Cationic C1 symmetric X-bridged metallocene olefin polymerization catalysts, their preparation methods and applications

Abstract

This invention proposes a cationic C1-symmetric X-bridged metallocene olefin polymerization catalyst, its preparation method, and its application, belonging to the field of olefin polymerization catalysts. The preparation method involves sequentially subjecting a C1-symmetric X-bridged metallocene halide to an alkylation reaction with an alkyl metal reagent and a dealkylation reaction with a soluble organoboron salt, thus preparing a C1-symmetric X-bridged metallocene alkyl cationic catalyst in a one-pot process. Its structure is shown in formula (III-1). The cationic metallocene catalyst proposed in this invention possesses stable structure, good solubility, high catalytic activity, and high temperature resistance.

Description

Technical Field

[0001] This invention belongs to the field of olefin polymerization catalysts, and particularly relates to cationic C1 symmetric X-bridged metallocene olefin polymerization catalysts, their preparation methods, and applications. Background Technology

[0002] Polyolefin resins are an important class of synthetic materials, possessing advantages such as light weight, high chemical stability, good electrical insulation, and good machinability, thus being widely used in various fields of daily life and industrial production. With the increasing application of polyolefin materials, the corresponding consumption and demand are also increasing year by year. The catalysts used in industrial production are gradually shifting from multiphase, multi-active-center Ziegler-Natta catalysts to single-active-center metallocene catalysts. Compared with Zn catalysts, metallocene catalysts have a single active center, ultra-high catalytic activity, and produce polymers with narrower molecular weight distributions and excellent mechanical properties. They also exhibit good copolymerization properties, such as efficiently catalyzing the copolymerization of ethylene and α-olefins.

[0003] Metallocene catalyst systems typically consist of a main catalyst and a co-catalyst. The main catalyst is a single metallocene compound, which itself has virtually no activity in catalyzing olefin polymerization. The co-catalyst is generally an alkylaluminoxane (such as MAO and its alkyl-modified MMAO) or an organoboron promoter / alkylaluminum system. During olefin polymerization, the metallocene needs to undergo alkylation and dealkylation reactions with the co-catalyst to form alkylmetallocene cationic active centers before it can initiate the polymerization reaction. Generally, the formed alkylmetallocene cationic active centers are relatively unstable and prone to deactivation over long periods of storage. Therefore, in metallocene-catalyzed olefin polymerization reactions, the catalyst alkylmetallocene cationic cation needs to be generated in situ in the reactor to participate in the catalytic olefin polymerization reaction.

[0004] Metallocene / MAO and metallocene / alkylaluminum / organoboron co-catalysts are two common catalytic olefin polymerization systems. The main catalyst and co-catalyst are separately metered into the polymerization reactor, where they generate active metallocene cationic catalyst centers in situ, thus initiating olefin polymerization. In industrial applications, methylaluminoxane (MAO) is often used as a co-catalyst, reacting with metallocene compounds in a one-step process to generate cationic metallocene catalysts in situ, and its catalytic activity is generally slightly higher than other catalytic systems. In catalytic olefin polymerization systems, MAO plays a dual role in activating the metallocene catalyst and removing impurities from the system. Metallocenes used in the synthesis of metallocene polyolefins, metallocene polyolefin elastomers, and novel cyclic polyolefins can all utilize MAO as a co-catalyst. However, MAO co-catalysts are expensive, sensitive to water and oxygen, and require large quantities (generally more than 1000 times that of metallocenes), leading to high production costs for polyolefin products. Furthermore, due to limitations imposed by foreign MAO production technology and the unstable quality of domestically produced MAO products, my country has long relied on imports for MAO co-catalysts, and the localization of MAO production remains a key factor restricting the industrialization of metallocene products in China. In comparison, the metallocene / alkylaluminum / organoboron compound catalytic system offers relatively low production costs and high catalytic activity for polyolefins, making it an ideal alternative to the metallocene / MAO catalytic system. Generally, this catalytic reaction system requires only a small amount of alkylaluminum for system impurity removal and metallocene alkylation, along with a low dose (1-10 times the metallocene concentration) of organoboron auxiliaries. However, the conversion of metallocene compounds to alkylmetallocene cations is more complex than the metallocene / MAO system, requiring a dialkylation process involving the reaction of metallocene and alkylaluminum, and a process where the organoboron auxiliaries remove one alkyl group from the dialkylmetallocene to generate a cation. This means that multiple pipelines are needed in the polymerization reaction system for transporting and reacting the metallocene, alkylaluminum auxiliaries, and organoboron auxiliaries, inevitably leading to complexity in material handling within the polymerization equipment and challenges in precise catalyst metering control. Meanwhile, organoboron additives (such as [PhN(Me)₂H][B(C₆F₅)₄] and [Ph₃C][B(C₆F₅)₄]) also suffer from low solubility in alkane (aromatic) solvents and degradation upon reaction with alkylaluminum. These problems inevitably make it difficult to control the concentration of the generated cationic alkyl metallocene active centers, thus affecting the performance of polyolefin products. One effective method to solve these problems is to directly use cationic alkyl metallocene catalysts with good stability and solubility.

