A catalyst containing a pnp ligand for selective tetramerization of ethylene and its preparation method and application

Abstract

The application relates to a catalyst containing a PNP ligand for selectively tetramerizing 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): in the formula, groups R 1 to R 3 are each independently selected from an alkyl group, an alkoxy group, an alkenyl group and an aromatic group, and groups R 1 to R 3 are not simultaneously aromatic groups; the group R 4 is selected from an alkyl group, an alkenyl group and an aromatic group; the group R 5 to R 8 are each independently selected from hydrogen, halogen, an alkyl group, an alkoxy group, an alkenyl group and an aromatic group. Compared with the prior art, the application can improve the 1-octene selectivity, reduce the cyclic C6 content and reduce the polymer content.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ethylene oligomerization, in particular to a catalyst containing PNP ligand for selective ethylene tetramerization and its preparation method and application. BACKGROUND

[0002] Linear alpha-olefins (LAO) are important chemical raw materials, which can be used to prepare lubricating oil, surfactant, 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 the comonomer content in HDPE is 1-2%). Ethylene oligomerization is an important method for producing linear alpha-olefins, which has great improvement in product quality compared with traditional methods such as wax cracking, coal extraction, and extraction separation, and has been widely used in industrial production.

[0003] Traditional ethylene oligomerization catalysts mainly use metal titanium, zirconium, iron, etc. These catalyst systems mainly follow the Cossee-Arlman mechanism, that is, ethylene molecules are inserted into the linear chain growth of the catalyst metal center, and the obtained linear alpha-olefins are usually normally distributed, which must be separated and purified according to the needs in industrial applications. Ethylene high-selective oligomerization mainly follows the metal cyclization mechanism, so that the produced alpha-olefins are Schulz-Flory distributed, and the product at the peak has a high content. This method provides an important way to produce alpha-olefins with specific carbon number. In recent years, the increasing demand for 1-hexene and 1-octene has made ethylene selective oligomerization a hot spot in industrial and academic research.

[0004] At present, reports on highly selective ethylene oligomerization mainly include 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 key role in product distribution, and the regulation of the catalyst structure depends on the changes in the skeleton and substituents of the ligand. In recent years, research in this field has focused on the catalytic mechanism and ligand design of ethylene selective oligomerization, and has achieved some important results. In 2002, British Petroleum reported that the Cr / PNP catalytic system was used to selectively prepare 1-hexene (Chem. Commun. 2002, 858). In 2003, Phillips Petroleum used the Phillips trimerization chromium catalyst developed to achieve industrialized ethylene trimerization (US5523507). my country's Sinopec (Yanshan) and PetroChina (Daqing) also successively adopted similar catalytic systems to achieve industrialized production of 1-hexene. The selective preparation of 1-octene by ethylene tetramerization is currently impossible to achieve industrialized production. 1-Octene can be used in the production of high-quality polyethylene (PE), polyolefin elastomers (POE), lubricant base oils (PAO), plasticizers, surfactants, and other applications. Compared to 1-hexene, 1-octene has higher economic value. In 2004, Sasol developed a selective ethylene tetramerization system using a Cr / PNP catalyst (WO2004056478), achieving a 1-octene selectivity of approximately 70%. Since the discovery of this catalyst system, extensive research has focused on modifying the PNP ligand. The ortho-phenyl substituent attached to the phosphorus atom significantly influences the catalytic results. The introduction of a methoxy group transforms the system from a tetramerization to a trimerization system (Chem. Commun., 2005, 622). In 2014, Sasol introduced a F atom at the ortho position of the phenyl group connected to the phosphorus atom in the PNP ligand (CN101646684A), which effectively reduced the content of cyclic C6 in the product and increased the overall selectivity of 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 the present invention is to overcome the defects of the above-mentioned prior art and provide a catalyst for selective tetramerization of ethylene containing PNP ligands, which has improved 1-octene selectivity, reduced cyclic C6 content and low polymer content, as well as its preparation method and application.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] The application is further to improve the selectivity of 1-octene and the activity of the catalytic system, and the alkyl and ortho halogenated aryl are creatively introduced into the PNP ligand. By introducing the alkyl with small steric hindrance and the ortho halogenated aryl, the 1-octene selectivity of the catalytic system is successfully improved to 85%, and the total selectivity of 1-hexene and 1-octene is improved to 94.5%, which can effectively improve the selectivity of 1-octene while reducing the cyclic C6. In addition, due to the stronger electron-donating ability of the alkyl than the phenyl, the introduction of the alkyl into the ligand increases the electron cloud density of the phosphorus atom, which can significantly increase the stability of the chromium metal active center, prolong the catalyst life, and effectively improve the activity of the catalytic system. The improvement of the catalyst life also reduces the degradation of the catalyst, and then the content of the polymer in the reaction is reduced to 0.05-0.1%, and the specific scheme is as follows:

[0008] An ethylene selective tetramerization catalyst containing a PNP ligand, characterized in that the catalyst comprises a ligand, a transition metal compound and an activator, wherein the chemical structure of the ligand is shown as formula (I):

[0009]

[0010] In the formula,

[0011] The group R 1 to R 3 Each is independently selected from an alkyl group, an alkoxy group, an alkenyl group, an aromatic group, and R 1 to R 3 Are not aromatic groups at the same time;

[0012] The group R 4 Is selected from an alkyl group, an alkenyl group and an aromatic group;

[0013] The group R 5 to R 8 Each is independently selected from hydrogen, halogen, an alkyl group, an alkoxy group, an alkenyl group and an aromatic group.

