CN116284514A - Constrained geometry cationic metallocene catalyst, its synthesis method and application - Google Patents

Abstract

The invention belongs to the technical field of olefin polymerization catalysts, and in particular relates to cationic metallocene catalysts with constrained geometric configurations, synthesis methods and applications thereof. The synthesis method comprises that under the protection of an inert gas, in an organic solvent, the titanocene dichloride compound represented by the formula (I-1) is reacted with an alkyl metal compound to obtain a compound having the formula (II-1). The first solution of the titanocene dialkyl compound; directly add the organoboron compound shown in the formula (II-2) to the above-mentioned first solution and carry out the second reaction, and distill under reduced pressure to obtain the compound having the formula (III-1 ) compounds shown. The obtained cationic catalyst with constrained geometry is mainly used for olefin polymerization reaction, has higher catalytic activity for ethylene polymerization, and has high temperature resistance performance, and is suitable for large-scale industrial production.

Description

Cationic metallocene catalysts of constrained geometry, their synthesis methods and applications

technical field

The invention belongs to the technical field of olefin polymerization catalysts, in particular to a method for synthesizing a cationic metallocene catalyst with restricted geometry.

Background technique

Polyolefin resins are widely used in various fields of daily life and industrial production. At present, my country's demand for polyolefin resin products is huge and increasing every year, and industrial production is also facing a process change from traditional Z-N catalyzed olefin polymerization technology to metallocene catalyzed olefin polymerization technology.

Compared with Z-N catalysts, metallocene catalysts have the advantages of single active center, high catalytic activity, narrow polymer molecular weight distribution, and good copolymerization performance. Among them, the most typical one is the constrained geometry metallocene catalyst (GCG), which is excellent in both ethylene homopolymerization and copolymerization. Generally speaking, when this type of metallocene catalyst is used alone, it does not have the activity of catalyzing olefin polymerization, and needs to be activated by an auxiliary agent (such as methylaluminoxane MAO, alkylaluminum/organoborate reagent) to convert it into a cation in situ Alkyl metallocene active centers catalyze olefin polymerization via olefin insertion and B–H elimination reactions.

Wherein, the auxiliary agent is generally selected from methylaluminoxane (MAO) or alkylaluminum and organic borate reagent. Although the metallocene/MAO catalyst system is relatively simple to generate cationic metallocene active centers (one-step generation of metallocene alkylation and cationic catalyst), the MAO promoter is expensive, consumes a lot, and the product production cost is high. Relatively speaking, the production cost of the metallocene/alkylaluminum/organoboron catalytic system is relatively low, but the system is complex and requires multi-step reactions to generate cationic metallocene alkyl active centers. The structure and properties of the resulting catalyst are unstable and easy to be placed for a long time deactivation, the activity of the catalyst is obviously reduced.

Contents of the invention

The present invention proposes a cationic metallocene catalyst with a constrained geometric configuration, its synthesis method and application, and adopts a one-pot method to synthesize a cationic metallocene catalyst with a stable configuration, and utilizes it to carry out olefin polymerization without adding other additives (such as organoboron), which can effectively avoid catalyst instability caused by direct in-situ reaction, and achieve the purpose of regulating product stability.

The present invention proposes a synthetic method of a constrained geometry cationic catalyst, comprising:

Under the protection of an inert gas, in an organic solvent, the titanocene dichloride compound represented by the formula (I-1) is first reacted with an alkyl metal compound to obtain a titanocene bis-alkane compound represented by the formula (II-1). A first solution of the base compound;

After directly adding the organoboron compound represented by the formula (II-2) to the above-mentioned first solution for the second reaction, distilling under reduced pressure to obtain the compound represented by the formula (III-1);

[N(R⁷)₂(R⁸)-H]⁺[B(C₆F₅)₄]^-式(II-2)；

[N(R ⁷ ) ₂ (R ⁸ )-H] ⁺ [B(C ₆ F ₅ ) ₄ ] ^- formula (II-2);

Wherein, ^R is selected from tetrahydropyrrole or piperidinyl;

^R is selected from hydrogen or methyl;

R and ^R are independently selected from substituted and ^{unsubstituted} alkyl and aryl;

^R is selected from tert-butyl, cycloalkylalkyl;

^R is selected from substituted or unsubstituted alkyl and aryl;

R ⁷ is selected from substituted or unsubstituted C ₂ -C ₂₀ alkyl groups;

R ⁸ is selected from a hydrogen atom, a methyl group and a phenyl group.

