Acetaldehyde oxidation at low and intermediate temperatures: An experimental and kinetic modeling investigation

Acetaldehyde oxidation was investigated in a jet-stirred reactor at temperatures from 460 to 900 K, equivalence ratios from 0.5 to 4.0 and pressures of 710-720 Torr. Reactive intermediates under low-temperature conditions, such as methylperoxy, methylhydroperoxide and ketohydroperoxide were detected using synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). A kinetic model for acetaldehyde oxidation was constructed by incorporating recent theoretical and modeling progress of acetaldehyde kinetics, as well as the calculated results of H-atom abstraction reactions of acetaldehyde by acetylperoxy, methylperoxy and methoxy in this work. The present model was then comprehensively validated against the measurements in this work and the experimental data from literature. Modeling analysis reveals that the main chain-branching pathways of acetaldehyde under low-temperature oxidation conditions are the decomposition of acetylhydroperoxide and methylhydroperoxide. The second O2-addition process was verified to exist in the low-temperature oxidation of acetaldehyde as ketohydroperoxide was observed, while its contribution to the overall reactivity was found to be minor under present investigated conditions. On the other hand, the sub-mechanism of acetylperoxy is crucial in the low-temperature regime while the methyl oxidation mechanism dominates in the negative temperature coefficient (NTC) region at all equivalence ratios investigated in this work.