A catalyst composition for ethylene oligomerization reaction

Abstract

The present invention provides a catalyst composition for ethylene oligomerization reaction, comprising a main catalyst and a co-catalyst, wherein the main catalyst is selected from at least one compound represented by formula (I), and the co-catalyst is selected from at least one active alkyl aluminum, wherein the active alkyl aluminum is a hydrolysis product of the alkyl aluminum compound represented by formula (II). The ethylene oligomerization reaction in which the catalyst composition participates is rapidly initiated, operates smoothly, has good reproducibility, has high catalyst activity, and is carried out at a relatively high temperature, avoiding the use of condensed water and reducing energy consumption. n X m Formula (II).

Description

Technical Field

[0001] The present invention relates to the technical field of ethylene oligomerization reaction, in particular to a catalyst composition for ethylene oligomerization reaction. Background Art

[0002] Linear α-olefins are straight-chain olefins with double bonds at the terminal ends of the molecules. They are widely used in polyethylene comonomers, surfactant synthesis intermediates, plasticizer alcohols, synthetic lubricants, and oil additives. In recent years, with the continuous development of the polyolefin industry, the global demand for α-olefins has grown rapidly.

[0003] The main industrial methods for producing linear α-olefins include wax cracking, ethylene oligomerization, extraction and separation, fatty alcohol dehydrogenation, internal olefin isomerization, and the Alfene process. Of these, wax cracking and fatty alcohol dehydrogenation have largely been phased out. Internal olefin isomerization, the Alfene process, and Exxon's ethylene oligomerization process have also remained largely unused due to technical and economic reasons. Extraction and separation are also rarely used. Statistics from 1997 indicate that α-olefins produced by ethylene oligomerization accounted for 94.1% of total α-olefin production. This demonstrates that ethylene oligomerization is a very important method for producing α-olefins. Currently, typical production processes for linear α-olefins include the SHOP process (US patent 3686351, 1972 and US patent 3676523, 1972), the Chevron process, and the Amoco process (Applied Homogeneous Catalysis with Organometallic Compounds. Vol. 1, VCH Publishers, New York, 1996: 245-256).

[0004] In recent years, the development of catalysts for ethylene oligomerization to produce α-olefins has primarily focused on nickel, zirconium, and chromium catalysts. Brookhart et al. reported that cationic Ni(II)-α,α'-diamine complexes are effective ethylene oligomerization catalysts (Organometallics, 1997, 16:2005-2007). Significant breakthroughs have also been made in chromium-based catalysts specifically for ethylene trimerization to 1-hexene, with numerous patents and publications (US Pat. No. 5,523,507). Furthermore, UOP and Union Carbide jointly developed the Linear-1™ process in 1992 and completed pilot testing in 1997. This process utilizes a homogeneous catalytic system with a specialized ligand, including nickel chloride, NaBHa, and the ligand 2-diphenylphosphono-1-naphthalenesulfonic acid, achieving nearly 100% yield of linear α-olefins.

[0005] In 1998, the Brookhart and Gibson groups discovered, almost simultaneously, that tridentate pyridine bis-imine complexes of Fe(II) and Co(II) could catalyze ethylene oligomerization. These catalysts exhibited high activity for ethylene oligomerization and high selectivity for linear α-olefins. In these tridentate bis-imine complexes, one of the ortho-substituents of the aniline group must be hydrogen, while the remaining substituents can be electron-donating groups such as methyl, ethyl, and isopropyl.

[0006] Chen Yaofeng et al. (CN1343664A, CN1142142C) found that in the tridentate complex of the above structure, if one of the ortho-substituents of aniline is hydrogen and the other substituents are electron-withdrawing groups such as halogen, it can also catalyze ethylene polymerization. Moreover, the complex with electron-withdrawing groups on aniline also has high activity and selectivity for linear α-olefins in catalyzing ethylene polymerization.

[0007] CN 107282115 A discloses a catalyst composition for an ethylene oligomerization process and its application. The composition comprises a chlorinated substituted-2-benzoyl-1,10-phenanthroline-2,6-diethylaniline iron(II) complex, an aluminum-containing co-catalyst, and tert-butyl hydroperoxide. The technical solution disclosed in this patent has high oligomerization activity, high selectivity for α-olefins, rapid initiation of the oligomerization reaction, smooth operation, and good reproducibility. Furthermore, the oligomerization reaction exhibits good activity even at very low Al / Fe ratios.

