Ligand compounds, catalyst compositions, ethylene oligomerization reaction catalysts, and ethylene oligomerization processes

Abstract

This invention relates to the field of ethylene oligomerization catalyst technology, and discloses ligand compounds, catalyst compositions, ethylene oligomerization reaction catalysts, and ethylene oligomerization methods. The ligand compounds have the structure shown in formula (1), where Ar1 and Ar2 are each independently selected from substituted or unsubstituted aryl groups and substituted or unsubstituted heteroaryl groups; R1 to R4 are each independently selected from hydrogen, C... 1‑15 Hydrocarbon group, substituted or unsubstituted C 1‑15 Hydrocarbon group, substituted or unsubstituted C 1‑15 The catalyst system provided by this invention features high selective oligomerization activity for ethylene and high selectivity for 1-hexene and 1-octene. It includes heteroalkyl groups, substituted or unsubstituted aryl groups, and R3 and R4 may be cyclic or non-cyclic.

Description

Technical Field

[0001] This invention relates to the field of ethylene oligomerization catalyst technology, specifically to ligand compounds, catalyst compositions, ethylene oligomerization reaction catalysts, and ethylene oligomerization methods. Background Technology

[0002] Linear alpha-olefins (LAOs) are an important class of chemical raw materials, widely used in the synthesis, processing, and production of chemical intermediates, epoxides, plasticizers, synthetic carboxylic acids, lubricants, surfactants, and rubber processing chemicals. Meanwhile, butene-1, hexene-1, and octene-1, among other LAOs, can be used as comonomers in the production of polyolefin products, representing one of the most important applications of LAOs and dominating LAO consumption. In particular, hexene-1 and octene-1, when used in the production of high-quality polyethylene, can significantly improve the mechanical properties, optical properties, tear strength, and impact strength of polyethylene.

[0003] In recent years, with the rapid development of the polyolefin industry, the consumption of LAOs has grown rapidly worldwide, especially the demand for hexene-1 and octene-1, which are comonomers for high-end polyolefin products.

[0004] Currently, the main production method for LAOs is ethylene oligomerization. This method yields products with a Schulz-Flory carbon number distribution, which, in addition to high-value-added hexene-1 and octene-1, also generates a large amount of butene-1 and other high-carbon-number linear α-olefins. Clearly, the Schulz-Flory carbon number distribution in ethylene oligomerization for LAO production is less economical than the direct preparation of hexene-1 and octene-1 via selective ethylene oligomerization. Selective ethylene oligomerization offers advantages such as high product purity, easy separation, and high raw material utilization.

[0005] The key to the selective oligomerization of ethylene to prepare hexene-1 and octene-1 lies in the design of the catalyst, especially the variation of the ligand structure in the catalyst. This has a decisive influence on the activity of the selective oligomerization reaction and the selectivity of the products, and has become a key research focus for researchers in this field. For example, patent US5523507 discloses that using a chromium / pyrrole system to catalyze the oligomerization of ethylene, the selectivity for 1-hexene reaches 93%, but the selectivity for 1-octene, which has higher added value, is very low. Patent WO2004056478 discloses a class of ethylene tetramerization catalyst systems. This catalyst system, using PNP-type ligands, can generate the tetramer product 1-octene of ethylene with a selectivity of up to 70%, but the selectivity for hexene-1 is only 10%. The total selectivity of the economically valuable products 1-hexene and 1-octene is only 80%, resulting in low atom economy. At the same time, the products increase the difficulty of separation.

[0006] The literature Journal of Catalysis, 394, 2021, 444-450 discloses a class of N-phosphoramide ligands of phosphacene and phosphacene for ethylene oligomerization. The introduction of phosphacene and phosphacene can improve the selectivity of octene-1 while maintaining high activity. However, the yield of high molecular weight polyethylene in the product is still high. In addition, the synthesis of ligands is difficult and costly, which makes it difficult to apply them on a larger scale.

[0007] The development of selective oligomerization catalysts for ethylene with excellent comprehensive performance remains a key research focus in this field. Summary of the Invention

[0008] Highly efficient selective oligomerization catalysts for ethylene, particularly those involving the design of ligand structures within the catalyst, are of worthy of attention in the field of ethylene oligomerization catalyst technology. To achieve this objective, the present invention provides the following technical solution.

[0009] The first aspect of this invention provides a class of P,N-ligands, specifically, ligand compounds having the structure shown in formula (1).

[0010]

[0011] In equation (1), n ​​is selected from 0, 1, 2;

[0012] Ar1 and Ar2 are each independently selected from unsubstituted aryl I, unsubstituted heteroaryl I, aryl I with substituent X1, and heteroaryl I with substituent X2; R1 to R4 are each independently selected from hydrogen, C 1-15 Hydrocarbon group, C with substituent Y1 1-15 hydrocarbon group, C 1-15 heterohydrocarbon group, C with substituent Y2 1-15 The substituents are: heteroaryl, aryl II, aryl II with substituent Y3, heteroaryl II, and heteroaryl II with substituent Y4; R3 and R4 may be cyclic or acyclic; each of the substituents X1, X2, Y1, Y2, Y3, and Y4 is independently selected from C1. 1-10 At least one of alkyl, aryl, and halogen atoms.

