Ligand compound, selective ethylene oligomerization catalytic composition, application of selective ethylene oligomerization catalytic composition and selective ethylene oligomerization reaction method

Abstract

The present invention relates to the technical field of ethylene oligomerization catalysts, and discloses a ligand compound, a selective ethylene oligomerization catalytic composition and application thereof, and a selective ethylene oligomerization reaction method, the ligand compound has a structure represented by a formula (1) # imgabs0 #, Ar and Ar'are independently selected from substituted or unsubstituted aryl or heteroaryl; 1, 2-positions are substituted or unsubstituted cyclic substituents. The ligand compound is applied to a selective ethylene oligomerization catalytic composition, high ethylene trimerization and tetramerization catalytic activity can be obtained, hexene-1 and octylene-1 selectivity is high, the high-molecular polymer content is low, the risk of scaling and blocking of a reaction pipeline in a continuous reaction can be greatly reduced, and the selectivity of ethylene oligomerization is high. Good industrial application prospects and economic values are realized.

Description

Technical Field

[0001] The invention relates to the technical field of ethylene oligomerization catalysts, and in particular to a ligand compound, an ethylene oligomerization catalyst composition and application thereof, and an ethylene oligomerization reaction method. Background Art

[0002] Linear α-olefins (LAOs) are an important class of chemical raw materials, and are also widely used in the synthesis, processing and production of chemical intermediates, epoxy compounds, plasticizers, synthetic carboxylic acids, lubricants, surfactants and rubber processing chemicals. At the same time, butene-1, hexene-1 and octene-1 in LAOs can be used as comonomers in the production of polyolefin products, which is one of the most important applications of LAOs and has occupied a dominant position in LAOs consumption. In particular, hexene-1 and octene-1 are used in the production of high-quality polyethylene, which 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 increased rapidly worldwide, especially the demand for hexene-1 and octene-1, which are comonomers of high-end polyolefin products.

[0004] At present, the main production method of LAOs is ethylene oligomerization. The carbon number of the product obtained by this method follows the Schulz-Flory distribution. In addition to high-value-added hexene-1 and octene-1, a large amount of butene-1 and other high-carbon linear α-olefins are also generated. Obviously, the production of LAOs by ethylene oligomerization with Schulz-Flory distribution is less economical than the direct preparation of hexene-1 and octene-1 by ethylene selective oligomerization. Selective ethylene oligomerization has the advantages of high product purity, easy separation, and high raw material utilization.

[0005] The key to the technology of preparing hexene-1 and octene-1 by selective polymerization of ethylene lies in the design of the catalyst, especially the change of the ligand structure in the catalyst, which has a decisive influence on the activity of the selective polymerization reaction of ethylene and the selectivity of the product, and has become the key research content of researchers in this field. US5523507A discloses the use of chromium / pyrrole system to catalyze the polymerization of ethylene, and the selectivity of 1-hexene reaches 93%. The document ACS Catal.2015,5,7095-7098 discloses a phosphoramide (PCN) ligand, which can catalyze the polymerization of ethylene to produce high molecular weight polyethylene and trimerization and tetramerization to produce hexene and octene after combining with transition metals. The selectivity of ethylene trimerization and tetramerization of this type of ligand is adjustable, but when it is necessary to obtain a higher selectivity of ethylene tetramerization, it is accompanied by the generation of more high molecular weight polyethylene, which increases the risk of fouling and blockage in the continuous reaction process. The document Organometallics 2020, 39, 967-987 discloses a class of phosphorus-alkyl substituted diphosphine ligands for ethylene polymerization. When the dialkyl phosphine substituent in the ligand is changed to a phospholane substituent, the reaction selectivity changes from ethylene polymerization to ethylene trimerization and tetramerization. However, this type of ligand has limited selectivity for the more economically valuable ethylene tetramerization to produce 1-octene, which limits its application.

[0006] The development of ethylene selective polymerization catalysts with excellent comprehensive performance is still a key research topic in this field. Therefore, it is crucial to develop efficient ethylene selective polymerization catalysts. Summary of the invention

[0007] The purpose of the present invention is to overcome the problems of insufficient selectivity of ethylene trimerization and tetramerization and high content of by-product high molecular weight polyethylene in the prior art, and to provide a ligand compound, a selective ethylene oligomerization catalytic composition and its application and a method for selective ethylene oligomerization reaction. The ligand compound is used in the selective ethylene oligomerization catalytic composition to increase the yield of hexene-1 and octene-1 and effectively inhibit the generation of by-product polyethylene.

[0008] In order to achieve the above object, the present invention provides a ligand compound in a first aspect, wherein the ligand compound has a structure shown in formula (1):

[0009]

[0010] wherein Ar and Ar' are each independently selected from substituted or unsubstituted aryl or heteroaryl;

[0011] The 1,2-positions are substituted or unsubstituted cyclic substituents.

[0012] The second aspect of the present invention provides a selective ethylene oligomerization catalytic composition, which comprises a transition metal compound, a ligand and an activator, wherein the ligand comprises the ligand compound described in the first aspect.

[0013] The third aspect of the present invention provides use of the above ligand compound or the above selective ethylene oligomerization catalytic composition in a selective ethylene oligomerization reaction.

