A catalyst containing a pnnp-f ligand for selective tetramerization of ethylene and its preparation method and application

Abstract

The present application relates to a kind of PNNP-F ligand-containing ethylene selective tetramerization catalyst and its preparation method and application.The catalyst includes ligand, transition metal compound and activator, wherein, the chemical structural formula of ligand is as shown in the following formula (I):In the formula, group R1-R2 each independently is hydrogen, halogen, alkyl, cycloalkyl, alkoxy, alkenyl or aromatic group, or R1 and R2 are connected together, form cyclic structure containing 3 to 10 atoms;Group R3-R5 each independently is alkyl, alkoxy, alkenyl or aromatic group;Group R6-R9 each independently is selected from hydrogen, halogen, alkyl, alkoxy, alkenyl or aromatic group.Compared with prior art, the present application has the advantages of improving 1-octene selectivity, reducing cyclic C6 content, low polymer content and the like.

Description

Technical Field

[0001] This invention relates to the technical field of ethylene oligomerization, specifically to a catalyst for selective tetramerization of ethylene containing PNNP-F 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%). Traditional ethylene oligomerization catalysis mainly follows the Cossee-Arlman mechanism, where ethylene molecules insert into the catalyst metal center and the linear chain grows. The resulting linear α-olefins usually exhibit a normal distribution, requiring separation and purification for industrial applications. Representative systems include titanium-based, zirconium-based, and iron-based systems. Chromium-catalyzed ethylene oligomerization, however, mainly follows a metal ring mechanism, producing α-olefins with a Schulz-Flory distribution, where the product at the peak has a higher proportion.

[0003] As research has deepened, it has been discovered that the structure of the catalyst plays a crucial role in product distribution; in other words, changes in the ligand skeleton and substituents determine the selective oligomerization effect of ethylene. In recent years, research in this field has focused on the catalytic mechanism of selective oligomerization of ethylene and ligand design, yielding some important results. In 2002, British Petroleum reported the use of PNP-type ligands with the structure PAr2N(R)PAr2 (Ar being an ortho-methoxy-substituted aryl group) for chromium-catalyzed highly selective trimerization of ethylene to prepare 1-hexene (Chem. Commun., 2002, 858-859). In 2004, Sasol successfully achieved ethylene tetramerization using the aforementioned PNP-type ligand / chromium catalytic system through substituent modification, with a selectivity of up to 67.5% for 1-octene (J. Am. Chem. Soc., 2004, 126, 14712-14713.). They also reported the use of PNNP-type ligands with the PPh2N(Me)N(Me)PPh2 structure for selective ethylene tetramerization.

[0004] Recent test results from the company (Dalton Trans., 2021, 50, 4345-4354) indicate that the PNNP system achieves a higher overall selectivity for 1-hexene and 1-octene (87.5%) compared to PNP ligands. However, the 1-octene selectivity is slightly lower than that of the PNP system, reaching only 62.4%, and the polymer yield is higher (1.4%). In 2014, Sasol introduced an F atom (CN101646684A) at the ortho position of the phenyl group linked to the phosphorus atom in the PNP ligand, effectively reducing the content of cyclic C6 in the product and increasing the overall selectivity for 1-C6 and 1-C8 (88.4%). However, the introduction of the F atom led to a decrease in the 1-octene content (43.1%). Summary of the Invention

[0005] 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 PNNP-F 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.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] To further improve the activity and 1-octene selectivity of the PNNP catalytic system, this invention creatively introduces an ortho-haloaryl group into the PNNP ligand, and optionally an alkyl group. By introducing the ortho-haloaryl group, this invention successfully increased the activity of the catalytic system to 4280 kg / g Cr·h. By simultaneously introducing alkyl groups with relatively low steric hindrance and ortho-haloaryl groups, this invention further increased the activity of the catalytic system to 5660 kg / g Cr·h, with a 1-octene selectivity of 77.3% and a total selectivity for 1-hexene and 1-octene of 96.0%. Since alkyl groups have a stronger electron-donating ability than phenyl groups, introducing alkyl groups into the ligand increases the electron cloud density of the phosphorus atom, which 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 effectively reducing the polymer content in the reaction. The specific scheme is as follows:

[0008] A catalyst for the selective tetramerization of ethylene containing a PNNP-F ligand, the catalyst comprising a ligand, a transition metal compound, and an activator, wherein the chemical structural formula of the ligand is shown in formula (I) below:

[0009]

[0010] In the formula, groups R1 to R2 are each independently hydrogen, halogen, alkyl, cycloalkyl, alkoxy, alkenyl, or aromatic groups, or R1 and R2 are connected together to form a cyclic structure containing 3 to 10 atoms; in other words, R1 and R2 are optionally connected together, wherein the optional features of the bond are indicated by dashed lines, and R1 and R2, as well as the two N atoms connected to R1 and R2, can together form a cyclic structure containing 3 to 10 atoms.

