.5~4.5):1.

[0056] In some embodiments, after the completion of step S5', the steps of quenching the reaction and separating and purifying the catalyst ligand having the structure of formula VII from the reaction solution are the same as the steps in step S5, and will not be repeated here.

[0057] S6' Under protective gas and room temperature conditions, a catalyst ligand with the structure of formula VII is subjected to a coordination reaction with NiBr2 activated by ethylene glycol dimethyl ether in an inert solvent to obtain a catalyst with the structure of formula II.

[0058] In some embodiments, the molar ratio of the catalyst ligand having the structure of formula VIII to NiBr2 activated by ethylene glycol dimethyl ether is (1~1.1):1.

[0059] The method of activating NiBr2 with ethylene glycol dimethyl ether in step S6' is the same as that in step S6, and will not be repeated here.

[0060] The fourth aspect of this application provides the use of a flexible amino-imine nickel catalyst provided in the first aspect or a flexible amino-imine nickel catalyst prepared according to the method provided in the second or third aspect in the preparation of polyethylene wax.

[0061] In some embodiments, under the conditions of a flexible amino-imine nickel catalyst, ethylene is polymerized to obtain polyethylene wax, wherein the polymerization temperature is 30°C to 70°C and the polymerization time is 40 min to 80 min.

[0062] Preferably, the polymerization reaction takes 60 minutes.

[0063] In some embodiments, the polyethylene wax has a molecular weight of 2.4 kg / mol to 9.5 kg / mol, a branching degree of 20-40 / 1000°C, and a melting point of 96°C to 120°C.

[0064] Compared with the prior art, this application has the following beneficial effects:

[0065] This application successfully developed a flexible cycloalkyl-substituted α-aminoimine nickel catalyst. By introducing flexible cycloalkyl groups at the ortho and para positions of the imine nitrogen atom in the catalyst, low-branched, high-molecular-weight LLDPE waxes can be efficiently prepared. The ligand framework and cycloalkyl group size have a significant regulatory effect on catalytic performance, providing a new strategy for customized PE wax materials. Compared with traditional α-diimine nickel catalysts, the polyethylene produced by the α-amine-imine nickel system has a higher melting point and lower molecular weight. Attached Figure Description

[0066] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0067] Figure 1 The 1H NMR spectrum of the catalyst ligand (L1) prepared in Example 1.

[0068] Figure 2 The carbon NMR spectrum of the catalyst ligand (L1) prepared in Example 1.

[0069] Figure 3 The mass spectrum of the catalyst ligand (L1) prepared in Example 1.

[0070] Figure 4 The 1H NMR spectrum of the catalyst ligand (L2) prepared in Example 2.

[0071] Figure 5 The carbon NMR spectrum of the catalyst ligand (L2) prepared in Example 2.

[0072] Figure 6 The mass spectrum of the catalyst ligand (L2) prepared in Example 2 is shown.

[0073] Figure 7 The 1H NMR spectrum of the catalyst ligand (L3) prepared in Example 3.

[0074] Figure 8 The carbon NMR spectrum of the catalyst ligand (L3) prepared in Example 3.

[0075] Figure 9 The mass spectrum of the catalyst ligand (L3) prepared in Example 3.

[0076] Figure 10 The 1H NMR spectrum of the catalyst ligand (L4) prepared in Example 4.

[0077] Figure 11The carbon NMR spectrum of the catalyst ligand (L4) prepared in Example 4.

[0078] Figure 12 The mass spectrum of the catalyst ligand (L4) prepared in Example 4. Detailed Implementation

[0079] The embodiments described in this specification are merely for explaining this application and are not intended to limit this application.

[0080] For simplicity, this paper only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an undefined range; and any lower limit can be combined with other lower limits to form an undefined range, just as any upper limit can be combined with any other upper limit to form an undefined range. Furthermore, although not explicitly stated, every point or individual value between the endpoints of a range is included within that range. Therefore, each point or individual value can serve as its own lower or upper limit and be combined with any other point or individual value, or with other lower or upper limits, to form an undefined range.

[0081] The present application is further illustrated below with reference to embodiments. It should be understood that these embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0082] The room temperature described in this application is 20℃~30℃.

[0083] Reagents and raw materials used in the examples: All organometallic reactions were carried out under nitrogen protection, and all solvents were dried and deoxygenated. Anhydrous methanol and ethanol were analytical grade and used directly. Toluene was dehydrated by molecular sieves, refluxed with metallic sodium under nitrogen protection, and distilled off before use.