[0005] C1-symmetric X-bridged metallocenes are an important class of metallocene catalysts, with ligands including fluorene, indene, and cyclopentadiene, as well as their related derivatives. Two ligands are linked by an X atom (which can be carbon, silicon, germanium, phosphorus, or boron) to form a bridged bis-celocene ligand. The metals are generally group IV elements such as titanium, zirconium, hafnium, and rare earth elements. The X-atom bridging of the bis-celocene generally gives metallocene catalysts good high-temperature stability and product stereoselectivity. Patents and literature have reported that C1-symmetric X-bridged metallocenes and MAO (and its modified products) exhibit good catalytic performance in the homopolymerization and copolymerization of olefins under activation conditions (for example, patents WO 92 / 01723, EP 0573403, EP 0427697 and literature Organometallics 2004, 23(8), 1777-1789, Macromolecules 2012, 45(8), 3289-3297 reported that C1-symmetric carbon-bridged metallocenes exhibited ultra-high activity in catalyzing the homopolymerization of propylene under MAO activation, yielding almost isotactic polypropylene; patents WO 00 / 24792, EP 0612768, WO 93 / 25590, WO 00 / 24793, EP 0708117, JP2006143900, US patents References 5,408,017 and 5,767,208, and the journal *Polymer Science Part A: Polymer Chemistry*, 1991, 29, 11, 1603-1607, report that a C1 symmetric carbon / silicon-bridged metallocene / MAO system exhibits good high-temperature stability and excellent catalytic performance in the copolymerization of ethylene and one or more α-olefins. Meanwhile, a C1 symmetric X-bridged metallocene / organoboron / alkylaluminum system also shows considerable catalytic performance. From an economic perspective, the metallocene / MAO system, due to the use of expensive MAO and its large dosage, results in high catalyst costs per ton of polyolefin production. Comparatively, the metallocene / organoboron / alkylaluminum system is more economical. However, the polymerization system also introduces the complexity of metallocene / organoboron / alkylaluminum material delivery and the problem of precise metering and control of catalyst additives. These problems will inevitably cause fluctuations in the concentration of the generated cationic metallocene alkyl active centers, which in turn leads to the complexity of process operation (such as the control of reaction system temperature and olefin feed rate) and affects the performance of polyolefin products. Summary of the Invention

[0006] This invention proposes a stable cationic C1 symmetric X-bridged metallocene catalyst with good solubility in aromatic solvents, its preparation method and application. The obtained cationic catalyst has a stable structure, good solubility, and high catalytic activity for olefin polymerization and copolymerization.

[0007] This invention proposes a method for preparing a cationic C1 symmetric X-bridged metallocene catalyst, comprising the following steps:

[0008] (1) Under the protection of an inert gas, in an organic solvent, a bridged metallocene dichloro compound having the structure shown in formula (I-1) and a compound alkyl metal compound having the structure shown in formula (I-2) are reacted first to give a bridged metallocene dialkyl compound having the structure shown in formula (II-1).

[0009] (2) Add a compound having the structure shown in formula (II-2) to the reaction system obtained in step (1), and perform a second reaction. Remove the solvent by vacuum distillation to obtain a compound having the structure shown in formula (III-1).

[0010] L(R 8 ) n Formula (I-2);

[0011] [N(R 9 )2R 10 -H][B(C6F5)4] Equation (II-2);

[0012]

[0013] in,

[0014] R 1 R 2 Independently selected from substituted or unsubstituted alkyl groups and substituted or unsubstituted aryl groups;

[0015] R 3 R 4 R 5 and R 6 Hydrogen, alkyl, or aryl groups selected independently;

[0016] R 7 It is selected from at least one of halogen, nitro, ester, amino, hydrogen, substituted or unsubstituted alkanes, and substituted or unsubstituted aromatics;

[0017] M is selected from titanium, zirconium, or hafnium;

[0018] X is selected from carbon, silicon, germanium, phosphorus, or boron;

[0019] L is selected from aluminum, lithium, or zinc;

[0020] R 8 Selected from substituted or unsubstituted alkyl groups and substituted or unsubstituted aryl groups;

[0021] R 9 Selected from substituted or unsubstituted C2-C20 Alkyl groups;

[0022] R 10 Selected from substituted or unsubstituted alkyl groups and substituted or unsubstituted aryl groups.

[0023] Furthermore, the alkyl group includes methyl, ethyl, isopropyl, or butyl;

[0024] Preferably, the aryl group comprises a substituted or unsubstituted phenyl group or a substituted or unsubstituted naphthyl group;

[0025] More preferably, R 9 Selected from C 18 H 37 ;R 10 Selected from hydrogen, methyl, or phenyl.

[0026] Furthermore, the molar ratio of the compound having the structure shown in formula (I-1) to the compound having the structure shown in formula (I-2) is 1:1-500;

[0027] Preferably, the molar ratio of the compound having the structure shown in formula (II-1) to the compound having the structure shown in formula (II-2) is 1:1-20.

[0028] Furthermore, the organic solvent includes at least one of aromatic hydrocarbons, ethers, and alkane solvents;

[0029] Preferably, the organic solvent includes at least one of toluene, tetrahydrofuran, diethyl ether, or n-hexane.

[0030] Furthermore, the temperature of the first reaction is -80℃ to 200℃; the temperature of the second reaction is -80℃ to 200℃.

[0031] Preferably, the temperature of the first reaction is 0-35℃; the temperature of the second reaction is 0-35℃;

[0032] Preferably, the reaction time of the first reaction is 1-10 hours; the reaction time of the second reaction is 1-10 hours.

[0033] The present invention also proposes a C1 symmetric X-bridged metallocene cationic catalyst prepared by any of the preparation methods described above.

[0034] This invention also proposes the application of any of the above-mentioned C1 symmetric X-bridged metallocene cationic catalysts in ethylene polymerization.

[0035] Furthermore, the ethylene polymerization reaction includes ethylene homopolymerization or ethylene copolymerization with α-olefins;

[0036] Preferably, the reaction temperature for the homopolymerization and copolymerization of ethylene or α-olefin is 0-200℃.

[0037] Furthermore, the polymerization solvent used in the ethylene polymerization reaction includes at least one of aromatic and alkane solvents;

[0038] Preferably, the polymerization solvent includes at least one selected from benzene, toluene, n-hexane, n-heptane, n-octane, n-decane, and dodecane.