[0014] Further, R 1 to R 3 At least one is selected from an alkyl group or an alkenyl group.

[0015] Further, the alkyl group is a C1-C 30 alkyl group, specifically including a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a n-pentyl group, a sec-pentyl group, an isopentyl group, a cyclopentyl group, a n-hexyl group, a sec-hexyl group, an isohexyl group, a cyclohexyl group, a n-heptyl group, a cycloheptyl group, a n-octyl group, a n-decyl group, a 2-methylcyclopentyl group and a 2,6-dimethylcyclohexyl group.

[0016] The alkenyl group is a C1-C 30alkenyl groups, specifically including 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, 2-methyl-2-cyclohexenyl;

[0017] said alkoxy is a C1-C 20 alkoxy groups, specifically including alkoxy groups selected from methoxy, ethoxy, n-propoxy, i-propoxy, n-butoxy, t-butoxy, cyclohexyloxy, cyclopentyloxy;

[0018] said aromatic groups are C4-C 30 aryl groups and derivatives thereof, 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, 2,4-dimethylphenyl, 2,4-diisopropylphenyl, 2,4-di-t-butylphenyl, 2,6-dimethylphenyl, 2,6-diisopropylphenyl, 3,5-dimethylphenyl, 3,5-di-t-butylphenyl, 2,4,6-trimethylphenyl, naphthyl, anthryl, biphenyl, 7-fluoro-1-naphthyl, 8-fluoro-1-naphthyl, 7-chloro-1-naphthyl, 8-chloro-1-naphthyl, 9-fluoro-1-anthryl, 9-chloro-1-anthryl, 8-fluoro-1-anthryl, or 8-chloro-1-anthryl;

[0019] said halogen is fluorine, chlorine, bromine, or iodine. Preferably, fluorine, chlorine, bromine.

[0020] In some embodiments, the ligand compound is one of the following, but it is understood that the scope of the present application is not limited to these examples:

[0021]

[0022]

[0023]

[0024] The transition metal in the catalyst system of the present application can be a transition metal compound commonly used in the art, the metal atom in the transition metal compound is the metal active center, which plays an important role in the catalytic process.

[0025] 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, and in particular, the corresponding transition metal compound is any chromium compound that enables the oligomerization, and the optional chromium compound includes a compound represented by the general formula CrR n wherein R n is an organic anion or a neutral molecule, R n contains 1 to 15 carbon atoms, and n is an integer from 0 to 6, and the valence of Cr is from 0 to 6. In particular, the R n group is an organic compound containing a carboxyl group, a β-diketonate group, and a hydrocarbon group, or other groups. From the viewpoint of ease of solubility and ease of handling, more suitable chromium compounds include one of chromium trichloride-tris(tetrahydrofuran) complex, (benzene)tricarbonyl chromium, chromium (III) octoate, chromium hexacarbonyl, chromium (III) acetylacetonate, chromium (III) naphthenate, chromium (III) 2-ethylhexanoate, chromium (III) acetate, chromium (III) 2,2,6,6-tetramethylheptanedionate, and chromium (III) chloride. Preferably, the chromium compound is selected from chromium trichloride-tris(tetrahydrofuran) complex, chromium (III) acetylacetonate, and chromium (III) 2-ethylhexanoate.

[0026] The activator in the catalyst system of the present application functions to activate the catalyst system. The activator useful in the present application 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.

[0027] Further, the activator includes one or a mixture of an alkyl aluminum compound, an aluminoxane compound, or an organoboron compound.

[0028] Further, the activator includes one or a mixture of an alkyl aluminum compound, an aluminoxane compound, an organoboron compound, an inorganic acid, or an inorganic salt.

[0029] In particular, the activator can be an alkyl aluminum compound, and the alkyl aluminum compound can be various trialkylaluminums such as trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, or tri-n-octylaluminum; the alkyl aluminum compound can also be an alkyl aluminum halide, an alkyl aluminum hydride, or an alkyl aluminum sesquichloride such as diethylaluminum chloride (AlEt2Cl) and triethylaluminum sesquichloride (Al2Et3Cl3).

[0030] Specifically, the activator can be an aluminoxane compound, which can be typically prepared by mixing water with an alkylaluminum compound (e.g., trimethylaluminum). The prepared aluminoxane oligomeric compound can be a linear compound, a cyclic compound, a cage compound, or a mixture thereof. Suitable aluminoxane compounds can be selected from the group consisting of methylaluminoxane (MAO), ethylaluminoxane, isobutylaluminoxane, modified aluminoxane, and methylaluminoxane from which volatile components are removed (DMAO), and the like.

[0031] Specifically, suitable boron compounds can include boroxin, triethylborane, triphenylborane, tris(pentafluorophenyl)borane, and the like. The organoboron compound can be used in a form mixed with the organoaluminum compound.

