Silica microspheres and methods for making the same

Abstract

This invention relates to silica microspheres and their preparation method. The preparation method includes the following steps: using a surfactant as a structure-directing agent, phenyltrimethoxysilane is hydrolyzed and condensed in an alcohol-water mixed solvent at 20°C to 40°C to obtain a polysilsesquioxane microsphere dispersion; an orthosilicate is added to the polysilsesquioxane microsphere dispersion, wherein the volume ratio of the orthosilicate to the phenyltrimethoxysilane is greater than or equal to 4:1; after the reaction, hollow silica microspheres are obtained by separation; or, an orthosilicate is added to the polysilsesquioxane microsphere dispersion, wherein the volume ratio of the orthosilicate to the phenyltrimethoxysilane is less than 4:1; after the reaction, mesoporous silica microspheres are obtained by separation and alcohol washing. The preparation method of this invention can be carried out under mild conditions, is simple and controllable, and has in-situ organic modification capabilities.

Description

Technical Field

[0001] This invention relates to the field of new materials technology, and in particular to silica microspheres and their preparation methods. Background Technology

[0002] Silica microspheres, due to their adjustable pore size distribution, high specific surface area, and excellent chemical stability, have become core functional materials in fields such as dye adsorption, chromatographic separation, catalytic reactions, and drug delivery.

[0003] However, commonly used preparation methods, such as template methods, self-templating methods, and spray drying methods, all have their limitations. Template methods require high-temperature calcination to remove the template agent, resulting in high energy consumption and a tendency for structural collapse. While self-templating methods do not require an external template, their reaction mechanisms are complex, and process control is difficult. Spray drying methods have high equipment requirements, and the resulting microspheres exhibit poor particle size uniformity. Furthermore, silica microspheres prepared by these methods often require further organic modification to achieve their functional applications. Summary of the Invention

[0004] Therefore, it is necessary to provide a silica microsphere and its preparation method to address the above problems. The preparation method can be carried out under mild conditions, is simple and controllable, and has the ability to modify organic compounds in situ.

[0005] A method for preparing silica microspheres includes the following steps:

[0006] Using a surfactant as a structure directing agent, phenyltrimethoxysilane was hydrolyzed and condensed in an alcohol-water mixed solvent at 20℃~40℃ to obtain a polysilsesquioxane microsphere dispersion.

[0007] Orthosilicate is added to the polysilsesquioxane microsphere dispersion, and the volume ratio of the orthosilicate to the phenyltrimethoxysilane is greater than or equal to 4:1. After the reaction, silica hollow microspheres are obtained by separation.

[0008] Alternatively, an orthosilicate is added to the polysilsesquioxane microsphere dispersion, wherein the volume ratio of the orthosilicate to the phenyltrimethoxysilane is less than 4:1, and after the reaction, the microspheres are obtained by separation and alcohol washing.

[0009] In one embodiment, the step of preparing the polysilsesquioxane microsphere dispersion includes: placing the phenyltrimethoxysilane and the surfactant in an alcohol-water mixed solvent, first hydrolyzing them at 20°C to 40°C and pH 2.0 to 7.0 for 1 min to 60 min, and then adjusting the pH to 9.0 to 11.0 and reacting for 1 h to 2 h.

[0010] In one embodiment, the polysilsesquioxane microspheres have a particle size of 50 nm to 100 nm.

[0011] In one embodiment, the surfactant is selected from cationic surfactants.

[0012] In one embodiment, the surfactant is selected from at least one of CTAB, DTAB, and OTAB.

[0013] In one embodiment, the volume ratio of the phenyltrimethoxysilane to the alcohol-water mixed solvent is 1:20 to 1:100.

[0014] In one embodiment, the alcohol in the alcohol-water mixed solvent is selected from methanol and / or ethanol;

[0015] And / or, the volume ratio of alcohol to water in the alcohol-water mixed solvent is 2:8 to 5:5.

[0016] In one embodiment, the orthosilicate is selected from at least one of methyl orthosilicate and ethyl orthosilicate.

[0017] In one embodiment, the step of separating the silica hollow microspheres after the reaction further includes calcining the silica hollow microspheres.

[0018] A silica microsphere prepared by the method described above.

