An olefin polymerization catalyst composition, its preparation method and application

Abstract

This invention relates to an olefin polymerization catalyst composition, its preparation method, and its applications. The catalyst composition is formed by the reaction of a catalyst precursor containing magnesium and halogen atoms, a metal halide, and an internal electron donor. The catalyst precursor is formed by the precipitation of a magnesium compound and a chlorine-containing compound after reaction in a single or mixed solvent of alkanes and haloaromatics. Compared with existing technologies, the catalyst composition of this invention has adjustable particle size, high catalytic activity, and can produce polymers with a viscosity-average molecular weight of 300,000 to 8,000,000, while maintaining high polymerization efficiency and producing polymer resins with a narrow particle size distribution.

Description

Technical Field

[0001] This invention belongs to the field of polymer catalysis technology, and relates to an olefin polymerization catalyst composition, its preparation method, and its application. Background Technology

[0002] Polyethylene (PE) is a thermoplastic resin polymerized from olefin monomers. It is odorless, non-toxic, chemically stable, and has good processability, with applications spanning packaging, pipes, wires and cables, daily necessities and injection molded products, industrial and engineering applications, fibers, lithium battery separators, and medical fields. Catalysts play a decisive role in the microscopic chain structure and macroscopic material properties of polyethylene, and the development of polyolefin resins is closely linked to advancements in polyolefin catalysts. Furthermore, resin properties directly determine the ease of processing and material performance. Global research investment in olefin coordination polymerization continues to grow, focusing on catalyst design optimization, innovation in polyolefin production processes, and expansion of product types. Highly efficient catalysts play a crucial role in improving product performance, reducing production costs, and simplifying production processes.

[0003] Currently, among the catalysts used in the industrial production of polyethylene, Ziegler-Natta catalysts are widely used due to their low cost, high catalytic activity, wide range of applicable monomers, and mild polymerization conditions. However, existing Ziegler-Natta polymerization catalysts using magnesium halides face challenges in controlling catalyst particle morphology and are costly. Oversized or ultrafine resin particles are difficult to swell and dissolve during processing, leading to defects in the product. Inhomogeneous resin particles also result in poor processing performance. Although resin sieving can obtain resin with a narrow particle size distribution, this also increases resin costs and wastes resources. For example, Chinese patent CN105658683B uses organometallic compounds to load magnesium-containing supports to form supported catalysts with catalytic activity of 140gPE / gCat ~ 26225gPE / gCat, resin D(50) of 41.5μm ~ 618μm, and particle size distribution span of 0.73~1.94. The preparation process of this catalyst is complicated, costly, and has low activity. In addition, the resin particle size distribution is wide, with both large particles and fine powder present.

[0004] For example, in the olefin polymerization catalyst provided by Chinese patent CN104662027B, a magnesium source is contacted with an organic halide and an alcohol in a solvent to form an organomagnesium precursor solution. This organomagnesium precursor solution is then contacted with a titanium compound and an internal electron donor to obtain a catalyst composition. The catalyst system includes the catalyst composition, a co-catalyst, and an external electron donor. However, this patent requires the additional introduction of an alcohol to prepare the magnesium compound solution for the catalyst precursor, and also necessitates the introduction of an external electron donor. The entire preparation method is cumbersome and exhibits low catalytic activity.

[0005] Therefore, it is urgent to address the problem of uneven resin particle size distribution by starting from the catalyst and its preparation process, and to develop catalyst technologies with high catalytic activity and adjustable catalyst particle size, while also having adjustable resin molecular weight and narrow resin particle size distribution. Summary of the Invention

[0006] The purpose of this invention is to provide an olefin polymerization catalyst composition, its preparation method and application, which has high catalyst activity, adjustable particle size, and can polymerize polyolefins with adjustable molecular weight from 300,000 to 8 million, and has a narrow particle size distribution.

[0007] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides an olefin polymerization catalyst composition comprising a catalyst precursor containing magnesium and halogen atoms, a metal halide, and an internal electron donor, reacted in an alkane solvent system. The catalyst precursor is obtained by precipitating a magnesium compound and a chlorine-containing compound after reaction in the solvent system. Here, the catalyst composition of the present invention does not require an external electron donor.

