An ethylene oligomerization catalytic system that reduces polymer adhesion and its application in the preparation of α-olefins.

Abstract

This invention discloses an ethylene oligomerization catalytic system for reducing polymer adhesion and its application, belonging to the technical field of ethylene oligomerization for the preparation of α-olefins. The catalytic system includes a catalytic ligand, a transition metal compound, a co-catalyst, and an antistatic agent. The structural formula of the ligand is shown in Formula I. The antistatic agent is selected from one or more of the following substances: 8168 ashless antistatic agent, DuPont 450 antistatic additive, PEG 200, and PEG 400. Using this catalytic system for the preparation of α-olefins via ethylene oligomerization can effectively reduce the adhesion of by-product polymers in the reactor while maintaining high catalytic activity and high selectivity for 1-hexene and 1-octene, thereby extending the operating cycle of the unit and avoiding unplanned shutdowns for cleaning caused by adhesion.

Description

Technical Field

[0001] This invention relates to the technical field of ethylene oligomerization for the preparation of α-olefins, and more specifically, to an ethylene oligomerization catalytic system that can reduce polymer adhesion and its application in the ethylene oligomerization for the preparation of α-olefins. Background Technology

[0002] Linear α-olefins (LAOs) are important chemical intermediates, widely used in the synthesis of lubricants, plasticizers, surfactants, and polyethylene comonomers. Among them, the selective oligomerization of ethylene, especially trimerization and tetramerization to prepare 1-hexene and 1-octene, is the mainstream process for the industrial production of high value-added α-olefins.

[0003] Currently, most existing ethylene oligomerization technologies employ homogeneous catalytic systems, whose core typically consists of transition metal precursors and catalytic ligands. In this catalytic process, byproduct polymers generated during the reaction easily adhere to the surfaces of internal components such as the reactor wall, agitator, and heat exchanger, as well as the interior of pipes (including adhesion, deposition, and scaling), leading to decreased heat transfer efficiency and consequently disrupting precise temperature control. This not only forces unplanned shutdowns for cleaning, causing economic losses, but also affects product quality uniformity due to frequent start-ups and shutdowns, fundamentally limiting the extension of the plant's operating cycle and the improvement of production efficiency.

[0004] For ethylene oligomerization catalytic systems composed of specific catalytic ligands, how to selectively add compatible additives so that the catalytic system can effectively suppress the adhesion of ethylene oligomerization by-product polymers in the reactor without interfering with catalytic activity and selectivity for the target α-olefin has always been a challenge for those skilled in the art. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a catalytic system based on PNNP framework ligands. Applying this catalytic system to the preparation of α-olefins via ethylene oligomerization can reduce the adhesion of by-product polymers within the reactor.

[0006] In a first aspect of the invention, an ethylene oligomerization catalytic system capable of reducing polymer adhesion is provided, the catalytic system comprising a catalytic ligand, a transition metal compound, and a co-catalyst, wherein the structure of the catalytic ligand is shown in Formula I:

[0007] Furthermore, the catalytic system also includes an antistatic agent.

[0008] In some embodiments of the first aspect of the invention, the antistatic agent is selected from one or more of the following substances: 8168 ashless antistatic agent, DuPont 450 antistatic additive, PEG 200, and PEG 400.

[0009] In some embodiments of the first aspect of the present invention, the antistatic agent is 8168 ashless antistatic agent.

[0010] In some embodiments of the first aspect of the invention, the antistatic agent is DuPont 450 antistatic additive.

[0011] In some embodiments of the first aspect of the invention, the transition metal compound is selected from chromium trichloride, chromium trichloride tetrahydrofuran complex, chromium dichloride, chromium dichloride tetrahydrofuran complex, chromium acetylacetonate, chromium tri(2-ethylhexanoate), chromium methyl dichloride tetrahydrofuran complex, triphenylchromium tetrahydrofuran complex, and carbonyl chromium. Preferably, chromium trichloride tetrahydrofuran complex, chromium acetylacetonate, and chromium tri(2-ethylhexanoate) are selected.