[0019] This invention utilizes the rigidity and hydrophobicity of the benzene ring in phenyltrimethoxysilane (PTMS) to inhibit excessive cross-linking during hydrolysis and condensation, causing only partial condensation to occur, thereby forming a polysilsesquioxane (PPSQ) microsphere framework that still encapsulates active PTMS oligomers. Furthermore, by controlling the volume ratio of orthosilicate to PTMS, silica microspheres with hollow structures or silica microspheres with multi-level mesoporous structures can be obtained. Moreover, the phenyl groups in PTMS are retained in the microsphere framework during the reaction, giving the resulting microspheres abundant organic functional groups, thus achieving in-situ organic hybridization and functionalization of the microspheres. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a TEM image of the hollow silica microspheres prepared in Example 1 of the present invention;

[0022] Figure 2 This is a TEM image of the hollow silica microspheres prepared in Example 2 of the present invention;

[0023] Figure 3 This is a TEM image of the silica hollow microspheres prepared in Example 3 of the present invention;

[0024] Figure 4 This is a TEM image of the hollow silica microspheres prepared in Example 4 of the present invention;

[0025] Figure 5 This is a TEM image of the hollow silica microspheres prepared in Example 5 of the present invention;

[0026] Figure 6 This is a TEM image of the silica hollow microspheres prepared in Example 6 of the present invention;

[0027] Figure 7 This is a TEM image of the hollow silica microspheres prepared in Example 7 of the present invention;

[0028] Figure 8 This is a TEM image of the silica microspheres prepared in Comparative Example 1 of the present invention;

[0029] Figure 9 This is a TEM image of the silica microspheres prepared in Comparative Example 2 of the present invention;

[0030] Figure 10 This is a TEM image of the silica microspheres prepared in Comparative Example 3 of the present invention;

[0031] Figure 11 This is a TEM image of the silica microspheres prepared in Comparative Example 4 of this invention;

[0032] Figure 12 This is a TEM image of the silica microspheres prepared in Comparative Example 5 of the present invention;

[0033] Figure 13 TEM image of PSSQ / SiO2-300 hollow microspheres prepared in Example 2 of this invention after calcination at 300℃;

[0034] Figure 14 TEM image of SiO2-700 hollow microspheres prepared in Example 2 of the present invention after calcination at 700℃;

[0035] Figure 15 BET adsorption-desorption curves of PSSQ / SiO2-300 hollow microspheres;

[0036] Figure 16 BET adsorption-desorption curves of SiO2-700 hollow microspheres;

[0037] Figure 17 This is a TEM image of the silica microspheres with a multi-level mesoporous structure prepared in Example 8 of the present invention;

[0038] Figure 18 This is a TEM image of silica microspheres with a multi-level mesoporous structure prepared in Example 9 of the present invention;

[0039] Figure 19 This is a TEM image of silica microspheres with a multi-level mesoporous structure prepared in Example 10 of the present invention;

[0040] Figure 20 This is a pore size distribution diagram of the silica microspheres with a multi-level mesoporous structure prepared in Example 8 of the present invention. Detailed Implementation

[0041] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments or examples only and is not intended to limit the invention. The optional scope of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0043] In this invention, numerical ranges are involved. Unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe features or characteristics, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0044] The method for preparing hollow silica microspheres provided by this invention includes the following steps:

[0045] S1, using a surfactant as a structure directing agent, phenyltrimethoxysilane is hydrolyzed and condensed in an alcohol-water mixed solvent at 20℃~40℃ to obtain a polysilsesquioxane microsphere dispersion;

[0046] S2, add orthosilicate to the polysilsesquioxane microsphere dispersion, wherein the volume ratio of the orthosilicate to the phenyltrimethoxysilane is greater than or equal to 4:1, and after reaction, separate to obtain hollow silica microspheres; or, add orthosilicate to the polysilsesquioxane microsphere dispersion, wherein the volume ratio of the orthosilicate to the phenyltrimethoxysilane is less than 4:1, and after reaction, separate and wash with alcohol to obtain mesoporous silica microspheres.

