Abstract

LaFeO3, LaNiO3 and substituted LaFe1-yNiyO3 (y=0.1, 0.2 and 0.3) perovskites were synthesized by the citrate method and used in the catalytic combustion of ethanol and acetyl acetate. Chemical composition was determined by atomic absorption spectrometry (AAS) and specific areas from nitrogen adsorption isotherms. Structural details and surface properties were evaluated by temperature-programmed reduction (TPR), infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), temperature-programmed desorption of oxygen (O2-TPD) and photoelectron spectroscopy (XPS). Characterization data revealed that total insertion of nickel in the LaFeO3 takes place for substitution y=0.1. However, NiO segregation occurs to some extent, specifically at higher substitutions (y>0.1). The catalytic performance of these perovskites was evaluated in the combustion of acetyl acetate and ethanol. Among these molecules, ethanol exhibited the lowest ignition temperature, and the catalytic activity expressed as intrinsic activity (mol m-2 h-1) was found to increase substantially with the nickel substitution. These results can be explained in terms of the cooperative effect of a LaFe1-yNiyO3 and NiO phases, whose relative concentration determines the oxygen activation capability and hence their reactivity. © 2008 Elsevier Inc. All rights reserved.