Preparation method and application of bimodal linear polyethylene chromium carbene catalyst

Abstract

The application discloses a preparation method and application of a bimodal linear polyethylene chromium carbene catalyst, and belongs to the technical field of chemical synthesis. The preparation method comprises the following steps: 1-nitro-2-aromatic sulfide benzene is prepared by taking 1-fluoro-2-nitrobenzene, aromatic mercaptan and potassium tert-butanolate as raw materials; 1-amino-2-aromatic sulfide benzene is prepared by taking 1-nitro-2-aromatic sulfide benzene and hydrazine hydrate as raw materials; 8-hydroxyimidazol[1,5-alpha] quinolinium salt is prepared by taking 1-amino-2-aromatic sulfide benzene, 8-hydroxyquinoline-2-methyl formaldehyde, formaldehyde solution and hydrogen chloride-1,4-dioxane solution as raw materials; and finally, the reaction is carried out by taking 8-hydroxyimidazol[1,5-alpha] quinolinium salt, silver trifluoromethanesulfonate, sodium bis(trimethylsilyl) amide and chromium trichloride as raw materials to obtain the bimodal linear polyethylene chromium carbene catalyst. According to the preparation method, the catalyst is effectively prevented from being poisoned, the catalytic activity of the catalyst is improved, and the catalyst has good thermal stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical synthesis, in particular to a preparation method and application of a bimodal linear polyethylene chromium carbene catalyst. BACKGROUND

[0002] As one of the most important ligands in metal organic chemistry, N-heterocyclic carbene has a unique electronic and spatial effect on metal center, which makes metal-N-heterocyclic carbene complexes widely used in catalysis, metal drugs and material science.

[0003] In 1991, Kevin's group first reported N-heterocyclic compounds with imidazo[1,5-a]quinoline skeleton (see J.Org Chem 1991, 56, 2400); in 2015, Nozaki's group reported bidentate imidazo[1,5-a]quinoline N-heterocyclic carbene compounds with rigid skeleton (see J.Am.Chem.Soc.2015, 137, 10934-10937). Compared with traditional imidazole N-heterocyclic carbene, imidazo[1,5-a]quinoline has a more rigid skeleton and stronger electron-donating ability, and a large number of studies have shown that the introduction of sulfur or phosphorus elements in polydentate ligands can further improve the catalytic activity and regioselectivity of metal center.

[0004] As one of the earliest metals used for olefin polymerization, chromium has attracted widespread attention from scholars since its inception. However, N-heterocyclic chromium carbene compounds, as classic olefin polymerization catalysts, have the problem of β-H elimination leading to catalyst poisoning. How to reduce the possibility of catalyst poisoning is one of the key problems to be solved in the field of N-heterocyclic chromium carbene compounds. SUMMARY

[0005] To solve the above technical problems, the purpose of the present application is to provide a preparation method and application of a bimodal linear polyethylene chromium carbene catalyst, so as to solve the problem of β-H elimination leading to catalyst poisoning in existing N-heterocyclic chromium carbene compounds.

[0006] The technical solution of the present application to solve the above technical problems is as follows:

[0007] A preparation method of a bimodal linear polyethylene chromium carbene catalyst, comprising the following steps:

[0008] (1) stirring and reacting 1-fluoro-2-nitrobenzene, aromatic mercaptan and potassium tert-butoxide in a solvent to obtain 1-nitro-2-aromatic sulfide benzene;

[0009] (2) mixing 1-nitro-2-aromatic sulfide benzene obtained in step (1) and hydrazine hydrate in a solvent, adding a catalyst for reflux reaction to obtain 1-amino-2-aromatic sulfide benzene;

[0010] (3) mixing 1-amino-2-aromatic thioether benzene, 8-hydroxyquinoline-2-carboxaldehyde, formaldehyde solution and hydrogen chloride-1,4-dioxane solution prepared in step (2) and stirring the mixture in a solvent to prepare 8-hydroxyimidazo[1,5-a]quinolinium salt;

[0011] (4) stirring 8-hydroxyimidazo[1,5-a]quinolinium salt, silver trifluoromethanesulfonate, sodium bis(trimethylsilyl)amide and chromium trichloride prepared in step (3) in a solvent to prepare

[0012] Further, in step (1), the molar ratio of 1-fluoro-2-nitrobenzene, aromatic thiol and potassium tert-butoxide is (0.8-1.2):(1.0-1.5):(1.0-1.5), the solvent is ethanol, and the stirring reaction is carried out at a temperature of 20-30°C for 10-15 hours.

