Catalysts for the selective oligomerization of ethylene comprising saturated aliphatic cyclic backbone bisphosphine ligands and their preparation and use

Abstract

The application relates to an ethylene selective oligomerization catalyst containing a saturated aliphatic ring skeleton biphosphine ligand and preparation and application thereof, the catalyst comprising a ligand, a transition metal compound and an activator, the chemical structural formula of the ligand being: wherein the groups R 1 to R 4 are each independently hydrogen, an alkyl group, an alkoxy group, an alkenyl group or an aromatic group; n is a positive integer, and the value range is 3-5; the transition metal in the transition metal compound is selected from iron, cobalt, nickel, copper, titanium, vanadium, chromium, manganese, molybdenum, tungsten or palladium; and the activator comprises an alkyl aluminum compound, an aluminoxane compound or an organic boron compound. Compared with the prior art, the catalyst provided by the application has higher catalytic activity and total selectivity of 1-hexene / 1-octene, and the polymer content is lower, so that the production cost is greatly reduced, the requirements of the industrial department can be met, and the catalyst has important application value.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of ethylene oligomerization, and relates to a catalyst for selective ethylene oligomerization containing a saturated aliphatic ring skeleton bidentate phosphine ligand as well as preparation and application thereof. BACKGROUND

[0002] Linear alpha-olefins (LAO) are important chemical raw materials, which can be used to prepare lubricating oil, surfactant, etc., and 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%). Traditional ethylene oligomerization catalysts mainly follow the Cossee-Arlman mechanism, that is, ethylene molecules are inserted into the linear chain growth of the catalyst metal center, and the linear alpha-olefins obtained are usually normally distributed, which must be separated and purified according to the needs in industrial applications, and the representative systems are titanium, zirconium, iron, etc. However, the chromium-catalyzed ethylene trimerization and tetramerization mainly follow the metal ring mechanism. With the continuous deepening of research, it is found that the structure of the Cr system ethylene trimerization and tetramerization catalyst, especially the connecting skeleton of the bidentate phosphine ligand and the substituents on the P atom, plays a key role in the selectivity of the products.

[0003] For the past two decades, the research in this field has focused on the catalytic mechanism of ethylene selective oligomerization and ligand design, and some important achievements have been made. In 2002, British Petroleum reported that PNP-type ligand with the structure of PAr2N(R)PAr2(Ar is an ortho-methoxy-substituted aryl group) was used in the chromium-catalyzed high-selectivity ethylene trimerization to prepare 1-hexene (Chem. Commun. 2002, 858-859). In 2004, Sasol successfully realized ethylene tetramerization by using the above-mentioned PNP-type ligand / chromium catalytic system through modification of the substituent group, and the selectivity of 1-octene was as high as 67.5% (J. Am. Chem. Soc. 2004, 126, 14712-14713.). In 2008, Sasol designed and synthesized a series of double-phosphine ligands with a carbon-bridged skeleton for catalyzing the selective trimerization and tetramerization of ethylene, among which the double-phosphine ligand with a phenyl bridge showed good catalytic performance, with an activity of 2240 kg / (g Cr / h), but the selectivity of 1-octene was only 56.8%, the total selectivity of 1-hexene and 1-octene was only 69.8%, and the content of PE was as high as 0.9%. In 2010, SK Energy of South Korea reported a series of DPPE-type ligands with a chiral skeleton and double-methyl substitution for catalyzing the selective tetramerization of ethylene (Organometallics, 2010, 29, 5805). Although the selectivity of 1-octene was as high as 59.2%, the activity was as high as 1930 kg / (g Cr / h), the total selectivity of 1-hexene and 1-octene was as high as 90.6%, but 0.7% of polymers were still produced in the product. Although high-activity catalytic systems continue to emerge, catalytic systems with high activity (>2000 kg / (g Cr / h)) and high total selectivity of 1-hexene / 1-octene (>90%) are still rare, and a large amount of solid polyethylene is produced in most of the catalytic systems, which affects the long-period operation of the equipment. SUMMARY

[0004] The purpose of the present application is to provide an ethylene selective oligomerization catalyst containing a double-phosphine ligand with a saturated aliphatic ring skeleton, as well as a preparation method and application thereof. The provided catalyst can further improve the total selectivity of 1-hexene / 1-octene and the activity of the catalytic system, and reduce the amount of polymer produced.

