Diimine ligands, late transition metal polyethylene wax catalysts, and preparation methods and applications thereof

Abstract

The present invention provides a diimine ligand having a general structure shown in Formula L, wherein R1 to R8 are independently selected from H, C1-C6 alkyl, C1-C6 alkoxy, C6-C 12 Aryl or halogen. The diimine ligand is prepared by acid catalysis using a 1,2-diketone compound having an isatin skeleton and a bulky hindered aromatic amine having an aniline skeleton. The present invention also provides a late transition metal polyethylene wax catalyst using the diimine ligand coordinated with a late transition metal salt. The catalyst has high catalytic activity over a wide temperature range and excellent high-temperature stability. The catalyst is used in the preparation of polyethylene wax, and the product has characteristics such as a narrow molecular weight distribution, low branching, and good chemical and physical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of polyethylene wax preparation, in particular to a diimine ligand, a late transition metal polyethylene wax catalyst containing the ligand, and a preparation method of the diimine ligand. Background Art

[0002] Polyethylene wax (PE-wax) is a polymer material formed by the polymerization of ethylene monomers. It appears as white granules or flakes with a molecular weight ranging from 1,000 to 10,000. This lower molecular weight gives PE wax distinct properties from conventional polyethylene. Its low viscosity, high softening point, and high hardness make it widely used in plastics processing. Furthermore, its non-toxicity, thermal stability, and low volatility expand its application in extreme environments such as low temperatures and high temperatures. Finally, PE wax has excellent pigment dispersion, which not only promotes uniform pigment distribution but also enhances the material's external lubricity and provides excellent internal lubrication, significantly improving dye processing efficiency. Therefore, PE wax has become a high-end material in polyethylene products.

[0003] Currently, the following three methods are mainly used in the industry to prepare polyethylene wax: by-product refining, polyethylene cracking, and direct ethylene polymerization. Among them, the by-product refining process is to purify and separate the oligomer components in the previous polyethylene production, while the polyethylene cracking process is to obtain polyethylene wax by cracking high molecular weight polyethylene through catalytic degradation. The polyethylene wax products obtained by the above two methods have a wide molecular weight distribution, many impurities, and poor performance, which makes it difficult to meet the needs of modern high-end fields. Only polyethylene wax generated by polymerization can meet the various indicators of the demand, and the polymerization method also meets the requirements of modern chemical industry for efficient atomic utilization and green production. However, the production of polyethylene wax from ethylene is a polymerization reaction, and its reaction degree is difficult to control. The catalyst is the core of the polymerization reaction, and it is necessary to design and prepare catalysts with better catalytic activity for production.

[0004] Late transition metal catalysts are metal organic catalysts formed by the coordination of late transition metals such as Fe, Co, Ni, and Pd with ligands containing elements such as N, O, and P. They are prone to undergo β-H elimination reactions to produce low molecular weight polymers. Therefore, compared with Ziegler-Natta (ZN) catalysts that mainly produce high-molecular polyethylene and metallocene catalysts with high costs, late transition metal catalysts have unique catalytic properties for ethylene polymerization and are catalysts with industrial potential for the preparation of polyethylene wax.

[0005] Currently, it is difficult to achieve both catalytic activity and thermal stability in the production of polyethylene wax using late transition metal catalysts. Increasing the temperature can accelerate the reaction rate, but as the reaction temperature increases, the late transition metal catalyst loses its activity. The literature "Mechanistic Studies of Pd(II)-α-Diimine-Catalyzed Olefin Polymerizations [J]. J Am Chem Soc, 2000, 122(28): 6686-6700" proposes that the poor thermal stability of late transition metal catalysts is due to the rotation of the N-C bond in the ligand, which causes the metal active center to deactivate. Based on this deactivation mechanism, researchers have mainly focused on improving the rigid structure and steric hindrance of the ligand to improve its thermal stability. Patent CN110092744A discloses a highly thermally stable transition metal complex containing tert-butyl asymmetric diiminopyridine for preparing polyethylene wax. This complex can be used as an ethylene polymerization catalyst. It has a single catalytic active center, high catalytic activity, and good thermal stability. However, the resulting polyethylene wax has a wide molecular weight distribution, and in particular, the amount of co-catalyst used is large (Al / Fe ≥ 1000), which hinders its practical application.

[0006] Further research is needed to design and synthesize a late transition metal catalyst with a stable rigid structure, which can improve thermal stability without reducing catalytic activity and be used for ethylene polymerization to produce high-quality polyethylene wax products. Summary of the Invention

[0007] The present invention aims to provide a diimine ligand, a late transition metal polyethylene wax catalyst containing the ligand, a preparation method of the diimine ligand, and application of the diimine ligand in the preparation of polyethylene wax, so as to overcome the above-mentioned defects in the background technology.

[0008] The present invention is achieved by adopting the following technical solutions:

[0009] The first aspect of the present invention relates to a diimine ligand having a general structure shown in Formula L, wherein R1 to R8 are independently selected from H, C1-C6 alkyl, C1-C6 alkoxy, C6-C 12 Aryl or halogen.

