A Shock Tube Study of H2 + OH → H2O + H Using OH Laser Absorption

Abstract

ABSTRACTThe rate constant for the reaction of hydroxyl radicals (OH) with molecular hydrogen (H2) was measured behind reflected shock waves using UV laser absorption of OH radicals near 306.69 nm. Test gas mixtures of H2 and tert‐butyl hydroperoxide (TBHP) diluted in argon were shock‐heated to temperatures ranging from 902 to 1518 K at pressures of 1.15–1.52 atm. OH radicals were produced by rapid thermal decomposition of TBHP at high temperatures. The rate constant for the title reaction was inferred by best fitting the measured OH time histories with the simulated profiles from the comprehensive reaction mechanism of Wang et al. (USC‐Mech v2.0) (2007). The measured values can be expressed in the Arrhenius equation as k1(T) = 4.38 × 1013 exp(–3518/T) cm3 mol−1 s−1 over the temperature range studied. A detailed error analysis was performed to estimate the overall uncertainty of the title reaction, and the estimated (2 – σ) uncertainties were found to be ±17% at 972 and 1228 K. The present measurements are in excellent agreement with the previous experimental studies from Frank and Just (Ber Bunsen‐Ges Phys Chem 1985, 89, 181–187), Michael and Sutherland (J Phys Chem 1988, 92, 3853–3857), Davidson et al. (Symp (Int) Combust 1988, 22, 1877–1885), Oldenborg et al. (J Phys Chem 1992, 96, 8426–8430), and Krasnoperov and Michael (J Phys Chem A 2004, 108, 5643–5648).In addition, the measured rate constant is in close accord with the non‐Arrhenius expression from GRI‐Mech 3.0 (http://www.me.berkeley.edu/gri_mech/) and the theoretical calculation using semiclassical transition state theory from Nguyen et al. (Chem Phys Lett 2010, 499, 9–15).