A method for preparing high-purity monodisperse nanometer spherical silica powder by silane hydrolysis

Abstract

The application discloses a silane hydrolysis preparation method of high-purity monodisperse nanometer spherical silica powder, and relates to the technical field of nanometer inorganic material preparation. The method uses tetraethyl orthosilicate as a silicon source, uses an alcohol-water mixed system as a reaction medium, carries out controlled hydrolysis and polycondensation reaction under ammonia catalysis, and realizes preparation of nanometer spherical silica powder with uniform particle size and excellent dispersity through stage-by-stage feeding, constant-temperature nucleation, growth control and low-ionic-impurity washing and purification. The method has the advantages of stable process, high repeatability, low impurity content, easy particle size control and suitability for large-scale continuous production, and can be widely applied in the fields of CMP polishing, electronic packaging, optical materials, lithium battery separator coating and catalytic carrier and the like.

Description

Technical Field

[0001] This invention relates to the field of nano-inorganic material preparation technology, and in particular to a method for preparing high-purity monodisperse nanosphere silica powder by silane hydrolysis. Background Technology

[0002] Silica (SiO2) is an important class of inorganic functional materials. Due to its high chemical stability, excellent thermal stability, low dielectric constant, large specific surface area, and ease of surface functionalization, it is widely used in chemical mechanical polishing (CMP), electronic packaging, optical coatings, precision ceramics, catalyst supports, biomedicine, lithium-ion batteries, and polymer composites. Especially in the fields of semiconductor polishing slurries, electronic-grade fillers, and high-end optical materials, higher requirements are placed on the purity, particle size uniformity, sphericity, and dispersion stability of silica particles.

[0003] Currently, the main methods for preparing nano-spherical silica include the gas-phase method, precipitation method, microemulsion method, and silanol hydrolysis method. Among them, the gas-phase method can obtain high-purity products, but it suffers from high equipment costs, high energy consumption, and severe particle agglomeration. Although the precipitation method is suitable for industrial production, the resulting particles have a wide particle size distribution and poor sphericity, which is difficult to meet the application requirements of high-end electronic materials.

[0004] In contrast, the hydrolysis-condensation method using tetraethyl orthosilicate (TEOS), also known as the classic Stöber method, has become an important technical route for preparing monodisperse spherical silica because it enables controlled nucleation and growth of silica particles in an alcohol-water-ammonia system. Related studies have shown that TEOS first undergoes hydrolysis under ammonia catalysis to generate silanols, which then form a Si-O-Si network structure through a condensation reaction, ultimately yielding spherical silica particles.

[0005] With the development of industries such as CMP polishing, electronic packaging, and high-frequency, high-speed copper-clad laminates, the following requirements have been placed on silicon dioxide materials:

[0006] 1. Narrow particle size distribution and high monodispersity;

[0007] 2. High sphericity and smooth surface;

[0008] 3. Low content of metal ion impurities;

[0009] 4. Excellent dispersion stability;

[0010] 5. It can be prepared stably on a large scale.

[0011] However, existing silane hydrolysis preparation technologies still have many shortcomings.

[0012] First, existing Stöber processes generally suffer from severe coupling between the nucleation and particle growth processes. When the local TEOS concentration is too high, secondary nucleation easily occurs in the system, leading to a wider particle size distribution and affecting monodispersity. Especially under scale-up production conditions, due to decreased mixing efficiency, local supersaturated regions are more likely to form, resulting in an increase in coarse and agglomerated particles.

[0013] Secondly, the ammonia concentration, water-to-alcohol ratio, and silicon source droplet acceleration rate in the reaction system have a significant impact on particle size. If the ammonia concentration is too high, the TEOS hydrolysis rate is too fast, easily generating a large number of fine crystal nuclei; while if the ammonia concentration is too low, the condensation reaction is insufficient, leading to uneven particle growth. In addition, although increasing the water content can improve the TEOS hydrolysis rate, it can also easily cause particle aggregation and deterioration of particle size distribution.

[0014] Furthermore, in existing industrial production, increasing the TEOS concentration or using rapid feeding methods is commonly employed to improve yield. However, this approach can easily lead to excessively high local instantaneous concentrations in the system, causing uneven condensation on the particle surface, resulting in decreased sphericity and exacerbated agglomeration. Simultaneously, some existing technologies only use ordinary deionized water for washing and purification, leading to high levels of residual metal ions such as Na, K, Ca, and Fe, which are insufficient to meet the requirements of electronic-grade and high-end optical-grade applications.

[0015] Existing patent technologies mainly focus on particle size control. For example, Chinese patent document CN103318899A discloses a method for controlling the particle size of monodisperse silica microspheres, which achieves the preparation of silica microspheres with different particle sizes by adjusting the concentrations of TEOS, water, and ammonia. However, its focus is on particle size control, and it does not address the issues of high purification and low agglomeration.

[0016] Chinese patent document CN104724713A discloses a method for controlling the particle size of monodisperse silica microspheres, which regulates particle size by changing reaction system parameters, but still has shortcomings in terms of industrial scale-up stability and control of metal impurities.

[0017] US Patent US20230382743 discloses a method for preparing high-concentration colloidal silica, which obtains high-concentration colloidal silica sol by increasing the solid content of the system. However, the high-concentration system is prone to increasing the collision frequency between particles, thereby causing particle agglomeration and deterioration of particle size distribution.

