Composite olefin polymerization catalyst and preparation method thereof

Abstract

The invention relates to the technical field of olefin catalysts, and particularly discloses a composite olefin polymerization catalyst and a preparation method thereof. The composite olefin polymerization catalyst comprises an inorganic-organic composite carrier and a titanium / zirconium bimetallic active center, the inorganic-organic composite carrier is prepared from raw materials including silicon dioxide, styrene-divinyl benzene and pyridine derivatives. The composite olefin polymerization catalyst prepared by the invention has the advantage of high catalytic activity.

Description

Technical Field

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

[0002] Polyolefin materials are widely used in fields such as packaging, automotive, electronics, medical devices, and aerospace due to their excellent mechanical properties, chemical stability, and processability. With the continuous improvement of material performance requirements in various industries, the market has put forward more stringent requirements for performance indicators such as the 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 a uniform molecular weight distribution; the medical device field requires materials to have excellent biocompatibility and stable physical and chemical properties. The olefin polymerization reaction is a key process for the industrial preparation of polyolefin materials, and the core lies in the performance optimization of the catalyst system. The stringent market requirements for polyolefin performance have brought new challenges to the activity and selectivity of olefin polymerization catalysts.

[0003] Although the Ziegler-Natta catalyst commonly used in industry currently occupies more than 70% of the polyolefin production capacity and has the advantages of mature technology and low cost, its multi-active center characteristic has become a technical bottleneck. Due to the non-uniform chemical environment of the active centers, the molecular weight distribution is wide and the stereoregularity fluctuates, making it impossible to precisely control the molecular structure. In addition, the ability to regulate the steric hindrance of the active centers is insufficient, resulting in uneven polymer chain branching degrees or stereoregularity defects, triggering physical entanglement between chains, which not only affects the processing performance of the product but also reduces the mechanical properties of the final product.

[0004] The patent application document with the publication number CN104448066A discloses a supported multi-metal olefin polymerization catalyst, its preparation method and application. The catalyst of this invention includes a porous carrier, a magnesium-containing carrier component and a transition metal titanium component supported on the porous carrier. Using a porous carrier, a soluble magnesium compound and a soluble non-magnesium metal compound as raw materials, while in-situ forming a composite carrier containing magnesium and non-magnesium metal components on the surface of the porous carrier, the loading of titanium is achieved. The preparation method of this invention is simple and the cost is low. However, while improving the activity of the catalyst, the regulation of the molecular regularity of polyolefins is not ideal. The orientation randomness of olefin monomers inserting into the active centers is relatively high, making it difficult to form an orderly arranged polymer chain structure, thereby reducing the molecular regularity. At the same time, chain transfer reactions are easily triggered, reducing the physical and chemical properties of polyolefins. In view of this, in response to the problems of catalytic activity and molecular structure regulation and optimization in the prior art, it is very necessary to develop a new catalyst system with both high catalytic activity and the ability to regulate the molecular structure for promoting the development of the polyolefin material-related industries. Summary of the Invention

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

[0006] In a first aspect, the present application provides a preparation method of a composite olefin polymerization catalyst, adopting the following technical solution: A preparation method of a composite olefin polymerization catalyst includes the following steps: loading a metallocene compound and titanium tetrachloride on an inorganic-organic composite support at a molar ratio of (0.5-2):1, activating the inorganic-organic composite support to form a titanium / zirconium bimetallic active center, and then loading a nitrogen-containing heterocyclic carboxylate compound in the inorganic-organic composite support to obtain the composite olefin polymerization catalyst; The inorganic-organic composite support is made of raw materials including silica, styrene-divinylbenzene, and pyridine derivatives.

[0007] By adopting the above technical solution, a pyridine derivative is introduced into the inorganic-organic composite support. The pyridine derivative forms a coordination with the metal active center, increasing the loading amount of the metal active center on the support and improving the catalytic performance of the catalyst. At the same time, the steric hindrance of the pyridine derivative regulates the stereoselectivity of monomer insertion, improving the regularity of polyolefin; the pyridine derivative locates metal ions through coordination, restricts the aggregation and migration of metal ions, forms a uniform active center, improves the consistency of olefin monomer insertion in the polymerization reaction, and improves the activity of the catalyst and the quality stability of the product.

[0008] Preferably, the preparation method of the inorganic-organic composite support includes the following steps: 1) Mix polyvinyl alcohol, deionized water, and tricalcium phosphate to obtain an aqueous phase; mix styrene, divinylbenzene, benzoyl peroxide, and silica to obtain an oil phase; 2) Add the oil phase to the aqueous phase, carry out a polymerization reaction to obtain a solid product, and then add the solid product to a mixed solution composed of a pyridine derivative and a solvent for impregnation treatment to obtain the inorganic-organic composite support.

