Abstract
New experimental results were obtained for the mutual sensitization of the oxidation of NO and methane in a fused silica jet‐stirred reactor operating at 10^5^ Pa, over the temperature range 800–1150 K. The effect of the addition of sulfur dioxide was studied. Probe sampling followed by online FTIR analyses and off‐line GC‐TCD/FID analyses allowed the measurement of concentration profiles for the reactants, stable intermediates, and final products. A detailed chemical kinetic modeling of the present experiments was performed. An overall reasonable agreement between the present data and modeling was obtained. According to the present modeling, the mutual sensitization of the oxidation of methane and NO proceeds via the NO to NO~2~ conversion by HO~2~ and CH~3~O~2~. The conversion of NO to NO~2~ by CH~3~O~2~ is more important at low temperatures (800 K) than at higher temperatures (850–900 K) where the production of NO~2~ is mostly due to the reaction of NO with HO~2~. The NO to NO~2~ conversion is favored by the production of the HO~2~ and CH~3~O~2~ radicals yielded from the oxidation of the fuel. The production of OH resulting from the oxidation of NO accelerates the oxidation of the fuel: NO + HO~2~ → OH+ NO~2~ followed by OH + CH~4~→ CH~3~. In the lower temperature range of this study, the reaction further proceeds via CH~3~ + O~2~→ CH~3~O~2~; CH~3~O~2~+ NO → CH~3~O + NO~2~. At higher temperatures, the production of CH~3~O involves NO~2~: CH~3~+ NO~2~→ CH~3~O. This sequence of reactions is followed by CH~3~O → CH~2~O + H; CH~2~O +OH → HCO; HCO + O~2~ → HO~2~ and H + O~2~ → HO~2~ → CH~2~O + H; CH~2~O +OH → HCO; HCO + O~2~ → HO~2~ and H + O~2~ → HO~2~. The data and the modeling show that unexpectedly, SO~2~ has no measurable effect on the kinetics of the mutual sensitization of the oxidation of NO and methane in the present conditions, whereas it frequently acts as an inhibitor in combustion. This result was rationalized via a detailed kinetic analysis indicating that the inhibiting effect of SO~2~ via the sequence of reactions SO~2~+H → HOSO, HOSO+O~2~ → SO~2~+HO~2~, equivalent to H+O~2~HO~2~, is balanced by the reaction promoting step NO+HO~2~ → NO~2~+OH. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: 406–413, 2005