Catalyst composite system for ethylene polymerization, catalyst component, catalyst, preparation method and application

Abstract

The invention discloses a catalyst composite system for ethylene polymerization, a catalyst component, a catalyst, a preparation method and application, and relates to the technical field of catalysts for ethylene polymerization, the composite system is prepared from the following raw materials: a magnesium-containing compound solution, a titanium compound I and an organic phosphorus compound II; the molar ratio of the magnesium element to the titanium compound I to the organic phosphorus compound II in the magnesium-containing compound solution is 1: (0.1-10.0): (0.05-5.0), preferably 1: (0.2-5.0): (0.1-2.5). The particle size distribution of the catalyst component is concentrated, the catalyst component has high polymerization activity and hydrogen regulation sensitivity when being used for ethylene polymerization, polyethylene powder prepared under the condition of low hydrogen / ethyl ratio has high stacking density, the stacking density can be larger than or equal to 0.35 g / ml, the content of fine powder with the size smaller than 75 microns is greatly reduced, and almost no fine powder exists.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts for ethylene polymerization, and more particularly to a catalyst composite system, catalyst components, catalysts and preparation methods and applications thereof for ethylene polymerization. Background Art

[0002] At present, Ziegler-Natta olefin polymerization catalysts still occupy a dominant position in the industrial production of polyolefins. In the slurry polymerization process of ethylene, in addition to requiring Ziegler-Natta catalysts to have high polymerization activity, the powder prepared by the catalyst is also required to have a high bulk density. This is because in some slurry polymerization processes, after the polymer / hexane slurry is centrifuged, the hexane carrying amount of the high bulk density powder is lower, which is conducive to reducing the energy consumption of powder drying and at the same time conducive to increasing the load of the drying unit, thereby increasing the load of the polymerization reaction unit; in addition, due to its excellent flow properties, the high bulk density powder is conducive to the efficient operation of the powder conveying unit of the industrial device, thereby enabling the industrial device to achieve a higher production load.

[0003] In order to obtain catalysts with uniform particles and good particle morphology, researchers tend to adopt the catalyst preparation method of dissolution-precipitation. As a representative of dissolution-precipitation catalysts, N-type polypropylene catalyst was successfully developed by Sinopec Beijing Chemical Research Institute in 1985 as an advanced polyolefin catalyst. However, when N-type polypropylene catalyst is directly used for ethylene polymerization, there are problems such as low catalytic activity and poor hydrogen adjustment performance. In order to take into account the high activity, excellent hydrogen adjustment performance and high bulk density of the prepared polymer powder, researchers have conducted a lot of exploration and research.

[0004] For example, in Chinese patent CN1086191C, magnesium chloride is used as a carrier and titanium tetrachloride is used as an active component. The preparation method of the catalyst is as follows: MgCl 2 Dissolve in the solvent system to form a uniform transparent solution, and then react with TiCl at low temperature 4 The solid catalyst is precipitated by slowly heating up the reaction. When the obtained catalyst component is used for ethylene polymerization, the catalytic activity of the catalyst is high and the catalyst particle morphology is also improved to a certain extent. However, due to the unsatisfactory polymer particle morphology, especially the unsatisfactory fluidity of the prepared polymer powder, it is difficult to fully meet the needs of industrial production when producing some grades of resins that have high requirements for polymer powder particle morphology and powder fluidity.

[0005] Therefore, it is necessary to develop a polyethylene catalyst that can prepare high activity and high hydrogen sensitivity, the catalyst can polymerize to obtain powder particles with high bulk density, and the prepared polymer powder should have good fluidity. Summary of the invention

[0006] In order to solve the problems existing in the prior art, the present invention provides a catalyst composite system, a catalyst component, a catalyst, a preparation method and an application for ethylene polymerization. The catalyst component and the catalyst containing the catalyst component of the present invention have high polymerization activity and hydrogen adjustment sensitivity, can catalyze ethylene polymerization to obtain powder particles with high bulk density, and the content of fine powder with a size of less than 75 μm in the polymerization powder is greatly reduced, and there is almost no fine powder.

[0007] One of the objects of the present invention is to provide a catalyst composite system for ethylene polymerization.

[0008] The composite system for ethylene polymerization catalyst of the present invention is prepared from raw materials comprising the following components:

[0009] A magnesium complex solution, a titanium compound I and an organophosphorus compound II;

[0010] The molar ratio of magnesium element, titanium compound I and organic phosphorus compound II in the magnesium-containing complex solution is 1:(0.1-10.0):(0.05-5.0), preferably 1:(0.2-5.0):(0.1-2.5).

[0011] Preferably,

[0012] The magnesium-containing complex solution is prepared by dissolving magnesium halide in an organic phosphorus compound I, an organic epoxy compound, an alcohol compound and an inert diluent; in the actual preparation process, the magnesium-containing complex solution is a uniform complex solution formed by dissolving magnesium halide in a solvent system of an organic phosphorus compound I, an organic epoxy compound, an alcohol compound and an inert diluent;

[0013] Preferably,

[0014] The molar ratio of the magnesium element, the organic phosphorus compound I, the organic epoxy compound, the alcohol compound and the inert diluent in the magnesium halide is 1:(0.1-3.0):(0.1-3.0):(0.1-3.0):(1-50), preferably 1:(0.5-1.5):(0.5-1.5):(0.5-1.5):(5-20).

[0015] Preferably,

[0016] The magnesium halide is at least one of magnesium chloride, magnesium bromide, magnesium fluoride and magnesium iodide, preferably magnesium chloride; and / or,

[0017] The organic epoxy compound is at least one of aliphatic olefins, aliphatic dienes, halogenated aliphatic olefins, oxides of halogenated aliphatic dienes, glycidyl ethers, and internal ethers; preferably, the organic epoxy compound has 2-8 carbon atoms; more preferably, the organic epoxy compound is at least one of ethylene oxide, propylene oxide, butylene oxide, butadiene oxide, butadiene dioxide, epichlorohydrin, methyl glycidyl ether, diglycidyl ether, and tetrahydrofuran, and further preferably at least one of ethylene oxide, propylene oxide, epichlorohydrin, and tetrahydrofuran; and / or,

[0018] The alcohol compound is a C1-C12 fatty alcohol and a substituted alcohol derived therefrom or a C7-C12 aromatic alcohol and a substituted alcohol derived therefrom, preferably at least one of methanol, ethanol, propanol, isopropanol, butanol, isobutanol, 2-ethylhexanol, n-octanol, dodecanol, benzyl alcohol, and phenylethyl alcohol, more preferably at least one of ethanol, isopropanol, butanol, 2-ethylhexanol, benzyl alcohol, and phenylethyl alcohol; and / or,

[0019] The inert diluent is C6-C10 alkane and its derivatives or C6-C8 aromatic hydrocarbon and its derivatives, preferably at least one of hexane, heptane, octane, decane, benzene, toluene and xylene.