[0032] Preferably, the activator can be selected from the group consisting of methylaluminoxane (MAO), ethylaluminoxane, isobutylaluminoxane, and modified methylaluminoxane (MMAO).

[0033] Further, the aluminoxane compound specifically includes modified methylaluminoxane MMAO-3A.

[0034] Further, 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, more preferably (0.5-2): 1.

[0035] 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.

[0036] A method for preparing a catalyst for the selective tetramerization of ethylene containing a PNP ligand as described above, which method comprises mixing the ligand, the transition metal compound, and the activator in advance or directly adding them to a reaction system to synthesize in situ, thereby obtaining a catalyst for the selective tetramerization of ethylene containing a bisphosphine ligand.

[0037] In some embodiments, the ligand of formula (I), the transition metal compound, and the activator can be mixed simultaneously or in any order in the presence or absence of a solvent, thereby providing an active catalyst. The mixing of the catalyst components can be performed at -20 to 250°C, and the presence of an olefin during the mixing of the catalyst components generally exhibits a protective effect, thereby providing improved catalytic performance. Further, the mixing of the catalyst components can be performed at a temperature range of about 20 to 100°C.

[0038] In some embodiments, the isolatable metal-ligand complex can be prepared in situ from a transition metal compound and a ligand of formula (I). The metal-ligand complex is then added to the reaction medium. Alternatively, the chromium compound and the ligand can be added separately to the reactor, whereby the chromium-ligand complex is prepared in situ. By in situ preparation of the complex is meant that the complex is prepared in the medium in which the catalytic reaction is taking place, and finally, the activator is added.

[0039] The use of a catalyst comprising a PNP ligand as described above for the selective tetramerization of ethylene to produce 1-octene.

[0040] Further, the reaction is carried out in an inert solvent at a temperature of 0-200°C, preferably 10-120°C, more preferably 15-100°C, further preferably 20-80°C, and most preferably 20-50°C, at a pressure of 10-5000 psig, preferably 100-2000 psig, more preferably 300-1000 psig, and most preferably 400-600 psig, and the concentration of the transition metal in the inert solvent is 0.01-10000 μmol / L, preferably 1-500 μmol / L, and more preferably 0.1-10 μmol / L.

[0041] Further, the inert solvent comprises one or a mixture of several of an alkane, an arene, an alkene, or an ionic liquid. Typical solvents include, but are not limited to, benzene, toluene, xylene, cumene, chlorobenzene, dichlorobenzene, fluorobenzene, n-heptane, n-hexane, methylcyclohexane, cyclohexane, 1-hexene, 1-octene, and the like, preferably toluene, methylcyclohexane.

[0042] Compared to the prior art, the present application has the following advantages:

[0043] (1) The present application creatively introduces both an alkyl group and an ortho-halogenated aryl group into the PNP ligand. By introducing an alkyl group and an ortho-halogenated aryl group with less steric hindrance, the content of cyclic C6 is significantly reduced, and the total selectivity of 1-hexene and 1-octene is improved under the condition of ensuring high selectivity of 1-octene. Since the electron-donating ability of an alkyl group is stronger than that of a phenyl group, the introduction of an alkyl group into the ligand increases the electron cloud density of the phosphorus atom, significantly increases the stability of the chromium metal active center, prolongs the catalyst life, and effectively improves the activity of the catalyst system. The improvement of catalyst life also reduces the degradation of the catalyst, thereby reducing the content of polymer in the reaction to 0.05-0.1%.

[0044] (2) In terms of activators, the present application uses a specially modified modified methylaluminoxane, which enables the catalyst system to achieve very high reactivity without the need for adding water;

[0045] (3) The application can further improve the selectivity of 1-octene by optimizing the process parameters. DETAILED DESCRIPTION

[0046] The following detailed description of the embodiments of the application is given on the premise of the technical solutions of the application, and detailed implementation manners and specific operation processes are given, but the protection scope of the application is not limited to the following embodiments.

[0047] Example 1

[0048] (1) Preparation of (2-F-Ph)2PCl

[0049] Magnesium powder (0.88 g, 36 mmol) was placed in a Schlenk reaction tube, and tetrahydrofuran (10 mL) was added under nitrogen protection, 5 drops of 1,2-dibromoethane were added dropwise, and the reaction was carried out for 3 minutes. Then, a solution of o-bromofluorobenzene (5.25 g, 30 mmol) in tetrahydrofuran (40 mL) was slowly added at 0°C, and the reaction was carried out for 1 hour. Then, the gray-black o-fluorophenyl magnesium bromide (30 mmol) tetrahydrofuran solution was obtained by filtration. Phosphorus trichloride (2.06 g, 15 mmol) was dissolved in tetrahydrofuran (10 mL) and cooled to -78°C. Then, the above-prepared o-fluorophenyl magnesium bromide (30 mmol) tetrahydrofuran solution (50 mL) was slowly added, and after the dropwise addition was completed, the temperature was slowly increased to room temperature and stirred for 5 hours. After the reaction was completed, the solvent was removed by suction, dissolved in ethyl ether (40 mL), filtered under anhydrous and anaerobic conditions, and the solvent was removed by suction to obtain a light yellow oily product. 31 P NMR (162 MHz, CDCl3) δ = 60.54 (t, J = 64.8 Hz).

