Phenyl-modified acenaphthenequinone alpha-diimine nickel catalyst and method of making same

Abstract

This invention discloses a phenyl-modified, biasymmetric (α-diimine) nickel olefin catalyst based on acenaphthoquinone as its framework, its preparation method, and its applications. The catalyst's structural formula is shown in Formula (I), where X is chlorine or bromine. The catalyst has a simple preparation process and, when used as a co-catalyst for ethylene polymerization, exhibits results contrary to conventional experimental observations: larger substituents lead to lower molecular weight, better flowability, and dispersibility in the polymerized product, showing broad application prospects in the elastomer field. Furthermore, this type of catalyst also exhibits good thermal stability and polymerization activity, demonstrating promising industrial application prospects. Formula (I).

Description

Technical Field

[0001] This invention relates to phenyl-modified acenaphthoquinone (α-diimine) nickel catalysts, their preparation methods and applications, and particularly to a phenyl-modified acenaphthoquinone biasymmetric α-diimine nickel catalyst, its preparation method and applications, and the application of using the catalyst to catalyze the polymerization of ethylene or propylene to obtain polyethylene or polypropylene. Background Technology

[0002] Polyolefins, as one of the most widely used synthetic polymers, have been extensively applied in all aspects of daily life. In the process of preparing polyolefins, the development and improvement of new catalysts are crucial factors driving the advancement and improvement of polyolefin production efficiency and product performance.

[0003] While pre-transition metal catalysts play a crucial role in olefin polymerization, the polyethylene structures they produce are almost always linear, making it impossible to prepare non-linear (e.g., branched) polymers. Post-transition metal catalysts, on the other hand, possess unique advantages such as lower oxygen affinity and stronger tolerance to polar groups. In 1995, Brookhart et al. pioneered the development of (α-diimine) nickel / palladium catalysts, the specific structural formula of which is shown in formula (Ⅳ). The "chain-walking" mechanism of this type of catalyst makes it possible to synthesize polymers with high activity and high molecular weight and high degree of branching, thus attracting widespread attention to transition metal catalysts in olefin polymerization. Equation (Ⅳ) Typically, many studies have focused on modifying the ortho-position group of the aryl group (R' in the formula) while maintaining the diimine backbone structure. When R' is a sterically hindered group, the molecular weight of the resulting polymer usually increases. This is mainly because the introduced sterically hindered substituent inhibits the β-H elimination reaction during chain growth, thereby suppressing chain transfer and resulting in a higher molecular weight of the final polymer. Long (J. AM. CHEM. SOC., 2013, 135(44): 16316-9), Chen (Chin. J. Chem., 2021, 40(2): 215-22), Dai (Organometallics., 2021, 41(2): 124-32) et al. utilized R' as a sterically hindered substituent, and the molecular weight of the resulting polymers all increased. In addition, the introduction of sterically hindered groups can, to some extent, help improve the thermal stability of the catalyst. However, although the polymer products prepared by this type of catalyst have high molecular weight, they have extremely high viscosity, making conventional injection molding and extrusion processing difficult. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a phenyl-modified acenaphthoquinone biasymmetric α-diimine nickel catalyst and its preparation method.

[0005] In a first aspect, the present invention provides a biasymmetric (α-diimine) nickel olefin catalyst, the chemical structure of which is shown in formula (I): Equation (I) Where X is chlorine or bromine.

[0006] In a second aspect, the present invention provides ligand compounds for the above-mentioned biasymmetric (α-diimine) nickel olefin catalyst, the structural formula of which is shown in formula (II): Formula (II) In a third aspect, the present invention also provides a method for preparing the above-mentioned ligand compound, comprising the following steps: 1) Acenathoquinone reacts with aniline containing a sterically hindered substituent via a ketamine condensation reaction to yield the compound shown in formula (III):

[0007] 2) The compound shown in formula (III) reacts with an asymmetric 3-methyl-[1,1'-biphenyl]-2-amine modified with a phenyl group via a ketamine condensation reaction to yield the ligand compound shown in formula (II):

[0008] In one embodiment of the present invention, the solvent used in step 1) above is selected from at least one of toluene, acetonitrile, acetic acid and anhydrous ethanol, preferably selected from at least one of toluene and acetonitrile.

[0009] In one embodiment of the present invention, the catalyst used in step 1) above is selected from at least one of p-toluenesulfonic acid and acetic acid.

[0010] In one embodiment of the present invention, the ratio of the catalyst, acenaphthoquinone, aniline with a large sterically hindered substituent, and solvent in step 1) above is 0.1-0.15 mmol: 1-1.1 mmol: 1-1.4 mmol: 5-10 mL.

