Metallocene polyethylene catalyst, preparation method, application and related product

Abstract

The invention provides a metallocene polyethylene catalyst, a preparation method, application and related products, and belongs to the technical field of catalytic chemistry. The metallocene polyethylene catalyst provided by the invention is prepared from a metallocene compound, methylaluminoxane and modified silica gel, the surface of the modified silica gel is modified by a silicate ester compound containing crown ether groups. Through surface modification of the crown ether functional group, on one hand, the loading effect of the silica gel carrier on the metallocene compound is improved, on the other hand, polar groups provided by the crown ether functional group can control static electricity generated in the stirring and mixing process of a reaction material mixture, and then product coalescence and shutdown inspection are reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalytic chemistry and relates to a metallocene polyethylene catalyst, a preparation method, an application and related products. Background Art

[0002] Commonly used catalysts in polyethylene production include Ziegler-Natta catalysts and metallocene catalysts. Metallocene catalysts have garnered widespread attention in recent years due to their high catalytic activity, well-defined catalytic center structure, flexible and adjustable microchemical structure, and excellent air stability. The mechanism of polyethylene synthesis catalyzed by metallocene catalysts is that the unique sandwich structure of the metallocene center coordinates with olefin molecules, initiating the polymerization reaction. By manipulating the microstructure of the metallocene catalyst, precise control of the molecular weight distribution of the resulting polyethylene can be achieved, facilitating the efficient production of polyethylene.

[0003] Chinese invention patent CN116178594A discloses an in-situ supported metallocene catalyst for olefin polymerization, its preparation method, and its application. This technology utilizes silanized oxamide to modify the silica gel surface. The amide group in the oxamide structure has the ability to adsorb and fix the metallocene compound, enhancing the catalyst's activity.

[0004] Chinese invention patent CN119350527A discloses a metallocene catalyst composition, its preparation method, and its application. This technology addresses the problem of static electricity generated during polyolefin gas-phase and slurry polymerization processes. By adding a melem-structured stabilizer, the metallocene catalyst composition is formed to regulate the entire reaction system and reduce static electricity. However, the stabilizer used in this technology is not bonded to the support surface. If the stabilizer is unevenly distributed, there is a risk of uneven distribution of the stabilizer's effectiveness.

[0005] The prior art has not yet provided a metallocene polyethylene catalyst that can simultaneously stabilize the reaction and increase adsorption by directly modifying the carrier material. Summary of the Invention

[0006] In view of this, and in response to the above-mentioned problems in the prior art, the object of the present invention is to provide a metallocene polyethylene catalyst, a preparation method, an application and related products.

[0007] In one aspect, the present invention provides a metallocene polyethylene catalyst, which is made of a metallocene compound, methylaluminoxane and modified silica gel; The surface of the modified silica gel is modified by compound I;

[0008] Compound I; Wherein, R is selected from C1-C3 hydrocarbon groups.

[0009] Furthermore, the R is one of methyl, ethyl, n-propyl or isopropyl.

[0010] As an example of the present invention, the R is ethyl.

[0011] Furthermore, the general formula of the metallocene compound is Cp*2MX n ; Wherein, in the metallocene compound, M is selected from Ti, Zr, Hf, Fe or rare earth metal elements, X is selected from one or more of halogen, alkoxy, and carboxylate, and n is an integer that satisfies the valence state of M.

[0012] As an example of the present invention, the metallocene compound is bis(propylcyclopentadienyl)hafnium(IV) dichloride.

[0013] As an example of the present invention, the metallocene compound is bis(cyclopentadiene)zirconium dichloride.

[0014] Furthermore, the proportion of the metallocene compound in the metallocene polyethylene catalyst is 0.1wt%-0.9wt%, the proportion of the methylaluminoxane in the metallocene polyethylene catalyst is 1wt%-30wt%, and the weight modification rate of the compound I is 2%-6%.

[0015] The term "wt%" means percentage by weight.

[0016] The term "weight modification rate of Compound I" refers to the percentage of the weight increase of the metallocene catalyst after modification by Compound I to the weight of the metallocene catalyst.

[0017] The proportion of the metallocene compound in the metallocene polyethylene catalyst can be any value within the range of 0.1-0.9wt%, including but not limited to 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9wt% or the range between any two thereof.

[0018] Wherein, the proportion of the methylaluminoxane in the metallocene polyethylene catalyst is any value in the range of 1-30wt%, including but not limited to 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30wt% or the range between any two thereof.

[0019] Wherein, the weight modification rate of the compound I is any value within the range of 2%-6%, including but not limited to 2%, 3%, 4%, 5%, 6% or the range between any two thereof.

[0020] Furthermore, the proportion of the metallocene compound in the metallocene polyethylene catalyst is 0.55wt%-0.81wt%, the proportion of the methylaluminoxane in the metallocene polyethylene catalyst is 10.76wt%-16.34wt%, and the weight modification rate of the compound I is 2.93%-5.00%.

