A catalyst for the selective tetramerization of ethylene containing ferrocene PNP ligands, its preparation and use

Abstract

The application relates to a catalyst containing a ferrocene PNP ligand for selective tetramerization of ethylene and a preparation method and application thereof, the catalyst comprising a ligand, a transition metal compound and an activator, wherein the chemical structural formula of the ligand is shown in the following formula (I): wherein groups R 1 to R 4 are each independently selected from an alkyl, alkoxy, cycloalkyl, alkenyl or aromatic group; groups R 5 to R 6 are each independently selected from hydrogen, halogen, alkyl, alkoxy, alkenyl, aromatic group. The catalyst is used for selective tetramerization of ethylene to generate 1-octene. Compared with the prior art, the application has the advantages of improving the selectivity of 1-octene, reducing the content of cyclic C6 and lowering the content of polymer.

Description

Technical Field

[0001] This invention relates to the field of ethylene oligomerization technology, specifically to a catalyst for selective tetramerization of ethylene containing ferrocene PNP ligands, its preparation method, and its application. Background Technology

[0002] Linear α-olefins (LAOs) are important chemical raw materials used in the preparation of lubricants, surfactants, etc. 1-Hexene and 1-Octene are indispensable comonomers in the synthesis of linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE) (the comonomer content in LLDPE is generally 8-10%, and in HDPE it is 1-2%). Ethylene oligomerization, as an important method for producing linear α-olefins, offers significant improvements in product quality compared to traditional methods such as wax cracking, coal extraction, and extraction separation, and is now widely used in industrial production.

[0003] Traditional ethylene oligomerization catalysis mainly utilizes titanium-based, zirconium-based, and iron-based catalysts. These catalytic systems primarily follow the Cossee-Arlman mechanism, where ethylene molecules insert into the catalyst metal center and undergo linear chain growth. The resulting linear α-olefins typically exhibit a normal distribution, requiring separation and purification for industrial applications. In contrast, highly selective ethylene oligomerization primarily follows a metal cyclization mechanism, producing α-olefins with a Schulz-Flory distribution, exhibiting high content at the peak product level. This method provides an important pathway for producing α-olefins with specific carbon numbers. In recent years, the increasing demand for 1-hexene and 1-octene has made selective ethylene oligomerization a hot topic in both industrial and academic research.

[0004] Currently, reports on highly selective oligomerization of ethylene mainly focus on dimerization, trimerization, and tetramerization to produce 1-butene, 1-hexene, and 1-octene. In these catalytic systems, the structural regulation of the catalyst plays a crucial role in product distribution, and the regulation of the catalyst structure depends on changes in the ligand skeleton and substituents. In recent years, research in this field has focused on the catalytic mechanism and ligand design of selective oligomerization of ethylene, and some important results have been achieved. In 2002, British Petroleum reported the use of PNP-type ligands with the PAr2N(R)PAr2 structure (Ar being an ortho-methoxy-substituted aryl group) for the highly selective trimerization of ethylene to produce 1-hexene catalyzed by chromium, with a selectivity of up to 91.5% (Chem. Commun. 2002, 858-859). In 2003, Phillips Petroleum achieved the industrial-scale trimerization of ethylene using its developed Phillips trichromium catalyst (US5523507). Sinopec (Yanshan) and PetroChina (Daqing) in my country subsequently adopted similar catalytic systems to achieve industrial-scale production of 1-hexene. However, the selective production of 1-octene via ethylene tetramerization is currently not industrial-scale. 1-Octene can be used to produce high-quality polyethylene (PE), polyolefin elastomers (POE), lubricating oil base oils (PAO), plasticizers, and surfactants. Compared to 1-hexene, 1-octene has higher economic value. In 2004, Sasol developed a selective tetramerization catalytic system for ethylene using a Cr / PNP catalyst (WO2004056478), achieving a 1-octene selectivity of up to 70.5%, while simultaneously generating 13% 1-hexene. 10 (hydrocarbons with 10 carbon atoms), C 12 The presence of numerous byproducts, including 12-carbon hydrocarbons and cyclic C6 hydrocarbons (6-carbon hydrocarbons), results in a low overall selectivity of only 83% for the high-value-added 1-hexene and 1-octene. Furthermore, the polymer content exceeds 2%, leading to polymer adhesion to the catalyst walls and entanglement of the agitator, thus affecting the continuous operation of the industrial plant. The polymer formation may be due to the degradation products in the catalyst causing high polymerization of ethylene.

[0005] Since the discovery of this catalytic system, extensive research has focused on the modification of PNP ligands. Because the substituents on the nitrogen (N) of PNP ligands are considered to play a crucial role in the selective ethylene tetramerization reaction, researchers have developed and studied many PNP ligands with different N-substituents. In 2007, Sasol synthesized PNP ligands with different alkyl and cycloalkyl substituents on the N-position, finding that increasing the steric hindrance of the N-position substituent improved the catalytic activity and the overall selectivity for 1-hexene and 1-octene (up to 89.5%). However, excessive steric hindrance also led to a decrease in the selectivity for 1-octene (J. Catal. 2007, 245, 279-284). In 2022, Barman et al. synthesized a PNP ligand with a m-trifluoromethylphenyl substituted N-position, finding that the selectivity for 1-octene was improved (up to 73.2%). However, this system suffers from high MMAO co-catalyst usage (Al / Cr ratio as high as 2000) and short catalyst lifetime (the activity decreased from 789 kg·g Cr when extended from 10 minutes to 30 minutes). -1 ·h -1 Reduced to 551 kg·g Cr -1 ·h -1 The catalyst exhibits several drawbacks, including a high content of cyclic C6 byproducts (up to 8.9%) and high polymer content (up to 0.8%). The short catalytic time (10 minutes) results in a short catalyst lifetime, low actual catalytic activity, and increased catalyst cost (ACS Omega, 2022, 7, 16333-16340). In the same year, the research group synthesized a class of PNP ligands with a triterpenoid skeleton substituted on the N-position. These ligands showed high selectivity for 1-octene (up to 74.1%) and a total selectivity for 1-hexene and 1-octene (up to 94.6%). However, this system also suffers from high MMAO co-catalyst usage (aluminum-chromium ratio as high as 2000), short catalytic time (10 minutes), and high polymer formation (up to 1.5%) (Chem.Comm. 2022, 58, 10044-10047). Summary of the Invention

[0006] The purpose of this invention is to overcome at least one of the defects of the prior art and provide a catalyst for selective tetramerization of ethylene containing ferrocene PNP ligands, which improves the selectivity of 1-octene, reduces the content of cyclic C6, and has a low polymer content, as well as its preparation method and application.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] To further improve the selectivity of 1-octene and the activity of the catalytic system, this invention creatively introduces a ferrocene framework onto the N atom of the PNP ligand and a phenyl or alkyl group onto the P atom. By introducing the ferrocene framework onto the N atom, the overall selectivity of 1-hexene and 1-octene can be improved without sacrificing the selectivity of 1-octene. This invention successfully improved the 1-octene selectivity of the catalytic system to 76.6%, and the overall selectivity of 1-hexene and 1-octene to 94.5%, effectively improving the selectivity of 1-octene while reducing the cyclic C6. Because the ferrocene contains an aromatic five-membered cyclopentadienyl ring, which is relatively smaller than the six-membered ring of the phenyl group, and because the ferrocene contains two five-membered aromatic rings chelated by iron atoms, and the other cyclopentadienyl ring not directly adjacent to the PNP can exert a steric hindrance effect for distal regulation, this effect can significantly increase the stability of the chromium metal active center, extend the catalyst lifetime, and effectively improve the activity of the catalytic system. The increased catalyst lifetime also reduces catalyst degradation, thereby allowing the polymer content in the reaction to be reduced to as low as 0.02-0.09%, as detailed below:

[0009] A catalyst for the selective tetramerization of ethylene containing a ferrocene PNP ligand, the catalyst comprising the ligand, a transition metal compound, and an activator, wherein the chemical structural formula of the ligand is shown in formula (I) below:

[0010]

[0011] In the formula,

[0012] Group R 1 To R 4 Each group is independently selected from alkyl, alkoxy, cycloalkyl, alkenyl, or aromatic groups;

[0013] Group R 5 To R 6 Each group is independently selected from hydrogen, halogen, alkyl, alkoxy, alkenyl, and aromatic groups.