[0005] The purpose of the present application can be achieved by the following technical solutions.

[0006] In one aspect, the present application provides an ethylene selective oligomerization catalyst containing a double-phosphine ligand with a saturated aliphatic ring skeleton, which comprises a ligand, a transition metal compound and an activator, and the chemical structural formula of the ligand is:

[0007] ,

[0008] wherein the group R 1 to R 4 each independently is hydrogen, alkyl, alkoxy, alkenyl or aryl group, n is a positive integer ranging from 1 to 5;

[0009] the transition metal in the transition metal compound is selected from iron, cobalt, nickel, copper, titanium, vanadium, chromium, manganese, molybdenum, tungsten or palladium;

[0010] the activator includes an alkyl aluminum compound, an aluminoxane compound or an organic boron compound.

[0011] further, the alkyl is methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, t-butyl, n-pentyl, s-pentyl, i-pentyl, cyclopentyl, n-hexyl, s-hexyl, i-hexyl, cyclohexyl, n-heptyl, cycloheptyl, n-octyl, n-decyl, 2-methylcyclopentyl or 2,6-dimethylcyclohexyl;

[0012] the alkoxy is methoxy, ethoxy, n-propoxy, i-propoxy, n-butoxy, t-butoxy, cyclohexyloxy or cyclopentyloxy;

[0013] the alkenyl is 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 or 2-methyl-2-cyclohexenyl;

[0014] the aryl group is 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.

[0015] further, the group R 1 to R 4each independently is ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, n-pentyl, cyclohexyl, cyclopentyl, phenyl, 2-fluorophenyl, 2-methoxyphenyl, or 4-t-butylphenyl.

[0016] Further, the group R 1 to R 4 one of which is alkyl and the other three are aryl. Preferably, the alkyl group here can be ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, n-pentyl, cyclohexyl, cyclopentyl, etc., and the aryl group can be phenyl, 2-fluorophenyl, 2-methoxyphenyl, 4-t-butylphenyl, etc.

[0017] 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, and more preferably (0.5-2): 1.

[0018] Further, the molar ratio of the activator to the transition metal element in the transition metal compound is (1-10000): 1, preferably (1-2000): 1, and more preferably (600-1000): 1.

[0019] Further, the activator in the catalyst system of the present application plays a role of activation in the catalyst system. The activator usable in the present application can be any compound which forms an active catalyst when mixed with the ligand and the transition metal compound. The activator can be used alone or in combination.

[0020] Specifically, the activator can be an alkylaluminum compound, which can be various trialkylaluminums such as trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, or tri-n-octylaluminum; an alkylaluminum halide, an alkylaluminum hydride, or an alkylaluminum sesquichloride such as diethylaluminum chloride (AlEt2Cl) and trichlorotriethylaluminum (Al2Et3Cl3).

[0021] Specifically, the activator can be an aluminoxane compound, which can be generally prepared by mixing water with an alkylaluminum compound (e.g., trimethylaluminum). The prepared aluminoxane oligomer compound can be a straight-chain 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 DMAO (methylaluminoxane from which volatile components are removed), etc., and an exemplary one can be modified methylaluminoxane MMAO-3A.

[0022] Specifically, the 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.