[0050] (2) Preparation of ligand L 1

[0051] (2-F-Ph)2PCl (10 mmol) was added dropwise to a solution of isopropylamine (12.5 mmol) and triethylamine (5 mL) in dichloromethane (10 mL) at 0°C, stirred for 30 minutes, then increased to room temperature and stirred overnight. Then, the mixture was suctioned to remove the solvent, then anhydrous ethyl ether (20 mL) was added to form a suspension, and the filtrate was obtained by filtration. The crude product was suctioned to remove the solvent under reduced pressure to obtain an oily crude product.

[0052] The crude product (0.5 g, 1.8 mmol) was dissolved in n-hexane (10 mL), and n-butyllithium (0.8 mL, 2.5 M hexane solution, 2.0 mmol) was added at -60°C. After 1 h, diethyl phosphorus chloride (0.45 g, 3.6 mmol) was added dropwise. After the dropwise addition was completed, the temperature was increased to room temperature and stirred overnight. After the reaction was completed, the mixture was filtered under anhydrous and anaerobic conditions, suctioned, recrystallized from n-hexane at -30°C, and the product L 1 (0.2 g, 24.0%).​1 H NMR (CDCI3) δ 0.86-0.96 (m, 6H), 1.00-1.09 (m, 6H), 1.48-1.57 (m, 4H), 2.83-2.96 (m, 1H), 7.13-7.28 (m, 6H), 7.61-7.71 (m, 2H). 31 P NMR (CDCI3) δ 45.72 (d, J = 25.8 Hz), 49.14 (br s).

[0053]

[0054] Example 2

[0055] Preparation of (2-F-Ph)(Ph)PCl

[0056] Phosphorus dichloride (1.25 g, 7 mmol) was dissolved in tetrahydrofuran (10 mL) and cooled to -78 °C, to which the above prepared o-fluorophenyl magnesium bromide (7 mmol) in tetrahydrofuran (10 mL) was slowly added dropwise, after the addition was completed, it was slowly warmed to room temperature and stirred for 5 hours, the reaction was complete, the solvent was removed by suction, dissolved in diethyl ether (40 mL), filtered under anhydrous and anaerobic conditions, the solvent was removed by suction to obtain the product as a light yellow oil. 31 P NMR (162 MHz, CDCI3) δ 70.91 (d, J = 65.5 Hz).

[0057] (2) Preparation of ligand L 2

[0058] (2-F-Ph)(Ph)PCl (10 mmol) was added dropwise to a solution of isopropylamine (12.5 mmol) and triethylamine (5 mL) in dichloromethane (10 mL) at 0 °C and stirred for 30 minutes, then warmed to room temperature and stirred overnight, the mixture was suctioned to remove the solvent, then anhydrous diethyl ether (20 mL) was added to form a suspension, filtered to obtain the filtrate, which was suctioned to remove the solvent under reduced pressure to obtain the crude product as an oil.

[0059] The crude product (0.5 g, 1.8 mmol) was dissolved in n-hexane (10 mL), n-butyllithium (0.8 mL, 2.5 M hexane solution, 2.0 mmol) was added at -60 °C, after 1 h, diethyl phosphorus chloride (0.45 g, 3.6 mmol) was added dropwise, after the addition was completed, it was warmed to room temperature and stirred overnight, the reaction was complete, filtered under anhydrous and anaerobic conditions, suctioned and dried, recrystallized from n-hexane at -30 °C to obtain the product L 2 (0.2 g, 34.0%). 1 ​H NMR (CDCI3) δ 0.89-0.97 (m, 6H), 1.06-1.15 (m, 6H), 1.53-1.63 (m, 4H), 2.71-2.82 (m, 1H), 7.18-7.28 (m, 5H), 7.42-7.49 (m, 3H), 7.61-7.68 (m, 1H). 31 P NMR (CDCI3) δ 40.58 (d, J = 36.2 Hz), 50.13 (br s).

[0060]

[0061] Example 3

[0062] Preparation of (Ph)(Et)PCI

[0063] In a dry 50 mL Schlenk tube purged and maintained with nitrogen, phenylphosphorous dichloride (1.79 g, 10 mmol) was taken and dissolved in 10 mL of tetrahydrofuran, the solution was then cooled to -78 °C, to this was added ethyl magnesium chloride (10.0 mL, 1.0 M in THF, 10 mmol) slowly, after complete addition, the reaction was continued at the same temperature for 30 min, then the reaction mixture was allowed to warm to room temperature and continued for 8 h, after completion the reaction was used as such without purification. 31 P NMR (162 MHz, CDCI3) δ = 83.7 (s).