[0014] Furthermore, R 1 To R 4 Same or different. Further, group R... 1 To R 4 Each is independently selected from alkyl, cycloalkyl, alkenyl, or phenyl.

[0015] Furthermore, the alkyl group is C1-C. 30Alkyl groups, specifically including methyl, ethyl, isopropyl, n-propyl, tert-butyl, n-butyl, sec-butyl, n-pentyl, sec-pentyl, cyclopentyl, tert-pentane, sec-pentyl, tert-hexyl, n-hexyl, sec-hexyl, isohexyl, cyclohexyl, n-heptyl, sec-heptyl, tert-heptyl, isoheptyl, neoheptyl, cycloheptyl, n-octyl, sec-octyl, tert-octyl, isooctyl, n-decyl, 3-methylcyclopentyl, 2,3-dimethylcyclopentyl, 2,4-dimethylcyclopentyl, 2,5-dimethylcyclopentyl, 2,3,4-trimethylcyclopentyl, 2,3,4,5-tetramethylcyclopentyl Alkane, 2-methylcyclopentyl, 2-ethylcyclopentyl, 2-n-propylcyclopentyl, 2-isopropylcyclopentyl, 2-methylcyclohexyl, 2,3-dimethylcyclohexyl, 2,4-dimethylcyclohexyl, 2,5-dimethylcyclohexyl, 2,6-dimethylcyclohexyl, 2,4,6-trimethylcyclohexyl, 2,3,4-trimethylcyclohexyl, 2,3,5-trimethylcyclohexyl, 2,3,6-trimethylcyclohexyl, 2,3,4,5,6-pentamethylcyclohexyl, benzyl, 2-hydroxycyclohexyl, 2-mercaptocyclohexyl, 2-methoxycyclohexyl, 2- Carboxycyclohexyl, 2-nitrocyclohexyl, 2-cyanocyclohexyl, 2-ethoxycyclohexyl, 2-chlorocyclohexyl, 2-fluorocyclohexyl, 2-bromocyclohexyl, 2-iodocyclohexyl, 2-aminocyclohexyl, 2-methylthiocyclohexyl, 2,3-dihydroxycyclohexyl, 2,4-dihydroxycyclohexyl, 2,5-dihydroxycyclohexyl, 2,6-dihydroxycyclohexyl, 3-chlorocyclohexyl, 3-fluorocyclohexyl, 3-bromocyclohexyl, 3-iodocyclohexyl, 3-methylcyclohexyl, 3-ethylcyclohexyl, 3-isopropylcyclohexyl, 3-n-propylcyclohexyl, 3-hydroxy Cyclohexyl, 3-methoxycyclohexyl, 3-ethoxycyclohexyl, 3-cyanocyclohexyl, 3-carboxycyclohexyl, 3-methylthiocyclohexyl, 3-mercaptocyclohexyl, 4-chlorocyclohexyl, 4-fluorocyclohexyl, 4-bromocyclohexyl, 4-iodocyclohexyl, 4-methylcyclohexyl, 4-ethylcyclohexyl, 4-isopropylcyclohexyl, 4-n-propylcyclohexyl, 4-hydroxycyclohexyl, 4-methoxycyclohexyl, 4-ethoxycyclohexyl, 4-cyanocyclohexyl, 4-carboxycyclohexyl, 4-methylthiocyclohexyl, or 4-mercaptocyclohexyl; wherein the alkenyl group is C1-C 30The alkenyl groups specifically include vinyl, allyl, 1-propenyl, 1-butenyl, 2-butenyl, 1-methyl-2-butenyl, 2-methyl-1-butenyl, 3-methyl-2-butenyl, 1-chloro-2-butenyl, 2-chloro-1-butenyl, 3-chloro-2-butenyl, 1-fluoro-2-butenyl, 2-fluoro-1-butenyl, 3-fluoro-2-butenyl, 1-bromo-2-butenyl, 2-Bromo-1-butenyl, 3-Bromo-2-butenyl, 1-Methoxy-2-butenyl, 2-Methoxy-1-butenyl, 3-Methoxy-2-butenyl, 1-Hydroxy-2-butenyl, 2-Hydroxy-1-butenyl, 3-Hydroxy-2-butenyl, 5-Hexenyl, 1-pentenyl, 2-pentenyl, 1-hexenyl, 2-hexenyl, 3-hexenyl, 1-heptenyl, 2-heptenyl, 3 -Heptenyl, 1-Octenyl, 2-Octenyl, 3-Octenyl, 4-Octenyl, 1-Nonenyl, 2-Nonenyl, 3-Nonenyl, 4-Nonenyl, 1-Cyclohexenyl, 2-Methyl-1-Cyclohexenyl, 3-Methyl-1-Cyclohexenyl, 4-Methyl-1-Cyclohexenyl, 5-Methyl-1-Cyclohexenyl, 6-Methyl-1-Cyclohexenyl, 2-Methoxy-1-Cyclohexenyl, 3-Methoxy -1-cyclohexenyl, 4-methoxy-1-cyclohexenyl, 5-methoxy-1-cyclohexenyl, 6-methoxy-1-cyclohexenyl, 2-chloro-1-cyclohexenyl, 3-chloro-1-cyclohexenyl, 4-chloro-1-cyclohexenyl, 5-chloro-1-cyclohexenyl, 6-chloro-1-cyclohexenyl, 2-cyclohexenyl, 3-cyclohexenyl, or 2-methyl-2-cyclohexenyl; wherein the alkoxy group is C1-C 20 The alkoxy group specifically includes alkoxy groups selected from methoxy, ethoxy, isopropoxy, n-propoxy, tert-butoxy, n-butoxy, sec-butoxy, n-pentoxy, sec-pentoxy, cyclopentoxy, tert-pentoxy, sec-pentoxy, tert-hexoxy, n-hexoxy, sec-hexoxy, isohexoxy, cyclohexoxy, n-heptoxy, sec-heptoxy, tert-heptyloxy, isoheptyloxy, neoheptyloxy, cycloheptoxy, n-octoxy, sec-octoxy, tert-octoxy, isooctoxy, or n-decoxy; the aromatic group is C4-C. 30Aryl groups and their derivatives, specifically including phenyl, o-nitrophenyl, m-nitrophenyl, p-nitrophenyl, p-fluorophenyl, o-fluorophenyl, p-ethylphenyl, o-ethylphenyl, m-ethylphenyl, m-fluorophenyl, p-chlorophenyl, o-chlorophenyl, m-chlorophenyl, 2,6-dichlorophenyl, 2,5-dichlorophenyl, 2,4-dichlorophenyl, 2,3-dichlorophenyl, 3,4-dichlorophenyl, 3,5-dichlorophenyl, p-ethylphenyl, and 2,6-difluorophenyl. 2,5-Difluorophenyl, 2,4-Difluorophenyl, 2,3-Difluorophenyl, 3,4-Difluorophenyl, 3,5-Difluorophenyl, 2,4-Dimethylphenyl, 2,3-Dimethylphenyl, 2,5-Dimethylphenyl, 2,6-Dimethylphenyl, 2,3-Diisopropylphenyl, 2,4-Diisopropylphenyl, 2,5-Diisopropylphenyl, 2,6-Diisopropylphenyl, 2,4-Di-tert-butylphenyl, 2,3-Di-tert-butylphenyl 2,5-Di-tert-butylphenyl, 2,6-Di-tert-butylphenyl, 2,4,6-trimethylphenyl, 2,3,4-trimethylphenyl, 2,4,6-trimethylphenyl, 2,4-dimethoxyphenyl, 2,3-dimethoxyphenyl, 2,5-dimethoxyphenyl, 2,6-dimethoxyphenyl, naphthyl, anthraceneyl, biphenyl, 7-fluoro-1-naphthyl, 8-fluoro-1-naphthyl, 7-chloro-1-naphthyl, 8-chloro-1-naphthyl, 9 -Fluoro-1-anthrayl, 9-chloro-1-anthrayl, 8-fluoro-1-anthrayl, 8-chloro-1-anthrayl, 7-methyl-1-naphthyl, 8-methyl-1-naphthyl, 7-nitro-1-naphthyl, 8-nitro-1-naphthyl, 7-methoxy-1-naphthyl, 8-methoxy-1-naphthyl, 7-hydroxy-1-naphthyl, 8-hydroxy-1-naphthyl, 7-cyano-1-naphthyl or 8-cyano-1-naphthyl; wherein the halogen is fluorine, chlorine, bromine or iodine.