[0084] Example 1

[0085] (1) Synthesis of 2,4,6-tricyclopentylaniline

[0086] Under a nitrogen atmosphere, AlCl3 (0.5 g) and dichloromethane (DCM, 60 mL) were added to a dry Schlenk flask. The Schlenk flask was placed in a -40°C cold trap, and benzene (90 mmol, 1.0 eq) and bromocyclopentane (RBr, 315 mmol, 3.5 eq) were injected into the flask using a syringe. The mixture was stirred for 5 hours. After the reaction was complete, hydrochloric acid was added to quench the reaction, and the product was extracted with water (3 × 100 mL) and dried with anhydrous magnesium sulfate. The dried filtrate was concentrated under reduced pressure, and ethanol was added to precipitate the desired solid. A white powder was obtained by filtration and vacuum drying. The obtained white powder (10 g, 35 mmol), DCM (45 mL), acetic anhydride (Ac2O, 45 mL), and acetic acid (AcOH, 23 mL) were added sequentially to a 500 mL round-bottom flask. The flask was placed in a cold trap and cooled to -10°C. HNO3 (10 mL) was carefully added to the flask. The temperature was adjusted to 0°C, and the mixture was stirred for 5 hours. After the reaction was complete, the reactants were quenched with NaHCO3 solution. The organic layer was separated, washed with water (3 × 100 mL), and dried with anhydrous magnesium sulfate. The dried filtrate was concentrated under reduced pressure, and ethanol was added to precipitate the desired solid. A white powder was obtained by filtration and vacuum drying. The obtained white powder (9 g, 27 mmol) was dissolved in a round-bottom flask lined with ethyl acetate (EA, 30 mL), and zinc powder (4 g) was added sequentially, followed by HCl (5 mL) until no more bubbles were generated. The mixture was stirred at 60 °C for 1 h, and the reaction was quenched with NaHCO3 solution. The organic layer was separated, washed with water (3 × 100 mL), and dried with anhydrous magnesium sulfate. The dried filtrate was concentrated under reduced pressure, and ethanol was added to precipitate the desired solid. The product C1, a yellow 2,4,6-tricyclopentylaniline powder, was obtained by filtration and vacuum drying, with a yield of 97%.

[0087] The preparation reaction formula is as follows:

[0088]

[0089] (2) Synthesis of catalyst ligand (L1)

[0090] A solution of 2,4,6-tricyclopentylaniline (5 mmol), 2,3-butanedione (2.4 mmol), and p-toluenesulfonic acid (10 mg) in toluene (20 mL) was stirred at 120 °C for 48 hours. Samples were taken every 3 hours during stirring and observed on a thin-layer chromatography plate until a principal spot was observed. The precipitate was then separated by filtration, washed with methanol (3 × 2 mL), and dried under vacuum to obtain the catalyst ligand intermediate (L1'), which was used directly in subsequent steps.

[0091] Under a nitrogen atmosphere, 1 mmol of the ligand intermediate (L1') was dissolved in 5 mL of toluene solution, and 2 mL of trimethylaluminum (Al(Me)3) was added. The resulting mixture was then stirred at 100 °C for 3 hours. After the reaction was complete, it was quenched with 10 mL of 1 M NaOH solution. 20 mL of dichloromethane was added, and the dichloromethane layer was washed with water (3 × 10 mL). The organic layer was extracted and dried over anhydrous magnesium sulfate for 30 minutes. Finally, a pale yellow powder (L1) was obtained by ethanol precipitation, with a yield of 96%.

[0092] The preparation reaction formula is as follows:

[0093]

[0094] NMR and mass spectrometry analyses were performed on L1, and the specific results are as follows:

[0095] NMR analysis: 1 H NMR (400MHz, CDCl3) δ 6.98 (d, J=14.6Hz, 4H, Ar-H), 4.68 (s, 1H, -NH-), 3.66 (p, J=8.7Hz, 2H, -CH-), 2.90 (ddq, J=48.5, 16.0, 7.6Hz, 4H, -CH-) , 2.03 (pd, J=11.0, 5.8Hz, 11H, -CH2-), 1.79 (d, J=10.9Hz, 19H, -CH2-), 1.63–1.51 (m, 21H, -CH2-), 1.29 (s, 6H, -CH3-).

