STRUCTURE AND ELECTRONIC EFFECTS OF COBALT FERRITES, CoxFe3-xO4, ON CATALYTIC DECOMPOSITION OF ISOPROPANOL Khalf-Alla M. ABD EL-SALAAM, Abd El-Aziz A. SAID*, Ahmed M. EL-AWAD, Ehsan A. HASSAN and Mohamed M. M. ABD EL-WAHAB Chemistry Department, Faculty of Science, Assiut University, 715 16 Assiut, Egypt Received December 14, 1993 Accepted May 10, 1994 The cobalt–ferrite spinel oxides Co x Fe 3-x O 4 (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 E σ values was discussed in terms of oxide semiconducting properties and of ion distribution in the octahedral-tetrahedral sites of the spi- nel 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. Correla- tions between the composition and electronic and catalytic properties of the catalysts are reported. Surface and bulk properties of ferrites have implications in several fields such as cata- lysis and electrocatalysis, corrosion of metal alloys, as well as electronic applications. The interesting physical and chemical properties of spinel ferrites arise from their activ- ity to distribute cations among available tetrahedral (t) and octahedral (o) sites 1 . Cobalt–ferrite spinels are of considerable industrial interest due to their catalytic activ- ity 2–5 , structural stability, long life-time and resistance to sintering. The high activity of the oxides was ascribed to the presence of Co 2+ on octahedral sites which initiated a cyclic electron transfer 6 . Stoichiometric CoFe 2 O 4 contains only Co 2+ and Fe 3+ . Semi- conducting properties of Co x Fe 3-x O 4 have been investigated with x < 1; the excess Fe 2+ acts as an electron donor, causing n-type semiconductivity. When x > 1, Co 3+ acts as an electron acceptor, causing p-type semiconductivity. However, it was already found that the wide variation of x in the cobalt–iron spinel system leads to a drastic change of its catalytic and electrical properties. However, little attention has been paid to the cata- Catalytic Decomposition of Isopropanol 1939 Collect. Czech. Chem. Commun. (Vol. 59) (1994) * The author to whom correspondence should be addressed.