Kinetic modeling of the CO/ H2O/O2/NO/SO2 system: Implications for high-pressure fall-off in the SO2 + O(+M) = SO3(+M) reaction

M. A. Mueller, R. A. Yetter, F. L. Dryer

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123 Scopus citations


Flow reactor experiments were performed to study moist CO oxidation in the presence of trace quantities of NO (0-400 ppm) and SO2 (0-1300 ppm) at pressures and temperatures ranging from 0.5-10.0 atm and 950-1040 K, respectively Reaction profile measurements of CO, CO2, O2, NO, NO2, SO2, and temperature were used to further develop and validate a detailed chemical kinetic reaction mechanism in a manner consistent with previous studies of the CO/H2/O2/NOx and CO/H2O/N2O systems In particular, the experimental data indicate that the spin-forbidden dissociation-recombination reaction between SO2 and O-atoms is in the fall-off regime at pressures above 1 atm The inclusion of a pressure-dependent rate constant for this reaction, using a high-pressure limit determined from modeling the consumption of SO2 in a N2O/SO2/N2 mixture at 10.0 atm and 1000 K, brings model predictions into much better agreement with experimentally measured CO profiles over the entire pressure range Kinetic coupling of NOx and SOx chemistry via the radical pool significantly reduces the ability of SO2 to inhibit oxidative processes. Measurements of SO2 indicate fractional conversions of SO2 to SO3 on the order of a few percent, in good agreement with previous measurements at atmospheric pressure Modeling results suggest that, at low pressures, SO3 formation occurs primarily through SO2 + O(+M) = SO3(+M), but at higher pressures where the fractional conversion of NO to NO2 increases, SO3 formation via SO2 + NO2 = SO3 + NO becomes important. For the conditions explored in this study, the primary consumption pathways for SO3 appear to be SO3 + HO2 = HOSO2 + O2 and SO3 + H = SO2 + OH Further study of these reactions would increase the confidence with which model predictions of SO3 can be viewed.

Original languageEnglish (US)
Pages (from-to)317-339
Number of pages23
JournalInternational Journal of Chemical Kinetics
Issue number6
StatePublished - Jun 2000

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry


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