[0021] Wherein, the proportion of the metallocene compound in the metallocene polyethylene catalyst is any value within the range of 0.55-0.81wt%, including but not limited to 0.55, 0.56, 0.57, 0.58, 0.59, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81wt% or the range between any two thereof.

[0022] Wherein, the ratio of methylaluminoxane to the metallocene polyethylene catalyst is any value in the range of 10.76-16.34 wt%, including but not limited to 10.76, 10.8, 10.9, 11.0, 11.1, 11.2, 11.3, 11.4, 11.5, 11.6, 11.7, 11.8, 11.9, 12.0, 12.1, 12.2, 12.3, 12.4, 12.5, 12.6, 12.7, 12.8, 12.9, 13.0, 13.1 %, 13.2%, 13.3%, 13.4%, 13.5%, 13.6%, 13.7%, 13.8%, 13.9%, 14.0%, 14.1%, 14.2%, 14.3%, 14.4%, 14.5%, 14.6%, 14.7%, 14.8%, 14.9%, 15.0%, 15.1%, 15.2%, 15.3%, 15.4%, 15.5%, 15.6%, 15.7%, 15.8%, 15.9%, 16.0%, 16.1%, 16.2%, 16.3%, 16.34%, or a range between any two of them.

[0023] Wherein, the weight modification rate of the compound I is any value within the range of 2.93%-5.00%, including but not limited to 2.93%, 2.94%, 2.95%, 2.96%, 2.97%, 2.98%, 2.99%, 3.00%, 3.01%, 3.02%, 3.03%, 3.04%, 3.05%, 3.06%, 3.07%, 3.08%, 3.09%, 3.10%, 3.11%, 3.12%, 3.13%, 3.14%, 3.15%, 3.16%, 3.17%, 3.18%, 3.19%, 3.20%, 3.21%, 3.22%, 3.23%, 3.24%, 3.25%, 3.26%, 3. 27%, 3.28%, 3.29%, 3.30%, 3.31%, 3.32%, 3.33%, 3.34%, 3.35%, 3.36%, 3.37%, 3.38%, 3.39%, 3.40%, 3.41%, 3.42%, 3.43%, 3.44%, 3.45%, 3.46%, 3.47%, 3.48%, 3.49%, 3.50%, 3.51%, 3.52%, 3.53%, 3.54%, 3.55%, 3.56%, 3.57%, 3.58%, 3.59%, 3.60%, 3.61%, 3.62%, 3.63%, 3.64%, 3.65%, 3.66%, 3.67%, 3.68%, 3.69%, 3.70%, 3.71%, 3.72%, 3.73%, 3.74%, 3.75%, 3.76%, 3.77%, 3.78%, 3.79%, 3.80%, 3.81%, 3.82%, 3.83%, 3.84%, 3.85%, 3.86%, 3.87%, 3.88%, 3.89%, 3.90%, 3.91%, 3.92%, 3.93%, 3.94%, 3.95%, 3.96%, 3.97%, 3.98%, 3.99%, 4.00%, 4.01%, 4.02%, 4.03%, 4.04%, 4.05%, 4.06%, 4.07%, 4.08%, 4.09%, 4.10 %, 4.11%, 4.12%, 4.13%, 4.14%, 4.15%, 4.16%, 4.17%, 4.18%, 4.19%, 4.20%, 4.21%, 4.22%, 4.23%, 4.24%, 4.25%, 4.26%, 4.27%, 4.28%, 4.29%, 4.30%, 4.31%, 4.32%, 4.33%, 4.34%, 4.35%, 4.36%, 4.37%, 4.38%, 4.39%, 4.40%, 4.41%, 4.42%, 4.43%, 4.44%, 4.45%, 4.46%, 4.47%, 4.48%, 4.49%, 4.50%, 4.51%, 4.52%, 4.53%, 4.54%, 4.55%, 4.56%, 4.57%, 4.58%, 4.59%, 4.60%, 4.61%, 4.62%, 4.63%, 4.64%, 4.65%, 4.66%, 4.67%, 4.68%, 4.69%, 4.70%, 4.71%, 4.72%, 4.73%, 4.74%, 4.75%, 4.76%, 4.7 7%, 4.78%, 4.79%, 4.80%, 4.81%, 4.82%, 4.83%, 4.84%, 4.85%, 4.86%, 4.87%, 4.88%, 4.89%, 4.90%, 4.91%, 4.92%, 4.93%, 4.94%, 4.95%, 4.96%, 4.97%, 4.98%, 4.99%, 5.00%, or a range between any two thereof.

[0024] As an example of the present invention, the proportion of the metallocene compound in the metallocene polyethylene catalyst is 0.81wt%, the proportion of the methylaluminoxane in the metallocene polyethylene catalyst is 16.34wt%, and the weight modification rate of the compound I is 2.93%.

[0025] As an example of the present invention, the proportion of the metallocene compound in the metallocene polyethylene catalyst is 0.63wt%, the proportion of the methylaluminoxane in the metallocene polyethylene catalyst is 13.71wt%, and the weight modification rate of the compound I is 4.71%.

