Flexible ortho-arylcycloalkyl substituted pyridine diimine iron and cobalt complex catalysts, methods for their preparation and use

Abstract

The application provides a flexible ortho-aryloxy cycloalkyl substituted pyridine diimine iron and cobalt complex catalyst and a preparation method and application thereof, and belongs to the technical field of olefin polymerization catalysis; a series of 2,4,6-tricycloalkyl arylamine compounds are introduced into 2,6-diacetyl pyridine, and with the change of the space volume of the cycloalkyl, the molecular weight and distribution of polyethylene can be controlled; the substituents in the complex are selected from cycloalkyl, and under the protection of a gas atmosphere, the ligand is reacted with FeCl2.4H2O and CoCl2.6H2O respectively to obtain the complex catalyst of the present application; the complex exhibits extremely high polymerization activity, up to 1.76*10 7 g / mol.h, and generates high linear polyethylene with different molecular weight ranges; and has good industrial potential.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of olefin polymerization catalysts, and particularly relates to a flexible ortho-aryl cycloalkyl substituted pyridine diimine iron and cobalt complex catalyst, a preparation method and application thereof. BACKGROUND

[0002] More than 20 years ago, UNC, DuPont, and Brookhart and Gibson of Imperial College independently discovered bis(imino)pyridine iron (II) and cobalt (II) catalysts that can be used for ethylene polymerization and oligomerization reactions, which are extremely likely to be used for producing high crystallinity polyethylene or high linear alpha-olefins with wide polydispersity. Due to their low cost and extremely high activity, they are widely welcomed in the industry and academia.

[0003] However, the high-temperature stability of the late transition metal catalyst is poor, and the chain termination rate will significantly accelerate with the increase of temperature, and the catalytic activity will gradually decrease with the increase of reaction temperature. Generally speaking, changing the steric hindrance and electronic effect of the ligand is the two main strategies for developing bis(imino)pyridine iron (II) and cobalt (II) catalysts for ethylene polymerization systems with promising applications. Among them, the N-ortho-aryl substituent in the bis(imino)pyridine iron (II) and cobalt (II) system plays the most important role in determining the polymerization activity and the molecular weight of the generated polyethylene, and is the most studied modification part. SUMMARY

[0004] In order to solve the above technical problems, the present application provides a flexible ortho-aryl cycloalkyl substituted pyridine diimine iron and cobalt complex catalyst, a preparation method and application thereof, which can regulate the polymerization activity of the catalyst in ethylene polymerization and the molecular weight and molecular weight distribution of the obtained polyethylene. The catalyst exhibits higher activity during polymerization, and generates polyethylene with higher molecular weight and wider molecular weight distribution.

[0005] To achieve the above purpose, the present application first provides a flexible ortho-aryl cycloalkyl substituted pyridine diimine iron and cobalt complex catalyst, which is shown in the following formula 1:

[0006]

[0007] wherein M is selected from any one of iron and cobalt, C A is selected from cycloalkyl, and the structural formula is shown in the following formula 2:

[0008]

[0009] Formula 2;

[0010] wherein n = 1, 2, 3, 4, 5, 6.

[0011] Based on one general inventive concept, the present application also provides a method for preparing a complex catalyst, comprising the following steps:

[0012] S1, preparing a 2,4,6-tricycloalkyl aryl-containing pyridine diimine ligand: placing 2,6-diacetylpyridine and a tricycloalkyl arylamine in a toluene solution containing p-toluenesulfonic acid, stirring at 120°C until only one main spot is shown on a thin layer chromatography plate, then evaporating the solvent under reduced pressure, diluting the remaining mixture with methanol, collecting the resulting yellow solid by filtration, and recrystallizing with dichloromethane and n-hexane to obtain the 2,4,6-tricycloalkyl aryl-containing pyridine diimine ligand;

[0013] S2, preparing a flexible ortho-aryl cycloalkyl-substituted pyridine diimine iron and cobalt complex catalyst: stirring the ligand prepared in S1 with ferrous chloride tetrahydrate and cobalt chloride hexahydrate in tetrahydrofuran under a protective gas atmosphere, removing the solvent, then washing the blue or green solid powder with diethyl ether, and drying under vacuum to obtain the flexible ortho-aryl cycloalkyl-substituted pyridine diimine iron and cobalt complex catalyst.