[0008] However, among the aforementioned technical solutions, the one proposed by Chen Yaofeng et al. involves a complex catalyst preparation process and has limited prospects for industrial application. The solution disclosed in CN 107282115 A requires a relatively low reaction temperature and uses chilled water as a cooling medium, resulting in high energy consumption. Consequently, none of the existing technologies can achieve a balance between catalytic activity and process costs. Summary of the Invention

[0009] In view of the above-mentioned problems existing in the prior art, one of the objects of the present invention is to provide a catalyst composition for ethylene polymerization reaction. By adopting a specific co-catalyst and a specific main catalyst, the ethylene polymerization reaction in which the catalyst composition participates is initiated rapidly, runs smoothly, has good repeatability, high catalyst activity, and the reaction is carried out at a higher temperature, avoiding the use of condensed water and reducing energy consumption.

[0010] A second object of the present invention is to provide an application of the catalyst composition corresponding to the first object.

[0011] A third object of the present invention is to provide an ethylene oligomerization product corresponding to the above-mentioned object.

[0012] To achieve one of the above purposes, the technical solution adopted by the present invention is as follows:

[0013] A catalyst composition for ethylene oligomerization reaction, comprising a main catalyst and a co-catalyst, wherein the main catalyst is selected from at least one compound represented by formula (I), and the co-catalyst is selected from at least one active alkyl aluminum, wherein the active alkyl aluminum is a hydrolysis product of the alkyl aluminum compound represented by formula (II).

[0014]

[0015] In formula (I), R1-R6 are the same or different and are independently selected from hydrogen, C1-C6 alkyl, halogen, C1-C6 alkoxy and nitro; R7 is present or absent and is selected from C1-C6 alkylene; R8 is present or absent and is selected from C1-C6 alkyl, halogen, C1-C6 alkoxy and nitro; n represents the number of substituents R8 and is an integer from 0 to 5; M is Fe(II), Co(II) or Ni(II);

[0016] AYR n X m Formula (II)

[0017] In formula (II), R is independently a linear or branched C1-C8 alkyl group; X is a halogen, preferably chlorine or bromine; n is an integer from 1 to 3, m is an integer from 0 to 2, and m+n is equal to 3.

[0018] In some preferred embodiments of the present invention, in formula (I), R1-R6 are the same or different, and are independently selected from hydrogen, methyl, ethyl, n-propyl, isopropyl, fluorine, chlorine, bromine, methoxy, ethoxy and nitro, preferably, R1-R6 are hydrogen; R7 is present or absent, and is selected from C1-C4 alkylene, preferably absent; R8 is present or absent, and is selected from methyl, ethyl, n-propyl, isopropyl, fluorine, chlorine, bromine, methoxy, ethoxy and nitro, preferably absent; n is 0, 1 or 2, preferably 0; M is Fe(II).

[0019] In some preferred embodiments of the present invention, the alkyl aluminum compound is selected from at least one of trimethyl aluminum, triethyl aluminum, tripropyl aluminum, triisobutyl aluminum, tri-n-hexylaluminum, tri-n-octylaluminum, diethylaluminum chloride and ethylaluminum dichloride; more preferably triethylaluminum.

[0020] In some preferred embodiments of the present invention, the catalyst composition further comprises an organic solvent. Preferably, the organic solvent is cyclohexane.

[0021] In some preferred embodiments of the present invention, the method for preparing the active alkyl aluminum comprises:

[0022] Step A: dissolving the alkyl aluminum compound in an organic solvent to obtain a solution containing the alkyl aluminum compound;

[0023] Step B: contacting the solution containing the alkyl aluminum compound with liquid water to generate the active alkyl aluminum;

[0024] Wherein, step A and step B are carried out under an inert atmosphere and / or ice bath conditions. Preferably, the inert atmosphere is a nitrogen atmosphere; the ice bath conditions include: a temperature of -10°C to 10°C, preferably -5°C to 5°C.

[0025] In some preferred embodiments of the present invention, in step A, the amount of the alkyl aluminum compound used is 100-2000 μmol, preferably 300-1000 μmol per milliliter of the organic solvent; more preferably, the organic solvent is cyclohexane.

