Nickel complex and preparation method and application thereof, catalyst composition and application thereof, and preparation method of polyethylene

Abstract

The invention relates to the technical field of polyolefin catalysts, and discloses a nickel complex and a preparation method and application thereof, a catalyst composition and application thereof, and a preparation method of polyethylene. The nickel complex has a structure as shown in a formula (I), and the structure contains a large-steric-hindrance substituent benzhydryl, so that the thermal stability of the complex can be improved. Meanwhile, when the complex is used as a catalyst in an ethylene polymerization reaction, the catalytic activity of the complex can reach 24.2 * 10 < 6 > g.mol <-1 > (Ni). H <-1 >, the molecular weight and molecular weight distribution of a polymer can be effectively regulated and controlled by changing the conditions of the polymerization reaction, and the weight-average molecular weight Mw of polyethylene is controlled within the range of 8.56 * 10 < 4 > g.mol <-1 > to 6.85 * 10 < 5 > g.mol <-1 >. # imgabs0 #

Description

Technical Field

[0001] The invention relates to the technical field of polyolefin catalysts, and in particular to a nickel complex and a preparation method and application thereof, a catalyst composition and application thereof, and a method for preparing polyethylene. Background Art

[0002] With the development of olefin resin material research and application, it has gradually become a necessary material for people's daily life, industrial and agricultural production, which has brought about great changes in people's living conditions and living standards. Among them, polyethylene materials have the characteristics of good chemical tolerance, low price, simple preparation, low density, good mechanical properties, etc., and can even obtain elastomer materials as potential rubber substitutes.

[0003] In 1995, Brookhart et al. originally reported that α-diimine nickel / palladium complex (Formula 1) was used to catalyze ethylene polymerization and copolymerization. It had moderate catalytic activity and obtained polyethylene products with certain branches and higher molecular weight. At the same time, the catalyst achieved the copolymerization of ethylene and polar monomers to obtain functionalized polyolefins.

[0004] R 1 For Me, iPr, R 2 For Me, iPr.

[0005] CN114163482A discloses a new fluorinated sterically hindered α-diimine nickel (II) complex, which has excellent effects in ethylene polymerization, has high thermal stability, can reduce the branching degree of polyethylene, obtain high molecular weight polyethylene, and enhance the plasticity and elasticity of polyethylene. However, the catalytic activity of the complex is relatively low, with a maximum catalytic activity of 5.65×10 6 g·mol -1 (Ni)·h -1 The maximum molecular weight of the polymer is only 9.5×10 4 g·mol -1 , and in the catalyst system, the co-catalyst is single.

[0006] CN101812145A discloses an α-diimine nickel complex olefin polymerization catalyst. The preparation method of the catalyst is simple and the cost is low. The catalyst can catalyze ethylene polymerization at a temperature of 80°C or higher to obtain high molecular weight polyethylene. Polyethylene with a molecular weight of 10 can be prepared within the range of 0-80°C. 2 kg / mol or more of polyethylene, but the catalytic activity of this compound is low.

[0007] However, the catalytic activity of the above catalysts is low, and the solvents and co-catalysts used are relatively single, which does not have advantages in industrial production and still needs further improvement. Summary of the invention

[0008] The purpose of the present invention is to overcome the problem of low catalytic activity of the existing catalysts used for olefin polymerization.

[0009] In order to achieve the above object, the first aspect of the present invention provides a nickel complex having a structure shown in formula (I):

[0010]

[0011] Wherein, in formula (I), each R 1 , R 2 Each independently selected from H, halogen, nitro, C 1-6 The alkyl group;

[0012] X is selected from F, Cl, Br, I.

[0013] The second aspect of the present invention provides use of the nickel complex described in the first aspect in olefin polymerization.

[0014] The third aspect of the present invention provides a method for preparing a nickel complex represented by formula (I), the method comprising:

[0015] In the presence of protective gas and organic solvent, the compound represented by formula (A), the compound represented by formula (B) and the compound NiX 2 Carrying out a first reaction to obtain a nickel complex represented by formula (I);

[0016]

[0017] Among them, in the compound NiX 2 wherein X is selected from F, Cl, Br, I;

[0018] In formula (B) and formula (I), each R 1 , R 2 The definition of is the same as that in the first aspect.

