Method for reducing polymer adhesion in ethylene oligomerization

Abstract

The invention provides a method for reducing polymer adhesion in ethylene oligomerization. According to the method, a double-kettle series polymerization process is adopted, a phosphine-nitrogen ligand, a chromium metal compound and a cocatalyst are added into a first reaction kettle, a nucleating agent is added into a second reaction kettle, the reaction is carried out in the first reaction kettle in the early stage and transferred to the second reaction kettle in the later stage for continuous reaction, oligomer is converted into high polymer through the nucleating agent, and the high polymer is stored in a particle form; therefore, the phenomenon that the oligomer winds the stirring paddle is reduced or avoided, the aggregation of the polymer in the reaction kettle is greatly reduced, and the operation time of the device is prolonged. The catalytic system can catalyze the ethylene oligomerization reaction with high activity, the catalytic activity reaches up to 10 * 10 < 6 > g product / (molCr.h), the overall selectivity of 1-hexene and 1-octene with high added values can reach 90% or above, and the phenomenon that a polymer is hung on a stirring paddle is greatly reduced.

Description

Technical Field

[0001] The invention belongs to the field of ethylene oligomerization catalysis and relates to a method for reducing polymer adhesion in ethylene oligomerization. Background Art

[0002] Linear α-olefins are an important type of industrial raw materials, widely used in many fields such as plasticizers, fatty acids, lubricant additives, polyolefins, etc. This year, with the structural upgrade of polyolefin products, high-carbon α-olefins (mainly 1-hexene and 1-octene) have received more and more attention. 1-Hexene and 1-octene are important raw materials for the development of high-end polyolefin products. As comonomers, polyethylene products produced by them have better impact resistance, tear strength and other properties. At present, the industrial production of α-olefins is still mainly based on ethylene polymerization, and the product supply mainly comes from Europe and the United States. Domestic olefins such as 1-octene are completely dependent on imports.

[0003] Sasol first disclosed the Cr / PNP / MAO catalytic system (J.AM.CHEM.SOC.2004,126,14712-14713) that can realize the tetramerization of ethylene to produce 1-octene, and achieved industrial production in 2014. The core of the ethylene tetramerization catalytic system is the PNP ligand. Researchers from relevant universities, enterprises, etc. have conducted a series of studies on the PNP ligand, and a large number of articles and patents have been reported. Patents CN104220402A, CN1160700A, CN1993180A, US20150080629A1, etc. report various improved PNP ligand compounds. Patents CN101605605A, US8609924B2, etc. disclose a method for preparing 1-octene by tetramerization of ethylene using a chromium catalyst containing a PCCP skeleton structure ligand. Under the same conditions, the polymerization activity is higher than that of the PNP ligand, but there is still a problem of a small amount of polymer enriched in the reactor. Patent CN105693488A discloses a multi-reactor series process for ethylene polymerization, which pre-reacts at a relatively low temperature, and introduces the reaction materials into a second reactor when the activity begins to decrease. This can avoid catalyst deactivation caused by high reaction activity in the early stage of the reaction, thereby improving catalytic efficiency.

[0004] The biggest difficulty in the industrial application of ethylene polymerization is the accumulation of polymers during the polymerization process, which affects the long-term operation of the device. The existing polymerization catalysts such as PNP and PCCP will produce a small amount of polymers during the reaction process, which will accumulate in the reactor and pipelines, seriously affecting the heat transfer of the reactor or blocking the pipeline. Summary of the invention

[0005] One of the purposes of the present invention is to provide a method for reducing polymer adhesion in ethylene oligomerization. The method can convert oligomers into polymers while ensuring high catalyst activity, store them in the form of particles, and flow out with the solvent, thereby reducing or avoiding oligomer entanglement with the stirring blade, greatly reducing polymer aggregation in the reactor, and extending the operating time of the device, making it more conducive to industrial continuous production.

[0006] In order to achieve the above invention objectives, this application adopts the following technical solutions:

[0007] A method for reducing polymer adhesion in ethylene polymerization, the method adopts a double-kettle series polymerization process, a phosphine-nitrogen ligand, a chromium compound and a promoter are added to the first reactor, a nucleating agent is added to the second reactor, the reaction is carried out in the first reactor in the early stage, and the reaction is transferred to the second reactor in the later stage to continue, the oligomer is converted into a polymer by the nucleating agent, and the polymer is stored in the form of particles and flows out with the solvent.

[0008] In view of the problems existing in the prior art, the present invention introduces a nucleating agent in combination with a double-reactor series process. The polymer in the reactor is converted into particles by adding a nucleating agent into the second reactor, thereby avoiding or greatly reducing the traditional phenomenon of polymer enrichment on the reactor wall or the stirring paddle, ensuring the long-term stable operation of the device, and providing a solution for industrial production.