[0012] In some embodiments of the first aspect of the present invention, the co-catalyst is an alkylaluminum co-catalyst or an organoboron co-catalyst, wherein the alkylaluminum co-catalyst is selected from one or more of trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, methylaluminoxane (MAO), modified methylaluminoxane (MMAO, triisobutylaluminum modified), ethylaluminoxane, isobutylaluminoxane, diethylaluminum chloride, ethylaluminum dichloride, and tris(pentafluorophenyl)aluminum; and the organoboron co-catalyst is selected from one or more of tris(pentafluorophenyl)boron, tetrafluoroborate, and tetra(pentafluorophenyl)boron.

[0013] In a second aspect of the invention, the application of the catalytic system described in the first aspect of the invention in the oligomerization of ethylene to prepare α-olefins is provided.

[0014] In a third aspect of the invention, a method for preparing α-olefins by ethylene oligomerization is provided, the method employing the catalytic system of the first aspect of the invention.

[0015] In some embodiments of the third aspect of the present invention, the method includes the following steps: In an ethylene atmosphere, the antistatic agent, co-catalyst, catalytic ligand and transition metal compound forming the main catalyst solution in the catalytic system are sequentially added to an organic solvent, and then hydrogen and ethylene are sequentially introduced to carry out an oligomerization reaction.

[0016] In some embodiments of the third aspect of the present invention, the initial concentration of the antistatic agent in the ethylene oligomerization reaction system is 3 to 30 mg / L, preferably 3 to 20 mg / L.

[0017] In some embodiments of the third aspect of the present invention, in the ethylene oligomerization reaction system, the initial molar concentration of the catalytic ligand is 0.002~1 mmol / L, the initial molar concentration of the transition metal compound is 0.002~1 mmol / L, and the initial molar concentration of the co-catalyst is 0.1~1000 mmol / L.

[0018] In some embodiments of the third aspect of the present invention, the temperature of the ethylene oligomerization reaction is 10~150 °C and the reaction pressure is 0.5~5 MPa.

[0019] In some embodiments of the third aspect of the invention, the organic solvent is selected from toluene, xylene, mesitylene, pentane, cyclopentane, methylcyclopentane, hexane, cyclohexane, methylcyclohexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, 1-hexene, 1-octene, 1-decene, dichloromethane, dichloroethane, chlorobenzene, o-dichlorobenzene, m-dichlorobenzene, and p-dichlorobenzene.

[0020] The present invention has the following beneficial technical effects compared with the prior art: This invention uses a PNNP framework ligand as the catalytic ligand for ethylene oligomerization, forming a catalytic system in situ with a transition metal compound, a co-catalyst, and an antistatic agent. This catalytic system, when used to catalyze ethylene oligomerization, effectively reduces the adhesion of by-product polymers within the reactor while maintaining high catalytic activity and high selectivity for 1-hexene and 1-octene. In exemplary embodiments of this invention, the catalytic activity is consistently above 5.8 × 10⁻⁶. 7 With a total selectivity of over 86% for 1-hexene and 1-octene (mol Cr·h), the amount of by-product polymer adhering to the reactor is as low as 0.02 wt%, which can effectively avoid blockage of the production equipment pipelines and avoid unplanned shutdowns for cleaning caused by by-product polymer adhesion, thus facilitating the long-term operation of industrial plants. Attached Figure Description

[0021] Figure 1 Nuclear magnetic resonance imaging of the PNNP framework ligand with the structure shown in Formula I in Embodiment 1 of the present invention. 31 P-spectrum.

[0022] Figure 2 This is a gas chromatogram of the ethylene oligomerization product in Example 3 of the present invention (internal standard is n-heptane).

[0023] Figure 3 This shows the polymer adhesion in the ethylene oligomerization reactor of Example 3 of the present invention after the reaction is completed and the reactor is opened.

[0024] Figure 4The polymer adhesion in the ethylene oligomerization reactor of Comparative Example 1 after the reaction is completed and the reactor is opened is shown. Detailed Implementation

[0025] The present invention will be described in detail below with reference to specific embodiments. These specific embodiments are only used to illustrate the present invention and do not constitute a limitation on the scope and substance of the present invention.

[0026] The catalytic system of the present invention is an ethylene oligomerization catalytic system designed based on a PNNP framework ligand with the structure shown in Formula I. This catalytic system is an in-situ catalytic system formed by the PNNP framework ligand, a transition metal compound, a co-catalyst, and an antistatic agent.