[0013] Preferably, in step (1), the molar ratio of 1-fluoro-2-nitrobenzene, aromatic thiol and potassium tert-butoxide is 1:1.2:1.2, the solvent is ethanol, and the stirring reaction is carried out at a temperature of 25°C for 12 hours.

[0014] Further, the chemical reaction formula of step (1) is as follows:

[0015]

[0016] Further, in step (2), the molar ratio of 1-nitro-2-aromatic thioether benzene, hydrazine hydrate and catalyst is (0.8-1.2):(3-5):(0.01-0.1), the solvent is ethanol, and the catalyst is palladium on carbon; the reflux reaction is carried out at a temperature of 80-90°C for 10-15 hours.

[0017] Preferably, in step (2), the molar ratio of 1-nitro-2-aromatic thioether benzene, hydrazine hydrate and catalyst is 1:4:0.05, the solvent is ethanol, and the catalyst is palladium on carbon; the reflux reaction is carried out at a temperature of 85°C for 12 hours.

[0018] Further, the chemical reaction formula of step (2) is as follows:

[0019]

[0020] Further, in step (3), the molar ratio of 1-amino-2-aromatic thioether benzene and 8-hydroxyquinoline-2-carboxaldehyde is 1:(1-1.3), the solvent is ethanol, and the stirring reaction is carried out at a temperature of 20-30°C for 50-100 hours.

[0021] Preferably, in step (3), the molar ratio of 1-amino-2-aromatic thioether benzene and 8-hydroxyquinoline-2-carboxaldehyde is 1:1, the solvent is ethanol, and the stirring reaction is carried out at a temperature of 25°C for 72 hours.

[0022] Further, the chemical reaction formula of step (3) is as follows:

[0023]

[0024] Further, the molar ratio of 8-hydroxyimidazo[1,5-a]quinolinium salt, silver trifluoromethanesulfonate, sodium bis(trimethylsilyl)amide and chromium trichloride in step (4) is (0.05-0.2):(0.05-0.2):(0.1-0.3):(0.05-0.2); the solvent is tetrahydrofuran; the reaction temperature is 20-30℃, and the reaction time is 20-60h.

[0025] Preferably, the molar ratio of 8-hydroxyimidazo[1,5-a]quinolinium salt, silver trifluoromethanesulfonate, sodium bis(trimethylsilyl)amide and chromium trichloride in step (4) is 0.1:0.1:0.2:0.1; the solvent is tetrahydrofuran; the reaction temperature is 25℃, and the reaction time is 48h.

[0026] Further, the chemical reaction formula of step (4) is as follows:

[0027]

[0028] Further, in the process of synthesizing the chromium carbene catalyst in step (4), the 8-hydroxyimidazo[1,5-a]quinolinium salt is first deprotonated at C-2 of the imidazole group by sodium bis(trimethylsilyl)amide as a strong base, then silver trifluoromethanesulfonate is added, and then metal exchange is performed with chromium trichloride.

[0029] Further, the chemical structure of the bimodal linear polyethylene chromium carbene catalyst is shown in formula I:

[0030] Formula I:

[0031] In the formula, Ar is any one of halogen or nitro-substituted C6-C 10 , C 12 , C 19 and C 32 aromatic groups.

[0032] The application of the bimodal linear polyethylene chromium carbene catalyst in the catalysis of ethylene polymerization reaction.

[0033] The application has the following beneficial effects:

[0034] The application provides a preparation method of a bimodal linear polyethylene chromium carbene catalyst, which is prepared by combining a nitrogen heterocyclic ligand of a bidentate imidazole[1,5-alpha]quinoline with chromium in a mode of regulating steric hindrance and electronic properties, so that the possibility of catalyst poisoning is effectively reduced, the catalytic activity of the catalyst in the catalytic ethylene polymerization reaction is effectively improved, the catalyst has good thermal stability, and the bimodal linear polyethylene can be efficiently produced. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The nuclear magnetic hydrogen spectrum of 1-naphthyl phenyl sulfide imidazole[1,5-alpha]quinolinium salt 1a prepared for Example 1 is shown in the following figure;

[0036] Figure 2 The nuclear magnetic carbon spectrum of 1-naphthyl phenyl sulfide imidazole[1,5-alpha]quinolinium salt 1a prepared for Example 1 is shown in the following figure;

