Nitrogen and phosphorus-containing compound, ethylene selective oligomerization catalyst composition, preparation method and ethylene oligomerization reaction method

Abstract

The invention discloses a compound containing nitrogen and phosphorus, an ethylene selective oligomerization catalyst composition, a preparation method and an ethylene oligomerization reaction method. The nitrogen and phosphorus-containing compound has the following structural general formula and is used as a ligand in the catalyst composition. According to the present invention, the PNP type ligand and the PCCP type ligand are connected to the same carbon chain, and the electronic performance and the steric hindrance of the substituent group of the catalyst ligand are adjusted so as to provide the ethylene selective oligomerization catalyst system with characteristics of good temperature resistance, high catalytic activity and high C6-C8 linear alpha-olefin selectivity, the invention aims to solve the problems of low reaction temperature and low total selectivity of C6-C8 linear alpha-olefin in the reaction in the existing ethylene oligomerization selective oligomerization technology. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to the field of catalytic materials for the selective trimerization and tetramerization of ethylene, and particularly to a nitrogen- and phosphorus-containing compound, an ethylene selective oligomerization catalyst composition, a preparation method, and an ethylene oligomerization reaction method. Background Art

[0002] Linear α-olefins (LAOs) are general raw materials for synthesizing olefin copolymers, plasticizers, detergents, and synthetic lubricants. Catalysts are the core of the process for producing α-olefins by ethylene polymerization. The most well-known catalytic systems are combinations of bidentate phosphine ligands and chromium, such as PNP, PN(C)nNP, and PCCP. Companies such as BP, Sasol, and SK Innovation, as representatives of this industry, have developed technologies for the selective trimerization and tetramerization of ethylene to produce 1-hexene and 1-octene. Although this selective oligomerization technology is currently considered to have reached the threshold of commercialization, there are still some key problems to be solved. The chromium-based catalysts with PNP and PNC structures reported by Danopoulos et al. catalyze the oligomerization of ethylene under the activation of methylaluminoxane, and the mass fraction of C6-C8 in the product reaches up to 52.28%. However, the selectivity in the catalytic reaction is still relatively low, and there is still much room for improvement. The ethylene selective oligomerization process mainly obtains linear α-olefins with a specific carbon number, and the obtained products have a high degree of linearization, good quality, and lower separation costs. The activity of the catalyst system and the selectivity of the target product are the keys to evaluating the advancement of this technology, and the structure of the ligand in the catalyst system plays an important role in this. Therefore, currently, new catalyst ligands are mainly designed to improve the selectivity of ethylene oligomerization.

[0003] Inevitably, a certain amount of high molecular weight polyethylene is produced during the ethylene tetramerization process, which will cause serious pipeline blockages in the process stream. As a feasible solution, it is considered to operate at a high temperature to dissolve the generated low molecular weight polyethylene, for example, above 100 °C. To meet this usage requirement, it is necessary to ensure that the catalyst system has excellent catalytic stability at high temperatures; however, most traditional chromium-based oligomerization catalysts cannot maintain their catalytic stability at higher reaction temperatures because they often undergo isomerization or degradation pathways at this time. Therefore, it is necessary to propose an ethylene selective oligomerization catalyst system with good temperature resistance, high catalytic activity, and high selectivity for C6-C8 linear α-olefins to solve the problem of by-product polymer blockage of pipelines during ethylene oligomerization. In addition, it is also necessary to solve the deficiencies that the contents of by-products methylcyclopentane and methylenecyclopentane are relatively high and the total selectivity of linear α-olefins is relatively low in the above catalytic system during the selective oligomerization of ethylene.

[0004] CN112916046A provides a ternary catalyst system and its application in ethylene oligomerization reaction. The ternary catalyst system is obtained by complexing raw materials mainly containing a phosphine-nitrogen ligand, a metal precursor centered on chromium, and a cocatalyst; the molar ratio of the metal precursor, the phosphine-nitrogen ligand to the cocatalyst is 1:0.1-10:1-1000, preferably 1:1-1.6:400-600; applying the obtained ternary catalyst system to the ethylene oligomerization reaction improves the selectivity of α-olefins in the ethylene oligomerization reaction, making the sum of the selectivities of 1-hexene and 1-octene in the oligomerization reaction reach more than 82%, but there is still room for optimization.

[0005] CN106853379A relates to the synthesis of a phosphine-amino phosphine structural framework ligand in a catalytic system for the selective oligomerization of ethylene to prepare α-olefins, and provides a ternary catalyst system with a chromium-centered metal precursor, a phosphine-amino phosphine compound as a ligand, an activator or a cocatalyst, and its catalytic high-selectivity ethylene trimerization to synthesize 1-hexene and tetramerization to synthesize 1-octene. Compared with the traditional PNP chromium-based catalyst system, it improves the co-selectivity of 1-hexene and 1-octene, reduces waxy products, and has mild reaction conditions and maintains high activity; however, the catalyst system of this invention has poor heat resistance.

[0006] CN111434667A discloses a fluorine-containing compound and its use as a ligand of an ethylene oligomerization catalyst composition. The fluorine-containing polymer is a bridged symmetric bisphosphine compound, and as a ligand of the catalyst for ethylene oligomerization, it can effectively improve the catalytic performance of the catalyst system, especially showing significantly improved catalytic performance in the ethylene oligomerization reaction.