[0047] Unlike silane coupling agents such as tetraethyl orthosilicate (TEOS) and vinyltrimethoxysilane (VTMS), which readily condense rapidly under alkaline conditions to form dense structures, in step S1 of this invention, the rigidity and hydrophobic properties of the benzene ring in phenyltrimethoxysilane (PTMS) are utilized to introduce steric hindrance and a hydrophobic barrier during the hydrolysis-condensation process. This effectively inhibits excessive cross-linking between silane molecules, causing only partial condensation to occur, rather than forming dense solid spheres in one step. The resulting polysilsesquioxane (PPSQ) microspheres have a loose skeletal structure, with incompletely polymerized and reactive PTMS oligomers still encapsulated within them.

[0048] Optionally, the steps for preparing the polysilsesquioxane microsphere dispersion include: placing the phenyltrimethoxysilane and the surfactant in an alcohol-water mixed solvent, first hydrolyzing at 20℃~40℃ and pH 2.0~7.0 for 1 min~60 min, then adjusting the pH to 9.0~11.0 and reacting for 1 h~24 h. Thus, through a two-step pH control strategy of acidic hydrolysis followed by alkaline condensation, PTMS undergoes only partial hydrolysis under acidic conditions, avoiding excessive cross-linking due to overly rapid hydrolysis. Subsequently, condensation is completed under alkaline conditions to form a stable PPSQ microsphere framework, while retaining active PTMS oligomers within.

[0049] It is understandable that acidic reagents such as formic acid, acetic acid, hydrochloric acid, and nitric acid, as well as alkaline reagents such as ammonia, sodium carbonate, sodium hydroxide, and potassium hydroxide, can be used to adjust the pH during the reaction process.

[0050] The surfactant is selected from cationic surfactants. Cationic surfactants are positively charged under acidic conditions and can form stable micelle templates with the negatively charged silanol groups generated by PTMS hydrolysis through electrostatic interactions, guiding the uniform nucleation and growth of PPSQ microspheres. Compared with nonionic or anionic surfactants, cationic surfactants have a stronger ability to regulate the PTMS hydrolysis and condensation process, and can obtain PPSQ microspheres with better sphericity and narrower particle size distribution.

[0051] Furthermore, surfactants with different carbon chain lengths can achieve flexible control over the particle size of PPSQ microspheres. The longer the carbon chain, the larger the micelle size, and the larger the resulting microsphere size, providing a simple means for subsequent on-demand adjustment of the hollow microsphere size. Preferably, the cationic surfactant is selected from at least one of hexadecyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide (DTAB), and octadecyltrimethylammonium bromide (OTAB).

[0052] Optionally, the volume ratio of the phenyltrimethoxysilane to the alcohol-water mixed solvent is 1:20 to 1:100. Within this volume ratio range, the concentration of PTMS in the reaction system is moderate, which ensures sufficient silicon source supply to form a complete PPSQ microsphere framework while avoiding excessive cross-linking and aggregation caused by excessive PTMS concentration.

[0053] Wherein, the alcohol in the alcohol-water mixed solvent is selected from methanol and / or ethanol; the volume ratio of alcohol to water in the alcohol-water mixed solvent is 2:8 to 5:5.

[0054] Optionally, the polysilsesquioxane microspheres have a particle size of 50 nm to 100 nm. PPSQ microspheres within this particle size range are more stable in the presence of a surfactant.

[0055] In step S2 of this invention, orthosilicate is added to the polysilsesquioxane microsphere dispersion. When the volume ratio of orthosilicate to PTMS is controlled to be greater than or equal to 4:1, the absolute amount of orthosilicate is sufficient to quickly penetrate into the interior of the PPSQ microspheres, expanding the PPSQ microspheres. A small amount of orthosilicate hydrolyzes and condenses on the surface of the microspheres under alkaline conditions to form SiO2, while the remaining orthosilicate diffuses from the interior to the shell and hydrolyzes and condenses to form SiO2. Since the density of orthosilicate is much lower than that of SiO2, significant volume shrinkage occurs during the conversion of orthosilicate to SiO2, thereby inducing the formation of cavities inside the microspheres. Finally, a hollow structure with SiO2 as the main component is formed in situ at room temperature. At the same time, the phenyl groups in PTMS are retained in the microsphere skeleton during the reaction, giving the resulting microspheres abundant organic functional groups, realizing in-situ organic hybridization and functionalization of hollow microspheres.

[0056] To maintain a suitable balance between permeation and shell formation, the volume ratio of orthosilicate to PTMS is preferably 4:1 to 16:1.

