Catalyst composition for selective oligomerization of ethylene and method for preparing α-olefins

Abstract

This application relates to the field of selective oligomerization technology of ethylene, and particularly to a catalyst composition for selective oligomerization of ethylene and a method for preparing α-olefins. The catalyst composition includes a main catalyst and a co-catalyst; the main catalyst includes a complex; the ligand of the complex is a compound represented by formula (I), and the coordinating metal is a group VIB-VIII metal element; the co-catalyst includes an organic compound containing aluminum. This catalyst composition can reduce the amount of polymer produced, increase the yield of α-olefins, maintain high activity at high temperatures, and exhibit good 1-octene selectivity.

Description

Technical Field

[0001] This application relates to the field of selective oligomerization of ethylene, and particularly to catalyst compositions for selective oligomerization of ethylene and methods for preparing α-olefins. Background Technology

[0002] Linear α-olefins (LAOs) are commonly used in many fields, including comonomers for linear low-density polyethylene (LDPE), preparation of surfactant intermediates, synthesis of lubricants, and plasticizers, and are an important chemical raw material in the petroleum industry. Among them, 1-octene, due to its moderate molecular weight, is a preferred comonomer for synthesizing high-performance polyolefins. Using 1-octene as a comonomer to prepare LLDPE significantly improves the tensile strength, impact strength, tear strength, puncture resistance, and environmental stress cracking resistance, making it widely used in packaging films and agricultural covering films for greenhouses and sheds.

[0003] Industrial processes for producing α-olefins are mainly divided into two categories: selective oligomerization and non-selective oligomerization of ethylene. Selective oligomerization, with its advantages of high atom utilization and good economic benefits, is currently the mainstream process for producing α-olefins. Among selective oligomerization processes, selective tetramerization of ethylene has attracted much attention due to its ability to produce 1-octene with high selectivity, becoming the core process route for 1-octene preparation.

[0004] In the process of selective oligomerization of ethylene to produce 1-octene, a small amount of polymer is generally generated. This polymer gradually accumulates during long-term operation, leading to reactor blockage and overpressure. There are two main solutions: one is to adjust the catalyst structure to reduce the generation of byproduct polyethylene (PE). Lee et al. (ChemCatChem, 2019, 11, 4351-4359) conducted detailed research in this area, but they have not achieved complete elimination of PE. Therefore, they can only increase the equipment's operating time and cannot fundamentally solve the blockage problem. The second solution is to increase the reaction temperature so that the generated PE dissolves in the solvent, thereby solving the reactor blockage problem. Sasol conducted detailed research in this area (Chem. Commun., 2005, 620-621, CN104220402B, etc.). However, in this study, increasing the reaction temperature led to a significant decrease in selective tetramerization activity and 1-octene selectivity, while increasing PE yield.

[0005] Therefore, it is necessary to develop an ethylene oligomerization method that can reduce polymer production and increase α-olefin yield. Summary of the Invention

[0006] Based on this, one or more embodiments of this application provide a catalyst composition for selective oligomerization of ethylene and a method for preparing α-olefins. The catalyst composition for selective oligomerization of ethylene can reduce the amount of polymer produced and increase the yield of α-olefins. In addition, it can maintain high activity at high temperatures and has good 1-octene selectivity.

[0007] One or more embodiments of this application provide catalyst compositions for selective oligomerization of ethylene, including a main catalyst and a co-catalyst;

[0008] The main catalyst includes a complex;

[0009] The ligands of the complex are compounds represented by formula (Ⅰ), and the coordinating metals are group VIB to VIII metal elements;

[0010] (I);

[0011] A1 and A2 are independently selected from substituted or unsubstituted C3-C, respectively. 10 Mixed aromatics;

[0012] R1 is selected from hydrogen, nitro, C1-C9 alkyl, C1-C9 alkoxy, or C6-C 20 Aryl;

[0013] R2 is absent or selected from C1-C9 alkyl groups;

[0014] R3 is absent or is selected from hydrogen;

[0015] The co-catalyst includes an organic compound containing aluminum.

[0016] In some embodiments, the molar ratio of the coordinating metal in the main catalyst to the aluminum element in the co-catalyst is 1:(500-1000).

[0017] In some embodiments, A1 and A2 are each independently selected from substituted or unsubstituted pyridine, quinoline, indole, oxazole, pyrrole, or 1,4-pyrazine; optionally, the substitution is C1-C4 alkyl substitution; and / or,

[0018] R1 is selected from hydrogen, nitro, C1-C4 alkyl, C1-C4 alkoxy, or C6-C 10 aryl; and / or,

[0019] R2 is absent or selected from C1-C4 alkyl groups.

[0020] In some embodiments, the complex further includes a coordinating anion;

[0021] Optionally, the coordinating anion includes at least one of organic and inorganic anions.

[0022] In some embodiments, the organic anion includes at least one selected from acetate ions, benzoate ions, and acetylacetone anions; and / or,

[0023] The inorganic anions include at least one of nitrate ions, sulfate ions, and halide ions.

[0024] In some embodiments, the aluminum-containing organic compound includes at least one of trimethylaluminum, triethylaluminum, diethylaluminum chloride, tributylaluminum, triisobutylaluminum, tripropylaluminum, trioctylaluminum, dimethylaluminum chloride, dimethylisobutylaluminum, dimethylethylaluminum, triphenylaluminum, triisopropylaluminum, trisec-butylaluminum, ethyldimethylaluminum, methylaluminoxane, and modified methylaluminoxane.

[0025] In some embodiments, the method for preparing the main catalyst includes the following steps:

[0026] The ligand, transition metal compound, and first organic solvent are mixed to obtain a mixture;

[0027] The mixture is subjected to a thermal reflux reaction;

[0028] After the hot reflux reaction is complete, the solvent in the reaction solution is removed to obtain a solid;

[0029] The solid was dissolved in methylcyclohexane, and a nonpolar solvent was added to the resulting solution for recrystallization to obtain the complex.

[0030] The transition metal compound is a salt containing metals from group VIB to VIII.

[0031] One or more embodiments of this application provide a method for preparing α-olefins, characterized by comprising the following steps:

[0032] The α-olefin was prepared by selective oligomerization of ethylene in the presence of a catalyst.

[0033] The catalyst includes the catalyst composition for selective oligomerization of ethylene described above.

[0034] In some embodiments, the step of performing ethylene oligomerization in the presence of a catalyst includes:

[0035] The ethylene, the catalyst, and the second organic solvent are mixed to obtain a mixture;

[0036] The mixture is reacted at a first temperature and a first pressure for a first time;

[0037] The first temperature is 90℃-110℃, the first pressure is 0.1MPa-10MPa, and the first time is 1min-120min.

[0038] In some embodiments, the amount of catalyst used in the mixture is 2 μmol / mL to 4 μmol / mL, based on the molar concentration of the coordinating metal element in the main catalyst.

[0039] The beneficial effects of this application are:

[0040] The catalyst composition for selective oligomerization of ethylene disclosed in this application utilizes a suitable main catalyst and co-catalyst. The main catalyst employs a special N-coordinated ligand structure, exhibiting strong interaction with the coordinating metal. The shorter metal-N bond length provides a more compact coordination environment compared to traditional PNP ligands, making the metal cycloheptane (the structure formed after the metal coordinates with three ethylene molecules) more inclined to further coordinate with ethylene, thereby effectively improving α-olefin selectivity. Furthermore, the high basicity of the ligand further enhances the coordination strength between the coordinating metal and the ligand, thus resisting disturbances in molecular thermal motion at elevated temperatures and significantly improving the high-temperature resistance of the main catalyst. When used in conjunction with a suitable co-catalyst, the main catalyst of this application can reduce polymer production, increase α-olefin yield, and maintain high catalytic activity and α-olefin selectivity even at high temperatures. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0042] Figure 1 This is a synthetic route diagram of the compound represented by formula (Ⅰ) in one embodiment of this application. Detailed Implementation

[0043] The present application is further described below with reference to embodiments and examples. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Furthermore, it should be understood that after reading the teachings of this application, those skilled in the art can make various alterations or modifications to this application, and these equivalent forms also fall within the protection scope of the appended claims.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0045] The term "alkyl" refers to a saturated hydrocarbon containing a primary (normal) carbon atom, or a secondary carbon atom, or a tertiary carbon atom, or a quaternary carbon atom, or a combination thereof. Phrases containing this term, such as "C1-C9 alkyl," refer to alkyl groups containing 1-9 carbon atoms, and each occurrence can independently be C1 alkyl, C2 alkyl, C3 alkyl, C4 alkyl, C5 alkyl, C6 alkyl, C7 alkyl, C8 alkyl, or C9 alkyl. Suitable examples include, but are not limited to: methyl (Me, -CH3), ethyl (Et, -CH2CH3), 1-propyl (n-Pr, n-propyl, -CH2CH2CH3), 2-propyl (i-Pr, i-propyl, -CH(CH3)2), 1-butyl (n-Bu, n-butyl, -CH2CH2CH2CH3), 2-methyl-1-propyl (i-Bu, i-butyl, -CH2CH(CH3)2), 2-butyl (s-Bu, s-butyl, -CH(C H3)CH2CH3), 2-methyl-2-propyl (t-Bu, t-butyl, -C(CH3)3), 1-pentyl (n-pentyl, -CH2CH2CH2CH2CH3), 2-pentyl (-CH(CH3)CH2CH2CH3), 3-pentyl (-CH(CH2CH3)2), 2-methyl-2-butyl (-C(CH3)2CH2CH3), 3-methyl-2-butyl (-CH(CH3)CH(CH3)2), 3-methyl-1-butyl (- CH2CH2CH(CH3)2), 2-methyl-1-butyl(-CH2CH(CH3)CH2CH3), 1-hexyl(-CH2CH2CH2CH2CH2CH3), 2-hexyl(-CH(CH3)CH2CH2CH2CH3), 3-hexyl(-CH(CH2CH3)(CH2CH2CH3)), 2-methyl-2-pentyl(-C(CH3)2CH2CH2CH3), 3-methyl-2-pentyl(-CH(CH3)CH( CH3)CH2CH3), 4-methyl-2-pentyl (-CH(CH3)CH2CH(CH3)2), 3-methyl-3-pentyl (-C(CH3)(CH2CH3)2), 2-methyl-3-pentyl (-CH(CH2CH3)CH(CH3)2), 2,3-dimethyl-2-butyl (-C(CH3)2CH(CH3)2), 3,3-dimethyl-2-butyl (-CH(CH3)C(CH3)3 and octyl (-(CH2)7CH3).

[0046] The term "alkoxy" refers to a group having an -O-alkyl group, i.e., an alkyl group as defined above connected to the parent nucleus via an oxygen atom. Phrases containing this term, such as "C1-C9 alkoxy," refer to alkyl moieties containing 1-9 carbon atoms, and each time it appears, it can be independently C1 alkoxy, C4 alkoxy, C5 alkoxy, C6 alkoxy, C7 alkoxy, C8 alkoxy, or C9 alkoxy. Suitable examples include, but are not limited to: methoxy (-O-CH3 or -OMe), ethoxy (-O-CH2CH3 or -OEt), and tert-butoxy (-OC(CH3)3 or -OtBu).

[0047] The term "aryl" refers to an aromatic hydrocarbon group derived from an aromatic ring compound by removing one hydrogen atom. It can be a monocyclic aryl, a fused-ring aryl, or a polycyclic aryl; for polycyclic compounds, at least one ring must be an aromatic ring system. For example, "C6-C..." 20 "Aryl" refers to an aryl group containing 6-20 carbon atoms, and each time it appears, it can be independently C6 aryl, C10 aryl, C14 aryl, C18 aryl, or C20 aryl. Suitable examples include, but are not limited to: benzene, biphenyl, naphthalene, anthracene, phenanthrene, dinaphthalene, triphenylene and their derivatives.

[0048] The term "heteroaryl" refers to an aryl group in which at least one carbon atom is replaced by a non-carbon atom, which can be a nitrogen atom, an oxygen atom, a sulfur atom, etc. For example, "C3-C 10 "Heteroaryl" refers to a heteroaryl group containing 3-10 carbon atoms, which can be independently C3, C4, C5, C6, C7, or C8 heteroaryl each time it appears. Suitable examples include, but are not limited to: furan, benzofuran, thiophene, benzothiophene, pyrrole, pyrazole, triazole, imidazole, oxazole, oxadiazole, thiazole, tetraazole, indole, carbazole, pyrroloimidazol, pyrrolopyrrole, thiophenolopyrrole, thiophenolothiophene, furanolopyrrole, furanolofuran, thiophenolofuran, benzoisoxazole, benzoisothiazol, benzoimidazol, pyridine, pyrazine, pyridazine, pyrimidine, triazine, quinoline, isoquinoline, o-diazonyl, quinoxaline, phenanthridine, primidine, quinazoline, and quinazolineone.

[0049] In this application, the CAS number of the modified methylaluminoxane is 206451-54-9.

[0050] One or more embodiments of this application provide catalyst compositions for selective oligomerization of ethylene, including a main catalyst and a co-catalyst;

[0051] The main catalyst includes a complex;

[0052] The ligands of the complex are compounds represented by formula (Ⅰ), and the coordinating metals are group VIB to VIII metal elements;

[0053] (I);

[0054] A1 and A2 are independently selected from substituted or unsubstituted C3-C, respectively. 10 Mixed aromatics;

[0055] R1 is selected from hydrogen, nitro, C1-C9 alkyl, or C6-C 20 Aryl;

[0056] R2 is absent or selected from C1-C9 alkyl groups;

[0057] R3 is absent or is selected from hydrogen;

[0058] The co-catalyst includes an organic compound containing aluminum.

[0059] In the compound shown in formula (I), the linking site of the heteroaryl groups represented by A1 and A2 is a C atom, and the adjacent N atom is a N atom; the CN bond is represented by a single bond, used to illustrate the positional relationship between the linking site C atom and the adjacent N atom, and not to illustrate specific aromaticity. For example, in some embodiments, in the compound shown in formula (I), the heteroaryl groups represented by A1 and A2 are pyridine rings, and the compound shown in formula (I) can be used... It can also be expressed as, The two Kekulé forms of aryl are indicated.

[0060] In the catalyst composition for selective oligomerization of ethylene in this application, the main catalyst adopts a special N-coordinated ligand structure (the compound shown in formula (Ⅰ)), which has a strong interaction with group VIB~VIII metal elements (such as Cr, Mo, W, Fe, Co, Ni, etc.). The metal-N bond length is shorter, and it has a more compact coordination environment compared with traditional PNP ligands. This makes the metal cycloheptane (the structure formed after the metal coordinates with three ethylene molecules) more inclined to further coordinate with ethylene, thereby effectively improving the selectivity of 1-octene.

[0061] In some embodiments, the coordination compound structure is as shown in formula (I'):

[0062] (I');

[0063] M is a metal from group VIB to VIII, and Q is a coordinating anion; in formula (I'), M coordinates with N to form a metal eight-membered ring.

[0064] n represents the number of coordinating anions, which is related to the metal valence state. Equation (I') is charge balanced.

