Experimental and kinetic modeling study of a-methylnaphthalene pyrolysis: Part I. Formation of monocyclic aromatics and small species

a-Methyl-naphthalene is a very important intermediate in fuel oxidation and a raw material in industrial and scientific fields. Unravelling its detailed chemistry is important for its practical applications. Pyrolysis of a-methyl-naphthalene (C11H10) is studied in a flow reactor at low and atmospheric pressures (30 and 760 Torr) using synchrotron vacuum ultraviolet photoionization molecular beam mass spectrometry (SVUV-PI-MBMS). A kinetic model is developed to predict the decomposition of a-methyl-naphthalene under pyrolytic conditions. A general map of a-methylnaphthalene thermal decomposition is presented according to the experimental observations and model analysis. Benzo[b]benzyl radical is the dominant primary product in a-methyl-naphthalene pyrolysis. Benzo[b]benzyl radical dissociates to monocyclic aromatics and small intermediates mainly via benzofulvenallene and ethynyl-indenyl. The yielded o-benzyne and cyclopent-1-en-3-yne then contributes to the formation of C5 – C8 species. Phenylacetylene has a direct formation route from a-methylnaphthalene by H-addition allyl-elimination. In addition to naphthalene (C10H8) and indene (C9H8) sub-mechanisms, C11 sub-mechanism is shown to be critical to unveil the degradation from bicyclic to monocyclic aromatics.