[0037] Figure 3 The nuclear magnetic hydrogen spectrum of 1-(2,4,6-triisopropylphenyl) phenyl sulfide imidazole[1,5-alpha]quinolinium salt 1b prepared for Example 2 is shown in the following figure;

[0038] Figure 4 The nuclear magnetic carbon spectrum of 1-(2,4,6-triisopropylphenyl) phenyl sulfide imidazole[1,5-alpha]quinolinium salt 1b prepared for Example 2 is shown in the following figure;

[0039] Figure 5 The nuclear magnetic hydrogen spectrum of imidazole[1,5-alpha]quinolinium salt ligand L1 prepared for Example 3 is shown in the following figure;

[0040] Figure 6 The nuclear magnetic carbon spectrum of imidazole[1,5-alpha]quinolinium salt ligand L1 prepared for Example 3 is shown in the following figure;

[0041] Figure 7 The nuclear magnetic hydrogen spectrum of imidazole[1,5-alpha]quinolinium salt ligand L4 prepared for Example 3 is shown in the following figure;

[0042] Figure 8 The nuclear magnetic carbon spectrum of imidazole[1,5-alpha]quinolinium salt ligand L4 prepared for Example 3 is shown in the following figure;

[0043] Figure 9 The hydrogen spectrum of polyethylene prepared by catalysis of the chromium carbene catalyst in the test example is shown in the following figure;

[0044] Figure 10 The carbon spectrum of polyethylene prepared by catalysis of the chromium carbene catalyst in the test example is shown in the following figure;

[0045] Figure 11 The GPC curve of polyethylene prepared by catalysis of the chromium carbene catalyst in the test example is shown in the following figure. DETAILED DESCRIPTION

[0046] The principles and features of the present application are described below with reference to the accompanying drawings, and the examples are used to explain the present application, but are not intended to limit the scope of the present application. If the specific conditions are not indicated in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If the manufacturer of the reagent or instrument is not indicated, it is a conventional product that can be purchased on the market.

[0047] Example 1:

[0048] A method for preparing a bimodal linear polyethylene chromium carbene catalyst, comprising the following steps:

[0049] (1) Preparation of 1-naphthalene-2-nitrophenyl sulfide

[0050] Under anhydrous and anaerobic conditions, 1.0 mmol of 1-naphthalene thiol, 1.2 mmol of o-fluoro nitrobenzene, and 1.2 mmol of potassium tert-butoxide were mixed, 15 mL of ethanol was added, stirred at room temperature for 12 h, after the reaction was completed, the solution was spin-dried, washed with ice ethanol three times, and 1-naphthalene-2-nitrophenyl sulfide was obtained as a yellow powder with a yield of 85%. 1 H NMR (400 MHz, CDCl3): δ = 8.25 (dd, J = 8.2, 1.6 Hz, 1H), 8.18 (s, 1H), 7.95-7.86 (m, 3H), 7.63-7.51 (m, 3H), 7.32-7.27 (m, 1H), 7.24-7.18 (m, 1H), 6.89 (d, J = 8.2 Hz, 1H).

[0051] (2) Preparation of 1-naphthalene-2-aminophenyl sulfide

[0052] Under anhydrous and anaerobic conditions, 1.0 mmol of 1-naphthalene-2-nitrophenyl sulfide, 4 mmol of hydrazine hydrate, and 0.05 mmol of palladium on carbon were mixed, 15 mL of ethanol was added, and the reaction was refluxed at 85°C for 12 h, after the reaction was completed, the solution was cooled to room temperature and filtered, 15 mL of water was added, extracted with dichloromethane three times, dried with anhydrous sodium sulfate, filtered, the filtrate was spin-dried, washed with n-hexane, and dried to obtain 1-naphthalene-2-nitrophenyl sulfide as a white powder with a yield of 88%. 1 H NMR (400 MHz, CDCl3) δ = 7.78 (d, J = 7.2 Hz, 1H), 7.73 (d, J = 8.7 Hz, 1H), 7.67 (d, J = 7.8 Hz, 1H), 7.57-7.50 (m, 2H), 7.47-7.39 (m, 2H), 7.33-7.26 (m, 2H), 6.83 (d, J = 7.7 Hz, 2H), 4.32 (s, 2H).

