A magnesia-alumina mixed oxide containing both acid sites (3.9 sites/nm(2)) Catalytic evaluation of isopropanol decomposition catalyzed with the magnesia-alumina oxide catalyst showed that acetone and propene as major products were formed through dehydrogenation and dehydration pathways. When water stream was present the inlet feedstock, the catalytic activity for isopropanol decomposition was found to be promoted or inhibited that strongly depends upon the reaction temperature. The selectivity to acetone, however, was significantly enhanced after water addition either isopropanol conversion increasing at a reaction temperature below 300 degrees C or decreasing at a temperature above 300 degrees C. A new reaction pathway of hydroxyls-assisted dehydrogenation was postulated. (c) 2005 Elsevier B.V. All rights reserved.