[0026] As an example of the present invention, the proportion of the metallocene compound in the metallocene polyethylene catalyst is 0.55wt%, the proportion of the methylaluminoxane in the metallocene polyethylene catalyst is 10.76wt%, and the weight modification rate of the compound I is 5.00%.

[0027] As an example of the present invention, the proportion of the metallocene compound in the metallocene polyethylene catalyst is 0.66wt%, the proportion of the methylaluminoxane in the metallocene polyethylene catalyst is 16.08wt%, and the weight modification rate of the compound I is 4.74%.

[0028] On the other hand, the present invention provides a method for preparing the above-mentioned metallocene polyethylene catalyst, comprising the following steps: S1, activating silica gel, mixing with a solution of compound I, and reacting to obtain modified silica gel; S2. Mixing the modified silica gel obtained in step S1 with a solution of methylaluminoxane, and stirring to obtain an aluminum-supported catalyst; S3. Mixing the aluminum-supported catalyst obtained in step S2 with a solution of the metallocene compound to support the catalyst and obtain a metallocene polyethylene catalyst.

[0029] Furthermore, the ratio of the weight of the silica gel in step S1, the molar amount of compound I, the weight of the methylaluminoxane in step S2, and the weight of the metallocene compound in step S3 is 11.8429-13.1166:0.625-1.2:1.66-2.75:0.08-0.15, in units of g:mmol:g:g.

[0030] As an example of the present invention, the ratio of the weight of the silica gel in step S1, the molar amount of the compound I, the weight of the methylaluminoxane in step S2, and the weight of the metallocene compound in step S3 is 12.0114:1:2.32:0.11, in units of g:mmol:g:g.

[0031] As an example of the present invention, the ratio of the weight of the silica gel in step S1, the molar amount of the compound I, the weight of the methylaluminoxane in step S2, and the weight of the metallocene compound in step S3 is 13.1166:0.625:2.75:0.15, in units of g:mmol:g:g.

[0032] As an example of the present invention, the ratio of the weight of the silica gel in step S1, the molar amount of the compound I, the weight of the methylaluminoxane in step S2, and the weight of the metallocene compound in step S3 is 11.8429:1.2:1.66:0.08, in units of g:mmol:g:g.

[0033] As an example of the present invention, the ratio of the weight of the silica gel in step S1, the molar amount of the compound I, the weight of the methylaluminoxane in step S2, and the weight of the metallocene compound in step S3 is 12.0179:1:2.32:0.11, in units of g:mmol:g:g.

[0034] Furthermore, in step S1, the reaction condition is reflux reaction for 12-36 hours.

[0035] The reflux reaction time may be any value within the range of 12-36 h, including but not limited to 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36 h or any range therebetween.

[0036] As an example of the present invention, in step S1, the reaction condition is reflux reaction for 24 hours.

[0037] Furthermore, in step S2, the stirring time is 6-18 hours, and the stirring temperature is 0-20°C.

[0038] The stirring time may be any value within the range of 6-18 hours, including but not limited to 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 hours or any range therebetween.

[0039] As an example of the present invention, in step S2, the stirring time is 12 hours.

[0040] The stirring temperature may be any value within the range of 0-20°C, including but not limited to 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20°C or any range therebetween.

[0041] As an example of the present invention, in step S2, the stirring temperature is 10°C.

[0042] Furthermore, in step S3, the temperature of the load is 30-46° C., and the load time is 10-14 hours.

[0043] The temperature of the load may be any value within the range of 30-46°C, including but not limited to 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46°C or any range therebetween.

[0044] As an example of the present invention, in step S3, the temperature of the load is 38°C.

[0045] The load time may be any value within the range of 10-14 hours, including but not limited to 10, 11, 12, 13, 14 hours or any range therebetween.

[0046] As an example of the present invention, in step S3, the load time is 12 hours.

[0047] In another aspect, the present invention provides the use of the metallocene polyethylene catalyst or the metallocene polyethylene catalyst prepared by the above preparation method in polyethylene production.

[0048] In another aspect, the present invention provides polyethylene prepared using the metallocene polyethylene catalyst or the metallocene polyethylene catalyst prepared by the above preparation method.

[0049] In the final aspect, the present invention provides compound I, which has the following structure:

[0050] Compound I; R is selected from C1-C3 hydrocarbon groups.

[0051] Furthermore, the R is one of methyl, ethyl, n-propyl or isopropyl.

[0052] As an example of the present invention, the R is ethyl.

[0053] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a metallocene polyethylene catalyst comprising a metallocene compound, methylaluminoxane, and modified silica gel; the surface of the modified silica gel is modified with a silicate compound containing crown ether groups. The surface modification with crown ether functional groups not only improves the silica gel's ability to support the metallocene compound, but also provides polar groups that control static electricity generated during the stirring and mixing of the reaction mixture, thereby reducing reaction agglomeration and requiring shutdown inspections. DETAILED DESCRIPTION

[0054] Terms and Claims of the Present Invention: 1. The articles "a", "an" and "the" include plural referents unless expressly limited to one or more referents otherwise.

