Phenyl-modified ethylacenaphthalene alpha-diimine nickel catalysts and methods for their preparation

Abstract

This invention discloses a phenyl-modified, biasymmetric (α-diimine) nickel olefin catalyst based on ethylene acenaphthene quinone 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. This 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 polymers with better flowability and dispersibility, showing broad application prospects in the elastomer field. Furthermore, this catalyst also exhibits good thermal stability and polymerization activity, demonstrating promising industrial application potential. Formula (I).

Description

Technical Field

[0001] This invention relates to phenyl-modified ethylene (α-diimine) nickel olefin catalysts and their preparation methods, particularly to a phenyl-modified ethylene acenaphthene biasymmetric α-diimine nickel catalyst, its preparation method and application, and its application in catalyzing 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 ethylene acenaphthene 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 ligands 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) Ethylene acenaphthene 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 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, ethylene acenaphthene, 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, ethylene acenaphthene, 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 shown in formula (II) is used as a ligand, and the nickel-containing compound complexed with the ligand is selected as ethylene glycol dimethyl ether nickel dibromide (DME)NiBr2, wherein the molar ratio of the ligand to (DME)NiBr2 is 1:1-1.2, preferably 1:1.1; the solvent 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 ethylacenaphthene bis-asymmetric (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, 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 ethylenaclairone (4.16 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 2:1 volume ratio of dichloromethane and petroleum ether to obtain intermediate of formula (III) with a mass of 12.1 g, yield: 96%.

[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 (0.629 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 0.33 g of ligand (II), yield: 41.5%.

[0032] Example 3, Preparation of catalyst of formula (I): Under a nitrogen atmosphere, ligand of formula (II) (0.159 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 0.2 g of catalyst of formula (I), with a yield of 98.5%.

[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. 15.4 g of polymer was then weighed. The catalytic activity was 15.4 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 51.5 × 10⁻⁶. 4 g / mol, polydispersity index of 1.83, and branching degree of 61.

[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 22.9 g of polymer was obtained. The catalytic activity was 22.9 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 58.5 × 10⁻⁶. 4 g / mol, polydispersity index of 1.82, and branching degree of 56.

[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 25.8 g of polymer was obtained. The catalytic activity was 25.8 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 60.5 × 10⁻⁶. 4 g / mol, polydispersity index of 1.85, and branching degree of 54.

[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 8.5 g of polymer was obtained. The catalytic activity was 8.5 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 51.2 × 10⁻⁶. 4 g / mol, polydispersity index of 1.68, and branching degree of 65.

[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 13.1 g of polymer was obtained. The catalytic activity was 13.1 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 94.4 × 10⁻⁶. 4 g / mol, polydispersity index of 1.82, and branching degree of 49.

[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 4.3 g of polymer was obtained. The catalytic activity was 4.3 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 25.6 × 10⁻⁶. 4 g / mol, polydispersity index of 1.76, and branching degree of 74.

[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 1.3 g of polymer was obtained. The catalytic activity was 1.3 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 16.6 × 10⁻⁶. 4 g / mol, polydispersity index of 1.79, and branching degree of 85.

[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 26.0 g of polymer was obtained. The catalytic activity was 5.2 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 20.7 × 10⁻⁶. 4 kg / mol, polydispersity index of 1.99, and branching degree of 82.

[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 0.34 g of 2,6-dimethylaniline ligand, yield: 46.1%.

[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 0.169 g of 2,6-dimethylaniline diimine nickel bromide complex was obtained with a yield of 89%.

[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 15.9 g of polymer was obtained. The catalytic activity was 15.9 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 129 × 10⁻⁶. 4 g / mol, polydispersity index of 1.73, and branching degree of 84.

[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 18.4 g of polymer was obtained. The catalytic activity was 18.4 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 120 × 10⁻⁶. 4 g / mol, polydispersity index of 1.94, and branching degree of 80.

[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 19.6 g of polymer was obtained. The catalytic activity was 19.6 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 114 × 10⁻⁶. 4 g / mol, polydispersity index of 1.96, and branching degree of 76.

[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 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 110 × 10⁻⁶. 4 g / mol, polydispersity index of 1.90, and branching degree of 87.

[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 10.5 g of polymer was obtained. The catalytic activity was 10.5 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 169 × 10⁻⁶. 4 g / mol, polydispersity index of 2.31, and branching degree of 74.

[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 6.7 g of polymer was obtained. The catalytic activity was 6.7 × 10⁻⁶. 6gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 54.2 × 10⁻⁶. 4 g / mol, polydispersity index of 1.81, and branching degree of 96.

[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 2.0 g of polymer was obtained. The catalytic activity was 2.0 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 29.9 × 10⁻⁶. 4 g / mol, polydispersity index of 1.85, branching degree of 103.

[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 30.5 g of polymer was obtained. The catalytic activity was 6.1 × 10⁻⁶. 6 gPE[mol(Ni)h] -1 The weight-average molecular weight of the polymer product is 38.2 × 10⁻⁶. 4 g / mol, polydispersity index of 2.10, and branching degree of 99.

[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, the present invention unexpectedly 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 the polymerization process, 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 smaller the molecular weight, the smaller the molecular weight. Therefore, the catalyst of formula (Ⅰ), which has greater steric hindrance, produces polymers with much smaller molecular weights in the polymerization of ethylene compared to 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 ethylene acenaphthene 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 ethyl 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) Ethylene acenaphthene 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, 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 biasymmetric (α-diimine) nickel olefin catalyst according to claim 1 in the catalytic polymerization of ethylene to prepare polyethylene.

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