Shock-tube and modeling study of acetaldehyde pyrolysis and oxidation

Pyrolysis and oxidation of acetaldehyde were studied behind reflected shock waves in the temperature range 1000–1700 K at total pressures between 1.2 and 2.8 atm. The study was carried out using the following methods, (1) time-resolved IR-laser absorption at 3.39 μm for acetaldehyde decay and CH-compound formation rates, (2) time-resolved UV absorption at 200 nm for CH2CO and C2H4 product formation rates, (3) time-resolved UV absorption at 216 nm for CH3 formation rates, (4) time-resolved UV absorption at 306.7 nm for OH radical formation rate, (5) time-resolved IR emission at 4.24 μm for the CO2 formation rate, (6) time-resolved IR emission at 4.68 μm for the CO and CH2CO formation rate, and (7) a single-pulse technique for product yields. From a computer-simulation study, a 178-reaction mechanism that could satisfactorily model all of our data was constructed using new reactions, CH3CHO (+M) → CH4 + CO (+M), CH3CHO (+M) → CH2CO + H2(+M), H + CH3CHO → CH2CHO + H2, CH3 + CH3CHO → CH2CHO + CH4, O2 + CH3CHO → CH2CHO + HO2, O + CH3CHO → CH2CHO + OH, OH + CH3CHO → CH2CHO + H2O, HO2 + CH3CHO → CH2CHO + H2O2, having assumed or evaluated rate constants. The submechanisms of methane, ethylene, ethane, formaldehyde, and ketene were found to play an important role in acetaldehyde oxidation. © 2007 Wiley Periodicals, Inc. 40: 73–102, 2008