Wustite phase transformations in iron catalysts for ammonia synthesis

摘要

The behaviour of wustite (ferrous oxide)during the catalyst preparation and its activationprocess has been studied. The M?ssbauer spectroscopyand X-ray diffraction have been used to follow wustitetransformations. Inside the wustite phase twodifferent wustite structures were found - oneattributed to the nonstoichiometric wustite and thesecond one, to the compound close to the?stoichiometric'' FeO. The relative contents of bothwustites depended on the cooling rate of the meltedprecursor. At the initial stage of activation, at lowtemperatures, nonstoichiometric ferrous oxide wastransformed into magnetite and a compound closer to thestoichiometric FeO. The last one decomposes furtherinto magnetite and metallic iron.