XAS characterization and CO oxidation on delta-allumina supported La, Mn, Co and Fe oxides

delta-Al2O3 supported La, Mn, Co and Fe containing catalysts were prepared by impregnation of delta-Al2O3 with citrate-type precursors and calcination at 1073 K. The catalysts were characterized by X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), X-ray absorption spectroscopy (XAS), and BET specific surface area determination. XRD revealed the presence of delta-Al2O3 in all cases and, at 30 wt.% of metal loading, of other single (alpha-Mn2O3 and alpha-Fe2O3) or mixed (LaAlO3, LaMnO3, CoAl2O4 and LaFeO3) oxide phases. XAS suggested the formation of some oxide phases also at lower loading. In particular, all Mn and 10 wt.% La-Mn containing samples revealed the formation of alpha-Mn2O3, while the 30 wt.% La-Mn bimetallic sample showed the formation of LaMnO3 perovskite. All Co containing samples revealed the presence of CoAl2O4 spinel. Fe containing samples showed the formation of alpha-Fe2O3, while La-Fe containing ones, that of LaFeO3 perovskite.