Ziegler-Natta catalyst silicon-magnesium composite carrier and preparation method thereof

Abstract

The invention provides a Ziegler-Natta catalyst silicon-magnesium composite carrier and a preparation method thereof, a continuous phase silicon solution is prepared by using a double template agent, the continuous phase silicon solution is mixed with a cross-linking agent and an initiator to obtain a dispersed phase, the dispersed phase is subjected to two-phase speed regulation mixing through a micro-fluidic chip to finally obtain double emulsion droplets, and then operations such as curing, template agent removal and acid etching are performed to obtain the Ziegler-Natta catalyst silicon-magnesium composite carrier. The preparation method comprises the following steps: preparing a spherical silicon dioxide carrier with more excellent performance, then carrying out magnesium source loading and post-treatment, and finally preparing the Ziegler-Natta catalyst silicon-magnesium composite carrier with monodispersity, hierarchical porous structure (micropore-mesopore-macropore), high loading rate and high mechanical strength, and is suitable for industrial-scale polypropylene catalyst production. The prepared catalyst carrier is more perfect in morphology and more uniform in particle size.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst preparation, and particularly relates to a Ziegler-Natta catalyst silicon-magnesium composite carrier suitable for industrial-scale polypropylene catalyst production, prepared by a microfluidic double template method, and a preparation method thereof. Background Art

[0002] In the development of polyolefin catalysts, researchers have loaded the active component (Ti compound) onto the surface of a support to maximize its catalytic activity, dispersing it at high density. Therefore, the role of catalyst supports in the iterative process of catalyst development has become increasingly important. To date, the most effective supports for Ziegler-Natta catalysts include SiO2 and Mg compounds (including MgCl2, Mg(OH)Cl, Mg(OEt)2, and MgR2 (R is an alkyl group). To date, the most widely used industrial polypropylene catalyst precursor is still MgCl2. However, due to limitations in preparation methods, MgCl2 supports suffer from poor morphology control, a limited number of active attachment points, and insufficient mechanical stability. In recent years, SiO2 has attracted increasing attention due to its narrower particle size distribution, stronger mechanical properties, and, in particular, its designable pore structure. However, the preparation process remains relatively complex. Therefore, it is imperative to develop a method for preparing a silicon-magnesium composite support that can simultaneously achieve coordinated control of morphology, pore structure, and strength.

[0003] Traditional Ziegler-Natta catalyst supports often utilize chemically prepared magnesium chloride alcoholates as spherical supports. However, these catalysts suffer from wide particle size distribution, limited active attachment sites, and insufficient mechanical strength, significantly limiting the performance of the resulting Ziegler-Natta catalysts. While the recently developed template method can manipulate pore structure, constructing multi-level pores requires multiple template removal steps, resulting in a complex process and the potential for disruption of the spherical morphology. Furthermore, existing technologies still face bottlenecks in controlling the monodispersity of the microspheres. Summary of the Invention

[0004] (1) Technical issues to be resolved

[0005] The present invention provides a Ziegler-Natta catalyst silicon-magnesium composite carrier and a preparation method thereof, in order to solve the technical problem of how to prepare a catalyst with more perfect carrier morphology, narrow particle size distribution, more active attachment sites and higher mechanical strength.

[0006] (2) Technical solution

[0007] In order to solve the above technical problems, the present invention provides a method for preparing a silicon-magnesium composite support for a Ziegler-Natta catalyst, the preparation method comprising the following steps:

[0008] S1. Preparation of double emulsion droplets

[0009] A silicon source, a macroporous template, a mesoporous template, and an acidic solution are mixed to form a continuous phase; a hydrophobic crosslinker and an oil-soluble initiator are mixed to form a dispersed phase; and the flow rates of the two phases are regulated by a microfluidic chip to generate monodisperse water / oil / water double emulsion droplets.

[0010] S2. In situ polymerization-sol-gel reaction

[0011] The double emulsion droplets are collected in a curing bath containing aqueous ammonia, where the following four reactions are carried out simultaneously to form a preform with an organic-inorganic hybrid network: a) condensation polymerization of the silicon source solution to form a skeleton; b) self-assembly of the macroporous template to form macropores; c) self-assembly of the mesoporous template to form mesopores; and d) polymerization of the hydrophobic crosslinker.