[0026] In some preferred embodiments of the present invention, in step B, the liquid water is added dropwise to the solution containing the alkyl aluminum compound. Preferably, the amount of water added is 0.1 to 5 moles, preferably 0.8 to 1.2 moles, per mole of the alkyl aluminum compound.

[0027] In some preferred embodiments of the present invention, step B is carried out under stirring at a speed of 300 to 1000 r / min; preferably, after the liquid water is added dropwise, stirring is continued for 5 to 60 minutes, preferably 20 to 40 minutes.

[0028] In some preferred embodiments of the present invention, in the catalyst composition, based on the total volume of the catalyst composition, the content of the main catalyst is 1 μmol / L to 500 μmol / L, preferably 10 μmol / L to 300 μmol / L, and more preferably 10 μmol / L to 100 μmol / L.

[0029] In some preferred embodiments of the present invention, in the catalyst composition, the molar ratio of aluminum in the co-catalyst to M in the main catalyst is 30:1 to less than 900:1, preferably 100:1 to 700:1, and more preferably 148:1 to 196:1.

[0030] To achieve the second of the above objectives, the technical solutions adopted by the present invention are as follows:

[0031] A use of the catalyst composition according to any one of the above embodiments as a catalyst in an ethylene oligomerization reaction.

[0032] To achieve the third of the above objectives, the technical solutions adopted by the present invention are as follows:

[0033] An ethylene oligomerization product obtained by using the catalyst composition described in any one of the above embodiments or according to the application described in any one of the above embodiments, preferably, in the ethylene oligomerization product, C6 to C 18 The content of olefins is 50 wt% or more, and / or C6~C 18 Among the olefins, the content of linear α olefins is 90 wt% or more, and / or the content of C4 olefins is 50 wt% or less.

[0034] In some preferred embodiments of the present invention, in the ethylene oligomerization product, C6 to C 18 The content of olefins is 60 wt% or more, preferably 65 wt% or more, more preferably 70 wt% or more.

[0035] In some preferred embodiments of the present invention, in the ethylene oligomerization product, C6 to C 18 Among the olefins, the content of linear α-olefins is 90 wt% or more, preferably 95 wt% or more, and more preferably 98 wt% or more.

[0036] In some preferred embodiments of the present invention, in the ethylene oligomerization product, C6 to C 18 The content of linear α-olefins in the olefins is 100 wt% or less, preferably 99.5 wt% or less, and more preferably 99.0 wt% or less.

[0037] In some preferred embodiments of the present invention, the content of C4 olefins in the ethylene oligomerization product is less than 40 wt%, preferably less than 30 wt%.

[0038] The beneficial effects of the present invention are at least in the following aspects:

[0039] First, the catalyst composition provided by the present invention is used to polymerize ethylene, and the obtained ethylene polymerization products include C4, C6, C8, C 10 、C 12 、C 14 、C 16 、C 18 、C 20 、C 22 etc. olefins; the selectivity of α-olefins can reach more than 96%.

[0040] Secondly, the catalyst composition provided by the present invention has high catalytic activity. The results show that its oligomerization activity can reach 3.71×10 7 g·mol(Fe) -1 ·h -1 Furthermore, the remaining reaction mixture was neutralized with an ethanol solution acidified with 5% dilute hydrochloric acid, but no polymer was obtained.

[0041] Third, the polymerization reaction is carried out under the action of the catalyst composition provided by the present invention. The polymerization reaction is initiated quickly, runs smoothly, has good repeatability, and can be carried out at a higher temperature, for example, above 50°C. Therefore, condensed water can be used as a cooling medium, reducing energy consumption. DETAILED DESCRIPTION

[0042] The present invention is described in detail below through examples, but the protection scope of the present invention is not limited to the following description.

[0043] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All reagents or instruments used, if the manufacturer is not specified, are conventional products that can be obtained through commercial channels.

[0044] In the following embodiment, the structural formula of the iron (II) complex of 2-benzoyl-1,10-phenanthroline-2,6-dimethylaniline chloride is as follows:

[0045]

[0046] In the following embodiments, unless otherwise specified, condensed water is used as the heat removal medium.

