Chromium-nickel bimetallic center complex catalyst and preparation method and application thereof

Abstract

The invention belongs to the technical field of coordination complex catalysts, and particularly relates to a chromium-nickel bimetallic center complex catalyst as well as a preparation method and application thereof. The preparation method comprises the following steps: adding isopropylamine, cyclohexylphenylphosphonium chloride and an acid-binding agent into a solvent for reaction to obtain a PNP ligand; the preparation method comprises the following steps: respectively dissolving a PNP ligand, chromium acetylacetonate and nickel acetylacetonate in a solvent to obtain a PNP ligand solution, a chromium acetylacetonate solution and a nickel acetylacetonate solution, and mixing and stirring the PNP ligand solution, the chromium acetylacetonate solution and the nickel acetylacetonate solution for reaction to obtain the chromium-nickel bimetallic center complex catalyst. The prepared chromium-nickel bimetallic center complex catalyst can be used for ethylene oligomerization reaction, ethylene molecules can be rapidly activated, the chain growth process can be accurately controlled, and the dual requirements of industrial production for high activity and high selectivity of the catalyst are met.

Description

Technical Field

[0001] This invention belongs to the field of coordination catalyst technology, specifically relating to a chromium-nickel bimetallic central coordination catalyst, its preparation method, and its application. Background Technology

[0002] Linear α-olefins (LAOs) are straight-chain olefin molecules with a double bond at the α-terminus. Due to their relatively reactive double bond structure, they are important raw materials in the petrochemical industry and are widely used in polymerization and hydrogenation processes. They play a crucial role in the synthesis of polyethylene, lubricants, plasticizers, alcohols, and surfactants. Among them, 1-octene is an important organic synthesis raw material with wide applications. Especially in recent years, the significant increase in demand for materials such as polyolefin elastomers (POE) and linear low-density polyethylene (LLDPE) has led to a continuous increase in the demand for 1-octene, thus giving it a very broad market prospect.

[0003] In industry, ethylene oligomerization is commonly used to prepare 1-octene. This method utilizes a specific catalyst (such as an alkylaluminum catalyst with chromium or other transition metal catalysts) in an organic solution to carry out a homogeneous reaction of selective tetramerization of ethylene to produce 1-octene. Compared with traditional methods for obtaining 1-octene, the ethylene oligomerization method for 1-octene preparation has advantages such as high selectivity, low energy consumption, and simple operation. Therefore, preparing a catalyst with high reactivity and good selectivity for 1-octene is crucial for the homogeneous preparation of 1-octene from ethylene oligomerization. However, it is often difficult to find a metal homogeneous catalyst with both high catalytic activity and high selectivity for 1-octene in existing technologies.

[0004] Chinese patent CN119346177A discloses a highly selective catalyst, its preparation method, and its application in the ethylene oligomerization reaction. The catalytic system includes a phosphine-containing ligand, a transition metal compound, an organic solvent, and a co-catalyst. The structural formula of the phosphine-containing ligand is shown below: , In the formula, n is an integer in the range of 2-10; R1, R2, and R3 are each independently selected from one or more combinations of C2-C9 alkyl, aryl, substituted alkyl, and substituted aryl groups. This patent exhibits high selectivity in the preparation of 1-octene, but its catalytic activity is relatively low. Chinese patent CN117504934A discloses a novel chromium-based catalyst and its preparation method. The catalyst preparation involves three steps: preparing dispersion A, preparing ligands, and performing a polymerization reaction. The solvent for dispersion A is dichloromethane, and the storage temperature is -10 to 10°C. The reaction vessel used for the polymerization reaction is evacuated for 1 to 3 hours. Although the catalyst in this patent has high activity, its selectivity in the preparation of 1-octene is poor. Summary of the Invention

[0005] The purpose of this invention is to provide a chromium-nickel bimetallic central complex catalyst to solve the problems of insufficient selectivity for 1-octene and poor reactivity of existing catalysts in ethylene oligomerization; this invention also provides a method for preparing the chromium-nickel bimetallic central complex catalyst and its application.