[0012] S3. Gradual removal of templates

[0013] First, the macroporous template in the preform is removed to form macropores on the preform; then the mesoporous template is removed to form mesopores on the preform; finally, the silanol groups remaining on the surface of the preform are etched with an acid solution to form micropores on the preform; thus, a silica gel having macropores, mesopores and micropores is obtained;

[0014] S4. Silicone thermal activation

[0015] The silica gel is placed in a suspension furnace and heated to activate the silica gel to obtain silica microspheres;

[0016] S5. Magnesium source loading

[0017] The silica microspheres obtained in step S4 are placed in a single-necked flask, an aqueous solution of a soluble magnesium salt is added to the flask, magnetically stirred at room temperature, and rotary evaporated in an inert gas flow using a rotary evaporator until the water is completely evaporated to obtain magnesium source-loaded silica, which is then placed in a glove box for later use;

[0018] S6. Preparation of Ziegler-Natta Catalyst Silicon-Magnesium Composite Support

[0019] The silicon dioxide loaded with magnesium source is placed in a suspension furnace for heating to remove free water and bound water contained in the solid, and at the same time convert the magnesium source into magnesium oxide to obtain a silicon-magnesium composite support for the Ziegler-Natta catalyst.

[0020] Furthermore, in step S1, the silicon source is one or more of tetraethyl orthosilicate, sodium silicate and silica sol; the macroporous template agent is one or more of polystyrene microspheres, polymethyl methacrylate microspheres, polylactic acid microspheres, silica microspheres and calcium carbonate microspheres, with a particle size of 0.1 to 50 μm; the mesoporous template agent is one or more of cetyltrimethylammonium bromide, cetylpyridinium chloride, polyoxyethylene-polyoxypropylene-polyoxyethylene, polyoxyethylene sorbitan monooleate, polystyrene-polyethylene oxide and cellulose nanocrystals, with a particle size of 2 to 100 nm; the acidic solution is one or more of hydrochloric acid, perchloric acid, phosphoric acid, sulfuric acid and sodium bisulfate, and H in the acidic solution is 0.1 to 50 μm. + The mass concentration of the substance is 0.05~0.5M; silicon source, macroporous template agent, mesoporous template agent, H + The calculated mass ratio of the acidic solution is 1:(0.1~0.6):(0.1~0.8):(1~1.4).

[0021] Furthermore, in step S1, the hydrophobic crosslinking agent is one or more of multifunctional acrylates, styrene derivatives and epoxy resins, and the oil-soluble initiator is one or more of a thermal initiator, a photoinitiator and a redox initiator; wherein the multifunctional acrylates include divinylbenzene, pentaerythritol triacrylate, trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, bisphenol A diglycidyl ether diacrylate, styrene derivatives include p-divinylbenzene, styrene-butadiene-styrene triblock copolymer, epoxy resins include bisphenol F epoxy resins, alicyclic epoxy resins, thermal initiators include azobisisobutyronitrile, azobisisoheptonitrile, benzoyl peroxide, dilauroyl peroxide, and photoinitiators include Irgacure 184, Darocur 1173. Diaryliodonium salt, redox initiator includes ammonium persulfate-tetramethylethylenediamine system, tert-butyl hydroperoxide-ascorbic acid system; the amount ratio of hydrophobic crosslinker to oil-soluble initiator is (20-50):1.

[0022] Furthermore, in step S1, the flow rate of the continuous phase is 0.5 to 2 mL / min, and the flow rate of the dispersed phase is 0.1 to 0.5 mL / min.

[0023] Furthermore, in step S2, the four reactions are carried out simultaneously at 40-60°C; the concentration of ammonia water is 10-30%; and the reaction time is 0.5-4h.

[0024] Furthermore, in step S3, the macroporous template agent is removed by: extracting polystyrene with a mixture of toluene and tetrahydrofuran; dissolving polymethyl methacrylate with a mixture of chloroform and acetone; dissolving polylactic acid with a strong alkaline aqueous solution; etching silica microspheres with hydrogen fluoride; complexing calcium carbonate with ethylenediaminetetraacetic acid or dissolving with dilute hydrochloric acid; removing the mesoporous template agent by: calcining hexadecyltrimethylammonium bromide at 400-600°C; extracting hexadecylpyridinium chloride with anhydrous ethanol reflux; calcining or extracting polyoxyethylene-polyoxypropylene-polyoxyethylene with supercritical carbon dioxide; washing polyoxyethylene sorbitan monooleate with acetone; dissolving the polystyrene segments in polystyrene-polyoxyethylene with a selective solvent; and enzymatically hydrolyzing or calcining cellulose nanocrystals; and the acidic solution used to treat the obtained silanol groups is one or more of hydrochloric acid, perchloric acid, phosphoric acid, sulfuric acid, and sodium bisulfate, and the H + The substance concentration is 0.05~0.5M.