[0013] As a preferred technical solution, the number of skeletal atoms of aryl I and heteroaryl I is independently selected from 6 to 30; the heteroatoms in heteroaryl I are independently selected from at least one of O, S, N, and P; the number of heteroatoms in heteroaryl I is 1 to 3; preferably, Ar and Ar2 are independently selected from phenyl, 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, 2-ethylphenyl, 3-ethylphenyl, 4-ethylphenyl, and 2-isopropylphenyl. The following are compounds: 3-isopropylphenyl, 4-isopropylphenyl, 2,4-dimethylphenyl, 2,4-diisopropylphenyl, 2,4-di-tert-butylphenyl, 2,6-dimethylphenyl, 2,6-diisopropylphenyl, 3,5-dimethylphenyl, 3,5-di-tert-butylphenyl, 2,4,6-trimethylphenyl, naphthyl, anthraceneyl, biphenyl, p-fluorophenyl, o-fluorophenyl, or m-fluorophenyl, preferably phenyl, 2,4,6-trimethylphenyl, or 2,6-diisopropylphenyl.

[0014] As a preferred technical solution, the number of skeletal atoms of the aryl II and heteroaryl II is independently selected from 5 to 10 (five-membered ring, six-membered ring, seven-membered ring, eight-membered ring, nine-membered ring or ten-membered ring); the heteroatoms in the heteroaryl II are independently selected from at least one of O, S, N and P.

[0015] The heteroaryl group II has 1-3 heteroatoms; the C 1-15 The hydrocarbon group is selected from C 1-15 Straight-chain or branched alkyl groups, C 3-10 cycloalkyl, C 6-14 Aryl, C 1-15 Alkyl groups, OC(=O)R6, CO(=O)R6, SO3R6, SO3N(R6)2, SO3Na, tri(C 1-6 Alkoxy)silyl-C 1-6 Alkyl, tri(C) 6-14 Aryloxy)silyl-C 1-6 Alkyl, tri(C) 3-10 Cycloalkoxy)silyl-C 1-6 Alkyl group; R6 is selected from H, straight-chain or branched C. 1-14 Alkyl groups, C with substituent Y5 1-14 Alkyl group; the substituent Y5 is selected from C 1-10 At least one of alkyl, aryl, and halogen atoms.

[0016] In some embodiments, R1 to R4 are each independently hydrogen, a C1-15 straight-chain or branched, substituted or unsubstituted alkyl group; or a substituted or unsubstituted C 3-10 cycloalkyl; or substituted or unsubstituted C 6-14aryl; or alkoxy, OC(=O)R6, CO(=O)R6, SO3R6, SO3N(R6)2 or SO3Na, where R6 represents H, and the C is straight-chain or branched, substituted or unsubstituted. 1-14 Alkyl; or tri(C1-C6-alkoxy)silyl-C1-C6-alkyl, tri(C6-C14-aryloxy)silyl-C1-C6-alkyl, or tri(C3-C10-cycloalkoxy)silyl-C 1-6 alkyl.

[0017] As a preferred technical solution, the ligand is selected from:

[0018]

[0019] A second aspect of the present invention provides a class of catalyst compositions comprising a transition metal compound, a ligand, and an activator, wherein the ligand comprises the ligand compound described in the first aspect; the general formula of the transition metal compound is MR. m M is selected from at least one metallic element from Groups IVB, VB, VIIB, VIII, and IB; R m R in the formula is selected from at least one of H2O, inorganic anions, organic anions, and organic neutral molecules; R m In this case, m is selected from any integer from 1 to 6.

[0020] The transition metal in this invention can be a commonly used transition metal compound in the art. The metal atoms in the transition metal compound are the active metal centers and play an important role in the catalytic process.

[0021] As a preferred technical solution, M is selected from at least one of iron, cobalt, nickel, copper, titanium, vanadium, chromium, manganese, molybdenum, tungsten and palladium.

[0022] In some embodiments, M is selected from at least one of chromium, molybdenum, tungsten, cobalt, titanium, tantalum, vanadium, zirconium, iron, nickel, or palladium.

[0023] As a preferred technical solution, the transition metal compound is selected from at least one of chromium trichloride-tris(tetrahydrofuran) complex, chromium tricarbonyl benzoate, chromium (III) octanoate, chromium hexacarbonyl, chromium (III) acetylacetone, chromium (III) naphthenate, chromium (III) 2-ethylhexanoate, chromium (III) acetate, chromium (III) 2,2,6,6-tetramethylheptanedione, and chromium (III) chloride. Preferably, the transition metal in the transition metal compound is selected from one of chromium, cobalt, titanium, iron, nickel, or palladium.