[0009] Preferably, the silica is prepared by an inverse emulsion-atomization method using sodium silicate and methyltrimethoxysilane as silicon sources.

[0010] By adopting the above technical solution, after sodium silicate and methyltrimethoxysilane are mixed, they are dispersed in the inverse emulsion system to form stable droplets. Silicon dioxide grows uniformly inside the droplets. The generated silicon dioxide has a high specific surface area and a coherent pore structure. At the same time, the hydrolysis of methyltrimethoxysilane introduces methyl groups, endowing silicon dioxide with hydrophobicity, increasing the pore diameter of silicon dioxide, and enhancing the mechanical strength of silicon dioxide, avoiding fragmentation due to shear stress during use, ensuring the integrity of its structure, and thus improving the loading efficiency and performance stability of the catalyst.

[0011] Preferably, the preparation method of the pyridine derivative comprises the following steps: S1: Mix sodium and ethanol, then add 2-dichloropyridine and carry out a substitution reaction to obtain intermediate A; S2: Take sulfuric acid, intermediate A and sodium bromate and mix them for reaction to obtain intermediate B; S3: Mix diisopropylamine and tetrahydrofuran, then add a hexane solution of n-butyllithium for reaction to obtain a base solution; Add the base solution to a mixed solution of intermediate B and tetrahydrofuran, react for a period of time, and then add diphenylphosphine chloride and carry out a substitution reaction to obtain the pyridine derivative.

[0012] By adopting the above technical solution, a pyridine derivative containing a diphenylphosphine structure is prepared. As a strong electron-donating ligand, diphenylphosphine increases the electron density of the metallocene center, making it easier for olefin monomers to insert into the metal-carbon bond, and improving the catalytic activity of the catalyst; at the same time, the steric structure of diphenylphosphine guides the reaction path of the substrate through the steric repulsion effect, inhibits the occurrence of side reactions, and thus improves the regularity of polyolefins.

[0013] Preferably, in the step 1), the mass ratio of styrene, divinylbenzene and silicon dioxide is (25 - 35):(20 - 25):1.

[0014] Preferably, in the step 2), the average particle size of the inorganic-organic composite support ≤ 80 μm.

[0015] Preferably, the mass ratio of sodium silicate to methyltrimethoxysilane is (4 - 7):1.

[0016] Preferably, the nitrogen-containing heterocyclic carboxylic acid ester compound is one of isopropyl 2,6-pyridinedicarboxylate, methyl 2,5-pyridinedicarboxylate and ethyl 2-pyridinecarboxylate.

[0017] In the second aspect, the present application provides a composite olefin polymerization catalyst prepared by the above method.

[0018] In summary, the present application has the following beneficial effects: 1. During the preparation of the styrene-divinylbenzene inorganic-organic composite support, silica is added to improve the stability of styrene-divinylbenzene and prevent the rupture of styrene-divinylbenzene due to swelling. The nano-porous structure of silica itself is retained in the matrix during the preparation of the inorganic-organic composite support, and new pores are generated at the interface between the matrix and silica, increasing the specific surface area of the inorganic-organic composite support and improving its loading capacity.

[0019] 2. A pyridine derivative is introduced into the inorganic-organic composite support. The pyridine derivative forms a coordination with the metal active center, increasing the loading amount of the metal active center on the inorganic-organic composite support and enhancing the catalytic performance of the catalyst. At the same time, the steric hindrance of the pyridine derivative regulates the stereoselectivity of monomer insertion, improving the regularity of polyolefins.

[0020] 3. As a strong electron-donating ligand, diphenylphosphine in the pyridine derivative 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 its catalytic activity. Description of the Drawings

[0021] Figure 1 It is the infrared characterization diagram of the inorganic-organic composite support prepared in Examples 1-3 of this application. Detailed Description of the Embodiments

[0022] The following further describes this application in detail with reference to the examples.

[0023] The raw materials in the examples and comparative examples of this application are all commercially available except as otherwise specified.

