Oxidation study of small hydrocarbons at elevated pressure. Part I: Neat 1,3-butadiene

To study the formation pathways of aromatic compounds in the oxidation process of soot precursors under different equivalent ratios (φ), two parts of work were carried out. The present work was the part I: the oxidation of 1,3-butadiene (1,3-C4H6) was studied in a jet-stirred reactor at high-pressure (12 atm) within a temperature range covering 575–1075 K, at fuel equivalence ratios (φ) of 0.5 and 3.0. Part II focused on the study of oxidation of a two-compound mixture of acetylene and 1,3-butadiene. Mole fraction profiles of 20 species obtained by GC/MS analysis were identified and quantified. The measured species profiles serve as a data base for the further development of a detailed chemical kinetic reaction mechanism AramcoMech 3.0 generated by Zhou et al. previously for describing the ignition delay time and laminar flame speed of 1,3-butadien. The resulting reaction mechanism comprising 625 species and 3188 reactions was found to be able to describe credibly the experimental species profiles. Rate-of-production (ROP) analysis reveals that addition reactions of H and OH radicals to 1,3-C4H6 are the major channels governing 1,3-C4H6 consumption under both fuel-lean and fuel-rich conditions. Acetylene (C2H2), vinyl acetylene (C4H4), and propargyl radicals (C3H3) are playing important roles within the formation of mono-aromatics. Here, benzene is mainly formed via the C2 + C4 pathways instead of the C1 + C5 routes. Furthermore, C3H3 radicals were found to play a key role within C6H5CH3 formation. Naphthalene are formed by the reactions of C6H6 and 1,3-C4H6 or C4H5N/I radicals. These results will enrich the understanding of elevated pressure chemistry of 1,3-C4H6 and facilitate to further model development and validation focusing on a more detailed description of the formation network of aromatic compounds.