[0023] Further, the transition metal in the transition metal compound is a metal active center and plays an important role in the catalytic process, and is preferably one of chromium, cobalt, titanium, iron, nickel or palladium. More preferably, the transition metal in the transition metal compound is selected from chromium, and specifically, the corresponding transition metal compound is any chromium compound capable of enabling oligomerization, and the optional chromium compound includes one of the general formula CrR m The compound is shown, wherein R m is an organic anion or a neutral molecule, R m generally contains 1-15 carbon atoms, m is an integer from 0 to 6, and the valence of Cr is 0-6. Specifically, the R m group is an organic compound containing a carboxyl group, a β-diketone group, and a hydrocarbon group, or other groups. From the perspective of easy solubility and easy operation, the more suitable chromium compounds include one of chromium trichloride-tris(tetrahydrofuran) complex, (benzene)tricarbonyl chromium, chromium (III) octoate, chromium hexacarbonyl, chromium (III) acetylacetone, chromium (III) naphthenate, chromium (III) 2-ethylhexanoate, chromium (III) acetate, chromium (III) 2,2,6,6-tetramethylheptanedione, and chromium (III) chloride. Preferably, the chromium compound is selected from chromium trichloride-tris(tetrahydrofuran) complex, chromium (III) acetylacetone, and chromium (III) 2-ethylhexanoate.

[0024] In the second aspect, the present application provides a preparation method of a catalyst for selective oligomerization of ethylene containing a saturated aliphatic ring skeleton double phosphine ligand, which pre-mixes the ligand, the transition metal compound and the activator or directly adds them to the reaction system for in-situ synthesis to obtain the catalyst for selective oligomerization of ethylene containing a saturated aliphatic ring skeleton double phosphine ligand.

[0025] In the third aspect, the present application provides an application of a catalyst for selective oligomerization of ethylene containing a saturated aliphatic ring skeleton double phosphine ligand, which is used for selective oligomerization of ethylene to generate 1-hexene and 1-octene.

[0026] Further, the reaction is carried out in an inert solvent, the reaction temperature is 0-200℃, the pressure is 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, and preferably 1-500 μmol / L.

[0027] Further, the temperature of the reaction is 35-80℃, and the pressure is 4-6 Mpa.

[0028] Further, the inert solvent includes one or more of alkane, arene, alkene or 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, etc., preferably toluene, methylcyclohexane.

[0029] Compared with the prior art, the present application can reach an activity of 6920 kg / g Cr / h for the catalytic system, and the total selectivity of 1-hexene and 1-octene can reach up to 97.4% by changing the size of the saturated aliphatic ring skeleton diphosphine ligand ring and introducing alkyl instead of phenyl on the phosphorus atom. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 Simulation structure and main structural parameters of chromium intermediates with different ring skeletons. DETAILED DESCRIPTION

[0031] The present application will be described in detail below with specific examples. The present embodiment is implemented on the premise of the technical solution of the present application, and detailed implementation and specific operation process are given, but the protection scope of the present application is not limited to the following examples.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0033] The selection scope of the terms "and / or", "or / and", "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of related listed items, including any two related listed items, any more related listed items, or all related listed items. It should be noted that when at least three items are connected by at least two conjunctions selected from "and / or", "or / and", "and / or", it should be understood that in the present application, the technical solution undoubtedly includes the technical solution connected by "logical and", and also undoubtedly includes the technical solution connected by "logical or".

[0034] In the present application, the technical features described in an open manner include both the closed technical solution consisting of listed features and the open technical solution containing listed features.

[0035] In the present application, when referring to numerical intervals, unless otherwise specified, the numerical intervals are considered to be continuous, and include the minimum and maximum values of the range, as well as every value between the minimum and maximum values. Further, when ranges are provided for integers, every integer between the minimum and maximum values is included. In addition, when multiple ranges are provided to describe a characteristic or a property, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein are to be understood to include any and all sub-ranges subsumed therein.

[0036] Only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with any other lower limit to form a range not explicitly recited, as can any upper limit be combined with any other upper limit to form a range not explicitly recited. In addition, each individual disclosed point or single numerical value can itself be combined as a lower limit or an upper limit with any other point or single numerical value or with other lower limits or upper limits to form a range not explicitly recited.