[0039] Further, the α-olefin includes at least one selected from propylene, 1-butene, 1-hexene, 1-octene, or 1-decene;

[0040] Preferably, the α-olefin is 1-octene.

[0041] This invention has the following advantages:

[0042] This invention proposes a stable cationic C1-symmetric X-bridged metallocene catalyst, its preparation method, and its application. By screening reactants and controlling reaction conditions, a one-pot in-situ preparation process is employed. The bridged metallocene dichloro compound with the structure shown in formula (I-1) is alkylated to obtain a bridged metallocene dialkyl compound with the structure shown in formula (II-1). Then, a dealkylation reaction is carried out with a long-chain organoboronate ammonium salt promoter with a good solubility (formula (II-2)) to obtain a compound with the structure shown in formula (III-1), i.e., the C1-symmetric X-bridged metallocene cationic catalyst. This method yields a high catalyst yield, reaching 97.1%, with a simple reaction route and mild conditions, making it suitable for large-scale industrial production. The resulting cationic catalyst exhibits structural stability, good solubility, and high catalytic activity for olefin polymerization and copolymerization. Compared to non-cationic catalysts, its activity can be doubled, and it also possesses high-temperature resistance, withstanding polymerization temperatures up to 180°C. Detailed Implementation

[0043] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0044] On one hand, embodiments of the present invention propose a method for preparing a cationic C1 symmetric X-bridged metallocene catalyst, comprising the following steps:

[0045] (1) Under the protection of an inert gas, in an organic solvent, a bridged metallocene dichloro compound having the structure shown in formula (I-1) and a compound alkyl metal compound having the structure shown in formula (I-2) are reacted first to give a bridged metallocene dialkyl compound having the structure shown in formula (II-1).

[0046] (2) Add a compound having the structure shown in formula (II-2) to the reaction system obtained in step (1), and perform a second reaction. Remove the solvent by vacuum distillation to obtain a compound having the structure shown in formula (III-1).

[0047] L(R 8 ) n Formula (I-2);

[0048] [N(R 9 )2R 10 -H][B(C6F5)4] Equation (II-2);

[0049]

[0050] in,

[0051] R 1 R 2 Independently selected from substituted or unsubstituted alkyl groups and substituted or unsubstituted aryl groups;

[0052] R 3 R 4 R 5 and R 6 Hydrogen, alkyl, or aryl groups selected independently;

[0053] R 7 It is selected from at least one of halogen, nitro, ester, amino, hydrogen, substituted or unsubstituted alkanes, and substituted or unsubstituted aromatics;

[0054] M is selected from titanium (Ti), zirconium (Zr), or hafnium (Hf);

[0055] X is selected from carbon (C), silicon (Si), germanium (Ge), phosphorus (P), or boron (B);

[0056] L is selected from aluminum, lithium, or zinc;

[0057] R 8 Selected from substituted or unsubstituted alkyl groups and substituted or unsubstituted aryl groups;

[0058] R 9 Selected from substituted or unsubstituted C2-C 20 Alkyl groups;

[0059] R 10 Selected from substituted or unsubstituted alkyl groups and substituted or unsubstituted aryl groups.

[0060] The method for preparing the cationic C1 symmetric X-bridged metallocene catalyst proposed in this invention involves screening reaction raw materials and controlling reaction conditions. A one-pot in-situ preparation process is employed. The bridged metallocene dichloro compound with the structure shown in formula (I-1) is alkylated to obtain a bridged metallocene dialkyl compound with the structure shown in formula (II-1). Then, a long-chain organoborate ammonium salt with a good solubility and the structure shown in formula (II-2) is added as a promoter, and the reaction proceeds to obtain a compound with the structure shown in formula (III-1), i.e., the C1 symmetric X-bridged metallocene cationic catalyst. This method yields a high catalyst yield, reaching 97.1%, with a simple reaction route and mild conditions, making it suitable for large-scale industrial production. When used for ethylene polymerization, the obtained cationic catalyst requires no additional boron promoter or alkylaluminoxane (MAO) addition. It exhibits structural stability, good solubility, high catalytic activity for olefin polymerization and copolymerization, and high-temperature resistance.

[0061] In a preferred embodiment of the present invention, the alkyl group includes methyl, ethyl, isopropyl, or butyl.

[0062] In a preferred embodiment of the present invention, the aryl group includes substituted or unsubstituted phenyl groups and substituted or unsubstituted naphthyl groups.

[0063] In a preferred embodiment of the present invention, R 9 Selected from C 18 H 37 R 10 Selected from hydrogen, methyl, or phenyl.

[0064] In a preferred embodiment of the present invention, the long alkyl chain organic borate ammonium salt auxiliaries [Me(C] are used. 18 H 37 )2N-H] + [B(C6F5)4] - Its good solubility ensures better reaction uniformity when reacting with metallocene dialkyl compounds to form monoalkyl metallocene catalyst active centers. Further experiments show that using long-chain organoboronate ammonium salts [Me(C]... 18 H 37 )2N-H] + [B(C6F5)4] - A replacement for the traditional boron auxiliaries [PhN(Me)2H] + [B(C6F5)4] - and [Ph3C] + [B(C6F5)4] -Deprotonated long-chain alkylamines can stabilize the structure of cationic metallocenes through interactions between the nitrogen atom and the cationic metallocene center. Simultaneously, the longer alkyl chain can reduce the polarity of the cationic metallocene, increasing its solubility in solvents. It should be noted that C6F5 represents pentafluorophenyl.

[0065] In a preferred embodiment of the present invention, R 1 R 2 Selected independently from methyl or phenyl; R 3 R 4 R 5 R 6 Independently selected from hydrogen or methyl; R 7 Selected from hydrogen or tert-butyl ( t Bu); M is selected from titanium (Ti), zirconium (Zr), or hafnium (Hf); X is selected from carbon, silicon, or germanium; L is selected from aluminum, lithium, or zinc; R 8 Selected from isobutyl ( i Bu); R 9 Selected from C 18 H 37 ;R 10 Selected independently from methyl.