[0008] Further, the general chemical formula of the magnesium compound is RMgX, wherein R is selected from alkyl, aryl, cycloalkyl, aralkyl, alkylaryl, dienyl, and alkenyl groups having 1 to 20 carbon atoms, and X is R, a halogen group, a C1-C20 alkoxide, or a siloxy group. More further, the magnesium compound is one or more of methyl magnesium chloride, ethyl magnesium chloride, n-propyl magnesium chloride, isopropyl magnesium chloride, n-butyl magnesium chloride, isobutyl magnesium chloride, tert-butyl magnesium chloride, n-pentyl magnesium chloride, isopentyl magnesium chloride, cyclopentyl magnesium chloride, n-hexyl magnesium chloride, cyclohexyl magnesium chloride, n-octyl magnesium chloride, 2-ethylhexyl magnesium chloride, phenyl magnesium chloride, and benzyl magnesium chloride. For obtaining a polymerization catalyst with a good shape, ethyl magnesium chloride, n-propyl magnesium chloride, isopropyl magnesium chloride, n-butyl magnesium chloride, or phenyl magnesium chloride are more preferred. Additionally, the magnesium compound may also be dialkyl magnesium or its derivatives.

[0009] Furthermore, the magnesium compound RMgX, obtained by reacting metallic magnesium with RX, is preferably used in its ether solution form. Examples of ethers include, but are not limited to, dialkyl ethers, such as diethyl ether, di-n-propyl ether, diisopropyl ether, di-n-butyl ether, diisobutyl ether, ethyl-n-butyl ether, and diisopentyl ether; or cyclic ethers, such as tetrahydrofuran. Among these, dialkyl ethers are preferred, and di-n-butyl ether or diisobutyl ether is particularly preferred.

[0010] Further, the chlorine-containing compound is one or more of chlorine, hydrogen chloride, chlorinated hydrocarbons, alkylchlorosilanes, arylchlorosilanes, carbon tetrachloride, alkylaluminum chloride, and alkylboron chloride. Even further, the chlorine-containing compound is one or more of methyltrichlorosilane, dimethyldichlorosilane, phenyltrichlorosilane, ethylaluminum dichloride, diethylaluminum chloride, isobutylaluminum dichloride, carbon tetrachloride, boron trichloride, ethylboron dichloride, and diethylboron chloride. More preferably, it is carbon tetrachloride, tetrachlorosilane, or phenyltrichlorosilane.

[0011] Furthermore, the metal halide is at least one of titanium tetrahalide and titanium alkoxytrihalide, wherein the titanium tetrahalide is titanium tetrachloride, titanium tetrabromide or titanium tetraiodide, and the titanium alkoxytrihalide is titanium methoxytrichloride, titanium ethoxytrichloride, titanium n-butoxytrichloride, titanium isobutoxytrichloride, titanium phenoxytrichloride or titanium ethoxytribromide.

[0012] Furthermore, the internal electron donor is one or more of the following: monoaliphatic carboxylic acid esters, polyaliphatic carboxylic acid esters, aromatic carboxylic acid esters, silicate compounds, and ether compounds. Specifically, it can be ethyl acetate, methyl formate, diethyl oxalate, dimethyl malonate, ethyl benzoate, dibutyl phthalate, ethyl orthosilicate, methyl orthosilicate, diethyl ether, dibutyl ether, etc.

[0013] In a second aspect, the present invention provides a method for preparing an olefin polymerization catalyst composition, comprising the following steps: S1. In a single or mixed solvent selected from alkanes and halogenated aromatics, add magnesium compound RMgX and chlorine-containing compound and stir to react, precipitate out, separate and wash to obtain the catalyst precursor; S2. In an alkane solvent system, the catalyst precursor reacts with a metal halide and an internal electron donor. After the reaction is complete, the resulting solid particles are washed and dried to obtain the olefin polymerization catalyst composition.

[0014] Furthermore, in S1, the molar ratio of magnesium compound RMgX to chlorine-containing compound is 1:0.5~10, the stirring reaction temperature is -20℃~150℃, and the time is 1~10 hours.

[0015] Furthermore, in S2, the amounts of the catalyst precursor reacting with the metal halide and the internal electron donor satisfy the following conditions: the molar ratio of the metal element in the metal halide to the Mg element in the catalyst precursor is 0.1~20:1, the molar ratio of the internal electron donor to the Mg element in the catalyst precursor is 0.05~0.5:1, the reaction temperature is 20~130℃, and the reaction time is 1~6h.

