Verfahren zur Herstellung von wasserfreiem Aluminiumfluorid

摘要

Anhydrous AlF3 is made by reacting an aqueous solution of NH4F with at least 1.9 times the amount of Al2O3 or its hydrate required to form (NH4)3 AlF6, separating the resultant mixture of tri-ammonium hexafluoroaluminate and unreacted alumina and drying and heating it to a temperature between 400 DEG C. and the melting point of the mixture. The first step may be effected in an ammonical solution at 65-125 DEG C. in a closed vessel. The precipitate, which need not be washed, is preferably heated gradually or stepwise to 480 DEG -550 DEG C. over a period of at least 20 minutes when a metastable form of AlF3 is formed. Faster heating gives the stable form.