[0055] 2. Numerical ranges: Unless expressly stated otherwise, all ranges or ratios disclosed herein are to be understood to include any and all subranges or subratios contained therein. For example, a range or ratio stated as 1 to 30 is to be considered inclusive of any and all subranges or subratios, integers, decimals, or subranges or subratios comprised therein, between a minimum of 1 and a maximum of 30, including any subranges or subratios, integers, decimals, or subranges or subratios comprised therein.

[0056] The following non-limiting examples are provided to enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way. The following are merely illustrative of the scope of the present invention, and those skilled in the art may make various changes and modifications to the present invention based on the disclosed content, which should also fall within the scope of the present invention.

[0057] The present invention will be further described below by way of specific examples. The various chemical reagents used in the examples of the present invention were obtained through conventional commercial channels unless otherwise specified. Unless otherwise specified, the contents described below are all by weight. Unless otherwise specified, it is understood that the experiments were conducted at room temperature.

[0058] In the following examples, information on some of the compound raw materials used is shown in Table 1.

[0059] Table 1

[0060] Bis(propylcyclopentadienyl)hafnium(IV) dichloride, also known as 1,1'-dipropylcyclopentadienyl hafnium dichloride, has the following chemical structure: .

[0061] In the following example, the structure of compound I is: .

[0062] The synthetic route is as follows:

[0063] in, The synthesis method of 18-crown-6-dianhydride (hereinafter referred to as 18-crown-6-dianhydride) is described in the prior art "Molecular Receptors. Functionalized and Chiral Macrocyclic Polyethers Derived from Tartaric Acid".

[0064] The synthesis method of (N-cyclohexylidene-3-triethoxysilyl-1-propylamine) refers to the description of Example 1 in the prior art JP2015107944A.

[0065] The synthesis steps are as follows: A four-necked flask was placed with a tetrafluoroethylene stirring bar. Each of the four necks was equipped with a thermometer, a Dean-Stark dropping funnel, and a tube connected to a Schlenk tube. A condenser was installed on the water-separating rectifier, and the Schlenk tube was connected to a nitrogen source. The entire reaction system was first flushed with nitrogen three times using the Schlenk tube. 50 mL of cyclohexanone was added to the flask, heated to 150°C using a heating mantle, and the water was removed by dry distillation. After cooling to room temperature, 18-crown-6-dianhydride (30.17 g, approximately 74.6 mmol) was added and dissolved. With stirring at 200 rpm, N-cyclohexylidene-3-triethoxysilyl-1-propylamine (45.01 g, approximately 149.3 mmol) was added dropwise to the flask using a dropping funnel. The addition was uniform and complete over 1.5 hours. The reaction was then stirred for an additional 3 hours. From the time the first drop of N-cyclohexylene-3-triethoxysilyl-1-propylamine enters the reaction solution system, the solution temperature is controlled to be no more than 35-40°C. After the reaction is completed, the solvent and the leaving group cyclohexanone are removed to obtain the product

[0066] (60 g, yield 99.17% based on 18-crown-6-dianhydride).

[0067] The NMR characterization of the product is as follows.

[0068] 1 H NMR (400MHz, CDCl3, δ ppm): 4.26-4.37(m, 4H, CH), 3.76-3.92(m, 8H,OCH2), 3.64-3.69(m, 12H, SiOCH2), 3.38-3.53(m, 8H, OCH2), 2.70-2.75(m, 4H, N-CH2), 1.56-1.64(m, 4H, CH2), 1.23-1.29(t, 18H, CH3), 0.63-0.66(m, 4H, Si-CH2).

[0069] 13 C NMR (100MHz, CDCl3, δ ppm): 172.2, 170.4, 74.2, 71.2, 70.5, 67.8, 63.0, 56.4, 43.1, 23.0, 15.5, 7.3.

[0070] Example 1 A method for preparing a metallocene polyethylene catalyst comprises the following steps: S1. Activate the silica gel. The activation method is to mix silica gel and aqua regia at a ratio of 1 g:5 mL, stir at 200 rpm at room temperature for 10 minutes, dilute with 10 times the amount of water, filter, wash with water until the pH of the washing solution reaches 7, and heat in a muffle furnace at 170°C for 24 hours under air atmosphere to obtain activated silica gel.

[0071] Compound I was mixed uniformly with xylene to obtain a 5 mmol / L xylene solution of Compound I. To 200 mL of this xylene solution, 12.0114 g of activated silica gel was added. The mixture was refluxed for 24 hours, filtered, and dried in a vacuum oven at room temperature to yield 12.7109 g of modified silica gel. The modified amount of Compound I was approximately 0.6995 g (12.7109 g minus 12.0114 g).

