The NO reduction by ethanol over barium promoted Pd/ZrO2 catalyst and the effect of the oxygen on the selectivity were studied. The catalysts were prepared by incipient wetness impregnation with 14.3% of Ba over zirconia and 1% of palladium. The specific surface areas were 58 and 47 m(2)/g and the dispersions of Pd were 37% and 30% for the Pd/ZrO2 and Pd-Ba/ZrO2 catalysts, respectively. The X-ray diffraction patterns indicate the presence of monoclinic zirconia phase on the support and BaCO3, which is decomposed at 715 and 815 degrees C. Temperature programmed desorption profiles of NO on Pd/ZrO2 and Pd-Ba/ZrO2 catalyst showed a huge amount N-2 formation for the promoted Ba catalyst. Catalytic results showed high NO conversion even at low temperature, in accordance with the TPD results and an increasing selectivity to N-2 when compared with Pd/ZrO2. The effect of O-2 in the NOx reduction with ethanol provoked less NO dissociation and lower selectivity to methane. (C) 2009 Elsevier B.V, All rights reserved.