Experimental and kinetic modeling of p-cymene pyrolysis under atmospheric and high pressures

Abstract

Metabolic engineering has provided extremely convenient conditions for the manufacture of terpenoids, many of which are considered to be promising alternatives of traditional fossil fuels due to their compatibility with the corresponding structures and properties. One of the terpenoid alternative fuels is p-cymene, a renewable bio-aromatics which may be an excellent aromatics surrogate in jet fuel. In this work, the pyrolysis of p-cymene was experimentally investigated by a tandem micro-reactor and GC–MS/FID online analysis system under 0.1 and 2.0 MPa. A detailed kinetic model containing 172 species and 804 reactions was constructed based on the reference of kinetic models of previous studies on single-branched aromatics pyrolysis, according to which the comparison of experimental and simulated mole fractions of species proves the reasonable reproducibility. ROP (Rate of Production) and sensitivity analysis were performed to further explain the consumption pathways of p-cymene and reactions of significant products. Combined with the calculated BDEs (Bond Dissociation Energies) of p-cymene, the benzylic CC bond scission reaction was determined to be the chain initiation reaction and its proportion decreases from 17.2% at 0.1 MPa to 13.6% at 2.0 MPa, which is mainly due to that high pressure is not conducive to the progress of unimolecular decomposition reaction. The H-abstraction reactions occurring at three sites of p-cymene serve as the most important reactions, accounting for nearly 70% of the total consumption of p-cymene. The ipso-substitution reactions also play an important role in p-cymene consumption, which are critical for the generation of toluene and cumene.