[0011] Each of the groups R3 to R5 is independently an alkyl, alkoxy, alkenyl, or aromatic group;

[0012] Groups R6 to R9 are each independently selected from hydrogen, halogen, alkyl, alkoxy, alkenyl, or aromatic groups.

[0013] Furthermore, the alkyl group is C1-C. 30 Alkyl groups, specifically including methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, sec-pentyl, isopentyl, cyclopentyl, n-hexyl, sec-hexyl, isohexyl, cyclohexyl, n-heptyl, cycloheptyl, n-octyl, n-decyl, 2-methylcyclopentyl, and 2,6-dimethylcyclohexyl;

[0014] The alkenyl group is C1-C. 30 The alkenyl groups specifically include vinyl, allyl, 1-propenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-methyl-2-butenyl, 2-methyl-1-butenyl, 3-methyl-2-butenyl, 5-hexenyl, 2-cyclohexenyl, 3-cyclohexenyl, and 2-methyl-2-cyclohexenyl.

[0015] The alkoxy group is C1-C. 20 The alkoxy group specifically includes alkoxy groups selected from methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, tert-butoxy, cyclohexyloxy, and cyclopentyloxy.

[0016] The aromatic group is C4-C. 30Aryl groups and their derivatives, specifically including phenyl, p-fluorophenyl, o-fluorophenyl, m-fluorophenyl, p-chlorophenyl, o-chlorophenyl, m-chlorophenyl, 2,6-difluorophenyl, 2,5-difluorophenyl, 2,4-difluorophenyl, 2,3-difluorophenyl, 3,4-difluorophenyl, 3,5-difluorophenyl, 2,6-dichlorophenyl, 2,5-dichlorophenyl, 2,4-dichlorophenyl, 2,3-dichlorophenyl, 3,4-dichlorophenyl, 3,5-dichlorophenyl, p-ethylphenyl, o-ethylphenyl, m-ethylphenyl Naphthyl, 2,4-dimethylphenyl, 2,4-diisopropylphenyl, 2,4-di-tert-butylphenyl, 2,6-dimethylphenyl, 2,6-diisopropylphenyl, 3,5-dimethylphenyl, 3,5-di-tert-butylphenyl, 2,4,6-trimethylphenyl, naphthyl, anthraceneyl, biphenyl, 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 or 8-chloro-1-anthrayl;

[0017] The halogen is fluorine, chlorine, bromine or iodine.

[0018] Furthermore, groups R1 to R2 are alkyl groups, and R1 and R2 are not connected;

[0019] Groups R3 to R4 are alkyl, cycloalkyl, phenyl, or substituted phenyl;

[0020] Group R5 is hydrogen, phenyl, or a substituted phenyl group.

[0021] Furthermore, at least one of the groups R3 to R4 is an alkyl, cycloalkyl, or substituted phenyl group; and group R5 is a substituted phenyl group.

[0022] Further, the alkyl group includes methyl, ethyl, or isopropyl, preferably isopropyl; the cycloalkyl group includes cyclohexyl; the substituted phenyl group includes o-fluorophenyl or 2,4-difluorophenyl, preferably 2,4-difluorophenyl.

[0023] 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 is 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; preferably, the transition metal in the transition metal compound is selected from one of chromium, cobalt, titanium, iron, 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. nIt typically contains 1 to 15 carbon atoms, where n is an integer from 0 to 6, and the valence state of Cr is from 0 to 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).

[0024] 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 a ligand and a transition metal compound. The activator can be used alone or in combination. 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. The molar ratio of the activator to the transition metal element in the transition metal compound is (600-1000):1, preferably (800-1000):1.

[0025] Furthermore, the molar ratio of the ligand to the transition metal element in the transition metal compound can be (0.1-10):1, or (0.5-2):1.