[0037] In the present application, unless otherwise specified, the temperature parameters allow for both constant temperature processing and processing within a certain temperature interval. The constant temperature processing allows for fluctuations within the accuracy of the instrument control. Fluctuations within a range of, for example, ±5°C, ±4°C, ±3°C, ±2°C, ±1°C are allowed.

[0038] In the present application, “suitable”, as used in “suitable combination”, “suitable manner”, “any suitable manner” and the like, is subject to the ability to implement the technical solutions of the present application, solve the technical problems of the present application, and achieve the intended technical effects of the present application.

[0039] In the present application, “further”, “even further”, “in particular” and the like are used for the purpose of description, and do not mean that the content is different, but should not be understood as limiting the scope of protection of the present application.

[0040] In the present application, “optionally”, “optional”, “optional” means that it can or can not be present, i.e. it means that it is selected from either of the two parallel schemes “has” or “has not”. If there are multiple “optionally” in a technical solution, unless otherwise specified, and there is no contradictory or mutually restrictive relationship, each “optionally” is independent.

[0041] In the description of the application, “multiple” means at least two, for example, two, three, etc., unless otherwise specifically limited.

[0042] Unless otherwise indicated, all formulations and tests herein occur in an environment of 25°C.

[0043] "comprising", "having", "including", "containing", "characterized by" or any other varying

[0044] All the embodiments and optional embodiments of the present application can be combined to form new technical solutions if no specific description is provided. All the technical features and optional technical features of the present application can be combined to form new technical solutions if no specific description is provided.

[0045] All the steps of the present application can be performed in sequence or randomly if no specific description is provided, and the sequence performance is preferred.

[0046] To further improve the total selectivity of 1-hexene / 1-octene and the activity of the catalytic system, and reduce the amount of polymer generated, the present application creatively introduces a fatty macrocyclic skeleton into the diphosphine ligand. The size of the fatty ring skeleton plays an important role in catalytic performance. The introduction of the fatty ring can limit the rotation of the double carbon skeleton of the diphosphine ligand, and compared with similar ligands with non-cyclic skeletons, it shows a certain rigidity. More importantly, the increase in the number of fatty ring atoms will directly affect several important structural parameters of the diphosphine ligand, such as the angle of P-Cr-P, the dihedral angle of P-C-C-P, and the distance between the two phosphorus atoms (i.e. P---P), thereby having an important influence on the catalytic performance.

[0047] To study the effect of the size of the cyclic skeleton on the key structural parameters of the ligand, the present application also uses DFT to theoretically simulate and calculate the structure of the chromium seven-membered ring intermediate of the key active intermediate ethylene coordination in the catalytic cycle. By comparing the chromium intermediates of the five-membered ring, six-membered ring and eight-membered ring skeletons, the simulated structures and main structural parameters such as Figure 1 are calculated and shown.

[0048] It can be seen from the DFT calculation results that changing the size of the skeleton ring carbon number can effectively regulate the key structural parameters of the ligand skeleton. In the process of increasing from a five-membered ring, a six-membered ring to an eight-membered ring, the dihedral angle (P-C-C-P) is reduced from 53.57 degrees to 41.66 degrees, and the distance between the two phosphorus atoms (P---P) and the P-Cr-P bond angle are also significantly reduced. The decrease of these key structural parameters can make the substituents on the phosphorus atom closer to the metal center, better protect the metal active center, and thus improve the stability of the catalyst, improve the catalytic activity, effectively reduce the degradation of the catalyst, and ultimately reduce the solid polyolefin produced by the degradation of the catalyst. Therefore, n can be 1, 2, 3, 4, 5, preferably 3, 4, 5.

[0049] The application will be further described below in conjunction with specific examples.