Further, the metal alkyl compound is lithium alkyl, zinc alkyl and aluminum alkyl.

Further, the molar ratio of the titanocene dichloride compound represented by the formula (I-1) to the metal alkyl compound is 1:1-500.

Further, the molar ratio of the titanocenedialkyl compound represented by the formula (II-1) to the organoboron compound represented by the formula (II-2) is 1:1-1.5.

Further, the organic solvent is an aliphatic hydrocarbon solvent; preferably, the aliphatic hydrocarbon solvent includes at least one of aromatic hydrocarbons, ethers and alkanes.

The present invention also proposes a cationic catalyst with a constrained geometry prepared by any one of the aforementioned synthesis methods.

The present invention also proposes the application of any one of the above-mentioned constrained geometry cationic catalysts in olefin polymerization.

Further, the olefin polymerization includes ethylene homopolymerization and ethylene copolymerization.

Preferably, the ethylene copolymerization reaction is a copolymerization reaction of ethylene and α-olefin; more preferably, the α-olefin is octene.

Further, no additives need to be added during the olefin polymerization reaction;

Preferably, the auxiliary agent is an organoboron compound.

Further, the ethylene copolymerization reaction method comprises the following steps: feeding ethylene into the reactor, adding an aliphatic hydrocarbon solvent and an α-olefin, adding an aluminum alkyl, stirring, adding a cationic constrained geometry catalyst, and raising the temperature to the reaction temperature, Pressure reaction, in product.

The present invention has the following advantages:

The preparation process of the stable cationic constrained geometry metallocene catalyst proposed by the present invention adopts the reaction of soluble organoboride and titanocene dialkyl compound, and generates a constrained geometry cationic catalyst with better solubility through a one-pot reaction, The reaction route of the process is simple, the conditions are mild, no intermediate separation is required, the required equipment can be greatly reduced, and equipment investment can be reduced. Moreover, the prepared cationic catalyst has a stable structure, good solubility, high catalytic ethylene polymerization activity, high temperature resistance, and is suitable for large-scale industrial production.

When the present invention uses a constrained geometry cationic metallocene catalyst with a stable structure to catalyze olefin polymerization, it does not need to add additional organoboron additives, and only needs to add a small amount of alkylaluminum reagent for impurity removal, and has high Excellent catalyst activity, high temperature resistance and copolymerization performance, and the obtained polymerization product has a higher molecular weight.

Description of drawings

The drawings constituting a part of the present invention are used to provide a further understanding of the present invention, and the schematic embodiments and descriptions of the present invention are used to explain the present invention, and do not constitute an improper limitation of the present invention. In the attached picture:

Fig. 1 is the NMR spectrum of metallocene compound 2a obtained in step (1) of Example 1 of the present invention;

Fig. 2 is the NMR spectrum of the cationic metallocene compound 4a obtained in step (2) of Example 1 of the present invention.

Detailed ways

It should be noted that, in the case of no conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

The present invention will be described in detail below in conjunction with specific examples.

In the prior art, the polymerization kettle often needs multiple pipelines to transport metallocene, MAO, alkylaluminum (impurity removal) and organic boron additives separately, which increases the complexity of the actual operation. Moreover, due to the instability of the flow rate of the catalytic system material in each pipeline and the uneven mixing reaction, it is easy to lead to the instability of the active center of the cationic alkyl metallocene, which in turn reduces its effectiveness and affects the catalytic activity and resin product performance.

The embodiment of the present invention proposes a method for synthesizing a constrained geometry cationic catalyst, comprising:

Under the protection of an inert gas, in an organic solvent, the titanocene dichloride compound represented by the formula (I-1) is first reacted with an alkyl metal compound to obtain a titanocene bis-alkane compound represented by the formula (II-1). A first solution of the base compound;

After directly adding the organoboron compound represented by the formula (II-2) to the above-mentioned first solution for the second reaction, distilling under reduced pressure to obtain the compound represented by the formula (III-1);

[N(R⁷)₂(R⁸)-H]⁺[B(C₆F₅)₄]^-式(II-2)；

[N(R ⁷ ) ₂ (R ⁸ )-H] ⁺ [B(C ₆ F ₅ ) ₄ ] ^- formula (II-2);

Wherein, R ¹ is selected from tetrahydropyrrole or piperidinyl; R ² is selected from hydrogen or methyl; R ³ and R ⁴ are selected from substituted and unsubstituted alkyl and aryl; R ⁵ is selected from tert-butyl, ring Alkylalkyl; ^R6 is selected from substituted or unsubstituted alkyl and aryl; ^R7 is selected from substituted or unsubstituted _C2 - _C20 alkyl; ^R8 is selected from hydrogen atom, methyl and phenyl .