[0096] 13 C NMR (101MHz, CDCl3) δ175.52 (C=N), 145.51, 145.32, 142.04, 140.54, 138.54, 133.3 9, 122.61, 122.17, 61.74 (CH3-C-NH-), 46.04 (-CH-), 45.93 (-CH-), 40.48 (-CH-), 36 .05 (-CH2-), 34.80 (-CH2-), 34.63 (-CH2-), 33.90 (-CH2-), 33.63 (-CH2-), 26.63 (- CH2-), 26.30 (-CH2-), 25.69 (-CH2-), 25.61 (-CH2-), 25.50 (-CH2-), 16.71 (-CH3-). 1H NMR spectrum as follows Figure 1 As shown, the horizontal axis f1 represents the first dimension of the frequency dimension, with units of ppm; the carbon NMR spectrum is as follows. Figure 2 As shown.

[0097] Mass spectrometry analysis: APCI-MS (m / z): Theoretical value (C 47 H 69 N2 + ): 661.5456, detected value, 661.5457, [M+H] + Mass spectrum as shown Figure 3 As shown, the horizontal axis m / z represents the mass-to-charge ratio.

[0098] (3) Synthesis of Ni1 complex

[0099] Under a nitrogen atmosphere, 0.2 mmol of the corresponding ligand (L1) was dissolved in 10 mL of dichloromethane. Then, NiBr2 activated with ethylene glycol dimethyl ether ((DME)NiBr2, 0.2 mmol, 62 mg) was added to the solution. The resulting mixture was stirred at room temperature for 12 h. After the reaction was complete, the solvent was concentrated by vacuum evaporation, washed with 4 × 5 mL of diethyl ether, filtered, and dried under vacuum to give an orange-red solid product (Ni1) in 85% yield.

[0100] The preparation reaction formula is as follows:

[0101]

[0102] The preparation method of ethylene glycol dimethyl ether activated nickel bromide [(DME)NiBr2] is as follows: nickel bromide trihydrate and triethyl orthoformate are dissolved in methanol solution and stirred and refluxed at 85°C for 12 h to obtain a dark green quicksand-like solid. Excess solvent is removed by vacuum evaporation, and ethylene glycol dimethyl ether is added. The mixture is stirred and refluxed at 90°C for 12 h, filtered while hot, and the precipitate is dried to obtain nickel bromide activated by ethylene glycol dimethyl ether.

[0103] Example 2

[0104] (1) Synthesis of 2,4,6-tricyclohexylaniline

[0105] Under a nitrogen atmosphere, AlCl3 (0.5 g) and DCM (60 mL) were added to a dry Schlenk flask. The Schlenk flask was placed in a -40°C cold trap, and benzene (90 mmol, 1.0 eq) and bromocyclohexane (315 mmol, 3.5 eq) were injected into the flask using a syringe. The mixture was stirred for 5 hours. After the reaction was complete, hydrochloric acid was added to quench the reaction, and the product was extracted with water (3 × 100 mL) and dried with anhydrous magnesium sulfate. The dried filtrate was concentrated under reduced pressure, and ethanol was added to precipitate the desired solid. A white powder was obtained by filtration and vacuum drying. The obtained white powder (10 g, 35 mmol), DCM (45 mL), Ac2O (45 mL), and AcOH (23 mL) were added sequentially to a 500 mL round-bottom flask. The flask was placed in a cold trap and cooled to -10°C. HNO3 (10 mL) was carefully added to the flask. The temperature was adjusted to 0°C, and the mixture was stirred for 5 hours. After the reaction was complete, the reactants were quenched with NaHCO3 solution. The organic layer was separated, washed with water (3 × 100 mL), and dried over anhydrous magnesium sulfate. The dried filtrate was concentrated under reduced pressure, and ethanol was added to precipitate the desired solid. A white powder was obtained by filtration and vacuum drying. The obtained white powder (9 g, 27 mmol) was dissolved in a round-bottom flask lined with ethyl acetate, and zinc powder was added sequentially, followed by HCl (5 mL) until no more bubbles were generated. The mixture was stirred at 60 °C for 1 h, and the reaction was quenched with NaHCO3 solution. The organic layer was separated, washed with water (3 × 100 mL), and dried over anhydrous magnesium sulfate. The dried filtrate was concentrated under reduced pressure, and ethanol was added to precipitate the desired solid. The product was obtained by filtration and vacuum drying to give a yellow 2,4,6-tricyclohexylaniline powder product in 27% yield.

[0106] The preparation reaction formula is as follows:

[0107]

[0108] (2) Synthesis of catalyst ligand (L2)

[0109] A solution of 2,4,6-tricyclohexylaniline (5 mmol), 2,3-butanedione (2.4 mmol), and p-toluenesulfonic acid (10 mg) in toluene (20 mL) was stirred at 120 °C for 48 hours. Samples were taken every 3 hours during stirring and observed on a thin-layer chromatography plate until a principal spot was observed. The precipitate was then separated by filtration, washed with methanol (3 × 2 mL), and dried under vacuum to obtain the ligand intermediate (L2'), which was used directly in subsequent steps.

