Phase separation characteristics in biphasic solvents based on mutually miscible amines for energy efficient CO₂ capture

Abstract

One of the challenges with regard to the aqueous amine-based CO₂ capture process is the considerable energy requirement for solvent regeneration. To overcome this challenge, a biphasic solvent was employed in this study. Here, the phase separation behavior of amine blends depending on the characteristic structures of the solvent component was investigated using a turbidity measurement apparatus. Amines were classified as (1) primary/secondary amines or tertiary/sterically hindered amines depending on the CO₂ reaction species, such as carbamate and bicarbonate (2) alkyl and alkanolamines, depending on the presence of a hydroxyl group, (3) chain and cyclic amines, and (4) mono- and polyamines depending on the molecular structure. Easy phase separation occurred in solvent blends containing polyamines such as DETA (diethylenetriamine), TETA (triethylenetetramine), and DEEA (2-(diethylamino) ethanol). The types with the greatest potential were the DETA/DEEA blended solvents. A phase separation could be determined based on the difference in the reaction rate with CO₂ and the low solubility between the carbamate species of DETA and DEEA.