[0024] More preferably, the transition metal in the transition metal compound is selected from chromium. Any chromium compound capable of enabling oligomerization can be used. Selectable chromium compounds include those with the general formula CrR.m The compound shown has R in its formula. m R is an organic anion or a neutral molecule. m The compound typically contains 1 to 15 carbon atoms, where m is an integer from 1 to 6, and the valence state of Cr is from 0 to 6. More preferably, it is at least one of chromium trichloride-tris(tetrahydrofuran) complex, chromium acetylacetonate (III), and chromium 2-ethylhexanoate (III). Specifically, the Rm group is an organic compound or other group containing a carboxyl group, a β-diketone group, or a hydrocarbon group. From the perspective of ease of solubility and handling, more suitable chromium compounds include one of chromium trichloride-tris(tetrahydrofuran) complex, (benzene)tricarbonyl chromium, chromium octanoate (III), chromium hexacarbonyl, chromium acetylacetonate (III), chromium naphthenate (III), chromium 2-ethylhexanoate (III), chromium acetate (III), 2,2,6,6-tetramethylheptanedione (III), and chromium chloride (III). Preferably, the chromium compound is selected from chromium trichloride-tris(tetrahydrofuran) complex, chromium acetylacetonate (III), and chromium 2-ethylhexanoate (III).

[0025] As a preferred technical solution, the inorganic anion is selected from at least one of halogen anions, nitrate, sulfate, nitrite, sulfite, carbonate, bicarbonate, hydroxide, chlorate, phosphate, phosphite, and silicate.

[0026] As a preferred technical solution, the organic anion is selected from organic acid radicals R'COO-, R'SO3-, and R' is selected from hydrogen, C 1-10 Substituted or unsubstituted alkyl, C 1-10 Substituted or unsubstituted cycloalkyl, C 6-12 At least one of the substituted or unsubstituted aryl groups.

[0027] As a preferred technical solution, the organic neutral molecule is selected from at least one of furan, tetrahydrofuran, pyridine, pyrrole, thiophene, benzofuran, and benzothiophene.

[0028] The activator in this invention plays an activating role in the catalyst system. The activator used in this invention can be any compound that forms an active catalyst when mixed with ligands and transition metal compounds. The activator can be used alone or in combination.

[0029] In some embodiments, the activator is selected from alkylaluminum compounds, aluminum oxane compounds, and organoboron compounds.

[0030] Specifically, the activator can be an alkylaluminum compound, which can be various trialkylaluminum compounds, such as trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, or tri-n-octylaluminum; the alkylaluminum compound can also be an alkylaluminum halide, an alkylaluminum hydride, or an alkylaluminum sesquichloride; preferably, the alkylaluminum halide is selected from diethylaluminum chloride (AlEt2Cl) and / or triethylaluminum chloride (Al2Et3Cl3); preferably, the alkylaluminum hydride is selected from at least one of aluminum hydride, dimethylaluminum hydride, diethylaluminum hydride, dibutylaluminum hydride, propylaluminum hydride, diisobutylaluminum hydride, lithium aluminum hydride, and tritert-butoxyaluminum hydride; preferably, the alkylaluminum sesquichloride is methylaluminum sesquichloride, ethyl sesquichloride, propyl sesquichloride, isopropyl sesquichloride, butyl sesquichloride, isobutyl sesquichloride, or tert-butyl sesquichloride.

[0031] Specifically, the activator can be an aluminum oxane compound, which is typically prepared by mixing water with an alkyl aluminum compound (e.g., trimethylaluminum). The prepared aluminum oxane oligomer can be a linear compound, a cyclic compound, a cage-like compound, or a mixture thereof. Suitable aluminum oxane compounds can be selected from methylaluminoxane (MAO), ethylaluminoxane, isobutylaluminoxane, modified aluminum oxanes, and methylaluminoxane DMAO with volatile components removed, etc.

[0032] Specifically, suitable boron compounds may include cycloboroxanes, triethylborane, triphenylborane, tris(pentafluorophenyl)borane, etc. Organoboron compounds may be used in combination with organoaluminum compounds.

[0033] Preferably, the activator can be selected from methylaluminoxane (MAO), ethylaluminoxane, isobutylaluminoxane, and modified methylaluminoxane (MMAO).

[0034] As a preferred technical solution, the aluminum oxane compound is selected from at least one of methylaluminoxane, ethylaluminoxane, isobutylaluminoxane, and modified aluminum oxane.

[0035] As a preferred technical solution, the organoboron compound is selected from at least one of cycloboroxane, triethylborane, triphenylborane, and tris(pentafluorophenyl)borane.

[0036] As a preferred technical solution, the amount of the transition metal compound is expressed in molar amounts of element M, and the molar ratio of the ligand compound to the transition metal compound is (0.01-100):1, preferably (0.1-1):1, more preferably (0.5-2):1; the molar ratio of the activator to the transition metal compound is (1-10000):1, preferably (1-2000):1.

[0037] In some embodiments, the molar ratio of the ligand compound to the transition metal can be from 0.01:1 to 100:1.

[0038] Preferably, the molar ratio of the ligand to the transition metal can be from 0.1:1 to 10:1.

[0039] More preferably, the molar ratio of the ligand to the transition metal can be from 0.5:1 to 2:1.

[0040] In some embodiments, the molar ratio of the activator to the transition metal can be from 1:1 to 10000:1.

[0041] Preferably, the molar ratio of the activator to the transition metal can be from 1:1 to 2000:1.

[0042] A third aspect of the present invention provides a class of ethylene oligomerization catalysts containing the ligand compound described in the first aspect or the catalyst composition described in the second aspect.

