Product formation in low-temperature (575 K � 700 K) oxidation of n-butane was investigated using tunable synchrotron photoionization time-of-flight mass spectrometry in a flow reactor at low pressure (4 Torr). These experiments probe the time-resolved formation of products following laser-photolytic chlorine initiation of the oxidation, and identify isomeric species by their photoionization spectra. The main oxidation products were observed at m/z = 56 (C4H8) and 72 (C4H8O), associated with chain-terminating HO2 and chain-propagating OH formation, respectively. Relative yields of the C4H8 (cis-2-butene, trans-2-butene, and 1-butene) and C4H8O product isomers (2,3-dimethyloxirane, 2-methyloxetane, tetrahydrofuran, ethyloxirane, butanal, and butanone) are in good agreement with the only available literature measurement from 753 K. Time-resolved formation of ketohydroperoxides (m/z = 104) was also observed, originating from the �second� oxygen addition to hydroperoxybutyl radicals and subsequent internal abstraction/dissociation leading to ketohydroperoxide + OH.

Unravelling autoignition chemistry of <i>n</i>-butane from isomer-resolved product formation measurements using synchrotron photoionization mass spectrometry

245th National Meeting (2013)

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Unravelling autoignition chemistry of n-butane from isomer-resolved product formation measurements using synchrotron photoionization mass spectrometry