[0019] The fourth aspect of the present invention provides a catalyst composition, which includes a main catalyst and a co-catalyst, wherein the co-catalyst is alkylaluminum chloride, and the main catalyst is the nickel complex catalyst described in the first aspect.

[0020] The fifth aspect of the present invention provides use of the catalyst composition described in the fourth aspect in an olefin polymerization reaction.

[0021] The sixth aspect of the present invention provides a method for preparing polyethylene, which comprises: in the presence of solvent I, under the action of the catalyst composition described in the fourth aspect, polymerizing ethylene.

[0022] The present invention provides a type of symmetrical α-diimine nickel complex containing diphenylmethyl, which has a large steric hindrance substituent diphenylmethyl and can improve the thermal stability of the complex. At the same time, the complex is used as a catalyst in olefin polymerization (especially ethylene polymerization), and its polymerization activity can reach 24.2×10 6 g·mol -1 (Ni)·h -1 By changing the polymerization reaction conditions, the molecular weight and molecular weight distribution of the polymer can be effectively regulated, and the weight average molecular weight of polyethylene M w Controlled at 8.56×10 4 g·mol -1 ~6.85×10 5 g·mol -1 Therefore, the nickel complex provided by the present invention has extremely high industrial application potential and market application prospects, and is expected to change the existing production mode of polyolefin elastomers. DETAILED DESCRIPTION

[0023] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0024] As mentioned above, the first aspect of the present invention provides a nickel complex having a structure shown in formula (I):

[0025]

[0026] Wherein, in formula (I), each R 1 , R 2 Each independently selected from H, halogen, nitro, C 1-6 The alkyl group;

[0027] X is selected from F, Cl, Br, I.

[0028] In the present invention, Ph in the structure of formula (I) represents a phenyl group.

[0029] Preferably, in formula (I), each R 1 , R 2 Each independently selected from H, F, Br, C 1-3 of alkyl.

[0030] Preferably, X is selected from Cl and Br.

[0031] According to a preferred embodiment, the nickel complex represented by formula (I) is selected from at least one of the following complexes:

[0032] Complex Ni1:R 1 = methyl, R 2 = methyl, X = Br;

[0033] Complex Ni2:R 1 =Ethyl, R 2 =ethyl, X = Br;

[0034] Complex Ni3:R 1 = isopropyl, R 2 =isopropyl, X = Br;

[0035] Complex Ni4:R 1 = ethyl, R 2 = methyl, X = Br;

[0036] Complex Ni5:R 1 = isopropyl, R 2 = methyl, X = Br;

[0037] Complex Ni6:R 1 =F, R 2 =F, X = Br.

[0038] As mentioned above, the second aspect of the present invention provides the use of the nickel complex described in the first aspect in olefin polymerization.

[0039] Preferably, the olefin is ethylene.

[0040] As mentioned above, the third aspect of the present invention provides a method for preparing a nickel complex represented by formula (I), the method comprising:

[0041] In the presence of protective gas and organic solvent, the compound represented by formula (A), the compound represented by formula (B) and the compound NiX 2 Carrying out a first reaction to obtain a nickel complex represented by formula (I);

[0042]

[0043] Among them, in the compound NiX 2 wherein X is selected from F, Cl, Br, I;

[0044] In formula (B) and formula (I), each R 1 , R 2 The definition of is the same as that in the first aspect.

[0045] In the present invention, the compound represented by formula (B) is synthesized with reference to Dalton Trans., 2015, 44, 12282. The compound represented by formula (A) can be synthesized by known techniques in the art or directly purchased, and the present invention is not limited thereto.

[0046] In the present invention, the compound NiX 2 By NiX 2 , NiX 2 At least one of the hydrates or solvates thereof is provided; for example, ethylene glycol dimethyl ether nickel bromide [(DME)NiBr 2 ], Nickel chloride hexahydrate (NiCl 2 6H 2 O).