[0064] Preparation of ligand L 3

[0065] Reference ligand L 2 Preparation of ligand L was carried out by using (Ph)(Et)PCI (3.6 mmol) instead of diethylphosphorous dichloride, the product L was obtained as a pale yellow solid by recrystallization from n-hexane at -30 °C 3 (0.2 g, 35.2 %). 1 H NMR (CDCI3) δ 0.91-1.03 (m, 3H), 1.06-1.15 (m, 6H), 1.82-1.93 (m, 2H), 2.85-2.89 (m, 1H), 7.20-7.32 (m, 7H), 7.40-7.48 (m, 6H), 7.61-7.68 (m, 1H). 31 P NMR (CDCI3) δ 52.38 (d, J = 33.1 Hz), 49.52 (br s).

[0066]

[0067] Example 4

[0068] ​Ligand L 4 Preparation of

[0069] Reference Ligand L 2 The preparation method of Ligand L was used, using cyclopentylamine (12.5 mmol) instead of isopropylamine, and the product L was obtained as a pale yellow solid by recrystallization from n-hexane at -30 °C. 4 (0.2 g, 37.5%). 1 H NMR (CDC13) δ 0.98-1.06 (m, 6H), 1.53 (dd, J = 15.6, 7.8 Hz, 2H), 1.53-1.68 (m, 8H), 1.98-2.05 (m, 2H), 3.68 (m, 1H), 7.07-7.17 (m, 6H), 7.18-7.35 (m, 3H). 31 P NMR (CDC13) δ 42.17 (d, J = 22.4 Hz), 49.14 (br s).

[0070]

[0071] Example 5

[0072] Ligand L 5 Preparation of

[0073] Reference Ligand L 2 The preparation method of Ligand L was used, using allylamine (12.5 mmol) instead of isopropylamine, and the product L was obtained as a pale yellow solid by recrystallization from n-hexane at -30 °C. 5 (0.2 g, 32.0%). 1 H NMR (CDC13) δ 0.96-1.07 (m, 6H), 1.48-1.58 (m, 4H), 3.32-3.42 (m, 2H), 5.18-5.29 (m, 2H), 5.85-5.93 (m, 1H), 7.05-7.15 (m, 5H), 7.35-7.42 (m, 3H), 7.61-7.71 (m, 1H). 31 P NMR (CDC13) δ 43.16 (d, J = 26.4 Hz), 50.16 (br s).

[0074]

[0075] Example 6

[0076] Ligand L 6 Preparation of

[0077] Reference Ligand L 2 The preparation method of Ligand L was used, using aniline (12.5 mmol) instead of isopropylamine, and the product L was obtained as a pale yellow solid by recrystallization from n-hexane at -30 °C. 6(0.3 g, 45.0%). 1 H NMR (CDC13) δ 0.96-1.06 (m, 6H), 1.58-1.68 (m, 4H), 6.80-6.85 (m, 3H), 7.18-7.42 (m, 7H), 7.45-7.53 (m, 3H), 7.55-7.60 (m, 1H). 31 P NMR (CDC13) δ 49.12 (d, J = 32.5 Hz), 50.10 (br s).

[0078]

[0079] Example 7

[0080] Preparation of ligand L 7

[0081] Preparation of ligand L 2 The preparation method of ligand L was used, using divinylphosphine chloride (0.43 g, 3.6 mmol) instead of diethylphosphine chloride, and the product L was obtained as a light yellow solid by recrystallization from n-hexane at -30 °C 7 (0.1 g, 19.5%). 1 H NMR (CDC13) δ 0.96-1.06 (m, 6H), 1.58-1.68 (m, 4H), 6.80-6.85 (m, 3H), 7.18-7.42 (m, 7H), 7.45-7.53 (m, 3H), 7.55-7.60 (m, 1H). 31 P NMR (CDC13) δ 49.12 (d, J = 32.5 Hz), 50.10 (br s).

[0082]

[0083] Example 8

[0084] Preparation of ligand L 8

[0085] Preparation of ligand L 2 The preparation method of ligand L was used, using dimethoxyphosphine chloride (0.43 g, 3.6 mmol) instead of diethylphosphine chloride, and the product L was obtained as a light yellow solid by recrystallization from n-hexane at -30 °C 8 (0.2 g, 24.2%). 1 H NMR (CDC13) δ 0.96-1.06 (m, 6H), 1.58-1.68 (m, 4H), 6.80-6.85 (m, 3H), 7.18-7.42 (m, 7H), 7.45-7.53 (m, 3H), 7.55-7.60 (m, 1H). 31 ​​P NMR (CDCI3) δ 40.5 (d, J = 19.6 Hz), 13.6 (s).

[0086]

[0087] Example 9

[0088] Preparation of ligand L 9

[0089] Reference ligand L 2 The preparation method of reference ligand L was used, 2,4-difluorophenyl magnesium bromide (7.0 mmol) was used instead of o-fluorophenyl magnesium bromide, and the product L was obtained as a light yellow solid by recrystallization from n-hexane at -30 °C 9 (0.2 g, 35.9%). 1 H NMR (CDCI3) δ 0.88-0.96 (m, 6H), 1.01-1.11 (m, 6H), 1.32 (s, 9H), 1.48-1.58 (m, 4H), 2.80-2.85 (m, 1H), 7.07-7.18 (m, 5H), 7.43-7.53 (m, 3H). 31 P NMR (CDCI3) δ 40.52 (d, J = 33.6 Hz), 50.12 (br s).

