Cleavable bridged polyolefin catalysts, methods of making and using the same

Abstract

The present application relates to a cleavable bridged polyolefin catalyst, its preparation method and application, the catalyst comprising a carrier and a metal active center anchored on the carrier through a linking group, the linking group containing a cleavable amide bond, and the metal active center being combined with a coordination group in the linking group through a coordination bond. Compared with the prior art, after the catalyst of the present application is used in an olefin polymerization reaction, the cleavable amide bond can be broken under acidic or basic conditions, so that the metal active center is completely separated from the carrier, the metal impurities can be efficiently removed through simple washing, the metal residues in the polyolefin product are significantly reduced, and the catalyst is suitable for the preparation of super-clean high-purity high-end polyolefin.

Description

Technical Field

[0001] This invention relates to the field of polyolefin technology, and in particular to a crackable bridged polyolefin catalyst, its preparation method, and its application. Background Technology

[0002] Currently, the global semiconductor industry is accelerating its progress towards advanced manufacturing nodes with feature sizes of 5nm and below. The purity requirements for the production environment, equipment, and key materials in integrated circuit manufacturing are extremely stringent. As indispensable wet electronic chemicals in the chip manufacturing process, the purity of materials such as ultrapure water, various high-purity acids, alkalis, solvents, etching solutions, stripping solutions, and CMP polishing slurries directly determines wafer yield and device reliability. The introduction of even trace amounts of metal ions, organic impurities, or submicron-sized particles can lead to transistor performance degradation, defects, or even failure. To ensure that these ultra-high purity wet electronic chemicals are not subject to secondary contamination throughout their entire lifecycle, from production, storage, and transportation to final use, the linings and container materials that come into direct contact with the chemicals must possess even higher standards of cleanliness.

[0003] Among them, semiconductor-grade polyolefin materials (such as polyethylene) are core raw materials for high-end ultra-clean packaging containers, and their preparation technology faces extremely challenging technical barriers. Not only must the material itself possess excellent chemical corrosion resistance, mechanical strength, and thermal stability, but the content of leached metal ions in the material must also be controlled at an extremely low level, which urgently requires breakthroughs in the preparation technology of ultra-high purity polyolefins for semiconductors.

[0004] In polyolefin production, catalysts not only determine the microstructure of the polymer, but their residues are also a major source of metallic impurities. For ultra-high purity polymer materials, residual catalysts are the primary "contaminants." Therefore, developing specialized catalysts with ultra-high activity and controllable metal composition, coupled with precise low-residue polymerization and post-processing techniques, is the key technology for preparing ultra-high purity polymer materials and a pressing technical problem that needs to be solved. Summary of the Invention

[0005] The purpose of this invention is to provide a crackable bridged polyolefin catalyst, its preparation method, and its application in order to solve the above-mentioned problems.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A cleavable bridged polyolefin catalyst includes: a support and a metal active center anchored on the support by a linking group, the linking group containing a cleavable amide bond (-NH-CO-), and the metal active center being linked to a coordinating group in the linking group by a coordinate bond.

[0008] The amide bond is a chemically cleavable site. After the olefin catalytic polymerization reaction is completed, it undergoes hydrolysis under acidic or alkaline conditions, which allows the metal active center to be completely removed from the support. Thus, metal impurities in the polymer product can be effectively removed through post-treatment steps such as washing, thereby improving the purity of the polymer.

[0009] Furthermore, one end of the linking group is connected to the support, and the other end contains the coordinating group, with the general structural formula: -L1-NH-CO-L2-coordinating group. Wherein, L1 is C1-C 10 Alkylenes or C1-C atoms containing oxygen, nitrogen, or silicon heteroatoms 10 Alkylene; L2 is C1-C 10 The ligand group is selected from carboxyl (-COOH), hydroxyl (-OH), mercapto (-SH), or amino (-NH2). Preferably, the ligand group is a carboxyl group, which can form a stable coordinate bond with the metal active center.

[0010] More preferably, L1 is a fragment containing silane coupling agent residues, such as a siloxane structure formed by supporting an aminosilane coupling agent and a support; L2 is a C1-C6 alkylene, such as ethylene (-CH2CH2-), propylene (-CH2CH2CH2-), or butylene. As a specific example, L1 is -(CH2)3-Si-O-Si-, L2 is -CH2CH2-, and the coordinating group is a carboxyl group.

[0011] Furthermore, the support is selected from porous organic polymers, mesoporous silica, molecular sieves, organic-inorganic hybrid porous materials, metal-organic framework materials, clay, or magnesium-based supports. Further, porous organic polymers (POPs) include, but are not limited to, covalent organic frameworks (COFs), hypercrosslinked polymers (HCPs), and conjugated microporous polymers (CMPs); mesoporous silica includes ordered mesoporous materials such as MCM-41, SBA-15, and KIT-6; molecular sieves include microporous zeolites such as ZSM-5, Beta, Y-type, and SAPO series; organic-inorganic hybrid porous materials include silanized porous materials and POSS-based hybrid materials; metal-organic framework materials (MOFs) include the MIL series, UiO series, and ZIF series; clays include montmorillonite, kaolin, and attapulgite; and magnesium-based supports include spherical magnesium chloride and magnesium compound supports (such as MgCl2, MgO, and Mg(OH)Cl).

[0012] As a preferred embodiment, to avoid introducing additional metal impurities into the catalyst and reduce the burden of metal removal during post-polymerization processing, the support is a non-metallic support, preferably a porous organic polymer, mesoporous silica, molecular sieve, or organic-inorganic hybrid porous material. When using the above-mentioned non-metallic support, the support itself does not contain metal elements, which can further reduce the total metal residue in the final polyolefin product, meeting the stringent requirements for metal impurities in high-end polyolefins (electrical grade, medical grade).