[0066] In an embodiment of the present invention, R 1 R 2 They can be the same or different. R 3 R 4 R 5 and R 6 They can be the same or different.

[0067] It should be noted that, in the embodiments of the present invention, R 2 It may or may not exist, depending on the type of X. For example, when X is carbon, silicon, or germanium, R 2 It exists, and R 2 Independently selected from substituted or unsubstituted alkyl groups, substituted or unsubstituted aryl groups; when X is phosphorus (P) or boron (B), R 2 It does not exist. R 7 It can be selected from only one of the following: halogen, nitro, ester, amino, hydrogen, substituted or unsubstituted alkanes, and substituted or unsubstituted aromatics, that is, only one substituent is substituted on the fluorene; R 7 It can also be selected from a variety of halogens, nitro groups, ester groups, amino groups, hydrogen, substituted or unsubstituted alkanes, and substituted or unsubstituted aromatics, that is, a combination of multiple substituents present on fluorene.

[0068] In embodiments of the present invention, M is independently selected from group IV metals titanium (Ti), zirconium (Zr), or hafnium (Hf). L(R) 8 ) n It can be alkylaluminum, organolithium, or organozinc.

[0069] In one embodiment of the present invention, the molar ratio of the compound having the structure shown in formula (I-1) to the compound having the structure shown in formula (I-2) is 1:1-500.

[0070] In a preferred embodiment of the present invention, the molar ratio of the compound having the structure shown in formula (I-1) to the compound having the structure shown in formula (I-2) is 1:2-3.

[0071] In one embodiment of the present invention, the molar ratio of the reaction between the compound having the structure shown in formula (II-1) and the compound having the structure shown in formula (II-2) is 1:1-20.

[0072] In a preferred embodiment of the present invention, the molar ratio of the reaction between the compound having the structure shown in formula (II-1) and the compound having the structure shown in formula (II-2) is 1:1-2.

[0073] In one embodiment of the present invention, the organic solvent includes at least one selected from aromatic hydrocarbons, ethers, and alkane solvents. Preferably, the alkane solvent includes at least one selected from toluene, tetrahydrofuran, diethyl ether, or n-hexane.

[0074] In one embodiment of the present invention, the temperature of the first reaction is -80℃ to 200℃; the temperature of the second reaction is -80℃ to 200℃. Preferably, the temperature of the first reaction is 0-35℃; the temperature of the second reaction is 0-35℃. More preferably, the temperature of the first reaction is 20-35℃; the temperature of the second reaction is 20-35℃.

[0075] In one embodiment of the present invention, the reaction time of the first reaction is 1-10 hours; the reaction time of the second reaction is 1-10 hours.

[0076] In one embodiment of the present invention, the preparation method of the cationic C1 symmetric X-bridged metallocene catalyst is carried out in a glove box under an inert nitrogen atmosphere, wherein the water and oxygen contents are both less than 0.1 ppm. In a preferred embodiment of the present invention, the inert gas includes at least one of nitrogen, helium, or argon.

[0077] On the other hand, embodiments of the present invention also propose a cationic C1 symmetric X-bridged metallocene catalyst prepared by any of the above preparation methods.

[0078] The cationic C1 symmetric X-bridged metallocene catalyst proposed in this invention has a stable structure and can be stored for a long time at room temperature under an inert atmosphere. Experimental results show that its catalytic activity is not affected after 30 days of storage. The catalyst itself is a brown liquid with good solubility in aromatic solvents. When this catalyst catalyzes olefin polymerization, no additional MAO or organoboron additives are required; only a small amount of alkylaluminum reagent system is needed for impurity removal to exhibit high catalytic activity. It also has good high-temperature resistance, with polymerization temperatures reaching 180°C, and the prepared polymers have high molecular weight and narrow molecular weight distribution.

[0079] Furthermore, this invention also proposes the application of any of the aforementioned cationic C1 symmetric X-bridged metallocene catalysts in ethylene polymerization. In the polymerization reaction, if a stable, highly soluble cationic metallocene alkyl active center solution is used, no additional boron auxiliaries or alkylaluminoxanes (MAO) are required. Precise delivery via a single metering pump eliminates the need for multiple pipelines to separately add metallocene, alkylaluminum, and boron auxiliaries for in-situ generation of active centers, thus maintaining a relatively stable concentration of the effective catalyst in the reaction system.

[0080] In one embodiment of the present invention, the ethylene polymerization reaction includes ethylene homopolymerization or ethylene copolymerization with α-olefins.

[0081] In one embodiment of the present invention, the polymerization solvent used in the ethylene polymerization reaction includes at least one of aromatic hydrocarbon solvents and alkane solvents; preferably, the polymerization solvent includes at least one of benzene, toluene, n-hexane, n-heptane, n-octane, n-decane, and dodecane.

[0082] In one embodiment of the present invention, the α-olefin includes at least one selected from propylene, 1-butene, 1-hexene, 1-octene, or 1-decene. Preferably, the α-olefin is 1-octene.

[0083] In one embodiment of the present invention, the temperature of the ethylene polymerization reaction is 0-200°C. Preferably, the temperature of the polymerization reaction is 90-180°C. More preferably, the temperature of the polymerization reaction is 90-140°C.

[0084] In one embodiment of the present invention, the ethylene polymerization reaction is carried out in a high-pressure batch reactor.

[0085] Specifically, the pressure of the ethylene polymerization reaction is 0.1–10 MPa; more specifically, the pressure of the ethylene polymerization reaction is 1–10 MPa.

