Characterization and catalytic properties of some perovskites

The perovskite oxides are promising catalysts for VOCs combustion. The purpose of this work is to comparatively evaluate catalytic activity of some simple perovskites with various cationic compositions in combustion reactions of acetone, benzene, propane and Pb free gasoline. Nanometer particles of nominal composition: GdAlO3, SrMnO3, SrCoO3 and MnFeO3 were prepared by the sol-gel self-combustion method followed by heat treatment at 1000 °C in air. The samples were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and nitrogen adsorption/desorption isotherms. All samples have perovskite type structure and the crystallite size is in the range of 40-89 nm. Catalytic testing evidenced that the degree of the catalytic activity varied considerably with the perovskite composition. Among the four perovskites, SrMnO3 is generally the most active catalyst at low temperatures. MnFeO3 and SrCoO3−x catalysts proved high catalytic activity in acetone conversion only. The change in the catalytic activity as a result of the modification of the perovskite composition may be explained either by the different reactivity of the active oxygen species involved in the catalytic oxidation, or by the variation in the number of active sites on the perovskite surface determined by the specific structural properties of each perovskite.