[0006] The structural formula of the chromium-nickel bimetallic central complex catalyst of the present invention is as follows: , In the formula, R 1 For chromium acetylacetone, R 2 It is nickel acetylacetonate.

[0007] The preparation method of the chromium-nickel bimetallic central complex catalyst of the present invention includes the following steps: (1) Isopropylamine, cyclohexylphenylphosphine chloride and an acid-binding agent are added to a solvent to react and obtain PNP ligands; (2) PNP ligand, chromium acetylacetone and nickel acetylacetone are dissolved in solvents to obtain PNP ligand solution, chromium acetylacetone solution and nickel acetylacetone solution. The PNP ligand solution, chromium acetylacetone solution and nickel acetylacetone solution are mixed and stirred to react and obtain chromium-nickel bimetallic center complex catalyst.

[0008] In step (1), the acid-binding agent is triethylamine, the molar ratio of isopropylamine to the acid-binding agent is 1:10-20, the solvent is dichloromethane or chloroform, the molar ratio of isopropylamine to the solvent is 1:123-156, and the molar ratio of isopropylamine to cyclohexylphenylphosphine chloride is 0.4-0.6:1.

[0009] The reaction time in step (1) is 14-15 hours and the reaction temperature is 0-30℃.

[0010] The structural formula of cyclohexylphenylphosphine chloride in step (1) is as follows: .

[0011] In step (1), cyclohexylphenylphosphine chloride is prepared from diphenylphosphine chloride.

[0012] The reaction equation for the preparation of PNP ligands in step (1) is as follows: .

[0013] The reaction equation for the preparation of the chromium-nickel bimetallic central complex catalyst in step (2) is as follows: .

[0014] In step (2), the molar ratio of chromium acetylacetone to nickel acetylacetone is 8-16:1, and the ratio of the number of moles of PNP ligands to the total number of moles of chromium acetylacetone and nickel acetylacetone is 1:1.5-4.5.

[0015] In step (2), the molar ratio of solvent to chromium acetylacetone is 29-100:1, preferably 40-60:1; the reaction temperature is room temperature, and the reaction time is 1-2 hours.

[0016] In step (2), the solvent is at least one of benzene, toluene, chlorobenzene or xylene.

[0017] The application of the chromium-nickel bimetallic central complex catalyst described in this invention involves adding the chromium-nickel bimetallic central complex catalyst, ethylene, and a co-catalyst to a solvent for oligomerization to obtain 1-octene.

[0018] The cocatalyst is at least one of methylaluminoxane, modified methylaluminoxane, triethylaluminum, or triisobutylaluminum, and the solvent is at least one of cyclohexane, 1,4-dioxane, cyclooctane, methylcyclohexane, or toluene.

[0019] The molar ratio of the co-catalyst to the chromium-nickel bimetallic central complex catalyst is 450-600:1, and the molar ratio of the chromium-nickel bimetallic central complex catalyst to the solvent is 1:487-1000.

[0020] The oligomerization reaction temperature is 30-60℃, preferably 35-50℃, the oligomerization reaction pressure is 30-50 atm, and the oligomerization reaction time is 30-50 min.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) By co-coordinating Cr and Ni bimetallic atoms onto organophosphine ligands, a symmetrical coordination mode is formed, resulting in multi-dimensional performance improvements: the electron cloud density inside the ligand is more uniform, significantly enhancing reaction stability; accelerating the ethylene molecule capture and cyclization rate, improving catalytic activity; lowering the electron migration energy barrier, promoting the formation of long carbon chain products, improving 1-octene selectivity and reducing byproducts. Compared with traditional PNP ligands, a benzene ring attached to the P atom is replaced by cyclohexane. Because the flexible alicyclic structure of cyclohexane can more flexibly adjust the spatial conformation compared to the rigid benzene ring, reducing the spatial hindrance to the binding of ethylene molecules, its saturated structure can more stably regulate the electron density of the P atom through the σ bond induction effect, forming a more synergistic coordination environment with the Cr and Ni bimetallic center, further amplifying the performance advantages brought by the structural design.

