Decomposition of acetaldehyde: Experiment and detailed theory

The classic pyrolytic decomposition of acetaldehyde has been examined to the higher temperatures used in combustion and also lower pressures with 85 laser-schlieren, shock-tube measurements of density gradient covering 40-500 torr and 1550-2400 K. This work is supplemented and modeled with a CASPT2 based variable reaction coordinate RRKM prediction of the dissociation kinetics. These RRKM predictions are then incorporated in good two-dimensional master equation fits of the strong falloff seen in the laser-schlieren experiments, and also that shown in some previous shock-tube results using UV absorption of the acetaldehyde as diagnostic. The laser-schlieren data provide not only unambiguous dissociation rates but also solid indications of the secondary chemistry. Modeling of the full density gradient profiles offers good estimates of rates for H-atom abstraction from both the acetaldehyde and the HCO radical, again at high temperatures.