[0013] Furthermore, the metal active center is a metallocene complex of a Group IV metal, including metallocene complexes of titanium, zirconium, or hafnium, wherein the metallocene complex is selected from at least one of metallocene complexes, bridged metallocene complexes, and monocyclopentadienyl metal complexes.

[0014] Furthermore, the metal active center is selected from at least one of the following compounds:

[0015] Di(perfluoroalkyl sulfonic acid)dimetallocene, wherein the perfluoroalkyl group is C4~C6. 12 The linear or branched perfluoroalkyl group, with the metal being titanium, zirconium or hafnium, preferably bis(perfluoroalkyl sulfonic acid) diacetic titanium, bis(perfluoroalkyl sulfonic acid) diacetic zirconium, or bis(perfluoroalkyl sulfonic acid) diacetic hafnium, and in some specific preferred embodiments bis(perfluorooctyl sulfonic acid) diacetic titanium or bis(trifluoromethanesulfonic acid) diacetic titanium.

[0016] Di(cyclopentadienyl)titanium dichloride, di(cyclopentadienyl)zirconium dichloride, or di(cyclopentadienyl)hafnium dichloride;

[0017] The substituted di(cyclopentadienyl) dihalogenated metal, wherein the substituent is selected from one or more of methyl, ethyl, n-butyl, tert-butyl, trimethylsilyl or phenyl, and the metal is titanium, zirconium or hafnium, such as di(methylcyclopentadienyl)titanium dichloride, di(n-butylcyclopentadienyl)zirconium dichloride, and di(pentamethylcyclopentadienyl)hafnium dichloride;

[0018] Bridged dicyclopentadienyl metal halide, wherein the bridging group is selected from ethylidene, dimethylsilyl or isopropylidene, and the metal is titanium, zirconium or hafnium, for example ethylidene-bridged di(cyclopentadienyl)zirconium dichloride;

[0019] Monocyclopentadienyl metal complexes, such as titanium trichloride (pentamethylcyclopentadienyl) and zirconium trichloride (pentamethylcyclopentadienyl);

[0020] Complexes of titanium tetrachloride, zirconium tetrachloride or hafnium tetrachloride with an electron donor, wherein the electron donor is selected from ethers, esters, alcohols or lactones;

[0021] Metal-oxygen complexes, such as tetrabutyl titanate, tetrabutyl zirconate, tetrabutyl hafnium oxide, or the corresponding oxygen clusters.

[0022] In a preferred embodiment, the catalyst has the following general structural formula: support-[Si-O-Si(CH2)] n -NH-CO-(CH2) m -COO] - [Ti(Cp)2X] + ;

[0023] Where n is an integer from 1 to 6; m is an integer from 1 to 4; Cp is cyclopentadienyl or its substituted derivatives (such as methylcyclopentadienyl, pentamethylcyclopentadienyl); X is perfluoroalkyl sulfonate (such as perfluorooctyl sulfonate, trifluoromethanesulfonate) or halogen (such as chlorine, bromine).

[0024] The present invention also provides a method for preparing the above-mentioned crackable bridged polyolefin catalyst, wherein a surface amino-functionalized support is reacted with a cyclic acid anhydride to obtain an intermediate support containing amide bonds, and then a coordination reaction is carried out with a metallocene complex to anchor the metal active center on the support, thereby obtaining the catalyst.

[0025] More specifically, the preparation method includes the following steps:

[0026] (a) Amin functionalization of the support surface: The support is suspended in anhydrous organic solvent (such as ultra-dry toluene, ultra-dry ethanol or ultra-dry tetrahydrofuran), an aminosilane coupling agent is added, and the reaction is carried out at 30-80°C for 2-8 hours. After washing (in sequence with toluene, ethanol, hexane, etc.) and vacuum drying (such as 80°C), the surface amino functionalized support is obtained.

[0027] (b) Construction of an intermediate support containing an amide bond linking group: The support obtained in step (a) is suspended in an anhydrous organic solvent (preferably anhydrous tetrahydrofuran), a cyclic anhydride is added, and the reaction is carried out at room temperature (20-30°C) under the protection of an inert gas (such as nitrogen or argon) for 8-24 hours. After thorough washing (with tetrahydrofuran, etc.) and vacuum drying (such as 60°C), an intermediate support containing an amide bond and a terminal carboxyl group is obtained.

[0028] (c) Anchoring of metal active sites: The support obtained in step (b) is suspended in an anhydrous organic solvent (preferably anhydrous dichloromethane), cooled to 0°C, and a metallocene complex solution (such as a dichloromethane solution of bis(perfluorooctylsulfonic acid)titanium diacene) is slowly added dropwise. The reaction is first carried out at 0°C for 1-4 hours, and then at room temperature for 8-16 hours. After washing (with dichloromethane and hexane until the washing solution is colorless) and vacuum drying, the catalyst is obtained.

[0029] Further, in step (a), the reaction temperature is preferably 40-60°C, and the reaction time is preferably 4-6 hours; the aminosilane includes, but is not limited to, 3-aminopropyltriethoxysilane (APTES), 3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane; the amount of the aminosilane coupling agent is 0.5-2.0 mmol / g carrier, for example, 1.0 mmol / g carrier.

[0030] Further, in step (b), the reaction time is preferably 12-18 hours; the cyclic anhydride includes succinic anhydride, glutaric anhydride or maleic anhydride, preferably succinic anhydride; the amount of the cyclic anhydride used is 1.0-2.0 mmol / g carrier, for example 1.2 mmol / g carrier.

