Polycyclic aromatic hydrocarbons from the high-temperature pyrolysis of pyrene

Abstract

The formation of polycyclic aromatic hydrocarbons (PAHs) from solid fuels is a complicated phenomenon involving many physical and chemical processes. In order to gain a better understanding of the types of reactions taking place during high-temperature PAH production, we carried out a pure compound pyrolysis program between 1200 and 1500 K. In this work, which deals with pyrene pyrolysis in a laminar flow drop tube furnace, we identified four classes of condensed phase reaction products—bipyrenes, their condensation or cyclodehydrogenation products, pyrene fragmentation products and soot. Statistical and steric factors—accounted for qualitatively by the molecular topology of the reaction products—were used to rationalize the relative abundance of the different products in the first two categories. The absence of PAH species that might arise from a sequential acetylene addition pathway (like benzo[e]pyrene, benzo[ghi]perylene, coronene, etc.) leads us to conclude that in our system the most important molecular weight growth channel involves direct polymerization of aromatics. Fragmentation products like triphenylene, cyclopenta[hi]acephenanthrylenes, and cyclopenta[cd]pyrene were also detected; however, based on evidence adduced from parallel studies, we think that high amounts of CPP in this and other studies result from isomerization rather than acetylene addition.