[0009] In one embodiment of the present invention, the phosphine-nitrogen ligand structure is shown in the following formula I:

[0010]

[0011] Wherein, R1, R2, R3, and R4 are each independently selected from one of alkyl, aryl, substituted alkyl, and substituted aryl; preferably, R1, R2, R3, and R4 are each independently selected from one of C2-C9 alkyl, aryl, substituted alkyl, and substituted aryl; more preferably, R1, R2, R3, and R4 are each independently selected from phenyl, benzyl, biphenyl, naphthyl, anthracenyl, vinyl, propenyl, isopropyl, tert-butyl, cyclohexyl, 4-methylcyclohexyl, 4-ethylcyclohexyl, 4-isopropylcyclohexyl, 2-methylphenyl, 4-methylphenyl, 2,4-dimethylphenyl, 2,6-dimethylphenyl, 2-ethylphenyl, 4-ethylphenyl, 2,4-diethylphenyl, 2,6-diethylphenyl, 2-isopropylphenyl , 4-isopropylphenyl, 2,4-diisopropylphenyl, 2,6-diisopropylphenyl, 2-butylphenyl, 4-butylphenyl, 2,4-dibutylphenyl, 2,6-dibutylphenyl, 4-methoxyphenyl, o-methoxyphenyl, 4-ethoxyphenyl, o-ethoxyphenyl, 2-(trimethylsilyl)phenyl, 3-(trimethylsilyl)phenyl, 4-(trimethylsilyl)phenyl, 2-fluorophenyl, 3-fluorophenyl, 4-fluorophenyl, 2-(trifluoromethyl)phenyl, 3-(trifluoromethyl)phenyl, 4-(trifluoromethyl)phenyl, 3,5-bis(trifluoromethyl)phenyl, 2-(tri-n-butylsilyl)phenyl, 3-(tri-n-butylsilyl)phenyl, 4-(tri-n-butylsilyl)phenyl.

[0012] In one embodiment of the present invention, the chromium compound is selected from one or more of organic salts, inorganic salts, coordination complexes, and organometallic complexes of chromium, preferably one or more of chromium acetylacetonate, chromium hexacarbonyl, chromium chloride, chromium (III) octoate, and tri(tetrahydrofuran)chromium trichloride.

[0013] In one embodiment of the present invention, the nucleating agent is selected from organic nucleating agents and / or inorganic nucleating agents, preferably at least one of carboxylic acid metal salts, phosphonic acid metal salts, sorbitol benzyl derivatives, and inorganic compounds, and more preferably at least one of sorbitol acetal, sorbitol, p-hydroxybenzoic acid, poly 4-methoxy-4′-acryloxybenzoic acid phenyl ester liquid crystal, stearate, and talc.

[0014] In one embodiment of the present invention, the co-catalyst is an alkyl aluminum co-catalyst, and the co-catalyst is preferably selected from at least one of trimethyl aluminum, triethyl aluminum, trioctylaluminum, triisobutyl aluminum, methylaluminoxane (MAO), modified methylaluminoxane (MMAO), and ethylaluminoxane, and more preferably methylaluminoxane and / or modified methylaluminoxane.

[0015] In one embodiment of the present invention, the molar ratio of the chromium compound to the phosphine-nitrogen ligand is 1:0.8-5, preferably 1:1-2.

[0016] In one embodiment of the present invention, the amount of the nucleating agent added is 0.1%-1% by mass of the reaction solvent, preferably 0.2%-0.6% by mass.

[0017] In one embodiment of the present invention, the molar ratio of the promoter to the chromium compound is 50-2000:1, preferably 100-1000:1.

[0018] In one embodiment of the present invention, the preparation method of the phosphine-nitrogen ligand in formula I is:

[0019] After dissolving N1,N3-dimethylbenzene-1,3-diamine, adding a tertiary fatty amine compound, and then adding the compound of formula II, reacting to obtain the phosphine-nitrogen ligand;

[0020]

