Comparison of the Kinetic Behaviors of Fe2O3 Spherical Submicron Clusters and Fe2O3 Fine Powder Catalysts for CO Oxidation

摘要

α-Fe2O3 spherical particles having an average diameter of ca. 420 nm and α-Fe2O3 fine particles (< 10 μm particle size) were prepared to examine as catalysts for CO oxidation. Kinetic studies on the catalytic reactions were performed in a flow reactor using an on-line gas chromatography system operated at 1 atm. The apparent activation energies and the partial orders with respect to CO and O2 were determined from the rates of CO disappearance in the reaction stage showing a constant catalytic activity. In the temperature range of 150-275 °C, the apparent activation energies were calculated to be 13.7 kcal/mol on the α-Fe2O3 spherical submicron clusters and 15.0 kcal/mol on the α-Fe2O3 fine powder. The Pco and PO2 dependencies of rate were investigated at various partial pressures of CO and O2 at 250 °C. Zero-order kinetics were observed for O2 on both the catalysts, but the reaction order for CO was observed as first-order on the α-Fe2O3 fine powder and 0.75-order on the α-Fe2O3 spherical submicron clusters. The catalytic processes including the inhibition process by CO2 on the α-Fe2O3 spherical submicron powder are discussed according to the kinetic results. The catalysts were characterized using XRD (X-ray powder diffraction), FE-SEM (field emission-scanning electron microscopy), HR-TEM (high resolution-transmission electron microscopy), and N2 sorption measurements.