[0014] A fourth aspect of the present invention provides a method for selective ethylene oligomerization, the method comprising: contacting ethylene with a catalyst under ethylene oligomerization conditions;

[0015] Wherein, the catalyst comprises the ethylene oligomerization catalyst composition described in the second aspect.

[0016] The inventors of the present invention have found in their research that the selectivity of hexene-1 and octene-1 in the selective polymerization of ethylene can be improved by introducing a heterocyclic structure containing P into the ligand. The reason for this may be that, compared with the case where P contains a straight-chain or branched substituent, the heterocyclic structure containing P connects two independent substituents through a chemical bond, thereby restricting the rotation of the substituent on P, so that the steric hindrance around the P atom is not too large, which is conducive to obtaining high ethylene trimerization and tetramerization selectivity; if the steric hindrance around the P atom is too large, it will make it difficult to form a metal seven-membered ring and a nine-membered ring during the selective ethylene polymerization, thereby losing selectivity; in addition, by modifying the P heterocyclic structure, such as introducing different steric hindrance substituents at the ortho position of P in the P heterocyclic ring, the steric hindrance around the P atom is not too small, which is more conducive to stabilizing the active intermediates in the catalytic process and obtaining excellent catalytic activity.

[0017] The selective ethylene oligomerization catalytic composition provided by the present invention is used in the selective ethylene oligomerization reaction, and can not only catalyze the selective trimerization of ethylene to generate 1-hexene, but also catalyze the selective tetramerization of ethylene to generate 1-octene with higher economic value, and the selectivity of trimerization and tetramerization can be changed by adjusting the catalyst substituent. The catalyst composition has high catalytic activity of ethylene trimerization and tetramerization, high selectivity of hexene-1 and octene-1, and low content of high molecular polymer, and can greatly reduce the risk of scaling and clogging of the reaction pipeline in the continuous reaction, and has good industrial application prospects and economic value. DETAILED DESCRIPTION

[0018] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0019] The first aspect of the present invention provides a ligand compound having a structure shown in formula (1):

[0020]

[0021] wherein Ar and Ar' are each independently selected from substituted or unsubstituted aryl or heteroaryl;

[0022] The 1,2-positions are substituted or unsubstituted cyclic substituents.

[0023] The inventors of the present invention have found in their research that the selectivity of hexene-1 and octene-1 in the selective polymerization of ethylene can be improved by introducing a heterocyclic structure containing P into the ligand. The reason for this may be that, compared with the case where P contains a straight-chain or branched substituent, the heterocyclic structure containing P connects two independent substituents through a chemical bond, thereby restricting the rotation of the substituent on P, so that the steric hindrance around the P atom is not too large, which is conducive to obtaining high ethylene trimerization and tetramerization selectivity; if the steric hindrance around the P atom is too large, it will make it difficult to form a metal seven-membered ring and a nine-membered ring during the selective ethylene polymerization, thereby losing selectivity; in addition, by modifying the P heterocyclic structure, such as introducing different steric hindrance substituents at the ortho position of P in the P heterocyclic ring, the steric hindrance around the P atom is not too small, which is more conducive to stabilizing the active intermediates in the catalytic process and obtaining excellent catalytic activity.

[0024] In the present invention, "cyclic substituent" refers to the residue formed by the cleavage of the covalent bond between any two atoms connected on the ring of a cyclic compound. For example, the residue formed by the cleavage of the covalent bond between any two atoms connected in cyclobutane can be represented by When the cyclic substituent is composed entirely of carbon atoms, it can be understood that in the ligand compound, the P atom is respectively connected to the two C atoms in the cyclic substituent through covalent bonds to form a P-containing heterocyclic structure.

[0025] The present invention has a wide selection range for the cyclic substituent. According to some preferred embodiments of the present invention, the cyclic substituent is a three-membered ring, a four-membered ring, a five-membered ring, a six-membered ring, a seven-membered ring or an eight-membered ring substituent consisting entirely of carbon atoms, preferably a four-membered ring and / or a five-membered ring substituent. In the above preferred case, it is beneficial to further improve the selectivity of the catalyst system for hexene-1 and octene-1.

[0026] According to some preferred embodiments of the present invention, the H atom on at least one carbon atom on the cyclic substituent ring may be substituted by a substituent. The present invention has no particular requirements for the position and number of the substituent.

[0027] The present invention has a wide range of choices for substituents on the substituted cyclic substituent. Preferably, the substituent of the substituted cyclic substituent is at least one of an alkyl group, an alkoxy group, a substituted or unsubstituted phenyl group and a benzyl group, for example, it may be at least one of a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an isopropyl group, an isobutyl group, a tert-butyl group, an isopentyl group, a tert-pentyl group, a cyclopentyl group, a cyclohexyl group, a 2,6-dimethylcyclohexyl group, a methoxy group, a benzyl group, a phenyl group, an o-methylphenyl group and a 2,6-dimethylphenyl group, preferably at least one of a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, a cyclopentyl group and a phenyl group.

[0028] According to a particularly preferred embodiment of the present invention, the cyclic substituent is a four-membered ring composed entirely of carbon atoms, and the ligand compound has a structure shown in formula (2):

[0029]

[0030] Wherein, R1, R2, R3, and R4 are each independently selected from hydrogen, methyl, ethyl, n-propyl, n-butyl, n-pentyl, isopropyl, isobutyl, tert-butyl, isopentyl, tert-pentyl, cyclopentyl, cyclohexyl, 2,6-dimethylcyclohexyl, methoxy, benzyl, phenyl, o-methylphenyl, or 2,6-dimethylphenyl. In the above preferred case, it is advantageous to obtain high selectivity of hexene-1 and octene-1 while obtaining high catalytic activity.

