Composition profiles and reaction mechanisms in a near-sooting premixed benzene/oxygen/argon flame

The structure of a near-sooting flat low-pressure laminar benzene-oxygen-argon flame was studied using a molecular beam mass spectrometer system. Mole fraction profiles of fifty-one species are presented and their mechanistic implications are discussed with regard to the decay of benzene and the formation of polycyclic aromatic hydrocarbons and soot. A mechanism is outlined for production of C 2 , C 3 , C 4 and C 5 species from initial attack of O atom on benzene. Trends observed as the fuel equivalence ratio is increased past the sooting limit suggest a sequential growth from polycyclic aromatic hydrocarbons of 120–210 amu to heavier species and then to soot. A critical step in mechanisms for rapid growth of aromatic structures by free radical addition reactions is the stabilization of the adduct by forming six-membered rings. A mechanism requiring methyl substitution on the aromatic ring is discussed.

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