[0021] wherein R1, R2, R3, and R4 are each independently selected from an alkyl group, an aryl group, a substituted alkyl group, and a substituted aryl group; preferably, R1, R2, R3, and R4 are each independently selected from an alkyl group, an aryl group, a substituted alkyl group, and a substituted aryl group of C2-C9; more preferably, R1, R2, R3, and R4 are each independently selected from a phenyl group, a benzyl group, a biphenyl group, a naphthyl group, an anthracenyl group, a vinyl group, a propenyl group, an isopropyl group, a tert-butyl group, a cyclohexyl group, a 4-methylcyclohexyl group, a 4-ethylcyclohexyl group, a 4-isopropylcyclohexyl group, a 2-methylphenyl group, a 4-methylphenyl group, a 2,4-dimethylphenyl group, a 2,6-dimethylphenyl group, a 2-ethylphenyl group, a 4-ethylphenyl group, a 2,4-diethylphenyl group, a 2,6-diethylphenyl group, a 2-isopropylphenyl group, a 4-isopropylphenyl group, a 2,4-diisopropylphenyl group, a 2,6-diisopropylphenyl group, a -butylphenyl, 4-butylphenyl, 2,4-dibutylphenyl, 2,6-dibutylphenyl, 4-methoxyphenyl, o-methoxyphenyl, 4-ethoxyphenyl, o-ethoxyphenyl, 2-(trimethylsilyl)phenyl, 3-(trimethylsilyl)phenyl, 4-(trimethylsilyl)phenyl, 2-fluorophenyl, 3-fluorophenyl, 4-fluorophenyl, 2-(trifluoromethyl)phenyl, 3-(trifluoromethyl)phenyl, 4-(trifluoromethyl)phenyl, 3,5-bis(trifluoromethyl)phenyl, 2-(tri-n-butylsilyl)phenyl, 3-(tri-n-butylsilyl)phenyl, 4-(tri-n-butylsilyl)phenyl; preferably, the molar ratio of N1,N3-dimethylbenzene-1,3-diamine, tertiary fatty amine compound and compound of formula II is 1:(1.5-3.5):(2.1-3.6).

[0022] In one embodiment of the present invention, the tertiary fatty amine compound is a C3-C15 tertiary fatty amine compound, preferably triethylamine and / or tripropylamine.

[0023] In one embodiment of the present invention, the solvent is selected from one or more of halogenated hydrocarbons, nitrile compounds, alkanes, and aromatic solvents, preferably one or more of dichloromethane, acetonitrile, n-hexane, n-heptane, and toluene.

[0024] In one embodiment of the present invention, the preparation method is carried out at -10 to 0°C for 8 to 30 hours.

[0025] In one embodiment of the present invention, the reaction temperature of the first reactor is 35-80°C, and the temperature of the second reactor is set to be 5-15°C higher than that of the first reactor.

[0026] In one embodiment of the present invention, hydrogen is introduced into the first reactor to carry out the polymerization reaction under an ethylene pressure of 2MPa-7MPa.

[0027] In one embodiment of the present invention, after the first reactor reacts for 15-60 minutes, the reaction solution is transferred to the second reactor and continues to react for 20-50 minutes.

[0028] In a more specific embodiment, the polymerization method of the catalyst composition of the present invention is as follows: preferably, both of the two kettles in series are stainless steel reactors, and refined methylcyclohexane or toluene is used as a solvent. The reactor is equipped with a pressure gauge and a thermocouple, mechanical stirring is adopted, and electric heating is equipped, and the temperature is controlled by circulating water in the cooling jacket. Before the reaction, the required reactor needs to be heated to 110-130°C, preferably about 120°C, and vacuumed for 2-4h, during which nitrogen is replaced three times, and then vacuumed and hydrogen is replaced three times. When the temperature is cooled to room temperature, the passage between the two kettles is closed, and the circulating oil bath temperature of the first reactor is set to 35-80°C, and the temperature of the second reactor is 5-15°C higher than that of the first reactor. The first reactor is sequentially added with a dehydrated and deoxygenated solvent and a quantitative alkyl aluminum cocatalyst, and the molar ratio of the alkyl aluminum cocatalyst / chromium compound is preferably 100:1-1000:1, stirring is turned on, and a nucleating agent is pre-added to the second reactor. After the temperature is constant, add the pre-configured phosphine-nitrogen ligand / chromium compound mixed solution into the first reactor, introduce hydrogen at 0.3-0.8Mpa, and carry out polymerization reaction at a temperature of 40-60°C and an ethylene pressure of 2MPa-6MPa. After the first reactor reacts for 15min-60min, the reaction liquid is transferred to the second reactor and continues to react for 20-50min, then the ethylene inlet valve is closed, the temperature is rapidly reduced with a low-temperature circulating water bath, the pressure is slowly released, and the reactor is unloaded to obtain the ethylene polymerization product.

[0029] Another object of the present invention is to provide an oligomeric polyethylene.

