Composite olefin polymerization catalyst and preparation method thereof

Abstract

This application relates to the field of olefin catalyst technology and specifically discloses a composite olefin polymerization catalyst and its preparation method. The composite olefin polymerization catalyst comprises an inorganic-organic composite support and a titanium / zirconium bimetallic active center; the inorganic-organic composite support is made from raw materials including silica, styrene-divinylbenzene, and a pyridine derivative. The composite olefin polymerization catalyst prepared in this application has the advantage of high catalytic activity.

Description

Technical Field

[0001] The present application relates to the technical field of olefin catalysts, and more specifically, to a composite olefin polymerization catalyst and a preparation method thereof. Background Art

[0002] Polyolefin materials are widely used in packaging, automotive, electronics, medical devices, aerospace, and other fields due to their excellent mechanical properties, chemical stability, and processability. As various industries continue to demand higher performance from materials, the market is placing more stringent demands on performance indicators such as molecular weight distribution, crystallinity, and mechanical strength of polyolefin products. For example, high-end wire and cable insulation materials require polyolefins to have a highly regular molecular structure and uniform molecular weight distribution; the medical device field requires materials to have excellent biocompatibility and stable physical and chemical properties. Olefin polymerization is a key process in the industrial preparation of polyolefin materials, and its core lies in the performance optimization of the catalyst system. The market's stringent requirements for polyolefin performance have brought new challenges to the activity and selectivity of olefin polymerization catalysts.

[0003] While the Ziegler-Natta catalyst currently used in industry accounts for over 70% of polyolefin production capacity and boasts mature technology and low costs, its multiple active centers present a technical bottleneck. The heterogeneous chemical environment of these active centers leads to a wide molecular weight distribution and fluctuating stereoregularity, making it difficult to precisely control the molecular structure. Furthermore, the inadequate steric control of these active centers results in uneven polymer chain branching or stereoregularity defects, triggering physical entanglements between chains. This not only affects product processing performance but also reduces the mechanical properties of the final product.

[0004] The patent application document with application publication number CN104448066A discloses a supported multi-metal olefin polymerization catalyst and its preparation method and application. The catalyst of this invention includes a porous support, a magnesium-containing support component and a transition metal titanium component supported on the porous support. A porous support, a soluble magnesium compound and a soluble non-magnesium metal compound are used as raw materials. A composite support containing magnesium and non-magnesium metal components is formed in situ on the surface of the porous support while titanium is supported. This invention has a simple preparation method and low cost. However, while this invention improves the catalyst activity, it is not ideal for regulating the molecular regularity of polyolefins. The orientation randomness of olefin monomers when inserted into the active center is high, making it difficult to form an ordered polymer chain structure, thereby reducing the molecular regularity. At the same time, it is easy to induce chain transfer reactions and reduce the physical and chemical properties of polyolefins. In view of this, for the problem of catalytic activity and molecular structure regulation optimization in the prior art, it is very necessary to develop a new catalyst system with both high catalytic activity and molecular structure regulation capabilities to promote the development of industries related to polyolefin materials. Summary of the Invention

[0005] In order to further improve the catalytic performance of olefin polymerization catalysts, the present application provides a composite olefin polymerization catalyst and a preparation method thereof.

[0006] In a first aspect, the present application provides a method for preparing a composite olefin polymerization catalyst, which adopts the following technical solution:

[0007] A method for preparing a composite olefin polymerization catalyst comprises the following steps: loading a metallocene compound and titanium tetrachloride on an inorganic-organic composite carrier at a molar ratio of (0.5-2):1, activating the inorganic-organic composite carrier to form a titanium / zirconium bimetallic active center, and then loading a nitrogen-containing heterocyclic carboxylate compound on the inorganic-organic composite carrier to obtain the composite olefin polymerization catalyst;

[0008] The inorganic-organic composite carrier is prepared from raw materials including silicon dioxide, styrene-divinylbenzene and pyridine derivatives.

[0009] By adopting the above technical solution, pyridine derivatives are introduced into the inorganic-organic composite carrier. The pyridine derivatives form coordination with the metal active center, increase the loading amount of the metal active center on the carrier, and improve the catalytic performance of the catalyst. At the same time, the steric hindrance of the pyridine derivatives regulates the stereoselectivity of monomer insertion and improves the regularity of the polyolefin; the pyridine derivatives position the metal ions through coordination, limit the aggregation and migration of metal ions, form uniform active centers, improve the consistency of olefin monomer insertion in the polymerization reaction, and improve the activity of the catalyst and the stability of product quality.

[0010] Preferably, the preparation method of the inorganic-organic composite carrier comprises the following steps:

[0011] 1) Mix polyvinyl alcohol, deionized water, and tricalcium phosphate to obtain an aqueous phase; mix styrene, divinylbenzene, benzoyl peroxide, and silicon dioxide to obtain an oil phase;

[0012] 2) adding the oil phase to the water phase to carry out polymerization reaction to obtain a solid product, and then adding the solid product to a mixed solution consisting of a pyridine derivative and a solvent for impregnation treatment to obtain an inorganic-organic composite carrier.