[0007] CN111434668A discloses a halogen-containing compound and a catalyst composition containing the halogen-containing compound. The halogen-containing compound is a bridged symmetric bisphosphine compound, and the catalyst composition containing the halogen-containing compound shows significantly improved activity and significantly improved selectivity in ethylene oligomerization, especially in ethylene trimerization and tetramerization reactions, and significantly reduces the generation of by-products such as cycloolefins and cyclides.

[0008] CN114160199A discloses a catalytic system for the selective trimerization and tetramerization of ethylene and its application. The catalytic system includes: a transition metal complex a, and the transition metal complex a is an organometallic compound of Group IVB-VIII; a cocatalyst b, and the cocatalyst is an organic compound containing an element of Group IIIA; wherein, the structure of the transition metal complex a is: By finely adjusting the structure of the catalytic system complex, the catalyst system effectively adjusts the steric hindrance of the catalytic active center for the selective oligomerization of ethylene, resulting in a catalytic active center with high catalytic activity, high total selectivity for the target products 1-hexene + 1-octene, low selectivity for by-products such as methylcyclopentane and methylenecyclopentane, and low content of by-product polymers. Summary of the Invention

[0009] The object of the present invention is to provide a nitrogen and phosphorus-containing compound, an ethylene selective oligomerization catalyst composition, a preparation method, and an ethylene oligomerization reaction method.

[0010] In the present invention, PNP-type ligands and PCCP-type ligands are connected to the same carbon chain, and by adjusting the electronic properties and steric hindrance of the substituents of the catalyst ligands, an ethylene selective oligomerization catalyst system with good heat resistance, high catalytic activity, and high selectivity for C6-C8 linear α-olefins is proposed to solve the problems of low reaction temperature and low total selectivity for C6-C8 linear α-olefins in the existing ethylene oligomerization selective oligomerization technology.

[0011] To achieve the above object, the present invention adopts the following technical solutions:

[0012] In the first aspect of the present invention, a nitrogen and phosphorus-containing compound is provided, and the general structural formula of the compound is shown in formula (I):

[0013]

[0014] In formula (I), n is the number of C atoms, which is an integer from 1 to 10; R 1 , R 2 , R 3 , R 4 may be the same or different and are independently selected from hydrogen, an alkyl group of C 1 -C 10 or an aryl group of C 6 -C 20 and its derivatives; R 1 and R 2 may also be fused with the connected P atom to form a ring, such as a three-membered ring, a four-membered ring, a five-membered ring or a more-membered ring.

[0015] The nitrogen and phosphorus-containing compound provided by the present invention can be mainly used as a ligand and can coordinate with transition metals, and the transition metals are selected from chromium, molybdenum, tungsten, cobalt, titanium, tantalum, vanadium, zirconium, iron, nickel, palladium.

[0016] According to the nitrogen and phosphorus-containing compound of the present invention, preferably, the alkyl group is C 1 -C 6alkyl; more preferably, the alkyl is selected from methyl, ethyl, isopropyl, n-butyl, tert-butyl, cyclopentyl, cyclohexyl; further preferably, the alkyl is C 1 -C 3 alkyl, such as the alkyl is selected from methyl, ethyl, isopropyl, etc.

[0017] For the nitrogen- and phosphorus-containing compound according to the present invention, preferably, the aryl is selected from phenyl, substituted phenyl;

[0018] The substituted phenyl includes 4-methylphenyl, 4-fluorophenyl, 4-methoxyphenyl, trifluoromethylphenyl, p-tolyl, 3,5-bis(trifluoromethyl)phenyl, 3,5-dimethyl-4-methoxyphenyl, etc. The derivatives of the aryl are selected from naphthyl, substituted naphthyl, fluorenyl, etc.

[0019] For the nitrogen- and phosphorus-containing compound according to the present invention, preferably, the structural formula of the compound is selected from one of the following formulas:

[0020]

[0021]

[0022] The second aspect of the present invention provides an ethylene selective oligomerization catalyst composition, wherein the ethylene selective oligomerization catalyst composition includes: a ligand, a transition metal compound, and an activator;

[0023] The ligand is any nitrogen- and phosphorus-containing compound provided in the first aspect of the present invention;

[0024] The transition metal compound is a metal compound of Group IVB-VIII;

[0025] The activator is a compound containing a Group IIIA metal;

[0026] The molar ratio of the ligand, the transition metal compound, and the activator is 1:(0.5-100):(0.1-5000).

[0027] For the ethylene selective oligomerization catalyst composition according to the present invention, preferably, the transition metal compound is a compound of chromium, molybdenum, tungsten, cobalt, titanium, tantalum, vanadium, zirconium, iron, nickel or palladium.

[0028] For the ethylene selective oligomerization catalyst composition according to the present invention, preferably, the transition metal compound is CrCl 3 (THF) 3 、CrCl 2 (THF) 2 、CoCl 3 or NiBr 2 .

[0029] According to the ethylene selective oligomerization catalyst composition of the present invention, preferably, the transition metal compound is a chromium compound. More preferably, the chromium compound is selected from the compounds represented by the general formula CrR n as shown, where R n is an organic anion or a neutral molecule, and R n usually contains 1 to 10 carbon atoms, n is an integer from 0 to 6, and the valence state of chromium corresponding is from 0 to 6; specifically, R n is an organic substance or its group containing a carboxyl group, a β-diketone group, and a hydrocarbon group. Considering the aspects of easy dissolution and easy operation, more suitable chromium compounds are chromium acetate, chromium isooctanoate, chromium n-octanoate, chromium acetylacetonate, diisoprene chromium, diphenyl chromium, CrCl 3 (THF) 3 , CrCl 2 (THF) 2 , (phenyl)tricarbonyl chromium or hexacarbonyl chromium.

