Preparation method of hollow silicon dioxide spherical particles

Abstract

The invention provides a preparation method of hollow silicon dioxide spherical particles, and belongs to the field of preparation of silicon dioxide. The preparation method comprises the following steps: providing a mixed solution of carbohydrate and calcium carbonate; granulating the mixed solution to obtain spherical particles; the preparation method comprises the following steps: mixing a wetting dispersant with silica sol, then adding boron nitride nanotubes, and uniformly stirring and dispersing to obtain a boron nitride nanotube-silica sol mixed solution; putting the spherical particles into a coating machine, spraying the boron nitride nanotube-silica sol mixed solution, and forming a boron nitride nanotube and silica mixed coating layer on the surfaces of the spherical particles to obtain coated spherical particles; and soaking the obtained coated spherical particles in an acid solution, carrying out solid-liquid separation to obtain a solid phase, and calcining the solid phase to obtain the hollow silicon dioxide spherical particles. By utilizing the excellent mechanical property and heat resistance of the boron nitride nanotubes, the prepared large-particle-size hollow spherical silicon dioxide particles cannot be broken due to large particle size, hollow structure and high-temperature calcination.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of silica, and in particular to a method for preparing hollow silica spherical particles. Background Art

[0002] Silica hollow microspheres are a new type of inorganic material with a size ranging from nanometers to micrometers. They have a hollow cavity, a large specific surface area, a narrow particle size distribution range, good dispersibility, good stability, a high melting point, and special mechanical, optical, electrical and other physical properties. The hollow part can also accommodate a large number of guest molecules. Due to their unique superior properties, they are often used as catalyst carriers, shape-selective absorbents, light fillers, and controlled delivery and release systems for drugs, pigments, cosmetics, etc.

[0003] Chinese Patent CN 114620737 A discloses a hollow silica and its preparation method and application. Elemental silicon powder is used to prepare hollow silica with a particle size of 20 nm - 1 μm through the interfacial diffusion, preliminary oxidation and hollowing of silicon atoms and hydroxyl groups in a hydrothermal reaction. Chinese Patent CN 118026191 A discloses a hollow silica microsphere and its preparation method. The preparation method includes mixing a template sphere solution with a basic catalyst to obtain solution A, separately taking a template sphere solution and a silicon source to obtain solution B, heating solution A and solution B, respectively pumping them into two inlet pipelines of a tee through metering pumps, making them collide and mix at the convergence of the tee, and flowing out through the outlet pipeline. After aging, ultrafine and gradient calcination treatment of the outflow product, hollow silica microspheres with an average particle size of 0.3 μm - 5 μm are obtained.

[0004] In the prior art, the prepared hollow silica microspheres have a small particle size, and there is no preparation method for large-particle-size hollow silica spheres. At present, there is an urgent need for a preparation method for large-particle-size hollow silica spheres with a simple synthesis process. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a method for preparing hollow silica spherical particles. By using the excellent mechanical properties and heat resistance of boron nitride nanotubes, the prepared large-particle-size hollow spherical silica particles will not break due to their large particle size, hollow structure and high-temperature calcination.

[0006] The object of the present invention is to provide a method for preparing hollow silica spherical particles, including the following steps:

[0007] Provide a mixed solution of a saccharide compound and calcium carbonate; granulate the mixed solution to obtain spherical particles;

[0008] Mix a wetting dispersant with silica sol, then add boron nitride nanotubes, and stir and disperse evenly to obtain a boron nitride nanotube-silica sol mixed solution;

[0009] Put the spherical particles into a coating machine, and spray the boron nitride nanotube-silica sol mixed solution into it to form a mixed coating layer of boron nitride nanotubes and silica on the surface of the spherical particles, thereby obtaining coated spherical particles;

[0010] Immerse the obtained coated spherical particles in an acid solution, perform solid-liquid separation to obtain the solid phase, and calcine the solid phase to obtain the hollow silica spherical particles.

[0011] In some embodiments of the present invention, the diameter of the spherical particles is 50 μm - 150 μm;

[0012] The diameter of the coated spherical particles is 100 μm - 200 μm;

[0013] The diameter of the hollow silica spherical particles is 100 μm - 200 μm.