[0065] For example, in some embodiments, M is trivalent Cr and n is 3. In some embodiments, M is divalent Ni and n is 2. In some embodiments, R3 is absent, and the compounds represented by formula (I) are exemplified below:

[0066] , , , , , , , , , , , , .

[0067] In some embodiments, R3 is hydrogen, and examples of compounds represented by formula (I) are as follows:

[0068] , .

[0069] When R3 is hydrogen, after A2 is deprotonated in coordination, it forms a coordinate bond with the coordinating metal through the N atom. Therefore, the complex no longer contains active hydrogen (R3).

[0070] In some embodiments, A1 and A2 are each independently selected from substituted or unsubstituted pyridine, quinoline, indole, oxazole, pyrrole, or 1,4-pyrazine; optionally, the substitution is C1-C4 alkyl substitution.

[0071] In some embodiments, R1 is selected from hydrogen, nitro, C1-C4 alkyl, C1-C4 alkoxy, or C6-C 10 Aryl.

[0072] In some embodiments, R2 is absent or selected from C1-C4 alkyl groups.

[0073] In some embodiments, A1 and A2 are the same, and R2 and R3 do not exist.

[0074] In some embodiments, A1 and A2 are different, R2 is absent or selected from C1-C9 alkyl groups, and R3 is absent or selected from hydrogen.

[0075] In some embodiments, the compound represented by formula (I) is selected from any of the following compounds:

[0076] , , , , , , , , , , , , , , .

[0077] The ligands of this application (the compound shown in formula (I)) have high basicity, which further enhances the coordination strength between the metal and the ligand, thereby resisting the disturbance of molecular thermal motion under increased temperature and greatly improving the high temperature resistance of the main catalyst.

[0078] In some embodiments, the catalyst composition for selective oligomerization of ethylene of this application exhibits an activity ≥900 kg / (g·M·h) for ethylene oligomerization at 90°C-110°C; M is a group VIB~VIII metal; preferably, M is Cr or Ni.

[0079] In some embodiments, the molar ratio of the coordinating metal in the main catalyst to the aluminum element in the co-catalyst is 1:(500-1000). More preferably, it is 1:(600-800). Examples include 1:500, 1:600, 1:700, 1:800, 1:900, 1:1000, etc.

[0080] The ligands used in this application (the compounds shown in Formula I) can be obtained by purchase or by preparation.

[0081] The preparation method of the compound shown in Formula I can be found in [reference needed]. Figure 1 . Figure 1 The definitions of A1, A2, R1, R2, and R3 are given above.

[0082] In some embodiments, the method for preparing the compound represented by Formula I includes the following steps:

[0083] 1) Add heterocyclic 1,2-carboxaldehyde ( ) to anhydrous magnesium sulfate in dichloromethane suspension. ), followed by the addition of heterocyclic 2-2-methylamine ( After mixing, the mixture was stirred at room temperature for 3 hours. The suspension was then filtered, and the filter cake was washed with dichloromethane. The solvent was evaporated and the mixture was then subjected to a vacuum of 60°C. o C-65 o Drying at C for 6-8 hours yields compound II;

[0084] The molar ratio of the heterocyclic 1-2-carboxaldehyde to the heterocyclic 2-2-methylamine and anhydrous magnesium sulfate is 1:1:(4.5-5.5);

[0085] The volume of dichloromethane used (mL) is 4000-5000 times the molar amount (mol) of the heterocyclic 1-2-carboxaldehyde raw material;

[0086] Preferably, the heterocyclic 1-2-carboxaldehyde is selected from one or more of pyridine-2-carboxaldehyde, quinoline-2-carboxaldehyde, indole-2-carboxaldehyde, oxazol-2-carboxaldehyde, pyrrole-2-carboxaldehyde, and 1,4-pyrazin-2-carboxaldehyde;

[0087] Preferably, the heterocyclic 2-2-methylamine is selected from one or more of pyridine-2-methylamine, quinoline-2-methylamine, N-methylindole-2-methylamine, oxazol-2-methylamine, N-methylpyrrole-2-methylamine, and 1,4-pyrazin-2-methylamine.

[0088] 2) Dissolve the compound of formula II in acetonitrile and cool to -5°C. o C, add glacial acetic acid to the solution, and then maintain it at -5. o An anhydrous ethanol suspension of sodium borohydride was slowly added dropwise to the solution at temperature C. After the addition was complete, the mixture was stirred at room temperature for 18 hours. Hydrochloric acid was then added to the reaction mixture to quench the reaction. After quenching, the system was heated to 60°C. o C and maintain for 2 hours. Filter the resulting white precipitate, concentrate the filtrate under vacuum, and redissolve it in water. Under fully cooled conditions, add sodium hydroxide granules to the resulting aqueous solution to adjust the pH to alkaline, yielding a red oily substance. Extract the red oily substance with diethyl ether, dry the obtained solvent, and then evaporate the solvent. (Vacuum 60-65°C) o Drying at C for 4-6 hours yields compound III;

[0089] The molar ratio of the compound shown in Formula II to glacial acetic acid and sodium borohydride is 1:1:(1.8-2.2);

[0090] The volume (mL) of acetonitrile used is 3000-4000 times the molar (mol) of the compound shown in Formula II;

[0091] The volume of ethanol used (mL) is 900-1200 times the molar amount of sodium borohydride used (mol);

[0092] Preferably, the hydrochloric acid concentration is between 11 mol / L and 12 mol / L.

[0093] 3) Anhydrous potassium carbonate and potassium iodide were suspended in freshly distilled acetonitrile. The compound shown in Formula III was also dissolved in freshly distilled acetonitrile and added dropwise to the suspension. N-(2-bromoethyl)phthalimide was added to the resulting suspension. The reaction system was refluxed for 24 hours, filtered, and concentrated under vacuum to obtain an oily substance. The oily substance was dissolved in dichloromethane and washed successively with saturated sodium bicarbonate solution and water. After removing the solvent by vacuum evaporation, hydrochloric acid was added to the resulting oily substance. This aqueous solution was washed with dichloromethane, and then sodium bicarbonate was added to adjust the pH to alkaline to obtain an orange solid. The solid was extracted with dichloromethane and the solvent was removed by evaporation. The compound shown in Formula IV was purified by column chromatography.

[0094] The molar ratio of the compound shown in Formula III to anhydrous potassium carbonate, potassium iodide, and N-(2-bromoethyl)phthalimide ethyl bromide is 1:3.5:0.01:(1.1-1.2).

[0095] The total volume (mL) of the freshly distilled acetonitrile used is 4000-6000 times the molar volume (mol) of the compound shown in Formula III;

[0096] The volume of dichloromethane used (mL) is 3000-4000 times the molar amount (mol) of the compound shown in Formula III;

[0097] Preferably, the hydrochloric acid concentration is 1.5 mol / L to 2.5 mol / L;

[0098] 4) Dissolve the compound shown in Formula IV in anhydrous ethanol. Add an anhydrous ethanol solution of hydrazine hydrate dropwise to the solution. Dilute the mixture with ethanol and reflux for 3 hours. Concentrate the reaction mixture under vacuum. Add hydrochloric acid to the residue to precipitate a solid. Heat the suspension at 50°C. o After stirring at C for two hours, the mixture was cooled to room temperature and stirred for another 24 hours. After filtration, the filtrate was concentrated under vacuum and dissolved in water. Sodium hydroxide solution was added to the aqueous solution to obtain a red oily substance. This oily substance was extracted with dichloromethane, dried, and the solvent was removed by evaporation under vacuum at 50°C. o C-60 o Drying at C for 4-6 hours yields the compound shown in formula V;

[0099] The volume (mL) of the ethanol solution of the hydrazine hydrate is 500-600 times the molar amount (mol) of the compound shown in Formula IV;

[0100] The volume (mL) of anhydrous ethanol used is 4000-5000 times the molar amount (mol) of the compound shown in Formula IV;

[0101] Preferably, the hydrochloric acid concentration is 11 mol / L-13 mol / L;

[0102] Preferably, the concentration of the sodium hydroxide aqueous solution is 2 mol / L-4 mol / L.

[0103] 5) Add substituted benzaldehyde to a suspension of anhydrous magnesium sulfate in dichloromethane, followed by the addition of the compound shown in Formula V. After mixing, stir at room temperature for 3 hours, filter the suspension, wash the filter cake with dichloromethane, evaporate the solvent, and then vacuum at 60°C. o C-65 o Drying at C for 6-8 hours yields compound I;

[0104] The molar ratio of the substituted benzaldehyde to the compound of formula V and anhydrous magnesium sulfate is 1:1:(4.5-5.5);

[0105] The volume of dichloromethane used (mL) is 4000-6000 times that of the molar amount (mol) of the compound shown in Formula V;

[0106] Preferably, the substituted benzaldehyde is selected from one or more of benzaldehyde, 4-methylbenzaldehyde, 4-methoxybenzaldehyde, 4-isopropylbenzaldehyde, 4-tert-butylbenzaldehyde, 4-nitrobenzaldehyde, and 4-phenylbenzaldehyde.

[0107] In some embodiments, the complex further includes a coordinating anion;

[0108] The coordinating anion includes at least one of organic anions and inorganic anions.

[0109] Further, the organic anion includes at least one selected from acetate ions, benzoate ions, and acetylacetone anions; and / or,

[0110] The inorganic anions include at least one of nitrate ions, sulfate ions, and halide ions.

[0111] In some embodiments, the aluminum-containing organic compound includes at least one of trimethylaluminum, triethylaluminum, diethylaluminum chloride, tributylaluminum, triisobutylaluminum, tripropylaluminum, trioctylaluminum, dimethylaluminum chloride, dimethylisobutylaluminum, dimethylethylaluminum, triphenylaluminum, triisopropylaluminum, trisec-butylaluminum, ethyldimethylaluminum, methylaluminoxane, and modified methylaluminoxane.

[0112] In some embodiments, the method for preparing the main catalyst includes the following steps:

[0113] The ligand (the compound shown in formula (I)), the transition metal compound, and the first organic solvent are mixed to obtain a mixture;

[0114] The mixture is subjected to a thermal reflux reaction;

[0115] After the hot reflux reaction is complete, the solvent in the reaction solution is removed to obtain a solid;

[0116] The solid was dissolved in methylcyclohexane, and a nonpolar solvent was added to the resulting solution for recrystallization to obtain the complex.

[0117] The transition metal compound is a salt containing metals from group VIB to VIII.

[0118] Optionally, the nonpolar solvent includes at least one of solvents such as diethyl ether, n-hexane, petroleum ether, and cyclohexane.

[0119] In some embodiments, since A1 and A2 in the ligands (the compound shown in Formula I) are different, adding nonpolar solvents of different polarities during the recrystallization step will result in the precipitation of two different complexes.

[0120] Understandably, when A1 and A2 are different and R3 is hydrogen, although two different complexes can be precipitated, a simple preliminary experiment can test whether the complex contains active hydrogen, thus discarding the complex containing active hydrogen and not conducting further catalytic activity testing. This is because, in the catalytic reaction, active hydrogen reacts with the co-catalyst, affecting the catalytic effect.

[0121] It is also understood that the complexes of this application do not contain active hydrogen. In some embodiments, the transition metal compound includes one or more of chromium acetylacetonate, chromium trichloride tris(tetrahydrofuran), chromium 2-ethylhexanoate, chromium benzoylacetone, chromium tris(2,2,6,6-tetramethyl-3,5-heptanoic acid), chromium hexafluoro-2,4-glutarate, and chromium acetate hydroxide. Optionally, the first organic solvent includes at least one of toluene, dichloromethane, methylcyclohexane, and acetonitrile.

[0122] In this embodiment, the temperature of the heat reflux is 80°C. o C-100 o C, the time is 24-72 hours.

[0123] Optionally, the molar ratio of the transition metal compound to the ligand is 1:(1.1-1.2). An appropriate excess of the ligand is beneficial for the full coordination of the transition metal.

[0124] Optionally, the volume (mL) of the first organic solvent is 4000-6000 times the molar amount (mol) of the compound shown in Formula I;

[0125] Optionally, the volume (mL) of methylcyclohexane used is 4000-6000 times the molar (mol) of the compound shown in I;

[0126] Optionally, the nonpolar solvent includes at least one of diethyl ether, n-hexane, petroleum ether, and cyclohexane;

[0127] Optionally, the volume (mL) of the nonpolar solvent used is 2000-4000 times the molar amount (mol) of the compound shown in Formula I.

[0128] One or more embodiments of this application also provide a method for preparing α-olefins, comprising the following steps:

[0129] The α-olefin was prepared by ethylene oligomerization in the presence of a catalyst.

[0130] The catalyst includes the catalyst composition for selective oligomerization of ethylene described above.

[0131] Understandably, the main catalyst and co-catalyst in the catalyst composition for selective oligomerization of ethylene do not need to be mixed before use, but are fed separately. The feeding method is determined by the properties of the co-catalyst itself. The co-catalyst is a highly flammable solid, so it is packaged and used as a solution diluted to a certain ratio and fed through a syringe or other liquid feeding device commonly used in the art.

[0132] Preferably, feeding the main catalyst first, followed by the co-catalyst, helps ensure the activity of the catalyst composition. In some embodiments, the step of carrying out ethylene oligomerization in the presence of a catalyst includes:

[0133] The ethylene, the catalyst, and the second organic solvent are mixed to obtain a mixture;

[0134] The mixture is reacted at a first temperature and a first pressure for a first time;

[0135] The first temperature is 90℃-110℃, the first pressure is 0.1MPa-10MPa, and the first time is 1min-120min.

[0136] Preferably, the α-olefin is 1-octene, and under the above conditions, the catalyst composition for selective oligomerization of ethylene has 1-octene selectivity at high temperature.

[0137] In some embodiments, the method carried out under a nitrogen atmosphere is as follows: before the reaction, the reactor is heated to 120°C-150°C, evacuated for 1-3 hours, purged with nitrogen, and after cooling to room temperature, the raw materials are added to carry out the reaction.

[0138] In some embodiments, the method for preparing α-olefins includes the following steps:

[0139] Before the reaction, heat the reactor to 120℃-150℃, evacuate for 1-3 hours, and replace with nitrogen.

[0140] After cooling to room temperature, ethylene is replaced 3-5 times. A second organic solvent is added to the reactor and mixed, followed by the addition of a catalyst to obtain a mixture. The mixture is then reacted at a first temperature and a first pressure for a first time.

[0141] In this embodiment, the first temperature is 0℃-110℃, the first pressure is 0.1MPa-10MPa, and the first time is 1min-120min. Preferably, the first temperature is 90℃-110℃, the first pressure is 4.5MPa-6MPa, and the first time is 30-90min.

[0142] Optionally, the second organic solvent is one or more of aliphatic hydrocarbons and aromatic hydrocarbons; preferably, the aliphatic hydrocarbon is n-heptane, pentane, cyclohexane or methylcyclohexane, and the aromatic hydrocarbon is one or more of toluene, xylene, ethylbenzene, n-propylbenzene and diphenylmethane.

[0143] In some embodiments, the amount of catalyst used in the mixture is 2 μmol / mL to 4 μmol / mL, based on the molar concentration of the coordinating metal element in the main catalyst.