[0030] According to the ethylene selective oligomerization catalyst composition of the present invention, preferably, the activator is at least one of an alkylaluminum compound, an alkylaluminoxane compound, and an organic boron compound; wherein, the alkylaluminoxane compound includes an alkylaluminoxane compound from which volatile components are removed.

[0031] According to the ethylene selective oligomerization catalyst composition of the present invention, preferably, the activator is selected from at least one of an alkylaluminum compound and an alkylaluminoxane compound; the alkylaluminum compound can be various trialkylaluminums, such as triethylaluminum (TEAL), 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 (AlEt 2 Cl) and diethylaluminum trichloride (Al 2 Et 3 Cl 3 ); the alkylaluminoxane compound can be selected from methylaluminoxane (MAO), ethylaluminoxane, isobutylaluminoxane, modified aluminoxane, and methylaluminoxane from which volatile components are removed (DMAO), etc.

[0032] According to the ethylene selective oligomerization catalyst composition of the present invention, preferably, the activator is a mixture of an alkylaluminum compound and an alkylaluminoxane; wherein, the alkylaluminum compound is triethylaluminum (TEAL), and the alkylaluminoxane compound is methylaluminoxane from which volatile components are removed (DMAO). More preferably, the molar ratio of triethylaluminum (TEAL) to methylaluminoxane (DMAO) is (0.01 - 100):1, and further preferably (0.1 - 10):1.

[0033] In the present invention, the alkylation ability of TEAL is relatively weak, making it more adaptable to the catalyst system proposed in the present invention; at the same time, DMAO can shield the influence of volatile components such as toluene on the catalyst complexation process, thereby improving the activity of the catalyst system. The mixture of the two can further reduce the dosage of the activator.

[0034] For the ethylene selective oligomerization catalyst composition according to the present invention, preferably, the molar ratio of the ligand, the transition metal compound, and the activator is 1:(0.5 - 100):(0.1 - 1000).

[0035] For the ethylene selective oligomerization catalyst composition according to the present invention, preferably, the molar ratio of the ligand, the transition metal compound, and the activator is 1:(0.5 - 100):(0.1 - 200).

[0036] For the ethylene selective oligomerization catalyst composition according to the present invention, preferably, the molar ratio of the transition metal compound and the activator is 1:(1 - 500).

[0037] For the ethylene selective oligomerization catalyst composition according to the present invention, preferably, the molar ratio of the transition metal compound and the activator is 1:(1 - 200).

[0038] The third aspect of the present invention provides a preparation method of the compound provided in the first aspect, wherein the preparation method includes the following steps:

[0039] (1) Prepare intermediate 1:

[0040]

[0041] Use a first organic solvent to separately prepare solutions of diphenylphosphine chloride alkynylamine triethylamine;

[0042] Under stirring conditions, sequentially drop the solutions of triethylamine and diphenylphosphine chloride into the THF solution of alkynylamine and react for a first predetermined time;

[0043] After the reaction ends, filter the reaction system and recrystallize the liquid product after removing the solvent to obtain intermediate 1;

[0044] (2) Prepare intermediate 2:

[0045]

[0046] At -78 °C, slowly drop n-butyllithium ① into the solution of intermediate 1. After reacting for a second predetermined time, drop R 1 R 2A solution of PCl was reacted at room temperature for a third predetermined time; then at -78 °C, n-butyllithium ② was slowly added dropwise thereto, and after reacting for a fourth predetermined time, R was added dropwise. 3 R 4 The solution of PCl was continuously reacted at room temperature for a fifth predetermined time; after the reaction was completed, the reaction system was filtered to obtain a solid powder intermediate 2.

[0047] (3) Preparation of the final product:

[0048]

[0049] A certain amount of intermediate 2, CuI and Cs were taken 2 CO 3 and added to N,N-dimethylformamide (DMF) solvent for standby; a certain amount of HPPh 2 was slowly added dropwise thereto, heated to 90 - 100 °C, and stirred for a sixth predetermined time; after the reaction was completed, the reaction system was cooled to room temperature, then the solvent was removed and further purified by distillation or column chromatography to obtain the final product.

[0050] According to the preparation method of the third aspect of the present invention, in step (1):

[0051] Preferably, the molar ratio of diphenylphosphine chloride, alkynylamine, and triethylamine is 1:(1 - 1.2):(1 - 2); the triethylamine is used as an acid-binding agent in this step, and its theoretical dosage is 1 equivalent, and generally a slightly excessive amount is used in the reaction, such as 1 - 2 times the amount, preferably 1.2 times the amount. The theoretical dosage ratio of diphenylphosphine chloride and alkynylamine is 1:1, and the alkynylamine can be slightly excessive, and its molar ratio is 1:(1 - 1.2), more preferably 1:1.

[0052] Preferably, the first organic solvent is tetrahydrofuran (THF) or dichloromethane; more preferably tetrahydrofuran (THF).

[0053] Preferably, the temperature of the reaction is -35 °C, and the first predetermined time is 8 - 12 h.

