Experimental and kinetic modeling investigation of rich premixed toluene flames doped with n-butanol

Abstract

n-Butanol is a promising renewable biofuel and has a lot of advantages as a gasoline additive compared with ethanol. Though the combustion of pure n-butanol has been extensively investigated, the chemical structures of large hydrocarbons doped with n-butanol, especially for aromatic fuels, are still insufficiently understood. In this work, rich premixed toluene/n-butanol/oxygen/argon flames were investigated at 30 Torr with synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). The blending ratio of n-butanol was varied from 0 to 50%, while the equivalence ratio was maintained at a quite rich value (1.75) for the purpose of studying the influence of n-butanol on the aromatic growth process. Flame species including radicals, reactive molecules, isomers and polycyclic aromatic hydrocarbons (PAHs) were identified and their mole fraction profiles were measured. A kinetic model of toluene/n-butanol combustion was developed from our recently reported toluene and n-butanol models. It is observed that the production of most toluene decomposition products and larger aromatics was suppressed as the blending ratio of n-butanol increases. Meanwhile, the addition of n-butanol generally enhanced the formation of most observed C2-C4 hydrocarbons and C1-C4 oxygenated species. The rate of production (ROP) analysis and experimental observations both indicate that the interaction between toluene and n-butanol in their decomposition processes mainly occurs at the formation of small intermediates, e.g. acetylene and methyl. In particular, the interaction between toluene and n-butanol in methyl formation influences the formation of large monocyclic aromatics such as ethylbenzene, styrene and phenylacetylene, making their maximum mole fractions decay slowly upon increasing the blending ratio of n-butanol compared with toluene and benzyl. The increase of the blending ratio of n-butanol reduces the formation of key PAH precursors such as benzyl, fulvenallenyl, benzene, phenyl and propargyl, which leads to a remarkable reduction in the formation of PAHs.

Product detection study of the gas-phase oxidation of methylphenyl radicals using synchrotron photoionisation mass spectrometry

“…1 In high-temperature and combustion-related studies, methylated benzenes are subjected to H-atom abstraction by OH, and other radicals, and chemical models consider the production and fate of both methylphenyl and benzyl radicals. [2][3] No direct detection of a methylphenyl radical within a combustion environment has been reported to our knowledge. The o-methylphenyl (o-MPh) radical, also known as the o-tolyl radical, is implicated in the oxidation of o-xylene, [4][5][6] and also in benzyl decomposition schemes.…”

Assessment of Soil Contamination by Gas Cloud Generated from Chemical Fire Using Metabolic Profiling and Associated Bacterial Communities

“…If C 8 H 7 radical accepts one hydrogen atom, ethenylbenzene can be produced. Another report also proved that styrene production from toluene combustion with butanol flame [15]. The explained products generated from toluene combustion can be phenylacetylene (ethynylbenzene), styrene (ethenylbenzene), ethylbenzene, indenyl, indene, and naphthalene.…”

Five vs. six membered-ring PAH products from reaction of o-methylphenyl radical and two C3H4 isomers

“…[21][22][23] Although no direct detection of a methylphenyl radical has been reported from such environments, existing chemical models of combustion incorporate the reactions of both benzyl and methylphenyl radicals. [24][25][26][27][28] Additionally, through H atom or CH3 loss, common during combustion, methylated and other functionalized PAHs could produce larger PAH analogues of the methylphenyl radical. [29][30] Once generated these radical species can undergo subsequent reactions with other hydrocarbons leading to unique product channels.…”