[0110] Under a nitrogen atmosphere, 1 mmol of the ligand intermediate (L2') was dissolved in 5 mL of toluene solution, and 1 mL of Al(Me)3 was added. The resulting mixture was then stirred at 100 °C for 3 hours. After the reaction was complete, it was quenched with 10 mL of 1 M NaOH solution. 20 mL of dichloromethane was added, and the dichloromethane layer was washed with water (3 × 10 mL). The organic layer was extracted and dried over anhydrous magnesium sulfate for 30 minutes. Finally, a pale yellow powder (L2) was obtained by ethanol precipitation, with a yield of 95%.

[0111] The preparation reaction formula is as follows:

[0112]

[0113] The L2 was analyzed by NMR and mass spectrometry, and the specific results are as follows:

[0114] NMR analysis: 1 H NMR (400MHz, CDCl3) δ6.94 (s, 4H, Ar-H), 4.16 (s, 1H, NH-), 3.34 (d, J=10.5Hz, 2H, -CH-), 2.45 (q, J=11 .7Hz, 4H, -CH-), 1.81 (dp, J=48.5, 14.3, 11.6Hz, 31H, -CH2-, CH3-), 1.55–1.14 (m, 38H, -CH2-, CH3-).

[0115] 13 C NMR (101MHz, CDCl3) δ175.68 (C=N), 146.50, 143.95, 143.63, 142.28, 135.90, 134.74, 122.23, 121.74, 62.20 (CH3-C-NH-), 44.48 (-CH-), 44.34 (-CH-), 39.13 (-CH-), 39.01 (-CH-), 34.81 (-CH2-), 34.75 (-CH 2-), 34.60 (-CH2-), 33.53 (-CH2-), 33.45 (-CH2-), 27.46 (-CH2-), 27.28 (-CH2-), 27.25 (-CH2-), 27.13 (-CH2-), 27.10 (-CH2-), 26.44 (-CH2-), 26.41 (-CH2-), 26.34 (-CH2-), 25.80 (-CH2-), 16.65 (-CH3-). The 1H NMR spectrum is as follows: Figure 4 As shown, the carbon NMR spectrum is as follows: Figure 5 As shown.

[0116] Mass spectrometry analysis: APCI-MS (m / z): Theoretical value C 53H 81 N2 + 745.6394, detected value, 745.6370, [M+H] + Mass spectrum as shown Figure 6 As shown.

[0117] (3) Synthesis of Ni2 complex

[0118] Under a nitrogen atmosphere, 0.2 mmol of the corresponding ligand (L2) was dissolved in 10 mL of dichloromethane. Then, (DME)NiBr2 (0.2 mmol, 62 mg) was added to the above solution, and the resulting mixture was stirred overnight at room temperature. After the reaction was complete, the solvent was concentrated by vacuum evaporation, washed with 4 × 5 mL of diethyl ether, filtered, and dried under vacuum to give an orange-red solid product (Ni2) in 80% yield.

[0119] The preparation reaction formula is as follows:

[0120]

[0121] The preparation method of ethylene glycol dimethyl ether activated nickel bromide [(DME)NiBr2] is the same as in Example 1.

[0122] Example 3

[0123] (1) Synthesis of catalyst ligand (L3)

[0124] Add 5 mL of acetonitrile solution (ACN) containing 5 mmol C1 to 2.4 mmol acenaphthene, and then add a few drops of acetic acid (AcOH). Stir the resulting mixture at 90 °C for 3 hours, separate the precipitate by filtration, wash with methanol (3 × 2 mL), and dry under vacuum to obtain the ligand intermediate (L3'), which can be used directly in subsequent steps without further purification.

[0125] Under a nitrogen atmosphere, 1 mmol of the ligand intermediate (L3') was dissolved in 5 mL of toluene solution, and 1 mL of Al(Me)3 was added. The resulting mixture was then stirred at 100 °C for 3 hours. After the reaction was complete, it was quenched with 10 mL of 1 M NaOH solution. 20 mL of dichloromethane was added, and the dichloromethane layer was washed with water (3 × 10 mL). The organic layer was extracted and dried over anhydrous magnesium sulfate for 30 minutes. Finally, a pale yellow powder (L3) was obtained by ethanol precipitation, with a yield of 95%.