[0016] Furthermore, in S1 and S2, the alkane solvent is a C5-C10 aliphatic hydrocarbon, and the haloaromatic solvent is preferably a chloroaromatic hydrocarbon.

[0017] Furthermore, in S2, the cleaning is carried out using alkane solvents, which includes a hot cleaning stage at 20~90℃ and a room temperature cleaning stage at room temperature, with each stage consisting of 1~8 cleaning cycles.

[0018] In a third aspect, the present invention provides an olefin polymerization catalyst composition for catalyzing the homopolymerization of ethylene, or in conjunction with... Applications in olefin copolymerization. Furthermore, in application, the catalyst composition is polymerized without the use of an external electron donor.

[0019] Furthermore, the catalyst of the present invention can be used in bulk polymerization of monomers in the liquid phase, slurry polymerization of monomers in an inert solvent, or gas-phase polymerization processes. Specifically, the polymerization temperature range can be 50–90°C, the polymerization pressure can be 0.1–5.0 MPa, and the polymerization time can be 0.1–10 hours, resulting in a particle size distribution with a viscosity-average molecular weight Mv of (30–800) × 10⁻⁶. 4 For polymers in the g / mol range, the desired polymer molecular weight can be obtained by adjusting the polymerization process during the polymerization reaction.

[0020] Compared with the prior art, the present invention has the following advantages: (1) The average particle size D50 of the prepared catalyst is 2~30μm, and the particle size of the catalyst can be adjusted.

[0021] (2) The catalyst component preparation process of the present invention is simple, and the entire reaction process does not require high energy-consuming links such as low temperature freezing, which are commonly used in known catalyst preparation technologies in the field, making it very suitable for industrial scale-up.

[0022] (3) The catalyst system of the present invention can produce polyolefins in a wide range of polymerization temperature. The average particle size of the obtained resin is controlled at 50 to 300 μm and the resin particle size distribution is less than 1.0, which meets the requirements of polyolefin products for the particle size of resin powder. Polyolefins with a viscosity-average molecular weight of 300,000 to 8 million can be obtained directly by controlling the polymerization process. Detailed Implementation

[0023] The present invention will now be described in detail with reference to specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0025] As used herein, the terms "and / or," "or / and," and "and / or" encompass any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected using at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that, in this application, the technical solution undoubtedly includes solutions connected by "logical AND," and also undoubtedly includes solutions connected by "logical OR."

[0026] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0027] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0028] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0029] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows temperature fluctuations within the precision range controlled by the instrument, such as ±5°C, ±4°C, ±3°C, ±2°C, or ±1°C.

[0030] In this document, the term "suitable" as used in phrases such as "suitable combination," "suitable method," and "any suitable method" refers to the ability to implement the technical solution of this application, solve the technical problem of this application, and achieve the expected technical effect of this application.

[0031] In this application, terms such as "further," "even more," and "particularly" are used for descriptive purposes and to indicate differences in content, but should not be construed as limiting the scope of protection of this application.

[0032] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0033] In the description of the application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0034] Unless otherwise specified, all preparations and tests described herein took place at 25°C.

[0035] The terms “comprising,” “including,” “containing,” “having,” “comprising,” or other variations thereof are intended to cover non-closed inclusion, and no distinction is made between these terms. The term “comprising” means that other steps and ingredients may be added without affecting the final result. The compositions and methods / processes of the present invention comprise, consist of, and substantially consist of the essential elements and limitations described herein, as well as any additional or optional ingredients, components, steps, or limitations described herein. No distinction is made between the terms “efficacy,” “performance,” “effect,” and “potency” herein.

[0036] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0037] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, but sequentially is preferred.

[0038] Example 1 In a 100 ml reaction flask, add 30 ml of n-heptane, a di-n-butyl ether solution containing 40 mmol of n-butylmagnesium chloride (concentration prepared to 1.0 mol / L), and 40 mmol of phenyltrichlorosilane. Stir at 1000 rpm and heat to 90 °C, maintaining this temperature for 1 hour. Catalyst precursor particles gradually precipitate. Cool the resulting suspension to room temperature, filter to remove the supernatant, and add 30 ml of n-heptane to the resulting filter cake, stirring and washing for 0.5 hours to complete one washing cycle. Repeat the same filtration and washing method with n-heptane twice more to obtain the catalyst precursor.

