METHOD FOR PRODUCING VERY PURE ALUMINUM OXYDES FROM IMPURE SOLUTIONS OF ALUMINUM CHLORIDE.

摘要

Process for the preparation of high purity alumina containing less than 0.1 weight percent of residual chlorine starting from impure aluminum chloride solutions, which process comprises a crystallization step to provide aluminum chloride hexahydrate crystals having a diameter of from about 400 to about 4000 micrometers in the presence of hydrochloric acid; washing the aluminum chloride hexahydrate crystals so obtained with pure hydrochloric acid; and pyrohydrolyzing the washed crystals of aluminum chloride hexahydrate at a temperature of from about 700 DEG to about 1300 DEG C., in which pyrohydrolysis a gas is forced through a layer of the washed aluminum chloride hexahydrate so as to remove the gaseous reaction products while obviating any possible movement of the solid by the gas, the process particularly producing transition aluminas simultaneously having a specific surface area greater than 100 m2/g and a chlorine content less than 0.1 weight percent.