[0030] A kind of oligomeric polyethylene, which is prepared by the above-mentioned catalytic method, and contains a nucleating agent component; preferably, the nucleating agent is selected from organic nucleating agents and / or inorganic nucleating agents, preferably at least one of carboxylic acid metal salts, phosphonic acid metal salts, sorbitol benzyl derivatives, and inorganic compounds, and more preferably at least one of sorbitol acetal, sorbitol, p-hydroxybenzoic acid, poly 4-methoxy-4′-acryloxybenzoic acid phenyl ester liquid crystal, stearate, and talc; preferably, based on the mass of the oligomeric polyethylene, the proportion of the nucleating agent is 0.02%-10% of the mass of the polyethylene, preferably 0.1%-5%.

[0031] Unless otherwise specified in the present invention, the pressures described are gauge pressures.

[0032] The ethylene oligomerization catalyst composition and polymerization method of the present invention have the following positive effects:

[0033] (1) The double reactor series process is adopted. The first reactor can ensure the high activity of the catalyst, and the nucleating agent in the second reactor can convert the oligomer into a polymer, which is stored in the form of particles and flows out with the solvent, thereby reducing or avoiding the entanglement of the oligomer with the stirring paddle, greatly reducing the aggregation of polymers in the reactor, and extending the operation time of the device, making it more conducive to industrial continuous production.

[0034] (2) The activity of the catalyst composition of the present invention for ethylene polymerization can reach 10×10 6 g product / (mol Cr·h), the total selectivity of 1-hexene and 1-octene is greater than 90%, the polymer adhesion phenomenon is greatly reduced, and the economic added value is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Attached Figure 1 This is the product adhesion condition after the second reactor of Example 2 was opened;

[0036] Attached Figure 2 This is the product adhesion situation after the second reaction kettle of Comparative Example 2 was opened. DETAILED DESCRIPTION

[0037] The following specific embodiments are only used to illustrate the present invention, but these examples are only part of the present invention and do not limit the application of the present invention in other fields.

[0038] Raw material source information:

[0039] N1, N3-dimethylbenzene-1, 3-diamine: 98%, Shanghai Xinkai Pharmaceutical Technology Co., Ltd.

[0040] Triethylamine: ≥99.5% (GC), Shanghai Aladdin Biochemical Technology Co., Ltd.

[0041] Tripropylamine: ≥99.5% (GC), Shanghai Aladdin Biochemical Technology Co., Ltd.

[0042] Diphenylphosphine chloride: 97%, Alfa Aesar (China) Chemicals Co., Ltd.

[0043] Dichloromethane: 99.5%, Shanghai Aladdin Biochemical Technology Co., Ltd.

[0044] Acetonitrile: 99.5%, Beijing Bailingwei Technology Co., Ltd.

[0045] 4-(Tri-n-butylsilyl)phenylphosphine chloride: 97%, Jiangsu Xinnok Catalyst Co., Ltd.

[0046] Ethyl acetate: 99.9%, Bailingwei Technology Co., Ltd.

[0047] Ethanol: analytical grade, Sinopharm Chemical Reagent Co., Ltd.

[0048] MMAO-3a (modified methylaluminoxane): concentration 7wt% Al, n-heptane solvent, Nouryon Chemicals (Ningbo) Co., Ltd.

[0049] MAO (methylaluminoxane), concentration 10wt%, toluene solvent, Nouryon Chemicals (Ningbo) Co., Ltd.

[0050] Chromium chloride tetrahydrofuran: 98%, Beijing Bailingwei Technology Co., Ltd.

[0051] Chromium acetylacetonate: 98%, Shanghai MacLean Biochemical Technology Co., Ltd.

[0052] (1,3:2,4)-Dibenzylidene sorbitol: >95%, Jiangsu Aikang Biopharmaceutical Research and Development Co., Ltd.

[0053] (1,3:2,4)-bis(3,4-dimethylbenzylidene) sorbitol: 99%, Shanghai MacLean Biochemical Technology Co., Ltd.

[0054] Paraben: 99.5%, Shanghai MacLean Biochemical Technology Co., Ltd.

[0055] Poly (4-methoxy-4′-acryloyloxybenzoic acid phenyl ester) liquid crystal: 99%, Jiangsu Xinnok Catalyst Co., Ltd.

[0056] Zinc stearate: analytical grade, Chengdu Dianchun Technology Co., Ltd.

[0057] 1,3:2,4-Di(p-methylbenzylidene)sorbitol: 99%, Shanghai MacLean Biochemical Technology Co., Ltd.

[0058] Instrument information:

[0059] NMR model: BRUKER AVANCE 400, manufacturer: Bruker, Switzerland.

[0060] The catalyst activity of the oligomerization reaction was determined by qualitative and quantitative analysis of the components in the reaction solution. The conditions of the GC analysis instrument used were as follows:

[0061] Instrument model: Shimadzu GC2010

[0062] Chromatographic column: DB-5 (30m 0.25mm 0.25μm)

[0063] Column temperature program: first maintain at 35°C for 10 min, then increase to 250°C at a rate of 10°C / min, and maintain at this temperature for 10 min.