[0013] Preferably, the silicon dioxide is prepared by an inverse emulsion-atomization method using sodium silicate and methyltrimethoxysilane as silicon sources.

[0014] By adopting the above technical solution, sodium silicate and methyltrimethoxysilane are mixed and dispersed in an inverse emulsion system to form stable droplets. Silica grows uniformly in the droplets. The generated silica has a high specific surface area and a coherent pore structure. At the same time, methyltrimethoxysilane is hydrolyzed to introduce methyl groups, which impart hydrophobicity to the silica, increase the pore size of the silica, and enhance the mechanical strength of the silica. This prevents breakage due to shear stress during use, ensures the integrity of its structure, and thereby improves the loading efficiency and performance stability of the catalyst.

[0015] Preferably, the preparation method of the pyridine derivative comprises the following steps:

[0016] S1: Mix sodium and ethanol, then add 2-dichloropyridine to carry out substitution reaction to obtain intermediate A;

[0017] S2: Sulfuric acid, intermediate A and sodium bromate are mixed to react to obtain intermediate B;

[0018] S3: Diisopropylamine and tetrahydrofuran are mixed, and then a hexane solution of n-butyl lithium is added to react to obtain a base liquid; the base liquid is added to a mixed solution of intermediate B and tetrahydrofuran, reacted for a period of time, and then diphenylphosphine chloride is added to carry out a substitution reaction to obtain a pyridine derivative.

[0019] By adopting the above technical scheme, pyridine derivatives containing diphenylphosphine structures are prepared. Diphenylphosphine acts as a strong electron-donating ligand to increase the electron density of the metallocene center, making it easier for olefin monomers to insert into the metal-carbon bond, thereby improving the catalytic activity of the catalyst. At the same time, the steric structure of diphenylphosphine guides the substrate reaction path through a spatial repulsion effect, inhibiting the occurrence of side reactions, thereby improving the regularity of the polyolefin.

[0020] Preferably, in step 1), the mass ratio of styrene, divinylbenzene and silicon dioxide is (25-35):(20-25):1.

[0021] Preferably, in step 2), the average particle size of the inorganic-organic composite carrier is ≤80 μm.

[0022] Preferably, the mass ratio of the sodium silicate to methyltrimethoxysilane is (4-7):1.

[0023] Preferably, the nitrogen-containing heterocyclic carboxylate compound is one of 2,6-pyridinedicarboxylic acid isopropyl ester, 2,5-pyridinedicarboxylic acid methyl ester and 2-pyridinedicarboxylic acid ethyl ester.

[0024] In a second aspect, the present application provides a composite olefin polymerization catalyst prepared by the above method.

[0025] In summary, this application has the following beneficial effects:

[0026] 1. Adding silica during the preparation of the styrene-divinylbenzene inorganic-organic composite carrier improves the stability of styrene-divinylbenzene and prevents styrene-divinylbenzene from breaking due to swelling. The nanoscale pore structure of silica itself is retained in the matrix during the preparation of the inorganic-organic composite carrier, and new pores are generated at the interface between the matrix and silica, thereby increasing the specific surface area of ​​the inorganic-organic composite carrier and improving the loading capacity of the inorganic-organic composite carrier.

[0027] 2. Pyridine derivatives are introduced into the inorganic-organic composite carrier. The pyridine derivatives form coordination with the metal active center, increase the loading amount of the metal active center on the inorganic-organic composite carrier, and improve the catalytic performance of the catalyst. At the same time, the steric hindrance of the pyridine derivatives regulates the stereoselectivity of the monomer insertion and improves the regularity of the polyolefin.

[0028] 3. Diphenylphosphine in pyridine derivatives acts as a strong electron-donating ligand, which increases the electron cloud density of the metal active center, making it easier for olefin monomers to insert into the metal-carbon bond and improving their catalytic activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is an infrared characterization image of the inorganic-organic composite carrier prepared in Examples 1-3 of the present application. DETAILED DESCRIPTION

[0030] The present application is further described in detail below with reference to the embodiments.

[0031] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available.

[0032] Example 1

[0033] The preparation method of the composite olefin polymerization catalyst of the present embodiment is as follows:

[0034] 1) Weigh 150g of deionized water and add it to a 250mL three-necked flask. Then add 0.9g of polyvinyl alcohol and stir at 200r / min for 15min. Heat to 90°C and continue stirring for 2h. After cooling to room temperature, transfer the mixture to a 1L three-necked flask and add 250g of deionized water and stir for 30min. Then add 2g of tricalcium phosphate and continue stirring for 30min to obtain the aqueous phase. Weigh 25g of styrene and 20g of divinylbenzene and add them to a 150mL beaker. Then add 0.9g of benzoyl peroxide and stir for 25min. Then add 1g of silica and continue stirring for 30min to obtain the oil phase.