[0047] Example 1

[0048] 1.1 Preparation of active alkyl aluminum solution

[0049] Under nitrogen protection and ice bath conditions (0°C), the following operation was performed: 715 μmol (calculated as aluminum element) of triethylaluminum was dissolved in 1 mL of cyclohexane, and then water was slowly added dropwise to the resulting solution under stirring conditions (300 rpm) (the amount of water added was such that the final molar ratio of water to triethylaluminum was 1:1). After the water addition was completed, stirring was continued for 30 minutes while maintaining the speed constant to obtain an ethylaluminoxane solution. Based on the amount of raw materials used, the concentration of ethylaluminoxane in the resulting ethylaluminoxane solution was calculated to be 715 μmol / mL.

[0050] 1.2 Ethylene oligomerization

[0051] (1) Replace the reactor through high-temperature drying, vacuum replacement and other operations to ensure that there is no water and oxygen in the reactor;

[0052] (2) replacing the reactor with ethylene to place the reactor in an ethylene environment;

[0053] (3) Anhydrous cyclohexane solvent was added to the reactor, followed by 1.37 mL of the prepared active alkyl aluminum solution and 2 mL of anhydrous cyclohexane solution of 2-benzoyl-1,10-phenanthroline-2,6-dimethylaniline iron (II) chloride complex (the concentration of 2-benzoyl-1,10-phenanthroline-2,6-dimethylaniline iron (II) chloride complex was 2.5 μmol / mL) to adjust the total amount of the catalyst composition to 100 mL, wherein the Al / Fe (molar ratio) was 196. After sufficient stirring, ethylene was introduced to initiate the oligomerization reaction.

[0054] (4) maintaining the ethylene pressure at 1 MPa and the reaction temperature at 50°C for 30 min;

[0055] (5) Stop the reaction, take out a small amount of the reaction product and analyze it by gas chromatography (GC). The specific analysis results are shown in Table 1.

[0056] Example 2

[0057] 1.1 Preparation of active alkyl aluminum solution

[0058] The process was basically carried out in the manner of step 1.1 of Example 1, except that "the amount of water added was such that the final molar ratio of water to triethylaluminum was 0.9:1".

[0059] 1.2 Ethylene oligomerization

[0060] The active alkyl aluminum solution prepared in this example was used to carry out an ethylene oligomerization reaction in the same manner as in Example 1. After the reaction was terminated, a small amount of the reaction product was taken out and analyzed by gas chromatography (GC). The specific analysis results are shown in Table 1.

[0061] Example 3

[0062] 1.1 Preparation of active alkyl aluminum solution

[0063] The process was basically carried out in the manner of step 1.1 of Example 1, except that "the amount of water added was such that the final molar ratio of water to triethylaluminum was 0.8:1".

[0064] 1.2 Ethylene oligomerization

[0065] The active alkyl aluminum solution prepared in this example was used to carry out an ethylene oligomerization reaction in the same manner as in Example 1. After the reaction was terminated, a small amount of the reaction product was taken out and analyzed by gas chromatography (GC). The specific analysis results are shown in Table 1.

[0066] Example 4

[0067] 1.1 Preparation of active alkyl aluminum solution

[0068] The process was basically carried out in the manner of step 1.1 of Example 1, except that "the amount of water added was such that the final molar ratio of water to triethylaluminum was 1.2:1".

[0069] 1.2 Ethylene oligomerization

[0070] The active alkyl aluminum solution prepared in this example was used to carry out an ethylene oligomerization reaction in the same manner as in Example 1. After the reaction was terminated, a small amount of the reaction product was taken out and analyzed by gas chromatography (GC). The specific analysis results are shown in Table 1.

[0071] Example 5

[0072] 1.1 Preparation of active alkyl aluminum solution

[0073] The process was basically carried out in the manner of step 1.1 of Example 1, except that "the amount of water added was such that the final molar ratio of water to triethylaluminum was 0.5:1".

[0074] 1.2 Ethylene oligomerization

[0075] The active alkyl aluminum solution prepared in this example was used to carry out an ethylene oligomerization reaction in the same manner as in Example 1. After the reaction was terminated, a small amount of the reaction product was taken out and analyzed by gas chromatography (GC). The specific analysis results are shown in Table 1.

[0076] Example 6

[0077] 1.1 Preparation of active alkyl aluminum solution

[0078] The process was basically carried out in the manner of step 1.1 of Example 1, except that the amount of water added was such that the final molar ratio of water to triethylaluminum was 3:1.