[0053] (3) Preparation of 1-naphthalenyl phenyl sulfide imidazolium [1,5-a] quinolinium salt 1a

[0054] The structure is:

[0055] To an ice-cooled flask was added 1 mmol of 1-naphthyl-2-aminophenyl sulfide dissolved in 5 mL of ethanol, and 1 mmol of hydrochloric acid-dioxane solution was added. The reaction was stirred at this temperature for 2 minutes, then 5 mmol of formaldehyde (40% mass fraction of formaldehyde aqueous solution) and additional ethanol (10 mL) were added, the reaction was warmed to room temperature and stirred under air for 1 h. After adding a portion of 1.0 mmol of 8-hydroxyquinoline-2-carboxaldehyde, the flask was sealed with a rubber septum and stirred at room temperature for 3 days. After the reaction was completed, the resulting mixture was spin-dried, dissolved in dichloromethane, and ethyl acetate was added to obtain a large amount of precipitate, which was collected by filtration and washed with ethyl acetate three times, and vacuum dried to obtain a yellow precipitate, which was 1-naphthyl phenyl sulfide imidazo[1,5-α] quinolinium salt 1a, with a yield of 80%.

[0056] The results of the nuclear magnetic experiment are shown in Figures 1-2 . 1 H NMR (400 MHz, DMSO-d6): δ = 10.14 (s, 1H), 8.51 (d, J = 8.4 Hz, 1H), 7.96 (d, J = 8.0 Hz, 1H), 7.62 (t, J = 7.9 Hz, 1H), 7.51 (d, J = 8.1 Hz, 1H), 7.40-7.09 (m, 13H) ppm. 13 C{ 1 H} NMR (100 MHz, DMSO-d6) δ = 149.26, 135.98, 133.86, 133.32, 133.05, 132.65, 132.45, 130.91, 129.86, 129.76, 129.60, 129.17, 129.02, 128.78, 127.99, 127.70, 127.50, 127.38, 127.31, 127.02, 119.87, 118.21, 117.04, 116.81, 115.38 ppm. HRMS (ESI, positive ions): m / z = 419.1213 (calcd for [1a-Cl + 419.1188).

[0057] (4) Preparation of chromium carbene compound 2a

[0058] The structure is:

[0059] In a nitrogen glove box, 0.1 mmol of ligand 1-(2,4,6-triisopropylphenyl) phenyl sulfide imidazolium [1,5-a] quinolinium salt was dissolved in 10 mL of super dry tetrahydrofuran, then 0.2 mmol of sodium bis(trimethylsilyl)amide was added to the solution, and the reaction was stirred at room temperature for 12 h. After the reaction was completed, the solid was separated by filtration, 0.1 mmol of silver triflate was added to the filtrate, and the reaction was stirred at room temperature for 12 h in the dark. After the reaction was completed, the solid was separated by filtration, 0.1 mmol of chromium trichloride was added to the filtrate, and the reaction was stirred for another 24 h in the dark. After the reaction was completed, the solid was separated by filtration, concentrated, and a large amount of diethyl ether was added to precipitate a white solid. The solid was collected by filtration, washed with diethyl ether, and dried to obtain chromium carbene compound 2a with a yield of 53%. Elemental analysis: C 56.3%, H 2.9%, N 4.8%, S 5.5%.

[0060] Example 2:

[0061] A method for preparing a bimodal linear polyethylene chromium carbene catalyst, comprising the following steps:

[0062] (1) Preparation of 1-(2,4,6-triisopropylphenyl)-2-nitrophenyl sulfide

[0063] Under anhydrous and anaerobic conditions, 1.0 mmol of 1-thiol-2,4,6-triisopropylbenzene, 1.2 mmol of o-fluoronitrobenzene, and 1.2 mmol of potassium tert-butoxide were mixed, 15 mL of ethanol was added, and the reaction was stirred at room temperature for 12 h. After the reaction was completed, the solution was rotary evaporated, and washed with ice ethanol three times to obtain a yellow powder, i.e., 1-(2,4,6-triisopropylphenyl)-2-nitrophenyl sulfide, with a yield of 95%. 1 H NMR (400 MHz, CDCl3): δ 8.28 (d, J = 7.6 Hz, 1H), 7.36-7.28 (m, 1H), 7.22-7.14 (m, 3H), 6.67 (d, J = 8.5 Hz, 1H), 3.61-3.47 (m, 2H), 3.05-2.91 (m, 1H), 1.32 (d, J = 6.9 Hz, 6H), 1.14 (d, J = 6.9 Hz, 12H).

