Propionaldehyde oxidation at intermediate temperatures

For intermediate temperatures (between about 200 and 400 °C) the oxidation is complicated by the onset of appreciable peracid and peracyl radical decomposition. There is no longer either a simple stoichiometry or a simple relationship between extent of the reaction and the pressure change appreciable production of low molecular weight material occurs (Fig. 27). The maximum rate of pressure decrease is proportional to the square of the initial aldehyde concentration and is independent of the 

At 220 °C peracid or peracid/aldehyde branching is still probable, and since for high O2/C2H5CHO ratios the kinetics resemble those obtained below 150 °C, the overall mechanism is almost certainly the same as that at the lower temperatures with additional complications arising from RCO decomposition and the subsequent reactions of C2H5 radicals. Since the amount of CO2 produced after the peracid maximum (Fig. 27) is approximately the same as the amount of peracid lost, it seems reasonable to suppose that, as at the lower temperature, CO2 is produced in the branching process. 

---