Alkenyl diphosphine bridging type catalyst ligand, catalyst composition and application of alkenyl diphosphine bridging type catalyst ligand and catalyst composition

Abstract

The invention relates to the technical field of ethylene polymerization, and provides an alkenyl diphosphine bridging type catalyst ligand, a catalyst composition and application of the alkenyl diphosphine bridging type catalyst ligand and the catalyst composition. The structure of the alkenyl diphosphine bridging type catalyst ligand is shown as a formula (I) # imgabs0 #, and R1 and R2 are the same or different and are respectively and independently selected from aryl groups; r3 is selected from alkyl, cycloalkyl and aryl; r4 and R5 are the same or different and are independently selected from hydrogen and alkyl; hydrogen on carbon of alkyl, cycloalkyl and aryl is optionally substituted by one or more substituents. The alkenyl diphosphine bridging type catalyst ligand provided by the invention is novel in structure, simple to prepare and relatively low in cost; the catalyst composition can effectively catalyze ethylene oligomerization reaction, is high in catalytic activity, mild and stable in reaction, good in repeatability, high in 1-octene selectivity and good in 1-hexene selectivity in C6 products, and has good industrial application prospects and economic value.

Description

Technical Field

[0001] The present invention relates to the technical field of ethylene polymerization, and more specifically to an alkenyl diphosphine bridged catalyst ligand, a catalyst composition and application thereof. Background Art

[0002] 1-Hexene and 1-octene are important organic raw materials and chemical intermediates, mainly used to produce high-quality polyethylene (PE), lubricant base oil, plasticizers, detergents, etc. Among them, linear low-density polyethylene (LLDPE) produced by copolymerization of 1-hexene or 1-octene with ethylene can significantly improve the various properties of PE, especially the mechanical properties, optical properties, tear strength and impact strength of polyethylene. The product is very suitable for packaging film and agricultural covering film for greenhouses, sheds, etc. The polyolefin plastomers and polyolefin elastomers produced by copolymerization of 1-octene and ethylene have a large market consumption and demand.

[0003] With the continuous development of the polyolefin industry, the demand for high-carbon chain α-olefins such as 1-hexene or 1-octene has increased rapidly worldwide. Copolymer-grade high-purity 1-octene is in short supply in the market, and its price is significantly higher than other long-chain α-olefins; therefore, the development of a process technology with higher selectivity for 1-octene has obvious economic benefits and social value. In addition, in the existing technology, there are more by-products such as cycloolefins and cyclized products in the C6 product, which is unfavorable to the economy of the entire process.

[0004] Since the 1970s, the research on olefin polymerization and oligomerization catalyzed by transition metal complexes has gradually attracted the attention of scientists. People have begun to work hard to study new catalysts and improve existing catalysts to improve the activity of catalysts and the selectivity of catalytic products. For example, Sasol's patent WO2004056478A1 discloses a PNP skeleton catalyst. In the ethylene tetramerization reaction, the C8 component selectivity is about 66wt%, the C6 component selectivity is about 21wt%, and the total selectivity of 1-hexene and 1-octene is about 84%. US20100137669A1 patent discloses a PCCP symmetric skeleton catalyst. In the ethylene tetramerization reaction, the catalyst is more stable than the PNP system, but the total selectivity of 1-hexene and 1-octene does not exceed 85%. The total selectivity of 1-hexene and 1-octene of existing transition metal complex catalysts still has room for further improvement.

[0005] Therefore, it is of great significance to improve the overall selectivity of 1-hexene and 1-octene in the reaction products, thereby improving the economic efficiency of the process. Summary of the invention

[0006] The object of the present invention is to provide an alkenyl diphosphine bridged catalyst ligand and a catalyst composition to solve the technical problem of low overall selectivity of 1-hexene and 1-octene in ethylene oligomerization products in the prior art.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] In a first aspect, the present invention provides an alkenyl diphosphine bridged catalyst ligand, the structure of which is shown in formula (I):

[0009]

[0010] In formula (I), R1 and R2 are the same or different and are independently selected from cycloalkyl and aryl; R3 is selected from alkyl, cycloalkyl and aryl; R4 and R5 are the same or different and are independently selected from hydrogen and alkyl; the hydrogen on the carbon of the alkyl, cycloalkyl and aryl is optionally substituted by one or more substituents.