[0016] In some embodiments, the ligand compound is one of the following substances, but it should be understood that the scope of the invention is not limited to these examples:

[0017]

[0018]

[0019]

[0020]

[0021] Furthermore, the alkyl group is methyl, ethyl, or isopropyl; the cycloalkyl group is cyclohexyl.

[0022] The transition metal in the catalyst system of this invention can be a transition metal compound commonly used in the art. The metal atom in the transition metal compound serves as the active metal center and plays an important role in the catalytic process. Further, the transition metal in the transition metal compound is selected from iron, cobalt, nickel, copper, titanium, vanadium, chromium, manganese, molybdenum, tungsten, nickel, or palladium; more preferably, the transition metal in the transition metal compound is selected from chromium. Specifically, the corresponding transition metal compound can be any chromium compound capable of enabling oligomerization, and selectable chromium compounds include those with the general formula CrR. n The compound shown has R in its formula. n R is an organic anion or a neutral molecule. n It typically contains 1-15 carbon atoms, where n is an integer from 0 to 6, and the valence state of Cr is between 0 and 6. Specifically, R... n The functional group is an organic compound or other functional 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)tricarbonylchromium, 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).

[0023] The activator in the catalyst system of 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. The activator includes alkylaluminum compounds, aluminoxane compounds, or organoboron compounds; the molar ratio of the ligand to the transition metal element in the transition metal compound is (0.01-100):1; the molar ratio of the activator to the transition metal element in the transition metal compound is (1-10000):1. Further, the aluminoxane compound specifically includes modified methylaluminoxane MMAO-3A; the molar ratio of the activator to the transition metal element in the transition metal compound is (400-700):1.

[0024] Furthermore, the activator includes alkylaluminum compounds, aluminum oxane compounds, or organoboron compounds.

[0025] Furthermore, the activator includes one or a mixture of several of alkylaluminum compounds, aluminoxane compounds, organoboron compounds, inorganic acids, or inorganic salts.

[0026] 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, such as diethylaluminum chloride (AlEt2Cl) and triethylaluminum chloride (Al2Et3Cl3).

[0027] 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.

[0028] Specifically, suitable boron compounds may include cycloboroxanes, triethylborane, triphenylborane, tris(pentafluorophenyl)borane, etc. Organoboron compounds may be used in combination with organoaluminum compounds.

[0029] Preferably, the activator can be selected from methylaluminoxane (MAO), ethylaluminoxane, isobutylaluminoxane, and modified methylaluminoxane (MMAO).

[0030] Furthermore, the aluminum oxane compound specifically includes modified methylaluminoxane MMAO-3A.

[0031] Furthermore, the molar ratio of the ligand to the transition metal element in the transition metal compound is (0.01-100):1, preferably (0.1-10):1, and more preferably (0.5-2):1;

[0032] The molar ratio of the activator to the transition metal element in the transition metal compound is (1-10000):1, preferably (1-2000):1, more preferably (600-1000):1, and most preferably (400-700):1.

[0033] A method for preparing a catalyst for selective tetramerization of ethylene containing ferrocene PNP ligands as described above, the method comprising: pre-mixing or directly adding the ligand, transition metal compound and activator into the reaction system for in-situ synthesis, thereby obtaining the catalyst for selective tetramerization of ethylene containing ferrocene PNP ligands.

[0034] 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 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 within a temperature range of approximately 20–100°C.

[0035] 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.

[0036] Application of a catalyst for the selective tetramerization of ethylene containing a ferrocene PNP ligand as described above, wherein the catalyst is used for the selective tetramerization of ethylene to produce 1-octene, the reaction is carried out in an inert solvent at a temperature of 0-200°C and a pressure of 10-5000 psig, and the concentration of the transition metal in the transition metal compound in the inert solvent is 0.01-10000 μmol / L; further, the reaction is carried out in an inert solvent at a temperature of 0-200°C, preferably 10-1 The reaction temperature is 20°C, more preferably 15-100°C, further preferably 20-80°C, and ultimately preferably 20-50°C; the reaction pressure is 10-5000 psig, preferably 100-2000 psig, more preferably 300-1000 psig, and ultimately preferably 400-600 psig; the concentration of the transition metal in the transition metal compound in the inert solvent is 0.01-10000 μmol / L, preferably 1-500 μmol / L, and more preferably 0.1-10 μmol / L.

[0037] The inert solvent includes one or more of alkanes, aromatics, alkenes, or 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., with toluene and methylcyclohexane being preferred.

[0038] Furthermore, the reaction temperature is 20-60℃ and the pressure is 400-600psig.

[0039] Compared with existing technologies, this invention creatively introduces a ferrocene framework onto the N atom of the PNP ligand and a phenyl or alkyl group onto the P atom. This invention successfully reduces the content of the cyclic C6 group, thereby improving the overall selectivity for 1-hexene and 1-octene while maintaining high selectivity for 1-octene. Because the aromatic five-membered ferrocene ring is relatively smaller than the six-membered ring of the phenyl group, and because the ferrocene contains two five-membered aromatic rings chelated by iron atoms, and the other ferrocene ring not directly adjacent to the PNP can exert a steric hindrance effect that significantly increases the stability of the chromium metal active center, prolongs the catalyst lifetime, and effectively improves the activity of the catalytic system. The increased catalyst lifetime also reduces catalyst degradation, thus allowing the polymer content in the reaction to be reduced to as low as 0.02%. Detailed Implementation

[0040] The embodiments of the present invention are described in detail below. These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments. Unless otherwise specified, % in the text can be considered as mass percentage.