[0022] (2) The chromium-nickel bimetallic central complex catalyst prepared in this invention can be applied to the ethylene oligomerization reaction, and its catalytic activity (oligomerization activity ≥ 1.6 × 10⁻⁶) has been verified by experiments. 7 g·mol-1 (Cat)·h -1 The selectivity for 1-octene is ≥80%. The bimetallic synergistic effect and the optimization of the ligand structure jointly ensure high catalytic efficiency, which can both rapidly activate ethylene molecules and precisely control the chain growth process, meeting the dual requirements of industrial production for high catalyst activity and high selectivity.

[0023] (3) The introduction of Ni metal can promote ethylene insertion growth and terminate chain growth in a timely manner through β-H elimination, thereby reducing the formation of high molecular weight polymers, reducing the amount of toxic metal Cr, significantly reducing the toxicity of the system, and improving production safety; at the same time, it extends the catalyst life and reduces its loss due to frequent catalyst replacement. In addition, after cyclohexane replaces part of the benzene ring in the ligand, it has better compatibility with the reaction system, reduces catalyst aggregation, extends life and reduces post-reaction processing costs, further compressing industrialization costs and achieving a balance between environmental protection and economy.

[0024] (4) The catalyst preparation process does not require complex equipment or harsh conditions, and the operation is simple and easy to carry out; the raw materials are widely available and readily available. In particular, the substitution of the benzene ring with cyclohexane in the PNP ligand avoids the synthetic complexity that may exist in benzene ring derivatives, further improving the availability of raw materials. Thanks to the optimized reaction pathway and stable molecular structure, the catalyst yield is ≥90%, which provides a solid foundation for large-scale industrial production and has significant technological transformation advantages.

[0025] (5) Mechanism: Electronic configuration of nickel (3d 8 4s 2 After binding with phosphine ligands, the regioselectivity (C4-C6) and reaction rate of ethylene insertion at specific sites are more precise and faster than those of other metals such as Cr. Therefore, the introduction of Ni atoms enables the chromium-nickel bimetallic complex catalyst to capture two ethylene molecules more precisely and rapidly than traditional chromium metal catalysts, forming a metal five-membered ring structure. The metal five-membered ring structure then rapidly transfers the two captured ethylene molecules to the Cr ligand via H transfer. Finally, the Cr metal center captures two ethylene molecules to form a metal nine-membered ring, which is then removed by H transfer to release 1-octene. At the same time, the introduction of Ni crowds out steric hindrance, thereby inhibiting the possibility of Cr further capturing ethylene to generate higher carbon numbers. Attached Figure Description

[0026] Figure 1 The image shows the phosphorus NMR spectrum of the PNP ligand in Example 1.

[0027] Figure 2 This is the electrospray ionization mass spectrum of the chromium-nickel bimetallic central complex catalyst in Example 1.

[0028] Figure 3The image shows a gas chromatogram of the reaction solution containing 1-octene in Example 1. In the image, a represents 1-hexene, b represents cyclohexane, c represents toluene, and d represents 1-octene. Detailed Implementation

[0029] The present invention will be further described below with reference to embodiments.

[0030] Example 1 Preparation of PNP ligands: In a nitrogen-filled glove box, 50 mL of dichloromethane, 2.26 g of cyclohexylphenylphosphine chloride, and 10 mL of triethylamine were sequentially added to a three-necked vacuum flask and stirred for 15 min to ensure thorough mixing. Then, 0.43 mL of isopropylamine was slowly added under ice bath conditions, and the mixture was stirred for 30 min. The reaction was then continued at room temperature for 14 h. After the reaction was completed, the precipitated amine salt was removed by negative pressure filtration, and dichloromethane was removed by vacuum distillation at 50 °C. Ethanol was then added at 80 °C to completely dissolve the precipitate, which was then transferred to an ice bath for 1 h to crystallize and precipitate a white solid. The white solid was filtered, collected, washed three times with diethyl ether, and dried in a 60 °C oven for 8 h to finally obtain the PNP ligand, with a calculated yield of 90.5%.

