Hollow spherical silicon dioxide particle and preparation method thereof

Abstract

The invention provides a preparation method of hollow spherical silicon dioxide particles. The preparation method mainly comprises the following steps: 1) preparing silicon dioxide sol with a certain concentration; 2) granulating by utilizing spray drying to obtain silicon dioxide powder; 3) performing static calcination on the powder through a roller kiln; and 4) spheroidizing the calcined powder by adopting a flame melting method to obtain the hollow spherical silicon dioxide particles. The particle size of the hollow silicon dioxide powder can be regulated and controlled by controlling the concentration of the silicon dioxide slurry, the calcining temperature and parameters in the spray drying and spheroidizing processes. The preparation method provided by the invention is simple and efficient to operate and easy for large-scale preparation.

Description

Technical Field

[0001] The invention belongs to the technical field of inorganic materials, and in particular relates to hollow spherical silicon dioxide particles and a preparation method thereof. Background Art

[0002] Hollow spherical silica is a non-toxic, odorless, and pollution-free inorganic non-metallic material with excellent insulation, corrosion resistance, and large specific surface area. It has become one of the research hotspots and can be widely used in many fields, such as drug loading, photocatalysis, electronics, energy, wastewater treatment, and macromolecular release systems. Hollow spherical silica is usually prepared by hard template or soft template method: using organic or inorganic materials such as surfactants, polymer microspheres, and calcium carbonate as template agents, silica microspheres are constructed through hydrolysis and condensation reactions of organic or inorganic silicon sources, and finally hollow spherical silica is obtained by removing the template. However, the template method for synthesizing hollow microspheres usually requires extraction, calcination, or chemical etching to remove the template, which is time-consuming and energy-consuming; and soft templates often have poor thermal stability and are easily affected by the pH of the system, ionic strength, etc., and the morphology of the synthesized hollow microspheres is also poorly controllable.

[0003] Patent CN109796019A discloses a method for preparing hollow silica nanospheres and its application. The method for preparing such hollow silica nanospheres is as follows: adding a silicon source precursor to a solution containing a carbon ball template, a catalyst, a dispersant and a surfactant, stirring and reacting for 3 to 4 hours; the dispersants used are ethanol and water; and the resulting solution is subjected to a hydrothermal reaction at 150 to 200°C. The obtained hydrothermal system is filtered, washed, dried, and the hollow silica nanospheres are obtained after removing the carbon ball template and the surfactant. However, this method is relatively complicated, time-consuming, energy-consuming, and costly.

[0004] Therefore, we propose a method for preparing hollow spherical silica particles. This technology is simple to operate and convenient for large-scale preparation; the resulting product has high sphericity, and its specific surface area and pore structure are easy to control. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a method for preparing hollow spherical silica particles. The method has simple process, high sphericity of the obtained product and is convenient for industrial production.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows: A method for preparing hollow spherical silicon dioxide particles comprises the following steps: 1) Mix silica sol and pure water and dilute to an appropriate concentration; 2) spray drying the diluted silica sol obtained in step 1) to obtain silica granulated powder; 3) statically calcining the silicon dioxide granulated powder obtained in step 2) through a roller kiln; 4) The calcined powder is spheroidized by a flame melting method to prepare hollow spherical silica particles.

[0007] Specifically, the silica sol in step 1) is one or both of silica sols prepared by physical method and chemical method. The particle size of silica in the sol in step 1) is 5-100 nm.

[0008] Furthermore, in step 1), the silica sol can be diluted with pure water to a solid content of 3%-30%, preferably 5%-25%.

[0009] Specifically, during spray drying in step 2), pressure or centrifugal spray drying is performed at an inlet temperature of 150°C-240°C (preferably 190°C-210°C), an outlet temperature of 90°C-130°C (preferably 100°C-110°C), and a rotation speed of 15000rpm-30000rpm (preferably 18000rpm-22000rpm). During pressure spray drying, the compressed air pressure is 0.1-0.8Mpa, preferably 0.2-0.6Mpa. The median particle size of the spherical silica obtained by spray drying is adjustable within the range of 5-60μm.

[0010] Specifically, in step 3), calcination is suitably performed at 100°C-750°C for 2-4h.

[0011] Furthermore, in step 4) of flame spheroidization, the feed amount of silicon dioxide is 2-150 g / min, and the temperature of flame spheroidization is formed by the mixed combustion of combustible gas and combustion-supporting gas, and the ratio of the two is preferably 1:2-3. The combustible gas is preferably at least one of methane, acetylene, etc., and the combustion-supporting gas is preferably oxygen. The flow rate of the combustible gas is 5-15 m / s. 3 / h, the combustion gas flow rate is 10-45m 3 / h.

[0012] The present invention also provides hollow spherical silicon dioxide particles prepared by the above preparation method.

[0013] In the present invention, the median particle size of the hollow spherical silica particles obtained after spheroidization can be adjusted within the range of 5-60 μm, thereby realizing the preparation of multi-scale spherical silica. The specific surface area of ​​the obtained hollow spherical silica particles can reach 2-50 m 2 / g, pore size can reach 8-55nm, and apparent density can reach 0.3-0.8g / cm 3 .

