IDENTIFICATION OF SOME NOVEL CYCLOPENTA-FUSED POLYCYCLIC AROMATIC-HYDROCARBONS IN ETHYLENE FLAMES

The product suite of polycyclic aromatic hydrocarbons (PAH) produced i n typical high-temperature (1300-1700 K) fuel-rich flames is character ized by the abundance of peripherally-fused cyclopenta-PAH (CP-PAH), t he most prominent of which are acenaphthylene (C12H8) and cyclopenta[c d]pyrene (C18H10) Although many other CP-PAH are thought to be present , their structural elucidation has been contingent on the availability of synthetic reference standards, and this has hindered their positiv e identification in flames. Previous studies using synthetic standards have resulted in the identification of a limited number of other CP-P AH including cyclopent[hi]acephenanthrylene, cyclopent[hi]aceanthrylen e and all three isomeric dicyclopentapyrenes. In this work, we report the identification in ethylene flames of three additional CP-PAH, benz o[ghi]cyclopenta[cd]perylene, cyclopenta[bc]coronene and cyclopenta[cd ]fluor anthene. Their positive identification was made possible by the availability of reference quantities of the authentic standards. Cycl openta[bc]coronene is a C26H12 PAH (324 u) formed by the peripheral fu sion of a C-5-ring to coronene. It is one of the five most abundant PA H in ethylene flames typically accounting for 4%-6% of the total PAH f or a range of flame types and operating conditions. Benzo[ghi]cyclopen ta[cd]perylene is a C(24)H(12)PAH (300 u) isomeric with coronene. Cycl openta[cd]fluoranthene is a C18H10 PAH presesent at low levels in the flames studied. It is much less abundant than its isomeric counterpart , cyclopenta[cd]pyrene, the most abundant PAH in ethylene flames. Iden tification of the three new PAH was accomplished by comparing spectral and chromatographic signatures with those of the references standards using gas chromatography/mass spectrometry and high performance liqui d chromatography with spectrometric diode-array detection. Selected sp ectral data are presented for the three new species.