[0020] Preferably,

[0021] The organophosphorus compound I and the organophosphorus compound II may be the same or different, and are independently selected from trimethyl phosphate, triethyl phosphate, tri-n-propyl phosphate, triisopropyl phosphate, tri-n-butyl phosphate, triisobutyl phosphate, tri-tert-butyl phosphate, tri-n-pentyl phosphate, triisopentyl phosphate, tri-n-hexyl phosphate, triisohexyl phosphate, tri-n-heptyl phosphate, triisoheptyl phosphate, tri-n-octyl phosphate, triisooctyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, tri-n-propyl phosphite, triisopropyl phosphite , at least one of tri-n-butyl phosphite, tri-isobutyl phosphite, tri-tert-butyl phosphite, tri-n-pentyl phosphite, tri-isopentyl phosphite, tri-n-hexyl phosphite, tri-isohexyl phosphite, tri-n-heptyl phosphite, tri-isoheptyl phosphite, tri-n-octyl phosphite, tri-isooctyl phosphite, triphenyl phosphite and di-n-butyl phosphite, preferably at least one of triethyl phosphate, tributyl phosphate, tri-isooctyl phosphate, triphenyl phosphate, triethyl phosphite, tributyl phosphite and di-n-butyl phosphite; and / or,

[0022] The titanium compound I is selected from the group consisting of TiX n (OR) 4-nThe compound wherein: X is a halogen, R is a C1-C14 aliphatic hydrocarbon group or a C6-C14 aromatic hydrocarbon group, n is any integer from 0 to 4, preferably at least one of titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, tetraethoxytitanium, tetrabutoxytitanium, triethoxytitanium monochloride, diethoxytitanium dichloride, and triethoxytitanium monochloride, and more preferably at least one of titanium tetrachloride, tetraethoxytitanium, and tetrabutoxytitanium.

[0023] A second object of the present invention is to provide a method for preparing a catalyst composite system for ethylene polymerization.

[0024] The preparation method of the composite system for ethylene polymerization catalyst of the present invention comprises:

[0025] The magnesium-containing complex solution is subjected to a first contact reaction with the titanium compound I to obtain an intermediate particle suspension, which is then subjected to a second contact reaction with the organophosphorus compound II until the solid in the intermediate particle suspension is completely dissolved to obtain the catalyst composite system.

[0026] Preferably,

[0027] The reaction temperature of the first contact reaction is -30°C to 20°C, and / or the reaction time is 0.1 to 1 hour; and / or,

[0028] The reaction temperature of the second contact reaction is -30°C to 20°C, and / or the reaction time is 0.1 to 2 hours.

[0029] Preferably,

[0030] The preparation of the magnesium-containing complex solution comprises dissolving magnesium halide in an organic phosphorus compound I, an organic epoxy compound, an alcohol compound and an inert diluent;

[0031] Preferably,

[0032] The preparation of the magnesium-containing complex solution comprises dissolving magnesium halide in an organic phosphorus compound I, an organic epoxy compound and an inert diluent and then adding an alcohol compound;

[0033] More preferably,

[0034] The dissolution temperature of the magnesium halide is 50-90° C., and / or the dissolution time is 1-6 hours.

[0035] The following solutions can be adopted:

[0036] (1) in the presence of an inert diluent, dissolving a magnesium halide in a solvent system containing an organic phosphorus compound I and an organic epoxy compound at 50-90° C. to form a transparent solution containing a magnesium complex, adding an alcohol compound during or after the solution is formed to ensure sufficient reaction, the reaction time being 1-6 hours, to obtain a magnesium complex solution;

[0037] (2) subjecting the above-mentioned magnesium-containing complex solution to a first contact reaction with the titanium compound I to obtain an intermediate particle suspension;

[0038] (3) The intermediate particle suspension is contacted with the organophosphorus compound II for a second reaction for 0.1-2 hours until the solid in the suspension is completely dissolved to obtain a magnesium-titanium catalyst composite system with higher transparency.

[0039] Among them, when the intermediate particle suspension is treated with the organophosphorus compound II, the solid in the intermediate particle suspension gradually dissolves, and a sufficient amount of the organophosphorus compound II can completely dissolve the solid in the intermediate particle suspension to obtain a transparent composite system containing magnesium and titanium. After the solid in the titanium-containing intermediate particle suspension is redissolved, a new micellar dissolution system can be formed, and the catalyst component particles reprecipitated from the system have a more regular morphology, and the distribution of active centers on the crystal surface of the catalyst component has its own uniqueness, so that the catalyst component can simultaneously have higher catalytic activity, better hydrogen adjustment sensitivity, higher polymer powder bulk density and higher polymer powder compactness, and the polymer crushing situation is also greatly improved. It is worth noting that insufficient amount of organophosphorus compound II cannot completely dissolve the solid in the catalyst intermediate suspension, and the expected effect cannot be achieved. Excessive amount will make it difficult to collect the catalyst particles. After further titanium treatment of the transparent composite system and addition of organic silicon compounds, the morphology of the solid catalyst component obtained is significantly improved. At the same time, the catalytic activity is higher, the sensitivity to hydrogen adjustment is better, especially the polymer powder packing density is higher, the compactness of the polymer powder is improved, and the polymer crushing situation is greatly improved, indicating that further treatment on the basis of the transparent composite system can prepare catalyst components with better performance.

[0040] A third object of the present invention is to provide a catalyst component for ethylene polymerization catalyst.

[0041] The catalyst component for ethylene polymerization catalyst of the present invention is prepared from components including a composite system, a titanium compound II and an organosilicon compound;

[0042] Preferably, the molar ratio of the magnesium element in the composite system, the titanium element in the titanium compound II and the organosilicon compound is 1:(1-50):(0.01-5.0), preferably 1:(5-20):(0.1-1.5).

[0043] Preferably,

[0044] The titanium compound II and the titanium compound I may be the same or different and are independently selected from the group consisting of n (OR) 4-n A compound wherein: X is a halogen, R is a C1-C14 aliphatic hydrocarbon group or a C6-C14 aromatic hydrocarbon group, n is any integer from 0 to 4, preferably at least one of titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, tetraethoxytitanium, tetrabutoxytitanium, triethoxytitanium monochloride, diethoxytitanium dichloride, and triethoxytitanium monochloride, more preferably at least one of titanium tetrachloride, tetraethoxytitanium, and tetrabutoxytitanium; and / or,

[0045] The organosilicon compound is silicon tetrachloride, silicon tetrabromide, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetra(2-ethylhexyloxy)silane, ethyltrimethoxysilane, n-propyltriethoxysilane, n-propyltrimethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, cyclopentyltrimethoxysilane, cyclopentyltriethoxysilane, 2-methylcyclopentyltrimethoxysilane, 2,3-dimethoxysilane, Methylcyclopentyltrimethoxysilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, tert-butyltriethoxysilane, n-butyltrimethoxysilane, n-butyltriethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane , monochlorotrimethoxysilane, monochlorotriethoxysilane, ethyltriisopropoxysilane, vinyltributoxysilane, trimethylphenoxysilane, methyltriallyloxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diisopropyldimethoxysilane, diisopropyldiethoxysilane, tert-butylmethyldimethoxysilane, tert-butylmethyldiethoxysilane, tert-amylmethyldiethoxysilane, dicyclopentyldimethoxysilane, dicyclopentyldiethoxysilane, methylcyclopentyldiethoxysilane, methylcyclopentyldimethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, tricyclopentylmethoxysilane, tricyclopentylethoxysilane, dicyclopentylmethylmethoxysilane, and at least one of cyclopentyldimethylmethoxysilane, preferably at least one of silicon tetrachloride, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane.