The embodiment of the present invention provides a one-pot method for synthesizing a soluble cationic catalyst of constrained geometry, using a soluble organoboride to react with a titanocene dialkyl compound, and the resulting cationic catalyst is soluble and stable in an aliphatic hydrocarbon solvent The properties are high, and it is no longer necessary to add additional organic boron additives when used in olefin polymerization, which increases the activity of olefin polymerization, relatively increases the molecular weight, and relatively narrows the molecular weight distribution.

In a preferred embodiment of the present invention, R ¹ is tetrahydropyrrolyl, R ² is hydrogen; R ³ and R ⁴ are the same, R ³ or R ⁴ are selected from methyl or phenyl; R ⁵ is tert-butyl; R ⁶ Is methyl or isopropyl; R ⁷ is an unsubstituted C ₁₈ alkyl group; R ⁸ is selected from methyl.

In a preferred embodiment of the present invention, the metal alkyl compound is lithium alkyl, zinc alkyl and aluminum alkyl. The alkyllithium includes methyllithium (LiCH ₃ ), ethyllithium, triisobutyllithium and the like. The aluminum alkyl may be triisobutylaluminum ( ^Ali Bu ₃ ).

In one embodiment of the present invention, the molar ratio of the titanocene dichloride compound represented by the formula (I-1) to the metal alkyl compound is 1:1-500. Preferably, the molar ratio of the titanocene dichloride compound represented by the formula (I-1) to the metal alkyl compound is 1:2.1.

In one embodiment of the present invention, the molar ratio of the titanocenedialkyl compound represented by the formula (II-1) to the organoboron compound represented by the formula (II-2) is 1:1-1.5. Preferably, the molar ratio of the titanocenedialkyl compound represented by formula (II-1) to the organoboron compound represented by formula (II-2) is 1:1-1.1. It should be pointed out that the titanocene dialkyl compound represented by the formula (II-1) is calculated based on the titanocene dichloride compound represented by the formula (I-1) according to the theoretical amount.

In the embodiment of the present invention, the organoboron compound represented by the formula (II-2) is a soluble organoboron compound containing a long chain of an alkyl group. Soluble organoborides can react with titanocene dialkyl compounds to form cationic catalysts with good solubility and constrained geometry, which is the key to ensure the stability of the structure of the cationic catalysts obtained in the present invention. On the contrary, when boron compounds with poor solubility in aliphatic solvents are used to react with titanocene dialkyl compounds, the resulting cationic catalysts are less stable, which is not conducive to the smooth progress of ethylene polymerization, which in turn affects the quality and activity of the products obtained in the polymerization reaction.

Specifically, the organic solvent includes at least one of aromatic hydrocarbons, ethers and alkanes. In the embodiment of the present invention, aromatic hydrocarbons, ethers and alkanes are all aliphatic hydrocarbon solvents, and organoboron compounds represented by formula (II-2) have better solubility in such solvents. Preferably, the organic solvent includes at least one of toluene, tetrahydrofuran, ether, and n-hexane.

Specifically, the reaction temperature of the first reaction is -78°C-100°C; preferably, the reaction temperature of the first reaction is 15-35°C. The reaction temperature of the second reaction is -78°C-100°C; preferably, the reaction temperature of the second reaction is 15-35°C.

Specifically, the time for the first reaction is 1-10 hours, and the time for the first reaction is 1-10 hours; preferably, the time for the second reaction is 5 hours, and the time for the second reaction is 3 hours.

Specifically, the inert gas includes at least one of nitrogen, helium or argon. Said under the protection of inert gas is specifically: carrying out in a glove box with an inert nitrogen atmosphere, and the content of water and oxygen is less than 0.1ppm.

An embodiment of the present invention also proposes a cationic catalyst with a constrained geometry prepared by any one of the aforementioned synthesis methods.

The cationic metallocene catalyst prepared by the method described in the embodiment of the present invention is a brownish-red liquid and has good solubility in aromatic hydrocarbon solvents. It has a stable structure and can be stored for a long time under an inert atmosphere at room temperature. It has good high temperature resistance, and the polymerization reaction temperature can reach 180°C.

