A method for preparing silica microspheres from organosilanes

Abstract

The present invention discloses a method for preparing silica microspheres from organosilanes. Ammonia water is added to a mixed lower alcohol to form a hydrolysis solution containing an alkaline catalyst, and then a mixed lower alcohol solution of organosilanes is added to the hydrolysis solution at a certain rate. A silica sol is formed by reacting at a certain temperature. Finally, through aging, negative pressure evaporation, washing, filtration, drying, and calcination, ultra-pure silica microspheres can be obtained. This method uses organosilanes as the silicon source. The silica microspheres prepared by the sol-gel method have good sphericity, low metal impurities, and narrow particle size distribution. By changing the proportion of components in the mixed lower alcohol, the particle size range can be controlled, and the adhesion between silica microspheres can be reduced. The lower alcohol and ammonia water solution in this process can be recovered by evaporation and condensation. The operation is simple, providing a reference for large-scale industrial production.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of silica microspheres, and specifically relates to a method for preparing silica microspheres from organosilane. Background Art

[0002] Due to its high mechanical strength, non-toxicity, excellent specific surface area and other advantages, silica microspheres have extremely high application value in the fields of catalysis, sensing, biomedicine, etc. And due to the bridging effect of hydroxyl groups on the surface, it has also attracted the attention of researchers in the fields of modification and compounding in the field of material preparation. At present, there are many methods for preparing silica microspheres, mainly including chemical deposition method, microemulsion method and sol-gel method. Among them, the chemical deposition method and the microemulsion method have high equipment requirements, high energy consumption, and a large amount of organic matter used cannot be recycled, which will lead to too high costs and is extremely easy to cause environmental pollution.

[0003] The sol-gel method uses low-carbon alcohol as a solvent, and organosilane hydrolyzes and condenses under the catalysis of ammonia water to form silica microspheres. Among them, organosilane is used as the silicon source, and ammonia water and low-carbon alcohol can be recycled by evaporation or filtration. This method not only prepares silica microspheres with good monodispersity and high sphericity, but also has a simple process, low equipment requirements, and most of the raw materials used can be recycled. However, due to its many influencing factors and large particle size distribution, it is difficult in industrial mass production. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing silica microspheres from organosilane in view of the difficulties in mass production of the prior art. This method uses organosilane as the silicon source, ammonia water as the catalyst, and low-carbon alcohol mixed in different proportions as the solvent. The prepared silica microspheres have good sphericity and narrow particle size distribution, and the low-carbon alcohol and ammonia water solution can be recovered by evaporation and condensation. The operation is simple, which provides a strong reference for large-scale industrial production.

[0005] To solve the above technical problems, the present invention provides a method for preparing silica microspheres from organosilane, which includes the following steps:

[0006] (1) Add 2-4 parts by mass of ammonia water and 6-10 parts by mass of mixed low-carbon alcohol to a reaction vessel, and stir and react at a rate of 120-150 r / min for 1-2 h to form a hydrolysis solution containing an alkaline catalyst;

[0007] (2) Mix 2-4 parts by mass of organosilane with 6-10 parts by mass of mixed low-carbon alcohol to form a silane-low-carbon alcohol solution, and add the silane-low-carbon alcohol solution to the reaction vessel containing the alkaline catalyst hydrolysis solution at a flow rate of 100-400 mL / min, and then stir and react at a rate of 120-150 r / min for 4-6 h to form a silica sol solution;

[0008] (3) After aging the silica sol formed in step (2) for 6 - 8 h, evaporate and remove the mixed lower - carbon alcohols and ammonia water in the silica sol under a negative pressure of 60 - 80°C and less than 0.1 MPa to obtain silica powder;

[0009] (4) Wash the silica powder obtained in step (3) 3 times through ethanol - pure water circulation, then put it into an oven and dry it at 100 - 120°C for 4 - 6 h, and then calcine it at 600 - 650°C for 6 - 8 h to obtain ultra - pure silica microspheres;

[0010] The mixed lower - carbon alcohols described in step (1) and step (2) are composed of methanol, ethanol and isopropanol, and the mass fraction of methanol is ≥80%.

[0011] Specifically, the organosilane is tetramethoxysilane.

[0012] In the present invention, organosilane is used as the silicon source, ammonia water is used as the catalyst, and different - proportion mixed lower - carbon alcohols are used as the solvent. Different - sized silica microspheres are prepared through the differences in physical properties of lower - carbon alcohols themselves, such as the flexibility of atomic arrangement, surface tension, dielectric constant, etc. The prepared silica microspheres have good sphericity and narrow particle - size distribution. By changing the proportion of components in the mixed lower - carbon alcohols, the particle - size range can be controlled, and the adhesion between silica microspheres can be reduced. The lower - carbon alcohols and ammonia - water solution in this process can be recovered by evaporation and condensation, and the operation is simple, providing a powerful reference for future large - scale industrial production. Description of the Drawings

[0013] Figure 1 It is the scanning electron microscope picture of the 350 - nm silica microspheres synthesized in Example 1.

