Adsorptive and catalytic properties of alumina-supported Pd-Mo catalysts

The adsorption properties of ethanol, CO, and NO on Pd, Mo, and Pd-20Mo/Al2O3 catalysts were studied using TPD and IR techniques as well as the reactions of NO + CO and ethanol + NO. The presence of Pd favored decomposition and dehydrogenation of ethanol, while Mo presented activity for oxidative dehydrogenation, The Pd-Mo catalyst showed better formation of N-2 on TPD of NO, probably due to the NO adsorption on partially reduced molybdenum oxide. DRIFT results for the NO + CO reaction on the Pd-20Mo catalyst exhibited bands which correspond to nitrate or nitrous complexes and hydroxyl groups besides NCO species. MoO3 addition to a Pd/Al2O3 catalyst favored the formation of acetaldehyde at lower temperatures. A redox mechanism was proposed to explain the molybdenum promotional effect on Pd in the CO + NO reaction, evidencing Mo as promoter when the reducible oxide reacts with NO, However, molybdenum oxide does not promote the ethanol + NO reaction and this may be due to different reaction mechanisms. (C) 2000 Academic Press.