[0010] The C1-C6 alkyl group includes a linear or branched alkyl group, such as but not limited to methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, pentyl or hexyl, preferably methyl, isopropyl or tert-butyl.

[0011] The C1-C6 alkoxy group includes methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, tert-butoxy, pentyloxy or hexyloxy.

[0012]

[0013] The C6-C 12 Aryl is a monovalent aromatic carbocyclic ring system having at least one aromatic ring or multiple condensed rings in which at least one ring is aromatic, for example, phenyl, naphthyl or biphenyl.

[0014] As a preferred technical solution, at least one of R1 to R5 is an electron-donating group, specifically selected from C1-C6 alkyl, C1-C6 alkoxy or phenyl; further preferably, among R1 to R5, at least one of R1, R2, and R5 is selected from C1-C6 alkyl, and the rest are H.

[0015] As a preferred technical solution, at least one of R6, R7, and R8 is an electron-donating group, specifically selected from C1-C6 alkyl, C1-C6 alkoxy, or phenyl.

[0016] Furthermore, when R6 is an electron-donating group, it is preferably a methyl group, an isopropyl group or a methoxy group; when R7 is an electron-donating group, it is preferably a methyl group, an isopropyl group or a methoxy group; when R8 is an electron-donating group, it is preferably a methyl group, an isopropyl group or a tert-butyl group.

[0017] As a preferred embodiment of the present invention, the diimine ligand is selected from any one of the following diimine ligand compounds:

[0018]

[0019]

[0020]

[0021] The diimine ligands of Formula L in the present invention use isatin and its derivatives as their backbone. The presence of a six-membered ring and an N-hetero-five-membered ring in isatin provides a certain degree of rigidity, enhancing the thermal stability of late transition metal catalysts when coordinated with metals to form catalysts. Furthermore, the presence of the N-hetero-five-membered ring in isatin, where the nitrogen atom has a higher electronegativity than the carbon atom, and the presence of a lone pair of electrons on the nitrogen atom allows for conjugation with the benzene ring and the diimine structure, further optimizing the catalyst's electronic structure.

[0022] The second aspect of the present invention relates to a method for preparing the aforementioned diimine ligand, specifically, using a 1,2-diketone compound of the general structure shown in Formula I and a bulky sterically hindered aromatic amine of the general structure shown in Formula II as raw materials through acid catalysis to prepare the diimine ligand. The specific reaction formula is as follows:

[0023]

[0024] The 1,2-diketone compound has isatin as the skeleton, and R1 to R5 can be the same or different groups, and are independently selected from H, C1-C6 alkyl, C1-C6 alkoxy, C6-C 12 Aryl or halogen. Preferably, at least one of R1 to R5 is an electron-donating group, specifically selected from a C1-C6 alkyl group, a C1-C6 alkoxy group, or a phenyl group. Further preferably, among R1 to R5, at least one of R1, R2, and R5 is an electron-donating group, and the others are H. More preferably, R2 is an electron-donating group, and the others are H. As a preferred embodiment, the 1,2-diketone compound is an isatin derivative in which the R2 substituent is methyl, methoxy, or isopropyl, and R1, R3, R4, and R5 are H.

[0025] The large sterically hindered aromatic amines are based on aniline as the skeleton, including but not limited to benzidine, naphthylamine, anthraceneamine and condensed ring aromatic amines and other similar structures. R6 to R8 can be the same or different groups, independently selected from H, C1-C6 alkyl, C1-C6 alkoxy, C6-C 12 Aryl or halogen. Preferably, the bulky sterically hindered aromatic amine is aniline, or an aniline derivative in which at least one of R6, R7, and R8 is not H. Further preferably, an aniline derivative in which at least one of R6, R7, and R8 is an electron-donating group, i.e., at least one of R6, R7, and R8 is selected from a C1-C6 alkyl group, a C1-C6 alkoxy group, or a phenyl group. More preferably, R6 is methyl, isopropyl, or methoxy, and / or R7 is methyl, isopropyl, or methoxy, and / or R8 is methyl, isopropyl, or tert-butyl.

[0026] As a preferred technical solution, the preparation method of the diimine ligand of the present invention comprises the following steps: dissolving the 1,2-diketone compound and the bulky sterically hindered aromatic amine in an organic aprotic polar solvent at a molar ratio of 1:2-2.5, adding a non-oxidizing organic strong acid as a catalyst, and fully reacting at 100-200°C, removing the solvent from the reaction mixture and purifying it to obtain the diimine ligand.

[0027] The organic aprotic polar solvent can be a commonly used solvent in the art, such as a mixture of toluene and DMSO. The non-oxidizing organic strong acid can be a commonly used organic strong acid substance in the art, such as p-toluenesulfonic acid. The reaction temperature is preferably 120-160°C, and the reaction time is generally between 12-36 hours. The solvent can be removed by conventional methods in the art, such as rotary evaporation. The product can be purified by conventional methods in the art, such as recrystallization.

[0028] The third aspect of the present invention relates to a late transition metal polyethylene wax catalyst, specifically a coordination compound formed by the diimine ligand having the general structure shown in Formula L and a late transition metal salt.

