Surface structure and acid–base properties of lanthanum oxide dispersed on silica and alumina catalysts

Abstract

Supported lanthanum oxide catalysts were prepared by the impregnation method, using an aqueous solution of lanthanum nitrate hexahydrate (La(NO₃)₃·6H₂O), then calcined at 920 K for 2 h. Characterization of the samples was carried out by X-ray diffraction, N₂-adsorption at −196 °C and IR spectroscopy of the calcination products. The surface acidity was studied by IR spectroscopy of adsorbed pyridine at different temperatures. GC was used to investigate the decomposition of propan-2-ol on the surface of the catalysts. X-ray diffractometry revealed that La₂O₃ crystallites are dispersed on the silica and alumina surfaces. The surface area of the support was decreased by increasing the loading level of La₂O₃. It was also found that the surface of the supported catalysts had strong different Lewis acid sites and basic sites. Propan-2-ol was found to decompose to acetone (dehydrogenation). The dehydration reaction gave propene as the sole product.