[0024] Example 1 The preparation method of the composite olefin polymerization catalyst in this example is as follows: 1) Weigh 150 g of deionized water and add it to a 250 mL three-necked flask. Then add 0.9 g of polyvinyl alcohol, stir at a speed of 200 r / min for 15 min, heat up to 90 °C, continue stirring for 2 h, cool to room temperature, transfer it to a 1 L three-necked flask, add 250 g of deionized water and stir for 30 min, then add 2 g of tricalcium phosphate and continue stirring for 30 min to obtain an aqueous phase; Weigh 25 g of styrene and 20 g of divinylbenzene and add them to a 150 mL beaker. Then add 0.9 g of benzoyl peroxide, stir for 25 min, add 1 g of silica and continue stirring for 30 min to obtain an oil phase; 2) Add the oil phase to the aqueous phase, heat up to 80 °C, react for 4 h, filter, wash, and dry to obtain a solid product. Then add the solid product to a mixed solution composed of 10 g of pyridine derivative and 100 g of methanol, impregnate for 2 h, filter, and dry to obtain an inorganic-organic composite support with an average particle size of 80 μm; 3) Dissolve 17.3 g of bis(pentamethylcyclopentadienyl)zirconium dichloride in 200 g of toluene, add 5 g of an inorganic-organic composite support, stir for 12 h, wash and dry after completion to obtain a metallocene-supported support; then dissolve 3.8 g of titanium tetrachloride in a mixed solution of 50 g of n-decane, 10 g of isooctanol, 1.5 g of methylmagnesium chloride and 20 g of hexane, cool to -20 °C, add the metallocene-supported support and stir for 2 h, heat up to 80 °C at a rate of 1 °C / min, continue to stir for 4 h, filter, wash, dry, perform vacuum treatment at 120 °C for 2 h, and then carry out gas-phase deposition 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.

[0025] The preparation method of the silica in this example is as follows: M1: Weigh 50 g of ethanol and add it to a three-necked flask, then add 8 g of sodium silicate and 2 g of methyltrimethoxysilane, stir and mix evenly, add hydrochloric acid to adjust the pH to 2, let it stand for 1.5 h, then add a mixed solution composed of 0.05 g of polyvinylpyrrolidone and 15 g of deionized water, and stir for 1 h to form silica sol. M2: Mix 80 g of n-heptane, 10 g of Span80, 5 g of Tween80, and 1.5 g of n-butanol evenly as the oil phase; atomize 10 g of silica sol through a pressure-type atomizing nozzle and slowly add it to the oil phase, stir at a rotation speed of 900 r / min for 1 h, reduce the stirring speed to 200 r / min, add ammonia water to adjust the pH to 6, react for 1 h, let it stand for 12 h, add 30 g of acetone and mix evenly, filter, wash, and dry to obtain silica.

[0026] The preparation method of the pyridine derivative in this example is as follows: S1: Weigh 120 g of ethanol and add it to a three-necked flask, add 7 g of sodium, stir for 30 min, add 17 g of 2-chloropyridine at a rate of 1 g / min, and at the same time control the temperature of the system during the addition of 2-chloropyridine not to exceed 40 °C. After the complete addition of 2-chloropyridine, transfer the reaction system to a reaction kettle, then raise the temperature of the system to 130 °C, react for 8 h, and perform extraction and concentration after the reaction to obtain intermediate A. S2: Take 95 g of sulfuric acid with a mass percentage concentration of 65% and add it to a four-necked flask, then add 4.5 g of intermediate A, stir for 20 min, add 6 g of sodium bromate, adjust the temperature to 25 °C and react for 4 h. 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 intermediate B. S3: Under nitrogen protection, 2.5 g of diisopropylamine and 17 g of tetrahydrofuran were mixed, the temperature was adjusted to -78 °C, and a mixed solution of 1.9 g of n-butyllithium and 13 g of hexane was added. The reaction was carried out for 20 min to obtain a base solution. 5.8 g of intermediate B and 4.5 g of tetrahydrofuran were mixed, the temperature was adjusted to -78 °C, then the base solution was added, and the temperature was kept for 10 min. 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 h. 1 g of deionized water was added to terminate the reaction, and extraction and washing were carried out to obtain a pyridine derivative.