[0011] According to some embodiments of the present invention, the alkyl group is C1 to C 20 Alkyl, preferably C1~C 10 The alkyl group is more preferably a C1-C6 alkyl group.

[0012] According to some embodiments of the present invention, the cycloalkyl group is C3 to C 20 Cycloalkyl, preferably C3~C 10 The cycloalkyl group is more preferably a C3-C6 cycloalkyl group.

[0013] According to some embodiments of the present invention, the aryl group is C6 to C 20 Aryl, preferably C6~C 10 The aryl group is more preferably a C6-C8 aryl group.

[0014] According to some embodiments of the present invention, the substituent is selected from C1 to C 20 Alkyl, C3~C 20 Cycloalkyl, C1~C 20 Alkoxy, C6~C 20 Aryl.

[0015] According to some embodiments of the present invention, the substituent is selected from C1 to C 10 Alkyl, C3~C 10 Cycloalkyl, C1~C 10 Alkoxy, C6~C 12 Aryl.

[0016] According to some embodiments of the present invention, the substituent is selected from C1-C6 alkyl, C3-C6 cycloalkyl, C1-C6 alkoxy, C6-C 12 Aryl.

[0017] According to some embodiments of the invention, the substituent is selected from at least one of methyl, ethyl, propyl, butyl, isobutyl, pentyl, isopentyl, hexyl, cyclopropyl, cyclopentyl, cyclohexyl, methoxy, ethoxy, propoxy, butoxy, phenyl, tolyl, ethylphenyl, propylphenyl, biphenyl and naphthyl.

[0018] According to some embodiments of the present invention, R1 and R2 are selected from cyclopropyl, cyclopentyl, cyclohexyl and phenyl.

[0019] According to some embodiments of the invention, R3 is selected from methyl, ethyl, propyl, n-butyl, isobutyl, tert-butyl, isopropyl, cyclopropyl, cyclopentyl, cyclohexyl, phenyl, and substituted phenyl.

[0020] According to some embodiments of the invention, R3 is selected from tert-butyl, isopropyl, cyclohexyl, and phenyl.

[0021] According to some embodiments of the present invention, R4 and R5 are the same or different, and are independently selected from hydrogen, methyl, ethyl, propyl, and butyl.

[0022] According to some embodiments of the present invention, R4 and R5 are the same or different, and are independently selected from hydrogen, methyl, and ethyl.

[0023] In a second aspect, the present invention provides a method for preparing the alkenyl diphosphine bridged catalyst ligand according to the first aspect, comprising:

[0024]

[0025] S1: Compound a, compound b, and triethylamine undergo a first reaction in a first solvent to obtain compound c;

[0026] S2: Compound d and phosphorus trichloride undergo a second reaction in a second solvent to obtain compound e;

[0027] S3: Compound c, compound e and triethylamine undergo a third reaction in a third solvent to obtain an alkenyl diphosphine bridged catalyst ligand as shown in formula (I);

[0028] Among them, R1 and R2 are the same or different and are independently selected from aryl; R3 is selected from alkyl, cycloalkyl and aryl; R4 and R5 are the same or different and are independently selected from hydrogen and alkyl; the hydrogen on the carbon of the alkyl, cycloalkyl and aryl is optionally substituted by one or more substituents.

[0029] According to some embodiments of the present invention, in step S1, the molar ratio of compound b, compound a and triethylamine is 1:0.01-10:0.5-10, preferably 1:1-3:1-3.