[0064] (2) Preparation of 1-(2,4,6-triisopropylphenyl)-2-aminophenyl sulfide

[0065] Anhydrous and anaerobic operating conditions, 1.0 mmol 1-(2,4,6-triisopropylphenyl)-2-nitrophenyl sulfide, 4 mmol hydrazine hydrate, 0.05 mmol palladium carbon were mixed, 15 mL of ethanol was added, 85°C reflux reaction for 12h, after the reaction was completed, it was cooled to room temperature and filtered, 15 mL of water was added, dichloromethane was added for extraction three times, dried with anhydrous sodium sulfate, then filtered, the filtrate was rotary evaporated, washed with n-hexane, and dried to obtain white powder, which was 1-naphthalene-2-nitrophenyl sulfide, with a yield of 90%. 1 H NMR (400 MHz, CDC13): δ = 7.13 (s, 2H), 6.93 (t, J = 7.5 Hz, 1H), 6.69 (d, J = 7.9 Hz, 1H), 6.59 (t, J = 7.6 Hz, 1H), 6.47 (d, J = 7.9 Hz, 1H), 4.03 (s, 2H), 3.70 (p, J = 6.8 Hz, 2H), 2.96 (p, J = 6.9 Hz, 1H), 1.32 (d, J = 7.0 Hz, 6H), 1.17 (d, J = 6.9 Hz, 12H).

[0066] (3) Preparation of 1-(2,4,6-triisopropylphenyl) phenyl sulfide imidazolium [1,5-α] quinolinium salt 1b

[0067] To an ice-cooled flask was added 1 mmol of 1-naphthalene-2-aminophenyl sulfide dissolved in 5 mL of ethanol, and 1 mmol of hydrochloric acid-dioxane solution was added. The reaction was stirred at this temperature for 2 minutes, then 5 mmol of formalin (40% mass fraction of formaldehyde aqueous solution) and additional ethanol (10 mL) were added. The reaction was warmed to ambient temperature and stirred under air for 1 hour. After adding a portion of 1.0 mmol of 8-hydroxyquinoline-2-carboxaldehyde, the flask was sealed with a rubber septum and stirred at room temperature for 3 days. After the reaction was completed, the resulting mixture was rotary evaporated, dissolved in dichloromethane, and ethyl acetate was added to precipitate a large amount of precipitate, which was collected by filtration and washed with ethyl acetate three times, and dried under vacuum to obtain a yellow precipitate, which was 1-(2,4,6-triisopropylphenyl) phenyl sulfide imidazolium [1,5-α] quinolinium salt 1b, with a yield of 85%.

[0068] The results of the nuclear magnetic experiment are shown in Figures 3-4

[0069] 1 ​H NMR (400 MHz, CDC13): δ = 10.65 (s, 1H), 8.07 (d, J = 9.2 Hz, 1H), 7.94 (s, 1H), 7.54-7.49 (m, 2H), 7.48-7.43 (m, 2H), 7.42-7.37 (m, 1H), 7.33-7.28 (m, 1H), 7.22 (d, J = 6.6 Hz, 1H), 7.14 (s, 2H), 6.66 (d, J = 8.0 Hz, 1H), 3.44 (p, J = 6.8 Hz, 2H), 2.93 (p, J = 6.9 Hz, 1H), 1.28 (d, J = 6.9 Hz, 6H), 1.14 (d, J = 6.9 Hz, 12H) ppm. 13 C{ 1 H} NMR (100 MHz, CDC13): δ = 154.02, 152.41, 137.05, 132.38, 131.03, 130.71, 129.88, 129.80, 129.33, 127.68, 126.08, 125.98, 122.52, 120.91, 119.50, 118.92, 118.07, 114.27, 113.41, 34.46, 32.45, 24.31, 23.91 ppm. HRMS (ESI, positive ions): m / z = 495.2465 (calcd for [1b-Cl] + 495.2279).

