An extended mechanism including high pressure conditions (700 bar) for toluene pyrolysis

Toluene pyrolysis was studied between 350 °C and 400 °C under 700 bar pressure using confined pyrolysis (gold cells). A detailed kinetic model consisting of 30 free-radical reactions was developed to describe the thermal cracking of toluene at low conversion. The mechanism considered is consistent with the experimental results concerning conversion as well as formation of the main products (benzene, methane, biaromatic compounds). This study shows that high pressure and low temperature are favorable to bimolecular reactions. Thus, additions of benzyl radicals to aromatic rings lead to the formation of biaromatic compounds. Yet, the most important conclusions concern the initiation reactions for which a bimolecular mechanism (or RRD: reverse radical disproportionation) needed to be considered. The relative importance of the monomolecular vs. bimolecular initiation mechanism changes as a function of temperature and pressure. The extension of the published mechanisms by our results allows to significantly increase the temperature–pressure domain for the modeling of toluene pyrolysis.