[0047] Preferably, the protective gas is selected from at least one of nitrogen and argon.

[0048] Preferably, the organic solvent is selected from at least one of acetic acid and formic acid.

[0049] Preferably, the compound represented by formula (A), the compound represented by formula (B) and the compound NiX 2 The molar ratio of the amount is 1:2-6:0.5-1. More preferably, the compound represented by formula (A), the compound represented by formula (B) and the compound NiX 2 The molar ratio of dosage is 1:2-4:0.8-1.

[0050] Preferably, the amount of the organic solvent used is 1-5 mL relative to 1 mmol of the compound represented by formula (B).

[0051] Preferably, the conditions of the first reaction include: a reaction temperature of 100-160° C., and a reaction time of 1-12 hours. More preferably, the conditions of the first reaction include: a reaction temperature of 110-130° C., and a reaction time of 3-8 hours. The inventors of the present invention have found that under the preferred conditions, not only can the production cost be reduced, but also a high yield of the compound of formula (I) can be obtained.

[0052] In the process of preparing the nickel complex represented by formula (I) of the present invention, it is preferably carried out under stirring conditions. The present invention has no particular limitation on the stirring speed, and those skilled in the art can select and adjust it as needed.

[0053] Preferably, the method further comprises: purifying the obtained nickel complex represented by formula (I). The purification method can be carried out according to purification methods known in the art, such as separation, filtration, washing, drying, etc. In order to obtain a nickel complex represented by formula (I) with higher purity, the present invention preferably adopts a purification method comprising the following steps:

[0054] The obtained nickel complex represented by formula (I) is evacuated of solvent with a vacuum pump, and then dissolved in anhydrous ether for precipitation; the precipitated material is then filtered, the solid phase product is washed with anhydrous ether, and finally dried.

[0055] The method for preparing the nickel complex of formula (I) provided by the present invention has the advantages of simple operation, mild reaction conditions and short preparation period. Meanwhile, the nickel complex of formula (I) prepared by the present invention can be used for catalyzing olefin polymerization reaction, preferably for catalyzing ethylene polymerization reaction, and has high catalytic efficiency.

[0056] As mentioned above, the fourth aspect of the present invention provides a catalyst composition, which includes a main catalyst and a co-catalyst, the co-catalyst is alkylaluminum chloride, and the main catalyst is the nickel complex catalyst described in the first aspect.

[0057] Preferably, the molar ratio of the content of the co-catalyst calculated as aluminum element to the content of the main catalyst calculated as nickel element is 20-2000:1. More preferably, the molar ratio of the content of the co-catalyst calculated as aluminum element to the content of the main catalyst calculated as nickel element is 200-600:1. Exemplarily, it can be 200:1, 300:1, 400:1, 500:1, 600:1, etc. The inventors of the present invention have found that under this preferred condition, when the catalyst composition is used to catalyze olefin polymerization, especially ethylene polymerization, its catalytic activity is higher.

[0058] Preferably, the alkylaluminum chloride is selected from diethylaluminum chloride (Et 2 AlCl), dimethylaluminum chloride (Me 2 AlCl), ethylaluminum dichloride (EtAlCl 2 ), dichloromethylaluminum (MeAlCl 2 ), ethylaluminum sesqui (EASC).

[0059] As mentioned above, the fifth aspect of the present invention provides the use of the catalyst composition described in the fourth aspect in olefin polymerization reaction.

[0060] Preferably, the olefin polymerization reaction is ethylene polymerization reaction.

[0061] As mentioned above, the sixth aspect of the present invention provides a method for preparing polyethylene, which comprises: in the presence of solvent I, under the action of the catalyst composition described in the fourth aspect, polymerizing ethylene.

[0062] Preferably, the conditions of the polymerization reaction include: a temperature of 20-110°C, a time of 5-60 min, and a pressure of 0.5-10 atm. Exemplarily, the temperature of the polymerization reaction is 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C; the time of the polymerization reaction is 5 min, 10 min, 15 min, 30 min, 45 min, 60 min; the pressure of the polymerization reaction is 0.5 atm, 1 atm, 5 atm, 10 atm.