An embodiment of the present invention also proposes the application of any one of the above-mentioned cationic catalysts with constrained geometry in olefin polymerization.

Specifically, the olefin polymerization includes ethylene homopolymerization and ethylene copolymerization.

Preferably, the ethylene copolymerization reaction is a copolymerization reaction of ethylene and α-olefin; more preferably, the α-olefin is octene.

In an embodiment of the present invention, no auxiliary agent is added during the olefin polymerization reaction; preferably, the auxiliary agent is an organoboron compound. The cationic metallocene catalyst of constrained geometry prepared by the method described in the examples of the present invention has already compounded the titanocene dialkyl compound and the organoboron compound in the cationic catalyst. Therefore, during the polymerization reaction, there is no need to add The auxiliary organic borate reagent only needs a small amount of aluminum alkyl to remove impurities in the environment. In this way, it can effectively avoid the catalyst produced by the in-situ reaction between the titanocene dialkyl compound (metallocene) and the auxiliary agent during polymerization. Unstable structure and properties, and reducing the loss in the process of adding raw materials and other issues.

In one embodiment of the present invention, the ethylene copolymerization reaction method comprises the steps:

Feed ethylene into the reaction kettle, add aliphatic hydrocarbon solvent and α-olefin, add aluminum alkyl, stir, add cationic constrained geometry catalyst, heat up to the reaction temperature, pressurize and react to obtain the product.

Preferably, when the temperature of the reactor is 60°C, the aluminum alkyl is added.

Specifically, the molar ratio of aluminum in the alkylaluminum to titanium in the catalyst is 50-300; preferably, the molar ratio of aluminum in the alkylaluminum to titanium in the catalyst is 100-150. It should be pointed out that the mole of titanium in the catalyst is based on the added amount of the reaction raw materials.

Specifically, the alkylaluminum includes triisobutylaluminum and the like. Wherein, the alkylaluminum is added in the form of solution. The concentration of the alkyl aluminum solution may be 0.05-0.5 mol/L.

Specifically, the reaction pressure is 1-10 MPa; preferably, the reaction pressure is 2 MPa. The reaction time is 5-20 minutes; preferably, the reaction time is 10 minutes. The temperature of the ethylene copolymerization reaction is 80°C-180°C; preferably, the temperature of the ethylene copolymerization reaction is 90°C-140°C.

Specifically, the equipment required for the reaction needs to be evacuated in advance and replaced by ethylene for at least 3 times before use. Such setting can make the reaction device an anhydrous and oxygen-free environment, which is beneficial for the reaction to proceed.

Specifically, after the reaction, the polymerization solution was poured into acidified ethanol with a volume ratio of concentrated hydrochloric acid/ethanol of 1:9 to terminate the reaction, washed with ethanol, and dried in vacuum to obtain a polymerization product.

The present invention will be described in detail below in conjunction with examples.

Example 1 A preparation method of a constrained geometry cationic catalyst (4a: R ³ =R ⁴ =Ph, R ⁶ =Me), comprising the following steps:

(1) Under the protection of inert gas, at room temperature, put compound 1a (250mg, 0.45mmol) in a 50mL round bottom flask, add 10mL of toluene, take 0.6mL of methyllithium (1.6M, 2.1eq) ether solution and add In the reaction solution, stirred at room temperature for 2 hours, the solution changed from black to dark red, and it was ready for use after the reaction was finished; in order to detect the intermediate product, a little sample was taken to filter out the lithium salt, and the solvent was distilled off under reduced pressure to obtain the dark red solid product 2a. NMR characterization was carried out, and the results are shown in Figure 1.

(2) Then the yellow oily compound 3a with equimolar amount of compound 1a

[NH(C ₁₈ H ₃₇ ) ₂ CH ₃ ][B(C ₆ F ₅ ) ₄ ] was added to the solution obtained in step (1), and the solution changed from dark red to brownish red to obtain a toluene solution of cationic metallocene compound 4a. This solution can be directly used in olefin polymerization reaction, and has good stability. After 40 days at room temperature, the catalytic performance remains basically unchanged.

In order to test the accuracy of the results, a small part of the 4a solution was taken out, the lithium salt was filtered out, and the solvent was dried under reduced pressure to obtain the brown-red viscous oily product 4a, which was characterized by NMR. The results are shown in Figure 2. It can be seen from Figure 2 that there is a methyl peak on Ti at 0.1ppm, and another methyl peak has been replaced, which is consistent with the result.