[0043] The fourth aspect of the present invention provides a method for preparing the above-mentioned catalyst composition, wherein raw materials containing a transition metal compound, an activator and a ligand compound are mixed at a temperature of -20°C to 250°C to obtain the catalyst composition, wherein the mixing temperature is preferably 20°C to 100°C.

[0044] In some embodiments, an active catalyst can be provided by simultaneously or in any order mixing of a ligand having the chemical formula (I), a transition metal compound, and an activator, with or without a solvent. The mixing of the catalyst components can be carried out at temperatures ranging from -20°C to 250°C, and the presence of olefins during the mixing process typically exhibits a protective effect, thereby providing improved catalytic performance. Furthermore, the mixing of the catalyst components can be carried out in a temperature range of approximately 20°C to 100°C.

[0045] In some embodiments, separable metal-ligand complexes can be prepared in situ from a transition metal compound and a ligand represented by formula (I). The metal-ligand complex is then added to a reaction medium. Alternatively, a chromium compound and the ligand can be added separately to the reactor, thereby preparing a chromium-ligand complex in situ. In-situ preparation of the complex refers to the preparation of the complex in the medium in which the catalytic reaction occurs, followed by the addition of an activator.

[0046] The fifth aspect of the present invention provides a method for ethylene oligomerization, wherein a raw material containing ethylene is contacted with a catalyst to undergo an ethylene oligomerization reaction, wherein the catalyst contains any of the above-described catalyst compositions or contains any of the above-described ligand compounds.

[0047] The method for the catalyst system of the present invention in the ethylene oligomerization reaction is further described below.

[0048] The present invention also provides a method for selective ethylene oligomerization using the above-described catalyst system.

[0049] The conditions for the ethylene oligomerization reaction include: a temperature of 0–200°C; an ethylene pressure of 0.1–50 MPa; and a reaction system consisting of ethylene-containing raw materials, catalyst, and solvent, wherein the concentration of the catalyst, calculated as M element, in the reaction system is 0.01–10000 μmol / L.

[0050] The contact takes place in the presence of an inert solvent, preferably C. 2-16 Substituted or unsubstituted alkanes, C 3-16 Substituted or unsubstituted cycloalkanes, C 2-16 Substituted or unsubstituted olefins, C 2-16 Substituted or unsubstituted cycloolefins, C 6-16 It consists of at least one of substituted or unsubstituted aromatic hydrocarbons and ionic liquids.

[0051] In some embodiments, ethylene oligomerization is carried out in an inert solvent, which may be an alkane, aromatic hydrocarbon, olefin, or ionic liquid. Typical solvents include, but are not limited to, benzene, toluene, xylene, cumene, chlorobenzene, dichlorobenzene, fluorobenzene, n-heptane, n-hexane, methylcyclohexane, cyclohexane, 1-hexene, 1-octene, etc., with toluene and methylcyclohexane being preferred.

[0052] In some embodiments, the reaction temperature for ethylene oligomerization is from 0°C to 200°C, preferably from 10°C to 120°C, and more preferably from 20°C to 100°C.

[0053] In some embodiments, the ethylene oligomerization reaction can be carried out at a pressure of 0.1 MPa to 50 MPa, preferably 1.0 MPa to 10 MPa.

[0054] In some embodiments, the concentration of the catalyst in the reaction system can range from 0.01 μmol metal / L to 10000 μmol metal / L, preferably from 1 μmol metal / L to 500 μmol metal / L, where the metal is a transition metal in a transition metal compound.

[0055] The highly active ethylene oligomerization catalyst system and the method for catalyzing ethylene trimerization and tetramerization provided by this invention can improve the yield of hexene-1 and octene-1 during ethylene oligomerization.

[0056] In a preferred embodiment, the products of the ethylene oligomerization reaction have a selectivity of 10% to 90% for hexene-1, a selectivity of 10% to 70% for octene-1, and a total selectivity of 50% to 99% for both hexene-1 and octene-1.

[0057] Unless otherwise specified, the data range given in this application is selected from any value within the range and includes the endpoint values ​​of the range.

[0058] This invention provides a catalyst system and a method for selective oligomerization of ethylene using the catalyst system, which can selectively catalyze the trimerization and tetramerization of ethylene to prepare hexene and octene. Compared with existing technologies, this catalyst system achieves high catalytic activity while also obtaining high selectivity for ethylene trimerization and tetramerization. The high selectivity for hexene-1 and octene-1 in the ethylene trimerization and tetramerization products is beneficial for reducing the production cost of hexene-1 and octene-1. Detailed Implementation

[0059] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0060] The method for preparing the ligand compounds of the present invention can be carried out by conventional ligand preparation methods in the art. For example, the ligand compounds of the present invention can be prepared by the following methods.

[0061] Step (1) Preparation of 1a:

[0062]

[0063] Compound a and base 1 from the first part (the molar amount of base 1 is 0.5 to 1 times the amount of compound a) are dissolved in solvent 1, such that the concentration of compound a in solvent 1 is 1 to 10 mol / L; phosphorus trichloride (the amount of which is 1 to 1.5 times that of compound a) is dissolved in solvent 1, such that the concentration of phosphorus trichloride in solvent 1 is 1 to 10 mol / L.

