Determination of the Rate Coefficients of the CH₄ + O₂ → HO₂ + CH₃ and HCO + O₂ → HO₂ + CO Reactions at High Temperatures

Abstract

Rate coefficients of the title reactions, R1 (CH4 + O2 → HO2 + CH3) and R2 (HCO + O2 → HO2 + CO) were obtained over T = 1610 ~ 1810 K and T = 200 ~ 1760 K, respectively, and at ρ = 7.1 µmol/cm3. A lean CH4/O2/Ar mixture (0.1% CH4, ϕ = 0.02) was heated behind reflected shock waves and the temporal OH absorption profiles were measured using a laser absorption spectroscopy. Reaction rate coefficients were elucidated by matching the experimental profiles via optimization of k1 and k2 values in the reaction simulation. The rate coefficient expressions derived are k1 = 1.46 × 1014 exp (−26 210 K/T) cm3/mol/s, T = 1610 ~ 1810 K and k2 = 1.9 × 1012 T0.176 exp (−245 K/T) cm3/mol/s, T = 200 ~ 1760 K.