[0054] Preferably, the removal of the solvent is achieved by vacuum drying.

[0055] Preferably, the recrystallization is carried out using n-hexane solvent.

[0056] According to the preparation method of the third aspect of the present invention, in step (2):

[0057] Preferably, the intermediate 1, n-butyllithium ①, R 1 R 2 PCl, n-butyllithium ②, R 3 R 4The molar ratio of PCl is 1:(1.02 - 1.05):1:(1.02 - 1.05):1; where n-butyllithium can be slightly in excess, for example, 1.02 - 1.05 times the equivalent amount is sufficient, and more preferably 1.02 times the equivalent amount.

[0058] Preferably, the solution of intermediate 1, R 1 R 2 the solution of PCl, R 3 R 4 the solution of PCl have the same solvent, which is diethyl ether or THF.

[0059] Preferably, the second predetermined time is 0.5 - 2 h; preferably, the third predetermined time is 2 - 3 h; preferably, the fourth predetermined time is 0.5 - 2 h; preferably, the fifth predetermined time is 2 - 3 h.

[0060] According to the preparation method of the third aspect of the present invention, in step (3):

[0061] Preferably, the dosage of CuI is 5 mol% - 8 mol% of intermediate 2, and more preferably 5 mol%; Cs 2 CO 3 the dosage of is 10 mol% - 15 mol% of intermediate 2, and more preferably 10 mol%.

[0062] Preferably, the molar ratio of HPPh 2 to intermediate 2 is 1:(1 - 1.6), and more preferably 1:1.5.

[0063] Preferably, the sixth predetermined time is 2 - 4 h.

[0064] Preferably, the removal of the solvent is carried out by vacuum drying.

[0065] For these reaction times, those skilled in the art understand that the end point of the reaction is judged by means of monitoring the consumption of the substrate during the reaction process, and the present invention does not limit the specific reaction time; the time ranges defined above are all relatively preferred time ranges for small-scale laboratory reactions, and can be specifically judged according to experimental monitoring.

[0066] The fourth aspect of the present invention provides a preparation method of the ethylene selective oligomerization catalyst composition provided by the second aspect, wherein the preparation method includes the following steps:

[0067] First, the ligand and the transition metal compound are separately dissolved in a second organic solvent for standby;

[0068] The solution of the ligand is slowly added dropwise to the solution of the transition metal compound, and after stirring for 7 - 12 h, complex 1 is obtained through filtration, washing, and drying.

[0069] The obtained complex 1 and the activator are used to obtain the ethylene selective oligomerization catalyst composition through a liquid-phase reaction or a solid-phase reaction; or the ethylene selective oligomerization catalyst composition is generated by an in-situ reaction during the ethylene selective oligomerization reaction. The reaction here can be a reaction between one, two, or three of the above-mentioned ligand, transition metal compound, and activator. The process of this reaction is also the aging (pre-complexation) process of the catalyst.

[0070] According to the preparation method of the fourth aspect of the present invention, preferably, the second organic solvent is dichloromethane or toluene.

[0071] According to the preparation method of the fourth aspect of the present invention, preferably, the washing is carried out using a n-hexane solvent.

[0072] According to the preparation method of the fourth aspect of the present invention, preferably, the drying is vacuum drying.

[0073] According to the preparation method of the fourth aspect of the present invention, preferably, the liquid-phase reaction is carried out under the action of a solvent; the solvent is selected from at least one of toluene, benzene, and its derivatives.

[0074] The fifth aspect of the present invention provides an ethylene oligomerization reaction method, which is carried out in the presence of the ethylene selective oligomerization catalyst composition provided in the second aspect of the present invention.

[0075] According to the ethylene oligomerization reaction method of the fifth aspect of the present invention, preferably, the reaction is carried out in a solvent, and the solvent is at least one of an alkane, an aromatic hydrocarbon, an alkene, or an ionic liquid. Typical solvents include, but are not limited to, benzene, toluene, xylene, cumene, n-heptane, n-hexane, methylcyclohexane, cyclohexane, 1-hexene, 1-octene, ionic liquids, etc., and methylcyclohexane is preferred.

[0076] According to the ethylene oligomerization reaction method of the fifth aspect of the present invention, preferably, the reaction temperature is 0 to 200 °C, more preferably 80 to 100 °C.

[0077] According to the ethylene oligomerization reaction method of the fifth aspect of the present invention, preferably, the reaction is carried out under a pressure of 0.1 to 50 MPa, more preferably 1.0 to 10 MPa.

[0078] According to the ethylene oligomerization reaction method of the fifth aspect of the present invention, preferably, the concentration of the catalyst composition in the reaction system is 0.01 to 1000 μmol metal / L, more preferably 0.1 to 10 μmol metal / L; the metal therein is the transition metal in the transition metal compound.

[0079] The beneficial effects of the present invention include:

[0080] (1) The ligand in the catalyst composition of the present invention is a diphosphine ligand of PNP type and PCCP type connected to the same carbon chain. Under the action of an activator, the ligand coordinates with a transition metal to form a binuclear metal complex; by adjusting the steric hindrance and electronic properties of the R 1 , R 2 , R 3 and R 4 groups in the ligand, the chemical environment of the ligand for the metal active center, i.e., the transition metal compound, can be effectively adjusted, so that the catalyst composition of the embodiments of the present invention for the selective oligomerization of ethylene can not only exhibit the better C8 selectivity of the PNP catalytic system, but also exhibit the characteristics of the high catalytic activity of the PCCP catalytic system, thereby making it easier to implement this catalytic system in industrial applications.