[0014] Preferably, the stirring time in step S1 is 72 h, and the molar ratio of 2,6-diacetylpyridine to tricycloalkyl arylamine is 1:2.5.

[0015] Preferably, the molar ratio of the 2,4,6-tricycloalkyl aryl-containing pyridine diimine ligand to ferrous chloride tetrahydrate or cobalt chloride hexahydrate in step S2 is 1:1.

[0016] Preferably, the stirring time in step S2 is 12 h, and the protective gas is selected from argon or nitrogen.

[0017] Based on one general inventive concept, the present application also provides a use of a flexible ortho-aryl cycloalkyl-substituted pyridine diimine iron and cobalt complex catalyst in catalyzing an ethylene polymerization reaction in a polymerization solvent.

[0018] Preferably, the catalyst in the ethylene polymerization reaction is a composite catalyst composed of the flexible ortho-aryl cycloalkyl-substituted pyridine diimine iron and cobalt complex catalyst and a cocatalyst.

[0019] Preferably, the cocatalyst includes any one of an alkyl aluminum, an aluminoxane, or a chlorinated alkyl aluminum, and the molar ratio of the flexible ortho-aryl cycloalkyl-substituted pyridine diimine iron and cobalt complex catalyst to the cocatalyst is 1:500-2000.

[0020] Preferably, the aluminoxane includes methyl aluminoxane or modified methyl aluminoxane, and the chlorinated alkyl aluminum includes diethyl aluminum chloride.

[0021] As preferred, the reaction temperature of the catalytic ethylene polymerization reaction is 20-80℃, the reaction time is 10-60 minutes, the reaction pressure is 0.4-1.5Mpa, and the polymerization solvent is at least one of toluene, n-hexane, cyclohexane and heptane.

[0022] The catalyst prepared by the scheme has the following catalytic mechanism:

[0023] The synthesis general formula of the flexible ortho-aryl cycloalkyl-substituted pyridine diimine iron (II) and cobalt (II) catalyst prepared by the scheme is as follows:

[0024]

[0025] Under the catalysis of p-toluenesulfonic acid, 2,6-diacetylpyridine and 2,4,6-tricycloalkyl arylamine undergo condensation reaction to generate the target bis(imino)pyridine ligand: pyridine diimine iron (II) and cobalt (II) (L1 and L2) with a high yield (83%-87%). At room temperature, the ligands L1-L2 are reacted with an equal amount of ferrous chloride tetrahydrate in tetrahydrofuran (THF) to generate the complexes Fe1-Fe2 (blue) with an excellent yield (91%-95%). Similarly, the ligands L1-L2 are reacted with an equal amount of cobalt chloride hexahydrate in tetrahydrofuran to easily generate the corresponding cobalt (II) complexes Co1-Co2 (green) with a high yield (91%-94%).

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] By adjusting the size of the cycloalkyl ring, the polymerization activity of the catalyst in ethylene polymerization and the molecular weight and molecular weight distribution of the obtained polyethylene can be regulated. The smaller the ring, the more conducive to the coordination and insertion of ethylene, and the catalyst exhibits higher activity in polymerization and generates polyethylene with higher molecular weight and wider molecular weight distribution. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings described below are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0029] Figure 1 Nuclear magnetic resonance hydrogen spectrum of the 2,4,6-tricyclopentyl aryl pyridine diimine ligand prepared for Example 1;

[0030] Figure 2NMR spectrum of the 2,4,6-tricyclohexylaryl pyridine diimine ligand prepared in Example 2;

[0031] Figure 3 Single crystal X-ray diffraction patterns of the complex catalyst prepared in Example 1, a is the single crystal X-ray diffraction pattern of the complex catalyst Fe1, b is the single crystal X-ray diffraction pattern of the complex catalyst Co1. DETAILED DESCRIPTION

[0032] In order to make the technical problems, technical solutions and advantages of the present application more clear, the following will be described in detail with reference to the accompanying drawings and specific examples.