[0031] Further, in step (c), the reaction time at 0°C is preferably 2 hours, and the reaction time at room temperature is preferably 12 hours; the amount of the metallocene complex used is 0.1-2.0 mmol / g carrier, preferably 0.5-1.0 mmol / g carrier.

[0032] This invention further provides the application of the above-mentioned crackable bridged polyolefin catalyst in olefin polymerization reactions. Specifically, the catalyst is used in the homopolymerization or copolymerization of ethylene, propylene, or α-olefins. After the polymerization reaction is completed, the amide bonds in the catalyst are broken by acidic or alkaline hydrolysis, and the metal active center is completely removed from the polymer product.

[0033] Furthermore, the hydrolysis treatment conditions are: acidic conditions with a pH of 1-3 (e.g., using aqueous solutions of hydrochloric acid, sulfuric acid, or citric acid) or alkaline conditions with a pH of 11-14 (e.g., using aqueous solutions of sodium hydroxide or potassium hydroxide), a temperature of 40-80°C, and a treatment time of 1-12 hours. After treatment, the detached metal active centers can be removed from the polymer by conventional washing (e.g., water washing, alcohol washing), yielding a high-purity polyolefin product with extremely low metal residue.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The catalyst provided by this invention anchors the metal active centers onto a support through linking groups containing cleavable amide bonds. After polymerization, the metal active centers can be completely detached from the support under acidic or alkaline conditions, and metal impurities can be efficiently removed by simple washing, significantly reducing metal residues in polyolefin products. When using non-metallic supports (such as porous organic polymers, mesoporous silica, molecular sieves, etc.), the introduction of metal elements is avoided, further improving polymer purity. Furthermore, the length of the linking groups and the type of metal active centers in the catalyst of this invention can be flexibly adjusted. The preparation method is simple, the conditions are mild, and it is easy to scale up for production, showing promising prospects for industrial applications. Detailed Implementation

[0036] The following description is provided to disclose the present invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples and are not intended to limit the scope of the invention; other obvious variations will be apparent to those skilled in the art. The basic principles of the invention defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the invention. Unless otherwise specified, the instruments or reagents used in the embodiments of the present invention are conventional commercial instruments or reagents.

[0037] Preliminary Example 1

[0038] Preparation of porous organic polymer support sample 1

[0039] Raw materials and reagents:

[0040] Divinylbenzene (CAS: 1321-74-0, DVB) should be washed with 5% NaOH aqueous solution to remove polymerization inhibitors before use, then washed with high-purity water until neutral, and dried with anhydrous sodium sulfate before use.

[0041] Azobisisobutyronitrile (CAS 78-67-1, AIBN);

[0042] Polyvinylpyrrolidone (PVP, K30, average molecular weight approximately 40,000).

[0043] Toluene, n-heptane, anhydrous ethanol, acetone, analytical grade; reagents must be anhydrous.

[0044] High-purity water: homemade in the laboratory;

[0045] Prepare the reaction mixture according to the following steps: In a 500 mL four-necked flask equipped with a mechanical stirrer, reflux condenser, thermometer, and nitrogen inlet, add 160 mL of anhydrous ethanol and 40 mL of high-purity water. After mixing thoroughly, add 2.0 g of stabilizer PVP and stir at room temperature until completely dissolved. Then add 50 mL of toluene and 30 mL of n-heptane as a mixed porogen and continue stirring for 15 min. Purge with high-purity nitrogen for 30 min to remove oxygen. Weigh 12.5 g of purified DVB and add it to the reaction flask. Weigh 0.125 g of initiator AIBN, dissolve it in 10 mL of anhydrous ethanol, and add it to the reaction system. Continue purging with nitrogen and stirring for 10 min to remove all oxygen. Heat to 70°C and react at this temperature for 12 h. Maintain a positive nitrogen pressure (approximately 0.02 MPa) throughout the reaction and control the stirring rate at 200 rpm. After the addition of the porogen, the reaction system forms a milky white dispersion, which gradually transforms into a stable suspension of spherical particles as the polymerization reaction proceeds.

[0046] After the polymerization reaction was completed, the reaction product was cooled to room temperature. The solid product was collected by suction filtration using a Buchner funnel and washed three times with 50 mL of anhydrous ethanol and three times with 50 mL of high-purity water to remove unreacted monomers and residual PVP. The washed solid product was placed in a Soxhlet extractor and extracted with acetone at 80°C for 24 h to remove porogens and linear oligomers. After extraction, the product was transferred to a vacuum drying oven and dried at 60°C and a vacuum of ≤-0.09 MPa for 12 h until constant weight. The dried product was passed through a 60-mesh sieve and a 140-mesh sieve sequentially. The spherical carriers that passed through the 60-mesh sieve and those that passed through the 140-mesh sieve were collected, with a particle size range of 106-250 μm. The product appeared as a white to milky white spherical powder.

[0047] Preliminary Example 2

[0048] Preparation of SBA-15 carrier sample 2

[0049] Raw materials and reagents:

[0050] Triblock copolymer P123 (EO 20 PO 70 EO 20 (average molecular weight approximately 5800, Sigma-Aldrich).