[0030] According to some embodiments of the invention, the first solvent comprises dichloromethane.

[0031] According to some embodiments of the present invention, in step S2, the molar ratio of compound d to phosphorus trichloride is 1:0.1-5, preferably 1:0.3-1.

[0032] According to some embodiments of the invention, the second solvent comprises diethyl ether.

[0033] According to some embodiments of the present invention, in step S3, the molar ratio of compound c, compound e and triethylamine is 1:0.1-10:0.1-10, preferably 1:1-3:1-3.

[0034] According to some embodiments of the invention, the third solvent comprises dichloromethane.

[0035] In a third aspect, the present invention provides a catalyst composition comprising the alkenyl diphosphine bridged catalyst ligand described in the first aspect, a transition metal compound and an aluminum-containing co-catalyst.

[0036] According to some embodiments of the present invention, the transition metal compound is selected from at least one of compounds of chromium, molybdenum, iron, titanium, zirconium and nickel.

[0037] According to some embodiments of the present invention, the transition metal compound is selected from at least one of chromium acetylacetonate, chromium isooctanoate, tri(tetrahydrofuran)chromium trichloride and di(tetrahydrofuran)chromium dichloride.

[0038] According to some embodiments of the present invention, the aluminum-containing co-catalyst is an organic aluminum compound.

[0039] According to some embodiments of the present invention, the aluminum-containing co-catalyst is selected from at least one of an alkyl aluminum compound, an alkoxy aluminum compound, and an alkyl aluminum chloride compound.

[0040] According to some embodiments of the present invention, the aluminum-containing co-catalyst is selected from at least one of methylaluminoxane, trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, diethylaluminum monochloride, ethylaluminum dichloride, ethylaluminumoxane and modified methylaluminumoxane.

[0041] According to some embodiments of the present invention, the aluminum-containing co-catalyst is selected from at least one of methylaluminoxane, triethylaluminum, and modified methylaluminoxane.

[0042] In the present invention, the modified methylaluminoxane may be an alkyl-modified methylaluminoxane, such as the conventional alkyl-modified methylaluminoxane MMAO in the art.

[0043] According to some embodiments of the present invention, the molar ratio of the transition metal compound, the alkenyl diphosphine bridged catalyst ligand shown in formula (I) and the aluminum-containing co-catalyst, calculated as the transition metal, is 1: (0.1-10): (1-1000), preferably 1: (0.25-2): (10-700), and more preferably 1: (0.5-2): (100-500).

[0044] In a fourth aspect, the present invention provides use of the catalyst composition described in the third aspect in an ethylene oligomerization reaction.

[0045] In a fifth aspect, the present invention provides a method for ethylene polymerization, comprising: in the presence of the catalyst composition described in the third aspect, continuously adding ethylene, hydrogen and an organic solvent into a reactor to carry out an ethylene polymerization reaction.

[0046] According to some embodiments of the present invention, in the ethylene polymerization reaction, the concentration of the catalyst composition is 0.1-10 μmol / L in terms of transition metal, based on the volume of the organic solvent. For example, when the transition metal is Cr, the concentration of the catalyst composition is 0.1-10 μmol / L in terms of Cr.

[0047] In the present invention, the reactor used for the ethylene polymerization reaction can be a hybrid reactor commonly used in the art, such as a tank reactor, a tubular reactor, a loop reactor, etc. containing an agitator or a mixing system.

[0048] According to some embodiments of the present invention, the organic solvent comprises an aliphatic hydrocarbon compound and / or an aromatic hydrocarbon compound.

[0049] According to some embodiments of the present invention, the aliphatic hydrocarbon compound is selected from at least one of straight-chain alkanes, branched-chain alkanes and cycloalkanes; preferably at least one of pentane, heptane, hexane, cyclohexane and methylcyclohexane.

[0050] According to some embodiments of the present invention, the aromatic hydrocarbon compound is selected from at least one of benzene, toluene, xylene, monochlorobenzene, dichlorobenzene, trichlorobenzene, monochlorotoluene and derivatives thereof.

