PROCESS FOR PRODUCING ALUMINAS OR FINELY DIVIDED ALUMINA-MAGNESIA SPINELS HAVING A HOMOGENEOUS POROUS STRUCTURE

摘要

Process for the preparation of a pure alumina or pure alumina-magnesia spinel powder, non stocchiometric, from compositions based on ammonium alum in which dehydration of the alum is carried out, characterized in that this dehydration is carried out so as to obtain dehydrated salts whose bulk density is less than 0.2 kg dm-3 and which this dehydration is followed by calcination according to a heating protocol comprising at least one intermediate level located between 750 and 850.degree.C. The process of the invention makes it possible to reliably prepare from ammonium alum, aluminas or spinels having specific surfaces of between 100 and 200 m2 / g, which are characterized by very high homogeneity guaranteeing a structure porous unimodal and tight. The aluminas and spinels prepared according to the invention can in particular be used in the manufacture of barriers for isotopic enrichment by gas diffusion, as well as in the polishing of metals and as catalyst or catalyst support.