[0011] In one embodiment of the present invention, the reaction time of step 1) above is 2-8 hours, preferably 3-6 hours.

[0012] In one embodiment of the present invention, step 1) above further includes the following step: using a mixed solvent of dichloromethane and petroleum ether or a mixed solvent of petroleum ether and ethyl acetate as eluent, the product is subjected to column chromatography in a silica gel column to obtain the product shown in formula (III).

[0013] In one embodiment of the present invention, the solvent used in step 2) is selected from at least one of toluene, acetonitrile, acetic acid and anhydrous ethanol, preferably at least one of toluene and acetonitrile.

[0014] In one embodiment of the present invention, the catalyst used in step 2) is selected from at least one of p-toluenesulfonic acid and acetic acid.

[0015] In one embodiment of the present invention, the ratio of the catalyst, acenaphthoquinone, aniline with a large sterically hindered substituent, and solvent in step 2) above is 0.2-0.5 mmol: 1-1.1 mmol: 1-1.4 mmol: 30-70 mL.

[0016] In one embodiment of the present invention, the reaction time of step 2) above is 6-16 hours, preferably 8-12 hours.

[0017] In one embodiment of the present invention, step 2) above further includes the following step: using a mixed solvent of dichloromethane and petroleum ether or a mixed solvent of petroleum ether and ethyl acetate as eluent to perform column chromatography on the product in a silica gel column to obtain the product shown in formula (II).

[0018] In a fourth aspect, the present invention also provides a method for preparing the catalyst shown in formula (I), comprising the following steps: under an inert gas atmosphere, complexing the compound shown in formula (II) with one of ethylene glycol dimethyl ether nickel dibromide, ethylene glycol dimethyl ether nickel dichloride, or nickel dichloride hexahydrate to obtain the catalyst described in the present invention. In the structural formula of the catalyst of the present invention, X is chlorine or bromine. In one embodiment of the present invention, X is selected as bromine. In another embodiment of the present invention, X is selected as chlorine.

[0019] In one embodiment of the present invention, under a nitrogen atmosphere, the compound represented by formula (II) is used as a ligand, and the nickel-containing compound complexed with the ligand is selected as nickel dimethyl ether dibromide (DME)NiBr2, wherein the molar ratio of the ligand to (DME)NiBr2 is 1:1-1.2, preferably 1:1.1; the solvent used is dichloromethane, the reaction temperature is 15-35 °C, preferably 25 °C, and the reaction time is 8-30 hours, preferably 16-24 hours.

[0020] In a fifth aspect, the present invention also provides a catalyst composition for catalyzing olefin polymerization, the composition comprising a main catalyst and a co-catalyst, the main catalyst being selected from the catalyst shown in formula (I), the co-catalyst being selected from at least one of alkylaluminum chloride, alkylaluminum and aluminoxane, and the olefin being ethylene or propylene.

[0021] In one embodiment of the present invention, the composition comprises a main catalyst and a co-catalyst, wherein the main catalyst is selected from the catalyst shown in formula (I), the co-catalyst is selected from at least one of alkylaluminum chloride, alkylaluminum and aluminoxane, and the olefin is ethylene or propylene.

[0022] Optionally, in the above catalyst composition, the aluminum oxane is methylaluminoxane (MAO), modified methylaluminoxane (MMAO), ethylaluminoxane, or isobutylaluminoxane.

[0023] Optionally, in the above catalyst composition, the alkylaluminum is trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, or tri-n-octylaluminum.

[0024] Optionally, in the above catalyst composition, the alkylaluminum chloride is diethylaluminum chloride, sesqui-diethylaluminum chloride, or ethylaluminum dichloride.

[0025] Considering the effectiveness and cost of the co-catalyst, in a preferred embodiment, the co-catalyst in the above-mentioned catalyst composition is alkyl aluminum chloride.

[0026] In a preferred embodiment, when alkylaluminum chloride is used as a co-catalyst, the molar ratio of metallic aluminum in alkylaluminum chloride to metallic nickel in the catalyst is referred to as the aluminum-nickel ratio, which ranges from 50 to 2000:1.

[0027] In a sixth aspect, the present invention also discloses the application of the catalyst shown in formula (I) in catalyzing the polymerization of ethylene and propylene to prepare polyethylene and polypropylene.