[0126] The preparation reaction formula is as follows:

[0127]

[0128] The L3 was analyzed by NMR and mass spectrometry, and the specific results are as follows:

[0129] NMR analysis: 1 H NMR (400MHz, CDCl3) δ7.82 (d, J=8.2Hz, 1H, Ar-H), 7.67 (d, J=8.3 Hz, 1H, Ar-H), 7.30 (dt, J=7.9, 3.9Hz, 2H, Ar-H), 7.11 (s, 1H, Ar-H), 7.09 (s, 1 H, Ar-H), 6.90 (s, 2H, Ar-H), 6.45 (dd, J=7.2, 2.8Hz, 2H, Ar-H), 3.78 (s, 1H, NH -), 3.13 (dp, J=50.9, 8.0Hz, 3H, -CH-), 2.95 (p, J=8.5Hz, 3H, -CH-), 2.28–1.9 7 (m, 9H, -CH2-), 1.93–1.77 (m, 11H, -CH2-), 1.74–1.41 (m, 31H, -CH2-, CH3-).

[0130] 13 C NMR (101MHz, CDCl3) δ174.98 (C=N), 145.94, 143.13, 142.82, 141.63, 138.80, 138.16, 134.42, 133.01, 131.01, 130.46, 128.47, 127.76, 127 .59, 124.00, 123.91, 122.56, 122.31, 121.81, 67.54 (CH3-C-NH-), 46.04 (-CH-), 45.99 (-CH-), 40.73 (-CH-), 40.45 (-CH-), 39.55 (-CH2-), 36.12 (-CH2-), 34.90 (-CH2-), 34.88 (-CH2-), 34.77 (-CH2-), 34.65 (-CH2-), 34.60 (-CH2-), 34.53 (-CH2-), 34.51 (-CH2-), 33.44 (-CH2-), 28.08 (-CH2-), 26.33 (-CH2-), 26.19 (-CH2-), 25.89 (-CH2-), 25.56 (-CH2-), 25.53 (-CH2-), 25.50 (-CH2-), 25.44 (-CH3-), 25.42 (-CH2-). The 1H NMR spectrum is as follows: Figure 7 As shown, the carbon NMR spectrum is as follows: Figure 8 As shown.

[0131] Mass spectrometry analysis: APCI-MS (m / z): Theoretical value C 55 H 69 N2 +757.5455, detected value, 757.5431, [M+H] + Mass spectrum as shown Figure 9 As shown.

[0132] (3) Synthesis of Ni3 complex

[0133] Under a nitrogen atmosphere, 0.2 mmol of the corresponding ligand (L3) was dissolved in 10 mL of dichloromethane. Then, (DME)NiBr2 (0.2 mmol, 62 mg) was added to the above solution, and the resulting mixture was stirred overnight at room temperature. After the reaction was complete, the solvent was concentrated by vacuum evaporation, washed with 4 × 5 mL of diethyl ether, filtered, and dried under vacuum to give an orange-red solid product (Ni3) in 75% yield.

[0134] The preparation reaction formula is as follows:

[0135]

[0136] The preparation method of ethylene glycol dimethyl ether activated nickel bromide [(DME)NiBr2] is the same as in Example 1.

[0137] Example 4

[0138] (1) Synthesis of catalyst ligand (L4)

[0139] Add 5 mL of acetonitrile solution containing 5 mmol of C2 to 2.4 mmol of acenaphthene, followed by a few drops of acetic acid. Stir the resulting mixture at 90 °C for 3 hours, then separate the precipitate by filtration and wash with methanol (3 × 2 mL). The ligand (L4') was dried under vacuum and used directly in subsequent steps without further purification.

[0140] Under a nitrogen atmosphere, 1 mmol of the ligand (L3') was dissolved in 5 mL of toluene solution, and 1 mL of AlCl3 was added. The resulting mixture was then stirred at 100 °C for 3 hours. After the reaction was complete, it was quenched with 10 mL of 1 M NaOH solution. 20 mL of dichloromethane was added, and the dichloromethane layer was washed with water (3 × 10 mL). The organic layer was extracted and dried over anhydrous magnesium sulfate for 30 minutes. Finally, a pale yellow powder (L4) was obtained by ethanol precipitation, with a yield of 95%.

