Structural and morphological properties of Co–La catalysts supported on alumina/lanthana for hydrocarbon oxidation

Abstract Two Al 2 O 3 (24 wt%)–La 2 O 3 (76 wt%) supported Co–La oxides with Co loading 4 wt% and different La content (1 and 9 wt%) were prepared by co-impregnation of the support, the aluminum–lanthanum oxide, with cobalt and lanthanum nitrates in aqueous solution and successive calcination at 800 °C for 4 h. The alumina–lanthana was synthesized by the sol–gel method. The samples were characterized by X-ray diffraction (XRD) and Rietveld refinement in order to identify the crystalline phases and their relative weight. H 2 -TPR (Temperature Programmed Reduction) experiments were recorded with the aim to identify the different Co phases present. Co 3 O 4 and LaCoO 3 were formed for La loading of 1%, whereas at higher La loading (9%) LaCoO 3 and La 2 O 3 oxide prevailed. In both catalysts LaAlO 3 phase was also detected. As observed by BET and SEM characterizations, the morphology of the two catalysts was somewhat affected by La:Co atomic ratio and differed dramatically from those of the reference bulk oxides, Co 3 O 4 and the mixed phase LaCoO 3 /La 2 O 3 . Activity tests in C 3 H 6 and CH 4 combustion were carried out in order to discriminate the catalytic properties of different phases formed (Co 3 O 4 , LaCoO 3 , La 2 O 3 , LaAlO 3 ).