[0046] A fourth object of the present invention is to provide a method for preparing a catalyst component.

[0047] The preparation method of the catalyst component of the present invention comprises:

[0048] The titanium compound II and the organosilicon compound are sequentially added dropwise to the composite system, so that solid particles are precipitated and then the temperature is continuously raised for reaction, and the precipitate is filtered and washed to obtain the catalyst component.

[0049] Preferably,

[0050] The dropping temperature is -30°C to 20°C, and / or the dropping temperature fluctuation does not exceed ±1°C; and / or,

[0051] The temperature of the heating reaction is 60-110° C., and / or, to ensure sufficient reaction, the reaction time is 0.5-6 hours, and / or, the heating rate is 0.1-1° C. / min, preferably 0.3-0.6° C. / min.

[0052] A fifth object of the present invention is to provide a catalyst for the polymerization of ethylene.

[0053] The catalyst for ethylene polymerization of the present invention comprises:

[0054] Catalyst components and organoaluminum compounds;

[0055] During the polymerization process, the organoaluminum compound acts as a co-catalyst together with the catalyst component to play a role in polymerization catalysis; the organoaluminum compound is added during the polymerization only as a co-catalyst, and the organoaluminum compound is not used in the catalyst component. The organoaluminum compound is not introduced into the catalyst component in order to prevent the organoaluminum compound from competing with the catalyst component or directly reacting with the catalyst component, which can effectively avoid the influence of the organoaluminum compound on the number and distribution of active centers in the catalyst component.

[0056] The molar ratio of the titanium element in the catalyst component to the aluminum element in the organic aluminum compound is 1:(20-200), preferably 1:(50-100).

[0057] Preferably,

[0058] The structural formula of the organoaluminum compound is AlR' d X' 3-d , wherein R' is hydrogen or a C1-C20 hydrocarbon group, X' is a halogen atom, and d is any integer from 0 to 3, preferably Al(CH 3 ) 3 、Al(CH 2 CH 3 ) 3 、Al(i-Bu) 3 、AlH(CH 2 CH 3 ) 2 、AlH(i-Bu) 2 、AlCl(CH2 CH3) 2 、Al 2 Cl 3 (CH 2 CH 3 ) 3 、AlCl(CH 2 CH 3 ) 2 、AlCl 2 (CH 2 CH 3 ), more preferably Al(CH 2 CH 3 ) 3 orAl(i-Bu) 3 .

[0059] The sixth object of the present invention is to provide a catalyst for use in ethylene polymerization.

[0060] Application of the catalyst of the present invention in ethylene polymerization;

[0061] Preferably,

[0062] The ethylene polymerization is homopolymerization of ethylene or copolymerization of ethylene and α-olefin; and / or,

[0063] The ethylene polymerization is slurry polymerization or gas phase polymerization;

[0064] More preferably,

[0065] The slurry polymerization medium includes saturated aliphatic hydrocarbons or aromatic hydrocarbons, preferably at least one of isobutane, hexane, heptane, cyclohexane, naphtha, raffinate, hydrogenated gasoline, kerosene, benzene, toluene, and xylene, and more preferably at least one of toluene, n-hexane, and cyclohexane.

[0066] Through the above technical scheme, it can be known that the present invention has discovered for the first time a transparent composite system containing magnesium and titanium. The particle size distribution of the catalyst component obtained by further titanium loading treatment based on the composite system is more concentrated, the polymerization activity and hydrogen adjustment sensitivity of the catalyst can be effectively improved, and at the same time, the bulk density of the polymerization powder is significantly improved, and the content of polymerization fine powder is greatly reduced. It can catalyze ethylene polymerization to obtain powder particles with high bulk density. The content of fine powder in the polymerization powder with a size of less than 75μm is greatly reduced, and there is almost no fine powder.

[0067] The catalyst component of the present invention has a concentrated particle size distribution and has high polymerization activity and hydrogen adjustment sensitivity when used for ethylene polymerization. Under the polymerization conditions of hydrogen partial pressure of 0.28MPa / ethylene partial pressure of 0.45MPa / temperature of 80°C / time of 2h, the polymerization activity of the catalyst can be greater than 30000gPE / gCat; under the polymerization conditions of hydrogen partial pressure of 0.58MPa / ethylene partial pressure of 0.15MPa / temperature of 85°C / time of 2h, the polymerization activity can be greater than 5000gPE / gCat, and the melt index can be greater than 260g / 10min. The polyethylene powder prepared under the condition of low hydrogen-ethylene ratio has a high bulk density, which can be ≥0.35g / ml, and the content of fine powder with a size less than 75μm is greatly reduced, and there is almost no fine powder. DETAILED DESCRIPTION

[0068] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0069] In the following embodiments and comparative examples of the present invention, unless otherwise specified, all raw materials are commercially available. Specific information is as shown in Table 1 below:

[0070] Table 1

[0071] raw material source Specification or brand Magnesium chloride Beijing Innochem Company 99% Anhydrous Magnesium Chloride Powder Magnesium fluoride Beijing Innochem Company 99.99% Magnesium Fluoride Magnesium iodide Aladdin 98% Magnesium Iodide Hydrate n-Hexane Beijing Innochem Company ≥95% chromatographic grade n-hexane Toluene Beijing Innochem Company ≥99.5% analytical pure toluene Xylene Beijing Innochem Company 99% analytical pure xylene Epichlorohydrin Beijing Innochem Company 99% Epichlorohydrin Ethylene oxide Aladdin 99.5% Ethylene Oxide Tetrahydrofuran Beijing Innochem Company ≥99.8% Chromatographic grade unstabilized tetrahydrofuran Tri-n-butyl phosphate Beijing Innochem Company ≥99%Tri-n-butyl phosphate Triisobutyl phosphate Aladdin 98% Triisobutyl Phosphate Triethyl phosphate Beijing Innochem Company 99+% Triethyl Phosphate Ethanol Beijing Innochem Company 99.7% analytical pure anhydrous ethanol Butanol Beijing Innochem Company 99.5% n-Butanol 2-Ethylhexanol Beijing Innochem Company 99% analytically pure isooctyl alcohol Titanium Tetrachloride Beijing Innochem Company 99% analytically pure titanium tetrachloride Tetraethoxytitanium Beijing Innochem Company 98% Tetraethyl Titanate Tetrabutoxytitanium Beijing Innochem Company ≥99% Tetrabutyl titanate Tetraethoxysilane Beijing Innochem Company 99% Tetraethyl silicate Tetrabutoxysilane Beijing Innochem Company 97% Tetrabutyl silicate Silicon tetrachloride Beijing Innochem Company 98% analytically pure silicon tetrachloride