[0072] S2. The modified silica gel obtained in step S1 was mixed with 100 mL of dry toluene to obtain a modified silica gel slurry. 23.2 g of a commercially available 10 wt% methylaluminoxane toluene solution was added, and the mixture was diluted to 100 mL with dry toluene to obtain a methylaluminoxane solution. The methylaluminoxane solution was added dropwise to the modified silica gel slurry, stirred at 10 ° C for 12 h, filtered, and washed twice with toluene and twice with n-hexane. The mixture was dried in a vacuum drying oven at room temperature to obtain 14.7450 g of an aluminum-supported catalyst. The methylaluminoxane loading was approximately 14.7450 g - 12.7109 g = 2.0341 g.

[0073] S3, under argon protection, the aluminum-loaded catalyst obtained in step S2 is mixed with 50mL of dry toluene to obtain an aluminum-loaded catalyst slurry. Bis(propylcyclopentadienyl)hafnium(IV)dichloride is mixed with dry toluene to make 10mL of 11mg / mL bis(propylcyclopentadienyl)hafnium(IV)dichloride solution. Bis(propylcyclopentadienyl)hafnium(IV)dichloride solution is dripped dropwise into the aluminum-loaded catalyst slurry under 300rpm stirring, and is warming up to 38 DEG C of reactions for 12h. Washed with toluene, dried under vacuum at room temperature, 14.8387g of metallocene polyethylene catalyst is obtained. The charged capacity of the metallocene compound is approximately 14.8387g-14.7450g=0.0937g.

[0074] Example 2 A method for preparing a metallocene polyethylene catalyst comprises the following steps: S1. Activate the silica gel. The activation method is to mix silica gel and aqua regia at a ratio of 1 g:6 mL, stir at 200 rpm at room temperature for 10 minutes, dilute with 10 times the amount of water, filter, wash with water until the pH of the washing solution reaches 7, and heat in a muffle furnace at 160°C under air atmosphere for 24 hours to obtain activated silica gel.

[0075] Compound I was mixed uniformly with xylene to obtain a 5 mmol / L xylene solution of Compound I. To 125 mL of this xylene solution, 13.1166 g of activated silica gel was added. The mixture was refluxed for 24 hours, filtered, and dried in a vacuum oven at room temperature to yield 13.5979 g of modified silica gel. The modified amount of Compound I was approximately 0.4813 g (13.5979 g minus 13.1166 g).

[0076] S2. The modified silica gel obtained in step S1 was mixed with 100 mL of dry toluene to obtain a modified silica gel slurry. 27.5 g of a commercially available 10 wt% methylaluminoxane toluene solution was added, and the mixture was diluted to 100 mL with dry toluene to obtain a methylaluminoxane solution. The methylaluminoxane solution was added dropwise to the modified silica gel slurry, stirred at 10 ° C for 12 h, filtered, washed twice with toluene and twice with n-hexane. Drying was performed in a vacuum drying oven at room temperature to obtain 16.2812 g of an aluminum-supported catalyst. The loading amount of methylaluminoxane was approximately 16.2812 g - 13.5979 g = 2.6833 g.

[0077] S3, under argon protection, the aluminum-loaded catalyst obtained in step S2 is mixed with 50mL of dry toluene to obtain an aluminum-loaded catalyst slurry. Bis(propylcyclopentadienyl)hafnium(IV)dichloride is mixed with dry toluene to make 10mL of 15mg / mL bis(propylcyclopentadienyl)hafnium(IV)dichloride solution. Bis(propylcyclopentadienyl)hafnium(IV)dichloride solution is dripped dropwise into the aluminum-loaded catalyst slurry under 300rpm stirring, and is warming up to 38 DEG C of reactions for 12h. Washed with toluene, dried under vacuum at room temperature, and obtained 16.4144g of metallocene polyethylene catalyst. The charged capacity of the metallocene compound is about 16.4144g-16.2812g=0.1332g.

[0078] Example 3 A method for preparing a metallocene polyethylene catalyst comprises the following steps: S1. Activate the silica gel. The activation method is to mix silica gel and aqua regia at a ratio of 1 g:4 mL, stir at 200 rpm at room temperature for 10 minutes, dilute with 10 times the amount of water, filter, wash with water until the pH of the washing solution reaches 7, and heat in a muffle furnace at 180°C for 24 hours under air atmosphere to obtain activated silica gel.

[0079] Compound I was mixed uniformly with xylene to obtain a 5 mmol / L xylene solution of Compound I. To 240 mL of this xylene solution, 11.8429 g of activated silica gel was added. The mixture was refluxed for 24 hours, filtered, and dried in a vacuum oven at room temperature to yield 12.5501 g of modified silica gel. The modified amount of Compound I was approximately 0.7072 g (12.5501 g minus 11.8429 g).

[0080] S2. The modified silica gel obtained in step S1 was mixed with 100 mL of dry toluene to obtain a modified silica gel slurry. 16.6 g of a commercially available 10 wt% methylaluminoxane toluene solution was added, and the mixture was diluted to 100 mL with dry toluene to obtain a methylaluminoxane solution. The methylaluminoxane solution was added dropwise to the modified silica gel slurry, stirred at 10 ° C for 12 h, filtered, washed twice with toluene and twice with n-hexane. Drying was carried out in a vacuum drying oven at room temperature to obtain 14.0723 g of an aluminum-supported catalyst. The loading amount of methylaluminoxane was approximately 14.0723 g - 12.5501 g = 1.5222 g.