[0031] According to some preferred embodiments of the present invention, in formula (1), Ar and Ar' are each independently selected from C6-C30 substituted or unsubstituted aryl or heteroaryl groups, and the substituent in the substituted aryl or heteroaryl group is selected from at least one of C1-C10 alkyl, aryl and halogen atoms, for example, the substituent may be at least one of methyl, ethyl, isopropyl, tert-butyl, aryl, chlorine atom and fluorine atom.

[0032] According to the present invention, the heteroaryl group refers to a group formed by replacing at least one C atom in the aromatic group with a heteroatom. Preferably, the heteroatom in the substituted or unsubstituted heteroaryl group may be at least one of oxygen, sulfur, nitrogen and phosphorus.

[0033] According to some preferred embodiments of the present invention, Ar and Ar' 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, anthracenyl, biphenyl, p-fluorophenyl, o-fluorophenyl or m-fluorophenyl, preferably phenyl, 2,4,6-trimethylphenyl or 2,6-diisopropylphenyl.

[0034] According to some preferred embodiments of the present invention, the ligand compound is selected from any one of the following compounds:

[0035]

[0036]

[0037] In the above formulae, Ph is phenyl, Dipp is 2,6-diisopropylphenyl, Mes is 2,4,6-trimethylphenyl, and o-Xyl is 2,6-dimethylphenyl.

[0038] In the above preferred case, it is beneficial to obtain high selectivity of hexene-1 and octene-1 while obtaining high catalytic activity.

[0039] The present invention has no particular limitation on the preparation method of the ligand compound, and the ligand compound can be prepared by conventional organic synthesis methods in the art, for example, it can be prepared according to the organic synthesis method provided in the document ACS Catal. 2015, 5, 7095-7098.

[0040] According to some preferred embodiments of the present invention, the method for preparing the ligand compound comprises:

[0041] (1) subjecting a phosphorus-containing heterocyclic compound to a silane coupling agent for silylation in the presence of a first base;

[0042] The structure of the phosphorus-containing heterocyclic compound is shown in formula (i), wherein the 1,2-positions are substituted or unsubstituted cyclic substituents;

[0043] (2) subjecting the product obtained in step (1) to a nucleophilic substitution reaction with compound II;

[0044] Wherein, compound II has a structure as shown in formula (ii);

[0045] Wherein, Ar and Ar' are the same as defined above, and X is selected from any one of the halogen atoms.

[0046] The selection range of the cyclic substituent is the same as described above and will not be repeated here.

[0047] According to a particularly preferred embodiment of the present invention, the phosphorus-containing heterocyclic compound is at least one of phospholane, 2,5-dimethylphospholane and 2,5-diethylphospholane.

[0048] The present invention has no particular requirements for the type of the silane coupling agent, and conventional silane coupling agents in the art may be used, such as trimethylchlorosilane and / or triethylchlorosilane.

[0049] According to the present invention, the presence of the first base is conducive to the forward progress of the silylation treatment. The present invention has no special requirements for the specific type of the first base, which can be a conventional organic base in the art, such as n-butyl lithium.

[0050] The present invention has no particular limitation on the sources of the phosphorus-containing heterocyclic compound, the silane coupling agent and the first base, and they can be purchased from commercial sources or prepared by a chemical reaction method known in the art.

[0051] According to some preferred embodiments of the present invention, the molar ratio of the phosphorus-containing heterocyclic compound to the silane coupling agent is 1:(1-2), preferably 1:(1.1-1.5).

[0052] According to some preferred embodiments of the present invention, the molar ratio of the phosphorus-containing heterocyclic compound to the first base is 1:(1-2), preferably 1:(1-1.2).

[0053] According to the present invention, the silanization treatment conditions include: reaction temperature of 20-30° C., reaction time of 1.5-3 h, preferably at room temperature.

[0054] The present invention has no particular requirement for the order of adding the first base, the phosphorus-containing heterocyclic compound and the silane coupling agent. Preferably, the first base is first mixed with the phosphorus-containing heterocyclic compound and then mixed with the silane coupling agent for silanization.

[0055] Preferably, the first mixing comprises: mixing the first base with the phosphorus-containing heterocyclic compound at -5°C to 5°C, and then stirring at 20-30°C for 0.5-2h.

[0056] Preferably, the second mixing comprises: mixing the product of the first mixing with a silane coupling agent at -5°C to 5°C, and then stirring at 20-30°C for 1.5-3h.

[0057] Preferably, the silanization treatment is performed under an inert atmosphere, and the inert atmosphere is preferably provided by nitrogen.

[0058] The present invention has no special requirements for the order of adding materials in the first mixing. Preferably, the first mixing method includes: adding the first base to the phosphorus-containing heterocyclic compound.

[0059] The present invention has no special requirements for the order of adding materials in the second mixing. Preferably, the second mixing method includes: adding a silane coupling agent to the product of the first mixing.

