Primary combustion intermediates in lean and rich low-pressure premixed laminar 2-methylfuran/oxygen/argon flames

Combustion intermediates in low-pressure premixed laminar 2-methylfuran (MF)/oxygen/argon flames with equivalence ratios of 0.8 and 1.5 were investigated using tunable synchrotron vacuum ultraviolet photoionization and molecular beam mass spectrometry. MF is a promising biofuel with great potential of being used in different fields, including the auto industry. However, the combustion chemistry of MF is not clear. Photoionization mass spectra of MF/oxygen/argon flames were recorded as well as the photoionization efficiency curves (PIEs) of the combustion intermediates. Ionization energies (IEs) were measured from the PIEs. The combustion intermediates were identified by comparing the measured IEs to those reported in the literature or calculated with the method ab initio. Possible reaction pathways of MF and its primary combustion derivatives were constructed on the basis of the combustion intermediates identified. H abstraction and the consecutive reaction products were identified, including furfural, (Z)-1-oxo-1,3,4-pentatriene, 2-ethylfuran, 2-vinylfuran, etc. 2-Oxo-2,3-dihydrofuran was also observed, which may originate from the OH addition products on the furan ring. Furan was not observed in the low-pressure MF flames. Substituted ketenes, (Z)-1-oxo-1,3,4-pentatriene and (E)-1-oxo-1,3-butadiene, were both detected in the low-pressure MF flames.