[0051] Tetraethyl orthosilicate (TEOS, purity ≥ 98%)

[0052] Hydrochloric acid (HCl, 36-38 wt%)

[0053] Anhydrous ethanol (analytical grade);

[0054] High-purity water: homemade in the laboratory;

[0055] Prepare according to the following steps:

[0056] Prepare the reaction mixture using a molar ratio of TEOS : P123 : HCl : H2O = 1.00 : 0.017 : 5.88 : 136. Weigh 4.0 g (approximately 0.69 mmol) of P123 into a 500 mL PTFE beaker, add 84 mL of high-purity water, and stir magnetically in a 35°C constant temperature water bath until P123 is completely dissolved, forming a clear and transparent solution. Slowly add 20 mL of concentrated hydrochloric acid (containing approximately 0.238 mol of HCl), and continue stirring for 30 min. Add 8.7 mL (approximately 0.0406 mol) of TEOS dropwise, maintaining rapid stirring at 35°C for 20 h. The reaction system gradually transforms from an initial homogeneous solution into a milky white sol-gel mixture.

[0057] The mixture was transferred to a 200 mL stainless steel high-pressure reactor lined with polytetrafluoroethylene (PTFE), sealed, and placed in a 100°C oven for hydrothermal crystallization for 24 h. After crystallization, it was allowed to cool naturally to room temperature. The product was filtered through a Buchner funnel, washed successively with high-purity water until the pH of the filtrate reached 7.0, and then washed three times with 50 mL of anhydrous ethanol. The filter cake was dried overnight in an 80°C oven to obtain a white solid powder.

[0058] The dried product was placed in a muffle furnace and heated to 550°C at a rate of 1°C / min. It was then calcined in air for 6 h to remove the P123 template agent and allowed to cool naturally to room temperature to obtain a white SBA-15 mesoporous molecular sieve support.

[0059] Preliminary Example 3

[0060] Preparation of spherical magnesium-based support samples 3

[0061] Raw materials and reagents:

[0062] Anhydrous magnesium chloride (MgCl2, purity > 99.99%);

[0063] Anhydrous ethanol (analytical grade);

[0064] Liquid paraffin (chemically pure, dehydrated and deoxidized by molecular sieves and activated aluminum before use);

[0065] Methyltrimethoxysilane (purity ≥ 98%);

[0066] n-Hexane (analytical grade, dried with molecular sieve before use);

[0067] High-purity nitrogen.

[0068] Prepare the solution as follows: Under nitrogen protection, dissolve 12.5 g of anhydrous magnesium chloride in 50 mL of anhydrous ethanol and stir at room temperature until completely dissolved to prepare a saturated solution (approximately 25 wt%). The resulting solution is then subjected to two-stage filtration: first, insoluble particles are removed through a 0.1 μm PTFE membrane, followed by fine filtration through a 0.05 μm PTFE membrane. The filtrate is then reserved.

[0069] The filtrate was mixed with 200 mL of deeply dehydrated and deoxygenated liquid paraffin and transferred to a high-speed shear emulsifier. The mixture was sheared at high speed for 10 min to form a homogeneous and stable oil-in-alcohol emulsion. The emulsion was quickly transferred to a 500 mL four-necked flask equipped with a mechanical stirrer, thermometer, and reflux condenser. High-purity nitrogen was introduced to replace the air and maintain a positive pressure (approximately 0.02 MPa). The temperature was raised to 55°C, and the stirring rate was controlled at 300 rpm. 3.0 mL (approximately 0.02 mol) of methyltrimethoxysilane was slowly added dropwise over approximately 30 min. After the addition was complete, the reaction was continued at 55°C for 3 h, and then the temperature was slowly raised to 70°C for 1 h to ensure the mechanical strength of the particles.

[0070] After the reaction was complete, heating and stirring were stopped, and the mixture was allowed to stand and separate into layers. The upper oil phase was discarded, and the lower spherical particles were washed five times with ultra-dry hexane, adding 50 mL each time, stirring and washing for 5 min each time, and then allowed to stand and separate into layers until the conductivity of the washing solution was constant (< 1 μS / cm). The washed spherical particles were transferred to a vacuum drying oven and dried at 60°C and a vacuum of < 0.1 kPa for 12 h to obtain a white, free-flowing spherical magnesium-based support.

[0071] Example 1

[0072] The cleavable bridged polyolefin catalyst Cat-1 was prepared using the following method:

[0073] The porous organic polymer carrier sample 1 prepared in Preliminary Example 1 was used as the carrier.

[0074] The support (5.0 g) was suspended in ultra-dry toluene (50 mL, solid-liquid ratio 1:10, g / mL), and 3-aminopropyltriethoxysilane (APTES, 1.0 mmol / g support) was added. The mixture was stirred at 40°C for 4 h. After the reaction was complete, the sample was washed three times each with toluene, anhydrous ethanol, and n-hexane (50 mL each time). The resulting solid was dried under vacuum at 80°C for 12 h to obtain the surface amino-functionalized support.

[0075] The above-mentioned surface-amino-functionalized support (approximately 5.0 g) was suspended in ultra-dry tetrahydrofuran (THF, 50 mL), and succinic anhydride (1.2 mmol / g support, i.e., 6.0 mmol) was added. The reaction was carried out at room temperature under nitrogen protection with stirring for 12 h. After the reaction was completed, the support was washed three times with THF (50 mL each time) and dried under vacuum at 60°C for 12 h to obtain the intermediate support (-NH-CO-CH2-CH2-COOH), which contains amide bonds and terminal carboxyl groups on its surface.

[0076] Di(perfluorooctylsulfonic acid)ditectonic acid was used as a metallocene complex. This metallocene complex was prepared according to the following steps: Dichloroditectonic acid (Cp₂TiCl₂, CAS: 1271-19-8, 1.0 mmol, 248.96 mg) was dissolved in anhydrous THF (50 mL) under nitrogen protection, and silver perfluorooctylsulfonic acid (CAS: 335-93-3, 2.0 mmol, approximately 1214 mg) was added. The mixture was stirred at room temperature for 2 h. After the reaction was complete, the AgCl precipitate was removed by filtration. The filtrate was concentrated and recrystallized from dichloromethane / n-hexane (volume ratio 1:1) to obtain di(perfluorooctylsulfonic acid)ditectonic acid in 85% yield.