[0014] In some embodiments of the present invention, centrifugal atomization drying granulation machine is selected for granulation. Among them, the rotation speed of the atomization disk is 2000 rpm - 3000 rpm, the inlet air temperature is 300 °C - 360 °C, and the outlet air temperature is 110 °C - 120 °C.

[0015] In some embodiments of the present invention, the concentration of the saccharide compound in the mixed solution is 10 - 20%, and the concentration of calcium carbonate in the mixed solution is 20 - 30%.

[0016] In some embodiments of the present invention, the saccharide compound is selected from one or more of glucose, sucrose, fructose, and water-soluble starch.

[0017] In some embodiments of the present invention, the boron nitride nanotubes are hexagonal boron nitride nanotubes with an average diameter of 50 - 70 nm and an average length of 10 - 30 μm.

[0018] In some embodiments of the present invention, the wetting dispersant is selected from polyethyleneimine; the present invention utilizes the wetting and dispersing of boron nitride nanotubes.

[0019] The concentration of the wetting dispersant in the boron nitride nanotube-silica sol mixed solution is 1 - 3%, the concentration of boron nitride nanotubes is 0.5 - 1%; the concentration of silica sol is 96 - 98.5%.

[0020] In some embodiments of the present invention, the coating machine is a fluidized bed coating machine, the inlet air temperature is 100 °C - 130 °C, the material temperature is 70 °C - 100 °C, the coating liquid feeding speed is 10 - 20 g / min, and the spray atomization pressure is 0.1 Mpa - 0.2 Mpa.

[0021] In some embodiments of the present invention, the acid is selected from one or more of hydrochloric acid, phosphoric acid, sulfuric acid, and nitric acid, and the soaking time is 8 - 24 h.

[0022] In some embodiments of the present invention, the calcination conditions are: calcination at 600 °C - 800 °C for 3 hours - 6 hours.

[0023] The above technical solutions of the present invention have the following advantages compared with the prior art:

[0024] The object of the present invention is to prepare hollow spherical silica particles with a large particle size, with a particle size of 100 μm - 200 μm. The present invention uses a saccharide compound and calcium carbonate to prepare spherical particles, and then coats a layer of silica and boron nitride nanotubes. After soaking in an acid solution and high-temperature calcination, the calcium carbonate and saccharide compound are removed, thereby forming a hollow structure in the silica sphere.

[0025] The housing contains boron nitride nanotubes. The present invention uses boron nitride nanotubes with the following characteristics: the average diameter of the boron nitride nanotubes is 60 nm, the average length is 10 - 30 μm, the tensile strength is 33 GPa, and it is still stable at 900 °C. The excellent mechanical properties and heat resistance of the boron nitride nanotubes enable the prepared hollow spherical silica particles with a large particle size not to break due to the large particle size, hollow structure, and high-temperature calcination. Specific Embodiments

[0026] The following is a further description of the present invention with reference to specific embodiments, so that those skilled in the art can better understand the present invention and be able to implement it, but the specific embodiments given are not intended to limit the present invention.

[0027] Example 1

[0028] This example provides a method for preparing hollow silica spherical particles, and the specific steps are as follows:

[0029] (1) Add 1.0 kg of sucrose to 7.0 kg of water and stir until completely dissolved, then add 2.0 kg of calcium carbonate to obtain a mixed solution.

[0030] (2) Pump the mixed solution in step (1) into a centrifugal atomization drying granulator for granulation. The rotation speed of the atomization disk is 3000 rpm, the inlet air temperature is 360 °C, and the outlet air temperature is 120 °C. The prepared spherical particles have a particle size of 50 μm - 90 μm.

[0031] (3) Add 0.1 kg of polyethyleneimine to 9.85 kg of silica sol, and add 0.05 kg of hexagonal boron nitride nanotubes with an average diameter of 60 nm and an average length of 20 μm, and stir to disperse evenly to obtain a boron nitride nanotube - silica sol mixed solution as a coating liquid.