[0018] In addition, US Patent 12098290B2 discloses a low-dielectric silica powder and its preparation method, which focuses on improving low-dielectric properties and resin bonding properties, but still lacks systematic optimization for precise nucleation control of monodisperse nanoscale spherical particles.

[0019] In summary, the existing technology still has the following problems:

[0020] (1) The nucleation and growth processes are difficult to separate effectively, resulting in a wide particle size distribution;

[0021] (2) Secondary nucleation and particle agglomeration are prone to occur during scale-up production;

[0022] (3) The surface uniformity of the particles is insufficient, and the sphericity is not high;

[0023] (4) The content of metal ion impurities is high, which makes it difficult to meet the requirements of electronic-grade applications;

[0024] (5) The high solids content system has poor stability and insufficient adaptability to continuous industrialization.

[0025] Therefore, developing a method for preparing monodisperse nanosphere silica powder with high purity, low metal impurities, highly uniform particle size, and excellent dispersibility through silane hydrolysis is of great significance for promoting the development of high-end electronic materials, CMP polishing, and new energy materials industries. Summary of the Invention

[0026] Based on the problems raised in the background technology mentioned above, this invention proposes a method for preparing high-purity monodisperse nanosphere silica powder by silane hydrolysis.

[0027] The technical solution is as follows:

[0028] A method for preparing high-purity monodisperse nanosphere silica powder by silane hydrolysis includes the following steps:

[0029] (1) Preparation of alkaline reaction system:

[0030] By weight, 80–110 parts anhydrous ethanol, 8–16 parts deionized water, and 3–8 parts ammonia were added to the reactor and stirred at 20–30°C for 20–40 minutes to obtain a homogeneous alkaline alcohol-water system; the ammonia concentration was 25–28 wt%.

[0031] (2) Silane precursor premixing:

[0032] According to the mass fraction, 16-28 parts of silane precursor and 8-18 parts of anhydrous ethanol are mixed to form a silicon source premix, and then 0.5-2 parts of resin adsorbent are added for deep impurity removal.

[0033] (3) Crystal nucleus formation:

[0034] Under a stirring speed of 350-700 rpm, the silicon source premixed solution is added to the alkaline alcohol-water system, and the reaction temperature is controlled at 25-35°C. After the addition is completed, the reaction continues for 0.5-2 hours to form uniform silicon dioxide crystal nuclei.

[0035] (4) Granule growth:

[0036] Continue the aging reaction for 4-8 hours to allow the silanol to undergo a condensation reaction and form monodisperse spherical silica particles;

[0037] (5) Solid-liquid separation and washing:

[0038] After the reaction is completed, centrifugation is performed, followed by washing with anhydrous ethanol 2 to 4 times and ultrapure water 1 to 3 times, with the amount of washing solution added each time being 2 to 5 times the mass of the obtained wet material;

[0039] (6) Drying treatment:

[0040] The washed material was vacuum dried at 50–80°C for 6–18 hours to obtain high-purity monodisperse nano-spherical silica powder.

[0041] Furthermore, in step (1), the conductivity of deionized water is ≤1μS / cm, the purity of anhydrous ethanol is ≥99.7%, and the purity of the silane precursor is ≥99.0%.

[0042] Furthermore, in step (2), the silane precursor is one or a combination of two of tetraethyl orthosilicate, tetramethyl orthosilicate, and tetrapropoxysilane.

[0043] Further, the preparation method of the resin adsorbent in step (2) is as follows: according to the mass fractions, 100-140 parts of mercapto-modified macroporous polystyrene resin, 12-18 parts of vinyl sulfonic acid, 0.8-4 parts of allyl cyanoacetate (CAS: 13361325), and 1000-1400 parts of dichloroethane are added to the reaction vessel, nitrogen gas is introduced to remove oxygen for 10-30 minutes, 0.5-1.5 parts of 2-hydroxy-2-methyl-1-phenyl-1-acetone (photoinitiator 1173) are added, stirred evenly, and then irradiated under 365nm ultraviolet light for 30-60 minutes, controlling the reaction temperature at 55-70℃; after the reaction is completed, the mixture is filtered, washed with ethanol 3-5 times, and dried to obtain the resin adsorbent.

[0044] Furthermore, the thiolized macroporous polystyrene resin is selected from one of D406Ⅱ, LSC400, Duolite™ GT73, Ambersep™ GT74, and Zhengguang D830.

[0045] Furthermore, in step (3), the droplet loading rate of the silicon source premixed liquid is 1.0 to 4.0 mL / min.

[0046] Furthermore, in step (3), the pH of the system is controlled to be 9.5 to 11.5.

[0047] Furthermore, in step (4), the particle growth stage is carried out using a constant temperature aging method, with an aging temperature of 28–38°C.

[0048] Furthermore, in step (5), the centrifugation speed is 4000-9000 rpm and the single centrifugation time is 5-20 min.

[0049] Furthermore, in step (6), the drying method is one of vacuum drying, freeze drying, or inert atmosphere drying; the vacuum degree is controlled to be -0.06 to -0.095 MPa.