[0039] Add 30 ml of n-heptane and 2 mmol of ethyl benzoate to the cleaned catalyst precursor, stir at 20 °C for 1 hour, then add 40 mmol of titanium tetrachloride while stirring, raise the temperature to 60 °C within 1 hour, and maintain the reaction for 1 hour. After the reaction is complete, filter while hot, add 40 ml of n-heptane to the filter cake, stir at 50 °C for 0.5 hours, filter while hot, and continue to perform hot cleaning of the filter cake twice more using the same method. After the cleaning is completed, cool to room temperature and wash once with 40 ml of hexane using the same method with stirring and filtration at room temperature. Keep the cleaned solid particles at 60–80 °C and dry in a flowing nitrogen environment for 6 hours to obtain catalyst 1, wherein Ti: 4.14 wt%, Mg: 18.37 wt%, and particle size D(50) = 5.16 μm.

[0040] Example 2 In a 100 ml reaction flask, add 30 ml of n-heptane, 40 mmol of di-n-butyl ether solution of n-butyl magnesium chloride (1.0 mol / L), and 40 mmol of methyltrichlorosilane. Heat to 90 °C with stirring at 1000 rpm and maintain the temperature for 1 hour. Catalyst precursor particles gradually precipitate. Cool the resulting suspension to room temperature, filter to remove the supernatant, and add 30 ml of n-heptane to the resulting filter cake and stir for 0.5 hours to complete one washing cycle. Repeat the same filtration and washing method with n-heptane twice more to obtain the catalyst precursor.

[0041] Add 30 ml of n-heptane and 2 mmol of ethyl benzoate to the cleaned catalyst precursor, stir at 20 °C for 1 hour, then add 40 mmol of titanium tetrachloride while stirring, raise the temperature to 60 °C within 1 hour, and maintain the reaction for 1 hour. After the reaction is complete, filter while hot, add 40 ml of n-heptane to the filter cake, stir at 50 °C for 0.5 hours, filter while hot, and continue to perform hot cleaning of the filter cake twice more using the same method. After the cleaning is completed, cool to room temperature and wash once with 40 ml of hexane using the same method with stirring and filtration at room temperature. Keep the cleaned solid particles at 60–80 °C and dry in a flowing nitrogen environment for 6 hours to obtain catalyst 2, Ti: 3.68 wt%, Mg: 20.26 wt%, particle size D(50) = 5.73 μm.

[0042] Example 3 In a 100 ml reaction flask, add 30 ml of n-heptane, 40 mmol of di-n-butyl ether solution of n-butyl magnesium chloride (1.0 mol / L), and 40 mmol of carbon tetrachloride. Stir at 1000 rpm and heat to 90 °C, maintaining the temperature for 1 hour. Catalyst precursor particles gradually precipitate. Cool the resulting suspension to room temperature, filter to remove the supernatant, and add 30 ml of n-heptane to the resulting filter cake, stirring and washing for 0.5 hours to complete one washing cycle. Repeat the same filtration and washing method with n-heptane twice more to obtain the catalyst precursor.

[0043] Add 30 ml of n-heptane and 2 mmol of ethyl benzoate to the cleaned catalyst precursor, stir at 20 °C for 1 hour, then add 40 mmol of titanium tetrachloride while stirring, raise the temperature to 60 °C within 1 hour, and maintain the reaction for 1 hour. After the reaction is complete, filter while hot, add 40 ml of n-heptane to the filter cake, stir at 50 °C for 0.5 hours, filter while hot, and continue to perform hot cleaning of the filter cake twice more using the same method. After the cleaning is completed, cool to room temperature and wash once with 40 ml of hexane using the same method with stirring and filtration at room temperature. Keep the cleaned solid particles at 60–80 °C and dry in a flowing nitrogen environment for 6 hours to obtain catalyst 3, Ti: 3.55 wt%, Mg: 20.51 wt%, particle size D(50) = 5.93 μm.