Example 2 A preparation method of a constrained geometry cationic catalyst (4b: R ³ =R ⁴ =Me, R ⁶ =Me), comprising the following steps:

(1) Under the protection of an inert gas, at room temperature, put compound 1b (400mg, 0.89mmol) in a 50mL round bottom flask, add 10mL of toluene, take 1.21mL of methyllithium (1.6M, 2.1eq) ether solution and add In the reaction solution, stir at room temperature for 2 hours, the solution turns from black to dark red, and it is ready to use after the reaction is finished;

(2) Then, an equimolar amount of yellow oily compound 3a and compound 1b was added to the solution obtained in step (1), and stirred at room temperature for 6 hours, the solution changed from dark red to brownish red, and a toluene solution of cationic metallocene compound 4b was obtained. This solution can be directly used in olefin polymerization reaction and has good stability. After 40 days at room temperature, the catalytic performance remains basically unchanged.

Example 3 A preparation method of a constrained geometry cationic catalyst (4c: R ³ =R ⁴ =Ph, R ⁶ = ⁱ Bu), comprising the following steps:

(1) Under the protection of an inert gas, at room temperature, put compound 1a (250mg, 0.45mmol) in a 50mL round bottom flask, add 10mL of toluene, and take 0.9mL of Ali ^Bu ₃ (1M, 2.1eq) in hexane Added in the reaction solution, stirred at room temperature for 5 hours, the solution changed from black to dark red, and a dialkyl metallocene was generated, which was ready for use after the reaction was completed;

(2) Slowly drop a toluene (10 mL) solution of 3a in an equimolar amount to compound 1a into the solution obtained in step (1), and react at room temperature for 3 hours to obtain a brown toluene solution of cationic metallocene catalyst 4c. The cationic metallocene solution can be directly used to catalyze olefin polymerization reaction, and has good stability. After 40 days at room temperature, the catalytic performance remains basically unchanged.

Example 4 A preparation method of a constrained geometry cationic catalyst (4d: R ³ =R ⁴ =Me, R ⁶ = ⁱ Bu), comprising the following steps:

(1) Under the protection of an inert gas, at room temperature, put compound 1b (400mg, 0.89mmol) in a 50mL round bottom flask, add 10mL of toluene, and take 1.21mL of Ali ^Bu ₃ (1M, 2.1eq) in hexane Added in the reaction solution, stirred at room temperature for 5 hours, the solution changed from black to dark red, and a dialkyl metallocene was generated, which was ready for use after the reaction was completed;

(2) Slowly add a toluene (10 mL) solution of 3a in an equimolar amount to compound 1b to the solution obtained in step (1), and react at room temperature for 3 hours to obtain a brown toluene solution of cationic metallocene catalyst 4d. The cationic metallocene solution can be directly used to catalyze olefin polymerization reaction, and has good stability. It was placed at room temperature for 40 days and used for catalytic olefin polymerization test, and the catalytic activity and performance remained basically unchanged.

Comparative Example 1 A preparation method of a constrained geometry cationic catalyst (4e: the boron promoter is [Ph ₃ C] ⁺ [B(C ₆ F ₅ ) ₄ ] ^- ) with poor solubility in aliphatic hydrocarbon solvents, including Follow the steps below:

(1) Under the protection of an inert gas, put compound 1a (200mg, 0.35mmol) in a 50mL round bottom flask at room temperature, add 10mL of toluene, and then the solution slowly turns dark red, and set aside after the reaction is completed;

(2) Slowly add [Ph ₃ C] ⁺ [B(C ₆ F ₅ ) ₄ ] ^-toluene (10mL) solution in an equimolar amount to compound 1a dropwise to the solution obtained in step (1), and react at room temperature for 3 hours, The lithium salt was filtered, and the solvent was drained to obtain a brown toluene solution of cationic metallocene catalyst 4e.

Test example 1 ethylene-octene polymerization reaction

(1) The reaction device was repeatedly evacuated at 120°C and replaced by ethylene for 3 times in advance, and then ethylene was introduced.

(2) Add 17.8ml of n-hexane and 7.2ml (1.5M) octene to the reaction kettle (30mL) which have been dehydrated and deoxygenated by sodium metal reflux.