[0064] Detector temperature: 300°C

[0065] Carrier gas: 1 bar

[0066] Air: 0.3 bar

[0067] Gas (H2): 0.3 bar

[0068] Product quality analysis is carried out using the internal standard method:

[0069]

[0070] Where m1 is the mass of a product, m is the mass of the internal standard, a1 is the peak area of ​​the product detected in the gas chromatograph, and a is the peak area of ​​the internal standard. k is a correction factor related to the substance being measured and the detection conditions.

[0071] Example 1

[0072] Preparation of phosphine-nitrogen ligand: Under anhydrous and oxygen-free conditions, 100mmol N1,N3-dimethylbenzene-1,3-diamine was dissolved in 200ml acetonitrile; 220mmol triethylamine was added dropwise to the reaction solution under stirring at -9°C, and 110mmol diphenylphosphine chloride was slowly added thereto. When the solution was stable and no longer released heat, 110mmol diphenylphosphine chloride was added, and the reaction was stirred for 2h, then the low-temperature constant temperature reaction bath was removed and stirred at room temperature for 15 hours. The reaction solution was purified by column chromatography (eluted with tetrahydrofuran, with a height-to-diameter ratio of 2), and then recrystallized at 76°C (the solvent was ethanol:ethyl acetate = 5:1) to obtain the phosphine-nitrogen ligand shown in the following formula L1:

[0073]

[0074] The NMR data of ligand L1 are as follows: 1H NMR (400MHz, CDCl3): 7.16-7.45(m,21H), 5.79-6.13(m,3H), 2.69(s,6H).

[0075] Polymerization reaction: Both of the two reactors in series are 500mL stainless steel reactors, and refined methylcyclohexane is used as the solvent. Take 5μmol of phosphine-nitrogen ligand and 3.5μmol of tetrahydrofuran chromium chloride in 10ml of refined methylcyclohexane, stir for 1.5h under nitrogen atmosphere and set aside. Before the reaction, the two required reactors need to be heated to 150℃ and vacuumed for 2h, during which nitrogen is replaced three times, and then vacuumed and hydrogen is replaced three times. When the temperature is cooled to room temperature, the passage between the two reactors is closed, and the circulating oil bath temperature of the first reactor is set to 50℃, and the circulating oil bath temperature of the second reactor is set to 60℃. 200mL of dehydrated and deoxygenated methylcyclohexane and 1750μmol MMAO-3a (7wt% Al n-heptane solution) are added to the first reactor in turn, and stirring is started. 0.462g of nucleating agent (1,3:2,4)-dibenzylidene sorbitol is added to the second reactor in advance. After the temperature is constant, add 10 ml of the pre-configured phosphine-nitrogen ligand and 3.5 μmol tetrahydrofuran chromium chloride mixed solution to the first reactor, introduce 0.5 MPa of hydrogen, and carry out polymerization reaction at a temperature of 50°C and an ethylene pressure of 4.5 MPa. After the first reactor reacts for 30 minutes, the reaction liquid is transferred to the second reactor and continues to react for 30 minutes at 55°C. After that, the ethylene inlet valve is closed, and the second reactor is quickly cooled to below 10°C with a low-temperature circulating water bath, and then the pressure is released. The reactor is disassembled at normal pressure, and the polymer morphology on the stirring paddle is observed. The ethylene polymerization reaction liquid is collected for activity analysis.

[0076] Example 2

[0077] Preparation of phosphine-nitrogen ligand: Under anhydrous and oxygen-free conditions, 50mmol N1,N3-dimethylbenzene-1,3-diamine was dissolved in 100ml dichloromethane; 120mmol tripropylamine was added dropwise to the reaction solution under stirring at -5°C, and 80mmol 4-(tri-n-butylsilyl)phenylphosphine chloride was slowly added thereto. When the solution was stable and no longer exothermic, 80mmol 4-(tri-n-butylsilyl)phenylphosphine chloride was added, and the reaction was stirred for 4.5h, and then the low-temperature constant temperature reaction bath was removed and stirred at room temperature for 15 hours. The reaction solution was purified by column chromatography (eluted with tetrahydrofuran, with a height-to-diameter ratio of 2), and then recrystallized at 76°C (the solvent was ethanol:ethyl acetate = 5:1) to obtain phosphine-nitrogen ligand L2.

[0078]

[0079] The NMR data of ligand L2 are as follows: 1H NMR (400MHz, CDCl3): 7.11-7.46

[0080] (m,17H), 5.79~5.98(m,3H), 2.79(s,6H), 0.27(s,36H).