[0041] A catalyst for the selective tetramerization of ethylene containing a ferrocene PNP ligand, its preparation method, and its application are disclosed. The preparation method involves pre-mixing or directly adding the ligand, a transition metal compound, and an activator to the reaction system for in-situ synthesis, thereby obtaining the catalyst for the selective tetramerization of ethylene containing the ferrocene PNP ligand. This catalyst is used for the selective tetramerization of ethylene to produce 1-octene. The reaction is carried out in an inert solvent at a temperature of 0-200°C and a pressure of 10-5000 psig. The concentration of the transition metal in the transition metal compound in the inert solvent is 0.01-10000 μmol / L. The inert solvent includes one or more of alkanes, aromatics, alkenes, or ionic liquids. In some embodiments, the reaction temperature is 20-60°C and the pressure is 400-600 psig.

[0042] The chemical structural formula of the ligand is shown in formula (I) below:

[0043]

[0044] In the formula, group R 1 To R 4 Each group is independently selected from alkyl, alkoxy, cycloalkyl, alkenyl, or aromatic groups; group R 5 To R 6 Each group is independently selected from hydrogen, halogen, alkyl, alkoxy, alkenyl, and aromatic groups. 1 To R 4 Same or different. In some embodiments, group R 1 To R 4Each is independently selected from alkyl, cycloalkyl, alkenyl, or phenyl. The alkyl group is methyl, ethyl, or isopropyl; the cycloalkyl group is cyclohexyl.

[0045] The transition metal in the transition metal compound is selected from iron, cobalt, nickel, copper, titanium, vanadium, chromium, manganese, molybdenum, tungsten, nickel, or palladium; the activator includes alkylaluminum compounds, aluminoxane compounds, or organoboron compounds; the molar ratio of the ligand to the transition metal element in the transition metal compound is (0.01-100):1; the molar ratio of the activator to the transition metal element in the transition metal compound is (1-10000):1. In some embodiments, the aluminoxane compound specifically includes modified methylaluminoxane MMAO-3A; the molar ratio of the activator to the transition metal element in the transition metal compound is (400-700):1.

[0046] Example 1

[0047] ligand L 1 The preparation steps are as follows:

[0048] (1) Preparation of ferroiodide

[0049] In a dry Schlenk reaction tube filled with argon, ferrocene (2.99 g, 16.1 mmol) and potassium tert-butoxide (217.7 mg, 1.94 mmol) were added, and the mixture was purged three times with nitrogen. Tetrahydrofuran (45 mL) was added, and the resulting yellow solution was cooled to -78 °C. Tert-butyllithium (23.7 mL, 1.7 M n-pentane solution, 40.3 mmol) was added dropwise, and the reaction was continued at -78 °C with stirring for 2 h. Then, elemental iodine (10.2 g, 40.3 mmol) was gradually added, and the reaction was brought to room temperature with stirring for 16 h. After the reaction was completed, 100 mL of saturated Na2S2O3 aqueous solution was added to the mixture to quench the reaction. The mixture was separated, and the aqueous phase was extracted with ethyl acetate (3 × 100 mL). The organic phases were combined, dried with anhydrous magnesium sulfate, filtered, and concentrated under reduced pressure to obtain the crude product. The crude product was purified by silica gel column chromatography to obtain a red oily compound (3.52 g, 11.3 mmol, 70%), which was then allowed to stand and solidified.

[0050] (2) Preparation of aminoferrocene

[0051] In a dry, argon-filled Schlenk reaction tube, ferrocene iodoforme (1.40 g, 4.5 mmol) was dissolved in anhydrous ethanol (9 mL). Copper iodide (87.6 mg, 0.46 mmol) and ferric oxide (73.6 mg, 0.46 mmol) were added to the solution. Ammonia solution (22 mL, 13.5 M) was added to the red suspension. The reaction mixture was heated to 90 °C for 6 h in a pressure vessel and then cooled to room temperature. Diethyl ether (100 mL) was then added, and the organic phase was washed with sodium hydroxide aqueous solution (3 × 50 mL, 1 M). The solution was dried over anhydrous magnesium sulfate, filtered, and concentrated under reduced pressure to obtain the crude product. Purification by silica gel column chromatography yielded a yellow-orange solid compound (0.70 g, 3.48 mmol, 77%).

[0052] (3) Ligand L 1 Preparation

[0053] In a dry Schlenk reaction tube filled with argon, diphenylphosphine chloride (644.4 mg, 2.92 mmol) was added dropwise to a solution of aminoferrocene (291.5 mg, 1.45 mmol) and triethylamine (0.45 mL, 3.22 mmol) in toluene (15 mL) at 0 °C and stirred for 0.5 h. The mixture was then brought to room temperature and stirred overnight. After the reaction was complete, the filtrate was filtered, the solvent was removed under reduced pressure, and the mixture was washed with diethyl ether (5 mL × 3). The solid was filtered to give an orange solid product L. 1 (388.0 mg, 47.0%). 1 H NMR (400MHz, CDCl3) δ1.30-1.40(m,5H),1.44-1.54(m,4H),7.04-7.12(m,8H),7.30-7.40(m,12H). 31 P NMR (162MHz, CDCl3) δ52.27(s),52.68(s).

[0054]

[0055] Example 2

[0056] ligand L 2 The preparation steps are as follows:

[0057] In a dry Schlenk reaction tube filled with argon, aminoferrocene (502.5 mg, 2.5 mmol) was added to diphenylphosphine chloride (485.5 mg, 2.2 mmol) and triethylamine (0.6 mL, 4.4 mmol). After stirring for 0.5 h, the mixture was transferred to room temperature and stirred overnight. The solvent was removed from the mixture, and anhydrous diethyl ether (20 mL) was added to form a suspension. The suspension was filtered to obtain the filtrate, which was then dried under reduced pressure to obtain an oily crude product.

[0058] The crude product (693.4 mg, 1.8 mmol) was dissolved in 10 mL of n-hexane. Butyllithium (0.8 mL, 2.5 M hexane solution, 2.0 mmol) was added at -60 °C. After 1 h, diethylphosphorus chloride (448.6 mg, 3.6 mmol) was added dropwise. After the addition was complete, the mixture was brought to room temperature and stirred overnight until the reaction was complete. The mixture was filtered through anhydrous and oxygen-free channels, dried under vacuum, and recrystallized from n-hexane at -30 °C to obtain product L. 2 (200.2 mg, 23.5%). 1 H NMR (400MHz, CDCl3) δ0.88-0.94(m,6H),1.30-1.40(m,5H),1.44-1.47(m,4H),1.69-1.76(m,4H),7.05-7.11(m,4H),7.32-7.39(m,6H). 31 P NMR (162MHz, CDCl3) δ51.23(s), 36.73(s).

[0059]

[0060] Example 3

[0061] ligand L 3 The preparation steps are as follows:

[0062] (1) Preparation of ethylphenyl phosphorus chloride

[0063] In a dry Schlenk reaction tube filled with argon, phenyl phosphorus dichloride (1.79 g, 10 mmol) was added, and tetrahydrofuran (10 mL) was added to dissolve it. The solution was then cooled to -78 °C, and ethyl magnesium chloride (10 mL, 1.0 M tetrahydrofuran solution, 10 mmol) was slowly added. After the addition was complete, the reaction was continued at this temperature for 0.5 h, and then the temperature was raised to room temperature for 8 h. The reaction was then used directly without purification after the reaction was completed.