[0027] The transition metal compound in the catalytic system of this invention can be a metal precursor capable of forming a complex in situ with the PNNP skeleton ligand of this invention. For example, the transition metal compound may be selected from: chromium trichloride, chromium trichloride tetrahydrofuran complex, chromium dichloride, chromium dichloride tetrahydrofuran complex, chromium acetylacetonate, chromium tri(2-ethylhexanoate), chromium methyl dichloride tetrahydrofuran complex, triphenylchromium tetrahydrofuran complex, and carbonyl chromium, preferably chromium trichloride tetrahydrofuran complex, chromium acetylacetonate, and chromium tri(2-ethylhexanoate).

[0028] The cocatalyst in the catalytic system of this invention can be a cocatalyst capable of activating the complex formed by the PNNP framework ligand and the transition metal to generate an active center. For example, the cocatalyst can be an alkylaluminum cocatalyst or an organoboron cocatalyst. The alkylaluminum cocatalyst is selected from one or a mixture of several of trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, methylaluminoxane (MAO), modified methylaluminoxane (MMAO, triisobutylaluminum modified), ethylaluminoxane, isobutylaluminoxane, diethylaluminum chloride, ethylaluminum dichloride, and tris(pentafluorophenyl)aluminum; the organoboron cocatalyst is selected from one or a mixture of several of tris(pentafluorophenyl)boron, tetrafluoroborate, and tetra(pentafluorophenyl)borate.

[0029] To eliminate static electricity generated on the surface of particles in the catalytic system of this invention and its application in the ethylene oligomerization reaction system, this invention adds an antistatic agent to the catalytic system. By improving the conductivity of the medium, the electrostatic attraction between particles and between particles and the reactor wall is eliminated, thereby reducing the adhesion of by-product polymers to the surfaces of internal components of the ethylene oligomerization reactor. In this invention, "adhesion" refers to the attachment, deposition, and scaling of by-product polymers from ethylene oligomerization on the surfaces of internal reactor components (including the agitator, inner coil, thermometer, and reactor wall).

[0030] Regarding the selection of the antistatic agent in the catalytic system of this invention, on the one hand, it should be compatible with other components in the catalytic system to avoid affecting catalytic activity; for example, it should avoid harmful reactions with ligands, co-catalysts, and transition metal compounds. On the other hand, the antistatic agent or its decomposition products should not contaminate the target α-olefin product (e.g., 1-hexene and 1-octene). Furthermore, the antistatic agent should remain stable under ethylene oligomerization conditions and not decompose to produce harmful substances. The antistatic agent of this invention can be selected from one or more of the following substances in combination: 8168 ashless antistatic agent, DuPont 450 antistatic additive, PEG200, PEG 400, preferably 8168 ashless antistatic agent.

[0031] When the catalytic system of the present invention is used for ethylene oligomerization, the antistatic agent in the catalytic system can be added to the reaction solvent before other components. Furthermore, the antistatic agent is added to the reaction system in the form of a solution, and the solvent is the reaction solvent for ethylene oligomerization.

[0032] When the catalytic system of the present invention is used for the oligomerization of ethylene to prepare α-olefins, the ratio of the PNNP backbone ligand to the co-catalyst, transition metal compound, and antistatic agent in the catalytic system can be controlled within a suitable range. Specifically, in the ethylene oligomerization reaction system, the initial molar concentration of the PNNP backbone ligand can be controlled at 0.002~1 mmol / L, preferably 0.005~0.1 mmol / L; the molar concentration of the transition metal compound is 0.002~1 mmol / L, preferably 0.005~0.1 mmol / L; and the molar concentration of the co-catalyst is 0.1~1000 mmol / L, preferably 2.5~50 mmol / L. The initial concentration of the antistatic agent in the reaction system can be controlled at 3~30 mg / L, preferably 3~20 mg / L.

[0033] When using the catalytic system of the present invention to prepare α-olefins by ethylene oligomerization, the temperature of the oligomerization reaction is 10~150 °C, preferably 30~80 °C, more preferably 40~50 °C; the pressure of the oligomerization reaction is 0.5~5 MPa, preferably 3~5 MPa.