[0029] The late transition metal is selected from Fe, Co, Ni or Pd. The late transition metal salt can be a halide of the late transition metal, such as a chloride or a bromide, including but not limited to ferric chloride, cobalt chloride, nickel bromide, nickel chloride, etc.

[0030] The inventors have discovered that a late-transition metal polyethylene wax catalyst using indigo carmine as a backbone exhibits unexpectedly high catalytic activity over a wide temperature range, with particularly excellent high-temperature stability. Polyethylene wax products prepared using this catalyst exhibit a narrow molecular weight distribution, low branching, and excellent chemical and physical properties. The specific mechanism of this activity is not yet fully understood, but it may be due to the following factors: Firstly, the presence of a benzene ring structure in indigo carmine can produce a conjugation effect with aniline compounds, improving the electronic structure of the catalyst; secondly, compared to other aromatic compounds, indigo carmine contains an N-heterocyclic five-membered ring, where the N atom has a different electronegativity than the C atom, further improving the electronic structure of the catalyst; and finally, the rigidity of the indigo carmine structure hinders N-C bond rotation to some extent, thereby improving the thermal stability of the catalyst.

[0031] Preferably, the late transition metal polyethylene wax catalyst is a nickel metal polyethylene wax catalyst having the general structure shown in Formula C:

[0032]

[0033] wherein X is chlorine or bromine.

[0034] The late transition metal polyethylene wax catalyst can be prepared using conventional methods for synthesizing coordination compounds. Taking the nickel metal polyethylene wax catalyst of the general structure shown in Formula C as an example, the following method can be used:

[0035] Under anhydrous and oxygen-free conditions, the diimine ligand and anhydrous nickel salt are added to a reaction vessel containing a solvent and reacted at 15-80° C. for 12-36 hours, wherein the molar ratio of the diimine ligand to the anhydrous nickel salt is 2-3:1. After the reaction is completed, the nickel metal polyethylene wax catalyst is obtained through post-processing. The reaction formula for the above synthesis is as follows:

[0036]

[0037] The solvent is not particularly limited, and for example, ultra-dry acetonitrile is used. The nickel salt is nickel chloride or nickel bromide, preferably nickel chloride. The post-treatment comprises cooling the product to room temperature, concentrating it by reduced evaporation, filtering out the solvent, and washing it multiple times with dry n-hexane.

[0038] The late transition metal polyethylene wax catalyst of the present invention is used to produce polyethylene wax by ethylene polymerization. Under the action of a co-catalyst, polyethylene wax is obtained at a relatively low pressure and with high catalytic activity. The obtained polyethylene wax has a narrow distribution, a low degree of branching, and excellent chemical and physical properties that can meet the requirements.

[0039] When producing polyethylene wax, the ethylene pressure is 0.1-10 MPa, preferably, the ethylene pressure is 0.1-2 MPa; more preferably, the ethylene pressure is 0.1-0.5 MPa.

[0040] The selected cocatalyst is mainly alkylaluminoxane, more preferably methylaluminoxane, modified methylaluminoxane or isobutylaluminoxane as the cocatalyst, and the molar ratio of the late transition metal polyethylene wax catalyst to the cocatalyst is 1:400-600.

[0041] The solvent used in the polymerization reaction is primarily an inert solvent, primarily consisting of chain alkanes and cycloalkanes with a boiling point not exceeding 120°C, and aromatic benzene derivatives. Aromatic benzene derivatives that are liquid at room temperature, have low viscosity, a boiling point not exceeding 110°C, and have low solubility in polyethylene wax are preferably used as the solvent, such as toluene, xylene, and chlorobenzene.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The present invention designs and synthesizes a diimine ligand with an indigo carmine skeleton, thereby obtaining a late transition metal catalyst containing the above-mentioned diimine ligand. The indigo carmine skeleton has higher rigidity and more suitable electron cloud density than the traditional 1,2-diketone structure, which can greatly improve the catalytic performance and stability of the catalyst. The synthesized late transition metal catalyst can have high catalytic activity in a wide range of 45-120°C, especially excellent high-temperature stability. When the reaction temperature is 120°C, the catalyst still has a catalytic activity of 6.35×10 6 When used to prepare polyethylene wax, the polyethylene wax product has the characteristics of narrow molecular weight distribution (PDI < 1.5), low branching degree (< 50 / 1000C), and good chemical and physical properties. DETAILED DESCRIPTION

[0044] The following description is intended to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are provided for illustrative purposes only and are not intended to limit the scope of the present invention. Those skilled in the art will readily appreciate other obvious variations. The basic principles of the present invention defined in the following description may be applied to other embodiments, variations, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the present invention.