[0064] (2) Ligand L 3 Preparation

[0065] Reference ligand L 2The preparation method uses ethylphenylphosphine chloride (621.4 mg, 3.6 mmol) instead of diethylphosphine chloride, and recrystallizes it from n-hexane at -30 °C to obtain a pale yellow solid product L. 3 (330.4 mg, 35.2%). 1 H NMR(400MHz, CDCl3)δ0.95-1.03(m,3H),1.30-1.40(m,5H),1.41-1.53(m,4H) ,1.68-1.81(m,1H),2.02-2.14(m,1H),7.04-7.17(m,6H),7.28-7.41(m,9H). 31 P NMR (162MHz, CDCl3) δ64.56 (s), 51.28 (s).

[0066]

[0067] Example 4

[0068] ligand L 4 The preparation steps are as follows:

[0069] Reference ligand L 2 The preparation method uses divinylphosphorus chloride (433.8 mg, 3.6 mmol) instead of diethylphosphorus chloride, and recrystallizes it from n-hexane at -30 °C to obtain a pale yellow solid product L. 4 (164.7 mg, 19.5%). 1 H NMR (400MHz, CDCl3) δ1.30-1.40(m,5H),1.42-1.49(m,4H),5.54-5.67(m,4H),6.44-6.56(m,2H),7.04-7.12(m,4H),7.31-7.41(m,6H). 31 P NMR (162MHz, CDCl3) δ51.28 (s), 31.10 (s).

[0070]

[0071] Example 5

[0072] ligand L 5 The preparation steps are as follows:

[0073] Reference ligand L 2 The preparation method uses dimethoxyphosphorus chloride (462.6 mg, 3.6 mmol) instead of diethylphosphorus chloride, and recrystallizes it from n-hexane at -30 °C to obtain a pale yellow solid product L. 5 (267.2 mg, 31.1%). 1H NMR (400MHz, CDCl3) δ1.30-1.40(m,5H),1.43-1.48(m,2H),1.53-1.58(m,2H),3.51-3.56(m,6H),7.06-7.12(m,4H),7.32-7.39(m,6H). 31 P NMR (162MHz, CDCl3) δ148.36 (s), 51.28 (s).

[0074]

[0075] Example 6

[0076] ligand L 6 The preparation steps are as follows:

[0077] Reference ligand L 2 The preparation method uses cyclohexylethyl phosphorus chloride (643.3 mg, 3.6 mmol) instead of diethyl phosphorus chloride to obtain a colorless oily product L. 6 (372.1 mg, 39.2%). 1 H NMR (400MHz, CDCl3) δ0.89-0.95(m,3H),1.30-1.70(m,21H),2.26-2.34(m,1H),7.04-7.12(m,4H),7.31-7.40(m,6H). 31 P NMR (162MHz, CDCl3) δ100.08(s),51.13(s).

[0078]

[0079] Example 7

[0080] ligand L 7 The preparation steps are as follows:

[0081] (1) Preparation of vinylphenyl phosphorus chloride

[0082] In a dry Schlenk reaction tube filled with argon, vinyl phosphorus dichloride (902.3 mg, 7 mmol) was dissolved in tetrahydrofuran (10 mL), cooled to -78 °C, and phenyl magnesium bromide (3.5 mL, 2 M tetrahydrofuran solution, 7 mmol) was slowly added. After the addition was complete, the mixture was slowly heated to room temperature and stirred for 5 h until the reaction was complete. The solvent was then removed, the mixture was dissolved in diethyl ether (40 mL), filtered through anhydrous and oxygen-free filter, and the solvent was removed again to give a pale yellow oily product.

[0083] (2) Ligand L 7 Preparation

[0084] Reference ligand L 2 The preparation method uses vinylphenyl phosphorus chloride (614.2 mg, 3.6 mmol) instead of diethylphosphorus chloride to obtain a colorless oily product L. 7 (422.5 mg, 45.2%). 1 H NMR (400MHz, CDCl3) δ1.30-1.40(m,5H),1.43-1.47(m,2H),1.48-1.53(m,2H) ,5.62-5.72(m,2H),6.47-6.60(m,1H),7.05-7.11(m,6H),7.30-7.40(m,9H). 31 P NMR (162MHz, CDCl3) δ52.50(s),51.22(s).

[0085]

[0086] Example 8

[0087] ligand L 8 The preparation steps are as follows:

[0088] Reference ligand L 2 The preparation method uses diisopropylphosphorus chloride (549.5 mg, 3.6 mmol) instead of diethylphosphorus chloride, and recrystallizes it from n-hexane at -30 °C to obtain a pale yellow solid product L. 8 (311.4 mg, 34.5%). 1 H NMR (400MHz, CDCl3) δ0.94(m,12H),1.30-1.40(m,5H),1.42-1.51(m,4H),1.82-1.93(m,2H),7.05-7.12(m,4H),7.31-7.40(m,6H). 31 P NMR (162MHz, CDCl3) δ51.28 (s), 36.73 (s).

[0089]

[0090] Example 9

[0091] ligand L 9 The preparation steps are as follows:

[0092] Reference ligand L 2 The preparation method uses methylphenylphosphine chloride (571.0 mg, 3.6 mmol) instead of diethylphosphine chloride, and recrystallizes it from n-hexane at -30 °C to obtain a pale yellow solid product L. 9 (347.9 mg, 38.1%). 1H NMR (400MHz, CDCl3) δ1.30-1.40(m,5H),1.43-1.51(m,4H),1.75(s,3H),7.02-7.12(m,6H),7.26-7.40(m,9H). 31 P NMR (162MHz, CDCl3) δ61.98 (s), 51.28 (s).

[0093]

[0094] Example 10

[0095] ligand L 10 The preparation steps are as follows:

[0096] Reference ligand L 2 The preparation method uses isopropylphenyl phosphorus chloride (672.1 mg, 3.6 mmol) instead of diethylphosphorus chloride, and recrystallizes it from n-hexane at -30 °C to obtain a pale yellow solid product L. 10 (350.8 mg, 36.4%). 1 H NMR (400MHz, CDCl3) δ1.05 (d, J = 7.6Hz, 6H), 1.30-1.40 (m, 5H), 1.42-1.52 (m, 4 H),1.71-1.85(m,1H),7.05-7.11(m,4H),7.13-7.19(m,2H),7.29-7.39(m,9H). 31 P NMR (162MHz, CDCl3) δ64.56 (s), 51.28 (s).

[0097]

[0098] Example 11

[0099] ligand L 11 The preparation steps are as follows:

[0100] Reference ligand L 2 The preparation method uses dicyclohexylphosphorus chloride (838.1 mg, 3.6 mmol) instead of diethylphosphorus chloride, and recrystallizes it from n-hexane at -30 °C to obtain a pale yellow solid product L. 11 (345.4 mg, 33.0%). 1 H NMR (400MHz, CDCl3) δ1.26-1.72(m,29H),2.31-2.41(m,2H),7.04-7.11(m,4H),7.30-7.41(m,6H). 31PNMR(162MHz,CDCl3)δ100.08(s),51.31(s).

[0101]

[0102] Example 12

[0103] ligand L 12 The preparation steps are as follows:

[0104] Reference ligand L 2 The preparation method uses cyclohexylphenyl phosphorus chloride (816.1 mg, 3.6 mmol) instead of diethylphosphorus chloride, and recrystallizes it from n-hexane at -30 °C to obtain a pale yellow solid product L. 12 (334.6 mg, 32.3%). 1 H NMR(400MHz, CDCl3)δ0.95-1.03(m,3H),1.30-1.40(m,5H),1.41-1.53(m,4H) ,1.68-1.81(m,1H),2.02-2.14(m,1H),7.04-7.17(m,6H),7.28-7.41(m,9H). 31 P NMR (162MHz, CDCl3) δ64.56 (s), 51.28 (s).