[0081] (2) The catalyst composition proposed by the present invention has the advantages of high catalytic activity, good thermal stability, high total selectivity of the target products 1-hexene and 1-octene, and low contents of by-products such as methylcyclopentane and methylenecyclopentane. Detailed Embodiments

[0082] To illustrate the present invention more clearly, the following further describes the present invention in conjunction with preferred embodiments. Those skilled in the art should understand that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the protection scope of the present invention.

[0083] All numerical specifications in the present invention (such as temperature, time, concentration, weight, etc., including the range of each of them) are generally approximate values that can be appropriately changed (+) or (-) in increments of 0.1 or 1.0. All numerical specifications can be understood as having the term "about" in front. It should be noted that the "total selectivity of C6-C8 linear α-olefins" in the text refers to the proportion of the total amount of C6-C8 linear α-olefins in the total products (all linear α-olefins and by-products).

[0084] Example 1

[0085] In this example, a nitrogen-phosphorus-containing compound (i.e., ligand), a catalyst composition are prepared, and the obtained catalyst composition is used in the ethylene oligomerization reaction, including the following processes:

[0086] 1. Preparation of the ligand [(Z)-N-(diphenylphosphoryl)-N-(2-(diphenylphosphoryl)-3-(1,1,3,3-tetraphenyltriphosphon-2-yl)allyl)-1,1-diphenylphosphineamine (L1)]:

[0087]

[0088] (1) Preparation of Intermediate 1:

[0089]

[0090] 2 g (9 mmol) of diphenylphosphine chloride, 0.5 g (9 mmol) of propargylamine, and 1.09 g (10.77 mmol) of triethylamine were separately placed into 20 mL vials, and 15 mL of THF was added to each for dissolution and standby.

[0091] Under strong stirring at -35 °C, the THF solutions of triethylamine and diphenylphosphine chloride were successively added dropwise to the THF solution of propargylamine, and the reaction was allowed to proceed for 8 h. The mixture was filtered and the liquid product was dried under vacuum to obtain the oily crude product intermediate 1. Then, it was recrystallized and purified using n-hexane to obtain 2.15 g of intermediate 1.

[0092] (2) Preparation of intermediate 2:

[0093]

[0094] At -78 °C, n-butyllithium (0.55 g, 8.52 mmol) was slowly added dropwise to a 15 mL diethyl ether solution of intermediate 1 (1 g, 4.18 mmol). After reacting for 3 h, an ether solution of diphenylphosphine chloride (1.84 g, 8.36 mmol) was added dropwise thereto, and the reaction was carried out overnight. After the reaction was completed, the mixture was filtered to obtain 2.53 g of the corresponding intermediate product 2.

[0095] (3) Preparation of the final product ligand:

[0096]

[0097] Intermediate 2 (1.5 g, 2.47 mmol), CuI (0.024 g, 0.13 mmol), and Cs 2 CO 3 (0.081 g, 0.25 mmol) were added to 20 mL of N,N-dimethylformamide (DMF) for standby. HPPh 2 (0.69 g, 3.71 mmol) was taken, and HPPh 2 was slowly added dropwise to the above standby solution, heated to 90 °C, and stirred for about 4 h. Then, the mixture was naturally cooled to room temperature and then dried in vacuo. After further purification by distillation or column chromatography, a colorless or light yellow product was obtained, which was ligand a.

[0098] 2. Preparation of the catalyst

[0099] In an N 2 environment, ligand L1 (2.55 mg, 2.52 μmol) was dissolved in dichloromethane (20 mL) for standby. Then, CrCl 3 ·(THF) 3A dichloromethane solution (0.89 mg, 2.40 μmol) was added dropwise to the above-prepared solution. After reacting at room temperature for 8 h, the solvent was evaporated to dryness. The obtained catalyst was washed with n-hexane and then filtered and dried by suction.

[0100] 3. Ethylene oligomerization reaction

[0101] A 100 mL reactor was heated and evacuated for 20 min, then purged with nitrogen several times and filled with ethylene. The temperature was raised to the predetermined temperature of 50 °C, and dehydrated methylcyclohexane (20 mL), 0.87 mL of MMAO-3A (modified methylaluminoxane), and the above catalyst were added. The oligomerization reaction was carried out at 50 °C and an ethylene pressure of 1 MPa. After reacting for 30 min, the reaction was cooled with an ice bath and depressurized, and the reaction was terminated with 10% acidified ethanol by mass fraction.

[0102] The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activities are shown in Table 2.

[0103] Example 2

[0104] Same as Example 1. The difference is that R of the ligand 1 is ethyl, R 2 is ethyl, R 3 is ethyl, R 4 is ethyl.

[0105] The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activities are shown in Table 2.

[0106]

[0107] Example 3

[0108] Same as Example 1. The difference is that R of the ligand 1 is isopropyl, R 2 is isopropyl, R 3 is isopropyl, R 4 is isopropyl. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activities are shown in Table 2.

[0109]

[0110] Example 4

[0111] Same as Example 1. The difference is that R of the ligand 1 is cyclopentyl, R 2 is cyclopentyl, R 3 is cyclopentyl, R 4 is cyclopentyl. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activities are shown in Table 2.

