The Formation of Polycyclic Aromatics, Fullerenes and Soot in Combustion. The Mechanism and the Environmental Connection

Despite the concern about environmental damage caused by toxic polycyclic aromatic hydrocarbons (PAH), the mechanisms that govern thermal build-up of these molecules are hardly known. Only some vague ideas exist, which are equally true for thermally formed hetero-PAH, e.g. benzofurans and dioxins. It is further not clear if complete combustion to H2O, CO2, and NO2, is a realistic goal in the practice of engines or incenerators. Flash vacuum thermolysis (FVT) techniques, provides a tool for description of mechanistic routes and for characterisation of reactive intermediates in PAH and hetero-PAH formation during combustion. On FVT six-membered ring PAH systems were found to undergo thermal transformations to cyclopenta-PAH. Some nitro-PAH gave hydroxy-PAH on FVT. Cyclopenta-PAH can conveniently be synthesized with preparative FVT.