110th Anniversary: Accurate Modeling of the Simultaneous Absorption of H2S and CO2 in Aqueous Amine Solvents

We present results concerning the application of soft statistical associating fluid theory (soft-SAFT), a molecular-based equation, for modeling the absorption of carbon dioxide and hydrogen sulfide in several aqueous amines, including monoethanolamine, diethanolamine, and N-methyldiethanolamine, at conditions of relevance for acid gas separation. The chemisorption of CO2 and H2S in aqueous amines was modeled through the formation of physically bounded CO2-amine and H2S-amine aggregates by explicitly considering strong intermolecular association forces. This approach eliminates the need to consider all speciation reactions, significantly reducing the number of fitted parameters required to describe the absorption process while providing a direct connection between each amine and the chemical reaction with the acid gases. The model predicts the absorption of H2S for different amine concentrations in excellent agreement with experimental data, showing high extrapolative capability. Soft-SAFT is also used to...