Effect of strontium and cerium doping on the structural characteristics and catalytic activity for C3H6 combustion of perovskite LaCrO3 prepared by sol–gel

Abstract

Two series of Sr- or Ce-doped La1 xMxCrO3 (x = 0.0, 0.1, 0.2 and 0.3) catalysts were prepared by thermal decomposition of amorphous citrate precursors followed by annealing at 800 8C in air atmosphere. The effect of Ce and Sr on the morphological/structural properties of LaCrO3 was investigated by means of thermogravimetric/differential thermal analysis (TG/DTA) of the precursors decomposition under air, Xray diffraction (XRD), electron paramagnetic resonance (EPR), transmission electron microscopy–X-ray energy dispersive spectroscopy (TEM–XEDS), SBET determination, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) techniques. The characterization results are employed to explain catalytic activity results for C3H6 combustion. It is shown that the lanthanum chromite perovskite structure is obtained upon thermal treatment of the sol–gel derived precursors at T > ca. 800 8C. The presence of the dopant generally induces the formation of segregated oxide phases in the samples calcined at 800 8C although some introduction of the Sr in the perovskite structure is inferred from EPR measurements. The oxidation activity becomes maximised upon formation of such doped perovskite structure.