[0072] Example 1

[0073] (1) Preparation of catalyst

[0074] In a reactor fully replaced with high-purity nitrogen, 4.0 g of magnesium chloride (42.0 mmol), 50 mL of toluene, 3.0 mL of epichlorohydrin, 9.0 mL of tri-n-butyl phosphate, and 4.4 mL of ethanol were added in sequence, and the molar ratio of magnesium chloride, tri-n-butyl phosphate, epichlorohydrin, ethanol and toluene was 1:0.8:0.9:1.8:11.2. The temperature was raised to 70°C with stirring, and the reaction was carried out at a constant temperature for 2 hours to obtain a magnesium-containing complex solution. The magnesium-containing complex solution was cooled to -10°C, and 10 mL of titanium tetrachloride was slowly added dropwise for no less than 30 minutes. The molar ratio of magnesium to titanium tetrachloride in the magnesium-containing complex solution was 1:2.2. After the addition was completed, an intermediate particle suspension was obtained. Then 15 mL of tri-n-butyl phosphate was added dropwise for no less than 30 minutes. The molar ratio of magnesium to tri-n-butyl phosphate in the intermediate particle suspension was 1:1.3. After the tri-n-butyl phosphate was added, a transparent composite system containing magnesium and titanium was obtained. 70 mL of titanium tetrachloride was slowly added dropwise, and then 5 mL of tetraethoxysilane was added dropwise. The molar ratio of magnesium, titanium tetrachloride and tetraethoxysilane in the composite system was 1:15.2:0.4. The temperature was gradually raised to 85°C at a heating rate of 0.5°C / min, and then the reaction was carried out for 1 hour. Stop stirring, let it stand, the suspension will quickly separate into layers, remove the upper clear liquid, wash twice with toluene, wash four times with hexane, and dry with high-purity nitrogen to obtain a solid catalyst component with good fluidity. Its performance parameters are shown in Table 2.

[0075] (2) Slurry polymerization

[0076] Homopolymerization with low hydrogen-ethylene ratio: A stainless steel reactor with a volume of 2L was fully replaced with high-purity nitrogen, and then 1L of hexane and 1.0mL of 1 mol / L triethylaluminum (1mmol) were added, and then the catalyst component prepared by the above method (containing 0.01mmol Ti) was added. The temperature was raised to 70°C, hydrogen was introduced to make the pressure in the reactor reach 0.28MPa (gauge pressure), and then ethylene was introduced to make the total pressure in the reactor reach 0.73MPa. Polymerization was carried out at 80°C for 2 hours. The polymerization results are shown in Tables 3 and 4.

[0077] Copolymerization with low hydrogen-to-ethylene ratio: A stainless steel reactor with a volume of 2 L was fully replaced with high-purity nitrogen, and then 1 L of hexane and 1.0 mL of 1 mol / L triethylaluminum (1 mmol) were added, followed by 5 mL of hexene, and then the catalyst component prepared by the above method (containing 0.01 mmol Ti) was added. The temperature was raised to 70° C., hydrogen was introduced so that the pressure in the reactor reached 0.28 MPa (gauge pressure), and then ethylene was introduced so that the total pressure in the reactor reached 0.73 MPa. Polymerization was carried out at 80° C. for 2 hours. The polymerization results are shown in Tables 3 and 4.

[0078] Homopolymerization with high hydrogen / ethylene ratio: A stainless steel reactor with a volume of 2 L was fully replaced with high-purity nitrogen, and then 1 L of hexane and 1.0 mL of 1 mol / L triethylaluminum (1 mmol) were added, and then the catalyst component prepared by the above method (containing 0.04 mmol Ti) was added. The temperature was raised to 75° C., hydrogen was introduced to make the pressure in the reactor reach 0.58 MPa (gauge pressure), and then ethylene was introduced to make the total pressure in the reactor reach 0.73 MPa. Polymerization was carried out at 85° C. for 2 hours. The polymerization results are shown in Tables 3 and 4.

[0079] The pressure inside the autoclave described in the above polymerization reaction is all absolute pressure.

[0080] Example 2

[0081] (1) Preparation of catalyst

[0082] In a reactor fully replaced with high-purity nitrogen, 4.0 g of magnesium chloride (42.0 mmol), 50 mL of toluene, 3.0 mL of epichlorohydrin, and 9.0 mL of tri-n-butyl phosphate were added in sequence, the temperature was raised to 70°C with stirring, 4.4 mL of ethanol was added, the molar ratio of magnesium chloride, tri-n-butyl phosphate, epichlorohydrin, ethanol and toluene was 1:0.8:0.9:1.8:11.2, and the reaction was carried out at a constant temperature for 2 hours to obtain a magnesium-containing complex solution. The magnesium-containing complex solution was cooled to -10°C, and 10 mL of titanium tetrachloride was slowly added dropwise for no less than 30 minutes. The molar ratio of magnesium to titanium tetrachloride in the magnesium-containing complex solution was 1:2.2. After the addition was completed, an intermediate particle suspension was obtained. Then 15 mL of tri-n-butyl phosphate was added dropwise for no less than 30 minutes. The molar ratio of magnesium to tri-n-butyl phosphate in the intermediate particle suspension was 1:1.3. After the tri-n-butyl phosphate was added, a transparent composite system containing magnesium and titanium was obtained. 70 mL of titanium tetrachloride was slowly added dropwise, and then 5 mL of tetraethoxysilane was added dropwise. The molar ratio of magnesium, titanium tetrachloride and tetraethoxysilane in the composite system was 1:15.2:0.4. The temperature was gradually raised to 85°C at a heating rate of 0.5°C / min, and then the reaction was carried out for 1 hour. Stop stirring, let it stand, the suspension will quickly separate into layers, remove the upper clear liquid, wash twice with toluene, wash four times with hexane, and dry with high-purity nitrogen to obtain a solid catalyst component with good fluidity. Its performance parameters are shown in Table 2.

[0083] (2) Slurry polymerization: Same as Example 1, using the above catalyst components, the polymerization results are shown in Tables 3 and 4.

[0084] Example 3

[0085] (1) Preparation of catalyst

[0086] In a reactor fully replaced with high-purity nitrogen, 2.6 g of magnesium fluoride (42.0 mmol), 11 mL of hexane, 0.6 mL of propylene oxide, 2.3 mL of triisobutyl phosphate, and 0.8 mL of butanol were added in sequence, and the molar ratio of magnesium fluoride, triisobutyl phosphate, propylene oxide, butanol and hexane was 1:0.2:0.2:0.2:2. The temperature was raised to 60°C with stirring, and the reaction was carried out at a constant temperature for 1.5 hours to obtain a magnesium-containing complex solution. The magnesium-containing complex solution was cooled to -29°C, and 0.9 mL of tetraethoxytitanium was slowly added dropwise for no less than 5 minutes. The molar ratio of magnesium to tetraethoxytitanium in the magnesium-containing complex solution was 1:0.1. After the addition was completed, an intermediate particle suspension was obtained. Then 1.2 mL of triisobutyl phosphate was added dropwise for no less than 5 minutes. The molar ratio of magnesium to triisobutyl phosphate in the intermediate particle suspension was 1:0.1. After the triisobutyl phosphate was added, a transparent composite system containing magnesium and titanium was obtained. 17.6 mL of tetraethoxytitanium was slowly added dropwise, and then 0.3 mL of tetrabutoxysilane was added dropwise. The molar ratio of magnesium, tetraethoxytitanium and tetrabutoxysilane in the composite system was 1:2:0.02. The temperature was gradually raised to 62°C at a heating rate of 0.2°C / min, and then the reaction was carried out for 0.5 hours. Stop stirring, let stand, remove the supernatant, wash twice with toluene and four times with hexane, blow dry with high-purity nitrogen to obtain a solid catalyst component. Its performance parameters are shown in Table 2.

