Ilmenite fluorination by ammonium hydrodifluoride: A new ammonium oxofluorotitanate

The reaction of ammonium hydrodifluoride with ilmenite is explored by therm ogravimetry, IR spectroscopy, chemical analysis, and X-ray powder diffracti on. The reaction is initiated at room temperature by feed stirring and prod uces off-stoichiometric ammonium fluorotitanate and ammonium fluoroferrate. The composition of the complexes depends on the admission of atmospheric o xygen. Iron(II) is responsible for the production of ammonium fluoroferrate with the perovskite structure; iron(III), for the production of complexes with the elpasolite structure. The thermal behavior of the latter, as well as that of ammonium fluorotitanate, is characterized by a reduction in the oxidation number of the metal due to the ammonium eliminated upon dissociat ion and by the formation of phases of variable composition. Dissociation ab ove 400 degreesC is accompanied by the evolution of a volatile titanium com pound that condenses at 300 degreesC in ammonium oxofluorotitanate.