[0050] Reaction Mechanism: Under ultraviolet light irradiation and the action of photoinitiators, the thiol groups (–SH) on the surface of thiolized macroporous polystyrene resin are activated to generate sulfur free radicals, which then undergo thiol-olefin free radical click addition reactions simultaneously with the carbon-carbon double bonds in vinyl sulfonic acid and allyl cyanoacetate molecules to form stable carbon-sulfur covalent bonds. This efficiently and uniformly grafts sulfonic acid, cyano, and ester functional groups onto the three-dimensional network framework of the resin, constructing a composite functional interface that combines strong acid ion exchange sites with multidentate chelating coordination centers.

[0051] Compared with the prior art, the present invention has the following advantages:

[0052] 1. By adopting a staged, rate-controlled dripping method, the nucleation process and the particle growth process are effectively separated, significantly reducing the probability of secondary nucleation, thereby obtaining monodisperse silica particles with a narrower particle size distribution;

[0053] 2. By optimizing the ethanol / water ratio and ammonia concentration, the uniformity of silanol polycondensation is improved, resulting in increased particle sphericity and a significant reduction in agglomeration.

[0054] 3. By using high-purity raw materials and multi-stage ultrapure washing processes, the content of metal impurities such as Na, Ca, and Fe can be effectively reduced, enabling the material to meet the requirements of electronic-grade applications.

[0055] 4. The process of this invention is mild, does not require high temperature and high pressure conditions, has low equipment requirements, and is suitable for continuous industrial scale-up production;

[0056] 5. The resulting product has excellent dispersibility and flowability, and can be widely used in CMP polishing fluids, optical fillers and lithium battery functional materials. Attached Figure Description

[0057] Figure 1 This is an electron microscope image of the high-purity monodisperse nanosphere silica powder prepared in Example 1.

[0058] Figure 2 This is an electron microscope image of the high-purity monodisperse nanosphere silica powder prepared in Example 2. Detailed Implementation

[0059] The features of the present invention are further illustrated below through embodiments, but the scope of protection of this patent is not limited to the embodiments.

[0060] Example 1

[0061] (1) Preparation of alkaline reaction system: Add 80kg of anhydrous ethanol, 8kg of deionized water and 3kg of ammonia water to the reactor; wherein the purity of anhydrous ethanol is ≥99.7%, the conductivity of deionized water is ≤1μS / cm, and the mass concentration of ammonia water is 25wt%; stir and mix at 20℃ for 20min to obtain a uniform, clear and transparent alkaline alcohol-water system.

[0062] (2) Silane precursor premixing: 16 kg of silane precursor and 8 kg of anhydrous ethanol were mixed to form a silicon source premix. In this case, tetraethyl orthosilicate was selected as the silane precursor with a purity of ≥99.0%. Then, 0.5 kg of resin adsorbent was added and stirred evenly to remove trace metal ions and organic impurities from the raw materials.

[0063] The preparation method of the resin adsorbent in step (2) is as follows: 100 kg of mercapto-modified macroporous polystyrene resin (D406 Ⅱ selected), 12 kg of vinyl sulfonic acid, 0.8 kg of allyl cyanoacetate and 1000 kg of dichloroethane are added to the reaction vessel, nitrogen gas is introduced to remove oxygen for 10 minutes, 0.5 parts of 2-hydroxy-2-methyl-1-phenyl-1-propanone (photoinitiator 1173) are added, and after stirring evenly, it is placed under 365 nm ultraviolet light for 30 minutes, and the reaction temperature is controlled at 55℃ throughout the process; after the reaction is completed, it is filtered, washed with ethanol 3 times, and vacuum dried to obtain the special resin adsorbent.

[0064] (3) Crystal nucleus formation: Set the stirring speed to 350 rpm and slowly add the above silicon source premixed solution to the alkaline alcohol-water system at a constant dropping rate of 1.0 mL / min; control the reaction temperature at 25℃ throughout the process and keep the pH of the system stable at 9.5; after the addition is completed, continue to stir the reaction at a constant temperature for 0.5 h, and uniform silicon dioxide crystal nuclei with uniform particle size and good dispersibility are formed in the system.

[0065] (4) Particle growth: The particle growth stage is carried out by constant temperature aging. The aging temperature is constant at 28℃ and the constant temperature aging reaction is carried out for 4 hours. The silanol in the system continues to undergo condensation reaction, the crystal nuclei grow uniformly, and finally form monodisperse spherical silica particles with uniform particle size and no agglomeration.

[0066] (5) Solid-liquid separation and washing: After the reaction is completed, centrifugation is performed. The centrifugation speed is set to 4000 rpm and the centrifugation time is 5 min. After centrifugation, the wet material is collected and washed twice with anhydrous ethanol and once with ultrapure water. The amount of washing liquid added each time is twice the mass of the wet material obtained, so as to fully wash away the residual ammonia, unreacted silane monomer and organic solvent in the system.

[0067] (6) Drying treatment: The washed wet material is placed in a vacuum drying oven with a vacuum degree controlled at -0.06MPa and vacuum dried at 50℃ for 6h to completely remove residual moisture and solvent from the material and finally obtain high-purity monodisperse nano-spherical silica powder.

[0068] Example 2

[0069] (1) Preparation of alkaline reaction system: Add 95kg of anhydrous ethanol, 12kg of deionized water and 5.5kg of ammonia water to the reactor; wherein the purity of anhydrous ethanol is ≥99.7%, the conductivity of deionized water is ≤1μS / cm, and the mass concentration of ammonia water is 26.5wt%; stir and mix at 25℃ for 30min to obtain a uniform, clear and transparent alkaline alcohol-water system.

