Flow reactor studies and kinetic modeling of the H 2 /O 2 /NO X and CO/H 2 O/O 2 /NO X reactions

Flow reactor experiments were performed over wide ranges of pressure (0.5–14.0 atm) and temperature (750–1100 K) to study H2/O2 and CO/H2O/O2 kinetics in the presence of trace quantities of NO and NO2. The promoting and inhibiting effects of NO reported previously at near atmospheric pressures extend throughout the range of pressures explored in the present study. At conditions where the recombination reaction H + O2 (+M) = HO2 (+M) is favored over the competing branching reaction, low concentrations of NO promote H2 and CO oxidation by converting HO2 to OH. In high concentrations, NO can also inhibit oxidative processes by catalyzing the recombination of radicals. The experimental data show that the overall effects of NO addition on fuel consumption and conversion of NO to NO2 depend strongly on pressure and stoichiometry. The addition of NO2 was also found to promote H2 and CO oxidation but only at conditions where the reacting mixture first promoted the conversion of NO2 to NO. Experimentally measured profiles of H2, CO, CO2, NO, NO2, O2, H2O, and temperature were used to constrain the development of a detailed kinetic mechanism consistent with the previously studied H2/O2, CO/H2O/O2, H2/NO2, and CO/H2O/N2O systems. Model predictions generated using the reaction mechanism presented here are in good agreement with the experimental data over the entire range of conditions explored. © 1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 705–724, 1999