[0035] 2) adding the oil phase to the aqueous phase, heating to 80°C, reacting for 4 hours, filtering, washing, and drying to obtain a solid product, which was then added to a mixed solution consisting of 10 g of a pyridine derivative and 100 g of methanol, immersed for 2 hours, filtered, and dried to obtain an inorganic-organic composite support with an average particle size of 80 μm;

[0036] 3) 17.3 g of bis(pentamethylcyclopentadienyl)zirconium dichloride was dissolved in 200 g of toluene, 5 g of the inorganic-organic composite support was added, and the mixture was stirred for 12 h. After stirring, the mixture was washed and dried to obtain a metallocene-supported support. Subsequently, 3.8 g of titanium tetrachloride was dissolved in a mixed solution of 50 g of n-decane, 10 g of isooctyl alcohol, 1.5 g of methylmagnesium chloride and 20 g of hexane. The mixture was cooled to -20°C, the metallocene-supported support was added, and the mixture was stirred for 2 h. The mixture was heated to 80°C at a rate of 1°C / min and stirred for 4 h. The mixture was filtered, washed, dried, and vacuum treated at 120°C for 2 h. The mixture was then vapor-deposited with 0.5 g of ethyl 2-pyridinecarboxylate under a nitrogen atmosphere at 120°C and 0.5 MPa for 4 h to obtain a composite olefin polymerization catalyst.

[0037] The preparation method of silicon dioxide in this embodiment is as follows:

[0038] M1: Weigh 50g of ethanol and add it to a three-necked flask. Then add 8g of sodium silicate and 2g of methyltrimethoxysilane and stir until evenly mixed. Then add hydrochloric acid to adjust the pH to 2. Let it stand for 1.5 hours. Then add a mixed solution consisting of 0.05g of polyvinyl pyrrolidone and 15g of deionized water and stir for 1 hour to form a silica sol.

[0039] M2: 80 g of n-heptane, 10 g of Span80, 5 g of Tween80, and 1.5 g of n-butanol were mixed evenly as the oil phase; 10 g of silica sol was atomized through a pressure atomizing nozzle and slowly added to the oil phase. The mixture was stirred at 900 r / min for 1 h, and the stirring speed was reduced to 200 r / min. Ammonia water was added to adjust the pH to 6. The mixture was reacted for 1 h, allowed to stand for 12 h, and 30 g of acetone was added and mixed evenly. The mixture was filtered, washed, and dried to obtain silica.

[0040] The preparation method of the pyridine derivative of this embodiment is as follows:

[0041] S1: Weigh 120g of ethanol and add it to a three-necked flask, add 7g of sodium, stir for 30min, add 17g of 2-chloropyridine at a rate of 1g / min, and control the system temperature not to exceed 40°C during the addition of 2-chloropyridine. After the 2-chloropyridine is completely added, transfer the reaction system to a reactor, then raise the system temperature to 130°C, and react for 8h. After the reaction is completed, extract and concentrate to obtain intermediate A;

[0042] S2: 95 g of 65% sulfuric acid was added to a four-necked flask, followed by 4.5 g of intermediate A. The mixture was stirred for 20 min, and 6 g of sodium bromate was added. The temperature was adjusted to 25°C and the reaction was continued for 4 h. After the reaction was completed, the mixture was placed in an ice-water bath, the pH was adjusted to 7.5 with aqueous ammonia, and the mixture was extracted. The mixture was dried over anhydrous magnesium sulfate and concentrated to obtain intermediate B.

[0043] S3: Under nitrogen protection, 2.5 g of diisopropylamine and 17 g of tetrahydrofuran were mixed, the temperature was adjusted to -78°C, a mixed solution of 1.9 g of n-butyl lithium and 13 g of hexane was added, and the reaction was carried out for 20 minutes to obtain a base liquid; 5.8 g of intermediate B and 4.5 g of tetrahydrofuran were mixed, the temperature was adjusted to -78°C, the base liquid was added, and the mixture was kept warm for 10 minutes. Then, a mixed solution of 6 g of diphenylphosphine chloride and 13.5 g of tetrahydrofuran was added, and the reaction was carried out for 1 hour. 1 g of deionized water was added to terminate the reaction, and the mixture was extracted and washed to obtain a pyridine derivative.

[0044] Example 2

[0045] The preparation method of the composite olefin polymerization catalyst of the present embodiment is as follows:

[0046] 1) Weigh 150g of deionized water and add it to a 250mL three-necked flask. Then add 1.5g of polyvinyl alcohol and stir at 250r / min for 15min. Heat to 90°C and continue stirring for 2h. After cooling to room temperature, transfer to a 1L three-necked flask and add 250g of deionized water and stir for 40min. Then add 1g of tricalcium phosphate and continue stirring for 30min to obtain the aqueous phase. Weigh 35g of styrene and 25g of divinylbenzene and add them to a 150mL beaker. Then add 1.2g of benzoyl peroxide and stir for 25min. Then add 1g of silica and continue stirring for 30min to obtain the oil phase.