[0064] Both solutions were simultaneously added to solvent 1 at 0℃ to -80℃, with the amount of solvent 1 being such that the concentration of compound a was 0.1 to 5 mol / L; then triethylamine (0.5 to 1 times the molar amount of compound a) was added; the solution was allowed to return to room temperature for 2 hours over 2 hours; the solvent was removed, and the residue was extracted three times with diethyl ether; the ether portions were combined, and the solvent was removed under reduced pressure to obtain compound 1a;

[0065] The base 1 is an acid-binding agent selected from triethylamine and pyridine;

[0066] The solvent 1 is selected from dichloromethane, trichloromethane, dichloroethane, toluene, diethyl ether, tetrahydrofuran, and chlorobenzene, with dichloromethane being preferred;

[0067] Step (2) Preparation of 1b:

[0068]

[0069] Compound b was added to solvent 2 to achieve a concentration of 0.1–5 mol / L, and the solution was cooled to 0°C–-20°C. Base 2 was added dropwise (1 mL / min) to the cooled solution of b, with a molar amount of base 2 equal to 1–1.1 times that of compound b. The suspension was then heated to room temperature and stirred for 2 hours (300–600 rpm). Then, compound b' was slowly added (1 mL / min), with a molar amount equal to that of compound b. The reaction was continued with stirring for 1–3 hours (300–600 rpm), and the solvent was removed under vacuum. The residue was dissolved in tetrahydrofuran and refluxed under argon for 12 hours. Distilled water (twice the molar amount of compound b) was then added, and the mixture was stirred at room temperature for 30 minutes (300–600 rpm). The solid was removed by filtration, and the remaining solvent was removed under vacuum to obtain compound 1b.

[0070] The alkali 2 is selected from lithium methyl, lithium n-butyl, lithium sec-butyl, lithium tert-butyl, lithium diisopropylamino, lithium sodium hydride, calcium hydride, sodium methoxide, and sodium ethoxide, with lithium n-butyl being preferred.

[0071] The solvent 2 is selected from diethyl ether, methyl tert-butyl ether, tetrahydrofuran, methyl tetrahydrofuran, and hexane, with diethyl ether and tetrahydrofuran being preferred;

[0072] Step (3) Preparation 1:

[0073]

[0074] Compound 1b was dissolved in solvent 2 to a concentration of 0.1–1 mol / L, and cooled to 0°C–-20°C. Then, an equimolar amount of base 2, equal to 1b, was slowly added (1 ml / min), producing a fluffy white suspension. The suspension was heated to room temperature and stirred for 2 hours (300–600 rpm). An equimolar amount of 1a, equal to 1b, was slowly added (1 ml / min) at room temperature. After the addition of 1a, stirring continued for 1 hour (300–600 rpm). The solution was filtered to remove a small amount of white solid, and then the solvent was removed under vacuum. The residue was suspended in hexane and stirred for 3 hours (300–600 rpm). After filtration and drying, compound 1 was obtained.

[0075] The present invention can be better understood through the following embodiments. The following embodiments are provided for illustrative purposes only and should not be construed as limiting the present invention.

[0076] The selective ethylene oligomerization catalytic composition provided by this invention can be used in selective ethylene oligomerization reactions. It can catalyze not only the selective trimerization of ethylene to 1-hexene, but also the selective tetramerization of ethylene to 1-octene, which has higher economic value. Furthermore, the selectivity of trimerization and tetramerization can be altered by adjusting the substituents in the catalyst. This catalyst composition exhibits high catalytic activity for both ethylene trimerization and tetramerization, with high selectivity for hexene-1 and octene-1.

[0077] Preparation Example 1

[0078] Methods for synthesizing ligands include:

[0079] Step (1) Preparation of 1a

[0080] N,N'-Dimethylethylenediamine (12.10 mL, 113.4 mmol) and triethylamine (11.14 mL, 78 mmol) were dissolved in dichloromethane (20 mL), as was phosphorus trichloride (11.88 mL, 136 mmol) in dichloromethane (20 mL). Both solutions were simultaneously added to dichloromethane (60 mL) at -40 °C. The solution was heated to -30 °C, and then the solution of triethylamine (11.14 mL, 78 mmol) in dichloromethane (20 mL) was added. The solution was allowed to return to room temperature over 2 hours. The solvent was removed, and the residue was extracted with diethyl ether (3 times × 100 mL). The ether fractions were combined, and the solvent was removed under reduced pressure to obtain 2-chloro-1,3-dimethyl-1,3,2-diazaphosphacyclopentane 1a.

[0081] Step (2) Preparation of 1b

[0082] 2,6-Dimethylaniline (6.2 mL, 50 mmol) was added to 100 mL of diethyl ether and cooled to 0 °C. To the cooled aniline solution, n-butyllithium (2.0 M solution in hexane, 26.0 mL, 52 mmol) was added dropwise (2 mL / min), resulting in a grayish-white solid. The suspension was heated to room temperature and stirred for 2 hours (300–600 rpm). Then, benzonitrile (5.2 mL, 51 mmol) was slowly added (1 mL / min), resulting in a suspension of a yellow-orange solid. Stirring continued for 1 hour (300–600 rpm), and the solvent was removed under vacuum. The residue was dissolved in tetrahydrofuran (150 mL) and refluxed overnight under argon to obtain a deep orange-red solution. Distilled water (2.0 mL, 110 mmol) was added, and the mixture was stirred at room temperature for 30 minutes (300–600 rpm). The solid was removed by filtration, and the remaining solvent was removed under vacuum, yielding a pale yellow solid. This solid was stirred in 80 mL of pentane to form a slurry and stirred for 2 hours (300–600 rpm). The slurry was filtered and dried under vacuum to give a white solid 1b.

