CO2 absorption by diethylenetriamine-based phase change absorbents: Phase change mechanism and absorption performance

Abstract

CO₂ phase change absorbents (CPCAs) have garnered significant attention for their potential to reduce energy consumption. However, suitable phase change agent is suffering from the selection among a wide range of organic solvents. In order to explore the phase separation mechanism and minimize screening efforts of CPCAs, the phase separation behaviors of the diethylenetriamine (DETA)-based absorbents constituted with different organic solvents were investigated, and the interaction energies revealed that the ion–dipole interaction is the dominant role in CO₂-riched absorbents. The intensification of the self-aggregation of organic solvents by the ion-water interaction, was proposed as the main reason for the differences in the phase separation behavior in different DETA-based absorbents. Based on the relative E_T(30) and relative dielectric constant of the organic solvent, a phase separation diagram can be drawn to predict the phase change behaviors of DETA absorbents. Among the DETA-based CPCAs, DETA + DMF + H₂O absorbents showed the largest CO₂-rich phase loading, and the optimized DETA + DMF + H₂O CPCA exhibited 200 % of the CO₂ cyclic loading compared to 30 wt% MEA aqueous solution.