[0031] The yield calculation is as follows: Yield = Actual number of moles of product / Number of moles of isopropylamine × 100%.

[0032] The PNP ligands were characterized using CDCl3 as solvent and TMS internal standard. 1 H-NMR (400MHz, CDCl3): δ0.974-1.062 (m, 2 H), 1.302-1.565 (m, 22 H), 3.591-3.739 (q, 1 H), 7.118-7.378 (m, 10 H). 13 C-NMR (101 MHz, CDCl3): δ 24.42, 26.05, 27.78, 28.62, 37.76, 51.92, 128.25, 130.64, 132.91, 140.01. The phosphorus NMR spectrum of the PNP ligand is shown below. Figure 1 , 31 P-NMR (162MHz, CDCl3): δ 91.57.

[0033] Preparation of chromium-nickel bimetallic center complex catalysts: 4.092 mmol of PNP ligand, 7.44 mmol of chromium acetylacetone, and 0.744 mmol of nickel acetylacetone were dissolved in toluene to obtain PNP ligand solution, chromium acetylacetone solution, and nickel acetylacetone solution, respectively, with a total toluene mass of 32 g. The PNP ligand solution, chromium acetylacetone solution, and nickel acetylacetone solution were mixed and stirred at room temperature for 1 h to obtain an orange solution, which is the chromium-nickel bimetallic central complex catalyst. The electrospray ionization mass spectrum of the chromium-nickel bimetallic central complex catalyst is shown in [Figure number missing]. Figure 2 .

[0034] Preparation of 1-octene: In a glove box, 4.092 mmol of the chromium-nickel bimetallic central complex catalyst was injected into a 2L batch reactor using a syringe. The reactor was evacuated and purged three times with nitrogen and ethylene gas, respectively. Then, methylaluminoxane and 168 g of cyclohexane, measured in the glove box, were added sequentially to the reactor at a molar ratio of 600:1 to the chromium-nickel bimetallic central complex catalyst. The reaction was mechanically stirred for 30 min at an oligomerization temperature of 45 °C and an oligomerization pressure of 40 atm to obtain a reaction solution containing 1-octene. The gas chromatogram of the 1-octene-containing reaction solution is shown below. Figure 3 The oligomerization activity of the chromium-nickel bimetallic central complex catalyst is 1.66 × 10⁻⁶. 7 g·mol -1 (Cat)·h -1 The selectivity for 1-octene was 82.8%.

[0035] Example 2 Preparation of PNP ligands: In a nitrogen-filled glove box, 53 mL of dichloromethane, 2.26 g of cyclohexylphenylphosphine chloride, and 16 mL of triethylamine were sequentially added to a three-necked vacuum flask and stirred for 15 min to ensure thorough mixing. Then, 0.5 mL of isopropylamine was slowly added under ice bath conditions, and the mixture was stirred for 30 min. The reaction was then continued at room temperature for 14 h. After the reaction was completed, the precipitated amine salt was removed by negative pressure filtration, and dichloromethane was removed by vacuum distillation at 50 °C. Ethanol was then added at 80 °C to completely dissolve the precipitate, which was then transferred to an ice bath for 1 h to crystallize and precipitate a white solid. The white solid was filtered, collected, washed three times with diethyl ether, and dried in a 60 °C oven for 8 h to finally obtain the PNP ligand, with a calculated yield of 90.7%.

[0036] The yield calculation is as follows: Yield = Actual number of moles of product / Number of moles of isopropylamine × 100%.

[0037] The preparation of the chromium-nickel bimetallic central complex catalyst was the same as in Example 1.