[0087] (2) Slurry polymerization: Same as Example 1, using the above catalyst components, the polymerization results are shown in Tables 3 and 4.

[0088] Example 4

[0089] (1) Preparation of catalyst

[0090] In a reactor fully replaced with high-purity nitrogen, 11.7 g of magnesium iodide (42.0 mmol), 252.7 mL of xylene, 9.9 mL of tetrahydrofuran, 20.7 mL of triethyl phosphate, and 19.0 mL of 2-ethylhexanol were added in sequence, and the molar ratio of magnesium iodide, triethyl phosphate, tetrahydrofuran, 2-ethylhexanol and xylene was 1:2.9:2.9:2.9:49.0. The temperature was raised to 80° C. with stirring, and the reaction was carried out at a constant temperature for 5 hours to obtain a magnesium-containing complex solution. The magnesium-containing complex solution was cooled to 19°C, and 129.2 mL of tetrabutoxytitanium was slowly added dropwise for no less than 60 minutes. The molar ratio of magnesium to tetrabutoxytitanium in the magnesium-containing complex solution was 1:9. After the addition was completed, an intermediate particle suspension was obtained. Then 35.0 mL of triethyl phosphate was added dropwise for no less than 60 minutes. The molar ratio of magnesium to triethyl phosphate in the intermediate particle suspension was 1:4.9. After the triethyl phosphate was added, a transparent composite system containing magnesium and titanium was obtained. 588.6 mL of tetrabutoxytitanium was slowly added dropwise, and then 19.3 mL of silicon tetrachloride was added dropwise. The molar ratio of magnesium, tetrabutoxytitanium and silicon tetrachloride in the composite system was 1:41:19.3. The temperature was gradually raised to 105°C at a heating rate of 0.9°C / min, and then the reaction was performed for 5 hours. Stop stirring, let stand, remove the supernatant, wash twice with toluene and four times with hexane, blow dry with high-purity nitrogen to obtain a solid catalyst component. Its performance parameters are shown in Table 2.

[0091] (2) Slurry polymerization: Same as Example 1, using the above catalyst components, the polymerization results are shown in Tables 3 and 4.

[0092] Example 5

[0093] (1) Preparation of catalyst: same as in Example 1.

[0094] (2) Slurry polymerization

[0095] Homopolymerization with low hydrogen-ethylene ratio: A stainless steel reactor with a volume of 2 L was fully replaced with high-purity nitrogen, and then 1 L of cyclohexane and 1.0 mL of 1 mol / L triisobutylaluminum (1 mmol) were added, and then the catalyst component prepared by the above method (containing 0.005 mmol Ti) was added. The temperature was raised to 70°C, hydrogen was introduced to make the pressure in the reactor reach 0.28 MPa (gauge pressure), and then ethylene was introduced to make the total pressure in the reactor reach 0.73 MPa. Polymerization was carried out at 80°C for 2 hours. The polymerization results are shown in Tables 3 and 4.

[0096] Homopolymerization with high hydrogen / ethylene ratio: A stainless steel reactor with a volume of 2 L was fully replaced with high-purity nitrogen, and then 1 L of heptane and 1.0 mL of 1 mol / L diethylaluminum chloride (1 mmol) were added, and then the catalyst component prepared by the above method (containing 0.05 mmol Ti) was added. The temperature was raised to 75° C., hydrogen was introduced to make the pressure in the reactor reach 0.58 MPa (gauge pressure), and then ethylene was introduced to make the total pressure in the reactor reach 0.73 MPa. Polymerization was carried out at 85° C. for 2 hours. The polymerization results are shown in Tables 3 and 4.

[0097] The pressure inside the autoclave described in the above polymerization reaction is all absolute pressure.

[0098] Comparative Example 1

[0099] (1) Preparation of catalyst

[0100] In a reactor fully replaced with high-purity nitrogen, 4.0g magnesium chloride (42.0mmol), 50mL toluene, 3.0mL epichlorohydrin, 9.0mL tri-n-butyl phosphate, and 4.4mL ethanol were added in sequence, and the molar ratio of magnesium chloride, tri-n-butyl phosphate, epichlorohydrin, ethanol, and toluene was 1:0.8:0.9:1.8:11.2, and the temperature was raised to 70°C under stirring, and the reaction was carried out at a constant temperature for 2 hours to obtain a magnesium-containing complex solution. The magnesium-containing complex solution was cooled to -10°C, 70mL titanium tetrachloride was slowly added dropwise, and then 5mL tetraethoxysilane was immediately added dropwise, and the molar ratio of magnesium element, titanium tetrachloride, and tetraethoxysilane in the system was 1:15.2:0.4, and the temperature was gradually raised to 85°C, and the heating rate was 0.5°C / min, and then the reaction was carried out for 1 hour. Stop stirring, let it stand, the suspension will quickly separate into layers, remove the upper clear liquid, wash twice with toluene, wash four times with hexane, dry with high-purity nitrogen to obtain a solid catalyst component, its performance parameters are shown in Table 2.

[0101] (2) Slurry polymerization: Same as Example 1, using the above catalyst components, the polymerization results are shown in Tables 3 and 4.

[0102] Comparative Example 2

[0103] (1) Preparation of catalyst

[0104] In a reactor fully replaced with high-purity nitrogen, 4.0 g of magnesium chloride (42.0 mmol), 50 mL of toluene, 3.0 mL of epichlorohydrin, 9.0 mL of tri-n-butyl phosphate, and 4.4 mL of ethanol were added in sequence, and the molar ratio of magnesium chloride, tri-n-butyl phosphate, epichlorohydrin, ethanol and toluene was 1:0.8:0.9:1.8:11.2. The temperature was raised to 70°C with stirring, and the reaction was carried out at a constant temperature for 2 hours to obtain a magnesium-containing complex solution. The magnesium-containing complex solution was cooled to -10°C, and 10 mL of titanium tetrachloride was slowly added dropwise for no less than 30 minutes. The molar ratio of magnesium to titanium tetrachloride in the magnesium-containing complex solution was 1:2.2. After the addition was completed, an intermediate particle suspension was obtained. Then 0.4 mL of tri-n-butyl phosphate was added dropwise for no less than 5 minutes. The molar ratio of magnesium to tri-n-butyl phosphate in the intermediate particle suspension was 1:0.04. After reacting for 1 hour, the suspension system did not redissolve, and the transparent state of the composite system was not reached. 70 mL of titanium tetrachloride was slowly added dropwise, and then 5 mL of tetraethoxysilane was added dropwise. The molar ratio of magnesium, titanium tetrachloride and tetraethoxysilane in the system was 1:15.2:0.4. The temperature was gradually raised to 85°C at a heating rate of 0.5°C / min, and then reacted for 1 hour. Stop stirring, let it stand, the suspension will quickly separate into layers, remove the upper clear liquid, wash twice with toluene, wash four times with hexane, dry with high-purity nitrogen to obtain a solid catalyst component, its performance parameters are shown in Table 2.