[0144] Preferably, the synthesis reaction of this application is carried out under a nitrogen atmosphere.

[0145] The following are some specific examples.

[0146] Raw material source:

[0147] All raw materials used in the examples are conventional raw materials in the art, and the purity specifications used are analytical grade or chemically pure.

[0148] Anhydrous magnesium sulfate: ≥99.0%, Sinopharm Chemical Reagent Co., Ltd.;

[0149] Dichloromethane: ≥99.0%, Sinopharm Chemical Reagent Co., Ltd.;

[0150] Glacial acetic acid: ≥99.0%, Sinopharm Chemical Reagent Co., Ltd.;

[0151] Sodium borohydride: ≥98.0%, Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0152] Anhydrous ethanol: ≥99.0%, Sinopharm Chemical Reagent Co., Ltd.;

[0153] Hydrochloric acid: 37%, Sinopharm Chemical Reagent Co., Ltd.;

[0154] Sodium hydroxide: ≥99.0%, Sinopharm Chemical Reagent Co., Ltd.;

[0155] Diethyl ether: ≥99.0%, Sinopharm Chemical Reagent Co., Ltd.;

[0156] Anhydrous potassium carbonate: ≥99.0%, Sinopharm Chemical Reagent Co., Ltd.;

[0157] Potassium iodide: ≥99.0%, Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0158] Acetonitrile: ≥99.0%, Sinopharm Chemical Reagent Co., Ltd.;

[0159] N-(2-Bromoethyl)phthalimide: ≥98.0%, Aladdin Biochemical Technology Co., Ltd.;

[0160] Sodium bicarbonate: ≥99.0%, Sinopharm Chemical Reagent Co., Ltd.;

[0161] Hydrazine hydrate anhydrous ethanol solution: 24%-26%, Aladdin Biochemical Technology Co., Ltd.;

[0162] Toluene: ≥99.0%, Sinopharm Chemical Reagent Co., Ltd.;

[0163] Pyridine-2-carboxaldehyde: ≥99.0%, Beijing Bailingwei Technology Co., Ltd.;

[0164] Quinoline-2-carboxaldehyde: ≥99.0%, Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0165] Indole-2-carboxaldehyde: ≥99.0%, Shanghai Maclean Biochemical Technology Co., Ltd.

[0166] Oxazole-2-carboxaldehyde: ≥99.0%, Jiangsu Xinnuoke Catalyst Co., Ltd.;

[0167] Pyrrole-2-carboxaldehyde: ≥98.0%, Yangzhou Chemical Co., Ltd.;

[0168] 1,4-Pyrazine-2-formaldehyde: ≥99.0%, Jiangsu Xinnuoke Catalyst Co., Ltd.;

[0169] Pyridine-2-methylamine: ≥99.0%, Beijing Bailingwei Technology Co., Ltd.;

[0170] Quinoline-2-methylamine: ≥99.0%, Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0171] N-Methylindole-2-methylamine: ≥99.0%, Shanghai Maclean Biochemical Technology Co., Ltd.;

[0172] Oxazol-2-methylamine: ≥99.0%, Jiangsu Xinnoco Catalyst Co., Ltd.;

[0173] N-Methylpyrrole-2-methylamine: ≥98.0%, Yangzhou Chemical Co., Ltd.;

[0174] 1,4-Pyrazine-2-methylamine: ≥99.0%, Jiangsu Xinnuo Ke Catalyst Co., Ltd.;

[0175] Benzaldehyde: ≥99.0%, Sinopharm Chemical Reagent Co., Ltd.;

[0176] 4-Methylbenzaldehyde: ≥99.0%, Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0177] 4-Methoxybenzaldehyde: ≥99.0%, Beijing Bailingwei Technology Co., Ltd.;

[0178] 4-Isopropylbenzaldehyde: ≥99.0%, Beijing Bailingwei Technology Co., Ltd.;

[0179] 4-tert-butylbenzaldehyde: ≥99.0%, Shanghai Maclean Biochemical Technology Co., Ltd.;

[0180] 4-Nitrobenzaldehyde: ≥99.0%, Jiangsu Xinnuoke Catalyst Co., Ltd.;

[0181] 4-Phenylenaldehyde: ≥99.0%, Yangzhou Chemical Co., Ltd.;

[0182] Chromium acetylacetone: ≥99.0%, Beijing Bailingwei Technology Co., Ltd.;

[0183] iPr-PNP: 98.0%, Jiangsu Xinnoco Catalyst Co., Ltd.;

[0184] iPr-PNP-F: 98.0%, Jiangsu Xinnoco Catalyst Co., Ltd.;

[0185] Methylcyclohexane solution of modified methylaluminoxane: 2.0 mol / L, Saen Chemical Technology (Shanghai) Co., Ltd., catalog number HLJ191224A;

[0186] Triisobutylaluminum in hexane solution: 1.0 mol / L, Saen Chemical Technology (Shanghai) Co., Ltd.

[0187] Test method:

[0188] The liquid products are characterized by gas chromatography to obtain the mass of each liquid product, and the solid products are separated, dried and weighed.

[0189] Gas chromatography analysis conditions: Sample injection temperature: 250℃; Column oven temperature: 35℃;

[0190] Heating program: First, maintain at 35℃ for 10 minutes, then increase to 250℃ at a rate of 10℃ / min, then maintain at 250℃ for 10 minutes, and then begin cooling down until room temperature;

[0191] Detector temperature: 250℃; Support: 1.0MPa; Air: 0.03MPa; Hydrogen: 0.03MPa;

[0192] The product was characterized using n-nonane as an internal standard, and the calculation method is as follows:

[0193] m1 / m = k × (a1 / a);

[0194] In the formula, m1 represents the mass of a certain substance, m is the mass of n-nonane, a1 is the peak area of ​​this substance measured in GC, and a is the peak area of ​​n-nonane measured in GC. k is a correction coefficient.

[0195] For experimental parameters not specified in the following specific embodiments, please refer to the guidelines given in this application document first, or refer to experimental manuals or other experimental methods known in the art, or refer to the experimental conditions recommended by the manufacturer.

[0196] Raw materials and reagents not specified in the following specific embodiments can be obtained commercially or prepared by those skilled in the art using known methods.

[0197] I. Preparation of catalyst compositions for selective oligomerization of ethylene

[0198] Example 1

[0199] This embodiment provides a catalyst composition for the selective oligomerization of ethylene according to this application. All synthesis steps are carried out under a nitrogen atmosphere, and the specific steps are as follows:

[0200] (1) Preparation of ligands for the main catalyst

[0201] 1) Pyridine-2-carboxaldehyde (5 mmol) was added to a 20 mL suspension of anhydrous magnesium sulfate (23 mmol) in dichloromethane, followed by pyridine-2-methylamine (5 mmol). The mixture was stirred at room temperature for 3 hours, filtered, and the filter cake was washed with dichloromethane. The solvent was evaporated and the mixture was dried under vacuum at 60 °C for 6 hours to obtain compound II.

[0202] 2) Compound II (4 mmol) was dissolved in acetonitrile (16 mL), cooled to -5 °C, and glacial acetic acid (4 mmol) was added to the solution. Then, a suspension of sodium borohydride (8 mmol) in anhydrous ethanol (8 mL) was slowly added dropwise while maintaining the temperature at -5 °C. After the addition was complete, the mixture was stirred at room temperature for 18 hours. Hydrochloric acid (12 mol / L) was then added to the reaction mixture to quench the reaction. After quenching, the system was heated to 60 °C and maintained for 2 hours. The resulting white precipitate was filtered, and the filtrate was concentrated under vacuum and redissolved in water. Under fully cooled conditions, sodium hydroxide was added to the resulting aqueous solution to adjust the pH to alkaline, yielding a red oily substance. This red oily substance was extracted with diethyl ether, and the solvent was dried. The solvent was then evaporated, and the mixture was dried under vacuum at 60 °C for 6 hours to obtain compound III.

[0203] 3) Anhydrous potassium carbonate (10.5 mmol) and potassium iodide (30 μmol) were suspended in freshly distilled acetonitrile (4 mL). Compound III (3 mmol) was dissolved in freshly distilled acetonitrile (8 mL) and added dropwise to the suspension. N-(2-bromoethyl)phthalimide (3.3 mmol) was added to the resulting suspension. The reaction mixture was refluxed for 24 hours, filtered, and concentrated under vacuum to obtain an oil. The oil was dissolved in dichloromethane (9 mL) and washed successively with saturated sodium bicarbonate solution and water. After removing the solvent by vacuum evaporation, hydrochloric acid (2 mol / L) was added to the resulting oil. This aqueous solution was washed with dichloromethane, and then sodium bicarbonate was added to adjust the pH to alkaline to obtain an orange solid. The solid was extracted with dichloromethane and the solvent was evaporated. Compound IV was purified by column chromatography.

[0204] 4) Compound IV (2 mmol) was dissolved in anhydrous ethanol (8 mL). 1 mL of anhydrous ethanol solution of hydrazine hydrate (2 mol / L) was added dropwise to this solution. The mixture was diluted with ethanol and refluxed for 3 hours. The reaction mixture was concentrated under vacuum. Hydrochloric acid (12 mol / L) was added to the residue, precipitating a solid. The suspension was stirred at 50°C for two hours, then cooled to room temperature and stirred for another 24 hours. After filtration, the filtrate was concentrated under vacuum and dissolved in water. Sodium hydroxide aqueous solution (2 mol / L) was added to the aqueous solution to obtain a red oil. The oil was extracted with dichloromethane, dried, and the solvent was evaporated. The residue was then dried under vacuum at 50°C for 6 hours to obtain compound V.

[0205] 5) Benzaldehyde (1.1 mmol) was added to a suspension of anhydrous magnesium sulfate (4.94 mmol) in dichloromethane (4 mL), followed by the addition of compound V (1.1 mmol). The mixture was stirred at room temperature for 3 hours, filtered, and the filter cake was washed with dichloromethane. The solvent was evaporated and the mixture was dried under vacuum at 60 °C for 8 hours to obtain compound I.

[0206] The proton NMR spectrum of compound I is as follows:

[0207] 1 H NMR (400MHz, CDCl3): δ 8.74 (s, 1H), 8.51 (d, J = 4.0 Hz, 2H), 7.80 -7.70 (m, 4H), 7.60 - 7.50 (m, 3H), 7.35 - 7.20 (m, 4H), 3.94 (s, 4H), 3.68(s, 2H), 2.78 (dt, J = 37.5 Hz, J = 5.8 Hz, 2H).

[0208] (2) Preparation of main catalyst

[0209] Chromium acetylacetone (0.5 mmol) and compound I (0.55 mmol) were heated under reflux in toluene (2.2 mL) for 24 hours at 80 °C. The solvent was removed under vacuum. The insoluble matter was dissolved in 3 mL of methylcyclohexane, and 2.2 mL of diethyl ether was added. The precipitated solid was filtered and then heated under vacuum at 50 °C. o The complex catalyst was obtained by drying at C for 5 hours.

[0210] Example 2

[0211] This embodiment provides a catalyst composition for the selective oligomerization of ethylene according to this application. All synthesis steps are carried out under a nitrogen atmosphere, and the specific steps are as follows:

[0212] (1) Preparation of ligands for the main catalyst

[0213] 1) Quinoline-2-carboxaldehyde (5 mmol) was added to a 20 mL suspension of anhydrous magnesium sulfate (22.5 mmol) in dichloromethane, followed by pyridine-2-methylamine (5 mmol). The mixture was stirred at room temperature for 3 hours, filtered, and the filter cake was washed with dichloromethane. The solvent was evaporated and the mixture was dried under vacuum at 60 °C for 6 hours to obtain compound II.

[0214] 2) Compound II (4 mmol) was dissolved in acetonitrile (12 mL), cooled to -5 °C, and glacial acetic acid (4 mmol) was added to the solution. Then, a suspension of sodium borohydride (7.2 mmol) in anhydrous ethanol (6.48 mL) was slowly added dropwise while maintaining the temperature at -5 °C. After the addition was complete, the mixture was stirred at room temperature for 18 hours. Hydrochloric acid (12 mol / L) was then added to the reaction mixture to quench the reaction. After quenching, the system was heated to 60 °C and maintained for 2 hours. The resulting white precipitate was filtered, and the filtrate was concentrated under vacuum and redissolved in water. Under fully cooled conditions, sodium hydroxide was added to the resulting aqueous solution to adjust the pH to alkaline, yielding a red oily substance. This red oily substance was extracted with diethyl ether, and the solvent was dried. The solvent was then evaporated, and the mixture was dried under vacuum at 60 °C for 6 hours to obtain compound III.

[0215] 3) Anhydrous potassium carbonate (10.5 mmol) and potassium iodide (30 μmol) were suspended in freshly distilled acetonitrile (4 mL). Compound III (3 mmol) was dissolved in freshly distilled acetonitrile (8 mL) and added dropwise to the suspension. N-(2-bromoethyl)phthalimide (3.3 mmol) was added to the resulting suspension. The reaction mixture was refluxed for 24 hours, filtered, and concentrated under vacuum to obtain an oil. The oil was dissolved in dichloromethane (9 mL) and washed successively with saturated sodium bicarbonate solution and water. After removing the solvent by vacuum evaporation, hydrochloric acid (2 mol / L) was added to the resulting oil. This aqueous solution was washed with dichloromethane, and then sodium bicarbonate was added to adjust the pH to alkaline to obtain an orange solid. The solid was extracted with dichloromethane and the solvent was evaporated. Compound IV was purified by column chromatography.

[0216] 4) Compound IV (2 mmol) was dissolved in anhydrous ethanol (8 mL). 1 mL of anhydrous ethanol solution of hydrazine hydrate (2 mol / L) was added dropwise to this solution. The mixture was diluted with ethanol and refluxed for 3 hours. The reaction mixture was concentrated under vacuum. Hydrochloric acid (12 mol / L) was added to the residue, precipitating a solid. The suspension was stirred at 50°C for two hours, then cooled to room temperature and stirred for another 24 hours. After filtration, the filtrate was concentrated under vacuum and dissolved in water. Sodium hydroxide aqueous solution (2 mol / L) was added to the aqueous solution to obtain a red oil. The oil was extracted with dichloromethane, dried, and the solvent was evaporated. The residue was then dried under vacuum at 50°C for 6 hours to obtain compound V.

[0217] 5) Benzaldehyde (1 mmol) was added to a suspension of anhydrous magnesium sulfate (4.5 mmol) in dichloromethane (4 mL), followed by the addition of compound V (1 mmol). The mixture was stirred at room temperature for 3 hours, filtered, and the filter cake was washed with dichloromethane. The solvent was evaporated and the mixture was dried under vacuum at 60 °C for 8 hours to obtain compound I.

[0218] The proton NMR spectrum of compound I is as follows:

[0219] 1 H NMR (400 MHz, CDCl3): δ 8.72 (s, 1H), 8.49 (s, 1H), 8.10 - 7.99 (m,2H), 7.86 - 7.39 (m, 9H), 7.33 - 7.09 (m, 3H), 3.93 (s, 4H), 3.36 (dt, J =36.5 Hz, J = 3.7 Hz, 2H), 2.90 - 2.70 (m, 2H).