[0038] Preparation of 1-octene: In a glove box, 4.092 mmol of the chromium-nickel bimetallic central complex catalyst was injected into a 2L batch reactor using a syringe. The reactor was evacuated and purged three times with nitrogen and ethylene gas, respectively. Then, methylaluminoxane and 400 g of cyclooctane, measured in the glove box, were added sequentially to the reactor at a molar ratio of 450:1 to the chromium-nickel bimetallic central complex catalyst. The reaction was mechanically stirred for 50 min at an oligomerization temperature of 60 °C and an oligomerization pressure of 50 atm to obtain a reaction solution containing 1-octene. The oligomerization activity of the chromium-nickel bimetallic central complex catalyst was 1.65 × 10⁻⁶. 7 g·mol -1 (Cat)·h -1 The selectivity for 1-octene was 81.6%.

[0039] Example 3 Preparation of PNP ligands: In a nitrogen-filled glove box, 40 mL of dichloromethane, 2.26 g of cyclohexylphenylphosphine chloride, and 6 mL of triethylamine were sequentially added to a three-necked vacuum flask and stirred for 15 min to ensure thorough mixing. Then, 0.35 mL of isopropylamine was slowly added under ice bath conditions, and the mixture was stirred for 30 min. The reaction was then continued at room temperature for 14 h. After the reaction was completed, the precipitated amine salt was removed by negative pressure filtration, and dichloromethane was removed by vacuum distillation at 50 °C. Ethanol was then added at 80 °C to completely dissolve the precipitate, which was then transferred to an ice bath for 1 h to crystallize and precipitate a white solid. The white solid was filtered, collected, washed three times with diethyl ether, and dried in a 60 °C oven for 8 h to finally obtain the PNP ligand, with a calculated yield of 90.4%.

[0040] The yield calculation is as follows: Yield = Actual number of moles of product / Number of moles of isopropylamine × 100%.

[0041] The preparation of the chromium-nickel bimetallic central complex catalyst was the same as in Example 1.

[0042] Preparation of 1-octene: In a glove box, 4.092 mmol of the chromium-nickel bimetallic central complex catalyst was injected into a 2L batch reactor using a syringe. The reactor was evacuated and purged three times with nitrogen and ethylene gas, respectively. Then, methylaluminoxane and 360.5 g of 1,4-dioxane, measured in the glove box, were added sequentially to the reactor at a molar ratio of 500:1 to the chromium-nickel bimetallic central complex catalyst. The reaction was mechanically stirred for 50 min at an oligomerization temperature of 30 °C and an oligomerization pressure of 30 atm to obtain a reaction solution containing 1-octene. The oligomerization activity of the chromium-nickel bimetallic central complex catalyst was 1.6 × 10⁻⁶. 7 g·mol -1 (Cat)·h -1 The selectivity for 1-octene was 81.2%.

[0043] Example 4 The preparation of PNP ligands was the same as in Example 1.

[0044] Preparation of chromium-nickel bimetallic center complex catalysts: 5.58 mmol of PNP ligand, 7.44 mmol of chromium acetylacetone, and 0.93 mmol of nickel acetylacetone were dissolved in benzene to obtain PNP ligand solution, chromium acetylacetone solution, and nickel acetylacetone solution, respectively, with a total benzene mass of 17.4 g. The PNP ligand solution, chromium acetylacetone solution, and nickel acetylacetone solution were mixed and stirred at room temperature for 2 h to obtain an orange solution, which is the chromium-nickel bimetallic center complex catalyst.

[0045] Preparation of 1-octene: 261g of 1,4-dioxane was used instead of 168g of cyclohexane, and the remaining operations were the same as in Example 1. The oligomerization activity of the chromium-nickel bimetallic central complex catalyst was 1.65 × 10⁻⁶. 7 g·mol -1 (Cat)·h -1 The selectivity for 1-octene was 80.6%.

[0046] Example 5 The preparation of PNP ligands was the same as in Example 1.

[0047] Preparation of chromium-nickel bimetallic center complex catalysts: 3.162 mmol of PNP ligand, 7.44 mmol of chromium acetylacetone, and 0.465 mmol of nickel acetylacetone were dissolved in xylene to obtain PNP ligand solution, chromium acetylacetone solution, and nickel acetylacetone solution, respectively, with a total xylene mass of 78.86 g. The PNP ligand solution, chromium acetylacetone solution, and nickel acetylacetone solution were mixed and stirred at room temperature for 1.5 h to obtain an orange solution, which is the chromium-nickel bimetallic center complex catalyst.