[0081] Polymerization reaction: 3.5 μmol of phosphine-nitrogen ligand and 3.5 μmol of chromium acetylacetonate were added to 10 ml of refined methylcyclohexane as the main catalyst, the amount of nucleation was 0.77 g (1,3:2,4)-di(3,4-dimethylbenzylidene) sorbitol, the amount of co-catalyst was 2100 μmol MAO (10 wt% Al toluene solution), 0.3 MPa of hydrogen was introduced, and the polymerization reaction was carried out at a temperature of 55°C and an ethylene pressure of 4 MPa. After the first reactor reacted for 40 minutes, the reaction liquid was transferred to the second reactor and continued to react at 60°C for 20 minutes before closing the ethylene inlet valve. The rest was the same as in Example 1. The experimental phenomenon of the second reactor is as follows Figure 1 As shown, the phenomenon of polymer hanging on the stirring paddle is significantly reduced.

[0082] Example 3

[0083] The preparation of the phosphine-nitrogen ligand is the same as in Example 1.

[0084] Oligomerization reaction: 5.5 μmol of phosphine-nitrogen ligand and 3.5 μmol of chromium acetylacetonate, 0.308 g of p-hydroxybenzoic acid as nucleating agent, 2450 μmol of MMAO-3a (7 wt% Al n-heptane solution), 0.5 MPa of hydrogen, and oligomerization reaction at 40°C and 6 MPa of ethylene pressure. After the first reactor reacted for 20 minutes, the reaction liquid was transferred to the second reactor and continued to react for 40 minutes at 55°C, and then the ethylene inlet valve was closed. The rest was the same as in Example 1.

[0085] Example 4

[0086] The preparation of the phosphine-nitrogen ligand is the same as in Example 1.

[0087] Oligomerization reaction: 4.5 μmol of phosphine-nitrogen ligand and 3.5 μmol of tetrahydrofuran chromium chloride, 0.616 g of poly-4-methoxy-4′-acryloxybenzoic acid phenyl ester liquid crystal added as nucleation agent, 1750 μmol of MAO (10 wt% toluene solution) added as cocatalyst, 0.5 MPa of hydrogen was introduced, and the oligomerization reaction was carried out at a temperature of 50° C. and an ethylene pressure of 5 MPa. After the first reactor reacted for 60 minutes, the reaction solution was transferred to the second reactor and continued to react for 20 minutes at 65° C., and then the ethylene inlet valve was closed. The rest was the same as in Example 1.

[0088] Example 5

[0089] The preparation of the phosphine-nitrogen ligand is the same as in Example 1.

[0090] Oligomerization reaction: 5 μmol of phosphine-nitrogen ligand and 3.5 μmol of chromium acetylacetonate, 0.154 g of zinc stearate as nucleating agent, 2450 μmol of MAO (10 wt% toluene solution) as promoter, 0.5 MPa of hydrogen, at 50°C and 4.5 MPa of ethylene pressure, was conducted. After the first reactor reacted for 50 min, the reaction liquid was transferred to the second reactor and continued to react for 25 min at 55°C before closing the ethylene inlet valve. The rest was the same as in Example 1.

[0091] Example 6

[0092] The preparation of the phosphine-nitrogen ligand is the same as in Example 1.

[0093] Polymerization reaction: 0.77 g of 1,3:2,4-di(p-methylbenzylidene)sorbitol as a nucleating agent was added to the second reaction kettle in advance, and the other steps were the same as those in Example 2.

[0094] Comparative Example 1

[0095] The preparation of the phosphine-nitrogen ligand is the same as in Example 1.

[0096] Polymerization reaction: single-pot polymerization, the reactor used is a 500mL stainless steel reactor, and refined methylcyclohexane is used as the solvent. Before the reaction, the two required reactors need to be heated to 150°C and evacuated for 3h, during which nitrogen is replaced three times, and then evacuated and hydrogen is replaced three times. After the temperature is cooled to room temperature, the passage between the two reactors is closed, and the temperature of the circulating oil bath of the reactor is set to 50°C. 200mL of dehydrated and deoxygenated methylcyclohexane, 2100μmol MMAO-3a (7wt% Al n-heptane solution), and 0.462g of nucleating agent 1,3:2,4-dibenzylidene sorbitol are added in sequence. After the temperature is constant, 10ml of the pre-configured silica gel-supported monophosphine ligand / chromium compound mixture is added to the reactor, and 0.5Mpa of hydrogen is introduced. The polymerization reaction is carried out at a temperature of 50°C and an ethylene pressure of 4.5MPa. After 60 minutes of reaction, the ethylene inlet valve was closed, and the second reactor was rapidly cooled to below 10°C using a low-temperature circulating water bath and then the pressure was released. The reactor was disassembled at normal pressure, the polymer morphology on the stirring paddle was observed, and the ethylene polymerization reaction liquid was collected for activity analysis.

