The formation of polycyclic aromatic hydrocarbons (PAHs) from solid fu
els is a complicated phenomenon involving many physical and chemical p
rocesses. In order to gain a better understanding of the types of reac
tions 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 f
urnace, we identified four classes of condensed phase reaction product
s-bipyrenes, their condensation or cyclodehydrogenation products, pyre
ne fragmentation products and soot. Statistical and steric factors -ac
counted for qualitatively by the molecular topology of the reaction pr
oducts-were used to rationalize the relative abundance of the differen
t products in the first two categories. The absence of PAH species tha
t might arise from a sequential acetylene addition pathway (like benzo
[e]pyrene, benzo[hi]perylene, coronene, etc.) leads us to conclude tha
t in our system the most important molecular weight growth channel inv
olves direct polymerization of aromatics. Fragmentation products like
triphenylene, cyclopenta[hi]acephenanthrylenes, and cyclopenta[cd]pyre
ne were also detected; however, based on evidence adduced from paralle
l studies, we think that high amounts of CPP in this and other studies
result from isomerization rather than acetylene addition.