[0090]

[0091] Example 10

[0092] Preparation of ligand L 10

[0093] Reference ligand L 2 The preparation method of reference ligand L was used, 2,4-difluorophenyl magnesium bromide (7.0 mmol) was used instead of o-fluorophenyl magnesium bromide, and the product L was obtained as a light yellow solid by recrystallization from n-hexane at -30 °C 10 (0.3 g, 35.2%). 1 H NMR (CDCI3) δ 0.88-0.96 (m, 6H), 1.01-1.11 (m, 6H), 1.32 (s, 9H), 1.48-1.58 (m, 4H), 2.80-2.85 (m, 1H), 7.07-7.18 (m, 5H), 7.43-7.53 (m, 3H). 31 P NMR (CDCI3) δ 40.52 (d, J = 33.6 Hz), 50.12 (br s).

[0094]

[0095] Example 11 ​​

[0096] Ligand L 11 Preparation of

[0097] Reference Ligand L 2 The preparation method of the ligand L was used, 2-fluoro-4-methoxyphenyl magnesium bromide (7.0 mmol) was used instead of o-fluorophenyl magnesium bromide, and the product L was obtained as a light yellow solid by recrystallization from n-hexane at -30 °C. 11 (0.3 g, 40.5%). 1 H NMR (400 MHz, CDC13) δ 1.18 (d, J = 46.5 Hz, 6 H), 3.77 - 3.93 (m, 1 H), 6.99 (td, J = 8.8, 4.4 Hz, 2 H), 7.09 (t, J = 7.4 Hz, 2 H), 7.27 - 7.42 (m, 14 H). 31 P NMR (CDCl3) δ 40.52 (d, J = 45.8 Hz), 52.6 (br s).

[0098]

[0099] Example 12

[0100] Ligand L 12 Preparation of

[0101] A solution of (2-F-Ph)2PCl (10 mmol) in tetrahydrofuran was added dropwise to a solution of isopropylamine (0.74 g, 12.5 mmol) and triethylamine (0.51 g, 5.0 mL) in dichloromethane (10 mL) at 0 °C, stirred for 30 minutes, then raised to room temperature and stirred overnight, after the reaction was completed, the solvent in the mixture was removed under reduced pressure, then anhydrous diethyl ether (20 mL) was added to form a suspension, filtered, and the filtrate was dried under reduced pressure to obtain an oily crude product, which was directly used in the next step without purification.

[0102] The crude product (0.5 g, 1.8 mmol) was dissolved in dichloromethane (10 mL), triethylamine (0.5 mL) was added, followed by dropwise addition of diphenyl phosphine chloride (0.8 g, 3.6 mmol), after the dropwise addition was completed, it was raised to room temperature and stirred overnight, the mixture was dried by solvent extraction, and the product L was obtained as a white solid powder by basic aluminum oxide column chromatography. 12 (0.2 g, 24.0%). 1 H NMR (400 MHz, CDC13) δ 1.18 (d, J = 46.5 Hz, 6 H), 3.77 - 3.93 (m, 1 H), 6.99 (td, J = 8.8, 4.4 Hz, 2 H), 7.09 (t, J = 7.4 Hz, 2 H), 7.27 - 7.42 (m, 14 H). 31P NMR (162 MHz, CDC13) δ = 52.5 (br s), 22.6 (br s).

[0103]

[0104] Example 13

[0105] Preparation of ligand L 13

[0106] Reference ligand L 13 The preparation method of reference ligand L was used, (2-F-Ph)2PCl was replaced by (2-F-Ph)(Ph)PCl (3.6 mmol), and the product L was obtained as a white solid by recrystallization from methanol. 13 (0.4 g, 45.2%). 1 H NMR (CDC13) δ 1.01-1.09 (m, 6H), 2.82-2.92 (m, 1H), 7.07-7.13 (m, 2H), 7.16-7.26 (m, 3H), 7.42-7.62 (m, 14H). 31 P NMR (CDC13) δ 46.20 (d, J = 35.6 Hz), 52.20 (br s).

[0107]

[0108] Example 14

[0109] Preparation of ligand L 14

[0110] Reference ligand L 1 The preparation method of reference ligand L was used, Ph2PCl (10 mmol) was used instead of (2-F-Ph)2PCl to obtain a crude product 1.3 g (5.3 mmol, 53.0%), the crude product (1.3 g, 5.3 mmol) was dissolved in n-hexane (20 mL), n-butyllithium (2.2 mL, 2.5 M hexane solution, 5.5 mmol) was added at -35 °C, diethyl phosphorus chloride (0.7 g, 5.3 mmol) (10 mL) was added dropwise after 1 h, the temperature was raised to room temperature after the dropwise addition was completed, and the mixture was stirred overnight, the reaction was complete, the mixture was filtered under anhydrous and anaerobic conditions, and the solvent was removed by suction, the product L was obtained by recrystallization from n-hexane. 14 (1.3 g, 75.2%). 1 H NMR (CDC13) δ 0.98-1.06 (m, 6H), 1.13-1.25 (m, 6H), 1.59-1.65 (m, 4H), 2.83-2.91 (m, 1H), 7.14-7.30 (m, 4H), 7.42-7.62 (m, 6H). 31 ​​P NMR (CDCI3) δ 43.80 (d, J = 25.4 Hz), 50.16 (br s).

