Preferential formation of aluminium chloride by chlorination of a highly reactive powder obtained from metakaolin or kaolin by hydrochloric acid treatment

Abstract

It has been found that highly reactive amorphous powders are obtained by treatment with concentrated hydrochloric acid of metakaolin or kaolin, followed by removal of the liquid by distillation and calcination of the residue. The result is a porous silica homogeneously mixed with chloride-containing alumina beginning to react with gaseous carbon tetrachloride at 450 K. At temperatures above 700 K aluminium chloride is formed in high yield and high selectivity. The reactivity of these powders is such that they are chlorinated even by gaseous silicon tetrachloride, a compound known to be stable towards metakaolinite up to 1300 K! Some advantages of technological relevance are listed in comparison to leaching and other dissolution processes.