[0079] 1.2 Ethylene oligomerization

[0080] The active alkyl aluminum solution prepared in this example was used to carry out an ethylene oligomerization reaction in the same manner as in Example 1. After the reaction was terminated, a small amount of the reaction product was taken out and analyzed by gas chromatography (GC). The specific analysis results are shown in Table 1.

[0081] Example 7

[0082] 1.1 Preparation of active alkyl aluminum solution

[0083] The same method as in Example 1.

[0084] 1.2 Ethylene oligomerization

[0085] The reaction was carried out in accordance with the method of step 1.1 of Example 1, except that the reaction temperature was 60° C. After the reaction was terminated, a small amount of the reaction product was taken out and analyzed by gas chromatography (GC). The specific analysis results are shown in Table 1.

[0086] Example 8

[0087] 1.1 Preparation of active alkyl aluminum solution

[0088] The same method as in Example 1.

[0089] 1.2 Ethylene oligomerization

[0090] The reaction was carried out in accordance with the method of step 1.1 of Example 1, except that the reaction temperature was 70° C. After the reaction was terminated, a small amount of the reaction product was taken out and analyzed by gas chromatography (GC). The specific analysis results are shown in Table 1.

[0091] Example 9

[0092] 1.1 Preparation of active alkyl aluminum solution

[0093] The same method as in Example 1.

[0094] 1.2 Ethylene oligomerization

[0095] The reaction was carried out in accordance with the method of step 1.1 of Example 1, except that the reaction temperature was 80° C. After the reaction was terminated, a small amount of the reaction product was taken out and analyzed by gas chromatography (GC). The specific analysis results are shown in Table 1.

[0096] Example 10

[0097] 1.1 Preparation of active alkyl aluminum solution

[0098] Under nitrogen protection and ice bath conditions (0°C), the following operation was performed: 715 μmol of triethylaluminum was dissolved in 1 mL of toluene, and then water was slowly added dropwise to the resulting solution under stirring conditions (300 rpm) (the amount of water added was such that the final molar ratio of water to triethylaluminum was 1:1). After the water addition was completed, stirring was continued for 30 minutes while maintaining the speed constant to obtain an ethylaluminoxane solution. Based on the amount of raw materials used, the concentration of ethylaluminoxane in the resulting ethylaluminoxane solution was calculated to be 715 μmol / mL.

[0099] 1.2 Ethylene oligomerization

[0100] (1) Replace the reactor through high-temperature drying, vacuum replacement and other operations to ensure that there is no water and oxygen in the reactor;

[0101] (2) replacing the reactor with ethylene to place the reactor in an ethylene environment;

[0102] (3) Add toluene solvent to the reactor, add 1.37 mL of the prepared active alkyl aluminum solution, add 2 mL of a toluene solution of a 2-benzoyl-1,10-phenanthroline-2,6-dimethylaniline iron (II) chloride complex (the concentration of the 2-benzoyl-1,10-phenanthroline-2,6-dimethylaniline iron (II) chloride complex is 2.5 μmol / mL), and adjust the total amount of the catalyst composition to 100 mL, wherein the Al / Fe (molar ratio) is 196. After sufficient stirring, introduce ethylene to initiate the oligomerization reaction;

[0103] (4) maintaining the ethylene pressure at 1 MPa and the reaction temperature at 50°C for 30 min;

[0104] (5) Stop the reaction, take out a small amount of the reaction product and analyze it by gas chromatography (GC). The specific analysis results are shown in Table 1.

[0105] Example 11

[0106] 1.1 Preparation of active alkyl aluminum solution

[0107] The same method as in Example 1.

[0108] 1.2 Ethylene oligomerization

[0109] The reaction was carried out in the same manner as in step 1.1 of Example 1, except that xylene was used instead of cyclohexane in Example 1. After the reaction was stopped, a small amount of the reaction product was taken out and analyzed by gas chromatography (GC). The specific analysis results are shown in Table 1.

[0110] Example 12

[0111] 1.1 Preparation of active alkyl aluminum solution

[0112] The same method as in Example 1.