[0081] S3, under argon protection, the aluminum-loaded catalyst obtained in step S2 is mixed with 50mL of dry toluene to obtain an aluminum-loaded catalyst slurry. Bis(propylcyclopentadienyl)hafnium(IV)dichloride is mixed with dry toluene to make 10mL of 8mg / mL bis(propylcyclopentadienyl)hafnium(IV)dichloride solution. Bis(propylcyclopentadienyl)hafnium(IV)dichloride solution is dripped dropwise into the aluminum-loaded catalyst slurry under 300rpm stirring, and is warming up to 38 DEG C of reactions for 12h. Washed with toluene, dried under vacuum at room temperature, 14.1496g of metallocene polyethylene catalyst is obtained. The charged capacity of the metallocene compound is approximately 14.1496g-14.0723g=0.0773g.

[0082] Example 4 Compared with Example 1, the only difference is that in step S3, bis(propylcyclopentadienyl)hafnium(IV) dichloride is replaced by bis(cyclopentadienyl)zirconium dichloride. The specific steps are as follows: S1. Activate the silica gel. The activation method is to mix silica gel and aqua regia at a ratio of 1 g:5 mL, stir at 200 rpm at room temperature for 10 minutes, dilute with 10 times the amount of water, filter, wash with water until the pH of the washing solution reaches 7, and heat in a muffle furnace at 170°C for 24 hours under air atmosphere to obtain activated silica gel.

[0083] Compound I was mixed uniformly with xylene to obtain a 5 mmol / L xylene solution of Compound I. To 200 mL of this xylene solution, 12.0179 g of activated silica gel was added. The mixture was refluxed for 24 hours, filtered, and dried in a vacuum oven at room temperature to yield 12.7223 g of modified silica gel. The modified amount of Compound I was approximately 0.7044 g (12.7223 g minus 12.0179 g).

[0084] S2. The modified silica gel obtained in step S1 was mixed with 100 mL of dry toluene to obtain a modified silica gel slurry. 23.2 g of a commercially available 10 wt% methylaluminoxane toluene solution was taken, and dry toluene was added and mixed to a volume of 100 mL to obtain a methylaluminoxane solution. The methylaluminoxane solution was added dropwise to the modified silica gel slurry, ultrasonically reacted for 3 h in an ice bath, and then stirred in a 10 ° C water bath for 12 h, filtered, washed twice with toluene and twice with n-hexane. Dry in a vacuum drying oven at room temperature to obtain 14.7612 g of an aluminum-supported catalyst. The loading amount of methylaluminoxane was approximately 14.7612 g - 12.7223 g = 2.0389 g.

[0085] S3, under argon protection, the aluminum-loaded catalyst obtained in step S2 is mixed with 50mL of dry toluene to obtain an aluminum-loaded catalyst slurry. Bis(cyclopentadiene) zirconium dichloride is mixed with dry toluene to make 10mL of 11mg / mL bis(cyclopentadiene) zirconium dichloride solution. Bis(cyclopentadiene) zirconium dichloride solution is dripped dropwise into the aluminum-loaded catalyst slurry under 300rpm stirring, and the mixture is warmed to 38°C and reacted for 12h. Washed with toluene, dried under vacuum at room temperature, and 14.8590g of metallocene polyethylene catalyst is obtained. The charged capacity of the metallocene compound is approximately 14.8590g-14.7612g=0.0978g.

[0086] Comparative Example 1 Compared with Example 1, the difference is that Compound I is not modified. The specific steps are as follows: S1. Activate the silica gel. The activation method is to mix silica gel and aqua regia at a ratio of 1 g:5 mL, stir at 200 rpm at room temperature for 10 minutes, dilute with 10 times the amount of water, filter, wash with water until the pH of the washing solution reaches 7, and heat in a muffle furnace at 170°C for 24 hours under air atmosphere to obtain activated silica gel.

[0087] S2. Mix 12.7232 g of the activated silica gel obtained in step S1 with 100 mL of dry toluene to obtain an activated silica gel slurry. Take 23.2 g of a commercially available 10 wt% methylaluminoxane toluene solution, add dry toluene and mix to 100 mL to obtain a methylaluminoxane solution. Add the methylaluminoxane solution dropwise into the modified silica gel slurry, ultrasonically react for 3 h in an ice bath, then stir in a 10 ° C water bath for 12 h, filter, wash twice with toluene and twice with n-hexane. Dry in a vacuum drying oven at room temperature to obtain 14.7420 g of an aluminum-supported catalyst. The methylaluminoxane loading is approximately 14.7420 g - 12.7232 g = 2.0188 g.