[0060] Preferably, the first base and the phosphorus-containing heterocyclic compound can be provided by a first base solution and a phosphorus-containing compound solution, respectively. The present invention has no particular limitation on the solvents in the first base solution and the phosphorus-containing compound solution, and conventional organic solvents in the art can be used, such as hexane and / or tetrahydrofuran. The solvents in the first base solution and the phosphorus-containing compound solution can be the same or different, and the present invention has no particular limitation on this.

[0061] Preferably, the concentration of the first alkaline solution is 1-3 mol / L.

[0062] Preferably, the concentration of the phosphorus-containing compound solution is 0.1-0.5 mol / L.

[0063] According to the present invention, preferably, step (1) further comprises: removing the solvent in the product obtained by silylation treatment under vacuum conditions. The present invention has no particular limitation on the method of removing the solvent, and it can be carried out in a conventional manner and under conventional conditions in the art.

[0064] The present invention has no particular limitation on the source of the compound II, which can be purchased from commercial sources or prepared using a chemical reaction method known in the art.

[0065] According to some preferred embodiments of the present invention, the preparation method of compound II comprises:

[0066] S1, performing imidization reaction on an amine compound and an amide compound containing a halogen substitution;

[0067] S2, subjecting the product obtained in step S1 to a halogenation reaction with a halide.

[0068] According to the present invention, the general structural formula of the amine compound can be expressed as Ar'NH 2 , wherein Ar' has the same definition as in the first aspect.

[0069] According to some preferred embodiments of the present invention, the amine compound is selected from at least one of aniline, 2,6-dimethylaniline and 2,6-diisopropylaniline.

[0070] According to the present invention, the general structural formula of the amide compound containing halogen substitution can be expressed as: Wherein, Ar has the same definition as in the first aspect, and X is any halogen atom, preferably a chlorine atom.

[0071] According to some preferred embodiments of the present invention, the halogen-substituted amide compound is benzoyl chloride.

[0072] According to some preferred embodiments of the present invention, the imidization reaction is carried out in the presence of an acid binder, and the acid binder may be a conventional organic base in the art, and the organic base may be, for example, an organic tertiary amine, such as triethylamine.

[0073] According to some preferred embodiments of the present invention, the molar ratio of the amine compound to the acid binding agent is 1:(1-1.5), preferably 1:(1-1.2).

[0074] According to some preferred embodiments of the present invention, the molar ratio of the amine compound to the halogen-substituted amide compound is 1:(1-2), preferably 1:(1-1.5).

[0075] According to some preferred embodiments of the present invention,

[0076] Preferably, the amine compound and the halogen-substituted amide compound can be provided by an amine compound solution and a halogen-substituted amide compound solution, respectively. The present invention has no particular limitation on the solvents in the amine compound solution and the halogen-substituted amide compound solution, and conventional organic solvents in the art can be used, such as alkanes and / or halogenated alkanes, such as at least one of dichloromethane, chloroform and tetrachloromethane. The solvents of the amine compound solution and the halogen-substituted amide compound solution can be the same or different, and the present invention has no particular limitation on this.

[0077] Preferably, the concentration of the amine compound solution is 0.1-1 mol / L.

[0078] Preferably, the concentration of the halogen-substituted amide compound solution is 0.1-0.5 mol / L.

[0079] The present invention has no particular requirements for the mixing method of the amine compound, the amide compound containing halogen substitution and the optional acid binding agent. Preferably, S1 comprises: first mixing the acid binding agent with the amine compound solution, then adding the amide compound solution containing halogen substitution, heating under reflux, and performing imidization reaction.

[0080] Preferably, the imidization reaction is carried out under an inert atmosphere, and the inert atmosphere is preferably provided by nitrogen.

[0081] According to some preferred embodiments of the present invention, the conditions of the imidization reaction include: temperature of 20-60° C. and time of 0.5-2 h.

[0082] Preferably, step S1 further comprises: washing and drying the product of the imidization reaction. The present invention has no particular limitation on the manner and conditions of the washing, and the detergent used for the washing may be water. The present invention has no particular limitation on the manner of the drying, and preferably, the drying comprises: contacting the product obtained by washing with a desiccant, and the desiccant is preferably magnesium sulfate. The present invention has no particular limitation on the amount of the desiccant, and those skilled in the art may select it according to actual needs.

[0083] The present invention has a wide range of halide choices in step S2, as long as it can undergo a halogenation reaction with the product obtained in step S1 to introduce halogen atoms. Preferably, the halide is phosphorus pentachloride.

[0084] Preferably, the molar ratio of the product obtained in step S1 to the halide calculated as halogen atoms is 1:(1-5), preferably 1:(1-3).

[0085] Preferably, the halogenation reaction is carried out in the presence of an organic solvent. The present invention has no particular limitation on the type of the organic solvent, for example, it may be toluene.

[0086] Preferably, the conditions of the halogenation reaction include: temperature of 20-80° C. and time of 12-24 h.

[0087] According to some preferred embodiments of the present invention, the preparation method further comprises: purifying the product obtained from the halogenation reaction. The purification can be performed, for example, by vacuum distillation, which is well known to those skilled in the art.

[0088] According to the present invention, in the step (2), the molar ratio of the product obtained in the step (1) to the compound II is 1:(1-2), preferably 1:(1-1.5).