[0050] Example 1:

[0051] Preparation of ligand L 1

[0052]

[0053] In a dry Schlenk tube, CuI (1 mmol), N,N'-dimethylethylenediamine (1 mmol), 25 mL of 1,4-dioxane were added, stirred for 1 min, 1-bromocyclohept-1-ene (10 mmol) was added, stirred for 1 min, then NaI (15 mmol), cesium carbonate (20 mmol) was added, stirred for 5 min, diphenyl phosphine oxide (10 mmol) was added, 110 o C was reacted for 20 h, the reaction was completed, the solvent was removed under vacuum, and the white solid product 1a was obtained by silica gel column separation and purification.

[0054]

[0055] In a dry Schlenk tube, 1a (5 mmol), diphenyl phosphine oxide (5 mmol), 20 mL of 1,4-dioxane were added, stirred uniformly, and tert-butoxy lithium (1 mmol) was added, 110 o C was stirred for 20 h, the reaction was completed, the solvent was removed under vacuum, and the white solid product 1b was obtained by silica gel column separation and purification. 1a and 1b were synthesized according to the known literature (Eur. J. Org. Chem. 2021, 3484-3491.).

[0056]

[0057] ​In a dry Schlenk tube, 1b (4 mmol), titanium tetraisopropoxide (2.2 mmol), (EtO)2MeSiH (24 mmol), 10 mL of toluene were added and heated at reflux for 2 h to give the white solid product L 1 (45%, 788.7 mg).

[0058] 1 H NMR (CDC13) δ 1.1-1.24 (m, 4H), 1.30 (t, 2H), 1.46-1.56 (m, 4H),1.50-1.52 (m, 2H), 7.14-7.16 (m, 8H) 7.39-7.43 (m, 12H).

[0059] Example 2

[0060] Ligand L 2 Preparation of

[0061]

[0062] Reference ligand L 1 Preparation method of using 1-bromo-1-octene (5.0 mmol, 1 eq) instead of 1-bromo-1- cycloheptene, to give the white solid product L 2 (1.3 g, 72.5%).

[0063] 1 H NMR (CDC13) δ 7.36–7.30 (m, 4H), 7.21–7.17 (m, 3H), 7.16–7.07 (m,13H), 2.63–2.50 (m, 2H), 2.22 (dd, J = 22.9, 13.2 Hz, 2H), 1.86–1.73 (m, 4H),1.64–1.55 (m, 2H), 1.48–1.31 (m, 4H).

[0064] Example 3

[0065] Ligand L 3 Preparation of

[0066]

[0067] Reference ligand L 1 Preparation method of using 1-bromo-1-octene (5.0 mmol, 1 eq) instead of 1-bromo-1- cycloheptene, to give the white solid product L3 (1.3 g,72.5%)). 1 H NMR (400 MHz, CDCl3) δ 1.53-1.69 (m, 8H), 1.39-1.64 (m, 6H), 1.95-2.04 (m, 2H), 7.14-7.24 (m, 12H), 7.45-7.58 (m, 8H).

[0068] Example 4

[0069] Preparation of ligand L 4 (1.3 g,72.5%)).

[0070]

[0071] Reference ligand L 1 The preparation method of ligand L was used, 1-bromocyclonon-1-ene (5.0 mmol, 1 eq) was used instead of 1-bromocyclopent-1-ene, and diphenyl phosphine oxide (5.0 mmol, 1 eq) was used instead of dicyclohexyl phosphine oxide to obtain white solid product L 4 (1.3 g,72.5%)). 1 H NMR (400 MHz, CDCl3) δ 0.96-0.97 (t, 6H), 1.29-1.31 (m, 8H), 1.55-1.65 (m, 4H), 1.69-1.72 (m, 5H), 7.15-7.20 (m, 8H), 7.45-7.55 (m, 7H).

[0072] Example 5

[0073] Preparation of ligand L 5 (1.3 g,72.5%)).