[0105] (2) Slurry polymerization: Same as Example 1, using the above catalyst components, the polymerization results are shown in Tables 3 and 4.

[0106] Comparative Example 3

[0107] (1) Preparation of catalyst

[0108] In a reactor fully replaced with high-purity nitrogen, 4.0 g of magnesium chloride (42.0 mmol), 50 mL of toluene, 3.0 mL of epichlorohydrin, 9.0 mL of tri-n-butyl phosphate, and 4.4 mL of ethanol were added in sequence, and the molar ratio of magnesium chloride, tri-n-butyl phosphate, epichlorohydrin, ethanol and toluene was 1:0.8:0.9:1.8:11.2. The temperature was raised to 70°C with stirring, and the reaction was carried out at a constant temperature for 2 hours to obtain a magnesium-containing complex solution. The magnesium-containing complex solution was cooled to -10°C, and 10 mL of titanium tetrachloride was slowly added dropwise for no less than 30 minutes. The molar ratio of magnesium to titanium tetrachloride in the magnesium-containing complex solution was 1:2.2. After the addition was completed, an intermediate particle suspension was obtained. Then 60 mL of tri-n-butyl phosphate was added dropwise for no less than 60 minutes. The molar ratio of magnesium to tri-n-butyl phosphate in the intermediate particle suspension was 1:5.3. After the tri-n-butyl phosphate was added, a transparent composite system containing magnesium and titanium was obtained. 70 mL of titanium tetrachloride was slowly added dropwise, and then 5 mL of tetraethoxysilane was added dropwise. The molar ratio of magnesium, titanium tetrachloride and tetraethoxysilane in the composite system was 1:15.2:0.4. The temperature was gradually raised to 85°C, and the heating rate was 0.5°C / min, followed by reaction for 1 hour. Stirring was stopped and allowed to stand. The suspension was difficult to separate, and a solid catalyst component with good fluidity was not obtained. Its performance parameters are shown in Table 2.

[0109] (2) Slurry polymerization: Same as Example 1, using the above catalyst components, the polymerization results are shown in Tables 3 and 4.

[0110] Comparative Example 4

[0111] (1) Preparation of catalyst

[0112] In a reactor fully replaced with high-purity nitrogen, 4.0g magnesium chloride (42.0mmol), 50mL toluene, 3.0mL epichlorohydrin, 9.0mL tri-n-butyl phosphate were added in sequence, the temperature was raised to 70°C under stirring, 4.4mL ethanol was added, the molar ratio of magnesium chloride, tri-n-butyl phosphate, epichlorohydrin, ethanol and toluene was 1:0.8:0.9:1.8:11.2, and the reaction was carried out at a constant temperature for 2 hours to obtain a magnesium-containing complex solution. The magnesium-containing complex solution system was cooled to -10°C, 70mL titanium tetrachloride was slowly added dropwise, and then 5mL tetraethoxysilane was immediately added dropwise, the molar ratio of magnesium element, titanium tetrachloride and tetraethoxysilane in the system was 1:15.2:0.4, and the temperature was gradually raised to 85°C, the heating rate was 0.5°C / min, and then the reaction was carried out for 1 hour. Stop stirring, let it stand, the suspension will quickly separate into layers, remove the upper clear liquid, wash twice with toluene, wash four times with hexane, dry with high-purity nitrogen to obtain a solid catalyst component, its performance parameters are shown in Table 2.

[0113] (2) Slurry polymerization: Same as Example 1, using the above catalyst components, the polymerization results are shown in Tables 3 and 4.

[0114] Comparative Example 5

[0115] (1) Preparation of catalyst

[0116] In a reactor fully replaced with high-purity nitrogen, 4.0 g of magnesium chloride (42.0 mmol), 50 mL of toluene, 3.0 mL of epichlorohydrin, and 9.0 mL of tri-n-butyl phosphate were added in sequence, the temperature was raised to 70°C with stirring, 4.4 mL of ethanol was added, the molar ratio of magnesium chloride, tri-n-butyl phosphate, epichlorohydrin, ethanol and toluene was 1:0.8:0.9:1.8:11.2, and the reaction was carried out at a constant temperature for 2 hours to obtain a magnesium-containing complex solution. The magnesium-containing complex solution was cooled to -10°C, and 10 mL of titanium tetrachloride was slowly added dropwise for no less than 30 minutes. The molar ratio of magnesium to titanium tetrachloride in the magnesium-containing complex solution was 1:2.2. After the addition was completed, an intermediate particle suspension was obtained. Then 0.4 mL of tri-n-butyl phosphate was added dropwise for no less than 5 minutes. The molar ratio of magnesium to tri-n-butyl phosphate in the intermediate particle suspension was 1:0.04. After reacting for 1 hour, the suspension system did not redissolve, and the transparent state of the composite system was not reached. 70 mL of titanium tetrachloride was slowly added dropwise, and then 5 mL of tetraethoxysilane was added dropwise. The molar ratio of magnesium, titanium tetrachloride and tetraethoxysilane in the system was 1:15.2:0.4. The temperature was gradually raised to 85°C at a heating rate of 0.5°C / min, and then reacted for 1 hour. Stop stirring, let it stand, the suspension will quickly separate into layers, remove the upper clear liquid, wash twice with toluene, wash four times with hexane, dry with high-purity nitrogen to obtain a solid catalyst component, its performance parameters are shown in Table 2.

[0117] (2) Slurry polymerization: Same as Example 1, using the above catalyst components, the polymerization results are shown in Tables 3 and 4.

[0118] Comparative Example 6

[0119] (1) Preparation of catalyst

[0120] In a reactor fully replaced with high-purity nitrogen, 4.0 g of magnesium chloride (42.0 mmol), 50 mL of toluene, 3.0 mL of epichlorohydrin, and 9.0 mL of tri-n-butyl phosphate were added in sequence, the temperature was raised to 70°C with stirring, 4.4 mL of ethanol was added, the molar ratio of magnesium chloride, tri-n-butyl phosphate, epichlorohydrin, ethanol and toluene was 1:0.8:0.9:1.8:11.2, and the reaction was carried out at a constant temperature for 2 hours to obtain a magnesium-containing complex solution. The magnesium-containing complex solution was cooled to -10°C, and 10 mL of titanium tetrachloride was slowly added dropwise for no less than 30 minutes. The molar ratio of magnesium to titanium tetrachloride in the magnesium-containing complex solution was 1:2.2. After the addition was completed, an intermediate particle suspension was obtained. Then 60 mL of tri-n-butyl phosphate was added dropwise for no less than 60 minutes. The molar ratio of magnesium to tri-n-butyl phosphate in the intermediate particle suspension was 1:5.3. After the tri-n-butyl phosphate was added, a transparent composite system containing magnesium and titanium was obtained. 70 mL of titanium tetrachloride was slowly added dropwise, and then 5 mL of tetraethoxysilane was added dropwise. The molar ratio of magnesium, titanium tetrachloride and tetraethoxysilane in the composite system was 1:15.2:0.4. The temperature was gradually raised to 85°C, and the heating rate was 0.5°C / min, followed by reaction for 1 hour. Stirring was stopped and allowed to stand. The suspension was difficult to separate, and a solid catalyst component with good fluidity was not obtained. Its performance parameters are shown in Table 2.