[0032] (4) Take 1.0 kg of the spherical particles from step (2) and put them into the material bin of the fluidized bed coater. Set the inlet air temperature to 100 °C and the material temperature to 70 °C. Spray the coating solution from step (3) using the side spray process to coat the spherical particles. The stirring speed of the coating solution is 200 rpm, the feeding speed of the coating solution through the diaphragm pump is 10 g / min, the atomization pressure is 0.1 Mpa, the coating time is 2 h, and the size of the coated spherical particles is 100 μm - 120 μm.

[0033] (5) Immerse the coated spherical particles in a hydrochloric acid solution with a pH value of 1.5 for 8 h, filter and wash with water until the pH of the filtrate is 5.6, and then put them into an oven at 105 °C for drying for 3 hours.

[0034] (6) Calcinate the spherical particles from step (5) at 600 °C for 6 hours to obtain hollow silica spherical particles with a diameter of 100 μm - 120 μm.

[0035] Example 2

[0036] This example provides a method for preparing hollow silica spherical particles, and the specific steps are as follows:

[0037] (1) Add 1.0 kg of glucose to 7.0 kg of water and stir until completely dissolved, then add 2.0 kg of calcium carbonate to obtain a mixed solution.

[0038] (2) Pump the mixed solution from step (1) into a centrifugal atomization drying granulator for granulation. The rotation speed of the atomization disk is 3000 rpm, the inlet air temperature is 360 °C, and the outlet air temperature is 120 °C. The obtained spherical particles have a particle size of 50 μm - 95 μm.

[0039] (3) Add 0.1 kg of polyethyleneimine to 9.85 kg of silica sol, and add 0.05 kg of hexagonal boron nitride nanotubes with an average diameter of 60 nm and an average length of 20 μm, and stir and disperse evenly to obtain a boron nitride nanotube - silica sol mixed solution as the coating solution.

[0040] (4) Take 1.0 kg of the spherical particles from step (2) and put them into the material bin of the fluidized bed coater. Set the inlet air temperature to 100 °C and the material temperature to 70 °C. Spray the coating solution from step (3) using the side spray process to coat the spherical particles. The stirring speed of the coating solution is 200 rpm, the feeding speed of the coating solution through the diaphragm pump is 10 g / min, the atomization pressure is 0.1 Mpa, the coating time is 2 h, and the size of the coated spherical particles is 100 μm - 130 μm.

[0041] (5) Immerse the coated spherical particles in a hydrochloric acid solution with a pH value of 1.5 for 8 h, filter and wash with water until the pH of the filtrate is 6.2, and then put them into an oven at 105 °C for drying for 4 hours.

[0042] (6) Calcinate the spherical particles obtained in step (5) at 600 °C for 6 hours to obtain hollow silica spherical particles with a diameter of 100 μm - 130 μm.

[0043] Example 3

[0044] This example provides a method for preparing hollow silica spherical particles, and the specific steps are as follows:

[0045] (1) Add 1.0 kg of water-soluble starch to 7.0 kg of water, stir and dissolve completely, and then add 2.0 kg of calcium carbonate to obtain a mixed solution.

[0046] (2) Pump the mixed solution obtained in step (1) into a centrifugal atomization drying granulator for granulation. The rotation speed of the atomization disk is 3000 rpm, the inlet air temperature is 360 °C, and the outlet air temperature is 120 °C. Spherical particles with a particle size of 50 μm - 90 μm are obtained.

[0047] (3) Add 0.1 kg of polyethyleneimine to 9.85 kg of silica sol, and add 0.05 kg of hexagonal boron nitride nanotubes with an average diameter of 60 nm and an average length of 20 μm, and stir to disperse evenly to obtain a boron nitride nanotube - silica sol mixed solution as a coating solution.

[0048] (4) Take 1.0 kg of the spherical particles obtained in step (2) and put them into the material bin of a fluidized bed coater. Set the inlet air temperature to 100 °C and the material temperature to 70 °C. Spray the coating solution obtained in step (3) using the side spray process to coat the spherical particles. The stirring speed of the coating solution is 200 rpm, the feeding speed of the coating solution through the diaphragm pump is 10 g / min, the atomization pressure is 0.1 Mpa, the coating time is 2 h, and the particle size after coating is 100 μm - 120 μm.