[0070] (2) Silane precursor premixing: 22 kg of silane precursor was mixed with 13 kg of anhydrous ethanol to form a silicon source premix. In this case, tetraethyl orthosilicate and tetramethyl orthosilicate were mixed in a 1:1 ratio as silane precursors with a purity of ≥99.0%. Then, 1.25 kg of resin adsorbent was added and stirred evenly to remove trace metal ions and organic impurities from the raw materials.

[0071] The preparation method of the resin adsorbent in step (2) is as follows: 120 kg of mercapto-modified macroporous polystyrene resin (LSC400 selected), 15 kg of vinyl sulfonic acid, 2.4 kg of allyl cyanoacetate, and 1200 kg of dichloroethane are added to the reaction vessel, nitrogen gas is introduced to remove oxygen for 20 minutes, 1.0 kg of 2-hydroxy-2-methyl-1-phenyl-1-propanone (photoinitiator 1173) is added, and after stirring evenly, it is placed under 365 nm ultraviolet light for 45 minutes, and the reaction temperature is controlled at 62℃ throughout the process; after the reaction is completed, it is filtered, washed with ethanol 4 times, and vacuum dried to obtain the special resin adsorbent.

[0072] (3) Crystal nucleus formation: Set the stirring speed to 525 rpm and slowly add the above silicon source premixed solution to the alkaline alcohol-water system at a constant dropping rate of 2.5 mL / min; control the reaction temperature at 30℃ throughout the process and keep the pH of the system stable at 10.5; after the addition is completed, continue to stir the reaction at a constant temperature for 1.25 h, and uniform silicon dioxide crystal nuclei with uniform particle size and good dispersibility are formed in the system.

[0073] (4) Particle growth: The particle growth stage is carried out by constant temperature aging. The aging temperature is constant at 33℃ and the constant temperature aging reaction is carried out for 6 hours. The silanol in the system continues to undergo condensation reaction, the crystal nuclei grow uniformly, and finally form monodisperse spherical silica particles with uniform particle size and no agglomeration.

[0074] (5) Solid-liquid separation and washing: After the reaction is completed, centrifugation is performed. The centrifugation speed is set to 6500 rpm and the centrifugation time is 12.5 min. After centrifugation, the wet material is collected and washed three times with anhydrous ethanol and twice with ultrapure water. The amount of washing liquid added each time is 3.5 times the mass of the wet material obtained, to fully wash away residual ammonia, unreacted silane monomers and organic solvents in the system.

[0075] (6) Drying treatment: The washed wet material is dried in an inert atmosphere with a vacuum degree controlled at -0.078MPa and dried at 65℃ for 12h to completely remove residual moisture and solvent from the material and finally obtain high-purity monodisperse nanosphere silica powder.

[0076] Example 3

[0077] (1) Preparation of alkaline reaction system: 104 kg of anhydrous ethanol, 14.5 kg of deionized water and 7 kg of ammonia water were added to the reactor; the purity of anhydrous ethanol was ≥99.7%, the conductivity of deionized water was ≤1 μS / cm, and the mass concentration of ammonia water was 27.2 wt%; the mixture was stirred at 28℃ for 35 min to obtain a uniform, clear and transparent alkaline alcohol-water system.

[0078] (2) Silane precursor premixing: 25.5 kg of silane precursor and 16 kg of anhydrous ethanol were mixed to form a silicon source premix. In this case, tetraethyl orthosilicate and tetrapropoxysilane were mixed in a 1:1 ratio as silane precursors. The purity of the silane precursor was ≥99.0%. Then, 1.7 kg of resin adsorbent was added and stirred evenly to remove trace metal ions and organic impurities from the raw materials.

[0079] The preparation method of the resin adsorbent in step (2) is as follows: 132 kg of mercapto-modified macroporous polystyrene resin (Duolite™ GT73), 17 kg of vinyl sulfonic acid, 3.2 kg of allyl cyanoacetate, and 1320 kg of dichloroethane are added to the reaction vessel, nitrogen gas is introduced to remove oxygen for 25 minutes, 1.3 kg of 2-hydroxy-2-methyl-1-phenyl-1-propanone (photoinitiator 1173) is added, and after stirring evenly, it is placed under 365 nm ultraviolet light for 52 minutes, and the reaction temperature is controlled at 66℃ throughout the process; after the reaction is completed, it is filtered, washed with ethanol 4 times, and vacuum dried to obtain the special resin adsorbent.

[0080] (3) Crystal nucleus formation: Set the stirring speed to 620 rpm and slowly add the above silicon source premixed solution to the alkaline alcohol-water system at a constant dropping rate of 3.3 mL / min; control the reaction temperature at 33℃ throughout the process and keep the pH of the system stable at 11.0; after the addition is completed, continue to stir the reaction at a constant temperature for 1.6 h, and uniform silicon dioxide crystal nuclei with uniform particle size and good dispersibility are formed in the system.

