OXIDATION OF CO BY NO OVER RH(111)

We have studied the oxidation of CO by NO aver a Rh(111) catalyst at pressures between 2 and 120 Torr, paying particular attention to the nitrogen containing products. Reacting 8 Torr of CO with 8 Torr of NO at between 525 and 675 K, we detect three products, CO2, N2O, and N2. All three products are formed with an apparent activation energy (Ea) near 33.5 kcal/mol. Within the range of temperatures and pressures we examined. N2O is the primary N-containing product-Rh(111) is about 70% selective for N2O. The selectivity for N2O is insensitive to reaction temperature, reactant pressure, and NO conversion. By varying the reactant pressure at three different temperatures, we determined that the CO2, N2O, and N2 production rates are all near zero order in both CO and NO pressure. The activation energies, reaction orders, and CO2 production rates we observe are in good agreement with previously reported measurements over Rh(111). The major new result of our work is our finding that N2O, not N2, is the dominant nitrogen-containing product of the CO + NO reaction over a Rh(111) catalyst at temperatures below 650 K. © 1993 Academic Press, Inc.