[0111]

[0112] Example 15

[0113] (1) Preparation of catalyst

[0114] In a dry and argon-filled Schlenk reactor, chromium acetylacetonate (0.28 mg, 0.80 μmol), ligand L 1 (0.35 mg, 0.96 μmol) and anhydrous methylcyclohexane (20 ml) were added, and after stirring for 5 minutes, modified methylaluminoxane MMAO-3A (0.4 mmol, 1.12 mol / L) was added. After reaction at room temperature for 5 minutes, it was ready for use.

[0115] (2) Ethylene oligomerization reaction

[0116] A 350 mL stainless steel autoclave was evacuated for 3 hours on an oil bath at 120°C to ensure anhydrous and oxygen-free environment in the reactor, and then cooled to the reaction temperature. The reactor was replaced with ethylene gas three times. Then the above prepared catalyst solution was immediately taken with a dry glass syringe and injected into the autoclave. The reactor was sealed, the stirring was started, and the ethylene gas was introduced. The pressure was adjusted to 500 psig, and the reaction was carried out at 40°C for 30 minutes. After the reaction was completed, the ethylene supply valve was closed, the temperature was cooled to 0°C, and the pressure was released. The reactor was opened, a quantitative internal standard of n-nonane was added and stirred uniformly. Then about 30 mL of 10 wt% aqueous HCl solution was used to quench the reaction, and a small amount of organic phase was filtered and subjected to GC analysis. The remaining mixture in the reactor was filtered, and the solid was added to 10 wt% aqueous HCl solution and stirred for 2 hours. After filtration, the solid was dried to constant weight and weighed. The data are shown in Table 1.

[0117] Example 16

[0118] The difference from Example 15 is that the ligand L 1 is replaced by ligand L 2 (0.34 mg, 0.96 μmol). The data are shown in Table 1.

[0119] Example 17

[0120] The difference from Example 15 is that the ligand L 1 is replaced by ligand L 3 (0.38 mg, 0.96 μmol). The data are shown in Table 1.

[0121] Example 18

[0122] Example 18 except that the ligand L 1 was replaced by the ligand L 4 (0.36 mg, 0.96 μmol), data in Table 1.

[0123] Example 19

[0124] Example 18 except that the ethylene oligomerization was carried out at 20 °C, data in Table 1.

[0125] Example 20

[0126] Example 18 except that the ethylene oligomerization was carried out at 60 °C, data in Table 1.

[0127] Example 21

[0128] Example 18 except that the amount of MMAO-3A was 0.32 mmol, data in Table 1.

[0129] Example 22

[0130] Example 18 except that the amount of MMAO-3A was 0.56 mmol, data in Table 1.

[0131] Example 23

[0132] Example 18 except that the reaction pressure for the ethylene oligomerization was 400 psig, data in Table 1.

[0133] Example 24

[0134] Example 18 except that the reaction pressure for the ethylene oligomerization was 300 psig, data in Table 1.

[0135] Example 25

[0136] Example 18 except that the ligand L 4 was replaced by the ligand L 5 (0.33 mg, 0.96 μmol), data in Table 1.

[0137] Example 26

[0138] Example 18 except that the ligand L 4 was replaced by the ligand L 6 (0.37 mg, 0.96 μmol), data in Table 1.

[0139] Example 27

[0140] Example 18 except that the ligand L 4 was replaced by the ligand L 7(0.33 mg, 0.96 μmol), data in Table 1.

[0141] Example 28

[0142] The difference to Example 18 is the ligand L used 4 is replaced by the ligand L 8 (0.34 mg, 0.96 μmol), data in Table 1.

[0143] Example 29

[0144] The difference to Example 18 is the ligand L used 4 is replaced by the ligand L 9 (0.35 mg, 0.96 μmol), data in Table 1.

[0145] Example 30

[0146] The difference to Example 18 is the ligand L used 4 is replaced by the ligand L 10 (0.39 mg, 0.96 μmol), data in Table 1.

[0147] Example 31

[0148] The difference to Example 18 is the ligand L used 4 is replaced by the ligand L 11 (0.36 mg, 0.96 μmol), data in Table 1.

[0149] Comparative Example 1

[0150] The difference to Example 18 is the ligand L used 4 is replaced by the ligand L 12 (0.45 mg, 0.96 μmol), data in Table 1.

[0151] Comparative Example 2

[0152] The difference to Example 18 is the ligand L used 4 is replaced by the ligand L 13 (0.43 mg, 0.96 μmol), data in Table 1.

[0153] Comparative Example 3

[0154] The difference to Example 18 is the ligand L used 4 is replaced by the ligand L 14 (0.32 mg, 0.96 μmol), data in Table 1.