[0113] 1.2 Ethylene oligomerization

[0114] The reaction was carried out in the same manner as in step 1.1 of Example 1, except that methylcyclohexane was used instead of the cyclohexane in Example 1. After the reaction was stopped, a small amount of the reaction product was taken out and analyzed by gas chromatography (GC). The specific analysis results are shown in Table 1.

[0115] Example 13

[0116] 1.1 Preparation of active alkyl aluminum solution

[0117] Methylaluminoxane obtained from a commercial route was used.

[0118] 1.2 Ethylene oligomerization

[0119] Methylaluminoxane obtained from a commercial source was used to replace the active alkyl aluminum in Example 1, and ethylene was polymerized in the same manner as in Example 1. After the reaction was terminated, a small amount of the reaction product was taken out and analyzed by gas chromatography (GC). The specific analysis results are shown in Table 1.

[0120] Example 14

[0121] 1.1 Preparation of active alkyl aluminum solution

[0122] Methylaluminoxane obtained from a commercial route was used.

[0123] 1.2 Ethylene oligomerization

[0124] The active aluminum alkyl in Example 1 was replaced with commercially available methylaluminoxane, and the Al / Fe (molar ratio) was adjusted to 1000. The remaining steps were carried out in the same manner as in Example 1 to carry out ethylene oligomerization. After the reaction was terminated, a small amount of the reaction product was removed and analyzed by gas chromatography (GC). The specific analysis results are shown in Table 1.

[0125] Comparative Example 1

[0126] 1.1 Preparation of active alkyl aluminum solution

[0127] The same method as in Example 1.

[0128] 1.2 Ethylene oligomerization

[0129] The reaction was carried out essentially in the manner of step 1.1 of Example 1, except that the "2-benzoyl-1,10-phenanthroline-2,6-diethylaniline iron (II) complex" in Example 1 was replaced with "2-benzoyl-1,10-phenanthroline-2,6-dimethylaniline iron (II) complex". After the reaction was terminated, a small amount of the reaction product was removed and analyzed by gas chromatography (GC). The specific analysis results are shown in Table 1.

[0130] Table 1

[0131]

[0132] From the data in Table 1 above, we can see that

[0133] First, the catalyst composition provided by the present invention has a high oligomerization activity. When ethylene is subjected to an oligomerization reaction in the presence of the catalyst composition provided by the present invention, the oligomerization reaction can be initiated rapidly.

[0134] Secondly, the content of undesirable C4 impurities in the oligomerization product is low, and the product distribution coefficient is high. The reaction system initiated by the catalyst composition provided by the present invention runs smoothly and has good repeatability.

[0135] Third, the catalyst composition provided by the present invention can react at a higher reaction temperature, which is easier to achieve than the reaction temperature of 30°C to 40°C commonly used in the art. As a result, condensed water can be used as a reaction heat removal medium, which reduces energy consumption compared to the chilled water required when using a reaction temperature of 30°C to 40°C as a reaction heat removal medium, and significantly improves its industrial application value.

[0136] Fourthly, as the reaction temperature increases, the catalyst composition provided by the present invention still maintains a high activity.

[0137] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation of 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 function.

Claims

1. A catalyst composition for ethylene oligomerization, comprising a main catalyst and a co-catalyst, wherein the main catalyst is selected from at least one compound represented by formula (I), and the co-catalyst is selected from at least one active alkyl aluminum, wherein: The active alkyl aluminum is a hydrolysis product of an alkyl aluminum compound represented by formula (II). Formula (I) In formula (I), R1-R6 are the same or different and are independently selected from hydrogen, C1-C6 alkyl, halogen, C1-C6 alkoxy and nitro; R7 is present or absent and is selected from C1-C6 alkylene; R8 is present or absent and is selected from C1-C6 alkyl, halogen, C1-C6 alkoxy and nitro; n represents the number of substituents R8 and is an integer from 0 to 5; M is Fe(II), Co(II) or Ni(II); AlR n X m Formula (II) In formula (II), R is independently a linear or branched C1-C8 alkyl group; X is a halogen; n is an integer from 1 to 3, m is an integer from 0 to 2, and m+n is equal to 3; The preparation method of the active alkyl aluminum comprises: Step A: dissolving the alkyl aluminum compound in an organic solvent to obtain a solution containing the alkyl aluminum compound; Step B: contacting the solution containing the alkyl aluminum compound with liquid water to generate the active alkyl aluminum; The amount of water added is 0.8 to 1.2 moles per mole of the alkyl aluminum compound.

