Influence of H₂O and O₂ on the Homogeneous Conversion of Toluene and the Underlying Reaction Mechanisms

Abstract

In this study, the impact of H2O and O2 on the homogeneous conversion of toluene at various temperatures and concentrations was investigated. Molecular dynamics simulations were performed using the ReaxFF force field to decipher the underlying high-temperature reaction dynamics among toluene, H2O, and O2. In the presence of both H2O and O2, the toluene conversion efficiency reached 98%, primarily producing H2 and CO. Toluene conversion and H2 and CO generation were strengthened under 1–2% O2 with 5–15% H2O. Conversely, elevated O2 (3%) and H2O (25–35%) hindered the combustible gas yield. Two principal H2 and CO formation pathways were identified: (1) Under high temperatures, H2O and O2 generate OH radicals, promoting toluene side chain conversion into (CHO) entities, which subsequently break down into H2 and CO. (2) The toluene-benzene ring disintegrates under OH radical activity. The resulting fragments, in the presence of H2O, produce H2 and CO. The simulation insights were validated by D2O and 18O2 isotope labeling experiments.