[0105]

[0106] Example 13

[0107] ligand L 13 The preparation steps are as follows:

[0108] Reference ligand L 2 The preparation method uses di-tert-butylphosphine chloride (650.5 mg, 3.6 mmol) instead of diethylphosphine chloride, and recrystallizes it from n-hexane at -30 °C to obtain a pale yellow solid product L. 13 (390.7 mg, 41.0%). 1 H NMR (400MHz, CDCl3) δ1.13(s,18H),1.30-1.40(m,5H),1.44-1.52(m,4H),7.05-7.11(m,4H),7.30-7.39(m,6H). 31 P NMR (162MHz, CDCl3) δ49.69 (s), 38.35 (s).

[0109]

[0110] Example 14

[0111] ligand L 14 The preparation steps are as follows:

[0112] Reference ligand L 1 The preparation method uses ethylphenylphosphine chloride (504.0 mg, 2.92 mmol) instead of diphenylphosphine chloride to obtain a pale yellow solid product L. 14 (263.5 mg, 38.4%). 1 H NMR (400MHz, CDCl3) δ1.01 (t, J = 8.3Hz, 6H), 1.30-1.40 (m, 5H), 1.44-1.47 (m, 4 H),1.64-1.81(m,2H),1.96-2.10(m,2H),7.10-7.18(m,4H),7.28-7.37(m,6H). 31 P NMR (162MHz, CDCl3) δ64.59(s), 64.50(s).

[0113]

[0114] Example 15

[0115] ligand L 15 The preparation steps are as follows:

[0116] Reference ligand L 1 The preparation method uses isopropylphenylphosphine chloride (545.2 mg, 2.92 mmol) instead of diphenylphosphine chloride to obtain a pale yellow solid product L. 15 (314.1 mg, 43.2%). 1 H NMR (400MHz, CDCl3) δ1.04 (d, J = 7.6Hz, 12H), 1.30-1.40 (m, 5H), 1.42-1.50 (m, 4H), 1.70-1.81 (m, 2H), 7.13-7.19 (m, 4H), 7.29-7.36 (m, 6H). 31 P NMR (162MHz, CDCl3) δ64.59(s), 64.50(s).

[0117]

[0118] Example 16

[0119] ligand L 16 The preparation steps are as follows:

[0120] Reference ligand L 1 The preparation method uses cyclohexylphenylphosphine chloride (662.1 mg, 2.92 mmol) instead of diphenylphosphine chloride to obtain a pale yellow solid product L.16 (330.5 mg, 39.2%). 1 H NMR (400MHz, CDCl3) δ1.30-1.64(m,25H),1.76-1.87(m,4H),7.15-7.21(m,4H),7.28-7.37(m,6H). 31 P NMR (162MHz, CDCl3) δ64.59(s), 64.50(s).

[0121]

[0122] Example 17

[0123] Ligand L1 7 The preparation steps are as follows:

[0124] Reference ligand L 1 The preparation method uses methylphenylphosphine chloride (463.2 mg, 2.92 mmol) instead of diphenylphosphine chloride to obtain a pale yellow solid product L. 17 (247.9 mg, 38.4%). 1 H NMR (400MHz, CDCl3) δ1.43 (s, 6H), 1.30-1.40 (m, 5H), 1.71 (d, J = 2.2Hz, 6H), 7.03-7.09 (m, 4H), 7.27-7.37 (m, 6H). 31 P NMR (162MHz, CDCl3) δ64.59(s), 64.50(s).

[0125]

[0126] Example 18

[0127] ligand L 18 The preparation steps are as follows:

[0128] Reference ligand L 1 The preparation method uses isopropylamine (85.7 mg, 1.45 mmol) instead of aminoferrocene to obtain a pale yellow solid product L. 18 (284.2 mg, 44.2%). 1 H NMR (400MHz, CDCl3) δ1.08 (d, J = 9.2Hz, 6H), 3.21-3.31 (m, 1H), 7.03-7.08 (m, 8H), 7.30-7.39 (m, 12H). 31 P NMR (162MHz, CDCl3) δ50.09 (s).

[0129]

[0130] Example 19

[0131] A catalyst for selective tetramerization of ethylene containing a ferrocene PNP ligand, its preparation method, and its application are disclosed below:

[0132] (1) Preparation of catalyst

[0133] In a dry Schlenk reaction tube filled with argon, chromium acetylacetone (0.28 mg, 0.80 μmol) and ligand L were added. 1 (0.55 mg, 0.96 μmol) and anhydrous methylcyclohexane (20 ml) were stirred for 5 minutes, and then modified methylaluminoxane MMAO-3A (0.4 mmol, 1.12 mol / L) was added. The mixture was reacted at room temperature for 5 minutes and then set aside for later use.

[0134] (2) Ethylene oligomerization

[0135] A 350 mL stainless steel high-pressure gas reactor was evacuated to a vacuum in a 120 °C oil bath for 3 hours to ensure an anhydrous and oxygen-free environment. It was then cooled to the reaction temperature, and the reactor was purged three times with ethylene gas. Immediately afterward, the prepared catalyst solution was injected into the high-pressure reactor using a dry glass syringe. The reactor was sealed, stirring was started, and ethylene gas was introduced, adjusting the pressure to 500 psig. The reactor was stirred at 40 °C for 30 minutes. After the reaction, the ethylene gas supply valve was closed, the reactor was cooled to 0 °C, the pressure was released, the reactor was opened, and a quantitative amount of nonane (internal standard) was added and stirred until homogeneous. The reaction was then quenched with approximately 30 mL of 10 wt% HCl aqueous solution. A small amount of the organic phase was filtered and subjected to GC analysis. The remaining mixture in the reactor was filtered, and the solid was collected. The solid was added to a 10 wt% HCl aqueous solution and stirred for 2 hours. After filtration, the solid was dried to constant weight and weighed. The data are shown in Table 1.

[0136] Example 20

[0137] The difference from Example 19 is that the ligand L used is... 1 Replace with ligand L 2 (0.51 mg, 0.96 μmol), data are shown in Table 1.

[0138] Example 21

[0139] The difference from Example 19 is that the ligand L used is... 1 Replace with ligand L 3 (0.50 mg, 0.96 μmol), data are shown in Table 1.

[0140] Example 22

[0141] The difference from Example 19 is that the ligand L used is... 1 Replace with ligand L 4 (0.45 mg, 0.96 μmol), data are shown in Table 1.

[0142] Example 23

[0143] The difference from Example 19 is that the ligand L used is... 1 Replace with ligand L 5 (0.46 mg, 0.96 μmol), data are shown in Table 1.

[0144] Example 24

[0145] The difference from Example 19 is that the ligand L used is... 1 Replace with ligand L 6 (0.53 mg, 0.96 μmol), data are shown in Table 1.

[0146] Example 25

[0147] The difference from Example 19 is that the ligand L used is... 1 Replace with ligand L 7 (0.50 mg, 0.96 μmol), data are shown in Table 1.

[0148] Example 26

[0149] The difference from Example 19 is that the ligand L used is... 1 Replace with ligand L 8 (0.48 mg, 0.96 μmol), data are shown in Table 1.

[0150] Example 27

[0151] The difference from Example 19 is that the ligand L used is... 1 Replace with ligand L 9 (0.49 mg, 0.96 μmol), data are shown in Table 1.