[0063] More preferably, the polymerization reaction conditions include: temperature of 30-70° C., time of 10-45 min, and pressure of 5-10 atm. The inventors found that under this preferred condition, the polymerization activity of the catalyst in catalyzing ethylene polymerization is more improved.

[0064] In the present invention, the polymerization reaction is preferably carried out under stirring conditions. The present invention has no particular limitation on the stirring speed, and those skilled in the art can select and adjust it as needed. For example, the stirring speed is 300-600 rpm.

[0065] Preferably, the solvent I is selected from at least one of toluene, o-xylene, dichloromethane, ethanol, tetrahydrofuran, n-hexane and cyclohexane.

[0066] Preferably, relative to 1 μmol of the main catalyst, the amount of the solvent I is 30-100 mL.

[0067] In the present invention, the polymerization reaction is preferably carried out under ethylene atmosphere.

[0068] In order to further improve the catalytic activity, the present invention provides a preferred method for preparing polyethylene, which comprises:

[0069] Under ethylene atmosphere and in the presence of solvent I, the main catalyst and the co-catalyst are reacted at a temperature of 20-110°C and a pressure of 0.5-10atm for 5-60min; the reaction liquid is then neutralized with a 10% hydrochloric acid ethanol solution (the volume ratio of hydrochloric acid to ethanol is 1:9) to obtain a polymer precipitate, which is then washed with ethanol and dried to obtain polyethylene.

[0070] The polyethylene preparation method provided by the present invention has mild reaction conditions, high catalytic activity, and a polymerization activity of up to 24.2×10 6 g·mol -1 (Ni)·h-1 The obtained polyethylene elastic material has a high weight average molecular weight (up to 6.85×10 5 g·mol -1 ), narrow molecular weight distribution (M w / M n =2.18-3.14), and the catalyst used has a strong regulating ability on polyethylene molecules.

[0071] The present invention will be described in detail below by way of examples. In the following examples, unless otherwise specified, the methods used are all conventional methods, and the raw materials are all conventional commercially available products.

[0072] In the example, the series of compounds represented by formula (B) were synthesized according to Dalton Trans., 2015, 44, 12282.

[0073] Example 1

[0074] Ni1 complex,

[0075] Under nitrogen atmosphere, 10.0 mmol of 2-diphenylmethyl-4,6-dimethylaniline (compound represented by formula (B-1)), 5.0 mmol of 1,2-diphenylethanedione (compound represented by formula (A)) and 5.0 mmol of (DME)NiBr 2 Dissolve in 15 mL of acetic acid, heat with stirring and reflux at 120°C for 6 h. After the reaction is completed, remove the solvent with a vacuum pump to concentrate the reaction solution, add ether for precipitation, collect the precipitate by filtration, wash with ether, and then dry to obtain a red powder (yield 61.5%), which is the Ni1 complex.

[0076] Elemental analysis results of Ni1 complex: C 56 H 48 Br 2 N 2 Ni (967.52) theoretical value: C, 69.52; H, 5.00; N, 2.90. Experimental value: C, 69.75%; H, 4.85%; N, 2.77%.

[0077] Example 2

[0078] Ni2 complexes,

[0079] Under nitrogen atmosphere, 10.0 mmol of 2-benzhydryl-4,6-diethylaniline (compound represented by formula (B-2)), 5.0 mmol of 1,2-diphenylethanedione and 5.0 mmol of (DME)NiBr2 Dissolve in 15 mL of acetic acid, heat with stirring and reflux at 120°C for 8 h. After the reaction is completed, remove the solvent with a vacuum pump to concentrate the reaction solution, add ether for precipitation, collect the precipitate by filtration, wash with ether, and then dry to obtain a red powder (yield 58.4%), which is the Ni2 complex.

[0080] Elemental analysis results of Ni2 complex: C 60 H 56 Br 2 N 2 Ni (1023.62) theoretical value: C, 70.40; H, 5.51; N, 2.74. Experimental value: C, 70.21%; H, 5.82%; N, 2.69%.