[0045] The instruments or reagents in the examples of the present invention that do not indicate the manufacturer are all conventional commercial instruments or reagents. The main reagents used in the examples are as follows (taking R1-methyl substituted Dianhong as an example, it means that R1 is methyl and the other R2 to R5 groups are all H):

[0046] R1-Methyl substituted Dian Hong (CAS: 2058-74-4 Sigma-Aldrich)

[0047] R2-methyl substituted Dianhong (CAS: 1127-59-9 Leyan Reagent)

[0048] R5-Methyl substituted Dianhong (CAS:1127-59-9Mecklin)

[0049] R2-isopropyl substituted isatin (CAS: 66232-59-5)

[0050] Sodium sulfate (CAS:7757-82-6Sigma-Aldrich)

[0051] Chloral hydrate (CAS: 302-17-0 Sigma-Aldrich)

[0052] Hydroxylamine sulfate (CAS:10039-54-0Sigma-Aldrich)

[0053] Concentrated hydrochloric acid (CAS:7647-01-0Sigma-Aldrich)

[0054] m-Isopropylaniline (CAS: 108-44-1Aladdin)

[0055] R6-Methyl substituted aniline (CAS:87-62-7Sigma-Aldrich)

[0056] R6-Bromo-substituted aniline (CAS: 608-3-0 Sigma-Aldrich)

[0057] R6-Isopropyl substituted aniline (CAS:24544-04-5Sigma-Aldrich)

[0058] R7-Methyl substituted aniline (CAS: 108-69-0 Sigma-Aldrich)

[0059] R8-Methyl substituted aniline (CAS: 106-49-0 Sigma-Aldrich)

[0060] 2,6-Diacetylpyridine (CAS:1129-30-2Sigma-Aldrich)

[0061] Salicylaldehyde (CAS:90-02-8Sigma-Aldrich)

[0062] Bis(triphenylphosphine)nickel(II) chloride (CAS:14264-16-5Sigma-Aldrich)

[0063] Tetrahydrofuran (CAS: 109-99-9 Sigma-Aldrich)

[0064] n-Hexane (CAS:110-54-3Sigma-Aldrich),

[0065] Diethyl ether (CAS: 60-29-7Aladdin)

[0066] Concentrated sulfuric acid (CAS:7664-39-9Aladdin)

[0067] Toluene (CAS: 108-88-3Sigma-Aldrich)

[0068] Dimethyl sulfoxide (CAS: 67-68-5 Sigma-Aldrich)

[0069] Ethanol (CAS: 64-17-5 Sigma-Aldrich)

[0070] Acetonitrile (CAS:75-05-8Sigma-Aldrich)

[0071] p-Toluenesulfonic acid (CAS: 6192-52-5 Sigma-Aldrich)

[0072] Unless otherwise specified, all solvents involved in the present invention need to be treated to remove water.

[0073] Among them, the synthesis steps and reaction formula of R2-isopropyl substituted isatin are as follows:

[0074]

[0075] A mixture of sodium sulfate (0.915 mol), distilled water (120 ml), chloral hydrate (0.109 mol), hydroxylamine sulfate (0.079 mol), 8.6 ml of concentrated hydrochloric acid (37%), and m-isopropylaniline (0.1 mol) dissolved in 60 ml of distilled water was gradually heated to 70° C. Subsequently, 100 ml of ethanol was added and the mixture was heated to reflux. After reacting for 1 hour, the mixture was poured into ice water, and the solid 3-isopropylisonitrosoacetanilide was collected by filtration and washed with water. The final yield of 3-isopropylisonitrosoacetanilide was 81%. Subsequently, 3-isopropylisonitrosoacetanilide (17 mmol) was slowly added to concentrated sulfuric acid (9 ml) under magnetic stirring at room temperature. After reacting for 15 minutes, the reaction mixture was poured into crushed ice and collected by filtration to obtain a mixture of products 1 and 2. Product 2 was subsequently purified using a forced crystallization method: a mixture of products 1 and 2 was dissolved in a minimal amount of DMSO. The DMSO was slowly added dropwise to a large amount of n-hexane solution. Due to the difference in polarity, solid product 1 precipitated. Filtration was repeated several times, and finally, product 2 dissolved in n-hexane was rotary evaporated and washed with distilled water. The final yield of R2-isopropyl-substituted isatin was 45%.

[0076] Examples 1-10

[0077] Preparation of ligands L1-L10.

[0078] Ligands L1-L10 were prepared according to the 1,2-diketone compounds and bulky hindered aromatic amines listed in Table 1.

[0079] Table 1 Raw materials and structural formulas of ligands L1 to L10

[0080]

[0081]

[0082]

[0083] Taking ligand L1 as an example, the synthesis steps and reaction formula are as follows:

[0084]

[0085] In a 250ml three-necked flask, add 100ml of mixed organic solvent (mixture of toluene and DMSO, wherein V 甲苯 :V DMSO =9:1), then R1-methyl substituted isatin (10 mmol) and aniline (21 mmol) were added and mixed evenly, followed by the addition of catalytic p-toluenesulfonic acid (10 μmol), and the mixture was refluxed at 120°C for 24 hours. After the reaction, the mixture was depressurized and distilled to remove the solvent, and the product was recrystallized and purified using ethanol solution to obtain ligand L1 with a final yield of 87%. (1 H 300MHz, DMSO): 7.62-6.81 (m, 14H, Ar-H), 3.55 (s, 3H, CH3). C 21 H 17 N3: Calculated values ​​(%): C, 81.00; H, 5.50; N, 13.49. Found (%): C, 81.24; H, 5.52; N, 13.41.