[0049] (5) Immerse the coated spherical particles in a hydrochloric acid solution with a pH value of 1.5 for 8 h, filter and wash with water until the pH of the filtrate is 5.8, and then put them into an oven at 105 °C for drying for 4 hours.

[0050] (6) Calcinate the spherical particles obtained in step (5) at 600 °C for 6 hours to obtain hollow silica spherical particles with a diameter of 100 μm - 120 μm.

[0051] Example 4

[0052] This example provides a method for preparing hollow silica spherical particles, and the specific steps are as follows:

[0053] (1) Add 1.5 kg of sucrose to 6.0 kg of water, stir and dissolve completely, and then add 2.5 kg of calcium carbonate to obtain a mixed solution.

[0054] (2) Pump the mixed solution from step (1) into a centrifugal atomization drying granulator for granulation. The rotation speed of the atomization disk is 3000 rpm, the inlet air temperature is 320 °C, and the outlet air temperature is 112 °C. Spherical particles with a particle size of 60 μm - 100 μm are obtained.

[0055] (3) Add 0.2 kg of polyethyleneimine to 9.73 kg of silica sol, and add 0.07 kg of hexagonal boron nitride nanotubes with an average diameter of 60 nm and an average length of 20 μm. Stir and disperse evenly to obtain a boron nitride nanotube - silica sol mixed solution as the coating liquid.

[0056] (4) Take 1.0 kg of the spherical particles from step (2) and put them into the material bin of a fluidized bed coater. Set the inlet air temperature to 105 °C and the material temperature to 75 °C. Spray the coating liquid from step (3) using the side - spray process to coat the spherical particles. The stirring speed of the coating liquid is 200 rpm, the feeding speed of the coating liquid through the diaphragm pump is 12 g / min, the atomization pressure is 0.1 Mpa, and the coating time is 2 h. The particle size after coating is 114 μm - 133 μm.

[0057] (5) Immerse the coated spherical particles in a hydrochloric acid solution with a pH value of 1.5 for 12 h, filter and wash with water until the pH of the filtrate is 5.9, and then put them in an oven at 105 °C for drying for 3 hours.

[0058] (6) Calcinate the spherical particles from step (5) at 700 °C for 4 h to obtain hollow silica spherical particles with a diameter of 114 μm - 133 μm.

[0059] Example 5

[0060] This example provides a method for preparing hollow silica spherical particles, and the specific steps are as follows:

[0061] (1) Add 1.5 kg of sucrose to 6.0 kg of water and stir until completely dissolved, then add 2.5 kg of calcium carbonate to obtain a mixed solution.

[0062] (2) Pump the mixed solution from step (1) into a centrifugal atomization drying granulator for granulation. The rotation speed of the atomization disk is 2500 rpm, the inlet air temperature is 330 °C, and the outlet air temperature is 115 °C. Spherical particles with a particle size of 72 μm - 122 μm are obtained.

[0063] (3) Add 0.2 kg of polyethyleneimine to 9.73 kg of silica sol, and add 0.07 kg of hexagonal boron nitride nanotubes with an average diameter of 60 nm and an average length of 20 μm. Stir and disperse evenly to obtain a boron nitride nanotube - silica sol mixed solution as the coating liquid.

[0064] (4) Take 1.0 kg of the spherical particles from step (2) and put them into the material bin of the fluidized bed coater. Set the inlet air temperature to 113 °C and the material temperature to 85 °C. Spray the coating solution from step (3) using the side spray process to coat the spherical particles. The stirring speed of the coating solution is 200 rpm, the feeding speed of the coating solution through the diaphragm pump is 12 g / min, the atomization pressure is 0.1 Mpa, the coating time is 2 h, and the particle size after coating is 130 μm - 158 μm.

[0065] (5) Immerse the coated spherical particles in a nitric acid solution with a pH value of 1.5 for 12 h, filter and wash with water until the pH of the filtrate is 6.0, and then put them into an oven at 105 °C to dry for 3 hours.

[0066] (6) Calcinate the spherical particles from step (5) at 700 °C for 4 hours to obtain hollow silica spherical particles with a diameter of 130 μm - 158 μm.

