High pressure studies of moist carbon monoxide nitrous oxide kinetics

Flow reactor experiments were performed over the pressure range of 3-15 atm and temperature range of 950-1123 K to study the reaction kinetics of CO/N2O/H2O/N-2 mixtures. Experimentally measured profiles of CO, CO2, N2O, NO, O-2, H2O, and temperature were used to constrain the development of a detailed chemical kinetic mechanism. For the first time, the catalytic effect of water vapor has been clearly measured and a quantitative treatment of its influence on the overall reaction rate has been possible. Even at the lowest level of water vapor achievable in the experiments (similar to 10 ppm), the reaction proceeded through the two-step straight-chain sequence of hydrogen atoms reacting with nitrous oxide, producing hydroxyl radicals, which then reacted with carbon monoxide to reform H-atoms and continue the chain. The direct reaction of carbon monoxide with nitrous oxide was found to be insignificant and not necessary in the model to predict the observed species profiles. However, the high-temperature rate constant of this reaction still remains in question. The results also show that pressure fall-off behavior of the reaction CO + O + M = CO2 + M must be included in the mechanism at intermediate temperatures and superatmospheric pressures. Finally, the detailed kinetic model developed predicts the measured species profiles over the entire range of conditions studied here, and is consistent with previously and concurrently studied mechanisms for N2O decomposition and reacting H-2/N2O mixtures. (C) 1997 by The Combustion Institute.