[0033] The following examples are used to illustrate the present application, but are not used to limit the scope of the present application. Modifications or replacements of the methods, steps or conditions of the present application, without departing from the spirit and essence of the present application, all belong to the scope of the present application.

[0034] If not specifically indicated, the technical means used in the examples are the conventional means well known to those skilled in the art; if not specifically indicated, the reagents used in the examples are commercially available.

[0035] The reagents and raw materials used in the examples: all the metal organic reactions are reacted under nitrogen protection, and the solvents are all treated by drying and oxygen removal. The anhydrous methanol and ethanol are analytical pure and are used directly. The toluene is dehydrated by molecular sieves, and then refluxed with sodium under nitrogen protection, and evaporated before use.

[0036] Preparation of flexible ortho-aryl cycloalkyl substituted pyridine diimine iron (II) and cobalt (II) catalysts in Example 1

[0037] S1, preparation of 2,4,6-tricycloalkylaryl pyridine diimine ligand: 2,6-diacetylpyridine (1.0 mmol, 1.0 equivalent) and cyclopentyl aniline (2.5 mmol, 2.5 equivalents) were placed in a toluene (20 mL) solution containing p-toluenesulfonic acid (20 mg), stirred at 120°C for 72 h until the thin layer chromatography plate showed only one main point. Then the solvent was removed by evaporation under reduced pressure. The remaining mixture was diluted with methanol (20 mL). The resulting yellow solid was collected by filtration and recrystallized with dichloromethane and n-hexane to obtain 2,4,6-tricyclopentylaryl pyridine diimine ligand with a yield of 83%;

[0038] The NMR analysis data of the ligand prepared in S1 are as follows:

[0039] 1H NMR (600 MHz, CDC13) δ 8.47 (d, J = 7.7 Hz, 2H, Py-H), 7.93 (dq, J = 11.6, 6.4, 5.9 Hz, 1H, Py-H), 7.05 (s, 4H, Ar-H), 3.03-2.96 (m, 2H, p-Cp-CH), 2.89-2.77 (m, 4H, o-Cp-CH), 2.25 (s, 6H, N=C-CH3), 2.11 (td, J = 7.6, 3.8 Hz, 4H, Cp-CH2), 2.04-1.98 (m, 4H, Cp-CH2), 1.89-1.47 (m, 40H, Cp-CH2). 13 C NMR (151 MHz, CDC13) δ 167.35 (C=N), 155.43, 145.92, 141.08, 136.85, 133.43, 122.26, 122.18, 46.10 (p-Cp-CH), 40.47 (o-Cp-CH), 34.85 (Cp-CH2), 34.07 (Cp-CH2), 34.04 (Cp-CH2), 25.91 (Cp-CH2), 25.87 (Cp-CH2), 25.58 (Cp-CH2), 17.39 (N=C-CH3).

[0040] The mass spectrometry data of the ligand prepared in S1 is as follows: HRMS (m / z): calcd for C51H68N3: 722.5413, found: 722.5328 [M+H]+.

[0041] The1H NMR spectrum of the ligand prepared in S1 is as shown in Figure 1

[0042] S2, Preparation of flexible ortho-aryl cyclopentyl substituted pyridine diimine iron (II) and cobalt (II) complex catalysts: under nitrogen atmosphere, the ligand prepared in S1 (0.2 mmol) was respectively stirred with ferrous chloride tetrahydrate (0.2 mmol), cobalt chloride hexahydrate (0.2 mmol) in tetrahydrofuran (10 mL) for 12 h, then the solvent was removed, and the blue (Fe complex), green (Co complex) solid powder was washed with diethyl ether and dried under vacuum, thus obtaining the corresponding flexible ortho-aryl cyclopentyl substituted pyridine diimine iron complex Fe1 (yield 95%) and flexible ortho-aryl cyclopentyl substituted pyridine diimine cobalt complex Co1 (yield 94%).

[0043] Elemental analysis was performed on the iron complex and cobalt complex prepared in step S2:

[0044] Elemental analysis: Fe1: calc. for C 51 H 67 ​Cl2FeN3: C, 72.16; H, 7.96; N, 4.95. Found: C, 72.24; H, 7.85; N, 4.89; Co1 : calc. for C 51 H 67 Cl2CoN3: C, 71.90; H, 7.93; N, 4.93. Found: C, 71.84; H, 7.86; N, 4.85.

