On the rate constants of OH + HO2 and HO2 + HO2: A comprehensive study of H2O2 thermal decomposition using multi-species laser absorption

Hydrogen peroxide (H2O2) and hydroperoxy (HO2) reactions present in the H2O2 thermal decomposition system are important in combustion kinetics. H2O2 thermal decomposition has been studied behind reflected shock waves using H2O and OH diagnostics in previous studies (Hong et al. (2009) [9] and Hong et al. (2010) [6,8]) to determine the rate constants of two major reactions: H2O2 + M → 2OH + M (k1) and OH + H2O2 → H2O + HO2 (k2). With the addition of a third diagnostic for HO2 at 227 nm, the H2O2 thermal decomposition system can be comprehensively characterized for the first time. Specifically, the rate constants of two remaining major reactions in the system, OH + HO2 → H2O + O2 (k3) and HO2 + HO2 → H2O2 + O2 (k4) can be determined with high-fidelity.No strong temperature dependency was found between 1072 and 1283 K for the rate constant of OH + HO2 → H2O + O2, which can be expressed by the combination of two Arrhenius forms: k3 = 7.0 × 1012 exp(550/T) + 4.5 × 1014 exp(−5500/T) [cm3 mol−1 s−1]. The rate constants of reaction HO2 + HO2 → H2O2 + O2 determined agree very well with those reported by Kappel et al. (2002) [5]; the recommendation therefore remains unchanged: k4 = 1.0 × 1014 exp(−5556/T) + 1.9 × 1011+exp(709/T) [cm3 mol−1 s−1]. All the tests were performed near 1.7 atm.