[0083] Step (3) Preparation of L1

[0084]

[0085] 1b (15.0 mmol) was dissolved in 50 mL of diethyl ether and cooled to 0 °C. Then, n-butyllithium (7.5 mL, 15 mmol, in 2.0 M hexane solution) was added dropwise (2 mL / min), producing a fluffy white suspension. The suspension was heated to room temperature and stirred for 2 hours (300–600 rpm). 1a (15.0 mmol) was slowly added at room temperature (1 mL / min). After the addition of 1a was complete, stirring was continued for 1 hour (300–600 rpm). The solution was filtered to remove a small amount of white solid, and then the solvent was removed under vacuum. The residue was suspended in 50 mL of hexane and stirred for 3 hours (300–600 rpm). After filtration and drying, solid L1 was obtained.

[0086] Preparation Example 2

[0087]

[0088] Using the same steps as in Preparation Example 1b, but replacing the benzonitrile with p-tolylacetonitrile, otherwise the same, we obtained 2b.

[0089] L2 was obtained by using the same steps as L1 in Preparation Example 1, but with the following reagents: 1a, 2b.

[0090] Preparation Example 3

[0091]

[0092] Using the same steps as in Preparation Example 1a, but replacing N,N'-dimethylethylenediamine with N,N'-diisopropylethylenediamine, otherwise the same, 3a was obtained.

[0093] L3 was obtained by using the same steps as L1 in Preparation Example 1, but with the following reagents: 3a, 2b.

[0094] Preparation Example 4

[0095]

[0096] Using the same steps as in Preparation Example 1a, but replacing N,N'-dimethylethylenediamine with N,N'-dimethyl-1,2-phenylenediamine, otherwise the same, we obtained 4a.

[0097] L3 was obtained by using the same steps as L1 in Preparation Example 1, but with the following reagents: 4a, 2b.

[0098] Comparative Preparation Example 1

[0099]

[0100] Example 1

[0101] A 1L stainless steel high-pressure reactor is heated to 130°C under vacuum and maintained for two hours. After purging with nitrogen and cooling to the reaction temperature, it is purged with ethylene three times before use.

[0102] Methylcyclohexane, modified methylaluminoxane MMAO-3A (purchased from Akzo-Nobel), ligand L1, and chromium tris(tetrahydrofuran)chloride (5 μmol) were sequentially added to a high-pressure reactor to obtain a mixture, which served as the catalyst. The total volume of the mixture was 300 mL, and the molar ratio of ligand L1:chromium tris(tetrahydrofuran)chloride:modified methylaluminoxane was 1.2:1:500. After the catalyst was added, the reactor was sealed, stirring was started (300–600 rpm), the ethylene feed valve was opened, and the ethylene pressure was controlled at 4 MPa. The reaction temperature was controlled at 60 °C by heating or cooling to carry out the ethylene oligomerization reaction.

[0103] After 30 minutes of reaction, the ethylene feed was stopped, the stirring was turned off, and the reactor was cooled to 10°C. After depressurization, 1.000–1.100 g of accurately weighed nonane was added to the reactor as an internal standard and stirred until homogeneous, obtaining a mixture. The reaction was quenched by adding 10 wt% hydrochloric acid aqueous solution, and the liquid product was collected for gas chromatography analysis. The solid product (the solid polymer produced in the reaction) was filtered, collected, washed with 10% hydrochloric acid aqueous solution and ethanol, dried, and weighed. The product composition was analyzed by gas chromatography using the internal standard method, and the catalyst activity was calculated. The results are shown in Table 1.

[0104] The activity of the catalyst is calculated using the following formula:

[0105]

[0106] Test methods for hexene-1 selectivity (wt%) and octene-1 selectivity (wt%):

[0107] The composition of the liquid product obtained after filtering the total reaction product is analyzed by gas chromatography with internal standard method. The content of hexene-1 / octene-1 in the liquid product can be calculated to determine its selectivity.

[0108] Example 2

[0109] The method of Example 1 was followed, except that ligand L1 was replaced with an equimolar amount of ligand L2, and the results are shown in Table 1.

[0110] Example 3

[0111] The method of Example 1 was followed, except that ligand L1 was replaced with an equimolar amount of ligand L3, and the results are shown in Table 1.

[0112] Example 4

[0113] The method of Example 1 was followed, except that ligand L1 was replaced with an equimolar amount of ligand L4, and the results are shown in Table 1.

[0114] Example 5

[0115] The method was followed in Example 4, except that the reaction temperature was controlled at 40°C. The results are shown in Table 1.

[0116] Example 6

[0117] The method was followed in Example 4, except that the reaction temperature was controlled at 80°C. The results are shown in Table 1.