[0014] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: 1) The hollow silica provided by the present invention has good sphericity and large specific surface area; 2) By regulating the solid content of the solution, nozzle speed, calcination and other key influencing factors during the spray drying process, a corresponding relationship between the particle size and structure regulation of spherical silica was established, and the stable regulation of the particle size of the hollow silica in the present invention was achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1-4 The SEM photos of four different hollow spherical silica prepared in Examples 1, 2, 3, and 4 are shown respectively; it can be seen from the figure that the prepared hollow spherical silica all have good sphericity; Figure 5-8 The particle size distribution diagrams of four different hollow spherical silica prepared in Examples 1, 2, 3 and 4 are shown respectively. DETAILED DESCRIPTION

[0016] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0017] In the following examples, unless otherwise specified, the raw materials used are common commercial products that can be directly purchased in the art.

[0018] In an embodiment, the temperature of the flame spheroidization is formed by the mixed combustion of a combustible gas and a combustion-supporting gas, and the mixing ratio of the combustible gas and the combustion-supporting gas is preferably 1:2-3. The combustible gas is preferably methane, and the combustion-supporting gas is preferably oxygen.

[0019] The silica sol is one or both of silica prepared by physical method and chemical method. Specifically, the organic base tetramethylammonium hydroxide, water and silicon powder are added into a three-necked flask at a mass ratio of 1:20:3, and reacted under stirring conditions, the water bath heating temperature is 85°C, and the reaction time is 8h. After the reaction, the unreacted silicon powder and impurities are removed by vacuum filtration to obtain the desired silica sol.

[0020] Example 1 A method for preparing hollow spherical silicon dioxide particles comprises the following steps: 1) Take 1L of silica sol, mix and stir it evenly with pure water, and dilute its concentration to 15% (i.e., solid content is 15%, referring to mass percentage, the same below), and the particle size of silica in the sol is 10nm; 2) centrifugally spray-dry the diluted silica sol in step 1) to obtain silica powder. The inlet temperature is set at 200°C, the outlet temperature is controlled at 110°C, and the nozzle speed of the atomizer is set at 25000rpm; 3) The obtained silica powder was calcined at 500°C for 2 h in a roller kiln and then spheroidized in a spheroidizing furnace using a flame melting method. The silica feed rate was 5 g / min and the methane flow rate was 8 m 3 / h, oxygen flow rate is 16.8m 3 / h. The median particle size was 35.7 μm (see Figure 5 ), specific surface area 7m 2 / g, apparent density 0.57g / cm 3 , hollow spherical silica particles with a pore size of 8.4nm.

[0021] Example 2 A method for preparing hollow spherical silicon dioxide particles comprises the following steps: 1) Take 1L of silica sol, mix and stir it evenly with pure water, and dilute its concentration to 15%. The particle size of silica in the sol is 10nm; 2) centrifugally spray-dry the diluted silica sol in step 1) to obtain silica powder. The inlet temperature is set at 200°C, the outlet temperature is controlled at 110°C, and the nozzle speed of the atomizer is set at 20,000 rpm; 3) After calcining the obtained silica powder at 500°C for 2h, the powder was spheroidized in a spheroidizing furnace by flame melting method. The silica feed rate was 5g / min and the methane flow rate was 8m 3 / h, oxygen flow rate is 16.8m 3 / h. The median particle size was 50.3 μm (see Figure 6 ), specific surface area 9m 2 / g, apparent density 0.72g / cm 3 , hollow spherical silica particles with a pore size of 12nm.

[0022] Example 3 A method for preparing hollow spherical silicon dioxide particles comprises the following steps: 1) Take 1L of silica sol, mix and stir it evenly with pure water, and dilute its concentration to 10%. The particle size of silica in the sol is 10nm; 2) Pressure spray drying the diluted silica sol in step 1) to obtain silica powder. The inlet temperature is set to 200°C, the outlet temperature is controlled at 110°C, and the pressure of the atomizer is set to 0.2Mpa; 3) After calcining the obtained silica powder at 500°C for 2h, the powder was spheroidized in a spheroidizing furnace by flame melting method. The silica feed rate was 5g / min and the methane flow rate was 10m 3 / h, oxygen flow rate is 20.1m 3 / h. The median particle size was 11.5 μm (see Figure 7 ), specific surface area 12.2m 2 / g, apparent density 0.37g / cm 3 , hollow spherical silica particles with a pore size of 53nm.