[0027] Example 2 The preparation method of the composite olefin polymerization catalyst in this example is as follows: 1) Weigh 150 g of deionized water and add it to a 250 mL three-necked flask. Then add 1.5 g of polyvinyl alcohol and stir at a speed of 250 r / min for 15 min. Heat up to 90 °C and continue stirring for 2 h. After cooling to room temperature, transfer it to a 1 L three-necked flask, add 250 g of deionized water and stir for 40 min. Then add 1 g of tricalcium phosphate and continue stirring for 30 min to obtain an aqueous phase. Weigh 35 g of styrene and 25 g of divinylbenzene and add them to a 150 mL beaker. Then add 1.2 g of benzoyl peroxide and stir for 25 min. Add 1 g of silica and continue stirring for 30 min to obtain an oil phase. 2) Add the oil phase to the aqueous phase, heat up to 90 °C, react for 3 h, filter, wash, and dry to obtain a solid product. Then add the solid product to a mixed solution composed of 12 g of pyridine derivative and 110 g of methanol, impregnate for 2.5 h, filter, and dry to obtain an inorganic-organic composite support with an average particle size of 70 μm. 3) Dissolve 4 g of zirconocene dichloride in 120 g of toluene, add 5 g of the inorganic-organic composite support, and stir for 10 h. After completion, wash and dry to obtain a metallocene-supported support. Then dissolve 3.8 g of titanium tetrachloride in a mixed solution of 50 g of n-decane, 10 g of isooctanol, 1.3 g of methylmagnesium chloride, and 20 g of hexane, cool to -20 °C, add the metallocene-supported support and stir for 2 h. Heat up to 80 °C at a rate of 1 °C / min and continue stirring for 4 h. Filter, wash, dry, and perform vacuum treatment at 120 °C for 2 h. Then carry out gas-phase deposition 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.

[0028] The preparation method of the silica in this example is as follows: M1: Weigh 40 g of ethanol and add it to a three-necked flask. Then add 7 g of sodium silicate and 1 g of methyltrimethoxysilane and stir to mix evenly. Then add hydrochloric acid to adjust the pH to 2.5, let it stand for 1.5 h, and then add a mixed solution composed of 0.02 g of polyvinylpyrrolidone and 15 g of deionized water, and stir for 1 h to form a silica sol. M2: Mix 75 g of n - heptane, 8 g of Span80, 6 g of Tween80, and 2 g of n - butanol evenly as the oil phase; atomize 8 g of silica sol through a pressure - type atomizing nozzle and slowly add it to the oil phase. Stir at a speed of 800 r / min for 1 h, reduce the stirring speed to 250 r / min, add ammonia water to adjust the pH to 6.5, react for 1 h, let it stand for 10 h, add 30 g of acetone and mix evenly, filter, wash, and dry to obtain silica.

[0029] The preparation method of the pyridine derivative in this example is as follows: S1: Weigh 130 g of ethanol and add it to a three - necked flask. Add 6 g of sodium and stir for 30 min. Add 15 g of 2 - chloropyridine at a rate of 1 g / min while controlling the temperature of the system not to exceed 40 °C during the addition of 2 - chloropyridine. After 2 - chloropyridine is completely added, transfer the reaction system to a reaction kettle, then raise the system temperature to 135 °C and react for 6 h. After the reaction is completed, carry out extraction and concentration to obtain intermediate A; S2: Take 90 g of sulfuric acid with a mass percentage concentration of 65% and add it to a four - necked flask. Then add 4.5 g of intermediate A and stir for 20 min. Add 7 g of sodium bromate, adjust the temperature to 35 °C and react for 3 h. After the reaction is completed, 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 intermediate B; S3: Under nitrogen protection, mix 3 g of diisopropylamine and 20 g of tetrahydrofuran, adjust the temperature to - 80 °C, add a mixed solution of 2 g of n - butyllithium and 13 g of hexane, and react for 20 min to prepare the base solution; mix 6 g of intermediate B and 4.5 g of tetrahydrofuran, adjust the temperature to - 78 °C, then add the base solution, keep warm for 10 min, then add a mixed solution of 6.5 g of diphenylphosphine chloride and 15 g of tetrahydrofuran, react for 1 h, add 1 g of deionized water to terminate the reaction, extract, and wash to obtain the pyridine derivative.