[0152] Example 28

[0153] The difference from Example 19 is that the ligand L used is... 1 Replace with ligand L 10 (0.51 mg, 0.96 μmol), data are shown in Table 1.

[0154] Example 29

[0155] The difference from Example 19 is that the ligand L used is... 1 Replace with ligand L 11 (0.56 mg, 0.96 μmol), data are shown in Table 1.

[0156] Example 30

[0157] The difference from Example 19 is that the ligand L used is... 1 Replace with ligand L 12 (0.55 mg, 0.96 μmol), data are shown in Table 1.

[0158] Example 31

[0159] The difference from Example 19 is that the ligand L used is... 1 Replace with ligand L 13 (0.51 mg, 0.96 μmol), data are shown in Table 1.

[0160] Example 32

[0161] The difference from Example 19 is that the ligand L used is... 1 Replace with ligand L 14 (0.45 mg, 0.96 μmol), data are shown in Table 1.

[0162] Example 33

[0163] The difference from Example 19 is that the ligand L used is... 1 Replace with ligand L 15 (0.48 mg, 0.96 μmol), data are shown in Table 1.

[0164] Example 34

[0165] The difference from Example 19 is that the ligand L used is... 1 Replace with ligand L 16 (0.56 mg, 0.96 μmol), data are shown in Table 1.

[0166] Example 35

[0167] The difference from Example 19 is that the ligand L used is... 1 Replace with ligand L 17 (0.43 mg, 0.96 μmol), data are shown in Table 1.

[0168] Example 36

[0169] The difference from Example 28 is that the ethylene oligomerization reaction was carried out at 20°C, and the data are shown in Table 1.

[0170] Example 37

[0171] The difference from Example 28 is that the ethylene oligomerization reaction was carried out at 60°C, and the data are shown in Table 1.

[0172] Example 38

[0173] The difference from Example 28 is that the amount of MMAO-3A used is 0.32 mmol, and the data is shown in Table 1.

[0174] Example 39

[0175] The difference from Example 28 is that the amount of MMAO-3A used is 0.56 mmol, and the data is shown in Table 1.

[0176] Example 40

[0177] The difference from Example 28 is that the reaction pressure for ethylene oligomerization is 400 psig, as shown in Table 1.

[0178] Example 41

[0179] The difference from Example 28 is that the reaction pressure for ethylene oligomerization is 600 psig, as shown in Table 1.

[0180] Comparative Example 1

[0181] The difference from Example 19 is that the ligand L used is... 1 Replace with ligand L 18 (0.43 mg, 0.96 μmol), data are shown in Table 1.

[0182] Table 1

[0183]

[0184]

[0185] As can be seen from Table 1, the catalyst provided by this invention can achieve high catalytic activity (the highest catalytic activity can reach 4050 kg·g Cr). -1 ·h -1 The selective tetramerization of ethylene was catalyzed by ferrocene and 1-octene selectively (with a maximum selectivity of 80.1%). Comparative Examples 20 and 1 show that introducing a ferrocene framework onto the nitrogen atom effectively reduces the content of cyclic C6 rings, significantly improving the overall selectivity of 1-hexene and 1-octene (up to 94.5%). Furthermore, the introduction of the ferrocene framework significantly enhances catalytic activity. Because the aromatic five-membered ferrocene ring is smaller than the six-membered ring of the phenyl group, and because ferrocene contains two five-membered aromatic rings chelated by iron atoms, and another ferrocene ring not directly adjacent to the PNP ring provides a steric hindrance effect that significantly increases the stability of the chromium metal active center, prolongs catalyst lifetime, and effectively improves the activity of the catalytic system. The increased catalyst lifetime also reduces catalyst degradation, allowing the polymer content in the reaction to be reduced to as low as 0.02-0.09%.

[0186] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A catalyst for the selective tetramerization of ethylene containing a ferrocene PNP ligand, characterized in that, The catalyst comprises a ligand, a transition metal compound, and an activator, wherein the chemical structural formula of the ligand is shown in formula (I) below: ， In the formula, Group R 1 To R 4 Each group is independently selected from alkyl, alkoxy, cycloalkyl, alkenyl, or aromatic groups; Group R 5 To R 6 Each group is independently selected from hydrogen, halogen, alkyl, alkoxy, alkenyl, and aromatic groups.

2. The catalyst for selective tetramerization of ethylene containing ferrocene PNP ligands according to claim 1, characterized in that, R 1 To R 4 Same or different.

3. The catalyst for selective tetramerization of ethylene containing ferrocene PNP ligands according to claim 1, characterized in that, Group R 1 To R 4 Each is independently selected from alkyl, cycloalkyl, alkenyl, or phenyl.