[0089] Preferably, the nucleophilic substitution reaction is carried out in an organic solvent. The present invention has no particular limitation on the type of the organic solvent. Preferably, the organic solvent is a halogenated hydrocarbon, such as chlorobenzene.

[0090] According to the present invention, step (2) comprises: mixing the product obtained in step (1) with compound II, heating under reflux, and performing a nucleophilic substitution reaction.

[0091] According to some preferred embodiments of the present invention, the conditions of the nucleophilic substitution reaction include: temperature of 100-150° C. and time of 2-12 h.

[0092] According to the present invention, preferably, the preparation method further comprises: purifying the product obtained in step (2). The purification can be carried out in a conventional manner and under conventional conditions in the art. Preferably, the purification method is recrystallization.

[0093] Preferably, the recrystallization solvent is a C5-C10 alkane, more preferably n-hexane.

[0094] The second aspect of the present invention provides a selective ethylene oligomerization catalytic composition, which comprises a transition metal compound, a ligand and an activator, wherein the ligand comprises the ligand compound described in the first aspect.

[0095] According to some preferred embodiments of the present invention, the general formula of the transition metal compound is MR n , wherein M is selected from at least one of metal elements of Group IVB, Group VB, Group VIIB, Group VIII, and Group IB, R is at least one of inorganic anions, organic anions, and organic neutral molecules, and n is a positive integer of 1-6.

[0096] Preferably, M is selected from at least one of iron, cobalt, nickel, copper, titanium, vanadium, chromium, manganese, molybdenum, tungsten and palladium, more preferably at least one of chromium, iron, cobalt, nickel and palladium, more preferably chromium. In the above preferred case, it is beneficial to obtain high selectivity of hexene-1 and octene-1 while obtaining high catalytic activity.

[0097] Preferably, the transition metal compound is selected from at least one of chromium trichloride-tri(tetrahydrofuran) complex, benzene tricarbonyl chromium, chromium (III) octoate, chromium hexacarbonyl, chromium (III) acetylacetonate, chromium (III) naphthenate, chromium (III) 2-ethylhexanoate, chromium (III) acetate, 2,2,6,6-tetramethylheptanedione chromium (III) and chromium (III) chloride, and more preferably at least one of chromium trichloride-tri(tetrahydrofuran) complex, chromium (III) acetylacetonate and chromium (III) 2-ethylhexanoate. Chromium (III) refers to the valence state of chromium in the transition metal compound being positive trivalent.

[0098] The present invention has no particular limitation on the type of the activator, which may be any compound that forms an active catalyst when mixed with the ligand and the transition metal compound. The activator may be a single compound or a combination of multiple compounds.

[0099] According to some preferred embodiments of the present invention, the activator is selected from at least one of an alkyl aluminum compound, an aluminoxane compound and an organic boron compound.

[0100] Preferably, the alkylaluminum compound is selected from at least one of trialkylaluminum, alkylaluminum halide, alkylaluminum hydride and alkylaluminum sesquichloride, preferably trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, diethylaluminum monochloride (AlEt 2 Cl) and triethylaluminum trichloride (Al 2 Et 3 Cl 3 ) at least one of.

[0101] The alkylaluminoxane compound can be at least one of a linear alkylaluminoxane compound, a cyclic alkylaluminoxane compound and a caged alkylaluminoxane compound. Preferably, the aluminoxane compound is selected from at least one of methylaluminoxane (MAO), ethylaluminoxane, isobutylaluminoxane and modified aluminoxane. The methylaluminoxane can also be methylaluminoxane (DMAO) from which volatile components have been removed.

[0102] The modified aluminoxane refers to methylaluminoxane or ethylaluminoxane modified from other alkanes, which is not limited in the present invention and can be commercially obtained, for example, it can be purchased from Akzo-Nobel with a modified methylaluminoxane brand of MMAO-3A and a CAS number of 146905-79-5.

[0103] Preferably, the organic boron compound is selected from at least one of boroxine, triethylborane, triphenylborane and tris(pentafluorophenyl)borane. In the present invention, the organic boron compound can be mixed with an organic aluminum compound and used as an activator.

[0104] According to some particularly preferred embodiments of the present invention, the activator is selected from at least one of methylaluminoxane, ethylaluminoxane, isobutylaluminoxane and modified methylaluminoxane.

[0105] According to some preferred embodiments of the present invention, the molar ratio of the ligand to the transition metal compound calculated as the transition metal element is (0.01-100): 1, further preferably (0.1-1): 1, preferably (0.5-2): 1. In the above preferred case, it is beneficial to obtain high selectivity of hexene-1 and octene-1 while obtaining high catalytic activity.

[0106] According to some preferred embodiments of the present invention, the molar ratio of the activator to the transition metal compound calculated as the transition metal element is (1-10000): 1, preferably (1-2000): 1. In the above preferred case, it is beneficial to obtain high selectivity of hexene-1 and octene-1 while obtaining high catalytic activity.

[0107] The present invention has no special requirements for the form of the composition. The above-mentioned ligand, transition metal compound and activator can be mixed simultaneously or in any order to provide the selective ethylene polymerization catalytic composition; the transition metal compound and the ligand can also be mixed to prepare a transition metal-ligand complex, which is then stored separately from the activator; or the ligand, transition metal compound and activator can exist independently.