[0112]

[0113] Example 5

[0114] Same as Example 1. The difference lies in that R of the ligand 1 is methyl, R 2 is phenyl, R 3 is methyl, R 2 is phenyl.

[0115] The distribution of the oligomerization product is shown in Table 1, and the experimental conditions and catalyst activity are shown in Table 2.

[0116]

[0117] Example 6

[0118] Same as Example 1. The difference lies in that R of the ligand 1 is ethyl, R 2 is phenyl, R 3 is ethyl, R 4 is phenyl.

[0119] The distribution of the oligomerization product is shown in Table 1, and the experimental conditions and catalyst activity are shown in Table 2.

[0120]

[0121] Example 7

[0122] Same as Example 1. The difference lies in that R of the ligand 1 is isopropyl, R 2 is phenyl, R 3 is isopropyl, R 4 is phenyl. The distribution of the oligomerization product is shown in Table 1, and the experimental conditions and catalyst activity are shown in Table 2.

[0123]

[0124] Example 8

[0125] Same as Example 1. The difference lies in that R of the ligand 1 is o-fluorophenyl, R 2 is o-fluorophenyl, R 3 is o-fluorophenyl, R 4 is o-fluorophenyl. The distribution of the oligomerization product is shown in Table 1, and the experimental conditions and catalyst activity are shown in Table 2.

[0126]

[0127] Example 9

[0128] Same as Example 1. The difference lies in that the reaction pressure is 5.0 MPa and the reactor is 500 mL. The distribution of the oligomerization product is shown in Table 1, and the experimental conditions and catalyst activity are shown in Table 2.

[0129] Example 10

[0130] Same as Example 2, except that the reaction pressure is 5.0 MPa and the reactor is 500 mL. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activity are shown in Table 2.

[0131] Example 11

[0132] Same as Example 3, except that the reaction pressure is 5.0 MPa and the reactor is 500 mL. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activity are shown in Table 2.

[0133] Example 12

[0134] Same as Example 8, except that the reaction pressure is 5.0 MPa and the reactor is 500 mL. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activity are shown in Table 2.

[0135] Example 13

[0136] Same as Example 9, except that the reaction temperature is 100 °C. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activity are shown in Table 2.

[0137] Example 14

[0138] Same as Example 10, except that the reaction temperature is 100 °C. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activity are shown in Table 2.

[0139] Example 15

[0140] Same as Example 11, except that the reaction temperature is 100 °C. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activity are shown in Table 2.

[0141] Example 16

[0142] Same as Example 12, except that the reaction temperature is 100 °C. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activity are shown in Table 2.

[0143] Comparative Example 1

[0144] The oligomerization reaction conditions are the same as those in Example 1, except that the ligand has the following structure. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activity are shown in Table 2.

[0145]

[0146] Comparative Example 2

[0147] The oligomerization reaction conditions were the same as those in Example 16, except that the ligand had the following structure. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activities are shown in Table 2.

[0148]

[0149] Comparative Example 3

[0150] The oligomerization reaction conditions were the same as those in Example 16, except that the ligand had the following structure. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activities are shown in Table 2.

[0151]

[0152] Comparative Example 4

[0153] The oligomerization reaction conditions were the same as those in Example 16, except that the ligand had the following structure. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activities are shown in Table 2.

[0154]

[0155] Comparative Example 5

[0156] The oligomerization reaction conditions were the same as those in Example 11, except that the ligand had the following structure. The distribution of the oligomerization products is shown in Table 1, and the experimental conditions and catalyst activities are shown in Table 2.

[0157]

[0158] Table 1 Comparison of the carbon number distribution of the oligomerization products

[0159] Example <![CDATA[C 4 > <![CDATA[1-C 4 ＝ > <![CDATA[C 6 ＝ > <![CDATA[1-C 6 ＝ > Methylcyclopentane Methylenecyclopentane <![CDATA[C 8 ＝ > <![CDATA[1-C 8 ＝ > <![CDATA[C 10+ ＝ > 1 1.3 0.7 45.9 45.1 2.8 3.1 40.7 40.3 6.2 2 1.4 0.8 37.7 37.1 2.7 2.7 49.4 48.0 6.1 3 0.6 0.4 63.2 63.0 1.1 0.9 26.6 25.0 7.6 4 0.3 0.1 79.6 79.2 0.7 0.9 10.7 9.6 7.8 5 1.6 1.0 50.8 50.1 2.8 2.5 36.5 35.3 5.8 6 1.2 0.9 46.3 44.6 2.2 2.4 42.9 42.0 5.0 7 1.3 0.7 67.6 67.0 1.3 1.1 23.6 22.3 5.1 8 0.8 0.3 57.0 55.9 1.0 1.1 32.6 32.0 7.5 9 0.7 0.4 32.2 31.6 0.9 1.0 61.7 59.8 3.5 10 0.7 0.3 19.2 18.4 1.2 1.1 74.7 74.1 3.1 11 0.3 0.1 54.5 53.7 0.1 0.2 42.3 41.0 2.6 12 0.6 0.2 45.7 44.7 0.4 0.3 50.1 49.7 2.9 13 1.2 0.7 54.6 53.9 1.0 1.2 38.2 37.6 3.8 14 1.1 0.3 25.8 24.4 0.8 0.9 68.8 67.6 2.6 15 0.3 0.1 61.1 60.0 0.1 0.1 36.1 35.0 2.3 16 0.8 0.3 46.9 46.2 0.2 0.3 49.4 48.5 2.4 Comparative Example 1 2.6 1.0 44.2 42.1 4.3 4.5 40.1 38.2 4.3 Comparative Example 2 1.4 0.3 48.5 47.9 2.6 2.9 42.6 42.7 2.0 Comparative Example 3 0.9 0.2 44.3 43.9 1.4 1.7 50.6 49.8 1.1 Comparative Example 4 0.8 0.3 40.1 39.6 1.0 1.2 55.0 55.2 1.9 Comparative Example 5 0.7 0.2 38.7 38.1 0.9 1.1 56.9 56.1 1.7