[0030] Example 3 The preparation method of the composite olefin polymerization catalyst in this example is as follows: 1) Weigh 150 g of deionized water and add it to a 250 - mL three - necked flask. Then add 1 g of polyvinyl alcohol and stir at a speed of 200 r / min for 25 min. Raise the temperature to 90 °C and continue stirring for 2 h. After cooling to room temperature, transfer it to a 1 - L three - necked flask, add 250 g of deionized water and stir for 30 min, then add 1.5 g of tricalcium phosphate and continue stirring for 30 min to obtain the aqueous phase; weigh 30 g of styrene and 22 g of divinylbenzene and add them to a 150 - mL beaker. Then add 1.2 g of benzoyl peroxide and stir for 30 min. Add 1 g of silica and continue stirring for 30 min to obtain the oil phase; 2) Add the oil phase to the water phase, heat up to 87 °C, react for 3.5 h, filter, wash, and dry to obtain a solid product. Then add the solid product to a mixed solution composed of 12 g of pyridine derivative and 110 g of methanol, impregnate for 2.5 h, filter, and dry to obtain an inorganic-organic composite support with an average particle size of 76 μm; 3) Dissolve 2.9 g of zirconocene dichloride in 100 g of toluene, add 5 g of the inorganic-organic composite support, stir for 10 h, wash and dry after completion to obtain a metallocene-supported support; then dissolve 3.8 g of titanium tetrachloride in a mixed solution of 50 g of n-decane, 10 g of isooctanol, 1.1 g of methylmagnesium chloride, and 20 g of hexane, cool to -20 °C, add the metallocene-supported support and stir for 2 h, heat up to 80 °C at a rate of 1 °C / min, continue to stir for 4 h, filter, wash, dry, perform vacuum treatment at 120 °C for 2 h, and then carry out gas-phase deposition 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.

[0031] The preparation method of the silica in this example is as follows: M1: Weigh 40 g of ethanol and add it to a three-necked flask. Then add 8 g of sodium silicate and 1.5 g of methyltrimethoxysilane, stir and mix evenly, add hydrochloric acid to adjust the pH to 2.5, let it stand for 1.5 h, and then add a mixed solution composed of 0.04 g of polyvinylpyrrolidone and 15 g of deionized water, stir for 1 h to form silica sol; M2: Mix 80 g of n-heptane, 8 g of Span80, 6 g of Tween80, and 2 g of n-butanol evenly as the oil phase; atomize 8 g of silica sol through a pressure-type atomizing nozzle and slowly add it to the oil phase, stir at a rotation speed of 900 r / min for 1 h, reduce the stirring speed to 250 r / min, add ammonia water to adjust the pH to 6.5, react for 1 h, let it stand for 10 h, add 30 g of acetone and mix evenly, filter, wash, and dry to obtain silica.

[0032] The preparation method of the pyridine derivative in this example is as follows: S1: Weigh 125 g of ethanol and add it to a three-necked flask. Add 6.5 g of sodium, stir for 30 min, add 15 g of 2-chloropyridine at a rate of 1 g / min while controlling the system temperature not to exceed 40 °C during the addition of 2-chloropyridine. After the complete addition of 2-chloropyridine, transfer the reaction system to a reaction kettle, then raise the system temperature to 130 °C, react for 6 h, perform extraction and concentration after the reaction is completed to obtain intermediate A; S2: Take 90 g of sulfuric acid with a mass percentage concentration of 65% and add it to a four-necked flask. Then add 4.5 g of intermediate A, stir for 20 min, add 6.5 g of sodium bromate, adjust the temperature to 30 °C and react for 3.5 h. After the reaction is completed, 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 intermediate B; S3: Under nitrogen protection, mix 2.7 g of diisopropylamine and 20 g of tetrahydrofuran, adjust the temperature to -80 °C, add a mixed solution of 2 g of n-butyllithium and 13 g of hexane, and react for 20 min to prepare a base solution; Mix 6 g of intermediate B and 4.5 g of tetrahydrofuran, adjust the temperature to -78 °C, then add the base solution, keep the temperature for 10 min, and then add a mixed solution of 6.2 g of diphenylphosphine chloride and 15 g of tetrahydrofuran, react for 1 h, add 1 g of deionized water to terminate the reaction, extract, and wash to obtain a pyridine derivative.

[0033] Comparative Example 1 The preparation method of the composite olefin polymerization catalyst in this comparative example is as follows: 1) Weigh 150 g of deionized water and add it to a 250 mL three-necked flask. Then add 0.9 g of polyvinyl alcohol, stir at a speed of 200 r / min for 15 min, heat up to 90 °C, continue to stir for 2 h, cool to room temperature and transfer it to a 1 L three-necked flask, add 250 g of deionized water and stir for 30 min, then add 2 g of tricalcium phosphate, and continue to stir for 30 min to obtain an aqueous phase; Weigh 25 g of styrene and 20 g of divinylbenzene and add them to a 150 mL beaker. Then add 0.9 g of benzoyl peroxide, stir for 25 min, add 1 g of silicon dioxide and continue to stir for 30 min to obtain an oil phase; 2) Add the oil phase to the aqueous phase, heat up to 80 °C, react for 4 h, filter, wash, and dry to obtain a solid product. Then add the solid product to a mixed solution composed of 10 g of pyridine derivative and 100 g of methanol, impregnate for 2 h, filter, and dry to obtain an inorganic-organic composite support with an average particle size of 80 μm; 3) Dissolve 17.3 g of bis(pentamethylcyclopentadienyl)zirconium dichloride in 200 g of toluene, add 5 g of the inorganic-organic composite support, stir for 12 h, wash and dry after completion to obtain a metallocene-supported support; Then dissolve 3.8 g of titanium tetrachloride in a mixed solution of 50 g of n-decane, 10 g of isooctanol, 1.5 g of methylmagnesium chloride and 20 g of hexane, cool to -20 °C, add the metallocene-supported support and stir for 2 h, heat up to 80 °C at a rate of 1 °C / min, continue to stir for 4 h, filter, wash, dry, perform vacuum treatment at 120 °C for 2 h, and then carry out gas-phase deposition 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.