(3) After the temperature of the reaction kettle drops to 60°C, add 3 mL of 0.1 mol/L triisobutylaluminum solution (triisobutyl n-hexane solution) under continuous stirring.

(4) After stirring for half a minute, add 1mL (3umol/mL) cationic constrained geometry catalyst (4a), heat up to the reaction temperature (90°C), and react under 2MP pressure for 10min.

(5) After the reaction, pour the polymerization solution into acidified ethanol with a volume ratio of concentrated hydrochloric acid/ethanol of 1:9 to terminate the reaction, wash with ethanol, and dry in vacuum to obtain the polymerization product.

Test example 2-4 ethylene-octene polymerization reaction

Same as Test Example 1, the difference is that in Step (4) of Test Examples 2-4, cationic constrained geometry catalysts 4b, 4c, 4d were added to replace 4a.

Test Example 5-8 Ethylene-Octene Polymerization Reaction (140°C High Temperature Reaction)

Same as Test Example 1, the difference is that the cationic constrained geometry catalysts 4a, 4b, 4c, 4d were added in step (4), and the reaction temperature in step (4) was 140°C.

Test Example 9-12 Ethylene-Octene Polymerization Reaction (Catalysts 4a, 4b, 4c, 4d are used after 40 days of storage)

With Test Example 1, the difference is that in step (4), the cationic constrained geometry catalysts 4a, 4b, 4c, 4d are stored in the glove box for 40 days (marked as 4a-40, 4b-40, 4c-40, 4d-40).

Test Example 13-16 Ethylene-Octene Polymerization Reaction (Catalysts 4a, 4b, 4c, 4d left for 4 days and reacted at a high temperature of 140°C)

Same as Test Example 1, the difference is that the cationic constrained geometry catalysts 4a, 4b, 4c, 4d were added in step (4), and the reaction temperature in step (4) was 140°C.

Comparative test example 1-1

Same as Test Example 1, except that in step (4), the catalyst 4e prepared in Comparative Example 1 was used instead of 4a.

Comparative test example 1-2

Same as Test Example 1, except that in step (4), the catalyst 4e prepared in Comparative Example 1 was used instead of 4a, and the reaction temperature in step (4) was 140°C.

Comparative test example 1-3

Same as Test Example 1, except that in step (4), the catalyst 4e prepared in Comparative Example 1 was stored in a glove box for 40 days (marked as 4e-40) and used again to replace 4a.

Comparative test example 1-4

With Test Example 1, the difference is that in step (4), the catalyst 4e prepared by Comparative Example 1 is stored in the glove box for 40 days before using (marked as 4e-40) to replace 4a; and in step (4) The reaction temperature was 140°C.

Comparative test example 2 ethylene-octene polymerization reaction (main catalyst and cocatalyst add respectively)

(1) The reaction device was repeatedly evacuated at 120°C and replaced by ethylene for 3 times in advance, and then ethylene was introduced.

(2) Add 16.3ml of a certain amount of n-hexane dehydrated and deoxygenated by metal sodium reflux and 7.2mL of octene into the reaction kettle (30mL).

(3) After the temperature of the reaction kettle dropped to 60° C., 3 mL of 0.1 mol/L triisobutylaluminum was added under continuous stirring, so that the Al/Ti molar ratio was 100.

(4) After stirring for half a minute, add 1mL main catalyst 1a (3umol/mL), and 1mL cocatalyst B1 (3.3umol/mL) ([NH(C ₁₈ H ₃₇ ) ₂ CH ₃ ][B(C ₆ F ₅ ) ₄ ] Concentration is the toluene solution of 3.3umol/mL), after being warmed up to reaction temperature, react 10min under 2MP pressure.

(5) After the reaction, pour the polymerization solution into acidified ethanol with a volume ratio of concentrated hydrochloric acid/ethanol of 1:9 to terminate the reaction, wash with ethanol, and dry in vacuum to obtain the polymerization product.

Comparative Test Example 3 Ethylene-Octene Polymerization Reaction

The same as Comparative Test Example 2, except that 4.5 mL of 0.1 mol/L triisobutylaluminum was added in step (3), so that the Al/Ti molar ratio was 150.

Comparative Test Example 4 Ethylene-Octene Polymerization Reaction

The same as Comparative Test Example 1, the difference is that the main catalyst 1a was placed in the glove box for 40 days (marked as 1a-40) before use.

The data obtained in the above test examples are shown in Table 1 below.