[0025] Furthermore, in step S4, the specific treatment steps for heating the silica gel in the quartz tube are as follows: first, the temperature in the quartz tube is raised from room temperature to 200°C for 1 hour, and the temperature is maintained for 1 hour, and then the temperature is continued to be raised to 300°C for 0.5 hours, and the temperature is maintained at 300°C for 1 hour. The heating is stopped and the silica gel in the quartz tube is allowed to cool naturally to room temperature. The entire process is always in a high-purity inert gas atmosphere, and the inert gas flow rate remains unchanged to ensure that the material in the quartz tube is always in a suspended state; finally, the silica microspheres obtained after the silica gel is activated are placed in a glove box under inert gas protection for standby use.

[0026] Furthermore, in step S5, the aqueous solution of the soluble magnesium salt is one or more of magnesium acetate, magnesium citrate, and magnesium chloride, and the solution concentration is 0.25 to 1 M; n(Mg):n(Si)=5% to 15%; the magnetic stirring time is 4 to 8 hours; and the rotary evaporation heating temperature is 100°C.

[0027] Furthermore, in step S6, the specific steps of heating the silica in the quartz tube are as follows: first, the temperature in the quartz tube is raised from room temperature to 200°C for 1 hour, and the temperature is maintained for 2 hours, and then the temperature is further raised to 300°C for 0.5 hours. After the temperature is raised to 300°C, the gas is switched from high-purity inert gas to dry air, and the temperature is maintained for 30 minutes, and then the temperature is further raised to 450°C for 1 hour, and the temperature is maintained for 2.5 hours. The temperature is raised to 600°C for 30 minutes, and the temperature is maintained for 1 hour before stopping heating. After the silicon dioxide in the quartz tube is cooled to 450°C, the dry air is replaced with a high-purity inert gas, and the tube is naturally cooled to room temperature to remove free water and bound water contained in the solid, and at the same time, the magnesium source is converted into magnesium oxide. The entire process is always in a high-purity inert gas atmosphere, and the inert gas flow rate is 200-700 mL / min to ensure that the silicon dioxide in the quartz tube is in a suspended state.

[0028] In addition, the present invention also provides a Ziegler-Natta catalyst silicon-magnesium composite support, which is prepared by the above method.

[0029] (3) Beneficial effects

[0030] The present invention provides a Ziegler-Natta catalyst silicon-magnesium composite support and a preparation method thereof. A continuous phase silicon solution is prepared using a dual-template agent, and the dispersed phase obtained by mixing with a crosslinker and an initiator is subjected to two-phase speed-controlled mixing via a microfluidic chip to ultimately obtain double emulsion droplets. The solution is then solidified, the template agent removed, and acid-etched to obtain a spherical silica support with improved performance. The support is then loaded with a magnesium source and post-treated to ultimately produce a Ziegler-Natta catalyst silicon-magnesium composite support with monodispersity, a multi-level pore structure (micropores, mesopores, and macropores), a high loading rate, and high mechanical strength. The support is suitable for industrial-scale polypropylene catalyst production. The prepared catalyst support has a more perfect morphology and a more uniform particle size.

[0031] The beneficial effects of the present invention specifically include:

[0032] 1. Monodispersity control. Microfluidics technology makes the microsphere diameter deviation smaller;

[0033] 2. Multi-stage mass transfer optimization. Macropores accelerate monomer diffusion, mesopores enrich active sites, and micropores stabilize metal components;

[0034] 3. Improved mechanical strength. The cross-linked network makes the carrier more compressive;

[0035] 4. Green process. Simultaneously construct multi-level pores in one step, reducing template removal steps and solvent usage. DETAILED DESCRIPTION

[0036] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below with reference to the embodiments.

[0037] Example 1

[0038] Standard carrier (CTAB+PS system)

[0039] S1. Preparation of double emulsion droplets

[0040] S1. Preparation of double emulsion droplets

[0041] A silicon source, a macroporous template, a mesoporous template and an acidic solution are mixed to form a continuous phase; a hydrophobic cross-linker and an oil-soluble initiator are mixed to form a dispersed phase; and the flow rates of the two phases are regulated by a microfluidic chip to generate monodisperse water / oil / water double emulsion droplets.

[0042] Among them, monodisperse means that a certain parameter of a substance has a uniform property. For example, a monodisperse system usually refers to a dispersed system with a single dispersed phase and a very narrow particle size distribution (that is, the particle sizes are mostly equal). The particle size distribution is normally distributed. Monodisperse spheres refer to spheres with very uniform shapes and sizes.