[0026] In some embodiments, the molar ratio of the activator to the transition metal may also be (1-2000):1.

[0027] In some embodiments, the activator is selected from alkylaluminum compounds, aluminoxane compounds, organoboron compounds, inorganic acids, or inorganic salts.

[0028] 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).

[0029] 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.

[0030] Specifically, suitable boron compounds may include cycloboroxanes, triethylborane, triphenylborane, tris(pentafluorophenyl)borane, etc. Organoboron compounds may be used in combination with organoaluminum compounds.

[0031] Furthermore, the activator can be selected from methylaluminoxane (MAO), ethylaluminoxane, isobutylaluminoxane, and modified methylaluminoxane (MMAO).

[0032] Furthermore, the aluminum oxane compound specifically includes modified methylaluminoxane MMAO-3A;

[0033] A method for preparing a catalyst for selective tetramerization of ethylene containing PNNP-F 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 PNNP-F ligands.

[0034] The preparation method of the catalyst system of the present invention will be further described below:

[0035] 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.

[0036] 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.

[0037] Application of a catalyst for the selective tetramerization of ethylene containing the PNNP-F 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 0.1-50 MPa, and 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. 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 methylcyclohexane. Further, the reaction temperature is 35-80°C, preferably 60-80°C; the pressure is 1-4 MPa, preferably 2-4 MPa.

[0038] In some embodiments, the reaction temperature for ethylene oligomerization is 0-200°C, preferably 10-120°C, and more preferably 20-100°C.

[0039] In some embodiments, the ethylene oligomerization reaction can be carried out at a pressure of 0.1-50 MPa, preferably 1.0-10 MPa.

[0040] In some embodiments, the concentration of the catalyst in the reaction system can range from 0.01 to 10,000 μmol metal / L, preferably 1 to 500 μmol metal / L, where the metal is a transition metal in a transition metal compound.

[0041] Compared with existing technologies, this invention creatively introduces an ortho-haloaryl group into the PNNP ligand, optionally with an alkyl group. By introducing the ortho-haloaryl group, the activity of the catalytic system is effectively enhanced. Simultaneously introducing sterically less hindrance alkyl and ortho-haloaryl groups significantly reduces the content of cyclic C6, improving the overall selectivity for 1-hexene and 1-octene while maintaining high 1-octene selectivity, and further enhancing catalytic activity. Since alkyl groups have a stronger electron-donating ability than phenyl groups, introducing alkyl groups into the ligand increases the electron cloud density of phosphorus atoms, significantly increasing the stability of the chromium metal active center, extending catalyst lifetime, and effectively improving the activity of the catalytic system. The increased catalyst lifetime also reduces catalyst degradation, thereby effectively reducing the polymer content in the reaction. Detailed Implementation

[0042] 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.

[0043] A catalyst for the selective tetramerization of ethylene containing a PNNP-F 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 PNNP-F 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 0.1-50 MPa. 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 35-80°C, preferably 60-80°C; the pressure is 1-4 MPa, preferably 2-4 MPa.

[0044] The chemical structural formula of the ligand is shown in formula (I) below:

[0045]

[0046] In the formula, groups R1 to R2 are each independently hydrogen, halogen, alkyl, cycloalkyl, alkoxy, alkenyl, or aromatic groups, or R1 and R2 are connected together to form a cyclic structure containing 3 to 10 atoms; groups R3 to R5 are each independently alkyl, alkoxy, alkenyl, or aromatic groups; groups R6 to R9 are each independently selected from hydrogen, halogen, alkyl, alkoxy, alkenyl, or aromatic groups.

[0047] 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 (600-1000):1, preferably (800-1000):1.

[0048] Example 1

[0049] ligand L 1 The preparation steps are as follows:

[0050] (1) Preparation of Ph2POH·BH3

[0051] The preparation method of this compound is described in Synlett., 2004, 2, 311-315.

[0052] Ph₂P(O)H (10 mmol, 1 eq) and tetrahydrofuran (300 mL) were added to a dry, argon-filled Schlenk flask. BF₃·Et₂O (40 mmol, 4 eq) and sodium borohydride (30 mmol, 3 eq) were then added. The mixture was heated under reflux for 3 h. After the reaction was completed, the mixture was cooled to room temperature, and dilute hydrochloric acid (1 mL) was added. The mixture was extracted with dichloromethane, dried the organic phase, and extracted by silica gel column chromatography to obtain a pale yellow oily compound (1.4 g, 63.0%).