[0057] When the volume ratio of orthosilicate to PTMS is controlled to be less than 4:1, the hydrolysis and condensation rate of orthosilicate on the surface of the microspheres is higher than its penetration rate into the interior of the PPSQ microspheres. Therefore, the orthosilicate mainly undergoes hydrolysis and condensation on the surface of the microspheres, forming a silica coating layer with mesoporous pore sizes of 1 nm to 3 nm. After alcohol washing, some CTAB template and PPSQ oligomers are selectively removed, while the PPSQ framework is retained as the core, thus forming a mesoporous structure of 3 nm to 10 nm inside. Finally, hybrid silica microspheres with a multi-level mesoporous structure are obtained. In this structure, the PPSQ microsphere core provides a large pore space as a material reservoir, while the small-pore mesoporous channels of the silica shell play a role in molecular sieving and mass transfer regulation. Therefore, when applied in macromolecular or fast reaction processes, the mass transfer performance and functional molecule loading capacity can be further improved.

[0058] To control excessive permeation of orthosilicate, the volume ratio of orthosilicate to PTMS is preferably greater than or equal to 1:1 and less than 4:1.

[0059] Optionally, the orthosilicate is selected from at least one of methyl orthosilicate (TMOS) and tetraethyl orthosilicate (TEOS). Both methyl orthosilicate and tetraethyl orthosilicate are commonly used silicon-based precursors. Under alkaline conditions, they have suitable hydrolysis and condensation rates, which allow them to fully penetrate into the interior of PPSQ microspheres without rapidly coating the surface of the microspheres due to excessive hydrolysis. Both are widely available and inexpensive, and their hydrolysis byproducts are methanol and ethanol, respectively, which are environmentally friendly and convenient for industrial application.

[0060] Optionally, the pH of the polysilsesquioxane microsphere dispersion is adjusted to 9-11, and then orthosilicate is added. This helps to control the hydrolysis and condensation rate of the orthosilicate, thereby promoting the formation of hollow structures.

[0061] It is understandable that the step of separating the silica hollow microspheres after the reaction also includes calcining the silica hollow microspheres. This removes the surfactant, and the calcination temperature can be adjusted as needed to remove the PPSQ microspheres, resulting in pure silica hollow microspheres.

[0062] Therefore, the preparation method of the present invention can overcome the defects of the prior art, such as high energy consumption of template method, complex and difficult-to-control mechanism of self-templating method, and poor particle size uniformity of spray drying method. It has the comprehensive advantages of mild process conditions, simple and controllable operation, uniform product morphology and in-situ organic hybridization function.

[0063] Furthermore, the present invention also provides silica microspheres obtained by the aforementioned preparation method. It is understood that the silica microspheres can be hollow silica microspheres or hybrid silica microspheres with a multi-level mesoporous structure. Specifically, the hollow silica microspheres include a silica shell and PPSQ distributed within the silica shell, or the hollow silica microspheres may only include a silica shell; the hybrid silica microspheres with a multi-level mesoporous structure have a core-shell structure, including a silica shell and a PPSQ microsphere core.

[0064] The technical solution of the present invention will be further described below through specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Unless otherwise specified, specific conditions in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used without specified manufacturers are all commercially available conventional products.

[0065] Example 1

[0066] Prepare an alcohol-water mixed solvent by mixing 30 ml of ethanol and 70 ml of water. Then, place 1 ml of PTMS and 0.4 g of CTAB into the alcohol-water mixed solvent and stir at 30 °C. Then, adjust the pH to 2.0 with dilute nitric acid and hydrolyze for 30 min. Then, adjust the pH to 10.5 with 5% ammonia and react for 30 min to obtain a PPSQ microsphere dispersion, wherein the particle size of the PPSQ microspheres is about 100 nm.

[0067] The pH of the PPSQ microsphere dispersion was adjusted to 10.5, and then 4 ml of TEOS was added to the dispersion. The reaction was allowed to proceed for 12 hours to obtain the final dispersion. The dispersion was then centrifuged and filtered to obtain the final product as shown in the image. Figure 1 The PSSQ / SiO2 hollow silica microspheres shown are shown.