[0108] The third aspect of the present invention provides use of the ligand compound described in the first aspect or the selective ethylene oligomerization catalytic composition described in the second aspect in a selective ethylene oligomerization reaction.

[0109] A fourth aspect of the present invention provides a method for selective ethylene oligomerization, the method comprising: contacting ethylene with a catalyst under ethylene oligomerization conditions;

[0110] Wherein, the catalyst comprises the ethylene oligomerization catalyst composition described in the second aspect.

[0111] The present invention has no particular requirements on the specific manner in which the ethylene oligomerization catalyst composition provides the catalyst.

[0112] According to some preferred embodiments of the present invention, the above-mentioned ligand, transition metal compound and activator may be mixed simultaneously or in any order to provide the selective ethylene oligomerization catalytic composition, and then added into the reactor.

[0113] The mixing can be performed in the presence or absence of a solvent, preferably, the mixing temperature is -20°C to 250°C, more preferably 20-100°C. In the above preferred case, the catalytic activity of the catalytic composition is further improved.

[0114] In other preferred embodiments, a separable metal-ligand complex can be prepared in situ from a transition metal compound and a ligand, and then the metal-ligand complex is added to a reactor, and finally an activator is added.

[0115] In other preferred embodiments, the transition metal compound, the ligand and the activator can be added to the reactor separately, thereby preparing the transition metal-ligand complex in situ. In the present invention, preparing the complex in situ means preparing the complex in the medium where the catalytic reaction occurs.

[0116] According to some preferred embodiments of the present invention, the contacting is carried out in the presence of an inert solvent, and the inert solvent is preferably at least one of alkanes, aromatic hydrocarbons, olefins and ionic liquids. 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., preferably toluene and / or methylcyclohexane.

[0117] Preferably, the amount of the inert solvent is such that the concentration of the catalyst calculated as transition metal is 0.01-10000 μmol / L, preferably 1-500 μmol / L. The above preferred embodiment is advantageous for obtaining high selectivity of hexene-1 and octene-1 while obtaining high catalytic activity.

[0118] Preferably, the ethylene oligomerization reaction conditions include: a temperature of 0-200°C, preferably 10-120°C, more preferably 20-100°C; and an ethylene pressure of 0.1-50 MPa, preferably 1-10 MPa.

[0119] The present invention will be described in detail below through examples.

[0120] Unless otherwise specified, the raw materials used were purchased from commercial sources.

[0121] The following preparation examples are used to illustrate the preparation of the ligand compounds in the present invention.

[0122] Preparation Example 1:

[0123] (1) Phosphorolane (10 mmol) was placed in a dry flask filled with nitrogen and dissolved in tetrahydrofuran (50 mL), and then cooled to 0°C. n-Butyl lithium ( n BuLi) solution (2.5M solution in hexane, 11 mmol) was added dropwise to the cooled solution, then warmed to room temperature and stirred for one hour. The solution was cooled back to 0°C and trimethylsilyl chloride (12 mmol) was added dropwise thereto. The solution was again allowed to warm to room temperature and stirred for two hours, and the solvent was removed under vacuum to obtain trimethylphospholylsilane.

[0124] (2) Add triethylamine (12 mmol) and aniline (12 mmol) to a dry, nitrogen-filled three-necked round-bottom flask equipped with a dropping funnel and a condenser, and dissolve them with dichloromethane (30 mL). Then, a solution of benzoyl chloride (12 mmol) in dichloromethane (30 mL) is added dropwise to the above amine solution. After the addition is completed, the resulting solution is refluxed at 40° C. for 1 hour. The solution is cooled and washed three times with 50 mL of distilled water, and then dried over magnesium sulfate. The solvent is removed in vacuo, toluene (30 mL) is added thereto to form a slurry, and solid phosphorus pentachloride is slowly added under vigorous stirring. After the solution is stirred overnight, the volatile components are removed in vacuo, and after reduced pressure distillation, N-phenylimine benzyl chloride is obtained.

[0125] (3) The trimethylphosphopentylsilane (10 mmol) and N-phenyliminobenzyl chloride (10 mmol) prepared above were dissolved in 15 mL of chlorobenzene, respectively. The two solutions were mixed in a flask, and the mixture was heated to 132° C. for reflux reaction for 4 hours. The reaction mixture was cooled to room temperature, the solvent was removed under vacuum, and recrystallized using n-hexane to obtain ligand L1.

[0126] The structure of L1 was characterized by nuclear magnetic resonance spectrum: 1H NMR (400MHz, CDCl3) δ = 7.60-7.45 (m, 6H), 7.42-7.30 (m, 8H), 6.99-6.87 (m, 2H), 6.10-5.81 (m, 2H), 1.77-1.30 (m, 8H). It was proved that L1 had the structure shown in formula (1), wherein Ar is phenyl, Ar' is phenyl, and the 1,2-positions are four-membered rings composed of carbon atoms.

[0127] Preparation Example 2

[0128] The method of Preparation Example 1 was followed, except that in step (2), an equimolar amount of 2,6-dimethylaniline was used to replace aniline. The prepared ligand was denoted as L2.

[0129] L2 has a structure represented by formula (1), wherein Ar is a phenyl group and Ar' is a 2,6-dimethylphenyl group.

[0130] Preparation Example 3

[0131] The method of Preparation Example 1 was followed, except that in step (2), an equimolar amount of 2,6-diisopropylaniline was used to replace aniline. The prepared ligand was denoted as L3.