[0014] Figure 2 It is the scanning electron microscope picture of the 500 - nm silica microspheres synthesized in Example 2.

[0015] Figure 3 It is the scanning electron microscope picture of the 700 - nm silica microspheres synthesized in Example 3.

[0016] Figure 4 It is the scanning electron microscope picture of the 950 - nm silica microspheres synthesized in Example 4.

[0017] Figure 5 It is the scanning electron microscope picture of the 250 - nm silica microspheres synthesized in the comparative example. Detailed Embodiments

[0018] The following examples can further clearly understand the present invention, but they do not limit the present invention.

[0019] Example 1

[0020] A method for preparing silica microspheres from organosilane, comprising the following steps:

[0021] (1) Add 2 g of ammonia water and 10 g of mixed lower alcohols to a reaction vessel, and stir and react at a rate of 150 r / min for 1 h to form a hydrolysis solution containing an alkaline catalyst;

[0022] (2) Mix 2 g of organosilane with 10 g of mixed lower alcohols to form a silane-lower alcohol solution, and add the silane-lower alcohol solution to the reaction vessel containing the hydrolysis solution of the alkaline catalyst at a flow rate of 400 mL / min. Then stir and react at a rate of 150 r / min for 4 h to form a silica sol solution;

[0023] (3) After aging the silica sol solution formed in step (2) for 6 h, evaporate and remove the mixed lower alcohols and ammonia water in the silica sol solution under a negative pressure of 60 °C and less than 0.1 MPa to obtain silica powder;

[0024] (4) Wash the silica powder in step (3) 3 times through an ethanol-pure water cycle, then place it in an oven and dry it at 120 °C for 4 h, and then calcine it at 650 °C for 6 h to obtain ultra-pure silica microspheres;

[0025] The mixed lower alcohols described in step (1) and step (2) are composed of 90% by mass of methanol, 7% by mass of ethanol, and 3% by mass of isopropanol.

[0026] Results of SEM scanning electron microscopy Figure 1 It can be seen that the synthesized silica microspheres have uniform particle sizes, with an average particle size of 350 nm, a distribution standard deviation of 2.64%, and slight adhesion.

[0027] Example 2

[0028] A method for preparing silica microspheres from organosilane, comprising the following steps:

[0029] (1) Add 3 g of ammonia water and 8 g of mixed lower alcohols to a reaction vessel, and stir and react at a rate of 130 r / min for 2 h to form a hydrolysis solution containing an alkaline catalyst;

[0030] (2) Mix 3 g of organosilane with 8 g of mixed lower alcohols to form a silane-lower alcohol solution, and add the silane-lower alcohol solution to the reaction vessel containing the hydrolysis solution of the alkaline catalyst at a flow rate of 100 mL / min. Then stir and react at a rate of 130 r / min for 5 h to form a silica sol solution;

[0031] (3) After aging the silica sol formed in step (2) for 7 h, evaporate the mixed lower carbon alcohols and ammonia water in the silica sol under a negative pressure of 60 °C and less than 0.1 MPa to obtain silica powder;

[0032] (4) Wash the silica powder in step (3) three times by ethanol-pure water circulation, then put it into an oven and dry it at 110 °C for 5 h, and then calcine it at 600 °C for 8 h to obtain ultra-pure silica microspheres;

[0033] The mixed lower carbon alcohols described in step (1) and step (2) are composed of 85% by mass of methanol, 10% by mass of ethanol and 5% by mass of isopropanol.

[0034] The results of SEM scanning electron microscopy Figure 2 It can be seen that the synthesized silica microspheres have uniform particle sizes, with an average particle size of 500 nm, a distribution standard deviation of 3.28%, and slight adhesion.

[0035] Example 3

[0036] A method for preparing silica microspheres from organosilane, comprising the following steps:

[0037] (1) Add 3 g of ammonia water and 6 g of mixed lower carbon alcohols to a reaction vessel, and stir and react at a rate of 140 r / min for 2 h to form a hydrolysis solution containing an alkaline catalyst;

[0038] (2) Mix 3 g of organosilane with 6 g of mixed lower carbon alcohols to form a silane-lower carbon alcohol solution, and add the silane-lower carbon alcohol solution to the reaction vessel containing the hydrolysis solution of the alkaline catalyst at a flow rate of 150 mL / min, and then stir and react at a rate of 120 r / min for 6 h to form a silica sol;

[0039] (3) After aging the silica sol formed in step (2) for 8 h, evaporate the mixed lower carbon alcohols and ammonia water in the silica sol under a negative pressure of 80 °C and less than 0.1 MPa to obtain silica powder;

[0040] (4) Wash the silica powder in step (3) three times by ethanol-pure water circulation, then put it into an oven and dry it at 120 °C for 6 h, and then calcine it at 650 °C for 7 h to obtain ultra-pure silica microspheres;

[0041] The mixed lower carbon alcohols described in step (1) and step (2) are composed of 80% by mass of methanol, 10% by mass of ethanol and 10% by mass of isopropanol.