[0067] Example 6

[0068] This example provides a method for preparing hollow silica spherical particles, and the specific steps are as follows:

[0069] (1) Add 1.0 kg of sucrose to 6.0 kg of water, stir and dissolve completely, and then add 3.0 kg of calcium carbonate to obtain a mixed solution.

[0070] (2) Pump the mixed solution from step (1) into a centrifugal atomization drying granulator for granulation. The rotation speed of the atomization disk is 2000 rpm, the inlet air temperature is 300 °C, and the outlet air temperature is 110 °C. The particle size of the obtained spherical particles is 80 μm - 130 μm.

[0071] (3) Add 0.25 kg of polyethyleneimine to 9.67 kg of silica sol, and add 0.08 kg of hexagonal boron nitride nanotubes with an average diameter of 60 nm and an average length of 20 μm, stir and disperse evenly to obtain a boron nitride nanotube - silica sol mixed solution as the coating solution.

[0072] (4) Take 1.0 kg of the spherical particles from step (2) and put them into the material bin of the fluidized bed coater. Set the inlet air temperature to 110 °C and the material temperature to 80 °C. Spray the coating solution from step (3) using the side spray process to coat the spherical particles. The stirring speed of the coating solution is 200 rpm, the feeding speed of the coating solution through the diaphragm pump is 12 g / min, the atomization pressure is 0.2 Mpa, the coating time is 2 h, and the particle size after coating is 150 μm - 180 μm.

[0073] (5) Immerse the coated spherical particles in a nitric acid solution with a pH value of 1.5 for 16 h, filter and wash with water until the pH of the filtrate is 6.0, and then put them into an oven at 105 °C to dry for 3 hours.

[0074] (6) The spherical particles obtained in step (5) are calcined at 650 °C for 4 hours to obtain hollow silica spherical particles with a diameter of 150 μm - 180 μm.

[0075] Example 7

[0076] This example provides a method for preparing hollow silica spherical particles, and the specific steps are as follows:

[0077] (1) 2.0 kg of sucrose is added to 5.5 kg of water and stirred until completely dissolved, and then 2.5 kg of calcium carbonate is added to obtain a mixed solution.

[0078] (2) The mixed solution obtained in step (1) is pumped into a centrifugal atomization drying granulator for granulation. The rotation speed of the atomization disk is 2000 rpm, the inlet air temperature is 350 °C, and the outlet air temperature is 118 °C. Spherical particles with a particle size of 100 μm - 150 μm are obtained.

[0079] (3) 0.3 kg of polyethyleneimine is added to 9.6 kg of silica sol, and 0.1 kg of hexagonal boron nitride nanotubes with an average diameter of 60 nm and an average length of 20 μm is added, and stirred and dispersed evenly to obtain a boron nitride nanotube - silica sol mixed solution as a coating solution.

[0080] (4) 1.0 kg of the spherical particles obtained in step (2) is placed in the material bin of a fluidized bed coater. The inlet air temperature is set to 130 °C, and the material temperature is 90 °C. The coating solution obtained in step (3) is sprayed using a side spray process to coat the spherical particles. The stirring speed of the coating solution is 200 rpm, the feeding speed of the coating solution through the diaphragm pump is 18 g / min, the atomization pressure is 0.2 Mpa, and the coating time is 2 h. The particle size after coating is 170 μm - 200 μm.

[0081] (5) The coated spherical particles are immersed in a nitric acid solution with a pH value of 1.5 for 20 h, filtered and washed with water until the pH of the filtrate is 5.7, and then placed in an oven at 105 °C and dried for 4 hours.

[0082] (6) The spherical particles obtained in step (5) are calcined at 800 °C for 3 hours to obtain hollow silica spherical particles with a diameter of 170 μm - 200 μm.

[0083] Comparative Example 1

[0084] This comparative example provides a method for preparing hollow silica spherical particles, which is similar to Example 1, except that boron nitride nanotubes are not added. The specific steps are as follows:

[0085] (1) 1.0 kg of sucrose is added to 7.0 kg of water and stirred until completely dissolved, and then 2.0 kg of calcium carbonate is added to obtain a mixed solution.

