Allene addition to a fuel-lean ethylene flat flame

Abstract

Two fuel-lean C 2H 4/O 2/Ar flames, one doped with allene, were analyzed using molecular-beam mass spectrometry (MBMS) and modeled. Flame conditions were ϕ = 0.70 and 56.4% Ar for the undoped flame and ϕ = 0.69, 56.5% Ar and [allene]/[C 2H 4] = 0.0242 for the doped flame, both at 4.000 kPa (30 Torr) with a 30.6 cm/s burner velocity at 300 K. Modeling and measurements agreed well for the major species, but H, O, and OH were overpredicted. Perturbation effects by allene addition included an increase in propargyl (C 3H 3) and C 6H 6 species in both experiments and the model. Modeling suggested that the major C 6H 6 species is benzene. Measurements done on the Chemical Dynamics Beamline of the Advance Light Source, within Lawrence Berkeley National Laboratory, using photoionization molecular-beam mass spectrometry supported the model predictions by determining that the major C 6H 6 species is benzene (45%), followed by 1,5-hexadiyne (35%), and fulvene (20%). Using the rate constants of Miller and Klippenstein [J. Phys. Chem. A 107 (39) (2003) 7783], the model predicted C 3H 3 self-combination reactions to be the major benzene formation route through direct formation as well as through formation of thermal fulvene and linear C 6H 6, which can then isomerize to benzene. Benzene is destroyed mainly through hydrogen abstraction to form phenyl and through O attack to form phenoxy. A major phenyl destruction path is to benzene. The ultimate destruction of benzene goes through phenyl and phenoxy. Both species undergo CO elimination by O addition to phenyl and decomposition of phenoxy to form cyclopentadienyl, which undergoes further oxidation to form CO, CO 2, and H 2O.