[0081] Example 3

[0082] Ni3 complexes,

[0083] Under nitrogen atmosphere, 10.0 mmol of 2-diphenylmethyl-4,6-diisopropylaniline (the compound represented by formula (B-3)), 5.0 mmol of 1,2-diphenylethanedione and 5.0 mmol of (DME)NiBr 2 Dissolve in 15 mL of acetic acid, heat with stirring and reflux at 120°C for 4 h. After the reaction is completed, remove the solvent with a vacuum pump to concentrate the reaction solution, add ether for precipitation, collect the precipitate by filtration, wash with ether, and then dry to obtain a red powder (yield 50.2%), which is the Ni3 complex.

[0084] Elemental analysis results of Ni3 complex: C 64 H 64 Br 2 N 2 Ni (1079.73) theoretical value: C, 71.19; H, 5.97; N, 2.59. Experimental value: C, 70.81%; H, 5.76%; N, 2.73%.

[0085] Example 4

[0086] Ni4 complex,

[0087] Under nitrogen atmosphere, 10.0 mmol of 2-benzhydryl-4-methyl-6-ethylaniline (compound represented by formula (B-4)), 5.0 mmol of 1,2-diphenylethanedione and 5.0 mmol of (DME)NiBr 2Dissolve in 15 mL of acetic acid, heat with stirring and reflux at 120°C for 6 h. After the reaction is completed, remove the solvent with a vacuum pump to concentrate the reaction solution, add ether for precipitation, collect the precipitate by filtration, wash with ether, and then dry to obtain a red powder (yield 57.2%), which is the Ni4 complex.

[0088] Elemental analysis results of Ni4 complex: C 58 H 52 Br 2 N 2 Ni(995.57) Theoretical value: C, 69.97; H, 5.26; N, 2.81. Experimental value: C, 70.35%; H, 5.32%; N, 2.83%.

[0089] Example 5

[0090] Ni5 complex,

[0091] Under nitrogen atmosphere, 10.0 mmol of 2-diphenylmethyl-4-methyl-6-isopropylaniline (compound represented by formula (B-5)), 5.0 mmol of 1,2-diphenylethanedione and 5.0 mmol of (DME)NiBr 2 Dissolve in 15 mL of acetic acid, heat with stirring and reflux at 120°C for 6 h. After the reaction is completed, remove the solvent with a vacuum pump to concentrate the reaction solution, add ether for precipitation, collect the precipitate by filtration, wash with ether, and then dry to obtain a red powder (yield 51.3%), which is the Ni5 complex.

[0092] Elemental analysis results of Ni5 complex: C 60 H 56 Br 2 N 2 Ni (1023.62) Theoretical value: C, 70.40; H, 5.51; N, 2.74. Experimental value: C, 70.65H, 5.18; N, 2.54%.

[0093] Example 6

[0094] Ni6 complex,

[0095] Under a nitrogen atmosphere, 10.0 mmol of 2-benzhydryl-4,6-difluoroaniline (the compound represented by formula (B-6)), 5.0 mmol of 1,2-diphenylethanedione and 5.0 mmol of (DME)NiBr 2Dissolve in 15 mL of acetic acid, heat with stirring and reflux at 120°C for 8 h. After the reaction is completed, remove the solvent with a vacuum pump to concentrate the reaction solution, add ether for precipitation, collect the precipitate by filtration, wash with ether, and then dry to obtain a red powder (yield 45.8%), which is the Ni6 complex.

[0096] Elemental analysis results of Ni6 complex: C 52 H 36 Br 2 N 2 Ni (983.37) theoretical value: C, 63.51; H, 3.69; N, 2.85. Experimental value: C, 63.73%; H, 3.28%; N, 2.74%.