[0086] Ligand L2

[0087] A 250ml three-necked flask was filled with 100ml of a mixed organic solvent (V toluene:V DMSO = 9:1). R2-methyl-substituted Dianhong (10mmol) and aniline (21mmol) were then added and mixed thoroughly. A catalytic equivalent of p-toluenesulfonic acid (10μmol) was then added and the mixture was refluxed at 120°C for 24h. After the reaction, the solvent was removed by distillation under reduced pressure, and the product was then recrystallized and purified using ethanol to obtain ligand L2 with a final yield of 81%. ( 1 H 300MHz, DMSO): 11.11 (s, 1H, NH), 7.55-6.82 (m, 13H, Ar-H), 2.75-1.88 (m, 3H, CH3). C 21 H 17 N3: Elemental analysis calculated values ​​(%): C, 81.00; H, 5.50; N, 13.49. Experimental determination values ​​(%): C, 81.15; H, 5.54; N, 13.47.

[0088] Ligand L3

[0089] A 250ml three-necked flask was filled with 100ml of a mixed organic solvent (V toluene:V DMSO = 9:1). R5-methyl-substituted Dianhong (10mmol) and aniline (21mmol) were then added and mixed thoroughly. A catalytic equivalent of p-toluenesulfonic acid (10μmol) was then added and the mixture was refluxed at 120°C for 24h. After the reaction, the solvent was removed by distillation under reduced pressure, and the product was then recrystallized and purified using an ethanol solution to obtain ligand L3 with a final yield of 85%. ( 1 H 300MHz, DMSO): 11.24 (s, 1H, NH), 7.45-6.02 (m, 13H, Ar-H), 2.83-1.95 (m, 3H, CH3). C 21 H 17 N3: Elemental analysis calculated values ​​(%): C, 81.00; H, 5.50; N, 13.49. Experimen tal values ​​(%): C, 81.07; H, 5.62; N, 13.53.

[0090] Ligand L4

[0091] A 250ml three-necked flask was filled with 100ml of a mixed organic solvent (V toluene:V DMSO = 9:1). R2-isomethyl substituted Dian Hong (10mmol) and aniline (21mmol) were then added and mixed thoroughly. A catalytic equivalent of p-toluenesulfonic acid (10μmol) was then added and the mixture was refluxed at 120°C for 24h. After the reaction, the solvent was removed by distillation under reduced pressure, and the product was then recrystallized and purified using an ethanol solution to obtain ligand L4 with a final yield of 77%. ( 1 H 300MHz, DMSO): 10.96 (s, 1H, NH), 7.56-6.90 (m, 13H, Ar-H), 3.05-2.08 (m, 7H, CH (CH3) 2). C 23 H 21 N3: Calculated values ​​(%): C, 81.38; H, 6.24; N, 12.38. Found (%): C, 81.46; H, 6.39; N, 12.40.

[0092] Ligand L5

[0093] A 250ml three-necked flask was filled with 100ml of a mixed organic solvent (V toluene:V DMSO = 9:1). R2-tert-butyl substituted Dianhong (10mmol) and aniline (21mmol) were then added and mixed thoroughly. A catalytic equivalent of p-toluenesulfonic acid (10μmol) was then added and the mixture was refluxed at 120°C for 24h. After the reaction, the solvent was removed by distillation under reduced pressure, and the product was then recrystallized and purified from an ethanol solution to obtain ligand L5 with a final yield of 72%. 1 H 300MHz, DMSO): 11.23(s,1H,NH), 7.61-6.75(m,13H,Ar-H), 2.95-1.05(m,9H,C(CH3)3). C 24 H 23 N3: Calculated values ​​(%): C, 81.55; H, 6.56; N, 11.89. Experimen-tal values ​​(%): C, 81.58; H, 6.59; N, 11.90.

[0094] Ligand L6

[0095] A 250ml three-necked flask was filled with 100ml of a mixed organic solvent (V toluene:V DMSO = 9:1). R2-isopropyl-substituted Dianhong (10mmol) and R6-methyl-substituted aniline (21mmol) were then added and mixed thoroughly. A catalytic equivalent of p-toluenesulfonic acid (10μmol) was then added and the mixture was refluxed at 120°C for 24h. After the reaction, the solvent was removed by distillation under reduced pressure, and the product was then recrystallized and purified using an ethanol solution to obtain ligand L6 with a final yield of 82%. ( 1 H 300MHz, DMSO): 11.40(s,1H,NH), 7.44-6.92(m,9H,Ar-H), 3.11-2.38(m,19H,CH(CH3)2). C 27 H 29 N3: Calculated values ​​(%): C, 81.99; H, 7.39; N, 10.62. Experimen-tal values ​​(%): C, 82.06; H, 7.49; N, 10.57.