4. The catalyst for selective tetramerization of ethylene containing ferrocene PNP ligands according to claim 1, characterized in that, The alkyl group is methyl, ethyl, isopropyl, n-propyl, tert-butyl, n-butyl, sec-butyl, n-pentyl, sec-pentyl, cyclopentyl, sec-pentyl, tert-hexyl, n-hexyl, sec-hexyl, isohexyl, cyclohexyl, n-heptyl, sec-heptyl, tert-heptyl, isoheptyl, neoheptyl, cycloheptyl, n-octyl, sec-octyl, tert-octyl, isooctyl, n-decyl, 3-methylcyclopentyl, 2,3-dimethylcyclopentyl, 2,4-dimethylcyclopentyl, 2,5-dimethylcyclopentyl, 2,3,4-trimethylcyclopentyl, 2,3,4,5-tetramethylcyclopentane. 2-Methylcyclopentyl, 2-ethylcyclopentyl, 2-n-propylcyclopentyl, 2-isopropylcyclopentyl, 2-methylcyclohexyl, 2,3-dimethylcyclohexyl, 2,4-dimethylcyclohexyl, 2,5-dimethylcyclohexyl, 2,6-dimethylcyclohexyl, 2,4,6-trimethylcyclohexyl, 2,3,4-trimethylcyclohexyl, 2,3,5-trimethylcyclohexyl, 2,3,6-trimethylcyclohexyl, 2,3,4,5,6-pentamethylcyclohexyl, benzyl, 2-hydroxycyclohexyl, 2-mercaptocyclohexyl, 2-methoxycyclohexyl 2-Carboxycyclohexyl, 2-Nitrocyclohexyl, 2-Cyanocyclohexyl, 2-Ethoxycyclohexyl, 2-Chlorocyclohexyl, 2-Fluorocyclohexyl, 2-Bromocyclohexyl, 2-Iodocyclohexyl, 2-Aminocyclohexyl, 2-Methylthiocyclohexyl, 2,3-Dihydroxycyclohexyl, 2,4-Dihydroxycyclohexyl, 2,5-Dihydroxycyclohexyl, 2,6-Dihydroxycyclohexyl, 3-Chlorocyclohexyl, 3-Fluorocyclohexyl, 3-Bromocyclohexyl, 3-Iodocyclohexyl, 3-Methylcyclohexyl, 3-Ethylcyclohexyl, 3-Isopropylcyclohexyl, 3-n-Propylcyclohexyl Hexyl, 3-hydroxycyclohexyl, 3-methoxycyclohexyl, 3-ethoxycyclohexyl, 3-cyanocyclohexyl, 3-carboxycyclohexyl, 3-methylthiocyclohexyl, 3-mercaptocyclohexyl, 4-chlorocyclohexyl, 4-fluorocyclohexyl, 4-bromocyclohexyl, 4-iodocyclohexyl, 4-methylcyclohexyl, 4-ethylcyclohexyl, 4-isopropylcyclohexyl, 4-n-propylcyclohexyl, 4-hydroxycyclohexyl, 4-methoxycyclohexyl, 4-ethoxycyclohexyl, 4-cyanocyclohexyl, 4-carboxycyclohexyl, 4-methylthiocyclohexyl, or 4-mercaptocyclohexyl; The alkenyl group is vinyl, allyl, 1-propenyl, 1-butenyl, 2-butenyl, 1-methyl-2-butenyl, 2-methyl-1-butenyl, 3-methyl-2-butenyl, 1-chloro-2-butenyl, 2-chloro-1-butenyl, 3-chloro-2-butenyl, 1-fluoro-2-butenyl, 2-fluoro-1-butenyl, 3-fluoro-2-butenyl, or 1-bromo-2-butenyl. 2-Bromo-1-butenyl, 3-Bromo-2-butenyl, 1-Methoxy-2-butenyl, 2-Methoxy-1-butenyl, 3-Methoxy-2-butenyl, 1-Hydroxy-2-butenyl, 2-Hydroxy-1-butenyl, 3-Hydroxy-2-butenyl, 5-Hexenyl, 1-Pentenyl, 2-Pentenyl, 1-Hexenyl, 2-Hexenyl, 3-Hexenyl, 1-Heptenyl, 2-Heptenyl alkenyl, 3-heptenyl, 1-octenyl, 2-octenyl, 3-octenyl, 4-octenyl, 1-nonenyl, 2-nonenyl, 3-nonenyl, 4-nonenyl, 1-cyclohexenyl, 2-methyl-1-cyclohexenyl, 3-methyl-1-cyclohexenyl, 4-methyl-1-cyclohexenyl, 5-methyl-1-cyclohexenyl, 6-methyl-1-cyclohexenyl, 2-methoxy-1-cyclohexene 3-methoxy-1-cyclohexenyl, 4-methoxy-1-cyclohexenyl, 5-methoxy-1-cyclohexenyl, 6-methoxy-1-cyclohexenyl, 2-chloro-1-cyclohexenyl, 3-chloro-1-cyclohexenyl, 4-chloro-1-cyclohexenyl, 5-chloro-1-cyclohexenyl, 6-chloro-1-cyclohexenyl, 2-cyclohexenyl, 3-cyclohexenyl or 2-methyl-2-cyclohexenyl; The alkoxy group is methoxy, ethoxy, isopropoxy, n-propoxy, tert-butoxy, n-butoxy, sec-butoxy, n-pentoxy, sec-pentoxy, cyclopentoxy, tert-pentoxy, sec-pentoxy, tert-hexoxy, n-hexoxy, sec-hexoxy, isohexoxy, cyclohexoxy, n-heptoxy, sec-heptoxy, tert-heptyloxy, isoheptyloxy, neoheptyloxy, cycloheptoxy, n-octoxy, sec-octoxy, tert-octoxy, isooctoxy, or n-decoxy. The aromatic groups are phenyl, o-nitrophenyl, m-nitrophenyl, p-nitrophenyl, p-fluorophenyl, o-fluorophenyl, p-ethylphenyl, o-ethylphenyl, m-ethylphenyl, m-fluorophenyl, p-chlorophenyl, o-chlorophenyl, m-chlorophenyl, 2,6-dichlorophenyl, 2,5-dichlorophenyl, 2,4-dichlorophenyl, 2,3-dichlorophenyl, 3,4-dichlorophenyl, 3,5-dichlorophenyl, p-ethylphenyl, 2,6-difluorophenyl, 2,5-difluorophenyl, 2,4-difluorophenyl, 2,3-difluorophenyl, 3,4-difluorophenyl, 3,5-difluorophenyl, 2,4-dimethylphenyl, 2,3-dimethylphenyl, 2,5-dimethylphenyl, 2,6-dimethylphenyl, 2,3-diisopropylphenyl, 2,4-diisopropylphenyl, 2,5-diisopropylphenyl, 2,6-dimethylphenyl, 2,3-diisopropylphenyl, 2,4-di-tert-butylphenyl, 2,3-di ... tert-Butylphenyl, 2,5-di-tert-butylphenyl, 2,6-di-tert-butylphenyl, 2,4,6-trimethylphenyl, 2,3,4-trimethylphenyl, 2,4,6-trimethylphenyl, 2,4-dimethoxyphenyl, 2,3-dimethoxyphenyl, 2,5-dimethoxyphenyl, 2,6-dimethoxyphenyl, naphthyl, anthraceneyl, biphenyl, 7-fluoro-1-naphthyl, 8-fluoro-1-naphthyl, 7-chloro-1-naphthyl, 8 -Chloro-1-naphthyl, 9-fluoro-1-anthrayl, 9-chloro-1-anthrayl, 8-fluoro-1-anthrayl, 8-chloro-1-anthrayl, 7-methyl-1-naphthyl, 8-methyl-1-naphthyl, 7-nitro-1-naphthyl, 8-nitro-1-naphthyl, 7-methoxy-1-naphthyl, 8-methoxy-1-naphthyl, 7-hydroxy-1-naphthyl, 8-hydroxy-1-naphthyl, 7-cyano-1-naphthyl or 8-cyano-1-naphthyl; The halogen is fluorine, chlorine, bromine or iodine.

5. The catalyst for selective tetramerization of ethylene containing ferrocene PNP ligands according to claim 4, characterized in that, The alkyl group is methyl, ethyl, or isopropyl; the cycloalkyl group is cyclohexyl.

6. The catalyst for selective tetramerization of ethylene containing ferrocene PNP ligands according to claim 1, characterized in that, The transition metal in the transition metal compound is selected from iron, cobalt, nickel, copper, titanium, vanadium, chromium, manganese, molybdenum, tungsten, nickel, or palladium; the activator includes alkylaluminum compounds, aluminum oxane compounds, or organoboron compounds; the molar ratio of the ligand to the transition metal element in the transition metal compound is (0.01-100):1; the molar ratio of the activator to the transition metal element in the transition metal compound is (1-10000):

1.

7. The catalyst for selective tetramerization of ethylene containing ferrocene PNP ligands according to claim 6, characterized in that, The aluminum oxane compound includes modified methylaluminoxane MMAO-3A; the molar ratio of the activator to the transition metal element in the transition metal compound is (400-700):

1.

8. A method for preparing a catalyst for selective tetramerization of ethylene containing a ferrocene PNP ligand as described in any one of claims 1-7, characterized in that, The method involves pre-mixing or directly adding ligands, transition metal compounds, and activators into the reaction system for in-situ synthesis, thereby obtaining a catalyst for the selective tetramerization of ethylene containing ferrocene PNP ligands.

9. The application of a catalyst for the selective tetramerization of ethylene containing a ferrocene PNP ligand as described in any one of claims 1-7, characterized in that, This catalyst is used for the selective tetramerization of ethylene to produce 1-octene. The reaction is carried out in an inert solvent at a temperature of 0-200℃ and a pressure of 10-5000 psig. The concentration of the transition metal in the transition metal compound in the inert solvent is 0.01-10000 μmol / L. The inert solvent includes one or more of alkanes, aromatics, alkenes, or ionic liquids.

10. The application of the catalyst for selective tetramerization of ethylene containing a ferrocene PNP ligand according to claim 9, characterized in that, The reaction temperature is 20-60℃ and the pressure is 400-600psig.

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