Physicochemical Properties of LaFeO3 Perovskite Prepared by Various Methods and Its Activity in the Oxidation of Hydrocarbons

LaFeO3 perovskites, obtained through co-precipitation of carbonates with (NH4)(2)CO3, co-precipitation of hydroxides with NaOH, citrate method, and through solid-state reaction using metal nitrates as precursors, were deposited on a heat-resistant foil support. Their physicochemical properties were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry and thermogravimetric analysis (DSC/TGA), and specific surface area measurements. DSC/TGA showed that phase transitions took place in the LaFeO3 perovskite up to 800-840 degrees C. Pure LaFeO3 perovskite phase was obtained only when the citrate method was used. The following decreasing order of methane and hexane oxidation activity at 700 degrees C was determined for the catalysts with the LaFeO3 perovskite obtained by different methods: citric acid > ammonium carbonate similar to metal nitrates > sodium hydroxide. LaFeO3 catalysts obtained at 700 degrees C in the presence of citric acid or ammonium carbonate can be used as three-way automotive exhaust catalysts or as catalysts in environmental protection.