[0070] (4) Preparation of chromium carbene compound 2b

[0071] The structural formula is:

[0072] In a nitrogen glove box, 0.1 mmol of ligand 1-naphthyl phenyl sulfide imidazolium [1,5-α] quinolinium salt was dissolved in 10 mL of super dry tetrahydrofuran, then 0.2 mmol of sodium bis(trimethylsilyl)amide was added to the solution, and the reaction was stirred at room temperature for 12 h. After the reaction was completed, the solid was separated by filtration, 0.1 mmol of silver triflate was added to the filtrate, and the reaction was stirred at room temperature for 12 h in the dark. After the reaction was completed, the solid was separated by filtration, 0.1 mmol of chromium trichloride was added to the filtrate, and the reaction was continued to stir in the dark for 24 h. After the reaction was completed, the solid was separated by filtration, concentrated, a large amount of diethyl ether was added, and white solid was precipitated. The solid was collected by filtration, washed with diethyl ether, and dried to obtain chromium carbene compound 2a with a yield of 50%. Elemental analysis: C 58.9%, H 5.1%, N 4.3%, S 4.9%.

[0073] Example 3:

[0074] Chromium carbene compounds were prepared using different N-substituted pyrazolylimidazo[1,5-a]pyridinium salts as shown in Table 1:

[0075] Table 1 Reaction examples of chromium carbene compounds prepared using different S-substituted imidazo[1,5-a]quinolinium salts

[0076]

[0077]

[0078]

[0079]

[0080] wherein imidazo[1,5-a]quinolinium salt ligand L1: The results of the nuclear magnetic experiment are shown in Figures 5-6 . 1 H NMR (400 MHz, CDC13): δ = 12.79 (s, 1H), 10.49 (d, J = 1.7 Hz, 1H), 8.03 (d, J = 8.2 Hz, 1H), 7.83 (d, J = 1.8 Hz, 1H), 7.64 (t, J = 7.8 Hz, 1H), 7.51-7.47 (m, 1H), 7.45 (t, J = 2.6 Hz, 2H), 7.44 (d, J = 1.6 Hz, 1H), 7.42-7.40 (m, 1H), 7.19 (d, J = 7.7 Hz, 1H), 2.48 (s, 3H) ppm. 13 C{ 1 H} NMR (100 MHz, CDC13): δ = 149.98, 136.13, 132.24, 131.01, 129.72, 128.94, 127.30, 127.13, 126.46, 126.10, 119.26, 119.09, 114.69, 113.70, 77.47, 77.16, 76.84, 15.67 ppm. HRMS (ESI, positive ions): m / z = 307.0900 (calcd for [L1-Cl] + 307.0987).

[0081] imidazo[1,5-a]quinolinium salt ligand L4: The results of the nuclear magnetic experiment are shown in Figures 7-8 . 1H NMR (400 MHz, CDC13): δ = 10.37 (s, 1H), 8.53 (d, J = 1.7 Hz, 1H), 7.87-7.84 (m, 1H), 7.80-7.74 (m, 3H), 7.72-7.67 (m, 3H), 7.59-7.55 (m, 3H), 7.50 (d, J = 7.9 Hz, 1H), 7.43-7.29 (m, 5H), 7.24 (d, J = 8.1 Hz, 1H) ppm. 13 C{ 1 H} NMR (100 MHz, CDC13): δ = 134.09, 133.85, 132.54, 132.33, 131.96, 131.07, 130.44, 129.73, 129.49, 129.44, 128.89, 128.77, 128.44, 127.71, 126.26, 119.20, 118.20, 115.32, 114.25 ppm. HRMS (ESI, positive ions): m / z = 369.1056 (calcd for [L4-Cl] + 369.1148).

[0082] Test Example:

[0083] The chromium carbene compound 2b prepared in Example 2 was taken as a catalyst for ethylene polymerization, and the polymerization process was as follows:

[0084] In a glove box, the super-dry toluene (25 mL) and the cocatalyst were added to a dry 50 mL high-pressure polymerization reactor, the chromium carbene compound 2b dissolved in 0.5 mL of dichloromethane was added, and after stirring uniformly, the reactor was sealed and removed from the glove box and transferred to a high-pressure polymerization pipeline. After replacing the nitrogen in the reactor with 5 atm of ethylene gas for 3 times, the ethylene pressure was adjusted. After adjusting the stirring rate and the temperature, when the temperature rose to the set value, the timing was started. After the reaction was completed, the reactor was cooled, the pressure in the reactor was released, and after adding a large amount of ethanol to quench the cocatalyst, the polymer was filtered and washed with ethanol repeatedly, and dried under vacuum at 60°C. The dried ethylene homopolymer was weighed, the catalyst activity was calculated, and the polymerization product was characterized.

[0085] The effect of the reaction conditions on the ethylene polymerization reaction of the chromium carbene compound 2b is shown in Table 2.