[0043] The continuous phase consisted of tetraethyl orthosilicate, cetyltrimethylammonium bromide (CTAB), polystyrene (PS) microspheres, and HCl in a molar ratio of 1:0.4:0.5:1. The dispersed phase consisted of divinylbenzene and azobisisobutyronitrile (AIBN) in a molar ratio of 30:1. Microfluidic parameters included a channel diameter of 400 μm, a continuous phase flow rate of 1 mL / min, and a dispersed phase flow rate of 0.25 mL / min.

[0044] S2. In situ polymerization-sol-gel reaction

[0045] The double emulsion droplets obtained in step S1 are collected in a curing bath containing aqueous ammonia, and the mixture is subjected to the following four reactions simultaneously in the curing bath to form a preform having an organic-inorganic hybrid network: a) condensation of the silicon source solution to form a skeleton; b) self-assembly of the macroporous template to form macropores; c) self-assembly of the mesoporous template to form mesopores; and d) polymerization of the hydrophobic crosslinker.

[0046] The curing bath solvent is an ethanol solution containing 10% NH3·H2O, the reaction temperature is 55°C, and the reaction time is 6 hours.

[0047] S3. Gradual removal of templates

[0048] First, the macroporous template PS was removed by toluene extraction to form macropores on the preform. The extraction conditions were: excess toluene, temperature 60°C, and extraction time 12 hours. The solid product was then filtered, and the mesoporous template CTAB was removed by calcination at 550°C for 4 hours. Finally, the silanol groups remaining on the preform surface were etched with 0.5M sulfuric acid solution to form micropores. The etching temperature was 80°C for 2 hours. The resulting silica gel had macropores, mesopores, and micropores.

[0049] S4. Silicone thermal activation

[0050] Silica gel is placed in a suspension furnace, and the inert gas inlet at the bottom is adjusted to keep the magnesium-source-loaded silica in a suspended state within the quartz tube. This state is maintained while heating the magnesium-source-loaded silica within the quartz tube. The specific heating procedure is as follows: first, the temperature within the quartz tube is raised from room temperature to 200°C for 1 hour, maintained at this temperature for 1 hour, then further raised to 300°C for 0.5 hours, maintained at 300°C for 1 hour, and then stopped heating. The silica gel within the quartz tube is allowed to cool naturally to room temperature. The entire process is conducted under a high-purity inert gas atmosphere with a constant inert gas flow rate to ensure that the material within the quartz tube remains suspended. Finally, the silica microspheres obtained after the silica gel activation are placed in a glove box under inert gas protection for later use.

[0051] S5. Magnesium source loading

[0052] A certain amount of the silica microspheres obtained in step S4 was placed in a single-necked flask, and a certain volume of 1M magnesium acetate aqueous solution was added to the flask, so that the final mixture had n(Mg):n(Si) = 10%. The mixture was magnetically stirred at room temperature for 6 h, and finally, the mixture was rotary evaporated in an inert gas flow using a rotary evaporator until the water was completely evaporated. The rotary evaporation heating temperature was 100°C to obtain silica loaded with a magnesium source, which was placed in a glove box for later use.

[0053] S6. Preparation of Ziegler-Natta Catalyst Silicon-Magnesium Composite Support

[0054] The silicon dioxide loaded with magnesium source is placed in a quartz tube of a suspension furnace, and the inert gas inlet at the bottom is adjusted to keep the silicon dioxide loaded with magnesium source in a suspended state in the quartz tube. Maintaining this state, the silicon dioxide loaded with magnesium source in the quartz tube is heated. The specific heating procedure is as follows: the temperature is raised from room temperature to 200°C, the heating time is 1 hour, and after maintaining this temperature for 2 hours, the temperature is further raised to 300°C, the heating time is 0.5 hours, and after the temperature is raised to 300°C, the gas is switched from high-purity inert gas to dry air, and the temperature is maintained for 30 minutes, and then the temperature is further raised to 450°C, the heating time is 1 hour, and the temperature is maintained for 2.5 hours, and the temperature is further raised to 600°C. The heating time is 30 minutes, and the temperature is maintained for 1 hour before heating is stopped. After the magnesium source-loaded silica in the quartz tube cools to 450°C, the dry air is replaced with a high-purity inert gas and the mixture is naturally cooled to room temperature to remove free and bound water in the solid and convert the magnesium source into magnesium oxide. The entire process is carried out under a high-purity inert gas atmosphere at a flow rate of 200 to 700 mL / min to ensure that the magnesium source-loaded silica in the quartz tube remains suspended. This removes free and bound water in the solid and converts the magnesium source into magnesium oxide, thereby obtaining a silicon-magnesium composite support for the Ziegler-Natta catalyst.

