Catalytic decomposition of carbondioxide over freshly reduced activated CuFe2O4 nano-crystals

Nano-crystallite copper ferrite (220 nm) was obtained by self flash combustion of a homogeneous mixture of one mole Cu(CH3COO)(2)(H2O)-H-. and two moles of Fe(CHCOO)(2)(OH)-O-.. The ferrite powder (220 nm) was activated mechanochemically by ball milling for 10, 20, 40 and 100 h in order to obtain smaller crystallite size; 134, 89, 50 and 99 nm crystals were obtained, respectively, and correlated to the enhancement in magnetic properties. Nano-crystallite (50 nm) CuFe2O4 were isothermally reduced in H-2 flow (1 1/min) at 400-600 degrees C prior to the formation of metallic Cu and Fe. The isothermal reduction profiles obtained in this study show a topochemical mode of reduction, by which the reduction process proceeds. The activation energy values for the reduction process through the initial, intermediate and final stages of reduction were calculated from Arrhenius equation to be 11.4, 55.44 and 65.79, respectively. CO2 was allowed to flow and decompose to carbon nano-tubes directly over the nano-wires metallic phase of iron and copper, freshly produced from the complete reduction of CuFe2O4 at 400-600 degrees C. The prepared, completely reduced and reoxidized CuFe2O4 compacts, were characterized by XRD, TEM, SEM and reflected light microscope. For the reoxidation process, it is found that the interfacial chemical reaction mechanism, the gaseous diffusion mechanism and the solid-state diffusion mechanism controlled the rate during the different stages of the reoxidation process. Also it is found that the reduction temperature affected the rate of reoxidation process through its different stages as the reduction process affects the porosity and reactivity of the pellets. (c) 2006 Published by Elsevier B.V.