[0047] 2) The oil phase was added to the aqueous phase, the temperature was raised to 90°C, the reaction was carried out for 3 hours, the reaction was filtered, washed, and dried to obtain a solid product, which was then added to a mixed solution consisting of 12 g of a pyridine derivative and 110 g of methanol, immersed for 2.5 hours, filtered, and dried to obtain an inorganic-organic composite support with an average particle size of 70 μm;

[0048] 3) 4 g of zirconocene dichloride was dissolved in 120 g of toluene, 5 g of an inorganic-organic composite carrier was added, and the mixture was stirred for 10 h. After stirring, the mixture was washed and dried to obtain a metallocene-supported carrier. Subsequently, 3.8 g of titanium tetrachloride was dissolved in a mixed solution of 50 g of n-decane, 10 g of isooctyl alcohol, 1.3 g of methylmagnesium chloride and 20 g of hexane, and the mixture was cooled to -20°C. The metallocene-supported carrier was added and stirred for 2 h. The mixture was heated to 80°C at a rate of 1°C / min and stirred for 4 h. The mixture was filtered, washed, dried, and vacuum treated at 120°C for 2 h. The mixture was then vapor-deposited with 0.5 g of isopropyl 2,6-pyridinedicarboxylate under a nitrogen atmosphere at 120°C and 0.5 MPa for 4 h to obtain a composite olefin polymerization catalyst.

[0049] The preparation method of silicon dioxide in this embodiment is as follows:

[0050] M1: Weigh 40g of ethanol and add it to a three-necked flask. Then add 7g of sodium silicate and 1g of methyltrimethoxysilane and stir until evenly mixed. Then add hydrochloric acid to adjust the pH to 2.5. Let it stand for 1.5 hours. Then add a mixed solution consisting of 0.02g of polyvinyl pyrrolidone and 15g of deionized water and stir for 1 hour to form a silica sol.

[0051] M2: Mix 75g of n-heptane, 8g of Span80, 6g of Tween80, and 2g of n-butanol evenly as the oil phase; atomize 8g of silica sol through a pressure atomizing nozzle, slowly add it to the oil phase, stir at 800r / min for 1h, reduce the stirring speed to 250r / min, add ammonia water to adjust the pH to 6.5, react for 1h, let it stand for 10h, add 30g of acetone and mix evenly, filter, wash, and dry to obtain silica.

[0052] The preparation method of the pyridine derivative of this embodiment is as follows:

[0053] S1: Weigh 130g of ethanol and add it to a three-necked flask, add 6g of sodium, stir for 30min, add 15g of 2-chloropyridine at a rate of 1g / min, and control the system temperature not to exceed 40°C during the addition of 2-chloropyridine. After the 2-chloropyridine is completely added, transfer the reaction system to a reactor, then raise the system temperature to 135°C, and react for 6h. After the reaction is completed, extract and concentrate to obtain intermediate A;

[0054] S2: 90 g of 65% sulfuric acid was added to a four-necked flask, followed by 4.5 g of intermediate A. The mixture was stirred for 20 min, and 7 g of sodium bromate was added. The temperature was adjusted to 35°C and the reaction was continued for 3 h. After the reaction was completed, the mixture was placed in an ice-water bath, the pH was adjusted to 7.5 with aqueous ammonia, and the mixture was extracted. The mixture was dried over anhydrous magnesium sulfate and concentrated to obtain intermediate B.

[0055] S3: Under nitrogen protection, 3 g of diisopropylamine and 20 g of tetrahydrofuran were mixed, the temperature was adjusted to -80°C, a mixed solution of 2 g of n-butyl lithium and 13 g of hexane was added, and the reaction was carried out for 20 minutes to obtain a base liquid; 6 g of intermediate B and 4.5 g of tetrahydrofuran were mixed, the temperature was adjusted to -78°C, the base liquid was added, and the mixture was kept warm for 10 minutes. Then, a mixed solution of 6.5 g of diphenylphosphine chloride and 15 g of tetrahydrofuran was added, and the reaction was carried out for 1 hour. 1 g of deionized water was added to terminate the reaction, and the mixture was extracted and washed to obtain a pyridine derivative.

[0056] Example 3

[0057] The preparation method of the composite olefin polymerization catalyst of the present embodiment is as follows:

[0058] 1) Weigh 150g of deionized water and add it to a 250mL three-necked flask. Then add 1g of polyvinyl alcohol and stir at 200r / min for 25min. Heat to 90°C and continue stirring for 2h. After cooling to room temperature, transfer to a 1L three-necked flask and add 250g of deionized water and stir for 30min. Then add 1.5g of tricalcium phosphate and continue stirring for 30min to obtain the aqueous phase. Weigh 30g of styrene and 22g of divinylbenzene and add them to a 150mL beaker. Then add 1.2g of benzoyl peroxide and stir for 30min. Then add 1g of silica and continue stirring for 30min to obtain the oil phase.