[0055] Example 2

[0056] High specific surface area carrier (F127+PMMA system)

[0057] Step S4 is the same as in Example 1;

[0058] S1. Preparation of double emulsion droplets:

[0059] The continuous phase consisted of silica sol, polyoxyethylene-polyoxypropylene-polyoxyethylene (Pluronic F127), PMMA microspheres, and HNO3 in a mass ratio of 1:0.3:0.5:1.1. The dispersed phase consisted of pentaerythritol triacrylate and ammonium persulfate (APS) in a mass ratio of 25:1. The microfluidic parameters included a channel diameter of 250 μm, a continuous phase flow rate of 0.8 mL / min, and a dispersed phase flow rate of 0.2 mL / min.

[0060] S2. In situ polymerization-sol-gel reaction

[0061] The double emulsion droplets obtained in step S1 are collected in a curing bath containing aqueous ammonia. The mixture undergoes the following four reactions simultaneously in the curing bath to form a preform with an organic-inorganic hybrid network: a) polycondensation of the silicon source solution to form a skeleton; b) self-assembly of the macroporous template to form macropores; c) self-assembly of the mesoporous template to form mesopores; and d) polymerization of the hydrophobic crosslinker. The curing bath solvent is an isopropanol solution containing 15% NH3·H2O, the reaction temperature is 45°C, and the reaction time is 8 hours.

[0062] S3. Gradual removal of templates

[0063] First, the macroporous template, PMMA, was removed by acetone extraction to form macropores on the preform. The extraction conditions were: excess acetone, temperature at 40°C, and extraction time for 18 hours. The solid product was then filtered, and the mesoporous template, F127, was removed by supercritical CO2 extraction at 35°C, extraction time for 4 hours, and extraction pressure at 15 MPa. Finally, 0.5M nitric acid was used to etch the remaining silanol groups on the preform surface to form micropores. The etching temperature was 50°C and the etching time was 1 hour. The resulting silica gel had macropores, mesopores, and micropores.

[0064] S4. Silicone thermal activation

[0065] Silica gel is placed in a suspension furnace, and the inert gas inlet at the bottom is adjusted to keep the magnesium-source-loaded silica in a suspended state within the quartz tube. This state is maintained while heating the magnesium-source-loaded silica within the quartz tube. The specific heating procedure is as follows: first, the temperature within the quartz tube is raised from room temperature to 200°C for 1 hour, maintained at this temperature for 1 hour, then further raised to 300°C for 0.5 hours, maintained at 300°C for 1 hour, and then stopped heating. The silica gel within the quartz tube is allowed to cool naturally to room temperature. The entire process is conducted under a high-purity inert gas atmosphere with a constant inert gas flow rate to ensure that the material within the quartz tube remains suspended. Finally, the silica microspheres obtained after the silica gel activation are placed in a glove box under inert gas protection for later use.

[0066] S5. Magnesium source loading

[0067] A certain amount of the silica microspheres obtained in step S4 was placed in a single-necked flask, and a certain volume of 0.8 M magnesium citrate aqueous solution was added to the flask, with the final mixture having n(Mg):n(Si) = 15%. The mixture was magnetically stirred at room temperature for 5 h, and finally, the mixture was rotary evaporated in an inert gas flow using a rotary evaporator until the water was completely evaporated. The rotary evaporation heating temperature was 100°C to obtain silica loaded with a magnesium source, which was placed in a glove box for later use.

[0068] S6. Preparation of Ziegler-Natta Catalyst Silicon-Magnesium Composite Support

[0069] The silicon dioxide loaded with magnesium source is placed in a quartz tube of a suspension furnace, and the inert gas inlet at the bottom is adjusted to keep the silicon dioxide loaded with magnesium source in a suspended state in the quartz tube. Maintaining this state, the silicon dioxide loaded with magnesium source in the quartz tube is heated. The specific heating procedure is as follows: the temperature is raised from room temperature to 200°C, the heating time is 1 hour, and after maintaining this temperature for 2 hours, the temperature is further raised to 300°C, the heating time is 0.5 hours, and after the temperature is raised to 300°C, the gas is switched from high-purity inert gas to dry air, and the temperature is maintained for 30 minutes, and then the temperature is further raised to 450°C, the heating time is 1 hour, and the temperature is maintained for 2.5 hours, and the temperature is further raised to 600°C. The heating time is 30 minutes, and the temperature is maintained for 1 hour before heating is stopped. After the magnesium source-loaded silica in the quartz tube cools to 450°C, the dry air is replaced with a high-purity inert gas and the mixture is naturally cooled to room temperature to remove free and bound water in the solid and convert the magnesium source into magnesium oxide. The entire process is carried out under a high-purity inert gas atmosphere at a flow rate of 200 to 700 mL / min to ensure that the magnesium source-loaded silica in the quartz tube remains suspended. This removes free and bound water in the solid and converts the magnesium source into magnesium oxide, thereby obtaining a silicon-magnesium composite support for the Ziegler-Natta catalyst.