[0081] (4) Particle growth: The particle growth stage is carried out by constant temperature aging. The aging temperature is constant at 36℃ and the constant temperature aging reaction is carried out for 7 hours. The silanol in the system continues to undergo condensation reaction, the crystal nuclei grow uniformly, and finally form monodisperse spherical silica particles with uniform particle size and no agglomeration.

[0082] (5) Solid-liquid separation and washing: After the reaction is completed, centrifugation is performed. The centrifugation speed is set to 7800 rpm and the centrifugation time is 16 min. After centrifugation, the wet material is collected and washed three times with anhydrous ethanol and twice with ultrapure water. The amount of washing liquid added each time is 4.2 times the mass of the wet material obtained, to fully wash away residual ammonia, unreacted silane monomers and organic solvents in the system.

[0083] (6) Drying treatment: The washed wet material is freeze-dried at 72°C for 15 hours with the vacuum degree controlled at -0.088MPa to completely remove the residual moisture and solvent inside the material, and finally obtain high-purity monodisperse nanosphere silica powder.

[0084] Example 4

[0085] (1) Preparation of alkaline reaction system: 110 kg of anhydrous ethanol, 16 kg of deionized water and 8 kg of ammonia water are added to the reactor; wherein the purity of anhydrous ethanol is ≥99.7%, the conductivity of deionized water is ≤1 μS / cm and the mass concentration of ammonia water is 28 wt%; stir and mix at 30℃ for 40 min to obtain a uniform, clear and transparent alkaline alcohol-water system.

[0086] (2) Silane precursor premixing: 28 kg of silane precursor was mixed with 18 kg of anhydrous ethanol to form a silicon source premix. In this case, tetramethyl orthosilicate and tetrapropoxysilane were used as silane precursor in a 1:1 ratio. The purity of the silane precursor was ≥99.0%. Then, 2 kg of resin adsorbent was added and stirred evenly to remove trace metal ions and organic impurities from the raw materials.

[0087] The preparation method of the resin adsorbent in step (2) is as follows: 140 kg of mercapto-modified macroporous polystyrene resin (Ambersep™ GT74), 18 kg of vinyl sulfonic acid, 4 kg of allyl cyanoacetate, and 1400 kg of dichloroethane are added to the reaction vessel, nitrogen gas is introduced to remove oxygen for 30 minutes, 1.5 kg of 2-hydroxy-2-methyl-1-phenyl-1-propanone (photoinitiator 1173) is added, and after stirring evenly, it is placed under 365 nm ultraviolet light for 60 minutes, and the reaction temperature is controlled at 70℃ throughout the process; after the reaction is completed, it is filtered, washed with ethanol 5 times, and vacuum dried to obtain the special resin adsorbent.

[0088] (3) Crystal nucleus formation: Set the stirring speed to 700 rpm and slowly add the above silicon source premixed solution to the alkaline alcohol-water system at a constant dropping rate of 4.0 mL / min; control the reaction temperature at 35℃ throughout the process and keep the pH of the system stable at 11.5; after the addition is completed, continue to stir the reaction at a constant temperature for 2 hours to form uniform silicon dioxide crystal nuclei with uniform particle size and good dispersibility in the system.

[0089] (4) Particle growth: The particle growth stage is carried out by constant temperature aging. The aging temperature is constant at 38℃ and the constant temperature aging reaction is carried out for 8 hours. The silanol in the system continues to undergo condensation reaction, the crystal nuclei grow uniformly, and finally form monodisperse spherical silica particles with uniform particle size and no agglomeration.

[0090] (5) Solid-liquid separation and washing: After the reaction is completed, centrifugation is performed. The centrifugation speed is set to 9000 rpm and the centrifugation time is 20 min. After centrifugation, the wet material is collected and washed with anhydrous ethanol 4 times and ultrapure water 3 times in sequence. The amount of washing liquid added each time is 5 times the mass of the wet material obtained, so as to fully wash away the residual ammonia, unreacted silane monomer and organic solvent in the system.

[0091] (6) Drying treatment: The washed wet material is placed in a vacuum drying oven with a vacuum degree controlled at -0.095MPa and vacuum dried at 80℃ for 18h to completely remove residual moisture and solvent from the material and finally obtain high-purity monodisperse nanosphere silica powder.

[0092] Comparative Example 1

[0093] (1) Preparation of alkaline reaction system: Add 80kg of anhydrous ethanol, 8kg of deionized water and 3kg of ammonia water to the reactor; wherein the purity of anhydrous ethanol is ≥99.7%, the conductivity of deionized water is ≤1μS / cm, and the mass concentration of ammonia water is 25wt%; stir and mix at 20℃ for 20min to obtain a uniform, clear and transparent alkaline alcohol-water system.

[0094] (2) Silane precursor premixing: 16 kg of silane precursor and 8 kg of anhydrous ethanol were mixed to form a silicon source premix. In this case, tetraethyl orthosilicate was selected as the silane precursor with a purity of ≥99.0%. Then, 0.5 kg of resin adsorbent mercaptoized macroporous polystyrene resin (D406 Ⅱ) was added and stirred evenly to remove trace metal ions and organic impurities from the raw materials.

[0095] (3) Crystal nucleus formation: Set the stirring speed to 350 rpm and slowly add the above silicon source premixed solution to the alkaline alcohol-water system at a constant dropping rate of 1.0 mL / min; control the reaction temperature at 25℃ throughout the process and keep the pH of the system stable at 9.5; after the addition is completed, continue to stir the reaction at a constant temperature for 0.5 h, and uniform silicon dioxide crystal nuclei with uniform particle size and good dispersibility are formed in the system.