[0118] Example 7

[0119] The method of Example 4 was followed, except that the amount of modified methylaluminoxane was adjusted so that the molar ratio of modified methylaluminoxane to tris(tetrahydrofuran)chromium was 1000:1. The results are shown in Table 1.

[0120] Comparative Example 1

[0121] The method of Example 4 was followed, except that ligand L4 was replaced with an equimolar amount of ligand DL1. The results are shown in Table 1.

[0122] Table 1

[0123]

[0124] In the above embodiments, the catalyst system provided by the present invention exhibits higher overall selectivity for ethylene trimerization and tetramerization than in the comparative embodiments. Furthermore, for the more economically valuable ethylene tetramer 1-octene, the catalyst system provided by the present invention achieves higher octene selectivity than the comparative example.

[0125] Furthermore, the catalyst system provided by this invention allows for flexible control of the selectivity for 1-hexene and 1-octene by conveniently altering the steric hindrance of the substituents on the catalyst ligands. Ligand L4 exhibits the highest catalytic activity due to its suitable steric hindrance and electronic effects; however, compared to L2, its slightly increased steric hindrance leads to a decrease in tetramerization selectivity and an increase in trimerization selectivity. At 40°C, the catalytic system achieves higher ethylene tetramerization selectivity; as the temperature increases, tetramerization selectivity decreases, trimerization selectivity increases, and catalytic activity improves.

[0126] The catalyst system provided by this invention has a novel ligand structure and is used for the selective oligomerization of ethylene to obtain products mainly of hexene and octene. It has high catalytic activity and high selectivity for hexene-1 and octene-1.

[0127] Any numerical value mentioned in this invention, if there is only a two-unit interval between any minimum and any maximum value, includes all values ​​that increase by one unit each time from the minimum to the maximum value. For example, if the amount of a component, or the value of a process variable such as temperature, pressure, or time, is stated as 50-90, in this specification it means specifically listing values ​​such as 51-89, 52-88… and 69-71 and 70-71, etc. For non-integer values, it may be appropriately considered that a unit is 0.1, 0.01, 0.001, or 0.0001. These are merely some specifically specified examples. In this application, in a similar manner, all possible combinations of numerical values ​​between the listed minimum and maximum values ​​are considered to have been disclosed.

[0128] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A ligand compound, characterized in that, The ligand compound has the structure shown in formula (1). In equation (1), n is selected from 0, 1, 2; Ar1 and Ar2 are each independently selected from unsubstituted aryl I, unsubstituted heteroaryl I, aryl I with substituent X1, and heteroaryl I with substituent X2; R1 to R4 are each independently selected from hydrogen, C 1-15 Hydrocarbon group, C with substituent Y1 1-15 hydrocarbon group, C 1-15 heterohydrocarbon group, C with substituent Y2 1-15 Heteroalkyl group, aryl II, aryl II with substituent Y3, heteroaryl II, heteroaryl II with substituent Y4; R3 and R4 may be cyclic or non-cyclic; The substituents X1, X2, Y1, Y2, Y3, and Y4 are each independently selected from C 1-10 At least one of alkyl, aryl, and halogen atoms.

2. The ligand compound according to claim 1, characterized in that, The number of skeletal atoms of the aryl I and heteroaryl I is independently selected from 6 to 30; The heteroatoms in the heteroaryl I are each independently selected from at least one of O, S, N and P; The heteroaryl I contains 1 to 3 heteroatoms; Preferably, Ar and Ar2 are each independently selected from phenyl, 2-methylphenyl, 3-methylphenyl, 4-methylphenyl, 2-ethylphenyl, 3-ethylphenyl, 4-ethylphenyl, 2-isopropylphenyl, 3-isopropylphenyl, 4-isopropylphenyl, 2,4-dimethylphenyl, 2,4-diisopropylphenyl, 2,4-di-tert-butylphenyl, 2,6-dimethylphenyl, 2,6-diisopropylphenyl, 3,5-dimethylphenyl, 3,5-di-tert-butylphenyl, 2,4,6-trimethylphenyl, naphthyl, anthracene, biphenyl, p-fluorophenyl, o-fluorophenyl, or m-fluorophenyl, preferably phenyl, 2,4,6-trimethylphenyl, or 2,6-diisopropylphenyl.

3. The ligand compound according to claim 1 or 2, characterized in that, The number of skeletal atoms of the aryl II and heteroaryl II is independently selected from 5 to 10; The heteroatoms in the heteroaryl II are each independently selected from at least one of O, S, N and P; The heteroaryl II contains 1-3 heteroatoms; The C 1-15 The hydrocarbon group is selected from C 1-15 Straight-chain or branched alkyl groups, C 3-10 cycloalkyl, C 6-14 Aryl, C 1-15 Alkyl groups, OC(=O)R6, CO(=O)R6, SO3R6, SO3N(R6)2, SO3Na, tri(C 1-6 Alkoxy)silyl-C 1-6 Alkyl, tri(C) 6-14 (Aryloxy)silyl-C 1-6 Alkyl, tri(C) 3-10 Cycloalkoxy)silyl-C 1-6 alkyl; The R6 is selected from H, straight chain, or branched C. 1-14 Alkyl groups, C with substituent Y5 1-14 alkyl; The substituent Y5 is selected from C. 1-10 At least one of alkyl, aryl, and halogen atoms.