[0155] Table 1

[0156]

[0157] As can be seen from Table 1, the catalyst provided by the present application has high catalytic activity, which can reach 3940 Kg / g Cr / h, and the selectivity of 1-octene reaches 77.2%, which can reach 85.0%. As can be seen from Comparative Example 15 and Comparative Example 1 and Example 16 and Comparative Example 2, by introducing an alkyl group with small steric hindrance, the selectivity of 1-octene is effectively improved, and the catalytic activity does not decrease obviously; as can be seen from Comparative Example 16 and Comparative Example 3, the introduction of a fluorine atom at the ortho position of the phenyl group can effectively reduce the content of cyclic C6, effectively improve the total selectivity of 1-hexene and 1-octene, and the introduction of a fluorine atom at the ortho position of the phenyl group can significantly improve the catalytic activity. In addition, since the electron-donating ability of the alkyl group is stronger than that of the phenyl group, the introduction of the alkyl group in the ligand increases the electron cloud density of the phosphorus atom, which can significantly increase the stability of the chromium metal active center, prolong the service life of the catalyst, and effectively improve the activity of the catalytic system. The improvement of the service life of the catalyst also reduces the degradation of the catalyst, thereby reducing the content of the polymer in the reaction to 0.05-0.1%.

[0158] The introduction of a fluorine atom at the ortho position of the phenyl group can effectively reduce the content of cyclic C6, effectively improve the total selectivity of 1-hexene and 1-octene, and the introduction of a fluorine atom at the ortho position of the phenyl group can significantly improve the catalytic activity. In addition, since the electron-donating ability of the alkyl group is stronger than that of the phenyl group, the introduction of the alkyl group in the ligand increases the electron cloud density of the phosphorus atom, which can significantly increase the stability of the chromium metal active center, prolong the service life of the catalyst, and effectively improve the activity of the catalytic system. The improvement of the service life of the catalyst also reduces the degradation of the catalyst, thereby reducing the content of the polymer in the reaction to 0.05-0.1%.

[0159] The above is only a preferred embodiment of the present application, and is not intended to limit the other forms of the present application. Any skilled person in the art can modify or change the above disclosed technical content to equivalent embodiments. However, any simple modification, equivalent change and modification of the above embodiments made according to the technical essence of the present application without departing from the technical solution of the present application still falls within the protection scope of the present application.

Claims

1. A catalyst for selective tetramerization of ethylene containing a PNP ligand, characterized in that: The catalyst includes a ligand, a transition metal compound and an activator, wherein the chemical structure of the ligand is shown below: ， Where, Group R 1 to R 3 are independently selected from alkyl, alkenyl, and aromatic groups, and R 1 to R 3 Not all aromatic groups; Group R 4 Selected from alkyl, alkenyl, and aromatic groups; Group R 5 to R 8 Each is independently selected from hydrogen, halogen, alkyl, alkoxy, alkenyl, and aromatic groups; R 1 to R 3 At least one is selected from alkyl or alkenyl; The alkyl group is C1-C 30 The alkyl group specifically includes 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; The alkenyl group is C1-C 30 The alkenyl group specifically includes 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; The alkoxy group is C1-C 20 The alkoxy group specifically includes an alkoxy group selected from methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, tert-butoxy, cyclohexyloxy, and cyclopentyloxy; The aromatic group is C4-C 30 Aryl and its 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 phenyl, 2,4-dimethylphenyl, 2,4-diisopropylphenyl, 2,4-di-tert-butylphenyl, 2,6-dimethylphenyl, 2,6-diisopropylphenyl, 3,5-dimethylphenyl, 3,5-di-tert-butylphenyl, 2,4,6-trimethylphenyl, naphthyl, anthracenyl, biphenyl, 7-fluoro-1-naphthyl, 8-fluoro-1-naphthyl, 7-chloro-1-naphthyl, 8-chloro-1-naphthyl, 9-fluoro-1-anthracenyl, 9-chloro-1-anthracenyl, 8-fluoro-1-anthracenyl or 8-chloro-1-anthracenyl; The halogen is fluorine, chlorine, bromine or iodine; 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 an alkyl aluminum compound, an aluminoxane compound or an organic boron compound; 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.

2. The catalyst for selective tetramerization of ethylene containing a PNP ligand according to claim 1, wherein: The aluminoxane compound specifically includes modified methylaluminoxane MMAO-3A.

3. A method for preparing a catalyst for selective tetramerization of ethylene containing a PNP ligand as claimed in claim 1 or 2, characterized in that: The method comprises the following steps: pre-mixing a ligand, a transition metal compound and an activator or directly adding them into a reaction system for in-situ synthesis, thereby obtaining a catalyst for selective ethylene tetramerization containing a PNP ligand.

4. Use of a catalyst for selective tetramerization of ethylene containing a PNP ligand as claimed in claim 1 or 2, characterized in that: The catalyst is used for the selective tetramerization of ethylene to produce 1-octene.

5. The use of a catalyst for selective tetramerization of ethylene containing a PNP ligand according to claim 4, characterized in that: The reaction is carried out in an inert solvent at a temperature of 0-200° C., a pressure of 10-5000 psig, and a concentration of the transition metal in the transition metal compound in the inert solvent of 0.01-10000 μmol / L. The inert solvent includes one or more of alkanes, aromatic hydrocarbons, alkenes or ionic liquids.

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