[0086] Specifically, the time for the ethylene polymerization reaction is 1 to 100 minutes; more specifically, the time for the ethylene polymerization reaction is 5 to 30 minutes.

[0087] In one embodiment of the present invention, the concentration of the catalyst in the ethylene polymerization reaction is 1–5 μmol / mL. Preferably, the concentration of the catalyst is 2 μmol / mL. More preferably, the concentration of the catalyst is a toluene solution of 2 μmol / mL.

[0088] In this embodiment of the invention, only a small amount of alkylaluminum is added to remove impurities from the system, which is sufficient to exhibit high catalytic activity. The alkylaluminum may be triisobutylaluminum.

[0089] The present invention will now be described in detail with reference to the embodiments.

[0090] Example 1 A method for preparing a cationic C1 symmetric X-bridged metallocene catalyst includes:

[0091]

[0092] Under inert gas (nitrogen) protection at room temperature, compound I-a (224 mg, 0.50 mmol) was placed in a 50 mL round-bottom flask, 10 mL of toluene was added, and 1.0 mL of Al was taken. i A hexane solution of Bu3 (1.0 M, 2.1 eq) was added to the reaction solution, and the mixture was stirred at room temperature for 5 hours. The solution changed from bright yellow to brownish-yellow, forming a dialkyl metallocene compound. After the reaction was complete, an equimolar amount of [NH(C)] was slowly added dropwise to the dialkyl metallocene compound. 18 H 37 A 10 mL solution of [B(C6F5)4] in toluene was reacted at room temperature for 3 hours to give a light brown cationic metallocene catalyst solution. Toluene was removed by vacuum distillation to give a brown, viscous oily product in 95.6% yield.

[0093] When the specific structure of the brown viscous oily product obtained in this invention was confirmed by nuclear magnetic resonance (NMR), the high-field methylene and methyl H peaks in the NMR were large and occupied the main part because the boron additive in the reaction raw material contained long alkyl chains and the catalyst after alkylation carried alkyl branches. In the end, the NMR result was dominated by several high-field peaks.

[0094] The resulting product was used for catalytic polymerization and exhibited the expected better performance, further proving that the product is the cationic catalyst obtained according to the reaction formula.

[0095] This cationic catalyst in toluene solution can also be used directly to catalyze olefin polymerization reactions and exhibits good stability. After being placed at room temperature under an inert gas environment for 30 days, its catalytic performance remains essentially unchanged.

[0096] Example 2 A method for preparing a cationic C1 symmetric X-bridged metallocene catalyst includes:

[0097]

[0098] Under inert gas (nitrogen) protection at room temperature, compound I-b (268 mg, 0.50 mmol) was placed in a 50 mL round-bottom flask, 10 mL of toluene was added, and 1.0 mL of Al was taken. i A hexane solution of Bu3 (1.0 M, 2.1 eq) was added to the reaction solution, and the mixture was stirred at room temperature for 5 hours. The solution changed from bright yellow to brownish-yellow, forming a dialkyl metallocene compound. After the reaction was complete, an equimolar amount of [NH4(C)2]2 was slowly added dropwise. 18 H 37 A 10 mL solution of toluene containing [B(C6F5)4] was reacted at room temperature for 3 hours to yield a light brown cationic metallocene catalyst solution. Toluene was removed by vacuum distillation to give a brown oily product in 97.1% yield.

[0099] This cationic catalyst solution can also be used directly to catalyze olefin polymerization reactions and exhibits good stability. After being placed at room temperature under an inert gas environment for 30 days, its catalytic performance remains essentially unchanged.

[0100] Example 3 A method for preparing a cationic C1 symmetric X-bridged metallocene catalyst includes:

[0101]

[0102] Under inert gas (nitrogen) protection at room temperature, compound I-c (286 mg, 0.50 mmol) was placed in a 50 mL round-bottom flask, 10 mL of toluene was added, and 1.0 mL of Al was taken. i A hexane solution of Bu3 (1.0 M, 2.1 eq) was added to the reaction solution, and the mixture was stirred at room temperature for 5 hours. The solution changed from bright yellow to brownish-yellow, forming a dialkyl metallocene compound. After the reaction was complete, an equimolar amount of [NH4(C)2]2 was slowly added dropwise. 18 H 37 A 10 mL solution of [B(C6F5)4] in toluene was reacted at room temperature for 3 hours to give a light brown cationic metallocene catalyst solution. Toluene was removed by vacuum distillation to give a brown oily product in 96.3% yield.

[0103] This cationic catalyst solution can also be used directly to catalyze olefin polymerization reactions and exhibits good stability. After being placed at room temperature under an inert gas environment for 30 days, its catalytic performance remains essentially unchanged.

[0104] Example 4 A method for preparing a cationic C1 symmetric X-bridged metallocene catalyst includes:

[0105]

[0106] Under inert gas protection at room temperature, compound I-d (278 mg, 0.50 mmol) was placed in a 50 mL round-bottom flask, 10 mL of toluene was added, and 1.0 mL of Al was taken. i A hexane solution of Bu3 (1.0 M, 2.1 eq) was added to the reaction solution, and the mixture was stirred at room temperature for 5 hours. The solution changed from bright yellow to brownish-yellow, forming a dialkyl metallocene compound. After the reaction was complete, an equimolar amount of [NH4(C)2]2 was slowly added dropwise. 18 H 37 A 10 mL solution of [B(C6F5)4] in toluene was reacted at room temperature for 3 hours to give a light brown cationic metallocene catalyst solution. Toluene was removed by vacuum distillation to give a brown oily product in 96.7% yield.

[0107] This cationic catalyst solution can also be used directly to catalyze olefin polymerization reactions and exhibits good stability. After being placed at room temperature under an inert gas environment for 30 days, its catalytic performance remains essentially unchanged.

