STRUCTURE AND ELECTRONIC EFFECTS OF COBALT FERRITES, COXFE3-XO4, ON CATALYTIC DECOMPOSITION OF ISOPROPYL-ALCOHOL

The cobalt-ferrite spinel oxides CoxFe3-xO4 (O < x < 3) have been prep ared by coprecipitation. Their structures were characterized by DTA, X -ray diffraction and IR spectra, and their surface properties were det ermined from nitrogen adsorption isotherms at -196 degrees C. Conducta nce of all the compositions was studied with and without isopropyl alc ohol. The variation of E(sigma) values was discussed in terms of oxide semiconducting properties and of ion distribution in the octahedral-t etrahedral sites of the spinel structures. The catalytic decomposition of isopropyl alcohol at 325 degrees C in a flow system allowed to Con clude that the inverse spinels formed in the iron-rich region are acti ve and selective sites for acetone formation, in contrast to the inver se spinels formed in the cobalt-rich region. On the other hand, the re gion of normal spinels showed low activity and selectivity to acetone formation. Correlations between the composition and electronic and cat alytic properties of the catalysts are reported.