[0096] (4) Particle growth: The particle growth stage is carried out by constant temperature aging. The aging temperature is constant at 28℃ and the constant temperature aging reaction is carried out for 4 hours. The silanol in the system continues to undergo condensation reaction, the crystal nuclei grow uniformly, and finally form monodisperse spherical silica particles with uniform particle size and no agglomeration.

[0097] (5) Solid-liquid separation and washing: After the reaction is completed, centrifugation is performed. The centrifugation speed is set to 4000 rpm and the centrifugation time is 5 min. After centrifugation, the wet material is collected and washed twice with anhydrous ethanol and once with ultrapure water. The amount of washing liquid added each time is twice the mass of the wet material obtained, so as to fully wash away the residual ammonia, unreacted silane monomer and organic solvent in the system.

[0098] (6) Drying treatment: The washed wet material is placed in a vacuum drying oven with a vacuum degree controlled at -0.06MPa and vacuum dried at 50℃ for 6h to completely remove residual moisture and solvent from the material and finally obtain high-purity monodisperse nano-spherical silica powder.

[0099] Comparative Example 2

[0100] (1) Preparation of alkaline reaction system: Add 80kg of anhydrous ethanol, 8kg of deionized water and 3kg of ammonia water to the reactor; wherein the purity of anhydrous ethanol is ≥99.7%, the conductivity of deionized water is ≤1μS / cm, and the mass concentration of ammonia water is 25wt%; stir and mix at 20℃ for 20min to obtain a uniform, clear and transparent alkaline alcohol-water system.

[0101] (2) Silane precursor premixing: 16 kg of silane precursor and 8 kg of anhydrous ethanol were mixed to form a silicon source premix. In this case, tetraethyl orthosilicate was selected as the silane precursor with a purity of ≥99.0%. Then, 0.5 kg of resin adsorbent was added and stirred evenly to remove trace metal ions and organic impurities from the raw materials.

[0102] The preparation method of the resin adsorbent in step (2) is as follows: 100 kg of mercapto-modified macroporous polystyrene resin (D406 Ⅱ selected), 0.8 kg of allyl cyanoacetate and 1000 kg of dichloroethane are added to the reaction vessel, nitrogen gas is introduced to remove oxygen for 10 minutes, 0.5 parts of 2-hydroxy-2-methyl-1-phenyl-1-propanone (photoinitiator 1173) are added, and after stirring evenly, it is placed under 365 nm ultraviolet light for 30 minutes, and the reaction temperature is controlled at 55℃ throughout the process; after the reaction is completed, it is filtered, washed with ethanol 3 times, and vacuum dried to obtain the special resin adsorbent.

[0103] (3) Crystal nucleus formation: Set the stirring speed to 350 rpm and slowly add the above silicon source premixed solution to the alkaline alcohol-water system at a constant dropping rate of 1.0 mL / min; control the reaction temperature at 25℃ throughout the process and keep the pH of the system stable at 9.5; after the addition is completed, continue to stir the reaction at a constant temperature for 0.5 h, and uniform silicon dioxide crystal nuclei with uniform particle size and good dispersibility are formed in the system.

[0104] (4) Particle growth: The particle growth stage is carried out by constant temperature aging. The aging temperature is constant at 28℃ and the constant temperature aging reaction is carried out for 4 hours. The silanol in the system continues to undergo condensation reaction, the crystal nuclei grow uniformly, and finally form monodisperse spherical silica particles with uniform particle size and no agglomeration.

[0105] (5) Solid-liquid separation and washing: After the reaction is completed, centrifugation is performed. The centrifugation speed is set to 4000 rpm and the centrifugation time is 5 min. After centrifugation, the wet material is collected and washed twice with anhydrous ethanol and once with ultrapure water. The amount of washing liquid added each time is twice the mass of the wet material obtained, so as to fully wash away the residual ammonia, unreacted silane monomer and organic solvent in the system.

[0106] (6) Drying treatment: The washed wet material is placed in a vacuum drying oven with a vacuum degree controlled at -0.06MPa and vacuum dried at 50℃ for 6h to completely remove residual moisture and solvent from the material and finally obtain high-purity monodisperse nano-spherical silica powder.

[0107] Comparative Example 3

[0108] (1) Preparation of alkaline reaction system: Add 80kg of anhydrous ethanol, 8kg of deionized water and 3kg of ammonia water to the reactor; wherein the purity of anhydrous ethanol is ≥99.7%, the conductivity of deionized water is ≤1μS / cm, and the mass concentration of ammonia water is 25wt%; stir and mix at 20℃ for 20min to obtain a uniform, clear and transparent alkaline alcohol-water system.

[0109] (2) Silane precursor premixing: 16 kg of silane precursor and 8 kg of anhydrous ethanol were mixed to form a silicon source premix. In this case, tetraethyl orthosilicate was selected as the silane precursor with a purity of ≥99.0%. Then, 0.5 kg of resin adsorbent was added and stirred evenly to remove trace metal ions and organic impurities from the raw materials.

