Energy efficient diethylenetriamine–1-propanol biphasic solvent for CO2 capture: Experimental and theoretical study

Biphasic solvents characterized by a substantially decreased regeneration heat consumption are promising alternative CO2 absorbents to typical monoethanolamine (MEA). In this study, 1-propanol was used as a phase splitter for diethylenetriamine (DETA) aqueous solvents. A tunable phase separation property was achieved by simply varying the concentration of 1-propanol. The 30 wt% DETA–50 wt% 1-propanol solvent exhibited the best phase separation properties with a volume ratio (rich–phase) of 41.7% and a rich loading of 6.54 mol/L. A molecular scale understanding of the phase separation mechanism was revealed through molecular dynamics simulations. Upon 1-propanol introduction, strong hydrogen bond interactions tended to be established between uncovered DETACOO– and DETAH+ and triggered the evolution of phase separation. Furthermore, 1-propanol functioned as an absorption activator by increasing the overall mass transfer coefficient (KG) from 2.11 to 3.22 × 10–10 mol/cm2·s·Pa. DETA–1-propanol achieved a regeneration heat of 2.12 GJ/t CO2, which was 46.9% lower than that of 5 M MEA. This study provides a molecular-scale understanding of the phase separation mechanism and a promising DETA–1-propanol biphasic solvent with favorable phase separation behavior, rapid CO2 absorption, high CO2 absorption capacity, and superior energy-saving regeneration.