[0051] According to some embodiments of the present invention, in the above-mentioned reaction, one or more of the catalyst compositions can be pre-mixed and then added to the reaction system together, or each component can be added to the reaction system separately; or the catalyst ligand and the transition metal compound can be pre-prepared into a complex, and then added to the reaction system together with the aluminum-containing co-catalyst.

[0052] According to some embodiments of the present invention, in the ethylene polymerization reaction, the volume ratio of hydrogen to ethylene is 1:(1-10000), preferably 1:(10-2000).

[0053] According to some embodiments of the present invention, the reaction temperature of the ethylene oligomerization reaction is 0 to 200°C, preferably 0 to 100°C, more preferably 30 to 100°C, and further preferably 40 to 75°C.

[0054] According to some embodiments of the present invention, the ethylene pressure of the ethylene oligomerization reaction is 0.1 to 20.0 MPa, preferably 0.5 to 10.0 MPa, and more preferably 2.0 to 6.0 MPa.

[0055] According to some embodiments of the present invention, according to some embodiments of the present invention, the ethylene oligomerization reaction includes ethylene trimerization reaction and ethylene tetramerization reaction.

[0056] The beneficial effects of the present invention are at least:

[0057] (1) The alkenyl diphosphine bridged catalyst provided by the present invention has a novel ligand structure, a simple preparation method and low cost.

[0058] (2) The catalyst composition provided by the present invention includes an alkenyl diphosphine bridged catalyst ligand, which can effectively catalyze the polymerization reaction of ethylene. The reaction is mild and stable, with good repeatability, high selectivity for 1-octene, and good selectivity for 1-hexene in the C6 product. The by-products such as cycloolefins and cyclized products are significantly reduced, and the catalyst composition has good industrial application prospects and economic value. DETAILED DESCRIPTION

[0059] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this patent in detail and do not limit the scope of protection of the present invention in any way.

[0060] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the raw materials, instruments and equipment used in the following examples, etc., can all be purchased on the market or can be obtained by existing methods; the reagent amounts, unless otherwise specified, are the reagent amounts used in conventional experimental operations; the experimental methods, unless otherwise specified, are all conventional methods.

[0061] In each embodiment and comparative example of the present invention, each performance data is tested according to the following test method:

[0062] (1) Nuclear magnetic resonance: The detection was performed using a Bruker AV400 nuclear magnetic resonance instrument; the detection conditions were: deuterated chloroform as the solvent.

[0063] (2) Room temperature test gas chromatography: Agilent 7890 chromatograph was used for detection; the detection conditions were: chromatographic column SE-54, high-purity nitrogen carrier gas, FID detector; the column temperature was raised using a two-step program.

[0064] It should be noted that, in the present invention, Bu is n-butyl, t Bu is tert-butyl, i Pr is isopropyl, Ph is phenyl, Me is methyl, Cy is cyclohexyl, and Cp is cyclopentyl.

[0065] Preparation Example 1

[0066] Preparation of catalyst ligand I 1 (R1=R2=Ph,R3= i Pr, R4=Me, R5=H)

[0067] (1) Phosphorus trichloride (5 mmol) was dissolved in diethyl ether (30 mL) and cooled to -78°C. Isopropenyl magnesium bromide (10 mL, 1 mol / L diethyl ether solution) was slowly added thereto. After the addition was complete, the temperature was slowly raised to room temperature and stirred for 5 hours to obtain a dienylphosphonium chloride stock solution.

[0068] (2) Diphenylphosphine chloride (15 mmol) was added dropwise to a solution of isopropylamine (18.8 mmol) and triethylamine (4.2 mL) in dichloromethane (10 mL) at 0°C, and the mixture was stirred for 30 min. The mixture was then heated to room temperature and stirred overnight. The solvent was drained from the mixture, and anhydrous ether (20 mL) was added to form a suspension. The filtrate was filtered and dried under reduced pressure to obtain the phosphine amine compound.