4. The ligand compound according to any one of claims 1-3, characterized in that, The ligands are selected from:

5. A catalyst composition, characterized in that, Including transition metal compounds, activators, and ligand compounds as described in any one of claims 1-4; The general formula of the transition metal compound is MR m ; M is selected from at least one metallic element from Group IVB, Group VB, Group VIIB, Group VIII, and Group IB; R m R in the formula is selected from at least one of H2O, inorganic anions, organic anions, and organic neutral molecules; R m m is selected from any integer from 1 to 6.

6. The catalyst composition according to claim 5, characterized in that, M is selected from at least one of iron, cobalt, nickel, copper, titanium, vanadium, chromium, manganese, molybdenum, tungsten, and palladium. Preferably, the transition metal compound is selected from at least one of chromium trichloride-tris(tetrahydrofuran) complex, chromium tricarbonylbenzene, chromium octanoate (III), chromium hexacarbonyl, chromium acetylacetone (III), chromium naphthenate (III), chromium 2-ethylhexanoate (III), chromium acetate (III), 2,2,6,6-tetramethylheptanedione (III), and chromium chloride (III). And / or, the inorganic anion is selected from at least one of the following: halide anion, nitrate, sulfate, nitrite, sulfite, carbonate, bicarbonate, hydroxide, chlorate, phosphate, phosphite, and silicate. And / or, the organic anion is selected from organic acid radicals R'COO-, R'SO3-, and R' is selected from hydrogen, C 1-10 Substituted or unsubstituted alkyl, C 1-10 Substituted or unsubstituted cycloalkyl, C 6-12 At least one of the substituted or unsubstituted aryl groups; And / or, the organic neutral molecule is selected from at least one of furan, tetrahydrofuran, pyridine, pyrrole, thiophene, benzofuran, and benzothiophene.

7. The catalyst composition according to claim 5 or 6, characterized in that, The activator is selected from at least one of alkylaluminum compounds, aluminum oxane compounds, and organoboron compounds; Preferably, the alkylaluminum compound is selected from at least one of trialkylaluminum, alkylaluminum halides, alkylaluminum hydrides, and alkylaluminum sesquichlorides; Preferably, the trialkylaluminum is selected from at least one of trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, and tri-n-octylaluminum; Preferably, the alkyl aluminum halide is selected from diethylaluminum chloride and / or triethylaluminum chloride; Preferably, the alkylaluminum hydride is selected from at least one of aluminum hydride, dimethyl aluminum hydride, diethyl aluminum hydride, dibutyl aluminum hydride, propyl aluminum hydride, diisobutyl aluminum hydride, lithium aluminum hydride, and tritert-butoxy aluminum hydride; Preferably, the alkylaluminum sesquichloride is: methylaluminum sesquichloride, ethyl sesquichloride, propyl sesquichloride, isopropyl sesquichloride, butyl sesquichloride, isobutyl sesquichloride, or tert-butyl sesquichloride; Preferably, the aluminum oxane compound is selected from at least one of methylaluminoxane, ethylaluminoxane, and isobutylaluminoxane; Preferably, the organoboron compound is selected from at least one of cycloboroxane, triethylborane, triphenylborane, and tris(pentafluorophenyl)borane.

8. The catalyst composition according to any one of claims 5-7, characterized in that, The amount of the transition metal compound is expressed in molar amounts of element M. The molar ratio of the ligand compound to the transition metal compound is (0.01–100):1, preferably (0.1–1):1, and more preferably (0.5–2):1; The molar ratio of the activator to the transition metal compound is (1-10000):1, preferably (1-2000):

1.

9. An ethylene oligomerization catalyst, comprising a ligand compound according to any one of claims 1-4 or a catalyst composition according to any one of claims 5-8.

10. An ethylene oligomerization method, wherein a raw material containing ethylene is contacted with a catalyst to undergo an ethylene oligomerization reaction, characterized in that, The catalyst contains a ligand compound as described in any one of claims 1-4 or a catalyst composition as described in any one of claims 5-8.

11. The method according to claim 10, characterized in that, The conditions for the ethylene oligomerization reaction include: The temperature ranges from 0 to 200°C, preferably from 10 to 120°C. The ethylene pressure is 0.1–50 MPa, preferably 1–10 MPa; The reaction system consists of ethylene-containing raw materials, catalyst, and solvent, and the concentration of the catalyst, calculated as M element, in the reaction system is 0.01–10000 μmol / L.

12. The method according to claim 10 or 11, characterized in that, The contact takes place in the presence of an inert solvent, preferably C. 2-16 Substituted or unsubstituted alkanes, C 3-16 Substituted or unsubstituted cycloalkanes, C 2-16 Substituted or unsubstituted olefins, C 2-16 Substituted or unsubstituted cycloolefins, C 6-16 It consists of at least one of substituted or unsubstituted aromatic hydrocarbons and ionic liquids.

13. The method according to claim 10, 11, or 12, characterized in that, In the products of the ethylene oligomerization reaction, The selectivity of hexene-1 is 10%–90%; The selectivity of octene-1 is 10%–70%; The overall selectivity for hexene-1 and octene-1 ranges from 50% to 99%.

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