[0053] (2) Ligand L 1 Preparation

[0054]

[0055] The method for synthesizing this ligand is described in Chem. Commun., 2017, 53, 4605-4608.

[0056] In a dry, argon-filled Schlenk flask, methanesulfonic anhydride (4.2 mmol, 1.2 eq), 1 (3.5 mmol, 1.0 eq), and dichloromethane (20 mL) were added. The mixture was cooled to -20 °C, and triethylamine (12.6 mmol, 3 eq) was slowly added dropwise. The reaction was carried out at -20 °C for 1 h. Then, tert-butyl hydrazide formate (12.6 mmol, 3 eq) was added to the solution, and the reaction was carried out at -20 °C overnight. After the reaction was completed, the organic phase was washed with dilute hydrochloric acid (1.0 M, 3 × 30 mL) and brine, dried, filtered, and the solvent was removed under reduced pressure. The product was purified by short silica gel column chromatography to give a white solid product 2 (579.0 mg, 50.1%).

[0057] In a dry, argon-filled Schlenk flask, 5 mL of 4.0 M methanol solution of hydrogen chloride was added, followed by 2 (4.0 mmol, 1.0 eq). The mixture was stirred overnight, and NaOH solution (1.0 M) was added until pH = 10. The solvent was removed under reduced pressure, and the aqueous phase was extracted with dichloromethane (10 mL × 3). The organic phases were mixed, washed with brine (50 mL), dried with magnesium sulfate, filtered, and the solvent was removed under vacuum. The residue was extracted by silica gel column chromatography to obtain compound 3 (570.7 mg, 62.0%) as a white solid powder.

[0058] In a dry, argon-filled Schlenk flask, 4 (5 mmol, 1 eq) (the synthesis of compound 4 is referenced to compound 1), triethylamine (15 mmol, 3 eq), and dichloromethane (20 mL) were added. The mixture was cooled to -20 °C, and 3 (2.85 mmol, 0.57 eq) was added to the solution. The mixture was stirred overnight at -20 °C. After the reaction was complete, the organic phase was washed with dilute hydrochloric acid (1.0 M, 3 × 30 mL) and brine. The mixture was dried, filtered, and the solvent was removed under reduced pressure. The product was purified by short silica gel column chromatography to give a white solid product 5 (387.6 mg, 29.3%).

[0059] In a dry, argon-filled Schlenk flask, compound 5 (5 mmol, 1 eq) was added to a tetrahydrofuran (4 mL) solution, followed by the slow addition of a sodium hydride tetrahydrofuran solution (20 mmol, 4.0 eq). The mixture was stirred at 55 °C for 45 min, and then iodomethane (40.0 mmol, 8 eq) was added. The mixture was stirred at 55 °C for 4 h. After the reaction was complete, the mixture was cooled to room temperature, and 10 mL of diethyl ether was added. Water (8 mL) was slowly added to quench any remaining sodium hydride. The mixture was separated, and the organic phase was washed with brine (50 mL). The solution was dried over anhydrous magnesium sulfate, filtered, and the solvent was removed. The product was purified by silica gel column chromatography to give a white solid product 6 (2.2 g, 90.0%).

[0060] In a dry, argon-filled Schlenk flask, 6 (5 mmol, 1 eq) and pyridine (15 mL) were added, heated to 80 °C, stirred for 2 h, and the pyridine was removed under reduced pressure to give a white solid product L. 1 (2.3g, 99.0%). 1 H NMR (400MHz, CDCl3) δ2.45-2.65(m,6H),6.85-6.96(m,10H),7.42-7.49(m,6H),7.65-7.70(m,2H).

[0061]

[0062] Example 2

[0063] ligand L 2 The preparation steps are as follows:

[0064] Reference ligand L 1 The preparation method uses (2-F-Ph)PhPOH·BH3 (5.0 mmol, 1 eq) instead of 4 to obtain a white solid product L. 2 . 1H NMR (400MHz, CDCl3) δ2.60-2.70(m,6H),7.15-7.20(m,9H),7.42-7.52(m,9H),7.60-7.65(m,1H).