[0023] Example 4 A method for preparing hollow spherical silicon dioxide particles comprises the following steps: 1) Take 1L of silica sol, mix and stir it evenly with pure water, and dilute its concentration to 25%. The particle size of silica in the sol is 10nm; 2) centrifugally spray-dry the diluted silica sol in step 1) to obtain silica powder. The inlet temperature is set at 200°C, the outlet temperature is controlled at 110°C, and the nozzle speed of the atomizer is set at 20,000 rpm; 3) After calcining the obtained silica powder at 500°C for 2h, the powder was spheroidized in a spheroidizing furnace by flame melting method. The silica feed rate was 5g / min and the methane flow rate was 8m 3 / h, oxygen flow rate is 16.8m 3 / h. The median particle size was 43.1 μm (see Figure 8 ), specific surface area 11.3m 2 / g, apparent density 0.68g / cm 3 , hollow spherical silica particles with a pore size of 11nm.

[0024] Example 5 A method for preparing hollow spherical silicon dioxide particles comprises the following steps: 1) Take 1L of silica sol, mix and stir it evenly with pure water, and dilute its concentration to 10%. The particle size of silica in the sol is 10nm; 2) The diluted silica sol in step 1) is pressure spray dried to obtain silica powder. The inlet temperature is set to 220°C, the outlet temperature is controlled at 110°C, and the pressure of the atomizer is set to 0.6Mpa; 3) After calcining the obtained silica powder at 500°C for 2h, the powder was spheroidized in a spheroidizing furnace by flame melting method. The silica feed rate was 5g / min and the methane flow rate was 10m 3 / h, oxygen flow rate is 20.1m 3 / h. The median particle size was 6 μm and the specific surface area was 15.8 m 2 / g, apparent density 0.32g / cm 3 , hollow spherical silica particles with a pore size of 13nm.

[0025] Example 6 A method for preparing hollow spherical silicon dioxide particles comprises the following steps: 1) Take 1L of silica sol, mix and stir it evenly with pure water, and dilute its concentration to 15%. The particle size of silica in the sol is 10nm; 2) The diluted silica sol in step 1) is pressure spray dried to obtain silica powder. The inlet temperature is set to 220°C, the outlet temperature is controlled at 110°C, and the pressure of the atomizer is set to 0.6Mpa; 3) After calcining the obtained silica powder at 105°C for 2h, it was spheroidized in a spheroidizing furnace by flame melting method, with the silica feed rate of 5g / min and the methane flow rate of 10m 3 / h, oxygen flow rate is 20.1m 3 / h. The median particle size was 14 μm and the specific surface area was 14.9 m 2 / g, apparent density 0.41g / cm 3 , hollow spherical silica particles with a pore size of 40nm.

[0026] Figure 1-4 SEM photos of four different hollow spherical silica prepared in Examples 1, 2, 3 and 4 are given respectively; it can be seen from the figures that the prepared hollow spherical silica all have good sphericity.

[0027] In summary, the present invention can achieve the regulation of the particle size of hollow silica powder by controlling the concentration of silica slurry, calcination temperature, and parameters in the spray drying and spheroidization processes, and the preparation method is simple to operate, efficient, and easy to scale up production.

[0028] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes that deviate from the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing hollow spherical silicon dioxide particles, characterized in that: The following steps are involved: 1) Mix silica sol with pure water and dilute to an appropriate concentration; 2) spray drying the diluted silica sol obtained in step 1) to obtain silica granulated powder; 3) statically calcining the silicon dioxide granulated powder obtained in step 2) through a roller kiln; 4) The calcined powder is spheroidized by a flame melting method to prepare hollow spherical silica particles.

2. The method for preparing hollow spherical silica particles according to claim 1, characterized in that: Step 1) The silica sol is one or both of silica sols prepared by physical method and chemical method.

3. The method for preparing hollow spherical silicon dioxide particles according to claim 1, characterized in that: In step 1), the silica sol is diluted with pure water to a solid content of 3%-30%.

4. The method for preparing hollow spherical silica particles according to claim 1, characterized in that: Step 1) The particle size of silicon dioxide in the sol is 5-100 nm.

5. The method for preparing hollow spherical silica particles according to claim 1, characterized in that: During the spray drying in step 2), pressure or centrifugal spray drying is performed at an inlet temperature of 150°C-240°C, an outlet temperature of 90°C-130°C, and a rotation speed of 15000rpm-30000rpm.

6. The method for preparing hollow spherical silicon dioxide particles according to claim 1, characterized in that: The median particle size of the spherical silicon dioxide obtained by spray drying in step 2) can be adjusted within the range of 5-60 μm.

7. The method for preparing hollow spherical silica particles according to claim 1, characterized in that: In step 3), calcination is performed at 100°C-750°C for 2-4 hours.

8. The method for preparing hollow spherical silica particles according to claim 1, characterized in that: Step 4) During the flame spheroidization process, the feed rate of silicon dioxide is 2-150 g / min, and the temperature of the flame spheroidization is formed by the mixed combustion of the combustible gas and the combustion-supporting gas, wherein the combustible gas is at least one of methane and acetylene, and the combustion-supporting gas is oxygen; the flow rate of the combustible gas is 5-15 m / min. 3 / h, the combustion gas flow rate is 10-45m 3 / h.

9. Hollow spherical silicon dioxide particles prepared by the preparation method according to any one of claims 1 to 8.

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