[0044] Example 4 In a 100 ml reaction flask, add 30 ml of n-heptane, 40 mmol of di-n-butyl ether solution of phenyl magnesium chloride (1.0 mol / L), and 40 mmol of phenyltrichlorosilane. Heat to 90 °C with stirring at 1000 rpm and maintain the temperature for 1 hour. Catalyst precursor particles gradually precipitate. Cool the resulting suspension to room temperature, filter to remove the supernatant, and add 30 ml of n-heptane to the resulting filter cake and stir for 0.5 hours to complete one washing cycle. Repeat the same filtration and washing method with n-heptane twice more to obtain the catalyst precursor.

[0045] Add 30 ml of n-heptane and 2 mmol of ethyl benzoate to the cleaned catalyst precursor, stir at 20 °C for 1 hour, then add 40 mmol of titanium tetrachloride while stirring, raise the temperature to 60 °C within 1 hour, and maintain the reaction for 1 hour. After the reaction is complete, filter while hot, add 40 ml of n-heptane to the filter cake, stir at 50 °C for 0.5 hours, filter while hot, and continue to perform hot cleaning of the filter cake twice more using the same method. After the cleaning is completed, cool to room temperature and wash once with 40 ml of hexane using the same method with stirring and filtration. Keep the cleaned solid particles at 60–80 °C and dry in a flowing nitrogen environment for 6 hours to obtain catalyst 4, Ti: 3.65 wt%, Mg: 24.17 wt%, particle size D(50) = 5.09 μm.

[0046] Example 5 In a 100 ml reaction flask, add 30 ml of n-heptane, 40 mmol of di-n-butyl ether solution of n-butyl magnesium chloride (1.0 mol / L), and 40 mmol of phenyltrichlorosilane. Heat to 90 °C with stirring at 1000 rpm and maintain the temperature for 1 hour. Catalyst precursor particles gradually precipitate. Cool the resulting suspension to room temperature, filter to remove the supernatant, and add 30 ml of n-heptane to the resulting filter cake and stir for 0.5 hours to complete one washing cycle. Repeat the same filtration and washing method with n-heptane twice more to obtain the catalyst precursor.

[0047] Add 30 ml of n-heptane and 2 mmol of dibutyl ether to the cleaned catalyst precursor, stir at 20 °C for 1 hour, then add 40 mmol of titanium tetrachloride while stirring, raise the temperature to 60 °C within 1 hour, and maintain the reaction for 1 hour. After the reaction is complete, filter while hot, add 40 ml of n-heptane to the filter cake, stir at 50 °C for 0.5 hours, filter while hot, and continue to perform hot cleaning of the filter cake twice more using the same method. After the cleaning is completed, cool to room temperature and wash once with 40 ml of hexane using the same method with stirring and filtration at room temperature. Keep the cleaned solid particles at 60–80 °C and dry in a flowing nitrogen environment for 6 hours to obtain catalyst 5, Ti: 4.19 wt%, Mg: 18.59 wt%, particle size D(50) = 5.23 μm.

[0048] Example 6 In a 100 ml reaction flask, add 30 ml of n-heptane, 40 mmol of di-n-butyl ether solution of n-butyl magnesium chloride (1.0 mol / L), and 40 mmol of phenyltrichlorosilane. Stir at 1000 rpm and heat to 90 °C, maintaining the temperature at 90 °C for 1 hour. Catalyst precursor particles gradually precipitate. Cool the resulting suspension to room temperature, filter to remove the supernatant, and add 30 ml of n-heptane to the resulting filter cake, stirring and washing for 0.5 hours to complete one washing cycle. Repeat the same filtration and washing method with n-heptane twice more to obtain the catalyst precursor.

[0049] Add 30 ml of n-heptane, 2 mmol of ethyl benzoate, and 40 mmol of titanium tetrachloride to the cleaned catalyst precursor. Increase the temperature to 60 °C within 1 hour and maintain the reaction for 1 hour. After the reaction is complete, filter while hot. Add 40 ml of n-heptane to the filter cake, stir at 50 °C for 0.5 hours, and filter while hot. Repeat the hot cleaning process twice more with the same method. After the cleaning, cool to room temperature and wash once with 40 ml of hexane using the same method with stirring and filtration. Dry the cleaned solid particles at 60–80 °C in a flowing nitrogen atmosphere for 6 hours to obtain catalyst 6, with Ti: 4.23 wt%, Mg: 19.15 wt%, and particle size D(50) = 5.31 μm.

