Low-temperature oxidation and cool flames of propane

A detailed analytical study of the cool-flame oxidation of propane has been carried out using a continuous-flow technique with a view to the further elucidation of the mechanism of the low-temperature oxidation of hydrocarbons. The formation of the three theoretically possible aldehydes has been demonstrated and the initially formed peroxide shown to be hydrogen peroxide. Measurements of the yields of the different products formed under varying conditions of temperature, composition and time of contact have been made and correlated with measurements of the luminous intensity and temperature of the flame. The results confirm the earlier conclusions of Norrish (1948) that aldehydes are the important branching agents in the temperature range of 300 to 400°C, and a detailed scheme based on that proposed earlier has been developed to account for the observations. The scheme has further been shown to allow of a simple explanation of the origin of the periodic character of the cool flame in terms of the thermal instability of the normal slow reaction.