[0070] Example 3

[0071] Magnetic carrier (Fe3O4@SiO2+CNC system)

[0072] S1. Preparation of double emulsion droplets:

[0073] Continuous phase: methyl orthosilicate, Fe3O4@SiO2 core-shell particles (800nm), cellulose nanocrystals (CNC), H3PO4, with a mass ratio of 1:0.3:0.5:1.1; dispersed phase: TMPTA and rgacure2959, with a mass ratio of 40:1; microfluidic parameters: channel diameter 600μm, continuous phase 2mL / min, dispersed phase 0.4mL / min.

[0074] S2. In situ polymerization-sol-gel reaction

[0075] The double emulsion droplets obtained in step S1 are collected in a curing bath containing aqueous ammonia. The mixture undergoes the following four reactions simultaneously in the curing bath to form a preform with an organic-inorganic hybrid network: a) polycondensation of the silicon source solution to form a skeleton; b) self-assembly of the macroporous template to form macropores; c) self-assembly of the mesoporous template to form mesopores; and d) polymerization of the hydrophobic crosslinker. The curing bath solvent is an isopropanol solution containing 25% NH3·H2O, the reaction temperature is 45°C, and the reaction time is 4 hours.

[0076] S3. Gradual removal of templates

[0077] The macroporous template, SiO2, was first removed by HF etching (5% HF concentration, 4 hours). The solid product was then filtered and the mesoporous template, CNC, was removed by high-temperature calcination at 500°C for 2 hours. Finally, the remaining silanol groups on the preform surface were etched with 0.1M perchloric acid solution at 30°C for 2 hours to form micropores. The resulting silica gel had macropores, mesopores, and micropores.

[0078] S4. Silicone thermal activation

[0079] Silica gel is placed in a suspension furnace, and the inert gas inlet at the bottom is adjusted to keep the magnesium-source-loaded silica in a suspended state within the quartz tube. This state is maintained while heating the magnesium-source-loaded silica within the quartz tube. The specific heating procedure is as follows: first, the temperature within the quartz tube is raised from room temperature to 200°C for 1 hour, maintained at this temperature for 1 hour, then further raised to 300°C for 0.5 hours, maintained at 300°C for 1 hour, and then stopped heating. The silica gel within the quartz tube is allowed to cool naturally to room temperature. The entire process is conducted under a high-purity inert gas atmosphere with a constant inert gas flow rate to ensure that the material within the quartz tube remains suspended. Finally, the silica microspheres obtained after the silica gel activation are placed in a glove box under inert gas protection for later use.

[0080] S5. Magnesium source loading

[0081] A certain amount of the silica microspheres obtained in step S4 was placed in a single-necked flask, and a certain volume of 1.4 M magnesium chloride aqueous solution was added to the flask, with n(Mg):n(Si) = 5% in the final mixture. The mixture was magnetically stirred at room temperature for 8 h, and finally, the mixture was rotary evaporated in an inert gas flow using a rotary evaporator until the water was completely evaporated. The rotary evaporation heating temperature was 100°C to obtain silica loaded with a magnesium source, which was placed in a glove box for later use.

[0082] S6. Preparation of Ziegler-Natta Catalyst Silicon-Magnesium Composite Support

[0083] The silicon dioxide loaded with magnesium source is placed in a quartz tube of a suspension furnace, and the inert gas inlet at the bottom is adjusted to keep the silicon dioxide loaded with magnesium source in a suspended state in the quartz tube. Maintaining this state, the silicon dioxide loaded with magnesium source in the quartz tube is heated. The specific heating procedure is as follows: the temperature is raised from room temperature to 200°C, the heating time is 1 hour, and after maintaining this temperature for 2 hours, the temperature is further raised to 300°C, the heating time is 0.5 hours, and after the temperature is raised to 300°C, the gas is switched from high-purity inert gas to dry air, and the temperature is maintained for 30 minutes, and then the temperature is further raised to 450°C, the heating time is 1 hour, and the temperature is maintained for 2.5 hours, and the temperature is further raised to 600°C. The heating time is 30 minutes, and the temperature is maintained for 1 hour before heating is stopped. After the magnesium source-loaded silica in the quartz tube cools to 450°C, the dry air is replaced with a high-purity inert gas and the mixture is naturally cooled to room temperature to remove free and bound water in the solid and convert the magnesium source into magnesium oxide. The entire process is carried out under a high-purity inert gas atmosphere at a flow rate of 200 to 700 mL / min to ensure that the magnesium source-loaded silica in the quartz tube remains suspended. This removes free and bound water in the solid and converts the magnesium source into magnesium oxide, thereby obtaining a silicon-magnesium composite support for the Ziegler-Natta catalyst.

