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 additive, but also is considered an important precursor of polycyclic aromatic hydrocarbons. To better understand the isoprene pyrolysis process, the pyrolysis experiments of isoprene in a flow reactor were performed 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, phenylacetylene, 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/CH 3 -abstraction, and H/CH 3 -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 experimental dataset of isoprene from this work and Grajales-González et al. H-addition reactions on the double bond and H-abstraction reactions by H/CH 3 radicals controlled the consumption of isoprene. The C–H bond dissociation reaction on the –CH 3 was the dominant unimolecular reaction in comparison with the isomerization reactions. Abundant aromatics were produced in isoprene pyrolysis, especially at atmospheric 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. [ABSTRACT FROM AUTHOR]