[0059] 2) The oil phase was added to the aqueous phase, the temperature was raised to 87°C, the reaction was carried out for 3.5 hours, the reaction was filtered, washed, and dried to obtain a solid product. The solid product was then added to a mixed solution consisting of 12 g of a pyridine derivative and 110 g of methanol, the mixture was immersed for 2.5 hours, filtered, and dried to obtain an inorganic-organic composite support with an average particle size of 76 μm;

[0060] 3) 2.9 g of zirconocene dichloride was dissolved in 100 g of toluene, 5 g of an inorganic-organic composite carrier was added, and the mixture was stirred for 10 h. After stirring, the mixture was washed and dried to obtain a metallocene-supported carrier. Subsequently, 3.8 g of titanium tetrachloride was dissolved in a mixed solution of 50 g of n-decane, 10 g of isooctyl alcohol, 1.1 g of methylmagnesium chloride and 20 g of hexane, and the mixture was cooled to -20°C. The metallocene-supported carrier was added and stirred for 2 h. The mixture was heated to 80°C at a rate of 1°C / min and stirred for 4 h. The mixture was filtered, washed, dried, and vacuum treated at 120°C for 2 h. The mixture was then vapor-deposited with 0.5 g of methyl 2,5-pyridinedicarboxylate under a nitrogen atmosphere at 120°C and 0.5 MPa for 4 h to obtain a composite olefin polymerization catalyst.

[0061] The preparation method of silicon dioxide in this embodiment is as follows:

[0062] M1: Weigh 40g of ethanol and add it to a three-necked flask. Then add 8g of sodium silicate and 1.5g of methyltrimethoxysilane and stir until evenly mixed. Then add hydrochloric acid to adjust the pH to 2.5. Let it stand for 1.5 hours. Then add a mixed solution consisting of 0.04g of polyvinyl pyrrolidone and 15g of deionized water and stir for 1 hour to form a silica sol.

[0063] M2: 80 g of n-heptane, 8 g of Span80, 6 g of Tween80, and 2 g of n-butanol were mixed evenly as the oil phase; 8 g of silica sol was atomized through a pressure atomizing nozzle and slowly added to the oil phase. The mixture was stirred at 900 r / min for 1 h, and the stirring speed was reduced to 250 r / min. Ammonia water was added to adjust the pH to 6.5. The mixture was reacted for 1 h, allowed to stand for 10 h, and 30 g of acetone was added and mixed evenly. The mixture was filtered, washed, and dried to obtain silica.

[0064] The preparation method of the pyridine derivative of this embodiment is as follows:

[0065] S1: Weigh 125g of ethanol and add it to a three-necked flask, add 6.5g of sodium, stir for 30min, add 15g of 2-chloropyridine at a rate of 1g / min, and control the system temperature not to exceed 40°C during the addition of 2-chloropyridine. After the 2-chloropyridine is completely added, transfer the reaction system to a reactor, then raise the system temperature to 130°C, and react for 6h. After the reaction is completed, extract and concentrate to obtain intermediate A;

[0066] S2: 90 g of 65% sulfuric acid was added to a four-necked flask, followed by 4.5 g of intermediate A. The mixture was stirred for 20 min, and 6.5 g of sodium bromate was added. The temperature was adjusted to 30°C and the reaction was continued for 3.5 h. After the reaction was completed, the mixture was placed in an ice-water bath, the pH was adjusted to 7.5 with aqueous ammonia, and the mixture was extracted. The mixture was dried over anhydrous magnesium sulfate and concentrated to obtain intermediate B.

[0067] S3: Under nitrogen protection, 2.7 g of diisopropylamine and 20 g of tetrahydrofuran were mixed, the temperature was adjusted to -80°C, a mixed solution of 2 g of n-butyl lithium and 13 g of hexane was added, and the reaction was carried out for 20 minutes to obtain a base liquid; 6 g of intermediate B and 4.5 g of tetrahydrofuran were mixed, the temperature was adjusted to -78°C, the base liquid was added, and the mixture was kept warm for 10 minutes. Then, a mixed solution of 6.2 g of diphenylphosphine chloride and 15 g of tetrahydrofuran was added, and the reaction was carried out for 1 hour. 1 g of deionized water was added to terminate the reaction, and the mixture was extracted and washed to obtain a pyridine derivative.