2. The catalyst composition according to claim 1, characterized in that In formula (II), X is chlorine or bromine.

3. The catalyst composition according to claim 1 or 2, characterized in that In formula (I), R1-R6 are the same or different and are independently selected from hydrogen, methyl, ethyl, n-propyl, isopropyl, fluorine, chlorine, bromine, methoxy, ethoxy and nitro; R7 is present or absent and is selected from C1-C4 alkylene; R8 is present or absent and is selected from methyl, ethyl, n-propyl, isopropyl, fluorine, chlorine, bromine, methoxy, ethoxy and nitro; n is 0, 1 or 2; M is Fe(II); and / or The alkyl aluminum compound is at least one selected from trimethyl aluminum, triethyl aluminum, tripropyl aluminum, triisobutyl aluminum, tri-n-hexylaluminum, tri-n-octylaluminum, diethylaluminum chloride and ethylaluminum dichloride.

4. The catalyst composition according to claim 3, characterized in that In formula (I), R1 to R6 are hydrogen.

5. The catalyst composition according to claim 3, characterized in that In formula (I), R7 does not exist.

6. The catalyst composition according to claim 3, characterized in that In formula (I), R8 does not exist.

7. The catalyst composition according to claim 3, characterized in that In formula (I), n is 0.

8. The catalyst composition according to claim 3, characterized in that The alkyl aluminum compound is triethyl aluminum.

9. The catalyst composition according to claim 1 or 2, characterized in that The catalyst composition also includes an organic solvent.

10. The catalyst composition according to claim 1 or 2, characterized in that Step A and Step B are carried out under an inert atmosphere and / or in an ice bath.

11. The catalyst composition according to claim 10, characterized in that The inert atmosphere is a nitrogen atmosphere; the ice bath conditions include: a temperature of -10°C to 10°C.

12. The catalyst composition according to claim 11, characterized in that The ice bath conditions include: a temperature of -5°C to 5°C.

13. The catalyst composition according to claim 1 or 2, characterized in that In step A, the amount of the alkyl aluminum compound used is 100-2000 μmol per milliliter of the organic solvent.

14. The catalyst composition according to claim 13, characterized in that In step A, the amount of the alkyl aluminum compound used is 300-1000 μmol per milliliter of the organic solvent.

15. The catalyst composition according to claim 1 or 2, characterized in that In step A, the organic solvent is cyclohexane.

16. The catalyst composition according to claim 1 or 2, characterized in that In step B, the liquid water is added dropwise to the solution containing the alkyl aluminum compound.

17. The catalyst composition according to claim 1 or 2, characterized in that Step B is carried out under stirring conditions, and the stirring speed is 300~1000r / min.

18. The catalyst composition according to claim 17, characterized in that After the liquid water was added dropwise, stirring was continued for 5 to 60 minutes.

19. The catalyst composition according to claim 17, characterized in that After the liquid water was added dropwise, stirring was continued for 20 min to 40 min.

20. The catalyst composition according to claim 1 or 2, characterized in that In the catalyst composition, the content of the main catalyst is 1 μmol / L to 500 μmol / L based on the total volume of the catalyst composition.

21. The catalyst composition according to claim 20, characterized in that In the catalyst composition, the content of the main catalyst is 10 μmol / L to 300 μmol / L based on the total volume of the catalyst composition.

22. The catalyst composition according to claim 21, characterized in that In the catalyst composition, the content of the main catalyst is 10 μmol / L to 100 μmol / L based on the total volume of the catalyst composition.

23. The catalyst composition according to claim 1 or 2, characterized in that In the catalyst composition, the molar ratio of aluminum in the co-catalyst to M in the main catalyst is 30:1 to less than 900:

1.

24. The catalyst composition according to claim 23, characterized in that In the catalyst composition, the molar ratio of aluminum in the co-catalyst to M in the main catalyst is 100:1 to 700:

1.

25. The catalyst composition according to claim 24, characterized in that In the catalyst composition, the molar ratio of aluminum in the co-catalyst to M in the main catalyst is 148:1 to 196:

1.

26. Use of the catalyst composition according to any one of claims 1 to 25 as a catalyst in ethylene oligomerization reaction.

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