[0097] Comparative Example 2

[0098] The preparation of the phosphine-nitrogen ligand is the same as in Example 1.

[0099] Polymerization reaction: No nucleating agent was added to the second reactor, and the rest was the same as in Example 2. Figure 2 shown.

[0100] The polymerization results of the examples are shown in Table 1. There is no adhesion phenomenon in the examples, and the activity of the catalyst combination can reach up to 10×10 6 g product / (molCr.h), wherein the selectivity of high value-added 1-hexene and 1-octene can reach 90%. The above results are better than those of the comparative example.

[0101] Table 1 Oligomerization results of Examples and Comparative Examples

[0102]

[0103]

[0104] Among them, 1-C6: 1-hexene; 1-C8: octene; Cy-C6H12: methylcyclopentane; Cy-C6H10: methylenecyclopentane.

Claims

1. A method for reducing polymer adhesion in ethylene oligomerization, characterized in that: The method adopts a double-kettle series polymerization process, wherein phosphine-nitrogen ligands, chromium compounds and co-catalysts are added to the first reaction kettle, and a nucleating agent is added to the second reaction kettle. The reaction is carried out in the first reaction kettle in the early stage and then transferred to the second reaction kettle for further reaction in the later stage. The oligomer is converted into a polymer by the nucleating agent and stored in the form of particles, which flow out with the solvent.

2. The method according to claim 1, characterized in that The phosphine-nitrogen ligand structure is shown in the following formula I: Wherein, R1, R2, R3, and R4 are each independently selected from one of alkyl, aryl, substituted alkyl, and substituted aryl; preferably, R1, R2, R3, and R4 are each independently selected from one of C2-C9 alkyl, aryl, substituted alkyl, and substituted aryl; more preferably, R1, R2, R3, and R4 are each independently selected from phenyl, benzyl, biphenyl, naphthyl, anthracenyl, vinyl, propenyl, isopropyl, tert-butyl, cyclohexyl, 4-methylcyclohexyl, 4-ethylcyclohexyl, 4-isopropylcyclohexyl, 2-methylphenyl, 4-methylphenyl, 2,4-dimethylphenyl, 2,6-dimethylphenyl, 2-ethylphenyl, 4-ethylphenyl, 2,4-diethylphenyl, 2,6-diethylphenyl, 2-isopropylphenyl , 4-isopropylphenyl, 2,4-diisopropylphenyl, 2,6-diisopropylphenyl, 2-butylphenyl, 4-butylphenyl, 2,4-dibutylphenyl, 2,6-dibutylphenyl, 4-methoxyphenyl, o-methoxyphenyl, 4-ethoxyphenyl, o-ethoxyphenyl, 2-(trimethylsilyl)phenyl, 3-(trimethylsilyl)phenyl, 4-(trimethylsilyl)phenyl, 2-fluorophenyl, 3-fluorophenyl, 4-fluorophenyl, 2-(trifluoromethyl)phenyl, 3-(trifluoromethyl)phenyl, 4-(trifluoromethyl)phenyl, 3,5-bis(trifluoromethyl)phenyl, 2-(tri-n-butylsilyl)phenyl, 3-(tri-n-butylsilyl)phenyl, 4-(tri-n-butylsilyl)phenyl.

3. The method according to claim 1 or 2, characterized in that: The chromium compound is selected from one or more of organic salts, inorganic salts, coordination complexes and organometallic complexes of chromium, preferably one or more of chromium acetylacetonate, chromium hexacarbonyl, chromium chloride, chromium (III) octoate and tri(tetrahydrofuran)chromium trichloride.

4. The method according to any one of claims 1 to 3, characterized in that The nucleating agent is selected from organic nucleating agents and / or inorganic nucleating agents, preferably at least one of carboxylic acid metal salts, phosphonic acid metal salts, sorbitol benzyl derivatives, and inorganic compounds, and more preferably at least one of sorbitol acetal, sorbitol, p-hydroxybenzoic acid, poly 4-methoxy-4′-acryloxybenzoic acid phenyl ester liquid crystal, stearate, and talc.

5. The method according to any one of claims 1 to 4, characterized in that The co-catalyst is an alkyl aluminum co-catalyst, and the co-catalyst is preferably selected from at least one of trimethyl aluminum, triethyl aluminum, trioctylaluminum, triisobutyl aluminum, methylaluminoxane (MAO), modified methylaluminoxane (MMAO), and ethylaluminoxane, and more preferably methylaluminoxane and / or modified methylaluminoxane.