[0110] The preparation method of the resin adsorbent in step (2) is as follows: 100 kg of mercapto-modified macroporous polystyrene resin (D406 Ⅱ selected), 12 kg of vinyl sulfonic acid, and 1000 kg of dichloroethane are added to the reaction vessel, nitrogen gas is introduced to remove oxygen for 10 minutes, 0.5 parts of 2-hydroxy-2-methyl-1-phenyl-1-propanone (photoinitiator 1173) are added, and after stirring evenly, the mixture is placed under 365 nm ultraviolet light for 30 minutes, and the reaction temperature is controlled at 55℃ throughout the process. After the reaction is completed, the mixture is filtered, washed with ethanol 3 times, and vacuum dried to obtain the special resin adsorbent.

[0111] (3) Crystal nucleus formation: Set the stirring speed to 350 rpm and slowly add the above silicon source premixed solution to the alkaline alcohol-water system at a constant dropping rate of 1.0 mL / min; control the reaction temperature at 25℃ throughout the process and keep the pH of the system stable at 9.5; after the addition is completed, continue to stir the reaction at a constant temperature for 0.5 h, and uniform silicon dioxide crystal nuclei with uniform particle size and good dispersibility are formed in the system.

[0112] (4) Particle growth: The particle growth stage is carried out by constant temperature aging. The aging temperature is constant at 28℃ and the constant temperature aging reaction is carried out for 4 hours. The silanol in the system continues to undergo condensation reaction, the crystal nuclei grow uniformly, and finally form monodisperse spherical silica particles with uniform particle size and no agglomeration.

[0113] (5) Solid-liquid separation and washing: After the reaction is completed, centrifugation is performed. The centrifugation speed is set to 4000 rpm and the centrifugation time is 5 min. After centrifugation, the wet material is collected and washed twice with anhydrous ethanol and once with ultrapure water. The amount of washing liquid added each time is twice the mass of the wet material obtained, so as to fully wash away the residual ammonia, unreacted silane monomer and organic solvent in the system.

[0114] (6) Drying treatment: The washed wet material is placed in a vacuum drying oven with a vacuum degree controlled at -0.06MPa and vacuum dried at 50℃ for 6h to completely remove residual moisture and solvent from the material and finally obtain high-purity monodisperse nano-spherical silica powder.

[0115] Test method:

[0116] 1. Particle size and particle size distribution test

[0117] The particle size and particle size distribution of the samples were determined using a dynamic light scattering (DLS) instrument (Malvern Zetasizer Nano ZS90). 0.02 g of silica powder was weighed and added to 100 mL of anhydrous ethanol, ultrasonically dispersed for 15 min, and then tested at 25℃ and a test angle of 173°. Each sample was tested in triplicate, and the average value was taken. Monodispersity was evaluated using the polydispersity index (PDI) and particle size distribution coefficient (CV). The DLS method is widely used in the Stöber method for silica particle size analysis.

[0118] The particle size distribution coefficient CV is calculated using the following formula:

[0119] CV = σ / Dn × 100%

[0120] in:

[0121] σ is the standard deviation of particle size;

[0122] Dn is the average particle size.

[0123] 2. Specific surface area test

[0124] The specific surface area was determined using the BET nitrogen adsorption method (Micromeritics ASAP 2460).

[0125] Test conditions:

[0126] Degassing temperature: 150℃;

[0127] Degassing time: 6 hours;

[0128] Test temperature: 77 K.

[0129] The BET method can effectively reflect particle dispersibility and pore structure characteristics.

[0130] 3. Metal impurity content test

[0131] The content of metallic impurities such as Na, K, Ca, and Fe was tested using ICP-OES (Agilent 5110).

[0132] The testing steps are as follows:

[0133] (1) Weigh 0.10 g of sample;

[0134] (2) Add KOH alkaline solution for alkaline hydrolysis;

[0135] (3) Heat to dissolve and then bring to a final volume;

[0136] (4) The metal element content was tested using ICP-OES.

[0137] This method can effectively avoid the safety issues caused by HF digestion.

[0138] 4. Zeta potential test

[0139] The zeta potential of the particles was measured using a Malvern Nano ZS90 to evaluate the particle dispersion stability.

[0140] Test conditions:

[0141] Dispersion medium: ethanol / water mixture;

[0142] pH: 10;

[0143] Temperature: 25℃.

[0144] When the absolute value of the Zeta potential is greater than 30 mV, it indicates that the particles have good dispersion stability.

[0145] Table 1 Test Results

[0146] Average particle size (nm) <![CDATA[Specific surface area m 2 / g]]> Zeta potential mV <![CDATA[SiO2 Purity %]]> Total metal impurities (ppm) Example 1 277 68 -39.8 99.967 31 Example 2 272 74 -41.5 99.971 27 Example 3 266 80 -43.3 99.976 22 Example 4 264 85 -45.0 99.980 19 Comparative Example 1 288 50 -30.5 99.921 54 Comparative Example 2 283 58 -34.9 99.945 42 Comparative Example 3 281 63 -35.8 99.952 39

[0147] Thiol-modified macroporous polystyrene resin, as a high specific surface area carrier, provides abundant reaction sites and good mechanical stability. Vinyl sulfonic acid introduces strongly acidic sulfonic acid groups, endowing the resin with efficient ion exchange capacity for alkali metal ions (Na⁺, K⁺, etc.). Allyl cyanoacetate, through its cyano and ester groups forming a multidentate coordination structure, synergistically achieves strong chelation of various heavy metals and harmful metal ions via thioether bonds. The photoinitiation system (365 nm UV + 1173) ensures that the reaction is completed rapidly and quantitatively under mild conditions, avoiding damage to the resin skeleton from high temperatures or strong acids and alkalis. The synergistic effect of these four components constructs a multifunctional adsorbent with both broad-spectrum metal impurity removal capability and high chemical stability, providing a crucial purification guarantee for the controllable preparation of high-purity nano-silica.