[0050] Comparative Example 1 In a 100 ml reaction flask, add 10 mmol magnesium powder, 30 mL toluene, 20 mmol benzyl chloride, and 10 mmol 2-ethylhexanol. Stir at 500 r / min and heat to 90 °C. React for 6 hours to obtain a catalyst precursor solution.

[0051] In a 500 ml reaction flask, 10 mL of titanium tetrachloride and 2 mmol of ethyl benzoate were added dropwise to the catalyst precursor solution. The temperature was raised to 60 °C within 1 hour and maintained for 1 hour. After the reaction was completed, the mixture was filtered while hot. 40 mL of n-heptane was added to the filter cake, and the mixture was stirred at 50 °C for 0.5 hours before being filtered while hot. The filter cake was then subjected to two more hot washes using the same method. After the reaction was completed, the mixture was cooled to room temperature and washed once with 40 mL of hexane using the same method with stirring and filtration. The washed solid particles were dried at 60–80 °C in a flowing nitrogen atmosphere for 6 hours to obtain catalyst 7, with Ti: 3.70 wt%, Mg: 17.20 wt%, and particle size D(50) = 6.31 μm.

[0052] Comparative Example 2 In a 100 ml reaction flask, add 10 mmol magnesium powder, 30 mL toluene, 20 mmol tert-butyl chloride, and 10 mmol 2-ethylhexanol. Stir at 500 r / min and heat to 90 °C. React for 6 hours to obtain a catalyst precursor solution.

[0053] In a 500 ml reaction flask, 10 mL of titanium tetrachloride and 2 mmol of ethyl benzoate were added dropwise to the catalyst precursor solution. The temperature was raised to 60 °C within 1 hour and maintained for 1 hour. After the reaction was completed, the mixture was filtered while hot. 40 mL of n-heptane was added to the filter cake, and the mixture was stirred at 50 °C for 0.5 hours before being filtered while hot. The filter cake was then subjected to two more hot washes using the same method. After the reaction was completed, the mixture was cooled to room temperature and washed once with 40 mL of hexane using the same method with stirring and filtration. The washed solid particles were dried at 60–80 °C in a flowing nitrogen atmosphere for 6 hours to obtain catalyst 8, with Ti: 2.20 wt%, Mg: 16.90 wt%, and particle size D(50) = 7.59 μm.

[0054] Comparative Example 3 Compared with Example 1, except that phenyltrichlorosilane was replaced with an equimolar amount of ethyl aluminum dichloride, other conditions remained unchanged, and catalyst 9 was obtained with Ti: 1.01 wt%, Mg: 20.26 wt%, and particle size D(50) = 5.82 μm.

[0055] Comparative Example 4 Compared with Example 1, except that n-butyl magnesium chloride was replaced with an equimolar amount of diethoxy magnesium, other conditions remained unchanged, resulting in catalyst 10 with Ti: 3.28 wt%, Mg: 19.73 wt%, and particle size D(50) = 5.69 μm.

[0056] Comparative Example 5 Compared with Example 1, except that ethyl benzoate was replaced with an equimolar amount of tetraethyl orthosilicate, other conditions remained unchanged, resulting in catalyst 11 with Ti: 2.17 wt%, Mg: 20.45 wt%, and particle size D(50) = 5.43 μm.

[0057] Example 7 Catalytic olefin polymerization and resin characterization.

[0058] (1) Homopolymerization of ethylene: Under nitrogen protection, 1.2 L of n-heptane and 0.5 g of triethylaluminum (TEA) were added to a 2 L stainless steel polymerization reactor. The reactor temperature was adjusted and kept stable. 20.0 mg of the catalyst from Examples 1-6 or Comparative Examples 1-5 was weighed and suspended in n-heptane. The suspension was then added to the reactor, the gas pressure was quickly adjusted, and a 2-hour timer was started, maintaining a constant gas pressure throughout the polymerization process. After the reaction was complete, the ethylene gas supply was stopped, and the gas in the polymerization reactor was slowly released. The mixture was filtered to obtain a white solid, which was then vacuum dried until constant weight to obtain the polymer. The mass, molecular weight, particle size, and distribution of the polyethylene product were measured, and the catalytic activity of the catalyst was calculated based on the obtained polymer mass.

[0059] The reaction conditions and results of the polymerization catalyzed by each catalyst are summarized in Table 1.

