Structure and Electronic Effects of Cobalt Ferrites, CoxFe3-xO4, on Catalytic Decomposition of Isopropyl Alcohol

Abstract

The cobalt ferrite spinel oxides CoxFe3-xO4 (O < x < 3) have been prepared by coprecipitation. Their structures were characterized by DTA, X-ray diffraction and IR spectra, and their surface properties were determined from nitrogen adsorption isotherms at -196 °C. Conductance of all the compositions was studied with and without isopropanol. The variation of Eσ values was discussed in terms of oxide semiconducting properties and of ion distribution in the octahedral-tetrahedral sites of the spinel structures. The catalytic decomposition of isopropanol at 325 °C in a flow system allowed to conclude that the inverse spinels formed in the iron-rich region are active and selective sites for acetone formation, in contrast to the inverse spinels formed in the cobalt-rich region. On the other hand, the region of normal spinels showed low activity and selectivity to acetone formation. Correlations between the composition and electronic and catalytic properties of the catalysts are reported.