[0068] Comparative Example 1

[0069] The preparation method of the composite olefin polymerization catalyst of this comparative example is as follows:

[0070] 1) Weigh 150g of deionized water and add it to a 250mL three-necked flask. Then add 0.9g of polyvinyl alcohol and stir at 200r / min for 15min. Heat to 90°C and continue stirring for 2h. After cooling to room temperature, transfer the mixture to a 1L three-necked flask and add 250g of deionized water and stir for 30min. Then add 2g of tricalcium phosphate and continue stirring for 30min to obtain the aqueous phase. Weigh 25g of styrene and 20g of divinylbenzene and add them to a 150mL beaker. Then add 0.9g of benzoyl peroxide and stir for 25min. Then add 1g of silica and continue stirring for 30min to obtain the oil phase.

[0071] 2) adding the oil phase to the aqueous phase, heating to 80°C, reacting for 4 hours, filtering, washing, and drying to obtain a solid product, which was then added to a mixed solution consisting of 10 g of a pyridine derivative and 100 g of methanol, immersed for 2 hours, filtered, and dried to obtain an inorganic-organic composite support with an average particle size of 80 μm;

[0072] 3) 17.3 g of bis(pentamethylcyclopentadienyl)zirconium dichloride was dissolved in 200 g of toluene, 5 g of the inorganic-organic composite support was added, and the mixture was stirred for 12 h. After stirring, the mixture was washed and dried to obtain a metallocene-supported support. Subsequently, 3.8 g of titanium tetrachloride was dissolved in a mixed solution of 50 g of n-decane, 10 g of isooctyl alcohol, 1.5 g of methylmagnesium chloride and 20 g of hexane. The mixture was cooled to -20°C, the metallocene-supported support was added, and the mixture was stirred for 2 h. The mixture was heated to 80°C at a rate of 1°C / min and stirred for 4 h. The mixture was filtered, washed, dried, and vacuum treated at 120°C for 2 h. The mixture was then vapor-deposited with 0.5 g of ethyl 2-pyridinecarboxylate under a nitrogen atmosphere at 120°C and 0.5 MPa for 4 h to obtain a composite olefin polymerization catalyst.

[0073] The preparation method of the silicon dioxide of this comparative example is as follows:

[0074] M1: Weigh 50g of ethanol and add it to a three-necked flask. Then add 8g of sodium silicate and 2g of methyltrimethoxysilane and stir until evenly mixed. Then add hydrochloric acid to adjust the pH to 2. Let it stand for 1.5 hours. Then add a mixed solution consisting of 0.05g of polyvinyl pyrrolidone and 15g of deionized water and stir for 1 hour to form a silica sol.

[0075] M2: 80 g of n-heptane, 10 g of Span80, 5 g of Tween80, and 1.5 g of n-butanol were mixed evenly as the oil phase; 10 g of silica sol was added to the oil phase, stirred at 900 r / min for 1 h, the stirring speed was reduced to 200 r / min, ammonia water was added to adjust the pH to 6, the reaction was carried out for 1 h, and the mixture was allowed to stand for 12 h. 30 g of acetone was added and mixed evenly, and the mixture was filtered, washed, and dried to obtain silica.

[0076] The preparation method of the pyridine derivative of this comparative example is as follows:

[0077] S1: Weigh 120g of ethanol and add it to a three-necked flask, add 7g of sodium, stir for 30min, add 17g of 2-chloropyridine at a rate of 1g / min, and control the system temperature not to exceed 40°C during the addition of 2-chloropyridine. After the 2-chloropyridine is completely added, transfer the reaction system to a reactor, then raise the system temperature to 130°C, and react for 8h. After the reaction is completed, extract and concentrate to obtain intermediate A;

[0078] S2: 95 g of 65% sulfuric acid was added to a four-necked flask, followed by 4.5 g of intermediate A. The mixture was stirred for 20 min, and 6 g of sodium bromate was added. The temperature was adjusted to 25°C and the reaction was continued for 4 h. After the reaction was completed, the mixture was placed in an ice-water bath, the pH was adjusted to 7.5 with aqueous ammonia, and the mixture was extracted. The mixture was dried over anhydrous magnesium sulfate and concentrated to obtain intermediate B.

[0079] S3: Under nitrogen protection, 2.5 g of diisopropylamine and 17 g of tetrahydrofuran were mixed, the temperature was adjusted to -78°C, a mixed solution of 1.9 g of n-butyl lithium and 13 g of hexane was added, and the reaction was carried out for 20 minutes to obtain a base liquid; 5.8 g of intermediate B and 4.5 g of tetrahydrofuran were mixed, the temperature was adjusted to -78°C, the base liquid was added, and the mixture was kept warm for 10 minutes. Then, a mixed solution of 6 g of diphenylphosphine chloride and 13.5 g of tetrahydrofuran was added, and the reaction was carried out for 1 hour. 1 g of deionized water was added to terminate the reaction, and the mixture was extracted and washed to obtain a pyridine derivative.