[0097] Example 7

[0098] Using Ni1 complex / Et 2 Ethylene polymerization catalyzed by AlCl system:

[0099] In an ethylene atmosphere, 25 mL of toluene, 50 mL of toluene solution containing the main catalyst Ni1 complex (2 μmol), and 0.8 mL of the co-catalyst Et 2 A toluene solution of AlCl (0.5 mol / L) and 25 mL of toluene were sequentially added to a 250 ml high pressure reactor, that is, the molar ratio of the co-catalyst calculated in terms of aluminum element to the main catalyst calculated in terms of nickel element was 200:1 (Al / Ni=200:1), the stirring speed in the reactor was controlled to be maintained at 400 rpm, and when the temperature of the reaction system reached 30°C, the ethylene pressure in the reactor was increased to 10 atm, and the temperature in the reactor was maintained at 30°C and the pressure was maintained at 10 atm, and the reaction was continued for 30 minutes. After the reaction was completed, stirring was stopped, and the reaction solution was quenched with a 10% hydrochloric acid ethanol solution (a solution with a volume ratio of hydrochloric acid to ethanol of 1:9) to obtain a polymer precipitate, which was washed with ethanol 3 times and then dried under vacuum to constant weight to obtain a polymer.

[0100] Polymerization activity: 7.8×10 6 g·mol -1 (Ni)·h -1 , polymer weight average molecular weight M w =6.56×10 5 g·mol -1 , PDI = 2.42 (polymer weight average molecular weight M w and molecular weight distribution PDI obtained by high temperature GPC test), polymer T m =74.2°C (polymer melting temperature T m obtained by DSC test).

[0101] Example 8

[0102] Using Ni2 complex / EtAlCl 2 The system catalyzes ethylene polymerization:

[0103] The method is similar to that of Example 7, except that the main catalyst of this example is Ni2 complex and the co-catalyst is EtAlCl 2 The polymerization solvent is n-hexane; that is, under ethylene atmosphere, 25 mL of n-hexane, 50 mL of n-hexane solution containing the main catalyst Ni2 complex (2 μmol), 0.8 mL of co-catalyst EtAlCl 2 n-hexane solution (0.5 mol / L) and 25 mL n-hexane were added into a 250 mL high pressure reactor in sequence;

[0104] The remaining steps are the same as those in Example 7;

[0105] Polymerization activity: 10.1×10 6 g·mol -1 (Ni)·h -1 , polymer weight average molecular weight M w =5.69×10 5 g·mol -1 , PDI = 3.01, polymer T m =57.0℃.

[0106] Example 9

[0107] Ethylene polymerization catalyzed by Ni3 complex / EASC system:

[0108] The method is similar to that of Example 7, except that the main catalyst of this example is Ni3 complex, the co-catalyst is EASC, and the polymerization solvent is n-hexane; the remaining steps are the same as those of Example 7;

[0109] Polymerization activity: 9.8×10 6 g·mol -1 (Ni)·h -1 , polymer weight average molecular weight M w =6.85×10 5 g·mol -1 , PDI = 2.18, polymer T m =63.2℃.

[0110] Example 10

[0111] Using Ni4 complex / Et 2 Ethylene polymerization catalyzed by AlCl system:

[0112] The method is similar to that of Example 7, except that the main catalyst of this example is Ni4 complex, and the polymerization solvent is n-heptane; the remaining steps are the same as those of Example 7;

[0113] Polymerization activity: 11.5×10 6 g·mol -1 (Ni)·h -1 , polymer weight average molecular weight M w =4.28×10 5 g·mol -1 , PDI = 2.56, polymer T m =67.0℃.

[0114] Embodiment 11

[0115] Using Ni5 complex / Et 2 Ethylene polymerization catalyzed by AlCl system:

[0116] The method is similar to that of Example 7, except that the main catalyst of this example is Ni5 complex, and the polymerization solvent is n-heptane; the remaining steps are the same as those of Example 7;

[0117] Polymerization activity: 9.6×10 6 g·mol -1 (Ni)·h -1 , polymer weight average molecular weight M w =5.86×10 5 g·mol -1 , PDI = 3.14, polymer T m =70.2℃.