[0034] The ethylene oligomerization solvent of the present invention is selected from toluene, xylene, mesitylene, pentane, cyclopentane, methylcyclopentane, hexane, cyclohexane, methylcyclohexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, 1-hexene, 1-octene, 1-decene, dichloromethane, dichloroethane, chlorobenzene, o-dichlorobenzene, m-dichlorobenzene, and p-dichlorobenzene.

[0035] The various aspects of the present invention will be further described in detail below through specific embodiments.

[0036] Example 1 1. Preparation of ligands for ethylene oligomerization catalysis: The catalytic system in this embodiment uses a PNNP framework ligand with the structure shown in Formula I, and uses Ph2PCH2CH2NH2 and o-dibromobenzene as raw materials. i The reaction proceeds under the action of Pr2EtN, and the synthetic route is as follows:

[0037] Specifically, an anhydrous and oxygen-free operating system, namely the Schlenk double-row system, was used. Ph₂PCH₂CH₂NH₂ (2.30 g, 10 mmol) and o-dibromobenzene (1.18 g, 5 mmol) were added in a round-bottom flask. i Pr₂EtN (1.7 mL, 10 mmol) was mixed thoroughly and refluxed with stirring at 138 °C for 5 h. Subsequently, it was cooled to room temperature and extracted with a mixture of deionized water (20 mL) and dichloromethane (15 mL). KOH (0.5 M, 15 mL) solution was added to the aqueous phase, followed by extraction with dichloromethane (15 mL). The combined organic phases were dried over anhydrous MgSO₄ and filtered through diatomaceous earth. Volatile substances were then removed by rotary evaporation. The residual solid was recrystallized in ethanol to give the product, weighing 1.48 g (56% yield). The structure of this product was determined by... 31 PNMR characterization and its preparation process confirmed that it is the target ligand shown in Formula I. 31 P spectrum as shown Figure 1 As shown.

[0038] The NMR data are as follows: 31 P NMR (162 MHz, C6D6): -21.65. 2. Ethylene oligomerization: In this embodiment, the ethylene oligomerization utilizes an in-situ catalytic system composed of a PNNP ligand, a transition metal compound, a co-catalyst, and an antistatic agent. Specifically, the ligand is a PNNP ligand with the structure shown in Formula I, the transition metal compound is chromium acetylacetone, the co-catalyst is MMAO-3A, ​​and the antistatic agent is 8168 ashless antistatic agent. The specific operation of the ethylene oligomerization reaction using this catalytic system is as follows: Catalyst pre-preparation: 66.6 mg of PNNP ligand with the structure shown in Formula I and 44 mg of chromium acetylacetone (a transition metal compound) were dissolved in 100 mL of methylcyclohexane solution to obtain a main catalyst solution with a concentration of 1.25 mmol / L; 50 mg of ashless antistatic agent 8168 produced by Innospec was dissolved in 100 mL of methylcyclohexane solution to obtain an antistatic agent solution with a concentration of 0.5 mg / mL.

[0039] After the 1L high-pressure reactor was installed and debugged, it was preheated to 120℃, vacuum dried for 5 hours, purged with ethylene gas three times, and then cooled to room temperature. 160 mL of dry methylcyclohexane was added as the reaction solvent, and the stirring speed was controlled at 200 rpm. Then, the following components were added to the reactor in sequence: (1) 10 mL of methylcyclohexane dilution containing 1.2 mL (0.5 mg / mL) 8168 ashless antistatic agent methylcyclohexane solution, so that the initial concentration of 8168 ashless antistatic agent in the reaction system is 3 mg / L; (2) 10 mL of methylcyclohexane dilution containing 0.39 g MMAO-3A (7wt% Al, methylcyclohexane solution, co-catalyst) to make the initial concentration of MMAO-3A in the reaction system 5 mmol / L; (3) 20 mL of methylcyclohexane dilution containing 1.6 mL (1.25 mmol / L) of the main catalyst (PNNP structure ligand and transition metal compound) so that the initial concentration of the ligand in the reaction system is 0.01 mmol / L and the initial concentration of chromium acetylacetone is 0.01 mmol / L.

[0040] Subsequently, the mixture was rapidly heated to 45 °C, and hydrogen was first introduced to 0.1 MPa, followed by ethylene to 4.5 MPa. The stirring rate was 200 rpm, and the mixture was maintained for 90 min.