[0060] Table 1. Summary of Evaluation Results of Catalytic Polyethylene Reaction in Each Example or Comparative Example

[0061] Note: The particle size distribution in Table 1 is the resin particle size Span value, defined as (D... 90 -D 10 ) / D 50 The viscosity-average molecular weight test method is GB / T 1632.3-2010; the catalyst particle size, resin particle size and distribution test methods are GB / T 11115-2009.

[0062] Referring to Table 1 above, Comparative Examples 1 and 2 used magnesium shavings, toluene, benzyl chloride / tert-butyl chloride, and alcohol to prepare catalyst precursor solutions, and the resulting catalyst supports were all regular δ-MgCl2. In comparison, the high-defect δ-MgCl2 catalyst support of Example 1 was easier to prepare, had a higher BET specific surface area, more crystal defects, and was more conducive to metal center loading. Therefore, under the same conditions, using the catalyst provided in Example 1, the resin particle size distribution of the ethylene homopolymer product was narrower, and the catalytic activity was higher. The reason for this is that, compared with conventional catalyst precursors such as magnesium chloride, the catalyst precursor of Example 1 of this invention is obtained by reacting magnesium compounds and chlorine-containing compounds in a solvent system and then precipitating it out. It is essentially amorphous δ-Mg chloride, characterized by high disorder, nanocrystals, many stacking faults, and broadened and dispersed XRD, which is particularly suitable as a support for polyolefin catalysts. Therefore, it can further improve the activity of polyolefin catalysts.

[0063] A comparison of Example 1 (catalyst 1) with Comparative Examples 3 to 5 (catalysts 9 to 11) reveals that, to meet the performance requirements of high catalytic activity and narrow resin particle size distribution of this invention, strict requirements are placed on the types of chlorine-containing compounds and magnesium compounds, as well as the types of internal electron donors, during the preparation of the catalyst precursor. For example, in Comparative Example 3, n-butylmagnesium chloride and ethyl aluminum dichloride are prone to alkyl side coupling reactions during the reaction, and in Comparative Example 4, magnesium diethoxy and phenyltrichlorosilane are prone to condensation reactions between substituted silanes during the reaction. These reactions severely degrade the catalyst activity. In addition, ethyl benzoate, as an aromatic monoester Lewis base, can stabilize the adsorption support steric surface and selectively poison random active centers in the catalyst system of Example 1. However, tetraalkoxysilane, being a tetraalkoxysilane, has extremely weak coordination ability and is prone to hydrolysis and condensation. Although it can act as a support modifier to assist in regulating the pore structure of the support, it cannot independently assume the role of an internal electron donor, leading to the deterioration of catalyst activity and other performance characteristics.

[0064] Furthermore, based on the corresponding experimental data from the various embodiments in Table 1, it can be seen that, under the same polymerization conditions, increasing the ethylene pressure increases the catalytic activity; decreasing the polymerization temperature decreases the activity; increasing the resin molecular weight, adding hydrogen can reduce the resin molecular weight, and the more hydrogen, the lower the molecular weight, thus adjusting the resin molecular weight.

[0065] Different magnesium compounds, chlorine-containing compounds, stirring rates, internal electron donors, and polymerization process conditions all have varying effects on the polymerization activity of the catalyst of this invention, as well as the particle size and molecular weight of the final polymer. By understanding these influencing factors and combining them with the characteristics of this invention's catalyst in adjusting polymer molecular weight through temperature, co-catalyst, and hydrogenation, a series of polymer products with different particle sizes and molecular weights can be further improved and enriched.

[0066] (2) Ethylene copolymerization: Under nitrogen protection, 1.2 L of n-heptane and 0.5 g of triethylaluminum (TEA) were added to a 2 L stainless steel polymerization reactor. The reactor temperature was adjusted and maintained at 75 °C. 20.0 mg of the above-mentioned catalyst 1 was weighed and suspended in n-heptane. The suspension was then added to the reactor, and the gas pressure (molality ratio of ethylene to propylene = 2:1) was rapidly adjusted, and a 2-hour timer was started, maintaining a constant gas pressure of 1.0 MPa throughout the polymerization process. After the reaction was completed, the gas supply was stopped, and the gas in the polymerization reactor was slowly released. The mixture was filtered to obtain a white solid, which was then vacuum dried until constant weight to obtain the polymer. The mass, molecular weight, particle size, and distribution of the polyethylene product were analyzed, and the catalytic activity of the catalyst was calculated based on the obtained polymer mass. The catalyst activity was found to be 31670 g-PE / g-Cat, and the viscosity-average molecular weight of the prepared polyethylene copolymer was 257 × 10⁻⁶. 4g / mol, with a particle size of approximately 134 μm and a particle size distribution SPAN value of 0.78.