[0160] Table 2 Experimental conditions and catalyst activities of the examples and comparative examples

[0161]

[0162] Note: * Refers to 1-C 6 ＝ +1-C 8

[0163] Under the experimental conditions of adding 2.4 μmol of the transition metal compound, 2.52 μmol of the ligand, an ethylene reaction pressure of 1 MPa, a reaction temperature of 50 °C, and MMAO-3A as the cocatalyst, the ethylene oligomerization reaction performance of Examples 1-8 was studied, and the reaction results are shown in Tables 1 and 2. The results show that increasing the steric volume of the P-alkyl substituents of the ligand can produce more 1-hexene fraction.

[0164] To investigate the influence of ethylene pressure on the catalytic performance of the catalyst, Examples 9 - 12 show the oligomerization results under an ethylene pressure of 5 MPa. Compared with a low ethylene pressure (1 MPa), the catalyst exhibits higher catalytic activity under a high ethylene pressure (5 MPa). Meanwhile, a high ethylene pressure can also increase the ethylene selective tetramerization product of the catalyst, producing more 1 - octene fractions and reducing the 1 - hexene selectivity of the system.

[0165] To investigate the influence of a high temperature of 100 °C on the catalytic performance of the catalyst, Examples 13 - 16 show the oligomerization results at a high temperature of 100 °C. It can be seen from the results that the total selectivity of the products of 1 - hexene and 1 - octene of the catalyst remains basically unchanged, and Example 16 also shows high activity. These results indicate that the catalytic system of the catalyst can maintain its stability at a very high temperature, so the 1 - octene selectivity of these catalysts is hardly affected at high temperatures.

[0166] It can be seen from the oligomerization reaction data in Tables 1 and 2 that compared with Comparative Example 1, the total selectivity of 1 - hexene and 1 - octene in Examples 1 - 8 increases significantly. Compared with Comparative Example 2, Examples 13 - 16 can maintain their stability at a higher temperature. The oligomerization reaction data of Comparative Examples 3 and 4 and Example 16, compared with other examples and comparative examples, reflect that the introduction of adjacent fluorine atoms can stabilize the intermediate, so the high activity of the catalytic system is maintained even at high temperatures.

[0167] Compared with Comparative Example 5, the catalytic activity of Examples 8 - 11 increases significantly.

[0168] Obviously, the above - mentioned examples of the present invention are merely examples for clearly explaining the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or alterations can be made based on the above description. It is impossible to enumerate all the implementation manners here. Any obvious changes or alterations derived from the technical solutions of the present invention still fall within the protection scope of the present invention.

Claims

1. A nitrogen- and phosphorus-containing compound, wherein, the general structural formula of the compound is shown as formula (I): In formula (I), n is an integer from 1 to 10; R 1 , R 2 , R 3 , R 4 may be the same or different and are each independently selected from hydrogen, an alkyl group of C 1 -C 10 or an aryl group of C 6 -C 20 and its derivatives; R 1 and R 2 may also be fused with the connected P atom to form a ring.

2. The compound according to claim 1, wherein, the alkyl group is selected from methyl, ethyl, isopropyl, n-butyl, tert-butyl, cyclopentyl, cyclohexyl.

3. The compound according to claim 1, wherein, the aryl group is selected from phenyl, substituted phenyl; the substituted phenyl includes 4-methylphenyl, 4-fluorophenyl, 4-methoxyphenyl, trifluoromethylphenyl, p-tolyl, 3,5-bis(trifluoromethyl)phenyl, 3,5-dimethyl-4-methoxyphenyl.

4. The compound according to claim 1, wherein, the structural formula of the compound is selected from one of the following formulas:

5. An ethylene selective oligomerization catalyst composition, wherein, the ethylene selective oligomerization catalyst composition includes: a ligand, a transition metal compound, and an activator; the ligand is the compound according to any one of claims 1-3; the transition metal compound is a metal compound of Group IVB to VIII; the activator is a compound containing a Group IIIA metal; the molar ratio of the ligand, the transition metal compound, and the activator is 1:(0.5-100):(0.1-5000).

6. The ethylene selective oligomerization catalyst composition according to claim 5, wherein, the transition metal compound is a compound of chromium, molybdenum, tungsten, cobalt, titanium, tantalum, vanadium, zirconium, iron, nickel, or palladium.