[0220] (2) Preparation of main catalyst

[0221] Chromium acetylacetone (0.5 mmol) and compound I (0.6 mmol) were heated under reflux in toluene (2.5 mL) for 24 hours at 80 °C. The solvent was removed under vacuum. The insoluble matter was dissolved in 2.5 mL of methylcyclohexane, and 2 mL of n-hexane was added. The precipitated solid was filtered and then heated under vacuum at 50 °C. o The complex catalyst was obtained by drying at C for 5 hours.

[0222] Example 3

[0223] This embodiment provides a catalyst composition for the selective oligomerization of ethylene according to this application. All synthesis steps are carried out under a nitrogen atmosphere, and the specific steps are as follows:

[0224] (1) Preparation of ligands for the main catalyst

[0225] 1) Indole-2-carboxaldehyde (5 mmol) was added to a 25 mL suspension of anhydrous magnesium sulfate (27.5 mmol) in dichloromethane, followed by pyridine-2-methylamine (5 mmol). The mixture was stirred at room temperature for 3 hours, filtered, and the filter cake was washed with dichloromethane. The solvent was evaporated and the mixture was dried under vacuum at 60 °C for 6 hours to obtain compound II.

[0226] 2) Compound II (4 mmol) was dissolved in acetonitrile (16 mL), cooled to -5 °C, and glacial acetic acid (4 mmol) was added to the solution. Then, while maintaining the temperature at -5 °C, a suspension of sodium borohydride (8.8 mmol) in anhydrous ethanol (10.56 mL) was slowly added dropwise. After the addition was complete, the mixture was stirred at room temperature for 18 hours. Hydrochloric acid (12 mol / L) was then added to the reaction mixture to quench the reaction. After quenching, the system was heated to 60 °C and maintained for 2 hours. The resulting white precipitate was filtered, and the filtrate was concentrated under vacuum and redissolved in water. Under fully cooled conditions, sodium hydroxide was added to the resulting aqueous solution to adjust the pH to alkaline, yielding a red oily substance. This red oily substance was extracted with diethyl ether, and the solvent was dried. The solvent was then evaporated, and the mixture was dried under vacuum at 60 °C for 6 hours to obtain compound III.

[0227] 3) Anhydrous potassium carbonate (10.5 mmol) and potassium iodide (30 μmol) were suspended in freshly distilled acetonitrile (6 mL). Compound III (3 mmol) was dissolved in freshly distilled acetonitrile (12 mL) and added dropwise to the suspension. N-(2-bromoethyl)phthalimide (3.6 mmol) was added to the resulting suspension. The reaction mixture was refluxed for 24 hours, filtered, and concentrated under vacuum to obtain an oil. The oil was dissolved in dichloromethane (12 mL) and washed successively with saturated sodium bicarbonate solution and water. After removing the solvent by vacuum evaporation, hydrochloric acid (2 mol / L) was added to the resulting oil. This aqueous solution was washed with dichloromethane, and then sodium bicarbonate was added to adjust the pH to alkaline to obtain an orange solid. The solid was extracted with dichloromethane and the solvent was removed by evaporation. Compound IV was purified by column chromatography.

[0228] 4) Compound IV (2 mmol) was dissolved in anhydrous ethanol (10 mL). 1.2 mL of anhydrous ethanol solution of hydrazine hydrate (2 mol / L) was added dropwise to this solution. The mixture was diluted with ethanol and refluxed for 3 hours. The reaction mixture was concentrated under vacuum. Hydrochloric acid (12 mol / L) was added to the residue, precipitating a solid. The suspension was stirred at 50 °C for two hours, then cooled to room temperature and stirred for another 24 hours. After filtration, the filtrate was concentrated under vacuum and dissolved in water. Sodium hydroxide aqueous solution (3 mol / L) was added to the aqueous solution to obtain a red oil. The oil was extracted with dichloromethane, dried, and the solvent was evaporated. The residue was then dried under vacuum at 50 °C for 6 hours to obtain compound V.

[0229] 5) Benzaldehyde (1.1 mmol) was added to a suspension of anhydrous magnesium sulfate (5.5 mmol) in dichloromethane (6 mL), followed by the addition of compound V (1.1 mmol). The mixture was stirred at room temperature for 3 hours, filtered, and the filter cake was washed with dichloromethane. The solvent was evaporated and the mixture was dried under vacuum at 60 °C for 8 hours to obtain compound I.

[0230] The proton NMR spectrum of compound I is as follows:

[0231] 1 H NMR (400 MHz, CDCl3): δ 8.74 (s, 1H), 8.51 (d, J = 3.7 Hz, 1H), 7.87- 7.65 (m, 4H), 7.60 - 7.50 (m, 4H), 7.35 - 7.18 (m, 3H), 7.12 - 7.05 (m,2H), 6.22 (s, 1H), 3.94 (s, 2H), 3.65 (s, 2H), 3.52 (dt, J = 36.9 Hz, J = 3.7Hz, 2H), 2.90 -2.75 (m, 2H).

[0232] (2) Preparation of main catalyst

[0233] Chromium acetylacetone (0.5 mmol) and compound I (0.6 mmol) were heated under reflux in toluene (3.6 mL) for 24 hours at 80 °C. The solvent was removed under vacuum, and the insoluble matter was dissolved in 2.8 mL of methylcyclohexane. 2 mL of diethyl ether was added to the solution, and the precipitated solid was filtered and dried under vacuum at 50 °C for 5 hours to obtain the complex catalyst.

[0234] Example 4

[0235] This embodiment provides a catalyst composition for the selective oligomerization of ethylene according to this application. All synthesis steps are carried out under a nitrogen atmosphere, and the specific steps are as follows:

[0236] (1) Preparation of ligands for the main catalyst

[0237] 1) Oxazol-2-carboxaldehyde (5 mmol) was added to a 22 mL suspension of anhydrous magnesium sulfate (23 mmol) in dichloromethane, followed by pyridine-2-methylamine (5 mmol). The mixture was stirred at room temperature for 3 hours, filtered, and the filter cake was washed with dichloromethane. The solvent was evaporated and the mixture was dried under vacuum at 60 °C for 6 hours to obtain compound II.

[0238] 2) Compound II (4 mmol) was dissolved in acetonitrile (15 mL), cooled to -5 °C, and glacial acetic acid (4 mmol) was added to the solution. Then, while maintaining the temperature at -5 °C, a suspension of sodium borohydride (8.0 mmol) in anhydrous ethanol (8 mL) was slowly added dropwise. After the addition was complete, the mixture was stirred at room temperature for 18 hours. Hydrochloric acid (12 mol / L) was then added to the reaction mixture to quench the reaction. After quenching, the system was heated to 60 °C and maintained for 2 hours. The resulting white precipitate was filtered, and the filtrate was concentrated under vacuum and redissolved in water. Under fully cooled conditions, sodium hydroxide was added to the resulting aqueous solution to adjust the pH to alkaline, yielding a red oily substance. This red oily substance was extracted with diethyl ether, and the solvent was dried. The solvent was then evaporated, and the mixture was dried under vacuum at 60 °C for 6 hours to obtain compound III.

[0239] 3) Anhydrous potassium carbonate (10.5 mmol) and potassium iodide (30 μmol) were suspended in freshly distilled acetonitrile (5 mL). Compound III (3 mmol) was dissolved in freshly distilled acetonitrile (10 mL) and added dropwise to the suspension. N-(2-bromoethyl)phthalimide (3.5 mmol) was added to the resulting suspension. The reaction mixture was refluxed for 24 hours, filtered, and concentrated under vacuum to obtain an oil. The oil was dissolved in dichloromethane (10 mL) and washed successively with saturated sodium bicarbonate solution and water. After removing the solvent by vacuum evaporation, hydrochloric acid (2 mol / L) was added to the resulting oil. This aqueous solution was washed with dichloromethane, and then sodium bicarbonate was added to adjust the pH to alkaline to obtain an orange solid. The solid was extracted with dichloromethane and the solvent was removed by evaporation. Compound IV was purified by column chromatography.

[0240] 4) Compound IV (2 mmol) was dissolved in anhydrous ethanol (8 mL). 1 mL of anhydrous ethanol solution of hydrazine hydrate (2 mol / L) was added dropwise to this solution. The mixture was diluted with ethanol and refluxed for 3 hours. The reaction mixture was concentrated under vacuum. Hydrochloric acid (12 mol / L) was added to the residue, precipitating a solid. The suspension was stirred at 50°C for two hours, then cooled to room temperature and stirred for another 24 hours. After filtration, the filtrate was concentrated under vacuum and dissolved in water. Sodium hydroxide aqueous solution (4 mol / L) was added to the aqueous solution to obtain a red oil. The oil was extracted with dichloromethane, dried, and the solvent was evaporated. The residue was then dried under vacuum at 50°C for 6 hours to obtain compound V.

[0241] 5) Benzaldehyde (1 mmol) was added to a suspension of anhydrous magnesium sulfate (5.2 mmol) in dichloromethane (4 mL), followed by the addition of compound V (1 mmol). The mixture was stirred at room temperature for 3 hours, filtered, and the filter cake was washed with dichloromethane. The solvent was evaporated and the mixture was dried under vacuum at 60 °C for 8 hours to obtain compound I.

[0242] The proton NMR spectrum of compound I is as follows:

[0243] 1 H NMR (400 MHz, CDCl3): δ 8.74 (s, 1H), 8.51 (d, J = 4.2 Hz, 1H), 7.79-7.70 (m, 3H), 7.65 - 7.50 (m, 4H), 7.39 - 7.03 (m, 3H), 3.94 (s, 2H), 3.80(d, J = 18.1 Hz, 2H), 3.37 (dt, J = 36.6 Hz, J = 3.7 Hz 2H), 2.89 - 8.79 (m,2H).

[0244] (2) Preparation of main catalyst

[0245] Chromium acetylacetone (0.5 mmol) and compound I (0.6 mmol) were heated under reflux in toluene (2.4 mL) for 24 hours at 80 °C. The solvent was removed under vacuum. The insoluble matter was dissolved in 2.5 mL of methylcyclohexane, and 2 mL of n-hexane was added. The precipitated solid was filtered and then heated under vacuum at 50 °C. o The complex catalyst was obtained by drying at C for 5 hours.

[0246] Example 5

[0247] This embodiment provides a catalyst composition for the selective oligomerization of ethylene according to this application. All synthesis steps are carried out under a nitrogen atmosphere, and the specific steps are as follows:

[0248] (1) Preparation of ligands for the main catalyst

[0249] 1) Pyrrole-2-carboxaldehyde (5 mmol) was added to a 20 mL suspension of anhydrous magnesium sulfate (23 mmol) in dichloromethane, followed by pyridine-2-methylamine (5 mmol). The mixture was stirred at room temperature for 3 hours, filtered, and the filter cake was washed with dichloromethane. The solvent was evaporated and the mixture was dried under vacuum at 60 °C for 6 hours to obtain compound II.

[0250] 2) Compound II (4 mmol) was dissolved in acetonitrile (15 mL), cooled to -5 °C, and glacial acetic acid (4 mmol) was added to the solution. Then, a suspension of sodium borohydride (8 mmol) in anhydrous ethanol (9 mL) was slowly added dropwise while maintaining the temperature at -5 °C. After the addition was complete, the mixture was stirred at room temperature for 18 hours. Hydrochloric acid (12 mol / L) was then added to the reaction mixture to quench the reaction. After quenching, the system was heated to 60 °C and maintained for 2 hours. The resulting white precipitate was filtered, and the filtrate was concentrated under vacuum and redissolved in water. Under fully cooled conditions, sodium hydroxide was added to the resulting aqueous solution to adjust the pH to alkaline, yielding a red oily substance. This red oily substance was extracted with diethyl ether, and the solvent was dried. The solvent was then evaporated, and the mixture was dried under vacuum at 60 °C for 6 hours to obtain compound III.

[0251] 3) Anhydrous potassium carbonate (10.5 mmol) and potassium iodide (30 μmol) were suspended in freshly distilled acetonitrile (5 mL). Compound III (3 mmol) was dissolved in freshly distilled acetonitrile (10 mL) and added dropwise to the suspension. N-(2-bromoethyl)phthalimide (3.6 mmol) was added to the resulting suspension. The reaction mixture was refluxed for 24 hours, filtered, and concentrated under vacuum to obtain an oil. The oil was dissolved in dichloromethane (10 mL) and washed successively with saturated sodium bicarbonate solution and water. After removing the solvent by vacuum evaporation, hydrochloric acid (2 mol / L) was added to the resulting oil. This aqueous solution was washed with dichloromethane, and then sodium bicarbonate was added to adjust the pH to alkaline to obtain an orange solid. The solid was extracted with dichloromethane and the solvent was removed by evaporation. Compound IV was purified by column chromatography.

[0252] 4) Compound IV (2 mmol) was dissolved in anhydrous ethanol (9 mL). 1.2 mL of anhydrous ethanol solution of hydrazine hydrate (2 mol / L) was added dropwise to this solution. The mixture was diluted with ethanol and refluxed for 3 hours. The reaction mixture was concentrated under vacuum. Hydrochloric acid (12 mol / L) was added to the residue, precipitating a solid. The suspension was stirred at 50 °C for two hours, then cooled to room temperature and stirred for another 24 hours. After filtration, the filtrate was concentrated under vacuum and dissolved in water. Sodium hydroxide aqueous solution (2 mol / L) was added to the aqueous solution to obtain a red oil. The oil was extracted with dichloromethane, dried, and the solvent was evaporated. The residue was then dried under vacuum at 50 °C for 6 hours to obtain compound V.

[0253] 5) Benzaldehyde (1.1 mmol) was added to a suspension of anhydrous magnesium sulfate (5.2 mmol) in dichloromethane (5 mL), followed by the addition of compound V (1.1 mmol). The mixture was stirred at room temperature for 3 hours, filtered, and the filter cake was washed with dichloromethane. The solvent was evaporated and the mixture was dried under vacuum at 60 °C for 8 hours to obtain compound I.

[0254] The proton NMR spectrum of compound I is as follows:

[0255] 1 H NMR (400 MHz, CDCl3): δ 8.74 (s, 1H), 8.51 (d, J = 4.3 Hz, 1H), 8.04(s, 1H), 7.81 - 7.71 (m, 3H), 7.61 -7.40 (m, 3H), 7.40 - 7.20 (m, 2H), 6.64(d, J = 13.4 Hz, 1H), 6.11 (dt, J = 14.1 Hz, J = 3.7 Hz, 1H), 5.88 (d, 1H), 3.94 (s, 2H), 3.70 - 3.50 (m, 4H), 2.95 - 2.75 (m, 2H).

[0256] (2) Preparation of main catalyst

[0257] Chromium acetylacetone (0.5 mmol) and compound I (0.55 mmol) were heated under reflux in toluene (2.5 mL) for 24 hours at 80 °C. The solvent was removed under vacuum. The insoluble matter was dissolved in 3 mL of methylcyclohexane, and 2 mL of diethyl ether was added. The precipitated solid was filtered and then heated under vacuum at 50 °C. o The complex catalyst was obtained by drying at C for 5 hours.

