Method for producing an alumina gel having a high dispersibility and a specific crystallite size

Patent metadata

Field	Value
Publication number	US-11577964-B2
Application number	US-202017011611-A
Country	US
Kind code	B2
Filing date	Sep 3, 2020
Priority date	Jan 29, 2016
Publication date	Feb 14, 2023
Grant date	Feb 14, 2023

Abstract

Process for preparing alumina gel in a single precipitation step consisting of dissolving an aluminium precursor, aluminium chloride, in water, at a temperature of 10° C. to 90° C. such that the pH of the solution is from 0.5 to 5, for a period of 2 to 60 minutes, then adjusting the pH to 7.5 to 9.5 by adding a basic precursor, sodium hydroxide, to the solution obtained to obtain a suspension, at a temperature of 5° C. to 35° C., and for 5 minutes to 5 hours, followed by a filtration step, said process not comprising any washing steps. Also, novel alumina gel having a high dispersibility index, in particular a dispersibility index of more than 80%, a crystallite dimension of 0.5 to 10 nm, a chlorine content of 0.001% to 2% by weight and a sodium content of 0.001% to 2% by weight, the percentages by weight being expressed with respect to the total weight of the alumina gel.

First claim

The invention claimed is:

1. A process for the preparation of an alumina gel, wherein the alumina gel has a dispersibility index of more than 80%, a crystallite dimension, obtained by the Scherrer X ray diffraction formula along the crystallographic directions [020] and [120], respectively, in the range of 0.5 to 10 nm and in the range of 0.5 to 15 nm, a chlorine content in the range 0.001% to 2% by weight and a sodium content in the range 0.001% to 2% by weight, the percentages by weight being expressed with respect to the total weight of the alumina gel,
the process comprising:
a single precipitation step (a) consisting of dissolving an acidic aluminium precursor, aluminium chloride, AlCl 3 , in water, at a temperature in the range 10° C. to 90° C. and for a period in the range of 2 to 60 minutes, to obtain a solution, in a manner such that the pH of the solution is in the range of 0.5 to 5, then adjusting the pH to a pH in the range of 7.5 to 9.5 by adding a basic precursor, sodium hydroxide, to the solution obtained in order to obtain a suspension, at a temperature in the range 5° C. to 35° C. and for a period in the range of 5 minutes to 5 hours, and

a filtration step b) of the suspension obtained at the end of step a) to obtain a precipitate,
said process not comprising any steps for washing the precipitate obtained at the end of the filtration step b).

2. The process as claimed in claim 1 , in which the acidic aluminium precursor, aluminium chloride, AlCl 3 , is dissolved in water at a temperature in the range 10° C. to 75° C.

3. The process as claimed in claim 1 , in which the pH of the solution of aluminium chloride, AlCl 3 , in water, is in the range 1 to 4.

4. The process as claimed in claim 1 , in which the pH is adjusted at a temperature in the range 10° C. to 30° C.

5. The process as claimed in claim 4 , in which the pH is adjusted at a temperature in the range 10° C. to 25° C.

6. The process as claimed in claim 1 , in which the pH is adjusted to a pH in the range 7.7 to 8.8.

7. The process as claimed in claim 1 , in which the preparation process also comprises a drying step for the filtered suspension obtained at the end of the precipitation step in order to obtain a powder, said drying step being carried out by drying at a temperature of 100° C. or more or by spray drying.

8. The process as claimed in claim 7 , in which the preparation process also comprises a shaping step of the powder obtained in order to obtain a green material.

9. The process as claimed in claim 8 , in which the shaping step is carried out by mixing-extrusion or by oil-drop.

10. The process as claimed in claim 8 , in which the shaped green material then undergoes a heat treatment step at a temperature in the range 500° C. to 1000° C., for a period in the range 2 to 10 h, in the presence or absence of a stream of air containing up to 60% by volume of water.

11. The process as claimed in claim 1 , wherein the alumina gel has a dispersibility index in the range of 85% to 100%.

12. The process as claimed in claim 11 , wherein the alumina gel has a dispersibility index in the range of 88% to 100%.

Assignees

• Ifp Energies Now

Inventors

• Boualleg Malika
• Lafon Olivier

Classifications

• B28B3/20

  wherein the material is extruded {(extrusion moulding of plastics B29C48/00)} · CPC title

• B01J13/006 Primary

  by precipitation, coagulation, hydrolyse coacervation · CPC title

• C01P2004/64

  Nanometer sized, i.e. from 1-100 nanometer · CPC title

• C01P2002/72

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

• C01F7/021

  After-treatment of oxides or hydroxides · CPC title