DRIFTS study of NO-H-2 reaction over Pd/Al2O3 with excess oxygen

Pd (0.1 wt.%)/Al2O3 catalyst was found to be active for the selective NO reduction employing H-2 (NO conversion > 90%) under excess O-2 at low temperatures (110-190degreesC) with good N-2 selectivity (about 70%). The selectivity towards N2O was sensitive to the reaction conditions and decreased as the temperature was raised. The maximum selectivity to NH3 occurred at 190 degreesC. The selectivity to N2O was inhibited greatly by O-2 at low temperatures. Gaseous O-2 promoted the selectivity to N-2 as well as the generation of adsorbed NH species in comparison to the reactions without O-2. In situ diffuse reflectance IR spectroscopy (DRIFTS) measurements suggested that there was competition between H-2 and other adsorbed species such as nitrates and water at low temperatures, and the rate determining step may be the adsorption and activation of H-2 over the catalyst. (C) 2004 Elsevier B.V. All rights reserved