[0074]

[0075] Reference ligand L 1 The preparation method of ligand L was used, 1-bromocyclonon-1-ene (5.0 mmol, 1 eq) was used instead of 1-bromocyclopent-1-ene, and diphenyl phosphine oxide (5.0 mmol, 1 eq) was used instead of dicyclohexyl phosphine oxide to obtain white solid product L 5 (1.3 g,72.5%)). 1 H NMR (400 MHz, CDCl3) δ 1.53-1.69 (m, 8H), 1.39-1.64 (m, 6H), 1.95-2.04 (m, 2H), 7.14-7.24 (m, 12H), 7.45-7.58 (m, 8H).

[0076] Example 6

[0077] (1) Preparation of catalyst

[0078] Into an anhydrous and anaerobic Schlenk tube, ligand L 1 (1.86 mg, 4.0 μmol), CrCl3(THF)3(1.50 mg, 4.0 μmol) and freshly distilled toluene (4 ml) were added. After stirring at room temperature for 30 minutes, the mixture was degassed, cyclohexane (10 mL) was added, and 2 mL of the suspension was taken. To the 2 mL suspension, cyclohexane (100 mL) and MMAO-3A (0.8 mmol, 1.12 mol / L) were added, and stirring was continued for 5 minutes.

[0079] (2) Ethylene oligomerization reaction

[0080] A 250 mL stainless steel autoclave was heated at 120 °C in an oil bath, and was vacuumed for 3 hours to make it anhydrous and anaerobic, and then cooled to the reaction temperature. The autoclave was purged with ethylene three times. Then, the catalyst solution prepared above was transferred into the autoclave using a dry glass syringe, the autoclave was sealed, the stirring was started, and ethylene gas was introduced, and the pressure was adjusted to 4.0 MPa. 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, the pressure was released, and the autoclave was opened. A certain amount of internal standard n-nonane was added and stirred uniformly. Then, the reaction was quenched with 10 wt% HCl aqueous solution (30 mL), and a small amount of organic phase was filtered and subjected to GC analysis. The remaining mixture in the autoclave was filtered, and the solid was added to 10 wt% HCl aqueous solution and stirred for 2 hours. After filtration, the solid was dried to constant weight and weighed. The data are shown in Table 1.

[0081] Example 7

[0082] The difference from Example 6 is that the ligand L 1 was replaced by ligand L 2 (1.92 mg, 4.0 μmol). The data are shown in Table 1.

[0083] Example 8

[0084] The difference from Example 6 is that the ligand L 1 was replaced by ligand L 3 (1.98 mg, 4.0 μmol). The data are shown in Table 1.

[0085] Example 9

[0086] The difference from Example 6 is that the ligand L 1 was replaced by ligand L 4(1.84 mg, 4.0 μmol), data in Table 1.

[0087] Example 10

[0088] The difference with Example 6 is the ligand L used 1 was replaced by the ligand L 5 (2.00 mg, 4.0 μmol), data in Table 1.

[0089] Example 11

[0090] The difference with Example 9 is that the ethylene oligomerization reaction was carried out at 80 °C, data in Table 1.

[0091] Example 12

[0092] The difference with Example 9 is that the amount of MMAO-3A used was 0.96 mmol, data in Table 1.

[0093] Example 13

[0094] The difference with Example 9 is that the reaction pressure for the ethylene oligomerization was 5.0 MPa, data in Table 1.

[0095] Example 14

[0096] The difference with Example 9 is that the reaction pressure for the ethylene oligomerization was 6.0 MPa, data in Table 1.

[0097] Comparative Example 1

[0098]

[0099] The difference with Example 4 is the ligand L used 1 was replaced by the ligand L 6 (1.83 mg, 4.0 μmol), data in Table 1, ligand L 6 was synthesized according to the literature (Organometallics, 2010, 29, 5805).

[0100] Comparative Example 2

[0101]

[0102] The difference with Example 4 is the ligand L used 1 was replaced by the ligand L 7 (1.83 mg, 4.0 μmol), data in Table 1, ligand L 7 was synthesized according to the literature (J. Am. Chem. Soc. 2004, 126, 14712-14713.).

