Some general aspects of aldehyde combustion

A few comments on some general aspects of aldehyde oxidation should be made, and the reader is also referred to Vol. 1 of this series for discussion of experimental techniques. 

For most static low temperature oxidation studies of aldehydes other than formaldehyde it is customary to use acid-washed pyrex vessels. With this surface condition and at temperatures below about 150 °C the oxidation proceeds with a pressure decrease corresponding approximately to the stoichiometry 

The change in temperature accompanying rapidly developing reactions such as cool flames has been used by Griffiths et al. [49] to monitor 

Flow systems [33 36, 53, 54] are not often used in aldehyde oxidation studies since it is not always easy to obtain kinetic data from them and there are problems associated with the purification of the relatively large amounts of reactant needed. However, they have been used successfully, particularly by Russian workers [33—36], to establish many features of formaldehyde oxidation. Under certain circumstances, flow systems offer special advantages. In particular, it may be possible to transform what may be a small separation in time between the cool flame and the second stage into a separation in distance of several centimeters along the axis of a flow reactor and thereby considerably facilitate analysis by means of a probe into a mass spectrometer [55—57] (see Sect. 5.2). 

This section describes the oxidation in the temperature range below that at which appreciable peracid, peracyl or acyl radical decomposition occurs. This is not an entirely satisfactory basis for classification since some peracid decomposition must occur if autocatalysis — a characteristic feature of aldehyde oxidation — is to take place. Furthermore, the proportion of RCO radicals generated which decompose depends not only on the temperature but also on the oxygen pressure. Nevertheless, provided that the oxygen pressure is sufficiently high and the temperature below about 150 °C, peracid formation is almost quantitative, at least over the first 50 % or so of reaction. 

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