[0069] (3) The phosphine amine compound (5 mmol) was dissolved in dichloromethane (10 mL), triethylamine (1.7 mL) was added, and then the mixture was added dropwise to the dienylphosphonium chloride reserve solution of step (1) at 0° C. After the addition was completed, the mixture was heated to room temperature and stirred overnight. The solvent of the mixture was drained, and a white solid powder, i.e., catalyst ligand I, was obtained by basic alumina column chromatography. 1 .

[0070] Preparation Example 2

[0071] Preparation of catalyst ligand I 2 (R1=R2=Ph,R3= t Bu, R4=R5=H)

[0072] The preparation method is the same as that of Preparation Example 1, except that isopropenylmagnesium bromide is replaced by vinylmagnesium bromide, and isopropylamine is replaced by tert-butylamine.

[0073] Preparation Example 3

[0074] Preparation of catalyst ligand I 3(R1=R2=Cy, R3=Cp, R4=R5=Me)

[0075] The preparation method is the same as that of Preparation Example 1, except that diphenylphosphine chloride is replaced by dicyclohexylphosphine chloride, isopropylamine is replaced by cyclopentylamine, and isopropenylmagnesium bromide is replaced by butenylmagnesium bromide.

[0076] Preparation Example 4

[0077] Preparation of catalyst ligand I 4 (R1=R2=Cp, R3=Ph, R4=Me, R5=H)

[0078] The preparation method is the same as that of Preparation Example 1, except that diphenylphosphine chloride is replaced by dicyclopentylphosphine chloride, and isopropylamine is replaced by aniline.

[0079] Preparation Example 5

[0080] Preparation of catalyst ligand I 5 (R1=R2=4-MePh, R3=2-biphenyl, R4=Me, R5=H)

[0081] The preparation method is the same as that of Preparation Example 1, except that diphenylphosphine chloride is replaced by di-(4-methylphenyl)phosphine chloride, and isopropylamine is replaced by 2-aminobiphenyl.

[0082] Preparation Example 6

[0083] Preparation of catalyst ligand I 6 (R1=R2=Ph,R3= i Pr, R4 = R5 = Bu)

[0084] The preparation method is the same as that of Preparation Example 1, except that isopropenylmagnesium bromide is replaced by di-(butyl)vinylmagnesium bromide.

[0085] Example 1

[0086] A 300 mL stainless steel polymerization autoclave was used. The autoclave was heated to 80°C, evacuated and replaced with nitrogen several times, then filled with ethylene for replacement, and then cooled to the set temperature. Methylcyclohexane was then added at 60°C, and 0.5 μmol of chromium acetylacetonate and 0.5 μmol of catalyst ligand I were also added. 1 and co-catalyst modified methylaluminoxane (MMAO), the total volume of the mixed solution is 100 mL, wherein chromium acetylacetonate, catalyst ligand I 1 The molar ratio of ethylene to MMAO is 1:1:1000, the reaction pressure is controlled at 4MPa, a mixed gas of ethylene and hydrogen (the volume ratio of hydrogen to ethylene is 1:1000) is introduced, and ethylene polymerization is carried out at 60°C.

[0087] After half an hour, the reaction was completed, the system was cooled to room temperature, the gas phase product was collected in a gas metering tank, the liquid phase product was collected in a conical flask, and 1 mL of ethanol was added as a terminator to terminate the reaction. The gas and liquid phase products were measured and analyzed by gas chromatography. The test results are shown in Table 1.

[0088] Example 2

[0089] The preparation method is similar to that of Example 1, except that the catalyst ligand I 1 Replaced with catalyst ligand I 2 The test results are shown in Table 1.

[0090] Example 3

[0091] The preparation method is similar to that of Example 1, except that the catalyst ligand I 1 Replaced with catalyst ligand I 3 The test results are shown in Table 1.

