Detailed kinetic modeling of the formation of toxic polycyclic aromatic hydrocarbons (PAHs) coming from pyrolysis in low-pressure gas carburizing conditions

Hydrocarbon pyrolysis in low-pressure gas carburizing conditions leads to gas phase reactions, which produce polycyclic aromatic hydrocarbons (PAHs), some of which, such as benzo[a]pyrene, are carcinogenic. Workers can be exposed to these PAHs during maintenance and cleaning operations of carburizing furnaces. The aim of the study is the prediction of the formation of sixteen PAHs considered as priority pollutants by the Environmental Protection Agency in the United States (US EPA). A model has been implemented in order to describe the reaction pathways leading to their formation. It was validated using experimental data from the literature, obtained during pyrolysis of different hydrocarbons such as acetylene and ethylene. Flux analyses were realized in order to determine main reaction pathways leading to benzene depending on the reactant. Simulations were also performed to compare PAH formation between acetylene, ethylene and propane pyrolysis.