[0041] After the reaction is complete, stop the ethylene supply, rapidly cool the reaction system to 10 °C, slowly depressurize, and discharge the liquid material mixed with polymer particles from the bottom valve of the reactor, weighing it. Add 2 mL of isooctanol to quench the reaction, let it stand for 30 minutes, take 10 g of the supernatant, add 2 g of n-heptane internal standard, dry with anhydrous Na₂SO₄, and perform gas chromatography analysis to obtain the mass of the liquid product and the selectivity of each component. In addition, filter out the settled polymer particles, air-dry them in a fume hood, and then dry them in a 100 °C oven to constant weight before weighing. Collect the polymer adhering to the internal components of the reactor (including the stirrer, inner coil, thermometer, and inner wall), air-dry them in a fume hood, and then dry them in a 100 °C oven to constant weight before weighing. The total product mass includes the sum of the liquid product mass and the polymer adhering to the reactor. The by-product polymer mass includes both the polymer adhering to the internal components of the reactor and the polymer particles mixed in the liquid material. The total amount of by-product polymer generated in the ethylene oligomerization product is the ratio of the mass of the two solid polymers to the mass of the total product. In this example, the total amount of polymer generated is 0.10 wt%, of which the adhesive polymer is 0.04 wt%. The results are summarized in Table 1.

[0042] The catalyst activity was calculated to be 7.2 × 10⁻⁶ using gas chromatography with internal standard method. 7 g / (mol Cr·h), the total selectivity of 1-hexene and 1-octene was 86.4%, and the specific composition of the ethylene oligomers is recorded in Table 1.

[0043] Example 2 The difference between Example 2 and Example 1 is that the amount of 8168 ashless antistatic agent added to the catalytic system is 10 mL of a methylcyclohexane dilution containing 2 mL (0.5 mg / mL) of 8168 ashless antistatic agent methylcyclohexane solution, that is, the initial concentration of 8168 ashless antistatic agent in the reaction system is 5 mg / L, and other conditions are the same as in Example 1.

[0044] Quantitative analysis using gas chromatography with internal standard method yielded a catalyst activity of 7.0 × 10⁻⁶ for the oligomerization of ethylene to prepare α-olefins using the catalytic system of this embodiment. 7 g / (mol Cr·h), the total selectivity of 1-hexene and 1-octene was 86.6%, and the specific composition of the ethylene oligomers is recorded in Table 1.

[0045] Furthermore, in the ethylene oligomerization product of this embodiment, the total amount of by-product polymer generated was 0.09 wt%, of which the amount of solid polymer (i.e., adhesive polymer) remaining in the reactor was 0.02 wt%. These results are summarized in Table 1.

[0046] Example 3 The difference between Example 3 and Example 1 is that the amount of 8168 ashless antistatic agent added to the catalytic system is 10 mL of a methylcyclohexane dilution containing 4 mL (0.5 mg / mL) of 8168 ashless antistatic agent methylcyclohexane solution, and the initial concentration of 8168 ashless antistatic agent in the reaction system is 10 mg / L. Other conditions are the same as in Example 1.

[0047] Quantitative analysis using gas chromatography with internal standard method yielded a catalyst activity of 6.9 × 10⁻⁶ for the oligomerization of ethylene to prepare α-olefins using the catalytic system of this embodiment. 7 The total selectivity for 1-hexene and 1-octene was 86.6% (g / (mol Cr·h)). The specific composition of the ethylene oligomer is recorded in Table 1. The gas chromatographic quantitative analysis chromatogram of the liquid fraction of the ethylene oligomer is shown in the figure. Figure 2 As shown.

[0048] Furthermore, in the ethylene oligomerization product of this embodiment, the total amount of by-product polymer generated was 0.08 wt%, of which the amount of solid polymer remaining in the reactor (i.e., adhered polymer) was 0.02 wt%. These results are summarized in Table 1. The adhesion of the solid polymer in the reactor after opening is as follows: Figure 3 As shown.

[0049] Example 4 The difference between Example 4 and Example 1 is that the amount of 8168 ashless antistatic agent added to the catalytic system is 10 mL of a methylcyclohexane dilution containing 8 mL (0.5 mg / mL) of 8168 ashless antistatic agent methylcyclohexane solution, that is, the initial concentration of 8168 ashless antistatic agent in the reaction system is 20 mg / L, and other conditions are the same as in Example 1.