[0258] Example 6

[0259] This embodiment provides a catalyst composition for the selective oligomerization of ethylene according to this application. All synthesis steps are carried out under a nitrogen atmosphere, and the specific steps are as follows:

[0260] (1) Preparation of ligands for the main catalyst

[0261] 1) 1,4-pyrazin-2-carboxaldehyde (5 mmol) was added to a 25 mL suspension of anhydrous magnesium sulfate (25 mmol) in dichloromethane, followed by the addition of pyridine-2-methylamine (5 mmol). The mixture was stirred at room temperature for 3 hours, filtered, and the filter cake was washed with dichloromethane. The solvent was evaporated and the mixture was dried under vacuum at 60 °C for 6 hours to obtain compound II.

[0262] 2) Compound II (4 mmol) was dissolved in acetonitrile (12 mL), cooled to -5 °C, and glacial acetic acid (4 mmol) was added to the solution. Then, a suspension of sodium borohydride (7.2 mmol) in anhydrous ethanol (7.2 mL) was slowly added dropwise while maintaining the temperature at -5 °C. After the addition was complete, the mixture was stirred at room temperature for 18 hours. Hydrochloric acid (12 mol / L) was then added to the reaction mixture to quench the reaction. After quenching, the system was heated to 60 °C and maintained for 2 hours. The resulting white precipitate was filtered, and the filtrate was concentrated under vacuum and redissolved in water. Under fully cooled conditions, sodium hydroxide was added to the resulting aqueous solution to adjust the pH to alkaline, yielding a red oily substance. This red oily substance was extracted with diethyl ether, and the solvent was dried. The solvent was then evaporated, and the mixture was dried under vacuum at 60 °C for 6 hours to obtain compound III.

[0263] 3) Anhydrous potassium carbonate (10.5 mmol) and potassium iodide (30 μmol) were suspended in freshly distilled acetonitrile (5 mL). Compound III (3 mmol) was dissolved in freshly distilled acetonitrile (10 mL) and added dropwise to the suspension. N-(2-bromoethyl)phthalimide (3.6 mmol) was added to the resulting suspension. The reaction mixture was refluxed for 24 hours, filtered, and concentrated under vacuum to obtain an oil. The oil was dissolved in dichloromethane (9 mL) and washed successively with saturated sodium bicarbonate solution and water. After removing the solvent by vacuum evaporation, hydrochloric acid (2 mol / L) was added to the resulting oil. This aqueous solution was washed with dichloromethane, and then sodium bicarbonate was added to adjust the pH to alkaline to obtain an orange solid. The solid was extracted with dichloromethane and the solvent was evaporated. Compound IV was purified by column chromatography.

[0264] 4) Compound IV (2 mmol) was dissolved in anhydrous ethanol (10 mL). 1.2 mL of anhydrous ethanol solution of hydrazine hydrate (2 mol / L) was added dropwise to this solution. The mixture was diluted with ethanol and refluxed for 3 hours. The reaction mixture was concentrated under vacuum. Hydrochloric acid (12 mol / L) was added to the residue, precipitating a solid. The suspension was stirred at 50 °C for two hours, then cooled to room temperature and stirred for another 24 hours. After filtration, the filtrate was concentrated under vacuum and dissolved in water. Sodium hydroxide aqueous solution (3 mol / L) was added to the aqueous solution to obtain a red oil. The oil was extracted with dichloromethane, dried, and the solvent was evaporated. The residue was then dried under vacuum at 50 °C for 6 hours to obtain compound V.

[0265] 5) Benzaldehyde (1 mmol) was added to a suspension of anhydrous magnesium sulfate (4.5 mmol) in dichloromethane (5 mL), followed by the addition of compound V (1 mmol). The mixture was stirred at room temperature for 3 hours, filtered, and the filter cake was washed with dichloromethane. The solvent was evaporated and the mixture was dried under vacuum at 60 °C for 8 hours to obtain compound I.

[0266] The proton NMR spectrum of compound I is as follows:

[0267] 1 H NMR (400 MHz, CDCl3): δ 8.70 (s, 1H), 8.57 - 8.41 (m, 4H), 7.78 -7.70 (m, 3H), 7.60 - 7.50 (m, 3H), 7.30 - 7.10 (m, 2H), 3.92 (s, 2H), 3.60 (dt, J = 32.4 Hz, J = 4.7 Hz 2H), 3.37 (dt, J = 35.9 Hz, J = 4.3 Hz, 2H), 2.81 - 2.60 (m, 2H).

[0268] (2) Preparation of main catalyst

[0269] Chromium acetylacetone (0.5 mmol) and compound I (0.6 mmol) were heated under reflux in toluene (2.5 mL) for 24 hours at 80 °C. The solvent was removed under vacuum. The insoluble matter was dissolved in 3 mL of methylcyclohexane, and 2 mL of cyclohexane was added. The precipitated solid was filtered and then heated under vacuum at 50 °C. o The complex catalyst was obtained by drying at C for 5 hours.

[0270] Example 7

[0271] This embodiment provides a catalyst composition for the selective oligomerization of ethylene according to this application. All synthesis steps are carried out under a nitrogen atmosphere, and the specific steps are as follows:

[0272] (1) Preparation of ligands for the main catalyst

[0273] 1) Pyridine-2-carboxaldehyde (5 mmol) was added to a 25 mL suspension of anhydrous magnesium sulfate (27.5 mmol) in dichloromethane, followed by pyridine-2-methylamine (5 mmol). The mixture was stirred at room temperature for 3 hours, filtered, and the filter cake was washed with dichloromethane. The solvent was evaporated and the mixture was dried under vacuum at 60 °C for 6 hours to obtain compound II.

[0274] 2) Compound II (4 mmol) was dissolved in acetonitrile (12 mL), cooled to -5 °C, and glacial acetic acid (4 mmol) was added to the solution. Then, while maintaining the temperature at -5 °C, a suspension of sodium borohydride (8.4 mmol) in anhydrous ethanol (9 mL) was slowly added dropwise. After the addition was complete, the mixture was stirred at room temperature for 18 hours. Hydrochloric acid (12 mol / L) was then added to the reaction mixture to quench the reaction. After quenching, the system was heated to 60 °C and maintained for 2 hours. The resulting white precipitate was filtered, and the filtrate was concentrated under vacuum and redissolved in water. Under fully cooled conditions, sodium hydroxide was added to the resulting aqueous solution to adjust the pH to alkaline, yielding a red oily substance. This red oily substance was extracted with diethyl ether, and the solvent was dried. The solvent was then evaporated, and the mixture was dried under vacuum at 60 °C for 6 hours to obtain compound III.

[0275] 3) Anhydrous potassium carbonate (10.5 mmol) and potassium iodide (30 μmol) were suspended in freshly distilled acetonitrile (5 mL). Compound III (3 mmol) was dissolved in freshly distilled acetonitrile (10 mL) and added dropwise to the suspension. N-(2-bromoethyl)phthalimide (3.3 mmol) was added to the resulting suspension. The reaction mixture was refluxed for 24 hours, filtered, and concentrated under vacuum to obtain an oil. The oil was dissolved in dichloromethane (9 mL) and washed successively with saturated sodium bicarbonate solution and water. After removing the solvent by vacuum evaporation, hydrochloric acid (2 mol / L) was added to the resulting oil. This aqueous solution was washed with dichloromethane, and then sodium bicarbonate was added to adjust the pH to alkaline to obtain an orange solid. The solid was extracted with dichloromethane and the solvent was evaporated. Compound IV was purified by column chromatography.

[0276] 4) Compound IV (1 mmol) was dissolved in anhydrous ethanol (5 mL). 1.2 mL of anhydrous ethanol solution of hydrazine hydrate (2 mol / L) was added dropwise to this solution. The mixture was diluted with ethanol and refluxed for 3 hours. The reaction mixture was concentrated under vacuum. Hydrochloric acid (12 mol / L) was added to the residue, precipitating a solid. The suspension was stirred at 50 °C for two hours, then cooled to room temperature and stirred for another 24 hours. After filtration, the filtrate was concentrated under vacuum and dissolved in water. Sodium hydroxide aqueous solution (2 mol / L) was added to the aqueous solution to obtain a red oily substance. The oily substance was extracted with dichloromethane, dried, and the solvent was evaporated. The residue was then dried under vacuum at 50 °C for 6 hours to obtain compound V.

[0277] 5) Add 1.1 mmol of 4-methylbenzaldehyde to a suspension of anhydrous magnesium sulfate (5.5 mmol) in dichloromethane (6 mL), followed by the addition of compound V (1.1 mmol). After mixing, stir at room temperature for 3 hours, filter the suspension, wash the filter cake with dichloromethane, evaporate the solvent, and dry under vacuum at 60 °C for 8 hours to obtain compound I.

[0278] The proton NMR spectrum of compound I is as follows:

[0279] 1 H NMR (400 MHz, CDCl3): δ 8.74 (s, 1H), 8.51 (s, 2H), 7.91 (s, 2H), 7.74 (s, 2H), 7.38 - 7.11 (m, 6H), 3.94 (s, 4H), 3.45 (dt, J = 36.9 Hz, J =4.4 Hz, 2H), 2.76 (dt, J = 35.7 Hz, J = 4.1 Hz 2H), 2.41 (s, 3H).

[0280] (2) Preparation of main catalyst

[0281] Chromium acetylacetone (0.5 mmol) and compound I (0.55 mmol) were heated under reflux in toluene (2 mL) for 24 hours at 80 °C. The solvent was removed under vacuum. The insoluble matter was dissolved in 3.3 mL of methylcyclohexane, and 1.1 mL of diethyl ether was added. The precipitated solid was filtered and then heated under vacuum at 50 °C. o The complex catalyst was obtained by drying at C for 5 hours.

[0282] Example 8

[0283] This embodiment provides a catalyst composition for the selective oligomerization of ethylene according to this application. All synthesis steps are carried out under a nitrogen atmosphere, and the specific steps are as follows:

[0284] (1) Preparation of ligands for the main catalyst

[0285] Add pyridine-2-carboxaldehyde (5 mmol) to a 20 mL suspension of anhydrous magnesium sulfate (25 mmol) in dichloromethane, followed by pyridine-2-methylamine (5 mmol). Mix and stir at room temperature for 3 hours. Filter the suspension, wash the filter cake with dichloromethane, evaporate to remove the solvent, and dry under vacuum at 60 °C for 6 hours to obtain compound II.

[0286] Compound II (4 mmol) was dissolved in acetonitrile (15 mL), cooled to -5 °C, and glacial acetic acid (4 mmol) was added to the solution. Then, while maintaining the solution at -5 °C, a suspension of sodium borohydride (8 mmol) in anhydrous ethanol (9.6 mL) was slowly added dropwise. After the addition was complete, the mixture was stirred at room temperature for 18 hours. Hydrochloric acid (12 mol / L) was then added to the reaction mixture to quench the reaction. After quenching, the system was heated to 60 °C and maintained for 2 hours. The resulting white precipitate was filtered, and the filtrate was concentrated under vacuum and redissolved in water. Under fully cooled conditions, sodium hydroxide was added to the resulting aqueous solution to adjust the pH to alkaline, yielding a red oily substance. This red oily substance was extracted with diethyl ether, and the solvent was dried. The solvent was then evaporated, and the mixture was dried under vacuum at 60 °C for 6 hours to obtain compound III.

[0287] Anhydrous potassium carbonate (10.5 mmol) and potassium iodide (30 μmol) were suspended in freshly distilled acetonitrile (6 mL). Compound III (3 mmol) was dissolved in freshly distilled acetonitrile (12 mL) and added dropwise to the suspension. N-(2-bromoethyl)phthalimide (3.5 mmol) was added to the resulting suspension. The reaction mixture was refluxed for 24 hours, filtered, and concentrated under vacuum to obtain an oil. The oil was dissolved in dichloromethane (12 mL) and washed successively with saturated sodium bicarbonate solution and water. After removing the solvent by vacuum evaporation, hydrochloric acid (2.5 mol / L) was added to the resulting oil. This aqueous solution was washed with dichloromethane, and then sodium bicarbonate was added to adjust the pH to alkalinity to obtain an orange solid. The solid was extracted with dichloromethane, and the solvent was evaporated to remove it. Compound IV was purified by column chromatography.

[0288] Compound IV (2 mmol) was dissolved in anhydrous ethanol (9 mL). 1 mL of anhydrous ethanol solution of hydrazine hydrate (2 mol / L) was added dropwise to this solution. The mixture was diluted with ethanol and refluxed for 3 hours. The reaction mixture was concentrated under vacuum. Hydrochloric acid (12 mol / L) was added to the residue, precipitating a solid. The suspension was stirred at 50 °C for two hours, then cooled to room temperature and stirred for another 24 hours. After filtration, the filtrate was concentrated under vacuum and dissolved in water. Sodium hydroxide aqueous solution (2 mol / L) was added to the aqueous solution to give a red oily substance. The oily substance was extracted with dichloromethane, dried, and the solvent was evaporated. The residue was then dried under vacuum at 50 °C for 6 hours to give compound V.

[0289] 4-Methoxybenzaldehyde (1.1 mmol) was added to a suspension of anhydrous magnesium sulfate (5.5 mmol) in dichloromethane (6 mL), followed by the addition of compound V (1.1 mmol). The mixture was stirred at room temperature for 3 hours, filtered, and the filter cake was washed with dichloromethane. The solvent was evaporated and the mixture was dried under vacuum at 60 °C for 8 hours to obtain compound I.

[0290] The proton NMR spectrum of compound I is as follows:

[0291] 1 H NMR (400 MHz, CDCl3): δ 8.74 (s, 1H), 8.51 (s, 2H), 7.81 - 7.31 (4H),, 7..35 - 7.26 (4H), 7.07 (d, J = 14.8 Hz, 2H), 3.94 (s, 4H), 3.79 (s, 3H), 3.01 (dt, J = 36.1 Hz, J = 4.2 Hz, 2H), 2.78 (dt, J = 35.7 Hz, J = 4.3 Hz, 2H).

[0292] (2) Preparation of main catalyst

[0293] Chromium acetylacetone (0.5 mmol) and compound I (0.6 mmol) were heated under reflux in toluene (2.5 mL) for 24 hours at 80 °C. The solvent was removed under vacuum. The insoluble matter was dissolved in 3 mL of methylcyclohexane, and 2 mL of diethyl ether was added. The precipitated solid was filtered and then heated under vacuum at 50 °C. o The complex catalyst was obtained by drying at C for 5 hours.

[0294] Example 9

[0295] This embodiment provides a catalyst composition for the selective oligomerization of ethylene according to this application. All synthesis steps are carried out under a nitrogen atmosphere, and the specific steps are as follows:

[0296] (1) Preparation of ligands for the main catalyst

[0297] Add pyridine-2-carboxaldehyde (5 mmol) to a 25 mL suspension of anhydrous magnesium sulfate (25 mmol) in dichloromethane, followed by pyridine-2-methylamine (5 mmol). Stir the mixture at room temperature for 3 hours, filter the suspension, wash the filter cake with dichloromethane, evaporate the solvent, and dry under vacuum at 60 °C for 6 hours to obtain compound II.