[0080] Comparative Example 2

[0081] The preparation method of the composite olefin polymerization catalyst of this comparative example is as follows:

[0082] 1) Weigh 150g of deionized water and add it to a 250mL three-necked flask. Then add 0.9g of polyvinyl alcohol and stir at 200r / min for 15min. Heat to 90°C and continue stirring for 2h. After cooling to room temperature, transfer the mixture to a 1L three-necked flask and add 250g of deionized water and stir for 30min. Then add 2g of tricalcium phosphate and continue stirring for 30min to obtain the aqueous phase. Weigh 25g of styrene and 20g of divinylbenzene and add them to a 150mL beaker. Then add 0.9g of benzoyl peroxide and stir for 25min. Then add 1g of silica and continue stirring for 30min to obtain the oil phase.

[0083] 2) adding the oil phase to the aqueous phase, heating to 80°C, reacting for 4 hours, filtering, washing, and drying to obtain a solid product, which was then added to a mixed solution consisting of 10 g of a pyridine derivative and 100 g of methanol, immersed for 2 hours, filtered, and dried to obtain an inorganic-organic composite support with an average particle size of 80 μm;

[0084] 3) 17.3 g of bis(pentamethylcyclopentadienyl)zirconium dichloride was dissolved in 200 g of toluene, 5 g of the inorganic-organic composite support was added, and the mixture was stirred for 12 h. After stirring, the mixture was washed and dried to obtain a metallocene-supported support. Subsequently, 3.8 g of titanium tetrachloride was dissolved in a mixed solution of 50 g of n-decane, 10 g of isooctyl alcohol, 1.5 g of methylmagnesium chloride and 20 g of hexane. The mixture was cooled to -20°C, the metallocene-supported support was added, and the mixture was stirred for 2 h. The mixture was heated to 80°C at a rate of 1°C / min and stirred for 4 h. The mixture was filtered, washed, dried, and vacuum treated at 120°C for 2 h. The mixture was then vapor-deposited with 0.5 g of ethyl 2-pyridinecarboxylate under a nitrogen atmosphere at 120°C and 0.5 MPa for 4 h to obtain a composite olefin polymerization catalyst.

[0085] The preparation method of the silicon dioxide of this comparative example is as follows:

[0086] M1: Weigh 50g of ethanol and add it to a three-necked flask. Then add 8g of sodium silicate and 2g of methyltrimethoxysilane and stir until evenly mixed. Then add hydrochloric acid to adjust the pH to 2. Let it stand for 1.5 hours. Then add a mixed solution consisting of 0.05g of polyvinyl pyrrolidone and 15g of deionized water and stir for 1 hour to form a silica sol.

[0087] M2: 80 g of n-heptane, 10 g of Span80, 5 g of Tween80, and 1.5 g of n-butanol were mixed evenly as the oil phase; 10 g of silica sol was atomized through a pressure atomizing nozzle and slowly added to the oil phase. The mixture was stirred at 900 r / min for 1 h, and the stirring speed was reduced to 200 r / min. Ammonia water was added to adjust the pH to 6. The mixture was reacted for 1 h, allowed to stand for 12 h, and 30 g of acetone was added and mixed evenly. The mixture was filtered, washed, and dried to obtain silica.

[0088] The preparation method of the pyridine derivative of this comparative example is as follows:

[0089] S1: Weigh 120g of ethanol and add it to a three-necked flask, add 7g of sodium, stir for 30min, add 17g of 2-chloropyridine at a rate of 1g / min, and control the system temperature not to exceed 40°C during the addition of 2-chloropyridine. After the 2-chloropyridine is completely added, transfer the reaction system to a reactor, then raise the system temperature to 130°C, and react for 8h. After the reaction is completed, extract and concentrate to obtain intermediate A;

[0090] S2: Take 95g of sulfuric acid with a mass percentage concentration of 65% and add it to a four-necked flask, then add 4.5g of intermediate A, stir for 20min, add 6g of sodium bromate, adjust the temperature to 25℃ and react for 4h. After the reaction, place it in an ice-water bath, adjust the pH to 7.5 with ammonia water, extract, dry with anhydrous magnesium sulfate, and concentrate to obtain a pyridine derivative.

[0091] Performance testing

[0092] The composite olefin polymerization catalyst prepared in Examples 1-3 and Comparative Examples 1-2 was used to catalyze the ethylene polymerization reaction. The polymerization kettle was alternately filled with hydrogen and evacuated three times. 1 L of hexane, 7 mg of the composite olefin polymerization catalyst, and 5 mmol of triethylaluminum were added. The reactor was heated to 80° C., and ethylene was introduced so that the total pressure in the reactor reached 3.0 MPa. The polymerization reaction was carried out at 80° C. for 4 hours. After the reaction was completed, the polymer powder was collected and dried to obtain polyethylene.

[0093] 1. Polymer molecular weight and molecular weight distribution were determined using high-temperature gel permeation chromatography (GPC). The polymer was dissolved in 1,2,4-trichlorobenzene at 150°C, and the standard sample was polystyrene with a narrow molecular weight distribution. The flow rate was 1.0 mL / min. The test results are shown in Table 1.

