Kinetic and thermodynamic issues in the formation of aromatic compounds in flames of aliphatic fuels

Abstract

We have formulated a chemical kinetic model to predict the growth of higher hydrocarbons in a lightly sooting C 2H 2/O 2/Ar flame. The predictions of the model compare favorably with the experimental results of Bastin et al. (Twenty-Second Combustion Symposium). Analysis of the mechanism shows that reactions of 1CH 2 play a central role in forming the C 3 and C 4 hydrocarbons that ultimately lead to ring formation. Several possibilities are considered for the cyclization reaction. The most likely candidates involve reaction complexes in which the hydrogen atoms are not optimally placed. This point is discussed in some detail. We argue that the “first ring” is most likely formed by reaction of two propargyl radicals, C 3H 3 + C 3H 3 ⇐ C 6H 5 + H or C 3H 3 + C 3H 3 ⇐ C 6H 6.