[0148] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.

Claims

1. A method for preparing high-purity monodisperse nanosphere silica powder by silane hydrolysis, characterized in that, Includes the following steps: (1) Preparation of alkaline reaction system: By weight, 80–110 parts anhydrous ethanol, 8–16 parts deionized water, and 3–8 parts ammonia were added to the reactor and stirred at 20–30°C for 20–40 minutes to obtain a homogeneous alkaline alcohol-water system; the ammonia concentration was 25–28 wt%. (2) Silane precursor premixing: According to the mass fraction, 16-28 parts of silane precursor and 8-18 parts of anhydrous ethanol are mixed to form a silicon source premix, and then 0.5-2 parts of resin adsorbent are added for deep impurity removal. (3) Crystal nucleus formation: Under a stirring speed of 350-700 rpm, the silicon source premixed solution is added to the alkaline alcohol-water system, and the reaction temperature is controlled at 25-35°C. After the addition is completed, the reaction continues for 0.5-2 hours to form uniform silicon dioxide crystal nuclei. (4) Granule growth: Continue the aging reaction for 4-8 hours to allow the silanol to undergo a condensation reaction and form monodisperse spherical silica particles; (5) Solid-liquid separation and washing: After the reaction is completed, centrifugation is performed, followed by washing with anhydrous ethanol 2 to 4 times and ultrapure water 1 to 3 times, with the amount of washing solution added each time being 2 to 5 times the mass of the obtained wet material; (6) Drying treatment: The washed material was vacuum dried at 50–80°C for 6–18 h to obtain high-purity monodisperse nano-spherical silica powder. In step (2), the resin adsorbent is prepared by reacting mercaptoized macroporous polystyrene resin, vinyl sulfonic acid, allyl cyanoacetate, and 2-hydroxy-2-methyl-1-phenyl-1-acetone.

2. The method for preparing high-purity monodisperse nano-spherical silica powder by silane hydrolysis according to claim 1, characterized in that: In step (1), the conductivity of deionized water is ≤1μS / cm, the purity of anhydrous ethanol is ≥99.7%, and the purity of the silane precursor is ≥99.0%.

3. The method for preparing high-purity monodisperse nano-spherical silica powder by silane hydrolysis according to claim 1, characterized in that: In step (2), the silane precursor is one or a combination of two of tetraethyl orthosilicate, tetramethyl orthosilicate, and tetrapropoxysilane.

4. The method for preparing high-purity monodisperse nano-spherical silica powder by silane hydrolysis according to claim 1, characterized in that: The preparation method of the resin adsorbent in step (2) is as follows: according to the mass fractions, 100-140 parts of mercapto-modified macroporous polystyrene resin, 12-18 parts of vinyl sulfonic acid, 0.8-4 parts of allyl cyanoacetate, and 1000-1400 parts of dichloroethane are added to the reaction vessel, nitrogen gas is introduced to remove oxygen for 10-30 minutes, 0.5-1.5 parts of 2-hydroxy-2-methyl-1-phenyl-1-acetone are added, and after stirring evenly, the mixture is placed under 365nm ultraviolet light for 30-60 minutes, and the reaction temperature is controlled at 55-70℃. After the reaction is completed, the mixture is filtered, washed with ethanol 3-5 times, and dried to obtain the resin adsorbent.

5. The method for preparing high-purity monodisperse nano-spherical silica powder by silane hydrolysis according to claim 4, characterized in that: The thiolized macroporous polystyrene resin is selected from one of D406Ⅱ, LSC400, Duolite™ GT73, Ambersep™ GT74, and Zhengguang D830.

6. The method for preparing high-purity monodisperse nano-spherical silica powder by silane hydrolysis according to claim 1, characterized in that: In step (3), the droplet addition rate of the silicon source premixed liquid is 1.0 to 4.0 mL / min.

7. The method for preparing high-purity monodisperse nano-spherical silica powder by silane hydrolysis according to claim 1, characterized in that: In step (3), the pH of the system is controlled to be 9.5 to 11.

5.

8. The method for preparing high-purity monodisperse nano-spherical silica powder by silane hydrolysis according to claim 1, characterized in that: In step (4), the particle growth stage is carried out using a constant temperature aging method, with an aging temperature of 28–38°C.

9. The method for preparing high-purity monodisperse nano-spherical silica powder by silane hydrolysis according to claim 1, characterized in that: In step (5), the centrifugation speed is 4000-9000 rpm and the centrifugation time is 5-20 min.

10. The method for preparing high-purity monodisperse nano-spherical silica powder by silane hydrolysis according to claim 1, characterized in that: In step (6), the drying method is one of vacuum drying, freeze drying or inert atmosphere drying; the vacuum degree is controlled to be -0.06 to -0.095 MPa.

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