[0028] The beneficial effects of this invention lie in providing a phenyl-modified acenaphthoquinone biasymmetric (α-diimine) nickel olefin polymerization catalyst with good thermal stability and polymerization activity. This catalyst, modified with highly hindered groups, exhibits unconventional properties, yielding lower molecular weight polymers instead of the expected higher molecular weight polymers during olefin polymerization. Furthermore, the polymers obtained by this catalyst also exhibit reduced branching, resulting in lower viscosity, better flowability, and easier processing. In addition, this type of catalyst has a low synthesis threshold, simple ligand synthesis, requires less co-catalyst, has high yield, and offers significant overall production cost advantages. Detailed Implementation

[0029] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0030] Example 1, Preparation of intermediate of formula (III): p-Toluenesulfonic acid (0.1 g, 0.6 mmol) was added to an anhydrous ethanol (80 mL) solution of 2,6-bis(diphenylmethyl)-4-methylaniline (8.8 g, 20 mmol) and acenaphthene (3.64 g, 20 mmol), and the mixture was refluxed for 24 h. The solvent was removed, and the residue was subjected to silica gel column chromatography with a mixed solvent of dichloromethane and petroleum ether in a volume ratio of 2:1 to obtain intermediate of formula (III) with a mass of 11.3 g, yield: 93.6%.

[0031] Example 2, Preparation of ligand (II): Zinc chloride (0.2 g, 1.5 mmol) was added to a solution of 3-methyl-[1,1'-biphenyl]-2-amine (0.275 g, 1.5 mmol) and intermediate of formula (III) (0.603 g, 1 mmol) in acetic acid (5 mL), and the mixture was refluxed for 30 min. The solvent was removed, and the residue was subjected to silica gel column chromatography with a mixed solvent of petroleum ether and ethyl acetate in a volume ratio of 30:1 to obtain 0.45 g of ligand (II), yield: 58.5%.

[0032] Example 3, Preparation of catalyst of formula (I): Under a nitrogen atmosphere, ligand of formula (II) (0.154 g, 0.2 mmol) and (DME)NiBr2 (0.062 g, 0.2 mmol) were dissolved in 20 mL of dichloromethane and stirred at room temperature for 24 hours. The dichloromethane was dried under vacuum and washed three times with 20 mL of diethyl ether each time. The diethyl ether was then dried under vacuum to obtain 0.18 g of catalyst of formula (I), with a yield of 90.9%.

[0033] The following examples illustrate catalytic ethylene polymerization: Example 4: Ethylene pressure polymerization was carried out under anhydrous and oxygen-free conditions. The ethylene pressure was 1 MPa, and the polymerization temperature was 60 °C. 1 L of heptane was poured into a 2000 mL stainless steel reactor, followed by the injection of 1.5 mL of a 2.0 mol / L diethylaluminum chloride toluene solution as a co-catalyst. 2 μmol of catalyst (I) was dissolved in 10 mL of toluene solution and injected. The ethylene pressure was increased to 1.0 MPa, and the mixture was stirred. After reacting for half an hour, the polymer solution was poured into an acidified ethanol solution for sedimentation. The polymer was filtered, washed several times with acidified ethanol, and vacuum dried at 60 °C to constant weight. 12.5 g of polymer was then weighed. The catalytic activity was 12.5 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 48.5 × 10⁻⁶. 4 g / mol, polydispersity index of 2.11, and branching degree of 63.

[0034] Example 5: The polymerization pressure in Example 4 was adjusted to 1.5 MPa, while other conditions remained unchanged. The polymerization product was vacuum dried at 60 °C to constant weight, and 18.7 g of polymer was obtained. The catalytic activity was 18.7 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 55.7 × 10⁻⁶. 4 g / mol, polydispersity index of 2.09, and branching degree of 59.

[0035] Example 6: The polymerization pressure in Example 4 was adjusted to 1.9 MPa, while other conditions remained unchanged. The polymerization product was vacuum dried at 60 °C to constant weight, and 21.9 g of polymer was obtained. The catalytic activity was 21.9 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 58.6 × 10⁻⁶. 4 g / mol, polydispersity index of 2.13, and branching degree of 56.

[0036] Example 7: The polymerization pressure in Example 4 was adjusted to 0.7 MPa, while other conditions remained unchanged. The polymerization product was vacuum dried at 60 °C to constant weight, and 6.5 g of polymer was obtained. The catalytic activity was 6.5 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 48.4 × 10⁻⁶. 4 g / mol, polydispersity index of 1.91, and branching degree of 68.

[0037] Example 8: The polymerization temperature in Example 7 was adjusted to 40 °C, while other conditions remained unchanged. The polymerization product was vacuum dried at 60 °C to constant weight, and 10.2 g of polymer was obtained. The catalytic activity was 10.2 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 90.2 × 10⁻⁶. 4 g / mol, polydispersity index of 2.15, and branching degree of 52.

