Method for preparing a catalyst support

A process for preparing a catalyst support for a reaction of Fischer-Tropsch type in the form of a powder, said support comprising alumina and silica and/or one or more derivatives thereof,

• wherein the process comprises:
• a stage (a) of preparing a first reactant, which first reactant comprises an alumina compound or precursor, and optionally alumina, in suspension in a solvent, wherein said preparing of the first reactant occurs in a first reactor (10), including a reaction for peptization of the alumina compound or precursor, in the presence of an acid, so as to form solid particles in at least partially colloidal suspension,
• a stage (b) of preparing a second reactant, which second reactant is based on silicic acid and/or on a compound or precursor of silicic acid, and optionally silica, in suspension or dissolved in a solvent, wherein said preparing of the second reactant occurs in a second reactor (20), including a controlled aging treatment of the silicic acid targeted at its polymerization up to a degree of conversion of the silicic acid of at most 70%, said second reactant resulting from stage (b), which is at a pH of at most 3.4,
• a stage (c) of mixing the two reactants resulting from the two reactors in a mixer or group of mixers (40, 41), in which the reaction between the two reactants takes place,
• and wherein the pH of the first reactant is adjusted to a value not exceeding a given maximum pH threshold (pHmax), said threshold having a value equal to 3.4, before its introduction into the mixer in the mixing stage (c), in order to obtain a mixture in the form of particles in suspension in a liquid phase.