Influence of the Oxygen Presence on Polycyclic Aromatic Hydrocarbon (PAH) Formation from Acetylene Pyrolysis under Sooting Conditions

Abstract

The concentration of sixteen polycyclic aromatic hydrocarbons (PAH), classified by the Environmental Protection Agency (EPA) as priority pollutants, and the soot amount obtained from acetylene conversion for different oxygen concentrations have been determined in a tubular reactor experimental system. The present work also reports concentrations of other products such as light gases, which are known as important in the soot-PAH formation process or because of their abundance in the experiment outlet gas stream. For an acetylene concentration of 30000 ppmv two types of studies have been performed namely a) the effect of reaction temperature was evaluated between 873 and 1323 K in absence and presence of oxygen (0 and 10000 ppmv) and b) the influence of the oxygen concentration between 0 and 50000 ppmv on product formation was considered for temperatures of 973 and 1223 K. Apart from CO as the main product formed from the conversion of C2H2 in the presence of oxygen, benzene, PAH, and soot are also formed in significant amounts. They are encouraged by the presence of oxygen in fuel rich conditions at the lowest temperatures studied but seem to be diminished when the temperature is increased. The results obtained at a reaction temperature of 973 K and different oxygen concentrations showed that the PAH concentration presents a maximum of around 10000 ppmv. Moreover, for a temperature of 1223 K, an increase of oxygen concentration causes a decrease of benzene/PAH/soot formation.