[0298] Compound II (4 mmol) was dissolved in acetonitrile (12 mL) and cooled to -5 °C. Glacial acetic acid (4 mmol) was added to the solution, followed by the slow addition of a suspension of sodium borohydride (7.2 mmol) in anhydrous ethanol (8 mL) while maintaining the solution at -5 °C. After the addition was complete, the mixture was stirred at room temperature for 18 hours. Hydrochloric acid (12 mol / L) was then added to the reaction mixture to quench the reaction. After quenching, the system was heated to 60 °C and maintained for 2 hours. The resulting white precipitate was filtered off, and the filtrate was concentrated under vacuum and redissolved in water. Under fully cooled conditions, sodium hydroxide was added to the resulting aqueous solution to adjust the pH to alkaline, yielding a red oily substance. This red oily substance was extracted with diethyl ether, and the solvent was dried. The solvent was then evaporated, and the mixture was dried under vacuum at 60 °C for 6 hours to obtain compound III.

[0299] Anhydrous potassium carbonate (10.5 mmol) and potassium iodide (30 μmol) were suspended in freshly distilled acetonitrile (5 mL). Compound III (3 mmol) was dissolved in freshly distilled acetonitrile (10 mL) and added dropwise to the suspension. N-(2-bromoethyl)phthalimide (3.3 mmol) was added to the resulting suspension. The reaction mixture was refluxed for 24 hours, filtered, and concentrated under vacuum to obtain an oil. The oil was dissolved in dichloromethane (10 mL) and washed successively with saturated sodium bicarbonate solution and water. After removing the solvent by vacuum evaporation, hydrochloric acid (2 mol / L) was added to the resulting oil. This aqueous solution was washed with dichloromethane, and then sodium bicarbonate was added to adjust the pH to alkalinity to obtain an orange solid. The solid was extracted with dichloromethane, and the solvent was evaporated to remove it. Compound IV was purified by column chromatography.

[0300] Compound IV (2 mmol) was dissolved in anhydrous ethanol (10 mL). 1.2 mL of anhydrous ethanol solution of hydrazine hydrate (2 mol / L) was added dropwise to this solution. The mixture was diluted with ethanol and refluxed for 3 hours. The reaction mixture was concentrated under vacuum. Hydrochloric acid (12 mol / L) was added to the residue, precipitating a solid. The suspension was stirred at 50 °C for two hours, then cooled to room temperature and stirred for another 24 hours. After filtration, the filtrate was concentrated under vacuum and dissolved in water. Sodium hydroxide aqueous solution (2 mol / L) was added to the aqueous solution to obtain a red oil. The oil was extracted with dichloromethane, dried, and the solvent was evaporated. The residue was then dried under vacuum at 50 °C for 6 hours to obtain compound V.

[0301] 4-Isopropylbenzaldehyde (1 mmol) was added to a suspension of anhydrous magnesium sulfate (4.5 mmol) in dichloromethane (5 mL), followed by the addition of compound V (1 mmol). The mixture was stirred at room temperature for 3 hours, filtered, and the filter cake was washed with dichloromethane. The solvent was evaporated and the mixture was dried under vacuum at 60 °C for 8 hours to obtain compound I.

[0302] The proton NMR spectrum of compound I is as follows:

[0303] 1 H NMR (400 MHz, CDCl3): δ 8.73 (s, 1H), 8.50 (d, J = 4.0 Hz, 2H), 7.95 (d, J = 5.2 Hz, 2H), 7.79 -7.60 (m, 2H), 7.38 - 7.11 (m, 5H), 3.94 (s, 4H), 3.64 (dt, J = 32.9 Hz, J = 3.7 Hz, 2H), 2.99 - 2.90 (m, 1H), 2.78 (dt, J =37.7 Hz, J = 3.9 Hz, 2H), 1.20 (d, J = 8.3 Hz, 6H).

[0304] (2) Preparation of main catalyst

[0305] Chromium acetylacetone (0.5 mmol) and compound I (0.6 mmol) were heated under reflux in toluene (2 mL) for 24 hours at 80 °C. The solvent was removed under vacuum. The insoluble matter was dissolved in 3 mL of methylcyclohexane, and 2 mL of diethyl ether was added. The precipitated solid was filtered and then heated under vacuum at 50 °C. o The complex catalyst was obtained by drying at C for 5 hours.

[0306] Example 10

[0307] This embodiment provides a catalyst composition for the selective oligomerization of ethylene according to this application. All synthesis steps are carried out under a nitrogen atmosphere, and the specific steps are as follows:

[0308] (1) Preparation of ligands for the main catalyst

[0309] Add 5 mmol of pyridine-2-carboxaldehyde to a 20 mL suspension of anhydrous magnesium sulfate (24 mmol) in dichloromethane, followed by 5 mmol of pyridine-2-methylamine. Stir the mixture at room temperature for 3 hours, filter the suspension, wash the filter cake with dichloromethane, evaporate the solvent, and dry under vacuum at 60 °C for 6 hours to obtain compound II.

[0310] Compound II (4 mmol) was dissolved in acetonitrile (12 mL) and cooled to -5 °C. Glacial acetic acid (4 mmol) was added to the solution, followed by the slow addition of a suspension of sodium borohydride (8 mmol) in anhydrous ethanol (7.2 mL) while maintaining the temperature at -5 °C. The mixture was stirred at room temperature for 18 hours after the addition was complete. Hydrochloric acid (12 mol / L) was then added to the reaction mixture to quench the reaction. After quenching, the system was heated to 60 °C and maintained for 2 hours. The resulting white precipitate was filtered off, and the filtrate was concentrated under vacuum and redissolved in water. Under fully cooled conditions, sodium hydroxide was added to the resulting aqueous solution to adjust the pH to alkaline, yielding a red oily substance. This red oily substance was extracted with diethyl ether, and the solvent was dried. The solvent was then evaporated, and the mixture was dried under vacuum at 60 °C for 6 hours to obtain compound III.

[0311] Anhydrous potassium carbonate (10.5 mmol) and potassium iodide (30 μmol) were suspended in freshly distilled acetonitrile (4 mL). Compound III (3 mmol) was dissolved in freshly distilled acetonitrile (8 mL) and added dropwise to the suspension. N-(2-bromoethyl)phthalimide (3.3 mmol) was added to the resulting suspension. The reaction mixture was refluxed for 24 hours, filtered, and concentrated under vacuum to obtain an oil. The oil was dissolved in dichloromethane (9 mL) and washed successively with saturated sodium bicarbonate solution and water. After removing the solvent by vacuum evaporation, hydrochloric acid (2 mol / L) was added to the resulting oil. This aqueous solution was washed with dichloromethane, and then sodium bicarbonate was added to adjust the pH to alkalinity to obtain an orange solid. The solid was extracted with dichloromethane, and the solvent was evaporated to remove it. Compound IV was purified by column chromatography.

[0312] Compound IV (2 mmol) was dissolved in anhydrous ethanol (10 mL). 1.1 mL of anhydrous ethanol solution of hydrazine hydrate (2 mol / L) was added dropwise to this solution. The mixture was diluted with ethanol and refluxed for 3 hours. The reaction mixture was concentrated under vacuum. Hydrochloric acid (12 mol / L) was added to the residue, precipitating a solid. The suspension was stirred at 50 °C for two hours, then cooled to room temperature and stirred for another 24 hours. After filtration, the filtrate was concentrated under vacuum and dissolved in water. Sodium hydroxide aqueous solution (4 mol / L) was added to the aqueous solution to obtain a red oil. The oil was extracted with dichloromethane, dried, and the solvent was evaporated. The residue was then dried under vacuum at 50 °C for 6 hours to obtain compound V.

[0313] 4-tert-butylbenzaldehyde (1 mmol) was added to a suspension of anhydrous magnesium sulfate (4.8 mmol) in dichloromethane (4 mL), followed by the addition of compound V (1 mmol). The mixture was stirred at room temperature for 3 hours, filtered, and the filter cake was washed with dichloromethane. The solvent was evaporated and the mixture was dried under vacuum at 60 °C for 8 hours to obtain compound I.

[0314] The proton NMR spectrum of compound I is as follows:

[0315] 1 H NMR (400 MHz, CDCl3): δ 8.74 (s, 1H), 8.51 (d, 2H), 7.88 (d, J = 12.2Hz 2H), 7.80 - 7.70 (m, 2H), 7.60 - 7.40 (m, 2H), 7.37 - 7.10 (m, 4H), 3.94(s, 4H), 3.10 (dt, J = 34.4 Hz, J = 3.7 Hz, 2H), 2.78 (dt, J = 36.6 Hz, J =3.8 Hz, 2H), 1.33 (s, 9H).

[0316] (2) Preparation of main catalyst

[0317] Chromium acetylacetone (0.5 mmol) and compound I (0.6 mmol) were heated under reflux in toluene (2.5 mL) for 24 hours at 80 °C. The solvent was removed under vacuum. The insoluble matter was dissolved in 3 mL of methylcyclohexane, and 2.2 mL of n-hexane was added. The precipitated solid was filtered and then heated under vacuum at 50 °C. o The complex catalyst was obtained by drying at C for 5 hours.

[0318] Example 11

[0319] This embodiment provides a catalyst composition for the selective oligomerization of ethylene according to this application. All synthesis steps are carried out under a nitrogen atmosphere, and the specific steps are as follows:

[0320] (1) Preparation of ligands for the main catalyst

[0321] Add pyridine-2-carboxaldehyde (5 mmol) to a 25 mL suspension of anhydrous magnesium sulfate (27.5 mmol) in dichloromethane, followed by the addition of pyridine-2-methylamine (5 mmol). After mixing, stir at room temperature for 3 hours. Filter the suspension, wash the filter cake with dichloromethane, evaporate the solvent, and dry under vacuum at 60 °C for 6 hours to obtain compound II.

[0322] Compound II (4 mmol) was dissolved in acetonitrile (16 mL), cooled to -5 °C, and glacial acetic acid (4 mmol) was added to the solution. Then, while maintaining the solution at -5 °C, a suspension of sodium borohydride (8 mmol) in anhydrous ethanol (9.6 mL) was slowly added dropwise. After the addition was complete, the mixture was stirred at room temperature for 18 hours. Hydrochloric acid (12 mol / L) was then added to the reaction mixture to quench the reaction. After quenching, the system was heated to 60 °C and maintained for 2 hours. The resulting white precipitate was filtered, and the filtrate was concentrated under vacuum and redissolved in water. Under fully cooled conditions, sodium hydroxide was added to the resulting aqueous solution to adjust the pH to alkaline, yielding a red oily substance. This red oily substance was extracted with diethyl ether, and the solvent was dried. The solvent was then evaporated, and the mixture was dried under vacuum at 60 °C for 6 hours to obtain compound III.

[0323] Anhydrous potassium carbonate (10.5 mmol) and potassium iodide (30 μmol) were suspended in freshly distilled acetonitrile (6 mL). Compound III (3 mmol) was dissolved in freshly distilled acetonitrile (12 mL) and added dropwise to the suspension. N-(2-bromoethyl)phthalimide (3.6 mmol) was added to the resulting suspension. The reaction mixture was refluxed for 24 hours, filtered, and concentrated under vacuum to obtain an oil. The oil was dissolved in dichloromethane (12 mL) and washed successively with saturated sodium bicarbonate solution and water. After removing the solvent by vacuum evaporation, hydrochloric acid (2 mol / L) was added to the resulting oil. This aqueous solution was washed with dichloromethane, and then sodium bicarbonate was added to adjust the pH to alkalinity to obtain an orange solid. The solid was extracted with dichloromethane, and the solvent was evaporated to remove it. Compound IV was purified by column chromatography.

[0324] Compound IV (2 mmol) was dissolved in anhydrous ethanol (10 mL). 1.2 mL of anhydrous ethanol solution of hydrazine hydrate (2 mol / L) was added dropwise to this solution. The mixture was diluted with ethanol and refluxed for 3 hours. The reaction mixture was concentrated under vacuum. Hydrochloric acid (12 mol / L) was added to the residue, precipitating a solid. The suspension was stirred at 50 °C for two hours, then cooled to room temperature and stirred for another 24 hours. After filtration, the filtrate was concentrated under vacuum and dissolved in water. Sodium hydroxide aqueous solution (3 mol / L) was added to the aqueous solution to obtain a red oil. The oil was extracted with dichloromethane, dried, and the solvent was evaporated. The residue was then dried under vacuum at 50 °C for 6 hours to obtain compound V.

[0325] 1 mmol of 4-nitrobenzaldehyde was added to a suspension of anhydrous magnesium sulfate (5.5 mmol) in dichloromethane (5 mL), followed by the addition of compound V (1 mmol). The mixture was stirred at room temperature for 3 hours, filtered, and the filter cake was washed with dichloromethane. The solvent was evaporated and the mixture was dried under vacuum at 60 °C for 8 hours to obtain compound I.

[0326] The proton NMR spectrum of compound I is as follows:

[0327] 1 H NMR (400 MHz, CDCl3): δ 8.74 (s, 1H), 8.51 (d, J = 14.4 Hz, 2H), 8.40- 8.20 (m, 2H), 8.20 - 8.00 (m, 2H), 7.85 - 7.60 (m, 2H), 7.40 - 7.10(m, 4H), 3.94 (s, 4H), 3.06 (dt, J = 35.2 Hz, J = 4.0 Hz, 2H), 2.78 (dt, J = 36.0 Hz, J = 4.4 Hz, 2H).

[0328] (2) Preparation of main catalyst

[0329] Chromium acetylacetone (0.5 mmol) and compound I (0.6 mmol) were heated under reflux in toluene (2 mL) for 24 hours at 80 °C. The solvent was removed under vacuum. The insoluble matter was dissolved in 3 mL of methylcyclohexane, and 2.2 mL of petroleum ether was added. The precipitated solid was filtered and then heated under vacuum at 50 °C. o The complex catalyst was obtained by drying at C for 5 hours.

[0330] Example 12

[0331] This embodiment provides a catalyst composition for the selective oligomerization of ethylene according to this application. All synthesis steps are carried out under a nitrogen atmosphere, and the specific steps are as follows:

[0332] (1) Preparation of ligands for the main catalyst

[0333] Add pyridine-2-carboxaldehyde (5 mmol) to a 25 mL suspension of anhydrous magnesium sulfate (22 mmol) in dichloromethane, followed by pyridine-2-methylamine (5 mmol). Mix and stir at room temperature for 3 hours. Filter the suspension, wash the filter cake with dichloromethane, evaporate to remove the solvent, and dry under vacuum at 60 °C for 6 hours to obtain compound II.

[0334] Compound II (4 mmol) was dissolved in acetonitrile (12 mL) and cooled to -5 °C. Glacial acetic acid (4 mmol) was added to the solution, followed by the slow addition of a suspension of sodium borohydride (8 mmol) in anhydrous ethanol (8 mL) while maintaining the solution at -5 °C. After the addition was complete, the mixture was stirred at room temperature for 18 hours. Hydrochloric acid (12 mol / L) was then added to the reaction mixture to quench the reaction. After quenching, the system was heated to 60 °C and maintained for 2 hours. The resulting white precipitate was filtered off, and the filtrate was concentrated under vacuum and redissolved in water. Under fully cooled conditions, sodium hydroxide was added to the resulting aqueous solution to adjust the pH to alkaline, yielding a red oily substance. This red oily substance was extracted with diethyl ether, and the solvent was dried. The solvent was then evaporated, and the mixture was dried under vacuum at 60 °C for 6 hours to obtain compound III.