[0108] Example 5 A method for preparing a cationic C1 symmetric X-bridged metallocene catalyst includes:

[0109]

[0110] Under inert gas protection at room temperature, compound I-e (342 mg, 0.50 mmol) was placed in a 50 mL round-bottom flask, 10 mL of toluene was added, and 1.0 mL of Al was taken. i A hexane solution of Bu3 (1.0 M, 2.1 eq) was added to the reaction solution, and the mixture was stirred at room temperature for 5 hours. The solution changed from bright yellow to brownish-yellow, forming a dialkyl metallocene compound. After the reaction was complete, an equimolar amount of [NH4(C)2]2 was slowly added dropwise. 18 H 37 A 10 mL solution of [B(C6F5)4] in toluene was reacted at room temperature for 3 hours to give a light brown cationic metallocene catalyst solution. Toluene was removed by vacuum distillation to give a brown oily product in 95.4% yield.

[0111] This cationic catalyst solution can also be used directly to catalyze olefin polymerization reactions and exhibits good stability. After being placed at room temperature under an inert gas environment for 30 days, its catalytic performance remains essentially unchanged.

[0112] Example 6 A method for preparing a cationic C1 symmetric X-bridged metallocene catalyst includes:

[0113]

[0114] Under inert gas protection at room temperature, compound I-f (309 mg, 0.50 mmol) was placed in a 50 mL round-bottom flask, 10 mL of toluene was added, and 1.0 mL of Al was taken. i A hexane solution of Bu3 (1.0 M, 2.1 eq) was added to the reaction solution, and the mixture was stirred at room temperature for 5 hours. The solution changed from bright yellow to brownish-yellow, forming a dialkyl metallocene compound. After the reaction was complete, an equimolar amount of [NH4(C)2]2 was slowly added dropwise. 18 H 37 A 10 mL solution of [B(C6F5)4] in toluene was reacted at room temperature for 3 hours to give a light brown cationic metallocene catalyst solution. Toluene was removed by vacuum distillation to give a brown oily product in 93.6% yield.

[0115] This cationic catalyst solution can also be used directly to catalyze olefin polymerization reactions and exhibits good stability. After being placed at room temperature under an inert gas environment for 30 days, its catalytic performance remains essentially unchanged.

[0116] Comparative Example 1 A method for preparing a cation-C1 symmetric X-bridged metallocene catalyst, using [PhN(Me)2H][B(C6F5)4] as a promoter, includes:

[0117]

[0118] Under inert gas protection at room temperature, compound I-c (286 mg, 0.50 mmol) was placed in a 50 mL round-bottom flask, 10 mL of toluene was added, and 1.0 mL of Al was taken. i A hexane solution of Bu3 (1.0 M, 2.1 eq) was added to the reaction solution, and the mixture was stirred at room temperature for 5 hours. The solution changed from bright yellow to brownish-yellow, forming a dialkyl metallocene compound. After the reaction was complete, an equimolar amount of toluene (10 mL) of [PhN(Me)2H][B(C6F5)4] solution was slowly added dropwise, and the reaction was continued at room temperature for 3 hours to obtain a brown cationic metallocene catalyst solution. Toluene was removed by vacuum distillation to give a dark brown oily product in 91.2% yield.

[0119] Comparative Example 2

[0120] No cationic catalyst preparation was performed. The main catalyst was selected from Ic at a concentration of 2 μmol / mL, and the co-catalyst B1 was selected from [NH(C 18 H 37 [B(C6F5)4], with a concentration of 2.2 μmol / mL, are both toluene solutions.

[0121] To more clearly compare the C1 symmetric X-bridged metallocene cationic catalyst structures obtained in Examples 1-5 of this invention with those obtained in Comparative Examples 1-2, they are listed below:

[0122]

[0123] Example 1: III-a: X = Si, R 1 =R 2 =Me,R 3 =R 4 =R 5 =R 6 =H,R 7 =H, M=Zr

[0124] Example 2: III-b: X = Si, R 1 =R 2 =Me,R 3 =R 4 =R 5 =R 6 =H,R 7 =H, M=Hf

[0125] Example 3: III-c: X = Si, R 1 =R 2 =Ph,R 3 =R 4 =R 5 =R 6 =H,R 7 =H, M=Zr

[0126] Example 4: III-d: X = C, R 1 =R 2 =Ph,R 3 =R 4 =R 5 =R 6 =H,R 7 =H, M=Zr

[0127] Example 5: III-e: X = Si, R 1 =R 2 =Ph,R 3 =R 4 =R 5 =R 6 =H,R 7 = t Bu, M = Zr

[0128] In addition to catalysts III-a, III-b, III-c, III-d, and III-e prepared sequentially in Examples 1 to 5, the catalysts prepared in Examples 1 to 5 were labeled III-a′, III-b′, III-c′, III-d′, and III-e′ after being stored in a glove box for 30 days.

[0129] The catalysts used in the comparative test examples included Ic, catalyst III-g obtained by reacting Ic with the conventional promoter [PhN(Me)2H][B(C6F5)4], and catalyst III-g obtained after storing catalyst III-g in a glove box for 30 days, which was labeled as III-g′.

[0130] Experimental Example 1-1 Polymerization of ethylene and 1-octene

[0131] The ethylene-octene polymerization reaction was carried out using the cationic catalyst obtained in Example 1, including the following steps:

[0132] (1) The reaction apparatus was evacuated repeatedly at 150°C and replaced with ethylene three times before ethylene was introduced and the pressure was adjusted to 0 MPa after exhaust.