[0038] Example 9: The polymerization temperature in Example 7 was adjusted to 80 °C, while other conditions remained unchanged. The polymerization product was vacuum dried at 60 °C to constant weight, and 3.4 g of polymer was obtained. The catalytic activity was 3.4 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 24.1 × 10⁻⁶. 4 g / mol, polydispersity index of 2.02, and branching degree of 77.

[0039] Example 10: The polymerization temperature in Example 7 was adjusted to 100 °C, while other conditions remained unchanged. The polymerization product was vacuum dried at 60 °C to constant weight, and 0.8 g of polymer was obtained. The catalytic activity was 0.8 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 15.6 × 10⁻⁶. 4 g / mol, polydispersity index of 2.04, and branching degree of 89.

[0040] Example 11: The amount of co-catalyst in Example 4 was adjusted to 1.5 mL with a concentration of 2.0 mol / L, and the amount of catalyst (I) was adjusted to 10 μmol. Other conditions remained unchanged. The polymerization product was vacuum dried at 60°C to constant weight, and 18.2 g of polymer was obtained. The catalytic activity was 3.64 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 19.9 × 10⁻⁶. 4 kg / mol, polydispersity index of 2.24, and branching degree of 86.

[0041] Comparative Example 1: A solution of 2,6-dimethylaniline (0.18 g, 1.5 mmol) and intermediate of formula (III) (0.629 g, 1 mmol) in toluene (50 mL) was reacted with p-toluenesulfonic acid (0.086 g, 0.5 mmol) and refluxed for 12 h. The solvent was removed, and the residue was subjected to silica gel column chromatography with a mixed solvent of petroleum ether and ethyl acetate in a volume ratio of 30:1 to obtain 0.31 g of 2,6-dimethylaniline ligand, yield: 44%.

[0042] Comparative Example 2: The ligand of formula (II) in Example 3 was replaced with the 2,6-dimethylaniline ligand synthesized in Comparative Example 1. Other operations were the same as in Example 3, and 0.154 g of 2,6-dimethylaniline diimine nickel bromide complex was obtained with a yield of 83%.

[0043] Comparative Example 3: The catalyst in Example 4 was replaced with the 2,6-dimethylaniline diimine nickel bromide complex synthesized in Comparative Example 2. All other operations were the same as in Example 4. The polymerization product was vacuum dried at 60 °C to constant weight, and 13.4 g of polymer was obtained. The catalytic activity was 13.4 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 126 × 10⁻⁶. 4 g / mol, polydispersity index of 1.87, and branching degree of 88.

[0044] Comparative Example 4: The catalyst in Example 5 was replaced with the 2,6-dimethylaniline diimine nickel bromide complex synthesized in Comparative Example 2. All other operations were the same as in Example 5. The polymerization product was vacuum dried at 60 °C to constant weight, and 14.5 g of polymer was obtained. The catalytic activity was 14.5 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 118 × 10⁻⁶. 4 g / mol, polydispersity index of 2.10, and branching degree of 83.

[0045] Comparative Example 5: The catalyst in Example 6 was replaced with the 2,6-dimethylaniline diimine nickel bromide complex synthesized in Comparative Example 2. All other operations were the same as in Example 6. The polymerization product was vacuum dried at 60 °C to constant weight, and 16.2 g of polymer was obtained. The catalytic activity was 16.2 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 112 × 10⁻⁶. 4 g / mol, polydispersity index of 2.12, and branching degree of 79.

[0046] Comparative Example 6: The catalyst in Example 7 was replaced with the 2,6-dimethylaniline diimine nickel bromide complex synthesized in Comparative Example 2. All other operations were the same as in Example 7. The polymerization product was vacuum dried at 60 °C to constant weight, and 6.6 g of polymer was obtained. The catalytic activity was 6.6 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 108 × 10⁸. 4 g / mol, polydispersity index of 2.06, branching degree of 90.

[0047] Comparative Example 7: The catalyst in Example 8 was replaced with the 2,6-dimethylaniline diimine nickel bromide complex synthesized in Comparative Example 2. All other operations were the same as in Example 8. The polymerization product was vacuum dried at 60 °C to constant weight, and 9.1 g of polymer was obtained. The catalytic activity was 9.1 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 165 × 10⁻⁶. 4 g / mol, polydispersity index of 2.48, and branching degree of 77.

[0048] Comparative Example 8: The catalyst in Example 9 was replaced with the 2,6-dimethylaniline diimine nickel bromide complex synthesized in Comparative Example 2. All other operations were the same as in Example 9. The polymerization product was vacuum dried at 60 °C to constant weight, and 4.7 g of polymer was obtained. The catalytic activity was 4.7 × 10⁻⁶. 6gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 52.0 × 10⁻⁶. 4 g / mol, polydispersity index of 2.01, branching degree of 99.

