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 ET(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.