[0068] Example 2

[0069] Prepare an alcohol-water mixed solvent by mixing 30 ml of ethanol and 70 ml of water. Then, place 1 ml of PTMS and 0.4 g of CTAB into the alcohol-water mixed solvent and stir at 30 °C. Then, adjust the pH to 7.0 with dilute nitric acid and ammonia and hydrolyze for 30 min. Then, adjust the pH to 10.5 with 5% ammonia and react for 30 min to obtain a PPSQ microsphere dispersion, wherein the particle size of the PPSQ microspheres is about 100 nm.

[0070] The pH of the PPSQ microsphere dispersion was adjusted to 10.5, and then 4 ml of TEOS was added to the dispersion. The reaction was allowed to proceed for 12 hours to obtain the final dispersion. The dispersion was then centrifuged and filtered to obtain the final product as shown in the image. Figure 2 The PSSQ / SiO2 hollow silica microspheres shown are shown.

[0071] Example 3

[0072] Prepare an alcohol-water mixed solvent by mixing 30 ml of ethanol and 70 ml of water. Then, place 1 ml of PTMS and 0.4 g of CTAB into the alcohol-water mixed solvent and stir at 30 °C. Then, adjust the pH to 7.0 with dilute nitric acid and ammonia and hydrolyze for 30 min. Then, adjust the pH to 10.5 with 5% ammonia and react for 30 min to obtain a PPSQ microsphere dispersion, wherein the particle size of the PPSQ microspheres is about 100 nm.

[0073] The pH of the PPSQ microsphere dispersion was adjusted to 10.5, and then 8 ml of TEOS was added to the dispersion. The reaction was allowed to proceed for 12 hours to obtain the final dispersion. The dispersion was then centrifuged and filtered to obtain the final product as shown in the image. Figure 3 The PSSQ / SiO2 hollow silica microspheres shown are shown.

[0074] Example 4

[0075] Prepare an alcohol-water mixed solvent by mixing 30 ml of ethanol and 70 ml of water. Then, place 2 ml of PTMS and 0.4 g of CTAB into the alcohol-water mixed solvent and stir at 30 °C. Then, adjust the pH to 7.0 with dilute nitric acid and ammonia and hydrolyze for 30 min. Then, adjust the pH to 10.5 with 5% ammonia and react for 30 min to obtain a PPSQ microsphere dispersion, wherein the particle size of the PPSQ microspheres is about 120 nm.

[0076] The pH of the PPSQ microsphere dispersion was adjusted to 10.5, and then 8 ml of TEOS was added to the dispersion. The reaction was allowed to proceed for 12 hours to obtain the final dispersion. The dispersion was then centrifuged and filtered to obtain the final product as shown in the image. Figure 4 The PSSQ / SiO2 hollow silica microspheres shown are shown.

[0077] Example 5

[0078] Prepare an alcohol-water mixed solvent by mixing 30 ml of ethanol and 70 ml of water. Then, place 2 ml of PTMS and 0.4 g of CTAB into the alcohol-water mixed solvent and stir at 30 °C. Then, adjust the pH to 7.0 with dilute nitric acid and ammonia and hydrolyze for 30 min. Then, adjust the pH to 10.5 with 5% ammonia and react for 30 min to obtain a PPSQ microsphere dispersion, wherein the particle size of the PPSQ microspheres is about 120 nm.

[0079] The pH of the PPSQ microsphere dispersion was adjusted to 10.5, and then 16 ml of TEOS was added to the dispersion. The reaction was allowed to proceed for 12 hours to obtain the final dispersion. The dispersion was then centrifuged and filtered to obtain the final product as shown in the image. Figure 5 The PSSQ / SiO2 hollow silica microspheres shown are shown.

[0080] Example 6

[0081] Prepare an alcohol-water mixed solvent by mixing 30 ml of ethanol and 70 ml of water. Then, place 1 ml of PTMS and 0.2 g of CTAB into the alcohol-water mixed solvent and stir at 30 °C. Adjust the pH to 7.0 with dilute nitric acid and ammonia, and hydrolyze for 30 min. Then, adjust the pH to 10.5 with 5% ammonia and react for 30 min to obtain a PPSQ microsphere dispersion, wherein the particle size of the PPSQ microspheres is about 100 nm.

[0082] The pH of the PPSQ microsphere dispersion was adjusted to 10.5, and then 8 ml of TEOS was added to the dispersion. The reaction was allowed to proceed for 12 hours to obtain the final dispersion. The dispersion was then centrifuged and filtered to obtain the final product as shown in the image. Figure 6 The PSSQ / SiO2 hollow silica microspheres shown are shown.

