Pyrolysis and oxidation of methyl acetate in a shock tube: A multi-species time-history study

High-temperature methyl acetate (MA) pyrolysis and oxidation were studied behind reflected shock waves using laser-absorption species time-history measurements of CO, CO2, OH and H2O. The shock tube experiments with very dilute fuel mixtures covered a temperature range of 1401–1605K for MA pyrolysis (0.2% MA/Ar) and 1423–1674K for MA oxidation (0.4% O2, ϕ=1), and pressures around 1.5atm. The dominant sensitivity of CO2 concentration to MA unimolecular decomposition reactions enabled accurate determination of the rate coefficient and dissociation branching ratio by monitoring the CO2 time-history during MA pyrolysis. A recent kinetic mechanism developed by Yang et al. [13] originally for interpreting flow reactor and low-pressure flame data was adopted to simulate and compare with the current shock tube data. The measured CO and CO2 time-histories during MA pyrolysis were both well-predicted by the modified Yang et al. [13] mechanism. A relatively complete description of MA oxidation behavior was given by measuring CO, CO2, OH and H2O time-histories at the same temperature and pressure (1480K, 1.5atm). A unique two-stage CO2 formation during MA oxidation was clearly observed in the measured CO2 time-histories over the entire temperature range, with the rapid pre-ignition CO2 formation analyzed to be associated with the initial MA dissociation. Despite the overprediction of MA ignition delay times by 18–40% between 1623 and 1423K, the kinetic model successfully captures the plateau levels and the peak values of all the measured species profiles, as well as simulates the characteristic two-stage formation of CO2 observed experimentally.