Shock-tube and modeling study of ethane pyrolysis and oxidation

Prolysis and oxidation of ethane were studied behind reflected shock waves in the temperature range 950-1900 K at pressures of 1.2-4.0 atm. Ethane dec ay rates in both pyrolysis and oxidation were measured using time-resolved infrared (IR) laser absorption at 3.39 mu m, and CO2 production rates in ox idation were measured by time-resolved thermal IR emission at 4.24 mu m. Th e product yields were also determined using a single-pulse method. The pyro lysis and oxidation of ethane were modeled using a reaction mechanism with 157 reaction steps and 48 species including the most recent submechanisms f or formaldehyde, ketene, methane, acetylene, and ethylene oxidation. The pr esent and previously reported shock tube data were reproduced using this me chanism. The rate constants of the reactions C2H6 --> CH3 + CH3, C2H5 + H - -> C2H4 + H-2 --> and C2H5 + O-2 --> C2H4 + HO2 were evaluated. These react ions were important in predicting the previously reported and thr present d ata, which were for mixture compositions ranging from ethane-Pith (includin g ethane pyrolysis) to ethane-lean. The evaluated rate constants of the rea ctions C2H5 + H --> C2H4 + H-2 and C2H5 + O-2 --> C2H4 + HO2 were found to be significantly different from currently accepted values. (C) 1999 by The Combustion Institute.