[0077] The intermediate support (4.0 g) was suspended in ultra-dry dichloromethane (40 mL) and cooled to 0°C. The amount of metallocene complex was calculated based on a Ti / COOH molar ratio of 0.4:1. Di(perfluorooctylsulfonic acid)titanium bis(perfluorooctylsulfonic acid) (1.92 mmol) was dissolved in ultra-dry dichloromethane (20 mL) and slowly added dropwise to the reaction system. The reaction was carried out at 0°C for 2 h, and then the temperature was raised to room temperature for another 12 h. After the reaction was completed, the supernatant was removed, and the solid was washed three times each with dichloromethane and n-hexane (30 mL each time) until the washings were colorless. The solid was dried under vacuum to obtain catalyst Cat-1, with the following structure:

[0078] Support -[Si-O-Si(CH2)3-NH-CO-CH2-CH2-COO]-[Ti(Cp)2(OSO2C8F 17 )).

[0079] Example 2

[0080] The cleavable bridged polyolefin catalyst Cat-2 was prepared using the following method:

[0081] The porous organic polymer prepared in Preliminary Example 1 was used as a carrier.

[0082] The support (5.0 g) was suspended in ultra-dry toluene (50 mL), and 3-aminopropyltriethoxysilane (APTES, 1.0 mmol / g support, i.e., 5.0 mmol) was added. The mixture was stirred at 40°C for 4 h. The sample was washed three times each with toluene, anhydrous ethanol, and n-hexane (50 mL each time), and dried under vacuum at 80°C for 12 h to obtain the surface amino-functionalized support.

[0083] The above-mentioned support (5.0 g) was suspended in ultra-dry THF (50 mL), and succinic anhydride (1.2 mmol / g support, i.e., 6.0 mmol) was added. The reaction was carried out at room temperature under nitrogen protection for 12 h. The sample was washed three times with THF (50 mL each time) and dried under vacuum at 60°C for 12 h to obtain an intermediate support containing an amide bond and a terminal carboxyl group.

[0084] Bis(trifluoromethanesulfonic acid) diacetictacenetate (CAS: 76262-87-8) was used as the metallocene complex. An intermediate support (4.0 g, surface carboxyl content approximately 1.2 mmol / g, total carboxyl groups approximately 4.8 mmol) was suspended in ultra-dry dichloromethane (40 mL) and cooled to 0°C. Bis(trifluoromethanesulfonic acid) diacetictacenetate (2.24 g, 4.8 mmol, Ti / COOH molar ratio 1:1) was dissolved in ultra-dry dichloromethane (20 mL) and slowly added dropwise to the reaction system. The reaction was carried out at 0°C for 2 h, then at room temperature for 12 h. The supernatant was removed, and the mixture was washed three times each with dichloromethane and n-hexane (30 mL each time) until the washings were colorless. Vacuum drying yielded the catalyst Cat-2, with the structure: support-[Si-O-Si(CH2)3-NH-CO-CH2-CH2-COO]-Ti(Cp)2(OSO2CF3).

[0085] Example 3

[0086] The cleavable bridged polyolefin catalyst Cat-3 was prepared using the following method:

[0087] Using SBA-15 prepared in Preliminary Example 2 as a support (pre-dried under vacuum at 150°C for 2 h), the support (5.0 g) was suspended in ultra-dry toluene (50 mL), and APTES (1.0 mmol / g support, i.e., 5.0 mmol) was added. The mixture was stirred at 50°C for 6 h. After washing three times each with toluene, anhydrous ethanol, and n-hexane (50 mL each time), the mixture was dried under vacuum at 80°C for 12 h to obtain surface-amino-functionalized SBA-15.

[0088] The above-mentioned support (5.0 g) was suspended in ultra-dry THF (50 mL), and succinic anhydride (1.2 mmol / g support, i.e., 6.0 mmol) was added. The reaction was carried out at room temperature under nitrogen protection for 18 h. The sample was washed three times with THF (50 mL each time) and dried under vacuum at 60°C for 12 h to obtain the intermediate support.

[0089] The preparation of bis(perfluorooctyl sulfonic acid) diacetic titanium was the same as in Example 1. The intermediate support (4.0 g, carboxyl content approximately 1.2 mmol / g, total carboxyl groups approximately 4.8 mmol) was suspended in ultra-dry dichloromethane (40 mL) and cooled to 0°C. Di(perfluorooctyl sulfonic acid) diacetic titanium (1.92 mmol, approximately 2.55 g) was weighed and dissolved in ultra-dry dichloromethane (20 mL) at a Ti / COOH molar ratio of 0.4:1, and slowly added dropwise. The reaction was carried out at 0°C for 2 h, followed by reaction at room temperature for 12 h. After washing and drying as in Example 1, catalyst Cat-3 was obtained, with the structure: SBA-15-[Si-O-Si(CH2)3-NH-CO-CH2-CH2-COO]-[Ti(Cp)2(OSO2C8F] 17 )).

[0090] Example 4

[0091] The cleavable bridged polyolefin catalyst Cat-4 was prepared using the following method:

[0092] SBA-15 prepared in Preliminary Example 2 was used as the support (pre-dried under vacuum at 150°C for 2 h). The support (5.0 g) was suspended in ultra-dry toluene (50 mL), and APTES (1.5 mmol / g support, i.e., 7.5 mmol) was added. The mixture was stirred at 60°C for 4 h. Washing and drying were performed as in Example 3.

