Formation of polycyclic aromatic hydrocarbons from contaminants in Claus feed

Abstract

In the Claus process, polycyclic aromatic hydrocarbons (PAHs) are the main precursors for soot particle formation. The presence of these contaminants in Claus furnace can lower its efficiency, reduce sulfur recovery, and increase the operational cost. Therefore, the formation of PAHs in the furnace must be minimized. The aim of this work is to study different reaction pathways that may lead to PAH formation through quantum chemical and kinetics calculations. These calculations include the density functional theory, transition state theory, and potential energy diagrams. Three pathways were studied in this work, where phenanthrene formation from naphthalene via the conversion of acenaphthylene was studied in Pathways 1 and 2, and Pathway 3 explored the development of phenanthrene from naphthalene by H and C2H2 additions. The energies of the reactants, products, and the transition states were optimized through B3LYP and M062X functionals as well and through CBS-QB3 composite method using Gaussian 09 software. The potential energy diagrams were plotted to visualize these reactions with their energies. The effect of our developed mechanism on PAHs formation inside Claus furnace was investigated thorough flame and Claus furnace simulations. It was found from an ethylene flame simulation that our mechanism corresponds to 61% increase in phenanthrene formation as compared to the mechanism without our reactions. Furthermore, Claus furnace simulation showed that the conditions used in industries are not suitable for large PAH destruction, and their optimization using detailed reaction mechanism could help in finding suitable conditions for aromatics destruction in the furnace.

Date of Award	May 2021
Original language	American English