[0092] Example 4

[0093] The preparation method is similar to that of Example 1, except that the catalyst ligand I 1 Replaced with catalyst ligand I 4 The test results are shown in Table 1.

[0094] Example 5

[0095] The preparation method is similar to that of Example 1, except that the catalyst ligand I 1 Replaced with catalyst ligand I 5 The test results are shown in Table 1.

[0096] Example 6

[0097] The preparation method is similar to that of Example 1, except that the catalyst ligand I 1 Replaced with catalyst ligand I 6 The test results are shown in Table 1.

[0098] Table 1

[0099]

[0100] From the data in Table 1, it can be seen that the catalytic activity of the catalyst composition provided by the present invention is 1.1×10 8 g·mol(Cr) -1 ·h -1The above, and the 1-octene selectivity can reach up to 77wt% or more, the content of 1-hexene in C6 also exceeds 90wt%, and the total selectivity of 1-hexene and 1-octene exceeds 90wt%. While maintaining a high 1-octene selectivity, the content of 1-hexene in C6 is greatly increased. Compared with the existing PNP ligand or PCCP ligand, the catalyst composition including the alkenyl diphosphine bridged catalyst ligand provided by the present invention has better catalytic performance. The change in the catalyst ligand structure affects the coordination ability and electronic effect of the ligand, and the complex formed with the metal is more suitable for ethylene polymerization reaction, which has a very obvious effect on the catalytic performance and effect.

[0101] It can be seen from the above test results that the catalyst composition provided by the present invention is used for ethylene oligomerization reaction, and the selectivity of 1-octene and 1-hexene in the product is very high. Since the polyolefin field, especially POE, C8-LLDPE, PAO new materials, etc., is in urgent need of copolymerization grade high-purity 1-octene or 1-hexene; therefore, the process technology with higher total selectivity of 1-octene and 1-hexene has obvious economic benefits and social value.

[0102] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. An alkenyl diphosphine bridged catalyst ligand, the structure of which is shown in formula (I), in, R1 and R2 are the same or different, and are independently selected from cycloalkyl and aryl; R3 is selected from alkyl, cycloalkyl and aryl; R4 and R5 are the same or different, and are independently selected from hydrogen and alkyl; the hydrogen on the carbon of the alkyl, cycloalkyl and aryl is optionally substituted by one or more substituents.

2. The alkenyl diphosphine bridged catalyst ligand according to claim 1, characterized in that: The alkyl group is C1~C 20 Alkyl, preferably C1~C 10 Alkyl, more preferably C1-C6 alkyl; And / or, the cycloalkyl group is C3 to C 20 Cycloalkyl, preferably C3~C 10 Cycloalkyl, more preferably C3-C6 cycloalkyl; And / or, the aryl group is C6~C 20 Aryl, preferably C6~C 12 Aryl, more preferably C6-C8 aryl; And / or, the substituent is selected from C1 to C 20 Alkyl, C3~C 20 Cycloalkyl, C1~C 20 Alkoxy, C6~C 20 Aryl; preferably selected from C1 to C 10 Alkyl, C3~C 10 Cycloalkyl, C1~C 10 Alkoxy, C6~C 12 Aryl; more preferably selected from C1~C6 alkyl, C3~C6 cycloalkyl, C1~C6 alkoxy, C6~C 12 Aryl; further selected from at least one of methyl, ethyl, propyl, butyl, isobutyl, pentyl, isopentyl, hexyl, cyclopropyl, cyclopentyl, cyclohexyl, methoxy, ethoxy, propoxy, butoxy, phenyl, tolyl, ethylphenyl, propylphenyl, biphenyl, and naphthyl.