[0034] The preparation method of the silica in this comparative example is as follows: M1: Weigh 50 g of ethanol and add it into a three-necked flask. Then add 8 g of sodium silicate and 2 g of methyltrimethoxysilane, stir and mix evenly. After that, add hydrochloric acid to adjust the pH to 2, let it stand for 1.5 h, and then add a mixed solution composed of 0.05 g of polyvinylpyrrolidone and 15 g of deionized water, stir for 1 h to form silica sol. M2: Mix 80 g of n-heptane, 10 g of Span80, 5 g of Tween80, and 1.5 g of n-butanol evenly as the oil phase; add 10 g of silica sol to the oil phase, stir at a rotation speed of 900 r / min for 1 h, reduce the stirring speed to 200 r / min, add ammonia water to adjust the pH to 6, react for 1 h, let it stand for 12 h, add 30 g of acetone and mix evenly, filter, wash, and dry to obtain silica.

[0035] The preparation method of the pyridine derivative in this comparative example is as follows: S1: Weigh 120 g of ethanol and add it into a three-necked flask. Add 7 g of sodium, stir for 30 min, add 17 g of 2-chloropyridine at a rate of 1 g / min, and at the same time control the system temperature not to exceed 40 °C during the addition of 2-chloropyridine. After 2-chloropyridine is completely added, transfer the reaction system to a reaction kettle, then raise the system temperature to 130 °C, react for 8 h, and perform extraction and concentration after the reaction to obtain intermediate A. S2: Take 95 g of sulfuric acid with a mass percentage concentration of 65% and add it into a four-necked flask. Then add 4.5 g of intermediate A, stir for 20 min, add 6 g of sodium bromate, adjust the temperature to 25 °C and react for 4 h. After the reaction, place it in an ice-water bath, adjust the pH to 7.5 with ammonia water, perform extraction, dry with anhydrous magnesium sulfate, and concentrate to obtain intermediate B. S3: Under nitrogen protection, mix 2.5 g of diisopropylamine and 17 g of tetrahydrofuran, adjust the temperature to -78 °C, add a mixed solution of 1.9 g of n-butyllithium and 13 g of hexane, and react for 20 min to prepare the base solution; mix 5.8 g of intermediate B and 4.5 g of tetrahydrofuran, adjust the temperature to -78 °C, then add the base solution, keep warm for 10 min, and then add a mixed solution of 6 g of diphenylphosphine chloride and 13.5 g of tetrahydrofuran, react for 1 h, add 1 g of deionized water to terminate the reaction, perform extraction and washing to obtain the pyridine derivative.

[0036] Comparative Example 2 The preparation method of the composite olefin polymerization catalyst in this comparative example is as follows: 1) Weigh 150 g of deionized water and add it to a 250 mL three-necked flask. Then add 0.9 g of polyvinyl alcohol and stir at a speed of 200 r / min for 15 min. Heat up to 90 °C and continue stirring for 2 h. After cooling to room temperature, transfer it to a 1 L three-necked flask, add 250 g of deionized water and stir for 30 min. Then add 2 g of tricalcium phosphate and continue stirring for 30 min to obtain the aqueous phase. Weigh 25 g of styrene and 20 g of divinylbenzene and add them to a 150 mL beaker. Then add 0.9 g of benzoyl peroxide and stir for 25 min. Add 1 g of silica and continue stirring for 30 min to obtain the oil phase. 2) Add the oil phase to the aqueous phase, heat up to 80 °C, react for 4 h, filter, wash, and dry to obtain a solid product. Then add the solid product to a mixed solution composed of 10 g of pyridine derivative and 100 g of methanol, impregnate for 2 h, filter, and dry to obtain an inorganic-organic composite support with an average particle size of 80 μm. 3) Dissolve 17.3 g of bis(pentamethylcyclopentadienyl)zirconium dichloride in 200 g of toluene, add 5 g of the inorganic-organic composite support, and stir for 12 h. After completion, wash and dry to obtain the metallocene-supported support. Then dissolve 3.8 g of titanium tetrachloride in a mixed solution of 50 g of n-decane, 10 g of isooctanol, 1.5 g of methylmagnesium chloride, and 20 g of hexane, cool to -20 °C, add the metallocene-supported support and stir for 2 h. Heat up to 80 °C at a rate of 1 °C / min and continue stirring for 4 h. Filter, wash, dry, and perform vacuum treatment at 120 °C for 2 h. Then, under a nitrogen atmosphere, perform gas-phase deposition with 0.5 g of ethyl 2-pyridinecarboxylate at 120 °C and 0.5 MPa for 4 h to obtain the composite olefin polymerization catalyst.