[0093] The above-mentioned support (5.0 g) was suspended in ultra-dry THF (50 mL), and succinic anhydride (1.5 mmol / g support, i.e., 7.5 mmol) was added. The reaction was carried out at room temperature under nitrogen protection for 24 h. The sample was washed three times with THF (50 mL each time) and dried under vacuum at 60°C for 12 h to obtain the intermediate support (carboxyl content of approximately 1.5 mmol / g).

[0094] Using bis(trifluoromethanesulfonic acid) diacetectic (CAS: 76262-87-8) as the metallocene complex, the anchoring procedure was the same as in Example 3. The intermediate support was 4.0 g (total carboxyl groups approximately 6.0 mmol). Bis(trifluoromethanesulfonic acid) diacetectic was weighed according to a Ti / COOH molar ratio of 0.4:1. The reaction and post-treatment were the same as in Example 1 to prepare the catalyst Cat-4, with the following structure:

[0095] SBA-15-[Si-O-Si(CH2)3-NH-CO-CH2-CH2-COO]- Ti(Cp)2(OSO2CF3).

[0096] Example 5

[0097] The cleavable bridged polyolefin catalyst Cat-5 was prepared using the following method:

[0098] The spherical magnesium-based support prepared in Preliminary Example 3 was used as the support (dried under vacuum at 60°C for 6 h before use). All solvents were dried to a water content of <10 ppm using molecular sieves. Under nitrogen protection, the support (5.0 g) was suspended in ultra-dry toluene (50 mL), and APTES (1.0 mmol / g support, i.e., 5.0 mmol) was added. The mixture was stirred at 40°C for 6 h. The mixture was washed three times each with ultra-dry toluene, ultra-dry ethanol, and ultra-dry n-hexane (50 mL each time), and dried under vacuum at 80°C for 12 h to obtain the surface amino-functionalized magnesium-based support.

[0099] The above-mentioned support (5.0 g) was suspended in ultra-dry THF (50 mL), and succinic anhydride (1.2 mmol / g support, i.e., 6.0 mmol) was added. The reaction was carried out at room temperature under nitrogen protection for 12 h. The sample was washed three times with ultra-dry THF (50 mL each time) and dried under vacuum at 60°C for 12 h to obtain the intermediate support.

[0100] The preparation of bis(perfluorooctyl sulfonic acid)titanium bis(SiO2) was the same as in Example 1. The intermediate support (4.0 g, carboxyl content approximately 1.2 mmol / g, total carboxyl groups approximately 4.8 mmol) was suspended in ultra-dry dichloromethane (40 mL) and cooled to 0°C. A metallocene complex (1.92 mmol) was weighed and dissolved in ultra-dry dichloromethane (20 mL) at a Ti / COOH molar ratio of 0.4:1, and slowly added dropwise. The reaction was carried out at 0°C for 2 h, followed by reaction at room temperature for 12 h. The mixture was washed three times each with ultra-dry dichloromethane and ultra-dry n-hexane (30 mL each time), and dried under vacuum to obtain the catalyst Cat-5, with the structure: spherical magnesium-based support -[Si-O-Si(CH2)3-NH-CO-CH2-CH2-COO]-[Ti(Cp)2(OSO2C8F] 17 )).

[0101] Example 6

[0102] The cleavable bridged polyolefin catalyst Cat-6 was prepared using the following method:

[0103] Using the spherical magnesium-based support prepared in Preliminary Example 3 as the support, the surface amino functionalization and succinic anhydride modification steps were the same as in Example 5. An intermediate support (carboxyl content 1.2 mmol / g) was obtained.

[0104] Di(cyclopentadienyl)titanium dichloride (Cp₂TiCl₂) was used as the metallocene complex. An intermediate support (4.0 g, total carboxyl group 4.8 mmol) was suspended in ultradry dichloromethane (40 mL) and cooled to 0°C. Cp₂TiCl₂ (1.20 g, 4.8 mmol, Ti / COOH molar ratio 1:1) was dissolved in ultradry dichloromethane (20 mL) and slowly added dropwise. The reaction was carried out at 0°C for 2 h, followed by 12 h at room temperature. Post-treatment was the same as in Example 2, with washings successively with dichloromethane and n-hexane, followed by vacuum drying to obtain the catalyst Cat-6, with the structure: magnesium-based support-[Si-O-Si(CH₂)₃-NH-CO-CH₂-CH₂-COO]-Ti(Cp)₂Cl.

[0105] Application Examples 1-6

[0106] Taking the preparation of polyethylene as an example, the catalyst prepared in the above examples was used for the polymerization of ethylene to prepare high molecular weight polyethylene, and the slurry polymerization process was adopted.

[0107] The specific steps are as follows: High-purity nitrogen was introduced three times into a 250 mL stainless steel high-pressure reactor (with jacketed temperature control), and then the reactor was vacuum dried at 150°C for 30 min. After cooling to room temperature, the reactor was pressurized to 0.2 MPa with ethylene gas, vented, and repeated three times to ensure an ethylene atmosphere inside the reactor. Under nitrogen protection, the co-catalyst methylaluminoxane (MAO, 0.1 mmol, calculated as Al) was dissolved in 100 mL of dry n-hexane and injected into the reactor. The reactor was stirred for 5 min at an ethylene pressure of 0.2 MPa. Then, the catalyst (catalyst Cat-1 to Cat-6) was dispersed in dry n-hexane (catalyst dosage 2 μmol, n-hexane volume 50 mL), injected into the reactor using a syringe, pressurized to 0.85 MPa and maintained constant, and the reaction temperature was controlled at 75°C. Ethylene was continuously added to maintain a constant pressure. After 2 h of reaction, the ethylene feed was stopped, the pressure was vented, and 20 mL of ethanol was added and stirred for 30 min to terminate the polymerization reaction. The reaction mixture was filtered, the solid polymer was collected, washed three times with deionized water, and dried under vacuum at 40°C to constant weight. The mass of polyethylene was weighed, and the catalyst activity was calculated (unit: g polyethylene·mol catalyst). -1 ·h -1 ).