[0048] Preparation of 1-octene: 394.32 g of methylcyclohexane was used instead of 168 g of cyclohexane, and the remaining operations were the same as in Example 1. The oligomerization activity of the chromium-nickel bimetallic central complex catalyst was 1.64 × 10⁻⁶. 7 g·mol -1 (Cat)·h -1 The selectivity for 1-octene was 80.2%.

[0049] Example 6 Preparation of PNP ligands: In a nitrogen-filled glove box, 50 mL of chloroform, 2.26 g of cyclohexylphenylphosphine chloride, and 10 mL of triethylamine were sequentially added to a three-necked vacuum reaction flask and stirred for 15 min to ensure thorough mixing. Then, 0.43 mL of isopropylamine was slowly added under ice bath conditions, and the mixture was stirred for 30 min. The reaction was then continued at room temperature for 14 h. After the reaction was completed, the precipitated amine salt was removed by negative pressure filtration, and chloroform was removed by vacuum distillation at 50 °C. Ethanol was then added at 80 °C to completely dissolve the precipitate, which was then transferred to an ice bath for 1 h to crystallize and precipitate a white solid. The white solid was filtered, collected, washed three times with diethyl ether, and dried in a 60 °C oven for 8 h to finally obtain the PNP ligand, with a calculated yield of 88.5%.

[0050] The yield calculation is as follows: Yield = Actual number of moles of product / Number of moles of isopropylamine × 100%.

[0051] Preparation of chromium-nickel bimetallic center complex catalysts: 1.86 mmol of PNP ligand, 7.44 mmol of chromium acetylacetone, and 0.93 mmol of nickel acetylacetone were dissolved in toluene to obtain PNP ligand solution, chromium acetylacetone solution, and nickel acetylacetone solution, respectively, with a total mass of 32 g of toluene. The PNP ligand solution, chromium acetylacetone solution, and nickel acetylacetone solution were mixed and stirred at room temperature for 1 h to obtain an orange solution, which is the chromium-nickel bimetallic center complex catalyst.

[0052] Preparation of 1-octene: In a glove box, 4.092 mmol of the chromium-nickel bimetallic central complex catalyst was injected into a 2L batch reactor using a syringe. The reactor was evacuated and purged three times with nitrogen and ethylene gas, respectively. Then, methylaluminoxane and 168 g of cyclohexane, measured in the glove box, were added sequentially to the reactor at a molar ratio of 600:1 to the chromium-nickel bimetallic central complex catalyst. The reaction was mechanically stirred for 40 min at an oligomerization temperature of 45 °C and an oligomerization pressure of 35 atm to obtain a reaction solution containing 1-octene. The oligomerization activity of the chromium-nickel bimetallic central complex catalyst was 1.61 × 10⁻⁶. 7 g·mol -1 (Cat)·h -1 The selectivity for 1-octene was 80.8%.

[0053] Comparative Example 1 Without adding nickel acetylacetone, the other steps were the same as in Example 1. The oligomerization activity of the prepared catalyst was 6.86 × 10⁻⁶. 6 g·mol -1 (Cat)·h -1 The selectivity for 1-octene was 72.8%.

[0054] Comparative Example 2 Without adding chromium acetylacetone, the other steps were the same as in Example 1. The oligomerization activity of the prepared catalyst was 5.34 × 10⁻⁶. 3 g·mol -1 (Cat)·h -1 The selectivity for 1-octene was 1.34%.

[0055] Comparative Example 3 Preparation of PNP ligands: In a nitrogen-filled glove box, 50 mL of dichloromethane, 1.95 g of diphenylphosphine chloride, and 10 mL of triethylamine were sequentially added to a three-necked vacuum reaction flask and stirred for 15 min to ensure thorough mixing. Then, 0.43 mL of isopropylamine was slowly added under ice bath conditions, and the mixture was stirred for 30 min. The reaction was then continued at room temperature for 14 h with stirring. After the reaction was completed, the precipitated amine salt was removed by negative pressure filtration, and dichloromethane was removed by vacuum distillation at 50 °C. Ethanol was then added at 80 °C to completely dissolve the precipitate. The precipitate was then transferred to an ice bath for 1 h to crystallize and precipitate a white solid. The white solid was filtered, collected, washed three times with diethyl ether, and dried in a 60 °C oven for 8 h to finally obtain the PNP ligand, with a calculated yield of 78.5%.

