Observation of cyclopenta-fused and ethynyl-substituted PAH during the fuel-rich combustion of primary tar from a bituminous coal

High-performance liquid chromatography (HPLC) with ultraviolet-visible (UV) diode-array detection was used to analyze the condensed-phase products fro m the fuel-rich combustion, at 1000 degrees C, of bituminous coal primary t ar. Experiments were performed using a quartz two-stage reactor consisting of a fluidized-bed reactor coupled to a tubular-flow reactor. Eight cyclope nta-fused polycyclic aromatic hydrocarbons (CP-PAH) were identified, four o f which have never before been observed as products of a bituminous coal an d have also never been observed from the fuel-rich combustion of any coal: cyclopent[hi]acephenanthrylene, cyclopenta[cd]fluoranthene, dicyclopenta[cd ,jk]pyrene, cylopenta[bc]coronene. In addition to these CP-PAH, two ethynyl -substituted PAH, 2-ethynylnaphthalene and 1-ethynylacenaphthylene, were id entified for the first time as bituminous coal products. Yields of individu al CP-PAH spanned a range of 4 orders of magnitude. Out of the eight CP-PAH identified, acenaphthylene was found to be the most abundant under all con ditions investigated. CP-PAH of higher ring number were present in successi vely lower amounts, consistent with CP-PAH formation via hydrocarbon growth reactions. CP-PAH yields decreased with increasing oxygen concentration, i ndicating that rates of CP-PAH oxidation exceeded those of CP-PAH formation under the conditions investigated. Possible mechanisms of CP-PAH formation are discussed, but the complexity of the starting fuel precludes definitiv e delineation of the reaction pathways leading to CP-PAH and ethynyl-substi tuted PAH during the fuel-rich combustion of tar.