[0067] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. An olefin polymerization catalyst composition, characterized in that, It is prepared by mixing and reacting three components—catalyst precursor, metal halide, and internal electron donor—in an alkane solvent system. The catalyst precursor is obtained by reacting magnesium compound and chlorine-containing compound in a solvent system and then precipitating the precipitate. The general chemical formula of the magnesium compound is RMgX, wherein R is selected from alkyl, aryl, cycloalkyl, aralkyl, alkylaryl, alkyldienyl and alkenyl groups having 1 to 20 carbon atoms, and X is a halogen group. The chlorine-containing compound is one or more of chlorine, hydrogen chloride, chlorinated hydrocarbons, alkylchlorosilanes, arylchlorosilanes, carbon tetrachloride, alkylaluminum chloride, and alkylboron chloride. The internal electron donor is one or a mixture of several of the following: ethyl acetate, methyl formate, diethyl oxalate, dimethyl malonate, ethyl benzoate, dibutyl phthalate, diethyl ether, and dibutyl ether. The metal halide is at least one of titanium tetrahalide and titanium alkoxy trihalide.

2. The olefin polymerization catalyst composition according to claim 1, characterized in that, The magnesium compound is one or more of the following: methyl magnesium chloride, ethyl magnesium chloride, n-propyl magnesium chloride, isopropyl magnesium chloride, n-butyl magnesium chloride, isobutyl magnesium chloride, tert-butyl magnesium chloride, n-pentyl magnesium chloride, isopentyl magnesium chloride, cyclopentyl magnesium chloride, n-hexyl magnesium chloride, cyclohexyl magnesium chloride, n-octyl magnesium chloride, 2-ethylhexyl magnesium chloride, phenyl magnesium chloride, and benzyl magnesium chloride.

3. The olefin polymerization catalyst composition according to claim 1, characterized in that, The chlorine-containing compound is one or more of methyltrichlorosilane, dimethyldichlorosilane, phenyltrichlorosilane, carbon tetrachloride, boron trichloride, ethyl boron dichloride, and diethyl boron chloride.

4. The olefin polymerization catalyst composition according to claim 1, characterized in that, The titanium tetrahalide is titanium tetrachloride, titanium tetrabromide, or titanium tetraiodide, and the titanium alkoxy trihalide is titanium methoxytrichloride, titanium ethoxytrichloride, titanium n-butoxytrichloride, titanium isobutoxytrichloride, titanium phenoxytrichloride, or titanium ethoxytribromide.

5. The method for preparing the olefin polymerization catalyst composition according to any one of claims 1-4, characterized in that, Includes the following steps: S1. In a single or mixed solvent selected from alkanes and halogenated aromatics, add magnesium compound RMgX and chlorine-containing compound and stir to react, precipitate out, separate and wash to obtain the catalyst precursor; S2. In an alkane solvent system, the catalyst precursor reacts with a metal halide and an internal electron donor. After the reaction is complete, the resulting solid particles are washed and dried to obtain the olefin polymerization catalyst composition. In S1, the molar ratio of magnesium compound RMgX to chlorine-containing compound is 1:0.5~10, the stirring reaction temperature is -20℃~150℃, and the time is 1~10 hours; In S2, the amounts of the catalyst precursor reacting with the metal halide and the internal electron donor satisfy the following conditions: the molar ratio of the metal element in the metal halide to the Mg element in the catalyst precursor is 0.1~20:1, the molar ratio of the internal electron donor to the Mg element in the catalyst precursor is 0.05~0.5:1, the reaction temperature is 20~130℃, and the reaction time is 1~6h.

6. The application of the olefin polymerization catalyst composition according to any one of claims 1-4, characterized in that, This catalyst composition is used to catalyze the homopolymerization of ethylene, or the reaction of ethylene with... -Olefin copolymerization.

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