Table 1

From the polymerization data in Table 1, it can be concluded that the restricted geometry metallocene cationic catalysts (Test Examples 1-4, Test Examples 5-8) were more efficient than those under the same conditions without additional addition of organoboron additives and a small amount of alkylaluminum. The non-cationic constrained geometry catalysts (comparative test examples 2-3) exhibit better catalytic activity and narrower molecular weight distribution.

After standing for 40 days, the four cationic catalysts can still maintain high catalytic activity, indicating that the configuration has good stability. And when using the boron compound [Ph ₃ C] ⁺ [B(C ₆ F ₅ ) ₄ ^] -time (comparative test example 1-3 and comparative test example 1-4) with poor solubility in aliphatic hydrocarbon solvent, the cationic catalyst is unstable , the reactivity decreased significantly after 40 days.

The non-cationic constrained geometry catalysts (comparative test examples 2-4) have low catalytic activity under the activation of a small amount of alkylaluminum reagent, which may be due to the alkylation of the catalyst after the alkylaluminum reagent removes impurities. Insufficient; and the in-situ reaction of the B1 co-catalyst makes the activation incomplete; in addition, a certain amount of loss will be caused in the pipeline during the addition of the main catalyst and co-catalyst, resulting in a decrease in catalyst activity.

Therefore, the present invention provides a synthesis method of a stable cationic geometric configuration catalyst, which lays a foundation for reducing industrial costs, reducing reaction steps, and promoting industrial production.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention within.

Claims (10)

1. A method of synthesizing a constrained geometry cationic catalyst, comprising:

under the protection of inert gas, in an organic solvent, performing a first reaction between a titanium-containing bis-chloride compound shown in a formula (I-1) and an alkyl metal compound to obtain a first solution containing a titanium-containing bis-alkyl compound shown in a formula (II-1);

directly adding an organoboron compound shown in a formula (II-2) into the first solution for a second reaction, and then performing reduced pressure distillation to obtain a compound shown in a formula (III-1);

[N(R ⁷ ) ₂ (R ⁸ )-H] ⁺ [B(C ₆ F ₅ ) ₄ ] ^- formula (II-2);

wherein R is ¹ Selected from tetrahydropyrrole or piperidinyl;

R ² selected from hydrogen or methyl;

R ³ and R is ⁴ Independently selected from substituted and unsubstituted alkyl and aryl groups;

R ⁵ selected from t-butyl, cycloalkylalkyl;

R ⁶ selected from substituted or unsubstituted alkyl and aryl groups;

R ⁷ selected from substituted or unsubstituted C ₂ -C ₂₀ Alkyl of (a);

R ⁸ selected from the group consisting of a hydrogen atom, a methyl group, and a phenyl group.

2. The synthesis method according to claim 1, wherein,

the alkyl metal compound is alkyl lithium, alkyl zinc and alkyl aluminum.

3. The synthesis method according to claim 1 or 2, wherein,

the molar ratio of the titanocene dichloride compound to the alkyl metal compound represented by the formula (I-1) is 1:1-500.

4. The synthesis method according to claim 1, wherein,

the molar ratio of the titanocene dialkyl compound having the formula (II-1) to the organoboron compound having the formula (II-2) is 1:1-1.5.

5. The synthesis method according to claim 1, wherein,

the organic solvent is aliphatic hydrocarbon solvent; preferably, the aliphatic hydrocarbon solvent includes at least one of aromatic hydrocarbons, ethers, and alkanes.

6. A constrained geometry cationic catalyst prepared by the synthetic method of any one of claims 1-5.

7. Use of a constrained geometry cationic catalyst according to claim 6 in olefin polymerization reactions.

8. The use according to claim 7, wherein,

the olefin polymerization comprises copolymerization of ethylene and alpha-olefin and homopolymerization of ethylene.

Preferably, the ethylene copolymerization is a copolymerization of ethylene and alpha-olefin; more preferably, the alpha-olefin is 1-octene.

9. The use according to claim 7 or 8, characterized in that,

no auxiliary agent is needed in the olefin polymerization reaction process;

preferably, the auxiliary agent is an organoboron compound.

10. The use according to claim 9, wherein,

the ethylene copolymerization reaction method comprises the following steps: introducing ethylene into a reaction kettle, adding an aliphatic hydrocarbon solvent and alpha-olefin, adding aluminum alkyl, stirring, adding a cation limiting geometric catalyst, heating to a reaction temperature, and carrying out pressurized reaction to obtain a product.

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