6. The method according to any one of claims 1 to 5, characterized in that The molar ratio of the chromium compound to the phosphine-nitrogen ligand is 1:0.8-5, preferably 1:1-2; and / or, the amount of the nucleating agent added is 0.1%-1% by mass of the reaction solvent, preferably 0.2%-0.6%; And / or, the molar ratio of the promoter to the chromium compound is 50-2000:1, preferably 100-1000:

1.

7. The method according to any one of claims 1 to 6, characterized in that The preparation method of the phosphine-nitrogen ligand in formula I is: After dissolving N1,N3-dimethylbenzene-1,3-diamine, adding a tertiary fatty amine compound, and then adding the compound of formula II, reacting to obtain the phosphine-nitrogen ligand; Wherein, R1, R2, R3, and R4 are each independently selected from one of alkyl, aryl, substituted alkyl, and substituted aryl; preferably, R1, R2, R3, and R4 are each independently selected from one of C2-C9 alkyl, aryl, substituted alkyl, and substituted aryl; more preferably, R1, R2, R3, and R4 are each independently selected from phenyl, benzyl, biphenyl, naphthyl, anthracenyl, vinyl, propenyl, isopropyl, tert-butyl, cyclohexyl, 4-methylcyclohexyl, 4-ethylcyclohexyl, 4-isopropylcyclohexyl, 2-methylphenyl, 4-methylphenyl, 2,4-dimethylphenyl, 2,6-dimethylphenyl, 2-ethylphenyl, 4-ethylphenyl, 2,4-diethylphenyl, 2,6-diethylphenyl, 2-isopropylphenyl , 4-isopropylphenyl, 2,4-diisopropylphenyl, 2,6-diisopropylphenyl, 2-butylphenyl, 4-butylphenyl, 2,4-dibutylphenyl, 2,6-dibutylphenyl, 4-methoxyphenyl, o-methoxyphenyl, 4-ethoxyphenyl, o-ethoxyphenyl, 2-(trimethylsilyl)phenyl, 3-(trimethylsilyl)phenyl, 4-(trimethylsilyl)phenyl, 2-fluorophenyl, 3-fluorophenyl, 4-fluorophenyl, 2-(trifluoromethyl)phenyl, 3-(trifluoromethyl)phenyl, 4-(trifluoromethyl)phenyl, 3,5-bis(trifluoromethyl)phenyl, 2-(tri-n-butylsilyl)phenyl, 3-(tri-n-butylsilyl)phenyl, 4-(tri-n-butylsilyl)phenyl; Preferably, the molar ratio of N1,N3-dimethylbenzene-1,3-diamine, the tertiary fatty amine compound and the compound of formula II is 1:(1.5-3.5):(2.1-3.6).

8. The method according to claim 7, characterized in that The tertiary fatty amine compound is a C3-C15 tertiary fatty amine compound, preferably triethylamine and / or tripropylamine; And / or, the solvent is selected from one or more of halogenated hydrocarbons, nitrile compounds, alkanes, and aromatic solvents, preferably one or more of dichloromethane, acetonitrile, n-hexane, n-heptane, and toluene; And / or, the preparation method comprises reacting at -10 to 0°C for 8 to 30 hours.

9. The method according to any one of claims 1 to 8, characterized in that The reaction temperature of the first reactor is 35-80°C, and the temperature of the second reactor is set 5-15°C higher than that of the first reactor; and / or, hydrogen is introduced into the first reactor to carry out an oligomerization reaction at an ethylene pressure of 2 MPa-7 MPa; And / or, after the first reactor reacts for 15-60 minutes, the reaction solution is transferred to the second reactor and continues to react for 20-50 minutes.

10. An oligomerized polyethylene, wherein the oligomerized polyethylene is prepared by the catalytic method according to any one of claims 1 to 9, characterized in that: The oligomeric polyethylene contains a nucleating agent component; Preferably, the nucleating agent is selected from organic nucleating agents and / or inorganic nucleating agents, preferably at least one of carboxylic acid metal salts, phosphonic acid metal salts, sorbitol benzyl derivatives, and inorganic compounds, and more preferably at least one of sorbitol acetal, sorbitol, p-hydroxybenzoic acid, poly-4-methoxy-4′-acryloxybenzoic acid phenyl ester liquid crystal, stearate, and talc; Preferably, based on the mass of the oligomeric polyethylene, the proportion of the nucleating agent is 0.02%-10% of the mass of the polyethylene, preferably 0.1%-5%.

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