Experimental and kinetic modeling studies of isoprene pyrolysis at low and atmospheric pressures

Isoprene (2-methyl-1,3-butadiene) is not only the main component in gasoline and a potential fuel addi-tive, but also is considered an important precursor of polycyclic aromatic hydrocarbons. To better under-stand the isoprene pyrolysis process, the pyrolysis experiments of isoprene in a flow reactor were per-formed at p = 30 Torr for T = 1056 - 1446 K, and p = 760 Torr for T = 850 - 1231 K. More than twenty pyrolysis species, especially radicals (methyl, propargyl, and but-2-yne-1-yl), isomers (allene/propyne, buta-1,2,3-triene/vinylacetylene, 1,3-butadiene/1-butyne), and aromatics (benzene, toluene, phenylacety-lene, styrene, indene, and naphthalene), were identified and their mole fraction profiles were measured using synchrotron vacuum ultraviolet photoionization mass spectrometry. The potential energy surfaces of the unimolecular decomposition, H/CH3-abstraction, and H/CH3-addition reactions of isoprene were also calculated using quantum chemical calculations at the CBS-QB3 level. Based on the experimental and theoretical results, a detailed kinetic model was developed and validated against the pyrolysis ex-perimental dataset of isoprene from this work and Grajales-Gonzalez et al. H-addition reactions on the double bond and H-abstraction reactions by H/CH3 radicals controlled the consumption of isoprene. The C-H bond dissociation reaction on the -CH3 was the dominant unimolecular reaction in comparison with the isomerization reactions. Abundant aromatics were produced in isoprene pyrolysis, especially at atmo-spheric pressure, which is ascribed to the high-level concentration of C(2)-C(4) hydrocarbons formation, such as acetylene, ethylene, allene, propyne, 1,3-butadiene, etc.(c) 2022 The Combustion Institute. Published by Elsevier Inc. All rights reserved.