[0096] Ligand L7

[0097] A 250ml three-necked flask was filled with 100ml of a mixed organic solvent (V toluene:V DMSO = 9:1). R2-isopropyl-substituted Dianhong (10mmol) and R6-bromo-substituted aniline (21mmol) were then added and mixed thoroughly. A catalytic equivalent of p-toluenesulfonic acid (10μmol) was then added and the mixture was refluxed at 120°C for 24h. After the reaction, the solvent was removed by distillation under reduced pressure, and the product was then recrystallized and purified from an ethanol solution to obtain ligand L7 with a final yield of 80%. 1 H 300MHz, DMSO): 11.27(s,1H,NH), 7.60-6.81(m,9H,Ar-H), 3.31-1.48(m,7H,CH(CH3)2). C 23 H 17 N3Br4: Elemental analysis calculated (%): C, 42.17; H, 2.62; N, 6.42; Br, 48.79. Experiential determination (%): C, 42.16; H, 2.69; N, 6.47; Br, 48.77.

[0098] Ligand L8

[0099] A 250ml three-necked flask was filled with 100ml of a mixed organic solvent (V toluene:V DMSO = 9:1). R2-isopropyl-substituted isatin (10mmol) and R6-isopropyl-substituted aniline (21mmol) were then added and mixed thoroughly. A catalytic equivalent of p-toluenesulfonic acid (10μmol) was then added and the mixture was refluxed at 120°C for 24h. After the reaction, the solvent was removed by distillation under reduced pressure, and the product was then recrystallized and purified from ethanol to obtain ligand L8 with a final yield of 77%. 1 H 300MHz, DMSO): 11.15(s,1H,NH), 7.77-6.92(m,9H,Ar-H), 3.19-1.35(m,35H,CH(CH3)2). C 35 H 45 N3: Calculated values ​​(%): C, 82.79; H, 8.93; N, 8.28. Experimen-tal values ​​(%): C, 82.86; H, 8.97; N, 8.47.

[0100] Ligand L9

[0101] A 250ml three-necked flask was filled with 100ml of a mixed organic solvent (V toluene:V DMSO = 9:1). R2-isopropyl-substituted Dianhong (10mmol) and R7-methyl-substituted aniline (21mmol) were then added and mixed thoroughly. A catalytic equivalent of p-toluenesulfonic acid (10μmol) was then added and the mixture was refluxed at 120°C for 24h. After the reaction, the solvent was removed by distillation under reduced pressure, and the product was then recrystallized and purified using an ethanol solution to obtain ligand L9 with a final yield of 72%. 1 H 300MHz, DMSO): 11.29(s,1H,NH), 7.45-6.93(m,9H,Ar-H), 3.34-1.55(m,19H,CH(CH3)2). C 27 H 29 N3: Calculated values ​​(%): C, 81.99; H, 7.39; N, 10.62. Experimen tal values ​​(%): C, 82.02; H, 7.47; N, 10.66.

[0102] Ligand L10

[0103] A 250ml three-necked flask was filled with 100ml of a mixed organic solvent (V toluene:V DMSO = 9:1). R2-isopropyl-substituted Dianhong (10mmol) and R8-methyl-substituted aniline (21mmol) were then added and mixed thoroughly. A catalytic equivalent of p-toluenesulfonic acid (10μmol) was then added and the mixture was refluxed at 120°C for 24h. After the reaction, the solvent was removed by distillation under reduced pressure, and the product was then recrystallized and purified using ethanol to obtain ligand L10 with a final yield of 89%. 1 H 300MHz, DMSO): 11.50(s,1H,NH), 7.52-6.88(m,11H,Ar-H), 3.16-1.37(m,13H,CH3 CH(CH3)2). C 25 H 25 N3: Calculated values ​​(%): C, 81.71; H, 6.96; N, 11.43. Experimen-tal values ​​(%): C, 81.78; H, 7.02; N, 11.59.

[0104] Examples 11-13

[0105] Preparation of ligands L1' to L3'.

[0106] Ligands L1' to L3' are not based on indigo carmine as the skeleton and are prepared by the following methods:

[0107] The synthesis steps of L1' are as follows:

[0108] In a 250ml three-necked flask, 2,3-butanedione (10mmol) and aniline (22mmol) were dissolved in 100ml of toluene solution. Catalytic-grade p-toluenesulfonic acid (10μmol) was added. The mixture was refluxed at 100°C for 24h with water removal. After the reaction, the toluene solvent was removed by vacuum distillation, and the solid product was recrystallized from hot ethanol. The final yield was 86%. The reaction equation is as follows:

[0109]

[0110] The synthesis steps of L2' are as follows:

[0111] To a 150ml three-necked flask, 3mmol of 2,6-diacetylpyridine and 3.4mmol of aniline were added, followed by 50ml of toluene, heated, stirred and refluxed. After half an hour of reaction, a catalytic amount of p-toluenesulfonic acid (10μmol) was added and the reaction was continued for 12h. Cooled to room temperature, the solvent was removed by rotary evaporation. Column chromatography was then performed on a basic alumina column (the eluent was a mixture of petroleum ether and ethyl acetate, V 石油醚 :V 乙酸乙酯 =100:1) to finally obtain the pyridine diimine ligand with a yield of 48%. The reaction formula is as follows:

[0112]

[0113] The synthesis steps of L3' are as follows:

[0114] Under argon, salicylaldehyde (0.2 mol) and 60 ml of anhydrous ethanol were added to a 250 ml three-necked flask. Aniline (0.02 mol) was then added to the flask using a constant pressure dropping funnel, followed by formic acid (0.5 ml). The mixture was heated to 80°C and allowed to react for 2 h. After cooling to room temperature, the mixture was distilled under reduced pressure and the product precipitated. The final product yield was 88%. The reaction equation is as follows:

[0115]

[0116] Examples 14-23

[0117] Preparation of catalysts C1-C10:

[0118] Under anhydrous and oxygen-free conditions, 100 ml of ultra-dry acetonitrile was added to a three-necked flask, and ligands L1-L10 (8.4 mmol) and anhydrous NiC12 (4 mmol) were added respectively. The reaction temperature was controlled at 55°C and the reaction time was 24 hours. After the reaction was completed, it was cooled to room temperature and concentrated by evaporation. The solvent was filtered out, washed several times with dry n-hexane, and dried to obtain catalysts C1-C10 respectively.

[0119] Examples 24-26

[0120] Preparation of Catalysts C1'-C3'.

[0121] Catalysts C1'-C3' were prepared by the following method using ligands L1'-L3' as ligands respectively:

[0122] Synthesis of catalyst C1':

[0123] To a single-necked flask, add the synthesized ligand (5 mmol) and anhydrous NiCl2 (11 mmol), followed by anhydrous acetonitrile. Nitrogen was then pumped in three times and refluxed at 55°C for 24 hours. After the reaction, cool to room temperature, concentrate under reduced pressure, filter, and wash with n-hexane to obtain a solid. The final yield was 77%. The reaction equation is as follows:

[0124]

[0125] Synthesis of catalyst C2':

[0126] The pyridine diimine ligand (1 mmol) prepared above and FeCl2·4H2O (1.2 mmol) were added to a 50 ml single-necked flask. The flask was then pumped with nitrogen three times to create a water-free and oxygen-free environment. Redistilled anhydrous ethanol was then added and stirred at room temperature. The reaction was continued for 12 hours. The mixture was filtered and washed with ether. The final product yield was 95%. The reaction formula is as follows:

[0127]

[0128] Synthesis of catalyst C3':

[0129] 40ml of freshly steamed THF, NaH (4mmol) were added to a 100ml three-necked flask and nitrogen was pumped in three times. Subsequently, the salicylaldimine ligand was slowly added dropwise to the flask using a constant pressure dropping funnel and stirred at room temperature for 3h. Unreacted NaH was removed by filtration. Finally, 40ml of toluene and (Ph3)2PhNiCl (1.5mmol) were added and stirred at room temperature for 12h. The filtrate was concentrated and n-hexane solution was slowly added until crystals were precipitated. Finally, the product was recrystallized from toluene and n-hexane solution to give a final product yield of 70%. The reaction formula is as follows:

[0130]

[0131] Application Examples

[0132] The catalysts C1-C10 and C1'-C3' obtained above, as well as catalyst C4' (metallocene catalyst titanocene dichloride, CAS: 1271-19-8) were used to prepare polyethylene wax and their properties were tested.

[0133] Reaction conditions were as follows: a 250ml stainless steel reactor was heated under vacuum at 150°C for 2 hours, then cooled to ambient temperature. The reactor was then pressurized to 1.2 atm with ethylene, vented, and re-pressurized with ethylene three times to ensure a full ethylene atmosphere. A cocatalyst, MAO (1 mmol), was dissolved in 100ml of dry toluene and injected into the reactor. Stirring was continued under 1.2 atm of ethylene pressure for 5 minutes. Finally, 50ml of a toluene-diluted solution of the catalyst (any of C1-C10, C1'-C4') (containing 2 μmol of catalyst) was added to the reactor via syringe and stirred thoroughly. Gaseous ethylene was continuously added during the entire reaction process, and the ethylene pressure was maintained at 10 atm. The reaction temperature was controlled at 45-120°C during the polymerization experiment. The polymerization process was completed after 1 hour of reaction. During post-treatment, acidic methanol (ethanol / hydrochloric acid in a mass ratio of 95:5) was added to inactivate the catalyst. The resulting precipitated polymer was collected, separated by rotary evaporation, and dried in a vacuum at 40°C to a constant weight to obtain a polyethylene wax sample.

[0134] 1. The catalytic activity of each catalyst was tested at different reaction temperatures. The catalytic activity was calculated based on the yield of the polyethylene wax sample, expressed as g polyethylene wax / (mol catalyst × h), as shown in Table 2.

[0135] Table 2 Catalytic activity of different catalysts at different temperatures (10 6 g PE / mol cat·h)

[0136]

[0137]

[0138] Note: “--” means not performed.

[0139] As shown in Table 2, the late transition metal catalysts C1-C10, which use isatin as the backbone of the diimine structure, have high catalytic activity at 45-120°C. The activity of the electron-donating group catalyst is better than that of the electron-withdrawing group catalyst (catalyst C7). From the catalyst structure, when the substituents on R2 and R6 have certain steric hindrance and electron-donating effects, the two interact with each other. For example, catalyst C8 has the best catalytic activity, with a catalytic activity of 11.45×10 at 75°C. 6 g PE / mol cat·h, it still has a value of 6.35×10 6 The catalytic activity of 100 g PE / mol cat·h is much higher than that of other non-isatin skeleton late transition metal catalysts.

