Competitive H₂S – CO₂ absorption in reactive aqueous methyldiethanolamine solution: Prediction with ePC-SAFT

Reactive absorption of CO₂ and H₂S in aqueous methyldiethanolamine (MDEA) solutions is considered within the ePC-SAFT equation of state. We demonstrate that ePC-SAFT can be employed in a predictive manner without regression of additional temperature-correlated terms. Mixed system predictions are tested using a consistent set experimental data covering a wide range of temperatures (313 K–413 K), partial pressures (0.001 kPa–1000 kPa), and MDEA mass fractions (0.05–w_MDEA 0.75 w_MDEA). Predicted partial pressures for acid gas absorption show good agreement for low MDEA fractions (w_MDEA < 0.5). Absorption selectivity in binary H₂S + CO₂ absorption is correctly predicted, with absolute average deviations of 57.18% and 79.32% for partial pressures of CO₂ and H₂S. We identify a significant deterioration in ePC-SAFT predictive power for the high-MDEA regime (w_MDEA > 0.5), likely originating from underlying assumptions in the Debye-Hückel electrolyte free energy treatment and representation of ionic species.