[0050] Quantitative analysis using gas chromatography with internal standard method yielded a catalyst activity of 6.5 × 10⁻⁶ for the oligomerization of ethylene to prepare α-olefins using the catalytic system of this embodiment. 7 g / (mol Cr·h), the total selectivity of 1-hexene and 1-octene was 86.7%, and the specific composition of the ethylene oligomers is recorded in Table 1.

[0051] Furthermore, in the ethylene oligomerization product of this embodiment, the total amount of by-product polymer generated was 0.11 wt%, of which the amount of solid polymer (i.e., adhesive polymer) remaining in the reactor was 0.03 wt%. These results are summarized in Table 1.

[0052] Example 5 The difference between Example 5 and Example 1 is that the antistatic agent in the catalytic system is replaced with DuPont 450 antistatic additive, and the amount added is 10 mL of a methylcyclohexane dilution containing 2 mL (0.5 mg / mL) of DuPont 450 antistatic agent methylcyclohexane solution. That is, the initial concentration of DuPont 450 antistatic agent in the reaction system is 5 mg / L. Other conditions are the same as in Example 1.

[0053] Quantitative analysis using gas chromatography with internal standard method yielded a catalyst activity of 6.2 × 10⁻⁶ for the oligomerization of ethylene to prepare α-olefins using the catalytic system of this embodiment. 7 g / (mol Cr·h), the total selectivity of 1-hexene and 1-octene was 86.8%, and the specific composition of the ethylene oligomers is recorded in Table 1.

[0054] Furthermore, in the ethylene oligomerization product of this embodiment, the total amount of by-product polymer generated was 0.08 wt%, of which the amount of solid polymer (i.e., adhesive polymer) remaining in the reactor was 0.05 wt%. These results are summarized in Table 1.

[0055] Example 6 The difference between Example 6 and Example 5 is that the amount of DuPont 450 antistatic additive added to the catalytic system is 10 mL of a methylcyclohexane dilution containing 4 mL (0.5 mg / mL) of DuPont 450 antistatic agent methylcyclohexane solution, that is, the initial concentration of DuPont 450 antistatic agent in the reaction system is 10 mg / L, and other conditions are the same as in Example 5.

[0056] Quantitative analysis using gas chromatography with internal standard method yielded a catalyst activity of 5.8 × 10⁻⁶ for the oligomerization of ethylene to prepare α-olefins using the catalytic system of this embodiment. 7 g / (mol Cr·h), the total selectivity of 1-hexene and 1-octene was 86.6%, and the specific composition of the ethylene oligomers is recorded in Table 1.

[0057] Furthermore, in the ethylene oligomerization product of this embodiment, the total amount of by-product polymer generated was 0.10 wt%, of which the amount of solid polymer (i.e., adhesive polymer) remaining in the reactor was 0.04 wt%. These results are summarized in Table 1.

[0058] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that no antistatic agent was added to the catalytic system of Comparative Example 1, while all other conditions were the same as those of Example 1.

[0059] Quantitative analysis using gas chromatography with internal standard method showed that the catalyst activity for the preparation of α-olefins via ethylene oligomerization using the catalytic system of Comparative Example 1 was 7.5 × 10⁻⁶. 7 g / (mol Cr·h), the total selectivity of 1-hexene and 1-octene was 86.5%, and the specific composition of the ethylene oligomers is recorded in Table 1.

[0060] In addition, in the ethylene oligomerization product of Comparative Example 1, the total amount of by-product polymer generated was 0.09 wt%, of which the amount of solid polymer (i.e., adhesive polymer) remaining in the reactor was 0.07 wt%. These results are summarized in Table 1.

[0061] After the ethylene oligomerization reaction is completed and the reactor is opened, the adhesion of the polymer inside the reactor is as follows: Figure 4 As shown in the figure, flocculent and scaling polymers can be observed in the inner coil and agitator of the reactor, and their quantity is significantly greater than in the example where an antistatic agent is used in the catalytic system.