[0088] S3, under argon protection, the aluminum-loaded catalyst obtained in step S2 is mixed with 50mL of dry toluene to obtain an aluminum-loaded catalyst slurry. Bis(propylcyclopentadienyl)hafnium(IV)dichloride is mixed with dry toluene to make 10mL of 11mg / mL bis(propylcyclopentadienyl)hafnium(IV)dichloride solution. Bis(propylcyclopentadienyl)hafnium(IV)dichloride solution is dripped dropwise into the aluminum-loaded catalyst slurry under 300rpm stirring, and is warming up to 38 DEG C of reactions for 12h. Washed with toluene, dried under vacuum at room temperature, and obtained 14.8002g of metallocene polyethylene catalyst. The charged capacity of the metallocene compound is approximately 14.8002g-14.7420g=0.0582g.

[0089] Comparative Example 2 A method for preparing a metallocene polyethylene catalyst comprises the following steps: S1. Activate the silica gel. The activation method is to mix silica gel and aqua regia at a ratio of 1 g:5 mL, stir at 200 rpm at room temperature for 10 minutes, dilute with 10 times the amount of water, filter, wash with water until the pH of the washing solution reaches 7, and heat in a muffle furnace at 170°C for 24 hours under air atmosphere to obtain activated silica gel.

[0090] Compound II was synthesized by referring to the synthesis method described in the prior art Chinese invention patent CN116178595A. The structure of compound II is as follows:

[0091] Compound II was mixed uniformly with xylene to obtain an 8.1 mmol / L xylene solution of Compound II. To 200 mL of the above xylene solution of Compound I was added 12.0088 g of activated silica gel. The mixture was refluxed for 24 hours, filtered, and dried in a vacuum oven at room temperature to yield 12.7114 g of modified silica gel. The modified amount of Compound I was approximately 0.7026 g (12.7114 g minus 12.0088 g).

[0092] S2. The modified silica gel obtained in step S1 was mixed with 100 mL of dry toluene to obtain a modified silica gel slurry. 23.2 g of a commercially available 10 wt% methylaluminoxane toluene solution was taken, and dry toluene was added and mixed to a volume of 100 mL to obtain a methylaluminoxane solution. The methylaluminoxane solution was added dropwise to the modified silica gel slurry, ultrasonically reacted for 3 h in an ice bath, and then stirred in a 10 ° C water bath for 12 h, filtered, washed twice with toluene and twice with n-hexane. Dry in a vacuum drying oven at room temperature to obtain 14.7373 g of aluminum-supported catalyst. The loading amount of methylaluminoxane was approximately 14.7373 g - 12.7114 g = 2.0259 g.

[0093] S3, under argon protection, the aluminum-loaded catalyst obtained in step S2 is mixed with 50mL of dry toluene to obtain an aluminum-loaded catalyst slurry. Bis(propylcyclopentadienyl)hafnium(IV)dichloride is mixed with dry toluene to make 10mL of 11mg / mL bis(propylcyclopentadienyl)hafnium(IV)dichloride solution. Bis(propylcyclopentadienyl)hafnium(IV)dichloride solution is dripped dropwise into the aluminum-loaded catalyst slurry under 300rpm stirring, and is warming up to 38 DEG C of reactions for 12h. Washed with toluene, dried under vacuum at room temperature, and obtained 14.8018g of metallocene polyethylene catalyst. The loading capacity of the metallocene compound is approximately 14.8018g-14.7373g=0.0645g.

[0094] In Examples 1 to 4 and Comparative Example 1, the modification rate of Compound I can be calculated as follows.

[0095] Weight modification rate of compound I = modification amount of compound I ÷ weight of metallocene catalyst × 100%.

[0096] In Comparative Example 2, the modification rate of Compound II can be calculated as follows.

[0097] The weight modification rate of compound II = the modification amount of compound II ÷ the weight of the metallocene catalyst × 100% = 0.7026 g ÷ 14.8018 g × 100% ≈ 4.75%.

[0098] In the above examples and comparative examples, the weight ratio of methylaluminoxane and the metallocene compound to the metallocene polyethylene catalyst can be calculated as follows.

[0099] The weight ratio of methylaluminoxane to the metallocene polyethylene catalyst = the loading amount of methylaluminoxane ÷ the weight of the metallocene catalyst × 100%.

[0100] The weight ratio of the metallocene compound to the metallocene polyethylene catalyst = the loading amount of the metallocene compound ÷ the weight of the metallocene catalyst × 100%.

[0101] Methylaluminoxane loading efficiency = methylaluminoxane loading amount ÷ methylaluminoxane feed amount × 100%.

[0102] Metallocene compound loading efficiency = metallocene compound loading amount ÷ metallocene compound feed amount × 100%.

[0103] Some of the calculation results are summarized in Table 2 below.

[0104] Table 2

[0105] Comparative Example 1 differs from Example 1 in that Compound I is not modified. While the loading efficiency for methylaluminoxane is similar between Example 1 and Comparative Example 1, the loading efficiency for the metallocene compound is significantly increased from 52.91% to 85.18%. In Comparative Example 2, which utilizes Compound II provided by prior art for modification, the loading efficiency for the metallocene compound is only increased to 58.64%.