[0103] Table 1

[0104]

[0105] As can be seen from Table 1, the catalyst provided by the present application has high catalytic activity, which can reach 6920 kg / g Cr·h at the highest, and the total selectivity of 1-hexene and 1-octene can reach 97.4% at the highest. By comparing Examples 6-8 and Comparative Example 1, it can be seen that the catalytic activity is significantly improved after introducing the cycloalkyl skeleton. By comparing Examples 9 and 10, it can be seen that when the phenyl group on the phosphorus atom is replaced by an alkyl group, the catalytic activity is further improved, the polymer content is significantly reduced, and the total selectivity of 1-hexene and 1-octene is significantly improved. In addition, by comparing Examples 9, Examples 11 to 14, it can be seen that the catalytic activity of the catalyst also shows good regulation characteristics with respect to temperature, pressure, etc.

[0106] The above description of the examples is for the purpose of enabling a person of ordinary skill in the art to understand and use the present application. Those skilled in the art can easily make various modifications to these examples, and apply the general principles described herein to other examples without having to go through creative labor. Therefore, the present application is not limited to the above examples, and improvements and modifications made by those skilled in the art based on the disclosure of the present application without departing from the scope of the present application should be within the scope of protection of the present application.

Claims

1. An ethylene selective oligomerization catalyst comprising a saturated alicyclic backbone bisphosphine ligand, characterized in that, The catalyst comprises a ligand, a transition metal compound and an activator, the chemical structural formula of the ligand is: ， wherein the group R 1 to R 4 each independently is hydrogen, alkyl, alkoxy, alkenyl, or an aromatic group; n is a positive integer, and ranges from 3 to 5; 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 comprises an alkyl aluminum compound, an aluminoxane compound or an organic boron compound.

2. The catalyst for the selective oligomerization of ethylene comprising a bisphosphine ligand with a saturated aliphatic ring skeleton according to claim 1, characterized in that, Group R 1 To R 4 Each of these can be ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, cyclohexyl, cyclopentyl, phenyl, 2-fluorophenyl, 2-methoxyphenyl, or 4-tert-butylphenyl.

3. The catalyst for the selective oligomerization of ethylene comprising a saturated alicyclic backbone bisphosphine ligand according to claim 2, characterized in that, R is a group of formula 1 R is a group of formula 4 one of R is alkyl and the other three are aryl.

4. The catalyst for the selective oligomerization of ethylene comprising a saturated alicyclic backbone bisphosphine ligand according to claim 1, characterized in that, 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 the selective oligomerization of ethylene comprising a bisphosphine ligand with a saturated aliphatic ring skeleton according to claim 1, characterized in that, The activator is modified methyl aluminoxane MMAO-3A.

6. A process for the preparation of a catalyst for the selective oligomerization of ethylene comprising a saturated alicyclic backbone bisphosphine ligand as claimed in any one of claims 1 to 5, characterized in that, The ligand, the transition metal compound and the activator are pre-mixed or directly added to a reaction system for in-situ synthesis to obtain a catalyst for ethylene selective oligomerization containing a saturated aliphatic ring skeleton bisphosphine ligand.

7. Use of a catalyst comprising a saturated alicyclic backbone diphosphine ligand for the selective oligomerization of ethylene according to any one of claims 1 to 5, characterized in that, The catalyst is used for ethylene selective oligomerization to generate 1-hexene and 1-octene.

8. Use of a catalyst comprising a saturated alicyclic backbone diphosphine ligand for the selective oligomerization of ethylene according to claim 7, characterized in that, The reaction is carried out in an inert solvent, the reaction temperature is 0-200℃, the pressure is 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.

9. Use of a catalyst comprising a saturated alicyclic backbone diphosphine ligand for the selective oligomerization of ethylene according to claim 8, characterized in that, The temperature of the reaction is 35-80℃, and the pressure is 4-6 Mpa; The inert solvent comprises one or more of alkane, arene, olefin or ionic liquid.

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