Correlation between the magnetism of non-stoichiometric zinc ferrites and their catalytic activity for oxidative dehydrogenation of 1-butene

Non-stoichiometric zinc ferrites, which were used as catalysts for the oxidative dehydrogentation of 1-butene, were synthesized by using co-precipitation and hydrothermal methods. Their atom local order was analyzed with Mossbauer spectroscopy and the refinement of the crystalline structures; their macroscopic magnetization was measured by the vibrating sample method. Their magnetic and catalytic properties depended on the synthesis conditions; the analysis of the local atom distribution shows that these properties were related to the occupation of the tetrahedral sites with iron ions. This occupation was larger when the ferrites were prepared under hydrothermal conditions than by co-precipitation. The parallelism between the macroscopic magnetization of the ferrites and their capacity of transforming 1-butene into butadiene, CO2 and 2-butene, by an oxidative dehydrogenation reaction, suggests. that the freezing of the magnetic moments in the octahedral sites could cause this catalytic behavior. (C) 2002 Elsevier Science B.V. All rights reserved.