[0133] (2) After the temperature of the reactor drops to 100℃, add 19.8mL of n-hexane dehydrated and deoxygenated by sodium reflux and 7.1mL of octene dried by calcium hydride reflux and 2mL of 0.1mol / L triisobutylaluminum n-hexane solution to the reactor (30mL) while stirring continuously; here, alkyl aluminum triisobutylaluminum is mainly used for impurity removal in the system;

[0134] (3) When the temperature of the reactor reaches 90℃, quickly add 1mL of 2umol / mL cationic catalyst III-a and react for 10min under 2MPa pressure;

[0135] (4) After the reaction is completed, the polymer solution is poured into acidified ethanol with a volume ratio of concentrated hydrochloric acid / ethanol of 1:9 to terminate the reaction. The polymer product is obtained by washing with ethanol and vacuum drying.

[0136] Experimental Examples 1-2, 1-3, 1-4, 1-5 Polymerization of ethylene and 1-octene

[0137] Similar to Experimental Example 1-1, the difference is that the cationic catalysts added in step (3) are replaced with III-b, III-c, III-d, and III-e, respectively.

[0138] Experimental Examples 1-6, 1-7, 1-8, 1-9, 1-10 Polymerization of ethylene and 1-octene

[0139] Similar to Experimental Example 1-1, the difference is that the cationic catalysts added in step (3) are III-a, III-b, III-c, III-d, and III-e, respectively, and the reaction temperature in step (3) is adjusted to 140℃.

[0140] Experimental Example 1-11 Polymerization of ethylene and 1-octene

[0141] Similar to Experimental Example 1-1, the difference is that the cationic catalyst added in step (3) is III-e, and the reaction temperature in step (3) is adjusted to 180℃.

[0142] Experimental Examples 2-1, 2-2, 2-3, 2-4, 2-5 Polymerization of ethylene and 1-octene

[0143] Similar to Experimental Example 1-1, the difference is that the cationic catalysts added in step (3) are replaced with III-a′, III-b′, III-c′, III-d′, and III-e′, respectively.

[0144] Experimental Examples 2-6, 2-7, 2-8, 2-9, 2-10 Polymerization of ethylene and 1-octene

[0145] The results are the same as those in Experiments 2-1, 2-2, 2-3, 2-4, and 2-5, except that the reaction temperature in step (3) is adjusted to 140℃.

[0146] Experimental Example 2-11 Polymerization of ethylene and 1-octene

[0147] Similar to Experimental Example 1-1, the difference is that the cationic catalyst added in step (3) is III-e′, and the reaction temperature in step (3) is adjusted to 180℃.

[0148] Comparative Test Example 1-1 Polymerization of ethylene and 1-octene

[0149] Similar to Experimental Example 1-1, the difference is that the cationic catalyst prepared in Comparative Example 1 added in step (3) is III-g.

[0150] Comparative Test Examples 1-2 Polymerization of ethylene and 1-octene

[0151] (1) The reaction apparatus was evacuated repeatedly at 150°C and replaced with ethylene three times before ethylene was introduced and the pressure was adjusted to 0 MPa after exhaust.

[0152] (2) When the temperature of the reactor drops to 100℃, add 19.8mL of n-hexane dehydrated and deoxygenated by sodium metal reflux, 7.1mL of octene dried by calcium hydride reflux, and 2mL of 0.1mol / L triisobutylaluminum n-hexane solution to the reactor (30mL) under continuous stirring.

[0153] (3) When the temperature of the reactor reaches 90℃, the catalyst obtained in Comparative Example 1 is used to add 1 mL of 2 μmol / mL metallocene catalyst Ic and 1 mL of 2.2 μmol / mL B1 toluene solution, and the reaction is carried out at 2 MPa pressure for 10 min.

[0154] (4) After the reaction is completed, the polymer solution is poured into acidified ethanol with a volume ratio of concentrated hydrochloric acid / ethanol of 1:9 to terminate the reaction. The polymer product is obtained by washing with ethanol and vacuum drying.

[0155] Comparative Test Examples 1-3 Polymerization of ethylene and 1-octene

[0156] Similar to Comparative Experiment 1-1, the difference is that the reaction temperature in step (3) is adjusted to 140℃.

[0157] Comparative Test Examples 1-4 Polymerization of ethylene and 1-octene

[0158] Similar to comparative test examples 1-2, the difference is that the reaction temperature in step (3) is adjusted to 140℃.

[0159] Comparative Test Examples 1-5 Polymerization of ethylene and 1-octene

[0160] Similar to Comparative Experiment 1-1, the difference is that the cationic catalyst added in step (3) is III-g′.

[0161] Comparative Test Examples 1-6 Polymerization of ethylene and 1-octene

[0162] Similar to comparative test examples 1-5, the difference is that the reaction temperature in step (3) is adjusted to 140℃.

[0163] Test Example 1 The polymers obtained in the experimental examples were used to test their properties using the following methods.

[0164] Equipment used:

[0165] Flat plate vulcanizing machine; electronic density meter; melt flow rate meter; high-temperature gel permeation chromatograph.

[0166] The testing method is as follows:

[0167] The polymer obtained from the test example was pressed into a sheet of uniform thickness in a mold using a flat vulcanizing machine at a set temperature of 120°C, which facilitates subsequent testing.

[0168] The density of the polymer was measured using a multifunctional electronic densitometer. The solution was anhydrous ethanol. The pressed sample was placed in the weighing area of ​​the density balance. After the reading stopped changing, the "SAMPLE" key was pressed. The weight of the sample was recorded. The sample was then transferred to the tray inside the balance. After the reading stabilized, the "SAMPLE" key was pressed again to obtain the density of the sample.

[0169] The melt flow rate (MFR) of the polymer was determined using a melt flow rate meter. The feed cylinder was heated to 190°C, and after the system stabilized, the cut sample was placed in and compacted downwards with the piston head. A 2.16 kg weight was placed on top, and the sample was cut into six segments after a timer was set. The total mass was then weighed, the average mass was calculated, and the melt flow rate was calculated using the formula: MFR = reference time · average mass of cut segments / cut interval time.

