Polycyclic aromatic hydrocarbons (PAH), soot and light gases formed in the pyrolysis of acetylene at different temperatures: Effect of fuel concentration

The effect of different inlet hydrocarbon concentrations (10,000, 20,000 and 30,000 ppmv) and reaction temperatures (873–1323 K) on PAH and soot formation from acetylene pyrolysis has been studied. 16 PAH considered by Environmental Protection Agency (EPA) as priority pollutants, together with light gases present at the outlet gas stream, have been quantified. Soot formed was collected on a filter at the reactor outlet. PAH found in the different phases (at the gas phase, adsorbed on soot, and/or stuck on reactor walls) were analysed by means of gas chromatography–mass spectrometry (GC–MS). Increasing fuel concentration and reaction temperature resulted in the increase in soot production together with decrease in the light gases at the reactor outlet. The acetylene conversion and the hydrogen concentration increased with the temperature, whereas benzene and the total PAH quantified showed a maximum around 1123 and 1223 K, respectively. In all cases, the concentration of products such as hydrogen, benzene, PAH and soot at the reactor outlet and the acetylene conversion increased with the reactant concentration. The temperature, at which the benzene showed a maximum concentration, was similar to the temperature where soot and PAH started to be formed. This suggests that benzene consumption leads to form PAH, which subsequently form soot, by following the well-known HACA (hydrogen abstraction/acetylene addition) mechanism.