Polar Aromatic Compounds in Soot from Premixed Flames of Kerosene, Synthetic Paraffinic Kerosene, and Kerosene–Synthetic Biofuels

Abstract

Polar Aromatic Compounds (PAC) adsorbed on soot produced in laboratory premixed flames of fossil kerosene (Jet A-1), Synthetic Paraffinic Kerosene (SPK), and Jet A-1 - synthetic biofuels (2,5-dimethylfuran, methyloctanoate, diethylcarbonate and 1-butanol) were characterized for the first time in the aim of shedding light on the combustion mechanisms and evaluating the environmental impact of these synthetic biofuels. The following families of compounds were fractioned from the soot extracts and further their relative abundances estimated: (a) oxa-AHs (xanthenes, benzoxanthene, alcoxy-AHs, furan…); (b) aldehydes-AHs, (c) ketones-AHs; (d) quinones-AHs; (e) aromatic monocarboxylic acids; (f) aromatic hydroxy-acids; (g) aromatic dicarboxylic acids; (h) nitrated-AHs (including amines, acridines, cinnoline derivatives, carbazoles…); (i) nitro-AHs. The results obtained point out that overall, soot from Jet A-1 - biofuels premixed flames are richer in PAC than soot from pure Jet A-1 and SPK. Out of the fuels studied, Jet A-1 - 1-butanol produces the highest concentrations of nitro-AHs (namely nitro-benzaldehydes), of aldehydes-AH and hydroxy-AHs (including two isomers of hydroxy-benzaldehyde); whereas Jet A-1 - diethylcarbonate produces the highest concentrations of quinone-AHs (especially phenanthrene-quinones) and large concentrations of nitrated-AHs. On the other hand, soot from Jet A-1 - methyloctanoate is the richest one in mono aromatic and dicarboxylic acids, aromatic hydroxyacids, nitrated-AHs, and esters. Combustion of the Jet A-1 - 2,5-dimethylfuran mixture emits the highest concentrations of ketone-AHs, and oxa-AHs (namely, furan derivatives). We should remark that although the soot samples were obtained from pre-mixed flames, the lab conditions being far from the industrial conditions, particularly in terms of pressure; the chemistry going on should not be so different that our findings could not be extrapolated to industrial conditions.