Multi-stage calcination method for making hollow silica spheres

Patent metadata

Field	Value
Publication number	US-2019367376-A1
Application number	US-201815995904-A
Country	US
Kind code	A1
Filing date	Jun 1, 2018
Priority date	Jun 1, 2018
Publication date	Dec 5, 2019
Grant date	—

Abstract

A method for forming hollow silica spheres by dissolving a hydrolyzable aryl silane in an aqueous solution of water and an acid to form a hydrolyzed silane solution, mixing the hydrolyzed silane solution with a hydroxide base to form a precipitate, and calcining the precipitate in a multi-stage calcination procedure that includes (a) heating to a first temperature of 180 to 240° C. with a first ramp rate of 3 to 10° C./min and holding the first temperature for 2 minutes to 2 hours, then (b) heating to a second temperature of 600 to 740° C. at a second ramp rate of 0.1 to 4° C./min, and holding the second temperature for 2 to 24 hours.

First claim

1 : A method for forming hollow silica spheres, the method comprising:
dissolving a hydrolyzable aryl silane in an aqueous solution comprising water and an acid to form a hydrolyzed silane solution; mixing the hydrolyzed silane solution with a hydroxide base to form a precipitate; and calcining the precipitate to form the hollow silica spheres, wherein the calcining is performed by
heating to a first temperature of 180 to 240° C. with a first ramp rate of 3 to 10° C./min and holding the first temperature for 2 minutes to 2 hours, then
heating to a second temperature of 600 to 740° C. at a second ramp rate of 0.1 to 4° C./min, and holding the second temperature for 2 to 24 hours.

2 : The method of claim 1 , wherein the hydrolyzable aryl silane is a trialkoxy(aryl) silane.

3 : The method of claim 1 , wherein the hydrolyzable aryl silane is trimethoxy(phenyl) silane.

4 : The method of claim 1 , wherein the acid is nitric acid.

5 : The method of claim 1 , wherein the hydroxide base is ammonium hydroxide.

6 : The method of claim 1 , wherein the first temperature is 195 to 210° C.

7 : The method of claim 1 , wherein the first ramp rate is 4 to 6° C./min

8 : The method of claim 1 , wherein the first temperature is held for 15 to 45 minutes.

9 : The method of claim 1 , wherein the second temperature is 650 to 670° C.

10 : The method of claim 1 , wherein the second ramp rate is of 1 to 2° C./min.

11 : The method of claim 1 , wherein the second temperature is held for 12 to 20 hours.

12 : The method of claim 1 , wherein a template is not employed for forming the hollow silica spheres.

13 : The method of claim 1 , wherein the hollow silica spheres comprise a silica-containing shell surrounding a core, wherein the silica-containing shell has a higher density of silica compared to the core.

14 : The method of claim 13 , wherein the hollow silica spheres have an average degree of hollowness, defined as a maximum peak intensity of the core divided by a minimum peak intensity of the silica-containing shell, each measured with transmission electron microscopy, of 3 to 8.

15 : The method of claim 13 , wherein the silica-containing shell has a thickness of about 150 to 210 nm, and the core has a diameter of about 100 to 230 nm.

16 : The method of claim 1 , wherein the hollow silica spheres have an average diameter of 500 to 530 nm.

17 : The method of claim 16 , wherein the hollow silica spheres are monodisperse with a coefficient of variation, defined as a ratio of the standard deviation to the mean diameter of the hollow silica spheres, of less than 5%.

18 : The method of claim 1 , wherein the hollow silica spheres have a solubility in water of 0.1 to 50 mg per 10 mL of water.

19 : The method of claim 1 , wherein the hollow silica spheres have a specific surface area of 350 to 450 m 2 /g.

20 : The method of claim 1 , wherein the hollow silica spheres have an average pore diameter of 1.7 to 8 nm with a cumulative pore volume of 0.02 to 0.035 cm 3 /g.

Assignees

• Univ Imam Abdulrahman Bin Faisal

Inventors

• Bozkurt Ayhan
• Anil Seyda Tugba Gunday
• Almessiere Munirah Abdullah
• Akhtar Sultan

Classifications

• C01B33/124 Primary

  Preparation of adsorbing porous silica not in gel form and not finely divided, i.e. silicon skeletons, by acidic treatment of siliceous materials · CPC title

• C01P2006/12

  Surface area · CPC title

• C01P2006/16

  Pore diameter · CPC title

• C01P2004/34

  hollow · CPC title

• C01B33/18 Primary

  Preparation of finely divided silica neither in sol nor in gel form; After-treatment thereof (preparation of aerogels by dehydrating gels C01B33/158; treatment to enhance the pigmenting or filling properties C09C) · CPC title