[0037] The preparation method of the silica in this comparative example is as follows: M1: Weigh 50 g of ethanol and add it to a three-necked flask. Then add 8 g of sodium silicate and 2 g of methyltrimethoxysilane, stir and mix evenly. Then add hydrochloric acid to adjust the pH to 2, let it stand for 1.5 h, and then add a mixed solution composed of 0.05 g of polyvinylpyrrolidone and 15 g of deionized water, and stir for 1 h to form silica sol. M2: Mix 80 g of n-heptane, 10 g of Span80, 5 g of Tween80, and 1.5 g of n-butanol evenly as the oil phase. Atomize 10 g of silica sol through a pressure-type atomizing nozzle and slowly add it to the oil phase. Stir at a rotation speed of 900 r / min for 1 h, reduce the stirring speed to 200 r / min, add ammonia water to adjust the pH to 6, react for 1 h, let it stand for 12 h, add 30 g of acetone and mix evenly, filter, wash, and dry to obtain silica.

[0038] The preparation method of the pyridine derivative in this comparative example is as follows: S1: Weigh 120 g of ethanol and add it to a three-necked flask. Add 7 g of sodium and stir for 30 min. Add 17 g of 2-chloropyridine at a rate of 1 g / min while controlling the temperature of the system not to exceed 40 °C during the addition of 2-chloropyridine. After the complete addition of 2-chloropyridine, transfer the reaction system to a reaction kettle, then raise the temperature of the system to 130 °C and react for 8 h. After the reaction is completed, carry out extraction and concentration to obtain intermediate A. S2: Take 95 g of sulfuric acid with a mass percentage concentration of 65% and add it to a four-necked flask. Then add 4.5 g of intermediate A and stir for 20 min. Add 6 g of sodium bromate, adjust the temperature to 25 °C and react for 4 h. After the reaction is completed, place it in an ice-water bath, adjust the pH to 7.5 with ammonia water, carry out extraction, dry with anhydrous magnesium sulfate, and concentrate to obtain the pyridine derivative.

[0039] Performance detection test Use the composite olefin polymerization catalysts prepared in Examples 1-3 and Comparative Examples 1-2 to catalyze the ethylene polymerization reaction. Alternately carry out hydrogen charging and vacuum pumping in the polymerization kettle three times. Add 1 L of hexane, 7 mg of the composite olefin polymerization catalyst, and 5 mmol of triethylaluminum. Heat the reaction kettle to 80 °C, introduce ethylene to make the total pressure in the kettle reach 3.0 MPa, and carry out the polymerization reaction at 80 °C for 4 hours. After the reaction is completed, collect the polymer powder, dry it, and obtain polyethylene.

[0040] 1. Determination of polymer molecular weight and molecular weight distribution: It is determined by high-temperature gel permeation chromatography; using 1,2,4-trichlorobenzene as the solvent, dissolve the polymer at 150 °C, and use polystyrene with a narrow molecular weight distribution as the standard sample to measure at 150 °C. The solvent flow rate is 1.0 mL / min. The test results are shown in Table 1.

[0041] Table 1 Performance test data of catalyst activity and polyethylene prepared by the catalysts of Examples 1-3 and Comparative Examples 1-2 2. Specific surface area test: Carry out specific surface area tests on the inorganic-organic composite supports prepared in Examples 1-3 and Comparative Examples 1-2. Use an Autosorb-IQ-MP specific surface area and pore size analyzer to analyze and determine the specific surface area and pore structure of the catalyst. Degassing conditions: Vacuum degassing at 300 °C for 6 h; Adsorption conditions: Nitrogen adsorption is carried out at liquid nitrogen temperature. The test results are shown in Table 2.