[0118] Example 12

[0119] Using Ni6 complex / Et 2 Ethylene polymerization catalyzed by AlCl system:

[0120] The method is similar to that of Example 7, except that the main catalyst of this example is Ni6 complex, and the polymerization solvent is n-heptane; the remaining steps are the same as those of Example 7;

[0121] Polymerization activity: 8.5×10 6 g·mol -1 (Ni)·h -1 , polymer weight average molecular weight M w =4.36×10 5 g·mol -1 , PDI = 2.35, polymer T m =63.2℃.

[0122] Embodiment 13

[0123] Using Ni4 complex / Et 2 Ethylene polymerization catalyzed by AlCl system:

[0124] In an ethylene atmosphere, 25 mL of toluene, 50 mL of toluene solution containing the main catalyst Ni4 complex (2 μmol), 1.6 mL of co-catalyst Et 2 A toluene solution of AlCl (0.5 mol / L) and 25 mL of toluene were sequentially added into a 250 ml high pressure reactor, i.e., the molar ratio of the co-catalyst in terms of aluminum element to the main catalyst in terms of nickel element was 400:1 (Al / Ni=400:1); the stirring speed in the reactor was controlled to be maintained at 400 rpm, and when the temperature of the reaction system reached 60° C., the ethylene pressure in the reactor was increased to 6 atm, and the temperature in the reactor was maintained at 60° C. and the pressure was maintained at 6 atm, and the reaction was carried out for 45 min. After the reaction was completed, stirring was stopped, and the reaction solution was quenched with a 10% hydrochloric acid ethanol solution to obtain a polymer precipitate, which was washed with ethanol 3 times and then dried under vacuum to constant weight.

[0125] Polymerization activity: 24.2×10 6 g·mol -1 (Ni)·h -1 , polymer weight average molecular weight M w =8.56×10 4 g·mol -1 , PDI = 2.21, polymer T m =41.3℃.

[0126] Embodiment 14

[0127] Using Ni1 complex / Et 2 Ethylene polymerization catalyzed by AlCl system:

[0128] The method is similar to that of Example 7, except that 25 mL of toluene, 50 mL of toluene solution containing the main catalyst Ni1 complex (2 μmol), and 8 mL of the co-catalyst Et 2 A toluene solution of AlCl (0.5 mol / L) and 25 mL of toluene were sequentially added into a 250 ml autoclave, so that the molar ratio of the co-catalyst calculated by aluminum element to the main catalyst calculated by nickel element was 2000:1; the remaining steps were the same as those in Example 7 to obtain a polymer;

[0129] Polymerization activity: 3.86×10 6 g·mol -1 (Ni)·h -1 , polymer weight average molecular weight M w=1.16×10 5 g·mol -1 , PDI = 2.48, polymer T m =57.9℃.

[0130] Comparative Example 1

[0131] The complex numbered 2 in CN114163482A was used as the main catalyst, Et 2 AlCl is used as a co-catalyst to catalyze ethylene polymerization:

[0132] Complex 2;

[0133] The method is similar to that of Example 7, except that the main catalyst of Example 7 is replaced by complex 2; the remaining steps are the same as those of Example 7 to obtain a polymer;

[0134] Polymerization activity: 2.01×10 6 g·mol -1 (Ni)·h -1 , polymer weight average molecular weight M w =6.34×10 4 g·mol -1 , PDI = 2.1, polymer T m =87.6℃.

[0135] Comparative Example 2

[0136] Using complex 1a in CN101812145A as the main catalyst, Et 2 AlCl is used as a co-catalyst to catalyze ethylene polymerization:

[0137] Complex 1a;

[0138] The method is similar to that of Example 7, except that the main catalyst of Example 7 is replaced by complex 1a; the remaining steps are the same as those of Example 7 to obtain a polymer;

[0139] Polymerization activity: 2.98×10 6 g·mol -1 (Ni)·h -1 , polymer weight average molecular weight M w =3.28×10 5 g·mol -1 , PDI = 2.3, polymer T m =76.4℃.

