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Kinetic modeling of the CO/H 2 O/O 2 /NO/SO 2 system: Implications for high‐pressure fall‐off in the SO 2 + O(+M) = SO 3 (+M) reaction
Author(s) -
Mueller M. A.,
Yetter R. A.,
Dryer F. L.
Publication year - 2000
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/(sici)1097-4601(2000)32:6<317::aid-kin1>3.0.co;2-l
Subject(s) - chemistry , nox , kinetic energy , dissociation (chemistry) , atmospheric pressure , reaction rate constant , analytical chemistry (journal) , partial pressure , atmospheric temperature range , reaction mechanism , thermodynamics , kinetics , oxygen , meteorology , catalysis , combustion , organic chemistry , physics , quantum mechanics
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 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 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 + O(+M) = SO 3 (+M), but at higher pressures where the fractional conversion of NO to NO 2 increases, SO 3 formation via SO 2 + NO 2 = SO 3 + NO becomes important. For the conditions explored in this study, the primary consumption pathways for SO 3 appear to be SO 3 + HO 2 = HOSO 2 + O 2 and SO 3 + H = SO 2 + OH. Further study of these reactions would increase the confidence with which model predictions of SO 3 can be viewed. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 317–339, 2000