[0084] The properties of the silicon-magnesium composite Ziegler-Natta catalyst supports finally prepared in Examples 1 to 3 are shown in Table 1.

[0085] Table 1 Properties of the composite carriers obtained in various examples

[0086]

[0087] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a silicon-magnesium composite support for a Ziegler-Natta catalyst, characterized in that: The preparation method comprises the following steps: S1. Preparation of double emulsion droplets A silicon source, a macroporous template, a mesoporous template, and an acidic solution are mixed to form a continuous phase; a hydrophobic crosslinker and an oil-soluble initiator are mixed to form a dispersed phase; and the flow rates of the two phases are regulated by a microfluidic chip to generate monodisperse water / oil / water double emulsion droplets. S2. In situ polymerization-sol-gel reaction The double emulsion droplets are collected in a curing bath containing aqueous ammonia, where the following four reactions are carried out simultaneously to form a preform with an organic-inorganic hybrid network: a) condensation polymerization of the silicon source solution to form a skeleton; b) self-assembly of the macroporous template to form macropores; c) self-assembly of the mesoporous template to form mesopores; and d) polymerization of the hydrophobic crosslinker. S3. Gradual removal of templates First, the macroporous template in the preform is removed to form macropores on the preform; then the mesoporous template is removed to form mesopores on the preform; finally, the silanol groups remaining on the surface of the preform are etched with an acid solution to form micropores on the preform; thus, a silica gel having macropores, mesopores and micropores is obtained; S4. Silicone thermal activation The silica gel is placed in a suspension furnace and heated to activate the silica gel to obtain silica microspheres; S5. Magnesium source loading The silica microspheres obtained in step S4 are placed in a single-necked flask, an aqueous solution of a soluble magnesium salt is added to the flask, magnetically stirred at room temperature, and rotary evaporated in an inert gas flow using a rotary evaporator until the water is completely evaporated to obtain magnesium source-loaded silica, which is then placed in a glove box for later use; S6. Preparation of Ziegler-Natta Catalyst Silicon-Magnesium Composite Support The silicon dioxide loaded with magnesium source is placed in a suspension furnace for heating to remove free water and bound water contained in the solid, and at the same time convert the magnesium source into magnesium oxide to obtain a silicon-magnesium composite support for the Ziegler-Natta catalyst.

2. The method for preparing a Ziegler-Natta catalyst silicon-magnesium composite support according to claim 1, wherein: In step S1, the silicon source is one or more of tetraethyl orthosilicate, sodium silicate and silica sol; the macroporous template agent is one or more of polystyrene microspheres, polymethyl methacrylate microspheres, polylactic acid microspheres, silica microspheres and calcium carbonate microspheres, with a particle size of 0.1 to 50 μm; the mesoporous template agent is one or more of cetyltrimethylammonium bromide, cetylpyridinium chloride, polyoxyethylene-polyoxypropylene-polyoxyethylene, polyoxyethylene sorbitan monooleate, polystyrene-polyethylene oxide and cellulose nanocrystals, with a particle size of 2 to 100 nm; the acidic solution is one or more of hydrochloric acid, perchloric acid, phosphoric acid, sulfuric acid and sodium bisulfate, and H in the acidic solution is 0.1 to 50 μm. + The mass concentration of the substance is 0.05~0.5M; silicon source, macroporous template agent, mesoporous template agent, H + The calculated mass ratio of the acidic solution is 1:(0.1~0.6):(0.1~0.8):(1~1.4).

3. The method for preparing a Ziegler-Natta catalyst silicon-magnesium composite support according to claim 1, wherein: In step S1, the hydrophobic crosslinking agent is one or more of a multifunctional acrylate, a styrene derivative, and an epoxy resin, and the oil-soluble initiator is one or more of a thermal initiator, a photoinitiator, and a redox initiator; wherein the multifunctional acrylate includes divinylbenzene, pentaerythritol triacrylate, trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, and bisphenol A diglycidyl ether diacrylate, the styrene derivative includes p-divinylbenzene, styrene-butadiene-styrene triblock copolymer, the epoxy resin includes bisphenol F epoxy resin, alicyclic epoxy resin, the thermal initiator includes azobisisobutyronitrile, azobisisoheptonitrile, benzoyl peroxide, and dilauroyl peroxide, and the photoinitiator includes Irgacure 184, Darocur 1173. Diaryliodonium salt, redox initiator includes ammonium persulfate-tetramethylethylenediamine system, tert-butyl hydroperoxide-ascorbic acid system; the amount ratio of hydrophobic crosslinker to oil-soluble initiator is (20-50):

1.

