Preparation of alpha-alumina in supercritical fluids07812.0263

Patent metadata

Field	Value
Publication number	US-2025368524-A1
Application number	US-202218722730-A
Country	US
Kind code	A1
Filing date	Dec 23, 2022
Priority date	Dec 23, 2021
Publication date	Dec 4, 2025
Grant date	—

Abstract

The present invention relates to a process for preparing α-alumina in supercritical fluids, to α-alumina obtained by the said process and to α-alumina particulates.

First claim

1 . A process for preparing alpha alumina, comprising the steps of:
(a) providing an aluminium precursor; (b) mixing the aluminium precursor with a base in a solvent; (c) aging the mixture of step (b) until the aluminium precursor is dissolved; (d) treating the solution of (c) at a temperature and pressure above the critical point of the solvent used.

2 . The process according to claim 1 , wherein the aluminium precursor is selected from aluminium nitrate, aluminium sulfate, aluminium chloride, or combinations thereof.

3 . The process according to claim 1 , wherein solvent is selected from water, ethanol, methanol, or combinations thereof.

4 . The process according to claim 1 , wherein the base is selected from sodium hydroxide, potassium hydroxide or a combination thereof.

5 . The process according to claim 1 , wherein mixing in step (b) is carried out at a temperature of from about 20° C. to about 100° C.

6 . The process according to claim 1 , wherein the pH of step (c) is between about 4 and about 6.

7 . The process according to claim 1 , wherein step (c) is carried out at a temperature of from about 25° C. to about 100° C.

8 . The process according to claim 1 , wherein the mixture of step (c) is stirred at a rate of between 20 rpm and 1500 rpm.

9 . The process according to claim 1 , wherein step (c) is carried out for at least 0.5 h.

10 . The process according to claim 1 , wherein step (c) is aged until the mixture is transparent, wherein the transparency is determined by DIN ISO 18748.

11 . The process according to claim 1 , wherein the temperature used in step (d) is from about 400° C. to about 1000° C. and the pressure used in step (d) is from about 10 bar to about 500 bar.

12 . The process according to claim 1 , wherein the reactor treats the reactants at the said temperature and said pressure for a time of between 5 ms and 50 days.

13 . An alpha-alumina made according to the process of claim 1 .

14 . A composition comprising alpha-alumina particulates, wherein up to about 10% of the particulates are in the form of a polyhedron having at least 12 faces.

15 . The alpha-alumina particulates of claim 14 , wherein the polyhedron is a hexagonal bipyramid or a truncated hexagonal bipyramid.

16 . The process according to claim 5 , wherein the pH of step (c) is between about 4 and about 6

17 . The process according to claim 16 , wherein step (c) is carried out at a temperature of from about 25° C. to about 100° C.

18 . The process according to claim 17 , wherein the mixture of step (c) is stirred at a rate of between 20 rpm and 1500 rpm.

19 . The process according to claim 18 , wherein step (c) is carried out for at least 0.5 h.

20 . The process according to claim 19 , wherein the temperature used in step (d) is from about 400° C. to about 700° C. and the pressure used in step (d) is from about 230 bar to about 500 bar.

Assignees

• Imertech Sas

Inventors

• Grenier Guillaume
• Quilfen Cyril

Classifications

• C01P2004/03

  obtained by SEM · CPC title

• C01P2002/72

  by d-values or two theta-values, e.g. as X-ray diagram · CPC title

• C01F7/308 Primary

  Thermal decomposition of nitrates · CPC title

• C01P2002/70

  defined by measured X-ray, neutron or electron diffraction data · CPC title

• C01F7/441

  by calcination · CPC title