[0132] L3 has a structure represented by formula (1), wherein Ar is a phenyl group and Ar' is a 2,6-diisopropylphenyl group.

[0133] Preparation Example 4

[0134] The method of Preparation Example 2 was followed, except that in step (1), an equimolar amount of 2,5-dimethylphospholane was used to replace phospholane, and the prepared ligand was denoted as L4.

[0135] L4 has a structure represented by formula (1), wherein Ar is a phenyl group and Ar' is a 2,6-dimethylphenyl group.

[0136] Preparation Example 5

[0137] The method of Preparation Example 4 was followed, except that an equal molar amount of 2,6-diisopropylaniline was used to replace 2,6-dimethylaniline. The prepared ligand was denoted as L5.

[0138] L5 has a structure represented by formula (1), wherein Ar is a phenyl group and Ar' is a 2,6-diisopropylphenyl group.

[0139] Preparation Example 6

[0140] The method of Preparation Example 4 was followed, except that in step (1), an equal molar amount of 2,5-diethylphospholane was used to replace 2,5-dimethylphospholane, and the prepared ligand was denoted as L6.

[0141] L6 has a structure represented by formula (1), wherein Ar is a phenyl group and Ar' is a 2,6-dimethylphenyl group.

[0142] Comparative Preparation Example 1

[0143] The method of Preparation Example 2 was followed, except that an equimolar amount of diisopropylphosphine was used to replace phospholane. The prepared ligand was recorded as DL1.

[0144] The structure of DL1 is shown below,

[0145] The following examples are used to illustrate the method for selective ethylene oligomerization provided by the present invention.

[0146] Example 1

[0147] A 1L stainless steel autoclave was heated to 130°C under vacuum and maintained for two hours, then replaced with nitrogen and cooled to the reaction temperature and replaced with ethylene three times before use.

[0148] Methylcyclohexane, modified methylaluminoxane (purchased from Akzo-Nobel, brand MMAO-3A, ​​CAS number 146905-79-5), ligand L1, di(acetylacetonate)chromium (2 μmol) were added to the autoclave in sequence, the total volume of the mixed solution was 300 mL, and the molar ratio of ligand L1: di(acetylacetonate)chromium: modified methylaluminoxane was 1.2:1:500. After the catalyst was added, the autoclave was sealed, stirring was started, the ethylene feed valve was opened, the ethylene pressure was controlled to 4 MPa, and the reaction temperature was controlled at 40°C by heating or cooling to carry out ethylene polymerization.

[0149] After the reaction was carried out for 30 minutes, the ethylene feed was stopped, the reaction stirring was turned off, and the reactor was cooled to 10°C. After the pressure was released, 1.000-1.100g of nonane was added to the reactor as an internal standard and stirred evenly. A 10wt% aqueous hydrochloric acid solution was added to the above mixture to quench the reaction, and the liquid phase product was collected for gas chromatography analysis. The solid high molecular polymer produced by the reaction was filtered, collected, washed with 10% aqueous hydrochloric acid solution, ethanol, and dried, and the mass was weighed. The product composition was analyzed by gas chromatography internal standard method, and the catalyst activity was calculated. The results are shown in Table 1.

[0150] The activity of the catalyst was calculated by the following formula:

[0151]

[0152] The test method of hexene-1 selectivity (wt%) and octene-1 selectivity (wt%) is as follows: the liquid product obtained after filtering the total reaction product is analyzed by gas chromatography internal standard method, and the content of hexene-1 / octene-1 in the liquid product is calculated to know its selectivity;

[0153] Polymer selectivity (wt%): The ratio of the mass of the solid product obtained by filtering the total reaction product, washing it, drying it, and weighing it to the total mass of the product is recorded as the polymer selectivity.

[0154] Embodiment 2-6

[0155] The method of Example 1 was followed, except that equimolar amounts of L2-L6 were used to replace L1. The results are shown in Table 1.

[0156] Example 7

[0157] The method of Example 4 was followed, except that an equimolar amount of triethylaluminum was used to replace the modified methylaluminoxane. The results are shown in Table 1.

[0158] Example 8

[0159] The method of Example 4 was followed, except that the reaction temperature was controlled to be 60° C. The results are shown in Table 1.

[0160] Example 9

[0161] The method of Example 4 was followed, except that the reaction temperature was controlled to be 80° C. The results are shown in Table 1.

[0162] Example 10

[0163] The method of Example 8 was followed, except that the ethylene pressure was controlled to be 5 MPa. The results are shown in Table 1.

[0164] Embodiment 11

[0165] The method of Example 8 was followed, except that the amount of modified methylaluminoxane used was such that the molar ratio of modified methylaluminoxane to di(acetylacetonate)chromium was 1000:1. The results are shown in Table 1.

[0166] Comparative Example 1

[0167] The method of Example 7 was followed, except that an equal molar amount of DL1 was used to replace L4. The results are shown in Table 1.

