The aim of this work is to study the effect of the thermal treatment at 350 and 500 degrees C on the structure of a Co/alumina-pillared montmorillonite catalyst. For this purpose, the X-ray powder diffraction patterns of the solids, the nitrogen physisorption data at -196 degrees C, the micropore-size distributions, the UV-vis and NIR spectroscopies of the dried materials, the gravimetric and differential thermal analyses, and the temperature-programmed reduction analyses of the supported cobalt catalysts have been analyzed and compared. The impregnation with cobalt and the temperature has modified the textural properties of the alumina-pillared clay supports, giving rise to a loss of surface area and micropore volume in the final catalysts. Co3O4 is the only cobalt oxide species detected in all the supported catalysts. The oxidation of propene at low concentrations over selected cobalt oxide catalysts shows that the structural characteristics of the support influence on the catalytic performance.