Determination of the Rate Coefficients of the SO2 + O + M → SO3 + M Reaction

Rate coefficients of the title reaction R-31 (SO2 + O + M -> SO3 + M) and R-56 (SO2 + HO2 -> SO3 + OH), important in the conversion of S(IV) to S(VI), were obtained, at T = 970-1150 K and rho(ave) = 16.2 mu mol cm(-3) behind reflected shock waves by a perturbation method Shock-heated heated H-2/O-2/Ar mixtures were perturbed by adding small amounts of SO2 (1%, 2%, and 3%) and the OH temporal profiles were then measured using laser absorption spectroscopy Reaction rate coefficients were elucidated by matching the characteristic reaction times acquired from the individual experimental absorption profiles via simultaneous optimization of k(31) and k(50) values in the reaction modeling (for satisfactory matches to the observed characteristic times, it was necessary to take into account R-56) In the experimental conditions of this study, R-31 is in the low-pressure limit The rate coefficient expressions fitted using the combined data of tills study and the previous experimental results are k(31.0)/[Ar] = 2 9 x 1035 T-6.0 exp(-4780 K/T) + 6.1 X 10(24) T-3.0 exp(-1980 K/T) cm(6) mol(-2) s(-1) at T = 300-2500 K. k(56) = 1.36 x 10(11) exp(-3420 K/T) cm(3) mol(-1) s(-1) at T = 970-1150 K Computer simulations of typical aircraft engine environments using the reaction mechanism with the above k(31.0) and k(56) expressions. gave the maximum S(IV) to S(VI) conversion yield of ca 3.5% and 2.5% for the constant density and constant pressure flow condition, respectively Moreover, maximum conversions occur at rather higher temperatures (similar to 1200 K) than that. where the maximum k(31.0) value is located (similar to 800 K) This is because the conversion yield is dependent upon not only the k(31.0) and k(56) values (production flux) but also the availability of H, O, and HO2 in the system (consumption flux) (C) 2010 Wiley Periodicals, Inc * Int J Chem Kinet 42 168-180, 2010