CO2 absorption in blended amine solvent: Speciation, equilibrium solubility and excessive property

Mixing different amines is a common method to develop better solvents for CO 2 capture. As the mixing provides more adjustability on the solvent properties, it introduces complex interaction between dissimilar amine molecules who may perform diverse role in the reactions. Here we studied CO 2 absorption in monoethanolamine (MEA), methyldiethanolamine (MDEA) and their mixtures thereof. The speciation profiles along with CO 2 loading were provided via NMR to reveal the competition/coordination of MEA and MDEA in participating the key reactions that drove CO 2 absorption (i.e. carbamate formation and amine protonation). Furthermore, the CO 2 loading of the solvents were measured under equilibrium for various temperature, CO 2 partial pressure. The excessive CO 2 loading was firstly introduced to analyze the loading data regarding the solvent composition. Accordingly, an excessive property model was applied for data correlation. The calculated CO 2 loading agreed well with experimental data with average absolution relative deviation of 1.7%.