Carbonyl sulfide removal from refinery tail-gas streams: Experimental and kinetic study of the hydrolysis reaction

Abstract

Carbonyl sulfide (COS) is a major pollutant of refineries. Nowadays, the most promising solution for its removal is represented by the hydrolysis reaction. In the perspective of the industrial application of this process, this work focused on the study of simulated refinery tail-gas streams, in which the effect of each component was addressed. In addition, since the understanding of the reaction kinetic is vital for designing new plant units for this technology, the Langmuir-Hinshelwood theory was employed to distinguish the role of each species in the reaction mixture. Through the experimental analysis, it was observed that the presence, in the effluent stream, of water and carbon dioxide in high concentrations inhibits the hydrolysis reaction. According to the thermodynamic analysis, the phenomenon must be related to the occurrence of competitive adsorption between both these components and COS. Through the computational analysis, it was observed that each species present in the hydrolysis system undergoes different adsorption mechanisms: single-site type for COS, cooperative adsorption in the case of H2O, and dissociative adsorption for CO2. Finally, the expression for the reaction rate obtained in this study was proven to be extendable to a large variety of different operating conditions, verified with a totally new set of experimental data.