[0083] Example 7

[0084] Prepare an alcohol-water mixed solvent by mixing 30 ml of ethanol and 70 ml of water. Then, place 1 ml of PTMS and 0.6 g of CTAB into the alcohol-water mixed solvent and stir at 30 °C. Then, adjust the pH to 7.0 with dilute nitric acid and ammonia and hydrolyze for 30 min. Then, adjust the pH to 10.5 with 5% ammonia and react for 30 min to obtain a PPSQ microsphere dispersion, wherein the particle size of the PPSQ microspheres is about 100 nm.

[0085] The pH of the PPSQ microsphere dispersion was adjusted to 10.5, and then 8 ml of TEOS was added to the dispersion. The reaction was allowed to proceed for 12 hours to obtain the final dispersion. The dispersion was then centrifuged and filtered to obtain the final product as shown in the image. Figure 7 The PSSQ / SiO2 hollow silica microspheres shown are shown.

[0086] Comparative Example 1

[0087] Prepare an alcohol-water mixed solvent by mixing 30 ml of ethanol and 70 ml of water. Then, place 1 ml of PTMS and 0.4 g of CTAB into the alcohol-water mixed solvent and stir at 50 °C. Then, adjust the pH to 7.0 with dilute nitric acid and ammonia and hydrolyze for 30 min. Then, adjust the pH to 10.5 with 5% ammonia and react for 30 min to obtain a PPSQ microsphere dispersion, wherein the particle size of the PPSQ microspheres is about 120 nm.

[0088] The pH of the PPSQ microsphere dispersion was adjusted to 10.5, and then 8 ml of TEOS was added to the dispersion. The reaction was allowed to proceed for 12 hours to obtain the final dispersion. The dispersion was then centrifuged and filtered to obtain the final product as shown in the image. Figure 8 The PSSQ / SiO2 silica solid microspheres shown are shown.

[0089] This comparison shows that the reaction temperature affects the product shape; if the temperature is too high, only solid spheres can be obtained.

[0090] Comparative Example 2

[0091] Prepare an alcohol-water mixture by mixing 30 ml of isopropanol and 70 ml of water. Then, add 0.4 g of CTAB to the alcohol-water mixture and stir at 30°C. Adjust the pH to 10.5 with 5% ammonia and react for 30 min. Next, add 8 ml of TEOS and react for 12 h to obtain a dispersion. Centrifuge and filter the dispersion to obtain the following... Figure 9 The SiO2 solid microspheres shown are shown.

[0092] Comparative Example 3

[0093] Prepare an alcohol-water mixed solvent by mixing 30 ml of propanol and 70 ml of water. Then, place 1 ml of PTMS into the alcohol-water mixed solvent and stir at 30 °C. Adjust the pH to 7.0 with dilute nitric acid and ammonia, and hydrolyze for 30 min. Then, adjust the pH to 10.5 with 5% ammonia and react for 30 min to obtain a PPSQ microsphere dispersion, wherein the particle size of the PPSQ microspheres is about 100 nm.

[0094] The pH of the PPSQ microsphere dispersion was adjusted to 10.5, and then 8 ml of TEOS was added to the dispersion. The reaction was allowed to proceed for 12 hours to obtain the final dispersion. The dispersion was then centrifuged and filtered to obtain the final product as shown in the image. Figure 10 The low-density PSSQ / SiO2 silica solid microspheres are shown.

[0095] Comparative Example 4

[0096] Prepare an alcohol-water mixture by mixing 30 ml of ethanol and 70 ml of water. Then, add 1 ml of PTMS, 8 ml of TEOS, and 0.4 g of CTAB to the alcohol-water mixture and stir at 30°C. Adjust the pH to 7.0 using dilute nitric acid and ammonia, and hydrolyze for 30 min. Then, adjust the pH to 10.5 using 5% ammonia and react for 30 min to obtain a dispersion. Centrifuge and filter the dispersion to obtain the following... Figure 11 The PSSQ / SiO2 silica solid microspheres shown are shown.

[0097] Comparative Examples 2 to 4 show that PTMS and surfactant are both indispensable, and the order in which PTMS and orthosilicate are added directly determines whether hollow microspheres can be obtained.