3. The alkenyl diphosphine bridged catalyst ligand according to claim 1 or 2, characterized in that: R1, R2 are selected from cyclopropyl, cyclopentyl, cyclohexyl, phenyl; and / or, R3 is selected from methyl, ethyl, propyl, n-butyl, isobutyl, tert-butyl, isopropyl, cyclopropyl, cyclopentyl, cyclohexyl, phenyl, substituted phenyl, preferably selected from tert-butyl, isopropyl, cyclohexyl, phenyl; And / or, R4 and R5 are the same or different, and are independently selected from hydrogen, methyl, ethyl, propyl, and butyl, preferably selected from hydrogen, methyl, and ethyl.

4. The method for preparing the alkenyl diphosphine bridged catalyst ligand according to any one of claims 1 to 3, characterized in that: include: S1: Compound a, compound b, and triethylamine undergo a first reaction in a first solvent to obtain compound c; S2: Compound d and phosphorus trichloride undergo a second reaction in a second solvent to obtain compound e; S3: Compound c, compound e and triethylamine undergo a third reaction in a third solvent to obtain an alkenyl diphosphine bridged catalyst ligand as shown in formula (I); Among them, R1 and R2 are the same or different and are independently selected from aryl; R3 is selected from alkyl, cycloalkyl and aryl; R4 and R5 are the same or different and are independently selected from hydrogen and alkyl; the hydrogen on the carbon of the alkyl, cycloalkyl and aryl is optionally substituted by one or more substituents.

5. The method for preparing an alkenyl diphosphine bridged catalyst ligand according to claim 4, characterized in that: In the step S1, the molar ratio of compound b, compound a and triethylamine is 1:0.01-10:0.5-10, preferably 1:1-3:1-3; and / or, the first solvent comprises dichloromethane; And / or, in step S2, the molar ratio of compound d to phosphorus trichloride is 1:0.1-5, preferably 1:0.3-1; and / or, the second solvent comprises diethyl ether; And / or, in step S3, the molar ratio of compound c, compound e, and triethylamine is 1:0.1-10:0.1-10, preferably 1:1-3:1-3; And / or, the third solvent comprises dichloromethane.

6. A catalyst composition, characterized in that The invention comprises the alkenyl diphosphine bridged catalyst ligand as described in any one of claims 1 to 3, a transition metal compound and an aluminum-containing co-catalyst.

7. The catalyst composition according to claim 6, characterized in that The transition metal compound is selected from at least one of compounds of chromium, molybdenum, iron, titanium, zirconium and nickel, and is preferably selected from at least one of chromium acetylacetonate, chromium isooctanoate, tri(tetrahydrofuran)chromium trichloride and di(tetrahydrofuran)chromium dichloride.

8. The catalyst composition according to claim 6 or 7, characterized in that The aluminum-containing co-catalyst is an organic aluminum compound, preferably at least one selected from an alkyl aluminum compound, an alkoxy aluminum compound and an alkyl aluminum chloride compound, more preferably at least one selected from methylaluminoxane, trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, diethylaluminum monochloride, ethylaluminum dichloride, ethylaluminumoxane and modified methylaluminumoxane, further preferably at least one selected from methylaluminumoxane, triethylaluminum and modified methylaluminumoxane.

9. The catalyst composition according to any one of claims 6 to 8, characterized in that The molar ratio of the transition metal compound, the alkenyl diphosphine bridged catalyst ligand represented by formula (I) and the aluminum-containing co-catalyst, calculated as transition metal, is 1:(0.1-10):(1-1000), preferably 1:(0.25-2):(10-700), and more preferably 1:(0.5-2):(100-500).

10. Use of the catalyst composition according to any one of claims 6 to 9 in ethylene oligomerization reaction.

11. A method for the polymerization of ethylene, comprising: In the presence of the catalyst composition according to any one of claims 6 to 9, ethylene, hydrogen and an organic solvent are continuously added to a reactor to carry out an ethylene oligomerization reaction; Preferably, the volume ratio of hydrogen to ethylene is 1:(1-10000), preferably 1:(10-2000).

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