[0056] The preparation of the chromium-nickel bimetallic central complex catalyst and the preparation of 1-octene were the same as in Example 1. The oligomerization activity of the chromium-nickel bimetallic central complex catalyst was 8.68 g × 10⁻⁶. 6 g·mol -1 (Cat)·h -1 The selectivity for 1-octene is 72%.

Claims

1. A chromium-nickel bimetallic central complex catalyst, characterized in that... The structure is as follows: ， In the formula, R 1 For chromium acetylacetone, R 2 It is nickel acetylacetonate.

2. A method for preparing the chromium-nickel bimetallic central complex catalyst according to claim 1, characterized in that... Includes the following steps: (1) Isopropylamine, cyclohexylphenylphosphine chloride and an acid-binding agent are added to a solvent to react and obtain PNP ligands; (2) PNP ligand, chromium acetylacetone and nickel acetylacetone are dissolved in solvents to obtain PNP ligand solution, chromium acetylacetone solution and nickel acetylacetone solution. The PNP ligand solution, chromium acetylacetone solution and nickel acetylacetone solution are mixed and stirred to react and obtain chromium-nickel bimetallic center complex catalyst.

3. The method for preparing the chromium-nickel bimetallic central complex catalyst according to claim 2, characterized in that... In step (1), the acid-binding agent is triethylamine, the molar ratio of isopropylamine to the acid-binding agent is 1:10-20, the solvent is dichloromethane or chloroform, the molar ratio of isopropylamine to the solvent is 1:123-156, and the molar ratio of isopropylamine to cyclohexylphenylphosphine chloride is 0.4-0.6:

1.

4. The method for preparing the chromium-nickel bimetallic central complex catalyst according to claim 2, characterized in that... In step (2), the molar ratio of chromium acetylacetone to nickel acetylacetone is 8-16:1, and the ratio of the number of moles of PNP ligands to the total number of moles of chromium acetylacetone and nickel acetylacetone is 1:1.5-4.

5.

5. The method for preparing the chromium-nickel bimetallic central complex catalyst according to claim 2, characterized in that... In step (2), the molar ratio of solvent to chromium acetylacetone is 29-100:1, the reaction temperature is room temperature, and the reaction time is 1-2 hours.

6. The method for preparing the chromium-nickel bimetallic central complex catalyst according to claim 2, characterized in that... In step (2), the solvent is at least one of benzene, toluene, chlorobenzene or xylene.

7. The application of the chromium-nickel bimetallic central complex catalyst according to claim 1, characterized in that... A chromium-nickel bimetallic complex catalyst, ethylene, and a co-catalyst are added to a solvent to carry out an oligomerization reaction to obtain 1-octene.

8. The application of the chromium-nickel bimetallic central complex catalyst according to claim 7, characterized in that... The cocatalyst is at least one of methylaluminoxane, modified methylaluminoxane, triethylaluminum, or triisobutylaluminum, and the solvent is at least one of cyclohexane, 1,4-dioxane, cyclooctane, methylcyclohexane, or toluene.

9. The application of the chromium-nickel bimetallic central complex catalyst according to claim 7, characterized in that... The molar ratio of the co-catalyst to the chromium-nickel bimetallic central complex catalyst is 450-600:1, and the molar ratio of the chromium-nickel bimetallic central complex catalyst to the solvent is 1:487-1000.

10. The application of the chromium-nickel bimetallic central complex catalyst according to claim 7, characterized in that... The oligomerization reaction temperature is 30-60℃, the oligomerization reaction pressure is 30-50 atm, and the oligomerization reaction time is 30-50 min.

Images