[0106] It can be seen that by modifying the silica gel surface with compound I, the loading efficiency of methylaluminoxane and the loading efficiency of the metallocene compound can be effectively improved. When the loading amount of methylaluminoxane and the metallocene compound is achieved at the same level, the feeding amount of methylaluminoxane and the metallocene compound can be saved.

[0107] Effect evaluation 1. Gas-phase ethylene polymerization The preparation methods provided in Examples 1-4, Comparative Example 1, and Comparative Example 2 were scaled up to prepare metallocene catalysts. The metallocene catalysts were used to catalyze the gas-phase olefin polymerization reaction of the Unipol polyethylene process. The specific synthesis process is as follows: Start the reactor. Hydrogen concentration: 100-110 ppm, ethylene concentration: 71%. Reactor pressure: 2.05 MPa, reactor temperature: 74°C. Start the programmed feed system, set the feed time to 75 seconds, and the feed level to 2 meters. Start the discharge control program and adjust the metallocene catalyst dosage according to the reaction status until the optimal state is achieved.

[0108] Run continuously for 24, 48, 72, and 96 hours to observe whether the catalytic reaction is stable or static electricity agglomeration occurs (if static electricity agglomeration occurs, the system must be stopped for inspection). The results are shown in Table 3 below (a "-" indicates a shutdown for inspection and termination of production).

[0109] Table 3

[0110] As can be seen, by modifying Compound I, Examples 1-4 allowed the catalysts to operate continuously for 96 hours without electrostatic aggregation. However, Comparative Examples 1 and 2 experienced electrostatic aggregation after 72 hours of continuous operation, forcing the plant to be shut down and terminated.

[0111] 2. Characterization of polyethylene products from gas phase polymerization Referring to the prior art CN119350527A, the weight-average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the vapor-phase synthesized polyethylene product were measured using gel permeation chromatography (GPC) and the method specified in GBT 16913.3-2008. Specifically, the polyethylene output was tested after 24 hours of continuous operation. The results are shown in Table 4 below.

[0112] Table 4

[0113] It can be seen that the polyethylene obtained by the gas-phase catalytic reaction of the metallocene catalysts provided in Examples 1 to 4 of the present invention has a narrow molecular weight distribution.

[0114] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A metallocene polyethylene catalyst, characterized in that Made of metallocene compounds, methylaluminoxane and modified silica gel; The surface of the modified silica gel is modified by compound I, and the structure of compound I is as follows: Wherein, R is selected from C1-C3 hydrocarbon groups.

2. The metallocene polyethylene catalyst according to claim 1, characterized in that The general formula of the metallocene compound is Cp*2MX n ; Cp* is a substituted or unsubstituted cyclopentadienyl group, the substituent being selected from C1-C 20 M is selected from Ti, Zr, Hf, Fe or rare earth metal elements, X is selected from one or more of halogen, alkoxy and carboxylate, and n is an integer that satisfies the valence state of M.

3. The metallocene polyethylene catalyst according to claim 1, characterized in that The proportion of the metallocene compound in the metallocene polyethylene catalyst is 0.1wt%-0.9wt%, the proportion of the methylaluminoxane in the metallocene polyethylene catalyst is 1wt%-30wt%, and the weight modification rate of the compound I is 2%-6%.

4. The method for preparing the metallocene polyethylene catalyst according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1, activating silica gel, mixing with a solution of compound I, and reacting to obtain modified silica gel; S2. Mixing the modified silica gel obtained in step S1, a solvent, and methylaluminoxane, and stirring to obtain an aluminum-supported catalyst; S3. Mixing the aluminum-supported catalyst obtained in step S2 with a solution of the metallocene compound to support the catalyst and obtain a metallocene polyethylene catalyst.

5. The preparation method according to claim 4, characterized in that In step S1, the activation comprises the following steps: mixing silica gel with aqua regia, stirring, filtering, washing, and heating.

6. The preparation method according to claim 4, characterized in that The ratio of the weight of the silica gel in step S1, the molar amount of compound I, the weight of the methylaluminoxane in step S2, and the weight of the metallocene compound in step S3 is 11.8429-13.1166:0.625-1.2:1.66-2.75:0.08-0.15, in units of g:mmol:g:g.

7. The preparation method according to claim 4, characterized in that In step S1, the reaction conditions are reflux reaction for 12-36 hours; In step S2, the stirring time is 6-18 hours, and the stirring temperature is 0-20°C; In step S3, the temperature of the load is 30-46° C., and the load time is 10-14 hours.

8. Use of the metallocene polyethylene catalyst according to any one of claims 1 to 3 or the metallocene polyethylene catalyst prepared by the preparation method according to any one of claims 4 to 7 in polyethylene production.

9. Polyethylene prepared using the metallocene polyethylene catalyst according to any one of claims 1 to 3 or the metallocene polyethylene catalyst prepared by the preparation method according to any one of claims 4 to 7.

10. Compound I, characterized in that The structure is as follows: R is selected from C1-C3 hydrocarbon groups.

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