[0121] (2) Slurry polymerization: Same as Example 1, using the above catalyst components, the polymerization results are shown in Tables 3 and 4.

[0122] The catalyst components prepared in step (1) of the above examples and comparative examples were subjected to the following tests:

[0123] 1. Relative weight percentage of titanium element in the catalyst component: determined by spectrophotometry.

[0124] 2. Particle size distribution of catalyst components: measured using Malvern laser particle size and shape analyzer.

[0125] The specific test results are shown in Table 2 below.

[0126] Table 2

[0127] serial number Ti(wt%) Average particle size D50 (μm) Particle size distribution Example 1 5.6 6.5 1.02 Example 2 5.8 6.8 1.08 Example 3 6.1 3.6 1.34 Example 4 5.5 8.7 1.29 Comparative Example 1 5.0 7.3 1.61 Comparative Example 2 5.3 6.9 1.52 Comparative Example 3 - - - Comparative Example 4 5.2 7.4 1.59 Comparative Example 5 5.3 7.1 1.56 Comparative Example 6 - - -

[0128] As shown in Table 2, compared with the catalyst component of the comparative example, the catalyst component prepared in the embodiment of the present invention has a smaller Span value of particle size distribution and a more concentrated particle size distribution.

[0129] The polymers obtained after the slurry polymerization in step (2) of the above examples and comparative examples were subjected to the following tests:

[0130] 1. Bulk density of polymer powder: Determined using ASTM D1895 test method for apparent density, bulk factor and pourability of plastics.

[0131] 2. Determination of polymer powder melt index (MFR): According to ASTM D1238-99, measured at a load of 2.16 kg and 190°C.

[0132] 3. Determination of polymer powder particle size distribution: The German Retsch sieving instrument was used for sieving and determination.

[0133] 4. Determination of polymerization activity: The ratio of the mass of the powder obtained after the polymerization reaction to the mass of the catalyst added is recorded as the polymerization activity of the catalyst.

[0134] The specific test results are shown in Tables 3 and 4 below.

[0135] Table 3

[0136]

[0137] As shown in Table 3, relative to the catalyst of the comparative example, the polymerization activity of the catalyst of the embodiment of the present invention under the conditions of low hydrogen to ethyl ratio and high hydrogen to ethyl ratio was improved to a certain extent; the powder melt index under the condition of high hydrogen to ethyl ratio was significantly increased, indicating that the hydrogen adjustment sensitivity under the condition of high hydrogen to ethyl ratio was greatly improved; the powder bulk density was significantly improved, and the powder bulk density under the condition of low hydrogen to ethyl ratio homopolymerization could be ≥0.35 g / mL.

[0138] Table 4

[0139]

[0140] As shown in Table 4, compared with the catalyst of the comparative example, the polymer powder prepared by the catalyst of the embodiment of the present invention has a significantly reduced content of fine powder with a size less than 75 μm, and almost no fine powder.

[0141] From the above conclusions, it can be seen that the present invention prepares a new transparent composite system containing magnesium and titanium, and the particle size distribution of the catalyst component obtained by further titanium loading treatment based on the composite system is more concentrated, the polymerization activity and hydrogen adjustment sensitivity of the catalyst can be effectively improved, and at the same time, the bulk density of the polymerization powder is significantly improved, and the content of polymerization fine powder is greatly reduced.

[0142] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A composite system for ethylene polymerization catalyst, Features The composite system is prepared from raw materials comprising the following components: A magnesium complex solution, a titanium compound I and an organophosphorus compound II; The molar ratio of magnesium element, titanium compound I and organic phosphorus compound II in the magnesium-containing complex solution is 1:(0.1-10.0):(0.05-5.0), preferably 1:(0.2-5.0):(0.1-2.5).

2. The composite system according to claim 1, Features: The magnesium-containing complex solution is prepared by dissolving magnesium halide in an organic phosphorus compound I, an organic epoxy compound, an alcohol compound and an inert diluent; Preferably, The molar ratio of the magnesium element, the organic phosphorus compound I, the organic epoxy compound, the alcohol compound and the inert diluent in the magnesium halide is 1:(0.1-3.0):(0.1-3.0):(0.1-3.0):(1-50), preferably 1:(0.5-1.5):(0.5-1.5):(0.5-1.5):(5-20).

3. The composite system according to claim 2, Features: The magnesium halide is at least one of magnesium chloride, magnesium bromide, magnesium fluoride and magnesium iodide, preferably magnesium chloride; and / or, The organic epoxy compound is at least one of aliphatic olefins, aliphatic dienes, halogenated aliphatic olefins, oxides of halogenated aliphatic dienes, glycidyl ethers, and internal ethers; preferably, the organic epoxy compound has 2-8 carbon atoms; more preferably, the organic epoxy compound is at least one of ethylene oxide, propylene oxide, butylene oxide, butadiene oxide, butadiene dioxide, epichlorohydrin, methyl glycidyl ether, diglycidyl ether, and tetrahydrofuran, and further preferably at least one of ethylene oxide, propylene oxide, epichlorohydrin, and tetrahydrofuran; and / or, The alcohol compound is a C1-C12 fatty alcohol and a substituted alcohol derived therefrom or a C7-C12 aromatic alcohol and a substituted alcohol derived therefrom, preferably at least one of methanol, ethanol, propanol, isopropanol, butanol, isobutanol, 2-ethylhexanol, n-octanol, dodecanol, benzyl alcohol, and phenylethyl alcohol, more preferably at least one of ethanol, isopropanol, butanol, 2-ethylhexanol, benzyl alcohol, and phenylethyl alcohol; and / or, The inert diluent is C6-C10 alkane and its derivatives or C6-C8 aromatic hydrocarbon and its derivatives, preferably at least one of hexane, heptane, octane, decane, benzene, toluene and xylene.