7. The ethylene selective oligomerization catalyst composition according to claim 5, wherein, The transition metal compound is CrCl 3 (THF) 3 、CrCl 2 (THF) 2 、CoCl 3 or NiBr 2 。 8. The ethylene selective oligomerization catalyst composition according to claim 5, wherein, The transition metal compound is a chromium compound, and the chromium compound is chromium acetate, chromium isooctanoate, chromium n-octanoate, chromium acetylacetonate, diisoprenylchromium, diphenylchromium, CrCl 3 (THF) 3 、CrCl 2 (THF) 2 、(phenyl)tricarbonylchromium or hexacarbonylchromium.

9. The ethylene selective oligomerization catalyst composition according to claim 5, wherein, the activator is at least one of an alkylaluminum compound, an alkylaluminoxane compound, and an organoboron compound; wherein, the alkylaluminoxane compound includes an alkylaluminoxane compound from which volatile components have been removed.

10. The ethylene selective oligomerization catalyst composition according to claim 5, wherein, the activator is selected from at least one of an alkylaluminum compound and an alkylaluminoxane compound.

11. The ethylene selective oligomerization catalyst composition according to claim 5, wherein, the activator is a mixture of an alkylaluminum compound and an alkylaluminoxane; wherein, the alkylaluminum compound is triethylaluminum, and the alkylaluminoxane compound is methylaluminoxane from which volatile components have been removed.

12. The ethylene selective oligomerization catalyst composition according to claim 11, wherein, the molar ratio of the triethylaluminum to the methylaluminoxane is (0.01-100):

1.

13. The ethylene selective oligomerization catalyst composition according to claim 5, wherein, the molar ratio of the transition metal compound to the activator is 1:(1-500).

14. A preparation method of the compound according to any one of claims 1-4, wherein, the preparation method includes the following steps: (1) Prepare intermediate 1: Use a first organic solvent to respectively prepare solutions of diphenylphosphine chloride, alkynylamine, and triethylamine; Under stirring conditions, a solution of triethylamine and diphenylphosphine chloride is successively added dropwise to a solution of alkynylamine and reacted for a first predetermined time; After the reaction is completed, the reaction system is filtered, and the liquid product is recrystallized after removing the solvent to obtain intermediate 1; (2) Preparation of intermediate 2: At -78 °C, n-butyllithium ① was slowly added dropwise to the solution of intermediate 1. After the second predetermined reaction time, R was added dropwise thereto. 1 R 2 A solution of PCl was added dropwise thereto at room temperature for the third predetermined reaction time. Then, at -78 °C, n-butyllithium ② was slowly added dropwise thereto. After the fourth predetermined reaction time, R was added dropwise. 3 R 4 A solution of PCl was added dropwise thereto and the reaction was continued at room temperature for the fifth predetermined reaction time. After the reaction was completed, the reaction system was filtered to obtain solid powder intermediate 2. (3) Preparation of the final product: Take a certain amount of intermediate 2, CuI and Cs 2 CO 3 Add to N,N-dimethylformamide solvent for standby; slowly drop a certain amount of HPPh 2 into it, heat to 90 - 100 °C, stir and react for the sixth predetermined time; after the reaction is completed, cool the reaction system to room temperature, then remove the solvent and further purify by distillation or column chromatography to obtain the final product.

15. According to the preparation method described in claim 14, wherein, in step (1), the molar ratio of diphenylphosphine chloride, alkynylamine, and triethylamine is 1:(1 to 1.2):(1 to 2).

16. According to the preparation method described in claim 14, wherein, In step (2), the molar ratio of the intermediate 1, n-butyllithium ①, R 1 R 2 PCl, n-butyllithium ②, R 3 R 4 PCl is 1:(1.02 to 1.05):1:(1.02 to 1.05):

1.

17. According to the preparation method described in claim 14, wherein, In step (3), the dosage of CuI is 5 mol% to 8 mol% of intermediate 2, and the dosage of Cs 2 CO 3 is 10 mol% to 15 mol% of intermediate 2; The HPPh 2 has a molar ratio with the intermediate 2 of 1:(1 to 1.6).

18. A method for preparing an ethylene selective oligomerization catalyst composition according to any one of claims 5-13, wherein, the preparation method includes the following steps: First, the ligand and the transition metal compound are separately dissolved in a second organic solvent for standby; The solution of the ligand is slowly added dropwise to the solution of the transition metal compound, and after stirring for 7 to 12 h, complex 1 is obtained through filtration, washing, and drying; The obtained complex 1 and the activator are used to obtain the ethylene selective oligomerization catalyst composition through a liquid-phase reaction or a solid-phase reaction; or the ethylene selective oligomerization catalyst composition is generated through an in-situ reaction during the ethylene selective oligomerization reaction.

19. According to the preparation method described in claim 18, wherein, the liquid-phase reaction is carried out under the action of a solvent; the solvent is selected from at least one of toluene, benzene, and its derivatives.

20. An ethylene oligomerization reaction method, which is carried out in the presence of the ethylene selective oligomerization catalyst composition described in claims 5-13.

21. According to the ethylene oligomerization reaction method described in claim 20, wherein, the reaction is carried out in a solvent, and the solvent is selected from at least one of benzene, toluene, xylene, cumene, n-heptane, n-hexane, methylcyclohexane, cyclohexane, 1-hexene, 1-octene, and ionic liquid.

22. According to the ethylene oligomerization reaction method described in claim 20, wherein, the reaction temperature is 0 to 200 °C; the reaction is carried out under a pressure of 0.1 to 50 MPa; the concentration of the catalyst composition in the reaction system is 0.01 to 1000 μmol metal / L.

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