[0042] The results of SEM scanning electron microscopy Figure 3It can be seen that the synthesized silica microspheres have uniform particle sizes, with an average particle size of 700 nm, a distribution standard deviation of 4.22%, and slight adhesion occurs.

[0043] Example 4

[0044] A method for preparing silica microspheres from organosilane, comprising the following steps:

[0045] (1) Add 4 g of ammonia water and 7 g of mixed lower alcohols to a reaction vessel, and stir and react at a rate of 120 r / min for 2 h to form a hydrolysis solution containing an alkaline catalyst;

[0046] (2) Mix 4 g of organosilane with 7 g of mixed lower alcohols to form a silane-lower alcohol solution, and add the silane-lower alcohol solution to the reaction vessel containing the hydrolysis solution of the alkaline catalyst at a flow rate of 300 mL / min. Then, stir and react at a rate of 120 r / min for 6 h to form a silica sol solution;

[0047] (3) After aging the silica sol solution formed in step (2) for 8 h, evaporate and remove the mixed lower alcohols and ammonia water in the silica sol solution under a negative pressure of 80 °C and less than 0.1 MPa to obtain silica powder;

[0048] (4) Wash the silica powder in step (3) 3 times through ethanol-pure water circulation, then place it in an oven and dry it at 100 °C for 6 h, and then calcine it at 650 °C for 8 h to obtain ultra-pure silica microspheres;

[0049] The mixed lower alcohols described in step (1) and step (2) are composed of 80% by mass of methanol, 5% by mass of ethanol, and 15% by mass of isopropanol.

[0050] The results of SEM scanning electron microscopy Figure 4 It can be seen that the synthesized silica microspheres have uniform particle sizes, with an average particle size of 950 nm, a distribution standard deviation of 2.33%, and slight adhesion occurs.

[0051] Comparative example:

[0052] A method for preparing silica microspheres from organosilane, comprising the following steps:

[0053] (1) Add 2 g of ammonia water and 10 g of methanol to a reaction vessel, and stir and react at a rate of 150 r / min for 1 h to form a hydrolysis solution containing an alkaline catalyst;

[0054] (2) Mix 2 g of organosilane with 10 g of methanol to form a silane-methanol solution, and add the silane-methanol solution to a reaction vessel containing an alkaline catalyst hydrolysis solution at a flow rate of 400 mL / min. Then, stir and react at a rate of 150 r / min for 4 h to form a silica sol solution;

[0055] (3) After aging the silica sol solution formed in step (2) for 6 h, evaporate and remove the mixed lower alcohols and ammonia water in the silica sol solution under a negative pressure of 60 °C and less than 0.1 MPa to obtain silica powder;

[0056] (4) Wash the silica powder obtained in step (3) 3 times through ethanol-pure water circulation, then place it in an oven and dry it at 120 °C for 5 h, and then calcine it at 650 °C for 8 h to obtain ultrapure silica microspheres.

[0057] According to the SEM scanning electron microscope results Figure 5 It can be seen that the synthesized silica microspheres have uniform particle sizes, with an average particle size of 250 nm and a distribution standard deviation of 5.83%, and serious adhesion occurs.

[0058] From the above examples and comparative examples, the conclusion can be drawn that the silica microspheres prepared by simply using methanol as a solvent have smaller particle sizes and serious adhesion occurs. Using different ratios of mixed lower alcohols with the same mass can increase the particle size of the silica microspheres and reduce the adhesion situation.

[0059] The above are only the preferred embodiments of the present invention and do not impose any formal restrictions on the present invention; any person skilled in the art can, without departing from the scope of the technical solution of the present invention, make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above, or modify it into equivalent embodiments with equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing silica microspheres from organosilanes, characterized in that, It includes the following steps: (1) Add 2-4 parts by mass of ammonia water and 6-10 parts by mass of mixed lower alcohols into a reaction vessel, and stir at a rate of 120-150 r / min for 1-2 h to form a hydrolysis solution containing an alkaline catalyst; (2) Mix 2-4 parts by mass of organosilane with 6-10 parts by mass of mixed lower alcohols to form a silane-lower alcohol solution, and add the silane-lower alcohol solution into the reaction vessel containing the hydrolysis solution of the alkaline catalyst at a flow rate of 100-400 mL / min, and then stir and react at a rate of 120-150 r / min for 4-6 h to form a silica sol solution; (3) After aging the silica sol solution formed in step (2) for 6-8 h, evaporate and remove the mixed lower alcohols and ammonia water in the silica sol solution under a negative pressure of 60-80 °C and less than 0.1 MPa to obtain silica powder; (4) Wash the silica powder in step (3) 3 times through ethanol-pure water circulation, then put it into an oven and dry it at 100-120 °C for 4-6 h, and then calcine it at 600-650 °C for 6-8 h to obtain ultra-pure silica microspheres; The mixed lower alcohols described in step (1) and step (2) are composed of methanol, ethanol and isopropanol, and the mass fraction of methanol is ≥80%.

2. The method for preparing silica microspheres from organosilanes according to claim 1, characterized in that: The organosilane is tetramethoxysilane.

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