[0094] Table 1 Catalyst activity and performance test data of polyethylene prepared by the catalysts of Examples 1-3 and Comparative Examples 1-2

[0095]

[0096] 2. Specific Surface Area Test: The inorganic-organic composite supports prepared in Examples 1-3 and Comparative Examples 1-2 were tested for specific surface area. The specific surface area and pore structure of the catalysts were determined using an Autosorb-IQ-MP surface and pore analyzer. Degassing conditions were vacuum degassing at 300°C for 6 hours, and nitrogen adsorption was performed at liquid nitrogen temperature. The test results are shown in Table 2.

[0097] Table 2 Specific surface area test data of the inorganic-organic composite carriers prepared in Examples 1-3 and Comparative Examples 1-2

[0098]

[0099] 3. Infrared analysis: The inorganic-organic composite supports prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to infrared analysis. Samples were prepared using the KBr pellet method and tested using a Fourier transform infrared spectrometer. The test wave number range was 4000 cm -1 Up to 400cm -1 The test results are as follows. Figure 1 shown.

[0100] Analysis of Examples 1-3 and Comparative Example 1 in combination with Table 1-2 shows that silica is prepared using the reverse emulsion-atomization method, and silica is compounded with styrene-divinylbenzene to form an inorganic-organic composite carrier with a high specific surface area, thereby increasing the loading amount of the active components of the catalyst and thus improving the activity of the catalyst; analysis of Examples 1-3 and Comparative Example 2 in combination with Table 1-2 shows that the introduction of diphenylphosphine in the pyridine derivative effectively improves the catalytic activity of the catalyst while improving the regularity of the polyolefin.

[0101] Analyze Examples 1-3 and combine Figure 1 It can be seen that 3025 cm - ¹ and 1492 cm - The absorption peaks of ¹ correspond to the aromatic ring CH stretching vibration and C=C skeleton vibration, while 2925cm - ¹ and 1450cm - The aliphatic CH vibrations of ¹ indicate the formation of a cross-linked network.

[0102] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for preparing a composite olefin polymerization catalyst, characterized in that: The method comprises the following steps: loading a metallocene compound and titanium tetrachloride on an inorganic-organic composite carrier at a molar ratio of (0.5-2):1 to form a titanium / zirconium bimetallic active center; and then loading a nitrogen-containing heterocyclic carboxylate compound on the inorganic-organic composite carrier to obtain a composite olefin polymerization catalyst; The inorganic-organic composite carrier is made of raw materials including silicon dioxide, styrene-divinylbenzene and pyridine derivatives; The nitrogen-containing heterocyclic carboxylate compound is one of 2,6-pyridinedicarboxylic acid isopropyl ester, 2,5-pyridinedicarboxylic acid methyl ester and 2-pyridinedicarboxylic acid ethyl ester; The preparation method of the pyridine derivative comprises the following steps: S1: Mix sodium and ethanol, then add 2-dichloropyridine to carry out substitution reaction to obtain intermediate A; S2: Sulfuric acid, intermediate A and sodium bromate are mixed to react to obtain intermediate B; S3: Diisopropylamine and tetrahydrofuran are mixed, and then a hexane solution of n-butyl lithium is added to react to obtain a base liquid; the base liquid is added to a mixed solution of intermediate B and tetrahydrofuran, reacted for a period of time, and then diphenylphosphine chloride is added to carry out a substitution reaction to obtain a pyridine derivative.

2. The method for preparing a composite olefin polymerization catalyst according to claim 1, wherein: The preparation method of the inorganic-organic composite carrier comprises the following steps: 1) Mix polyvinyl alcohol, deionized water, and tricalcium phosphate to obtain an aqueous phase; mix styrene, divinylbenzene, benzoyl peroxide, and silicon dioxide to obtain an oil phase; 2) adding the oil phase to the water phase to carry out polymerization reaction to obtain a solid product, and then adding the solid product to a mixed solution consisting of a pyridine derivative and a solvent for impregnation treatment to obtain an inorganic-organic composite carrier.

3. The method for preparing a composite olefin polymerization catalyst according to claim 1 or 2, wherein: The silicon dioxide is prepared by using sodium silicate and methyltrimethoxysilane as silicon sources through an inverse emulsion-atomization method.

4. The method for preparing a composite olefin polymerization catalyst according to claim 2, wherein: In the step 1), the mass ratio of styrene, divinylbenzene and silicon dioxide is (25-35):(20-25):

1.

5. The method for preparing a composite olefin polymerization catalyst according to claim 2, wherein: In the step 2), the average particle size of the inorganic-organic composite carrier is ≤80 μm.

6. The method for preparing a composite olefin polymerization catalyst according to claim 3, characterized in that: The mass ratio of the sodium silicate to methyltrimethoxysilane is (4-7):

1.

7. A composite olefin polymerization catalyst prepared by the preparation method according to any one of claims 1 to 6.

Images