The oxidation of n-butane and n-heptane in a CFR engine. Isomerization reactions and delay of autoignition

During the oxidation of n-butane in a flow system and also in a motored CFR engine (600 rpm) hydrogen peroxide, primary and secondary butylhydroperoxides, and peracetic acid are formed. In the CFR engine these peroxides appear only when the compression ratio is larger than 10:1 ( T max = 650 K). No autoignition has been observed. A comparison of n-butane and n-heptane oxidation is presented. Isomerization reactions, which are correlated with the alkane structure and the octane number, account for the differences in the experimental results.