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

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, AlCl3, 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).