Effect of the presence of hydrogen sulphide on the formation of light gases, soot and PAH during the pyrolysis of ethylene

The formation of light gases, soot, and 16 polycyclic aromatic hydrocarbons (EPA-PAH), classified as priority pollutants by the United States Environmental Protection Agency (USEPA), has been studied during the pyrolysis of mixtures of ethylene with hydrogen sulfide (H2S) in a tubular flow reactor setup. The study was made using a constant concentration of ethylene and different inlet concentrations of H2S, in a temperature range from 1075 to 1475 K. The light gases produced were quantified by a chromatographic method. The soot amount formed was also quantified at the outlet of the reactor. The speciation of the individual EPA-PAH compounds was made by a combination of Soxhlet extraction, extract concentration by a rotary evaporator, and gas chromatography coupled to mass spectrometry. The present study shows that, under pyrolysis conditions, there is an effective interaction between H2S and hydrocarbons, forming significant amounts of CS2 and bonding sulfur to soot. The presence of H2S in the pyrolysis of ethylene contributes to slightly decrease the formation of soot and EPA- PAH, which indicates a positive effect of the sulfur compound under pyrolysis conditions