[0086] Table 2. Results of the ethylene polymerization condition screening of the chromium carbene compound 2b

[0087]

[0088] The polymerization conditions in the table are: 2 μmol chromium carbene compound 2b, 20 mL toluene, 0.5 mL dichloromethane; Al b = AlClMe2; Activity c : 10 3 g (PE) · mol -1 (Cr) · h -1 ; 16 d The catalyst is 1-(2,4,6-triisopropylphenyl) phenyl sulfide imidazolium [1,5-α] quinolinium salt 1b, 17 d The catalyst is CrCl3, 18 d Only AlMe2Cl is used as the catalyst.

[0089] According to Table 2, the activity of chromium carbene compound 2b is 965 × 10 3 g (PE) mol -1 (Cr) h -1 at 70°C, and high polymers insoluble in toluene are obtained, which indicates that imidazol [1,5-α] quinoline with a sulfur-containing side arm group has good thermal stability. The chromium carbene compound 2b prepared in the present application significantly improves the catalytic activity for ethylene polymerization compared with other commonly used catalysts. After the obtained polymers are subjected to nuclear magnetic resonance spectroscopy and gel chromatography analysis, it is found that the polymerization products are all bimodal linear polyethylene, and the results are shown in Figures 9-11

[0090] The above description is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.​

Claims

1. A method for preparing a bimodal linear polyethylene chromium carbene catalyst, characterized in that: The following steps are involved: (1) 1-Fluoro-2-nitrobenzene, aromatic thiol and potassium tert-butoxide are stirred and reacted in a solvent to prepare 1-nitro-2-aromatic sulfide benzene; (2) mixing the 1-nitro-2-aromatic sulfide benzene obtained in step (1) and hydrazine hydrate in a solvent, adding a catalyst and conducting a reflux reaction to obtain 1-amino-2-aromatic sulfide benzene; (3) mixing the 1-amino-2-aromatic sulfide benzene obtained in step (2), 8-hydroxyquinoline-2-carboxaldehyde, formaldehyde solution and hydrogen chloride-1,4-dioxane solution, stirring and reacting in a solvent to obtain 8-hydroxyimidazo[1,5-α]quinolinium salt; (4) stirring the 8-hydroxyimidazo[1,5-α]quinolinium salt obtained in step (3), silver trifluoromethanesulfonate, sodium bis(trimethylsilyl)amide and chromium trichloride in a solvent to obtain; The chemical structure of the obtained bimodal linear polyethylene chromium carbene catalyst is shown in Formula I: Formula I: ; Where Ar is 、 、 、 、 、 、 、 、 、 and Any one of them.

2. The method for preparing a bimodal linear polyethylene chromium carbene catalyst according to claim 1, wherein In the step (1), the molar ratio of 1-fluoro-2-nitrobenzene, aromatic thiol and potassium tert-butoxide is (0.8-1.2): (1.0-1.5): (1.0-1.5); the solvent is ethanol; the stirring reaction temperature is 20-30° C., and the reaction time is 10-15 h.

3. The method for preparing a bimodal linear polyethylene chromium carbene catalyst according to claim 1, wherein In step (2), the molar ratio of 1-nitro-2-aromatic sulfide benzene, hydrazine hydrate and catalyst is (0.8-1.2): (3-5): (0.01-0.1); the solvent is ethanol, and the catalyst is palladium carbon; the reflux reaction temperature is 80-90° C., and the reaction time is 10-15 h.

4. The method for preparing a bimodal linear polyethylene chromium carbene catalyst according to claim 1, wherein In step (3), the molar ratio of 1-amino-2-aromatic sulfide benzene to 8-hydroxyquinoline-2-carboxaldehyde is 1:(1-1.3); the solvent is ethanol; the stirring reaction temperature is 20-30°C, and the time is 50-100 hours.

5. The method for preparing a bimodal linear polyethylene chromium carbene catalyst according to claim 1, wherein In the step (4), the molar ratio of 8-hydroxyimidazo[1,5-α]quinolinium salt, silver trifluoromethanesulfonate, sodium bis(trimethylsilyl)amide and chromium trichloride is (0.05-0.2):(0.05-0.2):(0.1-0.3):(0.05-0.2); the solvent is tetrahydrofuran; the reaction temperature is 20-30°C, and the reaction time is 20-60 h.

6. Use of the bimodal linear polyethylene chromium carbene catalyst according to any one of claims 1 to 5 in catalyzing ethylene polymerization.

Images