[0168] Table 1

[0169]

[0170] It can be seen from the results in Table 1 that the use of the catalyst of the present invention for ethylene selective tetramerization catalysis can effectively change the selectivity of ethylene trimerization and tetramerization by changing the ligand structure in the catalyst. Under the optimized catalyst structure and reaction conditions, higher catalytic reaction activity and ethylene trimerization and tetramerization selectivity, and ethylene tetramerization selectivity can be obtained compared with the comparative example. At the same time, the solid polymer obtained by the catalyst has low selectivity, which is conducive to using the catalyst in a continuous production device, reducing problems such as pipeline blockage caused by the large-scale generation of solid polymers, and has a high industrial application value.

[0171] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A ligand compound, It is characterized in that The ligand compound has a structure shown in formula (1), wherein Ar and Ar' are each independently selected from substituted or unsubstituted aryl or heteroaryl; The 1,2-positions are substituted or unsubstituted cyclic substituents.

2. The ligand compound according to claim 1, in, In formula (1), Ar and Ar' are each independently selected from a C6-C30 substituted or unsubstituted aryl or heteroaryl group, and the substituent in the substituted aryl or heteroaryl group is selected from at least one of a C1-C10 alkyl group, an aryl group and a halogen atom; Preferably, the heteroatom in the substituted or unsubstituted heteroaryl group is at least one of oxygen, sulfur, nitrogen and phosphorus; Preferably, Ar and Ar' 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, anthracenyl, 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, in, The cyclic substituent is a three-membered ring, four-membered ring, five-membered ring, six-membered ring, seven-membered ring or eight-membered ring substituent composed entirely of carbon atoms, preferably a four-membered ring and / or a five-membered ring substituent, more preferably a four-membered ring substituent; Preferably, the substituent of the substituted cyclic substituent is at least one of an alkyl group, an alkoxy group, a substituted or unsubstituted phenyl group and a benzyl group, preferably at least one of a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an n-pentyl group, an isopropyl group, an isobutyl group, a tert-butyl group, an isopentyl group, a tert-pentyl group, a cyclopentyl group, a cyclohexyl group, a 2,6-dimethylcyclohexyl group, a methoxy group, a benzyl group, a phenyl group, an o-methylphenyl group and a 2,6-dimethylphenyl group.

4. A selective ethylene oligomerization catalytic composition, It is characterized in that The composition comprises a transition metal compound, a ligand and an activator, wherein the ligand comprises the ligand compound according to any one of claims 1-3.

5. The composition according to claim 4, in, The general formula of the transition metal compound is MR n , wherein M is selected from at least one of metal elements of Group IVB, Group VB, Group VIIB, Group VIII, and Group IB, R is at least one of inorganic anions, organic anions, and organic neutral molecules, and n is a positive integer of 1-6; Preferably, M is selected from at least one of iron, cobalt, nickel, copper, titanium, vanadium, chromium, manganese, molybdenum, tungsten and palladium, more preferably at least one of chromium, iron, cobalt, nickel and palladium, more preferably chromium; Preferably, the transition metal compound is selected from at least one of chromium trichloride-tri(tetrahydrofuran) complex, benzene tricarbonyl chromium, chromium (III) octoate, chromium hexacarbonyl, chromium (III) acetylacetonate, chromium (III) cyclohexaneate, chromium (III) 2-ethylhexanoate, chromium (III) acetate, 2,2,6,6-tetramethylheptanedione chromium (III) and chromium (III) chloride, and more preferably at least one of chromium trichloride-tri(tetrahydrofuran) complex, chromium (III) acetylacetonate and chromium (III) 2-ethylhexanoate.

6. The composition according to claim 4 or 5, in, The activator is selected from at least one of an alkyl aluminum compound, an aluminoxane compound and an organic boron compound; Preferably, the alkylaluminum compound is selected from at least one of trialkylaluminum, alkylaluminum halide, alkylaluminum hydride and alkylaluminum sesquichloride, preferably at least one of trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, diethylaluminum monochloride and triethylaluminum trichloride; Preferably, the aluminoxane compound is selected from at least one of methylaluminoxane, ethylaluminoxane, isobutylaluminoxane and modified aluminoxane; Preferably, the organic boron compound is selected from at least one of boroxine, triethylborane, triphenylborane and tris(pentafluorophenyl)borane.

7. A composition according to any one of claims 4 to 6, in, The molar ratio of the ligand to the transition metal compound calculated as the transition metal element is (0.01-100):1, more preferably (0.1-1):1, and preferably (0.5-2):1; Preferably, the molar ratio of the activator to the transition metal compound calculated as the transition metal element is (1-10000):1, preferably (1-2000):

1.

8. Use of the ligand compound according to any one of claims 1 to 3 or the selective ethylene oligomerization catalytic composition according to any one of claims 4 to 7 in a selective ethylene oligomerization reaction.

9. A method for selective ethylene oligomerization, the method comprising: include: contacting ethylene with a catalyst under ethylene oligomerization reaction conditions; Wherein, the catalyst comprises the ethylene oligomerization catalyst composition according to any one of claims 4 to 7.

10. The method according to claim 9, in, The contacting is carried out in the presence of an inert solvent, and the inert solvent is preferably at least one of an alkane, an aromatic hydrocarbon, an alkene and an ionic liquid; Preferably, the inert solvent is used in an amount such that the concentration of the catalyst calculated as transition metal is 0.01-10000 μmol / L; Preferably, the ethylene oligomerization reaction conditions include: a temperature of 0-200°C, preferably 10-120°C; The ethylene pressure is 0.1-50 MPa, preferably 1-10 MPa.

Images