[0086] (2) Pump the mixed solution from step (1) into a centrifugal atomization drying granulator for granulation. The rotation speed of the atomization disk is 3000 rpm, the inlet air temperature is 360 °C, and the outlet air temperature is 120 °C. Spherical particles with a particle size of 50 μm - 90 μm are obtained.

[0087] (3) Add 0.1 kg of polyethyleneimine to 9.85 kg of silica sol and stir to disperse evenly to obtain a coating solution.

[0088] (4) Take 1.0 kg of the spherical particles from step (2) and put them into the material bin of a fluidized bed coater. Set the inlet air temperature to 100 °C and the material temperature to 70 °C. Spray the coating solution from step (3) using the side spray process to coat the spherical particles. The stirring speed of the coating solution is 200 rpm, the feeding speed of the coating solution through the diaphragm pump is 10 g / min, the atomization pressure is 0.1 Mpa, and the coating time is 2 h. The particle size after coating is 100 μm - 120 μm.

[0089] (5) Immerse the coated spherical particles in a hydrochloric acid solution with a pH value of 1.5 for 8 h, filter and wash with water until the pH of the filtrate is 5.6, and then put them in an oven at 105 °C for drying for 3 hours.

[0090] (6) Calcinate the spherical particles from step (5) at 600 °C for 6 hours to obtain non-spherical silica.

[0091] Comparative Example 2

[0092] This comparative example provides a method for preparing hollow silica spherical particles, which is similar to Example 1, except that flaky hexagonal boron nitride is used instead of boron nitride nanotubes. The specific steps are as follows:

[0093] (1) Add 1.0 kg of sucrose to 7.0 kg of water and stir until completely dissolved, then add 2.0 kg of calcium carbonate to obtain a mixed solution.

[0094] (2) Pump the mixed solution from step (1) into a centrifugal atomization drying granulator for granulation. The rotation speed of the atomization disk is 3000 rpm, the inlet air temperature is 360 °C, and the outlet air temperature is 120 °C. Spherical particles with a particle size of 50 μm - 90 μm are obtained.

[0095] (3) Add 0.1 kg of polyethyleneimine to 9.85 kg of silica sol, add 0.05 kg of flaky hexagonal boron nitride with an average particle size of 6 μm, and stir to disperse evenly to obtain a boron nitride nanotube - silica sol mixed solution as the coating solution.

[0096] (4) Take 1.0 kg of the spherical particles from step (2) and put them into the material bin of the fluidized bed coater. Set the inlet air temperature to 100 °C and the material temperature to 70 °C. Spray the coating liquid from step (3) using the side spray process to coat the spherical particles. The stirring speed of the coating liquid is 200 rpm, the feeding speed of the coating liquid through the diaphragm pump is 10 g / min, the atomization pressure is 0.1 Mpa, the coating time is 2 h, and the size of the coated spherical particles is 100 μm - 120 μm.

[0097] (5) Immerse the coated spherical particles in a hydrochloric acid solution with a pH value of 1.5 for 8 h, filter and wash with water until the pH of the filtrate is 5.6, and then put them into an oven at 105 °C and dry for 3 hours.

[0098] (6) Calcinate the spherical particles from step (5) at 600 °C for 6 hours to obtain non-spherical silica.

[0099] Comparative Example 3

[0100] This comparative example provides a method for preparing hollow silica spherical particles, which is similar to Example 1, with the difference being that the amount of boron nitride nanotubes is reduced. The specific steps are as follows:

[0101] (1) Add 1.0 kg of sucrose to 7.0 kg of water and stir until completely dissolved, then add 2.0 kg of calcium carbonate to obtain a mixed solution.

[0102] (2) Pump the mixed solution from step (1) into a centrifugal atomization drying granulator for granulation. The rotation speed of the atomization disk is 3000 rpm, the inlet air temperature is 360 °C, and the outlet air temperature is 120 °C. The obtained spherical particles have a particle size of 50 μm - 90 μm.

