A comparative study of the oxidation of toluene and the three isomers of xylene

This paper presents an experimental and modeling study of the oxidation of toluene, ortho-xylene, meta-xylene, and para-xylene in a jet-stirred reactor. In order to facilitate comparisons, the same experimental conditions were used for the four reactants, i.e. temperatures from 600 to 1100 K, a pressure of 1.07 bar, a residence time of 2 s, an initial fuel mole fraction of 0.005, and equivalence ratios of 0.5, 1 and 2. Compared to literature studies using the same type of reactor, due to higher residence time and initial fuel mole fraction, a higher number of oxygenated aromatic products was quantified and some reactivity was observed at lower temperatures, especially for ortho-xylene, which started to react from 700 K. For this fuel, the formation of phthalan, an aromatic compound including an oxetane ring and indicating low-temperature oxidation chemistry, was confirmed. A new detailed kinetic model combining literature mechanisms was proposed and allowed well predicting the reactivity of the four methylated benzenes of interest with an acceptable simulation of most of the quantified products. Flowrate and sensitivity analyses were made to highlight the similarities and to explain the difference of reactivity between the four investigated reactants.