[0098] Comparative Example 5

[0099] Prepare an alcohol-water mixed solvent by mixing 30 ml of ethanol and 70 ml of water. Then, place 1 ml of VTMS and 0.4 g of CTAB into the alcohol-water mixed solvent and stir at 30 °C. Then, adjust the pH to 7.0 with dilute nitric acid and ammonia and hydrolyze for 30 min. Then, adjust the pH to 10.5 with 5% ammonia and react for 30 min to obtain a PVSQ microsphere dispersion, wherein the particle size of the PVSQ microspheres is about 100 nm.

[0100] The pH of the PVSQ microsphere dispersion was adjusted to 10.5, and then 1 ml of TEOS was added to the dispersion. The reaction was allowed to proceed for 12 hours to obtain the final dispersion. The dispersion was then centrifuged and filtered to obtain the final product as shown in the image. Figure 12 The PVSQ / SiO2 porous silica microspheres shown are shown.

[0101] As can be seen from this comparative example, orthosilicates and vinyltrimethoxysilanes can only produce porous microspheres, not hollow microspheres. Silane coupling agents that react too quickly cannot produce hollow spheres by this method.

[0102] The PSSQ / SiO2 hollow silica microspheres obtained in Example 2 were calcined at 300°C for 4 hours to remove CTAB, resulting in the following... Figure 13 The PSSQ / SiO2 silica hollow microspheres shown are designated as PSSQ / SiO2-300 hollow microspheres. The PSSQ / SiO2 silica hollow microspheres obtained in Example 2 were calcined at 700°C for 4 hours to remove CTAB and PPSQ, yielding the following... Figure 14 The silica hollow microspheres shown are denoted as SiO2-700 hollow microspheres.

[0103] The BET adsorption-desorption curves of PSSQ / SiO2-300 hollow microspheres and SiO2-700 hollow microspheres are as follows: Figure 15 and Figure 16 As shown, the BET data is shown in Table 1.

[0104] Table 1

[0105]

[0106] Accurately weigh 20 mg each of PSSQ / SiO2-300 hollow microspheres and SiO2-700 hollow microspheres, add them to 40 ml of 400 mg / L methylene blue or methyl orange solution for adsorption, test the absorbance of the dye solution before and after adsorption, and calculate the adsorption performance of the two microspheres for the dye. The results are shown in Table 2.

[0107] Table 2

[0108]

[0109] As shown in Tables 1 and 2, the introduction of phenyl groups can significantly enhance the adsorption capacity of microspheres for dye molecules. Even though the specific surface area of ​​PSSQ / SiO2-300 hollow microspheres is more than 20% lower than that of SiO2-700 hollow microspheres, its adsorption performance for cationic dyes can still be improved by more than 50% (based on the maximum equilibrium adsorption capacity of 400 mg / L dye solution). The adsorption of anionic dyes has also achieved a huge improvement from 0 to 31.041 mg / g (the maximum equilibrium adsorption capacity of 400 mg / L dye solution).

[0110] Example 8

[0111] Prepare an alcohol-water mixed solvent by mixing 30 ml of ethanol and 70 ml of water. Then, place 1 ml of PTMS and 0.3 g of CTAB into the alcohol-water mixed solvent and stir at 30 °C. Then, adjust the pH to 2.0 with dilute nitric acid and hydrolyze for 30 min. Then, adjust the pH to 10.5 with 5% ammonia water and react for 30 min to obtain a PPSQ microsphere dispersion, wherein the particle size of the PPSQ microspheres is about 100 nm.

[0112] The pH of the PPSQ microsphere dispersion was adjusted to 10.5, and then 1 ml of TEOS was added to the dispersion. The reaction was allowed to proceed for 12 hours to obtain the final dispersion. The dispersion was then centrifuged, filtered, and the resulting product was washed with anhydrous ethanol to obtain the final product. Figure 17 The image shows hybrid silica microspheres with a multi-level mesoporous structure.

[0113] Example 9

[0114] Prepare an alcohol-water mixed solvent by mixing 30 ml of ethanol and 70 ml of water. Then, place 1 ml of PTMS and 0.3 g of DTAB into the alcohol-water mixed solvent and stir at 30 °C. Then, adjust the pH to 2.0 with dilute nitric acid and hydrolyze for 30 min. Then, adjust the pH to 10.5 with 5% ammonia and react for 30 min to obtain a PPSQ microsphere dispersion, wherein the particle size of the PPSQ microspheres is about 100 nm.