[0045] Mass spectrometry analysis of the iron complex Fe1 and the cobalt complex Co1 prepared in step S2:

[0046] Fe1 : MALDI-TOF-MS (m / z): calc. for C 51 H 67 ClFeN3: 812.44, found: 812.58 [M-Cl]+; Co1 : MALDI-TOF-MS (m / z): calc. for C 51 H 67 ClCoN3: 815.44, found: 816.00 [M-Cl]+.

[0047] The single crystal structure of the flexible ortho-arylcyclopentyl-substituted pyridine diimine iron complex obtained in this example is shown in Figure Figure 3 (a):

[0048] The single crystal structure of the flexible ortho-arylcyclopentyl-substituted pyridine diimine cobalt complex obtained in this example is shown in Figure Figure 3 (b):

[0049] Preparation of flexible ortho-arylcycloalkyl-substituted pyridine diimine iron (II) and cobalt (II) catalysts

[0050] S1. Preparation of 2,4,6-tricycloalkylaryl-containing pyridine diimine ligand: 2,6-diacetylpyridine (1.0 mmol, 1.0 equivalent) and cyclohexyl aniline (2.5 mmol, 2.5 equivalents) were placed in a solution of p-toluenesulfonic acid (20 mg) in toluene (20 mL) and stirred at 120 °C for 72 h until the thin layer chromatography plate showed only one main spot. The solvent was then evaporated under reduced pressure. The remaining mixture was diluted with methanol (20 mL). The resulting yellow solid was collected by filtration and recrystallized using dichloromethane and n-hexane to obtain the 2,4,6-tricyclohexylaryl-containing pyridine diimine ligand in 83% yield.

[0051] The NMR analysis data of the ligand prepared in S1 are:

[0052] 1H NMR (400 MHz, CDC13) δ 8.37 (d, J = 7.8 Hz, 2H, Py-H), 7.92 (t, J = 7.8 Hz, 1H, Py-H), 6.98 (s, 4H, Ar-H), 2.49 (td, J = 9.7, 8.3, 3.0 Hz, 2H, p-Cy-CH), 2.36 (td, J = 10.1, 8.7, 2.9 Hz, 4H, o-Cy-CH), 2.26 (s, 6H, N=C-CH3), 1.82 (ddd, J = 71.7, 30.2, 11.7 Hz, 30H, Cy-CH2), 1.57 - 1.14 (m, 30H, Cy-CH2). 13 C NMR (101 MHz, CDC13) δ 167.40 (C=N), 155.78, 144.39, 142.82, 136.98, 134.63, 122.03, 121.94, 44.57 (p-Cy-CH), 39.35 (o-Cy-CH), 34.88 (Cy-CH2), 33.76 (Cy-CH2), 33.55 (Cy-CH2), 27.33 (Cy-CH2), 27.24 (Cy-CH2), 27.20 (Cy-CH2), 26.47 (Cy-CH2), 26.42 (Cy-CH2), 17.49 (N=C-CH3).

[0053] Mass spectrum analysis of the ligand prepared in S1 : HRMS (m / z): calcd for C57H80N3: 806.6347, found: 806.6257 [M+H]+.

[0054] The1H NMR spectrum of the ligand prepared in S1 is shown in Figure 2

[0055] S2, Preparation of flexible ortho-arylcyclopentyl-substituted pyridine diimine iron (II) and cobalt (II) complex catalysts: After stirring the ligand prepared in S1 (0.2 mmol) with ferrous chloride tetrahydrate (0.2 mmol), cobalt chloride hexahydrate (0.2 mmol) in tetrahydrofuran (10 mL) for 12 h under nitrogen atmosphere, the solvent was removed, then the blue (Fe complex), green (Co complex) solid powder was washed with diethyl ether and dried under vacuum, thus the corresponding flexible ortho-arylcyclopentyl-substituted pyridine diimine iron complex Fe2 (yield 91%) and flexible ortho-arylcyclopentyl-substituted pyridine diimine cobalt complex Co2 (yield 91%) were obtained.