[0170] The weight-average molecular weight (Mw), number-average molecular weight (Mn), and relative molecular mass distribution (PDI = Mw / Mn) of the polymeric product were characterized and determined using high-temperature gel permeation chromatography. First, a mixed solution with a mass fraction of 0.1%–0.4% was prepared. Then, the polymeric product was dissolved by shaking in trichlorobenzene after multiple refluxes at 150°C for 12 hours. The solution was filtered and sampled, using polystyrene as a standard, and the determination was performed at 150°C with a solvent flow rate of 1.0 mL / min. Parameters k = 40.6, a = 0.727.

[0171] The results of the catalytic olefin polymerization experiments are shown in Table 1.

[0172] Table 1

[0173]

[0174]

[0175] From Table 1, we can obtain:

[0176] (1) Without the addition of organic boron additives and with a small amount of alkyl aluminum, the prepared bridged metallocene cationic catalyst exhibits better catalytic activity and a narrower molecular weight distribution than the non-cationic silicon bridged catalyst under the same conditions.

[0177] (2) After 30 days of storage, these cationic catalysts still maintained high catalytic activity with little change, indicating good stability of this configuration. The non-cationic catalysts showed even lower catalytic activity under activation with small amounts of alkylaluminum reagents, possibly because the alkylaluminum reagents, after removing impurities, did not sufficiently promote alkylation of the catalyst, thus reducing the effectiveness of the co-catalyst [NH(C)]. 18 H 37Incomplete activation of [B(C6F5)4] resulted in a decrease in the concentration of the active site (Examples 1-3, 1-8, Comparative Examples 1-2, and 1-4).

[0178] (3) Comparative data (Experimental Examples 1-3, Comparative Experimental Example 1-1, Experimental Example 1-8, Comparative Experimental Example 1-3, Experimental Example 2-3, Comparative Experimental Example 1-5) show that the use of long alkyl chain organoboronate ammonium salt auxiliaries [NH(C 18 H 37 The cationic catalysts prepared from [B(C6F5)4] and [PhN(Me)2H][B(C6F5)4] exhibit significantly different activities, with the former showing higher activity and better stability. Therefore, this invention provides a method for preparing a stable bridged metallocene cationic catalyst, laying the foundation for reducing industrial costs, minimizing reaction steps, and promoting industrial production.

[0179] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a cationic C1 symmetric X-bridged metallocene catalyst, characterized in that, Includes the following steps: (1) Under inert gas protection, in an organic solvent, a bridged metallocene dichloro compound having the structure shown in formula (I-1) is reacted with triisobutylaluminum to give a bridged metallocene dialkyl compound having the structure shown in formula (II-1). (2) Add a compound having the structure shown in formula (II-2) to the reaction system obtained in step (1), and perform a second reaction. Remove the solvent by vacuum distillation to obtain a compound having the structure shown in formula (III-1). Formula (I-1); Equation (II-1); [N(R 9 )2R 10 -H][B(C6F5)4] Equation (II-2); Equation (III-1); in, R 1 R 2 Independently selected from methyl, ethyl, isopropyl, butyl, phenyl, or naphthyl; R 3 R 4 R 5 and R 6 The hydrogen, methyl, ethyl, isopropyl, butyl, phenyl, or naphthyl groups selected independently; R 7 It is selected from at least one of hydrogen, methyl, ethyl, isopropyl, butyl, phenyl, or naphthyl; M is selected from titanium, zirconium, or hafnium; X is selected from carbon, silicon, and germanium; R 9 Selected from C 18 H 37 ; R 10 Selected from methyl, ethyl, isopropyl, butyl or phenyl.

2. The preparation method according to claim 1, characterized in that, The molar ratio of compounds with the structure shown in formula (I-1) to triisobutylaluminum is 1:1-500.

3. The preparation method according to claim 2, characterized in that, The molar ratio of the compound having the structure shown in formula (II-1) to the compound having the structure shown in formula (II-2) is 1:1-20.

4. The preparation method according to claim 1, characterized in that, The organic solvent is selected from at least one of aromatic solvents, ether solvents, and alkane solvents.

5. The preparation method according to claim 4, characterized in that, The organic solvent is selected from at least one of toluene, tetrahydrofuran, diethyl ether, or n-hexane.

6. The preparation method according to claim 1, characterized in that, The temperature of the first reaction is -80℃ to 200℃; the temperature of the second reaction is -80℃ to 200℃.

7. The preparation method according to claim 6, characterized in that, The temperature for the first reaction is 0-35℃; the temperature for the second reaction is 0-35℃. The reaction time for the first reaction is 1-10 hours; the reaction time for the second reaction is 1-10 hours.

8. The cationic C1 symmetric X-bridged metallocene catalyst prepared by the preparation method according to any one of claims 1 to 7.

9. The application of the cationic C1 symmetric X-bridged metallocene catalyst of claim 8 in the ethylene polymerization reaction.

10. The application according to claim 9, characterized in that, The ethylene polymerization reaction is either a homopolymerization of ethylene or a copolymerization of ethylene with α-olefins.

11. The application according to claim 10, characterized in that, The reaction temperature for homopolymerization of ethylene or copolymerization of ethylene with α-olefins is 0-200℃.

12. The application according to claim 10, characterized in that, The polymerization solvent used in the ethylene polymerization reaction is selected from at least one of aromatic and alkane solvents.

13. The application according to claim 12, characterized in that, The polymerization solvent is selected from at least one of benzene, toluene, n-hexane, n-heptane, n-octane, n-decane, and dodecane.

14. The application according to claim 10, characterized in that, The α-olefin is selected from at least one of propylene, 1-butene, 1-hexene, 1-octene, or 1-decene.

15. The application according to claim 14, characterized in that, The α-olefin is 1-octene.

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