[0108] The obtained polyethylene sample was purified by the following method: the polyethylene sample was mixed with citric acid aqueous solution (pH=2) at a ratio of 1g: 50 mL, stirred at room temperature for 2 h, filtered, washed with ultrapure water until the filtrate was neutral, and dried under vacuum at 40°C to obtain a high-purity polyethylene sample.

[0109] Comparative Example 1

[0110] The main catalyst is the common supported metallocene catalyst Cat-7, which does not contain cleavable amide bond linkages in its structure, and the metal active center is directly supported on the surface of the support.

[0111] The specific preparation method is as follows: Using the porous organic polymer support sample 1 prepared in Preliminary Example 1 as the support, the support (4.0 g) was suspended in ultra-dry dichloromethane (40 mL) and cooled to 0°C. The bis(perfluorooctyl sulfonic acid) diacetictene (1.92 mmol) prepared in Example 1 was dissolved in ultra-dry dichloromethane (20 mL) and slowly added dropwise to the reaction system. The reaction was carried out at 0°C for 2 h, then raised to room temperature and continued for 12 h. After the reaction was completed, the supernatant was removed, and the solid was washed three times each with dichloromethane and n-hexane (30 mL each time) until the washings were colorless. The solid was then dried under vacuum to obtain the catalyst Cat-7.

[0112] Catalyst Cat-7 was used to prepare high molecular weight polyethylene via ethylene polymerization using a slurry polymerization process. Polyethylene was synthesized using the same preparation method as in the application example described above.

[0113] Comparative Example 2

[0114] The preparation of polyethylene using a traditional Ziegler-Natta catalyst is as follows:

[0115] High-purity nitrogen was purged three times into a 250 mL stainless steel high-pressure reactor (with jacketed temperature control), followed by vacuum drying at 150°C for 30 min. After cooling to room temperature, the reactor was pressurized to 0.2 MPa with ethylene gas, vented, and this process was repeated three times to ensure an ethylene atmosphere within the reactor. Under nitrogen protection, the co-catalyst triethylaluminum (AlEt3, 0.5 mmol, based on Al) was dissolved in 100 mL of dry n-hexane and injected into the reactor. The reactor was stirred for 5 min at 0.2 MPa ethylene pressure. Then, the supported titanium tetrachloride catalyst (TiCl4 / MgCl2) was dispersed in dry n-hexane (catalyst amount 10 μmol based on titanium, n-hexane volume 50 mL), injected into the reactor using a syringe, pressurized to 0.85 MPa and maintained constant, and the reaction temperature was controlled at 60°C. Ethylene was continuously added to maintain a constant pressure. After 1 h of reaction, the ethylene feed was stopped, the pressure was vented, and 20 mL of ethanol was added and stirred for 15 min to terminate the polymerization reaction. Filter the reaction mixture, collect the solid polymer, wash it three times with deionized water, dry it under vacuum at 40°C to constant weight, and weigh the polyethylene.

[0116] The following tests were performed on polyethylene samples before and after refining:

[0117] 1. Catalyst activity: Calculated based on the weight of polyethylene, the amount of catalyst (calculated as titanium), and the reaction time, in gPE·(mol Ti). -1·h -1 ;

[0118] 2. Molecular weight determination: The weight-average molecular weight (Mw) and molecular weight distribution of the polyethylene samples were determined by gel permeation chromatography (GPC).

[0119] 3. Determination of Metal Impurity Content in Samples: The test was conducted according to standards GB / T 36244-2018 and HJ 700-2014. Specific steps: Accurately weigh 1 g of polyethylene sample into a polytetrafluoroethylene digestion vessel, add 7 mL of concentrated nitric acid, cap the vessel, and place it in a microwave digester. Digestion was performed according to the programmed temperature rise. After complete digestion, the sample was cooled and transferred to a 50 mL volumetric flask, then diluted to volume with ultrapure water. The content of major metal ions such as titanium and aluminum in the digestion solution was determined using ICP-OES. The residual metal content was calculated based on the sample mass and dilution factor.

[0120] For detailed test results, please refer to Tables 1 and 2.

[0121] Table 1 Test Results

[0122]

[0123] As shown in Table 1, the catalysts provided in the examples exhibit excellent ethylene polymerization performance: their activity is significantly higher than that of traditional Ziegler-Natta catalysts, and the resulting polyethylene has a high molecular weight and narrow molecular weight distribution, demonstrating the high activity and single-center catalytic characteristics of metallocene catalysts. Compared with ordinary supported metallocene catalysts, the catalysts in the examples are comparable to or superior in terms of activity, molecular weight, and distribution. Combined with subsequent purification treatment, the metal residue in the bulk material can be significantly reduced, demonstrating the advantages of high activity, narrow distribution, and easy metal removal.

[0124] Table 2. Metal impurity content (mg / kg)

[0125]

[0126] Note: ND indicates not detected.