[0042] Table 2 Specific surface area test data of the inorganic-organic composite supports prepared in Examples 1-3 and Comparative Examples 1-2 3. Infrared analysis: The inorganic-organic composite carriers prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to infrared analysis. The samples were prepared by the KBr tablet pressing method, and the obtained samples were tested using a Fourier transform infrared spectrometer. The test wavenumber range was 4000 cm -1 to 400 cm -1 . The test results are as shown in Figure 1 .

[0043] Analysis of Examples 1-3 and Comparative Example 1 and in combination with Tables 1-2 shows that using the reverse emulsion-atomization method to prepare silica and combining silica with styrene-divinylbenzene to form an inorganic-organic composite carrier has a relatively high specific surface area, which increases the loading amount of the catalyst active component and thus improves the activity of the catalyst; analysis of Examples 1-3 and Comparative Example 2 and in combination with Tables 1-2 shows that the introduction of diphenylphosphine in the pyridine derivative effectively improves the catalytic activity of the catalyst and at the same time improves the regularity of polyolefins.

[0044] Analysis of Examples 1-3 and in combination with Figure 1 shows that the absorption peaks at 3025 cm - ¹ and 1492 cm - ¹ correspond to the stretching vibration of aromatic ring C-H and the skeletal vibration of C=C. At the same time, the aliphatic C-H vibrations at 2925 cm - ¹ and 1450 cm - ¹ indicate the formation of a cross-linked network.

[0045] This specific embodiment is only an interpretation of the present application and is not a limitation of the present application. Those skilled in the art can make modifications to this embodiment without creative contributions according to needs after reading this specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A preparation method of a composite olefin polymerization catalyst, characterized in that, It includes the following steps: A metallocene compound and titanium tetrachloride are loaded on an inorganic-organic composite support at a molar ratio of (0.5-2):1 to form a titanium / zirconium bimetallic active center. Then, a nitrogen-containing heterocyclic carboxylic acid ester compound is loaded in the inorganic-organic composite support to obtain a composite olefin polymerization catalyst. The inorganic-organic composite support is made from raw materials including silica, styrene-divinylbenzene, and a pyridine derivative.

2. The preparation method of a composite olefin polymerization catalyst according to claim 1, characterized in that, The preparation method of the inorganic-organic composite support includes the following steps: 1) Polyvinyl alcohol, deionized water, and tricalcium phosphate are mixed to obtain an aqueous phase; styrene, divinylbenzene, benzoyl peroxide, and silica are mixed to obtain an oil phase. 2) The oil phase is added to the aqueous phase for a polymerization reaction to obtain a solid product. Then, the solid product is added to a mixed solution composed of a pyridine derivative and a solvent for an impregnation treatment to obtain the inorganic-organic composite support.

3. The preparation method of a composite olefin polymerization catalyst according to claim 1 or 2, characterized in that, The silica is prepared by a reverse emulsion-atomization method using sodium silicate and methyltrimethoxysilane as silicon sources.

4. The preparation method of a composite olefin polymerization catalyst according to claim 1 or 2, characterized in that, The preparation method of the pyridine derivative includes the following steps: S1: Sodium and ethanol are mixed, and then 2-dichloropyridine is added for a substitution reaction to obtain intermediate A. S2: Sulfuric acid, intermediate A, and sodium bromate are mixed for a reaction to obtain intermediate B. S3: Diisopropylamine and tetrahydrofuran are mixed, and then a hexane solution of n-butyllithium is added for a reaction to obtain a base solution. The base solution is added to a mixed solution of intermediate B and tetrahydrofuran, and after reacting for a period of time, diphenylphosphine chloride is added for a substitution reaction to obtain the pyridine derivative.

5. The preparation method of a composite olefin polymerization catalyst according to claim 2, characterized in that, In step 1), the mass ratio of styrene, divinylbenzene, and silica is (25-35):(20-25):

1.

6. The preparation method of a composite olefin polymerization catalyst according to claim 2, characterized in that, In step 2), the average particle size of the inorganic-organic composite support is ≤80 μm.

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

1.

8. The preparation method of a composite olefin polymerization catalyst according to claim 1, characterized in that, The nitrogen-containing heterocyclic carboxylic acid ester compound is one of isopropyl 2,6-pyridinedicarboxylate, methyl 2,5-pyridinedicarboxylate, and ethyl 2-pyridinecarboxylate.

9. A composite olefin polymerization catalyst prepared by the preparation method according to any one of claims 1-8.

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