[0141] The preparation reaction formula is as follows:

[0142]

[0143] NMR and mass spectrometry analyses were performed on L4, and the specific results are as follows:

[0144] NMR analysis: 1H NMR (400MHz, CDCl3) δ7.81 (d, J=8.2Hz, 1H, Ar-H), 7.66 (d, J=8.3Hz, 1H, Ar-H), 7 .29 (d, J=8.1Hz, 2H, Ar-H), 7.09 (d, J=9.9Hz, 2H, Ar-H), 6.89 (s, 2H, Ar-H), 6.44 (d, J=7.1Hz, 2H, Ar-H), 3.72 (d, J=7.1Hz, 1H, -NH-), 3.32–2.74 (m, 6H, -CH-), 2. 27–1.99 (m, 9H, -CH2-), 1.87 (s, 11H, -CH2-), 1.71–1.42 (m, 43H, -CH2-, -CH3-).

[0145] 13 C NMR (101MHz, CDCl3) δ174.20 (C=N), 145.07, 144.32, 143.98, 143.11, 138.70, 135.80, 134.93, 134.05, 131.24, 130.61, 128.5 1, 127.83, 127.70, 123.90, 123.42, 122.09, 121.97, 121.70, 121.12, 67.49 (CH3-C-NH-), 44.69 (-CH-), 44.52 (-CH-), 39.00 (- CH-), 38.86 (-CH-), 35.01 (-CH2-), 34.98 (-CH2-), 34.66 (-CH2-), 33.66 (-CH2-), 33.56 (-CH2-), 32.63 (-CH2-), 32.37 (-CH2-), 27.36 (-CH2-), 27.16 (-CH2-), 27.11 (-CH2-), 27.00 (-CH2-), 26.72 (-CH2-), 26.36 (-CH2-), 26.29 (-CH2-), 23.80 (-CH3-). The 1H NMR spectrum is as follows: Figure 10 As shown, the carbon NMR spectrum is as follows: Figure 11 As shown.

[0146] Mass spectrometry analysis: APCI-MS (m / z): Theoretical value C 61 H 81 N2 + : 841.6394, test value, 841.6364, [M+H] + Mass spectrum as shown Figure 12 As shown.

[0147] (2) Synthesis of Ni4 complex

[0148] A Ni4 complex was synthesized by reacting a ligand in dichloromethane with (DME)NiBr2 (DME = 1,2-dimethoxyethane). Under a nitrogen atmosphere, 0.2 mmol of the corresponding ligand (L4) was dissolved in 10 mL of dichloromethane. Then, (DME)NiBr2 (0.2 mmol, 62 mg) was added to the solution, and the mixture was stirred overnight at room temperature. After the reaction was complete, the solvent was concentrated by vacuum evaporation, washed with 4 × 5 mL of diethyl ether, filtered, and dried under vacuum to give an orange-red solid product (Ni4) in 79% yield.

[0149] The preparation reaction formula is as follows:

[0150]

[0151] The preparation method of ethylene glycol dimethyl ether activated nickel bromide [(DME)NiBr2] is the same as in Example 1.

[0152] Examples of Ni1~Ni4 applications in catalytic ethylene polymerization:

[0153] Application Examples 1-12 were prepared using the following methods:

[0154] First, a 350mL thick-walled pressure-resistant bottle with a magnetic inlet was placed in an oven at 100℃ for 6 hours, and then introduced into a glove box by purging nitrogen. Next, 40mL of toluene was added to the pressure-resistant bottle, which was then removed and connected to a high-pressure gas pipeline carrying ethylene gas, and the temperature was raised to the required level. Simultaneously, a vacuum pump was turned on to evacuate the polymerization gas pipeline, and the pump was turned off after 3 minutes. Ethylene was introduced, and under an ethylene atmosphere, a nickel complex (2.0μmol) dissolved in 2mL of dichloromethane and modified methylaluminoxane (MMAO, 200μmol) were injected into the polymerization pressure-resistant bottle using a syringe. The ethylene pressure reducing valve was slowly adjusted to raise the required polymerization pressure and maintained, and the time was recorded. Finally, the polymerization reaction was terminated, and a large amount of 5% (by volume) acidified anhydrous ethanol was added. The polymer precipitated, filtered, washed repeatedly with anhydrous ethanol, and dried in a vacuum drying oven at 60℃ for 24 hours.