4. The method for preparing a silicon-magnesium composite support for a Ziegler-Natta catalyst according to claim 1, wherein: In step S1, the flow rate of the continuous phase is 0.5 to 2 mL / min, and the flow rate of the dispersed phase is 0.1 to 0.5 mL / min.

5. The method for preparing a Ziegler-Natta catalyst silicon-magnesium composite support according to claim 1, wherein: In step S2, the four reactions are carried out simultaneously at 40-60° C.; the concentration of aqueous ammonia is 10-30%; and the reaction time is 0.5-4 h.

6. The method for preparing a silicon-magnesium composite support for a Ziegler-Natta catalyst according to claim 1, wherein: In step S3, the macroporous template is removed by: extracting polystyrene with a mixture of toluene and tetrahydrofuran; dissolving polymethyl methacrylate with a mixture of chloroform and acetone; dissolving polylactic acid with a strong alkaline aqueous solution; etching silica microspheres with hydrogen fluoride; complexing calcium carbonate with ethylenediaminetetraacetic acid or dissolving with dilute hydrochloric acid; removing the mesoporous template by: calcining hexadecyltrimethylammonium bromide at 400-600°C; extracting hexadecylpyridinium chloride with anhydrous ethanol reflux; calcining or extracting polyoxyethylene-polyoxypropylene-polyoxyethylene with supercritical carbon dioxide; washing polyoxyethylene sorbitan monooleate with acetone; dissolving the polystyrene segments in polystyrene-polyoxyethylene with a selective solvent; and enzymatically hydrolyzing or calcining cellulose nanocrystals. The acidic solution used to treat the obtained silanol groups is one or more of hydrochloric acid, perchloric acid, phosphoric acid, sulfuric acid, and sodium bisulfate, and the H + The substance concentration is 0.05~0.5M.

7. The method for preparing a silicon-magnesium composite support for a Ziegler-Natta catalyst according to claim 1, wherein: In step S4, the specific treatment steps for heating the silica gel in the quartz tube are as follows: first, the temperature in the quartz tube is raised from room temperature to 200°C for 1 hour, and the temperature is maintained for 1 hour, and then the temperature is further raised to 300°C for 0.5 hours, and the temperature is maintained at 300°C for 1 hour. The heating is stopped and the silica gel in the quartz tube is allowed to cool naturally to room temperature. The entire process is always in a high-purity inert gas atmosphere, and the inert gas flow rate remains unchanged to ensure that the material in the quartz tube is always in a suspended state; finally, the silica microspheres obtained after the silica gel is activated are placed in a glove box under inert gas protection for standby use.

8. The method for preparing a silicon-magnesium composite support for a Ziegler-Natta catalyst according to claim 1, wherein: In step S5, the aqueous solution of the soluble magnesium salt is one or more of magnesium acetate, magnesium citrate, and magnesium chloride, and the solution concentration is 0.25 to 1 M; n(Mg):n(Si)=5% to 15%; the magnetic stirring time is 4 to 8 hours; and the rotary evaporation heating temperature is 100°C.

9. The method for preparing a silicon-magnesium composite support for a Ziegler-Natta catalyst according to claim 1, wherein: In step S6, the specific steps of heating the silica in the quartz tube are as follows: first, the temperature in the quartz tube is raised from room temperature to 200°C for a heating time of 1 hour, and the temperature is maintained for 2 hours, and then the temperature is continued to be raised to 300°C for a heating time of 0.5 hours. After the temperature reaches 300°C, the gas is switched from high-purity inert gas to dry air, and the temperature is maintained for 30 minutes, and then the temperature is continued to be raised to 450°C for a heating time of 1 hour, and the temperature is maintained for 2.5 hours. The temperature is continued to be raised to 600°C for a heating time of 30 minutes, and the heating is stopped after the temperature is maintained for 1 hour. After the silica in the quartz tube is cooled to 450°C, the dry air is changed to a high-purity inert gas, and the silica is naturally cooled to room temperature to remove the free water and bound water contained in the solid, and the magnesium source is converted into magnesium oxide. The whole process is always in a high-purity inert gas atmosphere, and the inert gas flow rate is 200-700 mL / min to ensure that the silica in the quartz tube is in a suspended state.

10. A Ziegler-Natta catalyst silicon-magnesium composite support, characterized in that The Ziegler-Natta catalyst silicon-magnesium composite carrier is prepared by the method according to any one of claims 1 to 9.

Images