[0049] Comparative Example 9: The catalyst in Example 10 was replaced with the 2,6-dimethylaniline diimine nickel bromide complex synthesized in Comparative Example 2. All other operations were the same as in Example 10. The polymerization product was vacuum dried at 60 °C to constant weight, and 1.1 g of polymer was obtained. The catalytic activity was 1.1 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 26.0 × 10⁻⁶. 4 g / mol, polydispersity index of 2.03, and branching degree of 105.

[0050] Comparative Example 10: The catalyst in Example 11 was replaced with the 2,6-dimethylaniline diimine nickel bromide complex synthesized in Comparative Example 2. All other operations were the same as in Example 11. The polymerization product was vacuum dried at 60 °C to constant weight, and 24.0 g of polymer was obtained. The catalytic activity was 4.8 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 32.3 × 10⁻⁶. 4 g / mol, polydispersity index of 2.21, branching degree of 102.

[0051] By comparing Examples 4-11 with Comparative Examples 3-10, it was found that compared to the 2,6-dimethylaniline diimine nickel bromide complex with two methyl groups on aniline, the method of introducing a larger benzene ring in the catalyst of Formula (I) resulted in a polymer with a different molecular weight than usual: appropriately increased steric hindrance would inhibit the β-H elimination reaction during chain growth, further inhibiting chain transfer, ultimately leading to a higher molecular weight polymer. However, this invention yielded a polymer with a smaller molecular weight. We speculate that this is because the introduction of the phenyl group in the catalyst shown in Formula (I) results in a larger encapsulation volume compared to the smaller methyl group, which means that from a steric hindrance perspective, ethylene is more difficult to coordinate with the catalyst shown in Formula (I) to form an active center. Furthermore, during polymerization, the molecular weight of the polymer product is determined by the chain growth and chain transfer reactions (i.e., the ratio k of the chain growth rate constant to the chain transfer rate constant). i / k t This is jointly determined by [various factors]. When the size of the substituent is too large, the coordination and insertion of ethylene are inhibited to some extent, leading to a smaller insertion rate constant, k. i / k tThe size decreases, leading to a smaller molecular weight. Therefore, the catalyst of formula (Ⅰ), which has greater steric hindrance, produces polymers with much smaller molecular weights in ethylene polymerization catalyzed by the sterically less sterically hindrance 2,6-dimethylaniline diimine nickel bromide complex, thus exhibiting unconventional properties. This property also results in lower branching of the polymer prepared by this type of catalyst, exhibiting better flowability and dispersibility, and easier processing. In summary, the unusual catalytic properties of the phenyl-modified acenaphthene quinone biasymmetric α-diimine nickel catalyst make it a promising candidate for applications in the elastomer field.

Claims

1. The biasymmetric (α-diimine) nickel olefin catalyst shown in formula (Ⅰ): Equation (I) in, X is chlorine or bromine.

2. The biasymmetric (α-diimine) nickel olefin catalyst according to claim 1, characterized in that: The double asymmetry includes a first asymmetry and a second asymmetry. The first asymmetry is that the aniline structures on both sides of the main skeleton acenaphthoquinone are different. The second asymmetry is that the aniline structure on the left side has a methyl group at position 2 and a phenyl group at position 6.

3. The compound represented by formula (II): Formula (II).

4. A method for preparing the compound according to claim 3, comprising the following steps: 1) Acenathoquinone reacts with aniline containing a sterically hindered substituent via a ketamine condensation reaction to yield the compound shown in formula (III): ； 2) The compound shown in formula (III) reacts with an asymmetric aniline modified with a phenyl group via a ketamine condensation reaction to yield the compound shown in formula (II): 。 5. A method for preparing the catalyst according to claim 1 or 2, comprising the following steps: under an inert gas protection environment, complexing the compound according to claim 3 with one of ethylene glycol dimethyl ether nickel dibromide, ethylene glycol dimethyl ether nickel dichloride, or nickel dichloride hexahydrate to obtain the catalyst according to claim 1 or 2.

6. A catalyst composition for catalyzing olefin polymerization, characterized in that, It comprises a main catalyst and a co-catalyst, wherein the main catalyst is selected from the catalyst according to claim 1 or 2, wherein the co-catalyst is selected from at least one of alkylaluminum chloride, alkylaluminum or aluminoxane, and the olefin is ethylene or propylene.

7. The application of the (α-diimine) nickel olefin catalyst according to claim 1 in the catalytic polymerization of ethylene to prepare polyethylene.

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