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

✍ Scribed by M. A. Mueller; R. A. Yetter; F. L. Dryer

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 548 KB
• Volume: 32
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/(sici)1097-4601(2000)32:6<317::aid-kin1>3.0.co;2-l

✦ Synopsis

Flow reactor experiments were performed to study moist CO oxidation in the presence of trace quantities of NO (0-400 ppm) and SO 2 (0-1300 ppm) at pressures and temperatures ranging from 0.5-10.0 atm and 950-1040 K, respectively. Reaction profile measurements of CO, CO 2 , O 2 , NO, NO 2 , SO 2 , 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/H 2 /O 2 /NO X and CO/H 2 O/N 2 O systems. In particular, the experimental data indicate that the spin-forbidden dissociation-recombination reaction between SO 2 and Oatoms 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 SO 2 in a N 2 O/SO 2 /N 2 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 NO X and SO X chemistry via the radical pool significantly reduces the ability of SO 2 to inhibit oxidative processes. Measurements of SO 2 indicate fractional conversions of SO 2 to SO 3 on the order of a few percent, in good agreement with previous measurements at atmospheric pressure. Modeling results suggest that, at low pressures, SO 3 formation occurs primarily through SO 2 ϩ O(ϩM) ϭ SO 3 (ϩM), but at higher pressures where the fractional conversion of NO to NO 2 increases, SO 3 formation via SO 2 ϩ NO 2 ϭ SO 3 ϩ NO becomes important. For the conditions explored in this study, the primary consumption pathways for SO 3 appear to be SO 3 ϩ HO 2 ϭ HOSO 2 ϩ O 2 and SO 3 ϩ H ϭ SO 2 ϩ OH. Further study of these reactions would increase the confidence with which model predictions of SO 3 can be viewed.