[0335] Anhydrous potassium carbonate (10.5 mmol) and potassium iodide (30 μmol) were suspended in freshly distilled acetonitrile (4 mL). Compound III (3 mmol) was dissolved in freshly distilled acetonitrile (8 mL) and added dropwise to the suspension. N-(2-bromoethyl)phthalimide (3.3 mmol) was added to the resulting suspension. The reaction mixture was refluxed for 24 hours, filtered, and concentrated under vacuum to obtain an oil. The oil was dissolved in dichloromethane (12 mL) and washed successively with saturated sodium bicarbonate solution and water. After removing the solvent by vacuum evaporation, hydrochloric acid (2 mol / L) was added to the resulting oil. This aqueous solution was washed with dichloromethane, and then sodium bicarbonate was added to adjust the pH to alkalinity to obtain an orange solid. The solid was extracted with dichloromethane, and the solvent was evaporated to remove it. Compound IV was purified by column chromatography.

[0336] Compound IV (2 mmol) was dissolved in anhydrous ethanol (10 mL). 1.1 mL of anhydrous ethanol solution of hydrazine hydrate (2 mol / L) was added dropwise to this solution. The mixture was diluted with ethanol and refluxed for 3 hours. The reaction mixture was concentrated under vacuum. Hydrochloric acid (12 mol / L) was added to the residue, precipitating a solid. The suspension was stirred at 50 °C for two hours, then cooled to room temperature and stirred for another 24 hours. After filtration, the filtrate was concentrated under vacuum and dissolved in water. Sodium hydroxide aqueous solution (2 mol / L) was added to the aqueous solution to obtain a red oil. The oil was extracted with dichloromethane, dried, and the solvent was evaporated. The residue was then dried under vacuum at 50 °C for 6 hours to obtain compound V.

[0337] 4-Phenylacetaldehyde (1 mmol) was added to a suspension of anhydrous magnesium sulfate (5 mmol) in dichloromethane (4 mL), followed by the addition of compound V (1 mmol). The mixture was stirred at room temperature for 3 hours, filtered, and the filter cake was washed with dichloromethane. The solvent was evaporated and the mixture was dried under vacuum at 60 °C for 8 hours to obtain compound I.

[0338] The proton NMR spectrum of compound I is as follows:

[0339] 1 H NMR (400 MHz, CDCl3): δ 8.72 (s, 1H), 8.60 - 8.20 (m, 2H), 8.00 -7.85 (m, 2H), 7.80 - 7.57 (m, 6H), 7.47 - 7.38 (m, 3H), 7.30 - 7.20 (m, 3H), 3.93 (s, 4H), 3.58 (dt, J = 36.2 Hz, J = 3.8 Hz, 2H), 2.79 (dt, J = 36.0 Hz, J = 4.4 Hz, 2H).

[0340] (2) Preparation of main catalyst

[0341] Chromium acetylacetone (0.5 mmol) and compound I (0.55 mmol) were heated under reflux in toluene (2.5 mL) for 24 hours at 80 °C. The solvent was removed under vacuum. The insoluble matter was dissolved in 2 mL of methylcyclohexane, and 1.5 mL of diethyl ether was added. The precipitated solid was filtered and then heated under vacuum at 50 °C. o The complex catalyst was obtained by drying at C for 5 hours.

[0342] Example 13

[0343] This embodiment provides a catalyst composition for selective oligomerization of ethylene according to this application. The preparation steps are the same as in Example 2, except that the preparation steps of the main catalyst are as follows:

[0344] Chromium acetylacetone (0.5 mmol) and compound I (0.6 mmol) were heated under reflux in toluene (2.5 mL) for 24 hours at 80 °C. The solvent was removed under vacuum. The insoluble matter was dissolved in 3.0 mL of methylcyclohexane, and 2.4 mL of cyclohexane was added. The precipitated solid was filtered and heated under vacuum at 50 °C. o The complex catalyst was obtained by drying at C for 5 hours.

[0345] Example 14

[0346] This embodiment provides a catalyst composition for the selective oligomerization of ethylene according to this application. All synthesis steps are carried out under a nitrogen atmosphere, and the specific steps are as follows:

[0347] (1) Preparation of ligands for the main catalyst

[0348] Pyridine-2-carboxaldehyde (5 mmol) was added to a 25 mL suspension of anhydrous magnesium sulfate (27.5 mmol) in dichloromethane, followed by the addition of N-methylindole-2-methylamine (5 mmol). The mixture was stirred at room temperature for 3 hours, filtered, and the filter cake was washed with dichloromethane. The solvent was evaporated and the mixture was dried under vacuum at 60 °C for 6 hours to obtain compound II.

[0349] Compound II (4 mmol) was dissolved in acetonitrile (12 mL) and cooled to -5 °C. Glacial acetic acid (4 mmol) was added to the solution, followed by the slow addition of a suspension of sodium borohydride (8 mmol) in anhydrous ethanol (9.6 mL) while maintaining the temperature at -5 °C. The mixture was stirred at room temperature for 18 hours after the addition was complete. Hydrochloric acid (12 mol / L) was then added to the reaction mixture to quench the reaction. After quenching, the system was heated to 60 °C and maintained for 2 hours. The resulting white precipitate was filtered off, and the filtrate was concentrated under vacuum and redissolved in water. Under fully cooled conditions, sodium hydroxide was added to the resulting aqueous solution to adjust the pH to alkaline, yielding a red oily substance. This red oily substance was extracted with diethyl ether, and the solvent was dried. The solvent was then evaporated, and the mixture was dried under vacuum at 60 °C for 6 hours to obtain compound III.

[0350] Anhydrous potassium carbonate (10.5 mmol) and potassium iodide (30 μmol) were suspended in freshly distilled acetonitrile (5 mL). Compound III (3 mmol) was dissolved in freshly distilled acetonitrile (10 mL) and added dropwise to the suspension. N-(2-bromoethyl)phthalimide (3.5 mmol) was added to the resulting suspension. The reaction mixture was refluxed for 24 hours, filtered, and concentrated under vacuum to obtain an oil. The oil was dissolved in dichloromethane (9 mL) and washed successively with saturated sodium bicarbonate solution and water. After removing the solvent by vacuum evaporation, hydrochloric acid (2 mol / L) was added to the resulting oil. This aqueous solution was washed with dichloromethane, and then sodium bicarbonate was added to adjust the pH to alkalinity to obtain an orange solid. The solid was extracted with dichloromethane, and the solvent was evaporated to remove it. Compound IV was purified by column chromatography.

[0351] Compound IV (2 mmol) was dissolved in anhydrous ethanol (8 mL). 1.1 mL of anhydrous ethanol solution of hydrazine hydrate (2 mol / L) was added dropwise to this solution. The mixture was diluted with ethanol and refluxed for 3 hours. The reaction mixture was concentrated under vacuum. Hydrochloric acid (12 mol / L) was added to the residue, precipitating a solid. The suspension was stirred at 50 °C for two hours, then cooled to room temperature and stirred for another 24 hours. After filtration, the filtrate was concentrated under vacuum and dissolved in water. Sodium hydroxide aqueous solution (2 mol / L) was added to the aqueous solution to obtain a red oil. The oil was extracted with dichloromethane, dried, and the solvent was evaporated. The residue was then dried under vacuum at 50 °C for 6 hours to obtain compound V.

[0352] Benzaldehyde (1 mmol) was added to a suspension of anhydrous magnesium sulfate (5 mmol) in dichloromethane (5 mL), followed by the addition of compound V (1 mmol). The mixture was stirred at room temperature for 3 hours, filtered, and the filter cake was washed with dichloromethane. The solvent was evaporated and the mixture was dried under vacuum at 60 °C for 8 hours to obtain compound I.

[0353] The proton NMR spectrum of compound I is as follows:

[0354] 1 H NMR (400 MHz, CDCl3): δ 8.74 (s, 1H), 8.53 (d, J = 3.1 Hz, 1H), 8.50 (d, J = 2.9 Hz, 1H), 7.82 - 6.87 (m, 13H), 6.30 (s, 1H), 3.94 (s, 1H), 3.70 -3.59 (m, 5H), 2.90 - 2.75 (m, 4H).

[0355] (2) Preparation of main catalyst

[0356] Chromium acetylacetone (0.5 mmol) and compound I (0.6 mmol) were heated under reflux in toluene (2.5 mL) for 24 hours at 80 °C. The solvent was removed under vacuum. The insoluble matter was dissolved in 3 mL of methylcyclohexane, and 2.2 mL of n-hexane was added. The precipitated solid was filtered and then heated under vacuum at 50 °C. o The complex catalyst was obtained by drying at C for 5 hours.

[0357] Example 15

[0358] This embodiment provides a catalyst composition for selective oligomerization of ethylene according to this application. The preparation steps are the same as in Example 4, except that the preparation steps of the main catalyst are as follows:

[0359] Chromium acetylacetone (0.5 mmol) and compound I (0.6 mmol) were heated under reflux in toluene (3 mL) for 24 hours at 80 °C. The solvent was removed under vacuum. The insoluble matter was dissolved in 3 mL of methylcyclohexane, and 2.4 mL of diethyl ether was added. The precipitated solid was filtered and then heated under vacuum at 50 °C. o The complex catalyst was obtained by drying at C for 5 hours.

[0360] Example 16

[0361] This embodiment provides a catalyst composition for the selective oligomerization of ethylene according to this application. All synthesis steps are carried out under a nitrogen atmosphere, and the specific steps are as follows:

[0362] (1) Preparation of ligands for the main catalyst

[0363] Add pyridine-2-carboxaldehyde (5 mmol) to a 25 mL suspension of anhydrous magnesium sulfate (22 mmol) in dichloromethane, followed by the addition of N-methylpyrrole-2-methylamine (5 mmol). After mixing, stir at room temperature for 3 hours. Filter the suspension, wash the filter cake with dichloromethane, evaporate to remove the solvent, and dry under vacuum at 60 °C for 6 hours to obtain compound II.

[0364] Compound II (4 mmol) was dissolved in acetonitrile (15 mL) and cooled to -5 °C. Glacial acetic acid (4 mmol) was added to the solution, followed by the slow addition of a suspension of sodium borohydride (7.2 mmol) in anhydrous ethanol (8 mL) while maintaining the solution at -5 °C. After the addition was complete, the mixture was stirred at room temperature for 18 hours. Hydrochloric acid (12 mol / L) was then added to the reaction mixture to quench the reaction. After quenching, the system was heated to 60 °C and maintained for 2 hours. The resulting white precipitate was filtered off, and the filtrate was concentrated under vacuum and redissolved in water. Under fully cooled conditions, sodium hydroxide was added to the resulting aqueous solution to adjust the pH to alkaline, yielding a red oily substance. This red oily substance was extracted with diethyl ether, and the solvent was dried. The solvent was then evaporated, and the mixture was dried under vacuum at 60 °C for 6 hours to obtain compound III.

[0365] Anhydrous potassium carbonate (10.5 mmol) and potassium iodide (30 μmol) were suspended in freshly distilled acetonitrile (4 mL). Compound III (3 mmol) was dissolved in freshly distilled acetonitrile (8 mL) and added dropwise to the suspension. N-(2-bromoethyl)phthalimide (3.6 mmol) was added to the resulting suspension. The reaction mixture was refluxed for 24 hours, filtered, and concentrated under vacuum to obtain an oil. The oil was dissolved in dichloromethane (12 mL) and washed successively with saturated sodium bicarbonate solution and water. After removing the solvent by vacuum evaporation, hydrochloric acid (2 mol / L) was added to the resulting oil. This aqueous solution was washed with dichloromethane, and then sodium bicarbonate was added to adjust the pH to alkalinity to obtain an orange solid. The solid was extracted with dichloromethane, and the solvent was evaporated to remove it. Compound IV was purified by column chromatography.

[0366] Compound IV (2 mmol) was dissolved in anhydrous ethanol (10 mL). 1.1 mL of anhydrous ethanol solution of hydrazine hydrate (2 mol / L) was added dropwise to this solution. The mixture was diluted with ethanol and refluxed for 3 hours. The reaction mixture was concentrated under vacuum. Hydrochloric acid (12 mol / L) was added to the residue, precipitating a solid. The suspension was stirred at 50 °C for two hours, then cooled to room temperature and stirred for another 24 hours. After filtration, the filtrate was concentrated under vacuum and dissolved in water. Sodium hydroxide aqueous solution (2 mol / L) was added to the aqueous solution to obtain a red oil. The oil was extracted with dichloromethane, dried, and the solvent was evaporated. The residue was then dried under vacuum at 50 °C for 6 hours to obtain compound V.

[0367] Benzaldehyde (1 mmol) was added to a suspension of anhydrous magnesium sulfate (4.5 mmol) in dichloromethane (4 mL), followed by the addition of compound V (1 mmol). The mixture was stirred at room temperature for 3 hours, filtered, and the filter cake was washed with dichloromethane. The solvent was evaporated and the mixture was dried under vacuum at 60 °C for 8 hours to obtain compound I.

[0368] The proton NMR spectrum of compound I is as follows:

[0369] 1 H NMR (400 MHz, CDCl3): δ 8.74 (s, 1H), 8.52 (d, J = 3.1 Hz, 1H), 8.49 (d, J = 2.9 Hz, 1H), 7.88 - 7.34 (m, 6H), 7.29 - 7.10 (m, 4H), 6.49 - 6.21 (m, 3H), 3.94 (s, 1H), 3.70 - 3.52 (m, 4H), 2.90 - 2.70 (m, 4H).

[0370] (2) Preparation of main catalyst

[0371] Chromium acetylacetone (0.5 mmol) and compound I (0.6 mmol) were heated under reflux in toluene (2 mL) for 24 hours at 80 °C. The solvent was removed under vacuum. The insoluble matter was dissolved in 2.5 mL of methylcyclohexane, and 1.8 mL of cyclohexane was added. The precipitated solid was filtered and then heated under vacuum at 50 °C. o The complex catalyst was obtained by drying at C for 5 hours.

[0372] Example 17

[0373] This embodiment provides a catalyst composition for selective oligomerization of ethylene according to this application. The preparation steps are the same as in Example 6, except that the preparation steps of the main catalyst are as follows:

[0374] Chromium acetylacetone (0.5 mmol) and compound I (0.6 mmol) were heated under reflux in toluene (2.5 mL) for 24 hours at 80 °C. The solvent was removed under vacuum. The insoluble matter was dissolved in 3 mL of methylcyclohexane, and 2.4 mL of petroleum ether was added. The precipitated solid was filtered and then heated under vacuum at 50 °C. o The complex catalyst was obtained by drying at C for 5 hours.

