Solubility of Carbon Dioxide and Hydrogen Sulfide in Aqueous N-Methyldiethanolamine Solutions

In this work, 72 new experimental solubility data points for H 2 S and CO 2 mixtures in aqueous N-methyldiethanol amine (MDEA) solutions at different methane partial pressures (up to 69 bara) are presented. They are correlated using an electrolyte equation of state (E-EOS) thermodynamic model. This model has already been used to estimate the CO 2 solubility in aqueous MDEA ( Huttenhuis et al. Fluid Phase Equilib. 2008, 264, 99−112) and the H 2 S solubility in aqueous MDEA ( Huttenhuis et al. Int. J. Oil, Gas Coal Technol. 2008, 1, 399−424). Here, the model is further extended to predict the behavior of CO 2 and H 2 S when they are present simultaneously in aqueous MDEA. The application of an equation of state is a new development for this type of system, i.e., of acid-gas−amine systems. The molecular interactions are described by Schwarzentruber et al.’s modification of the Redlich−Kwong−Soave equation of state, with terms added to account for ionic interactions in the liquid phase. The model is used to describe acid-gas solubility data for the CO 2 −H 2 S−MDEA−H 2 O system reported in the open literature and experimental data reported here for the CO 2 −H 2 S−MDEA−H 2 O−CH 4 system.