[0155] Comparative Example 1

[0156] The preparation method of this comparative example is basically the same as that of Application Example 1, except that the type of catalyst used is different. The catalyst used in this comparative example is Ni5, which has the following structural formula:

[0157]

[0158] Comparative Example 1 was prepared using the following method:

[0159] First, a 350mL thick-walled pressure-resistant bottle with a magnetic inlet was placed in an oven at 100℃ for 6 hours, and then introduced into a glove box by purging nitrogen. Next, 40mL of toluene was added to the pressure-resistant bottle, which was then removed and connected to a high-pressure gas pipeline carrying ethylene gas, and the temperature was raised to the required level. Simultaneously, a vacuum pump was turned on to evacuate the polymerization gas pipeline, and the pump was turned off after 3 minutes. Ethylene was introduced, and under an ethylene atmosphere, a nickel complex (2.0μmol) dissolved in 2mL of dichloromethane and MMAO (200μmol) were injected into the polymerization pressure-resistant bottle using a syringe. The ethylene pressure reducing valve was slowly adjusted to raise the required polymerization pressure and maintained, and the time was recorded. Finally, the polymerization reaction was terminated, and a large amount of 5% (by volume) acidified anhydrous ethanol was added. The polymer precipitated, filtered, washed repeatedly with anhydrous ethanol, and dried in a vacuum drying oven at 60℃ for 24 hours.

[0160] The table below shows the experimental conditions for ethylene polymerization provided by this invention: catalyst (Cat.), temperature (T), yield (Yield), catalytic activity (Act.), and polymer molecular weight (M). n Polymerization results data such as polymer molecular weight distribution (PDI) and degree of branching (B).

[0161] Table 1. Statistical Table of Performance Test Results of Polyethylene Wax

[0162]

[0163] a Polymerization conditions: catalyst 2.0 μmol, toluene = 40 mL, [Al] / [Ni] = 200, ethylene pressure 6 atm, time = 60 minutes;

[0164] b The unit of active Act is 10. 4 g·mol -1 ·h -1 ;

[0165] c Polymer molecular weight M n The molecular weight distribution of PDI was determined by gel permeation chromatography (GPC) at 150 °C in trichlorobenzene and polystyrene standards; c Polymer molecular weight M n The unit of molecular weight is kg / mol.

[0166] d Branching degree refers to the number of branches per 1000 carbon atoms, determined by... 1 Measured by H NMR nuclear magnetic resonance method;

[0167] e Melting point T m Measured by differential scanning calorimetry (DSC).

[0168] Table 1 shows that, under activation with 200 equivalents of MAO, these nickel complexes exhibit low to moderate catalytic activity (10⁴–10⁵ g / (mol Ni·h)), producing low molecular weight (2.4–9.5 kg / mol) and high melting point (96–120 °C) poorly branched (20–40 / 1000 °C) polyethylene waxes. As the polymerization temperature increases from 30 °C to 50 °C, and then to 70 °C, the catalytic activity gradually decreases, and the molecular weight and melting point of the resulting polyethylene wax decrease, while the degree of branching increases. The main chain and axial substituents of the catalyst have a significant impact on both the polymerization activity and the polymer molecular weight.

[0169] The aminoimine nickel catalyst used in Comparative Example 1 did not introduce cycloalkyl groups, and the polymer it catalyzed had a high molecular weight, reaching 81.3 kg / mol.

[0170] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A flexible amino-imine nickel-based catalyst, characterized in that, It has a structure as shown in Formula I or Formula II: 、 ， R1 and R2 are each independently selected from at least one of cyclopentyl and cyclohexyl.

2. A method for preparing a flexible amino-imine nickel-based catalyst according to claim 1, characterized in that, Includes the following steps: S1. Under a protective gas atmosphere, at least one of bromocyclopentane and bromocyclohexane, a Lewis acid catalyst, and benzene are added to an inert solvent to cause at least one of bromocyclopentane and bromocyclohexane to undergo an alkylation reaction with benzene to obtain an alkyl-substituted aromatic compound A; the alkylation reaction is carried out at a temperature of -50℃ to -30℃ for a time of 4h to 6h. S2. The alkyl-substituted aromatic compound A is mixed with acetic anhydride, acetic acid, and an inert solvent, cooled to -10°C to -5°C, and a nitrating agent is added to carry out a nitration reaction to obtain nitroalkylbenzene compound B; the nitration reaction is carried out at a temperature of -5°C to 5°C for 4 to 6 hours; the nitrating agent is nitric acid. S3. Dissolve the nitroalkylbenzene compound B in ethyl acetate, add zinc powder, and then add hydrochloric acid until no bubbles are generated in the solution. Then carry out a reduction reaction at 55℃~70℃ for 1h~1.5h to reduce the nitro group in the nitroalkylbenzene compound B to an amino group to obtain aminoalkylbenzene compound C. S4. The aminoalkylbenzene compound C is condensed with 2,3-butanedione in a mixed solution of toluene and p-toluenesulfonic acid to form a catalyst ligand intermediate having the structure of formula III. The condensation reaction is carried out at a temperature of 110℃~130℃ for a time of 45h~55h. ， R1 is selected from at least one of cyclopentyl and cyclohexyl; S5. Under protective gas conditions, the catalyst ligand intermediate with the structure of formula III and trimethylaluminum are dissolved in toluene, and then reacted at 90℃~110℃ for 2.5h~3.5h to obtain the catalyst ligand with the structure of formula IV. ， R1 is selected from at least one of cyclopentyl and cyclohexyl; S6. Under protective gas and room temperature conditions, a catalyst ligand with the structure of formula IV is subjected to a coordination reaction with NiBr2 activated by ethylene glycol dimethyl ether in an inert solvent to obtain a catalyst with the structure of formula I.