[0115] The pH of the PPSQ microsphere dispersion was adjusted to 10.5, and then 2 ml of TEOS was added to the dispersion. The reaction was allowed to proceed for 12 hours to obtain the final dispersion. The dispersion was then centrifuged, filtered, and the resulting product was washed with anhydrous ethanol to obtain the final product. Figure 18 The image shows hybrid silica microspheres with a multi-level mesoporous structure.

[0116] Example 10

[0117] Prepare an alcohol-water mixed solvent by mixing 30 ml of ethanol and 70 ml of water. Then, place 1 ml of PTMS and 0.3 g of DTAB into the alcohol-water mixed solvent and stir at 30 °C. Then, adjust the pH to 2.0 with dilute nitric acid and hydrolyze for 30 min. Then, adjust the pH to 10.5 with 5% ammonia and react for 30 min to obtain a PPSQ microsphere dispersion, wherein the particle size of the PPSQ microspheres is about 100 nm.

[0118] The pH of the PPSQ microsphere dispersion was adjusted to 10.5, and then 3 ml of TEOS was added to the dispersion. The reaction was allowed to proceed for 12 hours to obtain the final dispersion. The dispersion was then centrifuged, filtered, and the resulting product was washed with anhydrous ethanol to obtain the final product. Figure 19 The image shows hybrid silica microspheres with a multi-level mesoporous structure.

[0119] The hybrid silica microspheres with multi-level mesoporous structures obtained in Examples 8-10 were subjected to pore size and BET tests. The pore size distribution diagram of Example 8 is shown below. Figure 20 As shown in Table 3, the BET data is as follows.

[0120] Table 3

[0121]

[0122] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0123] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing silica microspheres, characterized in that, Includes the following steps: Using a surfactant as a structure directing agent, phenyltrimethoxysilane was hydrolyzed and condensed in an alcohol-water mixed solvent at 20℃~40℃ to obtain a polysilsesquioxane microsphere dispersion. Orthosilicate is added to the polysilsesquioxane microsphere dispersion, and the volume ratio of the orthosilicate to the phenyltrimethoxysilane is greater than or equal to 4:

1. After the reaction, silica hollow microspheres are obtained by separation. Alternatively, an orthosilicate is added to the polysilsesquioxane microsphere dispersion, wherein the volume ratio of the orthosilicate to the phenyltrimethoxysilane is less than 4:1, and after the reaction, the microspheres are obtained by separation and alcohol washing.

2. The method for preparing silica microspheres according to claim 1, characterized in that, The steps for preparing polysilsesquioxane microsphere dispersions include: placing the phenyltrimethoxysilane and the surfactant in an alcohol-water mixed solvent, first hydrolyzing them at 20℃~40℃ and pH 2.0~7.0 for 1 min~60 min, and then adjusting the pH to 9.0~11.0 and reacting for 1 h~2 h.

3. The method for preparing silica microspheres according to claim 1 or 2, characterized in that, The particle size of the polysilsesquioxane microspheres is 50 nm to 100 nm.

4. The method for preparing silica microspheres according to claim 1 or 2, characterized in that, The surfactant is selected from cationic surfactants.

5. The method for preparing silica microspheres according to claim 4, characterized in that, The surfactant is selected from at least one of CTAB, DTAB, and OTAB.

6. The method for preparing silica microspheres according to claim 1 or 2, characterized in that, The volume ratio of the phenyltrimethoxysilane to the alcohol-water mixed solvent is 1:20-1:

100.

7. The method for preparing silica microspheres according to claim 1 or 2, characterized in that, The alcohol in the alcohol-water mixed solvent is selected from methanol and / or ethanol; And / or, the volume ratio of alcohol to water in the alcohol-water mixed solvent is 2:8 to 5:

5.

8. The method for preparing silica microspheres according to claim 1, characterized in that, The orthosilicate is selected from at least one of methyl orthosilicate and ethyl orthosilicate.

9. The method for preparing silica microspheres according to claim 1, characterized in that, The step of separating the silica hollow microspheres after the reaction also includes calcining the silica hollow microspheres.

10. A silica microsphere obtained by the preparation method according to any one of claims 1 to 9.

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