4. The composite system according to any one of claims 1 to 3, Features: The organophosphorus compound I and the organophosphorus compound II may be the same or different, and are independently selected from trimethyl phosphate, triethyl phosphate, tri-n-propyl phosphate, triisopropyl phosphate, tri-n-butyl phosphate, triisobutyl phosphate, tri-tert-butyl phosphate, tri-n-pentyl phosphate, triisopentyl phosphate, tri-n-hexyl phosphate, triisohexyl phosphate, tri-n-heptyl phosphate, triisoheptyl phosphate, tri-n-octyl phosphate, triisooctyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, tri-n-propyl phosphite, triisopropyl phosphite , at least one of tri-n-butyl phosphite, tri-isobutyl phosphite, tri-tert-butyl phosphite, tri-n-pentyl phosphite, tri-isopentyl phosphite, tri-n-hexyl phosphite, tri-isohexyl phosphite, tri-n-heptyl phosphite, tri-isoheptyl phosphite, tri-n-octyl phosphite, tri-isooctyl phosphite, triphenyl phosphite and di-n-butyl phosphite, preferably at least one of triethyl phosphate, tributyl phosphate, tri-isooctyl phosphate, triphenyl phosphate, triethyl phosphite, tributyl phosphite and di-n-butyl phosphite; and / or, The titanium compound I is selected from the group consisting of TiX n (OR) 4-n The compound wherein: X is a halogen, R is a C1-C14 aliphatic hydrocarbon group or a C6-C14 aromatic hydrocarbon group, and n is any integer from 0 to 4; preferably at least one of titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, tetraethoxytitanium, tetrabutoxytitanium, triethoxytitanium monochloride, diethoxytitanium dichloride, and trichloromonoethoxytitanium, and more preferably at least one of titanium tetrachloride, tetraethoxytitanium, and tetrabutoxytitanium.

5. A method for preparing a composite system for ethylene polymerization catalyst according to any one of claims 1 to 4, Features The method comprises: The magnesium-containing complex solution is subjected to a first contact reaction with the titanium compound I to obtain an intermediate particle suspension, which is then subjected to a second contact reaction with the organophosphorus compound II until the solid in the intermediate particle suspension is completely dissolved to obtain the catalyst composite system.

6. The method for preparing the composite system according to claim 5, Features: The reaction temperature of the first contact reaction is -30°C to 20°C, and / or the reaction time is 0.1 to 1 hour; and / or, The reaction temperature of the second contact reaction is -30°C to 20°C, and / or the reaction time is 0.1 to 2 hours.

7. The method for preparing the composite system according to claim 5, Features: The preparation of the magnesium-containing complex solution comprises dissolving magnesium halide in an organic phosphorus compound I, an organic epoxy compound, an alcohol compound and an inert diluent; Preferably, The preparation of the magnesium-containing complex solution comprises dissolving magnesium halide in an organic phosphorus compound I, an organic epoxy compound and an inert diluent and then adding an alcohol compound; More preferably, The dissolution temperature of the magnesium halide is 50-90° C., and / or the dissolution time is 1-6 hours.

8. A catalyst component for ethylene polymerization catalyst, prepared from components including a composite system, a titanium compound II and an organosilicon compound; the composite system is a composite system as described in any one of claims 1 to 4 or a composite system prepared by the method as described in any one of claims 5 to 7; Preferably, the molar ratio of the magnesium element in the composite system, the titanium element in the titanium compound II and the organosilicon compound is 1:(1-50):(0.01-5.0), preferably 1:(5-20):(0.1-1.5).

9. The catalyst component according to claim 8, Features: The titanium compound II and the titanium compound I may be the same or different and are independently selected from the group consisting of n (OR) 4-n A compound wherein: X is a halogen, R is a C1-C14 aliphatic hydrocarbon group or a C6-C14 aromatic hydrocarbon group, and n is any integer from 0 to 4; preferably at least one of titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, tetraethoxytitanium, tetrabutoxytitanium, triethoxytitanium monochloride, diethoxytitanium dichloride, and triethoxytitanium monochloride, and more preferably at least one of titanium tetrachloride, tetraethoxytitanium, and tetrabutoxytitanium; and / or, The organosilicon compound is silicon tetrachloride, silicon tetrabromide, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetra(2-ethylhexyloxy)silane, ethyltrimethoxysilane, n-propyltriethoxysilane, n-propyltrimethoxysilane, decyltrimethoxysilane, decyltriethoxysilane, cyclopentyltrimethoxysilane, cyclopentyltriethoxysilane, 2-methylcyclopentyltrimethoxysilane, 2,3-dimethoxysilane, Methylcyclopentyltrimethoxysilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, tert-butyltriethoxysilane, n-butyltrimethoxysilane, n-butyltriethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane , monochlorotrimethoxysilane, monochlorotriethoxysilane, ethyltriisopropoxysilane, vinyltributoxysilane, trimethylphenoxysilane, methyltriallyloxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, diisopropyldimethoxysilane, diisopropyldiethoxysilane, tert-butylmethyldimethoxysilane, tert-butylmethyldiethoxysilane, tert-amylmethyldiethoxysilane, dicyclopentyldimethoxysilane, dicyclopentyldiethoxysilane, methylcyclopentyldiethoxysilane, methylcyclopentyldimethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, tricyclopentylmethoxysilane, tricyclopentylethoxysilane, dicyclopentylmethylmethoxysilane, and at least one of cyclopentyldimethylmethoxysilane, preferably at least one of silicon tetrachloride, tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane.

10. A method for preparing the catalyst component according to claim 8 or 9, Features The method comprises: The titanium compound II and the organosilicon compound are sequentially added dropwise to the composite system, so that solid particles are precipitated and then the temperature is continuously raised for reaction, and the precipitate is filtered and washed to obtain the catalyst component.

11. The method for preparing the catalyst component according to claim 10, Features: The dropping temperature is -30°C to 20°C, and / or the dropping temperature fluctuation does not exceed ±1°C; and / or, The temperature of the heating reaction is 60-110° C., and / or the reaction time is 0.5-6 hours, and / or the heating rate is 0.1-1° C. / min, preferably 0.3-0.6° C. / min.

12. A catalyst for ethylene polymerization, comprising the catalyst component as claimed in claim 8 or 9 or the catalyst component prepared by the method of claim 10 or 11, Features The catalyst comprises: Catalyst components and organoaluminum compounds; The molar ratio of the titanium element in the catalyst component to the aluminum element in the organic aluminum compound is 1:(20-200), preferably 1:(50-100).

13. The catalyst according to claim 12, Features: The structural formula of the organoaluminum compound is AlR' d X' 3-d , wherein R' is hydrogen or a C1-C20 hydrocarbon group, X' is a halogen atom, and d is any integer from 0 to 3, preferably Al(CH 3 ) 3 、Al(CH 2 CH 3 ) 3 、Al(i-Bu) 3 、AlH(CH 2 CH 3 ) 2 、AlH(i-Bu) 2 、AlCl(CH 2 CH3) 2 、Al 2 Cl 3 (CH 2 CH 3 ) 3 、AlCl(CH 2 CH 3 ) 2 、AlCl 2 (CH 2 CH 3 ), more preferably Al(CH 2 CH 3 ) 3 orAl(i-Bu) 3 .

14. Use of the catalyst according to claim 12 or 13 in ethylene polymerization; Preferably, The ethylene polymerization is homopolymerization of ethylene or copolymerization of ethylene and α-olefin; and / or, The ethylene polymerization is slurry polymerization or gas phase polymerization; More preferably, The slurry polymerization medium includes saturated aliphatic hydrocarbons or aromatic hydrocarbons, preferably at least one of isobutane, hexane, heptane, cyclohexane, naphtha, raffinate, hydrogenated gasoline, kerosene, benzene, toluene, and xylene, and more preferably at least one of toluene, n-hexane, and cyclohexane.

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