Synergistic effect of blended amines on carbon dioxide absorption: Thermodynamic modeling and analysis of regeneration energy

Chemical absorption using amine-based aqueous solutions is a promising approach for limiting CO2 emissions. This study evaluated the performance of commercial amines, including monoethanolamine (MEA), diethanolamine (DEA), diisopropanolamine (DIPA), N-methyldiethanolamine (MDEA), triethanolamine (TEA), and 2-amino-2-methyl-1-propanol (AMP), along with their binary mixtures, with a focus on their synergistic effect in reducing the regeneration energy. The thermodynamic behavior of these aqueous amine systems for CO2 capture was analyzed using the electrolyte nonrandom two-liquid model; the shortcut method was used to estimate the regeneration energy. The CO2 loading ratio, concentrations of the molecules and ions in the liquid phase, heat of absorption, pH, and regeneration energy were included in the analysis. Amine blending was found to synergistically lower the regeneration energy in the following two cases. First, blending carbamate-forming and non-carbamate-forming amines enhanced carbamate formation, thereby increasing the CO2 cyclic capacity and reducing the regeneration energy in the DIPA-MDEA and DEA-AMP systems. Second, the MEA-MDEA system revealed an optimal blending ratio for balancing different heat components (sensible, reaction, and latent heat). These findings offer a guide for selecting and blending amines to optimize the CO2 capture performance.