[0065]

[0066] Example 3

[0067] The preparation of ligand L3 follows these steps:

[0068] Reference ligand L 2 The preparation method uses (2-F-Ph)PhPOH·BH3 (5.0 mmol, 1 eq) instead of 1 to obtain a colorless oily product L. 3 . 1 H NMR (400MHz, CDCl3) δ1.30-1.40(m,6H),7.15-7.25(m,10H),7.38-7.48(m,6H),7.66-7.70(m,2H).

[0069]

[0070] Example 4

[0071] ligand L 4 The preparation steps are as follows:

[0072] Reference ligand L 1 The preparation method uses 1,3-dibromopropane (5.0 mmol, 1 eq) instead of iodomethane to obtain a pale yellow oily product L. 4 . 1 H NMR (400MHz, CDCl3) δ1.3-1.32(m,4H),1.4-1.46(m,10H),1.53-1.57(m,8H),3.3-3.3 2(m,4H),5.23-5.24(m,1H),5.43-5.45(m,1H),7.14-7.15(m,4H),7.43-7.45(m,6H).

[0073]

[0074] Example 5

[0075] ligand L 5 The preparation steps are as follows:

[0076] Reference ligand L 1 The preparation method uses iReplacing 1 with Pr2POH·BH3 (5.0 mmol, 1 eq) yielded a yellow oily product L. 5 . 1 H NMR (400MHz, CDCl3) δ0.92(d,J=5.8Hz,12H),1.51-1.60(m,2H),2.49(d,J=10.6Hz,6H),7.13-7.20(m,6H),7.60-7.70(m,2H).

[0077]

[0078] Example 6

[0079] ligand L 6 The preparation steps are as follows:

[0080] Reference ligand L 1 The preparation method used Et2POH·BH3 (5.0 mmol, 1 eq) instead of 1 to obtain a white powder product L. 6 . 1 H NMR (400MHz, CDCl3) δ0.96 (m, 6H), 1.48-1.58 (m, 4H), 2.47 (d, J = 10.6Hz, 6H), 7.14-7.25 (m, 6H), 7.56-7.66 (m, 2H).

[0081]

[0082] Example 7

[0083] ligand L 7 The preparation steps are as follows:

[0084] Reference ligand L 1 The preparation method used CyPhPOH·BH3 (5.0 mmol, 1 eq) instead of 1 to obtain a colorless oily product L. 7 . 1 H NMR (400MHz, CDCl3) δ1.40-1.60 (m, 11H), 1.90-1.96 (d, J = 10.3Hz, 6H), 7.15-7.25 (m, 8H), 7.42-7.48 (m, 3H), 7.61-7.71 (m, 2H).

[0085]

[0086] Example 8

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

[0088] Reference ligand L 1 The preparation method uses i PrPhPOH·BH3 (5.0 mmol, 1 eq) was substituted for 1 to give a colorless oily product L. 8 . 1 H NMR (400MHz, CDCl3) δ0.92 (d, J = 5.2 Hz, 6H), 1.60-1.65 (m, 1H), 2.47 (d, J = 10.8 Hz, 6H), 7.20-7.28 (m, 8H), 7.39-7.44 (m, 3H), 7.60-7.68 (m, 2H).

[0089]

[0090] Example 9

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

[0092] Reference ligand L 1 The preparation method used EtPhPOH·BH3 (5.0 mmol, 1 eq) instead of 1 to obtain a yellow oily product L. 9 . 1 H NMR (400MHz, CDCl3) δ0.80-0.90(m,3H),1.48-1.52(m,2H),2.47-2.57(d,J=10.2Hz,6H),7.15-7.25(m,8H),7.42-7.52(m,3H),7.65-7.69(m,2H).

[0093]

[0094] Example 10

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

[0096] Reference ligand L 6 The preparation method uses (2,4-F2-Ph)2POH·BH3 (5.0 mmol, 1 eq) instead of (2-F-Ph)2POH·BH3 to obtain a yellow oily product L. 10 . 1 H NMR (400MHz, CDCl3) δ0.96-1.02(m,6H),1.48-1.52(m,4H),2.57-2.65(d,J=10.4Hz,6H),6.75-6.85(m,2H),7.12-7.22(m,4H).