[0375] Example 18

[0376] This embodiment provides a catalyst composition for the selective oligomerization of ethylene according to this application. All synthesis steps are carried out under a nitrogen atmosphere, and the specific steps are as follows:

[0377] (1) Preparation of ligands for the main catalyst

[0378] 1,4-pyrazin-2-carboxaldehyde (5 mmol) was added to a 20 mL suspension of anhydrous magnesium sulfate (27.5 mmol) in dichloromethane, followed by the addition of pyridine-2-methylamine (5 mmol). The mixture was stirred at room temperature for 3 hours, filtered, and the filter cake was washed with dichloromethane. The solvent was evaporated and the mixture was dried under vacuum at 60 °C for 6 hours to obtain compound II.

[0379] Compound II (4 mmol) was dissolved in acetonitrile (16 mL) and cooled to -5 °C. Glacial acetic acid (4 mmol) was added to the solution, followed by the slow addition of a suspension of sodium borohydride (8.8 mmol) in anhydrous ethanol (10.5 mL) while maintaining the temperature at -5 °C. After the addition was complete, the mixture was stirred at room temperature for 18 hours. Hydrochloric acid (12 mol / L) was then added to the reaction mixture to quench the reaction. After quenching, the system was heated to 60 °C and maintained for 2 hours. The resulting white precipitate was filtered off, and the filtrate was concentrated under vacuum and redissolved in water. Under fully cooled conditions, sodium hydroxide was added to the resulting aqueous solution to adjust the pH to alkaline, yielding a red oily substance. This red oily substance was extracted with diethyl ether, and the solvent was dried. The solvent was then evaporated, and the mixture was dried under vacuum at 60 °C for 6 hours to obtain compound III.

[0380] Anhydrous potassium carbonate (10.5 mmol) and potassium iodide (30 μmol) were suspended in freshly distilled acetonitrile (6 mL). Compound III (3 mmol) was dissolved in freshly distilled acetonitrile (12 mL) and added dropwise to the suspension. N-(2-bromoethyl)phthalimide (3.6 mmol) was added to the resulting suspension. The reaction mixture was refluxed for 24 hours, filtered, and concentrated under vacuum to obtain an oil. The oil was dissolved in dichloromethane (12 mL) and washed successively with saturated sodium bicarbonate solution and water. After removing the solvent by vacuum evaporation, hydrochloric acid (2 mol / L) was added to the resulting oil. This aqueous solution was washed with dichloromethane, and then sodium bicarbonate was added to adjust the pH to alkalinity to obtain an orange solid. The solid was extracted with dichloromethane, and the solvent was evaporated to remove it. Compound IV was purified by column chromatography.

[0381] Compound IV (2 mmol) was dissolved in anhydrous ethanol (10 mL). 1.2 mL of anhydrous ethanol solution of hydrazine hydrate (2 mol / L) was added dropwise to this solution. The mixture was diluted with ethanol and refluxed for 3 hours. The reaction mixture was concentrated under vacuum. Hydrochloric acid (12 mol / L) was added to the residue, precipitating a solid. The suspension was stirred at 50 °C for two hours, then cooled to room temperature and stirred for another 24 hours. After filtration, the filtrate was concentrated under vacuum and dissolved in water. Sodium hydroxide aqueous solution (2 mol / L) was added to the aqueous solution to obtain a red oil. The oil was extracted with dichloromethane, dried, and the solvent was evaporated. The residue was then dried under vacuum at 50 °C for 6 hours to obtain compound V.

[0382] 4-Methylbenzaldehyde (1 mmol) was added to a suspension of anhydrous magnesium sulfate (5.5 mmol) in dichloromethane (6 mL), followed by the addition of compound V (1 mmol). The mixture was stirred at room temperature for 3 hours, filtered, and the filter cake was washed with dichloromethane. The solvent was evaporated and the mixture was dried under vacuum at 60 °C for 8 hours to obtain compound I.

[0383] The proton NMR spectrum of compound I is as follows:

[0384] 1 H NMR (400 MHz, CDCl3): δ 8.74 (s, 1H), 8.65 - 8.45 (m, 4H), 7.98 -7.15 (m, 7H), 4.05 - 3.56 (m, 6H), 2.80 - 2.61 (m, 2H), 2.41 (s, 3H).

[0385] (2) Preparation of main catalyst

[0386] Chromium acetylacetone (0.5 mmol) and compound I (0.6 mmol) were heated under reflux in toluene (2 mL) for 24 hours at 80 °C. The solvent was removed under vacuum. The insoluble matter was dissolved in 3.6 mL of methylcyclohexane, and 2.4 mL of diethyl ether was added. The precipitated solid was filtered and then heated under vacuum at 50 °C. o The complex catalyst was obtained by drying at C for 5 hours.

[0387] Example 19

[0388] This embodiment provides a catalyst composition for selective oligomerization of ethylene according to this application. The preparation steps are the same as in Example 18, except that the preparation steps of the main catalyst are as follows:

[0389] Chromium acetylacetone (0.5 mmol) and compound I (0.6 mmol) were heated under reflux in toluene (3 mL) for 24 hours at 80 °C. The solvent was removed under vacuum. The insoluble matter was dissolved in 3.5 mL of methylcyclohexane, and 2 mL of n-hexane was added. The precipitated solid was filtered and then heated under vacuum at 50 °C. o The complex catalyst was obtained by drying at C for 5 hours.

[0390] Example 20

[0391] This embodiment provides a catalyst composition for the selective oligomerization of ethylene according to this application. All synthesis steps are carried out under a nitrogen atmosphere, and the specific steps are as follows:

[0392] The preparation method is the same as in Example 1, except that chromium acetylacetone is replaced with an equimolar amount of chromium trichloride tris(tetrahydrofuran).

[0393] Example 21

[0394] This embodiment provides a catalyst composition for the selective oligomerization of ethylene according to this application. All synthesis steps are carried out under a nitrogen atmosphere, and the specific steps are as follows:

[0395] The preparation method is the same as in Example 1, except that chromium acetylacetone is replaced with an equimolar amount of nickel chloride.

[0396] Comparative Example 1

[0397] This comparative example provides another catalyst composition for the selective oligomerization of ethylene, and all synthesis steps are carried out under a nitrogen atmosphere, as follows:

[0398] (1) Preparation of ligands for the main catalyst

[0399] Commercially available iPr-PNP (shown in Formula A) was used as the ligand;

[0400] .

[0401] (2) Preparation of main catalyst

[0402] Chromium acetylacetone (0.5 mmol) and iPr-PNP (0.6 mmol) were heated under reflux in toluene (2.5 mL) for 24 hours at 80 °C. The filtrate was removed under vacuum, and the insoluble matter was dried under vacuum to obtain the main catalyst MET.1.

[0403] Comparative Example 2

[0404] This comparative example provides another catalyst composition for the selective oligomerization of ethylene, and all synthesis steps are carried out under a nitrogen atmosphere, as follows:

[0405] (1) Preparation of ligands for the main catalyst

[0406] Using commercially available iPr-PNP-F (as shown in Formula B) as the ligand,

[0407] .

[0408] (2) Preparation of main catalyst

[0409] Chromium acetylacetone (0.08 mmol) and iPr-PNP-F (0.08 mmol) were heated under reflux in toluene for 24 hours at 80 °C. The filtrate was removed under vacuum, and the insoluble matter was dried under vacuum to obtain the main catalyst MET.2.

[0410] Comparative Example 3

[0411] This comparative example provides another catalyst composition for the selective oligomerization of ethylene, and all synthesis steps are carried out under a nitrogen atmosphere, as follows:

[0412] (1) Preparation of ligands for the main catalyst

[0413] The ligands provided in this comparative example were obtained by referring to the synthesis scheme of ligand L1 in J. Catal., 394, 444-450, and their structures are shown in Formula C.

[0414] .

[0415] (2) Preparation of main catalyst

[0416] Chromium acetylacetone (0.5 mmol) and ligand C (0.6 mmol) were heated under reflux in toluene for 24 hours at 80 °C. The filtrate was removed under vacuum, and the insoluble matter was dried under vacuum to obtain the main catalyst MET.3.

[0417] Comparative Example 4

[0418] This comparative example provides another catalyst composition for the selective oligomerization of ethylene, and all synthesis steps are carried out under a nitrogen atmosphere, as follows:

[0419] (1) Preparation of ligands for the main catalyst

[0420] The ligands provided in this comparative example were obtained by referring to the synthesis scheme of ligand L1 in Dalton Trans., 45, 17020-17209, and their structures are shown in Formula D.

[0421] .

[0422] (2) Preparation of main catalyst

[0423] Chromium acetylacetone (0.5 mmol) and ligand D (0.6 mmol) were heated under toluene and refluxed for 24 hours at 80 °C. The filtrate was removed under vacuum, and the insoluble matter was dried under vacuum to obtain the main catalyst MET.4.

[0424] The structures of the intermediates (compounds II, III, IV, and V) and ligands (compound I) obtained in each example are summarized in Tables 1-3.

[0425] Table 1. Intermediates for Examples 1-8, 13, 15, 17, and 20-21

[0426]

[0427] Table 2 Intermediates for Examples 9-12, 14, 16, and 18-19

[0428]

[0429] Table 3. Ligands (Compound I) for Examples 1-21

[0430]

[0431] II. Preparation of 1-Octenene

[0432] The catalyst compositions prepared in Examples 1-21 and Comparative Examples 1-4 were subjected to ethylene oligomerization catalytic activity tests, and were respectively recorded as Application Examples 1-21 and Application Comparative Examples 1-4. The reaction conditions in each application example are shown in Table 4.

[0433] Ethylene oligomerization was carried out in a 500 mL high-pressure reactor. The reactor was heated to 120 °C and evacuated for 3 hours. After several nitrogen purgings, ethylene was introduced and the reactor cooled to room temperature. 200 mL of methylcyclohexane was then added to the reactor, followed by the main catalyst and modified methylaluminoxane. The mixture was subjected to ethylene oligomerization at 90 °C–100 °C and 4.0 MPa–6.0 MPa for 60 min. The molar concentration of the complex in the system was 1 μmol / mL (calculated as chromium). The amount of modified methylaluminoxane used is shown in Table 4 (calculated as Al / M molar ratio). M represents Cr or Ni.

[0434] Table 4. Application Examples: Distribution of Oligomerization Products and Catalyst Activity

[0435]

[0436] As shown in Table 4, the catalyst compositions of the embodiments of this application exhibit lower polymer selectivity (below 1.0%) compared to the comparative examples, but also higher yields, with a 1-octene selectivity exceeding 60%. Furthermore, the catalyst compositions of the embodiments of this application also possess high reactivity, reaching 600 kg / (g·Cr·h) or higher (superior to commercial catalysts in the art). In some preferred embodiments, the catalyst compositions of the embodiments of this application achieve reactivity exceeding 900 kg / (g·Cr·h), with a polymer selectivity below 0.9%, and even better 1-octene selectivity, reaching 69% or higher.

[0437] As can be seen from Table 4, the catalyst compositions of the examples all reacted at high temperatures and maintained good activity and selectivity, showing potential for industrial application.

[0438] The technical features of the above-described embodiments and examples can be combined in any suitable manner. For the sake of brevity, not all possible combinations of the technical features in the above-described embodiments and examples are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0439] The embodiments described above merely illustrate several implementation methods of this application and should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Furthermore, it should be understood that after reading the above teachings, those skilled in the art can make various alterations or modifications to this application, and the equivalent forms obtained also fall within the protection scope of this application. It should also be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the protection scope of the appended claims. Therefore, the protection scope of this patent application should be determined by the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A catalyst composition for the selective oligomerization of ethylene, characterized in that, The main catalyst and the cocatalyst; The main catalyst comprises a complex; The ligand of the complex is a compound shown in formula (I), and the coordination metal is a metal element of Group VIB-VIII; （Ⅰ）； A1 and A2 are independently selected from substituted or unsubstituted C3-C, respectively. 10 Mixed aromatics; R1is selected from hydrogen, nitro, C1-C9alkyl, C1-C9alkoxy or C6-C 20 aryl; R2 is absent or selected from C1-C9 alkyl; R3 is absent or selected from hydrogen; The cocatalyst comprises an organic compound containing aluminum element.

2. The catalyst composition for the selective oligomerization of ethylene according to claim 1, characterized by the fact that, The molar ratio of the coordination metal in the main catalyst to the aluminum element in the cocatalyst is 1:(500-1000).

3. The catalyst composition for the selective oligomerization of ethylene according to claim 1, characterized by the fact that, A1 and A2 are each independently selected from substituted or unsubstituted pyridine, quinoline, indole, oxazole, pyrrole or 1,4-pyrazine; and / or, the substitution is substituted by C1-C4 alkyl; and / or, R1is selected from hydrogen, nitro, C1-C4alkyl, C1-C4alkoxy or C6-C 10 aryl; and / or, R2 is absent or selected from C1-C4 alkyl.

4. The catalyst composition for the selective oligomerization of ethylene according to claim 1, characterized by the fact that, The complex further comprises a coordination anion, and the coordination anion comprises at least one of an organic anion and an inorganic anion.

5. The catalyst composition for the selective oligomerization of ethylene according to claim 4, characterized by the fact that, The organic anion comprises at least one of acetate ion, benzoate ion and negative ion of acetylacetone; and / or, The inorganic anion comprises at least one of nitrate ion, sulfate ion and halogen ion.

6. The catalyst composition for the selective oligomerization of ethylene according to claim 1, characterized by the fact that, The organic compound containing aluminum element comprises at least one of trimethylaluminum, triethylaluminum, dichlorodiethylaluminum, tributylaluminum, triisobutylaluminum, tripropylaluminum, trioctylaluminum, dimethylaluminum chloride, dimethylisobutylaluminum, dimethylethylaluminum, triphenylaluminum, triisopropylaluminum, tri-sec-butylaluminum, ethyldimethylaluminum, methylaluminoxane and modified methylaluminoxane.

7. The catalyst composition for the selective oligomerization of ethylene according to any one of claims 1 to 6, characterized in that, The preparation method of the complex comprises the following steps: Mixing the ligand, the transition metal compound and the first organic solvent to obtain a mixed solution; Performing a hot reflux reaction on the mixed solution; After the hot reflux reaction is completed, removing the solvent in the reaction solution to obtain a solid; Dissolving the solid with methylcyclohexane, adding a non-polar solvent to the obtained dissolving solution to perform recrystallization, and preparing the complex; The transition metal compound is a salt containing a metal element of Group VIB-VIII.

8. A process for the preparation of α-olefins, characterized in that, The method comprises the following steps: Performing selective oligomerization of ethylene in the presence of a catalyst to prepare the α-olefin; The catalyst comprises the catalyst composition for selective oligomerization of ethylene according to any one of claims 1-7.

9. The method of producing an alpha-olefin according to claim 8, wherein The step of performing oligomerization of ethylene in the presence of a catalyst comprises: Mixing the ethylene, the catalyst and the second organic solvent to obtain a mixed solution; Reacting the mixed solution at a first temperature and a first pressure for a first time; The first temperature is 90-110°C, the first pressure is 0.1-10 MPa, and the first time is 1-120 min.

10. The method of producing an α-olefin according to claim 9, wherein In the mixed solution, the amount of the catalyst is 2-4 μmol / mL in terms of the molar concentration of the coordination metal element in the main catalyst.

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