[0140] 2. Polyethylene wax sample performance test

[0141] Some polyethylene wax samples were selected for further performance testing and analysis. The selected samples E1-E8 are as follows:

[0142] The polyethylene wax sample obtained by polymerization of catalyst C1 at 45 °C is denoted as E1;

[0143] The polyethylene wax sample obtained by polymerization of catalyst C2 at 60 °C is denoted as E2;

[0144] The polyethylene wax sample obtained by polymerization of catalyst C3 at 75 °C is denoted as E3;

[0145] The polyethylene wax sample obtained by polymerization of catalyst C5 at 60 °C is denoted as E4;

[0146] The polyethylene wax sample obtained by polymerization of catalyst C6 at 75 °C is denoted as E5;

[0147] The polyethylene wax sample obtained by polymerization of catalyst C7 at 60 °C is denoted as E6;

[0148] The polyethylene wax sample obtained by polymerization of catalyst C8 at 75 °C is denoted as E7;

[0149] The polyethylene wax sample obtained by polymerization of catalyst C10 at 45°C is marked as E8.

[0150] For comparison, some comparison samples E1' to E5' are selected, as follows:

[0151] The polyethylene wax sample obtained by polymerization of catalyst C1' at 60 °C is denoted as E1';

[0152] The polyethylene wax sample obtained by polymerization of catalyst C2' at 45 °C is denoted as E2';

[0153] The polyethylene wax sample obtained by polymerization of catalyst C3' at 75 °C is denoted as E3';

[0154] The polyethylene wax sample obtained by polymerization of catalyst C4' at 75°C is recorded as E4'.

[0155] Polyethylene wax sample E5' was prepared by free radical initiation. The specific preparation method was as follows: the polymerization pressure was increased from 10 atm to 100 atm, the catalyst was replaced with 5 μmol of dibenzoyl peroxide (BPO), and the polymerization reaction was carried out at 85°C to obtain the product.

[0156] Samples E1-E8 and samples E1'-E5' were tested using the following method:

[0157] 1. Molecular weight determination

[0158] Molecular weight determination includes weight-average molecular weight (Mw) and number-average molecular weight (Mn): determined by gel permeation chromatography (GPC) in accordance with GB / T 27843-2011, "Polymers in Chemicals - Determination of Low Molecular Weight Content - Gel Permeation Chromatography (GPC)." The molecular weight distribution index (PDI) of polyethylene wax is determined by the ratio of the measured weight-average molecular weight to the number-average molecular weight.

[0159] 2. Determination of branching degree

[0160] The degree of branching of polyethylene wax was calculated by H NMR spectrum.

[0161] 3. Drop melting point viscosity determination

[0162] The drop melting point is determined in accordance with GB / T 8026-2014 “Determination of drop melting point of petroleum waxes and petroleum fats”.

[0163] The specific test results are shown in Table 3.

[0164] Table 3 Polyethylene wax sample performance determination

[0165] Mw PDI Degree of branching ( / 1000C) Drop melting point (℃) E1 7840 1.36 47 115 E2 5170 1.33 24 84 E3 5430 1.48 35 86 E4 6820 1.32 21 94 E5 6510 1.27 27 92 E6 5190 1.44 36 85 E7 5750 1.12 11 89 E8 3860 1.40 37 57 E1’ 11540 1.72 68 125 E2’ 38700 1.92 132 136 E3’ 15600 1.85 144 129 E4’ 7420 1.31 49 96 E5’ 1970 4.65 38 33

[0166] As shown in Table 3, the polyethylene wax obtained in the present invention has an average weight-average molecular weight of 3800-8000, a molecular weight distribution between 1.1-1.5, and a low degree of branching (<50 / 1000C), which is a polyethylene wax with excellent performance. Compared with polyethylene waxes obtained by other types of late transition metal catalysts, the present invention has a moderate molecular weight, a tight molecular weight distribution, and a low degree of branching, which can meet market demand. The performance of the E4' sample prepared using the commonly used metallocene catalyst titanocene dichloride (high cost, poor high temperature resistance, and inability to polar solvents) is comparable. The other comparative samples (E1', E2', E3', and E5') have a higher molecular weight distribution index and poor product consistency.

[0167] Those skilled in the art will appreciate that the above embodiments are intended to be illustrative only and are not intended to limit the present invention. The objectives of the present invention have been fully and effectively achieved. The functions and principles of the present invention have been demonstrated and illustrated in the embodiments. Any variations or modifications may be made to the embodiments of the present invention without departing from the principles described.

Claims

1. A late transition metal polyethylene wax catalyst, characterized in that It is a coordination compound formed by a diimine ligand and a late transition metal salt, specifically a nickel metal polyethylene wax catalyst having the general structure shown in Formula C: Wherein X is chlorine or bromine, R1 to R8 are defined according to the corresponding substituents of Formula L2 to Formula L10; the diimine ligand is specifically selected from any one of the following diimine ligand compounds of Formula L2 to Formula L10:

2. Use of the late transition metal polyethylene wax catalyst according to claim 1 in the preparation of polyethylene wax.

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