[0097]

[0098] Example 11

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

[0100] Reference ligand L 6 The preparation method uses (2-F-4-OMe-Ph)2POH·BH3 (5.0 mmol, 1 eq) instead of (2-F-Ph)2POH·BH3 to obtain a yellow oily product L. 11 . 1 H NMR (400MHz, CDCl3) δ0.86-0.96(m,6H),1.45-1.52(m,4H),3.81(s,6H),6.73-6.80(m,2H),7.12-7.22(m,4H).

[0101] Example 12

[0102] A catalyst for selective tetramerization of ethylene containing PNNP-F ligand, its preparation method, and its application are as follows:

[0103] (1) Preparation of catalyst

[0104] In a dry Schlenk reaction tube filled with argon, chromium acetylacetone (0.28 mg, 0.80 μmol) and ligand L were added. 1 (0.45 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.

[0105] (2) Ethylene oligomerization

[0106] A 350 mL stainless steel high-pressure gas reactor was evacuated to a vacuum state in an oil bath at 120 °C for 3 hours to ensure an anhydrous and oxygen-free environment. The reactor was then cooled to the reaction temperature, and the gas inside 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. The temperature and pressure were adjusted, and the reaction was stirred for 30 minutes. After the reaction was complete, the ethylene gas supply valve was closed, the reactor was cooled to 0 °C, the pressure was released, the reactor was opened, a quantitative amount of nonane (internal standard) was added, and the mixture was stirred thoroughly. The reaction was then quenched with approximately 30 mL of a 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 and drying to constant weight, the solid was weighed. The data are shown in Table 1.

[0107] Example 13

[0108] Same as Example 10, except that the ligand L used is... 1 Replace with ligand L 2 (0.43 mg, 0.96 μmol), data are shown in Table 1.

[0109] Example 14

[0110] Same as Example 10, except that the ligand L used is... 1 Replace with ligand L 3 (0.45 mg, 0.96 μmol), data are shown in Table 1.

[0111] Example 15

[0112] Same as Example 10, except that the ligand L used is... 1 Replace with ligand L 4 (0.46 mg, 0.96 μmol), data are shown in Table 1.

[0113] Example 16

[0114] Same as Example 10, except that the ligand L used is... 1 Replace with ligand L 5 (0.38 mg, 0.96 μmol), data are shown in Table 1.

[0115] Example 17

[0116] Same as Example 10, except that the ligand L used is... 1 Replace with ligand L 6 (0.35 mg, 0.96 μmol), data are shown in Table 1.

[0117] Example 18

[0118] Same as Example 10, except that the ligand L used is... 1 Replace with ligand L 7 (0.38 mg, 0.96 μmol), data are shown in Table 1.

[0119] Example 19

[0120] Same as Example 10, except that the ligand L used is... 1 Replace with ligand L 8 (0.41 mg, 0.96 μmol), data are shown in Table 1.

[0121] Example 20

[0122] Same as Example 10, except that the ligand L used is... 1 Replace with ligand L 9(0.40 mg, 0.96 μmol), data are shown in Table 1.

[0123] Example 21

[0124] Same as Example 10, except that the ligand L used is... 1 Replace with ligand L 10 (0.39 mg, 0.96 μmol), data are shown in Table 1.

[0125] Example 22

[0126] Same as Example 10, except that the ligand L used is... 1 Replace with ligand L 11 (0.41 mg, 0.96 μmol), data are shown in Table 1.

[0127] Example 23

[0128] The difference from Example 17 is that the ethylene oligomerization reaction was carried out at 20°C, and the data are shown in Table 1.

[0129] Example 24

[0130] The difference from Example 17 is that the ethylene oligomerization reaction was carried out at 60°C, and the data are shown in Table 1.

[0131] Example 25

[0132] The difference from Example 17 is that the amount of MMAO-3A used is 0.32 mmol, and the data is shown in Table 1.

[0133] Example 26

[0134] The difference from Example 17 is that the amount of MMAO-3A used is 0.56 mmol, and the data is shown in Table 1.

[0135] Example 27

[0136] The difference from Example 17 is that the reaction pressure for ethylene oligomerization is 400 psig, as shown in Table 1.

[0137] Example 28

[0138] The difference from Example 17 is that the reaction pressure for ethylene oligomerization is 300 psig, as shown in Table 1.

[0139] Comparative Example 1

[0140] Same as Example 10, except that the ligand L used is... 1 Replace with ligand L 12 (0.41 mg, 0.96 μmol), L 10The structure is as follows, and its synthesis is referenced in Dalton Trans., 2021, 50, 4345–4354. Data are shown in Table 1.