[0140] Comparative Example 3

[0141] Using complex C4 in CN104250270A as the main catalyst, Et 2 AlCl is used as a co-catalyst to catalyze ethylene polymerization:

[0142] Complex C4;

[0143] The method is similar to that of Example 7, except that the main catalyst of Example 7 is replaced by complex C4; the remaining steps are the same as those of Example 7 to obtain a polymer;

[0144] Polymerization activity: 2.26×10 6 g·mol -1 (Ni)·h -1 , polymer weight average molecular weight M w =1.08×10 5 g·mol -1 , PDI = 2.6, polymer T m =98.6℃.

[0145] It can be seen from Examples 7 to 14 of the present invention that when the catalyst provided by the present invention is used to prepare polyethylene, the catalyst has high catalytic activity, and the resulting polymer has a high molecular weight and a low melting point, which meets the characteristics of a polyolefin elastomer.

[0146] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A nickel complex, characterized in that The nickel complex has a structure shown in formula (I), Wherein, in formula (I), each R 1 , R 2 Each independently selected from H, halogen, nitro, C 1-6 The alkyl group; X is selected from F, Cl, Br, I.

2. The nickel complex according to claim 1, wherein In formula (I), each R 1 , R 2 Each independently selected from H, F, Br, C 1-3 The alkyl group; Preferably, the nickel complex represented by formula (I) is selected from at least one of the following complexes: Complex Ni1:R 1 = methyl, R 2 = methyl, X = Br; Complex Ni2:R 1 = ethyl, R 2 =ethyl, X = Br; Complex Ni3:R 1 = isopropyl, R 2 =isopropyl, X = Br; Complex Ni4:R 1 = ethyl, R 2 = methyl, X = Br; Complex Ni5:R 1 = isopropyl, R 2 = methyl, X = Br; Complex Ni6:R 1 =F, R 2 =F, X = Br.

3. Use of the nickel complex according to claim 1 or 2 in olefin polymerization.

4. A method for preparing a nickel complex represented by formula (I), characterized in that: The method includes: In the presence of a protective gas and an organic solvent, a compound represented by formula (A) is subjected to a first reaction with a compound represented by formula (B) and a compound NiX2 to obtain a nickel complex represented by formula (I); Wherein, in the compound NiX2, X is selected from F, Cl, Br, I; In formula (B) and formula (I), each R 1 , R 2 The definitions are the same as those in claim 1 or 2.

5. The method according to claim 4, wherein: The molar ratio of the compound represented by formula (A), the compound represented by formula (B) and the compound NiX2 is 1:2-6:0.5-1; Preferably, the molar ratio of the compound represented by formula (A), the compound represented by formula (B) and the compound NiX2 is 1:2-4:0.8-1; Preferably, the conditions of the first reaction include: reaction temperature of 100-160° C., and reaction time of 1-12 hours.

6. A catalyst composition, characterized in that The catalyst composition comprises a main catalyst and a co-catalyst, the co-catalyst is alkylaluminum chloride, and the main catalyst is the nickel complex catalyst according to claim 1 or 2.

7. The catalyst composition according to claim 6, wherein The molar ratio of the co-catalyst calculated in terms of aluminum element to the main catalyst calculated in terms of nickel element is 20-2000:1; Preferably, the molar ratio of the co-catalyst calculated as aluminum element to the main catalyst calculated as nickel element is 200-600:

1.

8. The catalyst composition according to claim 6 or 7, wherein The alkylaluminum chloride is selected from at least one of diethylaluminum chloride, dimethylaluminum chloride, ethylaluminum dichloride, dimethylaluminum dichloride, and ethylaluminum sesquichloride.

9. Use of the catalyst composition according to any one of claims 6 to 8 in olefin polymerization; Preferably, the olefin polymerization reaction is ethylene polymerization reaction.

10. A method for preparing polyethylene, characterized in that: The method comprises: in the presence of solvent I, under the action of the catalyst composition described in any one of claims 6 to 8, polymerizing ethylene; Preferably, the polymerization reaction conditions include: temperature of 20-110° C., time of 5-60 min, and pressure of 0.5-10 atm.

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