3. A method for preparing a flexible amino-imine nickel-based catalyst according to claim 1, characterized in that, Includes the following steps: S1' Under a protective gas atmosphere, at least one of bromocyclopentane and bromocyclohexane, a Lewis acid catalyst, and benzene are added to an inert solvent to cause at least one of bromocyclopentane and bromocyclohexane to undergo an alkylation reaction with benzene to obtain an alkyl-substituted aromatic compound A; the alkylation reaction is carried out at a temperature of -50℃ to -30℃ for a time of 4h to 6h. S2'. The aromatic compound A is mixed with acetic anhydride, acetic acid, and an inert solvent, cooled to -10°C to -5°C, and a nitrating agent is added to carry out a nitration reaction to obtain nitroalkylbenzene compound B; the temperature of the nitration reaction is -5°C to 5°C, and the time is 4h to 6h; the nitrating agent is nitric acid. S3' Dissolve the nitroalkylbenzene compound B in ethyl acetate, add zinc powder, and then add hydrochloric acid until no bubbles are generated in the solution. Then carry out a reduction reaction at 55℃~70℃ for 1h~1.5h to reduce the nitro group in the nitroalkylbenzene compound B to an amino group to obtain aminoalkylbenzene compound C. S4'. The aminoalkylbenzene compound C is mixed with acenaphthene and acetonitrile, and then acetic acid is added dropwise. After the addition is complete, an acid-catalyzed condensation reaction is carried out at 85℃~95℃ to obtain a catalyst ligand intermediate with the structure of formula VI. The acid-catalyzed condensation reaction takes 2.5h~3.5h. ， R2 is selected from at least one of cyclopentyl and cyclohexyl; S5' Under protective gas conditions, the catalyst ligand intermediate with the structure of formula VI is dissolved with trimethylaluminum in an inert organic solvent, and then reacted at 90℃~110℃ for 2.5h~3.5h to obtain the catalyst ligand with the structure of formula VII. ， R2 is selected from at least one of cyclopentyl and cyclohexyl; S6' Under protective gas and room temperature conditions, a catalyst ligand with the structure of formula VII is subjected to a coordination reaction with NiBr2 activated by ethylene glycol dimethyl ether in an inert solvent to obtain a catalyst with the structure of formula II.

4. The preparation method according to any one of claims 2 or 3, characterized in that, The total amount of bromocyclopentane and bromocyclohexane to the molar ratio of benzene is (3.2~3.6):

1.

5. The preparation method according to claim 2, characterized in that, The preparation method satisfies at least one of the following conditions: (1) In step S4, the molar ratio of the aminoalkylbenzene compound C to 2,3-butanedione is (2~2.1):1; (2) The molar ratio of the catalyst ligand intermediate having the structure of Formula III to the trimethylaluminum is (3.5~4.5):

1.

6. The preparation method according to claim 3, characterized in that, The preparation method satisfies at least one of the following conditions: (1) In step S4', the molar ratio of the aminoalkylbenzene compound C to acenaphthoquinone is (2~2.1):1; (2) The molar ratio of the catalyst ligand intermediate with the structure of formula VI to the trimethylaluminum is (3.5~4.5):

1.

7. The application of the flexible aminoimine nickel catalyst according to claim 1 or the flexible aminoimine nickel catalyst obtained by the preparation method according to any one of claims 2 to 6 in the preparation of polyethylene wax.

8. The application according to claim 7, characterized in that, Under the conditions of the flexible amino-imine nickel catalyst, ethylene is polymerized to obtain polyethylene wax. The polymerization temperature is 30℃~70℃ and the polymerization time is 60min.

9. A polyethylene wax prepared according to any one of claims 7 to 8.

10. The polyethylene wax according to claim 9, characterized in that, The polyethylene wax has a molecular weight of 2.4 kg / mol to 9.5 kg / mol; the degree of branching of the polyethylene wax is 20 to 40 / 1000°C; and the melting point of the polyethylene wax is 96°C to 120°C.

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