[0141]

[0142] Table 1

[0143]

[0144]

[0145] As shown in Table 1, the catalyst provided by this invention exhibits high catalytic activity, reaching a maximum of 6540 kg / g Cr·h, with a maximum 1-octene selectivity of 79.1% and a maximum total selectivity of 96.1% for 1-hexene and 1-octene. Comparative Examples 10 and 1 show that the introduction of ortho-haloaryl groups effectively enhances the activity of the catalytic system and significantly reduces the polymer content in the product. Comparative Examples 10 and 15 demonstrate that the simultaneous introduction of sterically less sterically hindered alkyl groups and ortho-haloaryl groups significantly reduces the content of cyclic C6, improving the total selectivity for 1-hexene and 1-octene while maintaining high 1-octene selectivity. Furthermore, the stabilizing effect of the electron-donating alkyl groups on the metal center prolongs the catalyst lifetime, making the catalyst less prone to degradation and further reducing the polymer content in the product.

[0146] 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 PNNP-F 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, groups R1 to R2 are each independently hydrogen, halogen, alkyl, cycloalkyl, alkoxy, alkenyl or aromatic groups, or R1 and R2 are connected together to form a cyclic structure containing 3 to 10 atoms. Each of groups R3 to R4 is independently an alkyl, alkoxy, alkenyl, or aromatic group, and at least one of groups R3 to R4 is an alkyl, cycloalkyl, or substituted phenyl group; Each of the groups R6 to R9 is independently selected from hydrogen, halogen, alkyl, alkoxy, alkenyl, or aromatic groups; Group R5 is a substituted phenyl group.

2. The catalyst for selective tetramerization of ethylene containing PNNP-F ligands according to claim 1, characterized in that, The alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, sec-pentyl, isopentyl, cyclopentyl, n-hexyl, sec-hexyl, isohexyl, cyclohexyl, n-heptyl, cycloheptyl, n-octyl, and n-decyl. The alkenyl groups include vinyl, allyl, 1-propenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-methyl-2-butenyl, 2-methyl-1-butenyl, 3-methyl-2-butenyl, and 5-hexenyl. The alkoxy groups include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, tert-butoxy, cyclohexyloxy, and cyclopentyloxy. The aromatic groups include phenyl, p-fluorophenyl, o-fluorophenyl, m-fluorophenyl, p-chlorophenyl, o-chlorophenyl, m-chlorophenyl, 2,6-difluorophenyl, 2,5-difluorophenyl, 2,4-difluorophenyl, 2,3-difluorophenyl, 3,4-difluorophenyl, 3,5-difluorophenyl, 2,6-dichlorophenyl, 2,5-dichlorophenyl, 2,4-dichlorophenyl, 2,3-dichlorophenyl, 3,4-dichlorophenyl, 3,5-dichlorophenyl, p-ethylphenyl, o-ethylphenyl, m-ethylphenyl, etc. 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, Anthrayl, 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; The halogen is fluorine, chlorine, bromine or iodine.

3. The catalyst for selective tetramerization of ethylene containing PNNP-F ligands according to claim 2, characterized in that, The alkyl group is methyl, ethyl, or isopropyl; the cycloalkyl group is cyclohexyl; and the substituted phenyl group is o-fluorophenyl or 2,4-difluorophenyl.

4. The catalyst for selective tetramerization of ethylene containing PNNP-F 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, 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.

5. The catalyst for selective tetramerization of ethylene containing a PNNP-F ligand according to claim 4, characterized in that, The aluminum oxane compound specifically includes modified methylaluminoxane MMAO-3A; the molar ratio of the activator to the transition metal element in the transition metal compound is (600-1000):

1.

6. A method for preparing a catalyst for selective tetramerization of ethylene containing a PNNP-F ligand as described in any one of claims 1-5, 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 PNNP-F ligands.

7. The application of a catalyst for the selective tetramerization of ethylene containing a PNNP-F ligand as described in any one of claims 1-5, 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 0.1-50 MPa. 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.

8. The application of the catalyst for selective tetramerization of ethylene containing a PNNP-F ligand according to claim 7, characterized in that, The reaction temperature is 35-80℃; the pressure is 1-4 MPa.

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