[0056] Elemental analysis was performed on the iron complex Fe2 and cobalt complex Co2 prepared in step S2:

[0057] ​Fe2: calc. for C57H79Cl2FeN3: C, 73.38; H, 8.53; N, 4.50. Found: C, 73.45; H, 8.36; N, 4.61; Co2: calc. for C57H79Cl2CoN3: C, 73.14; H, 8.51; N, 4.49. Found: C, 73.26; H, 8.49; N, 4.32.

[0058] Mass spectrometry analysis of the iron complex F2 and cobalt complex Co2 prepared in step S2:

[0059] Fe2: MALDI-TOF-MS (m / z): calc. for C 57 H 79 ClFeN3: 896.53, found: 896.83 [M-Cl]+; Co2: MALDI-TOF-MS (m / z): calc. for C 57 H 79 ClCoN3: 899.53, found: 899.83 [M-Cl]+.

[0060] Experimental Example 1: Investigation of the effect of the complexes F el and Co el prepared in Example 1 on the catalysis of ethylene polymerization

[0061] A 350 mL thick-walled pressure-resistant glass reactor was connected to a high-pressure gas line after drying for 3 h at 90 °C, then the reactor was adjusted to the desired polymerization temperature (80 °C), 48 mL of toluene and 1 mmol of methylaluminoxane (MAO) were added to the reactor under an ethylene atmosphere, then 1 micromole of catalyst in 2 mL of dichloromethane was injected into the polymerization system using a syringe. The reactor was pressurized under rapid stirring and the ethylene pressure was maintained at 6 atm. After 10 min, the pressure reactor was vented, the polymer was precipitated in ethanol, filtered and dried in a vacuum at 50 °C for at least 24 h.

[0062] Table 1 below provides the experimental conditions for the ethylene polymerization of the preferred catalysts provided in this experimental example; polymer molecular weight (Mw), polymer molecular weight distribution (PDI) and other polymerization results data.

[0063] Table 1: Effect of the catalysts prepared in Example 1 on the catalysis of ethylene polymerization

[0064]

[0065]

[0066] In the table: activity is 10 6g / (mol Cat h), Mw is the number average molecular weight, Mw / Mn is the molecular weight distribution.

[0067] Example 2 to investigate the effect of the complexes Fe2 and Co2 prepared in Example 2 on the polymerization of ethylene

[0068] A 350 mL thick-walled pressure-resistant glass reactor was connected to a high-pressure gas line after drying at 90 °C for 3 h. Subsequently, the reactor was adjusted to the desired polymerization temperature (80 °C). Under an ethylene atmosphere, 48 mL of toluene and 1 mmol of methylaluminoxane (MAO) were added to the reactor, and then 1 micromole of catalyst in 2 mL of dichloromethane was injected into the polymerization system using a syringe. Under rapid stirring, the reactor was pressurized and the ethylene pressure was maintained at 6 atm. After 10 min, the pressure reactor was vented, the polymer was precipitated in ethanol, filtered, and dried at 50 °C under vacuum for at least 24 h.

[0069] Table 2 below provides the experimental conditions for the polymerization of ethylene using the preferred catalysts of this experimental example; polymer molecular weight (Mw), polymer molecular weight distribution (PDI), and other polymerization results data.

[0070] Table 2 Effect of the catalysts prepared in Example 2 on the polymerization of ethylene

[0071] Entry Cat. T / ℃ Yield / g Act. b ]] M w c ]]> M w / M n c ]]> T m (°C) d ]] 1 Fe2 20 0.67 4.02 47.0 6.23 134 2 Fe2 40 1.33 7.98 26.5 4.70 132 3 Fe2 60 1.25 7.50 21.6 4.14 130 4 Fe2 80 0.44 2.64 11.9 4.12 128 5 Co2 20 0.60 3.60 3.4 2.66 108 6 Co2 40 0.71 4.26 2.8 2.61 109 7 Co2 60 0.71 4.26 2.3 2.31 107 8 Co2 80 0.63 3.78 2.1 2.13 106

[0072] Activity: 10 6 g / (mol Cat h), Mw is the number average molecular weight, Mw / Mn is the molecular weight distribution.

