Novel process for the preparation of high purity alumina from ammonium alum

摘要

Process for preparing high purity aluminas from ammonium alum, the process comprising separately dehydrating the alum and thereafter thermally decomposing the dehydrate, wherein the thermal decomposition is carried out by forcing a gas through a layer of the dehydrated alum so as to continuously remove the gaseous reaction products formed without removal of solids by the carrier gas, and providing improved productivity of high purity transition aluminas having specific surfaces above 125 m. sup.2 /g and/or bulk densities above 0.2 g/cm.sup.3, the transition aluminas so obtained being characterized by their greater reactivity for the preparation of corundum so that corundum having a bulk density greater than 0.4 g/cm.sup.3 can be economically prepared.