[0062] Table 1: Catalytic reaction results of the catalytic systems in Examples 1-6 and Comparative Example 1

[0063] As shown in Table 1, the in-situ catalytic system composed of the PNNP ligand with the structure shown in Formula I, a transition metal compound, a co-catalyst, and an antistatic agent, can effectively reduce the amount of scaling polymers generated in the ethylene oligomerization products while maintaining high activity and selectivity in catalyzing the oligomerization of ethylene to prepare 1-hexene and 1-octene. The catalytic activity is consistently above 5.8 × 10⁻⁶. 7 The total selectivity for 1-hexene and 1-octene both exceeded 86%, and the amount of adhesive polymer generated was less than 0.05 wt%.

[0064] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0065] The above embodiments are only used to illustrate the technical solutions of the present invention and should not be used to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments or equivalent substitutions can be made to some of the technical features without departing from the essence and scope of the present invention. Such modifications or equivalent substitutions still fall within the scope of the present invention.

Claims

1. An ethylene oligomerization catalytic system for reducing polymer adhesion, the catalytic system comprising a catalytic ligand, a transition metal compound, and a co-catalyst, characterized in that, The structure of the catalytic ligand is shown in Formula I: Furthermore, the catalytic system also includes an antistatic agent.

2. The catalytic system as described in claim 1, wherein, The antistatic agent is selected from one or more of the following substances: 8168 ashless antistatic agent, DuPont 450 antistatic additive, PEG 200, and PEG 400.

3. The catalytic system as described in claim 1, wherein, The antistatic agent is 8168 ashless antistatic agent.

4. The catalytic system as described in claim 1, wherein, The antistatic agent is DuPont 450 antistatic additive.

5. The catalytic system as described in claim 1, wherein, The transition metal compound is selected from chromium trichloride, chromium trichloride tetrahydrofuran complex, chromium dichloride, chromium dichloride tetrahydrofuran complex, chromium acetylacetone, chromium tri(2-ethylhexanoate), chromium methyl dichloride tetrahydrofuran complex, triphenylchromium tetrahydrofuran complex, and carbonyl chromium.

6. The catalytic system as described in claim 1, wherein, The cocatalyst is an alkylaluminum cocatalyst or an organoboron cocatalyst. The alkylaluminum cocatalyst is selected from one or more of trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, methylaluminoxane (MAO), modified methylaluminoxane (MMAO, triisobutylaluminum modified), ethylaluminoxane, isobutylaluminoxane, diethylaluminum chloride, ethylaluminum dichloride, and tris(pentafluorophenyl)aluminum. The organoboron cocatalyst is selected from one or more of tris(pentafluorophenyl)boron, tetrafluoroborate, and tetra(pentafluorophenyl)boron.

7. The application of the catalytic system according to any one of claims 1 to 6 in the preparation of α-olefins by ethylene oligomerization.

8. A method for preparing α-olefins via ethylene oligomerization, characterized in that, The method employs the catalytic system as described in any one of claims 1 to 6.

9. The method of claim 8, wherein, The method includes the following steps: In an ethylene atmosphere, the antistatic agent, co-catalyst, catalytic ligand and transition metal compound forming the main catalyst solution in the catalytic system are sequentially added to an organic solvent, and then hydrogen and ethylene are sequentially introduced to carry out an oligomerization reaction.

10. The method of claim 9, wherein, The initial concentration of the antistatic agent in the ethylene oligomerization reaction system is 3~30 mg / L.

11. The method of claim 10, wherein, The initial concentration of the antistatic agent in the ethylene oligomerization reaction system is 3~20 mg / L.

12. The method of claim 9, wherein, In the ethylene oligomerization reaction system, the initial molar concentration of the catalytic ligand is 0.002~1 mmol / L, the initial molar concentration of the transition metal compound is 0.002~1 mmol / L, and the initial molar concentration of the co-catalyst is 0.1~1000 mmol / L.

13. The method of claim 9, wherein, The temperature for ethylene oligomerization is 10~150 ℃, and the reaction pressure is 0.5~5 MPa.

14. The method according to claim 9, wherein, The organic solvent is selected from one of toluene, xylene, mesitylene, pentane, cyclopentane, methylcyclopentane, hexane, cyclohexane, methylcyclohexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, 1-hexene, 1-octene, 1-decene, dichloromethane, dichloroethane, chlorobenzene, o-dichlorobenzene, m-dichlorobenzene, and p-dichlorobenzene.

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