[0127] As shown in Table 2, the cleavable bridged polyolefin catalysts provided in the examples can efficiently remove metal impurities after washing following polymerization. Specifically, in Examples 1-4, which use non-metallic supports, the titanium residue after purification is reduced to 0.1–0.3 mg / kg, and the aluminum residue to 2.5–3.8 mg / kg, significantly lower than Comparative Examples 1 and 2. Even in Examples 5-6, which use magnesium-containing supports, the titanium residue after purification is controlled at 0.8–0.9 mg / kg, while the magnesium residue cannot be completely removed due to the magnesium support itself. In contrast, Comparative Example 1 lacks cleavable amide bonds, preventing the complete detachment of metallic titanium from the support, resulting in a much higher titanium residue after purification than in the examples. Comparative Example 2, due to its multi-center characteristics and the presence of magnesium in the support itself, exhibits high metal residue. This invention, by introducing cleavable amide bond linking groups, enables the metal active centers to detach from the support after polymerization, achieving efficient removal of metal impurities from the polymer bulk through simple washing. This is expected to meet the stringent requirements for polymer metal residue in high-end polyolefins (such as semiconductors and medical-grade products).

[0128] 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. A crackable bridged polyolefin catalyst, characterized in that, include: carrier; as well as The active metal center is anchored on the carrier by a linking group; The linking group contains a cleavable amide bond, and the metal active center is linked to the coordinating group in the linking group via a coordinate bond.

2. The crackable bridged polyolefin catalyst according to claim 1, characterized in that, One end of the linking group is connected to the carrier, and the other end contains the coordination group. Its general structural formula is: -L1-NH-CO-L2-coordination group; Where L1 is C1-C 10 Alkylenes or C1-C atoms containing oxygen, nitrogen, or silicon heteroatoms 10 Alkylene; L2 is C1-C 10 alkylene or direct bond; The coordinating group is selected from carboxyl, hydroxyl, mercapto, or amino groups.

3. The crackable bridged polyolefin catalyst according to claim 2, characterized in that, L1 is a fragment containing silane coupling agent residues, and L2 is a C1-C6 alkylene group.

4. The crackable bridged polyolefin catalyst according to claim 1, characterized in that, The carrier is selected from porous organic polymers, mesoporous silica, molecular sieves, organic-inorganic hybrid porous materials, metal-organic framework materials, clay or magnesium-based carriers.

5. The crackable bridged polyolefin catalyst according to claim 1, characterized in that, The metal active center is a metallocene complex of a Group IV metal, including metallocene complexes of titanium, zirconium, or hafnium, and the metallocene complex is selected from at least one of metallocene complexes, bridged metallocene complexes, and monocyclopentadienyl metal complexes.

6. The crackable bridged polyolefin catalyst according to claim 5, characterized in that, The metal active center is selected from at least one of the following compounds: Di(perfluoroalkyl sulfonic acid)dimetallocene, wherein the perfluoroalkyl group is C4~C6. 12 Straight-chain or branched perfluoroalkyl groups, with metals of titanium, zirconium, or hafnium; Di(cyclopentadienyl)titanium dichloride, di(cyclopentadienyl)zirconium dichloride, or di(cyclopentadienyl)hafnium dichloride; The substituted di(cyclopentadienyl) dihalogenated metal, wherein the substituent is selected from one or more of methyl, ethyl, n-butyl, tert-butyl, trimethylsilyl or phenyl, and the metal is titanium, zirconium or hafnium; Bridged dicyclopentadienyl metal halide, wherein the bridging group is selected from ethylidene, dimethylsilyl or isopropylidene, and the metal is titanium, zirconium or hafnium; Monocyclopentadienyl metal complexes; Complexes of titanium tetrachloride, zirconium tetrachloride or hafnium tetrachloride with an electron donor, wherein the electron donor is selected from ethers, esters, alcohols or lactones; Metal-oxygen complexes.

7. The method for preparing a pyrolytic bridged polyolefin catalyst according to claim 1, characterized in that, The catalyst is prepared by reacting a surface amino-functionalized support with a cyclic acid anhydride to obtain an intermediate support containing amide bonds, which is then coordinated with a metallocene complex to anchor the metal active center.

8. The method for preparing a pyrolytic bridged polyolefin catalyst according to claim 7, characterized in that, Includes the following steps: (a) Amine functionalization of the carrier surface: The carrier is suspended in an anhydrous organic solvent, an aminosilane coupling agent is added to react, and the carrier is obtained by washing and drying. (b) Construction of intermediate support containing amide bond linkage group: The support obtained in step (a) was suspended in anhydrous organic solvent, a cyclic acid anhydride was added, and the reaction was carried out at room temperature under inert gas protection. After washing and drying, an intermediate support containing amide bond was obtained. (c) Anchoring of metal active sites: The support obtained in step (b) is suspended in an anhydrous organic solvent, a metallocene complex is added and reacted, and then washed and dried to obtain the catalyst.

9. The method for preparing a pyrolytic bridged polyolefin catalyst according to claim 8, characterized in that, Step (a) involves reacting at 30-80°C for 2-8 hours, wherein the aminosilane comprises 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane or N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and the amount of the aminosilane coupling agent is 0.5-2.0 mmol / g carrier. And / or, step (b) is carried out at room temperature under inert gas protection for 8-24 hours, wherein the cyclic anhydride includes succinic anhydride, glutaric anhydride or maleic anhydride, and the amount of the cyclic anhydride is 1.0-2.0 mmol / g carrier; And / or, in step (c), the reaction is first carried out at 0°C for 1-4 hours, and then at room temperature for 8-16 hours, wherein the amount of the metallocene complex is 0.1-2.0 mmol / g carrier.

10. The application of the crackable bridged polyolefin catalyst according to any one of claims 1-6 in olefin polymerization reaction, wherein after the polymerization reaction is completed, the metal active centers in the catalyst are removed from the polymer by acidic or alkaline hydrolysis treatment.

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