[0073] The results in Tables 1 and 2 show that all the iron(II) and cobalt(II) complexes exhibit very high polymerization activity (up to 1.76 x 10 7 g / mol h) and produce high linear polyethylenes with different molecular weight ranges (weight average molecular weight Mw = 2.1-232.8 kg / mol) during the polymerization of ethylene.

[0074] The size of the cycloalkyl ring and the metal species have a significant influence on the polymerization of ethylene. Smaller cyclopentyl substituents are more advantageous than the corresponding cyclohexyl groups for increasing the polymerization activity of the iron(II) and cobalt(II) complexes and the molecular weight of the polyethylenes produced. For complexes with the same ligands, under otherwise identical conditions, the iron(II) species produces polyethylenes with higher molecular weight and broader molecular weight distribution than the corresponding cobalt(II) species.

[0075] The catalysts of this type of complex exhibit great potential for industrial applications, which fully demonstrates the great value of this type of complex catalyst for further research and development.

[0076] The above merely describes the preferred embodiments of the present application, and the protection scope of the present application is not limited to the above. Any improvement and transformation obtained by those skilled in the art without departing from the technical concept of the present application shall be considered as the protection scope of the present application.

Claims

1. Use of a flexible para-arylcycloalkyl substituted pyridine diimine cobalt complex catalyst in the polymerization of ethylene in a polymerization solvent, characterized in that, The catalyst in the ethylene polymerization reaction is a complex catalyst composed of a flexible ortho-aryl cycloalkyl substituted pyridine diimine cobalt complex catalyst and a cocatalyst; the complex catalyst is shown in the following formula 1: ， Formula 1; wherein M is cobalt, C A is selected from cycloalkyl, and has the following structural formula 2: ， Formula 2; Wherein, n = 3 or 4; The cocatalyst includes any one of alkyl aluminum, aluminoxane, chlorinated alkyl aluminum, and the molar ratio of the flexible ortho-aryl cycloalkyl substituted pyridine diimine cobalt complex catalyst to the cocatalyst is 1:500-2000.

2. Use according to claim 1, characterized in that, The preparation method of the complex catalyst includes the following steps: S1, preparing a 2,4,6-tricycloalkyl aryl containing pyridine diimine ligand: placing 2,6-diacetylpyridine and tricycloalkyl arylamine in a toluene solution containing p-toluenesulfonic acid, stirring at 120℃ until only one main point is shown on the thin layer chromatography plate, then evaporating the solvent under reduced pressure, diluting the remaining mixture with methanol, filtering to collect the obtained yellow solid, and recrystallizing with dichloromethane and n-hexane to obtain the 2,4,6-tricycloalkyl aryl containing pyridine diimine ligand; S2, preparing a flexible ortho-aryl cycloalkyl substituted pyridine diimine cobalt complex catalyst: stirring the ligand prepared in S1 with cobalt chloride hexahydrate in tetrahydrofuran under a protective gas atmosphere, removing the solvent, then washing the green solid powder with diethyl ether, and drying under vacuum to obtain the flexible ortho-aryl cycloalkyl substituted pyridine diimine cobalt complex catalyst.

3. Use according to claim 2, characterized in that, The stirring time in the step S1 is 72h, and the molar ratio of the 2,6-diacetylpyridine to the tricycloalkyl arylamine is 1:2.

5.

4. Use according to claim 2, characterized in that, The molar ratio of the 2,4,6-tricycloalkyl aryl containing pyridine diimine ligand to the cobalt chloride hexahydrate in the step S2 is 1:

1.

5. The use according to claim 2, characterized in that, The stirring time in the step S2 is 12h, and the protective gas is selected from argon or nitrogen.

6. Use according to claim 1, characterized in that, The aluminoxane includes methyl aluminoxane or modified methyl aluminoxane, and the chlorinated alkyl aluminum includes diethyl aluminum chloride.

7. The use according to claim 1, characterized in that, The reaction temperature for the catalytic ethylene polymerization reaction is 20-80℃, the reaction time is 10-60 minutes, the reaction pressure is 0.4-1.5Mpa, and the polymerization solvent is at least one of toluene, n-hexane, cyclohexane, and heptane.

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