[0103] (3) Add 0.1 kg of polyethyleneimine to 9.85 kg of silica sol, and add 0.01 kg of boron nitride nanotubes with an average diameter of 60 nm and an average length of 20 μm, and stir to disperse evenly to obtain a boron nitride nanotube - silica sol mixed solution as the coating liquid.

[0104] (4) Take 1.0 kg of the spherical particles from step (2) and put them into the material bin of the fluidized bed coater. Set the inlet air temperature to 100 °C and the material temperature to 70 °C. Spray the coating liquid from step (3) using the side spray process to coat the spherical particles. The stirring speed of the coating liquid is 200 rpm, the feeding speed of the coating liquid through the diaphragm pump is 10 g / min, the atomization pressure is 0.1 Mpa, the coating time is 2 h, and the size of the coated particles is 100 μm - 120 μm.

[0105] (5) Immerse the coated spherical particles in a hydrochloric acid solution with a pH value of 1.5 for 8 h, filter and wash with water until the pH of the filtrate is 5.6, and then put them into an oven at 105 °C and dry for 3 hours.

[0106] (6) Calcinate the spherical particles in step (5) at 600 °C for 6 hours to obtain hollow silica spherical particles with partial cracking.

[0107] Obviously, the above embodiments are merely examples for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or alterations can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. And the obvious changes or alterations derived therefrom are still within the protection scope of this invention.

Claims

1. A method for preparing hollow silica spherical particles, characterized in that, It includes the following steps: Provide a mixed solution of a saccharide compound and calcium carbonate; granulate the mixed solution to obtain spherical particles; Mix a wetting dispersant with silica sol, then add boron nitride nanotubes, and stir to disperse evenly to obtain a boron nitride nanotube-silica sol mixed solution; Put the spherical particles into a coating machine, spray the boron nitride nanotube-silica sol mixed solution, so that a mixed coating layer of boron nitride nanotubes and silica is formed on the surface of the spherical particles to obtain coated spherical particles; Soak the obtained coated spherical particles in an acid solution, perform solid-liquid separation to take the solid phase, and calcine the solid phase to obtain the hollow silica spherical particles.

2. The preparation method according to claim 1, characterized in that, The diameter of the spherical particles is 50 μm - 150 μm; The diameter of the coated spherical particles is 100 μm - 200 μm; The diameter of the hollow silica spherical particles is 100 μm - 200 μm.

3. The preparation method according to claim 1, characterized in that, Centrifugal atomization drying granulation machine is selected for granulation. Among them, the rotation speed of the atomization disk is 2000 rpm - 3000 rpm, the inlet air temperature is 300 °C - 360 °C, and the outlet air temperature is 110 °C - 120 °C.

4. The preparation method according to claim 1, characterized in that, The concentration of the saccharide compound in the mixed solution is 10 - 20%, and the concentration of calcium carbonate in the mixed solution is 20 - 30%.

5. The preparation method according to claim 1, characterized in that, The saccharide compound is selected from one or more of glucose, sucrose, fructose and water-soluble starch.

6. The preparation method according to claim 1, characterized in that, The boron nitride nanotubes are hexagonal boron nitride nanotubes with an average diameter of 50 - 70 nm and an average length of 10 - 30 μm.

7. The preparation method according to claim 1, wherein The wetting dispersant is selected from polyethyleneimine; The concentration of the wetting dispersant in the boron nitride nanotube-silica sol mixed solution is 1 - 3%, the concentration of boron nitride nanotubes is 0.5 - 1%; the concentration of silica sol is 96 - 98.5%.

8. The preparation method according to claim 1, wherein, The coating machine is a fluidized bed coating machine, the inlet air temperature is 100 °C - 130 °C, the material temperature is 70 °C - 100 °C, the feeding speed of the coating liquid is 10 - 20 g / min, and the spray atomization pressure is 0.1 Mpa - 0.2 Mpa.

9. The preparation method according to claim 1, characterized in that, The acid is selected from one or more of hydrochloric acid, phosphoric acid, sulfuric acid and nitric acid, and the soaking time is 8 - 24 h.

10. The preparation method according to claim 1, characterized in that, The conditions for calcination: calcine at 600 °C - 800 °C for 3 hours - 6 hours.